Study of Stress-Analyzing System by Speckle Photography

Abstract

The point-by-point measurement of in-plane displacement was conducted by the pointwise filtering approach of speckle photography. Young's fringes analysis is based on the 2D fast Fourier transform (FFT) and bounded Newton-Raphson algorithm. Many Young's fringes patterns were taken by a charge coupled devices (CCD) and analyzed by the image-processing system developed in my laboratory. The displacement obtained using speckle photography is not as smooth as that obtained by the finite-element analysis. Therefore, the displacement data were smoothed by 2D FFT and the least-squares method. Then, stress-intensity factors of asymptotic solution derived by Sun and Jih were evaluated using the displacement data obtained using speckle photography by applying the least-squares method. From the nodal displacement calculated using the stress-intensity factor, the stress-strain analysis was conducted by using the latter algorithm of the finite element method (FEM). Finally, the stress-strain relationship was discussed in terms of comparison between the speckle photography and finite-element analysis.