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陈辉, 闫文韬. 激光选区熔化增材制造中的粉体热动力学行为. 力学学报, 2021, 53(12): 3206-3216. DOI: 10.6052/0459-1879-21-403
引用本文: 陈辉, 闫文韬. 激光选区熔化增材制造中的粉体热动力学行为. 力学学报, 2021, 53(12): 3206-3216. DOI: 10.6052/0459-1879-21-403
Chen Hui, Yan Wentao. Dynamic behaviours of powder particles in selective laser melting additive manufacturing. Chinese Journal of Theoretical and Applied Mechanics, 2021, 53(12): 3206-3216. DOI: 10.6052/0459-1879-21-403
Citation: Chen Hui, Yan Wentao. Dynamic behaviours of powder particles in selective laser melting additive manufacturing. Chinese Journal of Theoretical and Applied Mechanics, 2021, 53(12): 3206-3216. DOI: 10.6052/0459-1879-21-403

激光选区熔化增材制造中的粉体热动力学行为

DYNAMIC BEHAVIOURS OF POWDER PARTICLES IN SELECTIVE LASER MELTING ADDITIVE MANUFACTURING

  • 摘要: 激光选区熔化(SLM)可以直接成形近全致密、性能接近锻件的复杂结构金属零件, 是金属增材制造(3D打印)领域的热点技术之一. SLM成形过程中粉末颗粒的热/动力学行为复杂, 与零件成形缺陷及力学性能紧密相关. 本文介绍了离散单元法(DEM)与计算流体力学(CFD)联合建模在SLM中的创新应用, 结合粉末床原位测试及成形在线监测, 探索SLM粉末铺设和粉末床熔融两个工艺环节的复杂粉体热/动力学行为机制. 研究发现, 粉末铺设过程中: 粉体的黏结效应、壁面效应和渗流效应3种机制相互竞争、共同支配粉末动力学行为并最终决定粉末床铺设质量. 粉末床熔融过程中: 熔池喷发的高温金属蒸汽带动环境保护气体形成内旋涡流, 由此驱动散体粉末形成复杂流固耦合运动, 导致粉末床飞溅与剥蚀现象; 热浮力效应对粉末运动不起主导作用. 文中提出了DEM-CFD双向动态耦合模型, 可以充分考虑离散粉末与熔池蒸发气体之间的热力耦合作用, 为SLM粉体熔融热/动力学行为的仿真模拟提供了一种新途径.

     

    Abstract: Laser selective melting (SLM) is one of the most popular technologies in the field of metal additive manufacturing (3D printing), which can directly fabricate complex metal parts with nearly full density and performance similar to forged one. The thermal and kinetic behaviour of powder particles in SLM forming process is complex, which has significant influences on the fusion defects such as pores and cracks and hence on the mechanical properties of the final fabricated parts. This paper introduces the innovative application of the discrete element method (DEM) and computational fluid dynamics (CFD) combined model in the simulation of SLM, and explores the thermal and kinetic behaviour mechanisms of the powder particles the powder spreading and powder melting processes of SLM, combined with in-situ testing and online monitoring on the fabrication process. During the powder spreading process of SLM, it is found that the adhesion effect, wall effect and percolation effect compete with each other to control the dynamic behaviour of powder particles and ultimately determine the packing quality of the deposited thin powder bed. In the process of powder bed melting, the high-temperature metal vapour jetting from the molten pool drives the environmental protection gas to form an internal vortex flow. Then, the vortex flow drives the discrete particles in the powder bed to form complex fluid-solid coupling motion, resulting in spattering and denudation in the powder bed. The thermal buoyancy effect from the laser heating has no dominant effect on powder motions such as spattering and denudation. In this paper, the bi-directional dynamic coupling DEM-CFD model is proposed, which can fully consider the thermodynamic coupling forces between the discrete powder particles and the metal vapour form the molten pool, and provides a new way for the simulation of the thermal-kinetic behaviours of powder particles in SLM such as spattering and denudation.

     

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