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The possibility of developing a model based on the concept of magnetic viscosity has been studied from the viewpoint of its ability to predict dynamic loop shape of different materials in both the voltage- and current-driven regimes. The applicability of the model to soft magnetic materials over a wide range of dB/dt is demonstrated by a number of examples. Index Terms--Magnetic hysteresis, magnetic viscosity, soft magnetic materials, time-domain analysis.

We have studied the ability of two one-dimensional (1-D) time-stepping models, both based on the concept of magnetic viscosity, to reproduce dynamic loops and losses in grain-oriented (GO) electrical steels under arbitrary magnetization regimes. We found that GO steels (0.3 mm thick) can be modeled quite accurately at magnetizing frequencies up to 200 Hz by a thin sheet representation, which is applied to a bulk material. At higher frequencies, acceptable results can be obtained through a finite-difference solver of a 1-D penetration equation whose applicability to GO steels can be explained in terms of domain wall bowing. Because of the inertial effect introduced by the magnetic viscosity, the average error in the loss prediction is reduced from 40% for the conventional classical method to 5% for the methods we studied. We demonstrated the accuracy of the models using two GO steels whose losses and B-H characteristics were measured by computer-controlled Epstein and single-sheet testers. Index Terms--Finite-difference time-domain analysis, grain-oriented steel, losses, magnetic hysteresis.

The magnetization reversal process of NiFe/Al-oxide/Co junction films is studied by performing Lorentz transmission electron microscopy (LTEM) and magnetic force microscopy experiments. Reversal mechanism and domain characteristics of the NiFe and Co layers showed very distinctive features.

We applied the Preisach model formalism as a nondestructive material testing method to theoretical systems described by the Jiles-Atherton model. We investigated 1) the influence of stress in the model with magnetomechanical effects on a Preisach-model-based parameter and 2) the sensitivity of the parameter with respect to variation of all the Jiles-Atherton model constants and of the traditional magnetic hysteresis variables. Index Terms--Jiles-Atherton model, nondestructive evaluation, Preisach model.

High speed composite rotors typically require containment structures to protect personnel and equipment from high energy rotor material and fragments that result from rotor burst events, which may occur during rotor overspeed. Loading to the containment structure during a burst event is a function of rotor design and containment geometry. A containment system proposed by The University of Texas at Austin Center for Electromechanics uses graphite-reinforced composite cylinders to dissipate radial kinetic energy from the rotor debris and reduce torque loads transmitted to the rotor housing and mounting hardware. Using an analogous mass-spring-damper system, a model was developed with bond graph techniques to estimate containment loads and response. The bond graphs, state equations, and simulation results are compared with experimental results. The model is able to predict the general trends observed in experimental data and is used as a design tool for containment systems.