基于X射线计算断层扫描图像的混凝土细观断裂模拟

Meso-scale fracture modelling of concrete based on X-ray computed tomography images

对混凝土试块进行了X射线计算机断层扫描(XCT)原位试验,提出了基于XCT图像的细观有限元断裂模型。此模型利用微观XCT图像信息高精度地模拟混凝土中的各相组成材料,即骨料、水泥浆以及孔洞,从而考虑了真实材料的非均质性。采用零厚度黏结裂缝单元进行了断裂模拟,裂缝单元被预先嵌入到水泥砂浆中以及其与骨料的交界面处,用于表征潜在裂纹。这些裂缝单元采用应力-相对位移本构关系来表征骨料咬合、裂缝面间的摩擦以及材料的黏结等作用。对该模型进行了混凝土单轴受拉数值仿真,通过与文献中试验以及模拟结果的对比,初步证实了该方法的有效性。

Meso-scale two-dimensional finite element models are developed for fracture modelling in concrete based on images from an in-situ microscale X-ray Computed Tomography test. In the models, the material heterogeneity is characterised by real multi-phases, namely, aggregates, cement and voids. Zero-thickness cohesive interface elements with normal/shear traction-separation constitutive laws are embedded within cement and on aggregate-cement interfaces to simulate potential cracks. Simulations of uniaxial tension tests were carried out. The results show good qualitative and quantitative agreement with experimental observa- tions and simulations from literatures.