Use of CTOD as crack driving force parameter for low-cycle thermal fatigue

Juha Kuutti, Iikka Virkkunen

Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

Abstract

Repeated exposure to rapid temperature transients causes gradual damage in material. This is called thermal fatigue. Thermal fatigue is an important degradation mechanism in nuclear power plant components and can limit the plant lifetime where thermal loads are present, e.g., due to turbulent mixing or change in plant operating conditions. The effects of the thermal load cycles include residual stresses, hardening or softening of the material and, finally, crack initiation and growth. Traditionally, thermal fatigue crack growth rates are estimated from the stress intensity factors calculated from uncracked stress distributions and the Paris' law. In the low-cycle regime, the use of weight function based stress intensity factor solutions derived under linear elastic assumptions is questionable due to considerable plasticity. On the other hand, numerical contour integral techniques are ill-suited for thermal cyclic loading. In this work, the use of the crack opening displacement as the crack driving force parameter is evaluated through simulations of a low-cycle thermal fatigue experiments. The use of the crack tip opening displacement avoids the traditional limitations in the numerical evaluation of the J-integral. The unique relationship between the crack opening displacement and J-integral is derived and the crack driving force is used in a crack growth assessment. The results show that the crack driving force calculated from the uncracked stress distributions overestimates the crack driving force significantly (as compared to values calculated from the crack opening displacement). The crack growth rate calculated with the Paris' law is in good agreement with the experimental results, when the crack driving force is computed from the crack opening displacement.
Original languageEnglish
Title of host publicationSMiRT-24, Conference on Structural Mechanics in Reactor Technology
PublisherInternational Assn for Structural Mechanics in Reactor Technology IASMiRT
Publication statusPublished - 2017
MoE publication typeA4 Article in a conference publication
Event22nd International Conference on Structural Mechanics in Reactor Technology 2013, SMiRT 22 - San Francisco, United States
Duration: 18 Aug 201323 Aug 2013
Conference number: 23

Publication series

NameTransactions of the International Conference on Structural Mechanics in Reactor Technology
ISSN (Print)0167-563X

Conference

Conference22nd International Conference on Structural Mechanics in Reactor Technology 2013, SMiRT 22
Abbreviated titleSMiRT 22
CountryUnited States
CitySan Francisco
Period18/08/1323/08/13

Fingerprint

Thermal fatigue
Cracks
Crack propagation
Thermal load
Stress intensity factors
Stress concentration
Fatigue crack propagation
Crack initiation
Crack tips
Nuclear power plants
Plasticity
Hardening
Residual stresses
Degradation

Cite this

Kuutti, J., & Virkkunen, I. (2017). Use of CTOD as crack driving force parameter for low-cycle thermal fatigue. In SMiRT-24, Conference on Structural Mechanics in Reactor Technology International Assn for Structural Mechanics in Reactor Technology IASMiRT . Transactions of the International conference on structural mechanics in reactor technology
Kuutti, Juha ; Virkkunen, Iikka. / Use of CTOD as crack driving force parameter for low-cycle thermal fatigue. SMiRT-24, Conference on Structural Mechanics in Reactor Technology. International Assn for Structural Mechanics in Reactor Technology IASMiRT , 2017. (Transactions of the International conference on structural mechanics in reactor technology).
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abstract = "Repeated exposure to rapid temperature transients causes gradual damage in material. This is called thermal fatigue. Thermal fatigue is an important degradation mechanism in nuclear power plant components and can limit the plant lifetime where thermal loads are present, e.g., due to turbulent mixing or change in plant operating conditions. The effects of the thermal load cycles include residual stresses, hardening or softening of the material and, finally, crack initiation and growth. Traditionally, thermal fatigue crack growth rates are estimated from the stress intensity factors calculated from uncracked stress distributions and the Paris' law. In the low-cycle regime, the use of weight function based stress intensity factor solutions derived under linear elastic assumptions is questionable due to considerable plasticity. On the other hand, numerical contour integral techniques are ill-suited for thermal cyclic loading. In this work, the use of the crack opening displacement as the crack driving force parameter is evaluated through simulations of a low-cycle thermal fatigue experiments. The use of the crack tip opening displacement avoids the traditional limitations in the numerical evaluation of the J-integral. The unique relationship between the crack opening displacement and J-integral is derived and the crack driving force is used in a crack growth assessment. The results show that the crack driving force calculated from the uncracked stress distributions overestimates the crack driving force significantly (as compared to values calculated from the crack opening displacement). The crack growth rate calculated with the Paris' law is in good agreement with the experimental results, when the crack driving force is computed from the crack opening displacement.",
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Kuutti, J & Virkkunen, I 2017, Use of CTOD as crack driving force parameter for low-cycle thermal fatigue. in SMiRT-24, Conference on Structural Mechanics in Reactor Technology. International Assn for Structural Mechanics in Reactor Technology IASMiRT , Transactions of the International conference on structural mechanics in reactor technology, 22nd International Conference on Structural Mechanics in Reactor Technology 2013, SMiRT 22, San Francisco, United States, 18/08/13.

Use of CTOD as crack driving force parameter for low-cycle thermal fatigue. / Kuutti, Juha; Virkkunen, Iikka.

SMiRT-24, Conference on Structural Mechanics in Reactor Technology. International Assn for Structural Mechanics in Reactor Technology IASMiRT , 2017. (Transactions of the International conference on structural mechanics in reactor technology).

Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

TY - GEN

T1 - Use of CTOD as crack driving force parameter for low-cycle thermal fatigue

AU - Kuutti, Juha

AU - Virkkunen, Iikka

PY - 2017

Y1 - 2017

N2 - Repeated exposure to rapid temperature transients causes gradual damage in material. This is called thermal fatigue. Thermal fatigue is an important degradation mechanism in nuclear power plant components and can limit the plant lifetime where thermal loads are present, e.g., due to turbulent mixing or change in plant operating conditions. The effects of the thermal load cycles include residual stresses, hardening or softening of the material and, finally, crack initiation and growth. Traditionally, thermal fatigue crack growth rates are estimated from the stress intensity factors calculated from uncracked stress distributions and the Paris' law. In the low-cycle regime, the use of weight function based stress intensity factor solutions derived under linear elastic assumptions is questionable due to considerable plasticity. On the other hand, numerical contour integral techniques are ill-suited for thermal cyclic loading. In this work, the use of the crack opening displacement as the crack driving force parameter is evaluated through simulations of a low-cycle thermal fatigue experiments. The use of the crack tip opening displacement avoids the traditional limitations in the numerical evaluation of the J-integral. The unique relationship between the crack opening displacement and J-integral is derived and the crack driving force is used in a crack growth assessment. The results show that the crack driving force calculated from the uncracked stress distributions overestimates the crack driving force significantly (as compared to values calculated from the crack opening displacement). The crack growth rate calculated with the Paris' law is in good agreement with the experimental results, when the crack driving force is computed from the crack opening displacement.

AB - Repeated exposure to rapid temperature transients causes gradual damage in material. This is called thermal fatigue. Thermal fatigue is an important degradation mechanism in nuclear power plant components and can limit the plant lifetime where thermal loads are present, e.g., due to turbulent mixing or change in plant operating conditions. The effects of the thermal load cycles include residual stresses, hardening or softening of the material and, finally, crack initiation and growth. Traditionally, thermal fatigue crack growth rates are estimated from the stress intensity factors calculated from uncracked stress distributions and the Paris' law. In the low-cycle regime, the use of weight function based stress intensity factor solutions derived under linear elastic assumptions is questionable due to considerable plasticity. On the other hand, numerical contour integral techniques are ill-suited for thermal cyclic loading. In this work, the use of the crack opening displacement as the crack driving force parameter is evaluated through simulations of a low-cycle thermal fatigue experiments. The use of the crack tip opening displacement avoids the traditional limitations in the numerical evaluation of the J-integral. The unique relationship between the crack opening displacement and J-integral is derived and the crack driving force is used in a crack growth assessment. The results show that the crack driving force calculated from the uncracked stress distributions overestimates the crack driving force significantly (as compared to values calculated from the crack opening displacement). The crack growth rate calculated with the Paris' law is in good agreement with the experimental results, when the crack driving force is computed from the crack opening displacement.

M3 - Conference article in proceedings

T3 - Transactions of the International Conference on Structural Mechanics in Reactor Technology

BT - SMiRT-24, Conference on Structural Mechanics in Reactor Technology

PB - International Assn for Structural Mechanics in Reactor Technology IASMiRT

ER -

Kuutti J, Virkkunen I. Use of CTOD as crack driving force parameter for low-cycle thermal fatigue. In SMiRT-24, Conference on Structural Mechanics in Reactor Technology. International Assn for Structural Mechanics in Reactor Technology IASMiRT . 2017. (Transactions of the International conference on structural mechanics in reactor technology).