Creep-Fatigue Flaw Growth Analysis to Support Elevated Temperature Flaw Size Acceptance Criteria

Creep fatigue-crack growth analyses using the EDF R5 V4/5, API 579-1/ASME FFS-1, and EPRI BLESS methodologies are carried out in an interative fashion on four components: superheater tube and pipe, and reheater tube and pipe. Three materials (Grade 22, Grade 91 and SS 304H) are considered and twelve flaw configerations, which varied in orientation, location and geometry.

The scope of the work is to calculate the largest initial flaw size for each case that satisfies the specified transient operating conditions: temperature, pressure, time, and cycles. The stresses are calculated via transient finite element analyses and software is developed to apply the three fracture mechanics methodologies. Extensive unit-testing is implemented to verify the codes and several hand calculations are done and included in the report. The results are compared in tabulated format and conclusions are drawn.

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