Experimental study on fatigue crack identification of 7075 aluminium alloy plate using combination NEWMS and TRA

According to nonlinear elastic wave modulation spectroscopy (NEWMS) and time reversal acoustic (TRA), a system is constructed to study the fatigue crack in 7075 aluminium alloy plate. Using different frequency excitation source (f1=270 kHz and f2=70 kHz), two types of samples, one is with the crack and the other is without the crack, are comparatively experimented. Intermodulation components (f+=f1+f2, f-= f1-f2 ) around the fatigue crack are analyzed. The experimental results show f± can be used to indicate the presence of the crack. The two-dimensional contour plot of the energy from the sample surface amplitude can be used to locate the crack position.