A user-defined micromechanical model was developed to investigate the fracture mechanism of asphalt concrete （AC） using the discrete element method （DEM）. A three-dimensional （3D） AC beam was built using the ＂F...A user-defined micromechanical model was developed to investigate the fracture mechanism of asphalt concrete （AC） using the discrete element method （DEM）. A three-dimensional （3D） AC beam was built using the ＂Fish＂ language provided by PFC3D and was employed to simulate the three-point bending beam test at two temperature levels： -10 ℃ and 15℃. The AC beam was modeled with the consideration of the microstructural features of asphalt mixtures. Uniaxial complex modulus test and indirect tensile strength test were conducted to obtain material input parameters for numerical modeling. The 3D predictions were validated using laboratory experimental measurements of AC beams prepared by the same mixture design. Effects of mastic stiffness, cohesive and adhesive strength on AC fracture behavior were investigated using the DEM model. The results show that the 3D DEM fracture model can accurately predict the fracture patterns of asphalt concrete. The ratio of stress at interfaces to the stress in mastics increases as the mastic stiffness decreases; however, the increase in the cohesive strength or adhesive strength shows no significant influence on the tensile strength.展开更多
针对目前缺乏水稻钵苗多株根系交织于基质形成独立钵体复合体基础模型研究的问题,同时为后续开展水稻钵苗移栽机构栽植过程探究机械-钵体互作规律提供理论基础,本文依据水稻钵苗根系物理机械特性与生长规律,提出了一种基于Matlab根系数...针对目前缺乏水稻钵苗多株根系交织于基质形成独立钵体复合体基础模型研究的问题,同时为后续开展水稻钵苗移栽机构栽植过程探究机械-钵体互作规律提供理论基础,本文依据水稻钵苗根系物理机械特性与生长规律,提出了一种基于Matlab根系数值模拟生长的水稻钵苗钵体复合体离散元模型建立方法。通过破坏性检测对移栽期水稻钵苗根系的几何形态与根系拓扑关系及基质相关参数进行测量与分析,结合钵盘边界因素及根-根、根-钵盘间交互生长特性,建立水稻根系生长规律相关特性函数,并通过Matlab程序设计获取水稻钵苗根系生长拓扑轨迹。利用分割排序法求解完整粒子中心坐标,依托EDEM软件平台分别将所建立的水稻钵苗根-基质离散元几何模型与EdinBurgh Elasto-Plastic Adhesion with Bonding接触力学模型结合,实现水稻钵苗钵体复合体离散元模型的建立。开展水稻钵苗钵体压缩和剪切试验对比研究,结果表明,仿真结果与试验结果趋向保持一致,误差满足相关要求,验证了水稻钵苗钵体复合体离散元模型的可行性。展开更多
基金Project(51208178)supported by the National Natural Science Foundation of ChinaProject(2012M520991)supported by China Postdoctoral Science Foundation
文摘A user-defined micromechanical model was developed to investigate the fracture mechanism of asphalt concrete （AC） using the discrete element method （DEM）. A three-dimensional （3D） AC beam was built using the ＂Fish＂ language provided by PFC3D and was employed to simulate the three-point bending beam test at two temperature levels： -10 ℃ and 15℃. The AC beam was modeled with the consideration of the microstructural features of asphalt mixtures. Uniaxial complex modulus test and indirect tensile strength test were conducted to obtain material input parameters for numerical modeling. The 3D predictions were validated using laboratory experimental measurements of AC beams prepared by the same mixture design. Effects of mastic stiffness, cohesive and adhesive strength on AC fracture behavior were investigated using the DEM model. The results show that the 3D DEM fracture model can accurately predict the fracture patterns of asphalt concrete. The ratio of stress at interfaces to the stress in mastics increases as the mastic stiffness decreases; however, the increase in the cohesive strength or adhesive strength shows no significant influence on the tensile strength.
文摘针对目前缺乏水稻钵苗多株根系交织于基质形成独立钵体复合体基础模型研究的问题,同时为后续开展水稻钵苗移栽机构栽植过程探究机械-钵体互作规律提供理论基础,本文依据水稻钵苗根系物理机械特性与生长规律,提出了一种基于Matlab根系数值模拟生长的水稻钵苗钵体复合体离散元模型建立方法。通过破坏性检测对移栽期水稻钵苗根系的几何形态与根系拓扑关系及基质相关参数进行测量与分析,结合钵盘边界因素及根-根、根-钵盘间交互生长特性,建立水稻根系生长规律相关特性函数,并通过Matlab程序设计获取水稻钵苗根系生长拓扑轨迹。利用分割排序法求解完整粒子中心坐标,依托EDEM软件平台分别将所建立的水稻钵苗根-基质离散元几何模型与EdinBurgh Elasto-Plastic Adhesion with Bonding接触力学模型结合,实现水稻钵苗钵体复合体离散元模型的建立。开展水稻钵苗钵体压缩和剪切试验对比研究,结果表明,仿真结果与试验结果趋向保持一致,误差满足相关要求,验证了水稻钵苗钵体复合体离散元模型的可行性。
