It has been known that very small distributed cracks can be observed on the surface of a smooth specimen subjected to corrosion fatigue. The fracture process can be characterized by the interaction and coalescence of these small distributed cracks. In order to analize this corrosion fatigue fracture process, high cycle fatigue tests were performed on carbon steel sheet specimens under completely reversed plane bending stresses in salt water (3.0%NaCl). Initiation and growth of cracks on the surface of smooth specimen were observed in detail during corrosion fatigue process. The distribution of crack lengths at a certain stress cycles was able to be explained by a statistical calculation which took into account both the variation of number of cracks during stress cycling and the scatter of crack growth rates.

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It has been known that very small distributed cracks can be observed on the surface of smooth specimen subjected to corrosion fatigue, and the fatigue crack growth rate is accelerated by the interaction and coalescence of them. In this report, following the previous report of the authors, the interaction and coalescence behaviour of the distributed cracks on the specimen surface were observed in detail. Based on the experimental results, distribution of corrosion fatigue crack lengths after a certain cycles can be estimated theoretically. These estimated distributions of crack lengths coincided with those obtained experimentally.

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Corrosion fatigue crack growth rate of a martensitic stainless steel has been measured at various stress cycle frequencies and stress ratios to elucidate crack growth and crack closure behaviors. Crack closure behavior is affected by plasticity-induced crack closure (PCC), corrosion products-induced crack closure as solid properties (ECC) and as viscoelastic properties (VCC). The load sharing capacity of the wedge effect as VCC is negligibly small, though crack closure behavior is varied by VCC. Meanwhile the wedge effect of ECC is exclusively effective resulting in a raised stress intensity to close the crack, thereby reducing growth rate. The wedge effect of ECC is much affected by stress cycle frequency, stress ratio and cathodic protection. The influence of stress ratios is diminished in da/dN-ΔK_eff diagram, and a single curve is obtained at both frequencies. da/dN at f=0.1 Hz is considerably greater than that at f=10Hz. da/dN under cathodic protection is less great than that under free corrosion at low ΔK_eff. da/dN is enhanced through stress-assisted dissolution and hydrogen embrittlement.

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Rotating bending fatigue tests were carried out on SUS304 stainless steel specimens having three drilled holes with equal distance at the critical section to investigate statistically the propagation behavior of surface cracks and their coalescence leading to a failure of the specimen. Based on the distribution characteristics of crack length at an arbitrary number of cycles, a statistical evaluation was made on the coalescence of cracks as a function of the number of cycles, and the fatigue life distribution was theoretically derived from the above evaluation assuming that the failure occurs immediately after the coalescence of cracks. The analytical results obtained are in good agreement with the experimental results of fatigue life distribution.

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In this paper, integral equation methods for boundary value problems of elastic bodies with cracks are investigated. We use Somigliana's identities to represent displacements in elastic bodies, and deduce integral equations from the boundary conditions on the crack surfaces. In these integral equations, unknown functions are displacement differences between the upper and the lower crack surfaces. Divergent integrals are contained and they are evaluated in the sense of Hadamard's finite parts. The integral equations are solved analytically for the case of penny-shaped crack. Methods for numerical solutions of the equations are also studied.

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Stress singularities near crack front edges are investigated. Firstly, the crack problems are formulated in the forms of the integral equations. Analysing the solutions of these equations, we derive the conditions by which the singular behaviour of stresses is determined. The stress singularities are calculated for several cases of a wedge shaped crack and a surface crack.

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The crack energy density ε and ε_J-integral which is the path independent expression of ε are applied to creep problem and it is shown that ε and its differential coefficient with respect to time ε^^._st are valid parameters to creep crack without any restriction on constitutive equation. The contents of the paper are as follows. (1) ε and ε^^._st are introduced as creep crack parameters and it is shown that ε^^._st can be evaluated by a path independent integral ε^^._st obtained by differentiating ε_J with respect to time. (2) It is pointed out that J'-integral (C*-parameter) can be evaluated by a newly-introduced ε^^._jst which is a path independent integral even to non-steady state creep, and the physical meaning of J' is clarified based on ε'_Jst. Also the relation between ε^^._st and J' is discussed and the role of J' is made clear. (3) The validities of ε and ε^^._st as creep crack parameters are numerically verified through finite element analyses.

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The fractographic features caused by impact loads and the correlation between the features and the underlying microstructure are studied. Specimens of structual steel SS41 are broken off by a gun-type testing machine or Charpy impact testing machine at various impact velocities. The fracture surfaces are observed and photographed using a scanning electron microscope (SEM) and the plated electrolytically with nickel. The specimens are cut on a plane perpendicular to the fracture surface. The cross sections are polished and etched. An optical photograph of the section reveals the profile of the surface and the underlying microstructure without any edge rounding. Matching the SEM photographs to the optical micrographs, the correlation between the fractographic features and the microstructure is discussed.

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The effects of variations of maximum effective stress and stress ratio on the behaviors of biaxial strain accumulations were experimentally investigated using thin-walled tubular specimens of a carbon steel subjected to combined cyclic axial load and steady internal pressure. When the maximum effective stress was changed with number of cycles keeping the stress ratio constant, the strain accumulating rate under biaxial stress condition was equal to the rate under uniaxial stressing. The rate of strain accumulation in biaxial stressing was smaller compared with the rate in the uniaxial condition when the stress ratio was changed with number of cycles. A constitutive equation of biaxial mechanical ratcheting is proposed. The predictions by the present equation agree well with the experimental observations.

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The roughening of free surface during plastic forming of metals, such as metal forming, is an important problem from a standpoint of surface finishing of the products as well as the fracture of the sheet metal. In the present paper, an analytical study is made of the relation between surface roughening and inhomogeneity of plastic deformation, especially for a range of relatively small strains. In order to simulate surface roughening, a model of inhomogeneous material is employed and elastic-plastic deformation of the model material is calculated by the finite element method. Based on the result of calculation, an equation is proposed which expresses the effect of strain, grain size and mode of deformation on the surface roughening.

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The formula for the torsional stiffness and those for the yield torque of small involute splined shaft couplings are derived under some assumptions. Then the four kinds of small splined shaft couplings are made and tested. Those torsional stress compared with the theoretical ones. Consequently it is found that the assumptions are suffucient for a practical use, and the formula are useful to estimate the torsional characteristics. Moreover the effects of some parameters on the torsional characteristics of the splined shaft couplings are studied with the formula. And some instruction for the miniaturization of the couplings are obtained.

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This paper deals with a theoretical investigation of the effects of heat and mass transfer on the impulsive pressure due to the collapse of a bubble in a compressible liquid. It is found that the dynamical behaviour of the bubble strongly depends on heat and mass transfer through the wall of the bubble. The smaller is the initial radius of the bubble, the more violently contracts the bubble, while the higher becomes an impulsive pressure, on the other hand, the shorter becomes the time duration of it. The higher is the temperature of the surrounding liquid, the more slowly contracts the bubble, and consequently it merely radiates a weak pressure wave.

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Experimental investigations were carried out to examine the effect of vortex generators on the characteristics of the flow around a circular cylinder in a cross flow in the range of subcritical Reynolds numbers. The Strouhal number, the static pressure distribtion, the R.M.S. values of the fluctuating pressure, the position of the separation of flow and the structure of the boundary layer have been measured. The flow patterns can be classified according to the position and the height of the generator rows, and the roughness Reynolds number. Characteristics of these flow patterns and the relationship among them were clarified.

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In the 1st report, concerning a single finite circular cylinder placed on a flat plate, it was made clear that the three-dimensional reattachment of a blow down flow from upper end of the cylinder and the formation of a pair of longitudinal vorices play an important role in the augmentation of heat transfer. Following this, this report describes the experimental results on the flow structure and local heat transfer characteristics influenced by (I) the change in the shape of protuberance (cube, square cylinder and circular cone) and (II) the mutual interaction of longitudinal vortices produced in a row by row of protuberances.

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Experiments in a upward gas-liquid two-phase flow inside two adjacent subchannels with different cross-sectional areas were performed to determine the flow rate of each phase in each subchannel. An analysis was also made of the influence of void fraction, frictional pressure drop and turbulent mixing rate of liquid on the distribution of flow rates. It was experimentally clarified that the superficial gas velocity measured at the larger subchannel exceeds that of the smaller subchannel for all the regimes tested such as slug, froth and annular flows, whereas such a simple tendency for gas phase does not exist for liquid phase velocity. The analysis suggests a strong interrelationship between the distributions of liquid flow rates and turbulent mixing rates.

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The information on the characterstics of liquid film, droplet entrainiment, and droplet deposition in a two-phase annular-mist flow is important for planning and designing nuclear reactors and steam generators. The available information is more limited on the characteristics of a liquid film mist flow in horizontal channels, where the gravity is an important factor. The purpose of this work is to clarify various characteristics of a liquid film mist flow in a horizontal rectanglar channel of 150 mm width and 50 mm height. The distribution of liquid droplet flow rates and the gas velocity profile in each cross-section of the channel in the axial direction were measured. The rates of deposition and entrainment were determined, using the distributions of the droplet flow rates obtained by a scoop method. Further, the rate of liquid droplet entrainment was correlated with the geometrical characteristics of the liquid film.

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In this report, first, the forced vibrations of a circular plate with a nonlinear dynamic vibration absorber are investigated theoretically. The plate is simply supported at the outer edge subjected to a sinusoidal motion of constant amplitude. The restoring force of the nonlinear dynamic vibration absorber is represented by a hardening spring having both linear and cubic nonlinear bahavior. In the analysis, the one-third order subharmonic and the third order superharmonic vibrations as well as the fundamental one are assumed. Second, it is demonstrated that the optimal tuning and damping parameters for a nonlinear magnetic dynamic vibration absorber with a hardening spring can be easily found by using the simplex method.

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After an experimental discussion on the characteristics of the generated thrust and friction of a linear induction motor with a phase-controlled power source, the positioning characteristics of a servomechanism having a linear motor as its actuator have been analyzed by simulations and experiments. The mechanism has been shown to be a stable positioning mechanism as second order system, though there may occur minute inching motions due to force variations in the vicinities of set points. As the inching motions cause deterioration of the response characteristics for small input values, an improvement of response is also discussed.

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For elucidating the effect of tooth fatigue on dynamic performance of case-hardened gears, the gears were fatigue-tested by a power circulating gear testing machine, and tooth root strain, vibration acceleration level, sound pressure level and so on were measured. The tooth failure mode was classified into two types; a tooth breakage by bending fatigue at the tooth fillet and a tooth breakage due to surface fatigue near the pitch point. In the same failure mode, the changing pattern of sound pressure level was the same even if the surface hardening method was different. The dynamic load, vibration and noise tended to increase as the tooth profile deteriorated.

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An internal gear which meshed with three planet gears in the same bearing condition and was supported through a thin cylinder was chosen as the subject of study. Stresses in profile shifted internal gears whose addendum modification coefficients were x=0.5 and -0.5 respectively were analyzed by the photoelastic method and were compared with those in the standard internal gear investigated in a previous work and consequently the following were revealed. The effect of an addendum modification on the fillet stresses produced in the internal gear increases with a decrease in both the rim thickness the number of teeth of internal gear.

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This paper presents a study on the surface durability and pitting failure of normalized steel spur gears with a smaller number teeth (z=13) from the viewpoints of the Hertz stress, specific sliding and position of pitch point in the range of engagement. The contact fatigue life of a normalized steel spur gear pair is governed by the pitting of a driver when the pitch point lies in the range of single tooth pair contact, which is common in practice. But when the pitch point lies in the range of double tooth pairs contact, the life is governed by the pitting of a driver or follower depending on the Hertz stress and specific sliding. The contact fatigue limit load of a pinion (driver) can be raised considerably by locating a pitch point in the range of double tooth pairs contact in the dedendum region of the driver.

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When a scoring failure occurs on involute spur or helical gears, their power transmitting characteristics become different from those before scoring initiation. Measured and analyzed states of tooth fillet stress show, that it increases considerably with progress of scoring. The increase of the maximum contact stress stays at somewhat lower level than that of the maximum fillet stress. The analysis on the thermal and lubricating conditions on or between tooth flanks shows, that the rise of frictional coefficients and bulk temperature owing to initiation of scoring is responsible for the progress of scoring. When the state of scoring is very severe, the gear vibrational excitation becomes generally very strong, but at the beginning stage of scoring the changing of gear vibrational excitation receives strong influence from gear dimensions : in some gears the initiation of scoring makes gear noise and vibration stronger, but in some other gears it makes them weaker.

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In the present paper, by using rate of load distribution of tooth and the same loaded condition as that in the dynamic condition, stresses and deformations of teeth and rim of spur gears with a thin rim were calculated, and the calculated results (by the finite element method) were compared with the experimental ones. Moreover, accuracy deterioration of spur gears with a thin rim was discussed. The following conclusions were obtained. (1) From the results of the present study, the stresses at the root fillet of tooth of spur gears with a thin rim and solid gears, their deformations under dynamic condition and the degree of accuracy deterioration of those spur gears when rate of load distribution was considered were clarified. (2) It was found that lag of a tooth intermeshed with No. 1 tooth corresponding to the spoke is maximum.

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A new method for separating independent peaks of an objective function defined in an n+1 dimensional Euclidean space composed of n decision variables and a performance index of a mechanism is developed by applying the Monte Carlo integration and its reliability is examined by numerical experiments. A method using the principle of relative peaking together with the method of reduction of the region on the basis of radii of gyration of a solid figure with respect to hyperplanes parallel to the axis of the performance index is also presented for finding the global maximum point of the objective function in each separated region. Moreover, the constants for generating the quasi-random numbers used in the Haselgrove method are extended upto the ones for the multiple integration of the 16th degree. As an example, an indicating balance with accuracy over 1/4000 is synthesized by using a Watt six-link mechanism having two prismatic pairs.

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Oil refinery and chemical plants are constructed by multi-national workers in developing contries. Productivity is defined as a function of actual man-hours and standard man-hours required to complete a job. The author will present equations showing the relationship between labor productivity of multi-national workers and labor cost on the construction site by using seven factors, ie, α: Work volume ratio by each nationality, β: average productivity, γγ: unit man-hour cost ratio, δ: performance factor of main nationality on the site, ζ: man-hour ratio, π: combined productivity, and λ: labor cost index such as [numerical formula] or [numerical formula] [numerical formula] or [numerical formula] and [numerical formula] or [numerical formula] When improving productivity by training, improvement of combined productivity and cost reduction are computed by these equations.

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