Artificial thermal strain method: A novel approach for the analysis and fast prediction of the thermal distortion

Understanding the thermal distortion induced by arc welding, laser, or induction heating is a challenge in academia and industry. This study presents the artificial thermal strain (ATS) method which was modified from strain as boundary (SDB) method, based on inherent strain theory, and its equivalent mechanical model to analyse the distortion mechanism. Experiments and numerical simulation of multi-pass laser bending of alloy 304 L were conducted, wherein the various kinds of inherent strain distributions and the boundary of effective inherent strain were examined. Further, the mechanism of bending angle reduction under lower line energy was evaluated by considering the inherent strain redistribution at each pass. The results indicate that the bending angle reduction in multi-pass laser scanning is determined by the size of the inherent strain area at low line energy. Moreover, a simplified plastic finite element model based on the ATS method was developed to predict the welding deformation of plate curvature induced by parallel laser scanning. Additionally, only 210 elements and 7 s was cost to perform with the deformation analysis, which indicates that the ATS model is effective in predicting thermal distortion. Meanwhile, the ATS method can provide theoretical guidance and fast prediction for the actual thermal processing in large welded structure and additive manufacturing in the future.