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International Journal of Automobile Engineering Research and Development (IJAuERD) ISSN 2277-4785 Vol. 3, Issue 2, Jun 2013, 81-88 Š TJPRC Pvt. Ltd.


M.Tech Student, Department of Automobile Engineering, BIST, Bharath University, Selaiyur, Chennai, Tamil Nadu, India


Project Supervisor, Professor, Department of Automobile Engineering, BIST, Bharath University, Selaiyur, Chennai, Tamil Nadu, India

ABSTRACT This paper presents the design connecting rod of internal combustion engine using the topology optimization. The objectives of this paper are to develop structural modeling, finite element analyze and the optimization of the connecting rod for robust design. The structure of connecting rod was modeled utilized SOLIDWORKS software. Finite element modeling and analysis were performed using MSC/PATRAN and MSC/NASTRAN software. Linear static analysis was carried out to obtain the stress/strain state results. The mesh convergence analysis was performed to select the best mesh for the analysis. The topology optimization technique is used to achieve the objectives of optimization which is to reduce the weight of the connecting rod. From the FEA analysis results, TET10 predicted higher maximum stress than TET4 and maximum principal stress captured the maximum stress. The crank end is suggested to be redesign based on the topology optimization results. The optimized connecting rod is 11.7% lighter and predicted low maximum stress compare to initial design. For future research, the optimization should cover on material optimization to increase the strength of the connecting rod.

KEYWORDS: Connecting Rods, MSC/PATRAN Software, MSC/NASTRAN Software INTRODUCTION Connecting rods are highly dynamically loaded components used for power transmission in combustion engines. The optimization of connecting rod had already started as early year 1983 by Webster and his team. However, each day consumers are looking for the best from the best. That’s why the optimization is really important especially in automotive industry. Optimization of the component is to make the less time to produce the product that is stronger, lighter and less cost. The design and weight of the connecting rod influence on car performance. Hence, it is effect on the car manufacture credibility. Change in the structural design and also material will be significant increments in weight and performance of the engine. Mirehei et al. (2008) were performed the study regarding the fatigue of connecting rod on universal tractor (U650) by using ANSYS software application and the lifespan was estimated. The authors also investigated that the stresses and hotspots experienced by the connecting rod and the state of stress as well as stress concentration factors can be obtained and consequently used for life predictions. Rahman et al. (2008a, 2009a) discuss about FEA of the cylinder block of the free piston engine. The 4 nodes tetrahedral (TET4) element version of the cylinder block was used for the initial analysis. The comparison then are made between TET4 and 10 nodes tetrahedral (TET10) element mesh while using the same global mesh length for the highest loading conditions (7.0 MPa) in the combustion chamber. A connecting rod is subjected to many millions of repetitive cyclic loadings. Therefore, durability of this


M. Ravichandran, R. Anbazhagan, Binu. K. Soloman & C. Jagadeesh Vikram

component is of critical importance. It is necessary to investigate finite element modeling techniques, optimization techniques and new design to reduce the weight at the same time increase the strength of the connecting rod itself. Shenoy (2004) was explored the weight and cost reduction opportunities for a production forged steel connecting rod. The study has dealt with two parts which are dynamic load and quasi-dynamic stress analysis of the connecting rod, and second to optimize the weight and cost. Shenoy and Fatemi (2005) were explained about optimization study was performed on a steel forged connecting rod with a consideration for improvement in weight and production cost. Weight reduction was achieved by using an iterative procedure. In this study weight optimization is performed under a cyclic load comprising dynamic tensile load and static compressive load as the two extreme loads. Yang et al. (1992) describes a successful process for performing component shape optimization should be focused on design modeling issues. A modular software system is described and some of the modules are widely available commercial programs such as MSC/PATRAN and MSC NASTRAN. The upper end (pin end) of a connecting rod is optimized under a variety of initial assumptions to illustrate the use of the system. The objectives of the study are to develop structural modeling of connecting rod and perform finite element analysis of connecting rod. The main objective is to develop topology optimization model of connecting rod. Finite Element Modeling and Analysis The connecting rod is one of the most important components in the internal combustion engine. Therefore, the initial design is compared to other design before performing the optimization. A simple three-dimensional model of connecting was developed using SOLIDWORKS software and finite element model was created using TET10 as shown in Figure given below. Mesh study was performed on the FE model to ensure sufficiently fines sizes are employed for accuracy of the calculated result depends on the CPU time. During the analysis, the specific variable and the mesh convergence was monitored and evaluated. The mesh convergence is based on the geometry, model topology and analysis objectives.

Figure 1: Connecting Rod-Analysis The uniformly distributed tensile load 180o on the inner surfaces of the crank end while the other part, pin end is restrain as in Figure 3. It is just same when load uniformly distributed on pin end surfaces, the crank end will restrain in all direction. This both cases also work exactly in compressive load. It shows the boundary condition of the connecting rod in three-dimensional FE model with load and constraints. In this study four finite element models were analyzed. FEA for both tensile and compressive loads were conducted. Two cases were analyzed for each case, Firstly, load applied at the crank end and restrained at the piston pin end, and secondly, load applied at the piston pin end and restrained at the crank end and the axial load was 26.7 kN in both tension and compression.


Design and Analysis of Connecting Rod by Using CFRP Material

Figure 2: Flowchart of Optimization Approach A TET10 was then finally used for the solid mesh. Mesh study is performed on FE model to ensure sufficiently fine sizes are employed for accuracy of calculated results but at computational time (CPU time). The Figure above shows the von-Mises stresses contour for TET10 meshes element at a high load level. Table 2 shows that TET10 mesh predicts higher von-Mises stresses than TET4 mesh. Specifically, TET10 mesh predicts the highest von-Mises stresses is 301 MPaat mesh size 4 mm. The comparison was made by using different length of mesh. Figure 5 and 6 show the variation of stress and displacement over the global edge length and it can be seen that the TET10 is always captured the higher values. Table 1 Properties Tensile strength, σUTS (MPa) Yield strength (0.2% offset),σYS (MPa) Young’s modulus, E (GPa) Percent elongation, %EL (%) Percent reduction in area, %RA (%)

Value 965.8 573.7 211.5 27% 25%

Table 2: Comparison between TET4 and TET10 with Stress and Displacement Mesh Size (mm) 16 12 8 4

TET4 22.4 32.7 49.5 67.6

TET10 107.0 142.0 261.0 301.0

TET4 0.060 0.111 0.145 0.201

TET10 0.351 0.475 0.604 0.850

Optimization Statement Objective of the optimization task was to minimize the mass of the connecting rod under the effect of a load range comprising the two extreme loads, the peak compressive gas load, such that the maximum, minimum, and the equivalent stress amplitude are within the limits of the allowable stresses. The production cost of the connecting rod was also to be minimized. Furthermore, the buckling load factor under the peak gas load has to be permissible. Mathematically stated, the optimization statement would appear as follows: Objective Minimize Mass and Cost Subject to 

Compressive load = peak compressive gas load.


M. Ravichandran, R. Anbazhagan, Binu. K. Soloman & C. Jagadeesh Vikram

Maximum stress < Allowable stress.

Side constraints (Component dimensions).

Manufacturing constraints.

Buckling load > Factor of safety x the maximum gas load (Recommended FOS, 3 to 6).

Loads Applied The load range under which the connecting rod was optimized is comprised of the compressive load of 4319 N. The compressive load of 4319 N is independent of the geometry of the connecting rod. The tensile load is, however, dependent upon the specific geometry, as it is a function of the mass, moment of inertia, and location of C.G. Table 3: Values for Shape Results Name "Shape Finder"

Figure 5.33

Scope "Model"

Target Reduction 20.00%

Predicted Reduction 9.24% to 9.51%

Observations from the Optimization Exercise 

The literature survey suggests that connecting rods are typically designed under static loads. It appears that different regions are designed separately with different static loads (i.e. such as in Sonsino and Esper, 1994). Doing so increases the number of steps in the design process. In contrast, a connecting rod could very well be designed under dynamic loads. Doing so would reduce the number of steps in the design process.

The applied load distribution at the crank end and at the piston pin end was based on experimental results (Webster et al., 1983). They were also used in other studies in the literature by Folgar et al. (1987) and Athavale and Sajanpawar (1991). Since the details were not discussed by Webster et al., the applicability of the loading to this connecting rod could not be evaluated.

With manual optimization under static axial loading, at least 9.24 % weight reduction could be achieved for the same fatigue performance as the existing connecting rod as shown in Fig 3. This is in spite of the fact that C-70 steel has 18% lower yield strength and 20% lower endurance limit. Clearly, higher weight reduction may be achieved by automating the optimization and more accurate knowledge of load distributions at the connecting rod ends. The axial stiffness is about the same as the existing connecting rod and the buckling load factor is higher than that for the existing connecting rod.

Considering Process Effects The output file generated after solving the static analysis is of .rst type (results file) which contains all information about stress values. This file was further processed using fe-safe for calculating the life of the component. The input parameters required for fe-safe software are the loading curve, the rst file generated from ANSYS, material data file and the type of algorithm used. Loading curve for fe-safe can be an auto generated sine wave of amplitude 1 or stress value plot generated from force-time graph. The force acting on small end of connecting rod was simulated with the help of ADAMS software inorder to input the load curve for fe-safe. The equivalent stress loading graph, corresponding to force vs. time graph, developed for fe-safe is shown in Figure 10.

Design and Analysis of Connecting Rod by Using CFRP Material


Figure 3: Contour Plot Displacement

Figure 4: Loading Graph for Finite Element-Safe The material properties for SAE 4340 steel is given as an input for calculating the number of cycles the connecting rod can withstand.

MANUFACTURING PROCESS EFFECTS INTO DESIGN The process selected for analyzing the effect of manufacturing on components was shot peening. Shot peening creates a compressive residual stress on the surface. Due to these stresses there is a crack closure effect on the surface preventing the cracks to propagate from the surface. It is possible to achieve a compressive stress of magnitudes -250 MPa, -480 MPa, -660 MPa and -870 MPa on the surface of connecting rod made of AISI 4340 due to shot peening [6]. It is possible to superimpose the compressive residual stresses in design phase itself. If the peak stresses in the loading curve being superimposed with a compressive stress of -250 MPa, the expected behaviour will be a reduction in the stress and it may lead to an improved life. The effective stress loading graph due to shot peening is given in Fig 4. Superimposed values of stress shows a reducing trend and are shown in Fig 4. The mean stress and alternating stress values of new superimposed stress curve are required to incorporate the effect of shot peening on fatigue life.

INDIVIDUAL DIFFERENCES IN THE STRESS-STRAIN RELATIONSHIP Gender Effects Women and men have different life span expectations, with women typically living seven years longer than do men. Furthermore, it appears that different stressors affect men and women, and that important differences exist in the vulnerabilities of women and men to stress. Type a Behavior Pattern One of the ways to determine the likelihood of stress and coping ability is to examine the Type A behavior


M. Ravichandran, R. Anbazhagan, Binu. K. Soloman & C. Jagadeesh Vikram

pattern. Type A behavior pattern is a complex of personality and behavioral characteristics, including competitiveness, time urgency, social status insecurity, aggression, hostility, and a quest for achievements. Type A behavior pattern is also referred to as coronary-prone behavior. Stress Stress is the unconscious preparation to fight or flee that a person experiences

when faced with any demand.

Stress does not necessarily have to be destructive. A stressor is the person or the event that triggers the stress response. Distress refers to the adverse psychological, physical, behavioral, and organizational

consequences that may arise as a

result of stressful events. Yield strength The stress at which a material exhibits a specified limiting deviation from the proportionality of stress to strain .The deviation is expressed in terms of strain also know as proof stress. Ultimate Tensile Strength The highest load applied in breaking a tensile test piece divided by the original cross sectional area of the test price. Young's Modulus In solid mechanics, Young's modulus (E) is a measure of the stiffness of a given material. It is also known as the Young modulus, modulus of elasticity, elastic modulus or tensile modulus (the bulk modulus and shear modulus are different types of elastic modulus). It is defined as the ratio, for small strains, of the rate of change of stress with strain. [1] This can be experimentally determined from the slope of a stress-strain curve created during tensile tests conducted on a sample of the material. Young's modulus is named after Thomas Young, the 18th Century British scientist. Usage The Young's modulus allows the behavior of a material under load to be calculated. For instance, it can be used to predict the amount a wire will extend under tension, or to predict the load at which a thin column will buckle under compression. Some calculations also require the use of other material properties, such as the shear modulus, density, or Poisson's ratio. Linear vs Non-Linear Materials are called linear, and are said to obey Hooke's law. Examples of linear materials include steel, carbon fiber, and glass. Rubber and soil (except at very low strains) are non-linear materials. Carbon Fibre Properties 

High Modulus of Elasticity 200 – 800 GPa.

Tensile Strength 2500 – 6000 MPa.

Density 1750 – 1950 Kg / m3.

Ultimate Elongation 0.3 – 2.5 %.

Carbon fibres do not absorb water.

Design and Analysis of Connecting Rod by Using CFRP Material

Carbon fibres are resistant to many chemical solutions.

Carbon fibres withstand fatigue excellently.

Carbon fibres do not show any creep or relaxied


FUTURE SCOPE The static FEA of the connecting rod has been performed by the use of the software Pro/E wildfire 3.0 for cad modeling and ANSYS WORKBENCH 9.0 for Finite Element Analysis. This work can be extended to study the effect of loads on the connecting rod under dynamic conditions. Experimental stress analysis (ESA) can also be used to calculate the stresses which will provide more reasons to compare the different values obtained. Now days a lot is being said about vibration study of mechanical component important role in its failure. So the study can be extended to the vibration analysis of the connecting rod. We can change the material of the connecting rod for better result. Changing the geometry, but as it was the restriction from customer end, this is not covered in this project. We can notice from the design that the factor of safety considered for the design is too large which results in the wastage of the material and also increases its cost. So the need of the hour is the optimization of the connecting rod which will lead to a revolution in the manufacturing sectors of the automobile industry.

CONCLUSIONS In order to compare the equivalent stresses due to the challenge at traction of the connecting rod’s foot, obtained through the two methods, the representation in Figure 12 was made. Using the classic method, the maximum values of the equivalent stresses in the outer and inner fibers were obtained, considering that the embedded section corresponds to the 1300 angle. It can be seen in Figure 12 that the equivalent stresses obtained with the finite element analysis in the interest zones, have approached values to those calculated with the classic method. Concomitantly, it can be observed that in the interest zones, the stress values are maximum, fact which confirms the theory.


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M. Ravichandran, R. Anbazhagan, Binu. K. Soloman & C. Jagadeesh Vikram


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