Loading...

Three-Dimensional Cohesive Modeling of Curved Crack Growth in Quasi-brittle Material Using Adaptive Technique

Sharifi, Mahdi | 2011

900 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42052 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Khoei, Amir Reza
  7. Abstract:
  8. Prediction of crack growth is one of the greatest achievements of continuum mechanics in 20th century. However, in spite of Griffith’s achievements, nowadays lots of subjects remain unchallenged in the field of Fracture Mechanics. Concrete and asphalt concrete are two of the most popular material in civil engineering and crack growth prediction in these materials are very important. Cohesive crack model is one of the models which is used for prediction of crack growth in quasi-brittle material such as concrete and it has been used widely in recent years because of simplicity and good agreement with experiment.The aim of this thesis is three-dimensional static and dynamic cohesive modeling of curved crack growth in quasi-brittle material. As a start, two-dimensional bilinear cohesive crack model has extended into three-dimensional model and then static modeling has carried out using this extended three-dimensional bilinear cohesive crack model and implemented in a finite element program. In this algorithm, no previous information about crack growth path is necessary and the media is not necessary to fill with cohesive elements. In this technique in every step, the crack growth direction is determined and then cohesive elements are only inserted in necessary places. The maximum principle stress criterion is employed for predicting the direction of extension of the cohesive crack in order to implement the cohesive elements. This criterion is modified because in three-dimensional problems, the normal to maximum stress direction is a plane instead of a vector. In dynamic crack propagation, a constitutive equation for time dependent cohesive crack was needed. For this matter, a new model is proposed, by investigation of existing models and combination of Bazant’s model and the idea of bilinear model. Furthermore, adaptive finite element technique is used for controlling error. In each step after the predicting the crack growth direction, new finite element mesh is generated in order to keep the error under the desired limit, then cohesive element is added and analysis is continued. In final chapter, some examples are analyzed numerically to demonstrate the validity and applicability of the technique.


  9. Keywords:
  10. Fracture Modeling ; Cohesive Crack ; Crack Growth ; Adaptive Finite Element Method ; Time Dependent Cohesive Crack

 Digital Object List

 Bookmark