Parameter and time delay estimation of ultrasonic multi-mode Lamb waves based on wavelet transform

This paper put forward using Wavelet Instantaneous Parameter Methods (WIPM) and the modulus maxima method of the Wavelet Transform (WTM), respectively, for time delay estimations of narrow-band and wide-band multi-mode (A₀ and S₀) Lamb waves. The methods are much higher resolution than Hilbert Instantaneous Parameter Methods (HIPM). WTM's resolution is the highest; WIPM's resolution is the second; and HIPM can not magnificently estimate the multi-mode time delay. As well as this paper puts forward the method of the reconstruction based on wavelet Transform modulus maxima to estimate attenuation coefficient of multi-mode ultrasonic Lamb wave A₀ and S₀. And the method indicated by experiment results is feasible for metal aluminum thin plate.