A simple measuring method of welding inherent deformation using inverse analysis

During welding, deformation is produced as an unavoidable consequence. Inherent deformation method, in which the inherent deformation is introduced into the elastic FEM as the initial strain is one of the effective methods to predict the welding deformation of large structures. When the weld length is long enough, inherent deformation is mainly governed by the heat input Q and the thickness of plate h. However, in assembling process of thin plates, the short weld with the length between 50-200mm is also often used especially for thin structures to reduce distortion. In this case, inherent deformation is influenced not only by the heat input but also by the length of weld. In this research, an efficient measuring method to estimate inherent deformation of plate under bead welding using inverse analysis is developed. Based on this inverse analysis, the inherent deformation is estimated by measuring the three-dimensional coordinates at small number of selected points. Further, using the estimated inherent deformation, the welding deformation of a plate is predicted as the forward analysis. The distribution characteristic of inherent deformation in short weld is also discussed in this paper.