Potential-Based Fracture Mechanics Using Cohesive Zone and Virtual Internal Bond Modeling

Abstract

233 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009.The characterization of nonlinear constitutive relationships along fracture surfaces is a fundamental issue in mixed-mode cohesive fracture simulations. A generalized potential-based constitutive theory of mixed-mode fracture is proposed in conjunction with physical quantities such as fracture energy, cohesive strength and shape of cohesive interactions. The potential-based model is verified and validated by investigating quasi-static fracture, dynamic fracture, branching and fragmentation. For quasi-static fracture problems, intrinsic cohesive surface element approaches are utilized to investigate microstructural particle/debonding process within a multiscale approach. Macroscopic constitutive relationship of materials with microstructure is estimated by means of an integrated approach involving micromechanics and the computational model. For dynamic fracture, branching and fragmentation problems, extrinsic cohesive surface element approaches are employed, which allow adaptive insertion of cohesive surface elements whenever and wherever they are needed. Nodal perturbation and edge-swap operators are used to reduce mesh bias and to improve crack path geometry represented by a finite element mesh. Adaptive mesh refinement and coarsening schemes are systematically developed in conjunction with edge-split and vertex-removal operators to reduce computational cost. Computational results demonstrate that the potential-based constitutive model with such adaptive operators leads to an effective and efficient computational framework to simulate physical phenomena associated with fracture. In addition, the virtual internal bond model is utilized for the investigation of quasi-brittle material fracture behavior. All the computational models have been developed in conjunction with verification and/or validation procedures.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD