Detection of internal micro defects by nonlinear resonant ultrasonic method using water immersion

A nonlinear resonant ultrasonic method using water immersion has been developed to detect micro defects in solids. This method allows us to reduce the strong nonlinearity of water and amplify the weak second harmonics generated at internal micro defects. In this method, both the fundamental and second harmonic frequencies are selected to match the resonant frequencies based on the resonant spectra of a sample. The detection of the micro defects in SiC _f/Ti composite has been demonstrated. nonlinear acoustics, higher harmonics, resonance, water immersion, contact acoustic nonlinearity, micro defect, composite.