TO ESTIMATE AND PREDICT TRIBOTECHNICAL PARAMETERS OF FRICTION PAIRS FROM SINTERED POWDER FRICTION MATERIAL WITH DIFFERENT STEEL COUNTERFACES FOR DISK FRICTION DEVICE

Approximating dependencies of tribotechnical parameters of friction pairs sintered powder friction material and different steel counterfaces of disk friction device on sliding speeds, obtained by results of tests on friction machine and intended for selection of materials of friction pairs, are given.

Modeling a Free Burnishing of a Powder Hollow Cylinder

The paper presents the results of the computer modelling of the stressed state and relative density when burnishing a porous hollow cylinder, made from copper sintered powder material. The mathematical model, based on the theory of porous bodies’ plasticity, is used for the analysis. The paper researches the impact of the initial porosity of the material on the effective stresses distribution, relative density and force change when free burnishing of hollow cylinders. It is ascertained that with the decrease of the initial porosity of the sintered material there is the increase of the burnishing force, stresses rate and relative density on the inner sur-face of a hollow cylinder. For porous materials at a certain stage of burnishing, the deformation zone is transformed into the compaction zone with a high relative density which de-creases while moving away from the inner surface of hollow cylinders. The maximum value of the relative density is implemented directly on the inner surface of hollow cylinders; along with this the density value is evenly distributed on the inner wall.

The Effects of Bending on Heat Pipes

A comprehensive three-dimensional numerical model is developed to evaluate the effect of bending on water-copper cylindrical heat pipes. This model distinguishes itself from other models by its ability to uniquely determine the operating pressure of the heat pipe based on the operating and physical conditions. The effects of one 90-degree bend and two 90-degree bends are evaluated on the performance of a heat pipe. Two types of wicks are considered: a screen mesh wick and a sintered powder wick. The obtained results show that bending does affect the vapor pressure drop; however, the changes are not significant when compared to the operating pressure of the heat pipe. If the bending is performed in a manner where the wick is not damaged and the liquid is not blocked from returning to the evaporator, the performance of the heat pipe will not be affected significantly. In addition, if the heat pipe is operating in the horizontal direction, where both evaporator and condenser legs are at the same level, bending does not affect the liquid pressure drop significantly; however, the screen mesh does provide a higher capillary limit. The results also showed that the effects of gravity can be important when bending heat pipes and consideration should be given for this factor. When the bent heat pipe works against gravity, the sintered powder wick heat pipes showed higher capillary limits.

Synthesis and Characterization of LiFe1-xGdxPO4/C (x = 0.01; 0.05; 0.07) for a Lithium Battery Cathode

Synthesis of LiFe1-xGdxPO4/C with (x = 0.01; 0.05; 0.07) have been carried out using a solid-state method from LiH2PO4, Fe2O3, Gd2O3, and Carbon. Al reactant are mixed and mashed with a ball milling for 8 hours, then heated at 80°C for 2 hours to evaporate free water. To complete the reaction, the sample then was sintered at two different temperature; first at 350°C for 6 hours and continue at 830°C for 10 hours under Argon gas (Ar) atmosphere. The sintered powder was characterized by XRD to determine the structure and phase purity. Sample LiFe1-xGdxPO4/C (x = 0.01; 0.05; 0.07) was adopted orthorhombic crystal structure and pnma space group, and no impurities detected. In general, the lattice parameter decreases with increasing Fe concentration, because of the size of the Fe3+ ion is smaller than that Gd3+ ion. Conductivities of LiFe0.93xGd0.07PO4/C, LiFe0.95Gd0.05PO4/C and LiFe0.99Gd0.01PO4/C are 2.17 x 10-4 S/cm, 1.54 x 10-4 S/cm, and 2.02 x 10-4 S/cm, respectively.

Investigation of the microhardness of the W-Ni-Fe powder alloy used for the restoration of machine parts

The paper presents the results of a study of the microhardness of the WNF-95 sintered electroerosive powder alloy. Powder alloy W-Ni-Fe95 was obtained by electroerosive dispersion of tungsten-containing waste in a kerosene medium. The resulting electroerosive powder alloy W-Ni-Fe 95was pressed in a vacuum chamber and sintered by the method of spark plasma sintering. The aim of this work was to study the microhardness of the WNF-95 sintered powder alloy obtained by the electroerosive dispersion of tungsten-containing waste in a kerosene medium. It has been established that the microhardness of samples sintered by the method of spark plasma sintering from particles of W-Ni-Fe 95alloy dispersed by electric erosion obtained in lighting kerosene is 2185.8 MPa and 2268.0 MPa, indicating their suitability for the manufacture of tungsten-nickel-iron alloys.

Methods for introducing carbon into the composition of structural powder materials

Durability and reliability of machines and mechanisms depends on the structural strength of the products from which they are made. The main requirement for any product is trouble-free operation under the conditions of the established operational period. This determines the requirements for structural materials, the main of which are technological, operational and economic. The production of sintered powder products ensures the lowest energy consumption and the lowest waste. The introduction of carbon into powder materials significantly increases the strength characteristics of the product.