Liquid storage tanks have often suffered buckling failures during earthquakes. In this paper, the buckling of fluid filled cyrindrical tanks under harmonic base excitation is studied using small plastic cyrindrical tanks made of polyester sheet, and two types of buckling mode are observed. The stress resulting from the frequency response (the circumferential wave numbers n=1) is calculated using an axisymmetric shell finite element program including the effect of fluid structure interaction. The static buckling stress criterion for a long cylinder subjected to pure bending is applied to the above calculation. The static buckling criterion proves to be fairly satisfactory in the restricted region under natural frequency of the fundamental mode.

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Buckling failures are often observed for tanks subjected to seismic load. In this paper, the dynamic buckling is studied, using small plastic cyrindrical tanks made of a polyester sheet. The static buckling tests of the fluid filled tanks subjected to lateral load, and the dynamic buckling tests under harmonic excitation by a shaking table are carried out, and the buckling modes are compared. The stress resulting from the frequency response (the circumferential wave numbers n=1 for horizontal excitation and n=0 for vertical excitation) is calculated using an axisymmetric shell finite element program including the effect of fluid structure interaction and static buckling stress criteria are applied to the above calculations in order to predict the appearance of buckling. The predictions are compared with test results and prove to be fairly satisfactory in the restricted region under the natural frequency of the fundamental mode.

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Two-dimensional elastic problems for he debonding of a circular elastic inclusion are formulated. It is assumed that a circular inclusion is bonded to the interior of an elastic infinite medium with different elastic properties, except for some portions which are regarded as interface cracks. The solutions are presented in the closed forms with integral terms which can not be evaluated analytically in problems with two or more cracks. Evaluating the terms numerically, the effects of the length and the location of the cracks and the elastic moduli of the inclusion and the infinite medium on the stress intensity factors are presented for cases with two interface cracks.

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When an excessive axial compressive load is applied to a thin-walled stepped circular tube, collapsing occurs locally at the stepped position. Thereafter, the portion with a smaller diameter intrudes into the portion with a larger diameter. Such deformation is developed under almost constant load. In this paper, using results of the elasto-viscoplastic properties for the materials, the authors dealt with this problem theoretically as being one of a large deformation with elasto-viscoplastic properties, and performed numerical analysis by the finite element method and the direct time integration method. The experimental apparatus was the block to block type impact testing machine. Characteristics of the load-deformation relation are studied for three kinds of configuration of the test pieces. Thus, the collapsing characteristics of stepped circular tubes due to the impact axial load were made clear.

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Interpretation of each contribution of a propagating elastic pulse is described in relation to the time record waveform. The experiment of mechanical impact with a tiny hard plastic ball on the end of rectangular plate was conducted to get the waveforms. The waveform shows good coincidence between the pulse locations and the calculated arrival times. Identification of each propagating path in a plate is made with recorded waveforms, and so does estimation of the arrival times to be taken to travel along the path with energy propagation velocity. Some of the remarkable features of pulse propagations are also described. In long time records, the waveforms are mainly composed of the edge modes emanating from each corner of the plate. The contributions of the reflected flexural waves, as well as those of edge waves, can be clearly detected in the real waveform records.

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The fractographic features of fracture surfaces which are produced by slow bend tests at various low temperatures, and the correlation between the features and the underlying microstructure are studied. V-notch specimens of mild steel SS41 are broken off by three-point slow bend tests at various low temperatures. The fracture surfaces are observed and photographed using scanning electron microscopy (SEM), and the sections perpendicular to the surfaces are observed and photographed using optical microscopy. Matching the SEM photographs to the optical micrographs, the correlation between the fractographic features and the microstructures is discussed. The drop in temperature has no effect on the relationship between the cleavage facet and the number of grains. The fractographic features of ferrite grain, as in a river pattern or cleavage step, become complex with a drop in temperature. A twin pattern occasionally makes a tongue or a cleavage step.

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The fracture behavior of notched plates and grooved shafts of polycarbonate under tension has been investigated for a wide range of notch geometries and dimensions of specimens. Careful observations were made on the fracture process at the notch root during tests. Bluntly notched specimens failed in a fully ductile manner with large shear bands, and sharply notched specimens failed in a brittle manner after the formation of a small crack at the tip of the plastic zone. By varying the notch root radius and thickness of plates we have been able to distinguish clearly how both influence the brittle-ductile transitions. The critical notch root radius at the brittle-ductile transition increases according to increased thickness of the plate. Experimental results were discuss-ed in terms of a combination of the maximum elastic stress at the notch root and the notch root radius. It has been established that applying a fracture criterion derived here, we can make an accurate estimate of the strength of notched polycarbonate specimens of any shape and size.

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In X-ray stress measurement of metals having a texture, the intensity of the diffracted X-rays is dependent on the direction of the stress measured, and is different from that of a randomly oriented metal. The relation between the nature of texture and the intensity of the diffracted beams is analyzed in the present paper and the texture in the cold-rolled steel sheet is determined by using the diffracted intensities in X-ray stress measurement. Then the X-ray elastic constant of the rolled sheet is calculated by considering the anisotropy of crystal and the presence of texture. The X-ray stress evaluated using the X-ray elastic constant thus obtained is in good agreement with the mechanically applied stress, indicating that the present method is applicable to the stress measurement in the case when the texture is not determined.

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This paper is concerned with a comparison of predicted strength based on the proposed way explained in the 1st report, and experimental results of adhesive joint strength. It is shown that the strength of scarf joints can be predicted by the strength law represented by stress, that of double lap joints can be predicted by strain, and that of single lap joints can be predicted by the energy release rate. The experiments on the effect of scarf angle on the strength of scarf joints, and on the effects of lap length, adherend thickness and adhesive thickness on the strength of double lap joints and single lap joints are performed. As a result, it is shown that the experimental strength agrees well with the predicted strength.

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Grain-size distributions of commercially pure aluminum, copper and 6·4 brass are approximated well with a log-normal distribution function, and it is shown that the median and the standard-deviation of distributions increase the strain-hardening exponent of sheet specimens of copper and 6·4 brass under tension. Both the simple equal-strain and equal-stress models of a composite flow curve are introduced, which are based on the flow stress rule of nth-power curve relation, connecting with the distribution function whose upper grain-size is bounded with 3·5 times the mean-grain diameter. The equal-strain model gives the lower flow stress limit, and the equal-stress model yields the upper one, and the experimental flow stress appears in between or closely around these two neighboring limits. Both models prove analytically that the median and the standard-deviation of distributions increase the strain-hardening exponent of a sheet metal under tension. The former model predicts the upper bound of the strain-hardening exponent and the latter one predicts the lower one, and experimental data on 6·4 brass are shown to appear in between them.

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The title problem was discussed to facilitate the formulation of constitutive models of cyclic plasticity under general multiaxial loading conditions. A series of plastic strain controlled cyclic tests was performed by applying combined axial force and torque to thin-walled tubular specimens of type 316 stainless steel at room temperature. These test consist of cyclic loadings of variable amplitudes along torsional, cruciform and circular plastic strain paths, and the combinations of cyclic loadings of different path shapes with equivalent cyclic hardening. The results of these tests showed that in the cases of torsional and cruciform cycles, the cyclic-hardening under prior cycles of larger amplitude was recoverable under the subsequent cycles of smaller amplitude, but in the case of circular cycles, the non-erasure of memory of the prior cycles was slightly observed. It was also found that the equivalence of cyclic-hardening among the cycles of different path shapes may be assumed in the formulation of a constitutive model of cyclic plasticity for general multiaxial loading conditions.

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Shape rolling of an angle beam was analyzed by the energy method, in which the kinematically admissible velocity field was expressed as the sum of basic velocity fields, and finite element division was applied in the previous paper. Here, most basic velocity fields were determined by a method similar to that proposed already, though some new velocity fields were defined concerning the position of the undeformed part of a billet and the curling of the billet after rolling. Rolling properties were obtained and some discussions were made from the mechanical standpoint : curling depends on the difference of circumferential velocities of the upper and lower rolls ; distortion of the cross section of a billet can be attributed to the reduction of the upper and lower parts of side portions of a billet, etc. Consequently, is was proved that the author's energy method can be applied to shape rolling successfully.

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