混凝土破坏过程的复合型界面损伤模型与数值模拟

在细观层次上将混凝土视为由骨料、水泥砂浆及其之间的界面过渡区组成的三相复合材料,以规则化有限元网格映射到混凝土随机骨料结构上,根据单元的位置确定单元的材料特性,把不在单一材料区域、包含界面过渡区的单元视为一种广义复合材料单元,建立复合型界面损伤模型。该模型将修正的Vogit-Reuss模型运用到复合材料单元,形成等效均质单元;复合材料单元的损伤通过其各组成材料的损伤体现,采用拉断的Mohr-Coulomb准则作为材料损伤的判据。应用复合型界面损伤模型,结合统计方法考虑材料细观非均匀性,模拟混凝土试件在单轴拉伸和单轴压缩载荷(端面为理想无摩擦情况)作用下的断裂过程。研究结果表明:该模型可以较好地反映混凝土材料的宏观力学行为,可以有效地模拟混凝土材料的断裂过程。

Composite interface damage model in concrete fracture process and associated numerical simulation

At mesoscopic scale,the concrete was regarded as a three-phase composite consisting of coarse aggregate,mortar matrix and interfacial transition zones.Regular mesh of finite element was projected on a generated random aggregate structure of concrete and different material properties were assigned to the respective elements according to element location in three phases.A composite interface damage model was established for the element including the interfacial transition zone but not located in the same material phase,which was considered as a composite element in a broader sense.Using the modified Voigt-Reuss averaging scheme,the influence of the interfacial transition zone was smeared into the composite element.The elastic constants of the composite element were defined in terms of the constitutive properties of both the adjacent materials and the interfacial transition zone as well as the geometry of the homogenized element.The Mohr-coulomb criterion with tension cutoff was utilized as damage threshold for all elements,especially for each material of the composite element.The proposed model were implemented in a FE code combined with statistical mechanics to take the heterogeneities on mesoscopic scale into consideration.Tensile and compressive uniaxial tests were simulated.The results obtained reproduce the main features of concrete behavior.