Multi-scale Algorithm Prediction And Attenuation Law Analysis Of Flexural Strength In Fatigue Damage Of Asphalt Mixture

Asphalt mixture is a multiphase heterogeneous composite material,which will produce deformation damage under the action of external environment and vehicle load.The mesostructure of asphalt mixture has an important influence on macroscopic properties.However,most of the current researches on fatigue damage of asphalt mixture are based on a large number of laboratory tests to obtain the mechanical parameters of the mixture,neglecting to explore the fatigue performance of asphalt mixture from the microscopic aspect.Therefore,this paper predicts the fatigue mechanical parameters of asphalt mixture by combining multi-scale algorithm and numerical simulation,and studies the mechanical attenuation properties of asphalt mixture in the fatigue process from a mesoscopic perspective.Firstly,the proportion of asphalt mixtures with different particle sizes AC-13C,AC-9.5,AC-4.75,AC-2.36 and AC-1.18 were determined.Then,strength and fatigue tests were carried out on each specimen based on semi-circular bending test,and mechanical strength parameters of asphalt mixtures with different particle sizes were obtained in the fatigue process.The results show that the crack resistance of asphalt mixture is mainly related to the amount of coarse aggregate in the material,and the tensile strength of asphalt mixture decreases gradually with the aggravation of fatigue damage degree.The strength attenuation law of asphalt mixture is slow in the early fatigue stage,and the strength of asphalt mixture decreases sharply in the late fatigue stage.Secondly,the microscopic image of asphalt mixture is analyzed,and the distribution law of geometric characteristic parameters of aggregate particles in asphalt mixture is statistically analyzed,and the corresponding two-dimensional mesoscale model is randomly generated according to the probability characteristic distribution of aggregate.Based on the multi-scale algorithm calculation program,the appropriate computational scale region is selected.The stiffness parameters of asphalt mixture AC-1.18 were taken as the initial iterative value and homogenized from small particle size aggregate to large particle size aggregate step by step.In this way,the stiffness parameters of asphalt mixture with different particle size were predicted.The results show that the stiffness parameters obtained have good convergence with the increase of the number of calculation models.Then,based on multi-scale idea and indoor semicircle bending test,using the finite element software to build the corresponding scales semicircle numerical model of bending specimen,through multi-level iteration to predict the next size flexural strength of asphalt mixture,and get the mixture in the process of fatigue damage analysis in lowering of flexural tensile strength,and with the increase of aggregate mixture particle size,The greater the dispersion of the predicted values.Finally,the mechanical strength parameters of asphalt mixture in the fatigue process obtained through laboratory tests were used as macroscopic verification,and compared with the mechanical strength parameters obtained through numerical simulation test of multi-scale algorithm,to verify the effectiveness of numerical simulation strength parameters of multi-scale algorithm.