Embrittlement of an elasto-plastic medium by an inclusion
File(s)
Published version
Author(s)
Cimbaro, Luca
Sutton, adrian
Balint, Daniel
Paxton, Anthony
Hardy, Mark
Type
Journal Article
Abstract
A mathematical model for the embrittlement of a long elastic-plastic crack by a relatively small, misfitting inclusion is presented. The model makes direct contact with the Dugdale–Bilby–Cottrell–Swinden model as a limiting case. The particular case of an oxide inclusion with a triangular cross-section at the tip of an intergranular crack in the Ni-based superalloy RR1000 at 650∘C is considered. The positive misfit of the intrusion provides an additional tensile load on the crack tip and on the plastic zone, raising the local stress intensity factor kI and the crack tip opening displacement Δu above those when the inclusion is replaced by a dislocation-free zone of the same length. It is shown that for a given misfit strain and inclusion shape, the enhancement of kI and Δu is controlled by a dimensionless parameter ω=(σ/σ1)c/(2l)−−−−−√ where σ is the applied stress, σ1 is the yield stress, c is the crack length and l is the length of the inclusion. The anti-shielding effect of the intrusion is significant only when ω≲6. As a result of the anti-shielding effect of the intrusion, the stress singularity at the crack tip always exceeds the compressive normal stress that exists within the thickest part of the intrusion when it is isolated. It is also shown that the gradient of the hydrostatic stress within the intrusion subjected to different applied stresses drives the oxygen diffusion and, hence, assists the oxidation at the grain boundary. The fracture toughness is considerably greater than that of a bulk sample of the oxide particle, which we attribute to the plastic zone.
Date Issued
2019-03
Date Acceptance
2019-01-11
Citation
International Journal of Fracture, 2019, 216 (1), pp.87-100
ISSN
0376-9429
Publisher
Springer Verlag
Start Page
87
End Page
100
Journal / Book Title
International Journal of Fracture
Volume
216
Issue
1
Copyright Statement
© The Author(s) 2019. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
Sponsor
Engineering and Physical Sciences Research Council
Rolls Royce Plc
Identifier
https://link.springer.com/article/10.1007%2Fs10704-019-00344-2
Grant Number
EP/L015579/1
2200-00074140
Subjects
Science & Technology
Technology
Materials Science, Multidisciplinary
Mechanics
Materials Science
Fracture
Inclusion
Embrittlement
Dugdale-Bilby-Cottrell-Swinden model
Ni-based superalloys
FATIGUE-CRACK-GROWTH
FREE ZONE MODEL
GRAIN-BOUNDARY OXIDATION
HIGH-TEMPERATURE
TIP OXIDATION
CYCLE FATIGUE
SUPERALLOY
MECHANISM
FRACTURE
STRESS
Mechanical Engineering & Transports
0905 Civil Engineering
0912 Materials Engineering
0913 Mechanical Engineering
Publication Status
Published
Date Publish Online
2019-02-19