New Spot Weld Fatigue Criteria and Fatigue Data Editing Technique

Abstract

Firstly, this paper presents new criteria for fatigue life prediction of spot weld. It starts with the presentation of the database used for this study. Then, two criteria for spot weld life prediction, based respectively on mechanical damage and fracture mechanics, are developed through a nonlinear multiple regression method of optimization. These criteria considerably improve the correlation between numerical and test results. Finally, an application of this study is led on a fatigue test of a full body-in-white with about 4000 spot welds.Secondly, this paper presents new fatigue data editing techniques. Existing fatigue data editing techniques are tested on a full body-in-white fatigue lifetime calculation. The load applied to the biw is complex, with several load application locations and directions. All the critical point have to be detected with the new strength signal. Existing fatigue data editing techniques are adapted and tested on a full body-in-white fatigue calculation. Since the time discretization point number of the new load signal obtained from the literature techniques is too high, two new fatigue data editing technique are developed and tested on a full body-in-white durability calculation. The damage values damages at both spot weld and sheet metal, predicted with these new simplified load signals, are close to the damages values calculated with the full load signal. In addition, the number of time discretization points is low, at least 4.2 inferior to the time discretization point number obtained with existing techniques.