Multi-scale analysis of Lamb wave propagation in a steel beam excited and sensed by piezoelectric transducers

The Multi Scale Technique (MTS) has been successful in this respect and has been able to explain the lamb waves generated in the steel beam. The result achieved through the analysis of the STFT algorithm confirmed that the variation of the dynamics involved is dependent on the variation of the sensors' distance to each other, irrespective of the values of the spectral frequencies. The experiment revealed that there is a direct proportion between time of flight and the sensors' distance. furthermore, it is proven that the group velocity is independent of the position of the sensors, and hence the hypothesis that the Dispersion Effect value will be ignored is verified. This is the reason why the proposed method that has been identified and discussed in this article is bound to prove its validity and usability to the ultrasonic structural health monitoring technique because of its capability to produce genuine models based on the wave propagation and attenuation. Analyzing the result of STFT output, it is understood that as the propagation interval increases, the direct relationship between the spreading levels of the lamb wave packets in the time-frequency domain is observed. It is understood that when the value of the correction terms expressed in terms of ε² and ε³ are smaller, the value of dispersion is smaller.

Keywords:

Method of multi scales , Ultrasonic structural health monitoring , Amplitude evolution , Time-frequency analysis , short-time fourier transform