Monitoring of fatigue crack under complex environment using guided waves

This paper presents an experimental study on monitoring of fatigue crack under complex environment using guided waves. An experimental set-up consisting of an electrical oven, a MTS testing machine and a monitoring system is established to perform the study. First, the combined effects of temperature, load and vibration on the propagation of guided waves in metallic structure is studied. Then, a statistical approach is proposed to detect fatigue crack under these combined effects. Damage feature is extracted after the guided wave signals are processed by Fourier transform. A Monte Carlo procedure is employed to estimate the probability density functions of the feature before and after cracking, respectively. By comparing the probability density functions, the probability of existence of fatigue crack is determined. Experimental study on a fatigue coupon under combined effects of temperature, load and vibration is conducted to demonstrate the effectiveness of the proposed method.