Kenji MACHIDA

Science University of Tokyo, 2641, Yamazaki, Noda-shi, Chiba, 278 Japan

(Received August 26, 1996; Accepted December 26, 1996)

The image-processing system based on a two-dimensional Fourier transform is presented for the analysis of Young's fringes pattern created from a double-exposure speckle photograph. The fringe spacing and orientation are determined using only one Young's fringes pattern without any other diffraction halo patterns. The stress-intensity factors of a mixed-mode interface crack were measured by speckle photography. A compact normal and shear specimen with an interface crack was employed. This specimen enables us to carry out the experiment under various kinds of mixed-mode loading. A steel and an epoxy resin were used as dissimilar materials. The displacement along the crack lines at the free surface was measured by speckle photography. The K_I and K_II values were determined by a least squares method using displacement data along the crack lines. Three-dimensional finite element analysis was carried out on the same specimen. An accuracy of stress intensity factors obtained by the speckle photography was discussed by comparison of results obtained by the finite element analysis.

Key words : speckle photography, Young's fringe, two-dimensional Fourier transform, finite element method, stress intensity factor, interface crack, mixed mode, displacement extrapolation

*Presented at 1996 International Workshop on Interferometory (IWI '96), August 27-29, Wako, Saitama, Japan.