Research On Nanoprocessing Performance Of Optical Quartz Glass

Optical quartz glass is widely used in high-technology field because of its unique optical properties and stable physical and chemical properties. Especially in the severe environment, it plays an irreplaceable position. But as we all know, the machining properties of quartz glass is very poor. In ultra-precision machining, it is very easy to appear some defects such as crack and damage, which severely hinders the application and development of quartz glass. However, the research develops slowly for limiting by nanoscale processing conditions and the nanoscale processing performance of quartz glass is not very clear at present. At the nanoscale, the simulation method gradually shows a huge advantage, especially the molecular dynamics simulation, which has become a powerful tool to research the material nanoprocessing performance. Based on the above issues and the status quo, this paper puts forward to use molecular dynamics simulation combination with nanoindentation experiment to research the nanomachining performance of quartz glass.In order to solve the problem of computing power, we have built a large-scale MD simulation platform based on CPU parallel technology, which can realize parallel computing on multiple computers. By means of the tests of the clusters, it can be found that the simulation scale can reach sub-micron level (hundreds of millions atoms) and the cluster speed ratio can reach 1.65.According to the real manufacturing process of quartz glass, the amorphous simulation model is achieved and the correctness of the model is verified through some specific parameters such as density (2.285g/cm3) and hardness (9.7?10.7Gpa). By the observation of microstructure, it is found that the microscopic defects in the silica glass will form due to losing of dense accumulation between atoms caused by restructuring of the Si-O bonds, which is having an influence on the subsequent machining.The mechanical properties, surface morphology, subsurface damage and the movement rule of internal defects are studied in the nano indentation simulation. The results show that the hardness and elastic modulus of quartz glass will reduce with the increase of the impression depth and the surface morphology of the nanoindentation does not show the phenomenon of obvious material accumulation. There are three kinds of movement of atomic defects:transfer, disappear and dense. The motion of atomic defects has certain effect on the change of mechanical properties and the formation of final damage.During nanoscratch simulation, the changes of the force exerted by the indenter and the temperature in different conditions, the movement of the defects and the mechanical properties of the scratched surface are researched. Results indicate that the deformation mechanism of material is densification rather than plastic flow, which is the reason of the increasing of the surface density. For different parameters, it is concluded that multiple processing will reduce the cutting force, which is conducive to the stability of scratches. According to the further analysis of the atomic structure in the scratched surface, it turns out that the hardness increased by 18% and the elastic resilience rate reduced by 8%. The fivefold defect is responsible for the change of the mechanical behavior.Finally the nanoindentation experiment is carried on to study the mechanical properties and surface morphology of materials. The results demonstrate that with the increasing of constant load, the nanohardness, elastic modulus, and elastic rebound rate are both decreasing, which proved the accuracy of the simulation. Compared the surface morphology of different load, it can be drawn that after the material density, the accumulation of material will become the main deformation rule, which can supply the deficiency of the simulation. At the end, the effects of load times and speed on the deformation and mechanical properties are researched.