Temperature Compensation Method of Lamb waves on Composite Plate using First Arrival Wave

Abstract

There are two basic methods of temperature compensation on isotropic plates, Optimal Baseline Selection(OBS) and Baseline Signal Stretch(BSS). The OBS method compensates the temperature using multiple baseline signals, while the BSS method using one baseline signals and stretch factor. However, in composite materials, the velocity of lamb waves differs from one direction to another. In this paper, a temperature compensation algorithm is proposed using the First Arrival Wavepacket(FAW) factor considering the propagation direction of lamb waves in composite plates. The proposed algorithm consists of two parts. First, Fast Fourier Transform (FFT) was used to filter the response signal in the space domain. Second, the signal was compensated by using the FAW factor for each separated signal. And the accuracy of the algorithm was improved by considering the group velocity and phase velocity of the numerical value of the lamb waves. The numerical value is calculated by using the stress-strain relation and the equation of motion for particles in the composite. Finally, the error of the signals was calculated using the Maximum Error of the Subtracted Signal(MESS). Also, the temperature compensation method using the proposed algorithm was verified by comparing the existing OBS/BSS method. Also, the compensated signal was compared with the experimental signal.