STUDY ON SOLIDIFICATION CRACKING OF LASER DISSIMILAR WELDED JOINTS BY USING IN-SITU OBSERVATION AND NUMERICAL SIMULATION

This study is aimed at developing a systematic method for evaluation and prediction of solidification cracking in laser dissimilar welded joints (laser DWJ). The initiation of solidification cracking was observed directly by using a high speed camera during U-type hot cracking testing while laser welding. The high temperature ductility curves were obtained based on the local critical strains of the solidification cracks, measured by investigating each frame of the observation film. The distribution of residual liquid metal during solidification was investigated by using both high magnification and in-situ observation. Moreover, material properties at the elevated temperatures were measured by using a developed tensile test. The weld strain during laser welding was calculated by 3D finite element analysis by using the material properties obtained. Consequently, all the results helped to provide a comprehensive understanding of solidification cracking in laser DWJ.