Fatigue Safety Design of Automotive Rear Sub-frame by Using CAE (Computer Aided Engineering) Static Analysis

Reducing vehicle weight and developing alternative materials, like aluminum and magnesium alloys, are current topics of interest in the automobile industries. Therefore, in the present study, the structure analysis of a rear sub-frame made by aluminum alloys (AA6061), with a tensile strength of 310 MPa, was performed using computer aided engineering (CAE) to investigate the lightweight design process. The reference material for the rear sub-frame was the commonly used SAPH440 steel. The maximum von Mises stresses obtained from the simulated strength analysis were normalized as the fatigue limit, and converted to the weight ratios of the same type as the fatigue safety factor suggested and named like that in present study. From these, it was suggested that the fatigue properties could be predicted from this static CAE simulation. A weight reduction ratio of 25% was achieved between the SAPH440 and AA6061 model. It was a useful method to satisfy the fatigue safety design by using a simple static analysis and weight factors.