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

该基金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开发升级变量从原子尺度，分子动力学模拟与原子结构和变形机制的明确描述。 尺度放大将提供一个框架的凝聚力的法律和相关的演变规律的变形变量沿着特定的滑移系统。 将采取系统的办法，包括以下任务：（i）三维晶格系统的分子动力学（MD）模拟，以模拟在各种力场下的韧性和脆性裂纹演化的演化，（ii）加速MD方法的开发，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，接着是局部原子结构和演化的量化，及（iv）发展能源-通过划分与不同物理机制相对应的总能量来控制过程区中裂纹扩展的基本规律。通过建立新的裂纹演化模型，更好的断裂韧性和延展性。 在加速分子动力学建模的进步将允许建模在应变率的现实实验。 与Sandia和Brown Deer Technology的合作将使可交付成果的技术转让得到更广泛的利用。 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强有力的互动，以了解他们工作的直接影响。

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.