International round robin test on Master Curve reference temperature evaluation utilizing Miniature C(T) specimen

Yamamoto, Masato*; Onizawa, Kunio; Yoshimoto, Kentaro*; Ogawa, Takuya*; Mabuchi, Yasuhiro*; Valo, M.*; Lambrecht, M.*; Viehrig, H.-W.*; Miura, Naoki*; Soneda, Naoki*

Small Specimen Test Techniques; 6th Volume (ASTM STP 1576), p.53 - 69, 2015/05

https://doi.org/10.1520/STP1576-EB

In order to ensure the robustness of the Master Curve technique, round-robin tests were performed using 0.16 inch-thick Mini-CT specimens by different investigators to see if consistent values can be obtained. All the specimens used were machined and pre-cracked by one fabricator from unique Japanese RPV material. Seven institutes participated in this exercise, and obtained valid values according to the ASTM E1921 standard. The scatter of values obtained was well within the uncertainty range defined in the standard, indicating the robustness of the Mini-CT specimen test technique. Throughout this activity, we could obtain 182 for a single material. We investigated the statistics of this large database, and found that there is no remarkable difference not only in the values but also in the fracture toughness distribution between the Mini-CT specimen and the standard size 1T-C(T) specimen results.

A Round robin propgram of master curve evaluation using miniature C(T) specimens, 3; Comparison of under various selections of temperature conditions

Yamamoto, Masato*; Kimura, Akihiko*; Onizawa, Kunio; Yoshimoto, Kentaro*; Ogawa, Takuya*; Mabuchi, Yasuhiro*; Viehrig, H.-W.*; Miura, Naoki*; Soneda, Naoki*

Proceedings of 2014 ASME Pressure Vessels and Piping Conference (PVP 2014) (DVD-ROM), 7 Pages, 2014/07

https://doi.org/10.1115/PVP2014-28898

The Master Curve (MC) approach for the fracture toughness reference temperature To is expected to be a powerful tool to ensure the reliability of long-term used RPV steels. In order to get sufficient number of data for the MC approach related to the present surveillance program for RPVs, the use of miniature specimens is important. The test technique for the miniature specimens (Mini-CT) of 4 mm thick had been verified the basic applicability of MC approach by means of Mini-CT for the determination of fracture toughness of typical Japanese RPV steels. A round robin (RR) program was organized to assure the robustness of the technique. As the third step of RR program, blinded tests were carried out. Precise material information was not provided to the participants. From the results obtained, the scatter range in was within the acceptable scatter range specified in the testing standard. The selection of testing temperature seems to give limited effect like that in larger specimens.

Hardening of Al-Cu-Mg alloy by energetic ion irradiation

Mitsuda, Tomoaki*; Kobayashi, Ippei*; Kosugi, Shinya*; Fujita, Naoki*; Saito, Yuichi; Hori, Fuminobu*; Semboshi, Satoshi*; Kaneno, Yasuyuki*; Nishida, Kenji*; Soneda, Naoki*; et al.

Journal of Nuclear Materials, 408(2), p.201 - 204, 2011/01

https://doi.org/10.1016/j.jnucmat.2010.10.013

First-principles molecular dynamics simulation of SiC devices; Generation of amorphous SiO/SiC interface

Miyashita, Atsumi; Yoshikawa, Masahito; Kano, Takuma; Onuma, Toshiharu*; Sakai, Takayuki*; Iwasawa, Misako*; Soneda, Naoki*

Annual Report of the Earth Simulator Center April 2004 - March 2005, p.287 - 291, 2005/12

Silicon carbide semiconductor device is expected to be used under a severe environment like the nuclear reactor and the space environment. On the semiconductor device interface, the electric charge state of the defect decides an electric characteristic. To emulate interfacial structure the interface structure is generated and the electronic geometry is decided by the first-principle molecular dynamics simulation with the earth simulator. The amorphous interface structure is made by medium-scale model of about 400 atoms. The heating temperature is 4000K, the heating time is 3.0ps, the speed of rapid cooling is -1000K/ps, and SiC movable layers in the interface are assumed to be 4 layers. In temperature 2200K the terminal was opened to make the layer more amorphous. The model has almost abrupt interface, however, some defects energy levels were still observed in the band gap. The energy levels are originated from interfacial oxygen. The localized electronic distribution of the dangling bond causes defect energy levels.

First-principles molecular dynamics simulation of oxide layers for SiC devices

Miyashita, Atsumi; Onuma, Toshiharu*; Sakai, Takayuki*; Iwasawa, Misako*; Yoshikawa, Masahito; Kano, Takuma; Soneda, Naoki*

no journal, , 

no abstracts in English