Research On The Influence Of The Shape And Position Characteristics Of Abrasive Grits And Their Ratio On The Thermo-mechanical Coupling Process Of Grinding

Grinding is a method to cut off the surplus materials by abrasive and abrasive tools.The removal effect is mainly due to the compound thermo mechanical coupling processing of a large number of abrasive grits randomly distributed in the shape,size and location of the grinding contact area and the surface materials of the workpiece.Grinding hardening is a new type of abrasive processing technology,which makes full use of the thermal mechanical coupling effect of grinding and combines the metallurgical physical process with grinding technology.It can make the phase transformation of the surface layer of the processed workpiece produce the strengthening tissue layer.As the input of grinding thermal mechanical coupling process,the difference of shape and position characteristics(shape,size and position)of effective abrasive grits in contact area will directly affect the grinding force and grinding heat,and then affect the surface quality of the workpiece to be processed.In the past,the study of grinding did not consider the influence of the shape and position of the abrasive grits,and often simplified the abrasive grits into the same geometric shape to simulate the grinding process.Based on this,this paper studies the influence of the shape and position characteristics of abrasive grits on the process of grinding thermo mechanical coupling.The main research work is as follows:Firstly,analytical model of single abrasive grit grinding force is established based on different shape and position characteristics of abrasive grits.The grinding force of single abrasive grit and the total grinding force of contact zone are calculated by combining three grinding processes and the distribution of undeformed chip thickness.Secondly,according to the heat transfer theory and convection heat transfer theory,the two-dimensional and three-dimensional finite difference heat transfer equations of grinding contact area under the action of single grit are established respectively by heat conduction partial differential equation.According to the established heat transfer equation,the two-dimensional and three-dimensional temperature field distribution of contact area at different times is solved based on the analytical model of grinding force of single grit with diffrent shape and position characteristics.The temperature field in the contact zone of single grit grinding is calculated and analyzed by the analytical method,and the results are compared with those of the finite difference method.Thirdly,a single abrasive grit grinding model is established by using finite element software,and the dynamic simulation of single grit grinding process with different shape and position characteristics is carried out.The distribution of grinding temperature field of single abrasive grit is obtained by solving the problem.The results of FEM simulation and FDM simulation are compared to reveal the analysis law.Forthly,the size and position of abrasive grits on the surface of grinding wheel in contact zone were modeled,putting forward that the temperature field in the grinding contact zone is generated by the discrete action of abrasive grits randomly distributed on the grinding wheel surface and the workpiece contact zone,and the influence of the shape and position distribution of abrasive grits on the coupled field of grinding was studied.The results show that,Firstly,based on the analytical modeling method of single grit,it can better reflect the characteristics of grinding process;the shape and position characteristics of grit have a significant impact on the grinding force and grinding temperature of single grit;the temperature field in the grinding contact area is not evenly distributed,but a discrete temperature field generated by the discrete heating of all abrasive grits participating in grinding.Secondly,there is a significant influence on the thermo mechanical coupling field of grinding hardening process by the different characteristic ratio of grinding grits in the contact area of grinding wheel.In order to obtain a more uniform temperature field,the grinding wheel with a larger ratio of pyramidal grits and a smaller ratio of spherical grits and conical grits should be selected;in order to obtain a higher temperature field distribution,the grinding wheel with a larger ratio of spherical grits and pyramidal grits should be selected.Through the research of this paper,it is found that the shape and position characteristics of abrasive grits directly affect the grinding force and grinding temperature of single grit,and then affect the thermal mechanical coupling mechanism of grinding process.The research results of the influence mechanism can be used to select or manufacture specific parameters of grinding wheel according to the processing demand,which provides valuable theoretical research for engineering practice.