The degree of water saturation has a significant influence on the tensile fatigue properties of Engineered Cementitious Composites (ECC). The half-saturated and saturated state ECC can be rapidly prepared by a vacuum saturation equipment. The fatigue tensile mechanical tests under five tensile stress levels and corresponding studies on the damage morphology, fatigue life, S-N relationship, fatigue strain and fatigue damage on dry, half-saturated, and saturarted state were conducted. The mathematical and statistical analysis method was also utilized to predict ECC’s fatigue life and strength with high confidence and high reliability, providing a reference for assessing structural safety. The study found that free water significantly reduces ECC fatigue strength, with fatigue life decreasing as water content increases. At 2 million cycles, fatigue strength reduction coefficients for 0%, 50%, and 100% water saturation are 0.623, 0.550, and 0.423, respectively. The three-parameter Weibull distribution best describes ECC fatigue life. Using this model, S-N and P-S-N curves were developed, incorporating confidence limits to derive γ-P-S-N relationships, ensuring high confidence and reliability.

中文翻译：

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水饱和度对ECC单轴等幅拉伸疲劳性能的影响及其疲劳寿命统计分析


水饱和度对工程水泥基复合材料 （ECC） 的拉伸疲劳性能有重大影响。半饱和和饱和态 ECC 可以通过真空饱和设备快速制备。开展了 5 个拉伸应力水平下的疲劳拉伸力学试验，并对干燥、半饱和和饱和状态下的损伤形态、疲劳寿命、S-N 关系、疲劳应变和疲劳损伤进行了相应的研究。采用数学和统计分析方法预测 ECC 的疲劳寿命和强度，具有高置信度和高可靠性，为评估结构安全性提供参考。研究发现，游离水会显著降低 ECC 疲劳强度，疲劳寿命会随着含水量的增加而缩短。在 200 万次循环时，0%、50% 和 100% 水饱和度的疲劳强度降低系数分别为 0.623、0.550 和 0.423。三参数 Weibull 分布最能描述 ECC 疲劳寿命。使用该模型，开发了 S-N 和 P-S-N 曲线，并结合了置信限来推导 γ-P-S-N 关系，确保了高置信度和可靠性。