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Title: The Role of Cold Work in Eddy Current Residual Stress Measurements in Shot-Peened Nickel-Base Superalloys

Abstract

Recently, it was shown that eddy current methods can be adapted to residual stress measurement in shot-peened nickel-base superalloys. However, experimental evidence indicates that the piezoresistivity effect is simply not high enough to account for the observed apparent eddy current conductivity (AECC) increase. At the same time, X-ray diffraction data indicates that 'cold work' lingers even when the residual stress is fully relaxed and the excess AECC is completely gone. It is impossible to account for both observations with a single coherent explanation unless we assume that instead of a single 'cold work' effect, there are two varieties of cold work; type-A and type-B. Type-A cold work (e.g., changes in the microscopic homogeneity of the material) is not detected by X-ray diffraction as it does not significantly affect the beam width, but causes substantial conductivity change and exhibits strong thermal relaxation. Type-B cold work (e.g., dislocations) is detected by X-ray, but causes little or no conductivity change and exhibits weak thermal relaxation. Based on the assumption of two separate cold-work variables and that X-ray diffraction results indicate the presence of type-B, but not type-A, all observed phenomena can be explained. If this working hypothesis is proven right, the separation ofmore » residual stress and type-A cold work is less critical because they both relax much earlier and much faster than type-B cold work.« less

Authors:
;  [1]
  1. Department of Aerospace Engineering and Engineering Mechanics, University of Cincinnati, Cincinnati, Ohio 45221-0070 (United States)
Publication Date:
OSTI Identifier:
20798232
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 820; Journal Issue: 1; Conference: Conference on review of progress in quantitative nondestructive evaluation, Brunswick, ME (United States), 31 Jul - 5 Aug 2005; Other Information: DOI: 10.1063/1.2184688; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; BEAM PROFILES; DISLOCATIONS; EDDY CURRENT TESTING; EDDY CURRENTS; HEAT RESISTING ALLOYS; HYPOTHESIS; NICKEL BASE ALLOYS; RELAXATION; RESIDUAL STRESSES; X-RAY DIFFRACTION

Citation Formats

Yu, F., and Nagy, P. B.. The Role of Cold Work in Eddy Current Residual Stress Measurements in Shot-Peened Nickel-Base Superalloys. United States: N. p., 2006. Web. doi:10.1063/1.2184688.
Yu, F., & Nagy, P. B.. The Role of Cold Work in Eddy Current Residual Stress Measurements in Shot-Peened Nickel-Base Superalloys. United States. doi:10.1063/1.2184688.
Yu, F., and Nagy, P. B.. Mon . "The Role of Cold Work in Eddy Current Residual Stress Measurements in Shot-Peened Nickel-Base Superalloys". United States. doi:10.1063/1.2184688.
@article{osti_20798232,
title = {The Role of Cold Work in Eddy Current Residual Stress Measurements in Shot-Peened Nickel-Base Superalloys},
author = {Yu, F. and Nagy, P. B.},
abstractNote = {Recently, it was shown that eddy current methods can be adapted to residual stress measurement in shot-peened nickel-base superalloys. However, experimental evidence indicates that the piezoresistivity effect is simply not high enough to account for the observed apparent eddy current conductivity (AECC) increase. At the same time, X-ray diffraction data indicates that 'cold work' lingers even when the residual stress is fully relaxed and the excess AECC is completely gone. It is impossible to account for both observations with a single coherent explanation unless we assume that instead of a single 'cold work' effect, there are two varieties of cold work; type-A and type-B. Type-A cold work (e.g., changes in the microscopic homogeneity of the material) is not detected by X-ray diffraction as it does not significantly affect the beam width, but causes substantial conductivity change and exhibits strong thermal relaxation. Type-B cold work (e.g., dislocations) is detected by X-ray, but causes little or no conductivity change and exhibits weak thermal relaxation. Based on the assumption of two separate cold-work variables and that X-ray diffraction results indicate the presence of type-B, but not type-A, all observed phenomena can be explained. If this working hypothesis is proven right, the separation of residual stress and type-A cold work is less critical because they both relax much earlier and much faster than type-B cold work.},
doi = {10.1063/1.2184688},
journal = {AIP Conference Proceedings},
number = 1,
volume = 820,
place = {United States},
year = {Mon Mar 06 00:00:00 EST 2006},
month = {Mon Mar 06 00:00:00 EST 2006}
}