Fatigue life analysis of the autobody in a sports utility vehicle and its improvement using the homogenization method

Fatigue life analysis and improvement of the autobody in a sports utility vehicle (SUV) were performed. The stress distribution under unit displacement excitation was obtained by the finite element (FE) method. A bilateral track model was adopted to obtain load spectra in accordance with the vehicle reliability test. The total life of the autobody was evaluated by the nominal stress method with the assumption of a uniaxial stress state, and thus the critical regions were determined. The life of components with critical regions was further investigated on the basis of multiaxial fatigue theory. The results show that some components near to the suspension are easy to damage because they are directly subjected to impact loading from the road. It is also indicated that the result from multiaxial fatigue analysis is more reasonable than that from the nominal stress method, which was verified by experimental results. Finally, topological optimization of the spot weld location in the critical region was carried out by the homogenization method to improve its fatigue life.