摘要:
A method and system for microstructural evaluation and degradation evaluation of an object (14) are provided. The method comprises insonifying at least one subvolume of the object with ultrasonic energy at a fundamental frequency and acquiring receive energy from the object at the fundamental frequency and at least one harmonic frequency thereof. A nonlinearity parameter is determined using the receive energy. The nonlinearity parameter is then used to determine a grain size for the subvolume of the object and a variation of the grain size within the object. The nonlinearity parameter is also used to determine fatigue damage or residual stress.