Energy-Based Crack Initiation Criterion for Viscoelastoplastic Materials with Distributed Cracks
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2014 American Society of Civil Engineers. Crack initiation is the premise of fracture. Various analytical models are available to elucidate its mechanisms, but some require many details that may not be suitable for engineering practice or some specify a single crack that is not applicable for a large number of distributed cracks. To fill this research gap, this paper aims to develop an energy-based crack initiation criterion for viscoelastoplastic materials with a distributed crack system using the energy that can be measured from the test. The composition and formulation of the criterion are determined by studying fracture behaviors and local energy redistribution around cracks in asphalt mixtures as typical viscoelastoplastic materials. The energy in the local nonlinear zone, the energy in the local energy release zones, and the surface energy of the material are identified to constitute the energy-based crack initiation criterion. The energy in the local nonlinear zone and local energy release zones are measured by designing repeated load tests to determine the critical condition for crack initiation, called the endurance limit. The surface energy of an asphalt mixture is composed of the surface energy of cohesion and surface energy of adhesion, which are measured from surface energy tests. Then the criterion is validated using the measured energy components. Statistical analysis is conducted on eight different types of asphalt mixtures and proves that the criterion is balanced at the point of crack initiation. The energy-based crack initiation criterion, along with repeated load tests, can act as a substitute for surface energy tests. Depending on the cracking pattern in the material, the surface energy solved from the criterion is the surface energy of cohesion, the surface energy of adhesion, or the combined product of both. When there is both cohesive and adhesive cracking, the calculated surface energy from the criterion can be used to separate cohesive cracking and adhesive cracking in the same material.