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Busi, M.*; Kalentics, N.*; Morgano, M.*; Griffiths, S.*; Tremsin, A. S.*; 篠原 武尚; Log
, R.*; Leinenbach, C.*; Strobl, M.*
Scientific Reports (Internet), 11, p.14919_1 - 14919_9, 2021/07
被引用回数：8 パーセンタイル：29.90(Multidisciplinary Sciences)Laser powder bed fusion is an additive manufacturing technique extensively used for the production of metallic components. Despite this process has reached a status at which parts are produced with mechanical properties comparable to those from conventional production, it is still prone to introduce detrimental tensile residual stresses towards the surfaces along the building direction, implying negative consequences on fatigue life and resistance to crack formations. Laser shock peening (LSP) is a promising method adopted to compensate tensile residual stresses and to introduce beneficial compressive residual stress on the treated surfaces. Using neutron Bragg edge imaging, we perform a parametric study of LSP applied to 316L steel samples produced by laser powder bed fusion additive manufacturing.
Busi, M.*; Kalentics, N.*; Morgano, M.*; Griffiths, S.*; Tremsin, A. S.*; 篠原 武尚; Log, R.*; Leinenbach, C.*; Strobl, M.*
Additive Manufacturing, 39, p.101848_1 - 101848_9, 2021/03
被引用回数：22 パーセンタイル：64.84(Engineering, Manufacturing)Laser powder bed fusion is an efficient technique for additive manufacturing of metallic materials. The quality of the material produced depends on the optimization of a large range of build parameters and the complex thermo- mechanical build process is prone to inducing detrimental material features such as porosity and residual stresses negatively affecting fatigue resistance and lifetime. Here we apply neutron Bragg edge radiography in a para- metric study on printing 316L steel. The parameters concerned are the laser scanning speed and strategy as well as the optional use of support structures. Analyses of the full field single shot wavelength-resolved Bragg edge radiography data enables to characterize local density inhomogeneities, as well as cracks, based on the long wavelength tail of the spectrum and variations of the stress field but also textural features based on the Bragg edge pattern. It is found that in the performed study not only respective differences in the residual stresses due to parameter variation are manifesting but also systematic irregularities due to machine imperfections (e.g. issues with the powder coater) are observed in the printed samples. The study supports the use of the parallel scanning strategy without supports and with the lower utilized scanning speed.
Martin, P. G.*; Jones, C. P.*; Cipiccia, S.*; Batey, D. J.*; Hallam, K. R.*; 佐藤 志彦; Griffiths, I.*; Rau, C.*; Richards, D. A.*; 末木 啓介*; et al.
Scientific Reports (Internet), 10, p.1636_1 - 1636_11, 2020/01
被引用回数：10 パーセンタイル：30.15(Multidisciplinary Sciences)Both the three-dimensional internal structure and elemental distribution of near-field radioactive fallout particulate material released during the March 2011 accident at the Fukushima Daiichi Nuclear Power Plant is analysed using combined high-resolution laboratory and synchrotron radiation X-ray techniques. Results from this study allow for the proposition of the likely formation mechanism of the particles, as well as the potential risks associated with their existence in the environment, and the likely implications for future planned reactor decommissioning. A suite of particles is analyzed from a locality 2 km from the north-western perimeter of the site north of the primary contaminant plume in an area formerly attributed to being contaminated by fallout from reactor Unit 1. The particles are shown to exhibit significant structural similarities; being amorphous with a textured exterior, and containing inclusions of contrasting compositions, as well as an extensive internal void volume bimodal in its size distribution. A heterogeneous distribution of the various elemental constituents is observed inside a representative particle, which also exhibited a Fukushima-derived radiocesium (
Cs, 
Cs and 
Cs) signature with negligible natural Cs. We consider the structure and composition of the particle to suggest it formed from materials associated with the reactor Unit 1 building explosion, with debris fragments embedded into the particles surface. Such a high void ratio, comparable to geological pumice, suggests such material formed during a rapid depressurisation and is potentially susceptible to fragmentation through attrition.
