Protection Against Local Failure for Impulsively Loaded Vessels

Significant changes were recently made in design limits for pressurized vessels in Section VIII, Division 3 of the ASME Code. There is now a local damage-mechanics based strain-exhaustion limit as well as a separate global plastic collapse limit. In addition, Code Case 2564 (Sec VIII, Div 3) has recently been approved to address impulsively loaded vessels. Recent studies have shown that local strain limits play a particularly important role for these impulsively loaded vessels. In this paper, the new local strain-exhaustion procedure, originally intended for static-pressure-loaded vessels, is evaluated for adequacy in conservatively predicting failure for impulsively loaded vessels. Based upon a symmetrically loaded cylindrical shell geometry, it is found that direct extension of the new local failure rules in the ASME Code to impulsively loaded vessels is unconservative. However, a hoop-strain local failure criterion predicts failures reasonably well.