沥青混合料四点弯曲试验疲劳失效准则分析

Fatigue Failure Criterion of Asphalt Mixture in Four-Point Bending Test

疲劳病害作为沥青路面常见病害被广泛研究,然而对于应变控制加载下的沥青混合料疲劳失效却缺乏精准的界定。基于损伤力学的疲劳研究方法常将模量衰减50%作为材料失效准则,而能量法利用的累计耗散能同样能较好地表征材料的疲劳损伤。首先,将疲劳加载时模量衰减的第三阶段初始点作为疲劳失效点,并认为与其判定的疲劳寿命相接近的疲劳失效准则为合理的准则;其次,基于疲劳-应变模型对比了5种不同疲劳失效准则下的疲劳寿命拟合优度,根据疲劳失效点的可观察性以及拟合优度进行疲劳失效准则合理性分析;最后,通过比选认为累计耗散能量比能够较好地定位材料的疲劳失效,并将累计耗散能量比变化率偏离稳定期变化率30%作为定量的疲劳失效判定点。

Fatigue disease is widely studied as a common disease of asphalt pavement,but there is no precise definition of fatigue failure of asphalt mixture under strain controlled loading.The fatigue research methods based on damage mechanics often take the modulus deterioration of 50%as the material failure criterion,while the cumulative dissipated energy used by the energy method can also better characterize the fatigue damage of materials.Firstly,the initial point of the third stage of modulus deterioration in fatigue loading was taken as the fatigue failure point,and the fatigue failure criterion which was close to its judged fatigue life was considered as a reasonable criterion.Secondly,the goodness of fit of fatigue life under five different fatigue failure criteria were compared based on the fatigue strain model,and the rationality of fatigue failure criteria was analyzed according to the observability and goodness of fit of fatigue failure points.Finally,it was considered that the cumulative energy dissipation ratio could better locate the fatigue failure of the material through comparison selection,and the change rate of the cumulative dissipated energy ratio deviating from the change rate of the stable period by 30%was as the quantitative fatigue failure determination point.