Fatigue Crack Width Detection Based on the Active Sensing Method: A Feasibility Study

Across multiple industries, metal fatigue damage is one of the most common failure types, and it will induce great loss if the fatigue damage cannot be detected in a timely manner. To predict the fatigue life of metal structures under practical service status, the fatigue test of metal materials is necessary. Current fatigue tests only focus on the total number of cycles before fatigue failure; however, the occurrence and expansion speed of cracks have not been studied before. Therefore, in this paper, based on the active sensing method, a feasibility study is developed to make crack growth detection of standard metal specimen during the fatigue testing. Two PZT patches are bonded on both sides of the crack on a specimen, which is caused by cyclic tension-compression loads. One patch works as the actuator, and the other one is used as the sensor. Based on the wavelet packet signal energy, a damage index is proposed to quantify the received signals and then represent the degree of crack width. The experimental results demonstrate that the received signal wavelet package energy decreases monotonically with enlarging crack width, and thus the effectiveness of the proposed method is verified.