Numerical Simulation Of Meso - Damage And Fracture Of Fully - Grade Concrete

As a kind of widely used multiphase quasi brittle composite material, studying concrete’s mechanical properties and damage fracture process is very important to practical engineering. In the past studies of macroscopic mechanical properties of concrete based on homogeneous medium hypothesis not only test cycle is long, the cost is high, and is influenced by various complicated factors to make the test result large discreteness, is difficult to reveal the concrete material under the action of load caused by crack initiation, expansion with the mesoscopic and macroscopic scales damage fracture failure process.This paper recognizes concrete as the three-phase composites consisting of aggregate, mortar and interface at the general mesoscopic mechanics foundation, combined with damage mechanics and computational mechanics numerical simulation of the deformation and damage of concrete fracture process.Firstly, considered the concrete aggregate shape and the distribution of the random characteristics, based on the monte carlo random sampling principle and matlab programming languages, given numerical image and 3-D specimen space noted immunohistochemical technology and different aggregate intrusion criterion greatly improve the efficiency of model of random aggregate of concrete automatically generated. Using matlab and comsol of the seamless combination, the two-dimensional random aggregate model is imported comsol software with triangular mesh subdivision technology to quickly generate concrete mesoscopic 2-D finite element model; Generating the background grid by comsol software is projected on the random aggregate model to automatically form a 3-D micromechanical finite element model of concrete and the identification of a mesoscopic three components. Numerical examples show that the algorithm in this paper generated automatically the concrete mesoscopic structure model and can completely satisfy the mass concrete high aggregate content the requirement of numerical simulation.Secondly, cleverly using matlab, comsol and the combination of finite element software programming to put concrete mesoscopic structure model into the nonlinear finite element analysis software, the concrete damage plasticity model reflects the mesoscopic constitutive relation of each composition, proposed in the specification of concrete under uniaxial stress-strain relationship method is applied to the mesoscopic damage evolution of each component of concrete damage plasticity model. By an explicit finite element method to solve, making concrete mesoscopic structure model of uniaxial static characteristic analysis implements smoothly.Finally, concrete under uniaxial tension, compression and splitting tensile test is numericalyl simulated. The paper analyzes the different aggregate shape, aggregate distributio, interface thickness and strength of mortar and interface, mesh size, strap width the influence of macro mechanical properties of concrete. The simulation results show that the aggregate shape and distribution of concrete have little effect on macroscopic mechanical properties; Interface is inside the concrete’s weak link; Relative to the mortar, the influence of macro mechanical properties of concrete interface is more significant; Appropriate grid size can meet the requirements of precision and save computational cost; Suitable for strap width split strength test may be more real; Numerical simulation of the ultimate strength and the regularity of crack extension and the literature of the given test data consistents. Beside the mesoscopic structure model established by this paper is effectiveness, rationality and validity.