Simulation on Magnetostriction Strain of Polymer-bonded Terfenol-D Composites

A model of magnetostrictive strain for polymer-bonded Terfenol-D composite is presented, which is composed of asubmodel for the average strain of Terfenol-D composite and a magnetostriction submodel for Terfenol-D particles.Simulated results show that the saturation magnetostriction λs is very closely with experimental results, althoughthere exists some difference between the calculated and the experimental results under low applied magnetic field.The saturation magnetostriction of the composites increases with the particle fraction (v1=72.5～90 vol. Pct) in thesimulated and experimental results, but the simulation result is not ideal when the particle fraction is higher than 85%.

Influence of arrangement field on magnetostrictive and mechanical properties of magnetostrictive composites

Non-aligned and aligned polymer-bonded Tb0.3Dy0.7Fe2 composites with 20%particle volume fraction were prepared under different arrangement fields(i.e.0,10 kA/m,20 kA/m,30 kA/m,60 kA/m and 100 kA/m)during their gel process.Static magnetostriction,dynamic magnetostriction,elastic modulus and compressive strength of all specimens were tested and compared. Experimental results indicate that all the parameters are positively dependent on the arrangement field.The dependence is significant at low field levels,the critical value of which is 30 kA/m for the composites fabricated.No obvious improvement of the properties can be observed for a larger field.Such critical values are defined as the optimal arrangement field to manufacture magnetostrictive composites.

Magnetostrictive Properties for Epoxy Bonded Tb_(1-x)Dy_xFe_2 Composites

The epoxy bonded Tb_(1- x )Dy_ x Fe_2 composites were prepared. The magnetostriction,dynamic magnetostrictive coefficient and magnetomechanical coupling coefficient of epoxy bonded Tb_(1- x )Dy_ x Fe_2 rod samples were measured by using multiple parameter magnetic measurement system. It is found that the magnetostriction,dynamic magnetostrictive coefficient and magnetomechanical coupling coefficient of epoxy bonded Tb_(0.3)Dy_(0.7)Fe_2 rod sample are higher than those reported. The reason for the high magnetostrictive properties of the sample was explained according to the theory of magnetization process. The result indicates that the epoxy bonded Tb_(0.3)Dy_(0.7)Fe_2 rod sample is of practical value.

Study on preparation technique and properties of magnetostrictive epoxy bonded Tb_(1–x)Pr_x(Fe_(0.4)Co_(0.6))_(1.93) composites

The magnetic and magnetostrictive properties of epoxy bonded Tb1-xPrx（Fe0.4Co0.6）1.93 （0.85≤x≤1.00） composites, prepared with different epoxy proportions using cold compression-molding technique, were investigated. It is found that the optimal conditions were with a compaction pressure of 100 MPa and a mass ratio of resin to powder of 5：100. The Tb0.1Pr0.9（Fe0.4Co0.6）1.93 composite rod had a high magnetostriction of 770 ppm at an applied magnetic field of 960 kA/m, whereas the Pr（Fe0.4Co0.6）1.93 composite reached 500 ppm at 400 kA/m. The good magnetostrictive properties of Pr（Fe0.4Co0.6）1.93 composite at low-field （≤400 kA/m） could be explained by its low anisotropy. These results indicated that the epoxy bonded Tb1-xPrx（Fe0.4Co0.6）1.93 rod samples for high Pr content of x=0.9-1.0 were of practical value.

Bonded Terfenol-D composites with low eddy current loss and high magnetostriction

Bonded Terfenol-D composites,with high electrical resistivity and low eddy current loss,can be used in an alternating magnetic field with high frequency.However,the nonmagnetic binder impairs the magnetostriction of the composites.To achieve high magnetostriction and low eddy current loss,the mixture of the alloy powder and binder was compressed at low pressure in an oriented magnetic field.After this,the aligned samples were recompressed by cold isostatic pressing（CIP）.Besides,the effect of particle size on the magnetostriction of the bonded Terfenol-D composites was also studied.The results showed that the bonded Terfenol-D composites had excellent magnetostriction when the particle size was 50-80 μm.The oriented magnetic field and CIP could improve the magnetostriction of the bonded composites,which reaches 1020×10-6.The bonded Terfenol-D composites had good compact structure and high density（7.24 g/cm3）.The magnetic loss of the bonded Terfenol-D composites was 192 mW/cm3 at a frequency of 100 kHz in a magnetic field of 960 A/m,which was about one third of that of casting Terfenol-D alloys.

Nonlinear dynamic characteristics and optimal control of a giant magnetostrictive film-shaped memory alloy composite plate subjected to in-plane stochastic excitation

The nonlinear dynamic characteristics and optimal control of a giant magnetostrictive film （GMF）-shaped memory alloy （SMA） composite plate subjected to in-plane stochastic excitation are studied. GMF is prepared based on an SMA plate, and combined into a GMF-SMA composite plate. The Van der Pol item is improved to explain the hysteretic phenomena of GMF and SMA, and the nonlinear dynamics model of a GMF-SMA composite cantilever plate subjected to in-plane stochastic excitation is developed. The stochastic stability of the system is analyzed, and the steady-state probability density function of the dynamic response of the system is obtained. The condition of stochastic Hopf bifurcation is discussed, the reliability function of the system is provided, and then the probability density of the first-passage time is given. Finally, the stochastic optimal control strategy is proposed by the stochastic dynamic programming method. Numerical simulation shows that the stability of the trivial solution varies with bifurcation parameters, and stochastic Hopf bifurcation appears in the process; the system＇s reliability is improved through stochastic optimal control, and the first- passage time is delayed. A GMF-SMA composite plate combines the advantages of GMF and SMA, and can reduce vibration through passive control and active control effectively. The results are helpful for the engineering applications of GMF-SMA composite plates.

Preparation and Compressive Stress Effect of Polymer Matrix RE-Fe Giant Magnetostrictive Composite

Polymer matrix RE-Fe giant magnetostrictire composite （GMPC） was prepared using bonding and magnetic field forming technique, and magnetostriction of samples was measured for different compressive stress. The experimental results show thai there is certain compressive effect in GMPC. And the influence of compressive stress on magnetostriction of sample was investigated. It offers essential reference for application and device design of GMPC.

Large magnetostriction of Nd_(0.2)Tb_(0.3)Dy_(0.5)Fe_(1.93)/epoxy composites in a wide temperature range

We report the magnetostrictive performance of the Nd_(0.2)Tb_(0.3)Dy_(0.5)Fe_(1.93)/epoxy composites.Measurement of M?ssbauer spectra and the XRD results indicate that the easy magnetic direction of the Nd_(0.2)Tb_(0.3)Dy_(0.5)Fe_(1.93)compound is along<111>direction with spontaneous magnetostrictionλ111 of1900 ppm.The<111>-oriented Nd_(0.2)Tb_(0.3)Dy_(0.5)Fe_(1.93)/epoxy composites with particle volume fractions of20 vol%-55 vol%were prepared.Magnetization measurements demonstrate that the composite is highly anisotropic.The raw material cost of Nd_(0.2)Tb_(0.3)Dy_(0.5)Fe_(1.93)is about 85%of that of the Terfenol-D(Tb_(0.3)Dy_(0.7)Fe_(2))composition.Nd_(0.2)Tb_(0.3)Dy_(0.5)Fe_(1.93)/epoxy composites possess comparable magnetostriction with those composites made of Tb_(0.3)Dy_(0.7)Fe_(2)particles.At room temperature,the magnetostrictionλ_Ⅱof the Nd_(0.2)Tb_(0.3)Dy_(0.5)Fe_(1.93)/epoxy composite reaches 420 ppm at a low field of 80 kA/m and about1000 ppm at 239 kA/m.In addition,the composite exhibits a large saturation magnetostrictionλ_Ⅱover1200 ppm from 300 to 100 K,suggesting its potential applications as a low-cost magnetostrictive material in a wide temperature range.Therefore,the current study offers an opportunity to widen the operating temperature range of the magnetostrictive composite.

Structure and magnetic properties of mechanically alloyed Tb_(0.2)Pr_(0.8)(Fe_(0.4)Co_(0.6))_(1.93) and magnetostriction of its epoxy composite

The C15 Laves phase with composition Tb0.2Pr0.8（Fe0.4Co0.6）1.93 was synthesized by mechanical alloying （MA） and subsequent annealing process. The structure and magnetic properties of Tb0.2Pr0.8（Fe0.4Co0.6）1.93 were investigated by means of X-ray diffraction （XRD）, a vibrating sample magnetometer, and a standard strain technique. The effect of annealing on the structure and magnetic properties was studied. The analysis of XRD shows that the high Pr-content Tb0.2Pr0.8（Fe0.4Co0.6）1.93 alloy with the single phase of MgCu2-type structure can be successfully synthesized by MA method. The sample annealed at 450℃ is found to have a coercivity of 196 kA/m at room temperature. An epoxy/Tb0.2Pr0.8（Fe0.4Co0.6）1.93 composite was produced by a cold isostatic pressing technique. A large magnetostriction of 400 ppm, at an applied magnetic field of 800 kA/m, was found for the composite. The epoxy-bonded Tb0.2Pr0.8（Fe0.4Co0.6）1.93 composite combines a high magnetostriction with a significant coercivitv, which is a oromising magnetostrictive material.

Vibration suppression of magnetostrictive laminated beams resting on viscoelastic foundation

The vibration suppression analysis of a simply-supported laminated composite beam with magnetostrictive layers resting on visco-Pasternak’s foundation is presented.The constant gain distributed controller of the velocity feedback is utilized for the purpose of vibration damping.The formulation of displacement field is proposed according to Euler-Bernoulli’s classical beam theory(ECBT),Timoshenko’s first-order beam theory(TFBT),Reddy’s third-order shear deformation beam theory,and the simple sinusoidal shear deformation beam theory.Hamilton’s principle is utilized to give the equations of motion and then to describe the vibration of the current beam.Based on Navier’s approach,the solution of the dynamic system is obtained.The effects of the material properties,the modes,the thickness ratios,the lamination schemes,the magnitudes of the feedback coefficient,the position of magnetostrictive layers at the structure,and the foundation modules are extensively studied and discussed.

Effects of manganese substitution on magnetic and magnetostrictive properties of Tb_(0.5)Dy_(0.5)(Fe_(1-x)Mn_(x))_(1.92)/epoxy composites with spherical single-crystal particles

Spherical Tb_(0.5)Dy_(0.5)(Fe_(1-x)Mn_(x))_(1.92)(x=0,0.05,0.10 and 0.15)single-crystal particles were prepared.The magnetic anisotropy of the alloy decreases as x increases from 0 to 0.15.Subsequently,we prepared giant magnetostrictive composites with these spherical Tb_(0.5)Dy_(0.5)(Fe_(1-x)Mn_(x))_(1.92)single-crystal particles.As a consequence,well<111>-orie nted Tb_(0.5)Dy_(0.5)(Fe_(1-x)Mn_(x))_(1.92)composites with 55 vol%Tb_(0.5)Dy_(0.5)(Fe_(1-x)Mn_(x))_(1.92)particles were obtained.The Tb_(0.5)Dy_(0.5)(Fe_(0.9)Mn_(0.1))_(2)composite manifests a good low-field magnetostrictive property and saturation magnetostriction at an axial pressure of 10 MPa,λ_(‖,saturation)≈2100 ppm,which is larger than that of the commercially available Terfenol-D(1400-1800 ppm).The preparation of composites with single crystal spherical powders may be an effective solution of developing high-performance magnetostrictive composites.

Coupling of the Magnetostriction and Hall Effect in the Porous Magnetorheological Composite

The first part of this paper is presents a method for producing the composite which shows ferromagnetic, highly-elastic and electrically-conducting properties. This composite consists of ferromagnetic particles of the size 0.15-0.25 mm made of the chemically pure iron. The mentioned particles were dispersed in the elastic porous silicone the matrix with pores of the size 0.15-0.25 mm. Colloidal graphite particles of the size not exceeding 0.5 μm were added to the matrix to increase electrical conductivity. The production method consist in mixing particles of iron, graphite and sodium chloride with non-polymerized silicone and rinsing salt particles by water after the matrix polymerization. In its second part the paper provides a description of the measurement system for longitudinal magnetostriction and the Hall voltage. The magnetic field with the induction of ± 8 T produced by the Bitter type magnet was applied to the composite samples. The supplying voltage was applied to these samples and the Hall voltage was measured at the electrodes glued to them. The longitudinal magnetostriction was measured by means of the capacitor with a variable capacity placed at the upper surface of these samples. The linear magnetostriction exceeding ± 6 % and the Hall voltage reaching ± 5.5 nV were detected by the conducted measurements. Both the longitudinal magnetostriction and the Hall voltage show nonlinear changes and hysteresis lopes during the magnetic field application and the supplying current flow. The coupling of these changes and other regularities observed in the investigated composites and especially their non-linearity and hysteresis, are discussed in the final part of the paper.

基于PZT/Terfenol-D双层复合结构的导波换能器研究

为了解决传统磁致伸缩换能器激励信号能量弱、检测效率低的问题,提出一种基于PZT/Terfenol-D双层复合结构的导波换能器以提高换能效率。首先,建立换能器的谐振磁电动力学模型,设计换能器结构;其次,对设计的换能器进行仿真,验证换能器模型的合理性及可行性,并对其进行结构优化;最后,制作样机进行试验,采集换能器的激励信号能量,与传统磁致伸缩换能器和PZT换能器进行对比,并对获取的各组超声导波信号进行滤波处理,计算各自信号的幅值平方和。试验结果表明:所设计的换能器激励信号幅值平方和为PZT换能器的1.49倍,大于传统磁致伸缩换能器与PZT换能器激励信号幅值平方的总和。

铁基软磁材料电抗器噪声特性

铁基软磁复合材料具有高磁导率、高磁感应强度、低铁损的特性,研究该材料为铁心的电抗器的振动噪声特性对电抗器减振降噪设计具有重要意义。文中基于有限元仿真模型,通过磁场-结构-声学多物理场耦合,对正常运行条件下电抗器的振动与噪声分布进行计算分析,并搭建电抗器噪声测量系统,分别测量硅钢铁心、混合铁心和铁基软磁铁心电抗器的噪声信号,进行试验验证。结果表明:混合铁心和铁基软磁铁心电抗器噪声明显低于硅钢铁心电抗器,混合铁心电抗器受电流变化影响最小。仿真数据显示,硅钢铁心电抗器磁致伸缩与麦克斯韦力噪声比值为1.15,磁致伸缩占比最大。铁基软磁铁心电抗器噪声小的主要原因是磁致伸缩效应小至可以忽略。

Magnetostrictive composite material-based polarimetric heterodyning fiber-grating laser miniature magnetic field sensor

A novel fiber-optic magnetic field sensor is demonstrated based on a dual-polarization fiber-grating laser, which is embedded in an epoxy resin-bonded magnetostrictive composite material with doped Terfenol-D particles. A simple structure is designed to convert the magnetic field-induced strain to transversal stress, which is applied to the fiber laser to produce beat note frequency changes for measurement purposes. The response of the proposed sensor is measured, and shows quite a good directivity and linearity with a sensitivity of 10.5 Hz/μT to the magnetic field. It also shows a large measurable range up to about 0.3 T.

VIBRATION SUPPRESSION OF CANTILEVER LAMINATED COMPOSITE PLATE WITH NONLINEAR GIANT MAGNETOSTRICTIVE MATERIAL LAYERS

In this paper, a nonlinear and coupled constitutive model for giant magnetostrictive materials （GMM） is employed to predict the active vibration suppression process of cantilever laminated composite plate with GMM layers. The nonlinear and coupled constitutive model has great advantages in demonstrating the inherent and complicated nonlinearities of GMM in re- sponse to applied magnetic field under variable bias conditions （pre-stress and bias magnetic field）. The Hamilton principle is used to derive the nonlinear and coupled governing differential equation for a cantilever laminated composite plate with GMM layers. The derived equation is handled by the finite element method （FEM） in space domain, and solved with Newmark method and an iteration process in time domain. The numerical simulation results indicate that the proposed active control system by embedding GMM layers in cantilever laminated composite plate can efficiently suppress vibrations under variable bias conditions. The effects of embedded placement of GMM layers and control gain on vibration suppression are discussed respectively in detail.

压电/磁致伸缩/环氧树脂层合复合材料的磁电效应及其频响特性

磁电复合材料在磁-电能量转换等领域具有重要的潜在应用价值,研究磁电复合材料在较高频率下的磁电耦合特性对于实际应用具有重要意义。本文中以0-3型的Terfenol-D(Tb0.30Dy0.70Fe2)/环氧树脂复合材料为磁致伸缩层,以PZT[Pb(Zr0.52Ti0.48)O3]压电陶瓷为压电层,制备了三明治结构的层合磁电复合材料。研究了Ter-fenol-D/环氧树脂复合材料层的磁致伸缩性质,并对所制备的层合磁电复合材料磁通密度、介电常数以及磁电电压系数等随频率和偏磁场的变化规律进行了系统研究。结果表明,由于Terfenol-D/环氧树脂复合材料的引入,层合磁电复合材料呈现出良好的频率响应特性,可靠工作范围大大拓宽。层合磁电复合材料具有优良的动态磁电耦合性能,在优化偏磁场630 Oe和共振频率69.6 kHz下的磁电效应高达21.2 V/cmOe。此外,层合磁电复合材料的磁电效应随偏磁场的变化发生明显变化,并存在优化偏磁场。对上述现象和结果进行了详细讨论,并给出了层合磁电复合材料的磁电耦合机制。

基于磁场传感器的层状磁电复合材料动态特性的有限元模型研究

依据Hamilton变分原理,运用有限元方法建立了用于磁场传感器的核心元件—磁电复合材料动态特性的有限元模型。应用所建立的模型求解了LT型Terfenol-D/PZT/Terfenol-D三层磁电复合材料的输出特性,并与实验结果进行对比分析。结果发现当静态偏置磁场为22.1 kA/m,正弦交流驱动磁场为7.4 kA/m、频率100 Hz时,计算结果和实验结果误差为0.9%。表明该模型适用于磁电复合材料输出特性为线性变化的区域。

超磁致伸缩复合材料的静态弹性模量及抗压强度

采用粘结技术制备出了性能良好的磁致伸缩复合材料,着重研究了合金含量、粉末粒度、磁场取向、粉末表面处理对样品的静态弹性模量及抗压强度的影响规律。结果表明,粉末粒度、粉末表面处理对复合材料的抗压强度及静态弹性模量均有较大的影响;合金含量、磁场取向对复合材料的静态弹性模量影响不大,其中合金含量对复合材料的抗压强度有较大的影响。

复合薄膜磁致伸缩系数求解及悬臂梁结构优化

建立了超磁致伸缩薄膜(GMF)的磁致伸缩系数求解模型用于分析磁机耦合转化关系,研究了模型的建立过程、推演机理及仿真结果。通过合理简化复合GMF变形,并以单层GMF的磁致伸缩系数表达式为基础,推演得出了复合GMF的磁致伸缩系数表达式。以具有正负磁致伸缩效应的复合GMF为研究对象,利用推演得出的复合GMF的磁致伸缩系数表达式,讨论了磁致伸缩镀层厚度对悬臂梁式GMF自由端挠度的影响规律。研究结果表明:在镀层总厚度一定且正磁致伸缩材料层与负磁致伸缩材料层厚度比为2.3时,不论是Cu基薄膜还是PI基薄膜,其变形能力均达到最大值,从而实现了正负复合薄膜悬臂梁的结构优化。