Concrete Aggregate Modeling And Numerical Simulation Based On Digital Image Technology

The concrete is considered as a kind of non-homogeneous composite materialscomposed of aggregates, cement mortar, cracks and pores, etc. Traditional mechanical modelmacroscopic, homogeneous and continuous and the corresponding theoretical analysis andnumerical simulation ignores the internal structure properties of materials, so it’s difficult todepict the mesoscopic mechanical behavior of material composition and the interactionbetween different materials. Digital Image processing technology provides a new method forfurther study in the mesoscopic structure features and mechanical properties of concrete. Themutual combine between digital image processing technology and finite element method isanother effective way to associate the mesoscopic structure features of concrete materials withmacroscopic mechanical response. From the perspective of the mesoscopic level, the concreteis considered as a kind of three-phase composite materials composed of coarse aggregate,cement mortar and bonded interface between them. Based on digital image theory and theimage processing tools of MATLAB, the aggregate boundary extraction of two-dimensionconcrete is developed for carrying out numerical analysis at meso-level. The results aremainly as follows:First, in order to solve the problems of aggregate edge producing and edge moving inconcrete image processing, a watered segmentation method combining morphologicalreconstruction with mark is proposed. The algorithm achieves the segmentation of aggregatesand cement mortar by adjusting structure radius and height threshold. The segmentationresults confirm that aggregate boundaries tally with the original image, and the algorithm hasgood applicability.Second, aggregate boundary coordinates are extracted based on aggregate boundarytracking algorithm of8-connected region. The main aggregate property parameters extractedcan be used to further research of geometrical properties of real aggregates.Third, ellipse aggregates and polygon aggregates are randomly generated based on theprogramming software of MATLAB and statistical theory. Meanwhile, the aggregate areagradation is introduced to measure the content and the distribution of aggregates, which canbe used to analyze different aggregate models. Fourth, the data exchange between MATLAB, AUTOCAD and ABAQUS software isaccomplished, and the size transformation problem of the concrete block by the image size tothe actual size is solved.Finally, the failure process of concrete is simulated under uniaxial tension by theconcrete mechanics model. The results confirm this method is valid, and the model can beused to further research of concrete deformation damage and mesoscopic mechanics analysis.