Techniques for Contact Considerations in Fatigue Life Estimations of Automotive Structures 2013-01-1201

Contacts or interactions commonly exist between adjacent components in automotive structures, and most of the time they dominate stress status of the components. However, when the routine pseudo stress approach is employed in fatigue life estimations, simulating contacts present special challenges. This may result in coarse stress status and corresponding coarser fatigue life estimations at the contact locations. In this paper, concept, development and procedures of two techniques to consider contacts in fatigue life estimations of automotive structures are described in detail. One is still pseudo stress approach based, but employs additional 1-D connection elements to simulate contacts. The other is nonlinear stress approach based, but equivalent constantly repeating cyclic critical load cases are introduced and utilized. The contacts are simulated by interface setup provided in the software. The equivalent constantly repeating cyclic critical load cases are generated by the equal damage rule. Fatigue analyses using the routine pseudo stress approach, the approach with contacts simulated by 1-D connection elements and the approach with nonlinear stress approach have been conducted and compared for an example of a cargo box on pickup truck. Correlations between the CAE estimations and proving ground test results are also included and discussed. It is concluded that both the techniques with contact considerations can predict not only the correct fatigue potential failure locations, but also better fatigue life estimations that have good correlations to test results.