Atomistic Simulation Based Crack Evolution Models for Crystal Plasticity FEM of Crystalline Metals

该资助的研究目标是开发多晶金属材料中基于物理的裂纹演化模型，用于晶体塑性有限元模型。 统一的变形-断裂模型将通过放大原子尺度、分子动力学模拟的变量来开发，并明确描述原子结构和变形机制。 升级将为沿着特定滑移系统的变形变量的内聚定律和相关演化定律提供框架。 将采用系统方法，包括以下任务：（i）3D晶格系统的分子动力学（MD）模拟，以模拟各种力场下延性和脆性裂纹演化的演化，（ii）开发加速MD方法，以模拟与实验一致的较长时间尺度，（iii）裂纹尖端变形机制的表征和识别，然后量化局部原子结构和演化，以及（iv）通过划分总原子，开发基于能量的定律来控制工艺区中的裂纹生长。不同物理机制对应的能量。通过建立新的裂纹演化模型，对于材料的分析和设计以获得更好的断裂韧性和延展性至关重要，这将给科学界带来好处。 加速分子动力学建模的进步将允许在真实实验的应变率下进行建模。 与桑迪亚和 Brown Deer Technology 的合作将实现可交付成果的技术转让，以供更广泛的利用。 学生将与桑迪亚国家实验室和一家小型开发公司的杰出研究人员进行密切互动，以了解他们的工作的直接影响。

The research objective of this grant is the development of physics-based crack evolution models in polycrystalline metallic materials for use in crystal plasticity finite element models. The unified deformation-fracture models will be developed by upscaling variables from atomic-scale, molecular dynamics simulations with explicit depiction of the atomic structure and deformation mechanisms. Upscaling will provide a framework for cohesive laws and associated evolution laws for deformation variables along specific slip systems. A systematic approach will be undertaken, encompassing the following tasks: (i) molecular dynamics (MD) simulations of 3D crystalline lattice systems to simulate the evolution of ductile and brittle crack evolution under a variety of force fields, (ii) development of accelerated MD methods to simulate longer time scales consistent with experiments, (iii) characterization and identification of crack tip deformation mechanisms, followed by quantification of the local atomic structure and evolution, and (iv) development of energy-based laws governing crack growth in the process zone by partitioning the total energy corresponding to different physical mechanisms.Benefits to the scientific community will be accomplished through the establishment of novel crack evolution models of critical importance in analysis and design of materials for better fracture toughness and ductility. Advancement in accelerated molecular dynamics modeling will allow modeling at strain rates of realistic experiments. Collaboration with Sandia and Brown Deer Technology will enable technology transfer of deliverables for broader utilization. Students will have strong interactions with eminent researchers at Sandia National Laboratories and a small-scale development company to see the direct impact of their work.