Testing and assessment of cracking in P91 steels under creep-fatigue loading conditions

Future green energy options dictate that renewable energy source must be utilized when available. This poses a challenge to conventional power plant, which has generally been designed for base-load conditions, as they now need to operate in a ‘flexible’ manner. This flexible operation, in high tempe...

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Main Authors:	Norhaida, Ab. Razak, Davies, Catrin Mair, Nikbin, Kamran M.
Format:	Article
Language:	English English
Published:	Elsevier Ltd 2018
Subjects:	TJ Mechanical engineering and machinery
Online Access:	http://umpir.ump.edu.my/id/eprint/20402/ http://umpir.ump.edu.my/id/eprint/20402/ http://umpir.ump.edu.my/id/eprint/20402/ http://umpir.ump.edu.my/id/eprint/20402/1/Testing%20and%20Assessment%20of%20Cracking%20In%20P91%20Steels%20Under%20Creep-Fatigue%20Loading%20Conditions.pdf http://umpir.ump.edu.my/id/eprint/20402/2/Testing%20and%20Assessment%20of%20Cracking%20In%20P91%20Steels%20Under%20Creep-Fatigue%20Loading%20Conditions%201.pdf

id	oai:umpir.ump.edu.my:20402
recordtype	eprints
spelling	oai:umpir.ump.edu.my:204022018-08-01T02:14:01Z http://umpir.ump.edu.my/id/eprint/20402/ Testing and assessment of cracking in P91 steels under creep-fatigue loading conditions Norhaida, Ab. Razak Davies, Catrin Mair Nikbin, Kamran M. TJ Mechanical engineering and machinery Future green energy options dictate that renewable energy source must be utilized when available. This poses a challenge to conventional power plant, which has generally been designed for base-load conditions, as they now need to operate in a ‘flexible’ manner. This flexible operation, in high temperature power plant components, could lead to a combination of creep and fatigue crack growth failure. Thus a better characterization of interactive creep-fatigue crack growth behaviour is required especially for assessing long term failure in plant. The industrial codes, such as R5 or BS7910, treat this interaction using linear accumulation of damage. However, this does not consider the degradation of properties and reduction in creep ductility in long term operations and their effect on the subsequent creep/fatigue behaviour. In this work creep-fatigue crack growth (CFCG) tests were performed on compact tension specimen of P91 steel in the as received and ex-service conditions at temperatures ranging between 600 °C to 625 °C, with the hold-times ranging from static to 600 s. The experimental results in addition to appropriate data from the literature have been analysed using stress intensity factor range, ΔK appropriate under fatigue control and the creep fracture mechanics parameter C* relevant under creep control. Scanning electron macroscopy (SEM) analysis confirms the influence of frequency on the mode of cracking. Within the scatter of experimental data for the present short term accelerated tests a linear cumulative damage rule can still predict the creep/fatigue interaction. However the effects due to low frequency cyclic loading as well as degraded the steel under ex-service conditions tending to reductions in creep ductility show factors of two or more faster cracking rates compared to as received static testing. Unavailability of long term tests at low stresses may pose additional problems under creep since creep is stress state controlled but fatigue in not. However using plane strain predictions of crack initiation and growth data using the NSW multiaxial ductility creep crack growth model suggest that conservative predictions of long term cracking can still be made under creep/fatigue and when there is a marked reduction creep failure ductility. Elsevier Ltd 2018-02 Article PeerReviewed pdf en http://umpir.ump.edu.my/id/eprint/20402/1/Testing%20and%20Assessment%20of%20Cracking%20In%20P91%20Steels%20Under%20Creep-Fatigue%20Loading%20Conditions.pdf pdf en http://umpir.ump.edu.my/id/eprint/20402/2/Testing%20and%20Assessment%20of%20Cracking%20In%20P91%20Steels%20Under%20Creep-Fatigue%20Loading%20Conditions%201.pdf Norhaida, Ab. Razak and Davies, Catrin Mair and Nikbin, Kamran M. (2018) Testing and assessment of cracking in P91 steels under creep-fatigue loading conditions. Engineering Failure Analysis, 84. pp. 320-330. ISSN 1350-6307 https://doi.org/10.1016/j.engfailanal.2017.08.007 10.1016/j.engfailanal.2017.08.007
repository_type	Digital Repository
institution_category	Local University
institution	Universiti Malaysia Pahang
building	UMP Institutional Repository
collection	Online Access
language	English English
topic	TJ Mechanical engineering and machinery
spellingShingle	TJ Mechanical engineering and machinery Norhaida, Ab. Razak Davies, Catrin Mair Nikbin, Kamran M. Testing and assessment of cracking in P91 steels under creep-fatigue loading conditions
description	Future green energy options dictate that renewable energy source must be utilized when available. This poses a challenge to conventional power plant, which has generally been designed for base-load conditions, as they now need to operate in a ‘flexible’ manner. This flexible operation, in high temperature power plant components, could lead to a combination of creep and fatigue crack growth failure. Thus a better characterization of interactive creep-fatigue crack growth behaviour is required especially for assessing long term failure in plant. The industrial codes, such as R5 or BS7910, treat this interaction using linear accumulation of damage. However, this does not consider the degradation of properties and reduction in creep ductility in long term operations and their effect on the subsequent creep/fatigue behaviour. In this work creep-fatigue crack growth (CFCG) tests were performed on compact tension specimen of P91 steel in the as received and ex-service conditions at temperatures ranging between 600 °C to 625 °C, with the hold-times ranging from static to 600 s. The experimental results in addition to appropriate data from the literature have been analysed using stress intensity factor range, ΔK appropriate under fatigue control and the creep fracture mechanics parameter C* relevant under creep control. Scanning electron macroscopy (SEM) analysis confirms the influence of frequency on the mode of cracking. Within the scatter of experimental data for the present short term accelerated tests a linear cumulative damage rule can still predict the creep/fatigue interaction. However the effects due to low frequency cyclic loading as well as degraded the steel under ex-service conditions tending to reductions in creep ductility show factors of two or more faster cracking rates compared to as received static testing. Unavailability of long term tests at low stresses may pose additional problems under creep since creep is stress state controlled but fatigue in not. However using plane strain predictions of crack initiation and growth data using the NSW multiaxial ductility creep crack growth model suggest that conservative predictions of long term cracking can still be made under creep/fatigue and when there is a marked reduction creep failure ductility.
format	Article
author	Norhaida, Ab. Razak Davies, Catrin Mair Nikbin, Kamran M.
author_facet	Norhaida, Ab. Razak Davies, Catrin Mair Nikbin, Kamran M.
author_sort	Norhaida, Ab. Razak
title	Testing and assessment of cracking in P91 steels under creep-fatigue loading conditions
title_short	Testing and assessment of cracking in P91 steels under creep-fatigue loading conditions
title_full	Testing and assessment of cracking in P91 steels under creep-fatigue loading conditions
title_fullStr	Testing and assessment of cracking in P91 steels under creep-fatigue loading conditions
title_full_unstemmed	Testing and assessment of cracking in P91 steels under creep-fatigue loading conditions
title_sort	testing and assessment of cracking in p91 steels under creep-fatigue loading conditions
publisher	Elsevier Ltd
publishDate	2018
url	http://umpir.ump.edu.my/id/eprint/20402/ http://umpir.ump.edu.my/id/eprint/20402/ http://umpir.ump.edu.my/id/eprint/20402/ http://umpir.ump.edu.my/id/eprint/20402/1/Testing%20and%20Assessment%20of%20Cracking%20In%20P91%20Steels%20Under%20Creep-Fatigue%20Loading%20Conditions.pdf http://umpir.ump.edu.my/id/eprint/20402/2/Testing%20and%20Assessment%20of%20Cracking%20In%20P91%20Steels%20Under%20Creep-Fatigue%20Loading%20Conditions%201.pdf
first_indexed	2018-09-07T02:38:36Z
last_indexed	2018-09-07T02:38:36Z
_version_	1610914638174617600

Testing and assessment of cracking in P91 steels under creep-fatigue loading conditions

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