Research On Coating Debonding Detection Method Based On Ultrasonic Lamb Wave

Bonded structures are widely used in chemical,aerospace and other fields,but during their use,they are affected by vibration damage,aging and other factors,and debonding often occurs,affecting the reliability of the structure and causing serious accidents.Therefore,it is of great significance to accurately detect the debonding defects of the bonding interface to ensure product quality and use safety.Ultrasonic Lamb wave is widely used in the detection of debonding of bonded structures due to its advantages of high detection efficiency,long propagation distance,and suitable for the detection of layered thin-walled structures.However,most of the Lamb waves currently used have the problem that they are insensitive to detecting small debonding,and on this basis,this paper studies the detection method of Lamb waves to detect small debonding of coatings.The main work of this article is as followsTaking the steel plate/coating bonded sheet as the detection object,the propagation principle of ultrasonic Lamb wave in the bonded structure is analyzed,the semi-analytical finite element method is used to obtain the dispersion curve of the structure,and the influencing factors of Lamb wave propagation in the bonded structure are analyzed through principles and experiments,and then the detection scheme of multi-mode Lamb wave detection coating with small debonding is obtained;The sensitivity of using single-mode Lamb wave and multi-mode Lamb wave method to detect the coating debonding area was compared;Aiming at the problem that it is difficult to identify patterns in multi-mode Lamb wave signals,CIVA software is used to simulate and generate multi-mode simulation signals with both A0 and S0 modes,and timefrequency analysis of the simulated signals is carried out by different time-frequency analysis methods,and time-frequency analysis of the multi-mode signals of the debonding experiment is carried out based on the above analysis results to achieve accurate mode identification;In terms of feature signal extraction,the multi-mode signal is separated and reconstructed by using the wavelet ridge extraction method based on image segmentation,the signal debonding feature parameters are extracted,the relationship between the feature parameters and the coating debonding area is established,and the energy change of the separation mode signal packet is used as the debonding recognition amount,and the support vector machine is used for the debonding area recognition.The results show that the resolution of the coating debonding area is Φ=3mm circular debonding,and it has good repeatability.The content studied in this paper has certain guiding significance for the detection of small debonding defects of bonded structural sheets.