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CORRELATION OF FATIGUE CRACK GROWTH BEHAVIOUR WITH CRACK CLOSURE IN PEENED SPECIMENS
Author(s) -
Zhu X. Y.,
Shaw W. J. D.
Publication year - 1995
Publication title -
fatigue and fracture of engineering materials and structures
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.887
H-Index - 84
eISSN - 1460-2695
pISSN - 8756-758X
DOI - 10.1111/j.1460-2695.1995.tb00906.x
Subject(s) - materials science , crack closure , peening , shot peening , paris' law , residual stress , crack growth resistance curve , fracture mechanics , metallurgy , composite material , structural engineering , engineering
Various residual stress conditions were introduced into the surface of a 7075‐T6 aluminium alloy by shot peening. This resulted in a considerable alteration in subsequent fatigue crack growth behaviour. A systematic investigation into the effects of a variety of conditions on fatigue crack propagation behavior was conducted. The degree of shot peening was established using the Almen scale and calibration strips. Changes occurred in crack re‐initiation lives, crack growth rate and hardness across the thickness profile. Residual stresses were introduced by various peening operations (such as different peening positions and loading specimens prior to and during peening). By measuring the crack opening level of peened specimens, changes in fatigue crack closure effect with respect to the crack extension in CT specimens are reported. The relations of re‐initiation life versus crack opening level and Almen levels, and of the crack closure effect versus Almen scales, were addressed experimentally. It was found that the improvement in re‐initiation life and the retarding effect of crack growth, both influenced by the Almen scales, are associated directly with the elevation of crack opening level, particularly at the stage of crack re‐initiation.