应力空间下混凝土动态劈拉损伤演化方程及损伤界点的确定

Determination of Critical Damage Point and Evolution Equation of Concrete's Dynamic Splitting Damage under Stress Space

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 explore the features of concrete dynamic splitting,we carried out splitting test under different strain rates and established the relationship between stress level and AE（ acoustic emission） energy number. Then,we put forward the concept of critical damage point and determined the evolution equation of dynamic splitting damage of concrete. On the basis of determining optimal critical point by using medical ROC（ receiver-operating characteristic） curve,we gave the stress level of concrete at critical damage point in splitting test. Results showed that 1）under high strain rate,stress lags when emission signal occurs at the first stage of damage; 2） AE phenomena at the second stage were similar to those with low strain rate after stress level exceeded a given value; 3） with the increase of strain rate,the stress level at critical damage point increased,and its range was [0.71,0.77]; 4） there is a linear relationship between stress level at critical damage point and logarithmic function of strain rate,and the strain rate of concrete at critical damage point in splitting test under stress space was 0.75.