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 引用本文: 谭援强, 肖湘武, 张江涛, 姜胜强. 尼龙粉末在SLS预热温度下的离散元模型参数确定及其流动特性分析[J]. 力学学报, 2019, 51(1): 56-63.
Tan Yuanqiang, Xiao iangwu, Zhang Jiangtao, Jiang Shengqiang. DETERMINATION OF DISCRETE ELEMENT MODEL CONTACT PARAMETERS OF NYLON POWDER AT SLS PREHEATING TEMPERATURE AND ITS FLOW CHARATERISTICS[J]. Chinese Journal of Theoretical and Applied Mechanics, 2019, 51(1): 56-63.
 Citation: Tan Yuanqiang, Xiao iangwu, Zhang Jiangtao, Jiang Shengqiang. DETERMINATION OF DISCRETE ELEMENT MODEL CONTACT PARAMETERS OF NYLON POWDER AT SLS PREHEATING TEMPERATURE AND ITS FLOW CHARATERISTICS[J]. Chinese Journal of Theoretical and Applied Mechanics, 2019, 51(1): 56-63.

## DETERMINATION OF DISCRETE ELEMENT MODEL CONTACT PARAMETERS OF NYLON POWDER AT SLS PREHEATING TEMPERATURE AND ITS FLOW CHARATERISTICS

• 摘要: 尼龙粉末是增材制造中常用的粉体材料,温度对其流动性有重要影响. 探索尼龙粉末增材制造预热温度下的流动性是研究选择性激光烧结(selective laser sintering, SLS)工艺中粉体铺展成形的基础. 选取SLS技术中的尼龙粉末为原材料,采用离散元数值方法,研究尼龙粉末的流动行为,是增材制造工艺数值模拟和铺粉工艺优化的研究热点. 以Hertz-Mindlin模型为基础,基于Hamaker理论模型和库伦定律,在尼龙粉末的接触动力学模型中引入范德华力和静电力,建立预热温度下尼龙粉末流动的离散元模型(discrete element method, DEM),通过对比相应实验结果,标定了该模型的参数. 对加热旋转圆筒中尼龙粉末流动过程进行了DEM数值模拟,校核了所建模型的正确性,并研究了粉体粒径分布对尼龙粉末流动特性的影响规律. 研究表明,尼龙粉末黏附力是静电力与范德华力的共同作用结果;随着粉体粒径的增大,尼龙粉末崩塌角增大,流动性增强;相对于高斯粒径分布,粒径均匀分布的尼龙粉末颗粒流动性更强. 研究结果可指导SLS中铺粉工艺的优化.

Abstract: Nylon powder is a commonly used powder material in Additive Manufacturing whose fluidity is closely related to temperature. Exploring powder fluidity at preheating temperature in Additive Manufacturing is the basis for studying the fluidity and spreading properties of powder in selective laser sintering (SLS) process. Choosing nylon powder in SLS technology as a raw material and the flow behavior of nylon powder is studied by discrete element method (DEM), which is a hot topic of numerical simulation and powder spreading process optimization in Additive Manufacturing. Based on Hertz-Mindlin model, Hamaker theory model and Coulomb's law, Van der Waals and electrostatic force are introduced to describe the contact dynamics of nylon powder at preheating temperature. The DEM model of nylon powder at preheating temperature was established based on the mechanical parameters and the rationality of the model was verified by comparing with the experimental results. The flow process of nylon powder in a heated rotating roller was simulated by DEM which checked the correctness of the model. The effects of particle size and particle size distribution on the flow characteristics of nylon powder were studied. The results show that the adhesion force of nylon powder is the result of the interaction of electrostatic force and van der Waals force. With the increase of particle size, the collapse angle of nylon powder decreases and the fluidity of nylon powder increases. And the nylon powder fluidity with uniform particle size distribution is stronger than that of Gaussian particle size distribution. The results can guide the optimization of powder spreading process in SLS.

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