SAINT-VENANT EFFECTS IN THE IOSIPESCU SPECIMEN

The main purpose of this paper is to explain the shear strain differen ces observed between the two faces of certain Iosipescu specimens. The different parasitic moments that can act on the specimen are investig ated and their effects assessed. Different Iosipescu fixtures from the literature are checked for these parasitic moments and it is shown th at modification of the Wyoming fixture can lead to the elimination of its parasitic in-plane and out-of-plane movements. Finally, it is show n that the strain differences that remain are caused by Saint-Venant e ffects due to the proximity of the loading points to the notch line bu t that averaging the strains between the two faces eliminates this eff ect. This is an important feature since for certain material configura tions (thick and transversely stiff specimens), preventing twisting of the fixture is not sufficient to enable the use of only one strain ga uge.