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OVERLOAD RETARDATION OF FATIGUE CRACK GROWTH IN A 9%Cr 1%Mo STEEL AT ELEVATED TEMPERATURES
Author(s) -
Cotterill P. J.,
Knott J. F.
Publication year - 1993
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.1460-2695.1993.tb00070.x
Subject(s) - materials science , crack closure , paris' law , residual stress , plasticity , growth retardation , metallurgy , composite material , fracture mechanics , pregnancy , genetics , biology
This paper describes an investigation into the effects of a single‐peak tensile overload on fatigue crack propagation in a 9%Cr 1 %Mo steel. Overloads were applied during cycling at a constant stress intensity range (Δ K ), and any consequent transients in growth rate were recorded. The severity of retardation rises as the magnitude of the applied overload is increased. The effect of temperature is complex, but a 525˚C retardation is significantly less marked than at 25 or 225˚C. Signs of crack face contact are seen on post‐overload fracture surfaces, but there is little crack branching. The dominant cause of overload retardation in this steel appears to be plasticity‐induced closure. At 525˚C, post‐overload dwell periods significantly reduce the severity of retardations. This is not observed at lower temperatures, indicating that the residual clamping stresses that lead to closure are gradually relieved at 525˚C.