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Prediction of the energy dissipation rate in ductile crack propagation
Author(s) -
ATKINS A. G.,
CHEN Z.,
COTTERELL B.
Publication year - 2003
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 - 10.1046/j.1460-2695.2003.00599.x
Subject(s) - dissipation , necking , materials science , fracture mechanics , monotonic function , shear (geology) , fracture (geology) , crack growth resistance curve , fracture toughness , mechanics , strain energy release rate , crack tip opening displacement , toughness , structural engineering , geometry , composite material , crack closure , thermodynamics , physics , mathematics , mathematical analysis , engineering
In this paper, energy dissipation rate D vs. Δ a curves in ductile fracture are predicted using a ‘conversion’ between loads, load‐point displacements and crack lengths predicted by NLEFM and those found in real ELPL propagation. The NLEFM/ELPL link was recently discovered for the DCB testpiece, and we believe it applies to other cracked geometries. The predictions for D agree with experimental results. The model permits a crack tip toughness R (Δ a ) which rises from J c and saturates out when (if) steady state propagation is reached after a transient stage in which all tunnelling, crack tip necking and shear lip formation is established. J R is always greater than the crack tip R (Δ a ) and continues to rise even after R (Δ a ) levels off. The analysis is capable of predicting the usual D vs. Δ a curves in the literature which have high initial values and fall monotonically to a plateau at large Δ a . It also predicts that D curves for CCT testpieces should be higher than those for SENB/CT, as found in practice. The possibility that D curves at some intermediate Δ a may dip to a minimum below the levelled‐off value at large Δ a is predicted and confirmed by experiment. Recently reported D curves that have smaller initial D than the D ‐values after extensive propagation can also be predicted. The testpiece geometry and crack tip R (Δ a ) conditions required to produce these different‐shaped D vs. Δ a curves are established and confirmed by comparison with experiment. The energy dissipation rate D vs. Δ a is not a transferable property as it depends on geometry. The material characteristic R (Δ a ) may be the ‘transferable property’ for scaling problems in ELPL fracture. How it can be deduced from D vs. Δ a curves (and by implication, J R vs. Δ a curves) is established.