Structure Design And Performance Optimi-zation Of Rare Earth Magnetostrictive Transducer

Acoustic nondestructive testing is one of the main methods of non-destructivetesting technology. Owing to the advantages of strong penetrating power, simpleequipment, convenient use, good safety, and larger detecting depth, it has been increas-ingly applied in bridges, roads, home-defense and medical fields and so on. A comple-te set of testing system is mainly composed of the source (that is, the transmittingtransducer), receives the sensor and data processing software of three parts. Thetransmitting transducer is the core of the detection system components, its performancehas a significant influence on the test results. Based on the working mechanism oftransducer and piezoelectric-piezomagnetic analogy method, This thesis studies thetransducer made of Terfenol-D materials,using the finite element software ANSYS tooptimize analysis of material parameters and structural parameters of the transduc-er.The main contents and results are as follows:(1) The output performance of terfenol-D rod was analysed. Three-dimensionalmodel of the Terfenol-D rod was established, and then each order modal shape magnetand the output response under different conditions were analysed. The results showthat resonance frequency of the Terfenol-D rod decreases with the increase of length-diameter ratio. Under four types of incentive singnals, square wave, triangle wave, sinewave, sawtooth waveform of the current four input signals, displacement response ofthe output waveform is roughly the same, but the square wave signal output transientresponse can reach maximum displacement, the residual vibration is the biggest, thesawtooth wave is the smallest.(2) It was found that radition head affected the output features of rare earth giantmagnetostrictive transducer. The transducer can be simplifed as Terfenol-D rod andradiation head two parts of model, how radiation head shape and material parametersaffect the output performance of transducer, and the real time information of transducerchanging electrial energy into mechanical vibration under resonance and non-resonance condition were analysed. The results show that, among the different radiation headshapes, rectangle radiation head tranducer can reach the lowest base frequency andmaximum dynamic displacement, among the different material radiation head,45#steeltranducer has the lowest base vibration frequency and maximum dynamic displace-ment. Under the condition of non-resonant low-frequency excitation, the output signalof the transducer is sinusoidal periodic signal of same frequency. Under the condition of resonance, the real-time displacement transducer is no longer a sinusoidal waveform,and its transient displacement is obviously improved which can reach125μm and ismore than transient output displacement of piezoelectric transducer.(3) The output performance of double excitation source transducer was analysed.Firstly, double excitation source was established, and there is a mass-block between thetwo terfenol-D rods. In this model, the length ratio of the two rods, the structure sizeand material parameters of the mass-block and radiation head mostly affect the outputfrequency. The results show that the frequency differences as the excitation length ratioof the excition rods varys, the fundamental frequency, second mode resonancefrequency and frequency interval decrease while radiation head and middle mass blockincrease both in radial and longitudinal directions. When the former radiation headadopts aluminium magnesium alloy rectangle radiation head and middle mass blockadopts brass, the interval between fundamental frequency and the second moderesonance frequency is smallest which makes the frequency band broadening becomepossible.This thesis is focused on the influence of material parameters and structuralparameters of the transducer on output performance, so as to provide the basis for thefurther development of rare earth giant magnetostrictive transducer.