き裂先端部近傍の変位場を用いた混合モード応力拡大係数評価法

概要

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This paper proposes a new method for evaluating mode I, mode II and mixed-mode stress intensity factors from displacement fields around a crack tip obtained by experimental or numerical methods. Using two displacement components on an orthogonal coordinate system, not only stress intensity factors but crack tip location, higher order terms in the series expansion of displacement fields and rigid body displacement components are determined simultaneously using nonlinear least-squares based on Newton-Raphson method. The validity is demonstrated by applying the proposed method to mixed-mode displacement fields obtained by digital image correlation, elasto-plastic displacement fields obtained by finite element method, and displacement fields around a fatigue crack obtained by electronic speckle pattern interferometry. The results show that the stress intensity factors are evaluated accurately from the displacement fields by the proposed method. Furthermore, they can be determined even if the material exhibits small scale plastic deformation. As stress intensity factors can be evaluated easily and accurately, it is expected that the proposed method can be applied to various fracture problems during experimental and numerical evaluation of structural components.
2006-07-25