The role of fractography in failure analysis 1_2

Donato FIRRAO: To perform failure analysis of broken components it is always important to assess whether the rupture was of the ductile or the brittle type in the case of fracture by overload, or in the case of fracture by fatigue.
Whereas in monophasic structures the above task is usually straightforward, it may become extremely difficult when the components have a complex microstructure, as in the case of pearlitic steel or of Al-Si cast alloys microstructures.
After a review of the methods to clean oxidized rupture surfaces, the interplay between metallography and fractography is illustrated by means of examples of real failure analysis cases encompassing either overload or fatigue fractures.
Means to hypothesize acceptable fracture toughness values by careful fractography analysis are also illustrated.