| Aluminum alloy cladding materials are widely used in aerospace,intelligent manufacturing and other fields because of their uniform stress distribution,good performance and light weight.Ultrasonic nondestructive testing technology is an important means to study the interface bonding state and characterize the bonding strength of aluminum alloy clad materials.At present,bubbles,holes and other local defects will appear at the bonding interface of aluminum alloy cladding materials in the process of manufacturing or use,which seriously affects the bonding quality of aluminum alloy cladding materials.If it cannot be detected in time,it will endanger the property and life of equipment and personnel.Based on this,an ultrasonic testing system specially used for testing the bonding state of aluminum alloy cladding materials and characterizing the interfacial bonding strength is designed and developed.The main work contents are as follows:1.Use COMSOL multiphysics finite element software to carry out pre research on aluminum substrate and carry out simulation analysis and experimental measurement on aluminum alloy cladding materials with different interface bonding states.The simulation results show that the echo of the signal can be basically distinguished by the sound source signal frequency of 20 MHz,the waveform resolution is good,and the smaller defect size can also be detected.In addition,the nonlinear coefficient of aluminum alloy clad material is related to the bonding state of the material.When the bonding state of the cladding material is good,the nonlinear coefficient of the material is small,and as the defect size gradually increases in the range of 0?8mm,the interface bonding state of the cladding material will also become worse,resulting in nonlinear effects.It is becoming more and more obvious that the nonlinear coefficients have obvious changes.The change rate of the nonlinear coefficients calculated by the finite element simulation is 86.66%,and the nonlinear coefficients calculated by the simulation and the defect size satisfy the fitting regression relationship of the polynomial function.The combined equation is: y = 0.3714a2-1.4006a+ 1.652,the correlation coefficient is 0.9914;the experimentally measured nonlinear coefficient variation rate is 87.91%,and the experimentally measured nonlinear coefficient and defect size satisfy the fitting regression relationship of the polynomial function,which is The fitted equation is: y = 0.3879a2-1.4641 a + 1.704 with a correlation coefficient of0.982.2.The simulation analysis and experimental measurement of aluminum alloy cladding materials with different bonding states show that the waveform characteristics in the ultrasonic echo signal diagram are obviously different with different bonding states.By comparing whether there is echo between interface wave and bottom wave,we can judge whether the composite material is completely debonded;Comparing the reflection echo amplitude of epoxy resin layer with good bonding and the defect echo amplitude of epoxy resin layer with defect state,we can qualitatively judge whether the bonding structure is defective,and then evaluate the bonding state of bonding materials.Through phased array s-scan technology and C-scan technology,we can qualitatively detect the defects in the bonding state of the interface and evaluate whether there are defects in the interface.While C-scan technology can also qualitatively distinguish that the dark area is the defect location of poor bonding,and quantitatively detect the defects in the bonding layer of aluminum alloy clad material and present them in the form of images.The error between the imaging defect size and the actual defect size is 5%.3.Build an ultrasonic testing system that can be used to detect the interface bonding quality of aluminum alloy clad materials,and study the relationship between ultrasonic characteristic parameters and defect size of aluminum alloy clad materials in different bonding states.Experiments show that different bonding states of aluminum alloy cladding materials will cause corresponding changes in ultrasonic characteristic parameters such as amplitude,sound velocity,sound attenuation coefficient and nonlinear coefficient.With the gradual increase of defect size in the range of 0 ? 8mm,the interface amplitude signal is basically the same,and its amplitude change rate is 6.07%.The amplitude of the defect wave increases with the increase of the defect size of samples in different binding states,and the change rate of the amplitude of the defect wave is 63.41%.The amplitude of the bottom wave decreases with the increase of the defect size of the samples with different bonding states,and the change rate of the amplitude of the bottom wave is 17.82%;As the defect size of the samples with different bonding states increases gradually in the range of 0 ? 8mm,the propagation velocity of ultrasonic wave in the laminated materials has a certain influence,but the overall trend has no obvious correlation,and the change rate of sound velocity of the samples is 3.24%;As the defect size of the bonding layer increases gradually in the range of0 ? 8mm,the sound attenuation coefficient increases gradually,and the attenuation degree of ultrasonic wave in the material increases;As the defect size of samples with different bonding states gradually increases in the range of 0 ? 8mm,the nonlinear effect becomes more and more obvious,the nonlinear coefficient of ultrasonic echo signal becomes larger and larger,and the change rate of nonlinear coefficient of samples is 87.91%.4.The tensile test is carried out by electronic universal testing machine,and the strength changes of samples with different interface bonding states are measured.The experiment shows that the aluminum alloy clad materials with different bonding states will cause differences in the interface bonding strength,and as the defect size of the adhesive layer increases,the interfacial bond strength shows a significant downward trend.5.Ultrasonic phased array detection technology obtains the ultrasonic characteristic parameters of samples in different bonding states,and obtains the interface bonding strength of samples in different bonding states through tensile test.It is found that with the change of defect size,the ultrasonic characteristic parameters and interface bonding strength show a certain change law.Therefore,the characterization relationship between ultrasonic characteristic parameters and interface bonding strength is established,and the defect amplitude value The sound attenuation coefficient,nonlinear coefficient and bonding strength have good linear fitting.In order to evaluate the ability of ultrasonic characteristic parameters to characterize the interfacial bonding strength,it can be seen from the analysis of stability and response sensitivity that the effect of using nonlinear coefficient to characterize the interfacial bonding strength of aluminum alloy clad materials is the best.The functional expression of bonding strength nonlinear coefficient is y = 2.0835?^(-0.161),and the correlation coefficient is 0.9981. |
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