Modelling Deformation and Crack Growth in a Dynamic Tear Specimen Using FEA

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Authors
  1. Pussegoda, N.
Corporate Authors
Defence R&D Canada - Atlantic, Dartmouth NS (CAN);BMT Fleet Technology Limited, Kanata Ont (CAN)
Abstract
The report describes modeling the deformation and crack growth in a DT specimen using Finite Element Analysis (FEA). The FE model was based upon a specimen having a fatigue crack grown from the pressed notch to a total crack depth of 14 mm and in this way, varied from the standard pressed notch crack starter. The initiation and growth of the crack from the tip of the pre-existing fatigue crack was modeled for the case of quasi-static monotonic loading to a final depth of 0.6W (W-specimen width). The material models required as input for numerical modeling of deformation was based on real stress-real strain data provided by DRDC (Atlantic) and two failure criteria were evaluated; strain-based (critical strain) or energy based (critical strain energy density) for the simulating growth of the crack. The model output was used to estimate the plastic zone sizes at crack initiation and at a crack extension of 1 mm during monotonic loading. The plastic zone size was in the same order as the specimen thickness indicating extensive plasticity at crack initiation. There was no significant deference in the plastic zone sizes for these two failure criteria. The plastic zone size was also not very sensitive to the three real stress-real strain curves evaluated. Explicit shear lip development was not an outcome from the model results, due to two primary reasons: (a) “different” failure conditions, through the thickness, that are not represented in the surface strains used to obtain the

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Keywords
Dynamic tear;Plastic Zone Radius;Shear lip
Report Number
DRDC-ATLANTIC-CR-2002-181 — Contractor Report
Date of publication
01 Dec 2002
Number of Pages
31
DSTKIM No
CA022689
CANDIS No
519670
Format(s):
CD ROM

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