Session: SE-09-01 Advanced Seismic Evaluation and Code (Joint session with C&S)

Paper Number: 153490

153490 - Very Low Cycle Fatigue Evaluation of Pipe Elbow Under Quasi-Static Loading and Experimental Validation 

Abstract: 

The International Atomic Energy Agency (IAEA) now emphasizes that the structural integrity of critical safety equipment and facilities must be ensured under both design-basis and beyond-design-basis earthquake. For ensuring structural integrity against earthquakes, it is crucial to apply proper elastic-plastic fatigue analyses. In this study, fatigue analyses were conducted on 90-degree elbows using the method proposed in ASME Code Case N-900, JSME Code Case NC-CC-008, and ASME Section VIII Div.2 Part 5.

The elbows used in the research were made from SA234 WPB carbon steel and SA403 WP316 stainless steel, materials used in primary and secondary piping systems of nuclear power plants. Quasi-static displacement-controlled cyclic loadings were applied at room and operation temperature. To simulate the pipe elbow tests, 3D elastic-plastic FE analyses were performed using two different cyclic hardening (bi-linear and Chaboche kinematic hardening) models. The FE analysis was validated by comparing the reaction forces from the experiments. The evaluation was conducted using the analysis data at the damage locations, and results were verified by calculating the Cumulative Usage Factor (CUF). For both SA234 WPB and SA403 WP316 Sch. 40 specimens, the results indicated that the number of damage cycles decreases under internal pressure in experiments but increases in evaluations. An attempt is made to explain this discrepancy using the ratcheting strain effect.

Presenting Author: Joo-Young Park Korea University

Presenting Author Biography: Joo-Young Park received a master’s degree in Mechanical Engineering from Korea University under the supervision of Professor Yun-Jae Kim. The primary research focus was on very low cycle fatigue.

Authors:

Joo-Young Park Korea University
Ki-Wan Seo Korea University
Hyun-Seok Song Korea University
Yun-Jae Kim Korea University
Jin-Weon Kim Chosun University
Do-Jun Shim Electric Power Research Institute