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Finite Element Modeling of Cohesive Crack Growth Using Adaptive Mesh Refinement

Majd Ardakani, Keivan | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: English
  3. Document No: 39250 (53)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Khoei, Amir Reza
  7. Abstract:
  8. Under Linear Elastic Fracture Mechanics (LEFM) assumptions, the stress at the crack tip is theoretically infinite. Clearly all materials have a finite strength, thus there will always be a plastified zone around the crack tip. If the size of plastic zone is not small compared to the crack size, then linear elastic assumptions are not applicable and a nonlinear model must be used. This damaged zone is referred to as a plastic zone for metals, and a fracture process zone for cementitious materials and ceramics. In this regard a discrete extrinsic cohesive crack model with bilinear traction separation constitutive law, i.e. softening function, is employed and crack propagation is investigated. The quality of mesh is steadily improved, during the crack growth, by the means of an adaptive mesh refinement technique. ‘A-posteriori’ error estimator together with a mesh generator which uses h-refinement method to generate the refined mesh is used. In order to improve the accuracy of adaptive mesh refinement, recovery solution calculated using Superconvergent Patch Recovery (SPR) technique, with polynomial order of 2, is replaced with exact solution which is unavailable. In this study mode I fracture will be investigated for a Single Edged notched Beam (SEB) and mixed-mode fracture will be investigated for a SEB, a plate with two holes and a concrete dam. The Results obtained show good agreement with experimental data and previous works in this area.
  9. Keywords:
  10. Cohesive Crack Model ; Adaptive Finite Element Method ; Mesh Refinement ; Superconvrgent Patch Recovery (SPR)Three Dimentional Method

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