Research On The Effect Of Rotating Abrasive Parameters On Polishing Process Of Crystalline Copper Via Molecular Dynamics

Ultra-precision polishing technology has become the key role in realizingintegrated circuit into nanoscale. In the process of the nanometer level, the deformationand removal mechanism of materials is significantly different from macro process. Asthe deformation and removal of materials is just on a few to several hundred atomiclayers, it is difficult to research the deformation theory of ultra-precision polishing byexperiment. Based on the discrete mechanics method, the molecular dynamics cansimulate the machining process on nano-scale and explain the micro mechanism,which has become an important method of researching the ultra-precision machining.In ultra-precision polishing process research, researchers generally use thetwo-body contact sliding model on the crystalline copper surface. However, there isless research on the three-body contact sliding model by using rotating abrasive.Because the two-body contact sliding model is simplified to scratching process, itcannot accurately describe the real polishing process. And the deformation andremoval mechanism of material in the two models must have a significantly different.So, in this article molecular dynamics method is adopted to simulate the three-bodycontact polishing process by using rotating diamond abrasive. According to the results,the effect of rotating diamond abrasive on the deformation and removal mechanism ofmaterials and the formation and movement of internal defects in materials is studied.The following aspects are included:Firstly, the types and properties of defects in the crystalline copper in polishingprocess with rotating abrasive are analyzed. Then, the deformation and removalmechanism of crystalline copper is studied. With increasing the penetration depth, thedeformation and removal mechanism of crystalline copper follows the regimes ofno-wear, condensing and ploughing. Cutting rarely happens in three-body contactsliding process. Crystalline copper mediates the plastic deformation by piling up thesurface atoms and generating the kinds of internal defects in the process. The dislocations, major defect type, glide hanging from the top surface or through thethickness toward the bottom surface along certain directions. They are highly mobileand thus participate in various interactions between themselves and with other defects.Besides, the simulation also reveals the relationship between the load of rotatingabrasive and the generating and gliding of two important types of dislocations, whichtangential force is relevant to surface glide dislocation loops and normal force to bulkglide dislocation loops.For further studies on the deformation and removal mechanism of crystallinecopper in polishing machining, the effects of the abrasive rotating velocity, rotatingangle, penetration depth and radius on defect evolutions and machined surface arediscussed. With increasing rotating velocity, the quantity and effect zone of all kinds ofdefects become larger to critical value and then decrease. When the abrasive rotatingdirection does not agree with its machining direction, the internal defects of crystallinecopper emit more on the rotating direction. With increasing penetration depth，thequantity of all kinds of defects becomes larger. With increasing abrasive radius, thedecreasing of relative depth leads to a large scope dislocations and effect zone.According to the studies in this article, further investigation of the effect ofabrasive machining direction, machining crystal surface and system temperature ondefect evolutions and machined surface is carried out. In the machining process, thedirect factor of defect evolutions and surface patterns is crystalline structure of theworkpieces. The dislocations glide along optimal slip system, among which majorprefer to straight or close to machining direction, minority to other optimal slip vectors.With increase of system temperature, the quantity of all kinds of defects has significantincrease.This investigation is not only a deeper study on the deformation and removalmechanism of crystalline copper in polishing machining, but also for betterdetermination of polishing process parameters. The research and analysis of thedeformation and removal mechanism in polishing process will provide a bettertheoretical guidance.