In the theory of the wave resistance of submerged body, the condition of the water surface is always linearized by now, and this seems true as far as we treat of a deep immersed body. It is not fair, however, as we do of shallower immersion.
The author gives a second approxmation to the water surface condition, and calculates the wave resistance and the vertical force acting on the submerged circular cylinder. The results are a) the effect of finite water surface disturbance rapidly decreases in the order (a/f) ⁴ as the immersion increases, where f is the immersion and a is the half radius of the cylinder, while the correction to the cylinder surface condition is of the order (a/f) ², and b) the both effects become comparable in the shallow immersion. (c. f. Figures.)

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In this paper the fluid motion and hydrodynamic characteristics of the submerged hydrofoil of finite span is examined in detail.
In §2 the velocity potential, in particular, its essential nature is discussed ; the three dimensional regular wave motions in the just abaft of the hydrofoil, in the limiting case that the Froude number is infinite, have analogy with the free vortex motions.
In §3 the induced velocity, vertical and horizontal, is examined ; the former is due to free vortex and regular wave motion, the latter due to local disturbances and equates approximately to that of two dimensional motion.
In §4 taking the assumption in the lifting line theory into account, the integral equation is introduced of determining the circulation distribution over the span of the submerged hydrofoil.
In §5 the numerical solution of the integral equation is obtained, applying the Nystrom's method.
In §6 the numerical examples are shown of effective circulation distribution, lift, vertical induced velocity and resistance of the submerged hydrofoil.

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The author considered the hydrodynamic characteristics of free-running screw propellers from the point of view of the lifting-surface theory and estimated lift-slope correction factors k₁ (ξ') of which the lifting-line theory corresponds to this theory through the medium. Then following results were obtained :
(i) k₁ (ξ') is effected mainly by the contour and the breadth of the blades.
(ii) k₁ (ξ') is mainly due to the self-interference of the blades whereas the mutual interference is secondary.
(iii) Skews have little influences on the values k₁ (ξ').

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In this paper, a general formula for the forces acting on a body moving under the surface of water is obtained as an application of the extended Lagally's formula. The problem of the wave resistance experienced by a body moving under the regular sea waves is also discussed.

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Since 1944, when one of the present Authors (INUI) and his collaborator calculated mathematically the wave-making resistance of ships in a shallow sea, necessity has long been recognized for making further quantitative investigations regarding to the practical adaptability of the theory. The following notes are aimed for clarifying the still remained question to what extent such a linearized wave-making theory can be safely applied in cases of a restricted water (b=h=finite) as well as a shallow water (h=finite, b=infinitive), where h denotes the depth of a water, b the width.
A 1.750 m mathematical model S-201, whose equivalent source distribution is known, is towed in the Tokyo University Tank at the depth of water h/L=1.371, 0.400, 0.300 and 0.200.
Comparatively good coincidence has been obtained between the calculated and measured wavemaking resistance, excluding the narrow critical range of F_h=0.820.95 where the KREITNER'S non-linear restricted water effect is clearly observed especially at the shoalest depth h/L=0.200.

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The wave profile measurements are made with two wall-sided, deep-drafted mathematical models (S-103, S-203) by applying the chemical film method, where the Benzoic Acid is effectively used for the first time, and found as pre-eminently suited to contrasting the flow phenomena on ship models such as wave profiles, initial still water lines, stream lines, and laminar flow area.
Comparisons are also made between the calculated and the observed wave profiles.
Coincidence is good along the models, but is unsatisfactory in the rear.
The principal cause might be safely ascribed to the fact that the wake intesity is always extinguishedly strong just on the narrow band in the vertical symmetrical plane (y=0).
Conclusions are then drawn that the present field of the mentioned comparisons between the theory and the observation must be extended from one dimension (on the line y=0, exclusively) to two dimensions, to which the photographic measurements by stereograph might be expected as essential.

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The author carried out some computations pertaining to ship motions among waves by the method that he presented at the Spring Meeting, and the results are compared with the experimentally measured results.

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The damping resistance of roll has been measured from the extinction curve of the free-rolling of a model. But this free-rolling method was hardly applicable to the roll of an angle over20° where free rolling damped immediately.
Giving forced oscillations of various amplitudes to a model ship by the newly devised gravity mechanism, and assuming the imput energy of the forced roll equal to the energy dissipated by the damping resistance, the authors have carried out some model experiments to determine the damping coefficients applicable to a large angle where the deck edge of the model was entirely immersed.
Fortunately, the authors were able to obtain some satisfying results, and have come to the following conclusions.
a) The forced oscillation method is applicable to a roll of large angle, even where the deck edge of the model is immersed, and the extinction coefficient obtained from this method agrees with that which is determined by the free-rolling method.
b) The extinction coefficient of roll increases suddenly when the rolling angle exceeds the angle of deck-edge-immersion.
c) The extinction curve was found to be approximated by following formula :
δθ=λθⁿ_m n=1.7 before deck edge immersion n= 3.2 after deck edge immersion where δθ is decreasing angle per swing, θ_m is the corresponding mean angle.

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There are many waves in the confused, fully arizen sea surface, which have various periods and different heights. But there may exist a groupe of waves whose period prevail and are most frequently observed. These waves can be determined analytically by applying the theory of Sverdrup-Munk to the sea surface under varying wind velocity :
(βu) ^5δ2= (β_mum) ^5δm2,
where : u is wind velocity, β is wave age, and δ is wave steepness, The suffix m denotes the maximum values in the centre of storm. This relation is shown in Fig. 1 which is calculated for every β_m=-0. 3, 0, 4, ……, 1.4 at u/um=1.
The state of every stage of at every moment in the storm can be analysed graphically by the equation
(5+2β/δdδ/d) u (t) dβ/dt+5βdu (t) /dt=1±2.5 (1-β) ²/β²
The distribution of integrated β-t curves for every 3 hours are given in Figs. 2 and 3, wherein the observed values of β areplotted.
These two graphs show that ocean winds have some agency of unification on waves. Observers on board of ship usually point out and record the waves which have the most regular time interval, or in other words, which have the maximum frequency of wave period and its wave height from over the confused sea. This wave will have originated at many different places and also have various phases over the wide area of sea surface, then we can readily acknowledge the Longuet-Higgins' theory, which have cited the statistical distribution of wave heights.
The wave age which observed most frequently is indicated in the waving, concentrated narrow bands which issue from the places of the minimum values where the wind velocity have reached at the maximum value. Before this period, wind velocity are always increasing, so waves which have larger ages are all suppressed, but waves with shorter ages are forced to grow up. Thus swells and seas coincide in the centre of storm. After the centre have passed, wind velocity decreases gradually, then ages of these unified waves increase.
The larger becomes the rate of increase of wind velocity, the minimum value of the wave age reaches to the smaller value. The above cited βm, is thus defined :
dβ/dt|u=u_m=0, or du/dt|u=u_m=0.04471+2.5 (1-β_m) ²/β_m³
The fact that the average value of this wind velocity gradient is about 2 m/sec. hour as is shown in Fig. 4, thenβ_m lies usually between 0.30.4. Observed values at X-ray are plotled in Fig. 5, also wave period is constant at every moment in the region of storm ; in Fig. 1 dotted lines show β_umm=βu, which are almost equal to (β_umm) ⁵δm= (βu) ⁵δ².
From the state of concentration of β, the statistical distribution of β. or wave period seem to be more narrow than that of Longuett-Higgins' wave height. distribntion or we may take practically, unique, which justifies ard agrees with their assumptions.

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The purpose of this paper is to consider the influence of ship forms upon the slamming and strength of ships going in waves. The self propulsion tests were performed in the experimental tank on two model ships, the U and V-form ship. Ship motions, acceleration, pressures, and stresses were measured on various wave lengths and heights. The comparative merits on the effect of ship forms are discussed from the experimental results.

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In order to investigate the effect of notch radius on the brittle fracture of steel, slow notch tensile tests were performed. Rimmed, semi-killed and HT 52 high tensile steels were tested. Test specimen used is shown in Fig. 1, and notch radii were varied in six stage, 0, 0. 05, J. 1, 0.25, 0.5 and 1.0 mm.
Transition phenomena of shear fracture percentage, stress, elongation, energy absorption and reduction in thickness are shown in Figs. 2-9.
Effect of notch radius on various transition temperatures can be seen in Table 3 and Figs. 10-12.
In notch tensile test, smaller notch radius might be more preferable to know both of fracture and ductility transition properties of steel.

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Slow notch bend tests with semi-killed, killed and HT 52 high tensile steels were performed. Fracture appearance transition temperatures Tii and energy transition temperatures are nearly the same, and transition temperatures in ductility criterion Ti, those in low energy level TrLE (10 kg-m/cm²) and those in reduction in thickness Trφ (4 %) and also nearly the same for three kinds of steels.
Results of slow bend tests are compared with the results of Charpy and Tipper tests in same steels. As to fracture appearance transition temperature, slow bend test is most sensitive and Tipper test is the next.

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A study was carried out to obtain the dimensions of main members in wooden ships after modifying the standard strength calculation, because an urgent need occured to revise the existing “Wooden Ship Construction Rule” in order to fit present situation.
Calculating the longitudinal and transverse stength by means of simple beam theory, basic dimensions of each member were obtained with newly determined allowable stress of wood. Then multiplying the rate of stress increase (construction coefficient), which was unavoidable in the lattice-like construction of the wooden ships containig many joints, by basic dimensions, the actual dimensions were obtained. As compared with those of existing “Rule”, the newlyobtained actual dimensions showed satisfactory results.

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There have been presented many investigations of the stress distribution of superstructure. In these investigations, it may be assumed that the H. H. Bleich's theory is most useful to estimate the longitudinal stress distribution of long deckhouse, however, shear lag effects are neglected in his theory so that this theory gives good agreement with experimental results in the case of long deckhouse except in the vicinity of the house ends, but is not appropriate to the case of short deckhouse.
In this paper, to obtain the stress distribution of short deckhouse, the authors present bending theory of superstructure taking into consideration of shear lag effects, and this theoretical values are compared with experimental results obtained by bending tests of box girders, with a good agreement.

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Present paper deals with the calculations on the coupled torsion-horizontal bending vibrations of the beam of variable cross section having ship-like form in which the motion is considered as the shearing vibration that has been investigated in the preceding paper. One of the results of the measurements of the coupled frequencies of the vibration of a cargo vessel is shown for comparisons with numerical results of the present theory.

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A series of slow notch bend tests was performed to investigate the effect of residual welding stress on brittle fracture of steel.
Chemical composition and mechanical properties of steel tested are shown in Table 1.
Following 9 types of test specimens were prepared. (Fig. 1).
(1) parent metal, as rolled, notched.
(2) parent metal, prebent at room temperature as shown in Fig. 2a, notch side tension, permanent deflection 2. 5mm.
(3) parent metal, prebent as shown in Fig. 2b, notch side compression, permanent deflection 2. 5mm.
(4) welded specimen, as welded, notched.
(5) welded specimen, similar to (2).
(6) welded specimen, similar to (3).
(7) welded specimen, pretensioned at elastic nominal stress of 25 kg/mm², then notched.
(8) do. pretensioned up to yield point. (9) do. pretensioned, permanent strain 2. 5% for 100mm gauge length.
Fracture test procedure is the same as Van der Veen test.
Temperatures were varied from 0° to -70°C. Fracture appearance are shown in Figs. 3-5.
Depth of fibre are shown in Figs. 6-8, and fracture appearance transition temperatures Till are listed in Table 3. Among welded specimens, type (4) (as welded) has highest (T_II = -18°C) and type (8) (pretensioned up to yield point) has lowest (T_II=-38°C) transition temperature.
Residual stress measurement was performed by resistance wire strain gauge. From the results of our experiment, we can conclude that residual welding stress has a pretty effect on brittle fracture of welded structure.

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This report is the third part of serial expriments which are being made to survay the effect of welding sequence on transverse shrinkage and residual stresses. In this report the analysis about the part of residual stress and dislocation through 1st to 4th serieses of experiment are mentioned. The size of specimen and welding conditions for each specimen were already stated in preceding papers.
The measurement of residual stress was performed using electric resistance-wire strain-gauges as shown in Fig. 1. The values of measured strain change and the distribution of residual stress are shown in Fig. 2 and 3, respectively.
The results obtained so far are summarized as follows.
1) When the specimen is welded by one block, the value of transverse stress σy is tensile along welding bead, but is compressive in the mother material taking its maximum value in the vicinity of weld and decreasing accordingly with the increase of distance from the weld. The value of longitudinal stress σx. is also tensile at the center of weld and gradually decreases in accordance with the increase of distance from the center. The maximum value of σx is larger than that of σy, reaching nearly the value of yield stress of mother material. The value of σy increases as the increase of degree of constraint as shown in Fig. 5.
2) When the specimen is welded by two or more blocks, there occurs a fairly different phenomenon. Though the average tendency is nearly the same as that in the case of one block, the distribution of residual stress becomes much complicated on the welding bead as shown in Fig. 3. This phenomenon was observed not only in case of block welding but also in multilayer sequence. Therefore, it seems to be meaningless to attempt to control the residual stresses on the weld zone by the change of welding sequence.
3) Dislocation occured by slitting along the weld line was also measured. The form of dislocation is quite similar to that of transverse shrinkage as shown in Fig. 6.
There exist close connections among transverse shrinkage, dislocation and transverse stress. These connections were studied from some viewpoints. For instance, some attempts to estimate the value of σy from the transeverse shrinkage were tried (Fig. 7 & 8).

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In Part I of this report the investigations on radial contraction and reaction stress occured in the central region due to circular patch-welds were stated. This second part concerns with the studies on residual stress occured in these specimens.
Distribution of measured strain and residual stress are shown in Fig. 2 and 3, respectively. In the region of patch welded plate, the signs of radial stress σγ and circumferential stress σθ are both tensile, on the other hand, σγ is positive and σθ, negative in the outer ring.
However, the distribution of residual stress does not constitute a fair curve, but a much complicated one along the welding bead. Therefore, it seems to be difficult to control the residual stress along the welding bead by the change of welding procedures.
When the specimen is cut along the weld line, elastic dislocation is produced according to the stress reliese due to slitting. The value of dislocation is fairly smaller than that of radial contraction.
Moreover, some investigations were made concerning with the radial contraction in block welding sequence. The effect of block length in block sequence and that of overlaying bead on radial contraction were studied.

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Tensile tests for many kinds of structural steels containing mild and high tensile steels have been performed in rolling, transverse and thickness direction. From these experimental results we knew that tensile strength exhibits little or no directional properties but ductility decreases markedly in the thickness direction. Moreover, the effect of this directionality on the fracture under combined stresses have been investigated by thin hollow cylindrical test specimens cutted from a thick pressure vessel steel.
The causes of their directionality were analyzed experimentally and we concluded that alignment and shape of microscopic inclusions may be main causes of the directionality of hot-rolled structural steels.

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Explosion tests were conducted on pipe specimens to determine the effect of stress annealing. Pipe specimens, 400 mm diameter, 800 mm height and 20 mm thickness, were welded in four longitudinal and one circumferential joints.
Specimen was filled of water to reduce the detonating effect of explosive shock wave, and then an explosive set in the center of pipe was detonated.
Evaluation of the performance of specimen was provided by checking the circumferential strain on circumferential butt joint.
Explosion test showed a remarkable difference which could not been examined by longitudinal bend test or V-notch Charpy impact test. Namely, the annealed specimen was fractured by explosion when the circumferential strain reached at 11%, while aswelded one at 6 %.

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The superiority of the service performance of the joints welded with low hydrogen electrodes is well proved by various weldability tests. However, this type of electrodes are highly sensitive to the operating condition during the welding process and such sensitivity is limiting or preventing an extensive employment of the low hydrogen electrodes.
The authors have made an investigation about the effect of welding procedure in relation with the blow hole which develops in the weldment, and also its effect on the fracture of welded joint, and then reached to the following conclusions.
1. The home made low hydrogen electrodes, comparison with imported ones, are far surpassed in the quality for the prevention of blow hole.
2. Both home made and imported ones showed only a slight difference in regard to three grades classified under AWS standard, but according to the size of diameter of electrodes the extent of devolopment of blow holes differed very noticeably.
3. The extent of the development of blow holes is lowered as the welding current grows higher, but this tendency does not follow the same course when the current became excee dingly high.
4. The development of blow holes is noticeable at the start of the bead, but if an arc striking was given prior to the start of the welding, or the tapered end type electrodes. were employed, we discovered, it acted very effectively for the prevention of blow holes.
5. When we classified extent of the development of blow holes, according to the grades specified in JIS, and viewing the result of the tension and fatigue tests of the welded joints, it appears that there was hardly any defference between the grades 34 and grades 12. but with the grades 56, the performance of the joint is degraded, yet still it showed about the same record that showed by that of ilmenite type electrodes.
6. We made study of the notch toughness of the welded joints stressed under the cyclic load by using the specimens containing artificial notch (V and key-hole notchs), then it was observed that such effect was noticeable in case of sharp notch even under the stress less than fatigue limit, but on the other hand, in case of round notch like the shape of a blow hole the effect was not so highly noticeable.
7. Viewing from what we stated above, we may say that when low hydrogen electrodes are employed, it is necessary to limit the development of blow- holes to the minimum extent by carring out the welding under the suitable process, nevertheless, it appears that to limit the extent of the utilization of this type of electrodes which possess highly superior weldability, just simply in fear of the development of blow holes by no means in an adequate measure.

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We intended to get one method to measure actual pressure occured on fore poppet of ship during its launching. It is almost impossible to confirm actual pressure and its variation on fore poppet based on travel, and there has been no simple and reliable method to confirm them so far. Here we have devised one method there-of. Four steel load cells are used as one unit having strain gages pasted around its side and put aline in a flat steel box. This unit is installed between wooden fore poppet and sliding way at six points. We could measure actual pressure and its variation of the above six points at both of port and starboard side 1y this device.

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The experiments of cathodic protection have been performed using Daiichi-Tetsuei Maru and four other ships during about one year. The used anode materials were magnesium and zinc plates. Then, following consideration were resulted.
(1) In the magnesium anode system it was difficult to control anode current and occured frequently over current, therefoe it was possible to damage the paint of ship and make faster consumption of magnesium anode.
(2) But in the zinc anode system current was less than that of magnesium. so it was necessary to have a number of zinc plates but easy to use. And from these performance a basis of cathodic protection and its methods were clear.

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An approximate method of computing disturbances of the terrestrial magnetic field on the sea bottom due to a wooden vessel, who is made of so-called non-magnetic materials for the most part and is dotted with magnetic materials on board, is presented theoretically and confirmed with the measured results of an actual vessel. Results of numerical calculations are shown as examples, which have been carried out in the preliminary design of a wooden mine-sweeper, not only on her magnetic field but also on the effectiveness of several kinds of degaussing coils.
Electro-magnetic field induced by an electric circuit on board, for instance, the magnetic sweeping cable, is also investigated together with the practicable method of reducing its effects.

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Recently, special considerations must be taken for accidents caused by corrosion, wear and ther·mal stress in main parts of the large marine diesel engine because of the temperature increase of combustion gas resulting from the supercharge by the exhaust gas turbine and the utilization of bunker oil. Piston crown is one of the parts which have heavy local temperature rise and thermal stress as the result of exposure to this high temperature combustion gas. According to stress calculations, maximum stress of piston crown is generated at first piston ring groove and, at the working condition of the engine, the fluctuating stress by gas pressure is superposed to statical thermal stress. If these superposed stress is larger enough than yield strength of the material employed, the high residual stress in reversed direction occurs by the stop of the en gine. In this way the stress is repeated in reversed directions over the yield strength of the material in the worst case. We discussed a method of calculation of stress mentioned above and some points to be specially considered for the strength of machine parts which show such a complicated stress hysteresis.

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In recent years, a number of propeller shaft sleeves have been damaged due to circumferential groovings which are produced at the fore part of sleeve supported by stern bush bearing.
The appearance of the groovings suggests erosion and it should be noted that they are usually confined to segmental areas approximately midway between the corresponding propeller blades.
In order to investigate the cause of such groovings, the author has made (a) the statistic analysis of eroded shafts, (b) the microscopic observation of eroded parts, (c) the measurement of lateral vibration of shaftings, (d) investigation on the growing mechanism of cavitation erosion by models and, (e) the study on the load distribution of plummer blocks and stern bush bearing, whereupon he presumes the cause of grooving erosion as follows :
(1) The lateral vibration of shafting does not attribute to resonance of natural frequency of shafting, but to forced vibration caused by exciting moment on screw propeller produced by wake fraction.
(2) The amplitude of the shaft vibration at the fore part of stern bush bearing map increase remarkably, where the load on aftermost plummer block is very small or negative.
(3) The lateral vibration of shaft in stern tube induces the pulsation of pressure of sea water between shaft and stern bush bearing.
(4) Such pulsation of sea water pressure may originate erosion due to cavitation, the pro gression of which will be greatly intensified by the corrosion of bronze sleeve by sea water.

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