Discrete element simulation and experimental study of powder spreading process in additive manufacturing
Discrete element simulation and experimental study of powder spreading process in additive manufacturing
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DOI：
10.1016/j.powtec.2016.11.002
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发表时间：
2017-01-01
影响因子：
5.2
通讯作者：
Sun, J.
中科院分区：
文献类型：
--
作者：
Haeri, S.;Wang, Y.;Sun, J.
将增材制造 (AM) 中使用的粉末铺展到致密的颗粒层上进行烧结，并逐层重复此过程以形成最终产品。使用离散元法 (DEM) 模拟棒状颗粒在实际增材制造设置中的扩散，以研究颗粒形状和操作条件对床质量的影响，其特征在于其表面粗糙度和固体体积分数。研究发现，较大的颗粒长宽比 A(r) 或较高的铺展器平移速度会导致较低的床质量，即较大的表面粗糙度和较小的体积分数。表面粗糙度随 A(r) 单调增加。然而，对于由以低平移速度移动的滚筒式撒布机形成的随机堆积的粉末床，体积分数在 A(r) = 1.5 处表现出最大值。还发现，在相同操作条件下，就准备床的质量而言，滚筒优于叶片撒布机。床的微观结构分析还显示了颗粒排列响应诱导流，这通过一组专门设计的实验得到了定性证实。此外，记录了具有混合长径比 (A(r)) 的粉末的形状偏析，使得具有较大 Ar 的颗粒倾向于积聚在床的上层。 (C) 2016 年作者。由 Elsevier B.V. 出版
Powders used in additive manufacturing (AM) are spread onto a compact layer of particles for sintering and this process is repeated layer by layer to form the final products. Spreading of rod-shaped particles in realistic AM settings is simulated using the discrete element method (DEM) to investigate the effects of particle shape and operating conditions on the bed quality, characterised by its surface roughness and solid volume fraction. It is discovered that larger particle aspect ratios, A(r), or higher spreader translational velocities result in a lower bed quality, i.e. a larger surface roughness and a smaller volume fraction. The surface roughness increases monotonically with A(r). However, the volume fraction exhibits a maximum at A(r) = 1.5 for randomly packed powder beds that are formed by the roller type spreaders moving at low translational velocities. It is also found that a roller outperforms a blade spreader in terms of the quality of the prepared bed at the same operating conditions. The micro-structural analysis of the beds also shows particle alignment in response to the induced flow, which is qualitatively confirmed by a set of purposely-designed experiments. In addition, a shape segregation is documented for powders with mixed aspect ratios (A(r)) such that particles with larger Ar tend to accumulate on the upper layers of the bed. (C) 2016 The Authors. Published by Elsevier B.V.