The effects of thermal cycling on the tensile properties of SiC particulate reinforced cast aluminum alloy have been studied. The results were discussed in terms of a microstructure controlled mechanism which is void growth, coalescence and debonding of SiC particle for tensile fracture. The ductilities of thermally cycled material is twice larger than that of as received material. The measurements of 3D shape of fracture surfaces show that the microvoid coalescence occured around of the SiC particle clusters. Based on the micro-mechanism of tensile fracture for the thermally cycled material simulations were conducted on void growth and debonding of the SiC particle/matrix interface. The predicted stress-strain behavior is consistent with the experimental results. The stress and strain field around the SiC particle were examined through the simulated results.

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Dependency of inelastic analysis results on constitutive equations prevents their application to structural designs. To overcome above difficulty, this study proposed a selection method of classical constitutive equations that give conservative solutions against design problems. The reason why classical equations were adopted is that results of detailed constitutive models depend strongly on load histories that are unclear in design stage.

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An simplified practical method has been developed to estimate the interactive force based on the vehicle deceleration in CTC (car-to-car) frontal crash. The adequacy and consistency of proposed method was verified by using the principle of conservation of energy. The calculated force-deformation curves revealed that the interactive force reached the maximum designed strength of the small light car based on the ODB test, while the force level was far below the corresponding design limit of the large heavy car. The relatively lower stiffness of the small light car resulted in absorbing a larger share of the total input energy of the system when crashed into the large heavy car. The maximum impact force and the end of crash force to asses CTC crash compatibility can be accurately estimated by the spot-damage model.

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This paper shows shear stress-strain relation of lead material to develop a numerical model. The specimens were composed of circumferential lead and two steel flanges. Vertical displacement and rotation of the upper and bottom flanges were constrained and horizontal displacements were applied to the upper flange of the specimens by a dynamic biaxial test device. The loading test results show the shear stress-strain relation in small and large strain and effect of the height-diameter ratio f specimens on stress-strain curve.

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In the conventional limit analysis, it is supposed that the circumferential plastic hinge line is formed at the same position in a plate. However, there would be a contradiction in this assumption and it is necessary to re-examine the hypothesis used in the conventional limit analysis. Because, from our previous experiments, it has been confirmed that the plastic hinge line spreads gradually. The elastic analysis under the constrained support conditions both inner and outer peripherally, which bending moment and membrane force act at the same time, is described in this paper. Especially, as the preliminary step for considering the model of numerical analysis, the finite deformation analysis will be compared with an infinitesimal one, and we will investigate how those results influence the model of the plastic analysis.

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Distributed parallel computing using PC cluster is applied for the actual configuration of nuclear power piping system. Actual configuration is modeled in 3-dimensional modeling leading to very high degrees of freedom to be indispensable for the use of parallel computing. First of all, the employed elements, such as 4-node tetrahedron element and 8-node hexahedron element are examined for their accuracy in structured mesh subdivision. The pipe bend and T-pipe are modeled by hexahedron elements, and analyzed in elastic-plastic large deformation case. The obtained numerical results agree well with experimental results.

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In this paper, we deal with an isothermal plane elastic problem of an inhomogeneous medium. As analytical model, we consider the plane elastic problem for an infinite medium with a Griffith crack subject to a uniformly distributed internal pressure on the crack surfaces. Making use of the fundamental equations system, which is already established in our previous paper, the analytical solution for such singular stress field are successfully developed. And the elastic behaviors are evaluated through the numerical calculations.

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This paper deals with the problem of the determing of the stress and the displacement of an elastic half space with a rigid spherical inclusion. It is assumed that the half space is subjected to a concentrated normal force at a point on the plane surface of the half space. A method of solution is presented for the problem by using the Green's functions for axisymmetric body force problems of an elastic half space. The problem is formulated by an integral equation with unknown functions of the intensities of distributed body forces. Stresses and displacements around the inclusion of the half space are shown by numerical calculations.

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The presence of near-surface inclusion or void are known to have detrimental effects on the tribological failure in rolling and sliding contact elements, such as bearings, rollers and rails etc.. This paper deals with the two-dimensional stress analysis in the half-space involved in a void or an rigid inclusion, subjected to the rolling-sliding contact with frictional heating. The complex variable formulation of Muskhelishivili is used to reduce the problem to a Fredholm integral equation. Attention is focused on the stress concentration due to the inclusion or void. The effects of the frictional coefficient and the depth of the inclusion or void on the stress concentration are considered numerically.

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The paper presents an asymmetric solution for the stresses and displaements in an elastic thick plate containing an oblate spheroidal inclusion under shear eigenstrain with an uniform gragient. For related eigenstrain problems, Jasiuk et al. solved the axisymmetric problem of the half-space with a spheroidal inhomogeneity under uniform normal eigenstrain and Tsuchida et al. treated the asymmetric problem under uniform shear eigenstrain. The stress distributions around inclusion are shown graphically.

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We study the growth of the void. where multiple seeds at the initial condition. A square unit cell with some atomic defects is constructed with nickel atoms and is subjected to the hydrostatic tensile load by using Molecular Dynamics. A same configured model with some small voids is simulated by using FEM. We observed the void growing and the void vanishing by the influence from the other voids. The behaviors of the voids initiation by the two methods. which are microscopic and macroscopic method. are compared to each other.

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A Green function for a radially inhomogeneous elastic solid is obtained exactly. Both impulsive and time-harmonic SH-wave sources are assumed. Wave front shapes and rays for transient waves are derived and the time-harmonic response is also obtained. Non-wave nature of the time-harmonic response is found in the case of constant velocity gradient.

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The present paper deals with the dynamic thermoelastic problem of a thin piezoelectric plate of crystal class 6mm, when not only a relaxation time in the temperature field but also an inertial effect in the elastic field is taken into account. One boundary surface of the thin plate is exposed to a uniform ambient temperature, whereas the other boundary surface is kept at the initial temperature. An exact solution to this problem is obtained by employing the Laplace transform technique. Numerical calculations have been carried out for a thin PZT-5A plate, and the numerical results are illustrated graphically.

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In this paper, we analyze the dynamics of piezothemoelastic laminate considering the effect of transverse shear. The analytical model is a rectangular laminate composed of fiber-reinforced laminates and piezoelectric layers. The model is assumed to be anti-symmetric angle-ply laminate with all edges simply supported. The behavior of the laminates is analyzed based on the first-order shear deformation theory. Closed solution of the deflection due to loads varying arbitarily with time are obtained.

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Stochastic temperature field in a nonhomogeneous plate with random thermal conductivity is analysed based on the Laplace transform and the perturbation method. The nonhomogeneous plate has the exponential variations in the thermal and mechanical properties in the direction of the thickness. The randomness of the thermal conductivity is considered to be a distribution function with random amplitude in the plate. Analytical expressions of the expected value and the variance for temperature and thermal stress are derived under the deterministic surface temperatures. Numerical calculations are carried out for the case that random variation in the thermal conductivity is a uniform distribution.

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This paper is concerned with the thermal buckling analysis of isotropic inhomogeneous rectangular plate subjected to the arbitrary thermal loads. Derivation of the fundamental system of equations is based on the classical plate theory. It is assumed that the inhomogeneous material properties such as the coefficient of linear thermal expansion α, the thermal conductivity λ, and Young's modulus of elasticity E are changed in the thickness direction with the power law, while Poisson's ratio γ is assumed to be constant. As an illustrative example, we consider the thermal buckling of the isotropic inhomogeneous rectangular plates due to uniform heat supply. Numerical calculations are carried out for several cases taking into account the variations of inhomogeneous material properties, aspect ratio and thickness of the plate.

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In this paper, an inverse determination method of thermal conductivity is proposed in functionally graded material plates (FGM plates) with the prescribed temperatures at the inner points. This method is based on piecewise nonhomogeneous approximate method (PNA method) developed in order to obtain an accurate analytical solution for the transient heat conduction problem in the FGM plate with arbitrary variation in thermal properties through the thickness by present authors and genetic algorithm (GA). The thermal conductivity in PSZ/SUS304 FGM plate is determined inversely. The ratio of the thermal stress to bending strength is estimated for the FGM plate with the thermal conductivity determined and the ceramic-rich FGM plate suitable for the relaxation of thermal stress.

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Recently, waste incineration of wooden waste has been prohibited because of the dioxin problem and the recycle of them has been needed. Particle board (PB) and medium density fiberboard (MDF) are prospective recycle products made of wooden waste. This paper treats unsteady temperature and thermal stresses when we add the higher insulation with the grading inside property for such wooden recycle boards. The analytical model was assumed that the recycle board with higher insulation was used as interior wall. One-dimensional unsteady heat transfer problem was analyzed by the change of variable, the Laplace transform and the perturbation method. Various FGM higher insulation boards with same average density are discussed because the thermal conductivity of wood is proper to the density. The different direction of heat flow inside of board in summer and winter is also discussed.

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This paper is concerned with the theoretical analysis of transient thermal stress problem of the functionally graded plate with temperature-dependent material properties taking into account the thermal radiation. We analyze the thermoelastic problem by means of the theory of laminated composites as one of the theoretical approximation. With the aide of a finite difference method for time variable and an iteration method, a semi-analytical solution can be obtained. Some numerical results for temperature change and stress distributions in a transient state are shown in figures. The influence of temperature-dependent material properties and thermal radiation is investigated.

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The elastoplastic thermal stress in a functionally graded material plate (FGM plate) which has arbitrary nonhomogeneties of thermal and mechanical properties and temperature distribution only through the thickness of the plate, is analyzed based on Mendelson's modified total strain and the incremental strain theory of plasticity under the prescribed variation in surface temperatures. The numerical calculations of thermal stress and plastic strain are carried out for Ni/Al_2O_3 FGM plate with the temperature-dependent initial yield stress and elastoplastic tangent modulus.

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Thermal stresses around two cracks in an infinite elastic layer between a ceramic-fiber-reinforced half-plane and a metallic half-plane are solved. The surfaces of the crack are assumed to be insulated. The boundary conditions are reduced to dual integral equations using the Fourier transform technique. To satisfy the boundary conditions outside the cracks, a difference in temperature at the crack surfaces and differences in displacements are expanded in a series of functions that vanish outside the crack. The unknown coefficients in each series are evaluated using Schmidt method. Stress intensity factors are then calculated numerically for several thicknesses of the layer.

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Repair method with bonded composite patches to cracked aluminum alloy panel of aircraft has attracted to extend the service life of aging aircrafts. In order to clarity the behavior of fatigue crack growth, fatigue experiments are performed for cracked aluminum panels repaired with a single-side composite path under service condition of aircraft. The effect of humidity on the repair efficiency can be found by comparing the results of crack growth under the humidity conditions of 90%, 50% and 25% RH at various temperatures.

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In the present paper, curing temperature of carbon fiber reinforced plastic (CFRP) laminates was estimated from room-temperature shapes which ware calculated theoretically and compared with experimental results. The analyzed model was CFRP laminate plate having a stacking sequence [0°/90°], and the specimens were made of unidirectional carbon fiber/epoxy prepreg. And room-temperature shapes of CFRP laminates are analyzed theoretically by means of classical lamination theory, correspondence principle and anisotropic thermoviscoelastic constitutive equations. Deflections were compared with experimental results under various conditions.

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This paper describes a microscopic structural optimization of fiber reinforced plastics using spatial estimation and a gradient optimization method. A residual component of a homogenized elastic tensor after microscopic fracture is maximized. Fixed grid model is used as microscopic FRP model. Homogenization method is used in order to calculate a macroscopic homogenized elastic tensor. A solution space is estimated using the Kriging method. The Grauss type semivariogram model is adopted in this paper. Gradient method is suitable to solve the optimization problem, which is estimated using the Kriging method, because gradient components on an estimated surface can be obtained without using a finite differential. In this paper, CSSL method is used as an optimizer. Using the proposed method, an estimated optimum solution to maximize the residual rigidity of GFRP is obtained, a validity and effectiveness of the method is confirmed.

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Resonant ultrasound spectroscopy (RUS) is widely used to evaluate the characteristics of small solid specimens like superconductor of a single crystal or anisotropic materials of fiber reinforced composites, for example. The elastic moduli of the solid body can be determined by measurement of the natural frequencies exited by a pair of Piezo-electronic transducer. In this paper, a numerical technique for the determination of the elastic constants in RUS testing is discussed. An alternative evaluation function for the search algorithm of the elastic moduli defined with determinant of the coefficient matrix is suggested here, and boundary element analysis is applied to calculate the eigen value of the 3 dimensional vibration on the solid body. Some numerical simulations for the Si single crystal are conducted to demonstrate the effectiveness of the present method.

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A new methodology for evaluating the crack closure stress in fatigue crack surfaces by ultrasonics is proposed. Echo amplitudes of 50 deg. Incidence of shear wave beam against the surface connected back wall cracks in steel specimens are used. In order to account for the exact effect of closure stress on ultrasonic response, the echo amplitude is analyzed based on the artificial application of additional closure stress. The initial closure stress at no load condition is determined by the standard compliance technique. Two empirical relationships among echo amplitude, crack depth and closure stress, are established. Based on these relations, the crack closure stress and crack depth of an unknown crack are determined by inverse analysis of the measured response of the crack. The method demonstrates an excellent capability of quantitative evaluation of crack closing stress as well as crack size.

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Pulsed holographic microscopy was applied to take photographs of rapidly bifurcating cracks on the both surfaces of PMMA plate specimens. The cracks were of the opening mode and propagated at a speed more than 600m/s. From the photographs, crack opening displacement (COD) of crack branches were measured along themselves. The results show that, two crack branches have different COD. This means that the bifurcation of crack was asymmetric. And each of the crack branches has the same COD on both side near the crack tip, that imply crack branches have two dimensional crack fronts. Even in this case, however, the CODs of one of the two branches on the both side were not same in the vicinity of bifurcation point. This fact indicates that crack bifurcation was three dimensional and bifurcated cracks retain three dimensional structure at bifurcation point after bifurcation.

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We applied shadow optical method of caustics to measure the thermal stress distribution around a cylindrical heater inserted in a thin disk of acrylic. The caustics pattern has a circular shape centered to the heater. Heating rate range is 0.25,0.5,0.75 and 1℃/sec. Caustics pattern appears at a certain stress value increase in diameter size up to reach the steady state as well increasing in brightness. A strong relation between caustics pattern and radial stress peak had been found. For that, Caustics experimental method could be used to show thermal stress distribution.

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Phase shifting moire interferometry was developed by using wedged glass plate. This technique was employed to measurement of thermal deformation of electronic package, Stacked-MCP (Multi Chip Package). A thermal loading was applied by heating the devices from room temperature 25℃ to an elevated temperature 100℃. The experimental results showed that large shearing and bending deformations were yielded. The microscopic strain distributions around the chips and resin were quantitatively determined.

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High-speed optical interferometry is applied to measure dynamic stress intensity factor of fast propagating cracks. The method of interferometry gives the true value of dynamic stress intensity factor when the measurement is carried out in the singular stress field that satisfies the plane stress condition. However, one cannot obtain the true K-value if it is measured within the three-dimensional stress field in the vicinity of the crack tips. In order to obtain the true value of dynamic stress intensity factor in the three-dimensional stress field, the present study makes a correction equation using the K-values measured by the interferometry. It is found that the measurement accuracy is about ±20% in the three-dimensional stress field when a crack is propagating in a PMMA specimen at a speed of 600m/s.

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Lacking the function coping with accident happened in the period between inspection and the absence of warning system for emergency are thought to be two main shortcomings of present maintenance method. To overcome these faults, E. M. technology have a lot of ability, the author thought. In concrete, many sensors are put to a machine/structure to maintein to change them so-called sensory structure for detecting damage happening instantly, and these sensors sent signals to warning system for judging whether they are dangerous state or not. Here, many thinking on the usage of sensors is talked, and an good example of this idea is explained. As conclusion some typical idea of the application of E. M. technology to maintenance are proposed.

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Optical methods in experimental mechanics, such as moire interferometry, speckle interferometry, and digital image correlation, are very valuable in areas where other methods of analysis are not available or impractical. In order to standardize the optical stress and strain measurement methods, TWA 26 (Technical Working Area 26) has been established in VAMAS (The Versailles Project on Advanced Materials and Standards). The meeting of TWA 26 was held during 2002 SEM Annual Conference on Experimental Mechanics in Milwaukee in June 2002. At the meeting, the activities for the standardization were reported by representatives from the United States, Europe and Japan. European group have already begun round robin tests and ASTM in the United States made a draft of the standard. Since the standardization activity in Japan is behind, it is necessary to start standardization activities.

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The evaluation of time dependent stresses in plastic spur gear tooth is important from the viewpoint of needs for producing high-precision and-strength gears. Few expreimental studies on stress analysis of plastic gear tooth have been reported. In this study, the authors attempt to measure and trace stress variation around gear tooth under engagement using the technique of white light photoelasticity with elliptical polarization. As the results, the experimental technique adopted is very useful for measurements of complex phenomena which is varying with time.

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This paper describes an experimental study on full-field stress separation from thermoelasticity and photoelasticity measurements and its application to estimation of stress intensity factor and the J-integral. Thermoelastic stress analysis (TSA) and photoelastic stress analysis (PSA) have been developed as full-field visualization methods of stress distribution. Only the sum of principal stresses can be measured by TSA, while only the difference of principal stresses can be measured by PSA. In this study, the hybrid stress separation measurement technique using both of these methods developed by the present authors was applied for determining distribution of all individual stress components in a center-cracked plate subjected to mechanical load. Stress intensity factor and the J-integral were calculated from the stress distribution. It was found that these fracture mechanics parameters can be evaluated with good accuracies by the present technique.

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It is shown that the strains of highly extensible materials such as elastomeric materials and polymer composites can be accurately measured by an image sensor PC mouse which is now becoming more and more popular as a computer input device. While in computer environments, mouse moves on the fixed pad and it measures its own movement, in this study, the movement of the specimen is measured by the mouse fixed in space. Conversion formula of strains from the Eulerian description to the ordinary Lagrangian one is presented.

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Strain measurement method in the whole view field using random pattern and image correlation is summarized in this paper. There are two major methods for the whole view field strain measurement, using regular grating and random pattern. Major advantage of the method using random pattern is considered that it is not necessary to use grid with regular pattern. Disadvantage is that it is not easy to adjust accuracy of the measurement using various sizes of the random pattern and also much calculation amount is required for correlation method. But CPU power has been raised rapidly these days and is overcoming the latter disadvantage. And also the resolution of CCD devices has increased recently. These progresses of technology in CPU and image capture devices realize remarkable progress in the whole field strain measurement using random pattern.

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In order to measure the displacement distributions on material surfaces, many types of image correlation method have been developed in various research fields. In this study, to measure highly accurate displacement field near a crack tip, the local correlation minimization method is proposed based on the image correlation scheme. First, the formulations of the image correlation and the local correlation minimization method are explained in this paper. Then, the corroboration of the local correlation minimization method is carried out by the measuring a known analytical near tip field under mixed-mode loading.

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Deformations of the surfaces of plastic films (nylon, polyethylene and linear low density polyethylene) used for liquid package gags under tensile loads are measured by a digital image correlation technique. The images, which are necessary for a digital image correlation, are captured by a CCD camera, and digitized by an image-processing devise. Several sets of two images, which are called a reference image and a deformed image, so as to determine deformations between the images are used for obtaining the deformations between the no-load condition and failure of the plastic films. The results show that characteristic deformations, which are probably due to molecular orientation in the plastic films, are measured.

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Distribution of COD in Silicon Nitride was measured at room temperature using Digital Image Correlation Method after cyclic bending fatigue tests. The cyclic fatigue tests with moving crack and stationary crack were performed under stress ratios R=0.1,0.5 and -1 at room temperature and 1273K. From the experimental results, the stress shielding effect under cyclic loading was discussed quantitatively. The stress shielding effect after the test at 1273K was more significant than that at room temperature under any stress ratio. Though the stress shielding effect under R=-1 was stronger than that under R=0.1 at room temperature, results obtained after the test at 1273K were found to be quite different.

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In this study, the deflection distribution of a cantilever is measured combining the holographic interferometry and phase-shifting digital holography. Holographic interferometry can measure with high accuracy, high sensitivity, and full-field by noncontacting. But the development processing of a film is troublesome by holographic interferometry. Digital holography record on CCD and it reconstructs it with a computer. Therefore, development processing is not needed and it is early reproducible by digital holography. Digital holography has the amplitudes information and phase information in digital information. By the holographic interferometer, the sum of complex amplitude before and after deformation is reconstructed. In this study, the sum of complex amplitude before and after deformation is calculated and reconstructed. Therefore, phase difference computed for digital information and the displacement of a nano-meter order will be able to measure with this method.

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The finite element method (FEM) is useful for the stress analysis and used widely in general. However, it is still not necessarily easy to obtain the highly accurate values of the stress intensity factors by FEM. Recently, a method for calculating the highly accurate values of the stress intensity factors has been proposed by H. Nisitani, based on the usefulness of the stress values at a crack tip calculated by FEM. This method is called the crack tip stress method. In this study, the interference effect of cracks in a strip or a round bar under tension is discussed based on the results of the crack tip stress method.

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It is well known that the tension-softening model can describe the macroscopic fracture behavior of quasi-brittle materials. The problem studied in this paper is a tension-softening behavior in brittle materials based on the growth of a non-coplanar parallel crack array. Crack growth analyses are performed numerically using the body force method. The problem calculated is a non-coplanar crack array subjected to uniform tensile stress at infinity. The maximum principal stress criterion is employed to determine the each crack growth direction and the global stress required for crack propagation. The tension-softening behavior is studied from the remote tensile stress and deformation of the numerical result. The deduced tension-softening curve is consistent with experimental data obtained for granites. This evidence revealed that the overlapping of non-coplanar cracks, i.e. the ligamentary bridging, is the main source of the tension-softening behavior of granites.

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In this paper, we consider arbitrary arrays of cracks in an infinite plate. In the analyses, we use the Body Force Method (BFM) by satisfying the traction-free conditions of crack edges, in which expressions of the body foce densities and resultant foce bondary conditions are introduced in order to get highly accurate results. Numerical calculation is performed for various arrays of cracks under tension.

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Since earthquakes that are heavier than the assumed one has broken out in recent years, the conventional earthquake-resistant plans of plant piping are inadequacy and rational plans by flexible views are searched for recently. This paper describes about elastic-plastic response in A6063S and SUS304. The experimental object used by this study has parallel two beams that have narrow parts. The seismic excitation tests by natural frequency were performed with several input levels. The dependability on displacement of damping ratio and natural frequency was studied. The correlation when plastic deformation arises in two places (series, parallel) was got. The result shows that SUS304 is more efficient than A6063S in dissipative energy of elastic-plastic vibration.

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A behavior of a wing crack growth near an interface of bonded materials is studied. The wing crack is a mode-I failure that emanates from the closed crack tip under compression. It was found that the wing crack becomes easier to grow when it propagates near a free boundary where a considerable outward deflection appearing on the boundary seems to assist the extension of wing crack. Different from the tensile crack, the wing crack shows no tendency to approach the free boundary and rather propagates almost parallel to a free edge.

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It is said that the cause of an earthquake is in most cases the local shear fracture of rock along a plate in the interior of earth. Therefore, it is important to know the shear fracture strength of rock in order to investigate the various phenomena of an earthquake. In this paper, a new specimen is proposed which can simulate the shear fracture behaviour in the underground.

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A mechanism for a development of a quasi-shear faulting in brittle solids under compression is studied. Brittle solids often exhibit a macroscopic shear failure under the application of compressive stresses. A possibility of a failure localization organized by a number of minute cracks of mode-I type into the inclination of principle shear is suggested as the mechanism of a formation of macroscopic-shear faulting. In order to evaluate this possibility, a computational crack propagation and coalescence analysis together with experiments using mortar samples is carried out.

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This paper discusses a fracture behavior of randomly distributed cracks using a numerical simulation. The cracks are initially distributed in a rectangle region. The directions and locations of the cracks are chosen at random, but the length is identical. The crack propagation from the initial distribution is analyzed under a uniaxial tension load using the body force method. The maximum principal stress criterion is used to determine the load and direction of each crack growth. The result indicated that the equivalent elastic moduli can be predicted analytically. The strength degradation behavior can be expressed as a function of a parameter including the crack density and the number of crack. While the tensile strength decreases with increasing the crack density, the fracture energy shows almost same value of fracture energy for the single crack fracture.

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The contribution of multiple cracking to toughening in rocks is examined. It has been reported that the fracture toughness is enhanced by multiple cracking for brittle micro-cracking materials such as rocks and the microscopic strength distribution of the material is responsible for the development of multiple cracking. In this paper, uniaxial tension and fracture toughness tests were carried out to determine the effect of multiple cracking on the fracture toughness based on a fracture energy method. The method is applied to experimental results obtained on a granite and marble. The experimental results indicated that the usefulness of the proposed method for evaluating the contribution of multiple cracking.

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