Research On Strain Rate Of Concrete Based On 3-D Meso-scale Model

The experimental results show that concrete is a typical rate sensitive material,and the growth mechanism of concrete strength is different under different loading rates.In engineering design and guidance,it is often assumed that concrete is an isotropic material.But from a mesoscopic point of view,concrete can be considered as a composite material of aggregate,mortar and interface transition zone.The establishment of real aggregate distribution and shape of mesoscopic concrete model,the simulation of concrete under different loading rate under uniaxial compression and compared with the test stress-strain curve,is a powerful tool of deep understanding mechanical characteristics and dynamic behavior of concrete.With the help of CT scanning technology,slice image of internal structure of concrete material was obatained,and use Matlab image processing technology to do a series of image processing for CT scanning image,such as image denoising and image enhancement,which can restore the true shape and distribution of aggregate.The processed CT images are intro duced into the medical software Mimics,and the three-dimensional grid is built,the material attributes are given,and the concrete specimens are reconstructed in three dimensions.With the help of Abaqus finite element platform,the numerical simulation results of the random spherical aggregate model and the CT scanning meso model are compared,and the grid convergence and applicability of the mesoscopic model based on CT scanning are verified.The extensometer and relay sensor of concrete and mortar are used in dynamic uniaxial compression test.In the strain rate range,this paper researched concrete strain rate effect on the compressive strength,elastic modulus and other mechanical properties,and obtained the stress under different loading rates strai n curve,comparative analysis on factors affecting test results.Mix proportion of mortar and conrete is consistent,and the stress-strain curve and compressive strength of concrete under different loading rates can be obtained;splitting tensile strength test aims to obtain concrete damage behavior and failure mode.Abaqus finite element based on the platform of concrete meso groups from the sorting plastic damage model using mesoscopic numerical model of concrete and mortar under different loading rate,t he tensile and compression test by the numerical simulation,comparative analysis of experimental and numerical results show that the 3D mesoscopic numerical model can simulate the concrete and mortar,the dynamic mechanical properties of concrete with dif ferent loading quantity and pull under the splitting behavior of tensile strength;with the increase of loading rate,concrete damage zone increased and the bandwidth is increased,and the damage is more complex cross connected.A concrete two-dimensional mesoscopic model,to study whether considering the influence of ITZ on concrete,tensile and compressive mechanical properties.The results show that there are interfacial transition zone effect and for tensile mechanical properties of concrete,it is more significant,while compression performance also has a certain impact but not very obvious.The strain rate increases will lead to increase the influence of ITZ.