Theoretical Research On The Quantitative Evaluation Of Micro-cracks On Glass Surface By Nonlinear Mixing Acoustic Method

Acoustic wave detection is an important method of structural non-destructive testing.Because of its small size,early micro-cracks have little effect on the linear parameters of acoustic wave propagation.The traditional linear acoustic method cannot effectively identify it.Nonlinear mixing acoustic method can effectively identify the micro-cracks in the structure,the quality evaluation of great value.Because the sound wave can propagate inside the material,it can also detect the internal defects of the structure.At present,the research on crack detection in nonlinear mixing mechanism is mainly qualitative analysis of cracks,and few studies on quantitative analysis.Based on the nonlinear acoustic theory,a physical model for the detection of nonlinear mixing acoustic mechanism is established.Taking the glass materials with surface micro-cracks as the research object,quantitative study the relationship between nonlinear acoustic signals and the modulation signal parameters,excitation signal parameters,crack parameters.Based on the above analysis,the selection of the modulation parameters is discussed,the suitable modulation parameters are given,the variation rules of the modulation parameters with different parameters are given,and explanations are given.The variation law of nonlinear side lobe is studied.The contact time of crack wall affects the magnitude of non-linear side lobe and the side lobe will lack.The modulation signal amplitude and crack width will affect the contact time,and the material boundaries affect sound wave propagation,the method of quantitatively evaluating the crack width and depth are given.Finally,the characteristics of nonlinear acoustic signals detected in different cracks are studied,the relationship between the side lobe signal and the contact depth is put forward to detect the internal cracks.The theoretical research in this paper provides a theoretical basis for experimentally testing the crack with nonlinear mixing mechanism.