Fatigue Life Reliability and Robustness of Aluminum Car Body U-Box Structure with Self-Piercing Riveted Joints

A fatigue life reliability and robustness study on an aluminum U-box structure representing a typical car body joint with self-piercing rivets is described that combines CAE analysis using a finite element model with analytical reliability and robustness (AR & R) numerical techniques. The application of the AR & R process involved is first explained. Then the aspects of U-box modeling and a computer design of experiments are discussed. Also, the analytical results obtained from computer analysis are given that include the main effects and sensitivities of control factors that affect the design and the main interaction effects. Based on the main effects plots and sensitivities, the optimal U-box design is described to maximize the fatigue life of the structure for various fatigue damage parameter levels. Finally, the fatigue life reliability and robustness is described and it is shown that certain combinations of gage thicknesses are required for the optimum U-box design where the most robust life response occurred at high fatigue damage parameter values and high load.