Research On The Chip-Formation Mechanism Of High-Speed Grinding For Material Of Difficult Machining

In thefieldofmodern manufacturing, for its excellent performance of high strength, high hardness and good wear resistance, engineering ceramics and other hard and brittle materials has been widely used in high-tech fields. However, there are still a series of problems for grinding of these difficult machining materials, how to achieve ductile grinding of brittle materials,, effectively control engineering ceramic grinding surface quality, such as improved surface roughness and control micro-cracks? How to improve the grinding efficiency of difficult machining materials? How to explain and use the theory of high-speed grinding, to achieve the perfect unity of high quality and high efficiency?such that the wear volume of grinding wheel is high and its associated high cost, the machined work-piece surface quality is hard to forecast and control, the poor processing performance leads to low productivity as well. During the high-speed and ultra-high speed grinding, hard and brittle materials could be removed in ductile mode, so as to achieve the high-quality grinding with improved surface integrity and controlled cracks.Based on the understanding of the techniques in hard and brittle materials grinding and the theory of high speed grinding, this paper studied dislocations and related theories, and techniques of molecular dynamic simulation, built a single-grit grinding cutting simulation model based on molecular dynamics software carried out simulation experiments and analyzed the results. based on dislocation theory, discussed the factors that effect the critical grinding depth of brittle materials and the relationship between them to further explain the high quality and efficient grinding mechanism of rapid feed shallow grinding.Based on dislocation theory, a model of interaction between single grit and work piece material during grinding process is built. Analyzed the movement of atoms when they are squeezed by grit, which give relevant explanations or results:1) the removal of material is accomplished by dislocation gliding. Achieved by accumulating plastic deformation of the material or product cracks in the internal barriers by stacking dislocations, normal stress generated longitudinal cracks and shear stress generated transverse cracks. Crack critical condition depends on the material the size of the internal stress. made the elastic deformation-deformation-brittle fracture phase boundaries, explained the mechanism of the ductile brittle transition.Based on LAMMPS molecular dynamics software carried out the relevant simulation experiments. Construct a single diamond abrasive grinding SiC surface models based on microscopic modeling method. and the model introduced dislocation structure. By controlling the different input parameters relevant results or conclusions drawn:(1) the use of high wheel speed Vs, the number of dislocations in the chip area decreased, the grinding force is reduced, and the grinding temperature increased. (2) maintain a certain wheel speed and material removal, increased work piece speed Vw while reducing the cutting depth ap, the number of dislocations in the chip area decreased, the grinding force is reduced, and grinding temperature decrease because the number of atoms squeezed.based on the MGKS1332/H high-speed precision CNC cylindrical grinding machine, related demonstration experiments are carried out. (1)increasing both the wheel speed and the workpiece speed can improve the surface roughness of grinding and improve grinding efficiency. (2)by observing the SEM photographs of SiC debris, found that under the conditions of high-speed grinding debris are more fragmented, and the debris is also showing significant plastic wear scar. (3) engineering experimental results verify the dislocation mechanism based on chip formation process and carbonization silicon single grain grinding forces and force ratio evolution trend, which shows the results of this research and its significance.