Subsurface defects have a significant impact on the precision and performance of nano-structures. In this paper, molecular dynamics simulation of nano-indentation is performed to investigate the effect of machining-induced subsurface defects on dislocation evolution and mechanical properties of materials, in which the specimen model with subsurface defects is constructed by nano-cutting conforming to reality. The formation mechanism of subsurface defects and the interaction mechanism between machine-induced defects and dislocation evolution are discussed. The hardness and Young's elastic modulus of single crystal copper specimens are calculated. The simulation results indicate that there exist stable defect structure residues in the subsurface of workpiece, such as atomic clusters, stacking fault tetrahedral, and stair-rod dislocations. Secondary processing of nano-indentation can restore internal defects of the workpiece, but the subsurface damage in the secondary processing area is aggravated. The nano-indentation hardness of specimens increases with the introduction of subsurface defects, which results in the formation of work-hardening effect. The existence of subsurface defects can weaken the ability of material to resist elastic deformation, in which the mutual evolution between dislocations and subsurface defects plays an important role.

中文翻译：

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加工引起的表面缺陷通过纳米压痕对位错演化和材料力学性能的影响。

次表面缺陷对纳米结构的精度和性能有重大影响。本文通过纳米压痕的分子动力学模拟研究了加工引起的表面缺陷对材料的位错演化和力学性能的影响，其中通过符合实际情况的纳米切割构造了具有表面缺陷的样品模型。讨论了地下缺陷的形成机理以及机加工缺陷与位错演化的相互作用机理。计算了单晶铜试样的硬度和杨氏弹性模量。仿真结果表明，工件表面存在稳定的缺陷结构残渣，如原子团簇，堆垛层错四面体，阶梯杆位错等。纳米压痕的二次加工可以恢复工件的内部缺陷，但是二次加工区域中的次表面损伤会加剧。样品的纳米压痕硬度随着表面缺陷的引入而增加，从而导致加工硬化作用的形成。表面缺陷的存在会削弱材料抵抗弹性变形的能力，其中位错与表面缺陷之间的相互演化起着重要的作用。