Development Of Testing Method And System For Characteristics Of Giant Magnetostrictive Rods

Rare-earth giant magnetostrictive materials,as new strategic functional materials,have excellent characteristics such as large magnetostrictive strain,high energy density,fast response speed,and wide working frequency.They are widely used in aerospace,low-frequency and high-power sonar systems,precision control,and many other military and civilian fields.However,a complete and normative standard system has not been established for the characteristics of giant magnetostrictive materials at home and abroad,the accuracy of the characteristics test needs to be enhanced,and the testing methods and devices need to be improved.In this thesis,the core element of the low-frequency and high-power giant magnetostrictive transducer—giant magnetostrictive rod is used as the research object.The static characteristics and dynamic characteristics test platforms were built,and the measurement methods and systems of their important mechanical and magnetic characteristics parameters and characteristics under AC working conditions were optimized,which provided a more reliable and effective way for the measurement of the characteristics of giant magnetostrictive rods.The main work and innovations of this thesis are as follows:(1)Aiming at the problem that the static chara cteristics of giant magnetostrictive materials in previous studies neglect the prestress changes caused by the giant strain of giant magnetostrictive rods during the test,a test platform for the static characteristics of giant magnetostrictive rods was de veloped and built.The research methods and status quo of the static magneto-mechanical coupling characteristics of giant magnetostrictive rods were elaborated in detail.The static test platform is composed of four modules: drive,test,signal acquisition,and pressure holding.The design of the prestress holding module was optimized,which used an adjustable mechanical device composed of a copper bloc k and disc springs in two different combinations.During the test,the prestress change caused by the high strain of the giant magnetostrictive rod can be reduced from 10.625% without p ressure holding device to below 1.134%.Experiments proved that this prestress holding device achieved a wide range of buffering and holding effects of the prestress.Finally,the rationality of the platform was verified by experiments and COMSOL finite element software.(2)The static characteristics test platform was used to systematically test and analyze the static characteristics of giant magnetostrictive rods,including magnetostrictive performance,piezomagnetic coefficient,Young's modulus,magneto-mechanical coupling coefficient,and B-H curve.And the change law of characteristic parameters under different magneto-mechanical coupling conditions was studied.Aiming at the problem of real-time acquisition and processing of experimental data during the test process,a LabVIEW-based comprehensive characteristics extraction system for giant magnetostrictive rods was built,which can be used for static and dynamic characteristics testing.The system combined with data acquisition boards can achieve the automatic collection and drawing of the B-H curve and magnetostriction curve.In addition,it can quickly and effectively analyze the experimental results.Aiming at the inherent defects of the preparation method of the giant magnetostrictive rods,the performance consistency of giant magnetostrictive rods was tested and analyzed.(3)Aiming at the problem that the eddy current has a greater influence on the magnetic field distribution and working temperature in the dynamic characteristics test of giant magnetostrictive rods,a test platform for the dynamic characteristics of giant magnetostrictive rods was built.The research methods and status quo of dynamic magneto-mechanical coupling characteristics of giant magnetostrictive rods were described,as well as the theoretical design method and composition of the platform.The coil was designed in layers to realize the real-time measurement of the magnetic field by a Hall probe.Besides,the sleeve was made of a silicon steel sheet cylinder,the slitting giant magnetostrictive rod was used to reduce the eddy current loss during the dynamic test,the slitting method was improved and the effect was compared.The performance changes of giant magnetostrictive rods under different excitation currents,excitation frequencies,bias magnetic fields,and prestress conditions were systematically tested,analyzed and summarized.