Session: SE-09-01 Advanced Seismic Evaluation and Code - 1

Paper Number: 106549

106549 - Very Low Cycle Fatigue Evaluation of Pipe Elbow and Experimental Validations: I- Quasi-Static Cyclic Loading Test 

The structural reliability of the nuclear power plants piping under BDBE (Beyond Design Basis Earthquake) condition is an important issue. This paper reports recent experimental and numerical works to develop accurate fatigue evaluation methods for piping components under very low cycle fatigue loading conditions.

Firstly, carbon steel pipe elbow test under very low cyclic loading conditions was performed.  In the test, two different pipe schedules were tested with and without internal pressure.  The quasi-static cyclic loading was applied to the specimen.  Failure location and cycles were measured from the test.  Then, various strain-based fatigue evaluation methods were applied to check their accuracy.  The methods include ASME BPVC Sec. III Code Case N-900 and ASME BPVC Sec. VIII Div. 2 Part 5. When evaluation results are compared with experimental failure cycles, it is found that
- The Code Case N-900 method gives very conservative results in all cases
- The ASME BPVC Sec. VIII Div. 2 Part 5 improves the assessment results compared to CC N-900, but still gives very conservative results in all cases.
To improve the accuracy of very low cycle fatigue evaluation results, the concept of the void shrinkage is incorporated into the method which is similar to ASME BPVC Sec. VIII Div. 2 Part 5.  It is found that
- The method incorporating the void shrinkage effect significantly improves the assessment results in all cases and still gives conservative results.
 

Presenting Author: Yun-Jae Kim Korea University

Presenting Author Biography: Yun-Jae Kim achieved his Ph.D. in Mechanical Engineering from Massachusetts Institute of Technology in May 1993.
He is currently a professor in the Department of Mechanical Engineering, Korea University.
He has conducted research in various fields of fracture mechanics including ductile crack growth, fatigue, creep, etc.

Authors:

Jong-Min Lee Korea University
Yun-Jae Kim Korea University
Hyun-Seok Song Korea University
Jin-Weon Kim Chosun University