Damage Research Of Concrete Based On Mesoscopic Model

Concrete material has a wide range of sources,good physical properties,easy molding advantages,which make it widely used in civil buildings and public buildings,and played an important role in the large-scale industrial and national defense construction projects.The damage evolution and failure mechanism of concrete have been studied in the fields of materials science,civil engineering and mechanics.One of which the key point is how to capture the location of internal crack of concrete material under the load and determine the evolution process of the crack.Acoustic emission testing technology can monitor the failure process of concrete under load and capture internal crack sources in real time.With more and more research devoted to the study of micro-level of concrete,numerical simulation is helpful to analyze and study the damage mechanism of concrete materials.This paper adopted advanced multi-channel AE system.to study the damage characteristics of concrete under compression loading and three-point bending loading.The variation of acoustic emission counting rate and amplitude reveals the compaction of micro holes,internal micro crack initiation,internal micro crack propagation,surface crack formation and coalescence failure in concrete compression process.Combined with the time difference localization algorithm,the acoustic emission source inside the specimen is located in the loading process,and the localization result reflects the dynamic change of the damage inside the concrete.In this paper,concrete is regarded as the three-phase composite material composed of aggregate,mortar matrix and interface transition zone.Based on the gradation theory,this paper obtained the number of particles of various aggregate sizes of concrete specimens Finally it used Monte Carlo method to realize random generation of aggregates and established the mesoscopic model of concrete.This paper used the plastic damage model of concrete to describe the weakening of strength and stiffness caused by micro-damage evolution in concrete,and give the change of damage parameters in the model with the experimental results.The damage process of concrete specimen under compression loading was simulated by using the finite element program and the concrete mesoscopic model.The results showed that the failure modes of concrete are taper and oblique under the compressive load.In this paper,the expansion finite element method is used to calculate the damage of concrete under three-point bending loading,the results showed that the crack propagation mainly spreads in the interface transition zone and cement mortar.