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A Statistical Test for Identifying the Number of Creep Regimes When Using the Wilshire Equations for Creep Property Predictions

Mark Evans Orcid Logo

Metallurgical and Materials Transactions A, Volume: 47, Issue: 12, Pages: 6593 - 6607

Swansea University Author: Mark Evans Orcid Logo

Abstract

A new parametric approach, termed the Wilshire equations, offers the realistic potential of being able to accurately lift materials operating at in-service conditions from accelerated test results lasting no more than 5000 hours. The success of this approach can be attributed to a well-defined linea...

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Published in: Metallurgical and Materials Transactions A
ISSN: 1073-5623 1543-1940
Published: Springer Science and Business Media LLC 2016
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URI: https://cronfa.swan.ac.uk/Record/cronfa29679
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spelling 2020-10-21T11:13:01.9274229 v2 29679 2016-08-31 A Statistical Test for Identifying the Number of Creep Regimes When Using the Wilshire Equations for Creep Property Predictions 7720f04c308cf7a1c32312058780d20c 0000-0003-2056-2396 Mark Evans Mark Evans true false 2016-08-31 MTLS A new parametric approach, termed the Wilshire equations, offers the realistic potential of being able to accurately lift materials operating at in-service conditions from accelerated test results lasting no more than 5000 hours. The success of this approach can be attributed to a well-defined linear relationship that appears to exist between various creep properties and a log transformation of the normalized stress. However, these linear trends are subject to discontinuities, the number of which appears to differ from material to material. These discontinuities have until now been (1) treated as abrupt in nature and (2) identified by eye from an inspection of simple graphical plots of the data. This article puts forward a statistical test for determining the correct number of discontinuities present within a creep data set and a method for allowing these discontinuities to occur more gradually, so that the methodology is more in line with the accepted view as to how creep mechanisms evolve with changing test conditions. These two developments are fully illustrated using creep data sets on two steel alloys. When these new procedures are applied to these steel alloys, not only do they produce more accurate and realistic looking long-term predictions of the minimum creep rate, but they also lead to different conclusions about the mechanisms determining the rates of creep from those originally put forward by Wilshire. Journal Article Metallurgical and Materials Transactions A 47 12 6593 6607 Springer Science and Business Media LLC 1073-5623 1543-1940 Activation Energy; Creep Rate; Regime Change; Stress Regime; Creep Mechanism 1 12 2016 2016-12-01 10.1007/s11661-016-3750-x COLLEGE NANME Materials Science and Engineering COLLEGE CODE MTLS Swansea University 2020-10-21T11:13:01.9274229 2016-08-31T15:17:36.1605944 College of Engineering Engineering Mark Evans 0000-0003-2056-2396 1 0029679-31082016151836.pdf evans2016v2.pdf 2016-08-31T15:18:36.9700000 Output 2074342 application/pdf Accepted Manuscript true 2017-10-06T00:00:00.0000000 false
title A Statistical Test for Identifying the Number of Creep Regimes When Using the Wilshire Equations for Creep Property Predictions
spellingShingle A Statistical Test for Identifying the Number of Creep Regimes When Using the Wilshire Equations for Creep Property Predictions
Mark Evans
title_short A Statistical Test for Identifying the Number of Creep Regimes When Using the Wilshire Equations for Creep Property Predictions
title_full A Statistical Test for Identifying the Number of Creep Regimes When Using the Wilshire Equations for Creep Property Predictions
title_fullStr A Statistical Test for Identifying the Number of Creep Regimes When Using the Wilshire Equations for Creep Property Predictions
title_full_unstemmed A Statistical Test for Identifying the Number of Creep Regimes When Using the Wilshire Equations for Creep Property Predictions
title_sort A Statistical Test for Identifying the Number of Creep Regimes When Using the Wilshire Equations for Creep Property Predictions
author_id_str_mv 7720f04c308cf7a1c32312058780d20c
author_id_fullname_str_mv 7720f04c308cf7a1c32312058780d20c_***_Mark Evans
author Mark Evans
author2 Mark Evans
format Journal article
container_title Metallurgical and Materials Transactions A
container_volume 47
container_issue 12
container_start_page 6593
publishDate 2016
institution Swansea University
issn 1073-5623
1543-1940
doi_str_mv 10.1007/s11661-016-3750-x
publisher Springer Science and Business Media LLC
college_str College of Engineering
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hierarchy_parent_id collegeofengineering
hierarchy_parent_title College of Engineering
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description A new parametric approach, termed the Wilshire equations, offers the realistic potential of being able to accurately lift materials operating at in-service conditions from accelerated test results lasting no more than 5000 hours. The success of this approach can be attributed to a well-defined linear relationship that appears to exist between various creep properties and a log transformation of the normalized stress. However, these linear trends are subject to discontinuities, the number of which appears to differ from material to material. These discontinuities have until now been (1) treated as abrupt in nature and (2) identified by eye from an inspection of simple graphical plots of the data. This article puts forward a statistical test for determining the correct number of discontinuities present within a creep data set and a method for allowing these discontinuities to occur more gradually, so that the methodology is more in line with the accepted view as to how creep mechanisms evolve with changing test conditions. These two developments are fully illustrated using creep data sets on two steel alloys. When these new procedures are applied to these steel alloys, not only do they produce more accurate and realistic looking long-term predictions of the minimum creep rate, but they also lead to different conclusions about the mechanisms determining the rates of creep from those originally put forward by Wilshire.
published_date 2016-12-01T03:41:15Z
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