A. Bergqvist

Preisach modeling of magnetostrictive hysteresis

Preisach‐type models are suggested for the description of strain hysteresis of magnetostrictive materials. It is pointed out that the strain hysteresis has some peculiar properties in comparison with magnetic hysteresis. These peculiarities of strain hysteresis are discussed in detail along with the identification problem for these models.

Magnetic vector hysteresis model with dry friction-like pinning

Abstract A phenomenological model of magnetic vector hysteresis is described. Magnetization is expressed as a superposition from the contributions of a large number of pseudoparticles. The free energy of individual particles is assumed to be the sum of a convex component representing anhysteretic behaviour, and a small ripple representing the influence of pinning sites. The ripple component is found to give a dry friction-like hysteresis mechanism. Some comparisons with experiments are given.

A stress-dependent magnetic Preisach hysteresis model

The authors present a generalization of the classical Preisach model which handles coupled magnetic and mechanical hysteresis. Magnetostrictive materials are known to have hysteresis with respect to both magnetic field H and mechanical stress lambda . To test the validity of the model, experiments where the two components H and lambda have been verified in many different ways have been performed on Terfenol-D and compared to results computed from the model. Some of these results are presented. This stress-dependent model is found to have an accuracy comparable to that of the classical Preisach model. >

A magnetostrictive electric generator

An electric generator based on the magnetostrictive effect is presented. Longitudinal oscillations of a Terfenol-D rod give rise to a varying flux which induces a current in a coil wound around the rod. A small prototype of such a device is discussed, and both calculations and experiments are performed. The problem of eddy current losses is addressed. >

Modelling eddy currents and hysteresis in a transformer laminate

A Cauer circuit model of a transformer laminate is presented. It considers saturation, eddy currents and hysteresis. The simulation results agree to experiments with an Epstein frame in the 10-200 Hz range. The paper includes a description of a computationally fast hysteresis model with few adjustable parameters and a physical approach to derive the Cauer circuit. The model can be used under various time-transient conditions and can easily be implemented into a larger system in a circuit simulation package, such as Saber, to study a transformers interaction with switching overvoltages, for example.

Experimental Testing Of An Anisotropic Vector Hysteresis Model

A vector hysteresis model is experimentally tested for two soft magnetic materials in the two-dimensional case. The model expresses net magnetization as a sum of contributions from a number of pseudoparticles, each one having a dry friction-like hysteresis mechanism. Five adjustable parameters are used to represent hysteretic properties. Comparisons between calculations and measurements on silicon-iron are made for hysteresis curves and rotational and alternating hysteresis losses.

Utilizing Anisotropic Preisach-type Models In The Accurate Simulation Of Magnetostriction

Magnetostriction models are being widely used in the development of fine positioning and active vibration damping devices. This paper presents a new approach for simulating 1-D magnetostriction using 2-D anisotropic Preisach-type models. In this approach, identification of the model takes into account measured flux density versus field and strain versus field curves for different stress values. Consequently, a more accurate magnetostriction model may be obtained. Details of the identification procedure as well as experimental testing of the proposed model are given.

A phenomenological magnetomechanical hysteresis model

To obtain accurate design tools for applications involving giant magnetostrictive materials, magnetomechanical hysteresis effects should be taken into account. The problem consists of determining the magnetization and mechanical strain from the combined past history of magnetic field and mechanical stress. In this work, coupled magnetomechanical hysteresis has been modeled by using simple path‐dependent differentials to accumulate the past history in functions related to the magnetization and strain through material‐dependent parameters. By using anhysteretic curves and a few additional parameters to characterize a material, major, and minor loops with respect to both field and stress have been calculated for Terfenol‐D and have shown good agreement with experiments.

A design technique for magnetostrictive actuators with laminated active material

A design technique is presented that can give an accurate estimation of magnetostrictive actuator performance when the active material is laminated. The method is to represent the laminated active material by an effective solid material with zero electrical conductivity and a modified constitutive law including the influence of eddy currents. A numeric evaluation has been made and comparisons with previous approaches are presented. The conclusion is that the technique is a feasible tool for design of magnetostrictive actuators with laminated active material with better accuracy, fewer parameters and higher computational speed than previously implemented methods.

Loss simulations in magnetostrictive actuators

Power losses in a magnetostrictive actuator have been studied. The system consists of a cylindrical rod of Terfenol‐D, a surrounding magnetic circuit to get a homogeneous flux, a mechanical load applied to the rod ends, and an electric coil. We consider transient operating conditions with time‐varying driving voltage. Nonlinearity and hysteresis are handled by using a magnetomechanical hysteresis model as the constitutive law. Eddycurrents and field constriction are taken into account by a finite difference representation of the diffusionequation for the active rod. Coil losses are trivially found through Ohm’s law. The influence of laminations in the magnetostrictive rod on the eddycurrent loss is examined using finite element methods.