In nuclear power plants, surface treatment including the shot peening is carried out after welding for the prevention of stress corrosion cracking. In this research, the authors developed evaluation systems of the persistence of compressive residual stresses due to shot peening based on the Idealized Explicit FEM which can conduct large-scale non-linear structure analyses in realistic computing time. The developed evaluation system was applied to the analysis of the compressive residual stress due to sho...
英字タイトル:
Study of behaver to relieve residual stress at the time of the shot peening

中性子回折法は中性子の優れた透過能を生かすことで、数十 mmメーターオーダーの材料深部の応力・ひずみを非破壊で測定できる唯一の測定技術として知られており、種々の機械構造物の残留応力測定を通して、高性能、高信頼性、長寿命化を目指した製品開発や構造設計に大きく貢献している [1]。一方、材料強度や破壊メカニズムを議論するうえでは、単に残留応力を測定するだけでなく、弾性ひずみ（応力）や集合組織、転位密度等のミクロ組織因子を定量的に評価することが重要である。 多くの実用材料は複数のミクロ組織（複合組織）で構成されているため、不均一な塑性変形を起こす特徴があり、これに起因して内部応力が発生する。例えば、曲げ加工した板材は、板厚方向にマクロな応力分布が発生する。これを第一種（残留）応力（マクロ応力）と呼び、残留応力測定の主たる対象となる。一方、二つ以上の異なる材料を一体的に組み合わせた複合材料や複合組織を有する合金は、相界面や結晶粒界近傍にミクロな応力分布が発生する。これを第二種（残留）応力（ミクロ応力）と呼び、マクロ応力と区別する必要がある [2, 3]。このミクロ応力に起因する弾性ひずみ等の情報を得るうえで、中性子回...

To validate the FEM simulation technique presented in the previous report, we made pipe butt welded joints between base metals of the same material SUS316L and between base metals of the dissimilar materials SUS316L and STPT370. Shot peening (SP) on the outer surface or the inner surface of these welded joints induces high compressive residual stresses on the surface. After heat treatment with the peak temperature of 623 K was applied to the welded joints, they retained high compressive residual stresses ...
英字タイトル:
Evaluation of the sustainability of compressive residual stress by introduced a stress improvement method (the second report) ?Residual stress change of welded joint with shot peening by thermal cycle and stress loading.

When the steel structure is built such as nuclear power plant, residual stress occurs in or near the welding joint and it may cause the stress collision cracking(SCC). Therefore, as prediction of SCC, surface treatment such as the shot peening(following SP) is carried out in the weld, but the case analyzed about residual stress reforming by the SP does not exist. So, we developed the analysis method that can predict compressive residual stress relaxation behavior during shot peening by modelling dynami...
英字タイトル:
Evaluation of the sustainability of compressive residual stress by introduced a stress improvement method (the first report) -Development of analysis method of the shot peening using idealized explicit FEM