多孔陶瓷材料力学特性的离散单元法定量模拟

Quantitative simulation of mechanical properties of porous ceramic materials by discrete element method

本文基于离散单元法,模拟研究了多孔陶瓷在拟静态加载条件下的力学响应特性.在数值试样制备上,采用各向同性压缩的方式获取不同固含率的数值试样,然后基于Coble烧结模型计算微观颗粒之间的接触尺寸.为考虑多体作用下固体键之间的空间耦合效应,对经典的Hertz接触模型进行了修正,引入了一反映晶粒间接触尺寸和晶粒间空间几何排列特性影响的校正因子.随后以部分烧结三氧化二铝陶瓷材料为研究对象,检验了所建立的离散单元法数值模拟方法的定量预测能力.模拟结果表明,所预测的有效杨氏模量和断裂强度与文献报道的实验数据能很好地定量吻合;对于含大孔洞的部分烧结三氧化二铝陶瓷材料的模拟结果表明,无论是孔洞之间的相互作用特性,还是孔洞排列型式对材料有效杨氏模量和断裂特性的影响,模拟结果都能与文献报道的理论分析结果和有限元分析结果定量吻合.这些定量对比结果表明,本文建立的离散单元法数值模拟方法,可以用来定量地预测多孔陶瓷的力学特性.

In this work, the mechanical response of porous ceramic was investigated by performing discrete element method (DEM) simulations. Isotropic packing strategy was adopted to prepare numerical samples with different densities. For each numerical sample, the contact size between particles was calculated using Coble's sintering model. To account for the spatial coupling effect between solid bonds under multi-contact condition, the classic Hertz contact model was modified by introducing a correct factor which reflects the influences of contact size in-between grains and the geometrical arrangement of grains. The quantitative predicting ability of the built DEM framework was then evaluated by using the partially sintered alumina ceramic as investigated system. It was demonstrated that the predicted effective Young's modulus and fracture strength are both in quantitative agreement with experimental data. As to partially sintered alumina ceramic containing large pores, both the interaction behavior between pores and the in fluence of the geometrical arrangements of pores on effective Young's modulus and fracture strength predicted by the theoretical analyses or finite element method were successfully captured by our DEM simulations. All these quantitative comparisons demonstrate that the built DEM framework can be used to quantitatively model the mechanical properties of porous ceramics.