Title page for ETD etd-061199-091236


Type of Document Master's Thesis
Author Durandurdu, Murat
URN etd-061199-091236
Title Molecular Statics Simulation in Aluminum
Degree Master of Science
Department Materials Science and Engineering
Advisory Committee
Advisor Name Title
Farkas, Diana Committee Chair
Marand, Hervé L. Committee Member
Reynolds, William T. Jr. Committee Member
Keywords
  • Fracture
  • Dislocations
  • Twinning
  • Cracks
  • Ductility
  • Atomistic Simulation
Date of Defense 1999-06-07
Availability unrestricted
Abstract
Effects of dislocation emission from a mode I crack and of pinning distances on the behavior of the crack and on fracture toughness in aluminum were studied by using the Molecular Statics Technique with atomic interactions described in terms of the Embedded Atom Method.

It was found that aluminum is a ductile material in which the cracks generate dislocations, blunting the cracks. The blunting and the dislocation shielding reduce the local stress intensity factor. Also, twinning, which has not been observed experimentally in Aluminum due to the high stacking fault, was obtained in the simulation. Probably, the low temperature facilitates twin formation.

The applied stress intensity factor required to propagate the crack tip increases at first, and then becomes constant as the maximum distance that the first dislocation can travel away from the crack tip increases. These effects can be attributed to dislocation shielding and crack blunting. The maximum distance of the emitted dislocations from the crack tip is the equilibrium distance for the largest simulation performed (400,000 atoms) while for the smaller simulations the dislocations are hindered by the fixed boundary condition of the model. On the other hand, the total local stress intensity factor at the crack tip and the local stress intensity factor along the slip plane remain basically constant as the maximum distance of the emitted dislocations from the crack tip increases. For distances larger than , these local stress intensity factors start to increase slightly.

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