Abstract
The fatigue crack initiation phenomenon in metals is essentially associated to the gliding of dislocations and the creation of slip bands which characterize irreversible damaging mechanisms at the grains scale. A multiscale approach is then interesting to establish a link between the scale of the structure submitted to cyclic loading and the scale of damage. Some stress based criteria were previously proposed in this framework based on the shakedown theories, as Dang Van or Papadopoulos ones. The same approach is developed in this paper in the usual Thermodynamics of Irreversible Processes (TIP) framework in order to study the link between dissipation, shakedown and fatigue damage. Some recent results in metals fatigue coming from infrared thermography experiments are then interpreted through the TIP; the proposed framework seems to be particularly relevant to define a more general feature for the study of the fatigue phenomenon.
Highlights
It is well known that the fatigue phenomenon in metals is essentially associated to the gliding of dislocations and the creation of slip bands which characterize irreversible damaging mechanisms at the grains scale
The High Cycle Fatigue (HCF) mesoscopic approach enables an extension of the concepts to Low Cycle Fatigue (LCF) fatigue which will further be addressed
A straightforward link between mechanical dissipation and fatigue damage stems from the high cycle metal fatigue theory of Orowan (1939), and the followers model of Dang Van (1973) and Papadopoulos (1987)
Summary
It is well known that the fatigue phenomenon in metals is essentially associated to the gliding of dislocations and the creation of slip bands which characterize irreversible damaging mechanisms at the grains scale. Mechanisms are the same in all the cases, the fatigue domains depending essentially on the spatial expansion of the plasticity These domains can rather be related to different scales: the grain in a REV in HCF and the complete material volume in LCF. The first extended discussion of the phenomena within a thermodynamical framework was certainly proposed by Luong (1995, 1998) and enables the determination of the fatigue limit by using infrared thermography technique, as illustrated in Fig. 6 coming from Luong (1998) This result is obtained for an XC55 steel specimen in HCF and shows that temperature rise The HCF mesoscopic approach enables an extension of the concepts to LCF fatigue which will further be addressed
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