Acoustoelastic imaging of stress fields

An acoustic technique for measuring inhomogeneous stress in externally loaded solids is described. This method requires a measurement of transit time of a longitudinal acoustic wave through a stressed thin metal specimen using a small‐diameter water‐coupled acoustic transducer. The transducer is mechanically scanned over the surface of the sample by a computer‐controlled system and transit‐time measurements are made at discrete points. Predictions of velocity variation with stress using the theory of nonlinear elasticity are employed to relate the acoustic transit time to stress levels at field points in the specimen. Stress‐field contour plots are developed and compared with theoretical results. Samples investigated include uniaxial tension specimens of aluminum and steel, an aluminum plate containing a central hole, and a double edge‐notched aluminum panel, both under far‐field tension.