We present a powder‐scale computational framework to predict the microstructure evolution of metals in powder bed fusion additive manufacturing (PBF AM) processes based on the hot optimal transportation meshfree (HOTM) method. The powder bed is modeled as discrete and deformable three‐dimensional bodies by integrating statistic information from experiments, including particle size and shape, and powder packing density. Tractions in Lagrangian framework are developed to model the recoil pressure and surface tension. The laser beam is applied to surfaces of particles and substrate dynamically as a heat flux with user‐specified beam size, power, scanning speed, and path. The linear momentum and energy conservation equations are formulated in the Lagrangian configuration and solved simultaneously in a monolithic way by the HOTM method to predict the deformation, temperature, contact mechanisms, and fluid‐structure interactions in the powder bed. The numerical results are validated against single track experiments. Various powder bed configurations, laser powers, and speed are investigated to understand the influence of dynamic contact and inelastic material behavior on the deformation, heat transfer, and phase transition of the powder bed. The formation of defects in the microstructure of 3D printed metals, including pores, partially, and unmelted particles, is predicted by the proposed computational scheme.

中文翻译：

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金属粉末床熔融增材制造的拉格朗日无网格中尺度模拟

我们提出了一种粉末级计算框架，以基于热最佳运输无网格（HOTM）方法预测粉末床熔融增材制造（PBF AM）过程中金属的微观结构演变。通过整合来自实验的统计信息（包括粒度和形状以及粉末堆积密度），将粉末床建模为离散且可变形的三维物体。拉格朗日框架中的牵引力可以模拟反冲压力和表面张力。激光束以热通量动态地施加到颗粒和基材的表面，并具有用户指定的束大小，功率，扫描速度和路径。线性动量和能量守恒方程是在拉格朗日构型中制定的，并通过HOTM方法以整体方式同时求解，以预测粉末床中的变形，温度，接触机理和流固耦合。数值结果针对单轨实验进行了验证。研究了各种粉末床配置，激光功率和速度，以了解动态接触和非弹性材料行为对粉末床变形，传热和相变的影响。通过提出的计算方案可以预测3D打印金属的微观结构中缺陷的形成，包括孔，部分和未熔融的颗粒。数值结果针对单轨实验进行了验证。研究了各种粉末床配置，激光功率和速度，以了解动态接触和非弹性材料行为对粉末床变形，传热和相变的影响。通过提出的计算方案可以预测3D打印金属的微观结构中缺陷的形成，包括孔，部分和未熔融的颗粒。数值结果针对单轨实验进行了验证。研究了各种粉末床配置，激光功率和速度，以了解动态接触和非弹性材料行为对粉末床变形，传热和相变的影响。通过提出的计算方案可以预测3D打印金属的微观结构中缺陷的形成，包括孔，部分和未熔融的颗粒。