Session: DA-03-01 Fatigue 1-Research on Effects of Surface Finishing and Mean Stress on Fatigue Lives of Notched Specimens

Paper Number: 121251

121251 - Research on Effects of Surface Finishing and Mean Stress on Fatigue Lives of Notched Specimens - Test Plan and Summary of Outcomes - 

   DFC and DFC2 subcommittees in the Japan Welding Engineering Society developed a new approach of fatigue analysis method. This fatigue analysis method has been made several modifications and incorporated into the JSME Environmental Fatigue Evaluation Method 2022 Edition (JSME S NF1-2022). Research on effects of surface finishing and mean stress on fatigue lives of notched specimens have been followed by DFC3 and DFC4 subcommittees. In this paper, overview of the outcomes of DFC3 and DFC4 subcommittees is introduced.
   In this series of research, effects of surface finishing on fatigue strength and relation between a fatigue strength reduction factor and mean stress correction have been investigated using notched specimens. Carbon steel STPT370 (equivalent to SA-106 Gr.A) and low alloy steel SFVQ1A (equivalent to SA-508 Gr.3 Cl.1 ) were employed as the test materials.
   Regarding effects of surface finishing, the fatigue strength reduction factor for surface finish effect, Ksf, which is defined as the ratio of fatigue strength between polished specimens and surface finished specimens, is employed. The validity of the Ksf equation that is incorporated into the JSME Environmental Fatigue Evaluation Method was confirmed by the DFC3 subcommittee. The applicability of this Ksf equation to notched specimens has been investigated. The fatigue strengths of polished notched specimens and as-machined notched specimens with Rz = 25 μm are compared to investigate the effects of surface finishing by machining on fatigue strength. Based on the experimental results, the applicability of the Ksf equation to notched specimens has been confirmed.
   The order of consideration of fatigue strength reduction factor and mean stress correction may not be considered if the Smith-Watson-Topper approach can be applied to mean stress correction. Hence, fatigue tests with mean stress have been performed to notched specimens, and the applicability of the Smith-Watson-Topper approach with stress concentration and mean stress have been confirmed based on the experimental results.
 

Presenting Author: Seiji Asada Mitsubishi Heavy Industries Ltd

Presenting Author Biography: - Graduated from Kobe University in March 1987
- Master’s degree from Kobe University in March 1989
- PhD from Kobe University in March 2009
- Joined Mitsubishi Heavy Industries in April 1989.
- Since joined in Mitsubishi heavy Industries, I have been in charge of designing and development of Reactor Pressure Vessels. Especially I have made a lot of effort at stress analysis, fatigue analysis, irradiation embrittlement issue of RPVs, fracture mechanics, and so on.
- Chair of SDO (Standard Development Organization) Convergence Board
- Member: [ASME Code Committee] BPV III, SG on Component Design, WG on Environmental Fatigue Evaluation Method
[JSME] Subcommittee on Nuclear, SG on Design and Construction, SG on Fatigue Evaluation, and so on.

Authors:

Seiji Asada Mitsubishi Heavy Industries Ltd
Akihiko Hirano Hitachi-GE Nuclear Energy, Ltd
Masao Itatani Toshiba Energy Systems & Solutions Corporation
Yoshihide Kitamura The Kansai Electric Power Co., Inc.
Takeshi Ogawa Aoyama Gakuin University