论文部分内容阅读
对5种不同几何尺寸与不同配合比的混凝土试件进行了不同加载速率下的单轴压缩试验,同步进行了声发射(AE)数据的采集;在对比分析AE参数与应力应变关系的基础上,进行了不同加载速率下的混凝土损伤机理与破坏机制研究;通过分析不同加载速率下的应力应变全曲线,研究了循环加卸载中的损伤破坏特性的速率效应;构建了基于AE参数的损伤变量模型,并基于该模型进行了动态损伤特性分析.结果表明:混凝土的峰值应力与弹性模量随加载速率的提高而增大,表现出明显的规律性;但峰值应变随加载速率的变化而表现出较大的离散性.峰值应力前的AE能量随加载速率的提高而增加;加载速率越大,上升幅度越大,峰前释放的能量越大,混凝土内部破坏越严重,残余能量不足以维持试件继续承受更多的循环加卸载而直接进入破坏阶段;峰后可完成的循环加卸载次数随着加载速率的提高而减少.在不同加载速率下材料损伤破坏的路径不同,但损伤起点与破坏终点是重合的;随加载速度提高,损伤破坏的路径变短,加载速率差异越大,损伤破坏路径差异越大;混凝土在不同应力阶段的损伤程度及破坏形态与加载速率有较强的相关性.加载速率的提高改变了混凝土的能量释放过程与方式,形成了不同的损伤破坏机制,在不同加载速率下的损伤破坏机理存在较大差异.
Uniaxial compression tests were carried out on five kinds of concrete specimens with different geometrical sizes and different mixing ratios under different loading rates. Acoustic emission (AE) data were collected simultaneously. On the basis of comparative analysis of the relationship between AE parameters and stress-strain , The damage mechanism and failure mechanism of concrete under different loading rates were studied. By analyzing the full curves of stress and strain under different loading rates, the rate effects of damage and damage characteristics during cyclic loading and unloading were studied. The damage variables based on AE parameters Model was established and the dynamic damage characteristics were analyzed based on the model.The results show that the peak stress and elastic modulus of concrete increase with the increase of loading rate and show obvious regularity, but the peak strain changes with the loading rate The AE energy before peak stress increases with the increase of loading rate.The larger the loading rate is, the larger the increasing amplitude is, the greater the energy released in front of the peak is, the more severe the damage is in the concrete, and the residual energy is not enough to maintain The specimen continues to undergo more cycles of loading and unloading and directly into the destruction stage; the number of cycles that can be accomplished after the peak is loaded and unloaded varies with loading The damage path is different under different loading rates, but the starting point of damage is coincident with the ending point of damage. With the increase of loading speed, the path of damage destruction becomes shorter, the greater the difference of loading rate and the difference of damage path The higher the damage degree and the damage morphology of the concrete at different stress stages have a strong correlation with the loading rate.Improvement of the loading rate changes the energy release process and the way of the concrete and forms different damage damage mechanisms.At different loading rates Under the damage damage mechanism there is a big difference.