加工時に生じる非弾性ひずみの影響を考慮した固有ひずみ法による残留応力推定手法の提案

DOI Web Site 被引用文献6件 参考文献1件

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  • Proposal of an Eigen-Strain Estimation for Determination of Residual Stresses Considering the Influence of Inelastic Strains by Machining or Heating

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It is indispensable to estimate welding residual stresses for assurance of structural integrity in welded structures. In order to asses a crack growth rate of an observed crack in weld zone, three-dimensional distribution of welding residual stress for whole structure have to be evaluated quantitatively, however it is impossible to estimate stress gradient in the thickness direction by conventional methods such as X-ray diffraction and the ultrasonic method. To make things worse, the estimated stresses by these methods can not be input to the FEM (Finite Element Method) model that has been used at design time for the assessment of the structural integrity. Then the eigen-strain method has been proposed. In this method, three-dimensional welding residual stresses are calculated by an elastic FEM analysis from eigen-strains those can be evaluated quantitatively by the inverse analysis from released strains measured by strain gauges while the geometric boundary condition or material properties of the object has been changed. However, inelastic strains are newly created during machining or heating, the estimation accuracy of this method becomes poor because in the eigen-strain method, the eigen-strains before and after measurements have to be the same. In this study, a calculation technique to evaluate eigen-strains included processing strains in removal process is shown, and effectiveness of this method is demonstrated numerically in the bead flush method. As a result, three-dimensional welding residual stresses for whole region were estimated accurately even if higher values of processing strain were added in the removal process.

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