Numerical Analysis Of Cracks In Asphalt Pavement Based On Fatigue Damage Mechanics

The fatigue crack, caused by repeated vehicle load, is one of the main forms of asphalt pavement damage. Essentially, it is the surface layer of asphalt pavement structure where fatigue damage and destruction occurred. Only to find out the fatigue crack formation process and crack propagation process of asphalt surface, can the anti-fatigue design of asphalt pavement more effectively. At room temperature the asphalt mixture can show some viscoplasticity, which indicate that the asphalt pavement will show some viscoplasticity in its majority work environment. It is undoubtedly biased that the scholars considered the asphalt as a viscoelastic material when studying the asphalt’s fatigue. As the traditional fatigue mechanics can only consider the formative stages of fatigue cracks, so it can not be used to study the fatigue cracks from the formation to the expansion. The fatigue damage mechanics, as fracture mechanics emerging discipline branch, can just make up for the shortcomings of traditional fatigue mechanics. In view of the above three aspects, this paper carried out the following tasks:1) In this paper, according to the fixed Burgers viscoelastoplastic model, the author derived the asphalt mixture elastoplastic damage constitutive equation in the second half sine loads, and get the expression of cumulative strain.2) By Analyzing and summarizing various fatigue damage damage model in the papers, and based on a lot of fatigue test data in papers, the author proposed an evolution model which can consider loading frequency, temperature and stress damage ratio.3) The author carried out asphalt splitting fatigue tests and used Origin software fit the parametric equations and damage constitutive equations successfully according to the tests fatigue life data.4) On the bases of the damage evolution equation and damage constitutive equations, the author use the ansys software to model the overall asphalt pavement structure, and analyzed the process of the formation and propagation of fatigue cracks in the asphalt surface under the vehicle loads. The effects of different thicknesses and different grassroots base modulus opposite layer fatigue cracks. Analysis of the surface layer in contact with the state of the surface layer of grass fatigue crack impact.