Mesoscale simulations of discrete defects in metals provide an ideal framework to investigate the micro-scale mechanisms governing the plastic deformation under high thermal and mechanical loading conditions. To bridge size and time-scale while limiting computational effort, typically the concept of representative volume elements (RVEs) is employed. This approach considers the microstructure evolution in a volume that is representative of the overall material behavior. However, in settings with complex thermal and mechanical loading histories careful consideration of the impact of modeling constraints in terms of time scale and simulation domain on predicted results is required. We address the representation of heterogeneous dislocation structure formation in simulation volumes using the example of residual stress formation during cool-down of laser powder-bed fusion (LPBF) of AISI 316L stainless steel. This is achieved by a series of large-scale three-dimensional discrete dislocation dynamics (DDD) simulations assisted by thermo-mechanical finite element modeling of the LPBF process. Our results show that insufficient size of periodic simulation domains can result in dislocation patterns that reflect the boundaries of the primary cell. More pronounced dislocation interaction observed for larger domains highlight the significance of simulation domain constraints for predicting mechanical properties. We formulate criteria that characterize representative volume elements by capturing the conformity of the dislocation structure to the bulk material. This work provides a basis for future investigations of heterogeneous microstructure formation in mesoscale simulations of bulk material behavior.

翻译：金属中离散缺陷的介观尺度模拟为研究高力热载荷条件下塑性变形的微观机制提供了一个理想框架。为了在限制计算量的同时跨越尺寸和时间尺度，通常采用代表性体积单元的概念。该方法考虑了代表整体材料行为的体积内的微观结构演化。然而，在具有复杂热力加载历史的设置中，需要仔细考虑建模约束（如时间尺度和模拟域）对预测结果的影响。本文以AISI 316L不锈钢激光粉末床熔融冷却过程中残余应力的形成为例，研究了模拟体积中异质位错结构形成的表征。通过一系列大规模三维离散位错动力学模拟，并结合激光粉末床熔融过程的热力学有限元建模，实现了这一目标。我们的结果表明，周期性模拟域尺寸不足可能导致反映原胞边界的位错图案。更大域中观察到的更显著的位错相互作用强调了模拟域约束对预测力学性能的重要性。我们制定了通过捕获位错结构与块体材料的一致性来表征代表性体积单元的标准。这项工作为未来在块体材料行为的介观尺度模拟中研究异质微观结构形成提供了基础。