Discrete-Continuum Dislocation Dynamics at Surfaces and Interfaces with Application to Plasticity of Nanolaminated Composites

表面和界面处的离散连续位错动力学及其在纳米层压复合材料塑性中的应用

• 批准号: 429421091
• 负责人: Professor Dr. Michael Zaiser
• 金额: --
• 依托单位: Lehrstuhl für Werkstoffsimulation
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/429421091?language=en
• 关键词: Discrete; Continuum; Dislocation; Dynamics; Surfaces

We develop improved dislocation dynamics simuation approaches to investigate plastic deformation of nanolaminated metal composites. Such composites combine different metals into layered structures with layer thicknessse in the nanometre range. Their plastic deformation properteies are governed by the interactions of crystal lattice dislocations with the bimaterial interfaces of the laminate. On the atomic scale, these interactions are similar to processes occuring at internal interfaces (grain and twin boundaries), as atomic re-arrangements control the nucleation, absorption or transmission of dislocations. However, in laminates consisting of elastically dissimilar materials the elastic boundary conditions at the interfaces lead to additional, long-ranged elastic interactions: Dislocations of an elastically weaker material are repulsed by an interface with a stronger material, whereas dislocations of the stronger material are attracted (Koehler Effect). At the same time, the dislocation stress fields and stress-induced dislocation interactions are modified by the boundaries. In discrete dislocation dynamics simulations of nanolaminate plasticity it is therefore essential to accurately evaluate the influences of the bimaterial interfaces on the internal stress fields which enter the driving forces for dislocation motion. In recent years, the so-called discrete-continuum method (DCM) has led to important progress in dislocation dynamics simulation of elastic surface and interface effects. DCM uses a hybrid method to evaluate dislocation-related internal stress fields by superimposing the singular stress fields of dislocation segments with a slowly varying internal stress field that derives from solution of a coarse grained eigenstrain problem and accounts for boundary conditions at surfaces and interfaces. However, the singular segment stress fields have always been evaluated using bulk expressions which are inaccurate near surfaces/interfaces, leading to a mismatch with the coarse grained solution and to an inaccurate representation of the forces acting on dislocations. We resolve this problem by accounting for analytical corrections to the singular stress fields near surfaces and interfaces as derived in recent years by Prof. Yuan, who participates in the Project as a Mercator Fellow. Our improved DCM approach will provide an accurate description of interface effects and complex deformation boundary conditions (nanoindentation) in plastic deformation of nanolaminates. We will exploit this capability to understand complex observations such as strength inversion in Cu-Au Laminates (the elastically stronger Cu may show more plastic deformation than the elastically weaker Au), and to analyze and optimize the behavior of graded nanolaminates under different loading conditions.

我们开发了改进的错位动力学模拟方法，以研究纳米胶质金属复合材料的塑性变形。这种复合材料将不同的金属组合为层厚度的分层结构。它们的塑性变形特性由晶格位错的相互作用与层压板的双质界面的相互作用。在原子量表上，这些相互作用类似于内部界面（晶粒和双边界）处发生的过程，因为原子重新排列控制了核的成核，吸收或传播。然而，在由弹性材料组成的层压板中，界面处的弹性边界条件会导致额外的，长期的弹性相互作用：弹性较弱的材料的位错被具有更强材料的界面排斥，而较强材料的脱位则吸引了较强的材料的位置（koehler效应）。同时，脱位应力场和应力诱导的脱位相互作用被边界修改。因此，在纳米氨酸塑料的离散脱位动力学模拟中，必须准确评估双质界面对内部应力场的影响至关重要。近年来，所谓的离散核法（DCM）导致了弹性表面和界面效应的脱位动力学模拟的重要进展。 DCM使用一种混合方法来评估与位错相关的内部应力场，通过将脱位段的奇异应力场叠加，其内部应力场较慢，从而源自粗粒状特征性特征性问题，并说明表面和接口处的边界条件。然而，始终使用在表面/接口附近不准确的散装表达式评估了奇异的片段应力场，从而导致与粗粒溶液的不匹配，并导致作用于错位的力的不准确表示。我们通过对近年来Yuan教授提出的分析性校正来解决该问题，该问题在表面和界面附近的奇异应力场和界面附近，他是Mercator研究员参加该项目的。我们改进的DCM方法将对纳米胺的塑性变形中的界面效应和复杂变形边界条件（纳米凹痕）提供准确的描述。我们将利用这种能力来理解复杂的观测值，例如Cu-Au层压板中的强度反转（弹性强的CU可能比弹性弱Au显示出更大的塑性变形），并在不同的负载条件下分析和优化分级纳米胺的行为。