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A 3-dimensional deformation (in-plane and out-of-plane deformation) measurement method is developed using digital cameras, which require no special equipment. This method is a non-contact method and it can sequentially measure over the entire photographed image. Furthermore, since image analysis is based on the technique of image matching, the method is applicable even when measuring deformation is large. In addition, since it is possible to use all pixels as measuring points, the number of available measuring points at one time is the same as the number of effective pixels of the camera. In this study, proposed method is applied to the sequential measurement of displacement under the strong lighting levels in arc welding. Through the comparison of the results measured by a 3-dimensional shape measurement system (LAT-3D) using a laser displacement gauge and digital caliper, quantitative validity of the proposed method is also verified.

Heavy thick steel plate is used for pipes and also ship structures, and multi-pass welding is usually adopted for the welding. Because of the heavy thickness, residual stress plays an important role, particularly in crack propagation. Implicit Finite Element Method (FEM) is often used as a welding analysis method to examine the residual stress of the welded plate, but it is not easily applied to multi-pass welding problems with tens of thousands of degrees of freedom, because of the huge computational time and memory consumption. Alternatively, it is possible to simulate the residual stress in shorter time with lower memory consumption by using Idealized Explicit Finite Element Method developed by the authors. Moreover, the computational time can be shortened by using Idealized Explicit FEM using a Graphics Processing Unit (GPU). In this research, Idealized Explicit FEM parallelized using a GPU is applied to the analysis of the residual stresses of the multi-pass welding joint of a pipe structure made of heavy thick steel plate. As the result, the residual stress simulated by the Idealized Explicit FEM corresponds to the measured residual stress. Furthermore, it is found that the grouping method may affect to the residual stress distribution.