Many reports for residual stress have been published, but they cannot be said successful togive a solution for this problem. To discuss the characteristics of residual stress, we mustconsider not only its magnitude but its process of growth. For the first step of this idea, we dealt with a rectangular plate under one-dimensionally distributed temperature as shownin Fig. 4, In this case thermal stress and its residual stress act practically only in thedirection of heating. In experiment breadth 5mm on the centre line of test piece 300×110×2.3mm was heated instantaneously from both sides and residual stress was measured byHeyn's method.
On the while, thermal stresses for every momentary temperature distribution were calculated by author's plastic theory and the residual stress was obtained for the last course. These results are shown in Fig. 10 & 13.
An example for the two-dimensionally distributed stress will be discussed in the second report.

View full abstract

For the purpose of clarifying the growing mechanism of thermal stress and residual stressdue to welding, we have studied the problem of rectangular plate under one-dimensionalthermal stress. In this report we have dealt with a plastic study of themal stress andresidual stress of circular plate heated at the centre, and it is an example of the problemsof two-dimensional thermal stress.
At high temperature the plate behaves plastic deformation, and when it cools down toroom temperature, residual stress grows in consequence of the restraint of the plastic strain.Under these idea, we have developed the theory. The thermal stresses for every momentarytemperature distribution were calculated by this theory and the residual stress was obtainedfor the last course. These results are shown in Fig. 7 and 8.
On the while, experiments were performed in order to verify our theory; 200 mmφ×6mmcircular plate was heated at its centre by welding and the residual stress was measuredby modified Sachs' method. The experimental value and theoretical one of residual stressare shown in Fig.13, and from this results it was verified that our theory is right.

View full abstract

Many theoretical and experimental investigations on reinforced rectangular plate have beenpublished. The former has two ways. One of them is to solve the partial differential equationof reinforced rectangular plate in equilibrium under the required boundary conditons, andthe other is by the method of strain energy.
In either case, we must solve simultaneous equations in final calculation. Especially inthe former case, simultaneous equations with infinite unknowns must be solved. Of course, we calculate simultaneous equations with finite unknowns approximately, but more termsare required for more accuracy in accordance with rigidity of reinforcement. And in thelatter case, that is to say, strain energy method, we meet similar difficulties.
The author proposed the following equation for rectangular plate with reinforcement at y-direction,
D(∂4w/∂x4+2∂4w/∂x2∂y2+∂4w/∂y4)=P-∑iEIiδ(x-xi)d4w/dy4x=xi
where w: deflexion of plate, D: rigidity of plate,
P: lateral load on plate, Ii: moment of inertia of i-th reinforcement,
δ(x-xi) Dirac's impulse function,
and he gave its solution as follows,
w=∑<m>n[a°mn-1/{(mπ/a)2+(nπ/b)2}2∑jAj∑<α>a°αnsinαπxj/a]sinmπx/asinnπy/b
where a°mn=4/abD1/{(mπ/a)2+(nπ/b)2}2∫a0∫b0P(ξ, η)sinmπξ/asinnπη/bdξdη
In case of the plate with one or two edges (opposite each other) clamped,
lim xj→0oraγj→∞ amn is taken for above amn,
where γj=2EIj/Da
From the results, he reduced the formulae for rectangular plate with clamped edges and without reinforcement.
Moreover, the author proposed a new calculation methodd of rectangular plate with concentrated load, by expressing the load in Dirac's impulse function. In this way, concentrated load is handled like uniformly distributed load.

View full abstract

The watertight work of the ship's hull is one of the most important works of the shipbuilding. During the last few years, remarkable improvements of the shipbuilding work havebeen attained by the large endevours of naval architects. However there are still some unsatisfactory facts in the watertight work.
In this paper, the author intends to discuss about some of those facts, clarify their origins, and investigate how to improve the watertight work of the ship's hull.

View full abstract

The present Rules were issued in the year 1943, and no alteration has been done since thattime. Recently, however, additions and amendments in large extent were adopted by theCommittee, and the revised Rules are expected to be made effective on next January. Theauthor intends to explain the outline of the revised Rules.

View full abstract

To study the effects of the forms of fishing-boats upon the resistance, the towing experimentsof forty-one models, in which the volume-length ratios, prismatic coefficients andbreadth-draught ratios are varied systematically within the following range, are carried out at the experimental tank of Tokyo University, and the results obtained are compared.
Volume-length ratio ∇(/L/10)³=7.5_??_15.0
Prismatic coefficient φ=0.55_??_0.75
Breadth-draught ratio B/T=2.2_??_3.0

View full abstract

In order to find the means of improving the hull efficiency of the single screw ship, a methodis proposed to culculate theoretically the thrust deduction coefficient. Principal assumptionsbeing; (i) the hull is the cylinder with vertical generating lines, (ii) the induced velocity causedby the propeller is obtained by the doublets uniformly distributed over the propeller disk.
If the water plane shape is represented by the third power series of the distance from the propeller, the thrust deduction coefficient is to be computed by the following formula.
t=1/π(√<c_s+1>+1){2(2α/1-w+√<c_s1>-1)(y₁/R-I₁)-(√<c_s+1>-1)I₂}
where, c_s: the thrust loading coefficient, α: the effective velocity factor along the surface of run, y₁: a half maximum breadth of the hull, R: the radius of the propeller, I₁, I₂: the functionof the hull shape only. Provided that c_s is not too large, the above formula can be approximated by
t=4α/π(√<C_s+1>+1)(1-w)(y₁/R-I₁)
The principal conclusions are following:-
1. t grows smaller as w, c_s, ε₀ (the angle of run) or the propeller immersion grows smaller.
2. t grows smaller as the Reynolds' number or the clearance between the propeller and the stern frame grows larger.
3. The hull efficiency grows larger as the Reynolds' number or t due to the hull shape grows smaller.
4. The most practical and effective means to improve the hull efficiency is to reduce the angle of run or to widen the clearance between the propeller and the stern frame.

View full abstract

In this paper the authors represent the principle, the mechanism, data of design and the results of calibrations of a newly designed torsionmeter which applied the “torsional magnets-striction effect” under an alternating magnetic field, and the results obtained on various kinds of sea trials with the new torsionmeters attached to the intermediate shafts of some twin-screw turbine steamers. This newly designed torsionmeter has the merits as follows:-
(1) It can record accurately the working torsion and numbers of revolution of each intermediate shaft continuously for a long time in the view of the operator
(2) No usages of special amplifier,
(3) It can record torsional vibration of each shaft.
(4) It works without regard to the direction of revolution and of the torsion of each shaft,
(5) It can make clear the time correlation between the changes of the torsion and the speed of revolution and the motion of the vessel or the handling of the main engines.
Attaching the torsionmeters of the new type to the intermediate shafts of three train ferry boats-twin screw turbine steamers-between Aomori and Hakodate, the authors and collaborators made various kinds of sea trials and obtained the following results in short.
(1) Continuous records of the torsion, numbers of revolution and the speed through the water not only on the measured mile course but also before and after of it, were obtained and it was made clear how they were changed during that period.
(2) The changes of the torsion, the speed of revolution of each shaft etc, during the turning trial were made clear.
(3) The changes of the torsion, the speed of revolution of each shaft, the ship speed, the steam-pressure in the high pressure turbine etc. during a backing trial were made clear. And the presumption made by Kinoshita and Nakajima in the previous paper read at the spring meeting of 1947 was verified that three maxima would appear in the working torsion (and thrust) of a shaft during the transition period of the change from going ahead to going astern or vice versa.
(4) Torsional vibration of each shaft were recorded.
(5) The shaft bearing and the sterntube losses ware measured and percentages of these losses to the power output were obtained.
From the the above mentioned results we can learn many new experimental facts. For instance, we can determine how long a ship must run in order to settle on a constant revolution, a constant torsion and a constant speed before she enters a measured mile course.

View full abstract

“Matsumoto”s torsion meter is used mainly for the purpose of measuring shaft horse power equipped on the intermediate shaft of marine engine. We divide, for convenince, this meter into two parts; the detecting part of shaft torsion and indicating part thus detected.
This device leaves detecting part as it is, but in indicating part use the special circuit involving “Ring-modulator” circuits. With this device, we can indicate torsion using ordinary voltmeter, without any special one, and by changing resistance in the circuit we can vary its sensibility in broad range without raising primary voltage.

View full abstract

1. Wave-making resistance and rolling angular velocity.
2. Calculation of wave heights produced by the rolling of cylinders with geometrical sections.
3. Wave-making resistances and sectional forms.

View full abstract

In this paper, the author investigated into the effect of the free surface of water upon the virtual mass of submerged solids moving parallel to the free surface, and obtained following results:
1) The virtual mass of solid decreases by the effect of the free surface.
2) The virtual mass is not effected by the velocity of the solid, and is always constant when the depth of the solid is constant.
3) The effect of the free surface is represented by the effect of a solid placed at the image point of the submerged solid against the free surface, and has negative velocity.

View full abstract

The ship on the voyage cannot maintain her course by herself alone, yaws under the disturbing forces such as gusts, winds and waves, and deviates gradually from her initial direction.
Accordingly pilots must always take the rudder in order to hold her course.
The actions of rudder are as follows:
ρ=κφ+λφ+μφ(κ, λ, μ>0)
where ρ Angle of rudder
φ Angle of yaw
κ, λ, μ Constants of the steering apparatus.
κφ restores the deviated course to initial direction.
λφ has the damping action on the oscillation of direction
μφ absorbs the impulsive energy of gusts and waves.

View full abstract

The manoeuverability of a tunny fishing boat under the strong wind was investigated for her three different conditions of trim, and the effects of the spanker and the bonito fishing platform on her manoeuverability were also studied separately. And the ranges of manoeuverabihity, or the limiting values of the direction and the velocity of the wind under which she can barely keep up her manoeuverability, were shown for these conditions. In the first half part of this report, there are given the results of a series of the wind-tunnel experiments with the image models of the above-water and the under-water portions of a tunny fishing boat carried out for the purpose of the above-mentioned investigation. And the distinctive features of the above-water portion of the fishing boat were made clear. In the latter half, the motion of the fishing boat under the strong wind with three different conditions of trim, or without aspanker, or with the bonito fishing platform, was solved using the experimental data obtained in the first half. In conclusion, the authors shew that the condition of even keel was the most fovourable for a fishing boat of this type to keep up her manoeuverability and safety, and that the excessive trim by the stern as well as by the bow was unfavourable, and they were convinaced quantitatively of the fact that the spanker played its part perfectly effectively under the oblique head wind and that the bonito fishing platform had almost no effect on the manoeuverability under the strong wind.

View full abstract