利用连接尺度方法的颗粒材料破碎数值分析

基于已有的颗粒材料连接尺度方法(BSM)1-2],发展了在细尺度上采用离散颗粒集合体模型与离散单元法(DEM)并引入了颗粒破碎模型,而在粗尺度上采用Cosserat连续体模型与有限单元法(FEM)的BSM。仅在有限局部区域内采用DEM从细观层次关注颗粒材料破碎现象,而在全域采用储存空间和花费时间较少的FEM,同时在粗细两个尺度采用不同的时间步长。讨论了颗粒材料发生破碎时,颗粒材料结构的承载能力与微结构的演变。数值算例结果说明了所提出可模拟破碎的BSM的可用性和优越性,以及颗粒破碎对颗粒材料微观力学行为的影响。

Numerical analysis of fragmentation of granular materials using bridging scale method

Base on the existing bridging scale method(BSM) proposed for granular materials,a version of BSM,taking into account the fragmentation of grains,is developed.A numerical model of fragmentation of granular medium is introduced into the proposed BSM,in which the discrete particles assembly model using the discrete element method(DEM) and the Cosserat continuum model using the finite element method(FEM) are adopted in fine and coarse scales respectively.In the proposed BSM,the fine scale analysis using the DEM is limited to a localized computational domain for the simulation of mechanical behaviors in granular media at the meso-scale,including fragmentation of grains,along with frictional sliding and loss of contacts between each pair of immediate neighboring particles.Meanwhile,the FEM analysis that costs much less in both storage space and computational time than that of the DEM is applied to cover the whole computational domain.Furthermore,different time steps are allowed to the time integration schemes used for the fine and coarse scales respectively.As a consequence,both computational efficiency and accuracy of the present BSM is greatly enhanced.The numerical example is performed to demonstrate the applicability and advantages of the proposed BSM taking into account the fragmentation of grains,in addition,the effects of fragmentation of grains on the carrying capacity of geo-structure and the evolution of meso-structure.