Digital Repository, CONVEGNO IGF XXII ROMA 2013

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Complex damaging analysys: integrated approach among fractography and other disciplines of evaluation and investigation
A. Scanavini, F. Papazzoni, D. Cassinera

Last modified: 2013-06-27


Failure analysis is a scientific discipline that, by means of the correct laboratory testing, allow to
identify the physical rootcauses of failure and describe how the component missed the designed expectation.
But a failed component is not just a fractured particular: for instance a deformed pipe under creep service
conditions could not present a fracture surface if its damage is detected in the second step of stationary creep
damage or a brazed vessel which loses inner pressure since the base material is affected by Liquid-Metal
A particular case of Failure Analysis is the fracture of mechanical components; in this case the aim of the
analysis is to identify the initiation points, the fracture mechanism and the eventual critical points.
This information, combined to the quantitative understanding of stressors, consents to formulate hypotheses
about the failure causes.
The right methodological modus operandi to approach a Failure Analysis, is constituted by a series of steps that
we may reassume in this way: Collecting of background data (design data, assembly data, specification data, base
material specifications, heat treatments, superficial coatings, etc), Inspection and sampling (to avoid
contamination and damaging of strategic sources of information like surfaces of fracture), Photographic
documentation as it, Macrographic analysis and Fractographic analysis.
This information combined allows to identify the mechanism of damaging (brittle, ductile or fatigue mechanism
or more often a great mix of the previous ones), the context of the rupture and the origin of the problem.
Further analysis such: Non Destructive Test (Visual Test, Magnetic particles Test, Ultrasonic Test, Penetrant
Test, Radiographic Test, Eddy Current Test and Metallographic Replica Test), Extensometric analysis, Material
characterization (chemical and mechanic properties), Micrographic examination and Micrographic and
Fractographic check in the origin point, synergically combined with the previous information, give us tools to
generate hypotheses about the root causes of the damaging.
In case of simple damage, every contribute fits with the others in a natural way.
In case of complex damage, the interaction between different discipline and competence rises to a critical point
and the scheduling of the inspection test is not so easy to define.
A series of practical examples will show how the synergism between the Fractographic analysis and the other
investigation methods guide successfully the analyst in the approach to complex cases characterized by multiples
boundary conditions.

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