Effect of Extraction Direction on Measurement of Stress Intensity Factor for Japanese Cypress Material by Caustics Method

摘要

The experimental method of caustics is a useful technique for the determination of the stress intensity factor K. In the case of wood, however, the caustic image can be not obtained clearly because of the roughness of surface. In this study, the caustics method is examined for an orthotropic Japanese cypress material under mode I loading by using a coating technique. Furthermore, a numerical method based on the 3D finite element method (3D-FEM), which can directly simulate the caustic image, is proposed. As a result, it is found that the minimum initial curve radius (r{sub}0){sup}(min) obtained in this study becomes small in comparison with isotropic materials, and the simulated results are nearly in agreement with the experimental images.