Research on the electromagnetic ultrasonic detection method of initiation crack based on multi-acoustic coefficients fusion

Abstract The traditional single acoustic coefficient cannot judge the different degrees of fatigue damage such as initiation crack and crack extension. Based on the law between the structural evolution of dislocation pile-up initiation crack and the acoustic coefficients, a multi-acoustic coefficients fusion feature-fatigue damage stage detection method is proposed, according to the ultrasonic echo time-domain signal peak-to-peak amplitude of linear characteristics and ultrasonic echo frequency-domain signal nonlinear characteristics as the multi-acoustic coefficient fusion features. The multi-acoustic coefficient fusion feature is obtained by using the multi-point detection signal of a single fatigue-damaged aluminium plate in order to determine the different fatigue stages such as initiation crack and crack extension. The fatigue damage stage is calibrated by microscopic observation, and the accuracy of electromagnetic ultrasonic detection in the fatigue damage stage is compared and analyzed. The results show that the multi-acoustic coefficient fusion feature can effectively provide fatigue damage degree characteristics compared to a single acoustic coefficient. The detection method of multi-acoustic coefficients fusion can provide early warning of initiation crack and crack extension damage, which provides a theoretical and experimental basis for the application of electromagnetic acoustic transducer (EMAT) assessment of fatigue damage in metallic materials.