The effect of normal and shear stresses on wave propagation through a fracture

A procedure is developed to measure the reflection and transmission of compression and shear waves across an interface between two blocks of aluminum with applied normal and shear stresses. This is accomplished by rotating the blocks relative to the applied force so the force vector has a normal and shear component. The measurements were taken at various different loads on blocks having no angle of rotation, with 5° and 10° angles of rotation. Strong qualitative comparisons were found that increasing the angle of rotation increased the amount of compression wave conversion to shear waves. The magnitude of the transmitted compression wave was much larger than predicted by current theory. This is explained by the concept of the actual area of contact and the stiffness distribution. Using these concepts quantitative comparisons are made.