试件初始缝长对混凝土双K断裂参数的影响

Influence of specimen initial crack length on double K fracture parameter of concrete

本文采用尺寸为 40 0mm× 40 0mm× 2 0 0mm ,初始缝高比分别为 0 2、 0 4、 0 5、 0 6的楔入劈拉试件 ,应用线性渐近叠加原理 ,利用试验中测得的最大荷载Pmax及对应的裂缝口张开位移CMODc 计算了混凝土裂缝的亚临界扩展量Δac,在此基础上利用虚拟裂缝模型并结合线弹性断裂理论 ,采用不同的闭合力方程计算了混凝土起裂断裂韧度KiniIc、失稳断裂韧度KunIc及临界裂缝尖端张开位移CTODc.结果表明 ,采用不同闭合力方程所计算的混凝土KiniIc值有所差异 ,但当试件缝高比大于或等于 0 4时KiniIc及CTODc 均与试件初始缝高比无关 ,而KunIc值则与初始缝高比无关 ,这表明双K断裂参数及CTODc 可以作为描述混凝土裂缝起裂、稳定扩展及失稳破坏全过程的材料常数 .

The experimental result of wedge splitting test is presented in this paper. The sub critical crack propagation length  Δ a c is calculated according to the maximum load P max  and corresponding crack mouth opening displacement CMOD c on the basis of linear asymptotic theory. Furthermore, the initial fracture toughness K ini I c , unstable fracture toughness K un I c  and critical crack tip opening displacement CTOD c are obtained by using the fictitious crack model combining with linear elastic fracture theory. The result shows that the unstable fracture toughness K un I c , initial fracture toughness K ini I c  and CTOD c are independent of a 0/h when a 0/h of the specimen is ≥0 4. While the K ini I c  calculated from different cohesive stress equation will not be constant.