Session: CS-16-01 Fatigue and Ratcheting Issues in Pressure Vessel and Piping Design-1

Paper Number: 152607

152607 - Chaboche Kinematic Hardening Model for Cyclic Ratcheting Simulation: Continuous and Discontinuous Hardening Materials 

Abstract: 

Ratcheting occurs when plastic deformation accumulates in a specific direction under asymmetric cyclic loading. In piping systems under seismic loads, the geometrical asymmetry of elbows and tees can induce ratcheting. Ratcheting behavior of piping has been reported in tests conducted by NIED in Japan (Nakamura et al., 2001) and the EPRI Piping and Fitting Dynamic Reliability Program (EPRI, 1994). Ratcheting fatigue failure was also observed in load-controlled quasi-static elbow tests (Lee et al., 2023).

The current elastic analysis-based fatigue assessment method is overly conservative for ensuring the integrity of nuclear power plant piping under large-amplitude seismic loads. To reduce conservatism, ASME Code Case N-900 and JSME Code Case NC-CC-008 present fatigue evaluation methods based on elastic-plastic analysis. However, the ASME Code Case does not specify a material hardening model for use in elastic-plastic analysis. For the JSME Code Case, a bi-linear kinematic hardening model is presented, which may not be suitable for predicting ratcheting behavior. To perform elastic-plastic fatigue assessment, a non-linear kinematic hardening model might be more appropriate. A procedure for calibrating the Chaboche kinematic hardening model using the monotonic stress-strain curve has been proposed (Kalnins et al., 2013; Weitze et al., 2014; Gilman et al., 2015). However, the kinematic hardening model determined by the method lies significantly below the original curve, thus requiring manual re-calibration. In addition, no specific method has been presented for materials with discontinuous hardening behavior.

In this study, a method for determining the parameters of the Chaboche kinematic hardening model with three backstress terms is presented. This method utilizes monotonic stress-strain curves. Kinematic hardening parameters can be determined through formulas, without the need for additional calibration procedures. In addition, a procedure for determining parameters is presented not only for continuous hardening materials but also for discontinuous hardening materials. The parameter determination procedure proposed in this study was validated through load-controlled cyclic loading notch bar tests. The notch bar tests involving two materials (SA508 Gr.1a - discontinuous yielding material, and SA312 TP316 - continuous yielding material) and various load ratios (R=-1 to 0) were simulated with determined Chaboche kinematic hardening model. In all cases, ratcheting behavior was predicted conservatively.

Furthermore, to verify the applicability to the pipe elbow, a quasi-static displacement-controlled cyclic loading test on a pipe elbow made of SA234 WPB carbon steel was simulated using both the bi-linear and Chaboche kinematic hardening models. The hoop-direction ratcheting strain measured on the elbow flank in the test could be properly predicted by the Chaboche kinematic hardening model, in contrast to the bi-linear model.

References

[1]    Izumi, Nakamura, Akihito, Otani, and Masaki, Shiratori. “Study on estimation method of seismic safety margin of aged piping system and equipment.” Technical note of the National Research Institute for Earth Science and Disaster Prevention, Vol. 220, (2001): pp. 1-78. http://doi.org/10.24732/nied.00001834
[2]    EPRI TR-102792-V2, “Piping and Fitting Dynamic Reliability Program-V2: Component Tests.” (1994)
[3]    Lee, Jong-Min, Kim, Jae-Yoon, Song, Hyun-Seok, Kim, Yun-Jae, and Kim, Jin-Weon. “Experimental validation of ASME strain-based seismic assessment methods using piping elbow test data.” Nuclear Engineering and Technology, Vol. 55, (2023): pp. 1616–1629. https://doi.org/10.1016/j.net.2023.01.027
[4]    Arturs, Kalnins, Jürgen, Rudolph, Adrain, Willuweit, “USING THE NONLINEAR KINEMATIC HARDENING MATERIAL MODEL OF CHABOCHE FOR ELASTIC-PLASTIC RATCHETING ANALYSIS”, Proceedings of the ASME 2013 Pressure Vessels and Piping Conference, Paper No. PVP2013-98150. https://doi.org/10.1115/PVP2013-98150
[5]    Willam, F. Weitze, P.E., Timothy, D. Gilman, “ADDITIONAL GUIDANCE FOR INELASTIC RATCHETING ANALYSIS USING THE CHABOCHE MODEL”, Proceedings of the ASME 2014 Pressure Vessels and Piping Conference, Paper No. PVP2014-28772. https://doi.org/10.1115/PVP2014-28772
[6]    Tim, Gilman, Bill, Weitze, Jürgen, Rudolph, Adrain, Willuweit, Arturs, Kalnins, “USING NONLINEAR KINEMATIC HARDENING MATERIAL MODELS FOR ELASTIC-PLASTIC RATCHETING ANALYSIS”, Proceedings of the ASME 2015 Pressure Vessels and Piping Conference, Paper No. PVP2015-45674. https://doi.org/10.1115/PVP2015-45674
 

Presenting Author: Hyun-Seok Song Korea University

Presenting Author Biography: Hyun-Seok Song received a master's degree in mechanical engineering from Korea University under the guidance of Professor Yun-Jae Kim. He is currently a PhD student in mechanical engineering at the Korea University. His main research subject is very low cycle fatigue.

Authors:

Hyun-Seok Song Korea University
Yun-Jae Kim Korea University
Jin-Weon Kim Chosun University
Do-Jun Shim Electric Power Research Institute