模拟月壤铺粉过程DEM数值仿真

空基激光选区熔化（SLM）技术与原位资源利用（ISRU）概念结合，有望解决地外大规模基地建设的工程难题。SLM铺粉过程对成形件性能和质量有重要影响。基于非球形粒子叠加球模型方法，建立模拟月壤颗粒几何模型；基于线性弹簧-阻尼接触作用模型、Hamaker理论及牛顿运动定律，建立颗粒动力学模型；采用三维离散单元方法（DEM）及软球模型，进行不同工况下模拟月壤在铺粉过程中的流变特性研究。结果显示:所提模型和方法能开展指定工况和环境参数的模拟月壤颗粒系统流动性和堆积行为数值仿真研究；月面低重力环境导致粉床表面粗糙度变大、堆积密度和平均配位数变小；通过降低铺粉速度和优化刮刀型面，可以有效改善月基铺粉的粉床质量，获得更密实和均匀的粉床结构。 

Numerical simulation of spreading process of lunar regolith simulant by DEM

Spaced-based Selective Laser Melting (SLM) technique in combination with In-Situ Resource Utilization (ISRU) concept can be an off-world manufacturing solution to the significant engineering challenge on the large-scale construction for extra-terrestrial bases. Powder spreading process in SLM has a major impact on the characteristics and quality of final part. The geometric shape of the lunar regolith simulant particles was modeled by means of a non-spherical particle superposition model method. The particle's dynamic model was established based on linear spring-damping contact model, Hamaker theory and Newton's laws of motion. A three-dimensional Discrete Elemeat Method (DEM) technique with soft-sphere approach was employed to investigate the rheological behavior of the lunar regolith simulant powder during spreading process under various conditions. The results show that the proposed model and method can be used to study the flowability and packing behavior of lunar regolith simulant powder system as a function of process and environmental condition parameters. Lunar reduced gravity leads to larger values of surface roughness and smaller values of packing density and averaged coordination number of powder bed; the quality of lunar regolith simulant powder bed during spreading process under lunar gravity can be improved by reducing spreading speed and geometrically optimizing blade type spreader profile, resulting in a denser and more uniform powder bed.