Prediction of Welding Deformation and Residual Stress by Elastic FEM Based on Inherent Strain (Report Ⅰ): Mechanism of Inherent Strain Production

摘要

The welding residual stress and the distortion are considered to be produced by the inherent strain. The plastic strain in bead welding computed through the Thermal-Elastic-Plastic analysis is an ideal example of the inherent strain, since there is no glove which may introduce additional mismatch. Such inherent strain produced in the welding process is primarily determined by the highest temperature reached and the constraint at each point. Thus, the mechanical phenomena in the bead welding process are closely analyzed by the Thermal-Elastic-Plastic FEM and the mechanism in which the inherent strain is produced is investigated from the aspect of the highest temperature reached and the constraint. Further, based on the knowledge obtained through the study, simple formulae to calculate the inherent strain distribution are proposed. Using the inherent strain given by the formulae, the welding residual stress and the distortion can be predicted by an Elastic FEM analysis.