NUCLEATION OF CRACKS FROM SHEAR-INDUCED CAVITIES IN AN a/b TITANIUM ALLOY IN FATIGUE, ROOM-TEMPERATURE CREEP AND DWELL-FATIGUE - Archive ouverte HAL
Journal Articles Acta Materialia Year : 2008

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.

Dates and versions

hal-00315980 , version 1 (02-09-2008)

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Cite

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, 2008, 56, pp.4450-4457. ⟨10.1016/j.actamat.2008.04.060⟩. ⟨hal-00315980⟩
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