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1 – 10 of over 2000Shaodi Zhao, Jiusheng Bao, Qingjin Zhang, Yan Yin, Xiaoyang Wang and Junwei Ai
This study aims to develop magnetic field-controlled friction braking technology, the preparation process of hard magnetic brake friction material was optimized and analyzed in…
Abstract
Purpose
This study aims to develop magnetic field-controlled friction braking technology, the preparation process of hard magnetic brake friction material was optimized and analyzed in this paper.
Design/methodology/approach
NdFeB, a rigid magnetic material, was selected as additive. Magnetic field orientation, a part of material preparation, was added to the preparation process. Experiments investigated the tribological properties of each brake lining sample. The preparation process of the hard magnetic friction material was optimized based on fuzzy theory by using analytic hierarchy process (AHP) methods and SPSS software. The microscopic morphology and the distribution and content of elements of friction lining samples prepared with or without orientation excitation voltage were analyzed by scanning electron microscope and energy dispersive X-ray microanalysis.
Findings
The results showed that the tribological properties of brake lining samples could be improved by process optimization and the oriented excitation voltage can effectively improve the properties of the brake lining.
Originality/value
The magnetic field orientation was added into the traditional preparation process, and a set of process parameters with the best tribological properties were obtained through optimization. It is believed that this research will be of great theoretical and practical significance to develop both new brake materials and active control technology of the braking process in the future.
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John Simkin, Alex Michaelides and Chris Riley
The paper seeks to present finite element methods for modelling hard magnetic material magnetisation and degradation “in service”. It aims to describe methods of representing the…
Abstract
Purpose
The paper seeks to present finite element methods for modelling hard magnetic material magnetisation and degradation “in service”. It aims to describe methods of representing the hysteretic behaviour of permanent magnets, and allowing for variations in the material characteristics caused by temperature and demagnetising fields.
Design/methodology/approach
A permanent magnet DC motor example is used to demonstrate the complete modelling cycle. The magnetisation of the ring‐segments of the stator magnets was modelled using a transient, non‐linear, eddy‐current solver. The rings were transferred to the PMDC motor. The de‐magnetisation of the magnets “in service” was studied as a function of load, operating armature current and temperature.
Findings
The effect of hard magnetic material de‐magnetization was accurately quantified. Its dependence on the reverse‐field armature currents and operating temperature was demonstrated. The benefits of accurately representing the material characteristics in PMDC motors were clearly identified.
Research limitations/implications
The model for hard magnetic materials under magnetizing and demagnetising fields can only be perfected by using measured data. The measurements are hard to perform, in particular the effect of demagnetising fields at an angle to the easy magnetization axis is very difficult to measure.
Originality/value
The paper enhances the understanding of the process of hard magnetic material magnetisation and demagnetisation, fully examining the mechanisms and their dependence on parameters such as magnetising and demagnetising fields and temperature. The paper demonstrates how FEA methods can help to design electrical machine by accurately representing magnetic material properties and processes.
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A.M. Michaelides, J. Simkin, P. Kirby and C.P. Riley
The purpose of this paper is to promote practical methods for the numerical modelling of hard magnetic materials and soft ferromagnetic materials in an engineering context (design…
Abstract
Purpose
The purpose of this paper is to promote practical methods for the numerical modelling of hard magnetic materials and soft ferromagnetic materials in an engineering context (design of electrical machines).
Design/methodology/approach
Objectives achieved by the use of a practical, semi‐empirical material model that needs modest material data and computer resources. Methods: a focused theoretical specification and algorithm development; use of actual material data for algorithm validation; incorporation in commercial engineering software as a test harness. Approach: a practical engineering scheme using a macroscopic material model based on readily available materials data. Scope: numerical model of hard magnetic and soft ferromagnetic materials; scalar and vector hysteresis, major and minor loops.
Findings
The limited practicality of much of the literature, especially vector hysteresis; successful use of the model in an existing non‐linear numerical solver; energy conservation gives confidence in the results; the electric motor provides a good validation test case.
Research limitations/implications
Possible future research: application to more complicated material properties such as magneto‐relaxation.
Practical implications
The paper extends the scope of computer‐aided engineering design of electrical machines. The impact on the developer: increased sale of an engineering software product. The impact on the design engineer: more efficient designs, reduced prototyping, reduced technical risk.
Originality/value
The algorithm that provides an effective material model; the focus on the practical issues of data and computational resources; the implementation of a theoretical construct in a large‐scale engineering design program. The value is to designers of electrical machines.
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This paper seeks to present some new designs of sliding bearings lubricated with magnetic fluids (ferrofluids) and the possibility of using them in modern bearing technology, in…
Abstract
Purpose
This paper seeks to present some new designs of sliding bearings lubricated with magnetic fluids (ferrofluids) and the possibility of using them in modern bearing technology, in new computer and audiovisual equipment among others.
Design/methodology/approach
The paper presents new designs of journal, thrust and journal‐thrust sliding bearings lubricated and sealed with magnetic fluids such as: magnetic fluid bearing bushing made of magnetizable material, pivot bearings with porous sleeve impregnated with ferrofluid, self‐aligning bearings, hydrodynamic ferrofluid bearings with spiral and herringbone grooves structure are presented. Moreover, examples are shown of applications in modern bearing technology.
Findings
The paper provides information about new designs of magnetic fluid sliding bearings assemblies and gives the main advantages of these bearings over conventional ball bearings, such as extremely low non‐repetitive run‐out (high‐accuracy of rotation), good damping and quietness of operation, maintenance free service and high reliability.
Originality/value
This paper offers some new designs of compact, low friction and self‐contained magnetic fluid sliding bearings and points up their practical applications.
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Johann Wilhelm and Werner Renhart
The purpose of this paper is to investigate an alternative to established hysteresis models.
Abstract
Purpose
The purpose of this paper is to investigate an alternative to established hysteresis models.
Design/methodology/approach
Different mathematical representations of the magnetic hysteresis are compared and some differences are briefly discussed. After this, the application of the T(x) function is presented and an inductor model is developed. Implementation details of the used transient circuit simulator code are further discussed. From real measurement results, parameters for the model are extracted. The results of the final simulation are finally discussed and compared to measurements.
Findings
The T(x) function possesses a fast mathematical formulation with very good accuracy. It is shown that this formulation is very well suited for an implementation in transient circuit simulator codes. Simulation results using the developed model are in very good agreement with measurements.
Research limitations/implications
For the purpose of this paper, only soft magnetic materials were considered. However, literature suggests, that the T(x) function can be extended to hard magnetic materials. Investigations on this topic are considered as future work.
Originality/value
While the mathematical background of the T(x) function is very well presented in the referenced papers, the application in a model of a real device is not very well discussed yet. The presented paper is directly applicable to typical problems in the field of power electronics.
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The paper aims to analyze the behavior of the Galfenol rods under bending conditions that are employed in a vibration energy harvester by illustrating the spatial variations in…
Abstract
Purpose
The paper aims to analyze the behavior of the Galfenol rods under bending conditions that are employed in a vibration energy harvester by illustrating the spatial variations in stress and magnetic field.
Design/methodology/approach
This paper describes a 3‐D static finite element model of magnetostrictive materials, considering magnetic and elastic boundary value problems that are bidirectionally coupled through stress and field dependent variables. The finite element method is applied to a small vibration‐driven generator of magnetostrictive type employing Iron‐Gallium alloy (Galfenol).
Findings
The 3‐D static finite element modeling presented here highlights the spatial variations in magnetic field and relative permeability due to the corresponding stress distribution in the Galfenol rods subjected to transverse load. The numerical calculations show that about 1.1 T change in magnetic flux density is achieved which demonstrates the effectiveness of the inspected vibration‐driven generator in voltage generation and energy harvesting. The model predictions agree with the experimental results and are coherent with the magnetostriction phenomenon.
Originality/value
This paper fulfils the behavior analysis of Galfenol rods under transverse load that includes both compression and tension. The compressive and tensile stresses contributions to change in magnetic flux densities in the Galfenol rods were calculated by which the effectiveness of the inspected vibration‐driven generator in voltage generation and energy harvesting is demonstrated.
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Tuomas Riipinen, Sini Metsä-Kortelainen, Tomi Lindroos, Janne Sami Keränen, Aino Manninen and Jenni Pippuri-Mäkeläinen
The purpose of this paper is to report on the developments in manufacturing soft magnetic materials using laser powder bed fusion (L-PBF).
Abstract
Purpose
The purpose of this paper is to report on the developments in manufacturing soft magnetic materials using laser powder bed fusion (L-PBF).
Design/methodology/approach
Ternary soft magnetic Fe-49Co-2V powder was produced by gas atomization and used in an L-PBF machine to produce samples for material characterization. The L-PBF process parameters were optimized for the material, using a design of experiments approach. The printed samples were exposed to different heat treatment cycles to improve the magnetic properties. The magnetic properties were measured with quasi-static direct current and alternating current measurements at different frequencies and magnetic flux densities. The mechanical properties were characterized with tensile tests. Electrical resistivity of the material was measured.
Findings
The optimized L-PBF process parameters resulted in very low porosity. The magnetic properties improved greatly after the heat treatments because of changes in microstructure. Based on the quasi-static DC measurement results, one of the heat treatment cycles led to magnetic saturation, permeability and coercivity values comparable to a commercial Fe-Co-V alloy. The other heat treatments resulted in abnormal grain growth and poor magnetic performance. The AC measurement results showed that the magnetic losses were relatively high in the samples owing to formation of eddy currents.
Research limitations/implications
The influence of L-PBF process parameters on the microstructure was not investigated; hence, understanding the relationship between process parameters, heat treatments and magnetic properties would require more research.
Originality/value
The relationship between microstructure, chemical composition, heat treatments, resistivity and magnetic/mechanical properties of L-PBF processed Fe-Co-V alloy has not been reported previously.
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Introduces papers from this area of expertise from the ISEF 1999 Proceedings. States the goal herein is one of identifying devices or systems able to provide prescribed…
Abstract
Introduces papers from this area of expertise from the ISEF 1999 Proceedings. States the goal herein is one of identifying devices or systems able to provide prescribed performance. Notes that 18 papers from the Symposium are grouped in the area of automated optimal design. Describes the main challenges that condition computational electromagnetism’s future development. Concludes by itemizing the range of applications from small activators to optimization of induction heating systems in this third chapter.
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Yanxia Liu, JianJun Fang and Gang Shi
The sources of magnetic sensors errors are numerous, such as currents around, soft magnetic and hard magnetic materials and so on. The traditional methods mainly use explicit…
Abstract
Purpose
The sources of magnetic sensors errors are numerous, such as currents around, soft magnetic and hard magnetic materials and so on. The traditional methods mainly use explicit error models, and it is difficult to include all interference factors. This paper aims to present an implicit error model and studies its high-precision training method.
Design/methodology/approach
A multi-level extreme learning machine based on reverse tuning (MR-ELM) is presented to compensate for magnetic compass measurement errors by increasing the depth of the network. To ensure the real-time performance of the algorithm, the network structure is fixed to two ELM levels, and the maximum number of levels and neurons will not be continuously increased. The parameters of MR-ELM are further modified by reverse tuning to ensure network accuracy. Because the parameters of the network have been basically determined by least squares, the number of iterations is far less than that in the traditional BP neural network, and the real-time can still be guaranteed.
Findings
The results show that the training time of the MR-ELM is 19.65 s, which is about four times that of the fixed extreme learning algorithm, but training accuracy and generalization performance of the error model are better. The heading error is reduced from the pre-compensation ±2.5° to ±0.125°, and the root mean square error is 0.055°, which is about 0.46 times that of the fixed extreme learning algorithm.
Originality/value
MR-ELM is presented to compensate for magnetic compass measurement errors by increasing the depth of the network. In this case, the multi-level ELM network parameters are further modified by reverse tuning to ensure network accuracy. Because the parameters of the network have been basically determined by least squares, the number of iterations is far less than that in the traditional BP neural network, and the real-time training can still be guaranteed. The revised manuscript improved the ELM algorithm itself (referred to as MR-ELM) and bring new ideas to the peers in the magnetic compass error compensation field.
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Martin Christopher Mapley, Geoff Tansley, Jo P. Pauls, Shaun D. Gregory and Andrew Busch
Additive manufacturing (AM) techniques have been developed to rapidly produce custom designs from a multitude of materials. Bonded permanent magnets (PMs) have been produced via…
Abstract
Purpose
Additive manufacturing (AM) techniques have been developed to rapidly produce custom designs from a multitude of materials. Bonded permanent magnets (PMs) have been produced via several AM techniques to allow for rapid manufacture of complex geometries. These magnets, however, tend to suffer from lower residual induction than the industry standard of injection moulding primarily due to the lower packing density of the magnetic particles and secondly due to the feedstock consisting of neodymium-iron-boron (Nd-Fe-B) powder with isotropic magnetic properties. As there is no compaction during most AM processes, increasing the packing density is very difficult and therefore the purpose of this study was to increase the magnetic properties of the PMs without increasing the part density.
Design/methodology/approach
Accordingly, this research investigates the use of anisotropic NdFeB feedstock coupled with an in-situ alignment fixture into an AM process known as selective laser sintering (SLS) to increase the magnetic properties of AM magnets. A Helmholtz coil array was added to an SLS machine and used to expose each powder layer during part fabrication to a near-uniform magnetic field of 20.4 mT prior to consolidation by the laser.
Findings
Permeagraph measurements of the parts showed that the alignment field introduced residual induction anisotropy of up to 46.4 ± 2.2% when measured in directions parallel and perpendicular to the alignment field. X-ray diffraction measurements also demonstrated a convergence of the orientation of the crystals when the magnets were processed in the presence of the alignment field.
Originality/value
A novel active alignment fixture for SLS was introduced and was experimentally shown to induce anisotropy in bonded PMs. Thus demonstrating a new method for the enhancement in energy density of PMs produced via AM methods.
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