Ultrasonic-shear-wave measurement of known residual stress in aluminum

Ultrasonic-shear-wave time-of-flight measurements were made at a nominal frequency of 4 MHz on both stressed and nonstressed sample disks of 2024 Al alloy. The stressed state of the first sample was produced by shrink-fitting a plug and ring to produce a calculated 130 MPa region of uniform compression in the plug, and a concomitant nonuniform tension and compression in the ring. Time-of-flight measurement scans across sample diameters were made using a piezoelectric-shear transducer with a viscous couplant and repeated using a contactless electromagnetic-acoustic transducer. The ultrasonic results were then compared with elasticity theory, assuming the acoustoelastic relationship between sound velocity and material strain. 14 ref.--AA(US).