Concrete Mesoscopic Damage Detection And Numerical Simulation Based On Acoustic Emission Technology

Concrete is one of the most widely used building materials.It is a complex composite material.Its mechanical properties mainly depend on the mechanical properties of the internal materials.The mechanical properties of concrete have always been the focus of research in the field of civil engineering.Many research results show that the damage and damage of concrete not only happens at the macro scale,but also at the micro scale,so it is very important to study the damage and fracture of concrete on the micro scale and the macro scale.In this paper,the mechanical properties of concrete single axis are studied by means of micromechanics including test method and numerical model.Three kinds of aggregate were used to study the effect of aggregate on the mechanical properties of concrete.In the test part,acoustic emission technology was used to dynamically monitor the damage evolution process of concrete,and random aggregate model was used in the numerical simulation.The specific work carried out in this paper is as follows:(1)The principle of ae technology is summarized,the significance of various parameters of ae is explained in detail,and the parameters such as energy,arrival time and ringing technology are mainly introduced to help analyze the parameters.A complete test procedure is established and the construction of each test instrument and test platform is introduced.(2)The cube specimens containing ellipsoid aggregate,coarse polyhedron aggregate and fine polyhedron aggregate were prepared,and the uniaxial compression experiment was carried out on them,and the whole damage evolution process was dynamically monitored by acoustic emission.According to the stress-strain curve,the failure processof concrete is divided into four stages: pre-stored microscopic damage stage,microscopic crack initiation stage,micro-damage development stage and crack forming stage.(3)Analyze the damage process of concrete through the characteristics of acoustic emission parameters in different stages.Through the acoustic emission data point cloud image analysis of three kinds of aggregate in concrete,ellipsoidal aggregates the initial micro cracks of concrete quantity minimum,coarse polyhedron aggregate number of initial micro cracks in most,in the early stages of loading because of the initial micro cracks can produce low energy impact signal,as load increases,the signal will also grow,and the energy value will appear the phenomenon of sudden release.(4)The random aggregate model is introduced in detail and its advantages are summarized.MATLAB was used to generate the aggregate model of the aggregate model,and the aggregate model was put into the specimen by combining with the coordinates of the aggregate drop point generated by monte carlo random Numbers.According to the theory of meso-mechanics,concrete is regarded as a three-phase composite material composed of aggregate,cement compound and interface.The three phases are respectively assigned with the CDP plastic model,the mesh is divided and the static uniaxial compression is simulated.(5)By comparing the simulation results with the test results,it is found that aggregate is the most important component determining the mechanical properties of concrete in the concrete specimens,and among the three kinds of aggregate,the mechanical properties of ellipsoidal aggregate are the best.In the test and simulation,the damage of concrete starts from the growth and evolution of microcracks,and the macroscopic mechanical properties of concrete are restricted by the microscopic structure,and the damage of the microscopic structure is the cause of the macroscopic damage.However,as the model is in a relatively ideal state,there is no initial micro-crack simulation,and the simulation data is relatively high compared with the experimental parameters,so the simulation of micro-cracks in the model is still an urgent problem to be solved.