A large-scale database MSDRD on mechanical properties of structural materials such as metals, composites and ceramics were constructed by The Research Group for Statistical Aspects of Materials Strength. In the previous paper, fatigue data of structural steels in a wide range of strength level were analysed from a statistical view point and it was reported that distribution characteristics of the fatigue life were distinctly affected by the strength level. Thus, main target of this work was focused on fatigue data of high strength steels compiled in the above database and statistical fatigue properties were analysed in particular attention to the effect of heat treatment conditions. It was finally found that the distribution pattern of the fatigue life for high strength steels was classified into single-mode and mixed-mode Weibull distributions depending on the strength level governed by the tempering temperature.

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In order to investigate the effect of molecular on fatigue characteristics in ultra high molecular weight polyethylene (UHMWPE), tension-tension fatigue tests with notched specimen were carried out in the present study. The effects of frequency and stress ratio were also investigated and fractography was discussed. Fatigue strength is not increased with increasing molecular weight. Samples made from particles which have smallest diameter or narrow particle size distribution show improved fatigue strength. Fatigue strength might be influenced by its high degree of crystallinity in spite of decreased tie molecule density. There is almost no effect of frequency on number of cycles to failure. However, the higher the frequency, the higher the crack tip temperature. Heat and strain rate effects must be considered in high polymer materials. In high stress ratio, S-N curves shift to high cycle side. The fatigue life of UHMWPE is influenced by both stress amplitude and mean stress.

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The fatigue properties of socket-weld-jointed pipes have not yet been investigated in detail. The fatigue limit and failure mode of socket-weld-jointed pipe specimens were revealed in a previous study. To extrapolate the very long fatigue lives which cannot be obtained experimentally, we analyzed the fatigue lives of socket-weld-jointed pipes using fracture mechanics. The results obtained are summarized as follows. (1) In most weld joints, the slit was formed between pipe and socket, and behaved like a crack. The stress intensity factors (K) of these slit like cracks were analyzed using the FEM. This crack is subjected to mixed mode I-II loading. K_θ had a maximum value in a direction at an angle of about 65 degrees to the axial direction. (2) About half of the weld joints had weld defects 0.5∼1.5mm high. This crack is subjected almost to mode I loading. (3) The propagation path angles were predicted to be 65∼85 degrees using the maximum principal stress criterion. This value is in good agreement with the experimental results. (4) The fatigue crack propagation lives were calculated using the da/dN-ΔK relation. The S-N diagram theoretically was compared with the test results. They were in good agreement. (5) For pipe maintenance, a map that could be used to evaluate the fatigue life from the stress and weld defect size was constructed.

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In order to investigate the effect of artificial small defects on torsional fatigue strength of high strength steel, fatigue tests for a maraging steel (HV≅740) containing a small hole of diameter=100, 200, and 500μm were carried out. Torsional fatigue limit of the maraging steel was determined by the threshold condition of non-propagating cracks emanating either at the edge of hole or the smooth part of the specimens depending on the diameter of hole. The critical diameter of hole (d_c) which does not influence torsional fatigue strength for several materials is between 100μm and 200μm regardless of hardness. Prediction equation for bending fatigue limit (σ_ω) by the √(area) parameter model was extendedly applied to predict torsional fatigue limit (τ_ω) for both smooth and holed specimens. The fatigue limits predicted by these method were in good agreement with the experimental results.

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The fatigue characteristics of Ti-Ni SMA coil springs under cyclic thermal and extension fatigue were investigated. The crack growth behavior and the fracture aspect were observed at several strain levels at three heating temperatures (60, 70 and 80°C). The cracks initiated on the inside surface of the coil springs and propagated in a direction almost perpendicular to the direction of maximum principal strain near the crack origin. The relations between crack growth rate (da/dN) and stress intensity factor range (ΔK_σ) and strain intensity factor range (ΔK_c) were found to be almost linear in a bilogarithmic graph. In particular, the da/dN-(ΔK_c) relation in the case of a 60°C heating temperature was almost same as that in the case of an 80°C heating temperature.

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The stress-intensity factors of a mixed-mode interface crack were measured by a speckle photography. A compact normal and shear specimen with an interface crack was employed. This specimen enables us to carry out the experiment under various kinds of mixed-mode loading. A steel and an epoxy resin were used as the dissimilar materials. The displacement along the crack lines at the free surface was measured by the speckle photography. The K₁ and K₁₁ values were determined by a least squares method using displacement data along the crack lines. The three-dimensional finite element analysis was carried out on the same specimen. The complex stress-intensity factor K associated with an elastic interface crack was discussed from three different approaches : virtual crack extension method, modified crack closure integral and displacement extrapolation. An accuracy of stress intensity factors obtained by the speckle photography was discussed by comparison of results obtained by the finite element analysis.

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Three-dimensional finite element analysis has been carried out on the compact normal and shear (CNS) specimens under mixed-mode loading. The complex stress-intensity factor K associated with an elastic interface crack is discussed by the virtual crack extension method. The effect of Young's modulus and Poisson's ratio on stress intensity factors is discussed under various kinds of mixedmode loading. The distribution of stress intensity factors along the crack front is investigated. A polynomial fitting is proposed to evaluate the stress-intensity factors at the midsection of CNS specimen with an interface crack subject to mixed-mode loading. It is possible to evaluate the stress intensity factors of CNS specimen with high accuracy by the present polynomial evaluation.

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The plane problem of an elastic elliptic inclusion containing a crack is solved. The problems are formulated in terms of system of singular integral equations on the basis of the body force method. In the numerical analysis, a fundamental solution for a point force acting at a point in an infinite plate containing the elliptic inclusion is used. Based on numerical results, the effect of the inclusion on the stress intensity factors of the crack is invenstigated.

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Molecular dynamics is applicable for only a small region of simulation. To simulate a large region, it is necessary to combine molecular dynamics with continuum mechanics. In the first report, we proposed a new model in which molecular dynamics was combined with micromechanics. Namely, we applied a molecular dynamics model to the crack tip region and a micromechanics model to the surrounding region, respectively. In this model, however, crack propagation simulation must be stopped when the crack tip reaches to the boundary of the two regions after the crack propagation. Therefore, in this paper, we improve the previous model by allowing the movement of the molecular dynamics region. Theoretically, the process of the crack propagation can be simulated endlessly with this advanced model. In order to examine the validity of the advanced model, we use α-iron in simulation. It is found that the result based on this advanced model is equal to the result with the previous model. Moreover, the result is almost equal to the Rice's solution.

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The characteristics concerning bones are poor with increasing the requirement for biomaterials, for example, artificial bones. There is, in particular, still very little knowledge about fracture toughness of bone. There is also still very little knowledge about the effect of microstructure on fracture toughness of bone. The effect of microstructure on fracture characteristics of compact bone of bovine was investigated with the cooperation of fractography in present study. The effect of anisotropy and moisture on both static and dynamic fracture toughness, K_Q and K_d was investigated. The static fracture toughness, K_Q is 1.5 times greater than the dynamic fracture toughness, K_d. Moisture and anisotropy influence the fracture toughness of bone. Fracture surface of wet sample is found to be more uneven than that of dry sample by fractgrapy on fracture toughness tested samples. The effect of moisture on crack propagation is confirmed by the observation of osteons. The osteons are sheared in zig-zag manner by the longitudinal load on wet sample while the crack propagates with shearing osteons in dry sample.

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To develop the fracture mechanics of ceramics, two types of cohesive crack models are investigated. Type A is a model which treats the bridging zone as a fictitious crack with cohesive stress distribution in which the crack develops when the crack tip stress intensity factor K_tip reaches K_up.c. Type B is a model which treats the whole fracture process zone as a fictitious crack with cohesive stress distribution. In contrast to type A. cohesive stress is distributed such that K_tip=0 and the crack will develop when the stress at the crack tip reaches σ_c. Numerical investigations for sample problems reveal that though both types of models are reasonable as mathematical models, it is difficult to determine the values of the parameters of the distribution function of cohesive stress for the type B model.

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The silicidation-induced stress that arises during Ni-silicide formation is discussed experimentally. The Ni-silicide films are formed by annealing of Ni films deposited on Si substrates. For this study, the silicidation process was observed using a scanning electron microscope, and film stress was determined by detecting curvature of the substrate surface. The residual stress in the films at room temperature increased after silicide formation, which occurs at high temperatures (above 300°C). The stress-increase process is discussed based on measurments both the changes in residual stress at a temperature of interest and thermal stress of Ni, Ni₂Si, and NiSi films. Silicidation-induced stress is defined as the discrepancy between the residual stress measured at a temperature of interest and the thermal stress predicted without silicidation. The silicidation-induced stresses in our experiments were determined to be about 340 MPa (Ni→Ni₂Si) and about 400 MPa (Ni₂Si→NiSi).

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A numerical study is made of the dynamic thermal stresses in a ceramic metal Functionally Graded Material (FGM) subjected to impulsive electromagnetic radiation. The radiation absorption is assumed to maintain a constant energy flux throughout the pulse duration, and to diminish exponentially with depth. Since the wave travel time is small compared with the time necessary to reach thermal equilibrium. the thermal diffusion term is ignored in the transient heat conduction equation. In treating problems, the material properties of FGM are assumed to be temperaturedependent. In this paper, a set of unified equations is presented, which is applicable to the propagation of plane, cylindrical and spherical waves in clastic media. The characteristic equations are then derived and the numerical procedures involving stepwise integration along the characteristics are established. Numerical calculations are carried out for various FGM plates, and the significance of the temperature-dependent material properties and the effects of composition distribution of the FGM on the magnitude of the dynamic thermal stresses are discussed.

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An experimental and analytical studies of thermal stress of thermally sprayed coating of 80Ni20Cr/SUS304 cylindrical member were performed to investigate a control method of residual stress of coating after thermal spraying. Temperature measurement during processes of thermal spraying, heating-up and cold thermal shock were made. Using these measured results, thermal stress analysis were carried out by FEM and a proposed simplified method. Thermal stress of coating obtained by FEM was compared with one by the simplified method and good agreement was obtained between them. Moreover, residual stress of coating after thermal spraying was measured by X-ray diffraction method and compared with estimated results. As a result, good agreement was obtained. Based on the simplified method, a control method of residual stress of coating after thermal spraying was proposed. According to this control method, compressive residual stress can be expected by controlling temperature of substrate properly in spite of relation of magnitude of thermal expansion coefficient of coating and that of substrate.

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A precise method for estimating the axial stress is proposed for a short and highly stressed bolts used for automobile. These bolts show non-linear extension for axial stress, because of local plastic deformation as well as non-uniform stress distribution in bolt cross section. The proposed method consists of (a) precise measurement of the time-of-flight of ultrasonic waves using a digital pulseecho technique, (b) construction of the calibration curves which take into account of non-linear extension due to non uniform stress distribution by simultaneous measurement of the axial elongation, time-of-flight of longitudinal and transverse waves and (c) estimating method of axial stress using the change in the time-of-flight and the assumed length of equally stressed parts. The axial stress is estimated within 1% error for one type bolts and within 2% error for another type bolts.

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A Non-destructive method is proposed for estimating residual stress distributions in a component due to shot peening. The method involves measuring the inherent strain distribution in a small plate, made of the same material and peened under the same shot peening conditions as the component, by layer removal technique. The residual stresses in the component are estimated from the measured inherent strain in the plate. An experiment was carried out to estimate axisymmetric residual stresses in a shot peened shaft. The results measured directly from the shaft show a good agreement with the results predicted by the proposed method.

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Thermal fatigue characteristics of die steel for hot working SKD 61 and improved SKD 61 were investigated. The cylindrical test bars with U-notch were directly immersed into Al-alloy melt kept at 923K, and then cooled quickly to water. The investigation led to the following conclusions : 1) The number of heat cracks of the improved SKD 61 was fewer than that of SKD 61. It was especially pronounced in the hardness of HRC 45 or more. 2) The heat crack length of SKD 61 and the improved SKD 61 became small as the hardness increased. The minimum value of heat crack length was obtained the specimen with HRC 50. The total length of heat cracks of the improved SKD 61 became about 1/4 that of SKD 61. The maximum length of it became about 2/5 of SKD 61. 3) The heat crack resistance of the improved SKD 61 is superior to the resistance of SKD 61, because the tensile strength of the improved SKD 61 is higher than that of SKD 61 over the whole testing temperature.

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This paper proposes one of automatic mesh generation method in preprocessing of a FEM by using an agent. In this paper, the 'agent' is defined as a kind of A-life (Artificial Life) system and it has three kinds of functions, 'split', 'deform' and 'mutate' (swap for diagonals). When FEM users give a number of mesh division, the agent repeatedly divides analytical region by using the function of 'split' and it changes the elements in the region to ideal shapes and areas by using other two functions. After this method is applied to a trapezoid model and it's effectiveness is confirmed, several kinds models (a square and a hexagonal array models of microscopic composite material and a mode 1 model in fracture mechanics) are automatically divided to the fine shapes nearly equaled an equilateral triangle. These examples consequently show that the proposed automatic mesh generation method by using the agent is a quite useful and a suitable for FEM analyses.

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To date, analytical study has not been conducted on the growth of grain boundary cavity under lattice diffusion creep, though the growth behavior has been intensely analyzed for grain boundary diffusion creep. In this study, the growth of periodic cavities along a grain boundary is numerically simulated by obtaining a finite element solution of the Laplace equation which governs the atom flux in the grains under lattice diffusion creep. It is found that the chemical potential on the cavity surface is higher than that in the grain boundary ahead of the cavity tip. This implies that the cavity growth is stable and it maintains quasi-equilibrium shape due to the efflux of atoms from the cavity surface to the grain boundary due to the lattice diffusion. The growth rate of the cavity diameter decelerates as the cavity grows in the early stage of a/W <0.3 (a : cavity half lengtn. W : half distance between adjacent cavities) ; it is almost constant in the middle stage of 0.3<a/W<0.6, and accelerates in 0.6<a/W.

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A unified constitutive model considering dynamic strain aging effect was developed in order to describe inelastic deformation behavior of the Modfied 9Cr-1Mo steel precisely. The inelastic behavior of the steel was summarized as follows. A rate dependent deformation was observed above 500°C, and there was no rate dependency under 400°C. However, stress relaxation behavior was observed even at rate independent temperature region. Further, a stress after relaxation depended on prior loading strain rate, and it showed a higher value as the strain rate was slow. A feature of the proposed constitutive model was that an applied stress consists of three stress components : a back stress, an overstress and an aging stress which corresponds to dynamic strain aging and shows a negative strain rate dependency. The aging stress was measured by strain rate change tests, and it showed larger values as the strain rates were slow and the temperatures were low. The backstress and the overstress were measured by strain dip tests. The backstress was approximately rate independent under 400°C, however it showed rate dependency above 500°C. The overstress showed larger values as the strain rates were fast and the temperatures were high. The material constants were determined systematically based on the measured values of each internal variable. In order to evaluate the validity of the constitutive model. numerical simulations were done for various inelastic deformation behavior of Mod. 9Cr-1Mo steel. The simulations agreed with experimental results very well in all cases.

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The fabrication conditions and the effect of heat treatment on the mechanical properties of sintered structural alloy steel compacts made by metal injection molding were studied. Specimens were made of gas-atomized SNCM439 steel powder, which was blended with a polyamide binder system. The compacts were debound in air at various temperatures between 513K and 553K and sintered in vacuum at 1623K for 7.2ks. The specimens were tempered at various temperatures between 373K and 873K after oilquenching from 1073K. The carbon control of sintered compacts decreased linearly with increasing in debinding terperature. This means that the carbon content of sintered compacts can be controlled accurately by the debinding terperature. The higher the debinding terperature was, the lower the tensile strength of sintered compacts and the higher the elongation became. The tensile strength of the heat-treated compacts decreased with increasing in tempering temperature, on the other hand, the elongation increased. Though the tensile strength of the heat-treated compacts was equivalent to that of the JIS SNCM439 steel, the elongation and the Charpy impact value were smaller because of the presence of small pores. Improving the density of the sintered compacts is considered to be efficient to get more ductility in the heat-treated compacts.

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The speckle intensity distributions of a laser beam reflected from a surface of a polycrystalline aluminum specimen were changed due to the plastic deformation of the specimen and were measured using the image processing technique. The cross section of the laser speckle pattern on a same gray level could be expressed quantitatively by an elliptic function ; the correlation between an aspect ratio of the ellipsoidal shape and the growth of anisotropy induced by the plastic deformation, the onset of yielding and localized deformation was studied in the preceding paper. In this paper, the effects of the grain size and the rolling reduction of an aluminum specimen upon both the reflected speckle intensity distribution of the laser beam from the surface of the specimen and the optical surface image obtained by the optical microscope under the plastic deformation were studied through the fractal dimensional analysis. The results obtained are summarized as follows ; (1) The speckle intensity distribution expanded with increase of plastic strain ; the degree of the expansion was increased with the growth of the grain size of specimen, while the change of aspect ratio was very small. (2) At the initial stage of the plastic deformation, the aspect ratio of rolled specimen rapidly decreased, and the change of the aspect ratio was dependent upon the rolling reduction of the specimen. (3) The good correlation between the plastic strain and the fractal dimension of the speckle intensity distribution due to the surface roughening of the specimen was obtained.

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Ti-N thin films were formed on unheated Si (100) substrate with evaporation of Ti by electron beam and simultaneous bombardment of N ion beam in the range of 1∼40 keV. The influence of N ion acceleration energies and the content ratios (N/Ti) on microstructrues and phases was investigated by x-ray diffraction (XRD), Auger electron spectroscopy (AES) and transmission electron microscopy (TEM). The XRD spectra revealed the formation regions of the single phases and the mixture phases for α-Ti, the stoichometric compounds TiN and Ti₂N at the various ion acceleration energies. The mechanical properties such as hardness, elastic modulus, adhesive strength and friction coefficient were also investigated. Nano-indentation studies showed that the hardness and the elastic moduli for each phase increased with increasing mixing layer thickness related to the ion acceleration energy. The single phase TiN and Ti₂N films prepared at higher ion energy showed the excellent mechanical properties in the hardness and adhesive strength. Relationship between other mechanical properties of the obtained films and their phases also discussed.

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This paper deals with an interaction problem of arbitrarily distributed elliptical inclusions under longitudinal shear loading. The problem is formulated as a system of singular integral equations with Cauchy-type or logarithmic-type singularities, where unknown functions are the densities of body forces distributed in the longitudinal directions of infinite bodies having the same elastic constants as those of the matrix and the inclusions. In order to satisfy the boundary conditions along the inclusions, four kinds of new fundamental density functions are applied. Then the body force densities are approximated by a linear combination of the fundamental density functions and polynomials. The calculations are carried out for several arrangement of the inclusions, and it is found that the present method yields rapidly converging numerical results for arbitrarily distributed elliptical inclusions.

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An elastic analysis of stress and deformation was attempted for anisotropic rectangular plates of the single-wall corrugated fiberboard (SWCF) supported by four edges under uniform loading. Stresses distirbution for square and rectanglar plates are discussed by this analysis. Results obtained are as follows. The deflection increases monotonically from zero at plate edges to maximum at the center. Support forces of edges increase from zero at those corners to maximum at those centers. The normal stress in the cross direction (CD) on surfaces of the kraftliner (KL) increases monotonically from zero at edges to maximum at the center. The normal stress in the machine direction (MD) on KL surfaces is symmetical at two maximum points along the MD center line of the plate. The shear stress of KL surfaces distributes antisymmetically, and becomes maximum at four coners and becomes zero on center lines of CD and MD.

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Deformation and stress of a thick cylinder are analyzed by use of only a two-dimensional theory, not a three-dimensional one. Most thick cylinders actually used, for example, tubes in heat exchangers, are partially subjected to internal pressure in the longitudinal direction in the manufacturing stage, but no practical and applicable methods in which elastic-plastic deformation and yield strength of a thick cylinder are dealt with easily in three dimensions have been developed from the viewpoint of field application. In this work an applicable method based on thin cylinder theory and experimental results is proposed. This method yields results which are consistent with the behavior of thick cylinders, and enables one-step elastic-plastic analysis of double thick cylinders, for example, expanding tubes in heat exchangers.

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In the previous paper or elastic-plastic analysis with experimental results for thick cylinder partially subjected to internal pressure in longitudinal direction, it was shown that the deformation, stress and yield strength of thick cylinders partially subjected to internal pressure can be analyzed by a method based on thin cylinder theory determined and experimental results. In this work. the method is developed for application to analysis of tube expansion mechanisms using double thick cylinder theory and a theory of extended deformation of a tube due to pressure application from both sides. The numerical solutions obtained by this method agree well with the experimental results for double thick cylinders, and this method makes it possible to analyze mechanisms of tube expansion in heat exchangers and elsewhere.

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This paper presents the closed-form solutions of a two-dimensional isotropic elastic medium (matrix) containing different isotropic elastic nonconcentric circular inclusions under uniform out-of-plane shear stresses at infinity as well as a point force or screw dislocation at a finite point. This analysis is based on the complex variable method using the Mobius transformation. Using these solutions, several numerical examples are shown by graphical representation.

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A new simple method for identifying the parameters in the constitutive equation for an elastic/visco-plastic material is proposed. In the proposed method, the time-histories of the input and output stresses in the split Hopkinson's bar test are measured, and a finite element calculation is performed using the measured time history of the input stress. The identification employing the Kalman filter is carried out by comparing the calculated results with the measured time history of the output stress. To demonstrate the usefulness of the proposed method, a split Hopkinson's bar test is performed using copper specimens, and two parameters characterizing the visco-plasticity are identified.

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The homogenization method has been known as a powerful tool to investigate the macroscopic material properties of composite materials, whose microstructures are periodic. This methodology can also be considered to be an advanced version of unit cell approach. However, the assumption of periodic structure becomes somewhat suspicious after the material has undergone a large deformation, because each unit cell also deforms finitely. In the context of homogenization method presented by Guedes and Kikuchi, the periodicity condition has to be satisfied rigorously. In this paper, a formulation which can rigorously satisfy the condition of periodicity even after the microstructure has undergone a finite deformation, is presented. It is accomplished by referring the initial undeformed configuration of microstructure, when we define the periodicity condition. Some simple numerical results of two-dimensional finite strain elasto-plastic problem are also presented and discussed. The outcome of the present research may find some application in analyzing Metal Matrix Composite Materials.

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An efficient inversion technique to determine elstic constants of anisotropic solids from the leaky surface acoustic wave (LSAW) is presented. In the present inversion two types of LSAW velocities, the leaky Rayleigh mode and the pseudo-leaky Rayleigh mode, have been used as knewn parameters, Both the velocities in specified directions on the solid surface can be obtained from either the phase change or the amplitude change of the ultrasonic reflection coefficient of the surface. The elastic constants are determined from the directional variations of both the LSAW velocities using an optimization procedure. Based on the investigations of the stability and accuracy of the solution in inverse problems defined on a cubic crystal, it has been shown that the use of dual mode LSAWs enables us to make better elastic constants determination with a high precision than the use of a single mode LSAW. In addition, it has been confirmed that, by performing a series of numerical simulations using a synthetic data and an experiment, all the elastic constants of the crystal can be determined accurately by the present inversion with the knowledge of the crystallographic orientation and the density.

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Some analyses of cylindrically anisotropic elastic composites with or without circular hole have been given for the cases of in-plane loading at infinity. This paper presents the closed-form solutions of stress and displacement for cylindrically anisotropic elastic composites with shear sliding and/or normal disbonding boundaries of the interfaces under axial force, twisting moment and pure bending moments as well as hygrothermal loads. Several numerical results are shown by graphical representation.

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The exact transient closed-form solutions for suddenly applied force or dislocation (displacement-jump), such as a crack or fault which travels at a constant velocity and a constant depth below the surface of an elastic half plane, are obtained in this study. The numerical results are shown for the various cases as follows. In the case of vertical downward line load, the retrograde particle rotation exists at the arrived point of Rayleigh wave, but in the case of upward vertical load, the direction of the rotation coincides with wave propagational direction. In the supersonic case, responses of the surface became in the opposite direction compared with subsonic case, and in inverse relation to moving velocity. In addition to these, the stress near the tip of moving dislocation, the response to both side extensional dislocation etc. are shown graphically.

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In the present paper, the order of stress singularity at the corner where four free surfaces and interface in the three-dimensional joints meet are investigated by solving an eigen equation derived from a finite element formulation. The order of stress singularity for three typical joints, refered to as 1/8-1/8 joint, 1/8-1/4 one and 1/8-1/2 one, consisted of two rectanglar blocks with different properties is investigated and compared with that for two-dimensional joints with the same cross section of three-dimensional joints. Dundurs'composite parameters, α_3D, and β_3D, for three-dimensional joints are newly intoduced and the order of stress singularity plotted on the ordinal Dundurs' parameters, α and β plane, is rearranged on α_3D-β_3D plane. The order of stress singularity at the vertex in the three-dimensional joints is larger than that in the two-dimensional ones, although, the bound vanishing the stress singularity little varies on the α_3D-β_3D plane. Furthermore, it was shown that the order of stress singularity at a vertex gathering some singular lines with different orders varies depending on a combination of material properties.

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A page-turning mechanism is used in Automated Teller Machines (ATM) to turn to a new page in a passbook to print. Conventionally, there are a friction roller and a pressing means in the mechanism in order to control the force used to turn over a page. A new page-turning mechanism and a simulator were developed to be both reliable and inexpensive. The present paper describes a page-turning simulator developed to treat a geometrically nonlinear deformation and contact problem. The simulator consisted of two parts : a geometrically nonlinear deformation program based on the updated Lagrangian approach, and a contact program based on a penalty method. Numerical studies for a new page turning mechanism were done a characteristics of a new friction roller, a page-turning simulation and an effect of initial imperfection for a page-turning mechanism.

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The friction welding for copper and aluminium is useful to minimize the diffusion thickness at the interface between copper and aluminium. The minimization of diffusion thickness is required for maintaining the joint strength. Because brittle intermetallic compounds are formed at the weld interface between copper and aluminium. These reaction diffusion behaviors at the interface between copper and aluminium, which have an important effect on weld joint degradation, have not fully been clarified. And, it is needed to evaluate the growth of intermetallic compounds for optimizing the joint strength. The experimental results showed that the reaction diffusion layers consisted of CuAl₂, CuAl and Cu₉Al₄. It is also confirmed that the each diffusion thickness can be observed the parabolic time dependence and Arrhenius type temperature dependence. And the order of reaction diffusion rate was CuAl₂>CuAl>Cu₉Al₄. A computer-aided interactive system has been developed, which enables to conveniently analyze the reaction diffusion behaviors and some problems were analyzed.

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An investigation is performed on the interfacial control of Glass/Polypropylene composites using polypropylene (PP) sheet treated by oxygen plasma. All T-peel tests for each treated specimen are carried out using an Autograph materials testing machine in order to estimate the strength of the interlaminar between the glass fabric and the PP resin. To determine the factors for controlling interfacial bond properties and delamination processes from the test results, two parameters were used, i. e. T-peel strength : calculated from tensile peaks in tension-displacement diagrams and T-peel amplitude : calculated from tensile alternations in it. The present plasma treatment increases the T-peel strength and amplitude about 50% and 120% higher than non-treated spacimens, respectively. These results that the properties of the interface between the fiber and the resin were effectively improved by this process. It was found that the T-peel strength was related to the surface energy of the PP sheet, which was calculated from the contact angle of distilled water. The T-peel amplitude was related to the fracture morphologies of the delamination surface.

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In recent years, interlaminar-toughened laminates are developed in which resin rich layers are placed in interlaminar regions in order to enhance the interlaminar fracture toughness of CFRP laminates. Tensile tests are conducted on CFRP cross-ply laminates with interlaminar resion layer at 0/90 interfaces. Transverse crack density is measured as a function of the laminate strain. To investigate temperature effect. tests are conducted at room temperature and 80°C. Laminate configurations are cross-ply (0/A/90_m/A/0) where A denotes interlaminar resin layer and m=4.8 and 12. The experimental results are compared with the theoretical prediction based on the two-dimensional analysis considering the interlaminar resin layers and thermal residual stresses. The validity of the energy criterion and strength criterion is discussed.

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A genetic algorithm is used to obtain the stacking sequence of the laminate that has the set of lamination parameters that are the closest to a set of target lamination parameters. In addition, the laminate is required to be balanced and to have no more than 4 contiguous plies of the same orientation in order to satisfy practical considerations. This problem is a constrained combinatorial optimization problem which is usually difficult to solve. The difficulty of enforcing constraints in genetic optimization is handled by introducing a new repair strategy. The new repair strategy does not alter genes but only changes decoding rules, and is similar in this respect to the way recessive genes operate in biology. The relationship between the reliability of the genetic algorithm and the probability of repair was investigated, and it is shown that 100% probability of repair is optimal when the target laminates include 45°plies, Since practical composite laminates usually include 45°plies, it is concluded that the repair strategy discussed herein should always be used with the optimization.

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The shear buckling analysis on laminated composite plates considering the out-plane shear deformation is presented using the pb-2 Ritz functions which consist of the product of a basic function and a two dimensional polynomial function. It is shown that the convergence of solutions for the buckling load of laminated composite plates is good as the number of polynomials is more than 30. Numerical results under shear load are obtained for cross-ply and angle-ply laminated composite plates, and the difference between the buckling factors in positive and negative shear load are discussed. The effects of material properties, plate aspect ratio, number of layers and lamination angle on buckling factors are investigated under simple supported and clamped edges. It is shown that the presented method considering the out of plane shear deformation can be widely used to analyze buckling behavior of composite plates with general boundary conditions.

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A double cleavage drilled compression (DCDC) specimen with fiber/matrix interface has been proposed and analyzed in mixed-mode using the boundary element method (BEM). At the same time, the experiments on this DCDC specimen were conducted for CFRP composites in order to examine the crack propagating behavior and calculate the interfacial fracture energy at the fiber/matrix interface. It was confirmed that the DCDC specimen with the hole offset from the mid plane has a mixed-mode stress distribution, and the effect of the mode II on interfacial fracture energy increases with the offset value. The DCDC specimen in mode I with bridge fiber at the mid plane is also analyzed. It is found that the transition from the mode I to the mixed-mode occurs when the bridge fiber with angle to the mid plane exists. It was shown that the DCDC test is a useful method for evaluating the interfacial behavior of fiber reinforced plastic materials. However, both experimental and analytical approaches are needed to achicve a quantitative evaluation of the fiber/matrix interface.

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The hardness of cementite spheroidized S 25 C steel was measured, using an AFM ultramicro hardness tester and a special lever that has a three-sided pyramidal diamond indenter with an apical angle of 60°. A clear AFM image of the specimen surface etched in a solution of 3% nitric acid and 97% alcohol enabled us to distinguish small cementite particles with a diameter of less than 1μm. Using AFM imaging, we obtained force-penetration curves for small cementite particles as well as the ferrite portion of S 25 C steel. The curves show yield behavior. Below the yield force where the penetration depth was less than 30 nm, the experimental curve agrees well with the theoretical one. The normalized yield stress, τ_y/G, is 0.46 for cementite particles and 0.24 for the ferrite portion. These values are nearly equal to those for glass and silicon, and for SNCM 439 steel, respectively. It is concluded that the hardness measurement of the materials containing small particles was realized in the nanoscopic region, using the AFM ultramicro hardness tester with a special lever having a three sided pyramidal diamond indenter with an apical angle of 60°.

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