PSI - Issue 17

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Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2019) 000 – 000

ScienceDirect ICSI 2019 The 3rd International Conference on Structural Integrity Creep- atche ing-fatigue life prediction of Procedia Structural Integrity 17 (2019) 555–561 bainitic 2.25Cr1MoV steel Zizhen Zhao a,b , Dunji Yu a , Xu Chen a * ICSI 2019 The 3rd International Conference on Structural Integrity Creep-ratcheting-fatigue life prediction of

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a School of Chemical Engineering and Technology, Tianjin University, Tianjin 300354, China b School of Mechanical and Automotive Engineering, Qilu University of Technology (Shandong academy of sciences), Jinan 250353, China

bainitic 2.25Cr1MoV steel Zizhen Zhao a,b , Dunji Yu a , Xu Chen a *

Abstract

Ratcheting fatigue behavior of bainitic 2.25Cr1MoV forged steel was investigated at 455 o C with various hold periods at peak and valley stress. The incorporation of peak stress holding widened stress-strain hysteresis loop, and this enlargement was more significant under peak/valley hold due to the created creep strain. Fatigue life was greatly shortened with the increase of mean stress or stress amplitude, and this reduction was accelerated when stress holding was involved. The extension of stress holding resulted in shorter fatigue life, but the fatigue lives were quite close when the sum of holding period was equal, regardless of the holding direction. Fatigue damage and creep damage in creep-ratcheting fatigue tests were estimated by the time fraction rule, and creep damage became dominant at long hold period, which was closely related to shortened fatigue lives with stress holding. The linear damage summation rule was used for fatigue life prediction, and it gave satisfactory predictions for peak holding mode. A new model was proposed by introducing stress ratio to consider the influence of asymmetric cycling, and estimates for peak/valley holding were greatly improved. a Scho l of Chemical Engineering and Techno ogy, T anjin Universi y, Tianjin 300354, China b School of Mechanical and Autom tive Engineering, Qilu University of Technology (Shandong academy of sciences), Jinan 250353, China Abstract Ratcheting fatigue behavior of bainitic 2.25Cr1MoV forged steel was investigated at 455 o C with various hold periods at peak and valley stress. The incorporation of peak stress holding widened stress-strain hysteresis loop, and this enlargement was more significant under peak/valley hold due to the created creep strain. Fatigue life was greatly shortened with the increase of mean stress or stress amplitude, and this reduction was accelerated when stress holding was involved. The extension of stress holding resulted in shorter fatigue life, but the fatigue lives were quite close when the sum of holding period was equal, regardless of the holding direction. Fatigue damage and creep damage in creep-ratcheting fatigue tests were estimated by the time fraction rule, and creep damage became dominant at long hold period, which was closely related to shortened fatigue lives with stress holding. The linear damage summation rule was used for fatigue life prediction, and it gave satisfactory predictions for peak holding mode. A new model was proposed by introducing stress ratio to consider the influence of asymmetric cycling, and estimates for peak/valley holding were greatly improved. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ICSI 2019 organizers. Keywords: Creep- ratcheting-fatigue, Stress holding, Creep damage, Life prediction

© 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ICSI 2019 organizers. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ICSI 2019 organizers.

* Corresponding author. Tel.: +86-13920573451; fax: +86-22-27403389. E-mail address: xchen@tju.edu.cn Keywords: Creep- ratcheting-fatigue, Stress holding, Creep damage, Life prediction

2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ICSI 2019 organizers.

* Corresponding author. Tel.: +86-13920573451; fax: +86-22-27403389. E-mail address: xchen@tju.edu.cn

2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ICSI 2019 organizers.

2452-3216  2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ICSI 2019 organizers. 10.1016/j.prostr.2019.08.074