Papers by Keyword: Powder Compaction

Abstract: The industrial applications of under shock wave have been investigated in our center. This paper concerns with the improvement of foods and wood using underwater shock wave. Underwater shock wave is easily generated by means of explosion of explosives or high voltage electric discharge in water. A detonating fuse and an electric detonator were used for generation of underwater shock wave, and apples were used as food sample for food processing experiments. The behavior of underwater shock wave was investigated by optical observations. The extraction and the amount of phenolic compounds in apple juice obtained from the shock treated sample were higher than that of control samples. It is considered that the underwater shock wave treatment for apples has a big possibility in food processing. The results of coffee bean and other food processing by underwater shock wave were presented at the conference. Moreover the properties of wood were well improved by shock loading. The resistance of wood has been improved significantly.

Abstract: Friction between powder and tools plays a major role during cold compaction of PM components with results on the inhomogeneous densification. The present work deals with a new method of compaction for PM components by using the friction force between die and compacts as an active pressing force in order to reduce the density gradient. The proposal technique consists in moving the container of the die, during pressing stage to the punch direction with a well determined speed. As a result, the friction force acts in the same sense as the pressing load with better distribution of powder flow during compaction. The experimental results of compaction parameters versus density have proved the decreasing of the density gradient by increasing die/punch speed rate. A sharp density gradient on the specimen height moving container contrarily to the punch.

Abstract: In this paper we present an anisotropic compaction model based on a generic modeling framework. The model is a generalization of Hill’s anisotropic model to compressible materials and reduces to a Cam-clay type model in the isotropic limit. The model has been calibrated using experimental data for a commercial steel powder obtained from a computer controlled triaxial cell in which the yield surface was probed following loading along different paths in stress and strain space. Closed-form analytical expressions are presented for the yield surface as a function of the inelastic strain. The model has been implemented in the general purpose finite element code ABAQUS. Simulations are presented which explore the effect of a detailed structure of the constitutive law on the compaction response.

Abstract: Dry-bag CIP process has become a very popular method in the large volume production of powder compacts in the P/M and ceramic industries. Intensive technological research on the Drybag equipment has been carried out to improve the dimensional accuracy and the productivity. In this study, the rubber mold design technology with FEM simulation during pressing has been introduced, in order to achieve higher dimensional preciseness, and criteria for the selection of Drybag equipment, namely the In-line type or Off-line type, have been established based on the powder flowability index proposed by Carr. Based on these research results, high productivity Off-line Drybag CIP equipment, which can realize good dimensional accuracy with high productivity, was developed even for non granulated powders with poor packing density. This paper describes the research results and the present status of the most advanced Off-line Dry-bag CIP equipment technologies.

Abstract: The deformation under radial pressure of rectangular dies for metal powder compaction has been investigated by FEM. The explored variables have been: aspect ratio of die profile, ratio between diagonal of the profile and die height, insert and ring thickness, radius at die corners, interference, different insert materials, i. e. conventional HSS, HSS from powders, cemented carbide (10% Co). The analyses has ascertained the unwanted appearance of tensile normal stress on brittle materials, also “at rest”, and even some dramatic changes of stress patterns as the die height increases with respect to the rectangular profile dimensions. Different materials behave differently, mainly due to difference of thermal expansion coefficients. Profile changes occur when the dies are heated up to the temperature required for warm compaction. The deformation patterns depend on compaction temperature and on thermal expansion coefficients.

Abstract: Powder compaction is a well-established process for manufacturing a wide range of products, including engineering components and pharmaceutical tablets. During powder compaction, the compacts (green bodies or tablets) produced need to sustain their integrity during the process and possess certain strength. Any defects are hence not tolerable during the production. Therefore, understanding failure mechanisms during powder compaction is of practical significance. In this paper, the mechanisms for one typical failure, capping, during the compaction of pharmaceutical powders were explored. Both experimental and numerical investigations were performed. For the experimental study, an instrumented hydraulic press (a compaction simulator) with an instrumented die has been used, which enable the material properties to be extracted for real pharmaceutical powders. Close attentions have been paid to the occurrence of capping during the compaction. An X-ray Computed Microtomography system has also used to examine the internal failure patterns of the tablets produced. Finite element (FE) methods have also been used to analyse the powder compaction. The experimental and numerical studies have shown that the shear bands developed at the early stage of unloading appear to be responsible for the occurrence of capping. It has also been found that the capping patterns depend on the compact shape.

Abstract: New powder compaction process, in which a Bingham semi-solid/fluid mold is utilized, is developed to fabricate micro parts. In the present process, a powder material is filled as slurry in a solid wax mold, dried and compressed by either of conventional pressing methods, such as isostatic pressing or die compaction. It is important to use slurry for filling because dry powder is hard to fill in the micro cavity. It is also essential to control process temperature to treat micro parts. The wax mold is heated during compaction and becomes semi-solid state, which can acts as a pressurized medium for isostatic compaction. Since the compacted micro parts are very fragile, the mold's temperature is controlled to higher than its melting point during unloading, to avoid breakage of the compacts. To demonstrate effectiveness of this process, some micro compacts of alumina are shown as examples.

Abstract: Metal cutting operations constitute a large percentage of the manufacturing activity. One of the most important objectives of metal cutting research is to develop techniques that enable optimal utilization of machine tools, improved production efficiency, high machining accuracy and reduced machine downtime and tooling costs. Machining process condition monitoring is certainly the important monitoring requirement of unintended machining operations. A multi-purpose intelligent tool condition monitoring technique for metal cutting process will be introduced in this paper. The knowledge based intelligent pattern recognition algorithm is mainly composed of a fuzzy feature filter and algebraic neurofuzzy networks. It can carry out the fusion of multi-sensor information to enable the proposed intelligent architecture to recognize the tool condition successfully.