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该文基于Paris公式,对具有应变硬化和多缝开裂特征的超高韧性水泥基复合材料(UHTCC)的疲劳裂缝扩展理论进行了理论研究,并通过试验进行验证。研究表明,Paris公式适用于UHTCC。其中:裂缝扩展参数由裂缝面积扩展A表示;与之相应,使用复合断裂能增长量ΔJ代替应力强度因子变化量ΔK。基于试验,该文求出UHTCC的疲劳裂缝扩展门槛值,即当疲劳过程中的断裂能幅值ΔJ小于某一临界值ΔJth时,疲劳裂缝不扩展。在疲劳过程中,UHTCC的裂缝覆盖面积随疲劳过程呈三阶段线性发展,与疲劳变形的发展趋势一致。UHTCC的疲劳裂缝扩展随疲劳最大荷载与荷载幅值的增大而加速发展。
Based on the Paris formula, the theory of fatigue crack growth of ultra-high toughness cementitious matrix composites (UHTCC) with strain hardening and multi-split cracking has been theoretically studied and verified by experiments. Research shows that Paris formula is suitable for UHTCC. Wherein, the crack propagation parameter is represented by the crack area extension A; correspondingly, the composite fracture energy increment ΔJ is used instead of the change of the stress intensity factor ΔK. Based on the test, the fatigue crack expansion threshold of UHTCC is obtained. That is, the fatigue crack does not expand when the amplitude of fracture energy ΔJ in fatigue is less than a certain threshold ΔJth. During the fatigue process, the crack coverage area of UHTCC shows a three-stage linear development with the fatigue process, which is consistent with the development trend of fatigue deformation. The fatigue crack propagation in UHTCC accelerates with the increase of fatigue maximum load and load amplitude.