Fatigue-creep damage interaction model of asphalt mixture under the semi-sine cycle loading

To describe the interaction of fatigue-creep damage of an asphalt mixture under the action of semi-sine cyclic loading reasonably, a direct tension fatigue test was carried out under four different stress levels (0.5, 1, 1.5, and 2 MPa) based on the fact that semi-sine fatigue stress can be decomposed into creeping stress and simple fatigue stress. In addition, tension-compression fatigue and static creep tests were carried out under four stress levels: 0.25, 0.5, 0.75, 1 MPa. For each test, five parallel tests were carried out at the same stress level. The Chaboche fatigue damage model and Kachanov creep damage model were employed to evaluate the damage evolution of the mixture both in the fatigue and creep tests. According to the test results, the damage evolution trends were revealed under different test processes and stress levels, and the damage evolution models of three different test methods were obtained. Then, based on the principle of semi-sine fatigue stress decomposition, a fatigue-creep damage interaction model considering the interaction of fatigue and creep damage was established using normalized parameters (X = N/N-f = t/t(R)) as the intermediate variable. The results indicated that the damage of asphalt mixture under the action of the semi-sine cyclic load was not a simple linear accumulation of fatigue damage and creep damage, but an overall result of the interaction of fatigue damage, creep damage, and fatigue-creep damage. The fatigue-creep damage interaction model provided a good fit with the experimental data and showed a high degree of consistency with the classical damage model. The model could be used to describe the damage evolution trend of asphalt mixture under the action of semi-sine cycle load and the interaction effect of fatigue damage and creep damage. (C) 2020 Elsevier Ltd. All rights reserved.