Concrete Cracking At The Meso-level Of Numerical Simulation

Concrete is a typical heterogeneous composite material, its mechanical properties depend on the mechanical properties of the material in each phase. In the test basis, using numerical simulation method can not only reflect the whole process of concrete damage, but also can reflect the aggregate content and shape, the interface transition zone (ITZ) and effect on macroscopic mechanical properties of concrete. A prerequisite for calculating model is reliable and effective in ensuring, can replace part of test, avoid the effects of test conditions and man-made errors on the results.Based on the micromechanics theory, concrete is considered as a three-phase composite composed of bonding interface between aggregate, mortar and both, aggregate model using MATLAB program to generate random distribution, and the use of the finite element analysis software ABAQUS, the failure process is simulated on the concrete specimen uniaxial tensile, compression using nonlinear finite single element method, and the microscopic and macroscopic failure links between damage are analyzed and discussed.Using the ABAQUS finite element analysis software on the random aggregate model of concrete of aggregate, mortar and interface are respectively meshed. On the concrete sample under uniaxial loading are studied by numerical simulation. The calculation results show that:the interface unit is the weak link in concrete, crack first appeared in the interface unit, and then extended to the mortar element adjacent, micro-cracks expanded, extension, merge, resulting in failure. This shows, the macroscopic mechanical properties of concrete by the mesoscopic structure constraints. The mesoscopic structure of concrete damage and destruction is caused by internal and foundation of the macro damage. The numerical simulation results and experimental results, the feasibility and validity of the model are proved.Through this study, the interface is the weak link in concrete, the damage and failure of concrete first occurs at the interface, the interface with the crack expansion, extension, merge, resulting in failure. The concrete meso-damage is the internal cause and basic macroscopic failure, and macroscopic destruction is the result of meso damage accumulation and development. The specific work is as follows: 1,0n concrete materials was investigated at the mesoscopic level theory of damage and fracture,the physical mechanism of failure mechanism of concrete material and fracture damage were studied.2,Using MATLAB program design language first meet the center coordinates of a given interval random distribution of aggregate particles, then according to the coordinates of the center of the qualified conditions are determined, the final generation of geometric model of circular and elliptical aggregate concrete.3,Introduces the basic principle of finite element method, the mechanical analysis and the application of isoparamentric element in this paper.4,The geometric numerical model representative volume element as the concrete specimens, the tensile, numerical simulation research for compression loads in uniaxial, find out the extension of internal crack of concrete. Analysis draws the conclusion on the obtained curve.5, The interface thickness were studied, so as to find out the effects of the interface thickness on the mechanical properties of concrete, which provides a basis for selection of the thickness of the interface numerical simulation of concrete.