Principal Stress Measurement by Propagation Velocity Estimation at No Stress Using Surface Anisotropy in Surface SH Wave Acoustoelasticity

The surface SH-wave acoustoelasticity is one of the acoustoelastic methods, which is a stress measurement method based on the phenomenon that the propagation velocity of elastic waves changes depending on the stress state. Surface SH-wave acoustoelasticity can measure the principal stress difference from the difference in propagation velocities of surface SH waves propagating in two orthogonal directions, but it cannot measure the principal stress itself. However, if the propagation velocity of the surface SH-wave in the stress-free state is known, it is possible to measure the principal stress in the surface SH-wave acoustoelastic method. Therefore, in this study, we attempted to measure the principal stress using the surface SH-wave acoustoelasticity by estimating the propagation velocity in the stress-free state using surface anisotropy, which is a stress-independent parameter of the surface structure. Experimental results demonstrated the possibility of using surface anisotropy to estimate the propagation velocity in the stress-free state and measure the principal stress within ±10 MPa as well as the principal stress difference.