Research on Duffing chaotic theory based nonlinear Lamb wave extraction and damage detection

As the nonlinear second harmonic signal generated by structural damage is often distorted by noise, the traditional damage index (nonlinear parameter β) will be distorted. Therefore, an improved Duffing-Holmes chaotic system is proposed to detect the weak second harmonic signal in the noise background, and the maximum Lyapunov exponent is used to quantify the damage degree. Experimental results show that Duffing chaotic system can detect weak second harmonic signal in strong noise background, and Lyapunov exponent has a good linear relationship with material damage degree. This method provides a feasible idea for early damage assessment of composite materials.