Abstract

The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC) Committee has recently developed a new Section XI (Nuclear Components Inspection) Division 2 Code [1] named “Reliability and Integrity Management (RIM).” RIM incorporates a new concept known as “System-Based Code (SBC)” originally due to Asada and his colleagues [2, 3], where an integrated approach from design to service inspection is introduced using three new types of statistical quantities: (1) “system reliability index,” or “system co-reliability target” for any system consisting of structures and components, (2) “structural co-reliability,” for any structure, and (3) “component co-reliability” for any component. In a recent paper published in the International Journal of Pressure Vessels and Piping, Fong, Heckert, Filliben, and Freiman [6] developed a new theory of fatigue and creep rupture life modeling for metal alloys at room and elevated temperatures such that the co-reliability of an uncracked component can be estimated from fatigue and creep rupture test data with simple loading histories. In this paper, we extend the theory to include a methodology to estimate the co-reliability of a cracked pipe from fatigue crack growth rate test data, probability of detection (POD) data, and nondestructive evaluation (NDE) of initial crack sizing data for simple loading histories. To illustrate an application of this new modeling approach, we present four numerical example case studies using (a) the fatigue failure data of six AISI 4340 steel specimens at room temperature (Dowling, N. E., 1973) for an uncracked steel pipe, and (b) the fatigue crack growth rate data of 17 specimens of 2024-T3 aluminum (von Euw, Hertzberg, and Roberts, 1972) for a cracked aluminum pipe (see discussion after Eq. (16)). The four cases are: (1) Uncracked and uninspected pipe. (2) Inspected pipe with a crack-found-location-and-size call. (3) Uncracked and inspected pipe with a no-crack-found call and a POD value. (4) Inspected pipe with a crack-found-location-and-size call and a structural health monitoring (SHM) program. Significance and limitations of this new fatigue life modeling approach to the estimation of component co-reliability of uncracked and cracked pipes are presented and discussed.

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