基于能量法的超高韧性纤维混凝土疲劳损伤特性

Fatigue damage characteristics of ultra high toughness cementitious composite based on energy method

为探究超高韧性纤维混凝土材料(UHTCC)在交通荷载下的疲劳损伤性能,通过不同应力水平、频率下的单轴压缩试验得到了应力-应变曲线,结果表明:随着循环次数的增加,疲劳曲线呈疏-密-疏的3阶段规律,同时应变增长非线性程度逐渐增大。加载频率和应力水平的增加均会降低试件的疲劳寿命。在单轴压缩循环试验基础上建立本构模型,模型预测应力路径与试验结果吻合良好,验证了模型的正确性和适用性。以能量法为基础,采用耗散能指标评价UHTCC疲劳损伤程度,得到了初始损伤(2%左右)和疲劳损伤因子发展规律。此外,研究还发现在高应力比条件下疲劳开裂具有突然性。

Experimental study of cylindrical samples under uniaxial cyclic compression was conducted to explore the effect of loading frequency and stress level on fatigue performance of ultra high toughness cementitious composite(UHTCC)under traffic loading. The results show that accumulation rate of stresscycle curves could be disassembled into three stage with increase in number of cycles. Meanwhile,nonlinearity of strain increases gradually. The increase of loading frequency and stress level would reduce the fatigue life of specimens. The constitutive model for UHTCC was proposed based on the basis of uniaxial compression cyclic tests. Moreover,the stress path predicted by the model is in good agreement with the experimental results,which verifies the correctness and applicability of this model. Fatigue damage propagation is characterized by dissipated strain energy(DSE)based on energy-based mechanistic approach(EBM). The initial damage(about 2%)is obtained and the development law of fatigue damage factor is revealed. Additionly,the fatigue cracking is fast at high stress ratio.