Study On Microscopic Model Of Concrete Considering Aggregate Shape

Concrete is a heterogeneous material,whose physical and mechanical properties are determined by the ingradients,proportions,mechanical properties and the bonding effects of the two major components invloing coarse aggregates and cement motar.The behavior at macroscale in failure process of concrete is important to the development of new kinds of concrete materials,design and evaluation of concrete structure.In this paper,the random aggregate model of concrete is studied,and the automatic generation of concrete mesoscopic model is realized by using Python programming language and ABAQUS commercial computing software,which provides the basis for repeating numerical sumulation of concrete.The major research work includes:The random aggregate generation and putting procedure of circular aggregate was worked out,and a circular aggregate multi-phase meso-scale model was developed.The random distribution of elliptic aggregate is completed by referring to the circular aggregate random casting algorithm.Based on affine transformation matrix of elliptic equation,the quadratic equation of arbitrary ellipse is obtained.The determinant of the quadratic matrix can determine whether the ellipse is separated from other ellipses or straight lines.Compared to other methods,the ellipse aggregates generated in this paper are more compact.Polygonal aggregates of arbitrarily shaped shapes are obtained by changing the polar angle and polar coordinates.The concavity and convexity of the aggregate is strictly defined by the convexity judgment algorithm.The algorithm of aggregate distribution is optimized from the view of efficiency.Finally,random aggregate extension of the aggregates was made by the aggregate invasion criterion with the aggregate area as the scale,and the two dimensional concrete convex polygonal aggregate model was successfully obtained.The meshing of the interface transition area(ITZ)is completed.By setting the grid transition area,the mesh distribution is optimized and the computational efficiency is improved.The non-uniform three-point bending beam and the uniaxially stretched concrete multiphase mesoscale model were established by using the ABAQUS secondary development program in Python language.The development process of cracked crack of three-point bending beam was studied and the effect of meso-structure on the macroscopic mechanical properties of concrete was studied by changing the shape of concrete aggregate,the strength of interface transition zone.The calculated results show that the macroscopic mechanical properties of concrete are proportional to the intensity of the interface transition zone.By comparing the numerical results of uniaxial tensile of polygonal aggregate and elliptical aggregate concrete,it is concluded that the shape of aggregate has a direct effect on the macroscopic mechanical properties.The numerical simulation technology of concrete failure process considering the meso-structural characteristics has laid a foundation for revealing the deep mechanism of concrete failure.