This report presents a general discussion and analysis of the mechanical instability in thin-walled cylinders subjected to combined stresses. Two instability conditions are postulated, one arising from a.máximum in the internal pressure, the other resulting from a máximum in the circumferential (hoop) load. Four different physical situations are investigated, and instability criteriá are formulated for each. These criteriá are then applied to two strain-hardening functions, namely, a power law and an exponential law;and equations for the stresses and strains att'ained at instability are developed in terms of the material constants of each law. Numerical valúes for these stresses and strains are obtained from the results of a tensile test bn Zircaloy-2. It is concluded that a máximum in the hoop load is not a suitable instability criterion, and that the exponential function affords a better description of the behavior of the Zircaloy-2 specimen.
展开▼
