Mode II Cracking Failure in Asphalt Concrete by Using a Non-conserved Phase Field Model

Abstract

Cracking failure in asphalt concrete has always been one of the most serious problems in pavement structures. Classical fracture mechanics is the most widely used method to analyze the initiation and propagation of cracks. In this paper, a new modeling and computational tool the phase-field method is proposed for modeling the Mode II cracking failure in asphalt concrete. This method describes the microstructure using a phase-field variable which assumes one in the intact solid and negative one in the crack region. The Mode II fracture toughness is modeled as the Mode II surface energy stored in the diffuse interface between the intact solid and crack void. To account for the growth of cracks, a non-conserved Allen-Cahn equation is adopted to evolve the phase-field variable. The energy-based formulation of the phase-field method handles the competition between the growth of surface energy and release of elastic energy in a natural way: the crack propagation is a result of the energy minimization in the direction of the steepest descent. Both the linear elasticity and phase-field equation are solved in a unified finite element frame work, which is implemented in the commercial software COMSOL. It was discovered that the crack propagation in phase-field agrees very well with the Griffith criterion.