THE 3D RECONSTRUCTION METHOD FOR QUASI-BRITTLE MATERIAL STRUCTURE AND APPLICATION

Physical and mechanical properties of quasi-brittle mater as well as its failure mechanism are determined by the material structure and the properties of each constituent. Therefore, it has become a developing trend to consider the actual structure of material as accurate as possible in numerical methods. In this paper, computerized tomography (CT) technology is employed to capture a serial of section images of the concrete material structure. Because the color density of CT image is uneven and annular distribution, a segment method based on annular zonal method and automatically identifying threshold is proposed to identify and characterize the concrete material structures from CT images. After that, the reconstruction methods for the 3D digitized solid model of material structure based on the vectorization of the BMP image and for the 3D grid model of material structure have been developed. Finally, the 3D grid model of the concrete material structure is transferred into the 3D Rock Failure Process Analysis (RFPA^3D) to build a numerical concrete specimen which can reflect the actual distribution of coarse aggregates, and the uniaxial compressive test of concrete is simulated. It is found that the results of the numerical test in which the actual distribution and geometry of coarse aggregates are taken into account are of comparability with the experimental results. The mechanical parameters and final failure patterns of the specimen from the numerical test are similar to those from the experimental test, which provides a new method for studying the mechanical behaviors of quasi-brittle materials such as concrete, rock and composite materials.