Investigation of Laser-Welded EH40 Steel Joint Stress with Different Thicknesses Based on a New Heat Source Model

High-strength steel (HSS) plates are widely used due to their superior performance. However, residual stresses generated during welding can exacerbate the initiation of fatigue cracks, and the accurate prediction of residual stresses is crucial. Therefore, thermo-mechanical behavior analysis of the EH40 joints was completed based on the proposed new heat source model. The thermo-elastoplastic finite element analysis was determined via thermo-mechanical coupling with fully parametric programming. The influence of laser welding power and joint thickness on peak temperature and gradient was clarified. Meanwhile, it was found that when the laser welding power increased from 9 kW to 22.5 kW and the joint thickness increased from 6 mm to 15 mm, the distribution trend of longitudinal residual stress in the weld zone was gradually altered from a “U” shape to a “W” shape, while the transverse stress was transformed from a “U” shape to an “M” shape. It was determined that the amplitude of longitudinal and transverse stress changed along the thickness direction of nodes and was directly proportional to the peak temperature. The above results imply that the peak temperature, maximum temperature gradient longitudinal, and transverse residual stress distribution in the weld zone and its vicinity were remarkably affected by laser welding power and joint thickness.