Pre-strained martensitic Shape Memory Alloy wires embeddedz into a composite material act against the stiffness of the host material if they are heated above their retransformation temperature, biasing their strain recovery. As a result, recovery stresses are generated in the composite, leading to a shift in resonance vibration frequency if the wires are placed along the neutral axis of a composite beam. Guidelines for quantification of the effects produced, as a function of SMA wire composition, volume fraction, level of pre-strain, and of host material stiffness are not available yet. In order to investigate the governing mechanisms of activation, adaptive composite materials based on Kevlar fiber reinforced epoxy matrices have been produced by embedding thin Shape Memory Alloy wires, 150 microns in diameter, during processing in an autoclave. A mold was specially designed to pre-strain the SMA wires and prevent their recovery during the cure cycle. Values of the degree of activation in the composite materials, in terms of maximal recovery force and of the corresponding maximal resonance vibration frequency shift will be presented as a function of the stiffness of the host material and SMA volume fraction. Preliminary guidelines for the optimization of these materials will thus be given.

We reported an electro-driven chemomechanical hydrogel showing quick responses with worm-like motility. The principle of the motion is based on the molecular assembly reaction of cationic surfactant and negatively charged hydrogel. And direction of complexation accompanying gel contraction is controlled by changing the polarity of the applied electric field. Both thermodynamics and kinetics of surfactant binding and diffusion are investigated experimentally and theoretically. We also reported shape memory hydrogel by order-disorder transition of alkyl side chain, and some examples od friction of hydrogels showing that frictional behaviors of hydorgels do not conform to Amonton's law.

Three types of shape memory ceramics were introduced. They were the irreversible shape memory silica glass, the reversible shape memory bi-ceramics glass and reversible shape memory silica and Si-C-O glassy fiber samples (the small size change) induced by thermal expansion.

Magnetorheological (MR) fluids are materials that respond to an applied magnetic field with a change in rheological behavior. Typically, this change is manifested by the development of a yield stress that monotonically increases with applied field. Interest in MR fluids derives from their ability to provide simple, quiet and rapid response interfaces between electronic controls and mechanical systems. In this paper, the basic composition and properties of example MR fluids are reviewed. Some contemporary applications of MR fluids are then discussed.

In micro-robotics and for micro-systems, one cannot simply scale down conventional actuators. Specific difficulties like friction forces between parts and the assembly have to be considered carefully and need a special design strategy adapted to this “micro-world”. Shape Memory Alloys (SMA) have strong potential in micro actuators. So far, most of SMA devices used the SMA material as a part of a mechanical system, which raised several problems when scaling down. In this paper, a concept of monolithic SMA micro-devices, which consists in considering the SMA as a mechanical system by itself, is presented. Several applications are shown to illustrate this concept.

Both the longitudinal (LA) Brillouin back-scattering spectra and dielectric permittivity along the [001] direction have been measured as a function of temperature for a relaxor ferroelectric single crystal (PbMg1/3Nb2/3O3)0.68(PbTiO3)0.32 (PMN-32%PT). A sharp ferroelectric phase transition (which is associated with a Landau-Khalatnikov-like phonon damping maximum) was observed near 445 K. As temperature increases, a diffuse phase transition was detected near 280 K. In addition, the nature of the thermal hysteresis for the dielectric permittivity confirms that these transitions (near 280 and 445 K for heating procedure) are diffuse first-order and first-order, It respectively. The dielectric data prove the existence of an electric dipolar relaxation process below 300 K.

A new method of packaging fiber Bragg gratings to stabilize their wavelength over temperature variations was developed using a grating mount fabricated from zirconium tungstate (ZrW2O8), a ceramic with a negative coefficient of thermal expansion (CTE). The principle of operation is based on the differences in CTE of the Bragg grating and grating mount, with the mount serving as a compensator for the thermo-optic effects of the fiber. As the temperature is elevated, the refractive index of the grating increases, shifting the reflection wavelength to longer wavelength. At the same time the ceramic grating mount contracts relieving some of the tension on the grating, causing a shift to shorter wavelength. Since these two effects offset each other, the thermal wavelength shift of the grating can be minimized or even eliminated. In addition to a description of the temperature-compensating device, the properties of zirconium tungstate are briefly discussed with emphasis on the processing of the ceramic grating mount. Thermal analysis data is given for zirconium tungstate with 5% polymer binder addition.

Suspension assemblies, the mechanical arm that supports the read/write head in a Hard Disk Drive (HDD), are incorporating piezoelectric motors for dual-stage actuation. With high displacements and high Curie Temperatures, lead zirconium titanate (PZT) is the preferred piezoelectric material for this application. In this study, commercially available PZT is studied for critical material properties that include strength, aging and particulate generation. An average PZT strength of 111.7 MPa and a Weibull parameter (m) of 12.18 was measured for the material. Aging rates of the dielectric constant vary between 1.9 to 3.2 % per time decade depending on the test condition. The attachment of PZT motors to the suspension assembly provides a method of sensing suspension resonance, shock and temperature fluctuations. Fast Fourier Transform (FFT) analysis of voltage generation of the PZT during drive operation identified a frequency of 6509 Hz that is within 0.2% of the measured resonance frequency of the suspension. The PZT generated several volts for shock events between 500 to 2000 G's of the suspension. Implications of the material parameters and potential sensing capabilities of the PZT are discussed.

This paper assesses the electrical characteristics of piezoelectric wafers for use in aeronautical applications such as active noise control in aircraft. Determination of capacitive behavior and power consumption is necessary to optimize the system configuration and to design efficient driving electronics. Empirical relations are developed from experimental data to predict the capacitance and loss tangent of a PZT5A ceramic as nonlinear functions of both applied peak voltage and driving frequency. Power consumed by the PZT is the rate of energy required to excite the piezoelectric system along with power dissipated due to dielectric loss and mechanical and structural damping. Overall power consumption is thus quantified as a function of peak applied voltage and driving frequency. It was demonstrated that by incorporating the variation of capacitance and power loss with voltage and frequency, satisfactory estimates of power requirements can be obtained. These relations allow general guidelines in selection and application of piezoelectric actuators and driving electronics for active control applications.

A chemical additive method was used to modify the composition and resultant properties of a commercially available 0.96(0.9lPb(Mg1/3Nb2/3)O3 - 0.09PbTiO3) - 0.04 BaTiO3 (PMN-PT-BT) ceramic. Without an additional ball-mixing process, several combinations of minor additives such as Fe, Ba, Sr, Zn and Ti were incorporated by the chemical method. Weak- and high-field characteristics including dielectric properties, induced strain and polarization, and associated hystereses were evaluated for the samples sintered at 1200°C for 4 hrs. All properties were found to depend on the chemical additives and temperature. Especially, the temperature dependence of high-field characteristics revealed different behavior from that reported for conventionally-prepared samples. For example, the samples containing 0.5 wt% SrO, 0.5 wt% ZnO, and 0.5wt% TiO2 did not exhibit a transition to piezoelectric behavior at the temperature expected from the dielectric measurements. Overall, the coating process has been successfully used to modify, and in some cases, enhance the high-field characteristics of PMN-based ceramics for electromechanical uses.

Piezoelectric ceramics are potential high-power electro-acoustic sources, and have been studied for many years. However, when these devices are driven under high level vibration, the electromechanical characteristics depart significantly due to the loss and nonlinear behavior in terms of elastic and dielectric properties. In this paper, we present results concerning the development of modified Pb(Mgl/3Nb2/3)O3-PbTiO3 (PMN-PT) ceramics for high-power application. We have focused efforts on base PMN-PT compositions close to the morphotropic phase boundary. Different mono-doping have been studied to understand the doping effects on the properties of PMN-PT ceramics and, moreover, to improve the properties for the high-power application. Of all the substitutents investigated in this study, Mn-doping was found the only one to improve the properties of PMN-PT significantly for high-power application by reducing the total loss (including mechanical loss as well as the dielectric loss), yet keeping the coupling factor constant. This work is supported by Office of Naval Research.

The effect of thermal cycling on the austenite to martensite (A→M) and martensite to austenite (M→A) transformation temperatures (TTs) of Ni49.8Ti50.2 and Ni49.8Ti40.2Hf10 shape memory alloys is investigated. Test specimens are from arc melted buttons homogenized at 900°C for 100 hours. Results show that the A→M and M→A TTs for the alloys decrease with increasing number of thermal cycles through the phase transformations. The A→M TT of the NiTiHf alloy stabilizes more quickly than the A→M TT of the NiTi alloy when cycled. However, the M→A TT of the binary NiTi alloy stabilizes more quickly than the M→A TT of the NiTiHf alloy when cycled.

Fe-Mn-Si based alloys exhibit the shape memory effect depending on their composition. Upon cooling, these alloys undergo a martensitic transformation γ (fcc) → ε (hcp), and a magnetic transition, at the Néel temperature, from paramagnetic to antiferromagnetic ordering in the γ-phase. In this work, the structural and magnetic phase transition temperatures were determined in an Fe-27Mn-2.5Si (in weight %) shape-memory alloy, using differential scanning calorimetry, dilatometry, electrical resistivity, Mossbauer spectroscopy, and X-ray diffraction. The transition temperatures measured by the different techniques were almost the same. It was observed, by calorimetry and electrical resistivity measurements, that the magnetic transition temperature upon cooling was very close and slightly higher than that of the start of the martensitic transformation, thus promoting the stabilization of the γ-phase. Consequently, the amount of thermally induced ε-martensite was very small. Mössbauer spectroscopy and X-ray diffraction measurements showed that only 10% of ε-martensite was formed upon cooling to quite low temperatures.

Several silicon boride phases such as SiB4, SiB6, SiB6-x, SiB6+x, and Si11B31, were previously reported. Among them, SiB6has proved to be a potentially useful material because of its excellent electrical conductivity, high degree of hardness, moderate melting point, and low specific gravity. The sintering conditions and thermoelectric properties of silicon boride (SiB6) ceramics produced by hot pressing were investigated in order to determine the suitability of this material for high-temperature thermoelectric applications as a smart material. The relative density increased with increasing sintering temperature. With a sintering temperature of 1923 K, a sintered body having a relative density of more than 99% was obtained. X-ray diffraction analysis showed no crystalline phase other than SiB6 in the sintered body. The specimens were prepared for measurement of the electrical conductivity and Seebeck coefficient by the D.C. four-terminal method. The thermal conductivity of SiB6 was obtained by calculation from the thermal diffusivity and specific heat capacity of the specimen. The electrical conductivity of SiB6 increased with increasing temperature. The electrical conductivity of the polycrystalline SiB6 (99% dense) was 0.5 to 1.1 × 103 S/m at 298 to 1273 K. The thermal conductivity decreased with increasing temperature in the range of room temperature to 1273 K. The thermal conductivity was 9.1 to 2.5 W/mK in the range of room temperature to 1273 K. The Seebeck coefficient of SiB6 increased with increasing temperature. The Seebeck coefficient of SiB6 was 140 × 10−6 V/K at 1273 K. The figure of merit Z of SiB6 increased with increasing temperature. The Z of SiB6 reached 8.1 × 10−6/K at 1273 K. The ZT value is useful to evaluate the ability of thermoelectric materials. The ZT value reached 0.01 at 1273 K. Based on the results, SiB6 showed very good thermoelectric material characteristics at high temperature.

The Au / PbZrxTi1-xO3 (PZT) ferroelectrics / YBa2Cu3O7-x (YBCO) superconductor / yttria-stabilized zirconia (YSZ) heterostructures were prepared on Si (100) substrate by KrF excimer laser ablation technique. The x-ray diffraction patterns showed that the PZT films prepared on YBCO / YSZ /Si at 550°C, O2 100 mTorr and a laser energy density of 2 J/cm2(5Hz) are pure perovskite and highly oriented with the (00l) orientation. The polarization (P)-electric field (E) characteristics showed the remanent polarization Pr of 23 µC/cm2 and coercive field Ec, of 35 kV/cm. Pr of the PZT capacitor degraded to one half of initial value after about 1010 switching cycles (50 kHz).

This paper provides an overview of magnetostrictive transducer technology. The bi-directional coupling between the magnetic and mechanical states of a magnetostrictive material provides a transduction mechanism that can be used both for actuation and sensing. The current interest in design of adaptive smart structures, coupled with the advent of materials that exhibit high sensor figures of merit, such as Metglas and giant magnetostrictive materials such as Terfenol-D has lead to a renewed interest in the engineering of optimized magnetostrictive transducer designs. A survey of recent applications for giant magnetostrictive materials as both sensors and actuators and their use in smart structure applications will be presented along with a brief discussion of some pertinent device design issues. Examples of magnetostrictive actuation used to produce displacements, force and acoustic waves are summarized. Magnetostrictive sensor configurations that measure motion, stress or force, torque, magnetic fields and target characteristics are discussed. A very brief look at transducer modeling and experimental results is included and schematics of a number of actuator and sensor configurations are presented.

A magnetostrictive peristaltic motor, similar to an INCHWORM® motor, was designed, built, and tested, using Terfenol-D® as the active element. Unlike the Kiesewetter motor, which uses a rod of Terfenol-D in a closely fitting cylindrical channel, in our design the Terfenol-D is in the form of a flat slab, held between two spring-loaded plates. With this configuration the motor is not affected by wear of the Terfenol-D surface. In order to avoid eddy currents, we used laminated Terfenol-D. Operating at 1600 Hz with a peak field of 430 oersteds, the speed at no load was observed to be 12 mm/sec, which is 65% of the theoretical value (the peak strain times the peristaltic phase velocity), probably because the surface flatness of the Terfenol-D slab was only a few times smaller than the height of the peristaltic bumps. The measured stalling force was 90 newtons, corresponding to 350 kPa load stress in the Terfenol-D, only 3.5% of the peak strain times the stiffness of the Terfenol-D. This force was in almost exact agreement with a model which took into account the force from the spring-loaded plates (needed to avoid slippage), the transverse stiffness of the Terfenol-D slab, and the finite bending stiffness of the stator. The model can be used to design optimized motors with improved force capability. We tried using composite Terfenol-D, consisting of Terfenol-D particles in an epoxy binder, but the speed and stalling force were lower, perhaps because it did not have a very uniform distribution of particles, and was not machined as flat as the laminated Terfenol-D. The motor was driven by a specially designed 3-phase power inverter and digital controller, and the large reactive power inherent in this kind of motor was reduced by putting it in series with resonant capacitors.

The mechanical energy absorption characteristics of several polymer matrix Terfenol-D composites were evaluated experimentally. Magnetostrictive composites absorb energy through domain level processes that couple mechanical and magnetic energies. The testing consisted of mechanically cycling the materials at different stress amplitudes (combined compression and tension) at a single frequency. Results indicate that the magnetostrictive composites exhibit a unique combination of high damping properties in conjunction with a relatively high modulus. The measured tan delta values for the materials are functionally dependent upon the stress amplitude. In general, as the stress amplitude increased, the damping or energy absorbed during one cycle decreased. Results also indicate that damping is directionally dependent (i.e. anisotropic) and that bias magnetic fields decrease the energy absorption. The volume fraction of the composites did not play a significant role in the magnitude of damping. This effect may be related to the inherent pre-stress imparted on the particle by the resin during cure.

The objective of this research and development program is to develop production methods to obtain thin strips of oriented crystalline Terfenol-D and to develop multi-layered driver rods for transducers that will operate over a broad spectrum into the MHz frequency range. To reach this goal, special methods must be used to minimize the amount of mechanical processing, such as machining, as the material is both brittle and expensive. A modified rapid solidification method has been developed to process Terfenol-D to obtain the desired geometric configuration of long thin strips. Currently, sections that are 500 mm long, 2 mm wide and 0.1 mm thick can be produced. In addition, this method enables the crystallographic orientation of the strips of Terfenol-D to be controlled to obtain the preferred orientation that will maximize the magnetostrictive displacement of the material. Magnetostrictive measurements have shown that the samples prepared by this approach have a 62 percent improved magnetostrictive performance when compared to non-oriented Terfenol-D. The ribbons have been consolidated into transducer driver rods. The magnetostrictive performance of the driver rods has been measured to be 60 percent of the as prepared ribbons. The reduction in performance is attributed primarily to the geometric placement of the ribbons inside the driver rods.

A simple model is proposed to relate strain, stress, field and anisotropy in a ferromagnetic shape memory alloy (FSMA) and experiments were performed to test the validity of the model. The model is presented as applied to the case of orthogonal field and load in a NiMn-Ga FSMA. The model predicts threshold-type strain behavior as field changes at constant load or as load changes with constant field. The measured behavior of strain with stress at constant field approximated the predictions of the model. Field-induced strain remained constant at about 6% with the addition of stress until such a stress was applied that the mechanical energy overcame the anisotropy of the sample and the strain was reduced to 0. The model's predictions of critical strain behavior with applied field at constant stress were qualitatively accurate at some stress levels, but under-predicted the field necessary to produce strain.