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Article type: Cover
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Published: December 30, 1982
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Article type: Index
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Article type: Appendix
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Published: December 30, 1982
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Ryoichiro SASANO, Kanenori YOKOTA, Hiroshi KURODA, Hitoshi HASHIMOTO, ...
Article type: Article
Pages
1-7
Published: December 30, 1982
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In shipbuilding, many sorts of measuring and datarecording tasks can be found in the production shops, and these tasks really occupy many man-hours, being compared with other works in production. Recently the remarkable development in the technology of electronics has made microprocessors and microcomputers available with very reasonable prices. The application of the these devices is expanding into various fields, taking advantages of the usefulness as a tool of automation and mechanization. Some examples of the application and development of microcomputers, as parts of machinery systems and devices in the following tasks in shipbulding, are reported in this paper. * measuring the thickness of coated paint. * measuring the dimensions of the container storage cells. * measuring the thickness of the chock-liners for main engine seats. * measuring the alignment of the center of the propeller shaft. * measurements in the test of the performance of the generators. These five microcomputer-applied devices have accomplished designed performance successfully, resulting in the remarkable reduction in man-hours of operation.
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Ken KINOSHITA, Kenichi SAIJO, Hironori YOKOMIZO
Article type: Article
Pages
9-14
Published: December 30, 1982
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Wave power absorber KAIMEI, which is one of floating attenuators of oscillating water column, is analyzed theoretically by using equivalent floating body approximation. Computations are carried out for two type sections, one of which is catamaran and another is a revised one with bottom plate, assuming uniform sections, and neglecting hydrodynamic interaction between sections as strip theory. The results are compared with experimental data and summarized as follows: 1) The method presented in this paper predicts both characteristics of motions and power absorption, qualitatively and semi-quantitatively. 2) But we may have to take into account viscous damping to heaving motion of the revised KAIMEI with bottom plate. 3) Calculated power absorption per width is almost same with each other in case of two catamaran KAIMEIs adopted in this paper. 4) The bottom plate is effective both to reduce the motions and to enlarge the power absorption.
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Norio TANAKA, Yoshiho IKEDA, Hidehiko OKADA
Article type: Article
Pages
15-23
Published: December 30, 1982
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In this paper, roll damping characteristics of small fishing vessels are investigated experimentally. Measurements of the roll damping, the sway damping and the cross-coupling dampings of four small fishing vessels are carried out to reveal that the ratio of the wave damping component and the viscous damping one strongly depends on the hull shape, the appendages, the location of the center of gravity and the loaded conditon. The roll damping of two fu11-scale vessels is also measured and shows fairly good agreement with model expriments. This result suggests that the scale effect on roll damping is not so significant for such a small fishing vessel.
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Yoshiho IKEDA, hiroto MIKI
Article type: Article
Pages
25-31
Published: December 30, 1982
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In this paper, the authors investigate a rational treatment of the viscous effect on a coupled motion of a ship in waves. In the linear theory, the non-linear viscous effects are taken into account by using equivalent linear forces obtained by linearizing the non-linear ones which are usually assumed to be proportional to the square of the each velocity component. Exactly speaking, however, the viscous forces are proportional to the square of the resultant local relative velocity. Then, it is more rational to use the equivalent forces obtained by linearizing the square of the resultant velocity. From this standpoint, a prediction method of the bilge keel effect on roll damping of a ship in sway-roll coupled motion is presented. The results of the present method show fairly good agreement with experimental ones which are obtained by sway-roll coupled forced motion tests.
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Hiroshi MINEMATSU
Article type: Article
Pages
33-41
Published: December 30, 1982
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Floating marine structures, in many cases, employ bodies of revolution as their component members. Prediction of hydrodynamic characteristics of these bodies could be very much simplified owing to their symmetry compared with other objects of general form. This is especially the case with vertical bodies of revolution. Several methods for calculating hydrodynamic forces on vertical bodies of revolution, which utilizes theri axial symmetry, have been proposed, and each of the may be said to posess its own merits. As for results of experiments, while many examples are known of measured vertical forces due to waves and forced heaving osci11ation, very few are available for the modes of sway and roll. In view of this, we carried out forced oscillation tests and wave-excited force tests with emphasis on sway and roll, using a model of an axisymmetric column with spherical footing. We also calculated hydrodynamic forces on a few bodies including the above said model by a source distribution method which employs ring elements and is similar in principle to that developed by Fenton. For examining accuracy of this method, we first compared the values by this method for the half-immersed sphere with those presented by Kim. Then, we compared the results by this method for the above said model with those by another well known method using quadrilateral elements, and with the results of the experiments. Good agreement observed in all of these comparisons may be said to show satisfactory accuracy of this theoretical method and, at the same time, high reliability of the results of the experiments.
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Matao TAKAGI, Haruo FURUKAWA, Ken TAKAGI
Article type: Article
Pages
43-52
Published: December 30, 1982
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The precizeness of the various hydrodynamic solutions of the two-dimensional oscillating floating-bodies with arbitrary shapes is examined. The methods of the solution which are used in this paper are as follows: a) Integral-Equation Method with Irregular Frequency (Abbriviated OSD) b) Integral-Equation Method without Irregular Frequency (MSD) c) Multipole Expansion Method with n-Parameters Conformal Mapping (GUT) d) Multipole Expansion Method without Conformal Mapping (DME) e) Hybrid Multipole Expansion Method (HME) The examined results show the followings: i) In the complex shapes the irregular frequencies disturb the preciseness of the calculation. Ogilvie's method) is usefull to remove the irregular frequencies from the integral-equation method. ii) GUT gives the correct solution in much less calculation time compared with the OSD or MSD. But, if we have a even slight difference between a given shape and the one inversely-mapped from the circle, the solution is not always good. iii) DME in which the boundary condition is satisfied just on the body gives fairly good solutions if the shape of a given body is near a circle. iv) HME which combine GUT with DME gives very hopeful results.
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Hisayoshi TATANO
Article type: Article
Pages
53-60
Published: December 30, 1982
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In this paper a towed barge was treated for improving her course stability and following results were obtained. 1) After some model experiments, skegs of the barge were replaced with a pair of wing type ones but the barge not only showed poor improvement in course stability but also a remarkable increase of resistance. 2) For shifting the center of lateral resistance to aft, the bottom forward of the model was trimmed down, the stern bottom was also trimmed and modified to fit a pair of skegs, keeping full breadth and full draft at the stern. By these reforms, the model showed superior ability as it was easily towed on a straight course by a tug-boat model. Accordingly, a full scale barge of this type might have good ability for keeping on course. 3) For judging course stability, Takekawa, et al have already showed us the following inequalities; A',B',C',D'>0 and A'B'C'-C'^2-A'^2D'>0. Now the author found out that total resistance coefficients in the B', C' and D' play an important role on scale effects of course stability of towed barges. Naturally, at a certain Froude number, the coefficient for a full scale barge is always smaller than that of the model's and because of this, a barge shows poor course stability comparad to that of the model.
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Yutaka MASUYAMA
Article type: Article
Pages
61-69
Published: December 30, 1982
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With the aim of estimating performance of a hydrofoil sailing boat, hydrodynamic characteristics of a hydrofoil system is investigated by model experiment and theoretical calculation. The foil types investigated are submerged horizontal foil, surface-piercing dihedral foil, inverted "T" foil as well as a hydrofoil system for a sailing boat, composed of these types of folis. The submerged horizontal foil and the surface-piercing dihedral foil have ogival section with round leading edge and inverted "T" foil has NACA 16-009 section. Experiments are made at the towing tank of Osaka University, speed beeing 2.5m/s and 3.0m/s corresponding to F_n of 3.02 and 3.62, and R_n of l.9×10^5 and 2.3×10^5 respectively. Theoretical calculations of hydrofoil performance including free surface effect are carried out by Wadlin's method and Nishiyama's lifting line theory. For the submerged horizontal foil, the Wadlin's and Nishiyama's theories agree well with experimental results. For the surface-piercing dihedral foil, the calculation of Nishiyama's theory gives satisfactory results compared with the experiments. On the other hand in applying Wadlin's theory to this foi1, the surface-piercing foil is replaced by a horizontal foi1 of the same span at the average immersion of the surface-piercing foil (mid-span point immersion). This simple replacement works well for the aspect ratios of greater than two. The effect of leeway for the foil system is also treated. At a small leeway angle, the effect of the down wash of front foil to back foil proved negligible.
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Sumitoshi MIZOGUCH
Article type: Article
Pages
71-83
Published: December 30, 1982
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In the strip methods of OSM, NSM and STF, the wave exciting forces are expressed in terms of the added-mass and damping coefficients evaluated at the encounter frequency, ω_e. In the Newman's strip method, however, they are expressed in terms of the coefficients as a function of the incident wave frequency, ω_o, In this paper, it is assumed that the diffraction potential for the vertical exciting forces is periodic in the x-direction (the x axis is positive forward), while the diffraction potential for the horizontal exciting forces is slowly varying in the x-direction. From these assumptions, it is obtained that the vertical exciting forces should be calculated on ω_o and the horizontal exciting forces should be calculated on ω_e. The exciting forces on a model of S-175 container ship in regular oblique waves are measured in IHI Seakeeping and Maneuvering Tank and the test results are compared with the calculations on ω_e and ω_o. The followings are conclusive results ; 1) Test results of heave exciting forces and pitch exciting moments are in good agreement with the calculations on ω_o, and show no effect on the forward-speed. 2) Test results of sway exciting forces and yaw exciting moments show a good agreement with the calculations on ω_e.
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Matao TAKAGI, Kimio SAITO
Article type: Article
Pages
85-91
Published: December 30, 1982
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In the previous papers a calculation method for the memory effect function, the hydrodynamic response for an impulse motion, was shown. In this paper the transient responses of a two-dimensional body are discussed. In the first part of the paper, the transient responses of a stepwisely or sinusoidaly heaving circular cylinder on still water are evaluated using the memory effect function. The results are compared with the asymptotic value and the steady state response respectively. In the second part of the paper, the transient responses of a linearly non-linearly moored circular cylinder in the regular waves are calculated. The comparisons between the results obtained from the equation of motion in the time domain and the ones from the equation of motion in the Frequency domain are made. Fairly large differences between the two results are recognized when the motion due to the natural frequency of the mooring system appears in an early stage depending on the conditions of the waves and the restoring forces.
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Kohei MATSUMOTO, Kenji ARIMA, Toshimasa SAITOH
Article type: Article
Pages
93-100
Published: December 30, 1982
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This paper presents a calculation method of anadded virtual mass for so-called HZ nozzle. The theoretical added mass is derived from velocity potentials of the two or three dimensional fluid region around HZ nozzle. Model experiments are carried out for five models. Natural frequencies and mode shapes in air and water are measured. The added virtual mass can be obtained from model test by use of similarity law. The calculated natural frequency by this method are found to give a good pridiction value by comparison with the measured value of actual ships.
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Toshimasa KAWANISHI, Wataru KATO, Takeshi SUZUKI
Article type: Article
Pages
101-105
Published: December 30, 1982
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The tension leg platform is a type of moored stable platform whose buoyancy exceeds the weight. The supplementary equilibriating downward force is supplied by tensioned vertical anchor wires. For such a platform, heave, roll and pitch motions will be suppressed. In order to design a reliable anchoring system, it is necessary to accurately predict the forces in the mooring legs induced by earthquake action and the platform motions. This paper presents analysis and a model test of response of a tension-leg single buoy mooring system subjected to earthquake excitation with consideration of hydro elasticity. Based on the results of the test, it can be confirmed that for the purpose of the design of T.L.P. the vertical component of earthquake must be sufficiently taken into consideration.
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Takeshi TANAKA, Ryoichi SUZAWA, Fumiyoshi KANATANI, Syuichi MURAMATSU, ...
Article type: Article
Pages
107-115
Published: December 30, 1982
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There are two kinds of high tensile steel plate for hull according to the yielding strength ; HT32 (32kgf/mm^2) and HT36 (36kgf/mm^2). Many shipyards in Japan have mainly used HT32, but recently started to study the use of HT36 in order to save ship propulsion energy by reducing hull steel weight, etc. Kawasaki Heavy Industries, Ltd. also has carried out various test for HT36 to be used in a 130,000-DWT bulk carrier, and established its welding construction process. This paper describes the results of various labolatory tests for HT36 and production tests in the actual ship.
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Mikihiro KOBAYASHI, Toshitsugu HIRAYAMA, Yoichi OMURA, Mitsuaki NAKASH ...
Article type: Article
Pages
117-123
Published: December 30, 1982
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As weight reducing is most important for SWATHS (Small Waterplane Area Twin Hull Ship) in attaining higher speed due to its sensitiveness, special structure system was applied to the main hull of the SWATHS, which was constructed in our yard, based on the following design concept. (i) Thickness of skin plates to be applied is so thin as to be sufficient for strength to lateral pressure. (ii) Instead of the above, main structural supports which consist of plate girders of I-section keep sufficient strength even though neglecting the skin plates effects. Nevertheless, there seems to be considerable effects of the thin skin plates. In order to clarifying the above concept and to confirm strutural characteristics in strength of new ship type, bending tests on actual SWATHS were carried out at our pier when completed. Results of the tests show the effectiveness of the thin plates and possibility of reducing weight with further study executed.
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Kouhei MATSUMOTO, Kenji ARIMA, Shuuji MURATA, Hiroaki KADOH
Article type: Article
Pages
125-134
Published: December 30, 1982
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A safety analysis against structural damage due to a hydrofoil boat impact on drifters of sea surface is an important problem because of its high speed running. In this paper, impact strength of foils of a hydrofoil boat on driftwood was investigated. In order to obtain the energy-absorbing ability of wood, dynamic impact test as well as statical bending test were carried out. The analytical method of impact strength was shown considering relation between the plastic collapse load of foils, the absorbed energy by wood and the lost kinetic energy of the boat. The method was applied to an impact analysis for a 130 passengers hydrofoil boat.
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Masakats MATSUISHI, Setsuo IWATA
Article type: Article
Pages
135-139
Published: December 30, 1982
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Recent studies have shown that concrete reinforced with short lengths or steel fibers possesses some improved characteristics when compared to ordinary concrete. The safety and durability of offshore structures is assured, if steel fiber reinforced concrete is placed over the surface of steel structures or if steel fiber reinforced concrete is used at the region of concrete structures where large tensile stress is induced. Steel fiber reinforced concrete is reintorced with short and discontinuous tibers, randomly oriented and uniformly dispersed. Because of the relatively small cracking strain of Portland cement concrete or mortal, initial cracking occurs at a relatively early stage. The matrix crack is bridged by discontinuous fibers. As the result, asignificant contribution of the fibers occurs after the matrix starts cracking. In the papel, the authurs carried out the probabilistic analysis of the number of fibers intersecting a cross section of the concrete normal to the direction of the applied tension. Fiber orientation and dispertion considered in the analysis are a one-dimensional random distribution, a two-dimensional random distribution and a three-dimensional random distribution. In the analysis, the restraint of fiber distribution by surtaces of the concrete are fully considered. The expected number of fibers contributing to the tensile strength can be increased by aligning the fibers with the loading direction.
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Masakatsu MATSUISHI, Setsuo IWATA
Article type: Article
Pages
141-148
Published: December 30, 1982
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Recent studies have shown that concrete reinforced with short lengths of steel fibers possesses some improved characteristics when compared to ordinary concrete. Steel fiber reinforced concrete (SFRC) is reinforced with short and discontinuous fibers, randomly oriented and uniformly dispersed. Because of the relatively small cracking strain of Portland cement concrete or mortal, initial cracking occurs at a relatively early stage. The matrix crack is bridged by discontinuous fibers. As the result, a signficant contribution of the fibers occurs after the matrix starts cracking. The authors carried out a series of pull-out tests on SFRC subjected to tensile loading. Empirical formula was obtained of peak pull-out loads of straight and/or inclined fibers. The authors also carried out the probabilistic analysis of the number of fibers contributing to tensile strength. In the present paper, the authors carried out theoretical analysis of the expected strength of SFRC. It was confirmed that the expected strength of SFRC could be increased by aligning the fibers with the loading direction.
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Kazuo KADA, Masakatsu BABA, Akira EMOTO, Yoshihiko SAKAGUCHI
Article type: Article
Pages
149-155
Published: December 30, 1982
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A comparatively small spherical tank can be supported by ring support system which support the tank along a latitude of the lower hemisphere (see Fig. 1). This report describes the study on the strength of the ring support system for a small spherical tank. The study has been made by the following methods : 1) Water test using a model tank of 3m diameter and 3.2mm shell thicness in upright condition and 30°heel condition. 2) FEM stress analysis for the mode1 tank and an actual tank. The main findings from the above study are as follows : 1) The stresses around the support ring measured in the model tank test agree well with the FEM analysis in both upright and 30° heel conditions, which proves the propriety of the analysis method. 2) The test in 30° heel condition proves that the specially designed stopper of the tank movement works effectively. 3) The FEM stress analysis for the actual tank proves that ring support system is practically applicable to an actual tank.
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Hiroo KADA, Koichi OSHIMA, Toshio HASHIZUME, Koji KAWAKATSU, Yoshio FU ...
Article type: Article
Pages
157-165
Published: December 30, 1982
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In this paper, the behaviour and the strength of simply supported plates (aspect ratio α=1,2 and α=∞ (infinitely long plates)) under combined loads of biaxial compression and hydrostatic pressure are theoretically investigated following the previous studies. At the sametime, effects of aspect ratio of plates on the behaviour and the strength are also discussed from these results. Results obtained in this study are summarized as follows: 1) Carrying out the analyses based on basic equations deduced to pursue the elastic behaviour of plates under such combined loads, characteristics of behaviours including buckling phenomena are clarified. 2) The compressive strength of such a plate is calculated in the same way as the previous paper), and characteristics of the compressive strength and the collapse mode of the plates (α=1,2 and ∞) are clarified. 3) From above results, it is found that in the case of plates having the small value of compessive loads ratio P_y/P_x effects of aspect ratio of the plate on the behaviour including buckling phenomena and the compressive strength are generally similar to those in the case of P_y/P_x=0, while in the case of plates having the large value of P_y/P_x those are different and in the case of comparatively thin plates the compressive strength for the plate of α=∞ is remarkably low in comparison with those for plates of α=1,2.
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Yasumitsu TOMITA, Yukio FUJIMOTO
Article type: Article
Pages
167-175
Published: December 30, 1982
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This paper presents a methed to estimate an actual load on ship structural members and proposes an allowable stress for fatigue strength of the members. The method for evaluation of the load was developed by fatigue analysis of the following conditions, that is, period of service years, crack length and stress concentration factor at the crack initiated position etc. Equations for the allowable stresses under various enviromental condition (in air and in sea water) were proposed, using ordinary S-N_c curve (N_c; crack initiation life) of notched specimens, S-N_p curve (N_p; crack propagation life) of cracked specimens and modified Miner rule for both of crack initiation and crack propagation, and assumed exponential distribution for wave bending stress. These equations can be applied not only to the crack initiation life but also to the crack propagation life for any limited survice period.
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[in Japanese], [in Japanese]
Article type: Article
Pages
177-182
Published: December 30, 1982
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[in Japanese]
Article type: Article
Pages
183-215
Published: December 30, 1982
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Article type: Appendix
Pages
217-219
Published: December 30, 1982
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Article type: Appendix
Pages
App2-
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Article type: Appendix
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Article type: Appendix
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Article type: Appendix
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Article type: Appendix
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Article type: Appendix
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Article type: Appendix
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Article type: Appendix
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Article type: Cover
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Article type: Cover
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Published: December 30, 1982
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