FATIGUE ANALYSIS OF LASER WELDED LAP JOINTS

Metal fabrication industries have shown increased interest in laser welding of sheet steel products in recent years. A lap joint is often selected because this joint configuration allows quality welding with less restrictive joint dimensional tolerances. Recent experiments in the fatigue performance of laser welded lap joints show that fatigue performance is dependent on weld pattern. This investigation establishes a technique for predicting the fatigue response of laser welded lap joints. A static stress analysis (Goland and Reissner) is combined with a cyclic stress-strain analysis (Nuber) to establish a model for calculating joint stress under cyclic loading. The model accounts for about 3/4 of the reduction in fatigue stress when comparing laser welded lap joints to unwelded, smooth material. The remaining 1/4 reduction is attributed to residual stress and/or material property alterations resulting from welding.