基于沥青混合料三维数值试样的非均匀性分析

Analysis of the heterogeneity using three-dimensional digital specimen of asphalt mixture

为了从三维细观尺度评价沥青混合料在荷载作用下的非均匀性,利用X-ray CT扫描沥青混合料试样,获取试样内部的精确三维细观结构,根据三维重构原理开发程序并建立了与混合料试样内部空间实际分布形态一致的三维数值试样,分别赋予集料、砂胶和空隙不同的材料属性,进行低温、快速加载条件下的间接拉伸虚拟仿真.结果表明:与基于三维均质体试样的数值模拟相比,三维数值试样内部的应力和应变分布都完全呈现不均匀状态,与实际试验状态更一致;有空隙时的平均应力集中因子(2.78)明显大于无空隙时的平均应力集中因子(1.42),表明空隙的存在明显增加了试样受荷载作用下的应力集中,该方法克服了传统数值模拟无法考虑各因素空间分布影响的局限性.

In order to evaluate the mechanical performance based on 3D （three-dimensional） microscale, the internal microstructure of asphalt mixture was accurately captured using X-ray CT. Afterwards, according to 3D reconstruction principle, the 3D digital specimens that reflect the realspatial distribution were built, and the properties of three constituents （aggregates, mastic and voids） were determined. Finally, the virtual test of indirect tensile test （IDT） was performed under low tem- perature and fast loading conditions. Compared to conventional numerical simulations based on homo-geneous specimens, the results indicate that the internal stresses, strain and displacements display completely heterogeneous distribution, which is agreed well with actual laboratory test. The stress concentration factor （2.78） before moving voids is significantly larger than that after moving voids（1.42）, which illustrates that the existing voids exacerbate the stress concentration when the specimen are loaded. This study overcomes the limitation of conventional numerical simulation method that ignores the spatial distribution of three constituents.