Numerical Simulation of Airflow Field in Grinding
With a view to find better ways for coolant delivery, the boundary layer of peripheral air of grinding wheel is simulated using finite volume method. By means of introducing Sparlart-Allmaras (SA) model into the mathematical model, the airflow field is calculated and pressure distributions and velocity distributions are obtained by simulations. An experiment is run to testify solutions of numerical simulation accordingly. The simulation solutions are in consistent with the experiment results on the whole. Therefore, this simulation method holds true for predicting the performances of airflow field around grinding wheel when grinding wheel rotates at high speeds. Based on the numerical solution results obtained in this paper, the causes to disadvantage of coolant delivery into the grinding zone are studied from the point of view of the pressure and velocity. In the end, one optimizing way of coolant delivery is specified and a few useful conclusions are drawn for applications of coolant delivery in the course of high speed grinding. Methods and conclusions of this research are available for perfection of grinding theory and applications of cooling in the future.
Study on heat transfer in super-high-speed grinding: energy partition to the workpiece in HEDG
Abstract Based on an analytical thermal model for deep grinding, in which the effect of the inclined angle ϕ of the heat source plane to its moving direction is taken into account, the relations of workpiece energy partition e to relevant grinding parameters are obtained. It is suggested that the inclined angle ϕ, grinding speed and also work feed all have strong influences on the energy partition to the workpiece. From the viewpoint of reducing the value e, a higher grinding speed, lower feed speed, relatively shallow cut and larger wheel size should be selected.
The Minimum Coefficient of Friction: What Is It?
Summary For many decades, researchers have widely believed that the frictional force is mainly due to adhesion, an assertion that has not been supported by experimental results. On the contrary, it has been shown that much of the frictional force between dry sliding surfaces in a typical engineering application is due to mechanical interactions. In this paper, a means of reducing the contribution of mechanical effects on friction through surface engineering is presented. Friction coefficient as low as 0.05 between dry sliding surfaces has been achieved when the mechanical interactions are eliminated. This result has been achieved based on a hypothetical model of an ideal surface for low friction. Model experiments were done using a hard smooth surface coated with a sub-micron thick elastomer layer. Such low friction in engineering systems without lubricants can have a major impact on the design of many precision machine components.