Session: CS-21-01 Constraint Effects on C&S

Paper Number: 123140

123140 - Plastic Constraint Correction Factor χ for Wes Standard on Brittle Fracture in Ductile-Brittle Transition Temperature Region 

In order to predict fracture behavior of a reactor vessel in the ductile-brittle transition temperature region under pressurized thermal shock, a plastic constraint correction factor χ is intended to be introduced into a Japan Welding Society standard. The WES standard will have two levels’ fracture assessments, Level I, a simplified assessment, and Level II, a detailed assessment. The plastic constraint correction factor χ for Level I will be provided by formulas with the parameters, yield strength σy, strength ratio Ry defined by the ratio of yield strength σy to ultimate strength σB , and the Weibull shape factor m with some application limitations. Further, the plastic correction factor χ should depend on geometry factors, such as flaw depth a, flaw aspect ratio a/c, and structure’s thickness. In this paper, sensitivity analyses were performed for thickness, flaw depth, flaw aspect ratio, strength ratio, and the Weibull shape parameter m to apply the plastic constraint correction factor χ for Level I assessment to various reactor vessels. Also, temperature dependency of the Weibull parameters, m and σu was investigated. Based on these results, the formulas of χ were revised and the application limitations for the parameters were expanded. This paper will be one of technical basis for the WES standard.  

Presenting Author: Kiminobu Hojo Mitsubishi Heavy Industries Ltd

Presenting Author Biography: Kiminobu Hojo joined Mitsubishi Heavy Industries I in 1983 and now Chief Staff Manager Expert. He studied local approach at Kernforshungszentrum Karsruhe (KfK) in Germany in 1993 and he has been engaged on structural integrity issues of nuclear power plants like LBB of cast stainless steel and low alloy steel pipes, PTS, thermal aging of CASS, thermal stratification, high cycle thermal fatigue. Now his major interest is constraint effect on fracture.
He is a member of subgroups and a chairman of a working group of JSME Codes and Standards Committee . He is also a member of working groups and a subgroup and Standard Committee of ASME Sec. XI.

Authors:

Kiminobu Hojo Mitsubishi Heavy Industries Ltd
Takatoshi Hirota Mitsubishi Heavy Industries
Yasuto Nagoshi Mitsubishi Heavy Industries
Takuya Fukahori Mitsubishi Heavy Industries
Kazuma Shimizu Osaka University
Masaki Shimodaira Japan Atomic Enegy Agency
Takuya Ogawa Toshiba Energy Sysems
Kenji Yasirodai Hitachi, Ltd.
Mitsuru Ohata Osaka University
Fumiyoshi Minami Osaka University