动态剪切作用下沥青疲劳裂纹萌生及扩展行为特征判别

    Identifying Fatigue Crack Initiation and Propagation Behavior of Asphalt Binder Under Dynamic Shear

    • 摘要: 由疲劳载荷引起的路面开裂是沥青路面的主要损坏形式之一。近年来基于时间扫描试验(time sweep,TS)和线性振幅扫描(linear amplitude sweep,LAS)试验的损伤力学分析方法,虽能够表征和评价沥青的疲劳性能,但并不能阐明沥青内部疲劳裂纹的演变发展过程。为了解决现有沥青疲劳建模方法不能精细化表征材料不同疲劳阶段损伤特征的问题,本文提出基于断裂力学的沥青疲劳裂纹萌生及扩展行为分析方法。研究表明,通过裂纹增长曲线可对TS疲劳试验中的疲劳裂纹萌生及扩展行为进行判别,裂纹扩展特性曲线则描述了LAS试验中的裂纹萌生及扩展行为特征;基于能量释放率的失效判据同时适用于LAS和TS试验的失效点判别。此外,LAS和TS试验均证明了沥青疲劳寿命主要取决于其裂纹扩展寿命,苯乙烯-丁二烯-苯乙烯嵌段共聚物(styrene-butadiene styrene block copolymer,SBS)改性剂的加入同时提高了裂纹萌生寿命和裂纹扩展寿命。

       

      Abstract: Fatigue cracking caused by repeated load is one of the main distresses of asphalt pavement diseases. In recent years, the fatigue performance of asphalt binder can be evaluated and distinguished by the damage mechanics approach based on time sweep (TS) and linear amplitude sweep (LAS) tests; however, the cracking development process cannot be captured and clarified. In this paper, fracture mechanics-based approach is proposed to address the problem that the damage characteristics of different asphalt fatigue phases can not be accurately characterized by existing asphalt fatigue modelling method, which reveals the specific phases during the fatigue process. The crack growth curve is proposed to identify the crack initiation and propagation behavior in the TS test, whereas in LAS test the crack propagation characteristic curve should be effectively utilized for such purpose. The energy release rate can be utilized as the unified failure identification for both LAS and TS tests. Additionally, both LAS and TS tests demonstrate that the fatigue resistance of asphalt binder is primarily determined by its crack propagation life. The addition of SBS modifier can both effectively improve the crack initiation life and crack propagation life.

       

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