A multi-scale failure-probability-based fatigue or creep rupture life model for estimating component co-reliability

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 named "Reliability and Integrity Management (RIM). RIM incorporates a new concept known as "System-Based Code (SBC) originally due to Asada and his colleagues (2001–2004), where an integrated approach from design to service inspection is introduced using an overall statistical quantity known as "reliability index," or, "co-reliability target." In this paper, we develop a new theory of fatigue and creep rupture life modeling for metal alloys at room and elevated temperatures such that the co-reliability target can be estimated from fatigue and creep rupture test data. To illustrate an application of this new modeling approach, we include two numerical examples using (a) the fatigue failure data of six AISI 4340 steel specimens at room temperature (Dowling, N. E., 1973) and (b) the creep rupture time data of 37 specimens of 1.3Mn-0.5Mo-0.5Ni steel plates at 500 C (NRIM, 1987). Significance and limitations of this new fatigue and creep rupture life modeling approach are presented and discussed.