J. Phys. IV France 10 (2000) Pr9-565-Pr9-570
Fatigue acceptable damage threshold and fatigue failure threshold according to a residual impact behaviour of an aluminium alloyC. Froustey1, T. Auzanneau1, 2, J.-L. Charles1 and J.-L. Lataillade1
1 LAMEFIP, Damage Mechanics, Reliability of Materials and Processes Engineering Laboratory, École Nationale Supérieure d'Arts et Métiers, Esplanade des Arts et Métiers, 33405 Talence cedex, France
2 Precision and Intelligence Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-5961, Japan
In a competitive economical context that nevertheless aims at gaining in safety, it is necessary to take into account the resistance of structural components in relation to their thermomechanical histories. Particularly, fatigue preloading influence with regard to residual dynamic strength is crucial, especially in the case of light alloys used in transport and aeronautic industries. The study has been carried out on a 2017A T3 aluminium alloy. To fatigue predamage, tensile-compression loadings are performed and the residual dynamic behaviour is characterized with tensile loading at the speed of 5 ms-l. Since a direct correlation between predamage configuration and residual response is not easy because of the high scattering effects with regard to fatigue phenomenon, an hybrid modal analysis method - sound emission / numerical - is used to detect the predamage level. Then, according to the classification obtained by this way, the evolution of the mechanical properties of pre-fatigued material under impact loading allows to define the best mechanical parameter for boundary thresholds determination between no-damage influence and weakened states. Hence, an acceptable damage threshold -damaged critical volume for which impact toughness is not affected by fatigue preloading- and a failure threshold -damaged critical volume for which we observe a fall of the mechanical properties- are established. Therefore, it is possible to estimate the fracture energy under impact loading for prefatigued specimens and therefore to predict a safe or a dangerous behaviour.
© EDP Sciences 2000