Stress Intensity Factors of a Mixed-Mode Interface Crack by Speckle Photography and Finite Element Analysis.

Abstract

The stress-intensity factors of a mixed-mode interface crack were measured by a 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 the dissimilar materials. The displacement along the crack lines at the free surface was measured by the speckle photography. The K1 and K11 values were determined by a least squares method using displacement data along the crack lines. The three-dimensional finite element analysis was carried out on the same specimen. The complex stress-intensity factor K associated with an elastic interface crack was discussed from three different approaches : virtual crack extension method, modified crack closure integral and displacement extrapolation. An accuracy of stress intensity factors obtained by the speckle photography was discussed by comparison of results obtained by the finite element analysis.