Stress Analysis of Mixed-Mode Crack by Speckle Photography

Abstract

The displacement around the crack tip of homogeneous and dissimilar materials was measured by speckle photography. A CNS specimen was employed to measure the displacement under the various mixed-mode loading. The displacement data obtained by speckle photography were not as smooth as that obtained by the finite element analysis. A large error arose in the evaluation of stress-intensity factors from the raw displacement data. Therefore, the displacement data were smoothed by 2-D fast Fourier transform and the least squares method. Then, stress-intensity factors of asymptotic solution derived by Sun and Jih were evaluated using the displacement data obtained from speckle photography by the least squares method. The stress-strain field near the crack tip evaluated by using the asymptotic solution was in good agreement with that of finite element analysis.