Evaluation of material degradation using nonlinear acoustic effect

Abstract

A method to measure the nonlinear effect of ultrasonic waves is suggested as a new approach for the effective evaluation of material degradation. In sonic wave propagation, nonlinear effect can be interpreted as the generation of higher order harmonic waves. The generation mechanism of higher order harmonic components due to nonlinear effect is firstly explained using nonlinear elasticity. Next, we attempt to measure how much higher order harmonic component was generated in the degraded material. For this purpose, a measurement system mainly based on a high power nonlinear ultrasonic signal analysis system that adopts heterodyne signal detection technique was constructed. From the results, we confirm that the nonlinear acoustic effect may be a useful technique for the evaluation of material degradation.