Electromagnetic Ultrasonic Nonlinear Detection Of Bonding Strength Of Metal Matrix Composites

Compared with the structure connected by bolt,rivet and other traditional methods,the glued structure has the advantages of light weight,less destructive,and tight combination,so it is widely used in aerospace,naval ships,motor vehicles and other industrial fields.The reliability of bonding structure mainly depends on the mechanical properties of bonding interface.How to accurately evaluate the mechanical properties of bonding interface has become the focus of scientific and engineering circles.The ultrasonic nonlinearity is very sensitive to the mechanical property degradation of the bonding layer,and it is an effective method to detect the reliability of the bonding structure.Electromagnetic ultrasonic has the advantages of no coupling medium,low requirements on the surface of the body under test and low detection cost.In this paper,the nonlinear electromagnetic ultrasonic detection of metal-nonmetal composite bonded structures is studied.Firstly,the correlation principle of electromagnetic ultrasonic and ultrasonic nonlinearity is introduced.On the premise of considering the attenuation of sound wave with propagation distance,the ultrasonic wave equation in solid media is re-solved,and the influence of propagation attenuation on the nonlinear coefficient is analyzed.The bonding layer model combining hydrogen bond and microcrack model is established,which explains the source of bonding and nonlinear effect of the bonding layer.At the same time,the model is dynamic and can approximate the performance degradation process of the bonding layer.In view of various sources of inherent nonlinearity,corresponding optimization and compensation methods are given to reduce the influence of inherent nonlinearity on the detection results.In order to improve the excitation efficiency of electromagnetic ultrasonic as much as possible,a kind of electromagnetic ultrasonic shear wave excitation probe was designed.Aiming at the problem of low signal-to-noise in electromagnetic ultrasonic nonlinear detection,the two-tree complex wavelet transform method is used to reduce the noise of the received signal,which can reduce the influence of the noise signal on the nonlinear detection effect.Through cyclic fatigue loading was prepared by a group of different bonding strength of specimen,with the help of high-energy ultrasonic detection of specimen nonlinear detection system,and the nonlinear detection was determined by the electromagnetic acoustic resonance technology the best frequency,combined with the inherent nonlinear suppression measures and signal noise reduction processing,approximate the quantitative relationship of bonding strength and ultrasonic nonlinear coefficient.The experimental results show that it is feasible to use electromagnetic ultrasound to detect the nonlinearity of the bonding structure,the electromagnetic ultrasonic shear wave transducer designed in this paper greatly improves the amplitude of the received signal,and the ultrasonic nonlinearity quantitative detection of the bonding strength can be realized approximately by combining the denoising processing and the inherent nonlinear suppression measures proposed in this paper.