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Title: A Study of Two Approaches to Higher-Order Single Crystal Plasticity

 [1];  [2]
  1. Los Alamos National Laboratory
  2. Georgia Inst of Technology
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Laboratory Directed Research and Development (LDRD) Program
OSTI Identifier:
Report Number(s):
DOE Contract Number:
Resource Type:
Resource Relation:
Conference: ICTAM 2016 ; 2016-08-21 - 2016-08-26 ; Montreal, Canada
Country of Publication:
United States

Citation Formats

Mayeur, Jason Rhea, and McDowell, David L. A Study of Two Approaches to Higher-Order Single Crystal Plasticity. United States: N. p., 2016. Web.
Mayeur, Jason Rhea, & McDowell, David L. A Study of Two Approaches to Higher-Order Single Crystal Plasticity. United States.
Mayeur, Jason Rhea, and McDowell, David L. 2016. "A Study of Two Approaches to Higher-Order Single Crystal Plasticity". United States. doi:.
title = {A Study of Two Approaches to Higher-Order Single Crystal Plasticity},
author = {Mayeur, Jason Rhea and McDowell, David L.},
abstractNote = {},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2016,
month = 8

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  • High-purity tantalum single crystal cylinders oriented with [011] parallel to the cylinder axis were deformed 10, 20, and 30 percent in compression. The engineering stress-strain curve exhibited an up-turn at strains greater than {approximately}20% while the samples took on an ellipsoidal shape during testing, elongated along the [100] direction with almost no dimensional change along [0{bar 1}1]. Two orthogonal planes were selected for characterization using Orientation Imaging Microscopy (OIM): one plane containing [100] and [011] (longitudinal) and the other in the plane containing [0{bar 1}1] and [011] (transverse). OIM revealed patterns of alternating crystal rotations that develop as a functionmore » of strain and exhibit evolving length scales. The spacing and magnitude of these alternating misorientations increases in number density and decreases in spacing with increasing strain. Classical crystal plasticity calculations were performed to simulate the effects of compression deformation with and without the presence of friction. The calculated stress-strain response, local lattice reorientations, and specimen shape are compared with experiment.« less
  • A compilation of recent experimental data on the forward peak resulting from the capture of target electrons into the continuum of bare, partly stripped and neutral projectiles is presented. The impact-parameter dependence and the dependence of the peak shape on the projectile charge state as well as on the angular acceptance is considered. An interpretation is attempted within the second-order Born theory and the impulse approximation. Results from Monte Carlo calculations at lower impact energies are also included.
  • The goal of this work is to formulate a constitutive model for the deformation of metals over a wide range of strain rates. Damage and failure of materials frequently occurs at a variety of deformation rates within the same sample. The present state of the art in single crystal constitutive models relies on thermally-activated models which are believed to become less reliable for problems exceeding strain rates of 10{sup 4} s{sup -1}. This talk presents work in which we extend the applicability of the single crystal model to the strain rate region where dislocation drag is believed to dominate. Themore » elastic model includes effects from volumetric change and pressure sensitive moduli. The plastic model transitions from the low-rate thermally-activated regime to the high-rate drag dominated regime. The direct use of dislocation density as a state parameter gives a measurable physical mechanism to strain hardening. Dislocation densities are separated according to type and given a systematic set of interactions rates adaptable by type. The form of the constitutive model is motivated by previously published dislocation dynamics work which articulated important behaviors unique to high-rate response in fcc systems. The proposed material model incorporates thermal coupling. The hardening model tracks the varying dislocation population with respect to each slip plane and computes the slip resistance based on those values. Comparisons can be made between the responses of single crystals and polycrystals at a variety of strain rates. The material model is fit to copper.« less