Research On Failure Mechanism Of Asphalt Mixture Viscoelastic Damage And Fracture

Damage will be initiated and even extended to crack at the internal flaws of asphalt mixture under the external environment and the load,which is the problem of road construction for many years.This is because the relaxation ability is decreased,which leads to the stress accumulation over the asphalt mixture strength and then damage occurs,so it has a significant value for research and engineering application value to study the relaxation damage of asphalt mixture.At present,most of the research on the rheological properties of asphalt mixture is based on creep test,but the cracking is mainly caused by the decrease of relaxation ability in low temperature environment and the formation of stress concentration.In addition,there is a lack of accuracy and simplicity in the analysis of the relaxation modulus of the integral constitutive relation.In view of this,in this paper,high viscosity asphalt sand is used as the study object,and the method is used in the combination of viscoelastic mechanics and damage mechanics.And then,a comprehensive study was carried out from the aspects of viscoelastic theory,indoor relaxation test and ABAQUS numerical simulation.Specific as follows:1.In terms of viscoelasticity,a new and efficient scheme of interconversion between relaxation modulus and creep compliance was presented.Creep compliance is substituted into the convolution relation,which was launched to be a transcendental equation by the Taylor series.Then,based on the Newton iteration method,the expression of relaxation modulus is obtained by using Mathmatica to solve the transcendental equation.Finally,the method is verified by comparison with the relaxation modulus obtained from the relaxation test.The results show that the calculated relaxation modulus obtained the relaxation modulus curves and relaxation tests obtained very close and can reflect the relaxation behavior of asphalt mixture.Therefore,the method is selected to study the relaxation characteristics of asphalt mixture conveniently and accurately.2.In terms of relaxation test,the temperature,the loading rate and the initial strain were selected as the variables to study the relaxation property of asphalt mixture by uniaxial compression relaxation test and uniaxial tension relaxation test.The initial strain value of relaxation test was first determined before the relaxation test was carried out.It turned out that the relaxation modulus was found to increase with the increase of the loading rate.The relaxation modulus of the specimen had ?-shaped curve under increased pressure with the mechanical property changes from linear elasticity to elastoplasticity till the damage occurs.The determination of the relaxation modulus was highly sensitive to the temperature,but the failure occurs earlier at low temperature.The GMM with 6 arms appeared to be the best phenomenological representation of the viscoelastic behavior of asphalt mixture,which provided a foundation for further study for relaxation damage model.3.In the numerical calculation,with the aid of ABAQUS finite element platform,the USDFLD subroutine is used to establish extended finite element model for simulating the I-shaped test of damage and fracture process of members and the damage initiation and propagation of crack propagation and evolution mechanism could be mastered,which verify the correctness of the damage model,but also provide theoretical support for the future of asphalt pavement crack control.The generalized Maxwell model with damage is used in the simulation,in which the damage is subject to the Weibull function.Innovation point of this paper:1.In terms of viscoelasticity,a new and efficient scheme of interconversion between relaxation modulus and creep compliance was presented which is based on the Boltzmann superposition principle and the relaxation modulus of high viscosity asphalt sand is determined by Newton iteration method.2.Coupled Weibull damage relaxation model is established.In the ABAQUS finite element platform,the USDFLD subroutine is used to simulate the relaxation process of asphalt mixture by secondary development.The dynamic process of crack propagation was simulated by extended finite element modeling.