API 579-1 (2021) Annex 9B — Mode I stress intensity factor $K_I$ library (plate, cylinder, sphere, hole, bar/bolt, nozzle, ring-stiffened, fillet weld — 42 solutions)
Based on API 579-1/ASME FFS-1 (2021) Annex 9B, this calculator selects a library solution by crack geometry and computes the Mode I stress intensity factor K_I. It covers 42 solutions across eight families:
Results are reported at the crack-front positions that apply to the geometry:
Each solution has one native stress form — membrane plus bending, a 4th-order through-wall polynomial (\sigma_0–\sigma_4) measured from the reference surface, or internal pressure — and the matching inputs are shown for the solution you pick (the form is not a free choice, since API 579 Table 9B.1 gives each solution one stress form). A crack-face pressure p_c is added into the membrane term. K_I is then assembled from the G_0–G_4 influence coefficients (Eq. 9B.12), or from the membrane and bending factors M_m/M_b (Eq. 9B.14). Table-based coefficients (Tables 9B.2–9B.22) are interpolated strictly within the printed grids, with no extrapolation.
Each solution has its own size validity domain (for example a surface polynomial needs 00.8) lose accuracy and should be re-characterised as through-wall in the Part 9 main flow; eight arbitrary-stress variants are handled by the separate weight-function calculator.
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