Debonding Defect Detection Of Multilayer Composite Structures Based On Mechanical Impedance Method

With the further society development,rapid economy growth and the growing development of China's modern science and engineering technology.sheer wood,precious metals and other alloy materials have become increasingly difficult to fully meet the real requirements of Chinese modern industrial construction and development,for their performance defects.This leads to that the demand for various composite materials with different properties and applications becomes increasingly urgent.Therefore,the production and application of composite materials are becoming more and more important.For the many inherent excellent properties of the composite material,they are widely applied in various industrial fields.However,the preparation of composite materials requires very sophisticated craftsmanship,and the composite material structure may have defects induced by various factors during the preparation process.Therefore,in order to ensure that the produced composite material meets the actual application requirements,the research on the detection technology of composite material structure defects is of great significance.Taking this as a starting point,this paper proposes a detection technology for debonding defects of multilayer composite materials based on mechanical impedance method.This method mainly converts the mechanical impedance of the vibration characteristics of the material into the load impedance of the transducer,and furtherly investigates the change of the mechanical impedance of the material by measuring the characteristics of the transducer,and ultimately completes the corresponding detection.In this paper,the propagation process of elastic waves in solid media are simulated and analyzed,the simulation is mainly for a single steel plate modelthe,using finite element analysis,the displacement response characteristics of the vibration receiving point are simulated.Based on the displacement response characteristic,the mechanical impedance value of each point is calculated,so as to analyze the mechanical impedance characteristic of the whole single-layer structure.The mechanical impedance value of the obtained single-layer structure model is used as a benchmark,and compared with the experimental results later,it is concluded that the existence of the defect has an effect on the mechanical impedance value in the test piece after being excited by vibration.On the basis of simulation,in this paper,a multi-layer composite structure debonding defect detection experimental platform is built,and different types of multi-layer composite structure composite model specimens were constructed to conduct subsequent experiments,the tests are carried out on different specimens for many times,the signals obtained in the above are used to extract the peak value of the output wave respectively,and after repeating the measurement for many times,the average displacement of the tested piece of the last test result is extracted.Based on the average of these displacements,the mechanical impedance values of the tested specimens under different model detection states are calculated.Based on the average of these displacements,the mechanical impedance values of the test specimens under different model detection states are calculated.By comparing the distribution rules of the mechanical impedance values in different test pieces,due to the change in the material of the test piece and the existence of the debonding defects,it is concluded that there are obvious differences in the mechanical impedance distribution rules of the test pieces,by comparing and analyzing the differences in mechanical impedance distribution,the detection of the presence or absence of debonding defects is completed.However,due to the complexity of the material and the high similarity and ambiguity of the displacement response signals,it is difficult to establish a standard resolution mode to distinguish the debonding types.Therefore,the author introduces BP neural network at the end of this article to classify the mechanical impedance data.Based on the above simulation and experimental data,this paper finally realizes the detection of the presence or absence of debonding defects in the multilayer composite structure,and recognition the types of debonding defects.