Digital Repository, ICF12, Ottawa 2009

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Dissipation and mean stress effect in HCF and LCF
E. Charkaluk, A. Constantinescu

Last modified: 2013-05-03


Fatigue damage is generally separated in two domains : Low Cycle Fatigue
(LCF) and High Cycle Fatigue (HCF) with a transition between limited and unlimited
endurance. Even if fatigue failure is the result of complex microscopic
phenomena which occur under cyclic loading, the common principal mechanism
responsible of the crack initiation is the plastic strains and the damage
developed in the grains due to irreversible dislocations motion. The essential
difference between HCF and LCF regimes is that the scale of the plastic localization
in a material volume is mesoscopic and respectively macroscopic. A
general framework was already proposed by Charkaluk and Constantinescu [4],
based on plastic dissipation, which allows to propose a unified vision of fatigue
by considering plastic dissipated energy per cycle as a damage indicator. Results
coming from temperature evolution measurements under cyclic loadings
reinforced this proposition but its principal drawback is its independence on
mean stress effect. In HCF as well as in LCF, this effect is then often postulated
with linear relations between shear stress and respectively dissipated energy and
maximal hydrostatic pressure [7, 1].

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