Papers by Keyword: Magnetoelasticity

Abstract: Amorphous magnetoelastic alloys show outstanding magnetic and magnetoelastic properties that make them excellent candidates for simple detection and actuation devices. The coupling between elastic and magnetic properties reflects in the dependence of the Young’s modulus with the applied magnetic field. We present a study of the change of the Young’s modulus with the applied magnetic field in ribbons of Fe-Ni-Co-Si-B composition. Strips of different lengths (L = 35, 30, 25, 20 mm) and widths (w = 5, 3.3, 2.5, 1.7 mm) have been measured and obtained results analyzed in terms of the different length-to-width ratios (4 < R < 21). From our observations, depth of the ΔE effect reduces and needed applied magnetic bias field for minimum Young’s modulus value increases as the strips shortens. In order to test the applicability of these materials in a situation of open/close simple designed gas valve, FEM simulations have been performed by using the experimentally measured Young’s modulus values, searching to estimate the maximum deflection of such a strip when working under applied constant pressure. Obtained useful deflection ranges from 1 mm to 10 mm, telling us about the feasibility of this amorphous magnetoelastic ribbons for simple gas valve applications.

Abstract: The paper considers the second order precession of the magnetization vector in a perpendicular magnetized anisotropic ferrite plate with magnetoelastic properties. The boundaries of the precession regimes on the frequency and amplitude of the alternating field were defined. The features of the precession of the magnetization vector regimes associated with magnetoelastic properties were revealed.

Abstract: The paper presents the possibility of using amorphous materials as cores of tensile stress sensors. Application of thermal annealing of the core to increase magnetoelastic sensitivity is presented. Important parts of measuring system are the signal processing circuit of the sensor and the sensor control system. The results of measurements of the characteristics of the sensors with signal processing circuit are presented.

Abstract: Actual trends in machinery maintenance point to the necessity of an on-line real-time monitoring of the condition of the lubricant oil. Excessive delay in replacing the lubricant oil can have catastrophic results, whereas doing it too early produces evident economic and environmental issues. Magnetoelastic materials offer a good sensing principle for assessing lubricant oil viscosity; which is one of the most important properties to assure its proper lubricant capacity. Among others, one of the most remarkable properties of this sensing principle is the capability of being used through a wide viscosity range. In this work, we describe the experiments performed to evaluate the usefulness of this technology for testing the viscosity of different test oils in order to develop a working device for on-line, real-time monitoring the quality of lubricant oils.

Abstract: Understanding of the relationship between stress and magnetic properties in nanostructures is of both fundamental and practical interest. In the present paper, we illustrate this statement with some recent research results. First, we will see how the magnetoelastic interaction in Dy films controls the magnetic structure at the nanoscale due to the presence of the structural defects and their associated strain fields. Then, it will be shown how the magnetoelastic contribution can dominate the total anisotropy in epitaxial (100) oriented Cu/Ni/Cu nanowires, where the film patterning process performed to produce the nanowires induces strain changes large enough to favor a net in-plane anisotropy transverse to the lines.

Abstract: Magneto-elastic bilayers (BLs), consisting of a magnetostrictive layer and a non-magnetic counter layer, show highest sensitivity with respect to bending. This paper describes a biomedical application in the field of sleep apnea screening. A multi-parametric detector fixed at the thorax contains two BLs. One BL yields a skin curvature sensor adjusting itself to curvature variations given by physiological activities. The second BL exhibits a free end thus working as a motion sensor. The two signals are fed into artificial neural networks for the detection of events like normal respiration and apneas, as well as body movements and position.

Abstract: In this paper we present new results on magnetic and magnetoelastic uniformity measurements on Fe78Si7B15 amorphous ribbons and wires. The measurements are performed using an automatic instrumentation device based on the magnetostrictive delay line technique, with the ability to determine the B(H) and (H) functions along the length of a ribbon with parametric control of field and frequency. According to these results, it has been determined that magnetic and magnetoelastic uniformity functions are subject to the history of the under test samples.

Abstract: Magnetic shape-memory alloys owe their exceptional properties primarily to the accompanying effects of a martensitic phase transformation. The twinning disconnection as elementary carrier of magnetic-field-induced deformation is the starting point of the present study. A disconnection is a line defect similar to a dislocation but located at an interface and exhibiting a step character besides a dislocation character. The mutual interaction of disconnections is fully tractable by the theory of dislocations. Due to the martensitic transformation, a hierarchical twin microstructure evolves, details of which are controlled through disconnection-disconnection interaction. Depending on the mutual orientation of twin boundaries on different hierarchical levels, twinning disconnections are incorporated in higher hierarchical twin boundaries forming disclination walls, or they stand off individually from those interfaces. Disconnections which stand off from interfaces contribute to magnetoelasticity, i.e. recoverable magnetic-field-induced deformation. Disconnections in disclination walls contribute to magnetoplasticity, i.e. permanent magnetic-field-induced deformation, if the twin thickness is large. In self-accommodated martensite with very thin twins, resulting from a martensitic transformation without training, the deformation is fully magnetoelastic and small. In single-domain crystals, resulting from effective thermo-magnetomechanical training, the deformation is fully magnetoplastic and large. Between these limiting cases, there is a continuous spectrum where, as a rule, the fraction of magnetoplastic strain and the total strain increase with increasing effectiveness of training.