Research on selective amplification nonlinear detection method based on inverse phase principle

Abstract To address the issue of the low amplitude of the second harmonic received during the nonlinear detection of carbon fiber composites, which is easily drowned by noise and results in poor detection sensitivity, a selective amplification nonlinear detection method based on the inverse phase principle is proposed. This study compares the efficiency of second harmonic generation and the sensitivity of nonlinear coefficients to crack parameters between traditional nonlinear detection methods and the proposed selective amplification nonlinear detection method. A mathematical model of the interaction between ultrasonic guided waves and microcracks was established based on nonlinear detection theory, and simulations and experiments were conducted according to the proposed method. The results demonstrate that the selective amplification nonlinear detection method enhances the amplitude of the second harmonic by more than 40% compared to traditional nonlinear detection, effectively improving the sensitivity of nonlinear detection. This provides a novel approach for characterizing the extent of damage in composites and holds significant practical engineering value.