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理想框架。为在限制计算代价的同时跨越尺寸与时间尺度，通常采用代表性体积单元概念。该方法考虑整体材料行为代表性体积内的微观结构演化。然而，在具有复杂热力加载历史的环境中，需仔细审视时间尺度与模拟域等建模约束对预测结果的影响。我们以AISI 316L不锈钢激光粉末床熔融冷却过程中残余应力形成为例，研究模拟体积内异质位错结构形成的表征。通过大规模三维离散位错动力学模拟结合LPBF工艺的热力有限元建模实现。结果表明：周期性模拟域尺寸不足可能导致位错图案反映主胞边界；较大模拟域中更显著的位错交互作用凸显了模拟域约束对力学性能预测的重要性。我们通过捕捉位错结构与基体材料的符合度，制定了表征代表性体积单元的标准。该工作为未来研究块体材料介观模拟中异质微观结构形成奠定了基础。