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Tetsuo Nishiyama
1960 Volume 1960 Issue 107 Pages
1-8
Published: 1960
Released on J-STAGE: September 16, 2009
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A NACA 4412 hydrofoil section was held stationary in an open flume containing streaming water. Pressure distributions were measured at 6 different submergence depths, 4 different speeds and 7 different angles of attack by 30 pressure taps arranged around the center of the hydrofoil span. These pressure distributions were integrated to obtain the lift and drag on the section.
In §3, the effect of the submergence depth on the pressure distribution was examined and then discussed the flow characteristics from the standpoints of the gravity effect, inertia effect, boundary layer separation, and ventilation.
In §4, two types of stall, ie laminar flow separation and turbulent flow separation were clarified from the standpoint of the resultant force at each submergence depth.
In §5, the effect of the submergence depth on the lift and drag was examined and, in particular, the stall characteristics were fully discussed.
In §6, the similar law was considered in detail for the shallowly submerged hydrofoil section characteristics and also the scale effect was examined.
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Daiichi Nakase, Akio Kaneda, Katsuo Otaka, Kenji Fujita
1960 Volume 1960 Issue 107 Pages
9-15
Published: 1960
Released on J-STAGE: September 16, 2009
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The varying hydro-dynamical pressure near the rotating propeller, named “surface force” by F. M. Lewis, was actually investigated on the twin-screw destroyer. Measured pressure variations consist of the blade frequency component and other higher frequency components. The autocorrelation functions and the frequency spectra were taken from the record of pressure variations, and it was learned that nearly all of the higher frequency components were as irregular as noise. Pressure variation amplitudes near the tip of propeller excluding such noise-components were in good agreement with the amplitudes estimated from the model test results.
Also, the varying stresses in the bottom shell near the tips of propeller were measured by means of the wire strain gauge, and it was noted that the measured stress variations roughly coincided with the estimated ones calculated from the measured pressure variations.
Several problems of the flexural vibration of ship's hull forced by the pressure variation, the local vibration and the determining the thickness of the bottom shell in the vicinity of propellers etc., may be presented from our investigation on this subject. Regarding these problems, further reports shall be published.
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Kiyoshi Tsuchida, Miki Hirano, Shichiro Kuroda, Hiraku Tanaka, Shoichi ...
1960 Volume 1960 Issue 107 Pages
17-26
Published: 1960
Released on J-STAGE: September 16, 2009
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This paper deals with the longitudinal stability of the submarine in the deeply submarged condition with controls locked, and presents a method of model experiments of the submarine.
Equation of motion of the submarine in the deeply submarged condition is shown in equation (1). Tank tests on models of ellipsoid were conducted to obtain the coefficients and derivatives in this equation. Three components tests were performed on a 4m model and forced oscillation tests on 2m and 4m models, with and without fins.
Typical examples of three components tests are given in Figs. 6 and 7 and those of forced oscillation tests in Figs. 8, 9 and 10.
Damping coefficients in pitching motion, -Cmq=
B/1/2. ρ∇4/S
V and added moment of inertia coefficients about centre of buoyancy,
K= (
I-
I1)/
I2 are shown in Fig. 12.
As an application of the equation of motion (1), stable region of velocity on an ellipsoid with and without fins are shown in Figs. 17 and 18.
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Tatsuo Jinnaka
1960 Volume 1960 Issue 107 Pages
27-31
Published: 1960
Released on J-STAGE: September 16, 2009
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The author once published the tables of some integrals appearing in some problems of surface-waves. In the present paper, the applications of these tables are showed for some periodic motions that is : (i) Calculations of wave elevation and induced pressure by a periodic point source, (ii) Calculation of flap-type wave generater, (iii) Two-dimensional source distribution for the heaving motion.
These examples show the Usefulness of application of periodic source distributions for some problems of surface waves.
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Fukuzo Tasai
1960 Volume 1960 Issue 107 Pages
33-46
Published: 1960
Released on J-STAGE: September 16, 2009
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We measured the two dimensional progressive wave height produced by forced heaving of the miscellaneous cylinders, and compared the amplitude ratio
A with the F. Ursell's results [1] and author's theoretical calculations [2]. As the result we could find that the measured
A showed generally fair coincidence wih that of the theoretical results. Moreover, the author studied the wedge effect, the effect of the deviation from the Lewis forms, and the effect of the heaving amplitude.
Many figures in this paper shows these results.
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Ryo Tasaki
1960 Volume 1960 Issue 107 Pages
47-54
Published: 1960
Released on J-STAGE: January 25, 2010
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The author carried out an experiment on the shipping water during the experiment of the propulsive performance of tanker models in regular head waves. The amount of shipping water per one cycle was measured and presented in Fig.4 versus model speed. After the calculation of relative motion of the bow to waves, it was found that water shipped on the forcastle deck even when the bow did not submerge into free ocean waves. This fact and further consideration show that when the free board at the bow is regarded as an allowance for shipping water, it must be reduced by the height of the statical swell-up of bow wave due to forward speed of the ship and the relative submergence of the bow must be increased by the height of the dynamical swell-up of water surface due to relative vertical velocity of the bow and waves.
The amount of shipping water at the beginning is approximately proportional to forward speed, encounter period and to square of wave height and to 2.5th power of the ratio of excess of water surface over the top of bowchock to the free board at the bow.
Then he shows a method to calculate the cumulative energy of the bow submergence in irregular heading seas and gives the time proportion of wet deck for a tanker of length
L=190.5 m as an example.
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Seiji Takezawa
1960 Volume 1960 Issue 107 Pages
55-61
Published: 1960
Released on J-STAGE: September 16, 2009
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The auther estimated from tank tests in regular waves the pitching motions of a ship in irregular seas, using of Neumann-Pierson's wave spectrum theory and St. Denis-Pierson's ship response theory, and then he compared them with actual ship data.
As the actual ship tests were carried out in high irregular seas at high speeds, he has considered especially the non-linear relation between pitching and wave height.
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Daikaku MANABE
1960 Volume 1960 Issue 107 Pages
63-69
Published: 1960
Released on J-STAGE: January 25, 2010
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Spectral distribution of oscillation of a ship has a strong peak at its frequency of resonance.
Then, index numbers of irregularity are as follows :
(I) By Cartwright & Longuet-Higgins (Theory of maxima)
ε
(n)2=1-ψ
0(2n+2)2/ψ
0(2n)ψ
0(2n+4)where, (-1)
nψ
(2n) means r. m. s. of oscillation, and for amplitude
n=0, for velocity
n=1, and for acceleration
n=2. Usually ε
2>ε′
2>ε″
2 so regularity increases toward higher time derivative.
For narrow-banded spectrum ε
2_??_ε′
2_??_ε″
2=0, but when it is widely distributed, ε
2_??_2/3, ε′
2_??_2/5, ε″
2_??_2/7.
(II) By Rice (Theory of envelope)
α
(n) =
Ppn√ (-1)
nψ
0 *(2n) where
p=2π
fm is circular frequency of resonance and
P is amplitude of resonance. (-1)
nψ
0 *(2n) causes slowly varying amplitude of oscillation and generally forms Gauss distribution above
f=0. So that.
(
a″/
a′)
2=1/3 (
a′/
a)
2·
These results are summarized by the author's index number
n″ -
n′=
n′-
n=1.
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Shin Tamiya
1960 Volume 1960 Issue 107 Pages
71-76
Published: 1960
Released on J-STAGE: September 16, 2009
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The effects of free water on decks are considered in relation to the transverse stability of ships.
First, the weight and the inclining moment of free water contained in a open rectangular tank are calculated for general cases and their graphical representations are obtained in a compact form.
Second, the general characters of stability curves of ships with free water on decks are explained and the calculating method of the curves is described, when the freeing ports are neglected but the houses, hatch coamings etc. are taken in count.
Examples of stability curves are shown for a rectangular ship (calculated) and a model of a steel fishing vessel (measured), in which the existense of negative stability range is ascertained.
Finally, an approximate integration of the rolling equation is worked out to see a character of ships motion.
In a inclining experiment, the changes of the trim of about 2 degrees are obtained, of which the effects upon transverse stability will be made clear in the near future by model experiments.
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Shuichi Iwata
1960 Volume 1960 Issue 107 Pages
77-82
Published: 1960
Released on J-STAGE: September 16, 2009
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In this paper the damping coefficient of roll for patrol boats engaged in Major Coasting Areas (generally, represented in N) has been investigated, and a method to obtain the damping coefficient of ship for any condition was presented, analysing results of tank experiments of nine models.
The mothod is ; first, a standard N for standard condition is obtained from a chart, (the N function of bilge keel size and C_??_ while d/B, KG/d
0 and K/B constant), then corrections for d/B, KG/d
0, K/B are done by properly prepared charts.
where C_??_= maximum sectional area coefficient of the ship d=draft of the ship
B=beam of the ship
KG=vertical position of center of gravity of the ship above base line d
0=standard draft
K=radius of gyration of the ship
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Part 4. Pitching motion
Seizo Motora
1960 Volume 1960 Issue 107 Pages
83-89
Published: 1960
Released on J-STAGE: September 16, 2009
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In this paper, the author states about the results of measurement of added moment of inertia and damping coefficieut about
y axis, i. e. for pitching motion.
A forced oscillation method same as was used by Golovato was employed for measuring device, and 14 series models varying
Cb and
L/B are used.
As the added moment of inertia and the damping of pitching motion vary with the frequency of the motion, values of them corresponding to the natural pitching frequency are choosen as the typical values when discussing the effect of ship forms.
A chart from which additional moment of enertia and damping coefficent of ships having arbitrary
Cb,
L/B and
d/B can be obtained is proposed in this paper.
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Part 5. Heaving motion
Seizo Motora
1960 Volume 1960 Issue 107 Pages
91-95
Published: 1960
Released on J-STAGE: September 16, 2009
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A forced oscillation method same as was used in the case of pitching was employed. The effects : of ship forms upon additional mass and damping force are discussed about the values corresponding to the ship's natural frequency.
It was found that the ratio additional mass to ship's own mass increases when
Cb and
B/L increases, that damping coefficent decreases when
Cb, increases and increases when
B/L increases. Charts of added mass coefficent and damping coefficent same as for pitching motion are also proposed in this paper.
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Heiya Yamamoto
1960 Volume 1960 Issue 107 Pages
97-103
Published: 1960
Released on J-STAGE: September 16, 2009
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Steering quality of a ship is affected by a time constant
TE of her steering gear. The time constant
TE depends upon the wheel advance angle of the steering gear. By reducing the wheel advance angle, the time constant
TE is decreased and steering quality of a ship may be improved.
This paper deals with the improvement of steering quality by reducing the time constant
TE The results obtained are as follows ;
(1) For small boats which have small time constant in steering, the effect of reducing the wheel advance angle may be remarkable.
(2) If the wheel advance angle is zero, starting angular acceleration of a rudder is abnormally large.
(3) For the conventional wheel advance angle 510°, calculated values of starting torques acting upon steering gears are very small compared with designed maximum torques of steering gears. From the viewpoint of the starting torque, the conventional wheel advance angle may be considered too small.
(4) Adequate reduction of the wheel advance angle compared with the conventional one does not result abnormal overload of a driving motor of a steering gear.
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Hitoshi Fujii
1960 Volume 1960 Issue 107 Pages
105-111
Published: 1960
Released on J-STAGE: September 16, 2009
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The present paper relates to experimental researches on rudder performance utilizing a free-running, self-propelled model.
Similarity between a free-model and an actual ship concerning their rudder torques, which mean a hydrodynamic moment about a rudder stock, may be assured by attaching an air-propeller to a model to provide an additional thrust that is necessary for skin friction correction.
Alternative tests have been carried out for three different balance ratios and a procedure to estimate a rudder torque in steering for an arbitrary balance ratio has been provided through analyzing the test results.
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Kohei Moriya, Masao Kinoshita, Ko Nishimaki, Yasuharu Terada, Akisuke ...
1960 Volume 1960 Issue 107 Pages
113-125
Published: 1960
Released on J-STAGE: September 16, 2009
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This paper describes the results of a series of expriments on the effectiveness of the longitudinal bulkhead which have been carried out with five simplified ship models. These models are fitted with longitudinal bulkheads of different lengths, number of rows, stiffening of bulkhead plates, end construction etc.
From these experiments, the following conclusions have been obtained :
(1) The shear-lag effect is remarkable only within the range approximately equal to 1. 2 times the depth of the longitudinal bulkhead from the bulkhead end. The remaining middle part is fully effective and the distribution of longitudinal bending stresses on the ship in this region can be-obtained from beam theory.
(2) Maximum shearing stresses in side shells and bulkhead plates near the end of bulkhead. are considerably larger than those of the middle part.
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Masao YOSHIKI, Ken TAKATA, Yoshiyuki YAMAMOTO, Shosuke TSURUTA
1960 Volume 1960 Issue 107 Pages
127-135
Published: 1960
Released on J-STAGE: September 16, 2009
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In the case of small vessels, the change of breadth of long hatches has been observed. In this paper the mechanism of this change is studied theoretically, and is confirmed by experiments using M. S. TETSURYU-MARU. The change is determined as the sum of horizontal displacements of the deck on each side of hatchway, and is partly due to the horizontal action from web frame to the deck and partly due to the shearing force acting at the ship sides. The deck is fixed elastically at the hatch ends, and the change of hatch breadth is almost equal to twice as large as that calculated assuming the deck is fixed at the both ends.
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Noritaka Ando
1960 Volume 1960 Issue 107 Pages
137-142
Published: 1960
Released on J-STAGE: September 16, 2009
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Bending test of rectangular plate in the condition of all edges built in is one of the most troublesome one.
In this fifth report, in order to experiment on the bending of orthogonally stiffened plate in such condition, adequate bending moments are given along four edges, in consequence, equivalent values. of all edges built in are obtained. Comparing these data with the value derived from the orthotropic plate theory illustrated in the first report, it shows fairly agreement between them, and it is, concluded that the orthogonally stiffened plate in such condition can be also expressed satisfactory by the orthotropic plate theory as shown in the preceding reports.
Some notes about the approximate method to derive the deflection of orthotropic rectangular plate with all edges built in are also given, as the regorous method is rather complicated.
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under Compression and Tension
Yoshio Fukumoto
1960 Volume 1960 Issue 107 Pages
143-149
Published: 1960
Released on J-STAGE: September 16, 2009
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When a box-shaped girder, which has a panel with an initial deflection as a part of it, the strength and rigidity of the girder is affected by the decrease of the rigidity of the panel. In this paper, the behaviour of the continuous panel with an initial deflection under compressive or tensile forces in two directions, was researched. And a numerical calculation of the effective rigidity was performed for the case that the force was in one direction.
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Practical Calculation Method
Toshimasa Okabe, Koichi Hori
1960 Volume 1960 Issue 107 Pages
151-161
Published: 1960
Released on J-STAGE: January 25, 2010
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In the previous report No. 1, the authors presented the analysis for 3 dimentional strength of cargo ship. In this report, to apply the various construction of ship, practical calculation methods were presented.
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-With Special Reference to the Effect of Longitudinal Members in Cargo Ships
Isao Yamaguchi
1960 Volume 1960 Issue 107 Pages
163-172
Published: 1960
Released on J-STAGE: September 16, 2009
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In order to make accurate calculation of the transverse strength of ships, it is necessary to take account of the effects of longitudinal members, variable cross-sections of structural members, shear deflecion, etc., but the introduction of these effects would make the calculation very complicated.
This paper deals with the approximate method of calculation by using diagrams to simplify the calculation. Investigations have been made here of the effect of longitudinal members upon the transverse members of cargo ships, and the effects of variable cross-sections of structural members and of shear deflection will be reported on the next occasion.
When the transverse strength is considered in three dimensions, having regard to the effects of centre and side girders, deck girders, etc., transverse members in the middle part of the hold are the weakest, and therefore the analysis has been concentrated to the middle part of the hold.
The results of the calculation according to this method have indicated fair agreement with those of the precise calculation, so that it is considered that this method has sufficient accurity in practical use. The author considers that this method, being simple in calculation, will be useful when strength calculation is made as a routine work.
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Yuzuru Fujita
1960 Volume 1960 Issue 107 Pages
173-177
Published: 1960
Released on J-STAGE: September 16, 2009
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The author had studied this problem and reported as the I st Report few years ago. In which, A. “modified Shanley model” was studied and the concept of tangent modulus theory was accepted as a, first approximation.
In this report, the author again treated the same problem more thoroughly by planning series of tests and a particular distribution of welding residual stresses i. e. “reversed” -specimens. (Here, “reversed” means that the flange ends of welded columns with I-section have tensile residual stresses, in stead of usual compressive residual stresses.)
The new end-fixtures which consist of two tapered circular wedges and driving worm gears, were designed to make the perfect alignment of columns easy.
The findings are follows :
(a) The “reversed” -specimen (which have reversed distribution of residual stress) may reach at the highest ultimate strength of annealed-specimen, but may not exceed that value by a great amount.
(b) The test results of high-tensile steel (Welten-50, YAWATA Iron & Steel Co. Ltd.) columns showed a good agreement with the theoretical calculation as well as in case of mild steel. columns in the 1st report.
(c) The tangent modulus load was again verified as a good design standard for welded columns.
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Yuzuru Fujita
1960 Volume 1960 Issue 107 Pages
179-185
Published: 1960
Released on J-STAGE: September 16, 2009
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The welded structures necessarily having welding residual stresses in their members, the influence of residual stresses on the instability problems is very important and has been studied by the author
(1), (2), (3). In this paper, the influence of residual stresses on the torsional-flexural buckling of thin open walled columns was mainly discussed. The general theory was developed and typical examples were illustrated.
The tests of columns with cruciform cross-section were refered to show the experimental verification.
The following was found :
(a) The influence of residual stresses on the buckling strength was remarkable in case of elastic torsional buckling as well as in case of plastic torsional buckling.
(b) The combined torsional flexural buckling load was well approximated by the torsional buckling load or flexural buckling load, whichever the lower.
(c) A fair agreement between the test results and calculation was obtained.
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Masao Yoshiki, Yuzuru Fujita, Tadahiko Kawai
1960 Volume 1960 Issue 107 Pages
187-194
Published: 1960
Released on J-STAGE: September 16, 2009
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Influence of residual stresses on the elastic buckling of plates is studied in this paper.
As a pilot research, theorctical as well as experimental investigations were carried out for square plates welded on the center line. Fairly good agreement between theory and experiment was obtained.
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Tadao Kusuda
1960 Volume 1960 Issue 107 Pages
195-202
Published: 1960
Released on J-STAGE: September 16, 2009
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The paper is concerned with the plastic design of thin plates made of a perfectly plastic material which obeys the stress-strain law of Prandtl and Reuss, under various types of boundary conditions. A rectangular plate with arbitrary boundary condition is subjected to either uniformly distributed or concentrated transverse load. Collapse loads of thin plates obtained by lower bound theory are compared with the results from upper bound theory for each case of boundary conditions.
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Large Plastic Deformations of Corrugated
Tamotsu Nagai
1960 Volume 1960 Issue 107 Pages
203-211
Published: 1960
Released on J-STAGE: September 16, 2009
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In this report, following the preceding paper, the large plastic deformations of the corrugated bulkhead are discussed under transverse impact at center such as considered inelastic impact when all edges of the bulkhead are supported.
From the view-point of perfect-plastic analysis, we are especially concerned about both maximum deflections and maximum impulsive loads by applying the simplified treatment, in the case of plate material having ideal characteristics of plastic bending moment
Mp (θ) such as expressed by
Mp0γ
1 (1 +γ
2θ) and keeping the ratio of two plastic moments due to bending or twisting, independent of angular velocity θ. In theoretical analysis, the shape of impulsive load is assumed rectanguler between impact duration 2
T.
Experiment was carried out using several specimens, and its results were compared with the theoretical results for the large permanent deformations, then the close agreements were obtained.
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The Effective Sectional Area of Deck
Ichiro Hishida, Hajimu Mano
1960 Volume 1960 Issue 107 Pages
213-220
Published: 1960
Released on J-STAGE: September 16, 2009
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In the first report, authors showed the base of new method to solve the problem of the longitudinal strength of wooden ships.
To apply the new method on actual ships, it is very important to research the characteristics of deck as a longitudinal member in wooden ships. Researching the relation between remarkable shear-lag which is observed at deck of wooden ships and deck construction, we find the way to estimate approximate stress distribution at deck. The stress values by this way are proved their accuracy by observed stress distributions at experiments on models and actual wooden ship.
Judging from the characteristic, the conclusion that in wooden ship the shear-lag effect at deck is not neglected, and the way estimating effective sectional area of deck as a longitudinal member in applying the new method in first report, are drawn.
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Hitoshi Nagasawa
1960 Volume 1960 Issue 107 Pages
221-228
Published: 1960
Released on J-STAGE: September 16, 2009
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This paper deals with the impact force which the ship receives from the quay-wall when she is pulled into the pier. In the first report, the theoretical analysis of the impact force was discussed and in this report the experimental analysis of it is detemined.
The experiment was held in the towing tank of Transportation Technical Research Institute in Mitaka and the model ship made of Brass was used.
The results of the experiment were generally good agreement with the theoretical analysis.
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Matao Takagi
1960 Volume 1960 Issue 107 Pages
229-233
Published: 1960
Released on J-STAGE: September 16, 2009
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This report is to do with the experimental results of the performance of the wall ventilator conducted by the present author. As the results of these experiments, the ventilation mechanism of the wall ventilator was made clearer, and it became evident, moreover, that to increase the ventilation efficiency, special attention should be given to the following three points :
1) As the ventilation action depends largely upon the aft pipe, it is highly desirable to design the aft pipe as large as possible.
2) Moreover, the ventilation efficiency has much to do with the shape of the passage from the main pipe to the aft pipe, and accordingly, it is important to make it hydrodynamically smooth.
3) It is highly desirable to make the diameter ratio of the fore pipe entrance to the aft pip moderate. In case when the ratio is excessively large, the fore pipe often disturbes the ventilation action due to the aft pipe only.
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Shojiro Okada, Takashi Ide, Matao Takagi, Keizo Miki
1960 Volume 1960 Issue 107 Pages
235-241
Published: 1960
Released on J-STAGE: September 16, 2009
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When installing the steering telemotor to the ship, the ship-builder must know what kind of effect is occurred to its performance by changing the specifications of the pipe lines and its liquids.
For this purpose, the authors have measured the steering wheel torque and pressure of each_parts by changing the liquid, the diameter of the pipe, and pipe length, at the shop.
The following points were made clear as the results of this experiments.
(1) The wheel torque can be calculated by the suitable assumption of the mechanical efficiency.
(2) Even when the rotating speed of the wheel is changed within the range of this experiment, there isn't any effect to the wheel torque.
(3) When changing the specification of the telemotor pipe line, there isn't any effect to the liquid viscosity resistance.
(4) The most causes for increasing the wheel torque is induced by the force for moving the, control rod of the Hele-Shaw pump and pressing reciever springs.
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Kiyoshi Takashiro
1960 Volume 1960 Issue 107 Pages
243-250
Published: 1960
Released on J-STAGE: September 16, 2009
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The author herewith proposes the new system of hydro-static calculation for the basic design of merchant ships as shown in Tables 1, 2 and 3.
This system is very convenient to use at any time and anywhere when desired.
The key points of this system are as follows : -
(1) The offsets of the water planes are non-dimensional, being easily obtainable by the percent scale as shown in Fig. 2
(2) The simplification of the calculation with the use of 5 constants, i. e., λ, β, δ, κ and κδ which are led from
L,
B and
d of the ship.
(3) The simplification of the integral of the water plane with the application of the 5·8·-1 rule and the 3·10·-1 moment rule. Only half of the numbers of the water planes are necessary : for the calculation as compared with the application of the Simpson's 1 st rule.
(4) The standardization of the units in the calculation.
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Tetsujiro Tomita
1960 Volume 1960 Issue 107 Pages
251-262
Published: 1960
Released on J-STAGE: September 16, 2009
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The first important means to reduce the hull vibration is to estimate the natural frequencies of the hull as accurately as possible at an early stage of designing in order to avoid resonance of the hull with the service revolution of the main shaft.
In this paper, a method to estimate the natural frequencies of the principal vibration modes, i. e. 2 node vertical and horizontal, 3 node vertical and horizontal vibrations of ordinary cargo ships and. tankers is proposed.
This method is considered to enable to estimate the natural frequencies as easily and quickly as. possible only by digital computation without any specially provided plan such as weight curve.
The main points in the procedure are as follows :
1) For the sake of convenience, weight and rigidity items are considered separately.
2) Weight items is dealt with in the following three parts, i. e. hull weight, added weight to the hull and added virtual weight due to the surrounding water.
3) Weight distribution is assumed as symmetrical amidships and the correction for asymmetry is. considered later.
4) Effective weight factor for the vibration when supported at the nodes of a free-free uniform beam is introduced and the correction for the difference between the actual nodes and the asummed ones is considered later.
5) As regards rigidity, the effectiveness is determined corresponding to the vibration mode and the hull form.
6) The correction for the effects of shear deflection and rotational energy are considered.
7) Finally, the mean of the ratios of frequencies obtained from the above procedure to that actually measured is introduced as an empirical correction factor.
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Tetsujiro Tomita
1960 Volume 1960 Issue 107 Pages
263-269
Published: 1960
Released on J-STAGE: September 16, 2009
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An experiment has been carried out at the laboratory of Prof. Kumai to find the effect of shallow water upon the added virtual mass of the cylinder models of the typical sections of cargo ship, especially great emphasis being placed on the effect of breadth-draught ratio.
As the result of this experiment, the increase fraction of the added virtual mass due to shallow water (
c) was disclosed as follows :
c=1.1 β
3 (
b/d) (
d/h)
2.2where, β : area coefficient of section
b : breadth of section
d : draught
h : depth of water
In the case of ship's form, the increase-fraction (
C) deduced when applying the above formula for lines of hulls can be expressed as follows :
C=1.19 (
B/d) (
d/h)
2.2Cbwhere,
B : moulded breadth
Cb : block coefficient
The natural frequencies at shallow water can be estimated according to the method described in the auther's previous paper : “The Estimation of the Principal Natural Frequncies of Hull”, and the coefficients of the increased added virtual mass necessary for the frequencies calculation are given in Fig. 3.
After comparison was given to the measured data and the calculated ones, this method has been confirmed to be satifactory for practical use.
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Fumiki Kito
1960 Volume 1960 Issue 107 Pages
271-275
Published: 1960
Released on J-STAGE: September 16, 2009
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The author has presented, in the previous paper, a theoretical formula which gives the value of virtual mass of water, with regard to vibration of side-walls of a rectangular water tank, full of water. The theoretical formula was obtained by calculation of kinetic energy of water, which is in vibration induced by the vibration of side-walls. This is an approximate calculation, and not a rigorous one. So, there arose the question about the degree of approximation of the given formula. In the present paper. this question is examined by taking into account higher modes of vibration of side-walls, and using the minimum principle of Lord Rayleigh. From the result of calculation, we see that the formula for virtual mass of water in the previous paper is sufficiently accurate, for practical use, at least for water tanks having ordinary proportions. The formula for virtual mass of water, for the case in which the water is only partially filled, is also given here.
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Intensity of Restraint and Residual Stress due to welding on the Actual Ships (40, 000 D. W. Oil Tankers) of which erection started simultaneously at Several Locations
Masataro Muto, Takatoshi Kurita, Yukio Kurihara
1960 Volume 1960 Issue 107 Pages
277-286
Published: 1960
Released on J-STAGE: September 16, 2009
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The measurement and comparison of residual stress on welding line of common block butt and master butt on side shell and upper deck (As restraint is not free in reality, it is locked in stress) was made for the actual ship of 40, 000 D. W. oil tanker, and, at the same time, the measurement and comparison of reaction stress of block butt and master butt made adopting the idea of the intensity of restraint stated in the Report No. 1, and, also, by comparing and examining the difference between the above two, the safety of master butt was confirmed.
Residual stress was computed based upon the result of the measurement of open strain which was made using the Gunnert Strain Gauge. As for reaction stress, the variation of strain was measured by means of Contact Strain Gauge and after that the order of reaction stress was estimated basing on the result of its measurement.
From these measurement, the followings have been given as a conclusion :
(1) There is almost no difference between the levels of residual stress on welding lines of master butt and common block butt on side shell and upper deck.
(2) As regards common block butt and master butt on side shell, the measurement of reaction stress which shows their intensity of restraint was carried out on every points of blocks. As a result, it was proved that the order of reaction stress is nearly zero and the intensity of restraint low.
(3) From the results stated in the above (1) and (2), it is judged that there will be no anxiety against the intensity of restraint of master butt in the Method of Erection Started Simultaneously at Several Locations which is adopted at our shipyard at present, provided that welding is properly done, and the master butt can be treated quite in the same way as in the case of common block butt.
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Yoshio Akita, Kazuo Ikeda
1960 Volume 1960 Issue 107 Pages
287-292
Published: 1960
Released on J-STAGE: September 16, 2009
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In the theory of the brittle crack propagation, the dynamical effects are added to the Griffith's energy condition. At room temperature, the plastic work done occuring in “shear lip” zone, was also considered besides the “surface work” proposed by Orowan. The conditions of the initiation of crack were obtained considering both the energy and : the yield stress. The mechanism of initiation in the SOD tests, Esso Brittle Temperature, and the temperature depending critical stress were obtained theoretically.
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Toshio Yoshida, Wasuke Matsunaga, Kiyoshi Terai, Fumiyoshi Kanatani
1960 Volume 1960 Issue 107 Pages
293-302
Published: 1960
Released on J-STAGE: September 16, 2009
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In carrying out the welding of the butt joints of the assemblies for ship's hull by means of the automatic submerged arc welding, there arises an important problem of preventing piercing with welding rod during welding process. Against the inaccurate processing of joint edge preparation, which is regarded to be the main cause of piercing, many researches have been conducted and counter-measures have been introduced. However, no satisfactory results have been obtained to date.
Therefore, the authors have devised a new edge form to replace the Unionmelt type edge preparation hitherto in use, thus attempting to solve this problem with its adoption. Known as Kawasaki's Z type, this new form is the improvement of the edge preparation now in practice at the Chantiers de 1' Atlantique in France. In comparison with the edge preparations hitherto in use, this new edge form devised by the authors has greater allowable limit of root opening against piercing with welding rod. Furthermore, it is much easier to make edge preparation. These advantages have been proved by the experiments carried out by the authors.
Moreover, the authors have already applied this new edge form to actual constructions and carried out single pass submerged arc welding to thick steel plates up to the thickness of 60 mm, thus obtaining successful results seen from the stand points of welding efficiency and joint performance.
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Etsuro Moriyama, Akisuke Urata, Akinori Morimoto
1960 Volume 1960 Issue 107 Pages
303-311
Published: 1960
Released on J-STAGE: September 16, 2009
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The three suction pump dredgers built at Hitachi Sakurajima Shipyard last year have adopted the new launching method called “Wire loosing and winding method”, by launching her slowly with wires which is rather different from the common sliding method.
The new method was adopted because :
(1) The ship type is an Ark. (2) All the outfittings were installed on the building way and her launching weight will be about 1, 000 ton. (3) Having special apparatus as the suction ladder and spuds on her fore and aft.
Under these conditions, the authors have considered of using this new methods not to cause any damage to the ways and to the side walls, also not to change the sliding direction by water stopping resistance, tidal current and wind pressure that work unequally to each part of her.
The launching way for the wire loosing and winding method was exactly the same as ordinary ships in using greases, but the chocking, loosing, winding and adjusting were all done from the ground by wires.
The authors have measured the tensile force which worked to the parts during the launching. These figures were submitted for reference to safety launchnig work and also it was checked and compared with the planned figures for the future reference.
The authors have confirmed at least that the arrangement and mechanism of the apparatus have met its purpose.
When the keel blocks were taken off, the authors found that the direct working tensile force was larger than its plan but the grease frictional coefficient was rather smaller than its plan showing 0.002-0.007, therefore the author consider that the dredger was in very easy condition to slide.
During loosing and winding the authors have noticed that the shock load did not work so much in this case but if the apparatus are not closely associated with its operation, she would become unbalanced by a large load that cannot be expected which is the most warning point for this dredger launching.
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Masami Fukuyama
1960 Volume 1960 Issue 107 Pages
313-318
Published: 1960
Released on J-STAGE: January 25, 2010
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In january 1960, 79 turbo-charged two stroke engines, totaling 520, 000 BHP had been in service for up to years. The service reports from numerous of these engines and our own investigations give a good basis of judging upon the functioning of the engines and directions for better maintenances.
The following items are mentioned particularly based on the service results.
(1) Control of turbo-charging system
(2) Problems for heavy oil burning affecting on cylinder performance
(3) Welded construction, etc.
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Junichi Sakuma
1960 Volume 1960 Issue 107 Pages
319-324
Published: 1960
Released on J-STAGE: September 16, 2009
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There are several reports on the erosion or corrosion of the propeller and its shafting. But we have as yet very little information on the stray current of them.
Recently, it have been shown that usually there exists the electric resistance (R) between hull and shafting on a running ship. This resistance appeared on all bearing surfaces of propeller shafting and engine. In this case, it may be assumed that the potential difference between the Zn anodes and propeller enforces to flow the stray current from sleeve surface to sterntube.
The present experiments were designed to secure the following two points.
(1) Posibility of stray current above mentioned. In this experimental circuit, when the outer resistance (equivalent to R) increase and exceed some value, the stray current start up on the surface of the brass specimen (equivalent to shaft sleeve).
(2) Suitability of the usual Zn anode protection.
As noted above, when the shafting become independent of the hull at running period, then the Zn anode on the hull a slight protecting effect on the propeller. If this anode should be attached to the front of the propeller boss, the effect is better than that, but is not sufficient.
The best method is to have good connection between main shaft and bearing with the pertinent ring and brush.
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Masaru Takeda, Shoichiro Kosuge
1960 Volume 1960 Issue 107 Pages
325-330
Published: 1960
Released on J-STAGE: January 25, 2010
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Marine propulsion engine with reduction gear has such merits that the engine becomes smaller in size and cheaper in price by increasing engine revolution, and as for the propeller, the revolution having the highest propulsive efficiency can be easily and voluntarily obtained by selecting a certain reduction ratio.
In spite of the fact that great benefits as above mentioned are given in case this engine is adopted in cargo or dredging ship, it has been rare to adopt geared diesel engine for such ship's except high speed diesel engine, for the reason that the diesel engine gives bad effects to the reduction gear by its large torque fluctuation. While, from several years on ward, our Yokohama Shipyard noticed of the utilization of the geared diesel engine having the aforesaid benefits and made the following design of it.
The feature of our design is that the reduction gear is coupled with diesel engine directly with allowable large fly wheel, which is the simplest and most effective system, and there is no slip of revolution between engine and reduction gear, compared with the case of using hydraulic or electric slip coupling.
One of the case is of the cargo sihp, “Matsuura Maru”, 3728 D. W. T, for the Mitsubishi Shipping Co., Ltd. The engine of this Ship is of 4 cycle single acting trunk piston with exhaust turbo charger (G 8 V 30/42, 513 rpm at 1200 PS) and is coupled with reduction gear with elastic sleeve spring “Hülsen” damper. The reduction ratio is 513/125 =4.1.
Each ship is now in service in satisfactory condition.
The utility of geared diesel engine was testified by its satisfactory operation and the analyzed value of measured torque fluctuation, which show the rightness and appropriateness of our design.
The photograph shows the pinion gear running in good condition. As a result of this test, it was proved that the measured torque fluctuation, was only 3%.
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Saburo Hara, Jiro Hoshino, Junichi Arai
1960 Volume 1960 Issue 107 Pages
331-339
Published: 1960
Released on J-STAGE: January 25, 2010
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The authors have carried out rotating bending fatigue tests of 150 mm specimens with force fitted flange having 350mmφ in external diameter and studied on fatigue strength of force fitted members as well as mechanism of fatigue crack origination.
The specimens have been made of three kinds of 0. 2% carbon steel, that is, one charge of 50 ton acid open-hearth steel and two charges of 6 ton electric furnace steel.
Small specimens of 10 mmφ having simillar shape have been taken from large specimens and tested for comparison.
The following facts have been revealed by the tests ;
(1) Fatigue strength of 150 mm φ specimens at 10
8 stress reversals was 8.0-9.5 kg/mm
2, and fatigue notch factor based upon 125 mmφ smooth surface specimens 2.80-2.00.
(2) Fatigue limit of 15mmφ specimens with forge steel, cast steel and cast iron bushes having 35 mmφ in external diameter was 14.0-14.5 kg/mm
2, and fatigue notch factor based upon 10 mmφsmooth surface specimen 1.92-1.55.
(3) The fatigue strength was decreased to 87% where bronze bushs were used, and increased to 106-108% where thin bushes having 25mmφ in external diameter were used.
(4) On the surface of fitted part of large specimens subjected to bending stress below the fatigue limit, fine cracks of non propagating nature were observed. The limit of stress at which cracks will originate was presumed about 5 kg/mm
2 at 2×10
7 stress reversals.
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Saburo Hara, Jiro Hoshino, Junichi Arai
1960 Volume 1960 Issue 107 Pages
341-349
Published: 1960
Released on J-STAGE: September 16, 2009
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The authors have newly designed and manufactured a large rotating bending fatigue test machine (Cantilever type, Max. bending moment 7 t-m, Standard diameter of specimen 125 mmφ) and tested specimens of 135 mm φ under sea water corrosion.
The specimens have been taken from steel bars forged from 1. 4 ton ingots made by acid open-hearth process (forged ratio = 6) and annealed in the furnace. The chemical and mechanical properties of the specimensare as shown below :
Chemical Properties Mechanical Properties
C 0.22 Tensile strength (kg/mm
2) 46.447.0
Si 0.23 Yield point (kg/mm
2) 24.024.5m
Mn 0.42 Elongation (50 mm, %) 36.837.2
P 0.013 Reduction of aea (%) 58.163.2
S 0.043
10 mm φ specimens of the same material having simillar shape have been also tested under sea water corrosion for comparison.
The following facts have been revealed by the tests :
(1) Fatigue strengths of 130 mm φ and 10 mm φ specimens at 10
8 stress reversal were 11.2kg/mm
2 and 3. kg/mm
2 respectively.
(2) Depth of cracks found on the corroded surface of specimens is calculated by the following formula :
l=C×log
10(N/Nc)
where
l : Depth of corrosion cracks (mm)
C : Constant, determined by the method of corrosion (=0.86 in this experiment)
Nc : Limit of stress reversal at which corrosion cracks will originate (=1.7×10
6 in this experiment)
N : No. of stress reversals.
(3) When N does not exceed 1.7×10
6, cracks will not originate.
(4) A reversal stress limit (σ
c) at which surface cracks have originated on large corroded specimens may be pressumed about 5kg/mm
2.
(5) There is also a reversal stress limit (σ
0) at which fine cracks on the non-corroded specimens begin to develope, σ
0 is assumed about 11 kg/mm
2 for the steel tested
(6) Failure of corroded specimens may occur when reversal stress has increased as the result of reduction of effective area by surface cracks and exceeds σ
0.
(7) Fatigue limit of large corroded specimens is designated by σ
0.
(8) There may be no fatigue limit for small corroded specimens.
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Shoichiro Yamada, Hideomi Matsunaga
1960 Volume 1960 Issue 107 Pages
351-365
Published: 1960
Released on J-STAGE: September 16, 2009
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In the 1st to 3rd reports, the authors investigated the effect of web dimensions and crankpin fillets on the statical bending and torsional strength and also the deflection of the webs by using single throw crankshaft models.
Timoshenko and Gessner gave the equations, based upon the theory of continuous beam, to solve the multi-throw crankshaft on many supports. The authors have modified these equations from the results of the foregoing tests, and analyzed the experimental results of the four-throw crankshaft, described in the Report No.15 of the Shipbuilding Reserch Association of Japan.
In the appendix, the results of the pure bending tests carried out on the single throw crankshafts used in the preceding tests are summarized.
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