The LIGA process consists of lithography, electroforming and molding has attracted attention in microstructure fabrication techniques. At the molding process of LIGA process, it is difficult to pull out from the mold that is assumed especially in the case of high aspect ratio structures. However, release from mold is improved by tapered structure. In this research, we have proposed a method for achieving tapered structure using the diffraction exposure technique which makes use of diffraction phenomenon. Diffraction is caused by providing a clearance between a resist structure and an X-ray mask. The fabricated structure was the lines and intermediate space whose processed depth was 200 µm and designated the taper angle of 5 degrees as set point. The variable parameters were the slit width, the X-ray dose and the gap between the X-ray mask and the resist structure. It is controlled that discovering the conditions for taper angle 5 degrees and inspecting the relationship between a taper angle and a mold releasability by electroforming and the molding of the LIGA process. We have fabricated the mold with taper angle of 2.5 degrees by electroforming. The Ni mold could partially copy the master pattern well.

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In this study, a micro metallic valve was designed and fabricated. All of the parts are made of metals, and assembled in a unit. Sheet metal with thickness of 20 µm was used as valve plate. Sheet metal forming was applied to form the 3D structure, and surface treatment with plating Au and coating SAM (Self-Assembled Monolayer) with functional groups was carried out in order to compensate the surface roughness and to improve sealing property of the valve. An equipment was developed for evaluating flow resistance of the valve. The influence of surface conditions on the valve properties including surface roughness, mechanical properties of surface coating was investigated experimentally. Furthermore, phenomena of micro flow between two walls with surface roughness in a gap of several microns were simulated by a FEM code. Evaluation of the properties shows that the surface treatment is very effective to compensate the surface roughness and the valve is highly functional.

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Coal ash is industry waste exhausted lots of amount by electric power plant. The particle sizes of coal ash, especially coal fly ash are very fine, and the chemical component are extremely resemble with Okinawa-Kucha clay. From the point of view that clay is composed of particles of micro meter size in diameter, we should try the application for fabrication of composite material using coal fly ash and clay. The comparison of the mechanical properties of composite material using coal fly ash and clay were performed during electric furnace burning and spark plasma sintering. As a result, the bending strength of composite material containing the coal ash 10% and fired at 1423K using the electric furnace after press forming at 30 MPa showed the highest value of 47 MPa. This phenomenon suggests a reinforcement role of coal ash particles to clay base material. In spark plasma sintering process, the bending strength of the composite material containing the clay 5-10% to fly ash base material fired at 1473K and pressured at 20 MPa showed the highest value of 88 MPa. This result indicates a binder effect of clay according to the liquid phase sintering of melted clay surrounding around coal fly ash particles surface.

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The adhesion of diamondlike carbon (DLC) films deposited on SKD11 substrates by Unbalanced Magnetron sputtering (UBMS) of a metal Cr and graphite target was investigated. DLC films, consist of Cr/C gradient interlayer and a-C:H layer, were prepared under various deposition conditions, and film-substrate adhesion was evaluated using adhesion energy equation proposed in our previous study. This equation was improved on the base of that of Bull et.al. with taking into consideration the compressive residual stress in the film. Deposition conditions (substrate bias voltage, ratio of CH₄ gas flow rate (CH₄ flow rate per total Ar and CH₄ gas), deposition temperature, deposition pressure, deposition time) were varied. From scanning electron microscope (SEM) observation of cross section of the film and analysis of electron probe micro analyzer (EPMA) for the detached area of the scratch track, it was confirmed that the films detached in the Cr/C interlayer. Adhesion energy changed characteristically and depended on the deposition conditions and corresponded to the Young's modulus of the film.

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Nonlinear transient behavior of a piezothermoelastic laminate including the dynamic deformation deviated arbitrarily from the equilibrium state is analyzed. As an analytical model, we consider a laminated beam composed of the elastic structural layers and the piezoelectric layers subjected to mechanical, thermal and electrical loads as disturbances or intended control procedures. The deformation of the beam is analyzed by the classical laminate theory and the von Kárman strain. Equations of motion in terms of displacements are obtained and they are analyzed through the Galerkin method. As a result, the dynamic deflection of the beam is found to be governed by the equation for a polynomial oscillator, and the following quantities are obtained: (1) the buckling temperature due to in-plane thermal and electrical loads; (2) the static large deflection due to combined in-plane and anti-plane loads; (3) the steady vibration deviated from the static equilibrium state; (4) transient large deformation with damping effect considered due to mechanical, thermal and electrical loads. Through these results, the characteristics of the transient deformation of the beam is discussed in detail.

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Mode I crack initiation properties under stress intensity pulses with durations of 25, 50 and 100 µs are investigated by experiment and discrete dislocation dynamics. The cleavage fracture initiation is examined under the consideration of the pile-up of dislocations against an obstacle ahead of the crack tip and the coalescence of piled-up dislocations. In the experiment, under very short pulse loads with the duration of less than 50 µs, the dynamic fracture toughness, K_Id remarkably increases and the crack tip opening displacement is closely correlated with K_Id. The numerical results are compared with the experimental ones in reasonable agreement.

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Moiré interferometry is a very sensitive optical method to measure the in-plane displacement of a solid specimen, and is useful to measure small deformation of solids. But, there often appears measurement error caused by the residual strain of the grating that is pasted on a specimen in Moiré interferometry. The present paper applies Moiré interferometry to the measurement of opening displacement of a notch in a plate specimen, and proposes a method to eliminate the error brought by the residual strain of the grating. The proposed method measures the change of the order of Moiré interference fringes with varying the tensile force applied to the specimen, and obtain the residual displacement of the grating and the true opening displacement of the notch. The experimental results show that the opening displacement given by the proposed method is proportional to the square root of the distance from the notch tip. This fact says that the proposed method is successful in eliminating the measurement error caused by the residual strain of grating, and can measure the true COD without any phase-shifting methods.

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Due to the coupling between the opening and sliding modes of an interfacial crack between a fiber and matrix, measuring the individual values of the interfacial strengths, specifically the normal and shear strengths, is very difficult. A method based on comparison between experimental and numerical results is proposed and implemented for estimating the normal and shear strengths along such an interface. We numerically simulate mixed-mode interfacial debonding in a transverse tensile test for a single-fiber composite coupon. The interface is modeled using cohesive elements which are subjected to a quadratic failure criterion. Frictional effects are also included when the stress states are comprised of shear and compressive modes.

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For atomic-level investigation of plasticity in amorphous metal, instability analysis which can rigorously describe unstable deformation of atomic structures is a key technique. However, the analytical method cannot be applied to large-scale amorphous metal because of the enormously-increasing computational load with respect to the number of atoms. In this study, an efficient instability analysis method for a large-scale atomic system is proposed using linear elements, and it is applied to cracked amorphous metal under tension. The proposed method successfully evaluates the instability criterion as well as the highly-localized unstable deformation. Moreover, the computational efficiency is considerably improved from the original one, enabling us to address mechanical instability problems in amorphous metal consisting of a great number of atoms.

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In this paper, the basic solutions of multiple parallel symmetric finite length cracks in a functionally graded material plane subjected to anti-plane shear stress loading were studied by the Schmidt method. The problem was formulated through Fourier transform into dual integral equations, respectively, in which the unknown variables are the jumps of displacements across the crack surfaces. To solve the dual integral equations, the jumps of displacements across the crack surfaces were directly expanded as a series of Jacobi polynomials. The results show that the stress intensity factors at the crack tips depend on the crack lengths, spacing of the cracks and the functionally graded parameter. It is also revealed that the crack shielding effect presents in functionally graded materials.

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