Tord Cedell

Magnetostriction, elastic moduli, and coupling factors of composite Terfenol‐D

Recently it was discovered that composites of Terfenol‐D alloys with an insulating binder produce very large magnetostrictions. Resistivities of these composites reach high values, making them attractive for high‐frequency applications which require small eddy current losses. In this paper the magnetostriction, magnetization, and Young’s moduli measurements made under constant magnetic field conditions and under constant flux conditions are reported. From these measurements, magnetomechanical coupling factors are calculated. The properties are compared to those of ordinary metallic Terfenol‐D and nickel. Two different types of composites were investigated. In the first type the composite has an isotropic structure and in the second type, anisotropic. It is shown that the anisotropic type is more desirable since it possesses both higher magnetostriction and higher coupling factors. It is also clearly shown that the magnetization process for the anisotropic type can be explained by a 180° domain wall motion followed by a magnetization rotation.

Evaluation of soft magnetic mouldable composite core motors

The objective of this paper is to evaluate a single-phase claw pole machine where the magnetic core is made of a soft magnetic mouldable composite material (SM2C). SM2C has low permeability but also very low remagnetization losses, which makes this kind of material very suitable for high frequency applications. Therefore, the high speed characteristics of the single-phase claw-pole machine are in focus on theoretical analysis and practical evaluations.

An integrated design of a machine with soft magnetic mouldable composite

This paper focuses on the design and the evaluation of a single-phase claw-pole machine that is integrated into a fan drive. The inner stator of the machine is manufactured by using a rotational moulding technology, which allows a high integrability when using plastic matrix Soft Magnetic Mouldable Composite - SM2C. The goal of the design is to develop a fan integrated drive where the major advantage is the inexpensive production method. The development of a control strategy and the respective control circuitry is part of the design process.

Process Simulation of Single and Dual Frequency Induction Surface Hardening Considering Magnetic Nonlinearity

A 2D computational model of single and simultaneous dual frequency induction hardening has been developed. Process specific aspects such as the nonlinear magnetic material behavior and phase transformation kinetics of quenched and tempered AISI 4140 are considered. Induction surface hardening experiments have been conducted for validation purposes. The measuring methodologies used to extract input data such as the magnetic material behavior, the current, and the effective heating time are presented. Metallurgical characterization and hardness profiles are compared with the results obtained from simulations. The temperature history, hardness depth profile, and hardness distribution are in good agreement.

Dynamic simulation and performance study of magnetostrictive transducers for ultrasonic applications

A dynamic simulation model of magnetostrictive actuators and transducers has been used to study the performance and thermal balance of an ultrasonic magnetostrictive power transducer. Electrically resistive, eddy current, mechanically resistive and hysteresis losses have been deduced when the transducer works against a purely mechanically resistive load of r a moderate driving current of 10 A and a frequency of 21 kHz. The eddy current losses can be reduced significantly by laminating the active material. However the hysteresis losses are the main source for heating the transducers. The power losses obtained from the dynamic simulations have been used as thermal sources in electro-thermal finite element calculations. The calculations show that free air convection is not enough to cool the actuator. Water cooling of the actuator with a flow of 6.8 l/min will decrease the active materials temperature to around 80 degrees C. This has been obtained by estimating the heat transfer and use the heat flow as sinks in the finite element calculations. The design of a magnetostrictive ultrasonic transducer must therefore comprise an optimal working point regarding magnetic biasing and mechanical pre-stress to minimize the hysteresis.

Induction heating using a 2-phase travelling wave setup

Abstract in Undetermined A laboratory implementation of a two-phase travelling wave induction heating setup is described. The focus is the development of a versatile power control system for multi-coil experiments and parameter studies. The drive system features high temporal accuracy, full real-time controllability, and integrated measurement technology, analyzed step wise. The performance was tested using a full pitch travelling wave inductor based on litz wire with a flux concentrator from a powder material. Thermographic images from the experiments are presented and the results are compared with simulations. The challenges related to multi-coil configurations are explained, many of which are difficult to predict from simulations. (Less)

Prototype based study of different winding configurations with SM 2 C core

This paper summarises the outcome of an experimental study, which is related to a winding arrangement in a stator core that is made of Soft Magnetic Mouldable Composite - SM2C. The comparison is made between a distributed concentrated winding and a modular wave-winding, where the modular wave-coils are distributed either axially or circumferentially. Manufacturability and high winding fill factor are vital for a low permeability stator core in order to gain a good machine performance and a low cost in combination with moulding technique. A number of stators are built and verified in order to learn the theoretical and practical issues related to wave-windings.

Design and prototyping a torus machine with a rotocast core.

A torus machine is considered to be an advantageous machine configuration that is impossible to produce using traditional laminated core technology. This paper presents a torus machine with the stator winding moulded into a composite core, using the RotoCast technology. The goal of the design and the prototyping is to study the advantages when dealing with a soft magnetic mouldable composite material (SM2C) while looking for alternative and inexpensive production methods.

Finite elements solutions to magnetostriction.I.: harmonic modelling

This work deals principally with linear finite element (FEM) modelling of highly magnetostrictive materials. This is accomplished by coupling the Maxwells equations to the wave equation by using the linearised tensor equations governing magnetostriction. The model in this paper deals with harmonic oscillations and the resulting FE-model is verified against simplified analytical solutions and differences in results are discussed. The magnetic part of the model is based on the reduced scalar potential. This way only a part of the solutions are dependent on the FE-solutions, giving a model which is less sensitive to the placing of the far-field boundary. Further in this work, no interface condition between abruptly changing permeabilities has been performed since the relative permeability of the medium examined is about five and the so-called near cancellation errors, which some workers in the field accuse to be due to the reduced scalar potential occur in regions of a high relative permeability.

Induction heating of carbon fiber composites: Investigation of electrical and thermal properties

Carbon fiber reinforced plastics, CFRP, are attractive materials not only because of their strength and stiffness but also because of their electrical conductivity and high thermal conductivity and diffusivity. One application where induction heating of CFRP is particularly interesting is tools for fast thermal cycling, beneficial in many industrial processes, for example in composite manufacturing. The electrical properties make it possible to heat with induction and the high thermal conductivity allows fast heat equalization. In order to control inducting heating of CFRP it is desirable to know the electrical and thermal properties of the composite. This work presents developed experimental methods that are used in an investigation of how the thermal and electrical properties of CFRP structures are affected by the fiber properties and composite structure. The experiments and simulations show that fiber type and fiber volume fraction are of great importance for the electrical and thermal properties. The relation between fiber volume fraction and equivalent resistivity is nonlinear and the experiments indicate that a fiber volume fraction exceeding 60% is necessary to achieve a fairly isotropic resistivity and uniform induction heating pattern.