Polycrystal plasticity as applied to the problem of in-plane anisotropy in rolled cubic metals
A fundamental property of cubic metals is that slip occurs on close-packed planes in close-packed directions, which for the f.c.c. case results in 12 /111/<110> slip systems. This crystallographic restriction on the plastic behavior causes significant crystallographic preferred orientation (texture), hence anisotropy, to develop once a large strain has been imposed. Moreover, whereas annealing can generally ''reset'' the flow stress and ductility, it does not generally randomize the texture: therefore most metallic materials have some degree of texture and consequent anisotropy. The problem of earing in deep drawing can be simply related to the variation of r-value with angle from the rolling direction, i.e. the in-plane anisotropy of the sheet. The r-value can be calculated from a given texture with the use of a polycrystal plasticity model. The Los Alamos polycrystal plasticity (LApp) code is based on the Bishop-Hill single crystal yield surface (SCYS) but with a mildly strain-rate sensitive modification where the stress exponent is of order 30. This modification of the SCYS removes the ambiguity of slip system selection inherent in the Bishop-Hill formulation and permits other phenomena to be treated such as latent hardening and pencil glide. The use of LApp to simulate texture formation and consequent anisotropy is described. Experimental textures in the form of X-ray pole figures are analyzed with a Williams-Imhof-Matthies-Vinel (WIMV) code, as implemented by Kallend, to give full orientation distributions (OD's). The OD obtained this way contains approximately 5000 points on a 5/degree/ by 5/degree/ lattice; this is used to assign weights to approximately 1000 discrete orientations for calculations with LApp. 11 refs., 2 figs.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 5933702
- Report Number(s):
- LA-UR-89-1241; CONF-890772-1; ON: DE89011181; TRN: 89-016531
- Resource Relation:
- Conference: Plasticity '89: international symposium on plasticity, Ton, Japan, 31 Jul 1989; Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ANISOTROPY
COPPER
TEXTURE
CRYSTAL STRUCTURE
CUBIC LATTICES
DRAWING
MATHEMATICAL MODELS
METALS
PLASTICITY
ROLLING
W CODES
COMPUTER CODES
CRYSTAL LATTICES
ELEMENTS
FABRICATION
MATERIALS WORKING
MECHANICAL PROPERTIES
TRANSITION ELEMENTS
360102* - Metals & Alloys- Structure & Phase Studies