The influence of the particle size distribution on the strength of the coated Al2O3 parts was studied, through the size and distribution of the sintered neck. The powder was heated in situ by a UV laser, and the relationship between the sintered neck waist diameter and the particle diameter was obtained under an image measuring apparatus. A particle packing model was established, and the distribution of the sintered neck was corresponding to the particle coordination point, then the projected area ratio of the sintered neck that was broken in a certain section was calculated. As for the coated Al2O3 powder with the resin content of 2%(mass fraction), the results indicate that the sintered neck waist diameter increases from 40μm to 100μm as the particle diameter increases from 75μm to 375μm. The packing simulation results show that the projected area ratio decreases from 0.2557 to 0.0823, as the particle diameter increases from 75-107μm to 300-375μm, which is consistent with the experimentally measured tensile strength of the coated Al2O3 powder. The 70/100, 100/140 mesh powder are mixed to simulate based on the mass ratios of 0:10, 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, 9:1, 10:0. The projected area ratio decreases from 0.1772 to 0.1264 and the porosity increases from 0.4511 to 0.4633. Considering the tensile strength and gas permeability, the optimization result is that the ratio is 7:3, the projected area ratio is 0.1481 and the porosity is 0.4596.
GUSTAFSON R , SPADA A T . Prototyping process produces sand molds, cores for production castings[J]. Journal of Applied Probability, 2002, 92 (2): 38- 39.
2
CHHABRA M , SINGH R . Rapid casting solutions:a review[J]. Rapid Prototyping Journal, 2011, 17 (5): 328- 350.
doi: 10.1108/13552541111156469
ZHANG X J , TANG S Y , ZHAO H Y , et al. Research status and key technologies of 3D printing[J]. Journal of Materials Engineering, 2016, 44 (2): 122- 128.
4
PHAM D T , DIMOV S , LACAN F . Selective laser sintering:applications and technological capabilities[J]. Proceedings of the Institution of Mechanical Engineers Part B Journal of Engineering Manufacture, 1999, 213 (5): 435- 449.
doi: 10.1243/0954405991516912
JI H C , ZHANG X J , PEI W C , et al. Research progress in ceramic 3D printing technology and material development[J]. Journal of Materials Engineering, 2018, 46 (7): 19- 28.
CHEN J Y , WU J M , CHEN A N , et al. Preparation and prop-erties of porous coal-series kaolin ceramics by selective laser sint-ering[J]. Journal of Materials Engineering, 2018, 46 (7): 36- 43.
7
WEN S F , SHEN Q W , WEI Q S , et al. Material optimization and post-processing of sand molds manufactured by the selective laser sintering of binder-coated Al2O3 sands[J]. Journal of Materials Processing Technology, 2015, 225, 93- 102.
doi: 10.1016/j.jmatprotec.2015.05.028
8
XU Z F , LIANG P , YANG W , et al. Effects of laser energy density on forming accuracy and tensile strength of selective laser sintering resin coated sands[J]. China Foundry, 2014, 11 (3): 151- 156.
9
CASALINO G , FILIPPIS L A C D , LUDOVICO A . A technical note on the mechanical and physical characterization of selective laser sintered sand for rapid casting[J]. Journal of Materials Processing Technology, 2005, 166 (1): 1- 8.
10
VISSCHER W M , BOLSTERLI M . Random packing of equal and unequal spheres in two and three dimensions[J]. Nature, 1973, 239 (5374): 504- 507.
11
JODREY W S , TORY E M . Simulation of random packing of spheres[J]. Simulation Transactions of the Society for Modeling & Simulation International, 1979, 32 (1): 1- 12.
12
ZHOU J H , ZHANG Y W , CHEN J K . Numerical simulation of random packing of spherical particles for powder-based additive manufacturing[J]. Journal of Manufacturing Science & Engineering, 2009, 131 (3): 031004.
13
SHI Y , ZHANG Y W . Simulation of random packing of spherical particles with different size distributions[J]. Applied Physics A, 2008, 92 (3): 621- 626.
doi: 10.1007/s00339-008-4547-6
14
DOU X , MAO Y J , ZHANG Y W . Effects of contact force model and size distribution on microsized granular packing[J]. Journal of Manufacturing Science & Engineering, 2014, 136 (2): 021003.
15
ZHOU J H , ZHANG Y W , CHEN J K . Numerical simulation of laser irradiation to a randomly packed bimodal powder bed[J]. International Journal of Heat and Mass Transfer, 2009, 52 (13/14): 3137- 3146.
16
CHENG Y F , GUO S J , LAI H Y . Dynamic simulation of random packing of spherical particles[J]. Powder Technology, 2000, 107 (1/2): 123- 130.
17
JIA T , ZHANG Y , CHEN J K , et al. Dynamic simulation of granular packing of fine cohesive particles with different size distributions[J]. Powder Technology, 2012, 218 (1): 76- 85.
18
HITTI K , BERNACKI M . Optimized dropping and rolling (ODR) method for packing of poly-disperse spheres[J]. Applied Mathematical Modelling, 2013, 37 (8): 5715- 5722.
doi: 10.1016/j.apm.2012.11.018
19
BERTEI A , CHUEH C C , PHAROAH J G , et al. Modified collective rearrangement sphere-assembly algorithm for random packings of nonspherical particles:towards engineering applic-ations[J]. Powder Technology, 2014, 253, 311- 324.
doi: 10.1016/j.powtec.2013.11.034
20
PARTELI E J R , POSCHEL T . Particle-based simulation of powder application in additive manufacturing[J]. Powder Technology, 2016, 288, 96- 102.
doi: 10.1016/j.powtec.2015.10.035
21
TOPIC N , POSCHEL T . Steepest descent ballistic deposition of complex shaped particles[J]. Journal of Computational Physics, 2016, 308, 421- 437.
doi: 10.1016/j.jcp.2015.12.052