HS-SHCC弯曲疲劳变形与疲劳寿命

Flexural Fatigue Deformation and Fatigue Life of HS-SHCC

摘要:

对抗压强度为83.41 MPa的高强应变硬化水泥基复合材料（HS-SHCC）试件进行了四点弯曲疲劳试验，研究了HS-SHCC试件在不同应力水平（0.70、0.80、0.85、0.90）下的裂缝扩展、跨中挠度及疲劳寿命.结果表明：HS-SHCC试件的疲劳寿命随着应力水平的提高而不断减小；HS-SHCC试件在弯曲疲劳荷载下呈现出多裂缝开裂的特征，随着应力水平的降低，试件表面的裂缝数量减少；当应力水平为0.70~0.85时，HS-SHCC试件的跨中挠度呈现出明显的快速发展、稳定发展、失稳三阶段，而当应力水平为0.90时，HS-SHCC试件的跨中挠度则表现出稳定发展和失稳两阶段特性；与普通SHCC相同，HS-SHCC试件的应力水平-疲劳寿命（λ-Nf）曲线呈现出双线性趋势.基于λ-Nf曲线和三参数Weibull分布理论，提出各失效概率下HS-SHCC的弯曲疲劳寿命预测模型，得出失效概率为0.05时HS-SHCC的疲劳强度极限（疲劳循环200万次）对应的最大应力水平为0.618.

Abstract:

Four-point bending fatigue tests were carried out on high strength strain hardening cementitious composite（HS-SHCC） specimens with compressive strength of 83.41 MPa. The crack propagation， mid-span deflection and fatigue life of HS-SHCC specimens at different stress levels （0.70、0.80、0.85、0.90） were studied. The results show that the fatigue life of HS-SHCC specimens decreases with the increase of stress level. The HS-SHCC specimens show multi-cracking characteristic under flexural fatigue loads. As the stress level decreases， the crack numbers on the surface of the specimens show a decreased trend. At the stress level 0.70-0.85， the mid-span deflection of HS-SHCC displays obvious three stages of rapid development， stable development and instability. At the stress level 0.90， the mid-span deflection of HS-SHCC specimens shows two stages of stable development and instability. Similar to ordinary SHCC， the stress level-fatigue life curves （λ-Nf curve） of HS-SHCC specimens show a bilinear trend. Based on the obtained λ-Nf curve and the three-parameter Weibull distribution theory， a flexural fatigue life prediction model of HS-SHCC under different failure probabilities is proposed. On this basis， the maximum stress level corresponding to the fatigue strength limit （corresponding to 2 million fatigue cycles） of HS-SHCC is predicted to be 0.618 when the failure probability is 0.05.