SIMULATION OF THE HOT-TENSION TEST UNDER CAVITATING CONDITIONS

A theoretical analysis of the isothermal hot-tension test under cavita ting conditions for sheet samples was performed using a ''direct-equil ibrium'' approach. The effects of cavity growth rate eta, initial cavi ty volume fraction C-nu 0, strain-rate sensitivity exponent m, and spe cimen taper on engineering stress-strain curves, strain profiles, and failure modes were established. For a given value of m, it was predict ed that the engineering stress-strain curves of cavitating and noncavi tating samples are almost coincident except near failure. In fact, dur ing quasistable deformation, the required load for a cavitating materi al is slightly higher than that for a noncavitating material because o f strain rate and effective area effects. Model, results also delineat ed the competition between failure controlled by localized necking vs fracture, the latter being defined by a critical-volume fraction of ca vities, Specifically, at low strain-rate sensitivities m and cavity gr owth rates eta, failure was predicted to be controlled by necking. By contrast, at high values of m and eta, fracture prior to localized nec king was predicted to predominate; in these cases, the cross-sectional area at the failure site was appreciable, thus resembling a form of b rittle fracture. The validity of the modeling approach was confirmed t hrough the analysis of data in the literature. However, model results did suggest that caution should be taken in the interpretation of expe rimental data because various combinations of C-nu 0 and eta can resul t in the same total elongation.