Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
徐 平光; 石島 暖大; Qiu, H.*; 諸岡 聡; Gong, W.*; 川崎 卓郎; Harjo, S.
no journal, ,
High strength steels for pipelines and high-pressure vessels are susceptible to hydrogen embrittlement (HE), which is typically characterized by a loss of tensile ductility. In addition to the conventional factors including microstructure, hydrogen content, strain rate, temperature, and residual stress, the crystallographic texture has recently been reported to affect the HE susceptibility of steel plates. Here, the anisotropic tensile deformation behaviors and the texture evolution were comparably evaluated by using hydrogen-charged and non-charged tensile samples to investigate the mutual effect of texture and hydrogen charging. The changes in normalized diffraction intensities show that 
110
//RD (RD: rolling direction) preferred orientation becomes stronger during the RD tensile deformation of hydrogen-charged and non-charged samples; the multiaxial stress field during necking deformation induces more evident weakening of final 110//RD preferred orientation in the non-hydrogen steel. It suggests that the in situ neutron diffraction is suitable to monitor the plastic deformation behavior of hydrogen-charged high strength steel. Moreover, during the RD extension, 110//RD texture component becomes strong and the 200//TD
200//ND components (TD: transverse direction; ND: normal direction) have a uniform pole density distribution, and the hydrogen charging accelerates the formation of this distribution. During the TD extension, 110//TD component becomes strong, 200//ND component disperses towards the circular direction 60
-tilted from ND, and the hydrogen charging accelerates such grain rotations. The appearance of higher maximum pole density of (200) pole figure shows good correspondence to lower uniform ductility of hydrogen-charged TD sample.
Harjo, S.; 及川 健一; 川崎 卓郎; Grazzi, F.*; 篠原 武尚; 田中 眞奈子*
no journal, ,
In this study, we used neutron diffraction mapping measurements to elucidate the Japanese sword's microstructure and discuss the manufacturing procedures. Mapping measurements using pulsed neutron diffraction with time-of-flight method were performed on a full-shape and test pieces of Japanese sword. The distributions of residual macroscopic stresses in the width and thickness directions are small. The stress in the longitudinal direction is compressive at the ridge side, turns to quite large tensile at the middle part of width, then drastically decreases to be quite large compressive at the edge side of about -650 MPa.
熊谷 正芳*; 秋田 貢一*; 黒田 雅利*; Harjo, S.
no journal, ,
本研究では比較的微視組織の変化が顕著となる塑性変形を伴う繰返し負荷を対象として、中性子回折のラインプロファイル解析により、繰り返し負荷によって変化するオーステナイトステンレス鋼の転位組織を評価した。供試材には固溶化処理したオーステナイトステンレス鋼SUS316Lを用いた。繰返し負荷はJ-PARCのMLF(BL19)の中性子ビームラインに設置して行ない、任意の繰返し数負荷後、荷重が0となる状態で保持して中性子測定を行なった。負荷前の転位密度は0.5
10
m
であったが、繰返し負荷に伴い転位密度が急激に増加し、繰返し数50回では710mと最も転位密度が高くなった。
五十嵐 誉廣; 小松 篤史; 加藤 千明; 坂入 正敏*
no journal, ,
海浜地区にある橋梁や原子力施設等の大型構造物は海塩の飛来による厳しい腐食環境に晒されている。施設の安全性確保および環境・エネルギー問題の観点から、大型構造物の主要材料である鉄鋼材料の大気腐食のメカニズムを解明することは重要なテーマの一つである。本研究では、大気腐食に対する影響因子として降雨,湿度を考慮した既存モデルに対し、新たに温度を考慮した大気腐食減量予測モデルの構築を行った。開発モデルにより、既存モデルによる過分な腐食量予測が修正され、より精緻な大気腐食減量の予測が可能となった。