Lamb wave phased array focusing imaging method based on frequency response function

Abstract

The invention discloses a Lamb wave phased array focusing imaging method based on a frequency response function. The method comprises the steps of arranging a piezoelectric sensor array on the surface of a measured structure, calculating a frequency response function of an excitation collection pair composed of an excitation array element and a collection array element according to a full-band response signal, and constructing a frequency dispersion pre-compensation signal, multiplying the frequency dispersion pre-compensation signal by a frequency response function in a frequency domain to obtain a frequency domain pre-compensation response signal, according to the distance from an acquisition array element to a focus of a coordinate position, compensating the frequency domain pre-compensation response signal after frequency dispersion to obtain a compensation signal after frequency domain frequency dispersion until all the sensor excitation acquisition pairs are traversed, and superposing the compensation signals after time domain frequency dispersion of all the sensor excitation acquisition pairs, taking the Hilbert envelope amplitude of the superposed signals at the focusing moment as a focus damage degree indication, assigning all pixel points for damage imaging, and enabling the value of each pixel point to be the damage degree indication value of the corresponding 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...

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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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