The most of piezoelectric ceramics have perovskite crystal structure, which can be characterized as a non-symmetry crystal lattice structure in a microscopic scale and a strong anisotropy in a macroscopic scale. Therefore, the macroscopic mechanical and functional properties of poly-crystalline ceramics are strongly affected by the microscopic non-homogeneous crystal structure. In this work, multi-scale finite element modeling procedure based on crystallographic homogenization method has been developed to estimate macroscopic properties considering distributions of crystal orientations. At first, the size and number effects of finite element in microscopic model on the macroscopic properties have been investigated. Next, the macroscopic dielectric, piezoelectric and elastic constants have been predicted by employing arbitrary microscopic crystal orientation distributions. Finally, the availability of our finite element procedure has been confirmed through comparison with result of the conventional self-consistent model.

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In this study, the dynamic response of a piezoelectric half-plane containing an internal or an edge crack perpendicular to the boundary under a normal impact is considered. The Laplace and Fourier transform techniques are used to formulate the problem in term of a singular integral equation. The singular integral equation is solved by using the Gauss-Jacobi integration formula. Numerical calculations are carried out, and the effects of the geometric parameters and the piezoelectric material properties on the dynamic energy density factors of an internal or an edge crack are shown graphically.

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In order to investigate the effect of loading frequency on stress-strain-temperature relationship in pseudoelastic behavior of Shape Memory Alloys (SMA), tensile tests of TiNi-SMA wire at loading frequencies ranging from 0.001 Hz to 1 Hz were performed, and the stress, strain and temperature of wire were measured simultaneously. Using our proposed thermo-mechanical analytical model of SMA, those pseudoelastic behaviors were simulated numerically as well. Results showed that the loading frequency strongly affects temperature change of the wire and the stress-strain hysteresis loop. The analytical model could predict the time history of stress-strain-temperature relationship with accuracy, and thus the validity of the model has been confirmed. Moreover, by examining the variation of each term of the heat balance equation, the thermo-mechanical mechanism of the pseudoelastic behaviors was also clarified.

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In order to clarify the effect of dislocations that are statistically stored dislocations (SSDs) and geometrically necessary dislocations (GNDs) on the characteristic length dependent micro-to macroscopic deformation behavior of polycrystalline metals, finite element simulations based on a crystal plasticity theory accounting for SSDs and GNDs have been performed for plane stress polycrystalline metals with different grain sizes. The dislocation lines constructed based on the edge and screw components of GNDs on the slip planes clarify that the grain boundary as well as sub-grain boundary act as the obstacles to dislocation motion and impede easy motion of dislocations. The density of SSDs and GNDs increases as the gain size decreases that yields the increase in the deformation resistance in macroscopic scale. The mean glide path distance and annihilation distance of dislocations strongly affect the micro-to macroscopic deformation behavior of polycrystalline metals. Hall-Petch-like relations between the macroscopic resistance of deformation and grain size are observed.

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The elasto-viscoplastic constitutive equation is formulated, based on the concept of continuum damage mechanics. It employs the viscoplastic strain given by Perzyna and extended by Murakami to consider the effect of damage. The unified form of damage evolution equation given by Lemaitre is extended to consider the effect of strain rate. The constitutive modeling is identified, based on static/dynamic tensile tests and fatigue tests for steels SM 490 A, SN 490 B and aluminums 2219-T 87, 6061-T 6. The identified model is used to predict the dynamic, tensile behaviors of pre-strained steels and the static/dynamic, tensile behaviors of pre-fatigued aluminums. The predicted results have agreed well with the corresponding experimental results.

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In this study, we simulate nanoscale copper precipitation process based on the vacancy jump model using Lattice Monte Carlo (LMC) method, where an activation energy is calculated from the first neighboring interaction model. We confirmed that status of copper clustering at temperature of 300 K is different from those of 600 K and 900 K at the same potential energy decrease, and copper clusters are formed more rapidly at higher temperature. We obtained a fact that process of copper clustering consists of the two phases which are formation phase, and coalescence and/or absorption phase.

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This paper deals with the problem of dynamic stability of composite laminated cylindrical shells subjected to static and periodic external pressure. First, the axially symmetric motion of the shell under loading is determined. Subsequently, certain perturbations are superimposed on this motion, and their behavior in time is investigated. The symmetric state of motion of the shell is called stable if the perturbations remain bounded. The solutions for the prebuckling motion and the perturbated motion are obtained by the use of Galerkin's method. Stability regions are examined by utilizing Mathieu's equation. The inevitability of dynamically unstable behavior is proved analytically and the effects of various factors, such as stacking sequences, fundamental natural frequency, driving amplitude of the vibration and dynamic unstable mode, are analytically clarified.

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In the present study, a mechanism of fractal image of laminates on lamination parameters is discussed in detail, and a stacking sequence optimization method using the mechanism is proposed for complicated structures that include both of in-plane and out-of-plane lamination parameters. The new method employs branch and bound method for the optimizations of stacking sequences. For the estimation of the fractal branch of stacking sequences, the new method requires approximation of the objective function of the optimizations with quadratic polynomials using both in-plane and out-of-plane lamination parameters. The new method is applied to a stacking sequence optimization problem of a maximization of buckling load of a hat type stringer structure. The method gives successfully optimal stacking sequences in a short time.

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The dynamic behavior of empty and water-filled aluminum alloy (A 6063 TD-T 3) pipes subjected to spherical projectile impact was investigated experimentally. The plastic deformation and crack growth of pipes were observed in the velocity range from 70 m/s to 260 m/s near their ballistic limit. For water-filled pipes, the plastic deformation was localized around the impact point and maximum plastic deformation was smaller than that of empty pipes. The impact velocities for crack initiation and perforation in the case of water-filled pipes were smaller than those in the case of empty pipes. In addition, the empirical equations for the energies of crack initiation and perforation of pipes were proposed. It is found that the velocities of crack initiation and cerforation for empty and water-filled pipes decrease gradually and the perforation velocities for empty and water-filled pipes approach to the same value as the pipe diameter is increased.

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In order to measure biaxial stresses by an electrodeposited copper foil with a microcircular hole both occurrence rate of slip bands at the periphery of microcircular holes in a copper foil and the number of cycles of grown grain occurrence in copper foil itself are used. However, it is necessary to stop the test frequently to seek the latter. In this report, in order to overcome this weakness, the posssibility of the use of grown grain density, which can be obtained to optional number of cycles, is examined. Namely, using three kinds of material adhered copper foil, the stress component which controlls the grown grain density in copper foil is examined under the combination of plane bending and cyclic torsion and the basic equations connecting the grown grain density, the stress amplitude and number of cycles are presented.

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An elastic stress formulation was expressed for side plates in the case of the corrugated fiberboard box shape (CFBS) supported by upper and lower edges under uniform compression loading, and the deformation continuity of neighbouring plates in side edges was considered by this expression. Then from this formulation, characteristic behaviors of stresses and strains were discussed, and the validity of the formulation was denoted by calculation results. Normal stresses and strains ε_xi, ε_yi in width (L_i: i = 1, 2) and height directions for the plate are symmetric to center lines of the width and the height, and shear stress is antisymmetric. And ε_xi positive andε_yi negative, and the maximum of ε_xi is at the center in the side plate and the maximum of ε_yi is in the upper or the lower edge in the side. The maximum value of ε_xi is about 1/8 to maximum value of |ε_yi |. ε_x1, ε_y1 and shear strain γ_xy1 in the side edge are equal to ε_x2, ε_y2 and γ_xy2 in its side edge of the neighbouring plate, and bending deformation in the side edge is equal to bending deformation in its side edge in the neighbouring plate, and the deformation is continuous in side edges.

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Piezoelectric materials are gradually expected in industrial areas from the excellent characteristics of the mechanical and electrical couplings such as the sensors and actuators. When such roles are expected in the piezoelectric materials, they are laminated in order to improve the efficiency. Therefore, it is important to study mechanical and electro-physical quantity in each layer by theoretical analysis sense. In this paper, two-dimensional electro elastic analysis is performed for an isotropic piezoelectric materials containing multilayered circular inclusions under out-of-plane mechanical and electrical loads at infinity. General solutions are provided in terms of complex functions and several numerical examples are shown by graphical representation.

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In recent years, composite materials and ceramics-metal joints are investigated from a view of fundamental technology for producing the industrial products. In these materials, the stress concentration frequently occurs at the vicinity of joint edges and it causes cracks there. In the present study, we derived the fundamental solution for a unit force acting a point interior a two-phase transversely isotropic material, which is a bonded structure of two transversely isotropic materials with different properties. We developed a three-dimensional boundary element program using the fundamental solution. We examined the continuity of displacements and stresses at the interface of two-phase transversely isotropic materials to check the correctness of the program. We conducted the stress analysis for joints of Ti-Mg and Mg-Zn and performed the eigen value analysis based on FEM, which is formulated using a intepolation function considering stress singularity at the vertex. We showed that the results of BEM and FEM are very agreed with each other, and the stress singularities of power law and logarithmic law occur at the vertex of the three-dimensional anisotropic joints.

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It is well-known that the stress field of 2-dimensional dissimilar materials relates to two independent elastic parameters and the effect of material combination on it is classified successfully by the so-called Dundurs' parameters (α, β). However, in case of 3-dimensional dissimilar materials, what parameter combination should be employed as the parameters like Dundurs' parameters for 2-dimensional problems has yet to be studied concretely, although it is known that three independent parameters are necessary. The authors discussed previously axisymmetric problems and showed that three independent parameters are necessary to deal with the problems and, as the parameters, the combination of (α, β, γ) (γ: product of two Poisson's ratios) is useful and effective. This paper purports to study the fundamental properties of (α, β, γ), which is expected as the parameter combination also for genera1 3-dimensional problems. The relations of (α, β, γ) to other possible parameter combinations are given first and it is shown that (α, β, γ) can exist only in the closed domain in the 3-dimensional space of (α, β, γ). Moreover, the stress concentration phenomenon at the interface edge peculiar to the axisymmetric problems is discussed. The distinction condition about it is given through theoretical consideration and its validity is confirmed by finite element analyses.

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This paper studies elementary and structural effects on mechanical properties of silicon incorporated amorphous hydrogenous carbon films. Fifteen kinds of the carbon films were prepared by plasma-enhanced chemical vapor deposition method of the penning ionization gauge discharge type using argon, acethylen and tetramethylsilane gases. X-ray photoelectron and Raman spectroscopes performed elementary and microstructural analyses of the carbon films, respectively. Nano-indentation tests were also carried out in order to characterize the reduced elastic modulus and hardness of the carbon films. Intermixture of the tetramethylsilane gas led to a formation of silicon-carbon bonding and an increase of hydrogen atoms in the films. Hydrogen atoms also increased with a reduction of the negative bias voltage at the film substrate. The reduced modulus and hardness of the carbon films ranged from 53 GPa to 163 GPa and from 9 GPa to 29 GPa, respectively. Better mechanical properties resulted from a reduction of tetramethylsilane gases and an increase of the negative bias voltage. The bias voltage especially had a larger influence on the mechanical properties than the gas flow rate. Molecular orbital calculations revealed that the role of a double bond of carbon atoms was likely significant for better mechanical properties of the carbon films.

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A new technique for producing a sharp pre-crack between a thin film and a substrate is developed utilizing the difference in interface strength. This is applied to a sputtered copper (Cu) thin film on silicon (Si substrate. A evaporated Cu thin film, which has poor adhesion to Si, is inserted between the sputtered Cu thin film and the Si substrate as a release layer. The release layer debonds from the substrate at very low load, and the process successfully introduces the sharp pre-crack along the interface. Using the specimen, the fracture toughness test is conducted and the critical strain energy release rate, G_c, is evaluated as about 1.90 J/m² for the sputtered Cu/Si interface.

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In order to clarify experimentally the damage process for the high strength steel in high and extremely high cycle regions and to propose a simulation model based on a new approach, rotating bending fatigue tests were performed with special focus on the effect of the role of the inclusion on the fatigue properties of high strength steel. The transition of fatigue crack initiation site from surface inclusion to internal one was observed with decreasing stress amplitude. The simulation model was proposed on the basis of the concept of a risk competition of defects, in which a virtual specimen has been constructed in the computer program and all inclusions were assumed to be equivalent to a crack origin. The results of the simulation were almost in accordance with the experimental results, and it was shown that this model could make the prediction of fatigue life of high strength steel in high and extremely high cycle regions.

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In order to investigate the effect of load frequency on the fatigue strength and fracture mechanism of a nickel-base superalloy, Inconel 718, fatigue tests were carried out under an ultrasonic frequency (19.5kHz) in ambient air environment. The results were compared with those obtained under conventional rotatary bending fatigue at a frequency of 50 Hz. Fatigue strength increased at ultrasonic frequency, which is mainly caused by the suppression of crack initiation and its growth at the early stage. Under both ultrasonic and rotary bending fatigue tests, most of fatigue life consumed in the growth of a crack smaller than 1 mm. In the ultrasonic fatigue, intergranular and cleavage crack propagations were observed in addition to striation, which was a dominant fracture mechanism in the conventional fatigue.

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Rotating bending fatigue tests were carried out for 18%Ni maraging steel in order to investigate the influence of reversion austenite on crack initiation and its propagation of maraging steel. Fatigue strength was increased by formation of reversion austenite. The increase in the fatigue strength was large near the fatigue limit. This was caused from that the crack initiation and its early propagation were suppressed by the formation of reversion austenite and the suppression was marked with decrease in stress level. Although the fatigue strength decreased by humidity, the formation of reversion austenite relieved the sensitivity of fatigue strength for humidity.

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In the present study a detection method of an overload application during stress cycles under constant amplitude was investigated. Also, the effect of a tensile overload was shown at three stress ratios: R = 0, -1.5, in order to understand the effects of R on crack propagation after an overload. At a baseline of R = 0, after an overload retardation in the crack propagation was observed. However, in the case of R = -1.5, the fatigue crack growth rate actually accelerated after a tensile overload. That behavior of crack propagation was tried to be detected by the information of strain waveform h; h = ε_y + 1.2λε_x, where, ε_y and ε_x are the local strains at the specimen axis, and λ is the strain range ratio Δε_y/Δε_x. The waveform shape of h was changed after the overloading. Also, the application of an overload can be detected by the variation of the strain range ratio λ. Specially, the present method is useful for cases of the crack propagation stage under negative R conditions.

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A phenomenological fatigue model for describing the effect of stress ratio on the off-axis tensile fatigue behavior of unidirectional fiber-reinforced composites has been developed. First, empirical fatigue parameters are briefly reviewed. The conventional strength ratio is useful in manipulating the directional nature of the off-axis fatigue strengths. Using a modified strength ratio that considers the effect of stress ratio, we can substantially remove both the off-axis angle dependence and the stress ratio dependence of the off-axis T-T and T-C fatigue data, and obtain a master S-N curve which is almost independent of the off-axis angle and stress ratio. The modified fatigue strength ratio is then generalized in terms of the non-dimensional effective stress that corresponds to an extension of the conventional strength ratio. By using the modified non-dimensional effective stress, the fatigue damage mechanics model proposed in the previous study is further extended to cope with both the off-axis angle dependence and the stress ratio dependence of the off-axis fatigue strengths. The capability of the proposed fatigue model to reproduce the off-axis S-N relationships for different stress ratios is demonstrated through comparisons with the experimental results on unidirectional glass and carbon fiber-reinforced polymer matrix systems.

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Using a new fatigue testing method by which fatigue cracks can be initiated and propagated in a film adhered to cover an elliptical through-hole in a base plate subjected to push-pull cyclic loads, cold rolled copper films of 100 and 30 μm thickness were fatigued under various stress amplitudes with a stress ratio of R=0. The effects of the film thickness and the rolling direction on fatigue fracture properties were studied using two types of specimens that the rolling direction was parallel and perpendicular to the loading direction. As a result, for the case of films of 30 μm thickness, the crack initiation was caused at lower stress amplitude in the film with the loading direction perpendicular than parallel to the rolling direction, and the fatigue crack propagates faster toward the parallel direction to the rolling direction than toward the perpendicular direction. There was a difference between the two types of specimen in crack observation on the specimen surface owing to the difference in the shape of grains stretched by rolling. The thinner the film thickness was, the lower the fatigue limit was and the higher the fatigue crack propagation rate was against the same stress intensity factor range, ΔK_est, evaluated from the crack opening displacement measured experimentally. The reason of the effects of thickness in the cold rolled pure copper film was probably that the crack propagates easier through the film thickness in the thin films than in the thick ones.

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Gigacycle fatigue characteristics of high speed tool steel, JIS SKH 51, was investigated under cantilever-type rotary bending fatigue tests in an open environment at room temperature. As a result of fatigue tests, S-N curve was clearly classified into two types of fracture modes by the different crack origins. One fracture mode occurred at the surface inclusion in the region of short fatigue life and high stress amplitude level. The other was at the subsurface inclusion in the region of long fatigue life and low stress amplitude level. The transition of crack initiation site from surface to subsurface appeared at about 2×10⁴ cycles and the stress amplitude for the transition was affected by the tempering temperature of the specimen. On the other hand, difference on fatigue life for internal fracture mode between specimens treated by different tempering temperature did not observed. Fatigue fracture mechanisms were discussed through the detailed observation of subsurface crack initiation site.

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In this study, bending properties of honeycomb sandwich curved panels have been investigated with three point bending experiments. As a result, it was found that the maximum load point of curved panels was about 10% higher than that of a flat panel, irrespective of a radius of curvature. Moreover, a deformation resistance was decreased with decreasing the radius of curvature. Therefore, an effect of a buckling on the bending property became small with decreasing radius of curvature. These depended on a shear buckling of single walls in cores within a span on three point bending test.

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This paper deals with the recycling of bearing steel grinding swarf by high-density consolidation. The grinding swarf was compacted at the pressing pressure from 98 to 588 MPa. The maximum density of 5.41 g/cm³ was obtained at the pressing pressure of 588 MPa. Metal recovery rate that is one of the most important factors in metal recycling depended on the density of the grinding swarf briquet. The metal recovery rate of about 90% was obtained at the density of 4.8 g/cm³. Chemical compositions of original bearing steel (SUJ 2) and recycled metals obtained from melting of grinding swarf briquets in air and Ar were evaluated.

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Three stage blazed plate fin body with ultra fine off-set fin (thickness×height×pitch×off-set pitch = 0.2 mm×1.2mm×1 .6mm×5mm) for 600 MWt High Temperature Gas Cooled Reactor Gas Turbin(HTGR-GT) system was fabricated and tested on its high temperature mechanical properties and the following results were derived. (1) tested body shows almost the same strength and fatigue behavior of SUS 304 as main structural material at elevated temperatures up to 873 K, (2) static and fatigue fracture mainly occurred at ultra fine off-set fin and (3) high temperature strength and fatigue life are improved by blazing technique to double side walls of the fin by Ni blaze material.

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When cemented hip replacement implants are developed using a finite element method (FEM), the validation of the inplants comparing with experimental tests and clinical survival data should be required. As the first step, the optimum shape of the femoral component of total hip arthroplasty (THA) was designed to minimize the stress peak in the cement mantle that is the primal cause for fixation failure. In the next step, the strain in the cement mantle surrounding the cemented femoral components of THA was measured using strain gauges embedded within the cement mantle adjacent to the developed femoral stem to validate the optimization results of FEM. As a result of this study, optimum shape of femoral component was developed and the FEM results were validated by strain gauge experiments.

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