Particle packing simulations based on Newtonian mechanics

Development of micro actuator using magnetic powder and elastic material (first report) - Theoretical formulation of magnetic force applied to micro particle

A simulation system for newly developed magnetic micro actuator is proposed and demonstrated in this paper. Magnetic energy and elastic deformation energy are formulated and used to derive deformation of the actuator. The deformation is determined by using the steepest descent method as the total energy is minimized.We prepare two types of actuators to demonstrate reliability of the developed simulation system. Deformation patterns observed here show good agreement with simulated ones. A grid type actuator deformed through multiple stages. This characteristic manner was also observed virtually in the simulation system. This system would be useful to design a new arrangement of pillar structures of the present actuator.

Development of micro actuator using magnetic powder and elastic material (second report) - Development of simulation and design system

Nd-Fe-B magnet, which possesses the highest magnetic performance, is fabricated by powder metallurgy process. The magnetic powder is compacted under an applied magnetic field for the particles' easy directions of magnetization to be oriented along the magnetic flux. It is widely known that the magnetic powder flows and moves during this process both by the applied magnetic field and by the applied pressure. Since this process determines the final properties of the magnet, it is of great importance to clarify the behavior of the powder during the process.In the present study, we focus on the flow behavior of Nd-Fe-B powder due to an applied magnetic field. An attempt is made to make clear the powder flow by in-situ observation with a transparent die set. An FEM-DEM simulation is also performed to investigate the flow of magnetic flux that affects the movement of the powder. It is thereby shown that simulated results of the flow of magnetic powder and change of the structure built-up by particles are in good agreement with experimentally derived ones.

Flow of magnetic powder in stepped cavity shape under applied magnetic field

Crystal Orientation Evaluation for Precursors of Sintered Magnets

A new computational system is proposed and developed to simulate magnetic powder behavior under applied magnetic field. It is well-known fact that magnetic powder builds up a chain or column structure in an applied magnetic field, but it is difficult to simulate accurately by conventional modeling. In the present paper, a Distinct Element Method (DEM) is developed and coupled with a magnetic FEM. Magnetic flux in the assembly of particles can be calculated by the FEM, thereby the force exerted to each particle can be obtained. The force is then use to simulate the movement of the particles by the DEM. A simple analysis of two magnetic particles in applied magnetic field shows a difference from that by the conventional simulation system. Further, the present simulation shows that the structures consist of not only simple chains of one particle wide but also columnar structure of two or more particles wide.

Simulation of Powder Behavior in Applied Magnetic Field by Coupled FEM-DEM Modeling

Column structure growth simulation of magnetic particles by Distinct Element Method coupled with magneto-FEM

We have performed $^{115}$In-NMR spectroscopy for Ni$_{2}$InSbO$_6$ with corundum-related crystal structure to reveal magnetic structures that develop in high magnetic fields. At low fields Ni$_{2}$InSbO$_6$ shows a helical magnetic order with a long wavelength because of its chiral and polar crystal structure. The field-induced magnetic state was not investigated by microscopic experiment because an extremely high magnetic field is required to modify the antiferromagnetically coupled helical structure. From the analysis of our $^{115}$In-NMR spectra obtained at high magnetic fields, we confirm that the canted antiferromagnetic structure appears in fields applied in the $[110]$ direction and the propagation vector of magnetic helix is rotated toward the field direction for fields in the $[001]$ direction. We discuss the effect of magnetic field that modifies the magnetic structure of an antiferromagnetic chiral magnet.

Masamichi Hirata

Papers

Simulation of Powder Behavior in Applied Magnetic Field by Coupled FEM-DEM Modeling

Column structure growth simulation of magnetic particles by Distinct Element Method coupled with magneto-FEM

Field-induced magnetic structures in the chiral polar antiferromagnet Ni$_2$InSbO$_6$