Papers by Keyword: Magnetostrictive

Abstract: Recently, the magnetoelectric (ME) effect is widely studied to apply in sensing applications. This paper proposes the investigation of ME effect in the bi-layer plate structure, which is the structure that allows deformation in the thickness direction. Mathematical models of the ME coefficients are developed using the constitutive equations of magnetostrictive and piezoelectric. Two modes of interest include longitudinal-transverse (L-T) and transverse-transverse (T-T) modes. Applying the models to the nanolayer of Terfenol-D/PZT in the assumingly low frequency regime yields the optimal thickness ratio of 0.34 for both modes. The maximum ME coefficients for 5, 10, and 10 nm thick structures are equal but occur at different resonant frequencies. They are approximately 480 and 240 mV/Oe cm for T-T and L-T modes, respectively. The maximum ME coefficients of the Terfenol-D/PZT plate structure are sufficiently high for nanoscale magnetic sensing applications.

Abstract: A new piston pump structure was designed by incorporating a rare earth giant magnetostrictive material as the driving source into the basic working principles of piston pumps. The operational process of the proposed magnetostrictive piston pump was analyzed according to the overall structure design, which includes a magnetostrictive rod, drive coils, pump cavity height, one-way valve and pre-pressure mechanism. Analysis was conducted on both the seal and self-suction capacity of the proposed design. The magnetostrictive piston pump was designed to simplify the structure of a conventional piston pump by requiring fewer moving parts, a small volume, being of light weight, and utilizing a precise controllable flow, among other advantages. An experimental prototype was built and an experimental system was designed to test flow and pressure characteristics. Output flow and pressure curves were obtained to analyze the flow instability when exposed to high currents. Experimental results demonstrate that the magnetostrictive piston pump achieves a maximum output flow of 550.65mL/min when the excitation current frequency is 50Hz, and achieves a maximum output pressure of 0.65MPA when the excitation current frequency is 10Hz.

Abstract: Soft magnetic material FeCoV is sensitive to magnetic field and its cost is lower than giant magnetostriction materials (Terfenol-D et al.). In the present investigation Pb (Mg_1/3Nb_2/3)O₃-PbTiO₃ (PMN-PT) with different thickness and FeCoV laminate with 0.8mm thickness were assembled into layer structure to study the effect of the PMN-PT volume fraction on the magnetoelectric coefficient of PMN-PT/FeCoV laminate composites. The ME coefficients and voltages have been characterized in the longitudinally magnetized and transversely polarized mode. The measurement was conducted under a static magnetic field superimposed with an alternating magnetic field. The influences of the static and the alternating field strength were discussed. The peak ME coefficient was obtained at 430 Oe. With the volume fraction of PMN-PT increased, the ME coefficient decreased within the experiment fraction. It can be explained by the module of M.I.Bichurin. A linear relationship was observed between the magnetoelectric voltage and the alternating field strength under a static field of 400 Oe. The ME voltage decreased when the PMN-PT volume fraction increased in the experiment fraction.

Abstract: The magnetoelectric (ME) effect induced in a multiferroic composite is potentially a key to improve the performance of the nanoread head in the future magnetic recording device. In this paper, the analysis of the 1-dimensional (1D) L-T mode model containing sandwiched structures of Terfenol-D/Lead zirconate titanate (PZT)/Terfenol-D nanomultiferroic composites is performed. The magnetostriction process is described using the 1D standard square law. The magnetoelectric coupling is then investigated. The piezoelectric response on the applied dc magnetic field and PZT to Terfenol-D thickness (t_p:t_m) ratio, is determined. The optimal electric field and potential across the PZT layer are achieved at 1.3:1 thickness ratio. The result agrees well with the associated magnetic field-induced strain profile. The peak ME coefficient is found at 1.37:1 thickness ratio.

Abstract: An energy harvester is presented to harvest ambient vibration energy using a cantilever beam and multiple Terfenol-D/PMN-PT/Terfenol-D laminate magnetoelectric transducers. The harvester uses eight magnets to make up a magnetic circuit arranged on the free end of the cantilever beam. The magnetic circuit can produce a high gradient magnetic field space. The multiple transducers are placed at the high magnetic field gradient position to make the best use of the magnetic field produced by the magnets. The nonlinear vibration and electrical-output performances of the harvester at resonance are analyzed. The theoretical results indicate that the prototype can produce a load power of 7.619 mW, which is sufficient to supply low consumption wireless sensor nodes.

Abstract: Giant magnetostrictive transducer in the work show strong magnetic mechanical coupling characteristics and nonlinear characteristics, its magnetic state and mechanical state influence each other, coupling process is very complicated, this paper according to the giant magnetostrictive material features, combined with the magnetic domain theory, establish the super magnetostrictive micro displacement actuator model, Explore stress and magnetic field changes, GMM inner magnetic strength change, and the change of strain. Join based on giant magnetostrictive actuator structure and working principle, from the principle of physics, mathematics phenomenological theory Angle to establish the combination of the mathematical model of giant magnetostrictive actuator: According to the actuator output power and output displacement, combined with the equation of motion establish output displacement - output force model. According to an internal magnetic induction intensity change, establish actuator induction voltage model; According to J-A model magnetization model. By using the finite element theory and the Hamilton principle of minimum potential energy, energy conservation principle to this mathematical model, and analyze the result.

Abstract: The element W, Mo with paremagnetism and grain refinement is selected according to the theory of magnetostrictive and fine grain strengthening method. The sample with low coefficient of thermal expansion (CTE) and high strength are made by W and Mo alloying of Fe-Ni36, forging and heat treatment. The mechanism of low coefficient of thermal expansion and high strength is analyzed by means of the results of Chemical analysis, metallographic and scanning electron microscopy, grain size, micro-hardness and CTE testing. The result shows: the strength of matrix is improved by W and Mo alloying, the CTE is lower at the same time.

Abstract: This paper reviews the characteristics of smart materials, such as Piezoelectrics (PZT), shape memory alloys (SMA) and mganetostrictive materials (Terfenol-D). Since the properties of these smart materials vary greatly in terms of free strain and actuation stress, there is a need to identify the optimum smart materials for a particular application. From the review and comparison of different types of pumps (based on PZT, SMA and Terfenol-D), we recognize that these pumps have their unique advantages in specific application fields.

Abstract: Equations for reconstructing 3D images of internal flaws are presented. Waveforms were measured from a simple reference sample to derive the response function of the probe, and the response function was calculated based on those waveforms. A sample with internal flaws was prepared to evaluate the reconstructed images of internal flaws derived by EMAT using magnetostrictives. 3D-images of an internal flaw could be derived using this response function.

Abstract: Loss characterization in magnetostrictors is one of the key issues for realizing reliable magnetomechanical transducers. Concerning with the hysteresis minor loop within a relatively linear area of magnetostrictive curve, there are three types of losses, elastic loss, magnetic loss and piezomagnetic coupling loss, similar to the loss mechanism of a piezoelectric (elastic, dielectric and piezoelectric losses) that our group has established recent years. By measuring accurately the mechanical quality factors QA for the resonance and QB for the anti-resonance in the admittance/impedance curve, we can derive these three physical losses. By introducing these losses factors we can characterize magnetostrictive losses using complex parameters.