For the buckling problem of circular cylindrical shells under axial compression, experimental results show that after the primary buckling, the secondary buckling takes place accompanying successive reductions in the number of the circumferential waves at every path jumping. In this paper we traced this successive buckling of circular cylindrical shells using the latest in general-purpose FEM technology with the static stabilizing method with the aid of artificial damping for the local instability. The studies accomplish a fully automatic and seamless simulation of the successive path jumping in the deep postbuckling region, and show a good agreement with Yamaki's experimental results.

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The finite element procedure for the three-dimensional adaptive trusses using shape memory alloys is formulated in the present study, in which the extended form of Brinson's constitutive equation considering the asymmetric tensile and compressive behavior is expressed in a tangentially incremental form. The validity of the present computational modeling is demonstrated by conducting numerical studies for the superelastic, shape memory behaviors of two-bar, nine-bar and twenty eight-bar adaptive trusses subjected to load and temperature changes. The proposed computational procedure is expected to be useful for the optimum design of the adaptive trusses with shape memory alloy bars.

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The interactive terms in the mesh superposition method are calculated approximately because the integrand has a discontinuity along the mesh lines in a superimposed global mesh. In this paper, the accurate numerical integration technique for a discontinuous integrand by the Delaunay triangulation is proposed. Integral ranges including discontinuous integrands are divided into triangles only with a continuum integrand. The exact solution is sum of the integral values calculated in all triangles. Appropriate triangle edges can be regenerated by the swapping algorithm even though generated triangles contain the inappropriate boundary lines which bring about a discontinuity. A comparison of the accuracy of numerical integration between the proposed technique and conventional approximate means and an application to a sensitivity calculation are investigated in the first example. The second example illustrates the swapping algorithm for the adjustment of generated triangles.

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This study was conducted to establish a non-destructive inspection method based on ultrasonic echo measurement. The method was mainly aimed to estimate the damage condition and remaining strength of glass-fiber reinforced plastic (GFRP). After immersion in hot water for 1 day-1 month (86.4 ks-2.42 Ms), the damage condition of GFRP was optically observed in detail and ultrasonic echo was measured over the surface. Further, the changes in the mass, Barcol hardness and bending strength were systematically investigated. Isolated delamination of glass-fiber cloths was found at the immersion period of 14 days. Then, its size and opening distance were rapidly increased. The results showed that such progress of delamination can be evaluated by the decrease in the ultrasonic echo parameter (V value) which was proposed in this study. The surface distribution and frequency distribution of V value gave more useful data to evaluate the damage condition. Furthermore, it was shown that the remaining strength of GFRP can be evaluated using V value as a damage parameter.

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Strict geometrical stability is required for the precise structures like telescopes. Unpredictable out-of-plane deformation is a serious problem when we use CFRP (Carbon Fiber Reinforced Plastic) laminate to the precise structure. This out-of plane deformation of symmetrical CFRP laminate mainly arise from combination effects of ply angle misalignment and temperature change. We discussed here is effective stacking sequence of CFRP laminate that mitigate the deformation caused by the ply angle misalignment. The analysis based on laminate theory was performed to calculate the thermal deformation. In this analysis, the random numbers were added to each layers as ply angle misalignments. The analytical results were obtained statistically by Monte Carlo method. Mohr's curvature circle was also incorporated to evaluate the deformation as P-V (peak to Valley) values. We performed the analysis with various stacking sequence. It was calculated that the symmetric cross-ply laminates deformed 10 times larger than the other quasi-symmetric laminates. In the case of the total ply number is less than 12, the stacking sequence in the laminate has a significant effects on the thermal deformation. However, if the total number ply number is more than 24, effect of stacking sequence on the thermal deformation becomes negligible. We also discussed the geometrical stability of CFRP mirror by considering unavoidable ply angle misalignment. It was presumed that the CFRP mirror can be used for wide range of wave length when the back structure was attached to CFRP laminates.

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A new evaluation method was proposed for the interfacial strength between a thin film and its substrate by nanoindenation test. In this method, the released energy due to a coating delamination is obtained by estimating the shapes of the unloading curve at the points just after and before delamination on the load-displacement curve. Shape of unloading curves can be assumed by obtaining the contact stiffness of thin films. To confirm the validity of the method, nanoindentation tests were conducted for polyimide (PI) coating / Si substrate specimens and the interfacial strength was evaluated. Three specimens that have different thickness were prepared. Contact stiffness of PI film bears a linear relationship with indentation load. Irrespective of the coating thickness, the values of the interfacial strengths converge. In addition, the values of strengths agree with the results obtained by the authors in the previous paper for the case that small scale yielding conditions are satisfied. For the case that indentation loading rate is high and the delamination occurs before the relaxation of film, it is necessary to measure the contact stiffness with each indentation loading rate.

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The Japanese sword is a weapon peculiar to Japan. The Japanese sword is interesting not only from the viewpoint of traditional crafts of arts, but also from the aspect of modern science and technology because the way of making and its functionality as a weapon are really consistent with science. The present study is concerned with the connection between tohshin (blade) and tsuka (hilt) of the sword. Only one mekugi-take (retaining peg made of bamboo) with about 5mm in diameter holds Nakago (tang) in the hilt. However the slender mekugi might not be broken, even though in the case of violent sword-fighting. This fact has been historically demonstrated in many battles by Japanese swords. In this study, using a Tachi being the typical Japanese sword, it is examined theoretically and experimentally from the viewpoint of impact engineering why a mekugi used in Japanese swords might not be broken. As a result, it is made clear that such a strong force as breaking mekugi-take does not act on it, because of the location of mekugi-ana (a hole for mekugi) in the tang, which has been made by the traditional code of sword-smiths.

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An analysis of dynamic behavior is carried out in the case when dynamic load with central symmetry is applied on the inner face of the cavity with central symmetry of the thick-walled elastic-plastic-viscoplastic sphere. Formulas are derived of propagation speeds of elastic-plastic-viscoplastic spherical waves. The theoretical formula is analytically proved to be strain rate and stress rate dependent. Ordinary differential equations among physical quantities are derived along characteristic curves. The propagation theory of spherical wave based on the elastic-plastic-viscoplastic constitutive equation is shown to contain that based on the elastic-plastic constitutive equation. Calculated examples are shown on the basis of the elastic-plastic-viscoplastic theory. A comparison is done of calculated results based on the elastic-plastic-viscoplastic theory with those based on the elastic-plastic theory.

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Welded structures in coast regions in Hokkaido prefecture are exposed to the severe environment such as a freeze-thawing of a liquid included with a chlorine ion Cl^- that is brought by a sea breeze and a snow melting agent during a winter season. On the other hand, it is well-known that Cl^- solution produces a pitting corrosion in an austenitic stainless steel. However, the relationship between the pitting corrosion occurred in the welded austenitic stainless steel and the freeze-thawing environment have not been clarified yet. In this work, the influence of freeze-thawing environment on a pitting corrosion occurred in the welded austenitic stainless steel in Cl^- solutions was investigated using SUS304 specimen with bead-on-plate welding. The specimen was fully immersed in FeCl₃ solution. The freeze-thawing environment was recreated by a temperature cycling from 20°C to -20°C. As a result, large-scale pitting corrosions was induced mostly in the area of a high tensile residual stress and a sensitive metallographic structure near weld line under the freeze-thawing environment. It is confirmed that the accelerated pitting corrosion phenomenon was introduced by a concentration cell corrosion due to a local concentration of chlorine ion Cl^- around weld line during freezing and thawing of the solution.

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In this research, in-plane shear moduli of plywood as obtained by a tension test of [±45] off-axis specimen were examined by varying the width of the specimen. The tension tests were conducted on five-plywood of Lauan (Shorea sp.) with various widths, and in-plane shear moduli of the specimens were measured. Flexural vibration tests and finite element calculations were independently conducted. A comparison among the results of the experimental and numerical analyses revealed that specimen should be wide and the gauge should have an appropriate length with respect to the specimen width to measure the in-plane shear modulus appropriately with reducing the influence of variation of normal strain in the width direction.

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