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为研究混凝土动态劈拉特性,进行了不同应变速率下的混凝土动态劈拉试验,建立劈拉应力水平与声发射能量数的数学关系式,明确了混凝土劈拉损伤演化方程,提出了损伤界点的概念。基于医学ROC曲线确定最佳临界点理论,分析出了混凝土劈拉破坏损伤界点所对应的应力水平。研究结果表明:高应变速率下,损伤第1阶段声发射信号开始产生时的应力滞后,当应力水平超过一定数值后,损伤第2段的声发射现象与低应变速率时的相似;损伤界点随着应变速率的提高向应力水平较高处推移,其变化范围为[0.71,0.77],且推移的规律服从线性分布,应力空间下混凝土劈拉损伤界点为0.75。
In order to study the dynamic splitting properties of concrete, the dynamic splitting tests of concrete under different strain rates were carried out. The mathematical relationship between the splitting tensile stress and the acoustic emission energy was established. The evolution equation of concrete splitting and pulling damage was clarified. the concept of. Based on the medical ROC curve to determine the optimal critical point theory, the stress level corresponding to splitting and breaking damage of concrete joints was analyzed. The results show that the acoustic lag at the second stage of damage is similar to that at low strain rate when the stress level exceeds a certain value under the high strain rate. With the increase of strain rate, the stress level is higher, and the range of variation is [0.71,0.77]. The law of displacement obeys the linear distribution, and the splitting tensile point of concrete under stress space is 0.75.