Marine propeller blades have been designed so far mainly with the object of obtaining higher propulsion efficiency. Meanwhile, fatigue failure of marine propeller blades lately has increased. The reason is thought to be that the recent tendency toward higher power for engines and higher speed for ships has increased the load on blades and the fatigue strength of propeller blades has become the critical point in their design. Accordingly, the establishment of fatigue design rules for marine propeller blades is necessary. For this purpose, the fatigue strength of blade materials must be determined. However, only a few data have been available on the fatigue strength of blade materials and most of those data have been obtained by rotating bending fatigue tests in which stress conditions differ greatly from those in full-size propeller blades. In general, fatigue strength is affected considerably by the stress conditions, so that those data are not sufficient to give a basis for fatigue design rules for marine propeller blades. From this point of view, fatigue tests and crack propagation tests were conducted on two kinds of propeller blade material, Ni·Al-bronze and Mn-bronze. The stress and environmental conditions of the tests were selected carefully to be close to those of full-size propellers in use. The effects of stress ratio, stress frequency and so on on the fatigue strength and the fatigue crack propagation characteristics of the blade materials were examined.

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In the present day of energy saving, the high-intensity ultrasonic homogenizer system has special interest as the system making the COM (Coal-Oil-Mixture), gasohol (gasolene-alchohol mixture) and emulsified fuel (gasolene-water mixture) . As its electrical power supply, the new application of thyristorized high-power inverters for an output frequency range in the extent of 15KHz to 30KHz are hopeful from whole points of view such as low cost system, high-power output adaptability, maintenance free, easiness of control procedure and so on.
This paper describes a steady-state performance analysis considering overlapping commutation-mode of high-frequency inverter using reverse-conducting thyristors (abbreviated by RTh type inverter) . The steady-state characteristics and operation of RTh type inverter for driving high-intensity ultrasonic homogenizer system are quantitatively discussed in comparison with the characteristics on the basic type of series-inverter. The inverter circuit is analyzed with R-C load modelling the ultrasonic transducer systems.

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MESJ Boiler Committee collected the failure data occurred in 15 steam ships launched about 1972, 1973 under the help of those ships' owners. Following the former report, which analyzed the serious failure out of above data, this report considers the statistical and physical characteristics of the boiler failures. The consideration shows some features of the boiler failure as follows. It is noted that the pattern of the failure rate with respect to time appears to have no random failure component, that is, the failure rate increases with time immediately from the end of the period of the early life failure which is about 1 year. Among the equipments composing the boler system the nine ones, that is, steam generating section, level meter, relief valve, pipings, ordinary valves, sootblower, GAH, FWC, and STC, have the main liability for the unreliability of the boiler system. Those failures account for 75% of total failures and 83% of serious ones. As for the failure phenomena leakage failures are predominant, and occupy the greater portion of the failures of the steam generating section, valves, pipings, FWC, and STC. Through the whole equipments the valve failures are remarkedly many, accounting for 31% of total failures, and about 50% of them are found at control valves. The greater part of FWC and STC failures are due to control valve defects.

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The block diagram of experimental ac-dc electric propulsion system is obtained containing detailed chopper switching phenomena on the chopper controlled motor which drives the alternator. Dynamic performance of experimental system on crash astern, assuming that ship speed is constant, is estimated by the MISS simulator managed on the multi-microprocessor system. The computed results using observed constants match those obtained from the tests. It is discussed on the analytical response of velocity and shaft torque of the propeller affected by the values of current limit of the propulsion motor, field time constant of the generator and integral gain of the automatic voltage regulator.

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According to experiment navigations of the training ship Fukae-Maru, 360 G.T. using C-P propeller, it is generally obtained the fact that the amount of fuel oil consumption can be decreased according as revolution of main engine becomes low and propeller pitch angle high on keeping ship speed constant. While above driving mode is applied to control the engine system, it is apt to force the Diesel engine to drive under torque rich condition, which may give the engine unexpected failure. To avoid troubles on driving Diesel engine applying experimental economical driving mode, authors propose an idea of engine control system, named Proportional Torque Control (PTC), which is applied to a combined system of engine and C-P propeller, that is, on any condition of driving the Diesel engine, the amount of shaft horse revolution of engine is kept less than that indicated by analytical power curve which is proportional to square velocity of engine. It is also discussed on practical PTC system about economic problem and control stability.

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