A Method for Measurement of Crack Opening Displacement of Fast Propagating Crack in Araldite B

The method of crack opening displacement (COD) has been used to obtain the energy release rate of fast propagating cracks just before and just after crack bifurcation. In the method, COD is measured on the microscopic photographs of the cracks. But, in the case of cracks in Araldite B, the corner made by a crack surface and a specimen surface is chipped out from the specimen, then, it is often difficult to measure CODs from the photographs of the cracks. The present study shows a method to measure the COD in the region where COD is difficult to be measured directly on the photograph. The accuracy of the method of the present paper is good enough that the measured CODs can give the energy release rate of the crack at bifurcation with the accuracy of about 7%.