Open AccessStrain-gradient effect on the crack tip dislocations density
Author(s) -
V.N. Shlyannikov,
A.V. Tumanov,
R. Khamidullin
Publication year - 2020
Publication title -
frattura ed integrità strutturale
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.368
H-Index - 19
ISSN - 1971-8993
DOI - 10.3221/igf-esis.54.14
Subject(s) - materials science , dislocation , crack tip opening displacement , plasticity , crack closure , crack growth resistance curve , finite element method , mechanics , strain hardening exponent , composite material , structural engineering , fracture mechanics , physics , engineering
In this study, the influence of a material’s plastic properties on the crack tip fields and dislocation density behavior is analytically and numerically analyzed using the conventional mechanism-based strain-gradient plasticity (CMSGP) theory established using the Taylor model. The material constitutive equation is implemented in a commercial finite element code by a user subroutine, and the crack tip fields are evaluated with novel parameters in the form of the intrinsic material length, characterizing the scale over which gradient effects become significant. As a consequence of the strain-gradient contribution, FE results show a significant increase in the magnitude of the stress fields of CMSGP when the material length parameter is considered. It is found that the density of geometrically necessary dislocations (GND) is large around the crack tip, but it rapidly decreases away from the crack tip. On the contrary, the density of statistically stored dislocations (SSD) is not as large as geometrically necessary dislocations around the crack tip, but it decreases much slower than GND away from the crack tip. A couple effect of material work hardening and the crack tip distance is identified.