Study On The Patch Of Magnetostrictive Transducer Based On Ultrasonic Guided Wave

In recent years,ultrasound guided waves have been applied to the health inspection of plates.It is a non-destructive inspection method that is advanced,efficient and couplant-free.Electromagnetic acoustic transducers(EMAT)are transducers that excite and receive ultrasound guided waves.Magnetostrictive patch transducer(MPT)is a type of EMAT that is capable of detecting non-ferromagnetic,non-metallic materials.In this paper,aluminium plates are used as the object of study.Based on the traditional MPT,three MPTs are designed and develop based on the magnetostrictive and piezoelectric effects.The main work of this paper is as follows:(1)The problem of describing stress waves in an isotropic plate is addressed on the basis of elastic mechanics and stress waves.Study the propagation mechanism of ultrasound guided waves in a free plate.Solve the dispersion equations for Lamb and SH waves in an elastic layer.Plotting the dispersion curves of Lamb and SH waves in aluminium plates.(2)The parameters of the giant magnetostrictive material Terfenol-D are described according to the magnetostrictive effect.Based on its excellent magneto-mechanical properties,a giant magnetostrictive patch transducer(GMPT)is designed.The PZT/Terfenol-D composite is modelled according to the piezoelectric effect.A magnetostrictive double patch transducer(MDPT)with a PZT/Terfenol-D patch is designed using its magnetoelectric effect at resonant frequencies.(3)Using COMSOL Multiphysics software,models of MPT,GMPT and MDPT are developed.The feasibility of the three transducers to excite ultrasound guided waves was verified by simulation.Shear horizontal wave-giant magnetostrictive patch transducer(SH-GMPT)is built on the basis of the GMPT,and the number of coil windings in the SH-GMPT is optimised.The patch volume ratio in the MDPT is optimised.(4)Three transducers are fabricated from the simulation results.Build an ultrasonic guided wave testing platform and evaluate the characteristics of the transducers through experiments.Design a magnet lifting device to determine the optimum lifting distance and operating frequency of the transducer.Demonstrate that the ultramagnetostrictive patch and the PZT/Terfenol-D double-layer patch can substantially increase the signal strength of MPT excitation.