Determination of plastic deformation with variable ultrasonic excitation positions

Abstract

For highly stressed mechanical components, the information about a beginning plastic deformation is of enormous importance. Therefore, nondestructive testing and structural health monitoring techniques are essential to examine components and to make statements about the mechanical integrity. In this work, the dislocation theory was extended and combined with ultrasonic wave excitation to obtain a dislocation description in isotropic materials. In the analytical derivation, the ultrasonic longitudinal waves were sent at different angles of attack relative to the uniaxial tensile load. The derived nonlinearity coefficients enabled the investigation as a function of these angles. The evaluated coefficient behaviour allows statements about the position of the ultrasonic excitation relative to the tensile load. Furthermore, a signature could be derived from which the degree of plasticity can be determined if a reference measurement is available. The newly derived coefficients and their behaviour make it possible to efficiently detect the beginning plastic deformation and to predict the position of the applied load vector.