A Study of Fatigue (Cyclic Deformation) Behavior in FCC Metals Using Strain Rate Change Tests

Abstract:

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Strain rate jump tests were performed during low cycle fatigue using plastic strain rate as the real time computed control variable. Test materials included OFE polycrystalline copper, AA7075-T6 aluminum, and 304 stainless steel. The evolution of dislocation interactions was observed by evaluating the activation area and true stress as a function of cumulative plastic strain. Activation area values for each of the three materials were evaluated from an initial state to saturation. All three materials exhibit a deviation from Cottrell-Stokes law during cyclic deformation. Tests performed on each of the three materials at saturation reveal a dependence of activation area on plastic strain amplitude for copper and aluminum but no such relationship for stainless steel. These results reflect a contrast between wavy slip for pure copper and 7075 aluminum versus planar slip for 304 stainless steel tested at room temperature. Dislocation motion in copper transitions from forest dislocation cutting [1-6] to increasing contributions of cross slip. Dislocation motion in 7075 aluminum and 304 stainless steel is controlled by obstacles that are characteristically more thermal than forest dislocations: obstacles in 7075-T6 aluminum are identified as solutes from re-dissolved particles; obstacles in 304 stainless steel are also solutes.

Info:

Periodical:

Key Engineering Materials (Volumes 378-379)

Edited by:

Dr. T. S. Srivatsan, FASM, FASME

Pages:

371-384

DOI:

10.4028/www.scientific.net/KEM.378-379.371

Citation:

G. C. Kaschner and J. C. Gibeling, "A Study of Fatigue (Cyclic Deformation) Behavior in FCC Metals Using Strain Rate Change Tests", Key Engineering Materials, Vols. 378-379, pp. 371-384, 2008

Online since:

March 2008

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Price:

$35.00

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