On The Stability of Superplastic Deformation Using Nonlinear Wavelength Analysis |
| Journal |
Key Engineering Materials (Volume 344) |
| Volume |
Sheet Metal 2007 |
| Edited by |
F. Micari, M. Geiger, J. Duflou, B. Shirvani, R. Clarke, R. Di Lorenzo and L. Fratini |
| Pages |
47-54 |
| DOI |
10.4028/www.scientific.net/KEM.344.47 |
| Online since |
July, 2007 |
| Authors |
Mohammad Nazzal,
Marwan K. Khraisheh
|
| Keywords |
AZ31 Mg Alloy, Finite Element Modeling, Stability Analysis, Superplastic Deformation |
| Abstract |
Optimum variable strain rate forming paths based on two multiscale deformation-based
stability criteria are developed. The first criterion is based on Hart’s linear stability analysis while in
the second criterion; we introduce a modified one dimensional nonlinear long wavelength analysis
introduced by Hutchinson and Neale [7] based on the well known 2-D Marciniak-Kuczynski
criterion. The stability criteria are calibrated for the AZ31 Mg alloy at 400 ºC yielding two different
variable strain rate forming paths. These paths show that the nonlinear wavelength analysis is more
sensitive to strain rate sensitivity and results in larger attainable uniform strains than Hart’s
approach especially at low strain rates. This result is demonstrated through finite element
simulations of a deep rectangular box using pressure profiles derived from the two variable strain
rate forming paths. The FE results clearly illustrate that Hart’s approach underestimates the amount
of uniform deformation and therefore prolongs the forming time to prevent failure compared to the
nonlinear analysis. |
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