Mesh dependence of failure criteria


  1. Link, R.
Corporate Authors
Defence R&D Canada - Atlantic, Dartmouth NS (CAN);MARTEC Ltd, Halifax NS (CAN)
For finite element analyses, the equivalent uniaxial stress-strain curve is commonly used to characterize constitutive models for metals. Practically, this amounts to obtaining experimental results from a load vs. axial extension curve which is converted to a stress-strain curve suitable for use in FEA analysis. The exact form of the curve is dependent on the problem formulation used; for large strain analysis, a true stress-true strain curve is usually employed. The constitutive characterization of uniaxial tests is complicated by two main factors. Firstly, non-uniform straining, or necking, occurs after the ultimate engineering stress has been reached, in essence nullifying the assumption of a uniaxial stress field. Secondly, because of the non-uniform straining, it has been shown that strain localizations occur that lead to numerical results dependent on mesh refinement. In this study, the effect of element size on failure strains for WT350 steel uniaxial tensile specimens was investigated. Two tension specimens of varying thickness were modelled using LS-DYNA with ten different element sizes using hexahedral and shell elements. It was found that the failure strains exhibited a marked dependence on element size, and that for practical FE analysis, constitutive models for necking as a function of element size should be investigated.

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Report Number
DRDC-ATLANTIC-CR-2011-240 — Contractor Report
Date of publication
01 Sep 2011
Number of Pages
Electronic Document(PDF)

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