Simulation and experimentation of nonlinear Rayleigh wave inspection of fatigue surface microcracks

The nonlinear ultrasonic inspection is a method that the higher harmonics generated by the interaction of ultrasound and fatigue damage, which is used to evaluate material properties. In this paper, the difference between experimental measurement and simulation analysis was discussed, based on the simulation and experimentation. The results of simulation and experimentation both show that the nonlinear coefficient increases, reaches the maximum near the wavelength of 0.3λ, and then decreases to a certain extent and stabilizes. The difference between the simulation and the experimentation is that the crack depth corresponding to the maxima of the nonlinear coefficient and the relative variation between the nonlinear coefficient and the peak are different. And the causes of the difference were analyzed according to the simulation results and experimental measurements, which provides a reliable basis for the further study of the evaluation mechanism of the nonlinear Rayleigh wave.