混凝土冲击劈拉实验与细观离散元数值仿真

Impact splitting tensile experiments of concrete and numerical modeling by meso-scale discrete elements

本文进行了混凝土霍普金森压杆冲击劈拉实验,实验结果反映了混凝土动态抗拉强度的应变率效应,实验观察到高应变率下混凝土的动态劈拉破坏模式。采用本文作者提出的基于背景网格的混凝土细观力学预处理方法,建立了混凝土颗粒离散元细观力学模型,对实验进行了细观数值仿真模拟;无论是在动强度提高规律还是动态破坏模式方面,细观数值仿真与实验结果均符合得较好,验证了该模型研究高应变率条件下混凝土材料动态力学性能的合理性与有效性;通过对不同应变率条件下数值仿真模型能量消耗的分析,说明在高应变率条件下,更加分散的裂纹形态与能量需求的增加是导致混凝土动强度提高的主要机理,加深了对混凝土材料动力特性的认识。

In this work, an impact splitting tensile experiment of concrete using Hopkinson pressure bar was performed. Strain-rate effects of concrete were reflected by the observed dynamic fracture patterns, and strength enhancement was observed in the experiment. A meso-scale discrete element model （DEM） of concrete was developed by pre-processing approach based on a background-grid search method. Using this model, numerical simulations of the test conditions in meso-scale were conducted. The simulated dynamic strength and fracture patterns agree well with the measurements, and hence the model is validated experimentally. The simulations show that higher strain rates cause more disperse patterns of fracture and more energy demand by structure failure, and this could be a major mechanism for the strain-rate effects. Thus, the numerical and experimental results in this study would shed light on understanding of the dynamic failure behavior of concrete.