# Shape Optimization of Two Cylinder Water Cooled Internal Combustion Engine’s Connecting Rod for Weight Reduction

DOI : 10.17577/IJERTV1IS3010

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#### Shape Optimization of Two Cylinder Water Cooled Internal Combustion Engine’s Connecting Rod for Weight Reduction

1 MR. P. M. KASUNDRA, 2 Dr. P. P. RATHOD, 3 MR. A.S.SORTHIYA

#### 2,3 Associate Professor at Government Engineering College, Bhuj, Gujarat, India,

Mechanical Engineering Department,

Abstract:-

This paper presents the design connecting rod of internal combustion engine using the Shape optimization for weight reduction. The objectives of this paper are to develop structural modelling, finite element analyse and the optimization of the connecting rod for robust design. The structure of connecting rod was modelled utilized Pro-E software and analysis was performed using Ansys 13 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 shape 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, TET 10 predicted higher maximum stress than TET 4 and maximum principal stress captured the maximum stress. The crank end is suggested to be redesign based on the Shape optimization results. The optimized connecting rod is 10% 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: Shape optimization, connecting rod, finite element analysis, minimum weight, linear static method.

1. 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. Thats 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

is optimized under a variety of initial assumptions to illustrate the use of the system. The objectives of the study are to develop structural modelling of connecting rod and perform finite element analysis of connecting rod. The main objective is to develop shape optimization model of connecting rod.

2. OPTIMIZATION APPROACH:-

The objective of optimization technique is to minimize the mass of the connecting rod and reduces the cost of production. The connecting rod subjected to tensile load at crank end, while using factor of safety 1.6 -1.7 maximum stress of the connecting rod monitored and make sure it is not over the allowable stress. The load of the connecting rod optimized is comprised of the tensile load of 86.4 kN at crank end. The optimization technique methodology flowchart is shown in Figure 1

Fig.1 Optimization Process Chart

3. FINITE ELEMENT MODELLING AND ANALYSIS:

The connecting rod is one of the most important components in the internal combustion engine (Rasekh et al., 2009). Therefore, the initial design is compared to other design before performing the optimization. A simple three- dimensional model of connecting rod was developed using Pro-E 5.0 software and finite element model was created using mesh size 1mm (Node 152873) as shown in Figure 3. 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 shape and analysis objectives. The uniformly distributed tensile load 120 on the inner surfaces of the crank end while the other part, pin end is restrain as in Figure 4. 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. In Figure 5, 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 analysed. FEA for both tensile and compressive loads were conducted. Two cases were analysed 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 86.4kN

Table.1 Properties of Connecting Rod Material (C70S6):-

 Tensile Yield Strength 550 MPa Tensile Ultimate Strength 900MPa Compressive Yield Strength 550MPa Compressive Ultimate Strength 600Mpa Poisson Ratio 0.3 Density 7850 Kg/m3 Youngs Modulus 210000 MPa

Fig. 2 3-D Model of Connecting rod

Fig.3 Mesh model of connecting rod (mesh size 1mm)

Fig.4 Load Apply on inner surface of connecting rod(120)

Fig.5 Constrain Apply on Pin End

.

Fig 6 Von Mises Stress in Compressive Load of 86400 N

Fig.7 Load Apply on inner surface of connecting rod(180)

Fig.8 Constrain Apply on Pin End.

Table 2. Comparison of Stress at Compressive load 864000 N and Tensile load 21600 N

 Sr.no Load condition Stress (MPa) 1 Crank Tensile 429.02 2 Pin Tensile 469.88 3 Crank Compressive 359.84 4 Pin Compressive 358.75
4. Optimization of Connecting Rod:-

The optimization of the connecting rod carried out using shape optimization technique. The optimization focused on the uncritical sections which need to be reduced. From the shape optimization, it is suggest the unnecessary shape and design of the connecting rod. The results of shape optimization of the connecting rod are shown in Figure 8.The main objective is to minimize the weight of the connecting rod as well as the total production cost. It can be seen that the optimized model is reduce the weight from initial design until the value converges. The implementation of these optimizations is to find out the best design and shape of the connecting rod to improve the performance and the strength especially at the critical location. The possible modification section of the optimized connecting rod is indicated in the figure.8 the section with lower value than initial value considered as the suggestion to be optimized in the new design. Table 2 shows the comparison between initial and optimize designs on max principles stress and mass of the connecting rod. The optimize connecting rod was choose as the best optimize design due to the lowest occurred stress and mass. Even though the mass of the optimize connecting rod is not the lowest, but the decision was also based on the maximum stress which is 353 MPa. Figure 10 shows the new Design of the connecting rod and mass of the connecting rod is 0.695 kg compare to initial design 0.785 kg which is 11.% lighter.

Fig.8 optimization Fig of Connecting rod (20%)

Figure 10: (a) Isometric 3D view of optimized design. Table 3 Weight optimization Table.

 Sr. Percentage Mass(kg) Optimize weight 1 10% 0.785 0.702 2 20% 0.785 0.614

Table 4 Result Comparison (20% optimized Weight)

 Sr no load Stress(MPa) 1 Original 86400 359.84 2 Optimized 86400 350.11
5. CONCLUSION:

The modelling of connecting rod and FE Analysis has been presented. Shape optimization were analysed to the connecting rod and according to the results, it can be concluded that the weight of optimized design is 20% lighter and maximum stress also predicted lower than the initial design of connecting rod. The results clearly indicate that the new design much lighter and has more strength than initial design of connecting rod. Material optimization approach will be considered for future research.

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