Non-linear property analysis of deformed metallic components using a longitudinal critically refracted wave

In order to apply the ultrasonic non-linear coefficient for non-destructive detection in actual engineering applications, the non-linear property of deformed metallic components is studied using a longitudinal critically refracted (LCR) wave. Firstly, dog-bone components are loaded in two different modes, which ensures that components with different stress states and the corresponding macroscopic deformation of components are measured. Then, online and offline non-linear ultrasonic experiments are conducted on pre-stress components and the relative non-linear coefficient is calculated. Experimental results indicate that the relative non-linear coefficient and the deformation state monotonically increase with stress levels and they have similar variation trends in both online and offline measurements. Furthermore, Pearson correlation coefficients between the relative non-linear coefficient and the macroscopic deformation are 0.988 and 0.9876 for two types of experiment, which indicates that they have a strong correlation relationship. The power-exponent function is applied to establish this dependence relationship. The index coefficients are 1.276 and 0.7305, respectively, and the difference may be due to the microstructure disparity caused by the different loading modes. Therefore, the interrelationship between the relative non-linear coefficient and the macroscopic deformation of metallic components can be applied to predict the variation of the relative non-linear coefficient from the macroscopic point, which is very convenient for damage detection in actual engineering applications.