Acoustoelastic determination of residual stress by measurement of resonance peaks and phase shifts

We made ultrasonic measurements of residual stress in a well-characterized specimen: an aluminum shrink-fit plate. We used various electromagnetic-acoustic transducers (EMATs) to generate and receive both shear and longitudinal waves. From the difference of velocities of orthogonally polarized shear waves (acoustic birefringence) we obtained the difference of principal stresses. From ratios of velocities of longitudinal and shear waves we obtained the sum of principal stresses. From the sum and difference we determined the principal stresses and found good agreement with theory. To obtain our ultrasonic data, we used two different techniques: measurement of resonant frequencies and phase shifts. We compared these methods both for accuracy and ease of implementation. For our experiments, phase shift measurements were superior.