Tools › Structures › Damage Tolerance › Crack Growth › Example

Paris-law life of a centre crack in 2024-T3 with the FAA Walker constants

ToolCrack Growth
SourceFederal Aviation Administration (2005). Fatigue Crack Growth Database for Damage Tolerance Analysis. DOT/FAA/AR-05/15, Office of Aviation Research, Washington, DC; Paris, P. C., and Erdogan, F. (1963). "A Critical Analysis of Crack Propagation Laws." Journal of Basic Engineering, Vol. 85, No. 4, pp. 528–533.
LevelProfessional

Problem

A 6 in wide 2024-T3 plate carries a centre crack of half-length 0.05 in under Δσ = 15 ksi at R = 0. With C = 1.67e-9 in/cycle per (ksi√in)^m and m = 3.273 at R = 0, K_IC = 30 ksi√in, find the critical crack size, the cycles to failure and an inspection interval for a 0.10 in detectable crack.

Inputs to Enter

  • Geometry: centre crack, finite width W = 6 in (secant correction); a_i = 0.05 in, a_d = 0.10 in
  • Δσ = 15 ksi, R = 0; material 2024-T3 L-T (FAA Walker constants), K_IC = 30 ksi√in, ΔK_th = 1.22 ksi√in (loaded by default)
Open the Crack Growth tool (loaded with this example)

Answers

  • ΔK at a_i = 5.946 ksi√in (6.534 MPa√m); critical half-length a_c = 1.076 in
  • N_f = 115,846 cycles (Simpson integration; the RK4 and closed-form Y = 1 checks agree within 2e-5)
  • Inspection interval = N(a_d → a_c)/2 = 33,434 cycles, three inspections before a_c; residual strength at a_i 75.68 ksi

Notes

Constants are the FAA database's Walker fit evaluated at R = 0; Dowling's Table 11.2 values could not be verified from an open source and are not offered.