The stress intensity factor is a measure of the stress field around a crack tip, and is defined as:
where da/dN is the crack growth rate, C and m are material constants, and ΔK is the stress intensity factor range. principles of fracture mechanics rj sanford pdf pdf work
The team concluded that the pipeline had failed due to a fatigue crack that had grown to a critical size. The crack had formed in the weld region, which had a lower toughness than the base metal. The stress intensity factor is a measure of
da/dN = C * (ΔK)^m
da/dN = 10^(-10) * (50 MPa√m)^2.5 = 2.5 * 10^(-5) inches/cycle C and m are material constants