Research On Nondestructive Testing Method Of Electromagnetic-Thermal-Acoustic Fusion

Non-destructive testing and evaluation methods play an important role in modern industry.Most of the detection methods,such as conventional detection methods and thermography,are based on a single physics field.Some detection methods based on thermoacoustic effects are widely used in the biomedical field,but there are few reports on metal nondestructive testing.Eddy current thermography itself contains eddy current and thermoacoustic effects.The existing literature usually conducts in-depth research on a certain detection method.In this paper,the eddy current induced thermoacoustic(ECITA)detection method based on electromagnetic induction heating and the electromagnetic-thermal-acoustic multiphysics fusion detection modality are studied.Based on the research of fusion detection mechanism,finite element simulation and experimental research were carried out.Firstly,this paper briefly introduces the influence of microscopic changes of materials on macroscopic physical properties,and analyzes the feasibility of using electromagnetics,thermal and acoustic properties for detection.The multi-physics coupled eddy current thermoacoustic detection method is studied and combined with eddy current detection and eddy current thermography detection to form an electromagnetic-thermal-acoustic multi-physics fusion testing method.The fusion principle of each physical field testing method in physical process and signal feature is studied.The influencing factors of each field detection are analyzed.The relationship between stress and conductivity,conductivity and detection result is elaborated.The common feature extraction methods and feature fusion methods for each physical field signal are studied.Secondly,the electromagnetic-thermal-acoustic fusion was simulated by COMSOL Multiphysics finite element simulation software.The distribution of electromagnetic field,temperature field and sound field under time-varying conditions was analyzed.The feasibility of electromagnetic energy converting to thermal energy and thermal energy converting to acoustic energy is verified,which also verifies the feasibility of eddy current thermoacoustic detection method based on electromagnetic induction.The effects of relative permeability,thermal conductivity and electrical conductivity of the test samples on the simulated signal were studied.A simulation application was developed and used in the testing system.Then,an electromagnetic-thermal-acoustic fusion detection system was built,and the experimental hardware system selection and software system design were introduced.The software system mixed with C#,MATLAB and Measurement Studio programming,embed infrared image acquisition software and simulation application,which can achieve the functions of simulation research,signal acquisition of various physical fields,data processing and file management.Finally,a set of tensile specimens with plastic deformation were tested using the established experimental system.It was found that the eddy current detection is greatly affected by the position of the sensor,and the thermography and thermoacoustic detection effects are better than eddy current detection.The effect of using dimension reduction fusion can be further improved.The experimental results are in good agreement with the theoretical and simulation analysis,and the feasibility of the electromagnetic-thermal-acoustic fusion detection method is verified.