Development of a Micromechanical Failure Model

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Authors
  1. Link, R.
  2. Jiang, L.
  3. Yuen, B.
Corporate Authors
Defence Research and Development Canada, Atlantic Research Centre, Halifax NS (CAN);MARTEC Ltd, Halifax NS (CAN)
Abstract
Steels exhibit a competitive failure mechanism that is dependent upon both temperature and strain rate. At elevated temperatures and relatively low strain rates, the failure mechanism is dominated by plastic void nucleation, growth and eventual void coalescence, while at lower temperatures and higher strain rates, a cleavage failure mechanism dominates. The competition between these micro-mechanisms determines the macroscopic fracture resistance and is quantified empirically through the ductile to brittle transition curves. The defence problem relates to capability of predicting when brittle fracture or ductile behaviour is expected under severe environmental or threat conditions, and help in the specification of material requirements to resist brittle fracture. A micro-mechanical failure model suitable to numerically model the ductile to brittle transition temperature in steels was investigated. Following a review of relevant approaches, the Johnson Cook Gurson constitutive equations were implemented within a user-defined material model in order to simulate the temperature and rate dependent ductile failure process. Cleavage fracture was modelled using a maximum principle stress criterion. The model was calibrated and validated against a dynamic tear specimen and reproduced the experimental ductile-to-brittle transition behaviour. Additional simulations involving polyurea coated steel dynamic tear specimens were modeled in order to determine whether the micro-mechanical fail
Keywords
FEM;user defined material model;LS-DYNA
Report Number
DRDC-ATLANTIC-CR-2012-183 — Contract Report
Date of publication
01 Nov 2012
Number of Pages
70
DSTKIM No
CA041580
CANDIS No
802780
Format(s):
Electronic Document(PDF)

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