Research on Nonlinear Ultrasonic Testing Technology on Fatigue Process of Metal Materials

Metal materials are prone to serious problems such as material performance degradation, fatigue damage and induced fatigue damage in the process of tension, compression or bearing alternating loads, resulting in heavy losses. Therefore, it is necessary to study the degradation of mechanical properties during material fatigue. When the ultrasonic wave propagates in the metal component, it interacts with the fatigue damage in the material, so that the ultrasonic waveform is distorted and high-order harmonic components are generated, which can be used to characterize the degree of material fatigue and mechanical property degradation. This paper takes YL12 aluminum alloy and 45 steel as the research objects, and uses the COMSOL software to simulate the propagation process of the surface wave in the sample. The specimen is cyclically loaded by a tensile machine, an ultrasonic nonlinear detection platform is built, excitation pulse signal, analyze frequency domain waveform, and the second-order relative nonlinearity of the specimen under different cyclic loading times is calculated. The linear coefficient is obtained, and the relative nonlinear coefficient shows a monotonically increasing trend with the increase of loading times during the fatigue process.