USE OF OFF-AXIS SH-WAVES TO MAP OUT 3-DIMENSIONAL STRESSES IN ORTHOTROPIC PLATES

An acoustical birefringence method is proposed to measure thickness-varying stresses in slightly orthotropic plates. In this method, off-axis SH-waves at various angles of incidence are propagated in the body's planes of material symmetry, and pass through a common point. The weighted sum of times-of-flight of waves propagating in one plane is subtracted from the corresponding sum in the orthogonal plane. To a first approximation, this difference is the local birefringence at the common point and as such can be related to components of the stress tensor there. The ability of the method to map out simple stress concentrations was tested analytically. Reasonably good spatial resolution was obtained, but the method underestimated the magnitudes.