Failure of a threaded pressurized vessel

A fracture mechanics analysis of a threaded pressure vessel, which has been welded to a plug of similar material is presented. Owing to the presence o f threads (circumferential notches) in a pressure vessel, premature fractur e may occur due to the propagation of a crack nucleating from the thread ro ot. In order to determine the internal pressure, which induces this fast fr acture, a semi-analytical approach is used which combines both linear elast ic fracture mechanics and finite element analysis. An estimation of the axi al stress required to propagate the crack is obtained from the fracture mec hanics approach, using the far-field axial stress in the threaded region re covered from a finite element analysis. Moreover, experimental evidence sub stantiates the validity of this type of composite analytical approach, by c onfirming both the rupture pressure and the residual hoop strain after frac ture. (C) 1999 Elsevier Science Ltd. All rights reserved.