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Study on Quality Control Utilizing Stress Concentration Factor of Welded Joint Toe using Laser Scanning Measurement for Chemical Tanker
Get PDFIn this study, the welded joint surface shapes of fatigue test specimens simulated as the cruciform welded joints between the transverse bulkhead and the double bottom were measured by a weld bead laser scanner and the stress concentration factors (KtL) of the welded joint of the specimens were calculated by using the conventional estimating equation with the measured geometrical data of the welded parts. In addition, the static FEM analysis was also conducted to obtain the stress concentration factors (KtF) using the same measured data.
Comparing the stress concentration factors KtL and KtF with the stress concentration factor KtS calculated by the conventional estimating method with silicon mold, it was shown that KtL and KtF values were about the same as that of KtS.
In addition, the representative value of the fatigue strength at 2×10 6 cycles for cruciform welded joint was derived considering the fatigue test results using the cruciform welded joint specimens and the results of previous studies, the allowable stress concentration factor (KtA) was presumed based on the representative value of fatigue strength and design S－N curve for cruciform welded joints.
As a result, it is proposed that the guarantee which fatigue crack initiation does not occur at the toe of welded joint can be valid when the geometry of weld joints in the cargo tank structure under construction at shipbuilding site is measured by using the weld bead laser scanner and immediately the stress concentration factor KtL or KtF is calculated and the value is evaluated less than KtA.
This is a revolutionary technique in terms of quality control and assurance of shipbuilding.departmental bulletin pape
Proof that the Center of Buoyancy is Equal to the Center of Hydrostatic Pressure —Part 2 : Semi-Submerged Circular Cylinder and Triangular Prism—
Get PDFWe recently proved that “ the center of buoyancy of floating bodies is equal to the center of hydrostatic pressure". This subject was an unsolved problem in physics and naval architecture, even though the buoyancy taught by Archimedes' principle can be obtained clearly by the surface integral of hydrostatic pressure. Then we thought that the reason why the vertical position of the center of pressure could not
be determined was that the horizontal force would be zero due to equilibrium in the upright state.
As a breakthrough, we dared to assume the left right asymmetric pressure field by inclining the floating body with heel angle θ. In that state, the force and moment due to hydrostatic pressure were calculated correctly with respect to the tilted coordinate system fixed to the body. By doing so, we succeeded in determining the center of pressure. Then, by setting the heel angle θ to zero in order to make it upright state, it could be proved that the center of hydrostatic pressure is equal to the well-known center of buoyancy, i.e., the centroid of the cross-sectional area under the water surface.
As noted above, we have already proved this problem for rectangular and arbitrarily shaped cross-sections, and published them here on viXra.org in English. Although the case of a semi-submerged circular cylinder and a triangular prism are also included in the proof of arbitrary shapes, we prove for each shape separately in this 2nd report, since they are two typical cross-sectional shapes along with rectangles. However, there is an essential difference in the proof between the two shapes . The reason is why the former does not change its underwater shape when inclined laterally, while the latter, like the rectangle, changes its cross-sectional shape when inclined. The present paper provides clear proofs for both shapes.departmental bulletin pape
A Study on Miniaturization of Wide-range Anode Power Supply for Hall Thruster
Get PDF長崎総合科学大学博士（工学）2022doctoral thesi
Current Situation and Issues of Acceptance of Students in Need of Japanese Language Guidance in Nagasaki Prefecture：Based on a MEXT survey, 2021 school year
Get PDFE(その他)departmental bulletin pape
Study on Application of SEA to Laminated Structures of Different Materials
Get PDFP(論文)This paper describes a method of construction of analytical SEA model for a laminated structure of different materials similar to the structure of tire tread. First, the transmittance was derived using the semi-infinite theory of bending waves in the longitudinal direction, and the coupling loss factors were obtained from area junction and structural volume. After that, the subsystem vibration energy normalized by the input power under arbitrary input was obtained, and compared with the experimental results by SEA using FEM constructed. As a result, the method is shown to work qualitatively well to the subsystem vibration energy normalized by the input power.departmental bulletin pape
Experimental Study on the Generation of a Group Wave and the Behaviors of a Floating Body in a Group Wave
Get PDFReproducing way of a group wave, which is a group of waves of relatively large height, in a wave basin and the behaviors of a floating body in a group wave are investigated experimentally. Rather than encountering a single extremely large wave, floating bodies could fall into more dangerous situation when they encounter a group wave. For example, if a floating body, after encountering the first wave of a group wave and inclining toward its weather side, happened to encounter the second wave, the wave could run up on the deck and further tilt the floating body and so on, which may finally evolve into a serious maritime accident.departmental bulletin pape
A Study on Nagasaki Peace Park through a Documentary Survey on Memorial Services for the A-Bomb Victims soon after the World War Ⅱ, with a focus point on the Location of the Ground Zero
Get PDFThis paper studies local newspapers soon after World War Ⅱ. The aim of this study is to take a new look at the spot of Ground Zero by checking memorial services for the A-bomb victims and reconsider the concept in Nagasaki Peace Park planning.departmental bulletin pape