Loading...

Modeling of Large Deformation Frictional Contact Using the Augmented-Lagrange Method

Taheri Mousavi, Mohaddese | 2009

440 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 39497 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Khoei, Amir Reza
  7. Abstract:
  8. The numerical modeling of engineering contact problems is one of the most difficult and demanding tasks in computational mechanics. Frictional contact can be observed in many problems; such as: crack propagation, metal forming operation, drilling pile etc. In metal forming operations the required shape changes are obtained by either of forming process, such as pressing, hammering, rolling or extruding the material between the tools which are much stiffer than shaped material. Because of large difference between deformability of the tool and material, relative movements occur in contact area. These relative movements produce the normal and tangential stresses, which have important role on metal flow and may cause serious in homogeneities in works products. Basically, Penalty method have been employed in the finite element solution of contact problems; another method for enforcing constraints is the augmented-Lagrangian technique and this method dosenot have the problem of the penalty method. In this paper, the augmented Lagrangian technique is employed to enforce constraints. The objective is to minimize the disadvantages of the penalty and Lagrange multiplier methods. It has an iteration procedure. The iteration begins with solving the nodal displacements and computing the contact forces using a simple penalty method. If the force is not small enough to ensure a sufficient convergence, the procedure will be repeated using an updated augmented force. For modeling plasticity theory of friction, the Coulomb's law of perfect friction has been used. The numerical modeling of frictional contact between the tool and material has characterized by the use of interface element. The top nodes of the interface elements are used to monitor contact with the tool. When the contact is registered, the appropriate integration points within the interface element become active and the frictional resistance is simulated. This method is independent of the magnitude of penalty number; avoiding the ill conditioning of the stiffness matrices. Also, the constraints are satisfied within a user defined required tolerance. This algorithm can be used effectively for applications where the contact pressures become very large in comparison with the material elastic parameters i.e. with rubber materials
  9. Keywords:
  10. Frictional Contact ; Augmented-Lagrangian Method ; Coulomb's Law ; Node to Edge Method

 Digital Object List

 Bookmark

No TOC