چكيده به لاتين
Abstract:
Asphalt is a composite material made of aggregate and bitumen and crack growth is one of the major failure modes in asphalt pavements. Annually huge amount of costs are spent on repair, maintenance and reconstruction of cracked asphalt overlays. The creation and propagation of cracks in the asphalt surface can be affected by various mechanical factors such as passing vehicles or temperature changes due to seasonal variations. In order to reduce the cost and time in evaluating the fracture behavior of asphalt mixtures, numerical methods are of special importance. As asphalt mixtures show linear and brittle behavior at their low temperature their behavior at these conditions can be investigated using Linear Elastic Fracture Mechanics (LEFM) theory. In addition, the fracture behavior of asphalt mixtures can also be influenced by the rate of loading. In other words, if the temperature and loading rates are low simultaneously, the behavior of asphalt materials will be viscoelastic. Therefore, for elastic behavior, temperature and loading rate should be low and high, respectively. There are various numerical methods for studying the behavior of asphalt failure, one of which is Cohesive Zone Model CZM Method. Bilinear method of this model includes three parameters which are named as initial stiffness, Tensile strength and Fracture Energy. The aim of this study is the experimental and numerical investigation of the fracture of an asphalt mixture under various fracture modes using mechanical tests and cohesive zone model. Mechanical tests were conducted on Semi Circular Bend (SCB) samples under various loading modes of I, II and combined I/II. The results show that the fracture behavior of asphalt is considerably dependent on load mode so that by changing the loading mode from one to two, Fracture Energy increases and adhesive strength reduces. The numerical results obtained from finite element modeling have a good compatibility with experimental results.
Keywords: asphalt mixtures, cohesive zone model, mode I and mode II fracture behavior, finite element method