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Direct Measurements of Slip Irreversibility in a Nickel Base Superalloy Using High Resolution Digital Image Correlation

39 Pages Posted: 15 Aug 2019 First Look: Accepted

See all articles by J.C. Stinville

J.C. Stinville

University of California, Santa Barbara (UCSB)

P.G. Callahan

University of California, Santa Barbara (UCSB)

M.A. Charpagne

University of California, Santa Barbara (UCSB)

M.P. Echlin

University of California, Santa Barbara (UCSB)

V. Valle

Universite de Poitiers - Institut Pprime

T.M. Pollock

University of California, Santa Barbara (UCSB)

Abstract

Fatigue crack nucleation in crystalline materials typically develops due to highly localized cyclic slip. During a fatigue cycle, reverse slip differs locally from slip in the forward direction particularly in precipitate-containing materials such as superalloys. In this paper we report the first direct measurements of irreversibility at the scale of individual slip planes in a polycrystalline nickel base superalloy. Quantitative measurements of the slip irreversibility is challenging to be performed for regions of material that have a size that captures the microstructure and its variability. High spatial resolution at the nanometer scale during experimental measurements is needed to observe slip localization during deformation. Moreover, large fields are also needed to obtain the material response over statistically representative populations of microstructural configurations. Recently, high resolution scanning electron microscope (SEM) digital image correlation (DIC) has been extended for quantitative analysis of discontinuities induced by slip events using the Heaviside-DIC method. This novel method provides quantitative measurements of slip localization at the specimen surface. In this paper, the Heaviside-DIC method is used to measure slip irreversibility and plastic accumulation in a nickel base superalloy. The local microstructural configurations that induces large amounts of plasticity and slip irreversibility are captured and correlated to crack nucleation locations.

Keywords: High Resolution Digital Image Correlation, Polycrystalline René 88DT Nickel Base Superalloy, Scanning Electron Microscopy Digital Image Correlation, Strain Localization and Accumulation, Slip Irreversibility, Low Cycle Fatigue, Heaviside-Digital Image Correlation

Suggested Citation

Stinville, J.C. and Callahan, P.G. and Charpagne, M.A. and Echlin, M.P. and Valle, V. and Pollock, T.M., Direct Measurements of Slip Irreversibility in a Nickel Base Superalloy Using High Resolution Digital Image Correlation. Available at SSRN: https://ssrn.com/abstract=3436406

J.C. Stinville (Contact Author)

University of California, Santa Barbara (UCSB)

Santa Barbara, CA 93106
United States

P.G. Callahan

University of California, Santa Barbara (UCSB)

Santa Barbara, CA 93106
United States

M.A. Charpagne

University of California, Santa Barbara (UCSB)

Santa Barbara, CA 93106
United States

M.P. Echlin

University of California, Santa Barbara (UCSB)

Santa Barbara, CA 93106
United States

V. Valle

Universite de Poitiers - Institut Pprime

Poitiers, 86961
France

T.M. Pollock

University of California, Santa Barbara (UCSB)

Santa Barbara, CA 93106
United States

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