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Investigation of Formability of Magnesium Sheets Using Hot FLD Testing and Comparison with Simulation

Anooshei, Hamed | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58332 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Akbarzadeh, Abbas
  7. Abstract:
  8. This study investigates the formability of AZ31B magnesium alloy under elevated temperatures and varying strain rates. Initially, the experimental die was designed and modeled using SolidWorks. Subsequently, thermal analysis of the die was conducted in ANSYS to ensure uniform temperature distribution during the process. Formability tests were performed at temperatures of 220, 280, and 330°C. At 330°C, the effects of strain rates (0.05 s⁻¹, 0.02 s⁻¹, and 0.003 s⁻¹) were examined to evaluate the combined influence of temperature and strain rate on the alloy’s formability. To calculate strains and construct Forming Limit Diagrams (FLDs), circular grids were electrochemically etched onto the specimens. Post-deformation, strains at various surface points were measured, and FLDs were plotted for each temperature and strain rate. Microstructural analyses were conducted to assess structural changes under different conditions. Additionally, anisotropy tests were performed to evaluate the dependence of the alloy’s mechanical properties on orientation. Results demonstrated that the alloy’s formability improves with increasing temperature and decreasing strain rate. Specifically, the FLD₀ value increased from 0.32 to 0.48 with rising temperature and from 0.41 to 0.58 with decreasing strain rate at 330°C. Microstructural analyses revealed that higher temperatures promote the activation of slip systems and dynamic recrystallization, enhancing deformation behavior. Furthermore, anisotropy tests indicated a reduction in anisotropy with increasing temperature, with the R̅ value decreasing from 2.67 at ambient temperature to 1.42 at 330°C. To analyze the plastic deformation characteristics, numerical simulations were implemented in Abaqus using the BBC2008, Barlat YLD2000-2d, and Hill1979 yield criteria. Comparison of simulation results with experimental data showed that the BBC2008 and Barlat YLD2000-2d criteria, by accurately modeling plastic anisotropy and the HCP structure’s anisotropic behavior, provided precise predictions of limiting strains and stress distributions. However, the Hill1979 criterion exhibited lower agreement due to oversimplified assumptions. These findings underscore the importance of employing advanced yield criteria for reliable simulation of AZ31B alloy formability
  9. Keywords:
  10. Forming Limit Diagram (FLD) ; Formability ; Simulation ; AZ31B Alloy ; Solid Work Software ; AZ31 Magnesium Alloy

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