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Journal of the Engineering Integrity Society

ENGINEERING INTEGRITY

March 2020 | Issue No. 48

TECHNICAL PAPER: An Investigation into the Failure Mechanisms of Coronary Stents

ALSO INSIDE: INSTRUMENTATION, ANALYSIS & TESTING EXHIBITION SILVERSTONE, 31 MARCH 2020 FATIGUE 2020, DOWNING COLLEGE, CAMBRIDGE 29 JUNE – 1 JULY 2020

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Contents: March 2020

Index to Advertisements.................................................................................... 5

INDEX TO ADVERTISEMENTS

Welcome and Goodbye...................................................................................... 6

Advanced Engineering 2020......................................50

Editorial..................................................................................................................... 7

CaTs3 / Zwick........................ 4

Diary of Events........................................................................................................ 7

Data Physics........................ 2

Technical Paper: An Investigation into the Failure Mechanisms of

DJB Instruments...............33

Coronary Stents .................................................................................................. 8

EIS............................................ 3

How It Works: Laser Doppler Vibrometry .................................................. 22

HEAD acoustics................51

Fatigue 2020.......................................................................................................... 25

M&P International...........52

Young Engineers.................................................................................................. 29

Sensor Technology..........41

Industry News....................................................................................................... 30

Sensors UK.........................32

Peter Watson Prize 2020................................................................................... 33

SOUNDCAM UK................29

Product News........................................................................................................ 34 Instrumentation, Analysis & Testing Exhibition........................................ 36 News from the Tipper Group........................................................................... 38 News from the Women’s Engineering Society.......................................... 39 News from Institution of Mechanical Engineers...................................... 40 News from British Standards........................................................................... 41 Inspiring the Next Generation........................................................................ 42 University of Wolverhampton Racing.......................................................... 43 Group News........................................................................................................... 44 Committee Members......................................................................................... 46 Corporate Member Profiles............................................................................. 48 Corporate Members........................................................................................... 50

Thank you to Serco, Derby, for hosting the October 2019 committee meetings.

If you would like to receive this journal electronically, please contact the Secretariat: info@e-i-s.org.uk

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Engineering Integrity contains various items of information of interest to, or directly generated by, the Engineering Integrity Society. The items of information can be approximately subdivided into three general categories: technical papers, topical discussion pieces and news items. The items labelled in the journal as technical papers are peer reviewed by a minimum of two reviewers in the normal manner of academic journals, following a standard protocol. The items of information labelled as topical discussions and the news items have been reviewed by the journal editorial staff and found to conform to the legal and professional standards of the Engineering Integrity Society.

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Welcome and Goodbye

‘Engineering Integrity’, the Journal of the Engineering Integrity Society is published twice a year.

ISSN 1365-4101/2020

The Engineering Integrity Society (EIS) Incorporated under the Companies Act 1985. Registered No. 1959979 Registered Office: c/o Hollis & Co., 35 Wilkinson Street, Sheffield S10 2GB

We are delighted that Rochelle Stanley has joined the EIS team as Managing Editor of our journal. Rochelle is highly experienced in technical and academic publishing and we look forward to working with her on new developments in the journal. Rochelle takes over from Catherine Pinder who looked after the journal for 27 years and has now taken a well-earned retirement. We wish Catherine well and would like to thank her for her steady hand in steering the journal through the 6choppy waters of five different honorary editors!

‘Engineering Integrity’ is lodged with the Agency for the Legal Deposit Libraries on behalf of the Bodleian Library Oxford University, the Cambridge University Library, National Library of Scotland, National Library of Wales and Trinity College Dublin.


Guest Editorial Welcome to the spring 2020 edition of the EIS journal. It is impossible to go online or listen to the news without hearing the latest story on climate change and the need to address the damaging behaviours of the human species.

(page 8). The paper, by Matt Crane of Bristol University, was presented at the society’s Peter Watson prize last October (page 33). Matt was Highly Commended in the competition and the judges noted the high quality of his research. The importance of supporting those at the start One facet of this narrative is the damage to the of their engineering careers is highlighted in the environment through the use of cars and other update on page 29. Our Young Engineers Seminars vehicles such as aircraft (page 40). With the have been running for four years and have been announcement from the UK government to ban well received by those who have been part of the the sale of combustion engine vehicles by 2035 programme. To further develop and enhance the (page 31) the need for a greener alternative has seminars and opportunities we can offer we are never been so great. Whilst many consumers regard currently conducting a review with the intention of this technology in its infancy, the reality is that the re-launching the programme in September. electric revolution is just around the corner. The important question is how we take the technology In previous issues we have highlighted the lack to the next level. Doubts over safety, cost, range of females within the engineering workforce and anxiety and infrastructure must all be resolved by it is heartening to learn that the UK has the most industry in the coming years. We are in a phase women researchers in the world (page 31). In an of rapid development and this makes it difficult ever-advancing technological world engineers play to predict the technology which will become the an important role in developing solutions to the industry standard. This subject is the theme of world’s biggest technological problems, and future the mini seminars at this year’s Instrumentation, research and development is essential to deliver Analysis and Testing Exhibition at Silverstone (page these innovations. One of the highlights for the 36). With experts from both industry and academia society in 2020 will be the return of our international offering insight into the challenges which will be conference, Fatigue 2020, to Downing College in faced and the opportunities presented, there will Cambridge (page 25). This summer’s meeting will be a wide range of topics under discussion. Dyrr see presenters travelling from across the world to Ardash from Williams Advanced Engineering is our present the latest research and innovations. With keynote speaker and his presentation “Road to EV: over 65 presentations covering many aspects Spark to Revolution” considers the challenges and of fatigue and durability there will be a very full opportunities of an industry that has focused on three-day programme with sessions including internal combustion for over 100 years. Crack Propagation, Additive Manufacturing and Experimental Methods. We hope that many of you An important role of the EIS is supporting will be able to join us in Cambridge. our younger engineers in their professional development. In this issue we are pleased to feature a technical paper “An Investigation Into Guest Editorial from the Instrumentation, Analysis the Fatigue Behaviour of Coronary Stent Alloys” and Testing Exhibition Sub-Committee

Diary of Events Instrumentation, Analysis and Testing Exhibition Silverstone Race Circuit | 31 March 2020 Fatigue 2020 | Downing College, Cambridge | 29 June – 1 July 2020 EIS AGM | Venue TBC | June 2020 Young Engineers Seminars | various dates throughout 2020 and 2021 Generation & Storage of Renewable Energy: Durability & Reliability | Filton | November 2020

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ENGINEERING INTEGRITY, VOLUME 48, MARCH 2020, pp.8–21. ISSN 1365-4101/2020

Matt Crane was Highly Commended in the Peter Watson Prize 2019 competition. His paper is reproduced here in full.

Technical Paper: An Investigation Into the Failure Mechanisms of Coronary Stents Matt Crane, Department of Mechanical Engineering, University of Bristol matt.crane28@gmail.com

Abstract The mechanism of fracture through fatigue is considered one of the primary concerns in the coronary stent industry. In the paper, the effects on fatigue life of the combined environmental factors of surface abrasion, corrosion and local plasticity are investigated. It is found that all contribute to the reduced fatigue life of SS316L wire specimens. This is done using a built-for-purpose fine wire fatigue test rig. Further to this, a Finite Element Analysis model is created to give insight to the stress state in balloon expandable coronary stents subjected to the loads of expansion and cyclic service. The analysis is based upon the recorded expansion of a Boston Scientific, 3.5mm diameter Synergy Drug Eluting Stent. Material data for the PtCr alloy used is limited, obstructing the model.

angioplasty alone, delayed restenosis – the process of narrowing of the artery after the procedure – is likely to occur. This can come about through a variety of mechanisms. During the compression of the lesions the artery wall is subject to high loads, causing collapse of the walls post dilation, as well as inflammation. This can result in the closure of the artery and a secondary blockage.

1. Introduction 1.1 Stenting Overview Cardiovascular disease (CVD) is the leading cause of mortality worldwide, killing 17 million people every year. Around 43% of these deaths can be attributed to the Coronary Heart Disease (CHD) subdivision [1]. This is the term given to ailments affecting the vessels that supply oxyegnated blood to the heart, providing the energy required for regular function. Two of the most common forms of CHD are atherosclerosis and arteriosclerosis. The former is characterised as the accumulation of calcifications within artery walls, decreasing lumen diameter, caused by low-density lipoprotein (LDL) (cholesterol) intake as part of a poor diet. The latter is defined as the hardening of artery walls, preventing normal contraction and expansion to regulate pressure. CHD can lead to full or partial blockage of coronary arteries, leading to angina and heart attacks [2]. A well-established method of treating CHD is balloon angioplasty followed by stent implementation. During balloon angioplasty, a guide wire with a catheter tube connected to a semi-compliant cylindrical balloon enters the cardiovascular system via a limb. A surgeon then navigates through the patients cardiovascular system to the location of the blockage, using fluoroscopy to visualise. Once the balloon arrives at the site of the blockage, the surgeon begins balloon inflation, applying pressure through use of a handoperated water pump. This clears the blockage by radially displacing any calcifications and/or blood clots towards the walls of the vessel. This increases the effective lumen diameter and restores blood flow. After 8

Figure 1: Image of implemented stent in pre-expanded coronary artery. Guide-wire catheter and deflated expansion balloon visible [1].

Another response to trauma is termed endothelial proliferation, where the cells lining the inner walls of the vessel multiply rapidly. With angioplasty alone, restenosis and relapse of angina symptoms occur in around 40% of cases [2]. In order to improve the success rate of the procedure, the Bare Metal Stent (BMS) was developed. Stents are fine metallic cylindrical trellises, implemented to support the vessel and prevent restenosis caused by collapse. The stent, initially crimped around a compliant balloon, is delivered to the location of artery blockage again using a catheter, post angioplasty. The balloon is then carefully inflated and the stent deforms plastically to match required vessel diameter. The introduction of the BMS to the treatment process saw the rate of restenosis drop to around 20–30% [3]. The interaction between stents and their accommodating arteries are complex and depend on a number of biological, chemical and mechanical factors. Although stents provide structure to the artery, they alone do little to inhibit the inflammatory response of the vessel. To counteract this, the Drug Eluting Stent (DES) was developed. These stents are coated in a drug that inhibits the natural proliferation response. This is done in such a way that the drug is gradually released to the surrounding cells for a finite period of time after implementation. This means that stent endothelialization is eventually possible, where cells grow to cover the stent, allowing it to effectively


become part of artery wall [4]. Through the use of DES, the rate of restenosis occurrence has dropped to <10% [3]. Since the first BMS was implemented in 1986, the use of stents has been ever increasing. In 2018, over 1.8 million stents were implemented in the US alone [5]. The net worth of the stent industry is ever growing, and is estimated to exceed $16 billion dollars worldwide by 2022 [6]. This has seen heavy investment into the engineering of stents, as companies look to take control of the market. Due to the competitive nature of the industry, detailed information regarding new and developing products is difficult to access. Unbiased insight must therefore be gained from independent studies and clinical performance data. 1.2 Literature Review Currently, on the market, there are over 100 varieties of vascular and non-vascular stents available. Not one of these designs is deemed optimum for all applications, and often the surgeon must select which is the most suitable for their patient [4]. From the literature, it is clear that there are several design parameters that leading stent companies and researchers prioritise, in terms of design, development and critical analysis. 1.2.1 Radial Strength Perhaps one of the more intuitive parameters, any stent design must be capable of withstanding the loads it is subjected to through normal application. The loads imposed by contraction of neighbouring cardiac muscles, altering vessel geometry, are difficult to predict due to the individuality of application. General pressure variations due to the cyclic nature of coronary artery pressure are easier to predict and must also be considered. Stent geometry must suffice such that induced stresses are below the yield of the selected material post expansion, so that unwanted permanent deformation, or even stent fracture, does not occur [4]. Keeping these stresses as far from failure stress, or below the fatigue limit, is also valuable in terms of preventing delayed fracture. Although radial strength is dependant on strut thickness, the parameter must be constrained to avoid disruption to blood flow. Studies have found that stents can cause turbulence, imposing increased shear forces on artery walls and impeding cell proliferation – the natural process of repair. This increases the rates of restenosis [7]. The increased scrutiny of material selection and geometry has seen stent thickness reduce to around 60 μm in the latest DES, with original BMSs being much thicker; around 150 μm thick. Decreasing this parameter is experimentally proven to decrease flow disruption [8]. 1.2.2 Fatigue Behaviour and Fracture Once implemented, stents are subject to periodic loading cycles as blood pressure varies from high during systole (heart contraction) to low during diastole (heart relaxation) [9]. Delayed stent fracture is commonplace, and has been reported to occur in 3%–18% of all stents implemented [10]. This can be attributed to fatigue. Protruding fractured struts may then interfere with surrounding artery walls, causing trauma and restenosis. Due to the complicated and application specific nature of fatigue, predictions are typically made empirically

using SN curves [11]. Although such data is useful in term of gauging the order of numbers of cycles to failure at specific stress amplitudes, it is imperative to recognise that these results are highly variable and dependant upon component geometry, manufacturing process and working environment. It is therefore advisable that any test data used to predict stent life should have been collected mimicking all application parameters as closely as possible. It is often found that the most relevant way to test stent material is to fatigue samples of fine wire, mimicking the bending of the thin struts characteristic of the trellis structure. From the literature, the most common materials used to manufacture balloon expandable stents are found to be Stainless Steels (specifically SS316L alloy) and cobalt chromium (CoCr L505 alloy) [9]. There is a standardised method of fatigue testing thin wire, recognised by ASTM, named Rotating Bending Fatigue. This involves constraining the ends of a sample in two chucks in such a way that a free bow U-bend is created. One chuck is thus rotated periodically in opposing directions to induce a known stress at the apex via pure bending [12].The setup is observable in Fig. 2 The arrangement allows for the wire to be suspended in an appropriate fluid, for corrosion simulation or cooling purposes. The results of rotary bend wire fatigue of CoCr L605 are observable in Fig. 3(a). Although no such literature is available for the SS316L alloy in thin wire form, a rough plot of the alloy’s fatigue properties is available from EDUPACK and is presented in Fig. 3(b) [14].

Figure 2: Thin Wire Rotary Bending Fatigue Tester, with arrows indicating the reversing rotation of chuck [13].

Specimens may be tested at frequencies of 100–50000 Hz. Although, a study carried out by Weaver et al. 2015 [17] found that the speed of testing has a significant influence on cycles to failure for given stress amplitude, with higher speeds increasing the cycles to failure by a factor of 4. This can be attributed to the increased temperature of the sample enhancing the ductility of the specimen. Heating effects are observably negated by suspending the sample in conductive fluid [17]. Stents are designed such that the stress amplitudes induced in standard application are predicted to be below the fatigue limits of materials selected, so it is deemed that unexpected mechanical and environmental factors are to blame. This could take the form of bending due 9


(a) (b) Figure 3: (a) SN curve results of rotary bend wire fatigue of 125 μm diameter wire specimens of L-605 alloy, tested in rotary bending at R=-1 in 37C, 0.9% saline solution at 60 Hz [15], (b) approximate SN curve of SS316L alloy, accuracy of data indicated by upper and lower bounds shown as blue and red markers respectively [16].

to the contraction of surrounding muscle and arteries, as previously mentioned. Plastic deformation created during deployment can also cause slip band extrusions that are considered susceptible to fatigue [11]. Surface abrasion due to relative motion between stent and artery wall calcification’s may go some way to producing surface defects and cracks that propagate according to fracture mechanics to see failure at loads far surpassed by predicted mechanical limits [11]. Marra et al. 2006 [18] carried out standard indentation tests on samples of calcifications retrieved post mortem to determine an average hardness value of around 700 MPa. This is comparable to the hardness value of stent materials. It would therefore be feasible that these calcification’s could cause surface abrasion, and therefore fretting wear as the two surfaces displace past one another. D. O. Halwani et al. 2012 [9] provided evidence that stents recovered from autopsy showed signs of surface wear in regions close to known calcifications, with roughness values of height 3.2 μm and depth 28 μm. Under Electron Microscope analysis, several fractured, recovered stents clearly show signs of crack initiation in the form of large deformations along slip bands. Slip band extrusions due to plasticity were also apparent. From inspecting the cross section of failure sites it is deducible that dislocations produced by abrasion and plasticity have propagated and resulted in failure. 1.2.3 Corrosion Effects The process of fatigue may also be accelerated due to corrosion, therefore, stent materials are selected based upon corrosion resistance. For the alloys frequently utilised in the industry, this resistance is critically dependant upon the formation of a passive oxide film to protect more susceptible inner material. This occurs via the reaction between cobalt – present in both alloys discussed – and oxygen in the atmosphere, to produce a comparatively inert Co(II)oxide layer. Under specific conditions, it is shown that chloride ions can displace oxygen, disrupting the passive film. Polarization corrosion resistance is an important consideration when selecting stent material. Part of the development of stents in the BMS and DES era has seen more corrosion resistant materials being selected and implemented. Cobalt chromium and platinum alloys have been selected in more recent stents to increase corrosion resistance, whilst also improving upon the mechanical 10

properties of stainless steel [19]. Mechanically, the oxide layer may also be worn away by noted abrasion between the stent surface and artery calcifications, or disrupted due to local plasticity during expansion of the stent [9]. In atmospheric conditions, this film would reform, although the decreased availability of oxygen in body fluids would inhibit this process [20]. Pitting corrosion, caused by a cathodic reaction between the freshly exposed metal surface with aid of an oxidizing agent manifests as small holes appearing on the surface of the metal. The breakdown of the passive film is found to increase polarization potential and therefore corrosion rate by [20]’s study, where abrasion between overlapping stents is the primary mechanism oxide layer disruption. The characteristic holes propagate and grow as metal dissolution occurs, working alongside mechanical crack initiation and propagation to increase the rate of fatigue. These effects are directly observable in the work of J. Bolton et al. 1983 [21], with the presence of saline solution and therefore chloride ions resulting in a dramatic decrease in fatigue life of stainless steel alloys. Human blood has a comparable salt concentration, and therefore it is to be expected that pitting corrosion occurs in vivo when similar materials are exposed. The characteristic holes are also observable in the D. O. Halwani et al. 2012 [9] study. Nakazawa et al. 2009 [9] also found, via autopsy inspection of high risk patients, 67% of patients with the most severe cases, termed grade 5 fractures, displayed visible corrosion. This is almost double the rate of those without any fracture present at only 37%. 1.2.4 Other Material Considerations Effective stent materials have low yield strength to allow plastic deformation during expansion, high Young’s Modulus to achieve minimal post-dilation recoil and work hardening to promote integrity and radial strength [4]. Stents must also be adequately radiopaque, a property dependant on the X-ray attenuation coefficient, which is proportional to the cube of atomic number. Moreover, the material selected must be compatible with vessel walls; the body must not reject the implant, causing a detrimental inflammatory response, resulting in restenosis [3].


1.2.5 Stent Designs Although there is large variation in stent geometry, the vast majority of commercially available coronary stents are categorised as ’sequential rings’ designs. Once expanded, the characteristics of which are deformable Z-shaped repeating units, or struts, around the circumference of the stent. Between sequences of repeat units are connecting members named bridges, which may take the form of a straight single beam or more complex geometries [4]. These bridges account for the longitudinal strength of stents, and the number of bridges per ring of struts has an inverse relationship with stent flexibility and conformance to individual arterial geometry [4]. 1.2.6 Finite Element Analysis Finite Element (FE) models are utilised in the industry to develop stent geometry. Through numerical methods, it is possible to obtain highly accurate predictions of stresses and displacements induced in deforming members. This gives detailed insight into residual stress distribution after expansion and induced stress amplitudes during service. FEA is a cheaper method of investigation than physical tests, as testing prototypes in labs and hospitals is expensive. Stent expansion, however, is a relatively complex problem. Expansive plasticity is apparent, as well as large deformation. There are many published studies of FEA models of stents. In which, there are a variety of methods of load approximation. These include internal pressure of the balloon acting directly on the stent’s inner surface [22], balloon-stent interference pressures due to balloon displacement [23], and more complex models, involving the interfaces between the balloon, stent, and artery [24]. This requires access to detailed mechanical property data of all components involved. Stress is found to be concentrated around the points of inflection, during both expansion and service. Larrosa, 2012 [25] also developed an FE technique by which the fatigue limits of components with complicated loading and very small defects, such as stents, can be established.

Through liaison with heart surgeons at Bristol Heart Institute (BHI), several samples of unexpanded coronary stents have been obtained, as well as the expansion devices used to inflate them. Stent expansion will be carried out and recorded under a high-resolution camera in order to obtain measurements of stent geometries. These geometries will form the basis of an FE simulation and analysis of stress distribution in these samples, during both expansion and general service. This will allow estimation of residual stresses prevalent post expansion, as well as a highly accurate estimate of induced stress amplitudes during service. Once this has been completed, efforts will be made to fatigue test either these stents directly or the materials they are manufactured from. Efforts will be made to replicate the corrosive and abrasive environment, similar to that in vivo. The results of said analysis will be compared with each other and to that of the literature, and from this the effects of corrosion and abrasion will be evaluated.

2. Methodology 2.1 Stent Inflation One of the Boston Scientific Synergy, 3.5 mm deployed diameter stents obtained from consultation with surgeons at BHI was inflated under a MONDO OPTIMA high-resolution camera. The stent is laser cut out of a PtCr alloy tubing, with thickness of 78 μm. The camera has image capturing and micrometer level measuring capabilities. In order to form the basis of the FE model, the key geometrical measurements were recorded of the crimped stent. The stent was then expanded at intervals of atmospheric pressure, and the key alterations were again recorded. The shape of the open cell repeated unit is observable in Fig. 4.

1.3 Focus of Study It is widely understood that fatigue life is highly dependant on crack initiation, considered to account for 90% of fatigue life, the remaining 10% accounting for propagation [11]. Through study of the literature and recommendations from several professionals in the industry, it has been decided that the main focus of the investigation will be the fatigue fracture of coronary stents in relation to corrosion and surface abrasion in vivo. Although there is literature available on both the effects of surface wear and corrosion on fatigue individually, there appears to be very little to no data produced as a result simultaneous study in the context of stents. 1.3.1 Aims and Objectives Firstly, calculations will be conducted in order to determine rough estimates of loads stents are subjected to by initially treating stents and the surrounding vessels as concentric cylindrical pressure vessels. Once complete, efforts will be made to improve this estimate by accounting for the stiffness of more realistic stent geometries. This will allow for the prediction of stress amplitudes and therefore service life during normal application when used in conjunction with SN curves from the literature.

Dimension label a b

c

Dimension size (mm) 0.732 0.432 0.121

d

0.1

Figure 4: CAD replicated model of repeated stent unit, dimensions labelled as follows: a) axial inflection to opposing inflection, b) circumferential inflection to next inflection, c) peak width, d) strut width (b) approximate SN curve of SS316L alloy. Initial geometry measurements in the associated table. 11


critical region, between 4â&#x20AC;&#x201C;5 atm pressure, the stent

(a) (b) Figure 5: (a) MONDO captures of stent at 3atm inflation pressure (left) and 5 atm inflation pressure (right). (b) Plot of stent dimensions as previously labelled against expansion balloon pressure.

Figure 6: Visualisation of unwrapped stent loading.

Intuitively, as the stent is expanded, (a) decreases and (b) increases. Image captures are observable in Fig 5(a). The results of deformation under varying balloon pressures are observable in Fig. 5(b), including the variation of stent Outer Diameter (OD). 2.2 Finite Element Analysis In order to investigate the induced stresses in individual struts of the Boston Scientific Synergy stent, an FEA model has been created to replicate expansion, followed by normal service. 2.2.1 Simplifications For the given purpose to gain an understanding of the stress distribution within a deforming stent, it is unnecessary to model all components and interfaces during expansion and normal service. Therefore, simplifications have been made to the loading and geometries tested. During stent expansion, the compliant balloon is initially folded inside the stent around the catheter. During the initial inflation stages, the balloon remains relatively relaxed. This results in applied internal pressure acting uniformly over the inner surface of the stent. In the 12

undergoes large deformation due to the formation of an elastic hinge across the entirety of the cross section, near the point of inflection. After yield, the modulus of the stent material is significantly reduced. Sensitivity to interface pressure is increased, so as to allow for incremental expansion towards the required final stent diameter, the balloon is then designed to support the majority of the applied pressure. Expansion becomes displacement controlled, as apposed to load controlled. To confirm the validity of the following simplifications and assumptions, the small expansion in the elastic regime is first considered. To model expansion below the elastic limit, the stent is treated as a thin walled pressure vessel with the balloon expansion pressure acting outwards upon it. The stress applied to the stent cross section, as a function of internal balloon pressure, is given by Eq. 1 (26). is instantaneous radius of stent, and is strut thickness. .

(1)

This load scenario is equivalent to that induced by cutting axially along all struts, securing along the


horizontal axis, and applying uniform pressure to the opposing end of each strut, as illustrated in Fig. 6. The repeating units of struts can be treated as in series, where load applied to the end of all struts is equivalent to that applied to one. Another figurative cut can then be made across the centre of the U bend, so a single strut, the simplest repeating unit of the stent architecture, can be considered. 2.2.2 Analytical Calculations The stent tested is manufactured from an unknown platinum-chromium alloy. The exact composition and mechanical properties are withheld for patenting reasons due to competition between stent companies. The material data is limited to Young’s modulus and yield strength, which are known to be 203 GPa and 480 MPa respectively. The force on the strut is equal to the integral of applied stress, , over the surface of the stent cross section at the point of application ( multiplied by the ). is also dependant upon the instantaneous radius of the expanded stent. To allow for reasonable loads to be estimated, the radius recorded during experimental stent expansion were utilised in calculations. .

.

(2)

(3)

To provide an analytical solution of stress with respect to load, the geometry of the single strut was approximated to that of a cantilever beam with fixed-guided end boundary conditions. The guided condition assumes no rotation or distortion of the end face of the beam, as to replicate the effects of the connection of another strut at the end face. [26] provides analytical solutions for both stress and displacement in the vertical direction, induced by an end load, given in Eqs. 2 and 3 respectively. is Young’s modulus of material, is distance from centroidal

axis to extremities of the bar, and is area moment of inertia about relevant bending axis. These solutions are valid for the linear elastic region, with stress and displacement proportional to applied load. The results of the analysis are conformable with the observed stent expansion. Plasticity onset once stress surpasses yield is found to be in the same region, between the load equivalent to inflating the balloon to between 4–5 atm. This is observable in stent inflation as the onset of large deformation – where the stent diameter increases dramatically in a single load increment. 2.2.3 Convergence Study The stent tested is manufactured from an unknown platinum-chromium alloy. Due to the absence of detailed stress-strain relations post yield, providing information regarding hardening behaviour, an elastic, perfectly plastic model was initially created. The geometry observed using the MONDO was replicated in the Autodesk Inventor, and imported into the ABAQUS software package. The part was created as a 2-D shell in plane stress. Boundary conditions enforcing 0 displacement and rotation in all necessary directions were applied to the bottom surface, and constraining rotation about the out-of-plane axis at the top surface. The load was applied as a uniform pressure over the top surface of the stent. In order to confirm the model's validity, a convergence study has been carried out. When meshing the geometry, hexahedral quadratic elements with reduced integration were employed as a structured mesh. As is well documented, seed size of the FE mesh decreases as the solution provided becomes more accurate. These results should be comparable to the results of the analytical calculations. A convergence study was carried out in order to find the critical mesh size required for convergence within 2% with halved seed size with equivalent load for 3 bar internal pressure – 0.0195N total force – within the elastic regime. As is observable in Fig. 7(a), the solution converged with seed size 0.00125. As is observable, maximum stress is concentrated

(a) (b) Figure 7: (a) Results of convergence study of maximum stress with 3 bar equivalent load applied, (b) Converged stress distribution in strut, with 3bar equivalent load. Stress in MPa. 13


around the inflection point, as is predicted by several other studies [22], [24]. This stress also conforms well with the analytical solution. Deformation was found to be 0.0018mm, very close to the analytical solution of 0.0022mm. The expansion observed during physical inflation was also 0.002mm. The model representation of a stent strut, along with the relations between internal pressure and end load, is therefore confirmed. 2.2.4 Post Expansion Loads After initial implementation, the load on the stent varies as the surrounding artery deforms cyclically under the pressure variation caused by the systole/diastole cycle of the heart. In order to estimate the stress amplitudes induced during service, loads due to pressure cycles and the interactions between the stent and artery wall must be modelled. Firstly, a comparison between the relative deformation under variable pressure of the stent and surrounding artery must be made. Again treating the artery as concentric thin walled pressure vessels, Eq.1 is applicable. Further to this it is possible to obtain radial strain via Eq. 4, where is radial strain. .

(4)

Firstly, the deformation of the vessel without the presence of the stent is considered. The average healthy systolic/diastolic pressure is 120/80 mmHg. However, as is customary, a worst case loading scenario must be assumed. Therefore, a high systolic blood pressure is assumed, and a low diastolic; 200/60 mmHg. This equates to 16.66/7.99 kPa gauge [1]. The average coronary artery thickness is around 0.75mm, and average elastic modulus of healthy arteries is 200 kPa [27]. It is assumed that internal body pressure, i.e the pressure acting radially inwards on the vessel, is atmospheric. Using Eq. 1 and 4 it is found that an artery with unloaded diameter 2.8 mm expands to 3.49/3.00 mm at systolic/diastolic pressures respectively. Subsequently, it is assumed that final diameter of the stent is 3.5mm, in order to support the vessel.

Figure 8: Semi-circular beam representation.

Once expanded, the stents effective stiffness is altered. Whereas the crimped stent can be approximated as a series of fixed/guided beams, when deployed the lattice becomes more open and straight beams are no longer deemed an acceptable model. An approximation is taken such that the stent can be treated as a series of semicircular beams. A new approximation of the force to displacement relationship must therefore established. 14

From Roarkâ&#x20AC;&#x2122;s, 2002 (26) displacement ( ) and applied load can be related. , the horizontal force, is again assumed as the product of hoop stress and the cross sectional area at the point of inflection. is that radius of the semi-circular beam. .

(5)

The stent in question is represented by 8 semicircular beams connected in series around the circumference. By accumulating the expected deformation of all 8 hoops it is therefore possible to attain approximate radial expansion of the stent at systolic and diastolic pressures as 9.54 and 6.36 E-05 mm. These deformations are minute compared to that of the artery, partially due to the reduced surface area that pressure acts over, therefore these deflections are assumed negligible. During the systole/diastole cycles, the stent is therefore not only subjected to tensile loads due to blood pressure, but also due to compressive pressure by the contracting surrounding artery during diastole. The hoop stress during systole ( ) is blood pressure alone. Hoop stress during diastole ( ) is diastolic blood pressure detracting the interference pressure created in preventing the artery from contracting to 3.33mm diameter. This is found as the difference of systolic and diastolic blood pressure. / are found as 26.60/10.62 kPa respectively. 2.3 Expansion Once the model is proven to be accurate, expansion was attempted. To allow for modelling in the plastic region, a slight alteration to the the elastic plastic model was made by utilising a small modulus of 20 MPa post yield. Increasing applied pressure causes the formation of an elastic hinge, where the entire cross section of the strut yields and provides no further resistance to expansion. Once this has occurred, any increase in load causes very large deformation, and the model breaks down. Therefore, displacement controlled load was applied the the stent surface to expand. The previous pressure model of loading is only accurate for the expansion region in which the material behaves elastically and the balloon is not taut. Once the balloon is taut, the stent must not only support pressure applied to the internal face, but force equilibrium must be established between the rigid expanding balloon and stent. Through studying the reaction force at the fixed end of the strut, it becomes possible to attain the force applied to each strut by the balloon in order to produce expansion to the required diameter of 3.5mm. In order to do so, the strut, originally 0.226mm in width, is expanded to 0.687mm (equivalent to a stent diameter of 3.5mm). 2.4 Fatigue Testing The initial proposal for the project was to purchase a test rig to fatigue test coronary stent samples received in the form of artery mimicking silicon tubing, with a fluid pump providing a high frequency variable pressure cycle similar to that produced in the coronary artery. Such apparatus exists, but were out of budget. It was thus decided that instead of fatigue testing the stents themselves, fine wire samples of common stent materials would be obtained and fatigued. Unfortunately, quotes


for medical grad CoCr L605 exceeded the project budget. Although, medical grade SS316L alloy fine wire is more readily available and was obtained in rounded 0.5 mm diameter [28]. Efforts were made to secure access to a ASTM Rotary Wire Fatigue Test rig, but the facilities were not available. A quote was requested for a rig from Blockwise Ltd., although this exceeded the project budget [13]. The possibility of using available test rigs was thus investigated. Unfortunately, none of the standard hydraulic fatigue test rigs accessible had loads cells with sensitivity adequate to accurately provide the loads required to fatigue fine wire. There was also no possibility of suspending the test specimens in blood emulating corrosive fluid by constraining the wire vertically in uniaxial tension. A test rig has therefore been design to meet the specific requirements. The initial concept was to constrain wire samples into a free bow U-bend by securing both ends vertically, and displace one end in both directions to induce a predictable stress in the apex of the bend. 2.4.1 Stress Amplitude Conveniently, it is possible to use the previously discussed Eq. 5 to derive stress amplitude in curved wire specimens. Through use of Eq. 6, from bending theory, stress and bending moment can be related. Solving Eq. 5 and 6 by eliminating returns the final result displayed in Eq. 7 [26]. .

(6)

.

(7)

Objective 1 - High Test Speed 2 - Variable Stroke 3 - Wire Constraints

4 - Durability 5 - Well Lubricated 6 - Suspension 7 - Cycle count 8 - Vibration resistance 9 - Easy Assembly and Disassembly

The Youngâ&#x20AC;&#x2122;s Modulus of SS316L is 200 GPa. Assuming that test samples are in 0.5 mm diameter fine wire form, constrained in 30 mm radius U-bends, Eq. 7 is utilised to calculate the induced stress values for different stroke lengths, as observable in Tab. 2.

Stress (MPa) 600 500 400 300 200 100

Stroke Length (mm) 16.7 13.9 11.1 8.40 5.62 2.81

Table 1: Stroke lengths in order to obtain stress amplitudes in SS316L samples.

2.4.2 Concepts and Design Specification In order to provide the reciprocating motion to deflect the U-bend, inspiration was originally taken from slider crank mechanisms such as that of a piston in many types of engine. Linear bearing technology was explored, with a wire clamp being connecting to a sliding mechanism constrained within a guiding track. This would allow for reciprocating actuation and controlled stroke length displacement. Doubts about the durability and attainable reciprocation speed of the mechanism were raised, and therefore an alternative mechanism was formulated. Here, a connecting rod again provides actuation, but in this instance is constrained through attachment to a lever arm via a pin. The other end of such arm is pinned in a

Details Rapidly reciprocating motion must be created, with sufficient speed to limit duration of high cycle tests. The stroke length of the test rig is required to be varied between several well defined displacement values as to conduct fatigue tests at varying stress amplitudes. A method of constraining the wire specimens vertically at ether end to induce a free bow U shape must be established, and this should be done in such a way as to avoid large stress concentrations at the fixtures, as is the case with many industrial fatigue testers. The test rig must be manufactured to have infinite fatigue life in comparison to the test specimens. All joints must be adequately lubricated as to allow smooth, continuous operation. The rig must be configures as to allow for wires to be suspended within a reservoir of appropriate fluid during testing. A method of counting the number of cycles the rig has undertaken must be created as to yield results of each test. The rig must display adequate vibration resistance as to counteract the forces imposed by high test speed and inevitable imbalance. Due to the nature of the two design configurations, the rig must be manufactured such that assembly/disassembly is straightforward and rapid. Due the preliminary design stage for a test rig, this is preferable in anticipation of future subtle alterations. Table 2: Design specification for Fatigue Test Rig.

15


Figure 9: CAD models of the sliding configuration (left) – labelled A – and lever arm configuration (right) – labelled B – produced in the Autodesk Inventor.

Figure 10: View of sample holders with specimen encased within silicone rubber tubing to prevent abrasion.

Figure 11: Assemblies of Configuration A and Configuration B (right).

fixed location. In order to explore both the sliding linear bearing and lever arm concepts, two similar designs are to be developed such that assembly is possible in two configurations. The sliding track mechanisms is labelled Configuration A, and the lever arm Configuration B. In order for the rig to be successful in fatigue testing the specimens to failure, the following design specification 16

must be adhered to. 2.4.3 Design Solution After testing, it was clear that the configuration utilising the linear bearing within the guiding track – Configuration A – was the superior solution in terms of vibration resistance and stability. The machine was far more balanced, and therefore operation was much


Table 3: Design solutions for specified test rig.

Objective 1 - High Test Speed

2 - Variable Stroke 3 - Wire Constraints

4 - Durability

5 - Well Lubricated 6 - Suspension 7 - Cycle count

8 - Vibration resistance 9 - Easy Assembly and Disassembly

Details A relatively high power (85W) electrical motor has been selected, which, based on calculations to tabulate induced torque due to wire deflection, is sufficient to run at several thousand rpm at full capacity. All joints have also been lubricated with bearings. A disc connecting the actuating lever arm to the motor shaft has been created with accurately drilled shaft holes at various radii. Aluminium clamps with reduced bending resistance due to through cut center sections have been created, with a small vertical radii cut through out to allow for wire constraint within silicon tubing. The clamps are tightened using a cap head screw through the horizontal plane. See Fig. 10. The rig is precision manufactured to negate the effects of wear as result of misalignment. All connecting rods are machined of at least 3 mm x 3 mm aluminium to ensure fatigue of the rig itself is infinite in comparison to that of the test specimens. [29] Self-lubricating polymer sleeve bearings were selecting as apposed to traditional roller bearings, allowing for longer service life without maintenance, smooth operating and high test speeds. Clamps have clearence from the base of the rig in both conifgurations so a 3-D printed reservoir can be placed underneath. The fluid level is such that samples are suspended throughout testing. To count the stress cycles, a small flag was attached on the circumference of the connecting disc. A Panasonic Through Beam (Fork) Photoelectric Sensor was installed, such that when the flag passes through the gate a 5v output signal is provided to an ARDUINO UNO SMDREV3 microcontroller. Flop down counting code has been written as to display the number of cycles since the start of operating period, allowing results of cycle to failure to be recorded autonomously. To reduce vibrations, absorbing feet have been used. To prevent bolts coming loose, nylocks have been deployed where applicable. The connecting disc was designed with mass concentrated at the outer diameter as to increase inertia and limit vibration induced by force and speed variation through the cycle. igus bearings are in the form of self lubricating sleeves that are constrained by push fitting into housing. All shaft constraints are eaily removed and the motor bracket and sensor have individual fixtures for each configuration.

smoother, allowing continual operation for several hours without maintenance. Configuration B experienced significant vibration, in one instance causing unscrewing of bolts securing the motor clips. This resulted in the offset of the motor axis and collision between the flag and light gate sensor, which was damaged and therefore had to be replaced. The average speeds without securing a test specimen present, with motor supply at 2V and 2.5A were found to be 2444 rpm and 2516 rpm for A and B respectively. It was declared that the longevity of the machine should be prioritised over slight increases in test speed. Therefore, Configuration A was selected to be used during testing.

accumulate with applied loads in the same manner as static loads, the mean stress value, , is somewhat unknown. This can effect fatigue life, although similar effects are expected due to the plastic deformation of a stent during expansion. These details can be negated as the main purpose of this investigation is to evaluate

The steps taken to fulfill the design specification are highlighted in table 3. 2.4.4 Test Method Stress amplitudes were selected as to test both above and below the elastic limit of the material, such that both high and low cycle fatigue is investigated [11]. Therefore, the specific tested were 150, 300, 450, 600 MPa. The wire is delivered pre-stressed, as it is coiled around a spool. This results in plastic deformation, and the wire naturally forms a curve, similar to that of the 30mm radius whilst clamped. Very little stress is therefore applied by constraining the wire into the â&#x20AC;&#x2122;free bow shape,â&#x20AC;&#x2122; meaning the , as is associated with fully reversed loading. As residual stresses caused by plasticity are known to

Figure 12: MONDO capture of 0.1 mm depth abrasion. 17


the effects of environmental factors on the fatigue life of components manufactured from SS316L. Maintaining constant test conditions between tests allows for comparison to be made between results. In order to mimic the effects of corrosion, blood emulating fluid was employed. This is in the form of Hankâ&#x20AC;&#x2122;s solution obtained from [30]. This has a near identical salt (NaCl) concentration to blood of 0.8% as well as identical pH of 7.4. In terms of pitting corrosion, the behaviour is identical. In order to mimic the effects of fretting wear due to calcifications, samples were prepared with surface abrasion. From the [9] study, abrasion marks were observed to be 5% of the smallest strut dimension. Surface abrasions of test samples were prepared to be macroscopically similar. In order to again create a worst case scenario, the SS316 wire samples were prepared with abrasions through 10% of wire thickness, corresponding to 0.1 mm depth. This was achieved using wire strippers, with one blunt edge. The wire was clamped and small rotary motion between the strippers and wire was utilised to create the abrasions. Once complete, the sample was checked using the MONDO to ensure the depth of incision was 0.1 +/-0.02 mm. Any inappropriate, over-abraded samples were discarded. Once abraded, the relevant samples will be suspended in Hankâ&#x20AC;&#x2122;s solution for a 72-hour period. This is to allow

corrosion to take place on the exposed inner material. The samples are given light abrasion with a file before being placed back in the suspending fluid during testing to remove oxide layer reformations caused by exposure to the atmosphere. Results were averaged over 3 repeats for each stress amplitude. Additionally, some samples were bent to full inversion before being abraded, as to mimic the effects of local plasticity. In total, 5 types of samples are to be prepared and tested: unabraded not suspended; unabraded suspended; abraded not suspended; abraded suspended; and finally abraded, suspended with significant plasticity.

3. Results 3.1 Fatigue

Figure 13: SN curves of SS316L samples of different preparation, fatigue limit indicated by literature represented by dashed line [14].

18

(a) (b) Figure 14: Stress contour plots of expanded strut before (a) and after (b) the removal of load. Von Mises stress displayed in MPa.


as previously explained. The critical force to bring about such is found to be 0.33 N, consistent with the findings of similar studies [31]. Deformation result in a maximum Load State Maximum Stress at stress amplitude of 796 MPa. Once the deformation Hinge (MPa) constraint is removed, the structure recoils by around Expanded 796.012 0.01 mm, and the residual stress is found to be 621 MPa. With the expansion loads removed, and the systolic Expanded 620.831 and diastolic service loads applied, maximum stress at with loading the hinge point is found to alter by +16.8 and -28.2 kPa removed respectively. This implies non-fully reversed loading, and Systolic loading 620.848 are, as predicted, stress amplitudes are far below the fatigue limits of the material indicated by the SN curves Diastolic loading 620.803 from the literature [14]. Therefore, it is to be anticipated that cycles to failure should vastly exceed those expected in normal service life. The point of maximum Table 4: Stroke lengths in order to obtain stress amplitudes in stress is identical for both loadings, with very little SS316L samples. visible difference between contour plots, explaining the emmittance of the systolic plot. From the relaxed plot , a good representation of residual stress state is observable, providing insight into the true stress state during service. Residual stresses are known to combine with applied stresses in superposition with them. Tensile mean stress loads, as observed in the expanded stent, are known the be detrimental to fatigue life [11]. In light of the model, more detailed investigation into the effects of quantified residual and applied stress amplitudes to such materials becomes possible.

Figure 15: Plot of base reaction force against strut width.

However, some inaccuracies are inevitable due to the lack of material data for the PtCr alloy. If such became available, hardening could be more effectively modelled in the software, improving the model. Despite the limitations, the model forms a solid basis for future innovation. It would be possible to alter stent dimensions to further investigate the effects of geometry on stresses induced and the behaviour of the stent during service. 4.2 Fatigue Testing

Figure 16: Stress contour after removal of expansion load and application of diastolic loading.

4. Discussion 4.1 Finite Element Analysis As observable from the contour plots, the stress is distributed through the strut as predicted by similar studies, with maximum stress at the inflection point [22]. Initially, deformation is linear with respect to applied load, but as the material yields, the creation of the plastic hinge results in large deformation for little applied load,

As is observable in Fig. 13 , environmental factors have a significant influence on the number of cycles to fatigue of the samples, with a reduction factor of up 104 in some instances when compared to Fig. 3(b). The unabraded samples, when suspended and not so, did not fail after 500,000 cycles. Due to time restrictions, It is therefore assumed that these samples are below the stress amplitude. At higher stress amplitudes, these samples failed as indicated by Fig. 13, although failure occurred at the stationary clamp. It can be deduced that stresses induced in this location were maximum, and not at the apex of the bend as predicted. This is caused by large bending angles induced at the clamp during reciprocation. It is also likely that plasticity was induced in this location whilst securing the wire in the clamp. However, good conformance to the literature is attained as with around 104 cycles to failure. This means that the results are not a true indication of the number of cycles to failure at these specific stress values. From the results, it is clear that when unabraded there is little to no reduction in fatigue life caused by suspension in the fluid. This can be explained by passive oxide layer disruption not occurring during suspension. All abraded samples, however, failed at the site of abrasion after less cycles than predicted by the literature. This is to be expected due to stress concentration at cracks caused by defects, enabling formation of persistent slip bands (PSBs) which cause crack initiation and allow a path from propagation to failure. The results also show that exposure to Hankâ&#x20AC;&#x2122;s solution results in lower cycles to failure in abraded 19


samples. This is anticipated as it is known that stainless steels are more susceptible to corrosion in salt solution fluid after disruption of the oxide layer. This results in material dissolution and weakening of the component. It is also notable that the introduction of plasticity at the area of maximum stress also reduces fatigue life. Again, this is to be expected as plasticity can also cause the formation of PSBs, as material layers are dislocated with respect to one another. The implications of the notable reduction in fatigue life due to environmental factors may influence future coronary stent material selection parameters. It is therefore confirmed that it is important to find more corrosion resistant materials for use in stent manufacture as common in industry, through the use of CoCr L605 and PtCr alloys. However, both materials also rely on the formation and maintained presence of a passive oxide film. If removed, due to abrasion, it is likely that similar reductions in fatigue life are to be expected. It is recommended that further studies into the use of corrosion resistant, inert, materials that are not dependant on such are conducted. As plasticity is inherently present in balloon-expanded stents, and is shown to reduce fatigue life, an area for more thorough research may be in the field of self-expanded stents. These stents are manufactured into the desired service dimensions, before being crimped inside a sheath. When the sheath is removed, due to elasticity, the stent returns to the desired dimensions. As present, the vast majority of stents implemented are balloon expanded. If it is possible to manufacture self-expanding stents absent of plasticity, it may be deemed preferable in terms of preventing fatigue failure. Although meaningful results have been achieved through testing, there are several notable shortcomings. Firstly, the way in which abrasion is created is fairly crude, and although care was taken to make all surface defects as similar as possible, a high level of consistency is unlikely. It may therefore be preferable to utilise highdimensional accuracy laser cutting to induce defects This should be done to a higher degree of dimensional similarity to those observable from post-mortem samples. It would also be preferable to test at stress amplitudes similar to those induced in service of stents. This would involve reduced stress amplitudes during testing, and therefore significantly increase testing times. This is impractical with the current setup, which runs at a maximum of 2200 rpm as a result in vibration and instability. Refinement to the rig is required. It may be preferable to further explore the lever arm mechanism by taking steps to balance the rig, as it did achieve higher test speeds due to a reduction in friction. With the current rig, tests also require constant monitoring to specimen failure. An electrical breaksensor, as observable in the ASTM [13] rotary bend wire tester, should therefore be an employed rotary tester. In order to prevent the failure at the stationary clamp, a guiding block of the correct radius may also be put in place to guide the wire and prevent extensive bending in this locations. Finally, to produce a more accurate representation of the effects of calcifications, the wire should be abraded in a similar manner by placing the wire in contact with material with comparable hardness and surface roughness during reciprocation. This could be in the form of a spring bedded surface that is able to keep in constant contact with the sample. Higher cycles 20

tests would also allow for the effects of corrosion fatigue alongside continuous abrasion to be better investigated. It is unlikely that the effects were fully investigated during the experiment as all abrasion was carried out before testing, and it is unlikely that the solution would have produced the same effects as in vivo due to limited rate of reaction and exposure time whilst fatiguing.

5. Conclusions It is observed that environmental factors result in significantly reduced fatigue life of SS316L test specimens. It is therefore likely that such are responsible for observed cases of implemented coronary stent fracture. As has been previously discussed, fatigue behavior is highly dependant on the exact composition, manufacturing processes, and geometry of the component tested. It is therefore necessary to test samples manufactured in as similar a fashion to stents as possible to confirm the findings. The SS316L alloy is also somewhat outdated in terms of stenting, and it would be more relevant to test CoCr-L605 or PtCr alloys. Refinement of the test rig manufactured is necessary to collate results relating to the smaller stress amplitudes and therefore higher cycles found by modelling the stent using Finite Element Analysis. Although results of stress amplitudes during normal service are produced, it may be preferable to include the effects of the surrounding artery and possibly the presence of lesions by creating a more detailed 3-D model. This would allow exploration of inevitably increased stresses due to bending of the entire structure. Also, it may be preferable to utilise the work of Larrosa, 2012 [25] to predict fatigue limits of stents with small defects, to evaluate the significance of stresses found.

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F. Migliavacca, L. Petrini, V. Montanari, I. Quagliana, F. Auricchio, and G. Dubini, “A predictive study of the mechanical behaviour of coronary stents by computer modelling,” Medical engineering & physics, vol. 27, no. 1, pp. 13–18, 2005.

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How It Works: Laser Doppler Vibrometry DON'T IGNORE THE FUNDAMENTALS This section of the journal usually describes the HOW IT WORKS of a specific technique or piece of equipment, however this article will focus on the process and pitfalls in developing a new component. Background Vibrations permeate our entire world, influencing everything from how we hear to how we communicate and itâ&#x20AC;&#x2122;s not just the human world vibration is important to, but virtually every living creature on the planet. Unlocking the secret world of vibrations allows us to engineer better, more refined products, longlasting machines or lighter-weight structures and materials. Vibrations are key to the radio frequency filters and guidance systems in our mobile phones, and they are even key to dispensing lifesaving drugs to asthma patients.

these vibrations in a level of detail that often defies conventional thinking. It allows us to measure structures that range from thinner than a human hair to the size of a suspension bridge. But what is behind this illuminating sensor technology? Doppler One of the key physics theories that enables this technology is the Doppler Effect. So first let us consider what that is.

A common way we experience the Doppler Effect in the modern world is when the ambulance Laser vibrometry is one method that allows drives past a pedestrian with siren blaring. As the engineers and scientists to measure and characterize ambulance speeds past the pedestrian the note of

Figure 1: The optical layout of a Laser Doppler Vibrometer. 22


Figure 2: Measurement of the vibration patterns on a brake disc.

the siren appears to drop in pitch. This is an example Vibrometer of the Doppler Effect. Interferometry As the ambulance moves closer during the period of each sound wave so the effective wavelength is The laser Doppler vibrometer works on the basis shortened giving a higher pitch since the velocity of of optical interference, whereby essentially two the sound is constant. Similarly as the ambulance coherent laser light beams, with their respective drives away from the pedestrian then the effective light intensities I1 and I2, are required to overlap. The wavelength increases giving an apparent drop in total intensity of both beams is not just the sum of pitch. To the ambulance driver nothing changes as the single intensities, but is modulated according to the note generated has not changed. the formula: Light can behave as just another form of wave and is in turn affected in the same way. If a wave is reflected by a moving object and detected by an instrument (as is the case with the LDV), the measured frequency shift of the wave can with a so-called “interference” term. This interference be described as: term relates to the path length difference between both beams. If this difference is an integer multiple of the light wavelength, the total intensity is four times a single intensity. where is the object’s velocity and λ is the wavelength of the emitted wave. To be able to conversely determine the velocity of an object, the (Doppler) frequency shift has to be measured at a known wavelength. This is done in the LDV by using a laser interferometer.

Optical Path Figure 1 shows how the physics is applied with a block wise layout in an LDV. The beam of the laser is split by beam splitter 1 into a reference beam and a measurement beam. After passing through beam splitter 2, the measurement beam is focused onto 23


Figure 3: Vibration deflection of ultrasonic dental descaler.

the sample, which reflects it. This reflected beam is now deflected by beam splitter 2 (see figure), and is then merged with the reference beam onto the detector.

If the object then moves towards the interferometer, this modulation frequency is increased, and if it moves away from the interferometer, the detector receives a frequency less than 40 MHz. This means that it is now possible to not only clearly detect the As the optical path of the reference beam is path length, but also the direction of movement too. constant over time ( r2 = const.) (with the exception of negligible thermal effects on the interferometer), Applications a movement of the sample (r1= r(t)) generates a light / dark pattern, typical of interferometry, on The simplest application of LDV provides a single the detector. One complete light / dark cycle on the laser point, which when reflected back off a subject detector corresponds to an object displacement provides a time-varying voltage proportional to the of exactly half of the wavelength of the light used. subject’s out-of-plane vibration. However, with the In the case of the helium neon laser often used for careful application of a little bit more engineering vibrometers, this corresponds to a displacement of and trigonometry we can add a number of different 316 nm. variations such as two laser points at a known angle to extract the in-plane vibration, three lasers Changing the optical path length per unit of time working in harmony on a single point again with a manifests itself as the measurement beam’s Doppler known geometrical relationship to extract tri-axial frequency shift. In metrological terms, this means vibration. that the modulation frequency of the interferometer pattern determined is directly proportional to Or by the application of microscope optics to the velocity of the sample. As object movement measure vibration on the nano-scale or conversely away from the interferometer generates the same using telescopic optics to work over great distances. modulation pattern (and modulation frequencies) Using the application of controllable mirrors to as object movement towards the interferometer, deflect the laser allows it to be positioned quickly this setup alone cannot unambiguously determine and accurately on a surface and then to scan a the direction the object is moving in. grid of measurement density unachievable with conventional sensor placement. For this purpose, an acousto-optic modulator (Bragg cell) that typically shifts the light frequency All of this is with no interference in the dynamic by 40 MHz is placed in the reference beam (for systems under inspection through the mass loading comparison purposes, the laser light’s frequency is of sensor placement, providing of course that there 4.74 · 1014 Hz). This generates a typical interference is a line of sight onto the subject. pattern modulation frequency of 40 MHz when the sample is at a standstill. Martin Cockrill Applications Manager, Polytec Ltd. 24


Engineering Integrity Society

Fatigue 2020

Downing College, Cambridge, UK 29 June - 1 July 2020

Sponsored by:

Rolls Royce PLC is pleased to support the Fatigue 2020 conference

info@e-i-s.org.uk | www.fatigue2020.com


Venue The conference will take place at Downing College, University of Cambridge. Cambridge is one of the most important and picturesque cities in East Anglia. It is the county town of Cambridgeshire and the seat of one of the oldest universities in the British Isles. Downing College was founded in 1800 through a bequest made by Sir George Downing. The Collegeâ&#x20AC;&#x2122;s beautiful neo-classical buildings are set in spacious and peaceful gardens in the centre of Cambridge. Exhibition There will be an accompanying exhibition of material testing systems, durability software tools and engineering services where delegates will have the opportunity to discuss the latest developments in the field of fatigue and durability. Accommodation En-suite accommodation is available at Downing College subject to availability. Please select the accommodation option on the booking form. Prices include bed and breakfast.

Fatigue 2020 As engineering modelling and simulation tools become ever more powerful and sophisticated there still remains the challenge of correlating the virtual world with both idealised laboratory testing and the wide, and potentially unexpected, range of service conditions experienced by machines and structures. These challenges are compounded by the advent of new materials, new ways of manufacturing components, new applications and new test and measurement techniques. At Fatigue 2020 we will seek to explore not only the latest developments in engineering modelling and simulation, advances in test and measurement techniques, innovations in manufacturing, and developments in materials science, but also the complex interrelations between all these topics that give rise to improvements in fatigue performance, durability and structural integrity.

Travelling Information The nearest airports are Stansted and Luton. Cambridge is easily reached by train. Downing College is located about ž mile from the railway station and is served by regular buses and taxis. Liability EIS as organiser is not liable for any changes in the programme due to circumstances beyond their control. The organisers are not liable for any losses, accidents or injuries to persons or damage to property of any kind. Participants must arrange their own insurance if considered necessary. Visa Visa applications must be applied for in your country of origin. Registration The booking form available at www.fatigue2020.com should be completed and emailed to the conference secretariat, Sara Atkin: info@e-i-s.org.uk


Provisional Programme Provisional Programme With over 65 presenters from across the globe the conference will offer a full programme across the three days. The full provisional programme including list of speakers can be found at: www.fatigue2020.com Keynote Lectures Very-high-cycle fatigue of additive manufactured materials - Professor Youshi Hong, Chinese Academy of Sciences Fatigue-crack propagation in high-entropy alloys at ambient to cryogenic temperatures – Professor Robert Ritchie, University of California 50 years of Fatigue Research: Progress and Perspectives – Professor Roderick Smith, Imperial College Overview of fatigue design in aerospace electrification Mukesh Patel, Safran

Conference Dinner Address Dame Julia King, The Baroness Brown of Cambridge DBE FREng FRS. Registration Fees

Monday 29 June Keynote: Mukesh Patel - Safran Session 1: Additive Manufactured Materials Session 2: Manufacturing

Session 3: Experimental Methods

Session 4: Additive Manufactured Materials II

Session 5: Modelling

Tuesday 30 June Keynote: Professor Youshi Hong - Chinese Academy of Sciences Session 6: Materials Session 7: Experimental Methods

Session 8: Thermomechanical Fatigue

Keynote: Professor Roderick Smith - Imperial College Session 9: Welds - hosted by TWI

Session 10: Assessment

Session 11: Environmental Fatigue

Session 12: Crack Propagation I

Wednesday 1 July 3 Day £465+VAT

Presenting Authors EIS Members £515+VAT Non Members £620+VAT Students & £330+VAT Retired Members

2 Day £390+VAT £500+VAT -

1 Day £215+VAT £260+VAT -

Please find all the latest information relating to the conference and details of how to book your place on the Fatigue 2020 website. www.fatigue2020.com We look forward to welcoming you to Cambridge.

Keynote: Professor Robert Ritchie - University of California Session 13: Crack Propagation

Session 14: Random Loading

Session 15: Composites

Session 16: Experimental Methods

Session 17: High Temperature

Session 18: Modelling II


Convenor John Yates (UK) International Scientific Committee AndrĂŠ Galtier (France) Andrea Carpinteri (Italy) Martin Bache (UK) Christophe Pinna (UK) Filippo Berto (Norway) Francesco Iacoviello (Italy) Hossein Farrahi (Iran) Youshi Hong (China) Jie Tong (UK) Johan Moverare (Sweden) Luca Susmel (UK) Liviu Marsavina - (Romania) Marc Geers (The Netherlands) Matteo Luca Facchinetti (France) Muhsin J Jweeg (Iraq) Alfredo Navarro (Spain) Phil Irving (UK) Robert Akid (UK) Michael Sangid (USA) Shahrum Abdullah (Malaysia) Thierry Palin-Luc (France) Yee Han Tai (UK)

Registered Address: Engineering Integrity Society, c/o HollisSociety, & Co., c/o Hollis & Co., 35 Wilkinson Street, Sheffield S10 2GB Registered Address: Engineering Integrity 35 Wilkinson Street, Sheffield, S10 2GB Business Registration No. 1959979. VAT Registration No. GB 443 7696 18. Registered Charity No. 327121 Business Registration No. 1959979. VAT Registration No. GB 443 7696 18. Registered Charity No. 327121


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Young Engineers Latest News

One of our main charitable activities is our series of Young Engineers Seminars. These seminars are designed to provide those at the start of their engineering careers with a unique opportunity to gain knowledge and skills, providing a broader foundation of technical knowledge and accelerating development.

The EIS Young Engineers Seminars have been running since 2016 and have proven to be a valuable resource for those at the start of their engineering careers. Through collaboration with industry and academia, the society has been able to offer engineers a unique experience at some prestigious engineering companies including JCB, Rolls Royce and HORIBA-MIRA. The feedback received from those attending the sessions has been extremely positive with many commenting that the days have contributed to their career development. Many of the engineers attending the sessions have chosen to further develop their relationship with the EIS, with some becoming

members of our committees. Due to the value of these seminars, seen by both attendees and the society, the EIS has started a dedicated working group to develop these activities further. It is the intention to continue to deliver high-quality events aimed at early career engineers and to provide support that will have a positive impact on as many young engineers as practical as part of the society’s ongoing charitable activity. The working group will continue with this development over the next few months, with the hope to re-launch the programme in September.

29


Industry News Tata Steel heralds sustainability strategy for the future of the automotive sector Henry Willis, Torque Agency Group

Tata Steel has outlined a future-facing strategy that will move the company into the next era for manufacturing in the automotive industry. Outlining short-, mediumand long-term ambitions, the plan developed by Tata Steel addresses three key areas: Electrification, autonomous driving and shared use; Digitalisation and service offering; and Sustainability. These plans project towards a future that Tata Steel predicts will be an automotive market based on mobility services using shared autonomous vehicles, with the majority of vehicle sales being on a business-to-business basis as fewer consumers own cars. Tata Steel predicts that by 2050, these will primarily be propelled by an electrified powertrain though other technologies, such as H2 fuel cells, will also increase in popularity until then. The plans will support vehicle manufacturers today and in the future as they develop the next generation of hybrid and electric vehicles. The short-term strategy outlines how Tata Steel deploys a range of lightweight steels for reducing weight and cost of crash components in vehicles that are more efficient by using less energy to move. In addition, deployment of reliable steel solutions for energy storage and E-motors will help to improve driving range and cost of the vehicles in the medium term while a longer-term strategy invests in the development of new solutions for a further optimisation in future generations. Digitalisation within the automotive value chain allows for through-chain material traceability and quality tracking, for a more efficient processing and continuous adaptation to customer-specific demands. Advanced engineering services improve the accuracy of simulations and reduce prototyping time and costs, while advanced digital services optimize processes by enabling predictive manufacturing. In the longer term, Tata Steel expects an overall faster time to market for new products that are tailored better to customer needs, ultimately supporting customers to achieve improved quality and a lower TCO. With sustainability as an overarching goal, Tata Steel has made various investments that contribute towards the overall sustainability of its manufacturing facilities. By using a Life Cycle Assessment service to help customers understand their carbon footprint, Tata Steel continues its commitment to throughchain sustainability. Tata Steel will furthermore support customers in their achievement of improved sustainability, by offering an advisory service focussed on bespoke projects within the three pillars of CO2 performance, circular economy and responsible 30

supply chains. As its ultimate ambition, Tata Steel has begun work on plans to make large asset investments to create the steel plant of the future – one key factor being implementing new technology to produce liquid steel, enabling up to 80% reduction in CO2. Basjan Berkhout, Marketing Manager Automotive at Tata Steel Europe, said: “We are committed to pioneering the next generation of steel products for car manufacturers, allowing them to further lightweight vehicles and reduce vehicle emissions as well as improving their manufacturing efficiencies. We have plans to create the steel plant of the future as we set out our commitment to sustainability. “In different ways, steel is expected to play an increasingly important role in the vehicle structure in the future as in our vision the most sustainable vehicles are built with steel. Steel is forever recyclable, and so can be the most sustainable material for cars, vans and trucks today and in the future.” Latest forecasts continue to predict increasing sales of electric vehicles over the next 30 years bringing an additional 4.2 million tonnes of advanced steels to the European market. Vehicle structure steel solutions, E-motor steel laminations and steel battery solutions are expected to see a sharp increase in demand stimulated by companies wanting to make their vehicles carbonneutral over their complete life cycle. www.tatasteel.com

Schneider Electric Power Nottingham University with Building Management System Upgrade Hugh James, Team Lewis

LONDON, UK – 22nd Jan 2020 – Schneider Electric, the leader in digital transformation of energy management and automation, are helping to power the University of Nottingham. Schneider Electric’s EcoStruxure Building solution oversees the University’s building management, optimising every operation. The system plays a pivotal role in reducing energy consumption and expenditure, while also enabling departments to drive greater cost savings through a better understanding of energy through a single platform. As a result, the University is seeing a 5% reduction to energy consumption and a 3% reduction on overall energy costs in areas where EcoStruxure has been deployed. The inherent usability and transparency of the new system has also driven other operational savings. Maintenance costs have been reduced by 25%, while workplace safety and comfort costs have also dropped by 25%.


The greatest benefits, however, are best seen outside of pure operational efficiency. In line with the University’s goal to slash its CO2 footprint, the Schneider Electric EcoStruxure solution has enabled it to improve its control of renewable technology by 75% and drastically reduce emissions. Occupant comfort has also been vastly upgraded – overall control of the building is up 70%, while temperature control is at 50%. Overall, with all the improvements made to the system the project will have effectively paid for itself within a staggering 7–10 years. Andy Nolan, Sustainability Director at the University of Nottingham, said: “The EcoStruxure architecture has helped us revolutionise how we manage the estate. It has improved every aspect of operations, from on-site energy efficiency, cybersecurity to comfort optimisation. We are already looking to expand our usage into EcoStruxure Building AdvisorTM.” Simon King, Account Manager, University of Nottingham at Schneider Electric, added, “We have implemented a transparent but effective system at the University that works across a very complex site with multiple applications and facilities, all of different ages with different architectures. Our EcoStruxure platform aims to give users complete visibility into operations and empowers them to intervene effectively to drive improvements and efficiencies.” www.se.com www.nottingham.ac.uk

UK Has The Most Women Researchers In The World David Bullock, Rhizome Media

• • •

UK employers now have 198,000 women working in R&D Extra 63,242 female researchers employed in the last decade. Positive progress on gender as UK increases its lead over second-placed Germany.

Manchester, 6th January 2020 – The UK is leading the way on gender equality in the workplace by employing the most women researchers in the world, a study by specialist tax relief firm Catax reveals today. The UK employs 197,596 women in research and development out of a total workforce of 510,980, analysis of the most recent figures by Catax found. Germany employs 173,700 female researchers, Japan 150,545, and Russia 142,290. The UK has employed an extra 63,242 women researchers in the past ten years, up from 134,354. In addition, the UK is increasing its lead over second-placed Germany, boasting 28,678 more researchers in the last year, up from a lead of 27,679 in 2015. Catax analysed the ratio of women to men working in research and development across the world and found the UK has climbed two places to 11th in the past decade. Over the past ten years, the UK’s proportion of women working in R&D has risen by 1.9% from 36.8% to 38.7%. However, Britain still trails surprisingly innovative nations such as Argentina (ranked first), Latvia (second) and Lithuania (third).

Latvia was the only EU country where the number of women in the workforce was greater than men, with 52.23% of researchers in R&D being female. Mark Tighe, chief executive of R&D tax relief specialists Catax, said: “Britain can be proud to call itself the world’s home for female R&D professionals, with almost 200,000 women researchers choosing to work in the UK. We’re setting an example for companies around the world to follow, and doing better all the time, recently increasing the gap over our nearest competitor, Germany. But we still have more to do in terms of improving gender balance in the workforce, with Argentina, Latvia and Lithuania all having more women than men researchers. There are still six men for every four women researchers in the UK, and industry must continue to work hard to make R&D a profession that is universally accessible to all.” www.catax.com

Petrol and Diesel Vehicle Ban 2035 Response to Government Announcement on Pulling Forward Ban on Petrol and Diesel Vehicle Sales The Institution of Mechanical Engineers

Following the recent announcement that the Government is pulling forward the ban on new internal combustion-engine vehicles to 2035, the Institution of Mechanical Engineers feels it is imperative to reinforce its findings on Accelerating Road Transport Decarbonisation published on 28 January 2020. The Institution of Mechanical Engineers would like to see a complete shift away from fossil fuel use in any part of our energy system and we must find solutions in the near term that can make the biggest and fastest reductions in our CO2 emissions. Steve Sapsford, Chair of the Institution of Mechanical Engineer’s Powertrain Systems and Fuels Group said, “In contrast to today’s announcement, there is not a 'onesize-fits all' solution. We are running the risk of assuming that all a vehicle’s GHG emissions are emitted at point of use. Whilst that might be where legislation has its current focus, we need to take a more holistic approach including the GHGs associated with vehicle production, use and disposal/recycling. Such life-cycle analysis is a technique for quantifying the environmental and human health impacts of a product over its life span and can often be referred to as 'cradle-to-grave analysis'. In our report, we demonstrate that all forms of propulsion technology, including renewable fuels, electricity and hydrogen could have a substantial impact on GHG emissions. Some, that are currently being ignored and side-lined by today’s announcement, could have a much larger impact in the short term. here are over 300 million passenger cars in circulation on European Roads and around 99% are powered by diesel or petrol. Sales of electric vehicles, including plug-in hybrids, represented 2.5% of new passenger vehicle sales in Europe in 2018. This means that over 97% of new vehicles are still powered by diesel or petrol and, once a new car is sold, its average life span is approximately 12 years. This clearly demonstrates that we simply do not have time to just wait for the increasing share of EVs to make a dent on the passenger car CO2 31


footprint. Indeed, as we accelerate the adoption of EVs, it is possible that we are accelerating the production of GHG emissions unless battery manufacture, which can represent a significant proportion of an electric vehicle’s lifetime GHG emissions, uses only renewable energy.” Dr Jenifer Baxter, Chief Engineer at the Institution of Mechanical Engineers added, “There is also the enormous challenge to scale up the associated infrastructure necessary to manage the transition to large-scale electrification in the timeframe put forward. A challenge with no delivery plan. This will not just be additional electricity capacity, but local network upgrades and millions of private and public charge-points, which must be ‘smart’ to prevent overloading the system at times of peak demand. This new transport paradigm will also require a new generation of engineers and technicians who have the skills to design and service both the vehicles themselves and the charging infrastructure. So, whilst we rightly continue to invest in electric vehicles we must also pursue and invest in renewable and low carbon fuels made from sustainable and net zero sources. These alternative fuels would be able to use the existing infrastructure, reducing consumer impact at the fuel pump and potentially avoiding the cost associated with new infrastructure to support electric vehicle adoption at pace.” Consequently, the Institution of Mechanical Engineers believes that by insisting that there is only one solution, today’s Government announcement side lines a significant complementary opportunity to reduce GHG emission associated with road transport.

have contributed to centrifugal pump efficiency levels and increased their competitiveness across a wider range of end use sectors. Overall demand for pumps has been supported by a number of sectors. These include industrial process sectors, particularly food and beverage processing, pharmaceuticals and hygienic and sanitary applications. Activity in the construction sector is also an important driver. The construction industry also represents a significant end-use sector for pumps. Many construction projects require mass flow of water to the site and centrifugal pumps are also used for heating, ventilating and air-conditioning. In addition, specialist pumps are used for transporting concrete and similar materials, such as grout. Overall UK construction output has experienced good growth between 2014 and 2017. In 2018, construction output increased by 3%, still showing positivity in the sector but growing at a slower rate in comparison to 2017 and 2016. If current growth is maintained into the medium term it is likely the industrial and manufacturing sector will provide a broad range of opportunities for manufacturers of pumps. The information was taken from the Pumps Market Report – UK 2019–2023 by AMA Research, which is available to purchase now at www.amaresearch.co.uk or by calling 01242 235724.

Contributions to Industry News may be emailed to managingeditor@e-i-s.org.uk. The nominal limit for entry is 200 words.

www.imeche.org

Moderate Growth for the Pump Market Roshni Patel, AMA Research

The UK Pump market was worth an estimated £848m in 2018, which is due to increase in 2019. Moderate growth is expected for the pump market in the short term, driven by the political and economic uncertainty while the UK negotiates an exit deal with the EU. The Pump market is complex and fragmented in terms of end-use applications and distribution channels. As a result, the market is influenced by many issues. It is very closely linked to conditions in key application industries such as water and sewage, power generation and industrial manufacturing. It is also linked to the construction sector. The positive performance of the manufacturing sector driven by demand for exports, particularly in 2017 and early 2018, has had a significant impact on pump demand. The manufacturing sector utilises pumps in several ways; either through direct use of pump products in the manufacturing process, or as a component of a product. This sector also influences the materials used and the manufacturing process of the pump itself, such as the cost and availability of raw materials. In addition, increased output from some manufacturing sectors will drive demand for specific types of pump. We cannot forget the impact of energy efficiency in the power generation industry with sources such as wind, solar, biofuels all supporting the pump market. In addition, the wider application of energy saving devices such as variable frequency drives and soft starters 32

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This annual prize is named after our founder, Peter Watson and was created to support young engineers at the start of their career, a cause Peter keenly supported throughout his working life. Last year we welcomed 9 finalists to the event held on 1 October at Derby County Football Club.

For dates please visit our website

Peter Watson Prize

The judges appreciated the wide variety of topics delivered throughout the afternoon including presentations on offshore energy, laser shock peening and fatigue of coronary stents. The overall prize was awarded to Alex O’Neill of University of Sussex and Jaguar Land Rover. Alex’s presentation on Predicting Tyre Behaviour on Different Road Surfaces was praised for his meticulous approach and professional presentation. Highly commended was Matt Crane, an undergraduate from Imperial College. Matt presented An Investigation Into the Fatigue Behaviour of Coronary Stent Alloys and we are pleased to bring you his full technical paper in this issue. In 2020 the Peter Watson Prize will be awarded at our Fatigue 2020 conference. We have had a fantastic response to our request for entrants and look forward to judging the presentations in Cambridge this summer.

33


Product News Vibration Research: ObserVR1000 Now Integrates Vibration, GPS, and Visual Data The ObserVR1000 is a compact, portable, batterypowered device for dynamic signal acquisition and analysis, with 16 channels that record vibration at sample rates up to 128kHz. Recent enhancements now support collection of data from a tachometer and a GPS antenna, while video is recorded with a GoPro camera. After field data capture, the vibration data, tachometer data, the GoPro video, and a GPS mapping display can all be synced in the tightly integrated ObserVIEW software and displayed in size-flexible windows. Large files are manipulated easily, using an intuitive user interface to quickly focus in on areas of interest. ObserVIEW supports editing, post processing and analysis with up 1 million FFT analysis lines of resolution, delivering extreme accuracy to resonance peak definition. Data files work seamlessly with Vibration Research controllers, implementing advanced shaker testing techniques such as Field Data Replication, random test profile generation, and Fatigue Damage Spectrum. Capable of autonomous operation, the ObserVR1000 is easily configured using an auto-TEDS feature that detects sensors automatically, helping to eliminate setup errors and reduce setup time. Engineers can use a phone app to interact with the ObserVR1000 and view live data to ensure that a recording is proceeding as expected. The ObserVR1000 is also a great tool for measuring and analyzing free-fall shock events. Users can set threshold values, establish tolerance limits and record continuous transient events. www.vibrationresearch.com

Thornton Tomasetti Launches BEACON, First-of-its-Kind Embodied Carbon Measurement Tool The open-source tool gives users the ability to develop carbon reduction strategies in real time. Thornton Tomasetti, the international engineering firm, has launched Beacon, an innovative embodied carbon measurement tool poised to change the way structural engineers understand and manage embodied carbon optimisation. The tool gives users the ability to measure embodied carbon, allowing for more informed decisions throughout the design process. Beacon is being introduced after a research and development process, led by Thornton Tomasetti’s CORE studio, a firm-wide virtual incubator focused on innovation through computational modelling and research. The tool is a sophisticated Autodesk Revit 34

plugin that generates a comprehensive data visualisation of a project’s embodied carbon. Beacon provides data in a manner similar to the engineer’s thought process, providing a clear visualisation of a project’s embodied carbon quantities by material type, building element and floor levels, allowing engineers to know exactly where embodied carbon can be minimised for optimisation. “Thornton Tomasetti continues to lead the industry’s efforts on efficient and environmentally conscious designs,” added Robert Otani, principal and chief technology officer at Thornton Tomasetti. “We decided to make Beacon an open-source and easy-to-use tool, so it can be shared at a global scale. We hope this unique and comprehensive tool will push the industry forward into developing innovative strategies that result in more sustainable and efficient structures.” Beacon’s launch follows Thornton Tomasetti’s November release of results from its multi-year, project-based embodied carbon measurement study. The study focused on identifying the type of structures, materials and components with the highest carbon emissions. “The built environment is estimated to be responsible for about 40% of global greenhouse gas emissions when building materials are factored in,” said Amy Seif Hattan, corporate responsibility officer at Thornton Tomasetti. “Therefore, it is up to us to help effect change. Beacon will help structural engineers address embodied carbon in new construction.” “We were first-day signatories of the UK Structural Engineers Declare Climate & Biodiversity Emergency, and by opening this tool up to the industry, we hope to help our structural engineering peers to reduce the embodied carbon quantities in their designs,” said Duncan Cox, a London-based senior associate in the firm’s Sustainability practice who headed up the firm’s eight-year embodied carbon measurement study. Beacon is currently available for download at the following website: https://core-studio.gitbook.io/ beacon/.

Racelogic VBOX 3iS The new VBOX 3iS from Racelogic uses GNSS, Inertial and CAN wheel-speed data to provide highly accurate position and velocity measurements, even in GPS obscured areas such as tunnels and urban canyons. Equally as impressive, the VBOX Indoor Positioning System provides the same 2cm accuracy indoors, without GNSS, and integrates with other VBOX equipment to offer a seamless transition between indoor and outdoor environments. www.racelogic.co.uk


IDT (UK) Ltd Cameras The X-Stream Mini range of cameras revolutionises high speed imaging. Choose between recording direct to a laptop or direct to large capacity SSD for sustained periods. Download times are a thing of the past. There are 4 cameras in the family, all with exceptional image quality. www.idt.uk.com

Prysmian Group launches record breaking cables for FTTx and 5G networks Lauren Wood, Proactive International PR

Sirocco HD cables provide the smallest diameters and highest fibre densities for microduct cables. Milan, 4 February 2020 – Prysmian Group, world leader in the energy and telecom cable systems industry, launches its Sirocco High Density range of microduct cables, providing world record diameters and fibre densities for blown microduct cables. The new range boasts fibre densities of up to 10.5 fibres per mm2, enabling increased fibre count cables to be offered for standard microduct sizes. Sirocco HD microduct cables utilize Prysmian’s BendBright-A2 200 µm single-mode (ITU-T G.657.A2) bend insensitive fibre, providing a solution that’s ready for evolved systems and truly future-proof. “Bendinsensitive fibre optic cables are a crucial part of the world’s shift towards flexible and reliable connectivity” states Ian Griffiths, Director R&D Telecom Business at Prysmian Group. “With their extreme fibre count and reduced diameter, Sirocco HD microduct cables make installation faster, more cost effective and more sustainable by reducing the impact on carbon footprint. Designed for installation into microducts, they are perfectly fit for blowing in high density access, FTTx and 5G networks”. Available in fibre counts from 96 to 552 and conforming to international standards for optical and mechanical performance, the Sirocco HD cables also benefit by the use of Prysmian’s PicoTube technology making them up to 20% smaller than previously available microduct cables. This makes it possible to install more fibres into congested duct space, and enables the use of smaller ducts for new installations, resulting in lower installation costs and the use of less raw materials. This provides benefits for both the total cost of network deployment and the environmental footprint. With these cables Prysmian Group continues to prove that it truly is a global manufacturer that leverages on its worldwide knowledge and capabilities to respond to the always growing technological challenges that its customers are facing. Sirocco HD product enhancements show the Group’s commitment to respond to the evolving needs of the market and to offer a scalable solution that’s high-density, physically compact, and easily deployable for a future-fit solution. www.prysmiangroup.com

ELeather makes the Global Cleantech 100 list for 2020 Emily Wong, Team Lewis

ELeather, the pioneer of engineered leather, is pleased to announce its inclusion on the Global Cleantech 100 list for 2020 for the sixth consecutive year. The Cleantech 100 list aims to find the top 100 private companies with the potential to make significant market impact over the next five to ten years. The list is evaluated by a panel of 87 industry experts, including investors and multinational corporation representatives. Voting is based on each company’s innovation potential, market share and ability to execute its vision. The companies on the list offer the most innovative and promising ideas in clean technology. One of the areas that the Cleantech list celebrates is advanced materials, which commends solutions that improve durability and efficiency as well as decreasing toxicity. ELeather’s engineered leather meets these criteria and more. Up to 75 per cent of traditional leather is unused and often destined for landfill. The company recognised this and developed a patented manufacturing process that takes the unused leather and combines it, using just the power of water. In addition, the process recycles 95 per cent of utilised water. The result is a high-performance material that is durable, versatile and luxurious. Large-scale uses of engineered leather span across transportation, public spaces and lifestyle markets, as well as athletic footwear. Engineered leather is natural, non-porous, easy to clean and hygienic. It’s also up to five times more durable than traditional types of upholstery used in the transport industry, improving travel experience through better looking, more sustainable and hygienic environments. “It’s an honour be part of the prestigious global Cleantech 100 list. Sustainability is at the core of everything we do,” said Nico den Ouden, Chief Commercial Officer at ELeather. “Our patented manufacturing process was designed to be as environmentally friendly as possible. I’m proud to see ELeather listed alongside other businesses using exciting and innovative technologies. As consumer interest in clean technology grows, we’re excited to work with new and existing customers and partners to supply advanced materials to an audience looking to make sustainable choices.” This announcement marks the start of an exciting year for ELeather, as it plans to launch a new aviation product that combines sustainability and performance with an added touch of luxury. In addition, the company will launch a new design-specific brand that will aim to help designers across all markets understand the properties and applications of engineered leather. The Global Cleantech 100 list was announced at the Cleantech Forum San Francisco, 27–29 January 2020. www.eleathergroup.com

Contributions to Product News may be emailed to managingeditor@e-i-s.org.uk. The nominal limit for entry is 200 words. 35


Instrumentation, Analysis and Testing Exhibition 31 March 2020, Silverstone

Once again the annual Instrumentation, Analysis and Testing Exhibition will take place this March in the Silverstone Wing at Silverstone Race Circuit. The exhibition attracts visitors from across the UK and is seen by many as the go-to event for testing and analysis technologies. With 65 exhibitors from sectors including Automotive, Aerospace, Motorsport, Rail, Off-Highway, Mechanical Handling, Civil Engineering, Industrial and Power Generation the exhibition is an excellent opportunity to see the latest equipment and technologies as well as being a great meeting point for the exchange of ideas and contacts.

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Attendance is free and visitors receive complimentary refreshments along with free parking. To complement the exhibition there will be a series of mini seminars under the theme “The Journey from IC to EVs: Challenges, Pitfalls and Opportunities”. The programme of 7 presentations throughout the day will cover a wide range of topics from well-respected engineers across several different sectors. This year’s keynote speaker is Dyrr Ardash from Williams Advanced Engineering who will present “Road to EV: Spark to Revolution”. The 21st century is seeing mega trends of population growth, urbanisation and climate change, which is driving a seismic shift in personal transportation. Automotive focused industries are adopting an increasing trend of electrification to respond to these growing challenges. Dyrr will take a customer-centric view on accelerating the attractiveness of electric vehicles to the mass market, where core customer attribute requirements of range, performance and safety need to be balanced. He will also consider the challenges and opportunities of an industry that has focused on internal combustion for over 100 years.

Free Mini Semina throughout the da

The Instrumentation, Analysis and Testing Exhibition opens at 10am on 31 March. More information and free registration is available at www.e-i-s.org.uk.

Exhibiting Companies 1G Dynamics Ltd HBM A&D Europe HEAD acoustics AcSoft Ltd IAC Acoustic Company UK Ltd Alphatech Ltd IDT (UK) Ltd Applied Measurements Ltd imc Test & Measurement GmbH Bruel & Kjaer UK Ltd Interface Force Measurements Campbell Associates iPetronik GmbH CaTs3 KDP Electronic Systems Ltd CentraTEQ Ltd Kistler Instruments Ltd Concorde Publishing LaVisionUK Ltd Correlated Solutions & M&P International UK Ltd Enabling Process Technologies Manner Sensortelemetrie GmbH Data Acquisition & Testing Mecmesin Services Ltd Moog Controls Ltd Data Physics UK Ltd Niche Vehicle Network Datron Technology Ltd PCB Piezotronics Ltd Delta Motion Peli Products (UK) Ltd Dewesoft UK Ltd Photo-Sonics International Ltd Elstar Elektronik AG Photron Europe Ltd Fischer Connectors Ltd Polytec Ltd Gantner Instruments Prosig Ltd GOM UK Ltd RDP Electronics Ltd Sensor Technology Ltd 36

Servotest Testing Systems Ltd Sherborne Sensors Shimadzu UK Ltd Siemens Digital Industries Software SOUNDCAM UK Spectral Dynamics (UK) Ltd Star Hydraulics Ltd Strainsense Ltd Techni Measure Ltd Thermal Vision Research THP Systems Ltd Torquemeters Ltd Transmission Dynamics United Electronic Industries Ltd VBOX Racelogic Vibration Research Vishay Measurements Group Vispiron Rotec GmbH Zwick


PROGRAMME The journey from IC to EVs: Challenges, Pitfalls and Opportunities

10.30am Keynote Road to EV: Spark to Revolution Dyrr Ardash – Williams Advanced Engineering

Register at

www.e-i-s.org.uk

ars ay!

11.15am How Driver-In-The-Loop Simulation is Providing a Short Circuit to EV Validation Gavin Farmer – Ansible Motion 11.45am Moving Forwards: Battery Propulsion for Rail Vehicles Ben Parry – Bombardier

12.15pm Electric Vehicle Batteries as Weapons of Mass Destruction Colin Freeman – Potenza Technology

1.00pm Design and Engineering of Fuel Cell Electric Vehicles Professor John Jostins – Coventry University & CEO of Microcab Industries Ltd 1.30pm Influence of electric vehicle high voltage electromagnetic fields on NVH sensors Bob Barrett – PCB Piezotronics 2pm The impact of EVs on the generation system and distribution networks including fast charging and using this to predict demand and the idea of wireless charging of electric vehicles including dynamic charging on the road Professor Liana Cipcigan – Cardiff University

37


News from the Tipper Group Aspiring Women Leaders Improving the representation of women in senior compan roles won't just happen without active measures to change the status quo. Faced with annual gender pay statistics, many UK engineering companies are trying different approaches to tackling the challenge of creating a more diverse workforce at all levels. But there is no easy fix. Recruiting more women at entrylevel roles can actually make the statistics initially appear worse as the lower pay of entry level jobs reduces the average pay for women, despite increasing their numbers. The real change for improving gender pay statistics comes when women are better represented in the top quartile of pay, i.e. within the senior roles of a company. Waiting for the ‘new recruits’ to progress in their careers is a long-term strategy, but how can companies find ways to help support established female staff to progress into leadership roles within the company.

First cohort on TWI's 'Inspiring Women Leaders' programme.

It’s tempting to question why they aren’t already in those jobs, and the reasons are numerous and complex (and therefore not easy to resolve quickly!). Some women choose to remain on the ‘front line’ of their role and see progression as moving into management and away from the technical work they enjoy. Some feel they are limited in their progression by working part-time (whether rightly or wrongly). Some lack the confidence to put themselves forward for senior roles, while other struggle to progress without benefitting from networking with senior staff to provide them with coaching and mentoring towards leadership. It’s not ultimately helpful to identify what’s ‘wrong’ with women who are failing to take on senior roles, nor to try and fix them as individuals. An interesting book which discusses many of these issues is “Stop Fixing Women – Why building fairer workplaces is everybody’s business” by Catherine Fox. She explains how it is necessary to fix the system, rather than fix the women, in order to achieve fairness in the workplace. She offers several ideas for how to do this, such as re-defining ‘merit’ within organisations that consider themselves meritocracies (but commonly end up using the term to justify prejudice), and imposing repercussions for behaviour which is discriminatory. Cultural change does take time, but is possible. So was TWI misguided, when in 2019 it implemented a strategy to provide leadership training to its aspiring 38

women leaders? Although it might initially sound like a ‘fix the women’ solution, the courses have proved to be well-received. Supporting female talent and progression at TWI is one of the key commitments in their Diversity and Inclusion strategy. TWI’s first ‘Inspiring Women Leaders’ programme, delivered by RTC Leadership & Coaching, got underway on 25 November 2019 with three days of empowering coaching and workshops. The twenty women on the course found they built friendships with colleagues in different parts of the company that they might not otherwise have got to know. It’s known that women learn best in single-gender classes, making the courses more effective in helping the delegates develop their leadership skills – not just for senior management but applicable to a range of roles where leadership skills are valuable. Although some female delegates were initially sceptical about the value of the course, the opportunity for introspection and taking time to focus on their own career path was appreciated. Some have found the course useful to talk through issues remaining from past career challenges. Some were surprised by the changes in feelings and attitudes about their careers the course has facilitated. Notwithstanding, with two further cohorts going through the course, TWI is sending a strong and welcome message to all female staff that it is investing seriously in their progression. In combination with ensuring unbiased systems for recruitment and promotion, and ongoing support and mentoring, there is every hope that TWI will achieve a better gender balance at all levels of the company. But what about the men? Won’t they get left behind? Well, no, because TWI values developing leadership skills in all its staff, and TWI is also currently partnering with Management Learning and Coaching (ML&C) to deliver a Management Development Programme (MDP) for directors and senior managers. It’s obviously still too soon to know whether TWI will achieve larger numbers of women within the top quartile in the pay statistics by training women in leadership. But it is hoped that offering courses like these will help evolve the narrative about diversity and inclusion across the company, and the workplace environment will attract the best leaders regardless of gender. Dr Philippa Moore Contact Us: The Tipper Group, TWI Ltd, Granta Park, Great Abington, Cambridge CB21 6AL Email: tippergroupevents@twi.co.uk Twitter: @TheTipperGroup


News from the Women's Engineering Society

The Gender Pay Gap in Engineering I was heartened to see the recent Report from the Royal Academy of Engineering and WISE: Closing the engineering gender pay gap which analysed responses from 42,000 engineers, making it a robust and reliable study. It can be downloaded here: https://www.raeng.org.uk/ publications/reports/closing-the-engineering-genderpay-gap.

Key findings show that people get confused about the difference between equal pay and the gender pay gap. Equal pay is paying men and women the same money for doing the same or similar work. It has been illegal to pay women less since 1970. The gender pay gap is the difference in average earnings for all men and women in an organisation, sector or the whole economy. Engineering has performed well, compared to the rest of the UK. The mean gender pay gap for engineers is 10.8%, with 16.2% for the UK, whereas the median pay gap for engineers is 11.4%, with 17.3% for the UK. What’s more the difference in pay between a male and female engineer is less than 1% when factors such as career level, role, employer, location and age are taken into account. It would be easy for engineering companies to pat themselves on the back and say well done, but the report also says that closing the gap will take concerted effort within the profession. The main reason for the pay gap is the high percentages of men in the top grades (91%) and upper pay quartiles (92%), so it’s important to raise up women to senior roles to help close the gap.

available. This is how gender pay gaps occur and pay transparency helps eliminate it. It’s important to understand why eliminating the gender pay gap matters to business, not only women. Young women entering the profession are checking the published pay gap reports and going where the gaps are lowest. With another 59,000 engineers needed each year to fill the skills gap, companies that reward women equally will attract the best talent. Public sector clients are asking about the gender pay gap and want to see plans to reduce it. Having a lower gender pay gap means winning business. Publishing an action plan to close the gender pay gap is seen as a commitment to diversity, and a commitment to employees. There are four recommendations from the report, firstly, understand the causes of the gender pay gap and the effective solutions. Analyse the data to understand your organisation’s gender pay gap. Introduce a transparent pay and progression policy with published salary ranges and publish a credible action plan. More detail in the report offers specific guidance and recommendations for line managers, HR departments and CEOs, along with the questions that employers and employees should ask.

For a start, transparency about pay structures and grades makes a big difference. Companies that have clearly defined pay ranges attached to career levels have even smaller pay gaps of 4.8% (mean) and 5.5% (median). This also helps at recruitment. Job adverts are written to attract the best talent, but it’s not always obvious whether that’s at a middle or senior level. Attaching a pay range to a job advert means women won’t waste their time applying for roles below their seniority and won’t undervalue themselves when asked about their desired salary.

Now that we are well-established in the 21st century, it’s ludicrous that we are still paying women less than men for the same work.

Imagine applying for a job and being asked for your current salary. Let’s say you earn the average salary for a UK engineer – around £40,000 and your potential new employer has budgeted around £50,000. If you’re offered £45,000 you might think you had a good deal, yet you’ve missed out on the £5,000 that the employer has now saved. And in this scenario men are more likely to negotiate whereas women will often accept what’s

The engineering sector is already closing the gender pay gap faster than the rest of the UK, and eliminating it entirely by paying men and women equally could soon be a badge of pride.

We know that bringing more women into the workplace helps businesses thrive. Greater diversity can help overcome the difficulties that can arise when all-male teams throw blame around rather than fix the issue. Even women’s lesser physical strength forces the rethink of processes that can often make them quicker and easier for everyone.

Elizabeth Donnelly Chief Executive Officer www.wes.org.uk 39


News from the Institution of Mechanical Engineers Electric aircraft require a new engineering approach. We’ve started work.

A long-haul flight emits more carbon dioxide per person than the average annual emissions caused by people living in many countries around the world. With a UK commitment to 'netzero' carbon emissions by 2050 and a boom forecast in air travel, electric aircraft are at the forefront of conversation. Such a radical change from conventional technology requires a new approach, however. At the University of Strathclyde’s Advanced Forming Research Centre (AFRC), we are working with the Department of Electronic and Electrical Engineering to form the Scottish arm of a hub that is combining expertise in electrical machines and manufacturing for the first time, aiming to put the UK at the forefront of an electrical revolution. The Future Electrical Machines Manufacturing (Femm) hub from the Engineering and Physical Sciences Research Council is a collaborative research project including the universities of Sheffield and Newcastle. It is looking at electrical machines for high integrity applications, one of which is propulsion systems for aircraft. We aim to revolutionise the design of these machines by bringing manufacturing to the start of the design process. The standard manufacturing route follows a design, model, validate, manufacture trajectory. When manufacture at the prototype stage doesn't work, a part reverts to the design phase. If we alter our approach, giving equal weighting to design and manufacture from the start, we can reduce the time spent making modifications along the way and work together to design a part that is structurally sound with an optimised manufacturing route. This altered approach works well for electric aircraft. We could retrofit aeroplanes, removing combustion engines and installing electric powertrains within aircraft that are not designed for it. Alternatively, we can design an optimised electric aircraft system, including electric propulsion and power systems. Electric aircraft could be completely redesigned around the new power source – this is a challenge that requires a melting pot of expertise to question every decision from all angles. Altering in a linear order will allow small changes, but we need to collaborate and change the way we look at the core problem to reach the 2050 target. We can do more by using modern manufacturing techniques such as additive manufacturing, radial forging and flow forming, which weren't widely available 20 years ago. Go further Through the Femm hub, a short-term goal is to lightweight electrical machines by using novel manufacturing techniques to manufacture non-active components. Currently, around 50% of the total mass of 40

machines consists of casings and housings that protect active components from the environment. Optimising the manufacture of these non-active components will allow us to remove weight while improving performance, enabling us to create electric engines that can go further. The power that can be generated by an electrical machine is dependent on factors such as the diameter of the machine and the speed at which it can be revved, so the heavier the machine, the more power needed. If you can lightweight it by 20–30%, you can generate more power, allowing an aircraft more time off the ground. We're looking at the possibilities to achieve this, and our sister centre within the National Manufacturing Institute Scotland, the Lightweight Manufacturing Centre, aims to develop lighter, more efficient, components for highvalue industries, including automotive and aerospace. It won't be one size fits all, however. We need to balance lightweighting with the structural integrity of parts. Design and manufacture will complement each other throughout the process. We expect situations where it will be advantageous to use composites over metals, for example, but this won’t be the only solution available, with high integrity metals still of critical importance and the use of hybrid structures still to be fully realised. A combination of a variety of solutions for each part will be required to create the optimal machine. We will have to be innovative and controlled in our approach to weighing up alternatives. Time to act While 2050 is 30 years away, we must act now to ramp up research, development and innovation across the UK. We need to review what we already have, to decide if we can upgrade existing models or redesign. In the short term through the Femm hub, the AFRC will develop projects in aerospace and other relevant sectors, aiming to remove mass from non-active components. Short term, collaboration will allow us to look at existing problems from a different view to develop solutions that will move the electric revolution forward. In the long term, there is a massive opportunity to revolutionise other major sectors and ensure the future of innovative manufacturing in the UK. Dr Jill Miscandlon Senior manufacturing engineer at the University of Strathclyde's Advanced Forming Research Centre


News from British Standards

Things still don't stand still in the world of standards. BSI's TPR/1/7 committee has been as busy as ever in recent months.

The committee’s BS 8887 series, entitled “Design for Manufacture, Assembly, Disassembly and End-of-Life Processing (MADE)”, has been growing for some ten years. The latest standard to be developed, Part 3: Guide to choosing an appropriate end-of-life design strategy (published in 2018), was aimed at helping design products where features are included from the beginning. These features give value at the end of in-service life. This has the potential to allow the initial investment in new material processing to give rise to a number of “lifetimes” of use, thus saving costs and reducing overall environmental impact.

h t t p : / / w w w. b s i g ro u p. c o m / e n / S t a n d a rd s - a n d Publications/About-standards/What-are-the-benefitsof-standards/ If you would like more information on any of the TPR/1 area projects or work programme or if you would like to get involved in any way in the work of the committee, please contact Sarah Kelly, Lead Standards Development Manager – Committee Manager for TPR/1, at BSI on the following email address: sarah.kelly@bsigroup.com. Sarah Kelly Lead Standards Development Manager

Work is beginning on looking into Part 4 of the series, to aid the triage process, when a used product is returned to the manufacturing system, to decide on the best ways to reuse its components. If the guidance of Part 3 has been used in its design, then the possible pathways are easily determined. The preferable outcome of remanufacturing will be the subject of other work, in collaboration with the work being done at the University of Strathclyde. Some consideration is also being given to a potential Part 5 of the BS 8887 series, which will help define the information generated during design and manufacture, and any further processing between lives that may be needed later for further processing. This would include the option of repurposing, where components may be reused in other products. The design of the new products would need to take account of the history of the components in order to make the decisions on their suitability. The mitigation of wear and structural fatigue may, for example, be necessary. With all of this new work and activity, TPR/1/7 (and the broader TPR/1 committee area, which looks after all of the design, specification and verification standards for mechanical engineering) is always looking for new committee members and experts to join its standards drafting groups, national committees and international working groups. Further general information on taking part in standards work can be found at : 41


Inspiring the Next Generation STEM and Electrification At the back end of 2019 I helped lead what was one of my biggest STEM events to date.

Between myself, as range safety officer, and my colleague, who managed the build station, we were able to get 230 children to manufacture and fire model rocket cars on a beautiful September Sunday. The event was a family fun day held for staff members of Rolls-Royce and their families as a thank you for their efforts throughout the year. The scale of this event has only ever been paralleled with the Derby Mini Maker Faire in October 2015 where the flat-packed launchers and kits we use were first developed in conjunction with the Joseph Whitaker School. Since 2015, we have managed to fire well over 2000 rocket cars at events in and around the East Midlands. The event was a fantastic success, made more exciting by the fact that we had a number of motor batches that decided they didn’t want to just burn, but instead explode for no apparent reason. This meant the children didn’t know whether their cars would speed along the guidewire gracefully or turn into smithereens in less than a second. The children absolutely loved this added level of uncertainty, which meant they had to retreat further from the cars during testing. The motors are the smallest commercial available rocket motors at just 45g and have a very short burn time, so the risks of injury are suitably minimised, but they do make a loud bang if they explode rather than burn. In December I received some very sad news regarding an outstandingly inspirational teacher, Phil Worsley, who I have been working with closely on rocket cars of all kinds for the past 7 years. Phil worked at the Joseph Whitaker School after retraining as a technology teacher in the 1990s and was the best example of a passionate teacher I have ever had the pleasure of meeting. Phil had supported Rolls-Royce on a number of occasions across the country at STEM events and the club he led won national and royal recognition, winning award after award for their work. Phil sadly was diagnosed with terminal cancer in March 2019 and passed away in early December. His death has left a huge chasm in the world of STEM but Phil’s legacy will continue through the children and adults he interacted with. As we start 2020, Rolls-Royce is embracing a new era of electrification and throughout this year we will be trying to embed the messages of electrification and digital engineering through our STEM activities. With climate change high on the agenda, we are aiming 42

to demonstrate ways in which we are working, as a business, to help solve the problems of the future. One such activity I am currently working on is the possibility of using drones in a design challenge for pupils. The problem with many drone STEM activities is that given the expense of drones, it is rare for all the pupils to be able to get to fly them. One of the ways of getting around this hurdle is to change the activity to one of a design challenge and then use a single drone to release a payload from a fixed altitude. The background and context to such an activity is the growing use of drones for things like natural disasters and humanitarian crises – where dropping medicines, food or surveying the area is critical to providing a rapid response. I have purchased a drone release electronic device, which has a remote control, allowing the pupils to release the payload themselves. Over the coming months I am working on a potential design challenge, which involves the students designing a capsule to allow a biscuit to survive a drop of at least 10m without using a parachute. I have decided to use biscuits to assimilate the fragile and precious nature of medical supplies rather than eggs. The advantage is also that the capsule will have a lower mass than one containing an egg so should be easier to fly underneath the drone. The aim is to do this activity at key stage 2 level although it could be extended into key stage 3 by initially doing experiments to compare the strength of different biscuits by dropping them from different fixed heights and plotting the results on a graph. I will also be working on a STEM link to the fastest electric powered aircraft, which is being built to fly at Farnborough later in the year. We will be linking some of our 3D printing demonstrations to the aircraft at public STEM events such as Big Bang to help demonstrate our need for creative problem solvers of the future. As ever, if anyone is interested in knowing more about how they can get involved in STEM please do not hesitate to contact me or your local STEMnet contract holder. Grant Gibson EngD BEng (Hons) Materials Technologist, Surface Engineering Rolls-Royce Plc. grant.gibson@rolls-royce.com 07469375700


University of Wolverhampton Racing

Sponsored by the EIS

2019 was another excellent year for the University of Wolverhampton Racing Team, competing in Formula Student, the F3 Cup and running 3 Plus 4 Club Sports in the AR Morgan Challenge. The Formula Student team spend months in the workshops and classrooms long before a wheel touches the tarmac at Silverstone. Our 2019 car, Wolf 5, was a complete rebuild, with almost every aspect improved, from full carbon bodywork, intricate titanium suspension uprights, lightweight brake calipers and a newer, lighter steering wheel. Wolf 5 made good progress through the scrutineering rounds, reaching the on-track competitions much more quickly than its predecessor. Unfortunately, during the drag race event, the throttle pedal stuck with the engine at wide-open throttle, preventing the driver from changing gears and necessitating a four-wheel lock-up. The UWR students worked through the night to repair the car, testing their engineering skills and knowledge. UWR finished 41st out of 81 teams, but considering some unforeseen misfortunes, UWR’s student engineers acquitted themselves well, and will take valuable experience into the 2020 season and the work place.

track position didn’t matter to UWR, only finishing the race, and finish it he did, securing the Class S P1, the Class S fastest lap and the Morgan Challenge Trophy. Congratulations to Tony Hirst and the UWR Morgan team on their superb season and stellar victory. Shane Kelly and the UWR F3 Cup team place 2nd in the 2019 F3 Cup! UWR’s F3 Cup Team secured 2nd place in the championship for the third time in four years of competing. An excellent qualification session boosted UWR’s hopes of stealing P1, especially after Shane Kelly made his best start of the season to lead Race 1. The hopes were short-lived though as Kelly lead for just one lap, the long straights of Snetterton allowing drivers whose engines favour straight-line speed to out-muscle the Racing Wolves. As time ticked away, three cars passed Kelly, leaving UWR to hold on for 4th place by the skin of their teeth.

UWR win the AR Motorsport Trophy, the Morgan Challenge Trophy and the Class S Championship. At a damp and slippery Snetterton, Hamilton-Smith lost control and span his Plus 4 Club Sport into the crash barrier. While Craig was unhurt, his car took significant damage to the front right wheel, suspension and chassis. Hamilton-Smith’s weekend was over before it could begin and Hirst had one hand on the trophy. Knowing that Tony would only have to finish Saturday’s race to win the title, he drove a circumspect qualifying round, securing 10th place and 1st in class.

Drama unfolded in Race 2, as after 19 minutes of the 20 minute, with Kelly again maintaining P4, a mechanical failure on the last lap forced UWR to retire and score 0 points. After the race, Shane Kelly said, “It’s been an amazing effort by a group of hard working students who never give up. We’ve had so much support from our partners and sponsors so a massive thank you to them too.” For more information, to follow us or to sponsor us visit:

By the second lap he had slipped from 10th to 15th and was concentrating hard on the slippery surface. Overall

wlv.ac.uk/UWR instagram.com/UWRacing twitter.com/UWRacing linkedin.com/company/uwracing

Images © Andi Rusyn Photography 43


Group News the range of industrial and academic sectors. It is our primary objective to organise and support seminars, exhibitions and training programmes with the aim of promoting the exchange of knowledge and information particularly for young engineers, and to facilitate technical exchange between academia and industry.

The sound and vibration challenges for emerging products, whether they are automotive, industrial or domestic are constantly changing.

We rely on the support and initiatives of our committee members within the group to promote NVH product development with young engineers. We are always keen to have new members to the committee who wish to make a difference in this field. Whether from an industrial or academic background, we welcome the participation and contribution of NVH engineers from around the world.

This is particularly true with the ongoing development of new materials and the pressure to deliver products that are environmentally friendly. The rapid development of electric motor and battery technology is a case in point.

As a committee member, we would value your knowledge, experience and ideas. Committee membership also provides an opportunity to make contact with a wide range of technical experts from across industries and universities.

In 2018 the SVPP Group organised a successful seminar and workshop day at Coventry University called "Electric Vehicle NVH: Not as quiet as you thought?".

Your commitment would involve contributions at meetings (3 times a year for a morning) either in person or over the phone and providing your ideas and inspiration in support of our activities.

Sound & Vibration Product Perception Group

This brought both an educational aspect to it with workshops on the measurement and analysis of motor noise, along with several technical papers covering some of the latest technical developments in the field. We will continue to support this field of noise and vibration through seminars and collaborative activities. The EIS SVPP committee represents the interests of the noise and vibration engineering field for the EIS and is made up of technical experts across 44

If you would be interested in joining our committee then please contact Sara Atkin (info@e-i-s.org.uk).

Dave Fish Chairman

Durability & Fatigue Group A major focus for the group over the last year has been preparation for Fatigue 2020 conference. Thanks to great efforts from our members, and especially from Sara (EIS Secretariat) we are looking forward to a well-organised event this summer, with good international participation. Please do look at the full article about Fatigue 2020 earlier in this issue, to read more. In our recent meetings, discussion has frequently turned to matters surrounding materials and components produced by additive manufacture; a deceptively concise term for a wide range of technologies, all of which are already finding commercial niches. This resulted in a very interesting seminar last year, with some great presenters from the industrial sector discussing current risks and rewards to adoption as we are now looking at a commercially viable equipment. While popular public awareness has grown rapidly for less structural applications, there is still a long way to go in fully understanding the implications â&#x20AC;&#x201C; and more importantly


to maintain the enthusiasm and momentum that David and those before him have provided. In the few years I have been attending the EIS I have seen some of the older faces retire taking with them their valuable expertise and skills. However, we still have many experienced and highly respected STMG members and I hope they continue to support us for as long as possible.

limitations – for using additive manufacture where durability is critical. We can certainly expect to see a lot more discussion at the conference and in future seminars. We have also been discussing the new strands of work which are rapidly emerging in the renewable and “green” energy industry. Historically, we have run a series of four meetings on the topic of “Wind, Wave, and Tidal” technologies, as there was considerable interest in the development of hardware for renewable power generation. Many of these structures are now being seen as mature technology, but there is new focus on whole power systems and especially the rapidly growing need for energy storage. Obviously, the urgent demand for electric vehicle technologies has been the most visible and public face, but moving increasingly to use power sources whose capacity varies outside operator control brings with it a need for energy storage on very large scales indeed. At a system level, there are a diverse range of durability challenges for renewable energy, and we are looking at developing a seminar around this later in the year. Finally, it has been pleasing to welcome participation from new members to the group, as well as others returning after a few years’ break. Several of our new group members have joined us after participating in the Young Engineers’ seminars, and are now helping further develop the future programme.

Peter Bailey Chairman

Simulation, Test Measurement Group

&

David Ensor has been chairman of the Simulation, Test & Measurement Group (STMG) since the beginning of 2017. Since then the committee has lost a few ‘old and wise’ faces as well as gaining new younger members. David has led a growing enthusiastic team who now support the group in addition to those who helped build it in the past. At the end of last year David announced that he was stepping down from the chair of the STMG for personal reasons. The STMG committee would like to thank David for his hard work and enthusiasm over the past few years and he leaves the group in good shape, with a growing active core of members. We are pleased David will continue as a member of the committee and wish him all the best for the future in his retirement, ‘assisting the police with their enquiries’ (in a professional capability of course) and his slot car racing ventures. Dave kindly suggested that I should take over the reins and at the last committee meeting I volunteered my services and was elected as the new STMG Chairman. Alex O’Neill agreed to support me in my duties and was duly elected as Deputy Chairman and I am grateful for his support. Alex is an active member of the Young Engineers Group and in 2019 was awarded the Peter Watson Prize, so I am sure he will have plenty to contribute. Both Alex and I, along with the rest of the team, look forward to supporting the EIS over the coming years and hope

The Effective Road Load Data Acquisition seminar was held on the 13th November 2019 at the MIRA Technology Institute (MTI), Nuneaton. In the past HORIBA-MIRA has hosted several EIS events on the Proving Ground including ‘The Fundamentals of Road Load Data’ and the November seminar was a great opportunity to use the new building which has excellent facilities for hosting events. This year presenters from HORIBA-MIRA, PCB Piezotronics, Millbrook, imc Test & Measurement GmbH and Birmingham City University all provided their valuable time, experience and enthusiasm to provide some very interesting presentations. We felt it was important to demonstrate the instrumentation in a classroom environment and set about finding a way to meet this challenge. To this extent we set about building a ‘Corner Suspension Rig’ on which the transducers, including a wheel force transducer could be installed and demonstrated. The demonstration was well-received and meant we could effectively demonstrate the principles without having to leave the venue leaving more time to focus on the presentations and discussions. Feedback from delegates was extremely positive and I’d like to thank everyone involved including the presenters, some of whom had travelled from overseas, the MIRA team who spent many hours designing and building the suspension rig, Sara for planning the whole event and the MTI for a perfect venue for the seminar.

Steve Payne Chairman 45


Committee Members

President: Professor Roderick A Smith, FREng. ScD Directors Peter Bailey, Instron Robert Cawte, HBM United Kingdom Graham Hemmings, Engineering Consultant Richard Hobson, Serco Rail Technical Services Nick Richardson, Servotest Norman Thornton, Engineering Consultant John Yates, Engineering Consultant

Chairman John Yates, Engineering Consultant

Vice Chairman Richard Hobson, Serco Rail Technical Services

Treasurer Graham Hemmings, Engineering Consultant

Company Secretary Nick Richardson, Servotest

EIS Secretariat Sara Atkin

Communications Sub Committee – ‘Engineering Integrity’ Journal of the EIS Honorary Editor Farnoosh Farhad

Managing Editor Rochelle Stanley

Sound & Vibration Product Perception Group Chairman David Fish, JoTech

Members Dave Boast, DB Engineering Solutions Mark Burnett, HORIBA-MIRA Martin Cockrill, Polytec James Herbert, Bruel & Kjaer UK Peter Jackson, European Acoustical Products Paul Jennings, Warwick University Chris Knowles, Consultant Andrew McQueen, Siemens Jon Richards, Honda UK Tony Shepperson, HEAD acoustics Keith Vickers, Bruel & Kjaer UK

Simulation, Test & Measurement Group Chairman Steve Payne, HORIBA-MIRA

Members Jack Allcock, Tata Steel Carl Babcock, Data Acquisition & Testing Services Ltd Dan Bailey, Instron Gian Matteo Bianchi, Jaguar Land Rover Connor Bligh, JCB Marc Brown, Vibration Research 46


Darren Burke, Servotest Lloyd Butler, DTR VMS Steve Coe, Data Physics (UK) Dave Copley, Consultant Robin Garvie, Airbus Graham Hemmings, Engineering Consultant Richard Hobson, Serco Rail Technical Services Jerry Hughes, Moog Jonathan Joy, Millbrook Virrinder Kumar, HBM United Kingdom Trevor Margereson, Engineering Consultant Alex O'Neill, Jaguar Land Rover/University of Surrey Tim Powell, MTS Systems Gary Rands, Siemens Nick Richardson, Servotest Paul Roberts, HBM Prenscia Raul Rodriguez, Hyster Yale Jarek Rosinski, Transmission Dynamics Norman Thornton, Engineering Consultant John Wilkinson, Engineering Consultant Darren Williams, Millbrook Proving Ground Scott Williams, Williams F1 Rob Wood, GOM Jeremy Yarnall, Data Acquisition and Testing Services Ltd

Durability & Fatigue Group Chairman

Robert Cawte, HBM United Kingdom

Secretary Peter Bailey, Instron

Members John Atkinson, Consultant Martin Bache, Swansea University Tom Bishop, Phoenix Materials Testing Andrew Blows, Jaguar Land Rover Amir Chahardehi, Atkins Energy Richard Cornish, Birmingham City University Farnoosh Farhad, Northumbria University Hassan Ghadbeigi, Sheffield University Lee Gilbert, Element Oliver Greenwood, Rolls Royce Phil Irving, Engineering Consultant Karl Johnson, Zwick Roell Group Chris Magazzeni, Oxford University Angelo Maligno, IISE, University of Derby Ali Mehmanparast, Cranfield University Andrew Mills, Siemens Giovanni De Morais, Dassault Systèmes Simulia Karen Perkins, Swansea University Davood Sarchamy, Airbus Giora Shatil, Darwind Jamie Shenton, JCB Andy Stiles, Aero Engine Controls John Yates, Engineering Consultant Committee members can be contacted via the EIS Secretariat, Tel: 01623 884225 47


Corporate Member Profiles CentraTEQ Ltd

Flintec

26A Richmond Road Solihull, B92 7RP

W4/5 Capital Point Capital Business Park, Wentloog Avenue Cardiff, CF3 2PW

Tel: +44 (0)121 706 2319 Email: info@centrateq.com Website: www.centrateq.com Contact: Jim Flanagan

Tel: +44 (0)2920 797959 Email: gareth.r@flintec.com Website: www.flintec.com/uk Contact: Gareth Roberts

As a provider of product integrity test systems, CentraTEQ is an agent for a number of international companies manufacturing a range of systems. These systems include Vibration Test Systems, Shock and Bump Testers, Vibration Controller and Package Test Systems.

Flintec is a world leader in the manufacture of precision strain gauge load cells and force sensors technologies. Established in 1968, Flintec has grown substantially, with our weighing technologies used by some of the biggest companies in the world.

Working with colleagues in the industry we are able to provide a turnkey solution integrating a number of disciplines into a single combined and complete test system.

Quality and precision encompasses everything we do. We have a global network of engineers, on hand to help with hardware and software development, no matter what the application.

Vibration, and durability testing is provided in our in-house laboratory.

Our office in Cardiff operates as a central engineering and sales hub, assisting customers across the world.

imc Test GmbH

Instron

&

Measurement

Voltastr. 5 13355 Berlin Germany

Tel: +49 (0)30 467090-0 Email: info@imc-tm.de Website: www.imc-tm.com Contact: Daniel Foerder imc Test & Measurement GmbH is a manufacturer and solution provider of productive test and measurement systems. Together with its customers, imc implements metrological solutions for research, development, service and production. Every day, customers use imc measurement devices, software solutions and test stands to validate prototypes, optimize products, monitor processes and gain insights from measurement data. imc consistently pursues its claim of providing services for “productive testing”. The company offers its customers top technological performance throughout the entire measurement chain. 48

Coronation Road, High Wycombe Buckinghamshire, HP12 3SY Tel: +44 (0) 1494 456815 Email: info_news@instron.com Website: www.instron.co.uk Instron is a leading provider of testing equipment for the material testing and structural testing markets. Instron’s products test the mechanical properties and performance of various materials, components and structures in a wide array of environments. A global company providing single-source convenience, Instron is a full-service materials testing company that manufactures and services testing instruments, systems, software and accessories. Instron’s proficiency in designing and building testing systems to evaluate materials ranging from the most fragile filament to advanced alloys, affords Instron’s customers a comprehensive resource for all their research, quality and service-life testing requirements. Information is also available on the company’s enhanced website at www.instron.com.


P.D.S. Hitech Ltd

The Hive Beaufighter Road Weston Super Mare, BS24 8EE Tel: + 44(0)1934 444222 Email: paul.sodzi@pds-hitech.co.uk Website: www.pds-hitech.co.uk Contact: Paul Sodzi PDS Hitech provides specialist engineering and technology expertise to Aerospace, Energy and Software sectors. Our highly experienced engineers in the aerospace sector specialise in structural analysis including static analysis, finite element analysis, fatigue & damage tolerance analysis, acoustic fatigue analysis and design of vehicle structures. Some of our current and past projects include Airbus A300, A310, A320 family, A330, A340, A350, A380, Boeing 737 and the Sea King Helicopter. Our technology consultants in the software sector work alongside businesses of various sizes to help them streamline their business processes and increase overall efficiency through intelligent apps and mobilised workflows. We are based near Bristol in South West England, UK.

StressMap Ltd

Atlas Building R29 G29 Harwell Campus Dicot, OX11 OQX Tel: +44 (0)7884 261484 Email: contact@stress-map.com Website: www.stress-map.com Contact: Prof. John Bouchard

Prosig

Link House, 44A High Street Fareham, Hampshire, PO16 7BQ Tel: +44 (0)1329 239925 Email: ben.huxham@prosig.com Website:www.prosig.com Contact: Ben Huxham Severn Thermal Solutions has a wide range of experience in design and manufacture of high temperature furnaces and environmental systems (Temperature chambers) for a wide variety of applications within industry and academia. We offer standard and custom engineered solutions including a range of laboratory and test equipment featuring tube furnaces, split furnace systems and temperature chamber. Applications range from small-scale research and development to full-scale production systems. Severn Thermal Solutions has earned an exceptionally good reputation around the world supplying market leading organisations with both standard and custom engineered solutions.

Techni Measure

Unit 4, Buccaneer Drive Auckley, Doncaster, DN9 3QP Tel: +44 (0) 3300 101490 Email: sales@techni-measure.co.uk Website: www.techni-measure.co.uk Contact: Ian Ramage

StressMap Ltd offers an â&#x20AC;&#x153;intelligent capabilityâ&#x20AC;? for measuring residual stresses in complex geometry structures of any size at competitive cost for diverse engineering applications.

Techni Measure was founded over 40 years ago, and can supply a wide range of sensors for measuring various parameters. Strain gauges and bonding accessories are available, as well as strain gauge based transducers for load, pressure and displacement.

We use a range of residual stress measurement methods including the Contour Method, X-ray diffraction, neutron diffraction, synchrotron diffraction and hybrid methods. We are the UK distributor for new generation X-ray diffraction measurement equipment for mapping residual stresses (X-Raybot) over complex geometric surfaces.

Piezoelectric sensors measure vibration, dynamic force and dynamic pressure, and we have various ways of measuring displacement based on resistive, inductive or capacitive technology. Orientation, inertial, and various different wireless systems are available, as well as pressure seals and temperature sensors.

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Corporate Members The following companies are corporate members of the Engineering Integrity Society. We thank them for their continued support which helps the Society to run its wide-ranging events throughout the year. AcSoft Alphatech Ltd ANV Measurement Systems Bruel and Kjaer CaTs3 CentraTEQ Correlated Solutions Dassault Systemes Data Acquisition and Testing Services Ltd Data Physics Datron Technology Dewesoft Flintec Gantner Instruments GOM HBM HEAD acoustics HORIBA-MIRA

Instron Interface Force Measurements imc Test and Measurement GmbH iPetronik Kistler M&P International Mecmesin Meggit Sensing Systems Micro Measurements Micro-Epsilon Millbrook MOOG MTS Systems Muller BBM Nprime PCB Piezotronics PDS Hitech Phoenix Materials Testing Ltd

Polytec Prosig Rutherford Appleton Lab Sensors UK Servotest Severn Thermal Solutions Siemens Star Hydraulics Strainsense StressMap Ltd Systems Services Techni Measure Torquemeters THP Systems Transmission Dynamics Variohm Vibration Research Zwick/Roell

4 & 5 November 2020 | NEC, Birmingham The UKâ&#x20AC;&#x2122;s largest annual gathering of engineering supply chain professionals

BOOK NOW T: +44 (0)20 3196 4300 | www.advancedengineeringuk.com AE_2020Advert_NEWBook_180x125.indd 1

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11/02/2020 16:18:13


The Mobile Binaural Family presented by HEAD acoustics SQuadriga III, SQobold, B2U Binaural recordings wherever you go: Combine our portable measurement units and highly-accurate binaural recording systems for smart recording and playback. Enjoy easy operation and reproducible aural accuracy.


Experts in Vibration m+p international supplies high-performance software and instrumentation for vibration control on a shaker, noise and vibration analysis, data acquisition and monitoring. Our products combine efficiency, accuracy, flexibility and test safety. Above this, we also offer consultancy and support to ensure successful outcomes for all of your applications.

www.ahlersheinel.de

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Tackle your unique challenges with m+p international’s engineering excellence.

m+p international (UK) Ltd Mead House Bentley, Hants GU10 5HY Phone: +44 1420 521222 sales.uk@mpihome.com

www.mpihome.com

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Engineering Integrity Issue 48 - March 2020  

March 2020 An Investigation into the Failure Mechanisms of Coronary Stents Instrumentation, Analysis and Testing Exhibition Fatigue 2020

Engineering Integrity Issue 48 - March 2020  

March 2020 An Investigation into the Failure Mechanisms of Coronary Stents Instrumentation, Analysis and Testing Exhibition Fatigue 2020