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

Abstract

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 (<i style="mso-bidi-font-style:normal">f</i>₁=270 kHz and <i style="mso-bidi-font-style:normal">f</i>₂=70 kHz), two types of samples, one is with the crack and the other is without the crack, are comparatively experimented. Intermodulation components (<i style="mso-bidi-font-style: normal">f₊</i>=<i style="mso-bidi-font-style:normal">f</i>₁<i style="mso-bidi-font-style:normal">+f</i>₂, <i style="mso-bidi-font-style: normal">f_-</i>= <i style="mso-bidi-font-style:normal">f</i>₁<i style="mso-bidi-font-style:normal">-f</i>_{2<i style="mso-bidi-font-style: normal"> </i>}) around the fatigue crack are analyzed. The experimental results show <i style="mso-bidi-font-style:normal">f_±</i> 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.