A Practical Design Process to Optimize Fatigue Performance for Chassis Components 2009-01-1227

In the chassis component design, meeting fatigue life requirements with minimum weight is one of critical tasks. Currently chassis components are optimized for minimizing the weight while meeting design requirements of stiffness and strength with topology and shape optimization. In early design phase, topology optimization is utilized to create the optimal material layout for the component within the given design space and constraints. Then shape optimization can be used to determine the final design shape with minimum weight. Recent technology advance makes automotive OEMs to shift to durability duty cycle as one of their component design specifications in order to design an efficient component. However, the duty cycle counts or fatigue life requirement can not be easily integrated with the current design optimization process. It is time consuming and involving numerous design iterations to directly consider the fatigue life requirement in the design optimization. In this paper we propose an effective optimization process to include the effect of the fatigue life requirement in shape optimization based on our current design optimization process. Our approach is to assess the Target Fatigue Life Equivalent Stress levels based on the fatigue life requirement, then defining them as design constraints in shape optimization to determine the final design shape. Thus we eliminate the fatigue calculations during the numerical iterations in shape optimization. The proposed design process is able to eliminate the “Trial and Error” approach for refining the design shape and provide design engineers with precise direction to where and how much the design changes should be made. An example is presented to demonstrate the efficiency of the proposed design optimization process.