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Evaluation of a semi-implicit numerical algorithm for a rate-dependent ductile failure model.

Description: A survey conducted in the mid-80's revealed that the mathematical descriptions of ductile fracture tended to apply to either tensile tests or spa11 tests. The objective behind the development of the TEPLA was then a unification of these disparate phenomena into a single model.
Date: September 1, 2002
Creator: Zocher, M. A. (Marvin Anthony); Zuo, Q. K. (Qiuhai K.) & Mason, T. A. (Thomas A.)
Partner: UNT Libraries Government Documents Department

Advanced characterization of twins using automated EBSD

Description: This poster describes resuns obtained using an automated, crystallographically-based technique for twin identification. The technique is based on the automated EBSD. The key features of the analysis are identification of potential twin boundaries by their misorientation character, identification of the distinct boundary planes among the symmetrically equiwlent candidates. and validation of these boundaries through comparison with the boundary and twin plane traces in the sample cross section. Results on the application of this technique to deformation twins in zirconium are analyzed for the effect of twin type and amount and sense of uniaxial deformation. The accumulation of strain tends to increase the misorientation deviation at least to the degree of the trace deviation compared with recrystalllzation twins in nickel.
Date: January 1, 2002
Creator: Wright, S. I. (Stuart I.); Bingert, J. F. (John F.); Mason, T. A. (Thomas A.) & Larsen, Ryan J.
Partner: UNT Libraries Government Documents Department

Advanced characterization of twins using automated electron backscatter diffraction

Description: This paper describes results obtained using an automated, crystallographically-based technique for twin identification. The technique is based on the automated collection of spatially specific orientation measurements by electron backscatter diffraction (EBSD) in the scanning electron microscope (SEM). The key features of the analysis are identification of potential twin boundaries by their misorientation character, identification of the distinct boundary planes among the symmetrically equivalent candidates, and validation of these boundaries through comparison with the boundary and twin plane traces in the sample cross section. Results on the application of this technique to deformation twins in zirconium are analyzed for the effect of twin type and amount and sense of uniaxial deformation. The accumulation of strain tends to increase the misorientation deviation at least to the degree of the trace deviation compared with recrystallization twins in nickel. In addition to the results on characterizing the twin character, results on extending the twin analysis to automated identification of parent and daughter material for structures exhibiting twin deformation are reported as well.
Date: January 1, 2002
Creator: Wright, S. I. (Stuart I.); Bingert, J. F. (John F.); Mason, T. A. (Thomas A.) & Larson, R. J. (Ryan J.)
Partner: UNT Libraries Government Documents Department

Crystallographic texture effects on mixed-mode strain localization for lower-symmetry metals

Description: A bifurcation analysis is used to understand the damage realized in flatplate gas-gun specimens that were machined from a highly-textured plate stock of Zr. These low-symmetry material specimens were tested to insipient failure and subsequently soft-recovered. Post-mortem data sets consisting of EBSD imaging of metallographic samples cut from the recovered targets show very different texture-dependent damage morphologies depending on the initial texturekarget orientation at impact.
Date: January 1, 2003
Creator: Maudlin, P. J. (Paul J.); Mason, T. A. (Thomas A.); Gray, G. T. (George T.), III; Bourne, N. K. & Bingert, J. F. (John F.)
Partner: UNT Libraries Government Documents Department

Zirconium deformation behavior: insights from EBSD measurements.

Description: The deformation of crystal-bar zirconium was investigated as a function of strain and strain rate through electron back-scattered diffraction (EBSD) characterization. The resultant data provided spatially resolved information on microstructure and texture evolution, individual twin system activity, and subsequent strain partitioning between twinned volume and parent grains. A range of deformation conditions was represented through quasi-static compression, 4-point beam bend tests at room and cryogenic temperature, and Taylor cylinder impact experiments. Effects from the interplay between slip and twinning deformation modes on anisotropic plasticity are considered in order to address the apparent trend toward isotropy at high rates. The role of various length scales on deformation behavior will be considered, along with the implications of these length scales on the assumptions typically invoked for plasticity modeling.
Date: January 1, 2001
Creator: Bingert, J. F. (John F.); Mason, T. A. (Thomas A.); Kaschner, G. C. (George C.); Maudlin, P. J. (Paul J.) & Gray, G. T. (George T.), III
Partner: UNT Libraries Government Documents Department