Non-destructive evaluation of discontinuous creep crack growth in 316H stainless steel
File(s)
Author(s)
Jones, Edmund
Type
Thesis
Abstract
Component life assessment is of great importance in the nuclear industry and has become of particular interest during the life extension of advanced gas cooled reactors (AGRs). Creep crack growth (CCG) is a significant failure mode for components in AGRs. Laboratory CCG tests are used to determine CCG laws that are applied to component life assessments. Accurate non-destructive evaluation (NDE) methods are critical for laboratory CCG tests to be valid and useful. The CCG tests currently use direct current potential drop (DCPD) measurement systems to evaluate the crack length. However, there have been concerns about the accuracy of the DCPD method for sizing discontinuous cracks as often found in CCG tests performed on 316H stainless steel.
This thesis investigates discontinuous cracking, a characteristic form of creep damage ahead of a stress concentration in 316H stainless steel. This thesis will show that DCPD is not effective at sizing discontinuous creep damage in examples presented in this work the real extent of damage was greater than three times the size predicted using DCPD. This has implications for the accuracy of component life assessments and CCG testing undertaken using DCPD over the past 40 years.
This thesis proposes an alternative measurement system to size creep damage during CCG testing. This alternative method uses a temporal Rayleigh wave ultrasound approach. The interaction of Rayleigh waves with different crack like defects is presented, showing the feasibility of a measurement systems using Rayleigh waves. The development of the practical measurement system to size creep damage in compact tension (CT) samples using waveguides is presented. This novel measurement systems performance is shown to outperform DCPD in a CCG test. The Rayleigh wave measurement system predicting the extent of a 1.4 mm discontinuous creep crack within 0.2 mm while DCPD predicted a crack length of 0.4 mm.
This thesis investigates discontinuous cracking, a characteristic form of creep damage ahead of a stress concentration in 316H stainless steel. This thesis will show that DCPD is not effective at sizing discontinuous creep damage in examples presented in this work the real extent of damage was greater than three times the size predicted using DCPD. This has implications for the accuracy of component life assessments and CCG testing undertaken using DCPD over the past 40 years.
This thesis proposes an alternative measurement system to size creep damage during CCG testing. This alternative method uses a temporal Rayleigh wave ultrasound approach. The interaction of Rayleigh waves with different crack like defects is presented, showing the feasibility of a measurement systems using Rayleigh waves. The development of the practical measurement system to size creep damage in compact tension (CT) samples using waveguides is presented. This novel measurement systems performance is shown to outperform DCPD in a CCG test. The Rayleigh wave measurement system predicting the extent of a 1.4 mm discontinuous creep crack within 0.2 mm while DCPD predicted a crack length of 0.4 mm.
Version
Open Access
Date Issued
2023-12-23
Date Awarded
2024-03-01
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Joseph Corcoran, Catrin M., Davies
Sponsor
Engineering and Physical Sciences Research Council
EDF Energy (Firm)
Publisher Department
Mechanical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)