関西造船協会誌

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This paper presents the test results which were carried out to examine suitability of a 9% nickel steel (quenched and tempered) for the materials of L.M.G. vessels. V-notch Charpy tests and ESSO tests were employed to investigate the fracture toughness at low temperature. Welded joints of the plates using Inconel type electrodes and austenitic stainless type ones were also tested. The results were obtained as follows : Brittle fracture did not initiate at a temperature of -190℃ or above, and also did not propagate at a temperature of -180℃ or above in the virgin plates of the steel. The critical temperatures of brittle fracture, however, were raised by annealing or other heat treatment. V-notch Charpy tests showed the lowest values at fusion zone of a weld, but no brittle fracture was produced by ESSO tests at a temperatures of -180℃ or above. V-notch Charpy values at low temperature were slightly decreased by plastic prestraining.

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A special silencer (desurger) was developed at Kawasaki Dockyard Co. Ltd. to attenuate noises in a wide range, caused by high speed pumps, motors and oil piping systems. This, as can be seen from Fig.2, comprises a perforated pipe surrounded by a gas vessel. The gas vessel is precharged rather like a rubber-bag accumlator. And then, some tests on this desurger were performed and the results were as follows ; (1) It is possible to attenuate some of the noise by the use of this device. (2) The cut off frequency of this device is relatively low, and it shows effective damping over a wide range of frequency. (3) Precharged gas pressure is effective over pressure ranges from 60 to 90 percent of the system pressure. (4) Small holes seem to bo more likely to the perforated pipe rather than large holes. Suitable design of a special silencer, can make relatively noiseless out-put.

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Anti-rolling characteristics of Flume tanks are investigated by series of bench tests, results of which are analysed and expressd in terms of (C sin δ)/ω and C cos δ. Generally speaking, (1) Large anti-rolling moment is expected for large l_n/l_T ratio. (2) The frequency at peak value of (C sin δ)/ω (ω_t^') is smaller than ω_t (frequency of tank water). (3) An emprical formula for ω_t is obtained in the form ; [numerical formula]

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In this paper, a method is presented for calculation of still water bending moments and trim which are directly related to determination of tank arrangements. Regarding hull structure as a simple beam supported at the ends and the bending moments due to weight and buoyancy, acting on the hull are obtained at an arbitrary point by this method. For estimation of the buoyancy, data of bending moment of ships built at our yard are used, and the trim is also calculated by this method. Though this method has higher accurcy than the conventional methods for our ships, there still remains room to be improved in accuracy. Meanwhile authors consider this method may also be used for determination of tank arrangements.

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