Creep damage and life assessment of thick-walled spherical reactor using Larson–Miller parameter

چکیده مقاله

Creep damage and remnant life histories of a thick-walled spherical reactor made of 316LN austenitic stainless steel (316LN SS) with temperature-dependent properties have been investigated. The Robinson linear life fraction damage rule in which time to ruptures are determined by Larson-Miller parameter (LMP) has been employed. The vessel is subjected to an internal pressure and a distributed temperature field. Due to high temperature field, creep is the major damage mechanism exhausting the lifetime of the reactor. An analytical solution followed by an iterative method using initial thermoelastic stresses at zero time and the stress rates has been developed to obtain effective stress histories. Rupture times are then calculated from LMP and the Robinson rule is used to obtain damage and remnant life histories. It has been found that for both uniform and distributed thermal field the creep damage at the inner surface of the sphere is more serious. It has also been found that effective stresses are decreasing with time in a uniform thermal field while they are increasing in the presence of thermal gradient. The results are validated using predictions of rupture life by the Japanese-98 FME equation.