Fatigue crack propagation evaluation for thin plate structures using a wireless ultrasonic sensing device

To avoid complicated material constants calculation of conventional analysis approaches, in this paper, a work is conducted on evaluation the feasibility of ultrasonic characteristic parameters in in-situ wireless monitoring of fatigue crack propagation process in a structure. An aluminum central cracked specimen was fabricated to simulate a damaged thin plate structure. A fatigue crack growth test was conducted on the specimen under uniaxial cyclic tensile load with a constant amplitude, and the crack was vision-based regularly detected. Simultaneously, the crack propagation was monitored in real time by a self-developed wireless ultrasonic sensing device. Based on a crack growth behavior analysis, a relationship is established between crack length and loading cycles. Meanwhile, the evolvement of ultrasonic signals with the crack growing is investigated, and a relationship was established between the crack length and the ultrasonic characteristic parameter. Ultimately, a connection is established between the loading cycles and the ultrasonic characteristic parameter, which contains the length information of the cracks. The proposed model shows a good agreement with experimental data with correlation coefficients all higher than 0.96, which indicates the proposed method has a great potential in evaluating fatigue cracks in thin plate structures.