A baseline-free crack detection using nonlinear acoustics

Abstract

A crack detection technique based on nonlinear acoustic is developed in this study. Lead Zinconate Titanate (PZT) materials are used for exciting and sensing acoustic waves. Acoustic waves at a chosen frequency are generated using an actuating PZT transducer and they travel through the target structure before being received by a sensing PZT wafer. Unlike all undamaged medium, a cracked medium exhibits acoustic nonlinearity which is manifested as harmonics and fractional subharmonics in the power spectrum of the sensed signal. Experimental results also show that the harmonic and sub-harmonic components increase in magnitude with increasing amplitude of the input signal. The proposed technique tells the presence of cracks by looking at the aforementioned two features and obviates the need for baseline data.