Fatigue Analysis of Lower Control Arm of an Sport Utility Vehicle

Abstract

This paper focuses on fatigue analysis of lower control arm of a Sport utility vehicle. Here the author is trying to analyze fatigue performance of existing material of lower control arm for static and lateral load. Then the weight reduction for the same model is done. Material selection for reduced model is done and checked for its fatigue performance for static load and lateral load. Analysis for the above is done in ANSYS software.

Introduction

The suspension system is one of the most important components of vehicle, which directly affects the safety, performance, noise level and style of it.

The vehicle suspension system is responsible for driving comfort and safety as the suspension carries the vehicle body and transmits all forces between body and road. Fatigue performance of the vehicle suspension system has received much attention in recent years due to its effect on life time of different parts, especially lower suspension arm. This can be increased by optimizing and design variables of automotive lower arm suspension system as well as its materials metallurgical parameters.

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The main objective of this study is to analyze the fatigue performance of existing lower control arm of an SUV. Design optimization for the same model is done by reducing the weight and changing the material and is checked for its safety.

Methodology

The model of lower control arm is done in SOLIDWORKS software. The model is imported to ANSYS software. AISI 1018 material is first applied to the model and static load is applied to analyze for its fatigue performance.

Fatigue performance of the model is also checked for its lateral force during cornering. Later the weight reduction of the model is done in SOLIDWORK and is imported to ANSYS. AISI 4130 material is applied for the reduced model and fatigue analysis is done for static load and lateral load.

Material Properties

AISI 1018 is chosen for its cost-effectiveness, while AISI 4130 is selected for its lightweight and performance-enhancing properties.

Force Calculation

• Under static condition:

1) Weight of the vehicle=m= 2440KG

Weight of the vehicle = 2080KG

Assume weight of person= 6*60=360KG

2) Weight of the vehicle at its center of gravity

W=m*g

=2440*9.81

W =23937 N

The loads on front and rear axles are found by using the equilibrium equations

(W)F =(W*LR)/L

(W)F = (23937*1185)/2700

(W)F =10506 N

(W)R = (W*LF)/L

(W)R = (23937*1515)/2700

(W)R= 13432 N

Load on front wheel is given by

= (10506/2) =5253 N

For further analysis we consider load on front wheel i.e. 5253 N acting on front lower suspension arms.

• Lateral Force:

Lateral force is calculated using formula

m=535 Kg, r=5.6 m

V=8.33m/s

Fy = mv2 /r

Fy= (535*8.332)/5.6

Fy = 6629.118 N

Finite Element Analysis

Finite Element Analysis is the best method to analyze the problem with virtual way. It caters to all the prerequisites of industry ready product with nearest optimal solution with respect to optimization.

Static Structural Analysis

Every problem whenever allowed to be solved for finite element analysis, first step it would be subjected to is a case of static structural analysis. Further, the work will be subjected to various other types of analysis.

Loading Conditions

The lower control arm is subjected to static load and lateral load. As per the calculation static load is 5253N and lateral load is 6629N.

Boundary Conditions

The lower control arm has three joints, where two joints are bushed to sub frame and another joint is housed to wheel with bearings. The lower control arm is applied with AISI 1018 material and checked for its stress concentration and deformation.

Optimization

Optimization is a common word currently in used CAE industry and it does save lot of amount in terms of material, design and quality aspect.

Conclusion

The weight of the lower control arm was found to be 8kg on optimizing the weight of lower control arm to 5kg. AISI1018 material is applied to model and is checked for its stress concentration and deformation. Yield strength after the analysis was found to be 314Mpa. AISI 4130 was applied to optimized model and yield strength was found to be 416Mpa.