Resrarch On 3D Numerical Model Construction Technology For Concrete Based On CT Image

Concrete is a kind of heterogeneous composites with aggregate,mortar,pore and interface.The complexity of the material composition determines the heterogeneity of the structure and the complexity of the physico-mechanical properties.In order to explore using numerical simulation technology for studying failure mechanism of concrete,based on the concrete CT scanning images,combined with micromechanics,industrial CT scanning technology,image processing technology,3D visualization technology,finite element numerical simulation,this paper designs the method of four-value segmentation for the concrete CT scanning images,and the establishment of two-dimensional and four-phase numerical model of concrete.Then,the method of concrete 3D finite element model based on concrete high precision scanning image is explored.The work and results are as follows:(1)Using industrial CT to realize fault scanning of concrete,757 concrete fault images are obtained.Through preliminary analysis,it is found that the images are dark-middle,bright periphery and the image gray histograms are only single peaks without obvious bimodal.This leads to taking the conventional global segmentation method to segment concrete CT scanning images is ineffective.According to the feature,this paper writes Matlab program,and proposes an image segmentation algorithm based on circular partition and region growth to separate the aggregate and the pore.Then by using Mimics to choose aggregate mask,the interface with the actual size is separated by the expansion function.Through the Boolean operation,the mortar phase is obtained.So as to realize the four-value division of concrete scanning images.(2)Based on the four-phase image segmentation,vectorization software is used to transform the four-value bitmap into concrete four-phase vector of concrete.Through Auto CAD,the optimization and proportional conversion of the vector drawing is completed.After that,it was imported into ABAQUS,and the 2D finite element numerical model is established.Based on the reasonable selection of constitutive relation and mechanical parameters of each phase,2D numerical simulation of the splitting process of concrete specimen is carried out,and the calculation results are analyzed.By law of distribution of tensile stress,rationality of the model is explained preliminarily and qualitatively.It is concluded that the material heterogeneity,the influence of the weak interface layer and pore lead to uneven distribution of stress of concrete mesco-model and its interface and pore appear stress concentration and are destroyed firstly.By comparing the measured results against the splitting tensile strength of the model and the theoretical formula results,it is showed that the splitting tensile strength of concrete according to the heterogeneous model is more realistic and quantitative,which verifies quantitative quantifying the rationality of the model.(3)Based on the high-precision industrial CT scanning image information of concrete,3D visualization technology based on two methods of 3D visualization surface rendering are explored,which mainly solves the problems of the optimization of model grid and node coordination problems of aggregate and mortar.A uniaxial compression simulation is processed in ABAQUS for the finite element model based on triangular patch,and its damage rule is analyzed,which verifies the rationality of the model.