Study On Friction Characteristics Of Structured Surface In Topological Grinding

In recent years,structured surfaces have attracted wide attention from scholars at home and abroad because of their remarkable improvement in surface properties.They have become one of the hot research directions in the field of tribology.Many manufacturing methods for structured surfaces include rolling,laser machining,milling,cutting,grinding,and other methods.However,for difficult-to-process materials or mass production,most methods often have problems such as high cost,low efficiency,and complex operation.Grinding can compensate for these shortcomings and realize the processing of difficult-to-process materials and efficient mass production.Therefore,the grinding method is used to obtain structured surfaces,and the friction properties of the ground structured surfaces are analyzed.The study on the grinding mechanism of the structured surface provides a theoretical basis for the structured friction-reducing surface’s design and process.Many geometric shapes of structured surface texture are inspired by nature,among which fish scale surface is the most common drag reduction surface.In this study,the research object is the structured fish scale surface to obtain the surface friction properties of the structural fish scale after grinding.The topographical characteristics of the surface of the structural ground fish scales are studied.The structure and arrangement properties of its units are analyzed.The corresponding structured ground scale surface model is established.The grinding process of structured ground fish scale surface is given,and the grinding wheel is designed.The micro-texture of the structure surface after grinding is analyzed.Based on the Reynolds equation,mathematical models of micro-ground texture and macro-ground scale elements are established.The formation mechanism and the effect of the hydrodynamic lubrication on the surface of the ground fish scale element are discussed.Under the lubrication condition,the friction coefficient and bearing capacity of the unit scale with ground micro texture and the structured ground scale surface of the whole layer is obtained through Fluent.At the level of fluid drag reduction,the friction coefficient and fluid drag coefficient of fish scale surface and structured ground fish scale surface are compared through Fluent.The fluid drag reduction performance of the ground fish scale unit on the surface of the structured ground fish scale composed of different distances is analyzed.The conclusion drawn from the above work is that the structured fish scale surface manufactured by grinding can improve the contact performance of the object and effectively reduce the fluid drag of the surface when the object moves in the fluid.The fish scale dimples made by grinding on the friction pair surface can improve the bearing capacity of the oil film,reduce the friction coefficient,and thus improve the lubrication effect.The lower the surface roughness of the structured ground scale obtained by grinding,the better the lubrication effect.On the overall lubrication level,the lubrication mechanism of the structured ground scale surface manufactured by grinding is similar to that of the ground scale unit,and the overall lubrication effect is greater than the sum of the functions of each ground scale unit.In terms of drag reduction,a stable vortex with the same size and shape is generated at the trough of each ground fish scale unit on the structured ground fish scale surface.Moreover,the rotation direction of these vortices is all in favor of the outflow field flow direction.The surface friction coefficient varies with the depth of the fish scale unit.The negative pressure gradient formed at the divergence gap leads to a decrease in the friction coefficient.A positive pressure gradient formed at the convergence gap leads to an increase in the friction coefficient.Compared with increasing the spacing in the direction parallel to the water flow,increasing the spacing perpendicular to the water flow can more effectively reduce the fluid drag on the structured ground fish scale surface.