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Article type: Cover
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Published: September 30, 1979
Released on J-STAGE: March 30, 2018
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Article type: Cover
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Published: September 30, 1979
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Article type: Appendix
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App1-
Published: September 30, 1979
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Article type: Appendix
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Published: September 30, 1979
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Susumu HASEGAWA, Hideyasu YAOI
Article type: Article
Pages
1-7
Published: September 30, 1979
Released on J-STAGE: March 30, 2018
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On both land and sea, it is very important to hold a good room-environment with healthful and comfortable delling, and with high work efficiency. Recently the law for land structures, such as the Sanitary Administration Law for Building Maintenance, has been established. So we are given a legal obligation to make reports on the measurement of the sanitary condition in a room. With reference to this Administration Law, we measured the room air environment in some ships now in commission, and checked several items in connection with the law. On board the coastwise ferry boats and the passenger boats on a voyage, we have made several observations on their inboard environment. The air environment both in the watching and living rooms, as far as we measured, is almost within the range of the Air Quality Standards for Building Maintenance. In general, the rooms seem to show a tendency of low humidity when they are heated. So special regard must be paid to the increase of moisture.
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Minoru MORI, Motoaki YANASE
Article type: Article
Pages
9-15
Published: September 30, 1979
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Antifouling paint on the shell bottom performs functions of making the surface of the shell bottom smooth and preventing an increase in frictional resistance by preventing the attachment of marine growth thereto. For three kinds of antifouling paints different in antifouling system, we have carried out a rotor test in sea water, and measured the surface roughness by using a surface roughness gauge and observed the paint film cross section by an electron scanning microscope. In regard to the leaching behaviour of antifouling agent and the change of paint film surface condition, the following results have been found : 1) The leaching rate of antifouling agent obtained in the rotor test in sea water is 70-150 times that in immersion test in still sea water. 2) To prolong the life of antifouling paint, it is effective to control the diffusion of antifouling agent in paint film. 3) In such conditions as in the rotor test in sea water, the surface roughness hardly changes. Thus, we have confirmed that this investigation is useful to clear the relation between the leaching behaviour of antifouling agent and the antifouling performance.
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Koichi MASUDA, Wataru KATO
Article type: Article
Pages
17-24
Published: September 30, 1979
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The present paper deals with the diffraction problems of water waves due to a floating type wave absorber which consists of the plural vertical plates. The method of solution is based on the finite element method combined with the source distribution method. Namely, by a fictitious juncture boundary, a fluid domain is divied into both outer regionand inner region. The velocity potential for the outer region is given by utilizing the source distribution on the fictitious juncture boundary. On the other hand, the velocity potential for the inner region is determined by the finite element method. Numerical results which were applied to the plural vertical plates show that the zero reflection and complete transmission are possible, and the number of the occurrence of the complete transmission is in proportion to the number of the fluid colums between the plates. The wave exciting forces (X-direction) which were calculated by the plural vertical plates show that the wave excitationless frequency existed. The two plates with the external damping gave better effect of the wave absorption than the two plates in the vicinity of a wave length where the motion of the fluid column between the plates is resonant.
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Tetsuro IKEBUCHI, Akira MASUMOTO
Article type: Article
Pages
25-33
Published: September 30, 1979
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In this paper a method is presented to obtain the slowly-varying force and its spectrum on vessels in irregular beam sea waves. The two-dimensional velocity potential which describes the flow around the vessel in two simultaneous waves is obtained correctly to second order in wave amplitude by means of regular pertubation method. Making use of this result, the slowly-varying force in irregular waves is calculated by direct integration of the hydrodynamic pressure on vessels. The expression of the spectrum of slowly-varying forces is derived from that of the slowly-varying force. Results of computations by present method are exhibited for a shallow-draft barge and compared with the results calculated by Pinkster's approximate method. From the comparison, it is comfirmed that Pinkster's method is not effective in a higher range of circular frequency in some cases.
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Koji MATSUNAGA, Kunio TANAKA, Takayoshi MIYANARI
Article type: Article
Pages
35-43
Published: September 30, 1979
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This paper presents the measured results of wave loads in model test basin, concerning the influence of Beam-draft ratio, by a systematic program. The motions with six degrees of freedom were measured simultaneously. The model has been chosen so as to have mean Length-Beam ratio of floating box type barges. The draft of barges in towing conditions is generally very shallow compared with ordinary ships, then three small draft conditions were selected to cover almost all Beam-draft range of barges. The model consists of four segments longitudinally jointed by load transducers of strain gauge type. The measurements were carried out in oblique regular waves with four different directions, at zero forward speed. Finally, comparing nondimensional measured results with those of ships with ordinary draft, it has become clear that the maximum value of vertical bending moment coefficient (M_v/ρgζ_aBL^2) showed almost the same magnitude, but of torsional moment coefficient (M_T/ρgζ_aBL^2) showed several times larger. The calculation by Ordinary Strip Method, done for reference, showed good coincidence with motions, but there were significant differences with wave loads.
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Yasushi HIGO, Shoichi NAKAMURA, Matao TAKAGI
Article type: Article
Pages
45-56
Published: September 30, 1979
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This paper deals with the resistance increase of the blunt bodies such as pontoons which are towed among the waves. The flow field is analyzed under the assumption of strip theory. However not only the transverse waves but also the longitudinal waves are taken into account for the resistance increase. Some numerical calculations give the encouraging results when Ω is less than 1/4, where Ω=_νU/g (ν : circular frequency of encounter between wave and body, U : advance speed of body, g : acceleration of gravity). When Ω is larger than 1/4, the two-dimensional treatment is improper.
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Yoji HIMENO, Taketoshi OKUNO
Article type: Article
Pages
57-68
Published: September 30, 1979
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Discussions are held about the higher-order terms in boundary layer problem, especially, the displacement effect and the pressure distribution in ship boundary layer. A new attempt is made on the calculation procedure of ship boundary layer including higher-order terms. A thin-ship solution of the boundary layer and wake problem is used in the potential flow calculation as the first approximation. It is found that this procedure enables us to calculate the boundary layer development near the ship trailing edge without numerical divergence at the first iterative stage of the higher-order calculation. The pressure variation in the layer can safely be predicted by considering only the effect of the centrifugal force, namely the terms of the surface curvature. The boundary layer equation including the curvature terms is also used.
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Seiichi ASANO
Article type: Article
Pages
69-75
Published: September 30, 1979
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The energy of secondary flow around the frame line, T_2, is calculated by making use of the slender-body theory on 21 model ships. It is found that T_2 has a peak on each half body of the ship and the value of the peak varies with the fullness of the half body. C_<DJ>=(T_2/2)/(1/2ρSV^2) is calculated when T_2 is equal to the mean value of the maximum T_2 for the fore body and the one for the aft body. Resistance tests are carried out on the model ships and their form factors are obtained to compare them with C_<DJ>. The results show that there is a clear relation between the form factor and C_<DJ> for the majority of these examples.
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Junkichi YAGI, Toshihiko FUNAKI, Yoichi HATTORI, Michio OTA, Shigeru H ...
Article type: Article
Pages
77-83
Published: September 30, 1979
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In the previous papers, studies were made on the racking deformation of hull girder under unsymmetrical concentrated loads. In this paper, unsymmetlical distributed loads on a ship hull in the regular oblique waves were estimated, and response function of the racking angle of a ocean going car carrier under the above loads was obtained by the analytical method in our previous papers. From these calculations, the following conclusions were obtained. 1) Racking loads imposed on ship hull in transverse direction is much larger than ones in vertical direction. 2) Respons function of the racking angle can be assumed to be proportional to wave height. 3) Response function of the racking angle becomes maximum at the maximum rolling motion.
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Junkichi YAGI, Yasumitsu TOMITA, Yukio FUJIMOTO, Takao OKUBO
Article type: Article
Pages
85-94
Published: September 30, 1979
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Fatigue strength criterion in intermediate cycle range was presented under two or three-dimensional stress conditions. Parameters affect to fatigue crack initiation life under these conditions are mainly stress biaxiality, stress gradient, mean stress and mean strain, etc. In this paper, effects of stress biaxiality and stress gradient on the life were investigated experimentally, and equivalent strain function ε_D, e_q was derived. Using this strain function, the fatigue life under various stress conditions can be evaluated with good accuracy, and the function ε_D, e_q is expressed as follows. ε_D,e_q=ε_1+3/4ε_2 where ε_1 and _2ε are maximum and medium principal strain amplitude at crack initiation point respectively. It was found that the effect of stress gradient is to increase the fatigue life, and amount of the increase is approximately constant irrespective of maginitude of the stress gradient.
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Ken-ichi KITAURA, Hiroo OKADA, Yoichiro OKAMURA, Yoshio FUKUMOTO
Article type: Article
Pages
95-102
Published: September 30, 1979
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In this paper, to obtain the basic data on impact fatigue behaviour, low-cycle impact fatigue tests are carried out on three kinds of the circular bar specimens of mild steels SS41 i.e., (A) smooth specimen, (B) circumferential U notched specimen (stress concentration factor K_t=1.8) and V notched specimen (K_t=5.7), under repeated impact tensile loads. From experimental results, the conclusion is summarized as follows : (1) The process of fracture of (A) and (B) specimens of which K_t-values are small is creep type and cyclic behaviour of permanent strain ε (=2・1n (d_0/d), d=diameter at the minimum cross section of each specimen under impact fatigue test and d_0=the initial value of d) is almost similar to ordinary low-cycle fatigue behaviour. Its process is divided into three stages and the 2nd. stage where permanent strain rate Δε_c is constant occupies most of fatigue life. (2) The relation between impact tensile stress σ^^- and Δε_c is expressed by σ^^-/σ_B=T^^-^α・S・(Δε_c/ε_f)^β …(a) where σ_B is ultimate strength of (A) specimen, T^^- is duration of maximum stress in one cycle, ε_f is ε at the time of fracture of each specimen under static tensile test and α, β and S are experimental constants. (3) The relation between Δε_c and impact fatigue life N_f is expressed by (Δε_c/ε_f)・N_f^m'=C' …(b) where m' and C' are material constants. (4) The process of fracture of (C) specimen of which K_t-value is large is crack type, but impact fatigue behaviour is formally expressed by Eqs. (a) and (b) as same as (A) and (B) specimens, when ε is estimated by using diameter d at the crack bottom as a matter of convenience. (5) The low-cycle impact tensile fatigue strength in this experiment is expressed by σ^^-(N_f・T^^-)^n'=D' …(c) where n' and D' are experimental constants. And n' decreases with increasing the value of K_t, while D' increases with increasing the value of K_t.
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[in Japanese], [in Japanese]
Article type: Article
Pages
103-109
Published: September 30, 1979
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Article type: Appendix
Pages
111-112
Published: September 30, 1979
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Article type: Appendix
Pages
113-
Published: September 30, 1979
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Article type: Cover
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Published: September 30, 1979
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Article type: Cover
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Published: September 30, 1979
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