A fundamental research has been performed for the evaluation of plastic deformation behavior of single crystal aluminum, with the interest mainly in the crystal rotation induced by the plastic deformation. To take into consideration the influence of dislocation density on hardening evolution, a dislocation density tensor, based on plastic deformation gradient, has been introduced into our elasto/crystalline viscoplastic FE code. FE analyses of uniaxial tension and the in-situ crystal orientation measurement by EBSD were executed as a means of verification. It has been found out by FE analyses and corresponding experiments that the larger the dislocation density, the smaller the hardening rate in the large elastic strain region. The numerical results on the rotations of orientation are shown to be in a fairly good agreement with the experimental results. It is shown that our FE code is effective for the prediction of mechanical behavior of crystals induced by plastic deformation.

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The stresses in a pipe flange connection with a gasket subjected to an internal pressure and an external bending moment are analyzed taking account the non-linearity and hysteresis of a spiral wound gasket and a joint sheet gasket by using an elasto-plastic finite element method (FEM). The effects of the internal pressure and the external bending moment on the contact gasket stress distributions are examined. Leakage tests were also conducted using an actual pipe flange connection with a gasket under an external bending moment. As a result, a difference in the new gasket constants is substantial between the PVRC values and the estimated values when the external bending moment is applied to the connection. The hub stress and variation in axial bolt force were also measured. Fairly good agreements are found between the calculated and experimental results. In addition, a method for determining the bolt preload in the pipe flange connection under the external bending moment is demonstrated for a given tightness parameter.

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In this research, the material constants of Gurson model for porous elastic-plastic materials are identified. Measurement data, obtained by simple experiments (compressive test and tensile test) with carbon steel (S25C) specimen, are used. The identification method is based on an inverse analysis using Bayes Formula and the finite element method. Preliminarily, sensitivity analyses are performed for verification of parameter-independency, and efficient identification procedure is proposed.

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A simple instrumentation system has been developed to determine the elastic moduli of engineering ceramics and their composites from the sound produced by the impact of a ball upon a specimen. In the system, a small rectangular bar specimen is suspended by thin ceramic threads. Using a fast Fourier transform analyzer, the natural frequencies are analyzed from the impact sound for the flexural and torsional vibration modes of the specimen. In this paper, elastic constants were evaluated from these frequencies using Timoshenko's beam theory, Saint-Venant's torsion theory and unconstrained optimization algorithm based upon quasi-Newton's method. Four-points bending test were conducted to measure anisotropic elastic shear moduli of the specimen. Elastic constants evaluated by the impact sound agreed well with those measured by the bending test.

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Damage evolution of random particulate composites is formulated by the combination of two distinct theories, micromechanics and damage mechanics. Damage mechanics is applied to filler particles to describe interfacial debonding, which in turn incorporated into Mori-Tanaka's mean field theory for stiffness prediction of damaged composites. The model uses an energy balance concept to account for nonlinear behavior due to particle debonding. With this model, the effects of particle volume fraction, size distribution and interfacial strength on damage development of composites are analytically investigated. Emphasis is also placed on the effect of partial debonding which plays a dominant role for damage induced anisotropy. It is found that the model can reproduce not only stress-strain relationship but also variation in Poisson's ratio observed in damage process.

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Postbuckling behaviors and load-carrying capacity of thin laminated plates under uniaxial compression have been discussed by many researchers. However, little research has been performed on the postbuckling behaviors and the secondary buckling phenomenon for thin laminated curved plate which occurs with further increase of load. In this paper, cross-ply laminated curved plates under uniaxial compression with initial imperfections which are simply supported along four edges is considered as an example. By a proposed method based on the second variation of total potential energy to judge the stability of postbuckling equilibrium state, the inevitability of secondary buckling is proven analytically, and the effects of various factors, such as dimension of curved plate, assumed virtual displacement pattern, postbuckling deflection pattern, amplitudes of initial imperfections and average axial shortening, on the secondary buckling values are clarified.

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A new type of smart structural material is described in this paper. The characteristics of this material is its ability to utilize temperature dependency of the thermally induced deformation of an unsymmetrical laminated plate and to apply heat generated by Joule heating of CFRP laminas as energy of laminate deformation. The unsymmetrical laminated plates composed of aluminum alloy CFRP and KFRP sheets were used as the basic material. It was found that thermal control of the material was possible by the PID control method using Joule heating characteristics. The shapes of the material at the arbitrary Joule-heating temperature were calculated by Rayleigh-Ritz minimization of the total potential energy. These calculations were compared with the results of Joule-heating experiments, and good agreements were obtained. It was confirmed experimentally that the material showed several types of basic adaptive responses.

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This paper is concerned with an axial compressive experiment on carbon steel thin-walled square pipes with a square hole in a short column range, supported with spherical seat. A digaonal line of the square hole pallels to the direction of the compressive load. It was found that the collapse of these carbon steel square pipes occurred as the local buckling of the flat wall with a hole. The buckling stress decreased as the open ratio increased. Consideration has been given to an empirical formula with the combination of the analysis based on the energy method with the experimental result. The result shows that this formula is in good agreement with those obtained experimentally for various ratio.

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Shape memory alloys (SMA) have the ability to "remember" their original shape, that is, a deformed SMA will recover its shape upon heating. According to recent research, the short column of the SMA resists buckling better than nearly all other engineering materials. We can call this effect 'Anti-buckling effect'. The purpose of this research is to improve the buckling properties for the column by using the SMA. First, we did the buckling test about the Al column inserted the SMA. As a result, we can achieve 1.9 times as large energy absorption as the Al column. Next, simulation was done about the combined column by Finite element method in order to reproduce the experimental result. Though there was a little error, simulation result was similar to experimental one. So we can design the column inserted the SMA using by Finite element method.

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In the industrial winding process of plastic films, the existence of air interlayer in film rolls leads to some roll defects, such as lateral slide, wrinkling and blocking, and the occurrence of such defects is strongly influenced by the interlayer pressure of the roll. With increasing demands for higher quality of film rolls without such defects, it is of vital importance to determine the optimal process conditions such as winding torque, nip and tension. For that purpose, an accurate estimation of the internal stress fields in film rolls is essential. This paper presents a new theoretical approach to the prediction of transient viscoelastic stress distributions, where a generalized Maxwell viscoelasticity and nonlinear compressibility of films are taken into account. Moreover, the effect of air-entrainment at the roll inlet is discussed based on the theory of elasto-hydrodynamic lubrication. The numerical solutions for the stress distributions agree fairly well with the corresponding experimental results of winding tests using an in-house pilot reel, and they show the significant influence of the viscoelasticity of a plastic film upon the stress level.

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A stress boundary value problem of a crack emanating from a circular hole in an infinite plane subjected to a constant magnetic field is studied. The infinite region with the cracked hole is mapped to the exterior of the unit circle by using a rational mapping function technique. Both paramagnetic and soft ferromagnetic materials are considered. Complex magnetic potential and stress functions are obtained using Cauchy integrals. The magnetic intensity and stress distribution are shown. The stress intensity factors of the crack tip for any arbitrary directions of the magnetic field can be calculated using the results of zero and forty-five degrees. It is noted that analysis on an arbitrary shape can be obtained by changing the coefficients in the mapping function.

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In this paper we analyze the stress intensity factor (SIF) of an inner-surface circumferential crack in a finite-length cylinder under thermal striping. The edges of the cylinder were rotation-restrained and the outer surface was adiabatically insulated. Inner surface of the cylinder was heated by a fluid with sinusoidal temperature fluctuation. We combined an analytical temperature solution for the problem and our SIF evaluation method for the crack, and as a result, showed that the transient SIF solution can be expressed in a generalized form by dimensionless parameters such as mean radius to wall thickness ratio R_m/W, Biot number B, normalized striping frequency Ω and Fourier number F_o. Finally, normalized SIF ranges for the 1 st cycle and steady state were given for these dimensionless parameters in tables.

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Fatigue tests of rolled bolt-nut joints were carried out under constant-amplitude loading and two-step loading with three primary stresses. The bolted joints failed in the threaded region at the root of the first thread where the nut and bolt were engaged. Experimental results indicated that cycles to failure of the secondary nominal stress amplitude, where the nominal stress was the load divided by the area of net section in the threaded region, depended on the primary stress and its cycle ratio. In order to know the local stress under elastic-plastic condition at the thread root where fatigue failure occurred, a simplified method based on Neuber' rule and Glinka's rule was investigated. Equivalent stress amplitude, which was a fully reversed stress amplitude, was investigated from the estimated local stresses under the loading cycles and the relation of stress amplitude with mean stress. As a result of investigation of experimental data using the equivalent stress, cycles to failure of the secondary equivalent stress amplitude depended on the cycle ratio of the primary stress and did not depend so much on the primary stress. The fatigue life prediction method based on the above result was proposed. The estimated fatigue life was generally in good agreement with the experimental results.

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ODA (Optically Dark Area) in the vicinity of inclusions at fracture origin has a crucial importance in the mechanism of ultralong life fatigue failure. From the authors' previous studies, it has been presumed that ODA is formed by the fatigue due to cyclic stress coupled with hydrogen which is trapped by the inclusion at fracture origin. The fracture morphology of ODA was observed by a SEM with low resolution, a SEM with high resolution, an AFM and a Laser microscope. The ODA observed by the SEM with low resolution revealed a granular morphology. However, the high resolution SEM images obtained by tilting the fracture surface identified that the true morphology of ODA was not granular but was very sharp and irregularly rough. In order to reveal the effect of hydrogen on the formation of ODA, the microstructure around the inclusions at fracture origin was investigated. The hardness in the vicinity of inclusions in Specimens QT which contained 0.7-0.9 ppm hydrogen was much lower than that for Specimens VQ which contained∼0.01 ppm hydrogen.

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A practical model of a temperature and strain-rate dependent dynamic constitutive equation for carbon steels is proposed. Unknown material constants involved in the proposed constitutive equation can be determined by the non-linear least squares method, which approximates ordinary-impact-test results with calculated values of elasto-plastic waves propagation analyses. In addition static stress-strain curves, longitudinal elastic modulus and yield stress, which are needed for elasto-plastic waves propagation analyses with the proposed constitutive equation, are expressed as a function of temperature. These results enable elasto-plastic waves propagation analyses under wide strain-rate and temperature ranges easily. The present paper has actually determined material constants involved in the proposed constitutive equation and compared the calculated results with measured ones. As a result, it has been confirmed that the proposed equation is applicable at a wide strain rate range and at a room temperature to less than one in which blue brittleness occurs.

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Relationship between the slip line and the orientation of grains in polycrystalline copper during tensile plastic deformation is studied. Slip plane of each grain is calculated from the orientation obtained using EBSD technique, and the slip line of specimen surface is observed by SEM image. A method of estimation of active slip plane in each grain of polycrystalline copper during tensile plastic deformation is proposed based on the experimental results. Direction of slip line is calculated from the geometrical relationship between the specimen surface and the slip plane whose orientation is obtained using EBSD method. The estimated results and the observed results are compared by use of their correlation factor. The constraint between grains in the normal direction to the specimen surface is expected to be smaller than that between grains in the surface plane. Namely, the active slip plane is decided from the condition that the component of the specimen inward direction or the direction on the specimen surface of the shearing stress on the slip plane is maximum. It is also shown that the small size grain deforms on the slip plane whose orientation is close to the active slip plane of the neighboring grain with the maximum size. The estimated results are in good agreement with the experimental results.

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Using a finite element method analyzed the mechanism of stress development during thermal oxidation of shallow grooves on the top of silicon substrates for 0.25-μm semiconductor devices. The resolved shear stress concentrated at the upper and lower corners of the substrates. The shear stress increased as the total amount of oxidation increased. The shear stress at the lower corner was about two times higher than that at the upper corner because of a three-dimensional effect. The stress at both corners strongly depended on the width of the silicon substrate and the oxidation temperature.

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A statistical analysis of ductile fracture surface has been made on a structural steel. Both the notched specimens with different notch acuity and the unnotched specimens were employed to obtain a wide range of stress triaxiality. A large number of dimples were examined to clarify the statistics of dimple size distribution. The ductile fracture surface was compased of variously sized dimples, and the dimple size distributions were expressed approximately by the composite Weibull distribution. Whereas, the extreme value plots of the maximum dimple size has been applied to characterize the statistical variation on the extensive ductile fracture surfaces. A clearly defined change in the ductile fracture surfaces associated with fracture strain was well expressed by plotting the distributions of the maximum dimple size in a given unit area on the extreme probability paper. Then, it should be noted that the extreme value analysis would be quite useful for quantitative fractographic analysis of ductile fracture surfaces.

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An analytical method for evaluating the unstable deformation mode of atomic structures is proposed. The instability criterion is given as positiveness of the minimum eigenvalue of matrix, which consists of second derivation of potential energy with respect to atomic coordinate. The eigenvector for the minimum eigenvalue indicates the relative displacement of atoms at the beginning of instability, which is the "unstable deformation mode". The validity of method is examined by tensile simulations of a cracked atomic structure under two different boundary conditions. Owing to the difference, two types of unstable deformation, crack propagation and dislocation emission, are observed in the simulations. The beginnings of instability and their unstable deformation mode are successfully picked up by the proposed method.

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In this study, mechanical properties of the femur with fixation using the Gamma nail and the compression hip screw, which is widely used as the fixation devices of trochanteric fracture, is investigated by three-dimensional finite element method. The results obtained are as follows. (1) On the medial and lateral surface of the intact femur, the stress distribution increases around the lower of trochanter. (2) The rigidity of the implanted femur increases, when the fixation is inserted in the fracture division, though the surface stress at the proximal part considerably decreases. (3) In the CHS fixation, the surface stress of the femur covered by the plate remarkably decreased. (4) The stress around the fourth screw rapidly increases, when double ends of the CHS plate contact the femur. (5) The CHS method is not suitable for the unstable fracture, because the stress of fracture division of the lesser trochanter considerably increases. (6) Mechanical properties of the implanted femur with Gamma nail are more similar to the intact femur than the implanted femur with CHS.

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