关键词: 脆性颗粒材料, 动态多尺度模型, 颗粒破碎, 动态加载, 阻尼

Abstract: The multiscale model for brittle granular materials generally involves three scales: elementary particles at the microscale, grains at the mesoscale, and grain piles at the macroscale. The multiscale model was created based on the discrete element method (DEM). To apply it to dynamic loading, parameters for two contact models and two bonding models were firstly analyzed, and connections between the micro and meso model parameters and the macro material constants were also discussed. Then, the dynamic multiscale model for quartz sand was created with the Hertz-Mindlin contact model and the parallel-bond model. Through selecting appropriate strength and local damping parameters, it is observed that the dynamic compression properties of the simulated sand agree well with the experimental results on quartz sand at both the meso and macro scale. With the calibrated model, the influence of the local damping mechanism which is closely related to dynamic loading, on the dynamic responses of the multiscale model was investigated. Results show that a higher damping level results in a stronger wave-attenuation ability of brittle granular materials. However, excessively high damping will result in an aberrant loading-velocity effect at both the meso and macro scale (the latter is actually the micro inertial effect induced by high damping). In addition, high damping can attenuate the waves emitted during the particle breakage process and reduce the breakage extent. At last, the multi-scale model was slightly modified and used to study the dynamic particle breakage property of brittle granular materials. The modified model can yield grain-size-distribution curves consistent with the experimental ones. Moreover, it can reveal the heterogeneous distribution of particle breakage at the space scale, which refers to the clustering phenomenon of microcracks caused by the interactions between the wave-producing and wave-attenuation mechanism in the particle breakage process.

Key words: brittle granular material, dynamic multi-scale model, particle breakage, dynamic loading, local damping