Avaliação de uma técnica de compactação do gesso odontológico como alternativa para a correta relação água/pó

The water-powder relationship is essential to achieve a proper performance of gypsum for prosthetic purposes. The ideal measure can be obtained with a balance, but this is clinically unavailable, once it is timeconsuming. A powder-compacting technique using a volume measurement is suggested in order to substitute the balance. The technique consists of using a gypsum meter within the gypsum bag. While the operator holds the gypsum meter with one hand, the palm of the other hand is pressed over the surface of the meter, supported by the ventral aspect of the fingers of the hand that is pressing. This procedure is based upon three compactation movements for each operator, then counting the average of compacting sample. Each of the ten operators repeated six times the procedure, and the final average was defined. The resulting samples for each procedure, of each operator, were weighted, and the statistical analysis showed significant differences (p = 0,006) among the operators.

Preparation, Microstructure Evaluation and Performance Analysis of Diamond-Iron Bonded Magnetic Abrasive Powder

The customary edged tool for machining is uneconomical for harder and hard to machine materials and furthermore the level of surface finish accomplished is not that great. As of late, a lot of consideration in mechanical engineering has been centered on finishing tasks. Not many investigations have been accounted for till date on the advancement of substitute magnetic abrasive powder (MAP). In this paper, to improve the finishing performance, the abrasive powder were prepared by mechanical alloying of diamond powder and iron (Fe) powder, compacting these with universal testing machine (UTM) and then sintered at different temperature in a sintering machine in an inert gas (H2) atmosphere. These compacts were crushed and sieved to obtain various sizes of MAP. This abrasive powder were micro-structurally examined. The results indicate that the densification increases and porosity decreases with increasing temperature. Moreover, the prepared bonded MAP has potential performance as a new MAP for fine finishing in Magnetic Abrasive Flow Machining (MAFM) process.

Consolidation Behavior of the Cu-Al2O3 Nanocomposite Powder

The consolidation process of agglomerated Cu – γ-Al2O3 composite nanopowder was investigated experimentally. Process includes powder compacting by uniaxial cold pressing, sintering in hydrogen atmosphere, and hot extrusion. The interdependence of alumina content, powder agglomeration, green density of compacts, and isothermal sintering behavior of powders was evaluated.

LEAD AND LEAD ALLOYS FOAMS PRODUCTION

<span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: SK; mso-fareast-language: CS; mso-bidi-language: AR-SA;" lang="SK">Low-cost techniques for the manufacturing of lead and lead-alloys foams have been investigated in this work. In particular the “sintering and dissolution process” (SDP) and “replication process” (RP) have been focused and discussed. The effects of some production parameters have been investigated too: powder compacting pressure, composition of the base metal, granulometry, sintering time and temperature. Spherical urea and NaCl have been employed in the SDP method while in the replication process the viscosity of the melt has been found fundamental. Furthermore melt infiltration in the NaCl particulate has been found much easier if pressure is applied. Lead recovery and recycling of exhaust batteries into foam-based electrodes has been examined too with a novel method for the direct conversion of Pb scrap into lead foam.</span>

Metal Explosion Chambers and their Application

The paper presents the principles of stress calculations for metal shells sustaining internal impulse loading. The designs of metal explosion chambers (EC) are described; examples of their utilization in scientific research and engineering applications are presented. Aside from conventional methods of the EC use, i.e. explosion welding, explosion hardening, powder compacting, synthesis of new materials, etc., recently the EC has found ever-widening applications in recycling discarded parts containing explosives, such as ammunition. The metal EC provides localization of every explosion damaging effect, improves the safety of works, and enables performing blasting operations both in industrial and laboratory conditions.

The Microscopic Study on the Basis of Finite Element Johnson-Cook Model to Powder Compacting Mechanism

Powder high speed compaction mechanism is still a controversial issue.In order to study the densification mechanism of powder in the high speed compaction process,the article aims to study the powder densification mechanism by using the discrete density volleyball accumulation model that MSC.MARC to Ti6A14V and to describe the microscopic deformation and temperature changes of powder with Johnson-cook model. By analyzing the speed and temperature changes of particles in different position node,we found that powder particles start to deform a lot within microsecond and fill the holes and gaps of the powder in the flow,so that the air in the particles will form high-pressure and high-energy in a relatively adiabatic environment and make the temperature high and partial melting of the particle surface. It proves that the consolidation is the major mechanism of particles’large deformation,heat and soften hot-melt process in a short time.

Residual Stress in Powder Metallurgy Green Compact

Residual stress in green compact is an important factor to influence the quality of the compact and corresponding powder metallurgy product. To understand the residual stress, a finite element model is set up to simulate the single and double action pressing, unloading and ejecting of powder compacting process. Results show that compaction type has significant influence on the rule of residual stress state and the double action pressing is more helpful to reduce the risk of cracking than the single action pressing. Also better lubricant condition is beneficial to improve residual stress in the green compact.