Abstract. This paper describes the results of interrupted tensile tests carried out on 99.95% pure copper specimens over a range of stress triaxiality conditions. The tested specimens were sectioned and polished to identify the conditions at which voids nucleate and coalesce before the final fracture takes place. Results show that void nucleation and coalescence both have a very strong dependence on stress triaxiality, but appear to be less sensitive to strain-rate. Based on the combined experimental and numerical results, a new criterion for void nucleation is proposed as a function of stress triaxiality. Rkurn6. Cet article pr6sente les resultats d' essais de traction interrompus obtenus sur des 6chantillons de cuirve a 99.95% pur dans des conditions de contraintes triaxiales. Les Cchantillous testes out dtk sectionnes et polis afm d' identifier les conditions de nucleation et de coalescence des vides avant que n'intewienne la rupture finale. Les resultats montrent que la nucleation et la coalescence des vides sont fortement dependantes de la triaxialite des coutraintes; mais sout moins sensibles aux taux de cisaillement. Base sur la combinaison de resultats numeriques et expdrimentaux, un nouveau critkre de nuclkation des vides est propose eu taut que fonction de la triaxialit6 des contraintes.

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