Papers by Keyword: Magnet

Abstract: In this publication we report on our progress in investigating the energy efficient production of rare earth permanent magnets by Laser Beam Melting in the powder bed (LBM). This innovative additive manufacturing process offers the potential to produce magnets of complex geometries without an energy intensive oven sintering step. Another advantage that increases the efficiency of this possible new process route is the high degree of material utilization due to a near net shape production of the magnets. Hence only little material is wasted during a post processing machining step. The main challenge in processing rare earth magnet alloys by means of LBM is the brittle mechanical behavior of the material and the change in microstructure due to the complete remelting of the magnet powder. We therefor expanded the parameter study presented in previous work in order to further increase relative density and magnetic properties of the specimens. In this context process stability and reproducibility could also be increased. This was achieved by investigating the impact of different exposure patterns and varying laser spot sizes. Simultaneously to the experiments the energy consumption of the LBM process was measured and compared with conventional rare earth magnet production routes.

Abstract: The article describes the high temperature winding wires, highly coercive permanent magnets, and electrical steels for high temperature starter-generators.

Abstract: Magnetically-separable enzyme system has been developed by adsorption, precipitation and cross-linking of enzymes in superparamagnetic hierarchically ordered mesoporous mesocellular silica (M-HMMS). The immobilization of xylanase within M-HMMS were compared between enzyme adsorption (EA), enzyme adsorption and cross-linking (EAC), and enzyme adsorption, precipitation and cross-linking (EAPC). EAPC includes higher enzyme activity immobilized within the matrix in comparison with the other methods. Furthermore, the immobilized enzyme is predicted to be prevented from leaching out of the matrix when exterior blow is being tested on the structure. Thus, the stability of the EAPC of this invention is anticipated to be maintained even after a long time passed since high enzyme activity compared with known method can be supported and immobilized within the matrix. Consequently, it is possible to improve performance of the enzymes by manipulating the preparation and operation condition.

Abstract: Micro-cracks on the edge surface of thin glass edge sheet have been identified as a key factor of catastrophic glass breakage. Hence, their removal will strengthen the thin glass substantially. This paper studies the glass edge finishing using magnetorheological finishing (MRF). The thin glass sheet edge is finished by shear force exerted by magnetorheological fluid, which is magnetically held by a specially designed magnetic wheel tool. All micro-cracks can be removed from the edge surface and the surface roughness improves from R_a 0.5 μm to R_a 0.03 μm.

Abstract: Forming processes are defined as to modify the shape of a work piece by deforming it, without the removal of material. To overcome a number of longstanding problems in conventional forming methods such as low production rates, difficulty in forming light weight components etc., an alternate approach of electromagnetic forming process is introduced. Electromagnetic forming (EMF) is a high speed forming process used to form thinwalled work pieces (usually sheets and tubes) that have high electrical conductivity, such as aluminium, copper etc. Electromagnetic tube compression processes, the design of an experimental set up for electromagnetic tube compression process are discussed in detail in this paper

Abstract: This paper describes process of an experimental evaluation of the necessary torque for disconnection of a magnetic connection mechanism. The paper describes basic information of a designed testing stand for an experimental evaluation of mechanical parameters of the automatic connection mechanism based on magnetic principle for use in self-reconfigurable modular robotic system. Also describes processing of measured values. Obtained values were then used in a mechanical design of the testing connection mechanism for verification of its other parameters.

Abstract: Electrical discharge machining (EDM) has the capability of machining all conductive materials regardless of hardness, and has the ability to deal with complex shapes. However, the speed and accuracy of conventional EDM are limited by probability and efficiency of the electrical discharges. To improve the machining speed and accuracy, we developed a 3-DOF controlled, high-speed, high-precision, magnetic/piezoelectric hybrid drive actuator. For the actuator, a voice coil motor type of magnetic bearing having a positioning stroke of a few millimeters is used to control the motion of an electrode in the thrust direction in order to speedily maintain a suitable distance from the workpiece. Moreover, two piezoelectric elements having high response speed and high precision are used to achieve the vibration of the electrode in the radial direction in order to immediately remove the debris between the electrode and the workpiece. The positioning performance of the actuator is evaluated through experiments, and the experimental results show that the actuator possesses a positioning resolution of 1μm, a bandwidth of 120Hz and a positioning stroke of 2mm in the thrust direction, and a positioning resolution of 0.05μm, a positioning stroke of 10μm at 1000Hz in the radial directions.

Abstract: Development for superconducting wires of materials such as Nb₃Al and the high-temperature superconductors (HTS such as REBCO, Bi2223, and Bi2212) has been carried out for high-field magnet applications. It is known that these types of wire exhibit very different characteristics and performance for different applications. The development of Nb₃Al wire for high-field accelerator magnet has resulted in remarkable achievements in critical current using a Rapid Heating and Quenching (RHQ) method by High Energy Accelerator Research Organization (KEK) and National Institute for Materials Science (NIMS). As one example of a characteristic of Nb₃Al, the strain sensitivity of the critical current in the RHQ-Nb₃Al wire is better than that of Nb₃Sn wire. A strain study is needed to further the development of a high-filed magnet; therefore, we have carried out experimental studies using the neutron diffractometer at J-PARC Takumi. Researchers have recently achieved the highest critical current density for REBCO wires in a high-field above 15 T. For this reason, REBCO wire has been considered for high-field magnet NMR applications in Riken. But several obstacles remain, including coil degradation, shielding current and thermal runaway. In this paper, R&D on recent advances for applications will be presented.

Abstract: In conventional Electrical Discharge Machining (EDM), the speed and accuracy are limited by probability and efficiency of the electrical discharges. To improve the machining speed and accuracy, we developed a high-speed, high-precision, 3-DOF controlled local actuator. For the actuator, a voice coil motor type of magnetic bearing having a positioning stroke of a few millimeters is used to control the motion of an electrode in the thrust direction in order to speedily maintain a suitable distance from the workpiece. Moreover, two piezoelectric devices having high response speed and high precision are used to achieve the vibration of the electrode in the radial directions to immediately remove the debris between the electrode and the workpiece. The positioning performance of the actuator was evaluated through experiments, and the experimental results show that the actuator possesses a positioning resolution of the order of micrometer, a bandwidth greater than 120Hz and a positioning stroke of 2mm.

Abstract: Nanocrystals are important to attain high performance in optical & magnetic materials such as phosphors, laser emitters and information recording media. They are also required in future devices that involve magnetoresistance, logic gates, magnetic resonance and metamaterials. Nanocrystals of oxides and nitrides (and oxynitrides) were studied as nanosized powders, nanowires and dispersed granular thin films. Recent advancements of such nanocrystals prepared at Hokkaido University are introduced in this paper. Nanocrystals were prepared in transparent conducting oxides, white LED phosphor oxides and oxynitrides and magnetic iron nitride. Nanowires were grown in semiconducting gallium oxynitride and magnetic nanogranular thin films were prepared both in oxide and nitride.