沥青混合料抗疲劳性能评价方法研究

发布时间：2018-02-15 20:54

本文关键词： 沥青混合料抗疲劳性能损伤力学加载模式控制能量　出处：《东南大学》2015年硕士论文　论文类型：学位论文

【摘要】：预测沥青混合料的疲劳寿命是道路结构设计中的基础性问题,对沥青混合料的抗疲劳性能进行评价和比较是材料研发中的重要环节。传统的室内小梁弯曲疲劳试验有两种加载控制模式：控制应力和控制应变,不同的加载模式模拟了道路结构中拉应力最大处的不同受力历程。比较不同材料的疲劳寿命曲线(S-N曲线)时,不同加载模式有着不同的评价结果,这给评价沥青混合料的抗疲劳性能带来了困难。本文将损伤力学中的材料疲劳损伤演化方程引入到道路结构有限元模型中,模拟了重复车轮荷载下柔性路面结构的损伤场发展过程。通过对面层底部拉应力最大处的变化过程进行分析发现,其损伤变量呈现出线性增长现象,这与半刚性路面基层的指数型增长有着明显差别。同时该处受力过程为应力逐渐减小,应变逐渐增大,体现出荷载向周围结构转移但变形仍然增大的趋势；也即其疲劳过程既不是应力不变状态,也不是应变不变状态。通过分析车轮下损伤区域与主要受力区域关系,本文提出了控制能量加载模式,即控制每次循环荷载时施加在小梁试件上的能量是相同的。此模式下施加在梁上的荷载随着小梁刚度减小而不断减小,同时小梁挠度不断增大,最后发生断裂。控制能量加载模式不仅与路面结构中核心损伤区实际受力过程更为符合,因此能更准确预测疲劳寿命,而且反映出了材料自身的力学特性。在相同能量荷载重复冲击下得到的材料疲劳寿命或者累积耗散能,可以将不同刚度大小的材料置于同一原则下进行比较。因此控制能量法是一种简单而有效的沥青混合料抗疲劳性能评价方法。采用此模式,论文对最高比例50%的不同旧料掺量AC20小梁进行了疲劳试验,证实了该方法的可行性和有效性。通过比较相同能量荷载加载下至断裂的循环次数,发现旧料掺量越大的混合料抗疲劳性能越好。
[Abstract]:Predicting the fatigue life of asphalt mixture is a basic problem in road structure design. Evaluating and comparing the fatigue resistance of asphalt mixture is an important link in the research and development of materials. There are two loading control modes in traditional indoor trabecular bending fatigue test: control stress and control strain. Different loading modes simulate the different stress course of the maximum tensile stress in the road structure. When comparing the fatigue life curve and S-N curve of different materials, different loading modes have different evaluation results. It is difficult to evaluate the fatigue resistance of asphalt mixture. In this paper, the material fatigue damage evolution equation in damage mechanics is introduced into the finite element model of road structure. The development process of damage field of flexible pavement structure under repeated wheel loading is simulated. By analyzing the variation process of maximum tensile stress at the bottom of the surface layer, it is found that the damage variable shows a linear growth phenomenon. This is obviously different from the exponential growth of semi-rigid pavement base. At the same time, the stress decreases gradually and the strain increases gradually, which reflects the trend of load transfer to the surrounding structure but the deformation is still increasing. In other words, the fatigue process is neither stress invariant nor strain invariant. By analyzing the relationship between the damage zone under the wheel and the main force region, the mode of controlling energy loading is proposed in this paper. That is to say, the energy applied to the trabecular beam specimen is the same when each cyclic load is controlled. In this mode, the load applied on the beam decreases with the decrease of the trabecular stiffness, and the deflection of the trabecular beam increases. Finally, fracture occurs. The controlled energy loading mode is not only more consistent with the actual stress process in the core damage zone of pavement structure, so it can predict the fatigue life more accurately. It also reflects the mechanical properties of the material itself. The fatigue life or cumulative dissipation energy of the material under repeated impact of the same energy load is obtained. Materials with different stiffness can be compared under the same principle. Therefore, the energy control method is a simple and effective method for evaluating the fatigue resistance of asphalt mixtures. The fatigue test of AC20 trabeculae with different ratio of 50% used materials is carried out, which proves the feasibility and effectiveness of this method. The cycle times from the same energy load to fracture are compared. It is found that the greater the content of the old material, the better the fatigue resistance of the mixture.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U414

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