This study investigates the influence of materials' dislocation source density and initial dislocation density on dislocation evolution mechanism during nanoindentation process. On the basic of discrete dislocation dynamics (DDD) algorithm, a novel 2.5D nanoindentation numerical model was by proposed by coupling with finite element (FE) contact analysis. In particular, new reduced integration method and stress transmission mode were performed in this simulation scheme. Results showed that the dislocation multiplication and slip behavior were both significantly impacted by the initial dislocation source density. Meanwhile, the influence of initial dislocation density focused on the spatial arrangement of discrete dislocations. In addition, transmission electron microscope (TEM) analysis was used to reveal the dislocation configurations during nanoindentation process. Typical dislocation patterns including Shockley partial dislocation and Frank partial dislocation were found in extrusion region, which verifies the reasonable slipping conditions of DDD simulation. The results of this study can be useful in developing DDD model and predicting dislocation evolution rules in nanoindentation.

本研究探讨了纳米压痕过程中材料的位错源密度和初始位错密度对位错演化机理的影响。在离散位错动力学（DDD）算法的基础上，结合有限元接触分析，提出了一种新型的2.5D纳米压痕数值模型。特别是，在该模拟方案中执行了新的简化积分方法和应力传递模式。结果表明，位错倍增和滑移行为都受到初始位错源密度的显着影响。同时，初始位错密度的影响集中在离散位错的空间排列上。此外，透射电子显微镜（TEM）分析用于揭示纳米压痕过程中的位错构型。在挤压区域发现了典型的位错模式，包括Shockley部分位错和Frank部分位错，验证了DDD模拟的合理滑移条件。这项研究的结果可用于开发DDD模型和预测纳米压痕的位错演化规则。