The team recommended that the pipeline be replaced with a new one, fabricated using a improved welding process and inspected regularly using non-destructive evaluation techniques.
The team also used the fracture toughness (KIC) to determine the critical stress intensity factor for the material. The fracture toughness is a measure of a material's resistance to fracture, and is defined as:
da/dN = 10^(-10) * (50 MPa√m)^2.5 = 2.5 * 10^(-5) inches/cycle principles of fracture mechanics rj sanford pdf pdf work
The team decided to apply the principles of fracture mechanics to analyze the failure. They used the stress intensity factor (K) to characterize the stress field around the crack tip.
da/dN = C * (ΔK)^m
The team also discovered that the pipeline had been subjected to a series of pressure cycles, with pressures ranging from 500 to 900 psi. These cycles had caused fatigue cracks to form and grow in the weld region.
K = (900 psi * √(π * 2 inches)) * 1.5 = 85 MPa√m The team recommended that the pipeline be replaced
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.
