The stress-strain state of metal in deformation zone under the screw compression is considered using a mathematical model of process. This model allows to determine the limiting tangential stresses in a workpiece at the exit of deformation zone, which do not lead to the destruction provided by twist in the process of deformation.
At present, hard-to-machine materials such as structural alloy steels with various chemical element additives – tungsten, chromium, etc. - are most widely used in engineering. When conventional finish methods are used for the treatment of hard-to-machine materials, the most important problems are the difficulty of obtaining work surfaces of a required quality in terms of accuracy, roughness and the physicochemical composition, and the low output. In the present paper, a finish method for metal treatment– grinding – is discussed. Zones of the formation of the surface stress state due to heating have been revealed: the zone of an insignificant increase in temperature in the contour of the contact of a grinding wheel and a work surface; the zone of the temperature intensive growth; and the zone of the temperature abrupt drop. The investigation has been conducted of the surface layer structure of high-strength and high-chromium steels during high-speed heating – grinding. The peculiarities of the change of the surface layer state of the above steels have been revealed after grinding with the use of conventional grinding wheels with a continuous cutting surface and a discontinuous cutting surface. Some recommendations are given for grinding of the high-strength 12Cr18Ni9 and high-chromium Cr12, Cr12Mo and Cr12V steels, taking into account the specific features of different technological situation characteristic of a specific grinding tool, a grinding tool grade, and conditions of grinding and cutting.
Abstract. The numerical simulation results of the flow of a gas-liquid medium over the high-temperature metal cylinder surface in a circular channel are presented. The flow over the solid metal cylinder with a variable cross-section by a gas-liquid medium is considered. Based on the mathematical model taking into account the cooling-media-flow axial symmetry relative to the cylinder longitudinal axis, the results of the numerical simulation of the process of solving the two-dimensional nonstationary problem of the coupled heat exchange of the gas-liquid medium flow and metal cylinder are obtained. The control volume approach is used for solving the differential equation system. The flow field parameters are calculated using the algorithm SIMPLE. For the iterative solution of linear algebraic equations, Gauss-Seidel method with under-relaxation is used. The numerical calculation results are obtained for the flow hydrodynamic parameters of the gas-liquid medium at cooling the high-temperature metal cylinder by taking into account vaporization. The values of temperatures, flow velocities, and vapour distribution in the computational domain are determined. The variation intensity of the metal cylinder surface temperature depending on the gas-liquid flow velocity is analyzed.
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