INFLUENCE OF ROUGH SURFACE OF DEPOSITED AREA ON QUALITY OF POWDER SPREADING DURING SELECTIVE LASER MELTING: DISCRETE ELEMENT SIMULATIONS
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摘要: 选区激光熔化中, 铺粉质量会极大地影响产品的最终质量. 然而, 成形区粗糙表面对铺粉质量影响的研究较少. 因此, 本文以成形区粗糙表面作为新的铺粉基板, 通过离散元法, 研究铺粉过程中成形区的表面形貌和工艺参数对铺粉质量的影响, 并分析铺粉过程中金属粉末在成形区粗糙表面的颗粒动力学和颗粒沉积机制. 结果表明, 将激光扫描方向与铺粉方向旋转一定角度可有效提高粉末层质量, 增加铺粉层厚可减小成形区粗糙表面对铺粉质量的影响. 减小搭接率可提高成形区对颗粒的滞留能力, 从而使更多的颗粒沉积在成形区, 提高粉床填充密度, 但是粉末颗粒会与成形区的粗糙表面碰撞, 产生颗粒迸溅现象. 此外, 铺粉过程中, 由于成形区粗糙度的增大, 成形区粗糙表面上的粉堆产生的强力链、力拱数量多于表面光滑的成形区. 在滚轮作用下, 力拱断裂导致颗粒重新排列, 形成致密的粉末层. 在成形区边界处, 力拱的产生会最终导致边界处的粉末层出现空斑缺陷. 本研究有助于通过优化工艺提高粉床质量.Abstract: The final quality of the printed products is greatly affected by the powder spreading in selective laser melting (SLM). However, little attention is paid on the influence of rough surface of deposited area on the quality of the powder spreading. Therefore, a rough deposited area is modeled as the new substrate for investigating the effect of surface morphology of the deposited substrate and processing parameters on the quality of powder bed during spreading using the discrete element method (DEM). The particle dynamic behavior and powder bed formation mechanism of metal powder on the surface of the deposited area during powder spreading are analyzed. The numerical results show that the quality of powder layer can be effectively improved by rotating the powder spreading direction to a certain angle along the laser scanning direction of the bottom layer, and the influence of the surface of deposited area can be significantly reduced by increasing the powder bed thickness. Reducing the hatch overlap rate can improve the retention capacity of particles in the deposited area, so that more particles are deposited in the deposited area, thereby increasing the packing density of the powder bed. But the powder collides with the rough surface of the deposited area causing more particles to splash. During spreading, the number of strong chains produced by the powder pile on the rough deposited area is more than that on the smooth deposited area due to the increase in roughness of the deposited area. Meanwhile, under the action of the roller, the force arch is destroyed and the particles are rearranged to form a dense powder layer. At the boundary of the deposited area, the generation of force arch will eventually lead to the appearance of vacancy defects in the powder layer at the boundary. The present study is helpful to improve the quality of powder bed during the powder spreading.
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Key words:
- selective laser melting /
- powder spreading /
- discrete element method /
- rough surface /
- powder bed
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图 4 铺粉策略: 铺粉方向与激光扫描方向的夹角分别为0°, 45°, 90°和光滑表面
Figure 4. Powder spreading strategy: the angle between the powder spreading direction and the laser scanning direction is 0°, 45° and 90° respectively and smooth surface
图 6 H=60 μm的粉末层表面轮廓测量示意图
Figure 6. An example of the measured surface profile of the powder layer with H=60 μm
图 7 不同层厚、夹角下的粉末层的填充密度与表面粗糙度
Figure 7. The packing density and surface roughness of powder layer with different gap height and angle
图 9 铺粉过程中粉末在不同角度下沿铺粉方向的总法向力
Figure 9. The total normal force of powder with different angles during spreading along spreading direction
图 11 不同搭接率下粉床的填充密度与表面粗糙度
Figure 11. The packing density and surface roughness of powder bed with different hatch overlaps
图 12 在成形区上铺粉时, 粉堆在不同搭接率下的总法向力
Figure 12. The total normal force of powder pile with different hatch overlaps during spreading at the deposited area
图 14 选定区域内, 粉堆中颗粒-颗粒的强接触数
Figure 14. The number of strong contacts between particles within powder pile in the selected region
图 15 (a)-(b)力拱的空间结构图, (c)铺粉过程中力拱的断裂与重组的演变图
Figure 15. (a)-(b) The structure of force arch and (c) evolution of force arch destroyed and rearranged during powder spreading
图 16 铺粉过程中不同搭接率下选定区域沿铺粉方向的颗粒速度
Figure 16. The particle velocity of the selected area along the spreading direction under different hatch overlaps during the powder spreading process
17 成形区的边界处, (a)强力链导致的空洞, (b)未出现空洞, (c)-(d)分别为(e)-(f)的剖面图, (e)-(f)为俯视角度下的粉末层形貌图
17. The boundary of the formed region. (a) Cavities caused by the strong force chains, (b) cavity-free, (c)-(d) are the cross-sections of (e)-(f), respectively. (e)-(f) are the top view of the powder layer morphology
图 17 成形区的边界处, (a)强力链导致的空洞, (b)未出现空洞, (c)-(d)分别为(e)-(f)的剖面图, (e)-(f)为俯视角度下的粉末层形貌图(续)
Figure 17. The boundary of the formed region. (a) Cavities caused by the strong force chains, (b) cavity-free, (c)-(d) are the cross-sections of (e)-(f), respectively. (e)-(f) are the top view of the powder layer morphology (continued)
图 18 粉末迸溅: (a)-(b)分别为颗粒与光滑、粗糙的表面碰撞; (c)-(d)分别为颗粒在碰撞之前, 以及碰撞之后颗粒反弹的运动轨迹
Figure 18. Powder splash: (a)-(b) collision of particles with smooth and rough surfaces, respectively; (c)-(d) trajectories of particles before and after the collision with the rough surface, respectively
表 1 铺粉模型参数
Table 1. Powder spreading parameters
Parameter Symbol Value length of build platform L/mm 3 width of build platform W/mm 1 roller diameter Dr/mm 5 spreading velocity V/(mm·s−1) 50 angular velocity ω/(rad·s−1) 2π gap height H/μm 40 ~ 70 track height h/μm 40 powder density ρ316L/(kg·m−3) 7.8 × 103 Young's modulus E/MPa 2.2 × 103 Poisson’s ratio ξ 0.3 restitution coefficient e 0.9 static friction coefficient μs 0.6 rolling friction coefficient μr 0.01 surface energy density γ/(mJ·m−2) 0.097[20] power diameter D/μm 10-40 
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[1] Schmeiser F, Krohmer E, Schell N, et al. Experimental observation of stress formation during selective laser melting using in situ X-ray diffraction. Additive Manufacturing, 2019, 32: 101028 [2] Guo M, Gu DD, Xi LX, et al. Selective laser melting additive manufacturing of pure tungsten: Role of volumetric energy density on densification, microstructure and mechanical properties. International Journal of Refractory, Metals & Hard Materials, 2019, 57: 133-164 [3] Larimian T, Kannan M, Grzesiak D, et al. Effect of energy density and scanning strategy on densification, microstructure and mechanical properties of 316 L stainless steel processed via selective laser melting. Materials Science and Engineering, 2020, 770: 138455.1-138455.13 [4] Rashid R, Masood SH, Ruan D, et al. Effect of scan strategy on density and metallurgical properties of 17-4 PH parts printed by selective laser melting (SLM). Journal of Materials Processing Technology, 2017, 249: 502-511 doi: 10.1016/j.jmatprotec.2017.06.023 [5] Olakanmi EO. Selective laser sintering/melting (SLS/SLM) of pure Al, Al-Mg, and Al-Si powders: Effect of processing conditions and powder properties. Journal of Materials Processing Technology, 2013, 213(8): 1387-1405 doi: 10.1016/j.jmatprotec.2013.03.009 [6] Boley C, Khairallah SA, Rubenchik AM. Calculation of laser absorption by metal powders in additive manufacturing. Applied Optics, 2015, 54(9): 2477-2482 doi: 10.1364/AO.54.002477 [7] Tran HC, Lo YL, Huang MH, et al. Analysis of scattering and absorption characteristics of metal powder layer for selective laser sintering. IEEE/ASME Trans-actions on Mechatronics, 2017, 22(4): 1807-1817 doi: 10.1109/TMECH.2017.2705090 [8] Haeri S. Optimisation of blade type spreaders for powder bed preparation in additive manufacturing using DEM simulations. Powder Technology, 2017, 321: 94-104 doi: 10.1016/j.powtec.2017.08.011 [9] Yao DZ, An XZ, Fu HT, et al. Dynamic investigation on the powder spreading during selective laser melting additive manufacturing. Additive Manufacturing, 2021, 37: 101707 [10] Chen H, Chen YX, Liu Y, et al. Packing quality of powder layer during counter-rolling-type powder spreading process in additive manufacturing. International Journal of Machine Tools & Manufacture, 2020, 153: 103553 [11] Xiang ZW, Yin M, Deng ZB, et al. Simulation of forming process of powder bed for additive manufacturing. Journal of Manufacturing Science & Engineering, 2016, 138(8): 081002 [12] Haeri S, Wang Y, Ghita O, et al. Discrete element simulation and experimental study of powder spreading process in additive manufacturing. Powder Technology, 2017, 306: 45-54 doi: 10.1016/j.powtec.2016.11.002 [13] Bai Y, Wagner G, Williams CB. Effect of particle size distribution on powder packing and sintering in binder jetting additive manufacturing of metals. Journal of Manufacturing Science and Engineering, 2017, 139(8): 081019 doi: 10.1115/1.4036640 [14] Parteli EJR, Poschel T. Particle-based simulation of powder application in additive manufacturing. Powder Technology, 2016, 288: 96-102 doi: 10.1016/j.powtec.2015.10.035 [15] Mussatto A, Groarke R, O'neill A, et al. Influences of powder morphology and spreading parameters on the powder bed topography uniformity in powder bed fusion metal additive manufacturing. Additive Manufacturing, 2021, 38: 101807 doi: 10.1016/j.addma.2020.101807 [16] Ma YF, Evan TM, Philips N, et al. Numerical simulation of the effect of fine fraction on the flowability of powders in additive manufacturing. Powder Technology, 2020, 360: 608-621 doi: 10.1016/j.powtec.2019.10.041 [17] Marchais K, Girardot J, Metton C, et al. A 3D DEM simulation to study the influence of material and process parameters on spreading of metallic powder in additive manufacturing. Computational Particle Mechanics, 2021, 8: 943-953 doi: 10.1007/s40571-020-00380-z [18] He Y, Hassanpour A, Bayly AE. Linking particle properties to layer characteristics: Discrete element modelling of cohesive fine powder spreading in additive manufacturing. Additive Manufacturing, 2020, 36: 101685 doi: 10.1016/j.addma.2020.101685 [19] Meier C, Weissbach R, Weinberg J, et al. Criti-cal influences of particle size and adhesion on the powder layer uniformity in metal additive manufacturing. Journal of Materials Processing Technology, 2019, 266: 484-501 doi: 10.1016/j.jmatprotec.2018.10.037 [20] Chen H, Wei QS, Zhang YJ, et al. Powder-spreading mechanisms in powder-bed-based additive manufacturing: Experiments and computational modeling. Acta Materialia, 2019, 179: 158-171 doi: 10.1016/j.actamat.2019.08.030 [21] Nan WG, Pasha M, Bonakdar T, et al. Jamming during particle spreading in additive manufacturing. Powder Technology, 2018, 338: 253-262 doi: 10.1016/j.powtec.2018.07.030 [22] Wang D, Liu Y, Yang YQ, et al. Theoretical and experimental study on surface roughness of 316 L stain-less steel metal parts obtained through selective laser melting. Rapid Prototyping Journal, 2016, 22(4): 706-716 doi: 10.1108/RPJ-06-2015-0078 [23] 冯一琦, 谢国印, 张璧等. 激光功率与底面状态对选区激光熔化球化的影响. 航空学报, 2019, 40(12): 423089-243 (Feng Yiqi, Xie Guoyin, Zhang Bi, et al. Influence of laser power and surface condition on balling behavior in selective laser melting. Acta Aeronautica et Astronautica Sinica, 2019, 40(12): 423089-243 (in Chinese) [24] Xiang ZW, Zhang MD, Yan R, et al. Powder-spreading dynamics and packing quality improvement for laser powder bed fusion additive manufacturing. Powder Technology, 2021, 389: 278-291 doi: 10.1016/j.powtec.2021.05.036 [25] Hanley KJ, O'sullivan C. Analytical study of the accuracy of discrete element simulations. International Journal for Numerical Methods in Engineering, 2017, 109(1): 29-51 doi: 10.1002/nme.5275 [26] Mahyar KA, Ian G, Reza GA. Rheological characterization of process parameters influence on surface quality of Ti-6 Al-4 V parts manufactured by selective laser melting. International Journal of Advanced Manufacturing Technology, 2018, 97: 1-15 doi: 10.1007/s00170-018-1803-6 [27] 梁平华, 唐倩, 冯琪翔等. 激光选区熔化单道扫描与搭接数值模拟及试验. 机械工程学报, 2020, 56(22): 56-67 (Liang Pinghua, Tang Qian, Feng Qixiang, et. al Numerical Simulation and Experiment of Single Track Scanning and Lapping in Selective Laser Melting. Journal of Mechanical Engineering, 2020, 56(22): 56-67 (in Chinese) [28] Bertoli US, Wolfer AJ, Matthews MJ, et al. On the limitations of volumetric energy density as a design parameter for selective laser melting. Materials & Design, 2017, 113: 331-340 [29] Yadroitsev I, Gusarov A, Yadroitsava I, et al. Single track formation in selective laser melting of metal powders. Journal of Materials Processing Technology, 2010, 210(12): 1624-1631 doi: 10.1016/j.jmatprotec.2010.05.010 [30] Chen X, Mu W, Xu X, et al. Numerical analysis of double track formation for selective laser melting of 316 L stainless steel. Applied Physics A, 2021, 127(8): 1-13 [31] Li C, White R, Fang XY, et al. Microstructure evolution characteristics of inconel 625 alloy from selective laser melting to heat treatment. Materials Science and Engineering A, 2017, 705: 20-31 doi: 10.1016/j.msea.2017.08.058 [32] Yang RY, Zou RP, Yu AB. Computer simulation of the packing of fine particles. Physical Review E, 2000, 62(3): 3900-3908 doi: 10.1103/PhysRevE.62.3900 [33] Zhou YC, Xu BH, Yu AB, et al. An experimental and numerical study of the angle of repose of coarse spheres. Powder Technology, 2002, 125: 45-54 doi: 10.1016/S0032-5910(01)00520-4 [34] Kruggel-Emden H, Wirtz S, Scherer V. A study on tangential force laws applicable to the discrete element method (DEM) for materials with viscoelastic or plastic behavior. Chemical Engineering Science, 2008, 63(6): 1523-1541 doi: 10.1016/j.ces.2007.11.025 [35] Johnson KL, Sridhar I. Adhesion between a spherical indenter and an elastic solid with a compliant elastic coating. Journal of Physics D: Applied Physics, 2001, 34(5): 683 doi: 10.1088/0022-3727/34/5/304 [36] 张江涛, 谭援强, 纪财源等. 增材制造中滚筒铺粉工艺参数对尼龙粉体铺展性的影响研究. 力学学报, 2021, 53(9): 2416-2426 (Zhang Jiangtao, Tan Yuanqiang, Ji Caiyuan, et al. Research on the effects of roller-spreading parameters for nylon powder spreadability in additive manufacturing. Chinese Journal of Theoretical and Applied Mechanics, 2021, 53(9): 2416-2426 (in Chinese) doi: 10.6052/0459-1879-21-240 -
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