混合モード衝撃下における中央切欠円板の動的エネルギー解放率の評価( 材料・構造の衝撃問題)

A new test method using diametral impacts of center-notched disk specimens is investigated numerically for measuring the dynamic fracture toughness under pure mode I, pure mode II and mixed-mode loadings. Changing the inclination angle θ of the center-notch relative to the line of loading, the impact fracture tests can be performed under the conditions in the arbitrary ratios of mode I to mode II loadings. Especially, pure mode I and pure mode II tests are achieved for (θ=0°) and θa23°(α/R=0.5) respectively, where 2α is the center notch length and R radius of the disk specimen. The dynamic energy release rates under the mdxed-mode impacts are easily evaluated from the mode I and II components of stress intensity factors, which are computed from the convolution integrals of the step-response functions. The step-response functions have been obtained by the finite element analyses for the specimen. Using this method. we can evaluate the dynamic energy release rates under the mixed-mode loading precisely.