Due to several indeterminate factors, the assessment of the durability performance of a vehicle body is traditionally accomplished using test methods. An analytical fatigue life prediction method (four-step durability process) that relies mainly on numerical techniques is described in this paper. The four steps comprising this process include the identification of high stress regions, recognizing the critical load types, determining the critical road events and calculation of fatigue life. In addition to utilizing a general purpose finite element analysis software for the application of the Inertia Relief technique and a previously developed fatigue analysis program, two customized programs have been developed to streamline the process into an integrated, user-friendly tool. The process is demonstrated using a full body, finite element model.
Fatigue life can be analytically predicted using the above-mentioned methodology when detailed local design information and correct body loads are available. However, up-front engineering requires durability assessment before this information is readily available. This motivates a root-cause analysis of durability problems which leads to the development of a set of generic design guidelines. These guidelines can be used in developing body design in the up-front phase.