OS10F042 Boundary Element Inverse Analysis with Regularization for Estimating Welding Residual Stress Distribution in Butt-Welded Plate

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  • OHTAKE Yasuhiro
    Department Numerical Engineering of Research Laboratory, IHI Corporation
  • KUBO Shiro
    Department of Mechanical Engineering, Osaka University

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This paper deals with an inverse problem for estimating welding residual stresses in a butt-welded plate from measured data. The welding residual stresses in the butt-welded plate are caused by inherent strains. Thus, the welding residual stresses are calculated from the inherent strains in the stress analysis, if the inherent strains are estimated from measurement data by inverse problem analysis. In previous papers, a method of thermo-elastic boundary element inverse analysis was proposed to estimate the inherent strains in the butt-welded plate. It was found in the papers that the accuracy of the evaluated inherent strain in the butt-welded plate was low when the location of the measurement points was far from the welding line or the number of measurement points was small. Thus, Tikhonov's regularization method was used to stabilize the solutions in the examination and to improve the accuracy of the evaluated values of the inherent strains in the butt-welded plate. However, the applicability of Tikhonov's regularization method to various kinds of inherent strain distributions remains to be established. This paper examines how the shape of the inherent strain distribution affects the accuracy of the estimated results. Trapezoidal and triangular inherent strain distributions were assumed in each analysis model of the butt-welded plate. Numerical simulations were conducted for those analysis models. In the simulations, measurement errors were included in stresses at measurement points. From all calculation results, it was found that the inherent strains in the butt-welded plate were evaluated in high accuracy from a few measured data by using Tikhonov's method regardless of the shape of the inherent strain distribution. Accordingly, it became clear that the proposed boundary element inverse analysis with Tikhonov's method was useful in evaluating the residual stresses in the butt-welded plate.

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