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The evolution of crack-tip stresses during a fatigue overload event

Steuwer, Axel LU ; Rahman, M.; Shterenlikht, A.; Fitzpatrick, M. E.; Edwards, L. and Withers, P. J. (2010) In Acta Materialia 58(11). p.4039-4052
Abstract
The mechanisms responsible for the transient retardation or acceleration of fatigue crack growth subsequent to overloading are a matter of intense debate. Plasticity-induced closure and residual stresses have often been invoked to explain these phenomena, but closure mechanisms are disputed, especially under conditions approximating to generalised plane strain. In this paper we exploit synchrotron radiation to report very high spatial resolution two-dimensional elastic strain and stress maps at maximum and minimum loading measured under plane strain during a normal fatigue cycle, as well as during and after a 100% overload event, in ultra-fine grained AA5091 aluminium alloy. These observations provide direct evidence of the material stress... (More)
The mechanisms responsible for the transient retardation or acceleration of fatigue crack growth subsequent to overloading are a matter of intense debate. Plasticity-induced closure and residual stresses have often been invoked to explain these phenomena, but closure mechanisms are disputed, especially under conditions approximating to generalised plane strain. In this paper we exploit synchrotron radiation to report very high spatial resolution two-dimensional elastic strain and stress maps at maximum and minimum loading measured under plane strain during a normal fatigue cycle, as well as during and after a 100% overload event, in ultra-fine grained AA5091 aluminium alloy. These observations provide direct evidence of the material stress state in the vicinity of the crack-tip in thick samples. Significant compressive residual stresses were found both in front of and behind the crack-tip immediately following the overload event. The effective stress intensity at the crack-tip was determined directly from the local stress field measured deep within the bulk (plane strain) by comparison with linear elastic fracture mechanical theory. This agrees well with that nominally applied at maximum load and 100% overload. After overload, however, the stress fields were not well described by classical K fields due to closure-related residual stresses. Little evidence of overload closure was observed sometime after the overload event, in our case possibly because the overload plastic zone was very small. Crown Copyright (C) 2010 Published by Elsevier Ltd. on behalf of Acta Materialia Inc. All rights reserved. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
field, crack-tip stress, Plasticity-induced closure, Stress intensity factor, Overload, Retardation
in
Acta Materialia
volume
58
issue
11
pages
4039 - 4052
publisher
Elsevier
external identifiers
  • wos:000278562800023
  • scopus:78449263067
ISSN
1873-2453
DOI
10.1016/j.actamat.2010.03.013
language
English
LU publication?
yes
id
f8f13201-64ca-4965-8462-68040a3a9e2e (old id 1631602)
date added to LUP
2010-07-21 10:31:54
date last changed
2018-05-29 12:13:26
@article{f8f13201-64ca-4965-8462-68040a3a9e2e,
  abstract     = {The mechanisms responsible for the transient retardation or acceleration of fatigue crack growth subsequent to overloading are a matter of intense debate. Plasticity-induced closure and residual stresses have often been invoked to explain these phenomena, but closure mechanisms are disputed, especially under conditions approximating to generalised plane strain. In this paper we exploit synchrotron radiation to report very high spatial resolution two-dimensional elastic strain and stress maps at maximum and minimum loading measured under plane strain during a normal fatigue cycle, as well as during and after a 100% overload event, in ultra-fine grained AA5091 aluminium alloy. These observations provide direct evidence of the material stress state in the vicinity of the crack-tip in thick samples. Significant compressive residual stresses were found both in front of and behind the crack-tip immediately following the overload event. The effective stress intensity at the crack-tip was determined directly from the local stress field measured deep within the bulk (plane strain) by comparison with linear elastic fracture mechanical theory. This agrees well with that nominally applied at maximum load and 100% overload. After overload, however, the stress fields were not well described by classical K fields due to closure-related residual stresses. Little evidence of overload closure was observed sometime after the overload event, in our case possibly because the overload plastic zone was very small. Crown Copyright (C) 2010 Published by Elsevier Ltd. on behalf of Acta Materialia Inc. All rights reserved.},
  author       = {Steuwer, Axel and Rahman, M. and Shterenlikht, A. and Fitzpatrick, M. E. and Edwards, L. and Withers, P. J.},
  issn         = {1873-2453},
  keyword      = {field,crack-tip stress,Plasticity-induced closure,Stress intensity factor,Overload,Retardation},
  language     = {eng},
  number       = {11},
  pages        = {4039--4052},
  publisher    = {Elsevier},
  series       = {Acta Materialia},
  title        = {The evolution of crack-tip stresses during a fatigue overload event},
  url          = {http://dx.doi.org/10.1016/j.actamat.2010.03.013},
  volume       = {58},
  year         = {2010},
}