Magnetostrictive vibration generation system

A shaker with a Terfenol-D rod actuator includes a mass coupled to both ends of the rod through a spring seat, a spring seat/adjuster and a spring washer. The actuator is mounted inside a cylindrical coil, which in turn is mounted inside a cylindrical permanent magnet, which in turn is mounted inside a cylindrical housing. An electrical drive system provides a predetermined excitation signal to the coil to cause the rod to vibrate under the influence of the magnetic field generated by the coil. One embodiment features a vibrating mass on one end of the rod. An implantable shaker includes a seal to leak-proof the shaker and a coating of Biomer™. The implantable shaker can be implanted in an animal to test tissue response to certain vibrations. According to another embodiment, the Terfenol-D rod actuator is held in place on one end with a pre-stress adjusting screw, which is threaded into the end of the housing and fixed in place with a jam nut. In all embodiments, a spring base is seated on one end of the rod actuator and forms an annular coaxial air gap between it and a spring seat, so that the air gap remains constant when the rod actuator vibrates and the spring base moves coaxially with respect to the spring seat

Galfenol Tactile Sensor Array and Visual Mapping System

The smart material, Galfenol, is being explored for its uses as a magnetostrictive material. This project seeks to determine if Galfenol can be used as a tactile sensor in a 2-D grid array, magnetic circuit system. When used within a magnetic circuit, Galfenol indicates induced stress and force as a change in flux, due to a change in permeability of the material. The change in flux is detected by Giant MagnetoResistive (GMR) Sensors, which produce a voltage change proportional to the field change. By using Galfenol in an array, this research attempts to create a sensory area. Galfenol is an alloy made of Iron and Gallium. FexGax, where 15 less than or equal to x less than or equal to 28, creates a material with useful mechanical and transduction attributes (Clark et al and Kell). Galfenol is also distinguished by the crystalline structure of the material. Two types currently exist: single crystal and polycrystalline. Single crystal has higher transduction coefficients than polycrystalline, but is more costly. Polycrystalline Galfenol is currently available as either production or research grade. The designations are related to the sample growth rate with the slower rate being the research grade. The slower growth rate more closely resembles the single crystal Galfenol properties. Galfenol 17.5- 18% research grade is used for this experiment, provided by Etrema Products Inc. The magnetic circuit and sensor array is first built at the macro scale so that the design can be verified. After the macro scale is proven, further development will move the system to the nano-level. Recent advances in nanofabrication have enabled Galfenol to be grown as nanowires. Using the nanowires, research will seek to create high resolution tactile sensors with spatial resolutions similar to human finger tips, but with greater force ranges and sensitivity capabilities (Flatau & Stadler). Possible uses of such systems include robotics and prosthetics

Quasi-Static Transduction Characterization of Galfenol

The objective of the work presented is characterization of the magnetoelastic transduction properties of single crystal and textured polycrystalline Fe-Ga alloys (Galfenol) under controlled mechanical, magnetic and thermal conditions. Polycrystalline samples of interest include a directionally solidified specimen, which possesses a favorable saturation magnetostriction output, and an extruded specimen, whose magnetostriction properties were significantly reduced by annealing. A brief discussion of the thermally controlled transducer used for the magnetic testing is presented first. Thereafter, the single crystal response to major-loop cyclic magnetic fields under different temperature and stress conditions, as well as its response to minor-loop cyclic magnetic fields and major-loop cyclic stress is examined. Next, the magnetic and magnetostrictive responses to major-loop cyclic magnetic field conditions are compared for the directionally solidified, extruded and single crystal specimens. The paper concludes with a magnetic characterization summary of the different Fe-Ga alloys examined

Temperature and stress dependencies of the magnetic and magnetostrictive properties of Fe0.81Ga0.19

It was recently reported that the addition of nonmagnetic Ga increased the saturation magnetostriction (λ100) of Fe over tenfold while leaving the rhombohedral magnetostriction (λ111) almost unchanged. To determine the relationship between the magnetostriction and the magnetization we measured the temperature and stress dependence of both the magnetostriction and magnetization from −21 °C to +80 °C under compressive stresses ranging from 14.4 MPa to 87.1 MPa. For this study a single crystal rod of Fe0.81Ga0.19 was quenched from 800 °C into water to insure a nearly random distribution of Ga atoms. Constant temperature tests showed that compressive stresses greater than 14.4 MPa were needed to achieve the maximum magnetostriction. For the case of a 45.3 MPa compressive stress and applied field of 800 Oe, the maximum magnetostriction at 80 °C decreases from its value at −21 °C by 12.9%. This small magnetostrictive decrease is consistent with a correspondingly small 3.6% decrease in magnetization over the same temperature range. This well-behaved temperature response makes this alloy particularly valuable for industrial and military smart actuator, transducer, and active damping applications. The measured value of Young’s modulus is low (∼55±1 GPa) and almost temperature independent. The large magnetostriction over a wide temperature range combined with the nonbrittle nature of the alloy is rare

Magnetostrictive vibration generation system

A shaker with a Terfenol-D rod actuator includes a mass coupled to both ends of the rod through a spring seat, a spring seat/adjuster and a spring washer. The actuator is mounted inside a cylindrical coil, which in turn is mounted inside a cylindrical permanent magnet, which in turn is mounted inside a cylindrical housing. An electrical drive system provides a predetermined excitation signal to the coil to cause the rod to vibrate under the influence of the magnetic field generated by the coil. One embodiment features a vibrating mass on one end of the rod. An implantable shaker includes a seal to leak-proof the shaker and a coating of Biomer™. The implantable shaker can be implanted in an animal to test tissue response to certain vibrations. According to another embodiment, the Terfenol-D rod actuator is held in place on one end with a pre-stress adjusting screw, which is threaded into the end of the housing and fixed in place with a jam nut. In all embodiments, a spring base is seated on one end of the rod actuator and forms an annular coaxial air gap between it and a spring seat, so that the air gap remains constant when the rod actuator vibrates and the spring base moves coaxially with respect to the spring seat.</p

Magnetostrictive vibration generation system

A shaker with a Terfenol-D rod actuator includes a mass coupled to both ends of the rod through a spring seat, a spring seat/adjuster and a spring washer. The actuator is mounted inside a cylindrical coil, which in turn is mounted inside a cylindrical permanent magnet, which in turn is mounted inside a cylindrical housing. An electrical drive system provides a predetermined excitation signal to the coil to cause the rod to vibrate under the influence of the magnetic field generated by the coil. One embodiment features a vibrating mass on one end of the rod. An implantable shaker includes a seal to leak-proof the shaker and a coating of Biomer™. The implantable shaker can be implanted in an animal to test tissue response to certain vibrations. According to another embodiment, the Terfenol-D rod actuator is held in place on one end with a pre-stress adjusting screw, which is threaded into the end of the housing and fixed in place with a jam nut. In all embodiments, a spring base is seated on one end of the rod actuator and forms an annular coaxial air gap between it and a spring seat, so that the air gap remains constant when the rod actuator vibrates and the spring base moves coaxially with respect to the spring seat.</p

FABRICATION OF A DIELECTRIC ELECTRO ACTIVE POLYMER TUBE ACTUATOR WITH PRE-STRAIN MECHANISM

ABSTRACT The aim of this paper is to discuss and present our work on the fabrication of a Dielectric Electro Active Polymer (DEAP) actuator with a pre-strain mechanism. In this study the actuator uses commercially available evaluation DEAP film from Danfoss Polypower A/S. The manufacturing process is presented as well blocked force and free displacement data for voltages ranging from 0 to 2500 volts. Challenges encountered during the manufacturing of the actuator are also described and possible solutions discussed. INTRODUCTION Dielectric electro active polymers (DEAP) belong to a specific class of materials within the electro active polymers (EAP) family that responds to electrical stimulation with significant deformation. DEAP can be used as actuators, sensors [1] and energy harvesting devices DEAP is essentially a compliant capacitor that consists of an elastomeric polymer film coated on both sides with compliant electrodes. When a voltage difference is applied between the electrodes, Maxwell stress is generated on the film which leads the elastomer to contract in thickness and expand the in-plan