Molecular Dynamics Research Of Surface Residual Stress On Nano-scale

With the rapid development of high-tech, such as in material science and microelectronics, etc, mechanical manufacturing technology has been developed from precision machining to ultra-precision machining, and cutting depth has reached nanometer level. The major change in processing methods and mechanism of nano machining will cause changes in machinery, metallurgy, physics, chemistry and other aspects of the machinined materials surface. Although these changes occur only in the workpiece surface, it may have fatal effect on its future using performance. Among these, surface residual stress in micro/nano scale has a very important effect on fatigue strength, stress corrosion, dimensional stability and other performances. Therefore, the research on measurements of residual stress has important practical significance for production and scientific experiments.With the development of surface engineering technology and microelectro mechanical systems, the traditional measuring methods, such as mechanical release measurement and nondestructive measurement, can hardly meet the measuring needs in micro/nano scale. Therefore, analysis and measurment of the residual stress of material surface have been carried out in this thesis based on micro/nano indentation experiments and combined with molecular dynamics simulation. Through literature investigation, theoretical modeling simulation, exprimental and comparative study, the following works have been completed:Firstly, using mechanics theory to establish the theoretical formula of the residual stress testing in micro/nano scale; and studying the theoretical basis of the residual stress testing by nanoindentation method in micro/nano scale;Secondly, establishing molecular dynamics model of the single crystal copper in nanoscale, using this model to make simulation research of surface residual stress testing in micro/nano scale, thus the correctness of the residual stress testing by nanoindentation method in nanoscale would be verified; and putting forward molecular dynamics simulation methods for large scale simulation. Thirdly, using molecular dynamics method to analyse the residual stress of single crystal copper in micro/nano scale, and being verified by experiments.At last, summarizing the study of full text; then putting forward the direction of further research work.