The existing one-dimensional constitutive model for shape memory alloys is extended to take into account the porosity and the strain rate effect by using the internal state variables representing the porosity and the martensite volume fraction. The proposed constitutive equation is applied to the simulations for the quasi-static and the dynamic behaviors of dense and porous shape memory alloys at various temperatures and strain rates. The calculated results are compared with the uniaxial test results for dense and porous NiTi alloys to illustrate the validity of the present constitutive modeling. It is expected that the finite element program implementing the proposed constitutive equation will be a powerful tool to predict the mechanical behaviors of various porous shape memory alloy devices.

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In recent years, composite materials including synthetic resins are widely used as structural materials for plates. For such structures, large-deflection is often allowed, so that large deformation analysis becomes necessary. To such an end, von Kármán large-deflection theory of plate bending has been mainly used. This theory is, however, based on essentially the same assumptions as those of classical Lagrange's thin plate theory for infinitesimal deformation, except that the magnitude of the deflection is permitted up to the order of the plate thickness. Thus the applicability of such a theory may be doubtful for thick plate. In this paper, we examine the applicability of the above theory to uniformly loaded clamped circular plates with various different thickness by comparing with appropriate numerical solutions. The numerical method enployed here is a three-dimensional finite element method based on the incremental finite-deformation theory formulated in convected coordinates. From the obtained numerical results, the applicability of the considered theory is confirmed if the magnitude of maximum deflection is within 4 times the plate thickness.

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In this paper, a mixed mode interfacial crack in three dimensional bimaterials is analyzed by singular integral equations on the basis of the body force method. In the numerical analysis, unknown body force densities are approximated by the products of the fundamental density functions and power series, where the fundamental density functions are chosen to express a two-dimensional interface crack exactly. The results show that the present method yields smooth variations of mixed mode stress intensity factors of a rectangular interface crack along the crack front accurately. The effect of crack shape on the stress intensity factor for 3D interface cracks is also discussed on the basis of present solution. Then, it is found that the stress intensity factors Ki and Km are always insensitive to the shear modulus ratio, and almost determined by Poisson's ratio alone. Distributions of stress intensity factors are indicated in tables and figures with varying the rectangular shape and Poisson's ratio.

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In this paper, a viscoelastic measuring method at a high frequency range for rubber compounds was proposed by using ultrasonic waves. Viscoelastic properties estimated by the present method were compared with those measured by the conventional dynamic viscoelastic method in conjunction with the frequency-temperature transformation principal for several rubber compounds containing either carbon black or silica particles. An appreciable difference can be identified between two methods. The reason for the discrepancy between these two methods was deduced due to the amplitude dependence of rubbers containing micro particles such as carbon black and silica. Furthermore, it is indicated that the maximum friction coefficient (Max-μ) of rubber compounds at wet condition could be estimated correctly by measuring tan δ of ultrasonic waves. Thus, it is shown that the ultrasonic viscoelasticity is beneficial one for estimating frictional characteristics and clarifying the mechanical behaviour of rubber compounds at a high frequency range.

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Composite materials combining peanut hull powder and poly lactic acid (PLA) resin were prepared by a compression molding method. The density, water absorption properties and bending properties of these composite materials were evaluated. The density of the composite materials was lower than the theoretical denity, which was calculated by using peanut hull density and PLA resin density, because of many cavities in peanut hull. The critical water absorption ratio and mass diffusivity increased with the increase in weight content of peanut hull. Especially, the critical water absorption ratio and mass diffusivity of the composite material with 75% weight peanut hull content were about 15 times and 2.4 times higher than those of PLA resin respectively. As a result of 3-point bending tests, the bending modulus of the composite materials improved as increasing in weight content of peanut hull up to 50%. At peanut hull weight content more than 25%, the bending strength decreased with an increase in weight content because of many cavities and the poor fiber/resin interfacial bonding. Furthermore, the cost performance of composite materials based on flexural rigidity, material cost and thickness was discussed.

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In order to establish an appropriate method for measuring the local hydrogen content distribution around a fatigue crack tip in austenitic stainless steels, secondary ion mass spectrometry (SIMS) and the hydrogen micro-print technique (HMPT) were applied to a fatigue crack in a type 304 stainless steel tested in a hydrogen gas environment. The main results obtained in this study are as follows. In the SIMS method, there is a measurement error based on the edge effect regarding hydrogen in water vapor on the fatigue crack surface, though it is visualized that a high content of hydrogen exists in the plastic zone at a fatigue crack tip propagated in hydrogen, compared to that on a smooth area fatigued in hydrogen. On the other hand, this hydrogen in the plastic zone is difficult to detect with HMPT. In this case, this is attributed to the difficulty for hydrogen atoms to be emitted from the sample. To detect the hydrogen, it is necessary to sputter atoms forcibly. In addition, it is understood that to analyze the local hydrogen distribution around a fatigue crack tip with SIMS not only qualitatively but also quantitatively, reduction of the error based on the edge effect is necessary.

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The fatigue behaviour of prestrained type 316 austenitic stainless steel has been studied. Two types of fatigue tests, conventional S-N tests in laboratory air and in 3%NaCl solution and stress-incremental tests, were performed. Tensile prestrains evaluated are 5%, 15%, 25% and 58%. In laboratory air, fatigue strength increased with increasing prestrain, which was attributed to both work hardening and strain-induced martensitic transformation. In 3%NaCl solution, the fatigue strengths for all specimens decreased compared with those in laboratory air and fatigue strength increased with increasing prestrain up to 15%, but above that prestrain, it decreased significantly. Corrosion pit generation and growth in transformed martensite phase were believed to be primarily responsible for the observed behaviour. Based on stress-incremental test results, the coaxing effect became less pronounced with increasing prestrain, disappeared at 15% and then again appeared at the larger prestrains of 25% and 58%. The observed prestrain dependence in corrosion fatigue behaviour and coaxing effect clearly indicated that different mechanisms had operated below and above the prestrain of approximately 15%. Possible mechanisms such as work hardening and strain-induced martensitic transformation were discussed.

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In recent years, with the background of weight saving and downsizing in machines and devices, it is important subject to downscale mechanical parts which are contained in them. So in this study, in order to achieve power transmission parts like a compact gearwheel which indicates high performance properties, hybrid surface modification was performed by combining Super Rapid Induction Heating and Quenching (SRIQ) which creates high fatigue strength and Diamond Like Carbon (DLC) coating which are well known for their high hardness, low friction and excellent wear resistance. And, in order to prevent the base material from decreasing its fatigue strength, DLC was coated by using Unbalanced Magnetron Sputtering (UBMS) method which can coat at low temperature. Rotational bending fatigue tests and friction-wear tests were carried out. It was clear that it is possible to keep high fatigue strength and to create excellent tribological properties at specimen surface by performed hybrid surface modification. Furthermore, it is possible to prevent increase in handling process because tempering process after quenching can be performed by heat process during DLC coating process.

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Thermal fatigue crack extension test had been conducted on cylindrical specimens of rotor casing material. Each specimen was initially notched circumferentially either circularly or half-elliptically along the inside surface, and subject repeatedly to thermal stress caused by sudden water-cooling on its inner surface after electric furnace heating. Test results show that the crack depth extension rate was decreased for larger notch depth and the specimens with circular notch show larger crack extension than those with half elliptical notch. Transient thermal and stress state of the specimen was analyzed by axi-symmetric FEM, and the numerical stress distribution was used to calculate the stress intensity factor and to perform crack extension analysis. For small circular notch, the elasto-plastic FEM analysis resulted better agreement with the experimental crack depth extension and Meshii's elastic method showed conservative estimation. For the half-elliptical notch, CRIEPI's influential function method showed good correlation with experimental results.

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This paper presents the numerical analysis of dynamic thermal stresses by the extended distinct element method (EDEM), which is a kind of the meshless methods. The new technique which radii of the elements of the EDEM are changed with the temperature of each element is proposed. The temperature of the element is calculated on the basis of the heat conduction between elements. By the comparison between the analytical result of Sternberg and Chakravorty and the numerical result obtained by the proposed method, it was confirmed that the method was effective for the dynamic thermal stress analysis. Numerical examples were also presented for the cases of a non-homogeneous plate subjected to the surface heating and a glass block with an initial crack subjected to the surface heating. From these numerical results, it was found that the method based on the EDEM is an efficient tool for analysis of dynamic thermal stresses.

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The report with which the form factor like axis compressive collapse and the factor analysis of the high strength steel of the lightening means are combined is not so seen for compressive collapse of the dynamic bend material. It aimed at the design manual making to be simply predictable of dynamic bend collapse load of the collision structure material from the structural design size and the material characteristic using the steel lamina hat material of a dynamic bend, and then, dynamic bend collapse load was defined from the dynamic bend examination and collision CAE analysis, and the adjustment examination of analytical accuracy was done in the first report of this text in this research. The main results obtained in this study are summalized as follows (1) An analytical condition that the correlation of the experiment value and collision CAE analysis result was able to be taken can have been done. (2) When the high-speed collision bend is examined, it is near the performance value that we request, and the difference influence of the experiment etc. of the load value arranged by the Energy Absorption (EA) conversion than the fulcrum reaction force is less. (3) When the high-speed collision bend by this research is examined, the influence of the material span is not seen. (4) The collapse load value calculated from fully plastic moment method, the experiment, and the analysis becomes the value of about 1/2 from fully plastic moment method.

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The effect of material thickness on plastic buckling behavior of thin-walled polygonal shell members was studied by numerical analysis. Moreover, the interaction between the thickness and the cross sectional shape on plastic buckling behavior of the members were clarified to establish a novel design scheme for the energy absorbing members of automobiles. FEM results showed that plastic buckling behavior was influenced by the interaction between the thickness and the width of planar regions of cross section, where the buckling load became larger as the thickness ratio of plane region decreased. On the other hand, the interaction between the thickness and the sectional area of ridgeline affected the stability of plastic buckling behavior, where the load became smaller in the case of the cross sectional area of ridgeline was not large enough. A novel design scheme controlling the plastic buckling behavior of thin-walled polygonal shell members was established to ensure high impact energy absorption on the basis of the above outcome. In addition, the validity of the design scheme was demonstrated through a practical design example of automobile parts.

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