Evaluation of Stress Intensity Factor for Cylindrically Anisotropic Material under Mode I, II and III Loadings by Caustics Method

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The stress intensity factors under mode I, II and III loadings are measured by caustics method, and the effect of those loading modes on the measurement accuracy is experimentally and numerically examined. Furthermore, a numerical method based on the 3D finite element method (3D-FEM), which can directly simulate the caustic images, is proposed. As a result, it is found that the minimum initial curve radius r_o^min obtained in this study depends on the type of loading that is of mode I or mode II. In the case of modeIII loading, however, the measured value of K agrees with the theoretical one regardless of the change of the initial curve radius r_o. And the simulated results are in good agreement with the experimental images.On the other hand, the caustics method is examined for an orthotropic Japanese cypress material under mode I loading by using a coating technique, and the results are compared with those of 3D-FEM. As a result, it is found that the determination of K_I using caustics method is valid for radial, tangential and transverse direction, when the initial curve radius r_o is larger than the minimum initial curve radius r_o^min obtained by this study, and the simulated results are nearly in agreement with the experimental images. Furthermore, there was a close correlation between the size of 3D-stress field and out-of-plane displacement near the notch tip.