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Investigation on Thermo-mechanical Behavior of AA5086 During Warm and Hot Rolling Operation

Asgharzadeh, Amir | 2014

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 46722 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Serajzadeh, Siamak
  7. Abstract:
  8. A mathematical model has been proposed to estimate the deformation pattern and the required power in cold plate rolling using the stream function method and upper bound theorem. In the first place admissible velocity distributions as well as the geometry of deformation zone were derived from the proposed stream functions. Then, the optimum velocity field was obtained by minimization of the power function computed based on the upper bound theorem. Then a steady state heat transfer equation has been solved in whole model using finite element method. In order to verify the predictions, rolling experiments on aluminum plates were conducted and also, a finite element analysis performed employing Abaqus/Explicit was carried out. The predicted deformation zone was then compared with the experimentally measured region as well as with the results of the finite element analysis. In addition of this work, warm and hot rolling behaviors of AA5086 were studied. Firstly, thermo-mechanical responses of the alloy were determined employing mathematical modeling performed by the finite element software, Abaqus/Explicit, and then the effects of process parameters including initial temperature and rolling speed on the distributions of temperature and plastic strain were investigated. In the next stage, rolling experiments at elevated temperatures were conducted under various deformation conditions and the changes in microstructure and mechanical properties were evaluated by means of tensile testing, hardness measurements, microstructural observations and the results of mathematical modeling. The results showed that the predicted deformation zone geometry and the temperature fit reasonably with the experimental results while much lower computational cost needs comparing to the fully finite element analysis. The results of mechanical testing showed that yield stress and hardness of the rolled plate decreased by increasing the rolling temperature and strain rate. Furthermore, non-uniform distributions of plastic strain and temperature were developed along thickness direction during rolling operations particularly for the case of hot rolling processes. As a result, it resulted in a non-uniform microstructure development in this direction. As a result, it resulted in a non-uniform microstructure development in this direction. Furthermore, partially recrystallized structure was clearly detected within the specimen rolled at 360°C while the fully recrystallized grains was observed for the case of rolling with initial temperature of 480°C
  9. Keywords:
  10. Stream Function ; Upper Bound Method ; Finite Element Method ; Dynamic Strain Aging ; Shear Band ; Rolling Process

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