Many theoretical investigations on the interaction forces and moments between two vessels which under way of parallel courses have been dealt with as two dimensional problem.
In this report, we solve the problem three dimensionally in the stationary case in deep water, and show that the interaction forces and moments are composed of the sum of symmetrical ones which have nearly same magnitude and opposite direction on each vessel, and the ones caused by the forerunning ship.
Moreover, comparing with the results of model experiments carried out at the circulating tank, we show that the interaction forces and moments can be approximated with the symmetrical ones only, when two ships are not so close each other.

抄録全体を表示

Two-dimensional values of hydrodynamic force and moment produced by swaying oscillation on the surface of a fluid were exactly calculated for cylinders with Lewis-form section.
Added mass coefficient of swaying oscillation K_x, progressive wave height ratio A, inertia coefficient of the moment K_sψ and coefficient of the damping moment α_sψ are shown in several figures and tables.

抄録全体を表示

After the characters of the ship oscillations among waves were discussed in Part I of this paper, the general aspects of the ship oscillations among irregular waves as a stochastic process were investigated here. The theoretical basis for the analysis of the stochastic process is already clear, however there are quite a few problems in numerical computations of the sample spectrum function, although that is used usually as the most convenient function to express the response to an irregular input.
The author tried to make clear the problems and improve the process in applying the method to the analysis of ship oscillations. After trying to make clear the limitations and defects of the spectrum analysis, the author discussed the character and the usefulness of the correlation functions of ship oscillations, which is not usually used being considered to be inferior to the spectrum in few points, and which the author still believes to be more informative to express the response, and is more convenient to be handled in some cases, rather than the spectra.

抄録全体を表示

The present paper relates to experimental researches on rudder performance utilizing a free running, self-propelled model.
Hardover to hardover steering tests have been carried out on four different balance ratios including the optimum one estimated by turning tests, and it is known that the balance ratio must be selected so as to prevent the abnormally large positive torque which may occur when the rudder is steered from port to starboard.
An interpretation for the complicated rudder performance during the turning tests have been tried using the results of behind tests and free model tests. As the results, the resonable values for normal force coefficients have been provided through considering the change of slip ratio of propeller and drift angle of ship, but it remains some problems to be investigated for the center of pressure.

抄録全体を表示

Following the paper of the same title on this Journal, vol. 109, the present paper treats at first with a procedure of obtaining resistance derivatives from free-running model steering experiments. This is carried out by analysing “steering quality indices” K', T'₁, T'₂ and T'₃ produced from frequency response analysis upon the test results, but using drift angle observed in circular turning and also estimating virtual mass and moment of inertia of a model from calculation or experiments. Thus free-model experiments may yield information not only for steering motion of a ship but for forces acting on her. Measurements of rudder force in circular turning may also be useful for getting informations on the forces through total-less-rudder moment procedure of Davidson and Schiff and through the similar procedure for lateral force.
Two new procedures of analysing the standard manoeuvre are also discussed and both are based upon the first-order equation of motion of integrated form of Eq. (5) The first of the two is to solve the simultaneous equations derived by applying the above equation for several particular instants during a test and the second utilizes the least square error method for the similar equations set up at a certain time interval.
A brief description upon radio-control instruments and measuring techniques for free-model experiments is finally presented. An illustrated system utilizing a conventional toy aeroplane radio-control is easy to construct and is enough to carry out various types of steering experiments. A new device for precision measuring of heading angle using a free-gyro and photo-transistor detector is introduced, with a current meter measuring ship speed, a photographic means of obtaining drift angle and wire-strain-gauge type rudder forces measurement.

抄録全体を表示

By analysing several actual records of steering, the author has approximated the dynamic characteristics of manual steering. And he has obtained the following results : it is resonable to consider that the value of gain constant lies between 0.5 and 3, and rate time between 0 and 5, for a well-trained helmsman.
The author has applied the above results to the estimation of the optimum values of the measure of maneuverability of ship.

抄録全体を表示

Analysis of the circle test on the actual ship has made it clear that even a low approach speed has influence on the turning circle and that a change in the helm angle tells on the turning circle due to the aspect ratio of the rudder. By making use of these results as well as that of the model test, the Hovgaard-Schoenherr formula was modified, and K3 value was sought with B/d as parameter.
In this way the turning circle has come to be estimated very simply.

抄録全体を表示

The author has tried to clarify the differences between two formulae, Lagally's and so-called linearized, and found that its cause lies in an approximate treatment of the boundary condition, but this is corrected in counting for the variation of the displacement volume.
In this stand point, however, we have to count the second approximation for the boundary condition. Fortunately, the wave resistance formula does not differ with two formulae, but for the trim and sinkage their difference is very serious one.
He explains theoretically and numerically these difference with experimental data which can be usefull.
In the mean time, he sugguests a simple formula which gives roughly a wave resistance from the recorded wave profile in a fairly wide range of ship speed.

抄録全体を表示

今春3月, 瀬戸内海航路高速客船くれない丸を供試船として, Waveless船型理論にもとづく超大型バルブの「船首波打消し」の実船試験が行なわれた。今回これを「水槽試験」・「実船試験」・「波形観測」の3篇にわけて報告する。以下はその第1部 (前篇) 「水槽試験」の報告であるが, ここでは他の2篇と異なり, 記述の範囲を今回行なわれた実船試験のみに限定しないで, くれない丸の計画当初から現船型決定の経緯にまでさかのぼり, くれない丸がその計画・建造・就航・実船試験の各時点において東大水槽におけるWaveless船型理論の発展の経過といかに交渉しあつたかをあきらかにすることに意を用いた。
Waveless船型理論では在来の水槽試験のほかに, 「波形分析」という新しい船型学的手法を重視する。今回も当然模型・実船の両方についてこの「波形分析」が試みられたが, この部分は一括して第3部 (後篇) 「波形観測」で取扱われている。
なお, 第2部 (中篇) 「実船試験」では, 中心となる速力試験のほかにZ操船試験と旋回試験とにもふれられている。

抄録全体を表示

この報告は高速客船くれない丸に関する研究報告の第2部をなすもので, 前報1) の後半に示した通常の意味での水槽試験 (抵抗・自航) と対応する実船の部分, すなわち速力試験における馬力計測結果とその解析を中心として述べたものである。このほかに実船では, 模型船**で現在のところ未だ実施されていないZ操船試験・旋回試験をも実施し, 船首波打消しの役目をもつ超大型バルブが, 速力性能に貢献する一方で船の操縦性能にどのような副作用を与えるかを模型にさきがけて直接実船についてしらべてみたので, その結果についても報告する。
くれない丸の実船試験およびこれに関連して行なわれた水槽試験の全般を通じて, もっとも特徴的なところは模型船および実船の造る波の波形観測と波形分析とである。その内容は模型・実船の各波形の相似性比較という見地から, 第3部に統一的に取扱うことにした。ただ本報告では実船においても波形観測を重視したところから, 速力試験の航走法にも従来にない新らしい試みがなされたことを付記した。

抄録全体を表示

この報告は, 今春行なわれたくれない丸の大型バルブによる船首波打消しの実船実験およびこれに先立つて行なわれた東大の2.5m模型水槽試験のうち, 波形分析という新しい船型学的研究方法を適用した部分について述べたものである。

抄録全体を表示

This paper describes an experimental survey of the bulbous bow effect on the resistance with fishing boat models of existing design and a comparative investigation between theoretical aspects based on the waveless hull form theory ignited by Prof. INUI¹⁾ and experimental results with a calculated model of known sink-source distribution and after advocating the necessity of an original development of unprecedented hull form for realizing actually waveless state, the paper gives some tank test results of self-propulsion and of seakindliness among waves with a model of exploratory design for practical waveless boats. These preferable results may stimulate the further persuit of another effective hull form for the bulb not protruding from the bow so as not to prevent from easy operation of, anchoring and steering.

抄録全体を表示

In order to investigate minimum resistance for high speed range, resistance tests and wave profile observations by two-dimensional models were carried out and compared with calculations.
The results show that the ship form of minimum resistance will be obtained by concentrating the displacement to bow and stern, and that the corrections for change of trim and displacement will be necessary at high speed to estimate the wavemaking resistance.
Calculations of resistance for actual ship forms are tried at the same time.

抄録全体を表示

This paper deals with a practical application of “Weveless Bow” theory, has been developed by Prof. T. Inui & T. Takahei.
In spite of a high speed practical ship form is treated for the subject of study, the results of experiments and calculations prove that the large bulbous bow according to “Waveless Bow” theory is certainly effective.
Seaworthiness and turning qualities on the same ship form will be mentioned in next reports.

抄録全体を表示

In the preceding two papers on the Waveless Stern (Part I, Part II), the author showed the results of resistance tests together with their theoretical analysis.
In this third paper, he deals with the propulsion characteristics of the Waveless Stern.
Prior to the tests, the optimum pitch distribution of the wake-adapted propeller was determined as approximately linear according to the usual circulation theory in reference to the wake survey results by the blade wheel method. The tests were carried out with the UNKEN A₄-40 Standard Propeller with constant pitch distribution (P/D=1.0) as the said wake adapted propeller.
In general, all of the propulsion coefficients take favourable turn with the waveless stern.
Summary of the results is given in Figs. 4 and 5.
The author also presents the contours and the profile sections for the wave patterns of the stern waves measured and analyzed by the stereophotogrammetry. They prove to be most valuable for clarifying the mechanism of the “waveless” status around the stern.

抄録全体を表示

Formerly, the critical value of roughness for plate studs having constant breadth was found by experiments.
The author, lately, carried out experiments to determine critical values of roughness for various shaped stimulators and observed the wake behind stimulators by means of the chemical film method, hot wire anemometer technique and milk injection. Critical values of roughness for various stimulators were determined by results obtained.
Moreover, resistance of various stimulators own were measured directly.
Using above-mentioned results, resistance of various stimulators placed on the flat plate were calculated and compared each other under various conditions. The superiority of studs was confirmed by these results.

抄録全体を表示

An expression for the velocity potential of the flow around an oscillating screw propeller is derived by using a Green's function. And the author presents an approximate integral equation by means of lifting-line techniques with the consideration mentioned in his previous paper.

抄録全体を表示

In the present report, the results of measurements of velocity of the slip stream caused by the Troost B 4-40 type propeller are arranged on the basis of the theoretical inquiries described in the first report, so that these results may conveniently be utilized for the calculation of the force acting on the rudder and other items. Furthermore, to examine the suitability of the current propeller theory by clarifying the property of the velocity-field of the slip stream, the comparison of the experimental results with the results of the numerical calculation carried out by adding various kinds of practical correcting calculation to the theoretical calculation stated in the first report, is executed. Some conclusions obtained from these results are as described in the following lines.
i) The correction coefficient of circulation based on the lifting surface theory must take a value of 0.700.85 at 0.7 R section (R : radius of propeller), in order that it may meet the experimental value, independently of the advance constant. Furthermore, it is nearly constant in all sections except the tip.
ii) With respect to the velocity distribution of the slip stream, the measured value quite agrees with the value calculated on the basis of the current propeller theory in relation to the peripheral component. With respect to the axial component and radial component, homever, the experimental value always become 1015 % larger than the calculated value in the vicinity of the propeller disk.

抄録全体を表示

Wind moment M_w' (cf. the previous paper in vol. 108 of this Journal) acting on a ship will much decrease when she moderately lists. Ships, therefore, with critical stability or, for example, the critical work ratio C=1 of the official “Stability Standard” in which a constant wind moment D_wW is used, will have the work ratio C_o' of about 2 if D_wW is replaced by M_w'. It may be supposed that the difference between these work ratios shows a margin for the secondary actions of steering, shifting of goods, shipping seas and so on which are not explicitly taken in the Standard and will be covered by adapting the constant moment. We shall now name the margin a residual stability because a ship still has some residue of stability in the above meaning although her reserve of stability in usual sense has been already lost.
The present work deals with the residual stability in two aspects, how much reduction in it will be caused by the secondary actions and what form of a stability curve will prove toughness to them. 21 ships were examined, however, under the simplified situations where (i) they were steered by helm 30° when their engines had been in cruising revolutions (denoted by the symbol r in the figures), (ii) weights on board were shifted (denoted by s), (iii) seas were shipped on exposed upper decks (by wa), (iv) sea water stayed in the deck houses (by wb) or, (v) sea water stayed in the under-deck spaces (by wc and wd), and, at the same time, under the actions of wind and waves provided in the Standard.
From the results of examinations, saying particularly about the characteristics of stability curves, ships with GM larger than about 7.5% of the beam and the range of stability less than about 50° are very week for the secondary actions.

抄録全体を表示

This paper is aimed to refine the former theory of the lateral statical stability in foil borne condition and, at the same time, establish a estimating method for the metacentric height of hydrofoil craft of surface piercing type.
Present theoretical method takes into account the following points
(1) the effect of the geometrical form of span of the hydrofoil
(2) the effect of the free water surface
(3) the effect of the angular velocity of roll and side slip velocity which have been unduly neglected in the former theory.

抄録全体を表示

According to the statistical theory, upper limit of maxima of random variables is infinity., but we suppose that there must be a certain definite value in the usual circumstances.
The author analysed this problem from distinguished characters of probability distribution function, and find the fact that there are two critical values, namely for short-time record of irregular phenomena, about 3% reliability and for long-time record 0.5% respectively.
When number of samples is small, probability density curve is likely to parabolla, but number increases it resembles asymptotically to Gauss or Rayleigh distribution. So that if we draw a tangent at the point of inflection on these idealized function, the position of the foot of this tangent may be corresponds to the highest value of maxima of short-time record. Next, the idealized distribution function has two maximum curvature. The one of the position of 'those center of maximum curvature indicates the well-known maximum frequency, so that the other too must have physically important meaning as well, and the author find empirically the fact that this corresponds to the highest value for long-time record.
This value is 2.62 times as large as the standard deviation of Gauss distribution, and 2.53 times as large as the mean value of Rayleigh distribution.
Existence of maxima is able to conceive on the cumulative density curve of at least thousands or tens of thousands of samples.

抄録全体を表示

The irregularity of the natural phenomena e. g. sea waves is expressed by Rayleigh distribution in short times. In the course of time the mean of this distribution varies approximately according to the logarithmico-normal distribution, and so the whole distribution and that of the maximum values in some portions of time may be also expressed by this distribution. The engineering quantities induced from these phenomena e. g. rolling angles of ships are also expressed by these distributions.
The logarithmico-normal distribution is made to fit better to statistical data, taking the lower limit not as zero and the upper limit not as infinity. The author has tried to decide these limits or parameters so that the skewness and the peakedness of values transformed from data by some function may agree to medians of those of sample values from the normal distribution. He has also calculated the error of the estimate of the rolling angle arising from the error of the estimation of parameters.
Rolling angles of ferry boat Sorachi-maru were measured in 32 voyages and their distribution in long times was calculated.

抄録全体を表示

This paper presents the results of a theoretical investigation of the motions and the midship bending moments of a ship running in regular waves. The results of theoretical calculation about T 2-SE-A1 show that the midship bending moments considering dynamical influences are affected by the ship speed and the weight distribution of ship.

抄録全体を表示

A T 2-SE-A1 tanker model was tested in the T. T. R. I. Model basin in order to determine longitudinal bending moments in regular waves. The hull of model was made of wood and cut at five sections. Each block of hull was connected by steel girder. Bending moments at five sections were obtained by measuring the bending stress on steel girder at the sections by means of resistance wire strain gages. Hydrodynamical forces acting on each part of hull were also measured. Tests were made in regular head waves having heights of h/L = 1/50 and 1/30, and lengths of λ/L =0.75, 1.00, 1.25 and 1.50.

抄録全体を表示

The aft end of longitudinal bulkhead in tanker is, in most cases, situated at or near the section where shearing force acting on the hull is maximum in its after body.
Therefore, it is one of the important problem in longitudinal strength of tankers that how much shearing force is loaded by longitudinal bulkhead.
The auther studied the problem both theoretically and experimentally. As the results, the aft end part of longitudinal bulkhead loads high percentage of the total shearing force has become clear.

抄録全体を表示

Most of the plating of ship structure is stiffened by inverted angles, and the strength of these stiffeners have been estimated by the simple beam theory. However, their bending rigidity and strength may be considerably reduced because of the unsymmetry of their cross sections.
In order to explain these phenomena, elastic behaviour of the inverted angle with plating under bending load was analysed considering effects of distortion of its cross section and torsion.
While, to examine the validity of the theory, bending tests were carried out and fair agreements between test results and calculated values were obtained. From these results, the relation between effectiveness and ratio of breadth to thickness of the angle was found.

抄録全体を表示

An experimental result on the load carrying capacity of circular plate under concentrated lateral load has been reported by the author in 1956 (J. of ZOSEN KIOKAI, Vol. 99). This paper is concerned with theoretical analysis on the result.
For elastic deformation, the membrane action will be considered, and the limit theorem will be applied to the plastic zone to obtain theoretical predictions which agree with the experimental result.

抄録全体を表示

The tests on the plastic collapse of a stiffened plate were conducted under a concentrated lateral load at center. The load-deflection curves have shown the distinct change in mode at the collapse load of a stiffened plate because of the plastic collapse of a stiffener. Hence the plastic method of design based on the simple plastic theory was realized by the tests to be applicable to the design of a stiffened plate subjected to lateral loads. The deflections of a stiffened plate in the plastic range were calculated with the consideration of the effects of membrane actions under simplified boundary conditions, and the theoretical analysis was confirmed by the test results.

抄録全体を表示

Recently the plastic design method has been brought into the structural design field in order to overcome many difficulties and defects caused by the so-called elastic design.
In this paper, the authors, therefore, studied the plastic design method to analyse the test results of bipod-type mast models with cylindrical sections.
Experiments were carried out on three series of specimens, i. e., B-series (plane frames) loaded in the plane of the specimen, T-series and P-series (space frames) loaded perpendicularly to the plane. In the latter case, both bending and twisting couples should be taken into account in the calculation.
The followings were obtained conclusively;
(1) Theoretical collapsing loads (ultimate loads) coincided well with the test results of both plane and space frames.
(2) The mechanisms (collapse mode) predicted by the plastic design showed satisfactory agreement with those of experiments and consequently the applicability of plastic design to space frames as well as plane frames was confirmed.
(3) In the case of bipod-type masts, it was found that the most economical value of μ (the ratio of full plastic moment at the top of mast to that at the bottom of mast), from the weight-saving standpoint, was approximately 0.4.

抄録全体を表示

In the previous report, the author described that recently it became a very important problem to estimate the intensity of resonant hull vibration and its allowable exciting force at the time of preliminary design of ship, and presented the method of its approximate calculations.
However, sometimes this method is compelled to have big safety factors, so, in this report the author investigated damping factor, virtual mass, mode factor, mode curve and etc. more deeply by analysing the many actual measured data, and found the more accurate method by modifying the previous one.

抄録全体を表示

In the precee ding reports, the auther have studied about the low-cycle fatigue properties of ship structural steel, by simple rotatary bending tests of round-notched specimens. Measuring the crack depth in its propagating stage by heat tinted method, the rate of crack growth was proved to be proportional to the current crack depth.
In this report, by some theoretical and experimental analysis, the proportional coefficient is explained to be a function of the dimensions of specimen, notch size, and testing procedures, and independent to the materials and applied stress values. Approximately it can be expressed by a power function of the stress amplitude, and the power index is identified by the slope of the σ-N diagram of the specimen.

抄録全体を表示

The “Light corrugated steel panel”, in this Report, is the thin steel sheet of 900-1200 m/m wide with longitudinal ridges, used chiefly for the partition of living quarter of merchant vessels and for the outside wall as the superstructure and the partition of living quarter of combatant vessels.
It has been made clear, through many researches in various respect on this subject, done in the past, that “Light corrugated steel panel” is excellent in structure strength and very effective in reducing the weight of material used.
With a view of ascertaining whether “Light corrugated steel panel” can be practicably used for the partition of steel vessels, i. e. through investigation of the butt-joint of “Light corrugated steel panel” and experiment with the model deck-structure made thereof, we have made further research with the result that its structural strength with fine finish has been proved quite satisfactory, while the man-hours worked as well as the weight of material used have been considerably reduced.
We have, thus, decided to put this method to the actual processing and adopted for building the entire partition wall and upper-deck structures of 450 ton A Type Submarine chaser with the permission of Defence Administration.
This report deals with the result of our research and experiment in this connection, the actual state of operation of the vessel built with this process and the stress to the super-structure made of “Light corrugated steel panel”.

抄録全体を表示

The present paper outlines a theoretical analysis on the shrinkage due to spot heating of a rectangular carbon steel plate with finite size. Elastic calculation based on the plane-stress condition was conducted, with an assumption that a negative dilatation-K was situated at the heating point. For the convenience of analysis, the rectangular region was transformed into a unit-sized circle, with one-to-one correspondence of the points in the respective regions.
Reasonable assumption of the magnitude of-K, which depends on the heating and cooling conditions, gave a satisfactory agreement between the calculated shrinkages and the measured ones, and the characteristics of shrinkages due to spot heating on a finite-sized plate was clearly demonstrated.

抄録全体を表示

In various welded structures welding will be done more or less under external restraint. The intensity of restraint will influence on the reaction stress and shrinkage in welded joints and especially on the first pass weld cracking. However the informations on the intensity of restraint in a welded joint which is related to reaction stress are left yet quantitatively unknown. As for the intensity of restraint the following definition was adopted ; intensity of restraint is equal to average value of transverse stress along weld line necessary to produce average elastic change of root gap of unit magnitude along the weld line. The intensity of restraint thus defined will be able to be obtained by using elastic theory for restrained specimens of simple shape, but it will be difficult for more complicated specimens and practical welded joints. In order to measure the intensity of restraint the authors designed a measuring apparatus called “Restraint Meter”. Principle of the restraint meter is as follows : Separating force is applied to both beveled edge planes of a joint before welding by the action of a wedge pushed into root gap of the joint and then the change of root gap is measured by displacement gauges. The separating force per unit change of root gap will be increased with the increase of restraint. The intensity of restraint can be obtained from the separating force.

抄録全体を表示

In the previous report the authors described the method of calculating the strain energy release rate when brittle crack propagates in residual stress field, but the present paper deals with the application of such calculation method to various experimental values.
In other words,
1) By means of graphic algebra the strain energy release rate was sought from the actually measured residual stress field.
2) The plastic surface energies at the times of the initiation and arrest of brittle fracture were sought and the values of 0.5 and 0.1kg-m/cm², respectively, were obtained.
3) Studies were made about the effect of notch shape upon the brittle fracture conditions.Moreover, the stress condition near the notch root was measured and discussed.

抄録全体を表示

In the previous report the authors reported various conditions for the loss of ductility of the toe of the first pass side welding during finishing pass side welding due to thermal strain. But the present paper deals with the investigation carried out in order to clarify the relation between such phenomenon and fracture mechanism seen from the stand point of material mechanics.
In other words, the authors sought the effects upon ductility of prestrain, aging, etc. by means of simple testing of round bar, etc. Moreover, concerning the notch at the toe of the first pass side welding, its relation with welding conditions and effects on fracture were studied. Further-more, root cracking conditions of one side multi-layer butt welding were also investigated.
The results of these investigations were as follows :
1) The effects of tensile strain and compressive strain upon ductility differ. The former reduces ductility by raising flow stress from the stand point of material quality while the latter causes it by complicated causes such as changes of notch shapes, triaxiality, etc.
2) Notch shape changes according to welding position and electrode diameter and, the effects of such notch conditions upon crack initiation have been recognized.
3) Similar to the toe of fillet welding, the multi-layer welding root of the butt joint initiates crack in accordance with the strain due to subsequent pass welding and notch conditions.

抄録全体を表示

In the previous reports, it was revealed that the prestraining treatment at blue shortness temperature range was remarkably harmful to notch toughness of steel, evaluated by Charpy impact test, whereas this treatment was slightly detrimental to the so-called retained ductility, measured by round bar tensile test.
To explain the contradictions between both effects of high temperature prestraining on retained ductility and notch toughness of steel thus treated, the authors investigated the conditions of fracture in the notched and unnotched specimens, combined with the varying effects of high temperature prestraining upon the cleavage and fibrous fracture stress curves, after scrutinizing the shapes of both curves of the steel prestrained by 10% at 300°C or 500°C by using notched bar tension specimen, suited notch shape of which for the present investigation had previously been searched and found out. In analysing test results, calculated distributions of plastic stress and strain in the notched bar tension specimen, as shown in the Appendix, were used.
As the final results, it could be clarified that the remarkable fall of notch toughness of steel after prestraining at 300°C would chiefly be attributable to the elevation of the flow stress curve, as well as that of the fibrous fracture stress curve in the lower range of strain. It was also revealed that there would be no intimate correlation between the mechanism determining the notch toughness and that determining so called retained ductility.

抄録全体を表示

Japan's first postwar submarine “Oyashio” was launched at No. 1 Building Berth at Kawasaki Dockyard on May 25, 1959. Representing the latest fabrication techniques in the construction of all-welded undersea craft, this vessel is now commissioned under the Japanese National Defense Agency.
This paper deals with the records of fabricating and welding techniques used for the construction of this craft. Summerized below are the points worthy of special mention :
1) Used for inner hull structure were weldable high tension steels, HT 50 and HT 60, and various quality tests were performed on each of the steel plates used.
2) The so-called unit cylinder assembling system was adopted in order to shorten the period of construction.
3) The length as well as the fabricating sequence of the unit cylinder assembly were decided in accordance with the results of the fabricating tests on models.
4) Many kinds of special jigs were devised in order to maintain the circularity of the inner hull structure and used successfully in the construction.

抄録全体を表示

NRL type crack starter explosion tests and explosion bulge tests of mother plate and welded specimens were conducted on 5 Japanese high strength steels, HT-50 (Mn-Si steel), HT-60 (Mn-Si steel, quenched and tempered), HT-70 (HY-80 steel type), HT-80 (T-1 steel type) and stainless clad steel (HT-50base).
As a result of crack starter test, FTP temperature of HT-70 was found to be -60°C, and was considered as a sufficient material for naval ship structures.
Bulge tests at room temperature and -20°C showed that welded specimens of all steels tested had almost same strength as their mother plates for explosive force. Stainless clad steel showed no superiority than 50 HT. No remarkable effect of preheat of welded specimen of HT-70 was observed. Various notch-toughness tests (2 mm V-, 2 mm U- and press notch charpy and drop weight tests) were also conducted and comparisons were made with the result of crack starter explosion test.

抄録全体を表示

It is the general practice under the normal conditions, to adopt the simultaneous welding by multiple workmen for block butt-joint of ship assembly.
In order to clarify the characteristic of this method, we have ascertained the characteristic of constraining force of material such as strong-back restraining the shrinking of butt-joint. We have then worked out an approximate formula in respect to how the value of constraining force of block butt-joint being effected and have analized the variance resulting from the increase in number of welders in accordance with the said formula. The result of analysis thus obtained through experiments on the actual ship assemblies are as follows : -
1. The characteristic of the constraining force of strong-back varies considerably according to its type, particularly the strong-back of wedge-chocking type showing the slipping and greatly reducing the constraining force when the shrinkage of bntt-joint exceeds over 0.3 m/m.
2. The constraining force of keel-block being very small-under 1/200 of those of the strong-back, it may be ignored when the constraining force of welded bntt-joint is discussed.
3. As the number of welder team increases, the constraining force at the beginning of welding decreases. For the ordinary block butt-joint, the constraining force in case of one welder being employed for 2 pieces of the material, decreases as low as 60-70% of the case of one welder for 5 pieces and its value seems to be around 10 kg/mm²/mm.
4. In case the constraining material is of such type as showing slip phenomenon, the slipping movement of block body increases rapidly with the constraining force decreasing suddenly as soon as the first layer of welding is started. For the ordinary block butt-joint, in case of one welder being employed for 2 pieces of the material, its constraining force decreases quite rapidly as the first welding layer reaches about 400 m/m.
5. As the characteristic of simultaneous welding of butt-joint by multiple welders varies according to the type and character of the constraining material, the advantage can be attained to the fullest extent by using the proper constraining material, i. e. the less the constant value of constraining force and the faster slipping, the better its result.
In practical application it is considered to be most desirous to get the best result by using the wedge-chocking strong-back placed diagonally.
While in Report No. 1 is described regarding the research and study of costraining materials and the simultaneous welding by multiple welders, as well as its theoretical analysis, we will observe and report the result of our experimental researches of the actual ship assembly in order to verify its theoretical analysis, in Report No. 2.

抄録全体を表示

In the crack propagation test where a crack was started by driving a wedge into a specimen with a pressed and aged notch, arrested cracks of several inches long were observed in many specimens having uniform stress and uniform temperature. And these phenomena may not be explained by the generally accepted Griffith theory of unstable fracture.
When a crack is stopped, it usually extends several inches farther at mid-thickness than it does on the surface of the plate, and the shear lips on both sutrface seems to prevent the opening of the crack faces and reduce the evergy supply at the tip of the crack. The resistance force against deformation of shear lips having various widths are measured by static tension test using the shear lips tension test specimens which are taken from the original tested specimens with arrested cracks. Considering this force will resist opening of the crack faces, it was superposed to the applied tensile stress which open the crack faces, and the rate of energy release at the tip of the submerged crack is calculated following Irwin's method.
The results of calculation reveal that the rate of energy release decrease with the increase of crack length and are reduced to sufficiently low value when the crack is arrested. The idea proposed in this paper on the influence of shear lips to crack propagation was duly justified by the measurement of the dynamic strain contours using electric resistance strain gauges located adjacent to the crack path.

抄録全体を表示

For several years, basic research, using slit type test specimens, has been conducted on a concept in weld joints which has been defined as the “coefficient of restraint”.
The corelation between this coefficient and the residual stress in weld joints, was determined by applying this concept of coefficient of restraint on actual structures.
The xperiments were made in two ways ;
(a) on models of solid structures having stiffeners or other similar restraining parts, and
(b) by measuring the coefficient of restraint on actual vessels.
The results were then compared with the basic theory.
It is hoped that the outcome of these experiments will prove to be an important basis for determining the welding sequence for joints that connect one block or unit structure to another.

抄録全体を表示

In the previous report we presented a possible mechanism of fracture of nodular cast iron, founded on the dislocation theory and confirmed by the combined tension-torsion tests of ferritic nodular cast iron in liquid nitrogen.
The present report first concerns the tension and torsion tests carried on the various types of nodular iron whose matrix is of ferrite with various grain sizes, of mixed structure of ferrite and pearlite, and of bull's eye structure. Through these experiments the authors have clarified the structural effect on the strength and ductility, which has proved to be consistent with the above theory.
They also report the charpy impact tests on the same materials, with the results consistent with the formula induced from the above theory.

抄録全体を表示

In general, the rates of released elastic strain energy, kinetic energy and work done required for creating new surfaces are the determinate factors governing the propagation of brittle fracture.
In the previous report, the dynamical stress field in a plate having an enlarging slit at a constant speed subjected to a uniform tensile stress normal to the direction of the crack was obtained.
In this report, the release rate of elastic strain energy in a plate having an enlarging slit at a constant speed was calculated by using the dynamical stresses obtained in the previous report. The release rate of elastic strain energy decreases with the crack speed ratio.

抄録全体を表示

The authors considered the energy condition of propagating crack based on the assumption that the surface energy absorbed at the tip of crack in newly created fracture surface is supplied from a circular region around the tip of crack. They represented the energy condition by eq. (11) and obtained the following conclusions;
(1) In a completely continuous material the limiting constatnt velocity of crack is equal to that of Rayleigh wave.
(2) In materials including no micro-cracks, the limiting constant velocity of crack propagation is nearly equal to and lower than that of Rayleigh wave.
(3) In real materials with micro-cracks, the fracture propagates discontinuously and the limiting constant velocity falls down to the order of experimental value. The measured crack velocity will scatter beyond the range of the experimental error.
(4) In low velocity state, the higher is the applied stress, the higher is the crack velocity. But, when the velocity of crack is nearly equal to that of Rayleigh wave, the applied stress affects little.
(5) When both the applied stress and the elastic modulus are constant, the larger the specified surface energy is, the lower the crack velocity is.
It has to be added that the discussion in this report is on the necessary condition for the crack propagation with a constant velocity and not on the necessary and sufficient condition for the brittle fracture propagation.

抄録全体を表示

In this paper, the authors state on a new practical method of analysis for results of the observation of the launching speed based on the energy method. According to this method, we can obtain every coefficients of resistances without using the launching acceleration, the accurate measurement of which is difficult. The calculated speeds obtained by using these coefficients come to in good agreement with the results of observation.

抄録全体を表示

This report describes an experimental investigation on the frictional resistance of steel plates, and the slip factor of riveted joints. Tests were conducted mostly on specimens of bolted joints, so as to find out a correlation between the frictional resistance and clamping forces in the joints.
The results obtained from this series of tests are as follows :
1) The friction coefficient (statical) of mild steel plates as rolled was approximately equal to 0.3.
2) Major slip load for a lap joint was about 0.6 times the clamping force where panheaded rivets were used, whereas about 0.3 times in the case of countersunk headed rivets.
3) Riveted joints subjected to a tensile force showed a minor slip at a load about 0.4 times the major slip load. After exceeding the major slip load they continued carrying load with a constant rate of displacement defined as the slip factor until reaching a plastic deformation of the specimen.
4) The slip factor depends mainly on thickness of plate, diameter and shape of rivet and fitness between rivet and rivet hole.
5) An approximate formula for the determination of the slip factor was obtained.

抄録全体を表示

In spite of the recent introduction of launching by ball method, it is prevalent that a great number of shipyards still adopt launching by tallow method, because of its relatively stable faculty as lubrication and the easiness in handling. While there have been published many results of experiment concerning the lubrication faculty of tallow, only few attempts were made for the study and experiments of coating thickness of tallow which is one of the factors closely related to the economy and safety of the use of tallow. Such thickness is determined solely based on the tradition of each company.
From the analysis of past launching data in Kawasaki Dockyard Company, Ltd., as well as from numerous experiments, the authors have succeeded in determining the thickness of tallow which is satisfactory from the view points of both experiment and theory.
By the use of these diagrams and formula, thickness of tallow required for launching will be determined from the minimum thickness required at each part of launching way multiplied by adequate safety factor. These diagrams and formula are based on the following factors.
1. Load
2. Temperature
3. Quality of tallow
4. Friction's loss
5. Lubricant
6. Roughness of coating surface
The result of thickness thus obtained has safely attained considerable economy in the amount of tallow.
Actual application method of tallow, as well as the result of experiment, is detailed below.

抄録全体を表示

The marine power plant is usually designed only from the standpoint of its steady state. However, the accurate knowledge of the kinetics of the marine plant is quite necessary for its advanced design, especially for its automation.
The kinetics of marine boilers and turbines have been investigated by some of the authors, but the transient characteristics of a whole plant have not been studied yet.
In this paper, the authors show the experimental results of the plant-kinetics as to a big steam tanker, which were measured during the starting, power change, astern-and inertia-tests. The test results are also analized with an analog computer. And it is confirmed that the marine steam plant can be simulated with a simple mathematical model.

抄録全体を表示

碇泊中の船舶では船体と軸系は常に同じ電位であるが, 航走しはじめる。と軸系の電位が船体より高くなるのが普通である。これは軸系の回転により軸系と船体とが油膜のため絶縁状態になるため, それぞれが別々の電位を示すようになり銅合金の軸系が船体の電位より高くなる。この種の船舶では船体は航走により所要電流は増加するが軸系が絶縁されるため, 軸系への電流がなくなるから碇泊時と大差ない電位になる。しかし一部の船舶では航走中も船体と軸系が接続されたままの状態のものがある。この場合はもちろん航走中も軸系と船体は同じ電位を示すが, 軸系は回転のため所要防食電流が増大するから電位は著るしく高くなる。しかしこのような例は比較的少く, 特種な機関のものを除いては新造船や大修理後の船で, ある期間このような状態になることがある。軸系と船体の接続関係は船体の腐食と密接な関係があり, 新造船に異状腐食が多いのはこのためである。今回東京都港湾局の曳船が新造直後より腐食が甚だしかつたためその原因の調査と対策を依頼された。調査の結果, 本船の腐食の原因は前述の軸系と船体との接続関係によるものであつた。その概況について報告する。

抄録全体を表示