Missing Cylinder Circumferential Surface Crack Solutions for API 579 Annex 9B

Abstract Eleven cylinder circumferential crack solution cases were found to be missing in the API 579-1/ASME FFS-1 Fitness-for-Service standard (API 579) in Annex 9B Table 9B.14 and Table 9B.15. This paper describes the missing crack solutions, describes the three-dimensional crack meshes used to compute new solutions, discusses the post-processing procedure for the superposition of axial load plus bending load cases, provides tables of the new crack solutions, and compares trend plots of the new crack solutions to neighboring crack cases. The crack solutions are given by geometry factor, G, values for four load cases, including uniform stress (G0 values), linear stress (G1 values), in-plane global bending stress (G5 values), and out-of-plane global bending stress (G6 values). To keep the crackfront in tension for the bending load cases, a superposition of bending plus axial stress is applied to the crack mesh. A post-processing procedure is used to subtract the effect of the uniform stress from the combined loading to get the bending load only crack solutions. Several of the crack cases have crack lengths long enough around the cylinder circumference for part of the crack front to be in the compressive stress region below the neutral bending axis. The resulting bending only geometry factor values for G5 and G6 can have negative values along part of the crack front. The new circumferential surface crack solutions are presented in several plots, showing the G values along the crack front for each load case. The plots show increasing G values with increasing crack depth, which helps to validate the new results. The new crack solutions are also compared to neighboring crack solutions from the API 579 tables and show very good agreement across a set of plots. The new crack solutions have been provided to the Fitness-for-Service Joint Committee for inclusion in a future edition of API 579.