SEDL / STP / STP453-EB / STP47362S

Correlation of Fractographic Features with Fracture Mechanics Data

Bates, R. C.
Fellow engineer and senior engineers, Westinghouse Research Laboratories, Pittsburgh, Pa.

Clark, W. G.
Fellow engineer and senior engineers, Westinghouse Research Laboratories, Pittsburgh, Pa.

Moon, D. M.
Fellow engineer and senior engineers, Westinghouse Research Laboratories, Pittsburgh, Pa.

Pages: 23    Published: Jan 1969

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Abstract

The fractographic features of failures produced in wedg-opening-loading type fracture toughness specimens tested under rising load and cyclic loading were evaluated for Ni-Mo-V and HP 9-4-25 alloy steels and aluminum alloys 5456-H321 and 7079-T6. Test variables included temperature and section size and, consequently, state of stress (plane strain versus nonplane strain). The characteristic fractographic features observed by means of electron microscopy then were compared with the fracture mechanics properties of the alloys. Correlations were found between: (1) fatigue striation spacing and cyclic stress intensity range, ΔK and (2) “stretched zones” (featureless area adjacent to the point where fast fracture initiated from a sharp defect) and the relative toughness of the material. These correlations can be used to provide failure analysis techniques capable of quantitatively evaluating the stress condition associated with failures from fractographic evidence alone.