Distribution of heat flow during electrical discharges diamond grinding

Abstract

DOI: https://doi.org/10.32820/2079-1747-2019-23-41-48

The paper shows that an increase in the speed of the longitudinal feed, as well as the depth of grinding, leads to an increase in the heat flux density. This is due to the increased level of thermodynamic loads due to an increase in the thickness of the layer being cut by a single grain. Along with multipass (pendulum) grinding, one-pass (deep) grinding became widespread, when the entire allowance for processing is removed in one working stroke. When this occurs, the increase in the length of the contact of the circle with the product, and the duration of thermal exposure is one to two orders of magnitude longer than with pendulum grinding. The peculiarity of grinding is the short time of exposure of the heat source in the presence of large specific loads in the zone of contact of the circle with the surface being treated. During the action of the diamond wheel, the thinnest layers of material (up to 1 micron) are heated to temperatures of 600 ... 1000 ° C. Following heating, there is a rapid heat removal to the deep layers of the material with the rates of cooling of the surface layers approximately the same as during heating. Such kinetics of thermal grinding processes contributes to the formation of structural changes in the surface layers of parts that are externally characterized by burns. In addition to prizhog, cracks are often observed on the surfaces of parts after grinding as a result of the action of instantaneous and total residual internal stresses resulting from non-uniform plastic deformation in different zones of the surface layer. Studies have shown that reducing the speed of the longitudinal feed can significantly reduce the thermal stress of the process. Thus, the analysis shows that the highest value of the heat flux density, as well as during pendulum grinding, is observed at γ = 0 °. In this case, the depth of grinding will be maximum, therefore, the cutting force and heat flux are the greatest. During deep grinding, an increase in the speed of the product leads to an increase in the density of the heat flux. This is due to an increase in the thickness of the cut layer by a single diamond grain. The analysis shows that with deep grinding the heat flux density reaches higher values ​​than with the pendulum. However, a corresponding adjustment of technological regimes can reduce the thermal stress of the process.