NUCLEATION OF CRACKS FROM SHEAR-INDUCED CAVITIES IN AN a/b TITANIUM ALLOY IN FATIGUE, ROOM-TEMPERATURE CREEP AND DWELL-FATIGUE

Abstract : In titanium alloys, dwell periods during room-temperature stress-controlled fatigue tests are responsible for substantial reductions in lifetime compared to pure fatigue loading. The mechanisms of such a creep-fatigue interaction have been investigated for alloy Ti6242. SEM and TEM observations revealed crack initiation by coalescence of shear-induced cavities nucleated at a/b interfaces in large colonies of a laths nearly parallel to the loading axis. The density and average size of cavities were larger in dwell-fatigue and creep than in fatigue. A qualitative micromechanical model of cavity nucleation based on discrete dislocation dynamics was developed. The number of cycles for cavity nucleation was computed as a function of the applied stress range. A finite threshold, dependent on the size of a laths colonies with similar orientation, was found. The simulations predict earlier cavity nucleation in creep or dwell-fatigue than in pure fatigue, which is consistent with the performed experiments.
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https://hal.archives-ouvertes.fr/hal-00315980
Contributor : Véronique Doquet <>
Submitted on : Tuesday, September 2, 2008 - 11:06:07 AM
Last modification on : Monday, April 8, 2019 - 3:01:32 PM

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Pierre Lefranc, Véronique Doquet, Michel Gerland, Christine Sarrazin-Baudoux. NUCLEATION OF CRACKS FROM SHEAR-INDUCED CAVITIES IN AN a/b TITANIUM ALLOY IN FATIGUE, ROOM-TEMPERATURE CREEP AND DWELL-FATIGUE. Acta Materialia, Elsevier, 2008, 56, pp.4450-4457. ⟨10.1016/j.actamat.2008.04.060⟩. ⟨hal-00315980⟩

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