Simulation Analysis And Experimental Research Of Typical Material’s Scratch Process

Micro/nano scratching is not only an important means of testing anti friction andwear resistance properties of coating materials and polymers, but also an importantprocessing method for micro/nano devices. The macroscopic properties of materialsare determined by the material’s inner micro-mechanical behavior. During the processof scratching, because of the coupled action of the probe, the subsurface material ofthe sample will produce different mechanical behaviors such as phase transition,plastic deformation, dislocation and fracture. The mechanical behaviors producedduring the nano scratching process have an great influence on the results ofmechanical properties test and surface quality of groove. Thus, how to improvematerial’s workability and performance stability become the key problem of nanoscratching process research.Therefore, in view of the above problems, this paper discusses the effects ofdifferent processing conditions and different surface states on the machining qualityof groove. By using indentation test, this paper compares the hardness of differentcrystal surfaces and different temperatures of mono-crystal silicon. In order to verifythe above simulation and break through the dependence on imported scratchinstrument, this paper designs a micro/nano scratch testing instrument, and has carriedon the corresponding structure design, fabrication, assembling, measuring and control,and test on mono-crystal silicon and copper. The specific contents are as follows:(1) This paper established smoothed particle hydrodynamics (SPH) model foroxygen free copper (OFC), and set the simulation parameters. Aimed at the influenceof residual stress on the groove surface quality, the simulation comparison of scratchperfect surface and cutting surface is performed. The residual stress on the scratchedchip, scratched groove surface quality and scratched force are studied.(2) A new double-tip scratch method is presented. At the same time, moleculardynamics models of double-tip and single-tip, and simulation parameters are set. Thispaper made a comparison of the scratched groove surface quality, Von Misestress distribution, tangential and lateral scratching force at different feed,scratching depth and crystal orientation of single-tip and double-tip. Results showed that double-tip scratch not only can improve the surface quality of scratched groove,also can improve scratching efficiency.(3) This paper simulated indentation process of mono-crystal silicon alongdifferent crystal plane and in different indentation temperature using the moleculardynamics. The phase transformation process of sub-surface’s mono-crystal silicon isanalyzed combining with the crystal defect analysis, crystal structure and mechanicalanalysis. The hydrostatic pressure, atoms of phase transformation, load-displacementand Von Mise stress are made a comparison on different surfaces. The relationshipbetween macroscopic mechanical properties such as hardness is established.Moreover, the influence of indentation temperature on mono-crystal silicon hardnessis studied.(4) Based on the simulation analysis, this paper designed a micro/nano scratchingtest device integrated with Olympus microscope. A two-axis load sensor is designedby integrating an structure of double shear beam and eight strain gauges. Adecoupling algorithm is presented to obtain the lateral load and the normal load. Thispaper made a finite element analysis of the key components of the device such asprecision drive unit, detection unit and the whole device. The error source andcomprehensive performance is analyzed. Moreover, the calibration and performanceanalysis of the two axis force sensor are also made. Finally, the scratching tests ofmono-crystal copper and mono-crystal silicon at different scratching depths arecarried on. At the same time, the material removal mechanism at different scratchingdepths is analyzed, and the effect of scratch depth on scratched surface quality of twokinds of materials is compared.