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International Journal of Mechanical and Production Engineering Research and Development (IJMPERD) ISSN 2249-6890 Vol. 3, Issue 3, Aug 2013, 1-8 Š TJPRC Pvt. Ltd.

COMPARATIVE STUDY OF SINGLE LEAVE LEAF SPRING IN CAE TOOL AND EXPERIMENTAL DATA OF LEAF SPRINGS IN AUTOMOTIVE VEHICLES S. D. RATHOD1, D. S. SHAH2 & S. A. BAN3 1

ME CAD/CAM (Mechanical), IVth Semester, SVIT Vasad, Gujarat India

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Assistant Professor, Mechanical Department, SVIT Vasad, Gujarat, India

ABSTRACT The work is carried out on the front end leaf spring of a commercial vehicle. The objective of this work is to Carry out computer aided design and analysis of a elliptical single leave leaf spring, with experimental design considerations and loading conditions. The material of the single leave leaf spring is 65Si7.The CAD model of the single leave leaf spring is prepared in Solid-Works and analyzed using ANSYS-14.0. The CAE analysis of the single leave leaf spring is performed for the deflection and stresses under defined loading conditions, using ANSYS-14.0. The experimental and CAE results are compared for validation. Using CAE tools the ideal type of contact and meshing element is determined in leaf spring model.

KEYWORDS: Computer Aided Engineering (CAE), Leaf Spring, 65Si7, Static Loading, Finite Element Analysis, FEM INTRODUCTION CAE tools are widely used in the automotive industries. In fact, their use has enabled the automakers to reduce product development cost and time while improving the safety, comfort, and durability of the vehicles they produce. The predictive capability of CAE tools has progressed to the point where much of the design verification is now done using computer simulation rather than physical prototype testing. CAE dependability is based upon all proper assumptions as inputs and must identify critical inputs. Even though there have been many advances in CAE, and it is widely used in the engineering field, physical testing is still used as a final confirmation for subsystems due to the fact that CAE cannot predict all variables in complex assemblies, therefore the validation of CAE results is important. The specimen under this research work consists of single leave elliptical leaf spring etc. CAE tools are being used to analyze the robustness and performance of single part. The finite element analysis (FEA) is a computing technique that is used to obtain approximate solutions to the boundary value problems in engineering. It uses a numerical technique called the finite element method (FEM). Using FEA single leave leaf spring is modeled using the discrete building blocks called elements. Each element has some equations that describe how it responds to certain loads. The sum of the response of all the elements in the model gives the total response of the design. CAE tool depends upon actual assumptions of the parts which act as input data. CAE has become an important technology with benefits such as lower costs and a shortened design cycle. Studies say that any design professional can save approximate 30% of time and cost by using CAE tools. In future CAE system will be major information provider to help design professionals in decision making. Mouleeswaran et al [1] describes static and fatigue analysis of steel leaf spring and composite multi leaf spring made up of glass fiber reinforced polymer using life data analysis. The dimensions of an existing conventional steel leaf spring of a light commercial vehicle are taken and are verified by design calculations. Static analysis of 2-D model of conventional leaf spring is also performed using ANSYS


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S. D. Rathod, D. S. Shah & S. A. Ban

7.1 and compared with experimental results. Hawang W et al [2] Fatigue of Composites – Fatigue Modulus Concept and Life Prediction Journal of Composite Materials.H. A. Al-Qureshi et al [3] has described a single leaf, variable thickness spring of glassfiber reinforced plastic (GFRP) with similar mechanical and geometrical properties to the multileaf steel spring, was designed, fabricated and tested. J.J.Fuentes et al [4] in this work, the origin of premature failure analysis procedures, including examining the leaf spring history, visual inspection of fractured specimens, characterization of various properties and simulation tests on real components, were used. Rajendran I, S. Vijayarangan et al [5] A formulation and solution technique using genetic algorithms (GA) for design optimization of composite leaf springs is presented here. Gulur Siddaramanna et al [6] explain the automobile industry has shown increased interest in the replacement of steel spring with fiberglass composite leaf spring due to high strength to weight ratio. Therefore; the aim of this paper is to present a low cost fabrication of complete mono composite leaf spring and mono composite leaf spring with bonded end joints. J.P. Hou et al [7] explained the design evolution process of a composite leaf spring for freight rail application. Peiyong et al [8] describes that the Leaf spring design was mainly based on simplified equations and trial-and-error methods. The simplified equation models were limited to the three-link mechanism assumption and linear beam theory. This work presents detailed finite element modeling and analysis of a two-stage multi-leaf spring, a leaf spring assembly, and a Hotchkiss suspension using ABAQUS. Muhammad Ashiqur et al [9] describes that the tapered cantilever beams, traditionally termed as leaf springs, undergo much larger deflections in comparison to a beam of constant cross-section that takes their study in the domain of geometric nonlinearity This paper studies response of a leaf spring of parabolic shape, assumed to be made of highly elastic steel. Leaf springs industries working with 65Si7 spring steel ,are using a very low factor of safety for weight reduction .To achieve this, experimental testing is done to predict the spring rate, bending stress and deflection. . M.L. Aggarwal et al [10] calculated fatigue strength of shot peened leaf springs from laboratory samples. The axial fatigue strength of EN45A spring steel specimen is evaluated experimentally as a function of shot peening in the conditions used for full-scale leaf springs testing in industries. The main objective of this work is to perform finite element analysis of single leave leaf spring. experimental results have been taken on a full scale static load testing machine, in which Single leave leaf spring is held under an axial load at centre till maximum deflection. These The Experimental results will be compared with FEA results for validation.

MATERIAL AND METHODS Material Properties and Design Parameters The table-1 The chemical composition of the material. Table 1: Chemical Composition of 65Si7 GRADE C% Si% Mn % P% S% Cr%

65Si7 0.51-0.62 0.15-0.35 0.65-0.95 .035 max .035 max 0.65-0.95


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Comparative Study of Single Leave Leaf Spring in CAE Tool and Experimental Data of Leaf Springs in Automotive Vehicles

Table 2: Material Properties Parameter Material Selected-steel Young’ Modulus, E Poisson’s Ratio BHN Tensile strength Ultimate Tensile strength Yield Single leaves length Spring stiffness Normal Static loading Density Behavior

Value 65Si7 2.1*105 N/mm2 0.266 455-461 460 Mpa 250 Mpa 1608 mm 66.20 mm 40000 N 0.00000785Kg/mm3 Isotropic

Multi Leaf Spring Geometry and Boundary Conditions The Geometry drawing of the single leave leaf spring is shown in the figure-1 below;

Figure 1: Geometry of Single Leave Leaf Spring Loading Conditions The static Loading condition of the single leave leaf spring involves the bottom side of two rollers of the freely supported at the free end. Loading conditions involves applying a point load at the centre of the main leave leaf. As per specifications the spring is drawn at inside length is reduce, therefore the load is applied in downward vertical direction to achieve initial no load condition. The loading conditions are shown below in the Figure-2.

Figure 2: Experimental Condition CAD Modeling & Finite Element Analysis CAD modeling software is dedicated for the specialized job of 3D-modeling. The model of the single leave leaf spring structures also includes many simple parts, which are difficult to make by any of other CAD modeling as well as


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S. D. Rathod, D. S. Shah & S. A. Ban

Finite Element software. CAD modeling of the complete Single leave Leaf Spring structure is performed by using Solid Works software. Solid Works is having special tools in generating surface design to construct typical surfaces, which are later converted into solid models. Solid model of all parts of the structures are then assembled to make a complete structure. The process of parts is very much analogous to general process of fabricating structures while real production. The CAD model of single leave leaf spring used for FE Analysis during modeling drawing is shown in figure-1 and figure2. Finite Element Analysis A stress-deflection analysis is performed using finite element analysis (FEA). The complete procedure of analysis has been done using ANSYS-14.0. To conduct finite element analysis, the general process of FEA is divided into three main phases, preprocessor, solution, and postprocessor. Preprocessor The preprocessor is a program that processes the input data to produce the output that is used as input to the subsequent phase (solution). Following are the input data that needs to be given to the preprocessor: i. Type of analysis ii. Element type. iii. Real constants iv. Material properties v. Geometric model vi. Meshed model vii. Loading and boundary conditions Solution Solution phase is completely automatic. The FEA software generates the element matrices, computes nodal values and derivatives, and stores the result data in files. These files are further used by the subsequent phase (postprocessor) to review and analyze the results through the graphic display and tabular listings. Postprocessor The output from the solution phase is in the numerical form and consists of nodal values of the field variable and its derivatives. For example, in structural analysis, the output is nodal displacement and stress in the elements. The postprocessor processes the result data and displays them in graphical form to check or analyze the result. The graphical output gives the detailed information about the required result data. The single leave leaf spring with all boundary conditions and material properties is imported in ANSYS-14.0, showing in figure-3, figure-4 and figure-5. The material used for the single leave leaf spring for analysis is 65Si7, Which has approximately similar isotropic behavior.

Figure 3: Meshing of Single Leave Leaf Spring


Comparative Study of Single Leave Leaf Spring in CAE Tool and Experimental Data of Leaf Springs in Automotive Vehicles

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Figure 4: No Separation Contact in Ansys-14.0

Figure 5: Boundary Condition in Ansys-14.0

RESULTS AND DISCUSSIONS As the finite element analysis of single leave leaf spring is performed using ANSYS-14.0 detailed above, in which all conditions are considered which were also considered for results taken by experimental testing. The single leave leaf spring showing deflections under full & half rated loads are shown in figure-6 and figure-7, as well as in tabular form taken from ANSYS-14.0.

Figure 6: Deformation at Full Load


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S. D. Rathod, D. S. Shah & S. A. Ban

Figure 7: Deformation at Half Load

RESULTS COMPARISON & DISCUSSIONS Table 3: Result Comparison at Full Load Parameters Normal Static Load Deflection Spring Rate Bending Stress

Experiment Results 40000 N 17.000 mm 2352.94 N/mm 5967.18 N/mm2

FEA Results 40000 N 17.895 mm 2235.26 N/mm 5027.20 N /mm2

Variation Nil 5.26% 5.00% 15.75%

As shown in the above table-3 deflection and the bending stress are compared for experimental and FEA results. The experimental deflection value is 17 mm and the FEA value is 17.895 mm i.e. a negligible difference is detected. On the other hand the bending stress is increased from 5967.18 N/mm2 to 5027.20 N/mm2 i.e. again a negligible difference is detected. Table 4: Result Comparison at Half Load Parameters Normal Static Load Deflection Spring Rate Bending Stress

Experiment Results 20000 N 9.000 mm 2222.23 N/mm 2983.59 N/mm2

FEA Results 20000 N 8.9475 mm 2235.26 N/mm 2513.60 N /mm2

Variation Nil 0.59% 0.58% 15.75%

As shown in the above table-4 the deflection and the bending stress with half rated load are compared for experimental and FEA results. The experimental deflection value is 9.00 mm and the FEA value is 8.9475 mm i.e. a negligible difference in Experimental and FEA value. On the other hand the bending stress is increased from 2

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N/mm to 2513.60 N/mm i.e. the experimental value is higher than the FEA value safe.

Figure 8: Load-Deflection curve for FEA Results

2983.59


Comparative Study of Single Leave Leaf Spring in CAE Tool and Experimental Data of Leaf Springs in Automotive Vehicles

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CONCLUSIONS Design and stress-deflection analysis of a multi leaf spring is carried out by finite element approach using CAE tools (i.e Solid Works, ANSYS 14.0). When the leaf spring is fully loaded, a variation of 5.26 % in deflection is observed between the experimental and FEA result, and same in case of half load, which validates the model and analysis. On the other hand, bending stress in both the cases is also close to the experimental results. The maximum value of equivalent stresses is below the Yield Stress of the material that the design is safe from failure.

REFERENCES 1.

Mouleeswaran Senthil kumar;sabapathy vijayarangan; (2007) “Analytical and Experimental Studies on Fatigue Life Prediction of Steel and Composite Multi-leaf Spring for Light Passenger Vehicles Using Life Data Analysis” Materials Science,Vol.-13,No. 2, p.p 141-146.

2.

Hawang, W., Han, K. S. (1986) Fatigue of Composites – “Fatigue Modulus Concept and Life Prediction” Journal of Composite Materials, vol-20, p.p. 154 – 165.

3.

H. A. Al-Qureshi (2001), “Automobile leaf springs from composite materials”, Journal of Material Processing Technology, vol-118,p.p 58-61.

4.

J.J.Fuentes,H.J. Agulilar,J.A.Rodriguez,E.J. Herrera (2008) , “Premature fracture in automobile leaf springs”, Engineering Failure Anlysis,vol-16,p.p 648-655.

5.

I. Rajendran, S. Vijayarangan, (2002) “Design and Analysis of a Composite Leaf Spring” Journal of Institute of Engineers India, vol-82 pp. 180 – 187

6.

Gulur Siddaramanna Shiva shanker, Sambagam Vijayaragan (2006), “Mono Composite Leaf Spring for Light Weight Vehicle Design, End Joint Analysis and Testing” Materials Science, vol-12, No-3,p.p 220-225.

7.

J.P. Hou; J.Y. Cherruault, I. Nairne, G. Jeronimidis, R.M. Mayer (2004), “Evolution of the eye-end design of a composite leaf springs for heavy axle loads”, Composite Structures vol-28,p.p 351-358.

8.

Peiyong Qin, Glenn Dentel, and Mikhail Mesh (2002), “Multi-Leaf Spring and Hotchkiss Suspension”, ABAQUS Users’ Conference.

9.

Muhammad Ashiqur Rahman*, Muhammad Tareq Siddiqui and Muhammad Arefin Kowser (2002), “Design and Non-Linear Analysis Of A Parabolic Leaf Spring”, Journal of Mechanical Engineering vol-ME 37,p.p 47-51.

10. Aggarwal M.L; Agarwal V.P;Khan R.A (2006)”A stress approach model for predicting fatigue life of shot peened EN45A springs steel”, International Journal of Fatigue,Elsevier publication,vol 28, p.p 1845-1853.


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The work is carried out on the front end leaf spring of a commercial vehicle. The objective of this work is to Carry out computer aided desi...

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