An original method, measurement devices and software tool for examination of magneto-mechanical phenomena
in wide range of SMART applications is proposed. In many Hi-End market constructions it is necessary to
carry out examinations of mechanical and magnetic properties simultaneously. Technological processes of fabrication
of modern materials (for example cutting, premagnetisation and prestress) and advanced concept of using
SMART structures involves the design of next generation system for optimization of electric and magnetic field
distribution. The original fast and higher than million point static resolution scanner with mulitsensor probes
has been constructed to measure full components of the magnetic field intensity vector H, and to visualize them
into end user acceptable variant. The scanner has also the capability to acquire electric potentials on surface to
work with magneto-piezo devices. Advanced electronic subsystems have been applied for processing of results
in the Magscaner Vison System and the corresponding software - Maglab has been also evaluated. The Dipole
Contour Method (DCM) is provided for modeling different states between magnetic and electric coupled materials
and to visually explain the information of the experimental data. Dedicated software collaborating with industrial parametric systems CAD. Measurement technique consists of acquiring a cloud of points similarly as in tomography, 3D visualisation. The actually carried verification of abilities of 3D digitizer will enable inspection of SMART actuators with the cylindrical form, pellets with miniature sizes designed for oscillations dampers in various construction, for example in vehicle industry.
The role of Smart Magnetic Materials (SMM) is still increasing. One type of SMM are Giant Magnetostrictive Materials (GMM) which can be represented by i.e. Terfenol-D. The biggest difficulty with mechanical application of GMM is its brittleness. On the other hand, increase of frequency generate meaningfully eddy currents. These disadvantages tend to search new solutions in a form of composite materials with giant magnetostriction (GMMC). The matrix for GMMC most often is an epoxy resin with magnetostrictive material inside (in a form of powder, flakes or tiny rods made of i.e. Terfenol-D). Several composites, with outstanding magnetostrictive properties, have been synthesized combining an epoxy resin with polycrystalline powders of Terfenol-D. Application of appropriate way of compression allowed to achieve composites consisting near 70% volume fraction of Terfenol-D powder in comparison with about 48% volume fraction of reinforcement in traditional production way. Composites had random and preferential grain orientation which was obtained by curing the material respectively with or without a magnetic field. The quasistatic magnetomechanical properties of the composites were investigated and compared with monolithic Terfenol-D alloy. The highest response was obtained for a perpendicular polarized composite. Investigated composite are promising magnetostrictive material enable to create a new type of actuators and magnetic field sensor.
Rising requirements for a new constructions, devices and machines force engineers to monitor them all day long.
An attractive solution seems to be applications of wireless sensors. However, there is a barrier limiting their
application, which is the need to supply them with an electrical power over extended period of time without
using additional wiring or batteries. The potential solution of this problem seems to be an energy harvesting.
Most methods of obtaining the energy from the external sources e.g. vibrations, is to use piezoelectric materials.
However, the amount of energy generated by piezoelectric materials is smaller than most electronic devices
need. Therefore a new method for generating a pulse of energy and conditioning for other loads devices must
be developed. This paper proposes a new energy harvesting device based on magnetostrictive material. In the
course of the experiments with using Terfenol-D rods as actuators and sensors it has been observed interesting
phenomenon. Mechanical impact (e.g.energy between 1J and 10J in infinite time) to magnetic core based on
Terfenol-D rod (diameter 5mm, length 10 mm), NdFeB permanent magnets and coil allowed get electric power
signal enough to supply device of 100 Ohm load on their active state (typical low power controller). In comparison
to the same magnetic circuit built with other typical ferromagnetic materials e.g. Armco iron, showed effect
10 times lower or none. Tests and experiments showed the important role of coupling Terfenol-D and NdFeB
permanent magnets, their configuration and variable coil parameters determined this effect. In regard to the
results the authors proposed the construction of a new impulse harvesting method based on Terfenol-D material
for low impedance load.
Smart Magnetic Materials (SMM) play growing role in materials science and applications. Due to variety of subjects connected with SMM we have confined ourselves to magnetorheological fluids (MRF), magnetorheological composites (MRC), Giant Magnetostrictive Materials (GMM) and Magnetovision Camera using MR sensors. The MRC used for tests was created by soaking porous material with Magnetorheological Fluid. The experimental set-up used for applying, acquisition, processing mechanical and magnetic signals is shown. Total influence of magnetic field H and amplitude of deformation on damping in tested MRC is presented. Examples of application are discussed. In the second part tests of GMM were performed for rare earth elements alloy (Terfenol-D). High effectiveness in transforming magnetic energy into mechanical one (actuator) as well as mechanical into magnetic (sensor) requires experimental determination and identification. Original stand used in research allowed to fix mechanical and magnetic loads, measurement of signals and signal processing. Exemplary results of model identification comprising own experimental data are presented. The next part of study was aimed at designing a system for measuring the strength of magnetic field surrounding a ferromagnetic specimen subjected to cyclic (or static) loading. A new type of camera for monitoring the magnetic picture of specimen and others objects was constructed. The measurement principle is based on the reverse magnetostriction effect (also called the Villari effect). No external magnetizing field is assumed. The measuring set-up is made up a precision computer controlled X-Y positioner and a basis unit whose main element is a single magnetoresistor or an array of magnetoresistors.
NiMnGa thin films have been deposited by magnetron sputtering
on Mo substrates using a Ni50Mn30Ga20 powder metallurgical
target. Independent from variation of substrate temperature
during the sputtering process the deposited films are found to
be polycrystalline. X-ray diffraction patterns show a decreasing
peak width and a shift to slightly higher Bragg angles with
increasing substrate temperature during sputtering, which is
even amplified when subsequent rapid thermal annealing is
applied. Annealing temperatures above 500°C lead to a
remarkable enhancement of the shape memory effect as well as
of the magnetostriction. Temperature induced martensitic
transformations have been measured by a cantilever deflection
technique and a cantilever resonance method. Martensitic start
temperatures (MS) range between 50 and 90°C depending on
composition and annealing temperature. Stress relief
upon the martensitic transformation ranges between 200 and
300 MPa whereas the magnetostrictive coupling constant b is
about 2 MPa. Magnetization measurements and Curie
temperature determination reveal ferromagnetic behavior
within the temperature range of the martensitic transformation.