Chaotic characteristics analysis of simulation signal of second harmonic generation effect

摘要

In order to deepen the understanding of nonlinear properties of specimen in the process of fatigue crack extension, the chaos and fractal theory are presented to analyze the second harmonic generation (SHG) signal of receiver in nonlinear ultrasonic system. Firstly the usefulness of chaos and fractal theory to analyze the SHG signal should be verified theoretically. By constructed the simulation signal of SHG effect, simulation signals with the character of chaotic was found, and it showed that the Lyapunov exponent was sensitive to weaker nonlinearity and unsusceptible to noise, and chaotic characteristic values could make up for inadequacies of the relative nonlinear coefficient.