Shigeyuki Tamura

Magnetic powder forming simulation subjected to pressing in magnetic field

Abstract Magnetic field forming is a promising method to produce high quality ferromagnetic materials. In this process, magnetic powder is formed in the high magnetic flux by the metal injection molding process. However the parameter of this process is very complicated and it is still difficult to obtain the optimum forming conditions. The analytical method is very effective tool to make such optimum forming design and to investigate the mechanism of the magnetic powder flow under applied magnetic field and pressing. We developed the coupling method of pressing load with magnetic field to simulate the magnetic field forming. In this method, granular modeling is utilized to simulate the mechanical behavior of the powder particles and the magnetic field is considered as a body force. In the numerical example, we analyzed the difference of the magnetic powder flow for pressing schedule and the preferred orientation of magnetizing of the magnetic powder is taken into account in the particle modeling.

Three-dimensional granular modeling for metallic powder compaction and flow analysis

Abstract Powder is a popular state of material for many industries. In powder metallurgy, it is important to know the behavior of the powder under applied stress to ensure accurate design and good quality. However, the mechanical behaviors of powder is not well understood. The authors consider that this is due in part to the difficulty in handling powder numerically. To investigate the fundamental mechanism of powder behavior, numerical simulation of the behavior of powder under mechanical compression and under applied vibration has been performed. To describe the mechanical behavior of powder in practical forming, granular modeling is a powerful tool. Allowing for the effect of three-dimensionality in the compaction and flowability is essential for precise description of powder behavior. In this paper, three-dimensional granular modeling is proposed and developed for metallic powder compaction and flow analysis. The validity of the method is demonstrated. Formulations based on the three-dimensional direct ball-element method (DBEM-3D) are presented and discussed briefly. In the numerical simulation, static powder compaction and vibration-induced powder behavior considered. The differences between two- and three-dimensional calculations are discussed.

MECHANICAL BEHAVIOR OF POWDER PARTICLE ON THE APPLIED VIBRATION

Powder is the popular state of material for the many parts of industries. In the powder metallurgy, it is important to know the powder behavior under applied stress for the accurate design and good quality assurance. But the mechanical behaviors of it has not been well known. We consider this is from the difficulty of handling powder numerically. To investigate the fundamental mechanism of powder behaviors, we performed experiment and numerical analysis for the powders on the applied vibration. In this experiment specimens of powder are on the vertical vibrator. And the dynamic location of powder particle are observed by a laser-displacement meter, at the same time dynamic flow of powder are observed by a high-speed video camera. From this experiment we found that the powder flow can be classified to several patterns and those patterns are strongly depending on the frequency and amplitude of applied vibration, particle size, and grain size distribution of the powder. In the numerical analysis we used the particle model. This calculation model refer to Cundall’s Distinct Element Method. We performed several numerical analysis on various conditions. From the result we considered the major parameter which determine the flowing pattern is the frictional conditions.

DIRECT SIMULATION OF GEOMETRIC CONFIGURATION AND MECHANICAL PROPERTIES CHANGE IN METALLIC AND CERAMIC POWDER FORMING

ABSTRACT Granular modeling has been proposed and developed to describe various mechanical behaviors of both metallic and ceramics powders in processing. In our developing methods, grain size distributions and gravity effect are directly taken into account in the initial element alignment of disc rigid elements. Local stiffness is assumed between elements to consider the actual resistances both in normal and tangential directions of the contact surface; this stiffness is determined by microscopic compressive testing where each granule is compressed to obtain directly the load-displacement relation. Through direct simulations, the differences of powder flow and consolidation processes can be discussed for uniaxial and quasi-isotropic compaction.

Modeling for Powder Compaction and Flow in the Thermal or Magnetic Fields

Various characteristic behaviors [1] are often seen in powder materials. Due to bridging and arching behaviors, where powder particles are locally stacked, the applied external stresses cannot be transferred to every spot of medium. At the presence of a binder material, powder-binder compound with high loading ratio of particles shows its intrinsic non-newtonian behaviors with locally varying viscosity coefficient.

GRANULAR PARTICLE MODELING FOR CERAMIC POWDER BEHAVIOR IN CONSOLIDATION AND SINTERING

Powder is the popular state of material for the almost part of our daily life, but the mechanical behaviors of it still have not been well known. We consider this is from the difficulty in handling powder numerically. To investigate the fundamental mechanism of powder behaviors, we performed numerical simulation for the powder behaviors on the compression. And the sinterability of the powder consolidation is discussed.