Fitness-for-Service Strategies for Impulsively Loaded Vessels

Abstract

Abstract High-explosive containment vessels are most commonly designed for repeated use, implying predominately elastic material behavior. Each explosive test imparts an impulse to the vessel wall. The vessel subsequently vibrates as a result of the internal blast loading, with amplitude diminishing exponentially in time due to structural damping. Flaws present in the vessel could potentially grow by fatigue during these vibrations. Subsequent explosive tests result in new sequences of vibrations, providing further opportunity for existing flaws to grow by fatigue. The obvious question is, ‘How many explosive experiments can be performed before flaws potentially grow to unsafe limits?’ The evaluation of remaining life and fitness-forservice of explosive containment vessels draws upon three interrelated codes and standards: Section VIII, Division 3 of the ASME Boiler and Pressure Vessel Code; API-579/ASME FFS-1; and ASME Code Case 2564. The paper discusses their implementation in determining the remaining life of dynamically loaded vessels that have seen service and are potentially damaged. In this paper, results of a representative explosive containment vessel are presented using actual flaw data for both embedded weld flaws and fragment damage. Because of the potentially large number of flaws that can be detected by modern non-destructive inspection methods, simplifying procedures are also presented for conservatively eliminating from further consideration the vast majority of the flaws that possess considerable remaining life.