Influences of shot-peening on fine grain steels

Recently, fine grain steel has been actively researched. However, as we know, the influence concerning the shot peening processing to fine grain steels has been few reported up to now. Therefore residual stress distribution near the surface of fine grain steel after shot-peening was measured by X-ray diffraction technology. Moreover, the hardening effect the distributed near the shot-peened surface was also estimated. The relationships between the effects of shot-peening and the grain size of material were discussed. Copyright © 2007 by The International Society of Off shore and Polar Engineers(ISOPE)

Influence of steel grain size on residual stress in grinding processing

金沢大学大学院自然科学研究科The fine-grained rolling steels NFG600 and the conventional usual rolling steels SM490 were processed by sand paper polishing and mechanical grinding to compare the residual stress generated after processing. The average grain size of NFG600 and SM490 is 3 μm and 15μm respectively. Therefore improvement of mechanical properties for such fine-grained steels is expected, it is important to understand the residual stress state of new fine-grained materials with processing. In this study, multi axial stresses of two kinds of specimens after polishing and grinding were measured by three kinds of analysis methods including cos-ψ method. As a result, as for σ33, the stress of NFG was compression, though that of SM490 was tension. © (2010) Trans Tech Publications

Probable detection of an eruptive filament from a superflare on a solar-type star

太陽型星のスーパーフレアから噴出する巨大フィラメントを初検出 --昔の、そして今の惑星環境や文明に与える脅威--. 京都大学プレスリリース. 2021-12-10.Solar flares are often accompanied by filament/prominence eruptions (~10⁴ K and ~10¹⁰⁻¹¹ cm⁻³), sometimes leading to coronal mass ejections that directly affect the Earth’s environment. ‘Superflares’ are found on some active solar-type (G-type main-sequence) stars, but the filament eruption–coronal mass ejection association has not been established. Here we show that our optical spectroscopic observation of the young solar-type star EK Draconis reveals evidence for a stellar filament eruption associated with a superflare. This superflare emitted a radiated energy of 2.0 × 10³³ erg, and a blueshifted hydrogen absorption component with a high velocity of −510 km s⁻¹ was observed shortly afterwards. The temporal changes in the spectra strongly resemble those of solar filament eruptions. Comparing this eruption with solar filament eruptions in terms of the length scale and velocity strongly suggests that a stellar coronal mass ejection occurred. The erupted filament mass of 1.1 × 10¹⁸ g is ten times larger than those of the largest solar coronal mass ejections. The massive filament eruption and an associated coronal mass ejection provide the opportunity to evaluate how they affect the environment of young exoplanets/the young Earth6 and stellar mass/angular momentum evolution

Influences of shot-peening on fine grain steels

Recently, fine grain steel has been actively researched. However, as we know, the influence concerning the shot peening processing to fine grain steels has been few reported up to now. Therefore residual stress distribution near the surface of fine grain steel after shot-peening was measured by X-ray diffraction technology. Moreover, the hardening effect the distributed near the shot-peened surface was also estimated. The relationships between the effects of shot-peening and the grain size of material were discussed. KEY WORDS: Fine grain steel; Shot-peening; Residual stress; Vickers hardness; X-ray; FWH