Estimation of Fatigue Limit for Aluminum Alloy Laser Welds Based on Dissipated Energy

Abstract Background Laser welding has a faster processing speed than other welding techniques. However, defects can occur under various welding conditions, and high safety and reliability are required for applying laser welding to actual mechanical structures. Objective This study focused on estimating the fatigue limit by dissipated energy which is the energy loss resulting in fatigue damage owing to localized plastic deformation. This study was conducted to determine whether the fatigue limit of aluminum alloy laser welds can be rapidly estimated using the dissipated energy. Methods In a test with a stepwise increase in stress amplitude, the dissipated energy and the strain were measured by infrared thermography and digital image correlation from displacement measurements with a visible camera, respectively. In the fatigue limit estimation using dissipated energy, the fatigue limit is determined by the empirical rule that the stress amplitude with increasing the dissipated energy is the estimated fatigue limit. Results Laser welds exhibited the highest dissipated energy at the fracture origin of the joint. Therefore, the crack initiation point of welded joints can be visualized by measuring the dissipated energy. If the boundary value of both groups in the domain decomposition method using the least-squares approximation is the estimated fatigue limit, the estimated fatigue limits for the aluminum alloy laser welds and those base material specimens are almost consistent with the actual fatigue limits. Conclusions The fatigue limit estimation using the dissipated energy can be applied to aluminum alloy laser welds.