一种基于离散元的模拟颗粒破碎方法

An approach for modelling particle breakage based on discrete element method

为模拟颗粒破碎对散体材料应力–应变特性产生的显著影响,提出了一种改进的基于离散元的模拟颗粒破碎的方法。首先将颗粒复杂的受力状态简化成颗粒球心附近的最大拉应力并假定颗粒破碎服从最大拉应力准则。当颗粒满足破碎条件时,将破碎颗粒的直径缩小。当由缩小颗粒直径导致的质量损失达到某一规定值时,向样本内的孔隙插入新颗粒。为模拟破碎产生碎片的颗粒级配,新生成的颗粒尺寸服从分形分布,同时,为考虑颗粒强度的变异性和尺寸效应,未破碎颗粒、已破碎颗粒和破碎产生的碎片的抗拉强度均服从Weibull分布。该方法满足质量守恒条件,且适用于能在超级计算机上并行运行的开源离散元软件。采用本文方法模拟了一维压缩和直剪试验并与室内试验结果进行对比,结果表明本文方法模拟颗粒破碎是可行的。

The particle breakage has a significant effect on the stress-strain behavior of granular materials. An improved approach for modelling the particle breakage is proposed based on the discrete element method（DEM）. This approach first simplifies the complicated stress condition into the maximum tensile one. A particle is allowed to break if the maximum tensile stress acting on it exceeds its tensile strength. The radius of the fractured particle is reduced. When the accumulated loss in mass reaches the critical value, new particles are inserted into the sample. The newly generated particles satisfy a fractal condition. In order to take the variability and size effect in particle strength into consideration, the tensile strengths of the uncrushed particles, the crushed particles and the newly generated particles all satisfy the Weibull distribution. This approach also obeys the mass conservation and can be implemented into the classical open-source package, which allows parallel computation in a multi-processor system. The validity of this approach is demonstrated by comparing the DEM simulation results of one-dimensional compression and direct shear tests with the data from the laboratory tests.