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

Paper Number: 105965

105965 - Constraint Effect on Fracture in Ductile-Brittle Transition Temperature Region (Report 3) 

In order to predict fracture behavior in the ductile-brittle transition temperature region of a structure with low constraint, a plastic constraint correction coefficient χ was proposed, which has the parameters of a shape factor of the Weibull distribution for the Weibull stress, stress intensity factor converted from J, KJ, and a yield ratio Ry, yield strength/ultimate strength. The coefficient χ was proposed for a simplified facture evaluation to predict an accurate fracture behavior under pressurized thermal shock with an assumed flaw shape, depth 10mm and flaw length 60mm of under clad cracking. Two additional tensile fracture tests using flat plate specimens with a semielliptical surface flaw were conducted and evaluated to accumulate the technical background based on the coupled model of the Beremin model and the GTN model. Finally, a guideline for fracture evaluation procedure using plastic constraint effect was provided in a report of the CAF subcommittee of the Japan Welding Engineering Society. The guideline has two procedures, a numerical approach and a simplified approach. The numerical approach requires calculations of the Weibull stresses with a parameter KJ after ductile crack growth of the focused structure model and a fracture toughness specimen model. The simplified model requires only KJ calculation of the focused structure and uses the coefficient χ. A summary of the guideline was described in the paper.

Presenting Author: Kiminobu Hojo Mitsubishi Heavy Industries

Presenting Author Biography: Kiminobu Hojo joined Mitsubishi Heavy Industries I in 1983 and now Chief Staff Manager Expert. He has been engaged on structural integrity issues of nuclear power plants like LBB of stainless, carbon and low alloy steel, PTS, 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. He is an associate editor of Journal of Pressure Vessel Technology.

Authors:

Kiminobu Hojo Mitsubishi Heavy Industries
Takatoshi Hirota Mitsubishi Heavy Industries
Yasuto Nagoshi Mitsubishi Heavy Industires
Takuya Fukahori Mitsubishi Heavy Industries
Kimihisa Sakima Mitsubishi Heavy Industries
Mitsuru Ohata Osaka University
Fumiyoshi Minami Osaka University