Simulation And Experimental Study On Nano-machining Of Monocrystal Silicon

With the rapid development of ultra precision machining technology, productswith high precision and high surface quality have been widely applied in the field ofscientific research, the traditional manufacturing industry and the national defenseindustry. Meanwhile, the development of those fields puts forward higherrequirement for machining accuracy and surface quality of materials. As a result ofcontacting type material removal between the cutter and work piece in traditionalmachining, sub-surface damage is inevitable, which has an impact on theperformance and service life of products. Therefore, it becomes a key issue toimprove ultra precision technology that decreases or even avoids such damages.However, observing the microworld is too difficult to become true in the scale ofnanometers because of the limitation of equipment and cost in experimental research,while molecular dynamics (MD) simulation method could make it easy to view themovement of atoms through the visual interface. Thus people can study themechanisim of material deformation and removal, as well as the factors influencingthe nano machining process in accordance with the MD simulation, which has agreat significance on ultra precison machining.First, the dissertation makes a systematic review of the current study on theMD simulation and experimental research, analyses the principles and methods ofMD simulation,and creates a MD model of monocrystal nano-machining accordingto suitable potential functions and initialization parameters. The variation of force,system temperature and interatomic potential is discussed by the MD simulation too.Second, characterization methods such as coordination number and labelingatoms in different layers have been adopted to study the law of transformation. Asthe surface atoms are tracked, their transformation law is analysed and the formationmechanism of the cuttings and finished surface is annouced. The impact of cuttingspeed, scartching depth, radius of indenter and crystal orientation of silicon on themachining is also studied.Lastly, force-depth curves of both nano-indentation and nano-scratching, aswell as mechanical characteristics of monocrystal silicon are given according toexperiments. The nano-indentation experiments are conducted by Nano IndenterG200, which demonstrates that the hardness and modulus turn down with increasedof loading. The nano-scratching experiments are conducted by Atomic ForceMicroscopy. Those experiments prove the veracity of MD simulation.