Development of magnetostrictive active members for control of space structures

The goal of this Phase 2 Small Business Innovative Research (SBIR) project was to determine the technical feasibility of developing magnetostrictive active members for use as truss elements in space structures. Active members control elastic vibrations of truss-based space structures and integrate the functions of truss structure element, actively controlled actuator, and sensor. The active members must control structural motion to the sub-micron level and, for many proposed space applications, work at cryogenic temperatures. Under this program both room temperature and cryogenic temperature magnetostrictive active members were designed, fabricated, and tested. The results of these performance tests indicated that room temperature magnetostrictive actuators feature higher strain, stiffness, and force capability with lower amplifier requirements than similarly sized piezoelectric or electrostrictive active members, at the cost of higher mass. Two different cryogenic temperature magnetostrictive materials were tested at liquid nitrogen temperatures, both with larger strain capability than the room temperature magnetostrictive materials. The cryogenic active member development included the design and fabrication of a cryostat that allows operation of the cryogenic active member in a space structure testbed

Design and application of magnetostrictive materials

Magnetostriction is the change in shape of materials under the influence of an external magnetic field. The cause of magnetostriction change in length is the result of the rotation of small magnetic domains. This rotation and re-orientation causes internal strains in the material structure. The strains in the structure lead to the stretching (in the case of positive magnetostriction) of the material in the direction of the magnetic field. During this stretching process the cross-section is reduced in a way that the volume is kept nearly constant. The size of the volume change is so small that it can be neglected under normal operating conditions. Applying a stronger field leads to stronger and more definite re-orientation of more and more domains in the direction of magnetic field. When all the magnetic domains have become aligned with the magnetic field the saturation point has been achieved. This paper presents the state of the art of the magnetostrictive materials and their applications such as: Reaction Mass Actuator, A standard Terfenol-D Actuator, Linear Motor Based on Terfenol-D (Worm Motor), Terfenol-D in Sonar Transducers, Terfenol-D Wireless Rotational Motor, Terfenol-D Electro-Hydraulic Actuator, Wireless Linear Micro-Motor, Magnetostrictive Film Applications, Magnetostrictive Contactless Torque Sensors and many other applications. The study shows that excellent features can be obtained by Magnetostrictive materials for many advanced applications

Vibration energy harvesting using Galfenol based transducer

In this paper the novel design of Galfenol based vibration energy harvester is presented. The device uses Galfenol rod diameter 6.35 mm and length 50mm, polycrystalline, production grade, manufactured by FSZM process by ETREMA Product Inc. For experimental study of the harvester, the test rig was developed. It was found by experiment that for given frequency of external excitation there exist optimal values of bias and pre-stress which maximize generated voltage and harvested power. Under optimized operational conditions and external excitations with frequency 50Hz the designed transducer generates about 10 V and harvests about 0,45 W power. Within the running conditions, the Galfenol rod power density was estimated to 340mW/cm3. The obtained results show high practical potential of Galfenol based sensors for vibration-to-electrical energy conversion, structural health monitoring, etc

Dynamic Simulation of a Fe-Ga Energy Harvester Prototype Through a Preisach-Type Hysteresis Model

This paper presents the modeling of an Fe–Ga energy harvester prototype, within a large range of values of operating parameters (mechanical preload, amplitude and frequency of dynamic load, electric load resistance). The simulations, based on a hysteretic Preisach-type model, employ a voltage-driven finite element formulation using the fixed-point technique, to handle the material nonlinearities. Due to the magneto–mechanical characteristics of Fe–Ga, a preliminary tuning must be performed for each preload to individualize the fixed point constant, to ensure a good convergence of the method. This paper demonstrates how this approach leads to good results for the Fe–Ga prototype. The relative discrepancies between experimental and computational values of the output power remain lower than 5% in the entire range of operating parameters considered

A finite element approach for the implementation of magnetostrictive material terfenol-D in automotive CNG fuel injection actuation

Magnetostriction is the deformation that spontaneously occurs in ferromagnetic materials when an external magnetic field is applied. In applications broadly defined for actuation, magnetostrictive material Terfenol-D possesses intrinsic rapid response times while providing small and accurate displacements and high-energy efficiency, which are some of the essential parameters required for fast control of fuel injector valves for decreased engine emissions and lower fuel consumption compared with the traditional solenoid fuel injection system. A prototype CNG fuel injector assembly was designed, which primarily included magnetostrictive material Terfenol-D as the actuator material, 1020 Steel having soft magnetic properties as the injector housing material, AWG copper wire as the coil material and 316 Stainless Steel having non-magnetic properties as the plunger material. A 2D cross-sectional geometry including the injector housing, coil, Terfenol-D shaft, and plunger, was modeled in both Finite Element Method Magnetics (FEMM) and ANSYS for 2D axisymmetric magnetic simulation. The magnetic simulations were performed in order to determine the coil-circuit parameters and the magnetic field strength to achieve the required magnetostrictive strain, and consequently, the injector needle lift. The FEMM magnetic simulations were carried out with four different types of AWG coil wires and four different injector coil thicknesses in order to evaluate the relationship between the different coil types and thicknesses against the achieved strain or injector lift. Eventually, the optimized parameter obtained from FEMM results analysis was verified against ANSYS electromagnetic simulation. Subsequently, a three dimensional replica of the CNG flow conduit was modelled in GAMBIT with the resultant injector lift. The meshed conduit was then simulated in FLUENT using the 3D time independent segregated solver with standard k-ε, realizable k-ε and RSM turbulent models to predict the mass flow rate of CNG to be injected. Eventually, the simulated flow rates were verified against mathematically derived static flow rate required for a standard automotive fuel injector considering standard horsepower, BSFC and injector duty cycle

Design and experimental verification of magneto-mechanical energy harvesting concept based on construction steel.

The development of self-powered system for powering small scale power electronic devices such as wireless networks and nodes, radio frequency based tags or readers and wireless sensors for applications like structural condition monitoring (SCM) and wireless data recording are getting very popular. The integration of vibration based energy harvesters with the above mentioned devices is a promising approach towards self-powered systems. The techniques of vibration based energy harvesting involve utilization of either piezo-electric or magnetostrictive materials. However, the active materials mostly employed in energy harvesters are either too expensive or are not commonly available. The objective of the study is to utilize construction material more specifically structural steel as an active material because of its abundant availability and practical applications in bridges buildings and rail tracks etc. The literature study regarding various energy harvesting techniques and their applications are presented first to emphasize the importance of vibration based energy harvesting. The prototype design of the proposed energy harvester including the design of mechanical grips and magnetic circuit are discussed in detail. Three different test samples are utilized in which two samples are constructed in the form of a stack using 1 mm and 1.5 mm thick steel sheets and the third sample is a solid steel bar with the dimensions of 20 mm x 20 mm. The free length and cross-sectional area of each sample are 100 mm and 400 mm2 respectively. The measurement method developed for single steel tester is utilized and a new method for obtaining magnetization curves is proposed in the study. In order to determine the effect of stress on magnetization curves, the test sample is first stressed statically using AC magnetization to obtain the stress dependent magnetization curves. It is observed that the permeability of the test material changes under tensile and compressive stress showing the stress dependent magnetic characteristic of the material. To experimentally verify the validity of measurement method and the proposed method, the test sample is stressed dynamically using DC magnetization inducing voltage in the pickup coil. The induced voltage is because of the inverse magnetostriction also known as Villari effect. The results from the solid steel sample and the sample made up of steel sheets are compared during cyclic loading. The steel sheet sample does not go into saturation because of the changing magnetic circuit length as well as the air gap caused by the buckling of individual sheets. Whereas, the induced voltage from the pickup coil starts dropping in case of solid sample which shows that the material is reaching saturation. To validate the magnetization curves obtained from the proposed method, the magnetizing current (I) for maximum ΔB (change in flux density) is calculated which is compared with the I at peak amplitude of the induced voltage curve. The results from the calculations do not take into the account the eddy current losses or hysteresis and therefore the measured results deviate slightly from the calculated results. The maximum power is measured at the point of maximum ΔB value by varying the load resistance for two different cases of cyclic loading. The average output power is measured 13.3 μW for cyclic loading from zero to -20 MPa and 8.76 μW for cyclic loading from 2.5 to 25 MPa at 11 Hz of mechanical vibration using 2.62 Ω load resistance

Performance of Smart Materials-Based Instrumentation for Force Measurements in Biomedical Applications: A Methodological Review

The introduction of smart materials will become increasingly relevant as biomedical technologies progress. Smart materials sense and respond to external stimuli (e.g., chemical, electrical, mechanical, or magnetic signals) or environmental circumstances (e.g., temperature, illuminance, acidity, or humidity), and provide versatile platforms for studying various biological processes because of the numerous analogies between smart materials and biological systems. Several applications based on this class of materials are being developed using different sensing principles and fabrication technologies. In the biomedical field, force sensors are used to characterize tissues and cells, as feedback to develop smart surgical instruments in order to carry out minimally invasive surgery. In this regard, the present work provides an overview of the recent scientific literature regarding the developments in force measurement methods for biomedical applications involving smart materials. In particular, performance evaluation of the main methods proposed in the literature is reviewed on the basis of their results and applications, focusing on their metrological characteristics, such as measuring range, linearity, and measurement accuracy. Classification of smart materials-based force measurement methods is proposed according to their potential applications, highlighting advantages and disadvantages

Optimal Material Selection for Transducers

When selecting an active material for an application, it is tempting to rely upon prior knowledge or commercial products that fit the design criteria. While this method is time effective, it does not provide an optimal selection. The optimal material selection requires an understanding of the limitations of the active material, understanding of the function, constraints and objectives of the device, and rigorous decision making method to ensure rational and clear material selection can be performed. Therefore, this work looks into the three most researched active materials (piezoelectrics, magnetostrictives and shape memory alloys) and looks at how they work and their difficulties. The field of piezoelectrics is vast and contains ceramics, plastics and cellular structures that couple the mechanical and electrical domain. The difficulty with piezoelectric ceramics is their small strains and the dependence of their coefficients on the ferroelectric domains. Giant magnetostrictives materials couple the mechanical and magnetic domains. They are generally better suited for low-frequency operations since they properties deteriorate rapidly with heat. Shape memory alloys are materials that couple thermal and mechanical domains. They have large strain but are limited in their force output, fatigue life and cycle frequency. Optimal material selection requires a formalized material selection method. In mechanical material selection, the formal material selection method uses function, constraints and objectives of the designer to limit the parameter space and allow better decisions. Unfortunately, active materials figures of merit are domain dependent and therefore the mechanical material selection method needs to be adapted. A review of device selection of actuators, sensors and energy harvesters indicates a list of functions, constrains and objectives that the designer can use. Through the analysis of these devices figures of merit, it is realized that the issue is that the simplification that the figures of merit perform does not assist in decision making process. It is better to use decision making methods that have been developed in the field of operational research which assists complex comparative decision making. Finally, the decision making methods are applied to two applications: a resonant cantilever energy harvester and an ultrasound transducer. In both these cases, a review of selection methods of other designers provides guidance of important figures of merit. With these selection methods in consideration, figures of merit are selected and used to find the optimal material based upon the designer preference