In this report, the crack propagations in several kinds of notched round bar specimens of SK 5 and SUS 50 steels are investigated. The main results are summarized as follows. (1) It is possible to estimate the S-N curves for any notched specimen by using the idea of ε₀, which has been often adopted to predict the endurance limit for crack initiation. (2) If the same crack length is obtained for the imposition of the same number of cycles, the crack propagation rates coincide with each other irrespective of the notch root radius and the materials. (3) In opposition to the results in (2), the effect of specimen shape appears on the crack propagation in the radial direction. (4) The index "m" for the formula dl/dN=CK^m or dl/dN=Cσ^m1ⁿ, is considered to be related with the gradient of S-N curve and varies from 4 to 5 depending on the stress amplitude.

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In the previous report, Flugge's and Mizoguchi's shell theories were improved to be applicable to problems of the general axisymmetric shell, and it was proved that these two theories and Sander's shell theory give almost the same results. In this report, Flugge's shell theory is modified to give better results. Donnell's shell theory for the cylindrical shell is also considered and is extended to problems of the general axisymmetric shell, then, these two theories are applied to some problems and the accuracy of these methods is investigated.

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In this paper, an analysis of contact stress and displacement in the case both ends of an elastic circular cylinder are compressed axisymmetrically or non-axisymmetrically on the plane surface of a semi-infinite elastic body, is made by neglecting the shearing stress on the contact surface. Solutions for the axisymmetric cases of a solid cylinder or a hollow cylinder under internal pressure are obtained in the form of the Bessel series by the iteration method satisfying the boundary conditions successively. Next, for the case of non-axisymmetric contact the method by the power series is applied, i.e., the solutions are expressed by the power series and satisfying the boundary conditions exactly leads to the simultaneous linear equations for the unknown coefficients in these series. Moreover, this non-axisymmetric problem can be solved by the above iteration method. Using the above-mentioned analyses numerical solutions are computed for various rigidities and heights of the cylinder.

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A plastic deformation whose strain trajectory has constant curvature is investigated on mild steel by applying the combined load of axial force and torsion to thin-walled tubular specimen. The experiment is performed by using a full-automatic complex loading testing machine. Experimental result shows that the relation between the magnitude of stress vector and the arc length of plastic strain trajectory depends mainly on the curveture, and the curve showing such a relation appears higher than the hardening curve for pure torsion. On the other hand, cyclic loading makes the curve lower than the hardening curve for pure torsion owing to the effect of cyclic softening. This may be an experimental evidence that the conventional flow theory is not satisfactory for complex loading. However, the flow theory may be found as a sufficient approximation to plastic deformation under complex loading with strain trajectory of constant radius of curvature larger than 2 percent.

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To make clear the dynamic characteristics of a rotating shaft exactly, we should take into consideration both the asymmetry of a shaft and the elasticity, especially the asymmetric elasticity of supports. The authors considered an idealized model, in which a disk was mounted at the center of a flat shaft with different bending rigidities in two mutually vertical directions corresponding to the principal axes of inertia of the section. The supporting parts of both ends were supported by springs in two vertical directions, as a concentrated masses system, in which masses were concentrated at the central disk part and supporting parts of both ends, and the equations of motion with periodic coefficients were derived in terms of springs. As a first step, analyses were made by the asymptotic method to know what effects would be caused to the unstable regions of this system by the asymmetry of the shaft, the rigidities of the supporting parts and their asymmetry, the internal and external dampings, and others, and in what relation these acted with each other. Some of the results of analyses have been experimentally confirmed.

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In the 1st report, the authors studied the unstable regions of a system in which a disk is mounted at the center of an asymmetrical elastic shaft, and is supported at both ends by asymmetrically elastic pedestals. However, in an actual rotating system, as inevitable errors in the qualities of materials and the machining processes are present in the shaft and disk, the forces of unbalance caused by them, effects of gravity in supporting horizontally, and others, must be taken into consideration. Hence, for the vibrational characteristics of the system, analysis of the unstable regions only is not sufficient. Analysis of forced vibrations is also required. To elucidate the vibrational characteristics of the system ranging from the first critical speed to the fourth critical speed, the authors have made analyses by using the asymptotic method in the same way as in 1st report, to know what are dynamic characteristics of such a system in relation to the relationship among the spring constant, the internal and external dampings, the magnitude of eccentricity in the shaft and disk, the angle of unbalance, gravity, and others. The vibrational phenomena in the neighbourhood of the first and second critical speeds at comparatively low speed regions have been experimentally confirmed.

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In the previous report, we proposed a method to calculate the development of the incompressible turbulent wake close to a flat plate. The calculated results were compared with experimental data in which the wake started from the turbulent boundary layers on both sides of a thin flat plate. The agreement between the calculated and the experimental results was very good, and we can conclude that the diffusion phenomenon of the turbulent near wake has been made clear both qualitatively and quantitatively. In that case the shape parameters of the boundary layers at the trailing edge of the plate were all equal to 1.45. Here in this report, we extend the previous method so that we can study the effect of the boundary layer profile and that of compressibility upon the development of the turbulent wake close to a flat plate. The calculated results show that the wake profiles is dependent on the boundary layer profile and compressibility. The agreement between the calculated and the experimental results is excellent.

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A two-dimensional flame in a boundary layer with uniform injection of propane gas from a porous flat plate parallel to a uniform air stream is treated in this study. The positions of the beginning of the flame in both directions parallel and normal to the plate are considered to be one of the most important factors for the stabilization of such a flame. In order to justify the experimental results of the positions, an analysis of both the mass balance at the flame sheet and the mass balance at the surface of the plate is briefly carried out by local similarity method and an experimental equation of an air stream-velocity. The influences of injection rate, mass flux of an air stream and the surface temperature of the plate on the positions are discussed qualitatively.

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All equipments of earth-moving machines (e.g. bulldozer, power-shovel) cut soil. In order to analyze the mechanism of soil cutting, a study on cutting of soil is made. The main results are as follows: (1) Cutting patterns of soils consist of the following three types-shear type (sand or plastic bentonite), flow type (plastic loam) and tear type (compacted loam). (2) Failure conditions of soils are investigated. Shear type and flow type are brought about by shear failure, and tear type by tensile failure. The difference between shear type and flow type occurs only from apparent difference of shear-line. (3) Experiments to measure the distributions of internal stresses in soils are carried out. From these results, the correspondence between cutting patterns and failure conditions is explained. (4) Comparison between cutting patterns of soils and cutting patterns in other fields (e.g. metal cutting) is made.

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Factors influencing formability in pure stretch-forming, combined-forming and deep-drawing are discussed from a new standpoint, that is, the formability assessment based on the components of the forming depth and the fracture mode. In pure stretch-forming, it is confirmed experimentally and by numerical analysis that the forming depth is markedly correlated to n-value, but little to r-value, although this depth attains a maximum at r=1.0∼1.5. In case a punch profile fracture occurs in combined-forming, the relative load-carrying capacity T_cr/(A_o*S_T) has a proportional relation with both the stretched-out and -in components, which are newly defined in the present investigation, and thus with the forming depth which equals the sum of the components. From considerations of this parameter T_cr/(A_o*S_T), a simple method to predict the limiting drawing ratio and the forming depth at the ratio is proposed.

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