Study On The Temperature Field In Surface Grinding

Grinding process is one of the most important processing methods in machining manufacture area , especially in the field of precision machining. It requires extremely high specific energy, and almost all of the energy is converted into heat which is concentrated in the grinding zone. This usually results in rise for the temperature of both the wheel and workpiece, and the tremendous temperature gradient appears in the surface layer of the workpiece. If the surface grinding temperature is beyond critical temperature in grinding zone, it will cause the surface thermal damages, such as surface burns, material oxidation, residual stresses, crack, etc. Thus the useful life period of the parts will be shortened and the reliability of the parts will be reduced. Meanwhile, the useful life period of grinding wheel will also be shortened. Therefore, the investigation of the grinding temperature is of importance theoretical and practical value. The temperature field in surface grinding is investigated through theoretical derivation, experimental analysis and numerical simulation in this paper. The main content of the paper contains following:(1)The temperature field in surface grinding is theoretically investigated. Different heat source distribution models which affect temperature distribution in workpiece, the rate of the workpiece surface temperature change and the position of the maximum grinding temperature are discussed. The generation of grinding heat and the transfer channels of energy in the grinding zone are analyzed. And three typical energy partitioning models are introduced.(2)The grinding temperature is experimental studied. The effects of the grinding parameter, the grinding manners and the grinding wheel properties on the grinding temperature are analyzed deeply on the basis of the experiment. It is found that the grinding temperature increases with the cutting depth, the wheel speed and the table speed. The cutting depth is primary and the wheel speed is secondary factor for the increasing of the grinding temperature. The temperature of the down-grinding is higher than that of the up-grinding, because of the different heat effect between the down-grinding and the up-grinding resulted from the formation mechanism and deformation of cutting chip. The temperature in the workpiece surface which is ground by CBN wheel is higher than that by aluminium oxide wheel as a result of the heat conduction performance of CBN grain is better than that of aluminium oxide grain.(3)The contact length between the wheel and workpiece is analyzed. It is found that the real contact length is significantly larger than the geometric contact length, especially at a small cutting depth or a high table speed. The contact length increases on the conditions of larger cutting depth, higher table speed or bigger wheel diameter. A high temperature makes the wheel and the workpiece soften seriously, consequently the real contact length increases.Wheel, workpiece and wheel grains deform subjected to the grinding force, thus the real contact length increases.(4)The temperature field in surface grinding is researched through the three dimensional numerical simulation. The physical properties of the workpiece material are considered to be non-linear according to the temperature. Three dimensional numerical simulations for some typical grinding conditions are carried out by using the triangle heat source distribution model under the forenamed varied material physical properties, and the temperature distribution of workpiece is obtained easily. The factors which can affect the grinding temperature field are analyzed such as the heat source distribution model, the grinding fluid and the varied physical properties of the workpiece material. The simulation results are compared with those obtained from experimental measurements. A good agreement is found between the FEM results and experimental observations. In order to verify the simulation results in the wet grinding, the outline of the workpiece is detected by the surface roughness device.