Crystallographic texture effects on mixed-mode strain localization for lower-symmetry metals Page: 2 of 4
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CRYSTALLOGRAPHIC TEXTURE EFFECTS ON MIXED-MODE
STRAIN LOCALIZATION FOR LOWER-SYMMETRY METALS
P.J. Maudlin', T.A. Mason', G.T. Gray III', N.K. Bourne2 and J.F. Bingert'
'Los Alamos National Laboratory, MS B216, PO Box 1663, Los Alamos, NM 87545
2Royal Military College of Science, Cranfield, Shrivenham, Swindon SN6 8LA, U.K.
ABSTRACT A bifurcation analysis is used to understand the damage realized in flat-
plate 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 texture/target orientation at impact.
INTRODUCTION: Strain localization resulting from material instability can be the
dominant mechanism in terms of accommodating large deformation. Consider the
example of one-dimensional (1D) compression where the specimen deforms
homogeneously in time and then becomes suddenly unstable resulting in three-
dimensional (3D) shear localization, large deformation and subsequent fracture. This
mechanical test scenario (usually perceived as undesirable) is usually interpreted as the
result of heterogeneous material stock, and is often the basis for rejection of the test
results or labeling the entire stock as "bad material'. In this effort we investigate an
ostensibly 1) plate impact test with post-mortem met llography of the recovered targets
to assess the damage mode (i.e., cavitation and shearing), and correlate the observations
with material bifurcation analysis. The material inve tigated is a highly-textured (basal
texture), pure Zr clock-rolled plate stock mechanically represented by rather classical
elastoplastic constitutive modeling as described by Maudlin et al. . This modeling
is based on standard metallic constitutive relationship s augmented with both elastic and
plastic anisotropy computed from texture measure ents of the initial material. This
elastoplastic information is utilized in an associative ow constitutive formulation using
unrotated (material frame) tensors to ensure materi frame indifference, and thus the
methodology is well suited to lower-symmetry metallic materials.
PROCEDURES, RESULTS AND DISCUSSION:
bifurcation analysis (Rudnicki and Rice ) for t
state-of-stress consistent with plate impact conditii
orientations and straining jumps. The magnitude of tl
in this Zr due to the crystallographic texture is indic-
Fig. 1; the difference in flow stress between the throu
material directions is a factor of four. The direction
further revealed by the yield surface projections
n-plane projection where the anisotropic non-sp
manifestation of the texture will be apparent in the bif
We proceed with an Eigensystem
he Zr plate under an uniaxial strain
ons, calculating localization plane
Le mechanical directionality present
ted by the stress-strain response in
gh-thickness (TT) and in-plane (IP)
ality of the Zr plastic response is
lso in Fig. 1; note the eccentric
serical shape suggests that some
zrcation analysis for this material.
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Maudlin, P. J. (Paul J.); Mason, T. A. (Thomas A.); Gray, G. T. (George T.), III; Bourne, N. K. & Bingert, J. F. (John F.). Crystallographic texture effects on mixed-mode strain localization for lower-symmetry metals, article, January 1, 2003; United States. (digital.library.unt.edu/ark:/67531/metadc934706/m1/2/: accessed January 20, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.