Technique d'observation de surface in situ (TOSIS) :

Applications à l’étude du phénomène de fissuration par fatigue-corrosion basse fréquence

In situ surface observation technique (issot) : applications to low frequency corrosion fatigue

Laboratoire de Mécanique Physique, URA CNRS 867, Université Bordeaux I

Abstract

An optical method named In Situ Surface Observation Technique (ISSOT) is presented in this paper. This method is used to detect crack nucleation from a flaw (here a pit) at mesoscopic scale during a triangular push-pull cycling test under the control of charge amplitude in aqueous solution ofMgCl2 at 117°C.

It can be found that the crack initiation time determined by using this technique represents 2 % of that estimated from a mechanical criterion. Moreover, the follow of the crack tip evolution by the ISSOT allows to measure average local crack growth rates. It has been shown that the variations of the latter were related to the effects of barriers such as grain boundaries, twin boundaries and grain boundaries triple junction.