A Focusing Imaging Method of Lamb Wave Phased Array Based on Frequency Response Function

Abstract

The invention discloses a Lamb wave phased array focusing imaging method based on a frequency response function. In the method, a piezoelectric sensor array is arranged on the surface of the structure to be measured, and according to the response signal of the full frequency band, the excitation array element and the excitation element composed of the acquisition array element are calculated. Collect the frequency response function of the pair to construct the dispersion precompensation signal; multiply the dispersion precompensation signal and the frequency response function in the frequency domain to obtain the frequency domain precompensation response signal; according to the distance from the acquisition array element to the focal point of the coordinate position, Compensating after dispersion of the frequency domain pre-compensation response signal to obtain a frequency domain dispersion compensation signal, until traversing all sensor excitation acquisition pairs, superimposing the time domain dispersion compensation signals of all sensor excitation acquisition pairs, The Hilbert envelope amplitude of the superimposed signal at the focusing moment is used as a focus damage indicator, and all pixels are assigned a value for damage imaging, and the value of each pixel is the damage indicator value corresponding to the focus position.

Description

technical field [0001] The invention belongs to the technical field of structure monitoring, in particular to a Lamb wave phased array focusing imaging method based on a frequency response function. Background technique [0002] Lamb wave is a kind of ultrasonic guided wave with high sensitivity and low attenuation propagating in thin plate structure, so it is widely used in the field of structural health monitoring. It plays an important role in aircraft blades and various plate-like and shell-like structures. It can warn of potential internal damage in time and provide protection for property safety and life safety. [0003] However, the Lamb wave also has the disadvantages of multi-mode and dispersion, which causes the dispersion of the echo energy, which reduces the positioning accuracy and identifiability of defects. The Lamb wave phased array focusing method is a damage monitoring method that concentrates energy to one point, so as to increase the arrival energy of th...

AI Technical Summary

Problems solved by technology

However, the disadvantages of both methods particularly affect their use. The first method is an easy-to-implement method, but has low accuracy and sensitivity to defect location; the second method has high sensitivity to defect identification. and high positioning accuracy, but because it needs to design and stimulate signals for monitoring each point, it takes a lot of time to detect even a small area

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