Unified lifting-line theory is developed for the hydrofoil of fully submerged and surface piercing type. The indirect and direct problems are discussed in some details in relation with the effect of the Froude number.
The disturbing velocity potential is derived from the linearized boundary condition on the free water surface. Then, from the boundary condition on the foil, a basic integral equation is obtained for the distribution of circulation over the span, from which the lift and resistance can be readily computed, and also the optimum condition is clarified.
Some numerical examples of practical interest are shown for the characteristics, and optimum circulation and minimum resistance in a specified condition of operation for the fully submerged and surface piercing hydrofoils.

抄録全体を表示

The authors apply the theorem of the wave-making resistance of ships that the resistance does not change by adding the wave-free distribution to or subtracting it from any distribution representing a ship to the derivation of the resistance formula of the slender ship and the deformation of the practical ship lines.
Firstly, the theory suggests a new resistance formula which tells that the resistance of a ship of a certain class equals to that of the submerged body on the keel line.
Secondly, it suggests also and is confirmed by the experiments that the sectional area curve of a ship determines the resistance except a few change of it corresponding to the well-known experience.

抄録全体を表示

It is theoretically well known that when the two bodies are running in the same direction and in a pair in water and/or on water surface, sometimes their total wave making resistance becomes smaller than that of the individual body due to the mutual interference of the waves caused.
The proposed semi-submerged ship of the least wave resistance consists of the submerged main hull of the so-called Rankine's ovoid and the surface piercing bridge having sectional area of square cosine curve.
Theoretically and experimentally, the combined hull form as mentioned above thus proves its capability of reducing the wave resistance tremendously in a certain specific speed range, i. e., the dimensions of bridge can be chosen so that the waves caused by the submerged hull running near surface may be diminished by the waves of the bridge at the specific speed.
Furthermore, it is investigated that the upper limit of the optimum speed range of this type of vessel is between 0.35 and 0.40 in Froude's number.

抄録全体を表示

In January 1961, JNR was granted a patent for “transmission shaft with thrust measuring unit”. This patent was applied for the port main shaft of the Tsugaru-maru, a newly-constructed ferry-boat plying between Aomori and Hakodate. This is the first successful application in the world of a thrustmeter in large ships. This thrustmeter has been so designed as to be able to withstand safely up to 0.1 million repetitions of the severest change imaginable. The strength and rigidity to bending and torsion of this unit have been found more than equal to those of other common intermediate shafts. The thrustmeter proved sensitive enough as planned; and the stability of zero base and sensitivity was found extremely good. The measurements of thrust and torque of Tsugaru-maru in the official speed test between mile-posts showed that the efficiency of the ship's controllable pitch propeller was higher than expected.

抄録全体を表示

It has been well known that there is an incompatibleness between the course keeping quality and the turing ability of ships, i. e., it will be impossible to improve the course keeping quality of a ship without spoiling her turning ability unless the rudder area is incleased drastically.
In this paper, the authors show a method of overcoming this incompatibleness by means of automatic control of helm angle. It is shown that an automatic control of helm angle proportional to the angular velocity as well as the angular acceleration of a ship will result in an effective change in the ship's stability derivatives, and that it is possible then to make a ship more stable on course.
Therefore, it will be possible to design a ship originally to have good turning ability with poor course keeping quality consequently, then apply the automatic control so that the ship becomes effectively to have good course keeping quality with rather poor turning ability.
In this way, one can switch the ship's maneuverability in dual way according to the circumstance, i. e., when a better course keeping quality is required, the automatic control will be applied superposed with the manual control to make the ship more stable on course, and when a better turning ability is required, the automatic control will be cut off so that the ship can turn more efficiently.

抄録全体を表示

Bending strength of corrugated plate of bulkhead has already been discussed by many authors including Nagai and Caldwell. Yagi has recently published the bending strength under inplane loads.
The problems about corrugated bulkheads have therefore been almost all solved insofar as the total strength is concerned. The local strength such as elastic buckling, however, seems to the authors not yet being well discussed.
In this paper the author first solved theoretically on the buckling phenomena due to both compression and bending, and then carried out experiments to examine the theoretical results for both cases. After comparing both theoretical and experimental results the good coincidence was obtained between them.

抄録全体を表示

In part 1, the compressive strength of corrugated panels is described, showing the fact that the corrugated plate will reach its maximum load when the part of corrugation with effective width, buckled plastically after the part of flat plate between corrugated waves, buckled elastically.
In part 2, shearing rigidity of corrugated plates is studied, and it is clarified that the corrugated plates for house wall may be treated with good accuracy as anisotropic plates having the equivalent shear modulus of elasticity G'=Gb/bw, where b=wave length and bw=girth length of a wave. The effective tensile modulus of corrugated plate is also given.
Experimental verifications are given to both compressive strength and shearing rigidity of the corrugated plates, showing a good agreement between the values of calculation and the results of experiments.

抄録全体を表示

In responce to the recent tendency of building extremely large vessels, partial applications of high strength steels to main hull constructions of ore-carriers have been attempted for their weight-saving purpose. In this paper, an analysis was made on the plastic moment of hybrid steel beams consisting of high strength steel flanges and/or plate connected by a mild steel web, to estimate the ultimate strength of such structures as deck plating or bottom shell plating together with the longitudinal beams or girders, which are subjected to bending caused by lateral loads as well as the axial thrust due to longitudinal bending of the ship. Interaction curves for axial thrust vs. plastic moment relations were first prepared for the design use.
Supplemental tests were then made on both a mild steel and a heat-treated high strength steel, in order to examine the influence of the strain rate and the thermal effects of welding upon the yield strength of the steels.
Having obtained the fundamental data on the mechanical properties of the steel in the inelastic range of the material, experimental tests were carried out on hybrid steel beam specimens of I-section and of stiffened plate-sections, which were subjected to axial thrust and lateral loads in a multi-loading type testing machine.
It was confirmed from the test results that the interaction relation between axial thrust and plastic moment of hybrid steel beams, which has been obtained by the simple plastic analysis, is generally valid. Also found is the fact that, when the axial thrust is small the plastic moment of the hybrid steel beams could be remarkably increased by using a high strength steel flange in the stiffener, while in the case of large axial thrust acted in the beam, high strength steel plate should be arranged in the plating in order to sustain a large amount of the plastic moment.

抄録全体を表示

This paper is concerned with the elastoplastic thermal stresses in rectangular plate subjected to repeated thermal cycles which has unsymmetrical temperature distribution. The basic assumptions and the theory used herein are the same as in the previous report. Hence, the general equations are briefly reviewed in dimensionless forms. Some numerical calculations are performed for the typical cases as shown in Fig. 1, in order to investigate the effects of repeating of the thermal cycles and strain-hardening of the material.
It is demonstrated that the uniform heating or cooling does not necessarily cause simultaneous loading or unloading respectively, and for such cases a step-by-step procedure in time must be used inevitably. The experimental verifications are also performed in which the thermally induced deflections and the residual stresses after the given thermal cycles are measured. Although it is indicated that the theoretical values are somewhat lower because of the notable hardening in the early stage of the plastic deformation of the material at elevated temperatures, the results of the analyses are practically good compared with the experimental measurements.

抄録全体を表示

Natural frequencies of the vertical vibration of bulk carriers and destroyers were calculated by means of a digital computer, with a special attention to the shear rigidity, and the results were compared with those of the measurements on their sea trials.
Both results showed good agreements in the lower mode, while in the higher mode there are discrepancies which are attributed to the estimation of the physical properties of ships. The ratio of calculated frequencies are nearly equal in the same type of ship and the empirical coefficients can be made for the similar ships.

抄録全体を表示

We consider the free vibration (of infinitesimally small amplitude) of an elastic circular bar, both ends of which are in state of fixed ends. This circular bar is supposed to be immersed in a water region which is made up by two parallel plane (rigid) walls. Starting from the differential equation for the transverse vibration of a straight elastic bar, wherein the effect of surrounding water is taken into account, the value of natural frequency of vibration is shown in a form of determinantal equation (of infinite order). Therefrom, an approximate formula for the natural frequency is also given.

抄録全体を表示

Investigations were previously performed about the effect of high temperature prestraining on the notch toughness and the characteristics of fracture stress curves of various structural steels.
In this report, similar studies were carried out on several weld metals, deposited by manual arc welding or submerged-arc method.
As the results of the tests on these deposited metals, the following were concluded.
(1) The effects of high temperature prestraining on the notch toughness were generally more remarkable than those for rolled steels. The most harmful prestraining temperature was about 200-300°C, which was the same for rolled steels.
(2) The prestraining by 10% at 200-300°C elevated mainly the left half of the fibrous fracture stress curve, or shortened the distance between both fracture stress curves, cleavage and fibrous. Such test results might correspond to the remarkable rise of transition temperature in V-Charpy test after such treatment.
(3) A good relationship was also found to the deposited weld metals as well as to the rolled steels, between the heights of both fracture stress curves and transition temperatures in V-Charpy test (see Fig. 15).

抄録全体を表示

It is very important for structural designer to evaluate properly the brittle fracture characteristics of steel plates. Though comparatively reliable data can be obtained from so called large scale laboratory tests, they are unsuitable for commercial acceptance test methods from the view point of efficiency, economy, etc.
On the other hand the interpretation of current commercial test such as Charpy test is rather obscure and evaluation of notch toughness of materials in relation to service failure depends almost solely on accumulation of experiences in service performances with the lack of accepted theoretical basis.
The present authors previously reported of the sucessful results of fracture mechanics analysis on the double tension test (brittle fracture propagation test) and new interpretation and method of analysis for such test results and further insisted that similar method of analysis and correlation study should be made on small size test. In this report the results of analysis based on abovementioned considerations are discussed in comparison with the results from double tension test.
Though there are something to be improved for the practical purposes, fundamental characteristics of the small size test of this sort have been clarified to some extent from fracture mechanics view point and some important data were obtained which will be available for future improvements in small size tests.

抄録全体を表示

In the previous report, the authors discussed the single and double-hole models and riveted joint as crack arresters and experimentally checked by brittle fracture propagation test. They concluded that the behavior of crack arrester for brittle fracture can be estimated on the basis of fracture mechanics considerations.
In this report a kind of fundamental crack arrester model i, e, patch type model is analized by elasticity theory and discussed its effectiveness and effect of its geometrical factors. Though experimental data are lacking the results of calculation would be useful for future consideration and optimum design of crack arrester for brittle fracture. Experimental check and additional discussions will be reported in the next report.

抄録全体を表示

Change of a slow crack or a fatigue crack which has been propagated from a weld defect or the stress concentrated zone, into a fast crack such as a brittle crack at a crack length provides a significcant meaning from a viewpoint of safety for welded structures.
In general, a notched tensile test specimen for mild steel fractures after the general yielding occured on the notch section. Therefore, the superpositions of additional stresses such as the impact stress due to wedge impact, the welding residual stress and the concentrated stress due to structural discontinuities, or metallurgical change on the tip of notch are needed for the brittle fracture initiation at low stress levels below yield point.
In this paper, under the consideration that the Griffith-Orowan energy condition for brittle crack initiation at low stress level can be satisfied when the stress field has been kept in elastic condition, the plastically deformed zone around the tip of notch has been greatly restricted by increased yield point. Further, since the longer notch results in the lower fracture stress, the deep notch test for high strength steel has been conducted at low temperatures, and the low stress fracture without any additional stress or metallurgical embrittlement has been successfully realized.
Next, the ESSO test with temperature gladient has been conducted to evaluate the plastic surface energies for brittle crack propagation and arrest, respectively, in order to compare with that for crack initiation evaluated from deep notch test.
The following conclusions have been developed :
(1) The Griffith-Orowan energy condition governed the brittle fracture initiation when the general yielding did not occur.
(2) The fracture strses-temperature-critical crack length relationship, at which a slow crack changed into a brittle crack, could be obtained by using at least two or three specimens.
(3) The plastic surface energies for brittle crack propagation and arrest were less than an order of 1/10 of that for brittle crack initiation at a temperature.
(4) The temperature at which the plastic surface enegy for brittle crack initiation was about 100-120°C lower than that for crack arresrt at a stress level for a 80 kg/mm² high strength steel tested.

抄録全体を表示

The behavior of the fatigue crack in a finite width plate and an infinite plate subjected to cyclic loading and corrosive action is examined theoretically. A crack propagation law is deduced assuming that a fatigue crack will extend when the damage accumulated at the tip of the crack reaches a critical value.
It is found that the rate of crack growth is affected by specimen width and type of loading ' (constant load or constant net stress). This shows a good agreement with the test results by Munse, et al. It is also concluded that the estimation of corrosion fatigue strength of an infinite plate is possible if the factors, k₀ and q₀ in eq. (26), is determined from a corrosion fatigue test of finite width plate.

抄録全体を表示

The major subject of the present report is concerned with the deformation of ship's bottom caused by welding. And it will be shown that the final shape of bottom on berth-lifting at ship's ends and shrinking fore & aft-is determined by the welding to the bottom and its vicinity, and not the main deck and above.
It will also be shown that the intensity of tensile reaction stress in main deck plate of the large tanker does not increase with the progress of welding work through construction period.
It follows from the above that the apparent sagging moment by which the weld-constructed ship tends to sag after her launching is not due to the welding internal stress which may be considered to be restricted on berth and released at water born, but the differences between the distribution of ship's own weight and reaction force by keel block and shore.

抄録全体を表示

In recent years, the productivity in shipbuilding has greatly been increased by means of “block” or subassembly method with aid of advanced welding technique and more fruitful results may well be expected through “three dimensional block” method in lieu of conventional flat block method.
However, when composing the massive, three dimedsional block is thought of, various problems must be solved such as the accuracy in dimension & shape of block, the area of assembly yard, crane capacity, and lifting pads etc.
The present paper is concerned with the three dimensional block method which has been established and placed successfully in use of cargo ship construction in this yard as the first attempt in the ordinary shipyard except the newly built, special shipyard in Denmark.

抄録全体を表示

Recently in the field of shipbuilding high speed computers have been used widely and contributed to not only reduction of man-hour but also improvement of exactness of calculations. As an example of numerical calculation of day scheduling of shipbuilding process, we have calculated numerically, using the method of linear programming, the day scheduling of the gas-cutting process among the many factors of which some linear relations are found. In this report, the process of the calculation and the result of practical use are shown.

抄録全体を表示

The so-colled “KIHANSEN”, a small wooden cargo ship whose length is about 20 meters or more, operates mainly on the Seto Inland Sea, a typical Archipelago in Japan. In the previous papers, the authors studied its safety with regards to its loading conditions, its particular ship form and construction, and complicated sea conditions under which the ship must navigate. And concluded that the causes of its casualties were 1) extraordinary length-breadth ratio (L/B), namely, about 3.8 2) undesirable loading conditions which are unsuitable with ship nature especially in case of carring heavy cargos, and 3) the unfavorable hold arrangements for seaworthiness, which allow shipping sea water easily.
In this paper, to confirm above conclusions, with deta of 164 serious ship casualties, the situations of affairs are examined and studied severally, and furthermore some designing problems are discussed in connection with the safety of this sort of ship.

抄録全体を表示

The defect of the SMOKE TYPE FIRE DETECTING SYSTEM installed on the bridge for early detection of fire in the cargo-holds is that the uniform detection of smoke has been impossible because of the non-uniform air-flow rates through the respective air-smoke suction pipes leading to the cargo-holds.
This paper reports that the air-flow rates in the air-smoke suction pipes are made uniform and as the result the smoke-detecting ability is improved by the application of the air-resistance controlling method.

抄録全体を表示