The mechanics properties of a certain automobile rear axle shell were studied and a large displacement, large strain elastoplastic finite element analysis was carried out. and the followings were obtained: the load-displacement curve at loading point, elastoplastic strain-load curve at the maximum stress point, elastoplastic stress-load curve in dangerous cross-section, and the yielding load at which the dangerous cross-section overall yield. The results show that elastoplastic finite element simulation results are much closer to the experimental corresponding results. Through optimization design in manufacturing system, the weight of the rear axle shell is greatly reduced as compared with the original design. Optimal design not only saves materials and reduces cost, but also greatly reduces the design time. The calculation results provide the necessary data for automobile rear axle design, strength evaluation and fatigue life estimate.

Two methods acquiring p-S-N curve for machine parts are given, namely directly searching out the p-S-N curve of the material from material database and using the idealized p-S-N curve. Reliability estimation methods of fatigue life of machine parts are derived under uniaxial constant amplitude load. Two kinds of circumstances (fixed stress and probabilistic stress) and two kinds of stress cycles (reversed cycle and unsymmetric reversed cycle) are considered. An iteration method is presented and the corresponding computer program is developed for estimating reliable life of machine parts. The engineering application results show that the calculated results are closer to experimental results. The suggested method can be convenient to fatigue reliability design of machine parts. It has good stimulative effect on popularization and application of existing anti-fatigue design method for machine parts, and high value of engineering application.