Post-failure life evaluation: A corrosion-fatigue case history

An AISI 1029 steel threaded rod belonging to a harbour crane fractured after ten years of service. Failure analysis, including metallography and both destructive and non-destructive testing, was carried out. Metallurgical properties and geometrical characteristics of the broken rod complied with the original design. The fractographic features were typical of fatigue fracture. Both a fracture mechanics approach and a conventional approach were employed to study the fatigue process. The real rate of crack growth was determined through scanning electron microscopy measurements. It is concluded that the failure was due to corrosion fatigue. An improved design is suggested.