Polymeric material is useful in daily life. Especially, Polypropylene has superior character in many fields. In this study, inelastic deformation properties of Polypropylene are obtained by using the inverse analysis on load-depth curve measured by micro-indentation tests. The new expression of polypropylene's rate dependent constitutive equation is presented and the Kalman's filter is used in the inverse analysis. It is found that the analytical determined inelastic constitutive equations are almost same as the actual stress-strain relations of Polypropylene which are obtained by compression tests at various strain rate.

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In the present paper, an interfacial strength between thin film and substrate is evaluated by laser ultrasonic waves. The laser beam is irradiated on the substrate which have a thin film on the lower side. The elastic-ultrasonic wave is excited by the laser beam, and it propagates in the transverse direction for the plate. The supersonic wave reflects on the back of monotony, becomes an expansion wave, and reaches the interface. Finally, delamination on the interface is caused by the expansion wave. In the present study, the interfacial stress is estimated by inverse analysis using Laplace-transformed boundary element method. The displacement history on the surface of the specimen can be related by interfacial stress by transfer function. The transfer function can be obtained by numerically by 3-dimensional analysis with boundary element method. The test specimens made from Al substrate and Ti thin film are used in the present study. It is confirmed that the interfacial strength between thin film and substrate is 30.5MPa from the present investigation.

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This paper investigates on the stresses, displacements and natural frequencies of an elastic thick walled square cylinder subjected to harmonically vibrating internal pressures. We show the influences of the thickness and the radius at the corners of cylinder on the natural frequencies. In a previous paper, a method of fundamental solution, that is body force distribution method, was presented for the problem. Here we apply it to the present problem.

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This paper investigates on the stress distributions and interface stresses of an infinite elastic plate with three slender rigid inclusions under tension. In a previous paper, it was shown that the tensile force acting on the central inclusion was smaller than that of the outside inclusion. This paper shows the influences of the length and distance between inclusions on the interface stresses.

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Thermoelectroelastic response of Two parallel axisymmetric cracks in a plate of a functionally graded piezoelectric material (FGPM) is studied under thermal shock loading conditions. It is assumed that the thermoelectroelastic properties of the strip vary continuously along the thickness of the strip, and that the crack faces are supposed to be insulated thermally and electrically. By using both the Laplace and Hankel transforms, the thermal and electromechanical problems are reduced to two systems 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 versus time for various geometric parameters are calculated.

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The thermoelectroelastic fracture of a functionally graded piezoelectric material (FGPM) strip with two parallel cracks under thermal loading is considered. The crack faces are supposed to be insulated thermally and electrically. Fourier transform techniques are used to reduce the mixed boundary value problems to two systems of singular integral equations. The singular integral equations are solved by using the Gauss-Jacobi integration formula. Numerical calculations are carried out, and detailed results are presented to illustrate the influence of the parameters of the geometric parameters on the stress and electric displacement intensity factors.

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A fundamental solution is shown for axisymmetric torsion problems of radially inhomogeneous elastic solids. We assume that the modulus of transverse elasticity varies with radial coordinate r in form of a power. The fundamental solution shown here is defined as a solution to the problem of the inhomogeneous elastic solid subjected to a torsional body force acting along a circle.

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In this paper, we investigated on crystal structure of complex perovskite-type oxides ABO_3 through first-principles calculation to develop novel biocompatible piezoelectric materials. Firstly, biocompatible homoelements were set to B site of new materials and 12 combinations were found. Secondly, their insulating properties were distinguished with electric band structure. Then, phonon properties in cubic structures were analyzed and the possibilities of structural phase transition from cubic structure to asymmetry one were investigated to get a high piezoelectricity. Finally, their characteristics of stable structures were analyzed.

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The thermo-electro-mechanical fracture problem of an infinite piezoelectric material containing a T-shaped crack is considered in this study. The problem is solved for an infinite piezoelectric material that is under a uniform heat flow, uniform mechanical loads in two directions and a uniform electric load far away from the crack region. The crack faces are supposed to be completely insulated. By using the Fourier transform, the thermal and electromechanical problems are reduced to systems of singular integral equations, respectively. The singular integral equations are solved numerically. Numerical calculations are carried out, and detailed results are presented to illustrate the influence of the thermo-electro-mechanical interaction on the stress and electric displacement intensity factors.

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In this study, the elastic-viscoplastic behavior of plain-woven GFRP laminates in which plain fabrics are stacked with misalignment is analyzed using a homogenization theory. For this, a novel boundary condition for unit cell analysis is proposed based on the periodicity and point-symmetry of internal structures in plain-woven laminates. Using the boundary condition, the homogenization theory for non-linear time-dependent composites developed by the authors is rebuilt for plain-woven laminates with misaligned plain fabrics. As an application of the present theory, the elastic-viscoplastic analysis of plain-woven glass fiber/epoxy laminates with misaligned plain fabrics is performed.

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Although estimating interlaminar fracture strength is a key issue in the design of composite structures, interlaminar fracture toughness tests are usually conducted only for unidirectional laminates. Since multidirectional laminates are used in composite structures, an understanding of delamination characteristics and prediction techniques for multidirectional laminates are needed. In this paper, the tensile tests of the L-shaped laminated specimens with the initial delamination were conducted for 0//90 interface. In addition, the numerical study by VCCT(Virtual Crack Closure Techniques) was performed to predict the test results.

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A topology optimization method for phononic crystals is developed for the design of sound barriers, using the level set approach. An optimal shape of periodic inclusions is found by minimizing the norm of transmittance for given incident waves at a frequency. We consider a layered structure which is composed of scatterers arranged periodically in horizontal direction while finite inclusions are distributed in vertical direction. The boundary conditions for the lower and the upper boundary of the unit cell are described by impedance matrices. Through a numerical example, the feasibility of the proposed method is demonstrated.

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Organic light emitting diode (OLED) is used for lighting utilized as display of television, mobile phone, digital camera, and so on. Luminescence spectrum and out-coupling efficiency of light from OLED structure depends on film thickness and optical indexes of thin film materials. The structural optimization of thin films is useful to satisfy a design specification. We developed the system which could simultaneously optimize film thickness and optical indexes of each layer by genetic algorithm. In this report, results of the optimization of OLED to increase the out-coupling efficiency with target spectrum are shown.

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Acoustic-wave propagation on semiconductor surface is studied by numerical simulation based on the molecular dynamics (MD) method. We investigate the effect of crystallographic anisotropy, finiteness of thickness of crystal slab, and the presence of defects on the wave propagations. Based on these analyses, we attempt to design atomic-level surface structure of Si for a surface acoustic-wave filter and lenses.

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