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1
Content available Development of a small Tsunami shelter and Its sea experiment of towing and drifting
Watanabe K., Mizuno S.
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
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2020
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Vol. 14, no. 1
75--81
EN
We developed a small Tsunami shelter. The design characteristics of this shelter are, its floater keeps the shelter floating even if the cabin space is fully flooded, the shelter can be self-recovered from the upside down situation when it rolls in the sea. When the shelter is washed away from the shore, it starts drifting. In that case, passengers might have to stay in the small cabin for several days. The length of the shelter is around 2m, which is much less than a typical life boat. So we carried out the first sea experiment using a real shelter with riding 8 passengers. In this paper, we’ll show the experimental results of motion sensor, towing force, as well as lessons learnt.
2
Content available The Age-Precipitations Structure Of Al-Mg-Ge Alloy Aged At 473K
Kawai A., Watanabe K., Matsuda K., Ikeno S.
Archives of Metallurgy and Materials
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2015
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Vol. 60, iss. 2A
969--970
EN
The Al-Mg-Ge alloy is one of the age-hardening aluminum alloy after solution heat treatment. It has been proposed that the age-precipitation behavior of Al-Mg-Ge alloy is different from that of Al-Mg-Si alloy according to our previous works about the microstructure on Al-Mg-Ge alloy over-aged at 523K. For example, The hardness of peak aged Al-1.0mass%Mg2Ge alloy is higher than that of Al-1.0mass%Mg2Si alloy. The precipitates in the over-aged samples have been classified as some metastable phases, such as the β’-phase and Type-A precipitates and equilibrium phase of β-Mg2Ge by TEM observation. There a few reports about microstructure on Al-Mg-Ge alloys observed by TEM for different aging times. The age-precipitations structure of Al-Mg-Ge alloy has not been became clear. In this work, TEM observation was investigated the microstructure on Al-1.0mass%Mg2Ge alloy for difference aging times aged at 473K.
PL
Stop Al-Mg-Ge należy do grupy stopów aluminium podatnych na obróbkę cieplną w postaci przesycania prowadzącą do utwardzenia wydzieleniowego. Na podstawie wcześniejszych badań dotyczących mikrostruktury stopu Al-Mg-Ge, starzonego w temp. 523K, przyjęto założenie, że proces utwardzania wydzieleniowego będzie zachodzić inaczej niż w przypadku standardowych stopów Al-Mg-Si. Zaobserwowano, że twardość starzonego stopu Al-1,0(%mas.)Mg2Ge jest wyższa od analogicznego stopu Al-1,0(%mas.)Mg2Si. Jednocześnie dzięki zastosowaniu mikroskopii TEM określono skład fazowy próbek po przestarzeniu. Występujące fazy w stopie Al-Mg-Ge to m.in. faza β’, wytrącenia typu A oraz faza równowagowa β-Mg2Ge. Dodatkowo, badania mikrostruktury z użyciem mikroskopii TEM wykonano dla różnych czasów starzenia stopu Al-1,0(%mas.)Mg2Ge, starzonego w temperaturze 473K.
3
Content available Tem Observation Of Precipitate Structures In Al-Zn-Mg Alloys With Additions Of Cu/Ag
Watanabe K., Matsuda K., Ikeno S., Yoshida T., Murakami S.
Archives of Metallurgy and Materials
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2015
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Vol. 60, iss. 2A
977--979
EN
Al-Zn-Mg alloy has been known as one of the aluminum alloys with the good age-hardening ability and the high strength among commercial aluminum alloys. The mechanical property of the limited ductility, however, is required to further improvement. In this work, three alloys, which were added Cu or Ag into the Al-Zn-Mg alloy, were prepared to compare the effect of the additional elements on the aging behavior. The content of Ag and Cu were 0.2at.% and the same as, respectively. Ag or Cu added alloy showed higher maximum hardness than base alloy. The particle shape and rod shape precipitates were observed in all alloys peak-aged at 423K. According to addition of Ag or Cu, the number density of the precipitates increased higher than that of base alloy.
PL
Al-Zn-Mg jest stopem, który można efektywnie poddawać procesowi utwardzania wydzieleniowego. Spośród różnorodnych stopów aluminium charakteryzuje się bardzo wysoką wytrzymałością mechaniczną, jednak jego ograniczona plastyczność jest cechą wymagającą poprawy. W toku prac przygotowano trzy stopy: stop bazowy Al-Zn-Mg oraz stopy zawierające dodatki Cu lub Ag, dla porównania wpływu tych dodatków na starzenie się materiału. Zawartość Ag i Cu wynosiła odpowiednio 0,2% at. Stopy z dodatkiem Ag lub Cu wykazywały większą twardość maksymalną w porównaniu ze stopem bazowym. We wszystkich stopach starzonych w temperaturze 423K obserwowano charakterystyczne wydzielenia, a ich koncentracja była odpowiednio większa dla stopów z dodatkiem Ag lub Cu.
4
Content available Tem Observation Of Age-Hardening Precipitation In Mg-Gd-Y Alloys As Different Gd/Y Ratio
Matsuoka Y., Watanabe K., Nakamura J., Lefebvre W., Saikawa S., Ikeno S., Matsuda K.
Archives of Metallurgy and Materials
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2015
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Vol. 60, iss. 2A
971--972
EN
In this study, the early stage of aging in Mg-Gd-Y alloys has been observed by transmission electron microscopy (TEM), high angle annular dark field – scanning transmission electron microscopy (HAADF-STEM) and calculations of images and electron density and bond overlap population (BOP) by first principal to understand the origin of precipitation in this alloy. The small hexagon of 0.37 nm is the first precipitate in this alloy, and this is the evidence of short range ordering of D019 structure. This is referred as the pre β”-phase. In the peak aged condition, β’ phase with bco structure was mainly observed.
PL
W pracy przedstawiono mikroskopowe obserwacje TEM wczesnego etapu starzenia stopów Mg-Gd-Y. Ponadto badania prowadzono z użyciem skaningowej transmisyjnej mikroskopii elektronowej. Wykorzystano zjawisko niekoherentnego rozpraszania w ciemnym polu i materiał obrazowano przy pomocy detektora pierścieniowego, który zbiera elektrony rozproszone pod dużymi kątami (HAADF-STEM). Przeprowadzono także analizę obrazów, obliczenie gęstości elektronowej i ilości nakładających się wiązań w celu zrozumienia źródła wydzieleń w ww. stopie. Pierwszym wytrąceniem w stopie jest mały sześciokąt o wielkości 0,37 nm, a dowodem tego jest uporządkowanie krótkiego zasięgu struktury D019.
5
Content available Dynamic characteristics measurements of a force transducer against small and short-duration impact forces
Djamal M., Watanabe K., Irisa K., Prayogi I. A., Takita A., Yamaguchi T., Fujii Y.
Metrology and Measurement Systems
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2014
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Vol. 21, nr 1
59--66
EN
A method for evaluating the dynamic characteristics of force transducers against small and short-duration impact forces is developed. In this method, a small mass collides with a force transducer and the impact force is measured with high accuracy as the inertial force of the mass. A pneumatic linear bearing is used to achieve linear motion with sufficiently small friction acting on the mass, which is the moving part of the bearing. Small and short-duration impact forces with a maximum impact force of approximately 5 N and minimum half-value width of approximately 1 ms are applied to a force transducer and the impulse responses are evaluated.
6
Content available remote Illumination method for high resolution imaging
Watanabe K.
Optica Applicata
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2011
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Vol. 41, nr 1
135--144
EN
Annularly distributed light is proposed to increase the spatial resolution when observing a water surface. When light with an annular distribution is used to illuminate the entrance pupil of an objective lens, an air -water interface can be illuminated with a Bessel beam, which is a focused beam formed by plane wave components at the same angle. If the optimum size and width of the annular light and radial polarization are chosen, a microscopic distribution is obtainable from the reflected light intensity. It is theoretically shown that the reflectance changes with the width of annular light and this allows to make water surface measurements. In order to clarify the spatial resolution, the electric field intensity distribution on the focusing plane is also calculated. From the full width at half maximum of the calculated distribution, it is shown that the annularly distributed light increases the spatial resolution by increasing the radius of the annular light and decreasing the wavelength of the light. It is also shown that a spatial resolution of a few hundred nanometers is achievable.
7
Evaluation of interlaminar shear stresses in a fiber-reinforced laminated beam by the ifrm theory
Kurashige M., Yamamoto K., Watanabe K.
Applied Mechanics and Engineering
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1998
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Vol. 3, no 4
601-619
EN
By using the linear IFRM theory, interlaminar shear stresses are estimated for a fiber-reinforced laminated beam subjected to a line force. The analysis for this estimation is fully three-dimensional. The beam has three layers. Its core is reinforced in the width direction, whereas its skins in the longitudinal direction. The skins are also assumed to have infinitesimal thickness for the sake of analytical simplicity. In spite of this assumption, inextensibility of the skin layers is valid, since the IFRM theory postulates that the materials are completely inextensible in fiber directions. The analytical results explain very well the observations of delamination shapes and justify applicability of various beam theories to the theoretical analysis of the observations in beam impact tests by use of a line nose impactor. It is also shown that the IFRM theory can explain the observed slight deviation of the delamination from the interface at its early stage.
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