Description
- Abstract:
- When deformed at elevated temperature and slow strain rates, some Al alloys exhibits superplasticity, the ability to sustain very large tensile elongations (sometimes over 1000%) prior to failure in a generally isotropic manner. This property has been exploited in industrial manufacturing processes such as superplastic forming and quick plastic forming. This dissertation investigated some aspects that are related to the deformation and failure of Al alloys at elevated temperature with numerical simulations of multiple time and length scales. First, a finite element method rigorously accounts for three main deformation mechanisms in superplasticity, namely the grain interior plasticity, grain boundary diffusion and grain boundary sliding is given. The method was used to predict the constitutive response and contribution of each mechanism to the total plastic strain based on microstructures of an assembly of grains. The microstructure finite element model is also used to conduct a systematic study of the mechanisms of void growth in polycrystalline Al AA5083 during elevated temperature straining. Second, to further understand the nature of grain boundary sliding, molecular dynamics simulations are used to investigate the effect of vacancies, Si and Mg impurities in the Al grain boundaries on grain boundary sliding. Finally, a multi-scale approach that links the microstructure based finite element model to the continuum scale finite element simulations of elevated temperature forming of Al alloys is proposed and used to study the bulge forming process. The work of this dissertation should be useful toward making reliable quantitive predictions of Al and similar superplastic alloys, and ultimately modifying and designing engineered superplastic materials that is suitable for various purposes.
- Notes:
- Thesis (Ph.D.) -- Brown University (2010)
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Citation
Du, Ningning,
"Multi-scale Modeling of Deformation and Failure Mechanisms of Al Alloys at Elevated Temperature"
(2009).
Mechanics of Solids Theses and Dissertations, Engineering Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://doi.org/10.7301/Z0445JSH
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Mechanics of Solids Theses and Dissertations
Theses and Dissertations for the Mechanics of Solids department.... -