Approche probabiliste de la rupture fragile et ductile à grandes vitesses de déformations

Abstract : In this work we have examined fracture initiations mechanisms on notches under dynamic loadings. Two kinds of fractures where examined : the brittle fracture of a glass and a molybdenum alloy TZM and the ductile fracture of a XC18 steel. Our work point out the interest of using notched specimens instead of craked specimens for fracture toughness evaluation and justifies the notch stress intensity factor approach. We have observed that the fracture mecanisms under static and dynamic loads are the same. However we have noticed an increase in the scattering of results in both types of fracture. This increase is explained by the multiactivation mecanism of structure defects. We have particulary shown this point for ductile fracture by observation of the number of cavity per fractured area. To solve this problem we have developped a microstatistic approach. Two possibilities are available : the numer of activated defects is unknown and a microstatistic model allows to know this number per volume unit from phenomenological results, the number of activated defects is experimentaly obtained and microstatistic allows to forsee phenomenological results. We have followed this approach in the case of ductile fracture of a steel. These two approaches although elementary got us promising results
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Hassan Gouair. Approche probabiliste de la rupture fragile et ductile à grandes vitesses de déformations. Autre. Université Paul Verlaine - Metz, 1994. Français. ⟨NNT : 1994METZ034S⟩. ⟨tel-01776721⟩

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