Various ideas have been suggested for avoiding the rapid cooling of weld zone which leads to the loss of strength of weld joint. It is considered that one of the most effective means among them is to contrive the deposition sequence of welding arc providing the slower cooling. The strategy often seems to be applied to welding process with rather longer weld beads involved.
The primary purpose of this report is to substantiate the validity of various deposition sequences. Hence, it is to be examined by three-dimensional finite difference methed and arc welding experiments how the deposition sequence employed affects the cooling cycle of weld zone. The effectiveness of the numerical procedure proposed here is verified by comparing numerical results of such important factors as cooling curve and cooling rates with those by experiment.

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It is necesary to arrange the system to monitor the operational condition by various methods to achieve the safe operation of the engine.Based on the idea that the information on the engine condition can be obtained from its vibration signal, this paper carries out the experiment of the diesel engine of the actural ship.The vibration was measured a long time (7800hours) by mean of a vibration sensor on the cylinder jacket. The hand touch can not recognize the time change of the vibration, but the three-dimensional expression of the vibration data through the frequency analysis allows the good understading of the change of the vibration.The vibration is always changing if the vibration is observed on the long running hours of engine basis even in the stationary operation (engine revolution: 103rpm) of the diesel engine.We executed the statical analysis as one method to estimate the condition of engine by the information from the vibration.
All the data of vibration was recorded on a normal engine condition, as a result we couldn't examine on an abnormal engine condition.Thus, the vibration data of low engine revolution (30rpm) was used as the data of abnormal condition in this analysis.As the result of the analysis, it is found that the abnormal can be recognized from above mentioned engine condition.We succeeded to make the statical model which can diagnose a engine conditon.

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Film cooling behavior in thin rectangular channel was experimentally studied by using water. Wavy temperature distributions on the wall just after the injection slit were observed in spite of the two-dimensional film. The low and high temperature regions corresponded to the high and low speed regions near the wall, respectively. The flow structure was similar to the streak flow in the usual turbulent boundary layer. In the usual turbulent boundary layer, the riblets are effective to reduce the inrushes of high speed main flow to the wall region corresponding to the streak flow behavior. So the riblets were used to reduce the inrushes of high speed main flow into the film in thin rectangular channel. By using appropriate riblets, approximately 30% increase of the cooling effectiveness was obtained.

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Preventing keyless propeller from slipping requires the estimation of torque transmitted from shaft to propeller, as accurate as possible, taking the major parameters of ship, shch as main engine power or displacement into account. Experienced slip accidents show that it is necessary to consider the crash astern condition in estimation of torque used for determining pull-up length of keyless propeller. This paper describes how to estimate the increasing rate of the the torque in crash astern condition compared with that in steady condition through theoretical analysis and measured data. As a result, the authors found out that the increasing rate of torque can be approximately represented as a function of propeller diameter.

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It is very important to investigate accurately the behavior of sea water component, especially of Mg hardness, for the boiler water qualtiy control of marine boilers. And also, important to investigate the behavior of PO₄^3-, especially when Mg²⁺ and OH^- coexist with it, for making the automatic control method proposed by the authors more feasible and reliable. Accordingly, this paper studies experimentally the behavior of Mg hardness when OH^- and/or PO₄^3- coexist, and when silica is mixed. Experiments were carried out at the condition of the same solution level with the water quality criterions adopted for actual boilers, by the use of an autoclave of which temperature and pressure adjusted as the same level with actual auxiliary boilers. The obtained results are summarized as follows.
(1) In the reaction model developed so far, It has been thought so far that almost all Mg hardness reacts to form Mg (OH) ₂ in the boiler water when the phosphate concentration is controlled appropriately by the alkali treatment. In this experiment, however, it was found that Mg reacts not only with OH-but also with PO₄^3-, and the mole ratio of reaction products Mg (PO₄) ₂ and Mg (OH) ₂, increases with the decrease of pH, that is, 0 at pH=12.0, and around 2 on pH 10.5.The mole ratio is hardly affected by the PO₄^3- concentration and the reaction temperature in the range of 1MPa-3Mpa.
(2) If SiO₂ is mixed together with Mg hardness in the feed water, MgSiO₃ is formed in boiler water. Its quantity increases with the increase of SiO₂. The rest of Mg hardness unreacted with SiO₂ is considered to react to form [Mg₃ (PO₄) ₂] _n⋅Mg (OH) ₂ as mentioned above, and it is resulted in that pH and PO₄^3- concentration are decreased.

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Fracture of a hook of a launching strop used for lifting a launch on a patrol vessel is investigated in detail. The hook was made of a precipitation hardening stainless steel (JIS SUS630) . No apparent deformation was observed in the hook and the fracture surface exhibited features of brittle fracture, such as chevron patterns in macroscopic observations and quasi-cleavage fracture in scanning electron microscopy. Hardness measurement revealed that the material was harder than expected from the prescribed heat treatment conditions. Charpy impact energy was less than one-half of the value in the literature. Elemental distribution maps obtained by electron-probe microanalysis showed segregations of the major additives including chromium, nickel and copper. The distribution patterns suggest that the segregations were formed during the die forging. These segregations may have formed low-toughness phases in the matrix. It is concluded that non-uniform microstructure with substantial segregation is responsible for the brittleness, or low toughness, probably caused by inadequate forging conditions such as low temperature and high pressing speed.

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