动荷载下基体强度对双丝拉拔混凝土试件影响的数值模拟研究

Numerical simulation of influence of matrix strength on twin fiber pullout concrete specimen under dynamic load

考虑材料的细观非均匀性,基于细观损伤力学和动力有限元方法,以二维真实破坏过程分析软件动态版(realistic failure process analysis-Dynamic,RFPA^(2D)-Dynamic)作为数值计算分析工具,建立了界面控制下的混凝土双丝拉拔动态数值模型,探讨了基体强度对纤维拔出性能的影响,模拟分析了拉拔试件从微裂纹萌生、扩展直至裂纹贯通的动态破坏全过程,并进行了声发射数值试验分析。结果表明:基体强度对拉拔试件的破坏模式具有显著影响,当基体强度较小时,试件破坏形式为双丝以及双丝之间基体的共同拔出破坏,基体中的损伤单元较多,试件声发射数较多;当基体强度增大时,表现为双丝各自的拔出破坏,试件发生界面脱粘破坏,基体中的损伤单元较少,试件的声发射数也相应较少。试件是否含骨料会影响基体内部应力波的传播模式,相较于水泥砂浆基体双丝拉拔试件而言,含骨料试件的损伤有所改善,试件的声发射数较少。

Dynamic numerical models of twin fibers pullout concrete under interfacial control have been created based on mesolevel damage mechanics and dynamic finite element method, with consideration of mesolevel material heterogeneity. The influence of matrix strength on mechanical property of twin fibers pull-out concrete has been studied by taking a numerical analysis tool,realistic failure process analysis-Dynamic(RFPA^(2D)-Dynamic), as numerical calculation and analysis tool. The dynamic failure process from microcrack initiation to crack penetration has been simulated. Acoustic emission(AE) accompanied with the failure process has also been studied. Numerical results show that the matrix strength has a significant influence on failure pattern of the pullout specimens. When the strength of the matrix is small, the failure mode of the specimens is the joint pull out failure of the two wires and the matrix between the two wires, with more damage units in the matrix and more AE numbers of the specimens. However, when the matrix strength of the matrix increases, the twin fibers are pulled out one by one, debonding failure occurs in the interface zone of the specimens, with fewer damage units in the matrix, and the AE number of the specimen is correspondingly less. Whether the specimen contains aggregate or not also leads to the difference of stress wave propagation mode inside the matrix. Compared with the cement mortar matrix double-wire drawing specimen, the damage of the specimen containing aggregate is improved, and the AE number of the specimen is less.