Numerical Simulation Analysis Of Damage And Failure Process Of Concrete Materials Based On Micromechanics

Based on the concrete micromechanics method,this paper considers that concrete is a three-phase composite heterogeneous material composed of aggregate particles,solidified cement mortar matrix and interface transition zone.The finite element method is used to conduct numerical simulation tests,and the failure process of concrete and recycled concrete under tensile and compressive loads is numerically simulated.It intuitively shows the appearance characteristics and damage development rules of cracks in the process of concrete and recycled concrete damage,and analyzes the control variables of important material parameters and other influencing factors that affect concrete damage,and compares the analysis results with the research results of many scholars.The main work of this paper is as follows:1.Based on the deformation method of expansion factor function,the deformation object is directly mapped point by point to produce the desired deformation effect so as to obtain aggregate particles close to the actual concrete shape.The random aggregate model of concrete with round aggregate,pebble aggregate,crushed stone aggregate and convex polygon aggregate in two-dimensional case is created.At the same time,the aggregate phase in the three-phase medium is shrunk many times as a whole,and a meso-random aggregate model of recycled concrete composed of five phase medium is established.2.According to the characteristic points of convex polygon random aggregate contour that are easy to capture and programmable.The MATLAB data output script and the ANSYS command flow are compiled by ourselves to realize the automation of the creation and analysis of convex polygon random aggregate model under the conditions of different gradation,aggregate content and interface thickness.On this basis,the influence of aggregate content,elastic modulus of aggregate,interface thickness and other factors on the elastic modulus of concrete is analyzed by numerical simulation method.The results show that the elastic modulus and volume fraction of aggregate are positively correlated with the elastic modulus of concrete,and the thickness of interface has little effect on the elastic modulus of concrete.3.The random model uniaxial compression and three-point bending tests of crushed stone aggregate concrete are numerically simulated by using ABAQUS’s own plastic damage criterion and constitutive model.On this basis,its mechanical properties and failure process are studied and analyzed.The results show that the failure of concrete is caused by the initiation,propagation and coalescence of internal cracks,and the root cause is the stress concentration in the interface transition zone of its weak structure.4.Create random aggregate models of recycled concrete with different aggregate shapes and sizes,and conduct uniaxial compression test simulation.The results show that the size effect causes the damage distribution in the small specimen to concentrate on both sides of the aggregate,showing the characteristics of less and dense,while the damage distribution in the larger specimen is relatively uniform;The change of aggregate shape will lead to the change of damage location and propagation path;At the same time,the strength of each phase medium material,the thickness of old mortar,the thickness of new interface,and the thickness of old interface have obvious effects on the mechanical properties of recycled concrete.