Study of the Acoustoelastic Effect in an Anisotropic Plastically Deformed Material

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The paper discusses the dependence of shear elastic waves birefringence on applied mechanical stress and preliminary plastic deformation of a material. A technique involving precision acoustic pulse echo measurements and software processing of the received time scan of signals from a piezoelectric transducer is described, which makes it possible to determine the propagation time of elastic waves with an accuracy of at least 0.5 ns. The dependences of the intrinsic acoustic birefringence and the acoustoelastic coefficient on plastic deformation in a carbon steel sample are investigated. After 12% plastic deformation of the sample, the average value of the acoustoelastic coefficient changes by 30%; the average value of the intrinsic acoustic birefringence changes by 60%. A correlation is observed between the intrinsic acoustic birefringence and the acoustoelastic coefficient. Using the theory of elastic wave propagation in a solid, the obtained experimental data are explained by manifestation of the acoustoelastic effect and the influence of the structural state on the effective elastic properties. The effect of plastic deformation on the accuracy of determining stress is qualitatively assessed. The error in determining stress during 1% plastic deformation is about 40 MPa, i.e., 13% of the yield strength for this material in the initial state.