Surface Acoustic Wave Measurements of Surface Cracks in Ceramics

摘要

An investigation of scattering from surface cracks has been conducted. In particular, the change in the reflection coefficient of a Rayleigh wave incident on a surface indentation crack has been measured as the sample is stressed to fracture. The acoustic measurements have been correlated with the stable crack extension that precedes final failure. The crack extension behavior in as-intended and annealed specimens was found to be appreciably different. The cracks in the annealed samples exhibited partial crack closure but little stable extension, whereas the cracks in the as-indented samples displayed both crack closure and irreversible crack growth. This behavior has been rationalized by invoking concepts based upon the residual stresses created by indentation. (Author)