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Overload effects on local fatigue crack-tip strain fields in plane stress samples
Last modified: 2011-02-25
Abstract
Conventional linear elastic fracture mechanics (LEFM) provides a rigorous basis for analysing subcritical
crack growth in terms of parameters (e.g. stress intensity factor (K), CTOD, J) that capture the local
conditions at the crack-tip, yet can be determined solely in terms of external, macroscopic loading and
geometrical parameters. However in many cases (e.g. for variable loading) the stress at the crack-tip cannot
easily be inferred solely from a global approach and local information is required. The advent of 3rd generation
synchrotron facilities has opened up the possibility of measuring local crack-tip strains under both plane strain
and plane stress. In this work, the behaviour of the crack-tip before, during, immediately after an overload event
is examined for fatigue cracks in thin (plane stress) stainless steel CT specimens. X-ray diffraction has revealed
large compressive residual stresses ahead of the crack, but no evidence for plasticity induced closure behind the
crack-tip.
crack growth in terms of parameters (e.g. stress intensity factor (K), CTOD, J) that capture the local
conditions at the crack-tip, yet can be determined solely in terms of external, macroscopic loading and
geometrical parameters. However in many cases (e.g. for variable loading) the stress at the crack-tip cannot
easily be inferred solely from a global approach and local information is required. The advent of 3rd generation
synchrotron facilities has opened up the possibility of measuring local crack-tip strains under both plane strain
and plane stress. In this work, the behaviour of the crack-tip before, during, immediately after an overload event
is examined for fatigue cracks in thin (plane stress) stainless steel CT specimens. X-ray diffraction has revealed
large compressive residual stresses ahead of the crack, but no evidence for plasticity induced closure behind the
crack-tip.
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