The present paper describes a method for evaluating the collapse load from the tension- and bending-displacement charts. The plastic constraint factor, the collapse load and the 02% proof strength all exceeded the upper bound solution. The two collapse mechanisms observed are tension and bending collapses. Interaction of tension and bending results in a larger collapse load than that obtained from evaluating photo-plastic fringe, especially under simultaneous tension and bending loadings. The maximum load yielded more easily the test collapse load than the two elastic-slope method.

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This paper investigates experimentally and analytically the cyclic fatigue crack growth in piezoelectric ceramics under electromechanical loading. Cyclic crack growth tests were conducted on PZT ceramics subjected to dc electric fields, and a finite element analysis was employed to calculate the maximum energy release rate for the permeable crack model. Based on bending experiments using single-edge precracked-beam specimens, cyclic fatigue crack growth rates are found to be sensitive to the maximum energy release rate and applied dc electric fields. Possible mechanisms for crack growth were discussed by scanning electron microscope (SEM) examination of the fracture surface of the PZT ceramics.

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"Ferroelectrics/ferroelastics" means a class of the material nonlinearity of electro-mechanical coupling problem, and it involves "domain switching" phenomena in each crystalline scale of ceramics. To solve such a kind of problem, conventional FEM for the electro-mechanical coupling problem would not be appropriate and hence, an alternative FEM, which will be proposed here, would be required. This is because the nonlinearity is mainly interpreted as the loss of material stability, which is usually described by using incomplete thermodynamic functions. To utilize the incomplete thermodynamic functions, finite element discretization should be consistent with them. It means that independent variable about electrics for the discretization should be vector potential ψ instead of scalar potential φ, which is called "electric voltage" and is used in the conventional FEM.

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For the purpose of measuring the strain field in nanoscale structures according to the change of photoluminescence(PL) from quantum dots(QDs), we have reported the enhancement and quench of PL from In_<0.5>Ga_<0.5>As QDs embedded in GaAs during nanoprobe indentation. With the increase of indentation force, the intensity of PL from QDs increased for more than 3 times firstly and then decreased when the forces increased further. Finally, the PL from QDs was totally quenched by the indentation force larger than a critical value. To clarify the mechanism, the simulation work were done based on the finite element method and strain-dependent k.p Hamiltonian. Results revealed that the hole accumulation was responsible for the PL enhancement while the crossover of energy bands caused the quench of PL.

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Recently, the photovoltaics of polycrystalline silicon cell have been extending its front into all over the world and it is also desired to establish the reliability assessment. This paper describes a strength evaluation of polycrystalline silicon for photovoltaic cell by use of the fracture mechanics taking into account the surface damage due to the manufacturing process such as a wafer slice. An attempt is made to evaluate the bending strength of polycrystalline silicon wafer and to evaluate the surface damage by TEM and Raman spectrometry. It is found the huge micro cracks exist at the surface, and these cracks can be modeled as through crack by using fracture mechanics analysis.

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Micromechanical analysis is performed to a composite material containing various orthorhombic reinforcements by using the modified equivalent inclusion method to heat conduction by Hatta Taya. The macroscopic thermal conductivity of the composite can be expressed as a function of the thermal conductivities and aspect ratios of constituents. As a result, the degree of anisotropy on the macroscopic thermal conductivity of the composite may be designed by the choice of the geometry and material of the reinforcement.

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Flexural rigidity of a porous resin/Al laminate is estimated experimentally by means of the 3-point bending test. It can be seen from the results that the change in value of the flexural rigidity of the laminate is convex with respect to its thickness and thus there exists the optimal thickness. A new model that the neutral volume in which the bending stress does not occur exists around the neutral plane of the beam is devised for the explanation of the change in flexural rigidity with thickness.

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The cryogenic tensile properties of carbon nanotube (CNT) / poly-dicyclopentadiene (poly-DCPD) composites has been investigated experimentally. Tensile tests were carried out with flat tensile specimens at room temperature and liquid nitrogen temperature (77K). The effects of temperature and CNT volume fraction on the tensile properties of CNT/poly-DCPD composites were discussed. Scanning electron microscope (SEM) was also used to study the fracture surfaces of CNT/poly-DCPD composites. It was shown that tensile properties of poly-DCPD with CNT are related to the morphology of CNT distributed in the poly-DCPD.

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In the present paper, numerical simulation about press-molding of glass lens is investigated. Since constitutive equation of glass depend on time-history and temperature, stress relaxation is observed on the glass subjected to applied loading, and these behaviors vary drastically depending on the temperature. In the present study, creep test has been conducted to determine the thermo-viscoelastic properties of glass. The creep function obtained by the experiment has been transformed into relaxation function employing Laplace transform. Shift factor which gives the relation between the time and temperature can be determined by creep test under several temperature. In the present analysis for press-molding of glass lens, history of the temperature and its distribution is computed by unsteady heat conduction analysis prior to the analysis of cooling sequence. The total FEM analysis for press-molding are executed taking into account the nonuniformly temperature distribution in the glass lens. Residual stresses under some processing conditions are estimated, and the optimal conditions of forming process are discussed in detail.

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In the present paper, unidirectional tensile test of glass specimens were carried out. Strain rate and temperature condition were varied in the material tests. Temperature and Strain-rate dependencies on the unidirectional tensile strength of the glass specimens were investigated in detail. Approximate expression which express the temperature and strain-rate dependencies was introduced from the experimental results, and the properties of the tensile strength were discussed on the standpoint of the thermo-viscoelasticity of the glass.

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The singularity of the stress field at the tip of a partially closed interface crack is discussed based on a non-uniform spring stiffness model that includes an inverse function of the radial distance from the crack edge. Two distinct non-oscillatory singular stress fields, corresponding to Mode I and II deformations, respectively, are found to coexist. An oscillatory singularity may also appear, but only when the two stiffness intensities are close to each other. This means that the oscillatory singularity exists when the normal and tangential interactions between the upper and lower crack faces are close.

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In the present study, cyclic fatigue tests were conducted on the cemented carbides under the high temperature environment. The tests were performed at two stress ratios, R=0.1 and 0.5. In addition to these cyclic fatigue tests, static fatigue tests at R=1 were also conducted to determine effects of cyclic stress, stress ratio and temperature on the fatigue crack propagation behavior of cemented carbides.

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A crack in a plate of a functionally graded piezoelectric material mathematically modeled by a non-homogeneous solid is studied under transient thermal loading conditions. It is assumed that initially the medium is at the uniform temperature and is suddenly subjected to a uniform temperature rise along the one of the traction-free boundaries. The crack faces are supposed to be completely insulated. Some material properties are assumed to be exponentially dependent on the distance from the crack line parallel to the boundaries of the plate. By using both the Laplace transform and Fourier transform, the thermal and electromechanical problems are reduced to a singular integral equation and a system of singular integral equations. The singular integral equations are solved numerically, and a numerical method is then employed to obtain the time dependent solutions by way of a Laplace inversion technique. The intensity factors vs. time for various material constants and geometric parameters are calculated.

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A mismatch of different material properties in joints may cause stress singularities, which lead to the failure of the bonding part. It is very important to reveal a stress singularity field for evaluating the strength of interface in three-dimensional joints. Furthermore, thermal residual stresses occur in a cooling process after bonding the joints, and the stress singularity for thermal stresses also occur. In the present study, the intensity of singular field at the edge in the interface Si-resin joint with different thickness in silicon is investigated using boundary elemant method.

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Tribological failures such as a pitting or a shelling are often caused from a subsurface crack. So in this study, the stress intensity factors are analyzed for a multiple kinked subsurface crack in a half space due to repeated rolling/sliding contact with frictional heat. On the bases of these results, for the case of bearing steel(SUJ2), using the maximum energy release rate criterion and the modified Paris power crack growth law, the crack growth path and the fatigue life until the tribological failure are predicted under repeated rolling/sliding contact. And the effects of the depth of an initial horizontal crack and the frictional coefficient (involved in the thermal effects) on the results are considered.

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Fatigue delay cycles and crack propagation behavior after a single tensile overload were investigated using two different specimens, the compact tension specimen (CT) and the center cracked panel specimen (CCP). Differences in the delay behavior between CT and CCP specimens were observed at the higher R ratio region, R>0.7. In the former, the delay cycles increased with an increase of R ratio at the higher R ratio region. While in the latter, the delay cycles decreased at the region. Mechanism for the different behavior was discussed in detail.

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We study constitutive behavior of helical strands under uniaxial tension. A helical strand has a hierarchical structure and its level considered here are single fiber, helical fiber bundle and helical cord. Based on the microscopic failure process of a fiber, we statistically formulate the macroscopic constitutive behavior of helical fiber bundles using a so-called fiber bundle model. We apply this constitutive relation to the next hierarchical level, helical cords, and present the constitutive relation of a helical cord consisting several fiber bundles.

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A pulse laser has been used to generate the ultrasonic transients in laser ultrasonic nondestructive testing specimen. In this study, the surface of the transparent ceramic cylinder is painted with black paint of high optical-absorption coefficient in order to absorb the laser energy. The surface of the cylinder is impulsively heated by the laser pulse, and the generated ultrasonic transients are measured by the transducer which is installed on the other surface of the cylinder. The experimental results are compared with the numerical results which are obtained by the characteristic method.

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The Doppler effect is discussed for flexure waves in a beam and a plate, three body waves (P, SV, SH) in an infinite solid, modal SH waves in a thick plate and Rayleigh wave on the surface of a semi-infinite solid. The exact closed form solution for each elasto-dynamic problem is obtained and the simple equation for the Doppler frequency shift is derived for all waves. It is shown that the Doppler frequency shift takes place continuously in the 2D plane problems, and that the most sensible wave for the Doppler frequency shift is the non-dispersion wave, such as the body wave and Rayleigh wave. The flexure and modal waves, which have the dispersion nature, is less sensible.

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Dynamic behavior of a piezothermoelastic symmetrical cross-ply rectangular laminate subjected to mechanical, thermal and electrical loads and simply-supported is investigated considering the effect of damping. The strain of the laminate is expressed by the dynamic deflection based on the classical layered theory and the von Karman theory. Then the stress of laminate is expressed by the strain as the constitutive equation. Using the von Karman strain and the piezothermoelastic constitutive equations, the equations of motion in terms of displacements are obtained. Then, the equations of motion are solved by the Galerkin method. The differential equation obtained by the method is analyzed by using Runge-Kutta method. Thereafter, we present the dynamic behavior of a piezothermoelastic laminate subjected to constant mechanical, thermal and electrical loads.

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The second-order statistics of the temperature and thermal stresses are evaluated in an axisymmetrically heated functionally graded annular disc of variable thickness with spatially random heat transfer coefficients (HTCs) on the heat dissipation surfaces. This annular disc is assumed to have arbitrary variations in the HTCs and material composition only along the radial direction. The randomness in the HTCs is considered to be a random field. The stochastic temperature field is analysed by considering the annular disc to be multilayered one with stepwise thickness variation, which has constant material properties and spatially constant but random HTCs in each layer. In order to evaluate the statistics, the Monte Carlo simulation method is employed with analytical solutions for the deterministic temperature and thermal stresses. The analytical solution for the thermal stresses is obtained thorough the piecewise power function approximation for Young's modulus. Numerical results demonstrate the effects of the material composition profile and thickness variation on the statistics of the temperature and thermal stresses.

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The two-dimensional unsteady thermal stresses in a plate are treated to simulate the state of artificial seasoning of wood in an oven. End face of lumber plate is assumed as a multi-layered plate, which has grading properties within each annual ring, in this two-dimensional problem. Interpolated Differential Operator (IDO) numerical scheme is applied to obtain the distributions of temperature and stresses. Material properties are assumed to be constant in each small unit mesh. The profiles within each unit mesh of temperature and displacements in x-direction and y-direction are assumed as polynomials of five degree, which consist of 15 terms. Although the unit mesh has nine nodes, only five nodes are used. The advantage of IDO numerical scheme is that the assumed polynomials of five degree for displacements in x-direction and y-direction satisfy the compatibility of strain automatically.

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This paper discusses a stochastic response analysis using the second-order perturbation-based homogenization method for fiber reinforced composites. The perturbation method is used for estimating stochastic characteristics such as the expectation or variance of a homogenized elastic tensor or a homogenized equivalent elastic constant of FRP. Those stochastic characteristics will be estimated using the first-order perturbation based homogenization method in case of linear stochastic response of a homogenized elastic property however, a stochastic response in some other problems considering non-linearity or large stochastic variation cannot be estimated accurately using the first-order perturbation method. In this paper, therefore, the second-order perturbation-based homogenization method is used for the estimation. At first, an outline of the second-order perturbation-based homogenization method is introduced. Also, the perturbation-based procedure for computing a perturbation term of a homogenized equivalent elastic constant is introduced. Those methods are applied to a stochastic analysis for a homogenization problem of FRP. From the numerical results, effectiveness and a problem of the second-order perturbation method are illustrated.

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This is the first attempt toward the development of robust design methodology applicable to gaskets-there is no such precedent in the sealing industry. This was achieved by drastically transforming the traditional approach toward the solution to leaking problem. This paper deals with a new all-metal gasket that incorporates strategically located circumferential annular lips that form seal lines with the flanges. The gasket, due to its special shape makes use of the material's spring effect, resulting in sealing performance. This approach is clearly distinct from the traditional one based on material development. By transforming a material development problem into one of mechanical design, we were able to optimize it using the Taguchi method. In FEM analysis, contact stress and deformation information was used to quantify leaking. Robust design methodology was developed and as a test case, a 25A sized industrial gasket was optimized using that methodology. Helium leak testing reveals considerable improvement in the sealing performance, hence verifying the applicability of the methodology developed.

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In recent years, it has been reported that organic/inorganic hybrid composites could show novel mechanical properties. In this study, viscoelasticity of epoxy/silica hybrid composites prepared with the acid anhydride curing agent viasol-gel method were investigated. The structure of hybrid composites was evaluated by Raman spectroscopic analysis. Dynamic modulus and glass transition temperature of the hybrid composites were measured by dynamic mechanical thermal analyzer.The DMTA results showed that the hybrid composites exhibited a thermoplastic behavior.

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Recently, piezo cables have been developed. It is a cable that has piezo-electric characteristics because the piezo cable is wrapped by a piezo-electric film around the wick line. This research tried to measure the strain in structural materials using this piezo cable. In the experiment, a displacement sensor, a strain gauge and a piezo cable were installed on the test piece, and that test piece was excited by constant amplitude. The output voltage with the piezo cable was measured, and compared with the displacement sensor or the strain gauge. The measured output voltage was similar to the strain gauge in proportion to the load amplitude. Therefore, the proposed piezo cable could be a possible sensor for strain measurement.

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Crack initiation and propagation were observed on perforated plates at elevated temperature by the CCD video camera. The test specimens are made of SUS304 stainless steel, and temperature is kept to be 550℃, and the geometry of the perforated plate specimens are changed by diameter size of the hole. The photographs of all cycles were recorded to obtain number of cycle of crack initiation(N_c). The results were compared with predictions by the stress redistribution locus (SRL) method and the Neuber's rule's method.

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Rotating bending fatigue tests were conducted in order to investigate effects of laser peening (LP) treatment on fatigue property of wrought aluminum alloys A7050-T7451 for aircraft structures. As the results, the LP treatment was effective for the fatigue property improvement of A7050-T7451 alloys, and the fatigue strength at 10^7 cycles of the LP treated alloys increased 50MPa for the non-treated alloys. It is assumed that the reasons of the fatigue property improvement are the work hardening and the grain refining in the surface layer by the LP treatment.

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A novel strain controlled, free standing tensile fatigue system was developed by using the combined PZT and micromachining technologies in order to conduct in-situ observation and assessment of high cycle fatigue behavior in LP-CVD poly Silicon thin films within a scanning electron microscope (SEM).

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It is important to know mechanical properties of micro structures fabricated as a micro machine component by micro-stereolithography(μSL). In the previous study, we reported that elastic modulus of a micro-cantilever fabricated by μSL is controllable by irradiation laser power and postcure processing time. In this study, micro-cantilevers are formed by changing lamination pitch (10μm to 25μm) and lamination orientation. Then, the relation between the load and the deflection of the cantilever is evaluated. Experimental results show that the elastic modulus of the cantilever decreases with the increase of the lamination pitch, also it depends on lamination orientation.

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Stress-strain hysteresis loops of several engineering plastics in compression at strain rates of nearly 600/s are determined using the standard split Hopkinson pressure bar. Four plastics or typical thermoplastics PA-6, PA-66, PC and POM are tested at room temperature. Cylindrical specimens with slenderness ratio (= height/diameter) of 0.5 are used in the Hopkinson bar tests, and those with slenderness ratio of 1.5 as specified in the ASTM Standards are used in the static tests. The low and intermediate strain-rate stress-strain hysteresis loops in compression are measured in an Instron testing machine. The effects of strain rate on Young's (or secant) modulus, 2.5% flow stress and dissipation energy (energy loss due to damping) are examined. It is demonstrated that the area within the stress-strain hysteresis loop (or dissipation energy) increases with increasing strain rate as well as strain, that is, all plastics tested exhibit intrinsic dynamic viscoelasticity and a high elastic aftereffect following complete unloading.

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Rotary bending fatigue tests were carried out on laser peened SUS316L and AC4CH with a pre-crack to investigate the effect of laser peening treatment on fatigue crack propagation properties in different f.c.c. materials. As the results, the surface crack propagation was prevented and the fatigue strength was improved in both materials. But there were differences in surface crack initiation life and restraint of surface crack growth in two materials. It is assumed that the reasons of the difference are the surface roughness and the surface hardness effects by LP treatment on SUS316L and AC4CH.

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In this paper, we have proposed an evaluation method for the initiation conditions of heat crack under thermal shock using the tensile test of a notched specimen. In some materials, such as hot rolling rolls and dies for aluminum die-casting, there is a problem of heat crack initiation, and the evaluation of heat crack resistance using test pieces was difficult until now. The thermal stress and stress gradient that occurred in such material were analyzed by the finite element method (FEM). The maximum stress when tensile stress was applied to the material with a notch was compared to the stress gradient of the thermal stress. As a result, the quantitative evaluation during the initiation conditions of a heat crack for materials became possible.

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The mode I interlaminar fracture behavior of the composite laminates reinforced with the Zanchor process, which is a novel through-the-thickness reinforcement technique utilizing an elaborated needling process, was studied on the basis of the experimental results of DCB tests. Experimental results demonstrated that the mode I interlaminar fracture toughness was improved effectively by the Zanchor reinforcement, where the fracture toughness, G_<IC>, increased almost linearly with the Zanchor density, Z. In addition, the fracture toughness, G_<IC>, increased drastically during the early stage of crack extension in the Zanchor reinforced composites, where the interlaminar crack propagated stably accompanied by a large amount of fiber bridgings. The above results suggested that the increase in mode I fracture toughness was the consequence of the fiber bridgings induced by the Zanchor process.

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In this study, RUS(resonant ultrasound spectroscopy) is suggested as a measurement method of residual stress in spherical specimens. At first, the model of spherical specimen is made for FEM and natural frequency of spherical specimen is calculated due to use this FEM model. Second, resonant frequency of spherical specimen is measured for RUS measurement system that consists of two transducers, spectrum-analyzer, and load cell. RUS is the measurement system due to compare calculated natural frequency for FEM with measured resonant frequency for experiment. As these results, calculated natural frequency is similar change to measured resonant frequency when residual stress is changed. So, RUS can be measured residual stress.

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The authors have performed micro computed tomography(μCT) with synchrotron radiation of SPring-8 to evaluate the fatigue crack propagation behavior inside specimens. A compact biaxial rotating bending fatigue testing machine was developed to make fatigue testing in SPring-8. Preparatory experiments demonstrated that the resulting data by the machine developed were consistent with the data by conventional Ono-type rotating bending fatigue testing machines. Fatigue crack propagation curves and da/dN-ΔK relation obtained by μCT corresponded to the data with replication technique on the surface of the specimens, however, it was also shown that the replication technique would not always present relevant information on the crack behavior.

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