Papers by Keyword: Magnetomechanical Effect

Abstract: To simulated the magnetization change at the instant of fracture, assume that the distribution of dislocation-magnetic dipole is consistent, the models of dislocation-magnetic dipole for tensile fracture and tensile-tensile fatigue fracture are established, respectively: The distribution of magnetic dipole for tensile fracture is linear increase from distant to the fracture zone, while the distribution of magnetic dipole for tensile-tensile fatigue fracture is converging only at the fracture zone. It is found that the established model can present the change of peak-to-peak in magnetization for tensile fracture and tensile-tensile fatigue fracture.

Abstract: The <110> grain oriented alloy was grown by zone melting directional solidification technique. The strain-stress curves of Tb0.3Dy0.7Fe2 <110> oriented alloy in different magnetic fields have been measured and the magnetic field dependence of Young’s modulus under different compressive stress has been confirmed. It is found that Young’s modulus gradually decreases with increasing the magnetic fields when the compressive stress is in the range of 15-25 MPa and changes a little in the range of 40-50 MPa. The experimental result indicates that the magnetic field has a marked effect on the Young’s modulus of the Tb0.3Dy0.7Fe2 <110> oriented alloy at a low compressive stress and its change should be considered during the design of magnetostrictive devices.

Abstract: The magnetic field of ferromagnetic components under service load and geomagnetic field increases is induced by the residual magnetic induction and spontaneous magnetization. The stress concentration positions can be determination by detecting the magnetic field and the fracture can be avoided. The magnetic intensities of the demagnetized samples are tested by metal magnetic memory test method. By tensile test, the relationship between the magnetic memory signals and tensile load is studied, and the metal magnetic memory characteristics of the demagnetized samples under condition that the load keeps a fixed value are obtained. The test result indicates that the magnetic intensities of the samples change greatly after demagnetized; the change of the magnetic intensity of each test point are much different with different tensile displacement; in the later period of hardening phase and necking phase, the magnetic intensity about the side of the stress concentration positions increases along with the increasing of tensile displacement, however that of the other side decreases, that is the gradient of Fracture position increases obviously. Basing on this result by testing the parts of components emphatically where the fatigue failure and breakdown appear easily, the abrupt accident can be avoided.

Abstract: The study was aimed at designing a system for measuring the distribution of magnetic field around different magnetic objects including Smart Magnetic Materials. A new type of 3D camera for monitoring the magnetic field intensity was constructed. The measurement principle is based on internal magnetics properties of materials and the reverse magnetostriction effect (also called the Villari effect). No external magnetizing field is assumed; the entire magnetic effect is due to magnetomechanical principles. A new generation of Honeywell magnetosensors were applied to measure field intensity in 3D. Small size of measurement area (1.5 mm3) allows quasi-local measurement of magnetic field. In the measurement head also Hall probes were alternately used. The aim of this stage of research was to construct the set for measurement of strength of a very weak magnetic field (10 A/m) around the magnetic objects. In scanner construction three axes for displacement in directions consistent with sensor axis were applied, which permits measuring magnetic field vector in geometrical coordination. Specialized software for data acquisition, processing and visualization of magnetic field vector has been written. In preliminary parts of the work magnetic scanner system allows determination of correspondence between mechanical and magnetic quantities. Main applications for this type of system are: reverse magnetostriction and magnetostriction in smart magnetic materials and composites, martensitic transformation induces plastic strain in shape memory alloys, NDT investigation, identification of local plastic deformation and texture of ferromagnetic materials, magnetic polygraphy and others. Measuring system may be used both as an entirely autonomous system as well as an integrated one, also through joint control with a typical mechanical testing systems for static and fatigue tests.

Abstract: The paper presents an application of giant magnetostriction phenomenon into particular vibration generator. It was assumed that the generator should enable tests of construction under local loads applied with broad spectrum of frequencies. Mass of a device must be minimal, it should exert large forces with large amplitudes and high efficiency. The applied material is Terfenol-D - an alloy of rare earth elements and iron which exhibits giant magnetostriction. It is a compound of Laves phases with cubic MgCu2 structure. Examinations ofmagnetomechanical properties of Terfenol preceded construction. The efficiency of transformation of magnetic energy into the mechanical one was tested. The key role in efficiency is played by initial compressing prestresses involved and stimulation by constant magnetic field. The output quantities of constructed device as force, displacement and frequency are completely controlled. The control system includes modern power DC amplifier. It was shown some experimental results of examination of the magnetostrictive actuator. Examples of generations of mechanical vibrations in various constructions enter the new area of applications of Smart Magnetic Materials.