Premium
AN ASSESSMENT OF CRACK CLOSURE AND THE EXTENT OF THE SHORT CRACK REGIME IN Q1N (HY80) STEEL
Author(s) -
James M. N.,
Knott J. F.
Publication year - 1985
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.1460-2695.1985.tb01202.x
Subject(s) - crack closure , materials science , wake , closure (psychology) , crack growth resistance curve , plasticity , crack tip opening displacement , composite material , structural engineering , mechanics , forensic engineering , fracture mechanics , engineering , physics , market economy , economics
— The paper addresses some aspects of the differences in fatigue crack growth rate behaviour and threshold values obtained for long through‐cracks, short through‐cracks and surface cracks. Attention is focused on plasticity induced closure in the wake behind the growing crack tip. For long cracks at high K max , closure is found to depend in a linear manner on K max , i.e. K op , increases with the size of the monotonic plastic zone. Closure increases at low δ K and this is primarily a consequence of the load shedding procedure. If short through‐cracks are prepared by machining specimens containing long cracks, a substantial part of the plastic wake is removed and this can produce marked effects on the closure contribution during subsequent growth. The length of crack “closed” in a long crack threshold test was found to be of the order of 1 mm. Cracks less than this length exhibited “short crack” behaviour: greater than this length, they behaved as “long cracks”, with plastic wake effects apparently fully operative. Small surface cracks exhibit “long crack” behaviour at lengths as short as 0.2 mm and reasons for this are discussed.