We present a relationship between delamination force for a bonded structure and a new intensity parameter of stress singularity at vertex on interface. Delamination test is carried out using a specimen made of Silicon plates bonded by resin, and relationship between delamination force and resin thickness is investigated. In addition, the intensity of stress singularity is computed by stress distribution and order of singularity. Boundary element stress analysis and finite element eigen analysis are carried out for three dimensional models to obtain the stress distribution and order of singularity. In the stress analysis, mechanical load is considered as the boundary condition. The novelty point of this paper is that a new intensity parameter, i.e., a critical parameter of intensity of stress singularity, K^3D_{1θθcritical} was defined. Consequently, it was confirmed that there is a relationship between the practical delamination force F and the parameter K^3D_{1θθcritical}.

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Utilization of scrap wood produced by thinning-out the Japanese larch forest is a serious problem to be solved. Since wood is comparatively easily strengthened by compressing it, depending on the future developments, a lot of usages of compressed wood can be expected in the future. On the other hand, the decay of wood damages the timber and it remarkably shortens the life of a wooden building. In this study, the investigation was carried out to aim to apply compressed wood produced by compressive forming to wooden buildings. The following conclusions were obtained as the first stage. 1)The compressed wood was produced through four processes of softening → compression → shape fixation → drying. Particularly, the condition of shape fixation is steam processing at 132°C for 70 min. 2)As for a useful index to clarify the situation of compression, it was found that “late wood ratio” is even better than “density”. 3)The accelerated decay tests for compressed woods and non-compressed woods were conducted. Then, these decayed woods were subjected to a uniaxial compression loading. As a result, it was found that, after the decay test, the compressive Young's modulus and the compressive strength of compressed woods are larger than those of solid wood. In point of residual strength for decay durability, compressed wood is superior to solid wood(non-compressed wood).

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In order to study the effect of loading mode on fatigue properties of high speed steel (0.7C-4Cr-0.1W-3 Mo-2V) in very high cycle regime, fatigue tests under axial loading and rotating bending condition were performed in laboratory air using the hourglass shaped specimen. From the experiment results, clear duplex S-N curve appeared in both loading conditions, that is, there were two curves composed of a surface failure mode and a subsurface failure mode. Fatigue life under axial loading condition was shorter than that under the rotating bending condition, especially in low stress amplitude level. The difference in fatigue lifetime and transition of failure mode between the loading modes was discussed from the viewpoint of inclusion size, applied stress distribution across the specimen section and residual stress in surface layer.

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The purpose of this study is to investigate aspects of ceramic thin film deposited on cemented carbide under cyclic sphere indentation loading and to clarify the possibility of the sphere indentation test to evaluate endurance characterizations of ceramic thin films. Three kinds of ceramic thin films were deposited onto cemented carbide WC-Co substrates. Cyclic sphere indentation tests were carried out by using spherical indenters of varying diameter 2R to investigate the aspects of crack initiation, wear progress, and delamination in ceramic film and to obtain the influence of the applied maximum load P_max on the cyclic number of crack initiation N_i in thin films. The main conclusions are the following. (1) Ring crack initiate at the lower load than that of a ring crack initiation load obtained by static sphere indentation test. (2) After ring crack initiate, wear of film progresses inside the contact area, and delamination in thin film occur. (3) Quantitative evaluation of wear is possible by measuring the cross-sectional shape of contact area. (3)The P_max - N_i relationships specifically depend on the diameter of spherical indenter 2R. (4) The effect of 2R on the relationship between tensile stress of film σ_r,i and N_i is smaller than that of the P_max - N_i relationship.

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Magnesium (Mg) is easy to be corroded in contact with other metals due to the formation of galvanic cell at the interface because it has the lowest negative standard electrode potential (SEP) in industrial metals. The traditional methods to evaluate corrosion resistance such as saltwater immersion test, salt spray test, and electrochemical corrosion test do not provide the effect of micro size metallic dispersoids on galvanic corrosion phenomena of Mg alloys, which is important and necessary. Therefore, in the present study, the corrosion resistance of Mg-Fe, Mg-Ni and Mg-Cu cast materials was evaluated using the surface potential difference (V_SPD) at the interface between the dispersoids and α-Mg matrix of each material. Salt water immersion test of the cast materials was also conducted to clarify the relationship between this factor and corrosion rate of initial galvanic corrosion phenomena. Organizational structure of dispersoids and potential gradient between the dispersoids and the matrix had little effect on the corrosion rate of Mg alloy. Corrosion rate increased with increasing both V_SPD at the interface and area fraction of the dispersoids in α-Mg matrix.

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Novel paint resistance and deposition models for numerical electrodeposition simulation are proposed. The paint resistance model considers the non-linear relationship between the film resistance and the paint thickness. The paint deposition model exactly takes account of the diffusive current which leads to the complex variation of the coulombic efficiency. Meanwhile, the Butler-Volmer equation is adopted as the polarization curve on the anodic and cathodic surface. A series of one-plate electrodeposition tests is performed to analyze the characteristics of the paint resistance and deposition behavior. The procedure for determining the parameters of the proposed models through the one-plate tests is also presented. The numerical simulation using the proposed models accurately reproduces the experimental results of the one-plate tests in comparison to the simulation using the conventional models. A series of 4-plate box electrodeposition tests is also performed; it reveals that additional improvements to the proposed models are necessary to simulate the deposition behavior under various stirring speeds.

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The authors investigate the overall structural balance of stiffness from the viewpoint of load transfer and load paths. The concept of load transfer balance is examined and graphically expressed using U^*. Index U^* is a new concept introduced by the authors to express load transfer in structures. The load transfer balance is calculated for an automotive body structure under conditions of vertical loading on the front suspension. The load transfer balance of a body affects the drivability of an automobile. Through the use of figures showing the U^* distribution along load transfer paths, the balance of load transfer is clearly expressed. From these figures, it is shown that frontal load is mainly transferred to the lower structure rather than to the upper structure in the vehicle body used in this study. Diagrams and histograms for U^*sum, which is the summation of two kinds of U^*s, are presented in this study to show the load transfer balance more precisely. These figures show that the transition of load transfer balance to the lower structure is caused by the stiffened support effect near the rear supporting points.

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Since the ductility of cast austenitic stainless steel pipes decreases due to thermal aging embrittlement after long term operation, not only plastic collapse failure but also unstable ductile crack propagation (elastic-plastic failure) should be taken into account for the structural integrity assessment of cracked pipes. In the fitness-for-service code of the Japan Society of Mechanical Engineers (JSME), Z-factor is used to incorporate the reduction in failure load due to elastic-plastic failure. However, the JSME code does not provide the Z-factor for axial cracks. In this study, Z-factor for axial cracks in aged cast austenitic stainless steel pipes was derived. Furthermore, an optimized failure assessment curve (FAC) for the two-parameter method, which can also derive elastic-plastic failure load, was obtained. Then, a comparison was made for the elastic-plastic failure load obtained from different analysis procedures. It was shown that the optimized FAC as well as the obtained Z-factor could derive reasonable elastic-plastic failure loads, although the failure loads were more conservative than those obtained by the two-parameter method using FAC obtained J-value solutions. The reference stress method was found to be applicable to evaluation of the FAC. It was concluded that elastic-plastic failure loads could be derived by the Z-factor and two-parameter methods in which FAC was obtained using J-value solutions, the optimized curve and the reference stress method.

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Nowadays, bend-insensitive silica optical fibers are innovating on optical fiber access networks and applications. However the radical decrease of the bending radius may cause delayed failure of the fibers when they are used in harsh environments, because the conventional theories to estimate the mechanical reliability of the bent portion are not applicable to such environments. Though one of the authors has driven an enhanced equation applicable to the fibers in high temperature and/or high humidity environments, the equation is not easy to evaluate because it requires numerical integration. We propose another simpler equation that we have driven from commonly-used conventional equations. Calculations for specific conditions were carried out using the parameters extracted from an empirical formula. It was found that the new equation can be much improved in precision by applying a correction coefficient to the proof test parameter in the equation. Accordingly, the reliability calculation can be easily carried out without numerical integration.

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This study examined the polymerization shrinkage of a light-cured composite resin in artificial cylindrical cavities. An analytical model was introduced to determine modulus E and displacement w of the resin as a function of the cavity depth. Shrinkage force P was expressed as the product of E and w. Analytical P values were then compared with the experimental data and following results were obtained: (1) The analytical P values can predict all the important features of the experimental data as a function of the cavity depth. (2) The shrinkage force was suggested to be dependent on the product of E and w. (3) The modulus and displacement of resin were also suggested to be expressed using the analytical model as a function of the cavity depth.

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