ECC轴拉循环加载变形与疲劳寿命

Uniaxial cyclic loading deformation and fatigue life of ECC

高延性水泥基复合材料(ECC)多用于结构的抗震补强,其疲劳性能是工程中关注的重点。为研究其疲劳性能,通过疲劳试验机进行单轴拉伸循环加载试验,利用数字图像相关(DIC)技术实时监测位移发展与开裂行为。分析ECC试件的动力变形、疲劳规律并建立疲劳方程。结果表明:ECC试件的应变和轴向位移发展规律相似,分为初始阶段、稳定发展阶段、加速变形阶段和破坏阶段;动应力比越小,应变发展越快,破坏发生时的累积轴向应变越大;刚度比发展曲线分为三部分:快速下降阶段、稳定下降阶段和破坏阶段;其疲劳寿命可较好服从双参数Weibull分布;通过建立两种形式的疲劳方程:S-lgN和S-lgN-F疲劳方程,将极限疲劳寿命带入平均寿命疲劳方程,针对本文配合比得到疲劳极限应力水平为70.80%,对应的疲劳极限强度为2.69 MPa。

Engineered cementitious composites(ECC)are mostly used for seismic reinforcement of structures,and their fatigue performance is a major concern in engineering.In order to study the fatigue performance of ECC,the uniaxial tensile cyclic loading test was performed by fatigue testing machine,and the displacement development and cracking behavior in real time were monitored by using digital image correlation(DIC)technology to analyze the dynamic deformation and fatigue law of ECC specimens and establish the fatigue equation.The results show that the strain and axial displacement of ECC specimens develop similarly,which are divided into the initial stage,stable development stage,accelerated deformation stage and damage stage.The smaller the dynamic stress ratio,the faster the strain development and the larger the accumulated axial strain when damage occurs.The stiffness ratio development curve is divided into three parts:Rapid decline stage,stable decline stage and damage stage.The fatigue life of the ECC specimen obeys the two-parameter Weibull distribution well.By establishing two forms of fatigue equations:S-lgN and S-lgN-F fatigue equations,the ultimate fatigue life is brought into the average life fatigue equation,and the fatigue ultimate stress level is 70.80%.The corresponding fatigue ultimate strength is 2.69 MPa.