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 initiating crack and acoustic coefficients, a multi-acoustic coefficients fusion feature-fatigue damage stage detection method is proposed. By extracting the nonlinear features as well as linear features of the multi-point detection signals for a single fatigue-damaged aluminum plate, achieves the fatigue damage state. Experiments verified multi-acoustic coefficients with different features corresponding to different fatigue stages such as initiation crack and crack extension.The peak points of the acoustic nonlinear coefficients are used for the judgment of the initiation crack stage, and the peak-to-peak amplitude of the acoustic linear coefficients are used for the judgment of the crack extension stage. Comparing and analyzing the results of electromagnetic ultrasonic detection and microscopic observation of different fatigue damage stages, the proposed method provides early warning of the initiation crack and crack extension by studying the characteristics of acoustic coefficients of different fatigue damage stages. This study provides theoretical and experimental basis for the application of electromagnetic ultrasonic assessment of fatigue damage in metallic materials.