The Study Of Magnetostrictive Transducer For Exciting SH Waves Based On Wiedemann Effect

At present,most of the nondestructive examination ways are based on Lamb wave.However,the dispersion characteristics and modal transformation phenomena during the process of propagation lead to the complexity of echo signal,which increases the difficulty of processing the signal.While the low modal of shear horizontal wave(SH wave)has no dispersion characteristics and modal transformation phenomena during propagation.Therefore,the propagation of shear horizontal wave is of great research and application prospects for ultrasonic guided wave nondestructive examination.A model for generating SH waves based on the Wiedemann Effect of magnetostriction is proposed in this paper.Torsional deformation could be generated in magnetostrictive material in a certain magnetic circuit.The transducer whose core element is made of magnetostrictive material could generate multidirectional SH waves for the tested sheets.In this paper,the excitation conditions and propagation characteristics of Lamb waves and SH waves are elaborated.The basic characteristics of magnetostrictive material are explained especially the Wiedemann Effect and the Matteucci Effect.The structure of the new-type magnetostrictive transducer is designed.The working principle of transducer to stimulate and receive SH waves is analyzed.The constitutive equations of Wiedemann Effect in two-dimensional coordinate system are deduced based on the constitutive equations of Joule Effect in one-dimensional coordinate.And then the wave equations which formulate the constitutive model of the transducer are calculated.The working process of transducer to stimulate SH waves is stimulated by finite element method,which aims to optimize the parameters of the transducer's structure and verify the feasibility of the transducer's regular work.The entity model of the transducer is manufactured and the experimental purpose and process are put forward,which guides the selection of experimental instruments and the building of the experimental platform.The collected and processed experimental data is analyzed to determine the modes of ultrasonic guided wave signals received by the transducers and ensure whether the transducer could successfully stimulate and receive SHO waves.Through the research of this subject,the basic principle and constitutive equations of Wiedemann Effect of magnetostrictive material is calculated and deduced,which preliminary proves the feasibility of the new-type transducer to stimulate SH waves.The conclusion that the new-type transducer could truly stimulate and receive SHO wave is corroborated with the finite element stimulation and experimental research.