Design Of Ultrasonic Guided Wave Detection System For Ferromagnetic Wire

The internal microstructure of ferromagnetic materials influences the mechanical properties of materials.If there are defects in the material,the properties of the materials will be changed,and the application in the engineering of mechanical parts performance drop or even failure.Whether ferromagnetic materials have defects in the early stage are very important for their later engineering applications.Fe-Ni alloy is a ferromagnetic material with high permeability.Fe-Ni alloy wire can be used to make displacement sensor.In the process of production of Fe-Ni alloy wire,the material is drawn through drawing,and when the drawing speed is too fast or the compression rate is too large,it may lead to the transverse cracks on the surface of the wire,and then affect the performance of the sensor.According to the above situation,this paper will test the transverse crack of ferromagnetic wire.The ultrasonic guided wave detection technology based on magnetostrictive principle has two advantages: the propagation loss of the ultrasonic guided wave is small,it can be used for long distance test,the detection efficiency is high,the coupling agent is not needed in the detection process,and the non-contact detection can be realized.Magnetostrictive ultrasonic guided wave detection technology can be applied to the detection of long distance components effectively.In this paper,based on the magnetostrictive theory and the ultrasonic guided wave theory,the detection system is designed to detect ferromagnetic wire,and the signal is analyzed to get the signal characteristics of the defect,thus the evaluation of the quality of ferromagnetic materials is achieved.The main contents of this paper are as follows:Firstly,the magnetostrictive theory and ultrasonic guided wave theory are introduced,and the longitudinal mode ultrasonic guidanceis selected for testing.The sensor model is simulated by Comsol.The sensor consists of three parts: permanent magnet,detection coil and magnetostrictive material itself.Secondly,the hardware circuit system is designed,including the control circuit with FPGA as the core,the ultrasonic excitation circuit and the ultrasonic receiving circuit,can realize the function of the ultrasonic guided wave excitation and reception,the signal amplification and filtering,the data acquisition and the USB communication.Thirdly,LabVIEW host computer is developed to realize the functions of sending commands and parameters to the slave computer,data processing and waveform display.Finally,the waveform signal is processed,including moving average filter,cross-correlation processing and hilbert transform,to achieve the judgment of the location and size of defects.Through the experiment,the test system designed in this paper can detect ferromagnetic materials quickly.It can judge the position and size of the defect,and the precision of the test result is high.It can realize the inspection of ferromagnetic material defects and the evaluation of the quality condition.