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Conference Paper

Potential implications of step loading in impression creep testing

Authors:

A. Bridges ,

Electric Power Research Institute, 1300 W. W.T Harris Blvd, Charlotte, NC 28262 USA
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D. Purdy

Electric Power Research Institute, 1300 W. W.T Harris Blvd, Charlotte, NC 28262 USA
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Abstract

The small sample impression creep test method has recently been of interest, as it can give a good indication of expected creep rates in uniaxial creep testing with minimal use of material. The compressively loaded test has also been shown to provide accurate results under multi-step loading conditions for a low alloy steel (½Cr½Mo¼V) to further extract value from a single test specimen. The Electric Power Research Institute (EPRI) has conducted step tests (step temperature and step loading changes) on another low alloy steel (Grade 22), as well as a tempered martensitic 9 Cr steel (Grade 91). Results have shown that there may be potential problematic areas when conducting step-up and step-down steps in these materials. Additional posttest evaluations have shown that material effects, such as strain hardening and strain softening, may add additional complexities when comparing strain rates of multi-stepped loaded stain rates. Hardness testing on posttest impression creep specimens have confirmed strain softening of tempered martensitic Grade 91 and no observed effect for an ex-service Grade 22 alloy. These findings have shown that careful considerations must be made before using creep rates obtained from multi-stepped loaded tests in situ of single loaded tests.
How to Cite: Bridges, A. and Purdy, D., 2018. Potential implications of step loading in impression creep testing. Ubiquity Proceedings, 1(S1), p.9. DOI: http://doi.org/10.5334/uproc.9
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Published on 10 Sep 2018.
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