Session: CS-10-01 Recent Developments in Japanese Codes and Standards

Paper Number: 61318

Start Time: Tuesday, July 13, 2021, 05:00 PM

61318 - Constraint Effect on Fracture in Ductile-Brittle Transition Temperature Region 

In order to predict fracture behavior of a structure with low constraint, bending fracture tests using flat plate specimens with a surface flaw, 1TC(T), and SE(B) specimens were performed at lower temperature in the ductile-brittle transition temperature (DBTT) region. The shape of the flat plate was 50mm thickness, 200mm width, and 500mm length. A semi-elliptical surface flaw of 5mm depth and 25mm length was introduced to the flat plate specimen. The thickness of SE(B) was 1T and the length was 250mm. Two types of SE(B) specimen with a shallow flaw or deep flaw were produced. The ratio of flaw depth to thickness (a/W) of a shallow flaw was 0.1 and that of a deep flaw was 0.5. The specimens’ material was low alloy steel. The tests of C(T) and SE(B) specimens were conducted at -80℃ and those of the flat plates were done at -120℃. All specimens showed cleavage fracture. The shape factor m, one of the Weibull parameters of the Beremin model, of the C(T) specimen or SE(B) specimen with a deep flaw determined by using each specimen’s type was between 130-150, which is unusually high. However, m determined by using both of SE(B) specimens with a/W=0.1 and 0.5 and the Toughness Scaling Model (TSM) was 26, which is a reasonable value. TSM is a calibration model of the Weibull parameters proposed by Gao, et al., so that σ_u of two types of specimens’ test data matches. The prediction analysis of the flat plate specimens using the Weibull parameters, m and σ_u, obtained by TSM was performed. As a result, the measured K_J of the flat plates specimens’ tests were located between the predicted 5% lower bound curve and 95% upper bound curve of for the flat plate specimen which was deduced by the SE(B) specimen’s test data. This means that the Weibull parameters of the Beremin model are temperature independent in the DBTT region if the fracture mode is secured as cleavage, and it is suggested that transferability from laboratory test specimens to a large specimen with low constraint which is similar to an actual structure is realized.

Presenting Author: Kiminobu Hojo Mitsubishi Heavy Industries Ltd

Authors:

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