STRESS-DISTRIBUTION DETERMINATION IN ISOTROPIC - MATERIALS VIA INVERSION OF ULTRASONIC RAYLEIGH-WAVE DISPERSION DATA

The possibility of using measurements of the dispersion of Rayleigh (s urface) waves propagating on pre-stressed, initially isotropic materia ls to determine the surface stress and gradients in such materials is analytically investigated. Using a first-order perturbation formula fo r the description of the acoustoelastic effect on Rayleigh waves, it i s shown that knowledge of the frequency dependence of the change in ph ase (or phase velocity) of the Rayleigh wave after propagating a certa in distance can, in theory, be used to determine the stress level at t he surface of the medium as well as its derivatives up to a given orde r. Basic questions concerning the uniqueness of the inversion are addr essed, and a formal method of inverting inhomogeneous bi-axial stress distributions is presented. The effect of the range of frequencies inc luded in the measurements is discussed and illustrated with a numerica l example. Copyright (C) 1996 Elsevier Science Ltd.