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Development of a Temperature-Dependent Constitutive Model for Anisotropic Metal Diaphragm Using Experimental Method

Ashrafian, Mohammad Mahdi | 2021

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 53980 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Hosseini Kordkheili, Ali
  7. Abstract:
  8. The purpose of this thesis is to use experimental and numerical tools to develop new constitutive models based on the Johnson Cook's model to predict the plastic deformation and failure of metallic diaphragms. Initially as the first case study, by designing and constructing a bulge test mechanism, the elastic-plastic behavior of 0.05 mm thickness pure aluminum diaphragms for a temperature range of 25-150℃ and large strains was extracted. Then, by presenting an innovative method, the biaxial stress-strain curves are transformed into uniaxial curves. By examining the observed behavior, a new constitutive model is developed based on the Johnson Cook's model. The ability of this constitutive model to predict the diaphragm’s plastic deformation at hot temperatures has been demonstrated by numerical simulations. In the second part of the thesis, by stretching the sample tests in different directions, it was found that the pure aluminum shell shows anisotropic behavior. The effects of this anisotropy on the hardening and yield behavior of material have been investigated. The results of numerical analysis indicate that the way of considering this anisotropy has an ignorable effect on the rupture behavior of the diaphragm. Finally, the development approach which is applied in this dessertation is employed to improve the Johnson-Cook constitutive model to provide an efficient viscoplastic characteristic model for predicting the stress-strain behavior of Ti-6Al-4V plates at very hot temperatures, as the second case study. The results show that the developed model has been able to provide better accuracy than the well-known constitutive models of Johnson-Cook and Arrhenius
  9. Keywords:
  10. Constitutive Model ; Stress-Strain Diagrams ; Johnson-Cook Model ; Plastic Deformation ; Titanium Alloy 6AL-4V ; Pure Aluminum Diaphragm

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