Modeling And Simulation Analysis Of Electromagnetic Ultrasonic Transducer

Electromagnetic ultrasonic testing technology is one of the important research directions in ultrasonic testing technology.At present,most of the ultrasonic testing uses piezoelectric ultrasonic testing technology.The piezoelectric ultrasonic transducer in this technology must be coated with a coupling agent when contacting the workpiece during detection,which is inconvenient to use in special environments such as ultra-high temperature.In the electromagnetic ultrasonic testing technology,the electromagnetic ultrasonic transducer is converted by the electromagnetic effect,thereby achieving non-contact detection,which provides great convenience for the detection process.At present,electromagnetic ultrasonic transducers generally have the problem of low conversion efficiency.How to optimize the structure of electromagnetic ultrasonic transducers and improve the efficiency of transduction are the key to the research of electromagnetic ultrasonic transducers.In this paper,three typical electromagnetic ultrasonic transducers are modeled and analyzed by finite element method.Firstly,the U-shaped electromagnetic ultrasonic surface wave transducer for aluminum plate detection is taken as the research object.The influence of the geometric parameters of the transducer on the surface eddy current and magnetic induction intensity of the aluminum plate is analyzed.The conclusion is as follows: within a certain range of parameters,reducing the lift distance and the cross-sectional area of the the serpentine coil,appropriately increasing the coil spacing can improve the transducing efficiency of the transducer;increasing the length,width and height of the U-shaped permanent magnet can improve the conversion.The energy conversion efficiency of the energy device and the width of the U-shaped permanent magnet have the greatest influence on the conversion efficiency.Secondly,taking the electromagnetic ultrasonic Lamb wave transducer for steel plate detection as the research object,the distribution characteristics of the magnetic field in the steel plate are obtained,and the following conclusions are obtained: within a certain parameter range,increasing the excitation current amplitude,coil spacing and coil foldback times of the serpentine coil,reducing the number of excitation current pulses,the distance of the coil lift-off,and the cross-sectional area of the coil can improve the transducing efficiency of the transducer;increasing the width and height of the square permanent magnet can improve the transducing efficiency of the transducer,and the influence of the width is greater.Finally,defects of different angles and depths are simulated,it is concluded that as the depth of the defect increases,the magnetostrictive displacement of the particle decreases,and the larger the defect angle,the easier it is to be detected.Finally,the T-mode guided wave transducer for steel tube testing is modeled and analyzed.The effects of coil excitation current parameters,coil geometric parameters and nickel strip properties on the magnetostrictive displacement of the particle are studied.The following conclusions are obtained: within a certain parameter range,increasing the excitation current amplitude 、the residual magnetic flux density of the nickel strip,and reducing the number of excitation current pulses、the excitation current frequency、the cross-sectional area of and the lift-off distance of the coil can improve the transducer conversion efficiency.In addition,simulations are carried out for the position of the defect in the pipeline,the depth of the defect,and the material of the pipe,it is found that the magnetostrictive displacement of the particle is significantly larger than that without defect,and the larger the defect depth is,the larger the magnetostrictive displacement of the particle is;When the material of the pipe changes,the magnetostriction coefficient of the material is larger,the magnetostrictive displacement of the particle is larger,and the defect in the pipe is more easily detected.The research content of this paper has certain reference value for the structural optimization design of electromagnetic ultrasonic transducer,improving the efficiency of energy conversion and the accuracy of defect detection.