Resume - Le test d'expansion de cylindre (ERT) est un test de conception simple pour etudier le comportement des materiaux en grande deformation et pour de grandes vitesses de deformation. Le test est realis& en placant un anneau mince du materiau d etudier dans un processus d'expansion radiale et en mesurant cette vitesse d'expansion. L'anneau est projete par un explosif ; le test n 'est pas devenu populaire d cause des problemes poses par le lan- cement de 1 'anneau par 1 'explosif,notamment sur les modifications des pro- prietes par l'onde de choc. Pour determiner l'aptitude de 1'ERT a determiner les propri6tGs des materiaux, une serie d'experiences a 6t6 concue sur un ma- teriau s6verement contr8le (un cuivre revenu sans oxygene). Les anneaux recu- per& ont 6t6 analyses et leur changement de durete determine. La comparaison entre les donnees de 1'ERT et celles obtenues avec des essais d i: =5x103 s-l a la barre dlHopkinson indique que la durete induite par choc est approxi- mativement equivalente d un ecrouissage de 5%. Les donnees de 1'ERT sur ce materiau pour des vitesses de deformation allant jusqu'a 2,3 x lo4 s-l sont presentees. Abstract - The freely expanding ring test (ERT) is a conceptually simple test for determining the stress-strain behavior of materials at 1 arge strains and at high strain rates. This test is conducted by placing a thin ring of test material in a state o f uniform radial expansion and then measuring its subsequent velocity- time h istory. The ring is usually propelled by a high explosive driving system. The test has not become pophlar in the materials property community, however, because there has been some concern about how the launching of the ring sample with an explosively generated shock wave might affect the properties to be measured. To determine the suitability of the ERT for these fundamental investigations, a series of experiments was performed on a carefully controlled material--oxygen-free electronic fully annealed copper. Recovered ring samples were analyzed and the change in hardness determined. Comparisons of the ERT data with t hat from Hopkinson bar tests at strain rates of about 5 x lo3 s-l indicate t hat the shock-induced hardness is approximately equivalent to a strain hardening of 5%. ERT data on this material at strain rates up to 2.3 x lo4 s-I are presented.