Our research focuses on the techniques for monitoring the current density distribution of the real-time electroplating. In the previous research, a novel technique to estimate electroplating current densities on plated surfaces from the data of the electric potentials in the plating cells has been developed for LSI fabrication technology. The technique described in this paper has been applied for a 2 dimensional (2D) analysis in our previous research work; however, the 2D approach limits the application of the proposed method. In this research, we applied the monitoring technique with 3 dimensional (3D) analysis. Although the inverse analysis using the 3D analysis tends to be large scale, it is important for the practical usage to monitor current density on target region accurately and efficiently. Therefore we have developed an efficient inverse analysis technique for monitoring of electroplating current density on the target region and verified the effectiveness of the proposed technique by using numerical simulations.

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This paper aims to clarify the delayed fracture mechanism for glass fiber reinforced plastics (GFRP) in corrosive environments. The GFRP under study is composed of plain NCR-glass cloth and vinylester resin, which both possess high corrosion resistance. In this study, the experimental conditions were performed in air, deionized water, and hydrochloric acid at 40°C. Static tensile tests of woven GFRP were performed to evaluate the mechanical properties and determine the experimental conditions for the constant tensile load tests in each environment. The mechanical properties of the woven GFRP decreased with its immersion into deionized water and hydrochloric acid. The stress-strain curve decreased intensely after the knee point especially in hydrochloric acid, which is possibly because of the damage accumulation generated by the solution and applied stress. Constant tensile load tests of the woven GFRP were performed to investigate the creep behavior and fracture time in each environment. The strain and strain rate increased in the tests in deionized water and hydrochloric acid, which are the result of decrease in the stiffness owing to immersion in each solution. In addition, delayed fracture occurred in deionized water and hydrochloric acid, and the lifetimes in hydrochloric acid were shorter than those in deionized water. Moreover, it was suggested from fracture surface observations that the delayed fracture of the woven GFRP under a constant tensile load in a corrosive environment is dominated by degradations in the fiber reinforcement and fiber/matrix interface.

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Lithium ion batteries are widely used for electrical devices. However, their degradation causes serious accidents such as fires or explosions. In order to detect the degradation of a lithium ion battery during charging and discharging in real time, an acoustic emission (AE) technique was applied and a clustering method was developed to extract AE signals caused by battery degradation. In this study, highly oriented pyrolytic graphite (HOPG) and a lithium metal were used as working and counter electrodes, respectively, and a glass fiber sheet was used as a separator. An ethylene carbonate / diethyl carbonate (EC/DEC) solution, which was used as the electrolyte solution, was sealed in a metallic shell. Degradation of this type of battery mainly occurred by gas evolution and fracture or exfoliation of the graphite electrode. During the first charging and discharging cycle, 499 AE signals were detected. AE signals were clustered by a method that was developed based on the waveform polarity, power spectrum, and enveloped waveform. These features were first clustered by correlation coefficients. AE signals which the Euclidean distance of each feature was close were clustered into the same cluster. AE signals were clustered into 43 clusters by this method. In order to characterize clustered AE signals from a degrading battery, the clustered signals were compared to artificial AE signals created by simulating degradation behavior in the battery. Gas evolution on an electrode in the battery was simulated by electrolysis of water. AE signals due to graphite fracture were simulated by mechanically fracturing the graphite in a Vickers indentation test. As a result, AE signals characterizing gas evolution were detected continuously during the cycle. This result constituted gas evolution phenomena in the battery. Fracture-related AE signals due to graphite electrode exfoliation tended to occur when the lithium intercalation rate changed. Thus, fracture or exfoliation of graphite was attributed to the formation of a solid electrolyte interface (SEI) or volume expansion/contraction due to lithium intercalation, respectively. Other classes AE signals were also discussed, of which some were attributed to the distortion of graphite.

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In order to enable hydrogen society in the near future, it is necessary to clarify the influence of hydrogen on the mechanical, physical and chemical properties of the materials used for hydrogen energy systems. In the case of rubbers, there is a particular danger of mechanical damage resulting from internal fracture, which occurs when high-pressure hydrogen gas is suddenly decompressed. Although our previous studies focused on fracture and deformation caused by high-pressure hydrogen decompression, the fracture and deformation of rubber materials under pressurization have not been studied. From this viewpoint, static crack growth tests of an unfilled sulfur-crosslinked ethylene-propylene-diene monomer (EPDM) rubber were conducted in hydrogen gas at 10 MPa and room temperature (around 25°C) by using a high-pressure hydrogen vessel with glass viewing ports. Deformation of the rubber during pressurization was hardly seen at ≤ 10 MPa, although hydrostatic pressure was applied and hydrogen gas penetrated into the rubber. The static crack growth rate for hydrogen gas at 10 MPa was consistent with that in air (0.1 MPa). A lot of facets with about 100 µm in size caused by the initiation and successive coalescence of secondary cracks ahead of the main crack were observed on the fracture surface of the specimens tested in air and hydrogen gas at 10 MPa, and these fracture surfaces showed a similar aspect. From these results, it was clarified that a hydrogen environment at ≤ 10 MPa did not influence the static crack growth characteristic of the rubber.

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In the fields of materials science and engineering, it is often required to measure surface temperatures of heated materials. Although infrared radiations are used for measuring surface temperature, they are not always acceptable for some applications because of the limitation in their ability. Therefore, it is required to develop an alternative technique for surface temperature measurements. In this work, a simple ultrasound method for measuring surface temperature distributions of a heated material is presented. A laser ultrasound scanning technique has been employed for non-contact measurements of surface temperature distributions. The principle of the methods is based on the temperature dependence of a surface acoustic wave (SAW). SAWs are generated at different positions on a material surface consecutively by pulsed laser irradiation scanning (Nd:YAG, wavelength=1064 nm, energy 200 mJ/pulse, pulse width 3 ns) using a one-dimensional galvanometer scanner, and each SAW is detected at a certain position using a laser interferometer based on photorefractive two-wave mixing (Nd:YAG, wavelength=532 nm, energy 200 mW). Based on the laser ultrasound scanning, a number of surfaced temperatures at different positions in series are obtained and are combined together to construct the overall temperature distribution. The proposed ultrasonic method has been applied to the surface temperature measurement of an aluminum plate whose single side is being heated. The surface temperature distributions determined by the present method almost agree with those measured using an infrared camera.

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Uniaxial and biaxial tests were conducted to investigate the deformation behavior of dual phase steel sheet with a tensile strength of 980 MPa. Detailed measurements were made of the contours of plastic work and the directions of plastic strain rate at different levels of work-hardening for linear stress paths in the first, second and fourth quadrants in the principal stress space. Cruciform specimens were used in the first quadrant and the pure shear yield stresses in the second and fourth quadrants were measured using combined tension-compression tests. The most appropriate anisotropic yield function for the material was determined by comparing the measured data with those calculated using selected yield functions. In-plane compression tests were also performed using the comb-shaped dies proposed by one of the authors. The measured work contours and directions of plastic strain rates were in good agreement with those calculated using the Yld2000-2d yield function with an exponent of 4. The stress-strain curves measured for the in-plane stress reversal tests were in fair agreement with those calculated using the Chaboche-Rousselier model; however, this model is not capable of reproducing the nonlinear behavior of the material during unloading.

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This paper describes a pushing-cut process of stacked polycarbonate (PC) sheets. In this work, the cutting line force of a 30°/90° facet blade on the upper PC work sheet and the deformation of its PC work sheet were simulated by an FEM code (MSC.MARC-2005R3) in order to reveal the effect of stacked structure on deformation flow of the PC work sheet mounted on a PC underlay. The deformation profile of the work sheet was observed with respect to indentation of the blade by varying the friction coefficients of the work sheet with the blade and that with the underlay, and also the anaphase work-hardening effect of the PC sheet was discussed for estimation of the final cutting stage.

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In recent years, due to the rapid progress of lightweight technology, the demand for lightweight mechanical and electronic parts has been increasing. To indicate an appropriate fastening guideline of magnesium alloy or aluminum alloy components is very important for safe use of lightweight components. In this study, tensile tests and tightening tests for magnesium alloy bolts and aluminum alloy bolts have been conducted to investigate the effectiveness of magnesium alloy bolts. The magnesium alloy bolts used in the tests were made of AZ31 and AZX912 (9Al-Zn-2Ca) magnesium alloy, and the aluminum alloy bolts were made of A5056 aluminum alloy. Test results showed that the tensile strength of the aluminum alloy bolts was higher than that of the magnesium alloy bolts. However the results of the tightening tests indicated that the tightening strength of the magnesium alloy bolts was greater than that of the aluminum alloy bolts. The reason the results were different in each test comes down to the magnitude of twisting torque. When a bolt is tightened to a specific clamping force, the bolt receives not only tensile force but also twisting torque. In general, the friction coefficient of aluminum alloy is higher than that of magnesium alloy. Hence an equivalent stress on the aluminum alloy bolts was larger than the same stress on the magnesium alloy bolts because the tightening torque generated when the aluminum alloy bolt was tightened, became larger than in the case of the magnesium alloy bolt. Accordingly the ultimate clamping force of an aluminum alloy bolt turned out to be less than that of a magnesium alloy bolt.

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This paper investigates the effect of the fiber discontinuity, caused by the prepreg cut in fabricating laminated structures, on the mechanical properties in CFRP laminates. Stress-strain relations under tensile loadings are obtained for unidirectional laminates that contain the fiber discontinuity, and damages in the laminates have also been observed. Nonlinear stress-strain relations at the center of the laminates have been found to be due to the interfacial debonding at discontinuous edge. In addition, it has been revealed that strains at distant from the fiber discontinuity increase sharply because the interlaminar shear stress is released by the interlaminar delamination that grows from the discontinuity. Finite element (FE) analysis model has been developed in order to calculate the stress distribution in the plates. The FE results have shown that stress concentrates in the fiber discontinuous edge with thicker discontinuous layer. Furthermore, shear-lag analysis model has also been proposed, and it has been shown that obtained stress distributions agree well qualitatively with the FE results.

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To improve the fatigue strength of the splined shaft used for a car's air conditioning compressor, press fit was added to the innermost part of the spline. This shaft connection consisting of a spline and press fit is called a "hybrid joint" in this study. A torsional fretting fatigue test was performed focusing on the effect of the amount of interference on the fatigue strength. The fatigue strength of the splined shaft was drastically increased by the hybrid joint. The fatigue strength of the hybrid joint was at most 8 times higher than that of the conventional spline-joint shaft. The fatigue strength as well as the failure mode of the hybrid-jointed specimens were changed depending on the amount of interference. The reason was that the relative slip was significantly reduced with an increase in the amount of interference. The specimen consisted of a shaft, a boss and a bolt. The hybrid joint prevented loosening of the bolt, while loosening of the bolt was found to occur in the conventional spline-joint shaft.

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The accuracy of dynamic stress-strain behavior for steel plate depends on how experimental technique is utilized properly. In the one bar method, one of the standardized high velocity tensile testing techniques, unfortunately, there is an apparent effect of the output bar supporting method on high strain rate tensile behavior of steel plate. If there is a little misalignment of the loading end of the output bar, lateral vibration of the end leads to an extraordinary-high initial stress peak on dynamic stress-strain curve. The author have been tried to find the optimum supporting condition of the metallic output bar end. Briefly speaking, at least one end of the plate specimen should be designed to be able to rotate in order to release inplane bending due to the misalignment of the bar, and no support or simple support with a V-shaped metallic support should be installed in the testing machine. However, these conditions were not enough to satisfy good reproducibility of the shape of dynamic stress-strain curves for the same specimen material. In this study, with a collar and a sheet made of polytetrafluoroethylene, the sliding energy at the contact area between the output bar and the supporting stand is tried to reduce. Good reproducibility has not been accomplished yet. Obtained experimental results suggest that some amount of contact pre-load should be introduced from the outer surface of the collar to reduce the lateral vibration of the output bar.

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In this study, tensile tests of the transparent conductive oxide (TCO) deposited on the polyethylene naphthalate (PEN) films (TCO + PEN films) used in dye-sensitized solar cells (DSCs) were carried out. In order to discriminate the AE signals in TCO from PEN films, PEN film specimens (TCO was removed by 17.5% hydrochloric acid) were also prepared. It was found from the tensile tests that many AE signals were detected in TCO + PEN films, while AE activity in PEN films was much lower. On the other hand, the electric resistance of TCO was also measured during tensile tests. The remarkable increase in AE event rate was recognized at the strain of ∼0.63%, while the electric resistance increased rapidly at the strain of 0.68%. These results demonstrated that the critical damage in TCO was detected by the measurement of AE signals more sensitively than the electric resistance measurement. To identify AE sources, in-situ observation of specimen during tensile test with AE measurement was carried out. During tensile test, cracks transverse to the loading direction in the TCO were found at the strain of 0.67%, and then saturated at the strain of ∼9%. Cracks parallel to the loading direction in TCO were initiated at the strain of 9.63%. On the other hand, the remarkable increase in AE event rate was recognized at the strain of ∼0.7%. It reached a peak at the strain of ∼2%, and then decreased, and increased again at the strain of ∼10%. It was then concluded that AE behavior corresponds to the cracking behavior in TCO. Consequently, it was suggested that AE technique could be a powerful technique for evaluating the damage accumulation process in DSCs.

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The effect of welding speed on the tensile properties and fracture behavior of friction stir welded AA6061-T6 butt joints was examined. AA6061-T6 sheets of 4.95 mm in thickness were friction stir welded in the butt joint configuration. The friction stir welding (or FSW) parameters were varied by altering a welding (or travel) speed of a cylindrical tool, keeping its rotational speed constant. Dumbbell-shaped specimens machined from the base material and the FS welded butt joints were used in the tension tests. The rate-independent Ludwik equation was used for the constitutive modeling of their plastic stress-strain behavior. It is shown that the FS welded butt joints exhibit reduced strength and ductility compared with the base material. This reduction is discussed from a microstructural point of view.

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In this study, in order to make high carbon steel coating by cold spray technique, spray conditions such as carrier gas temperature and pressure etc. were investigated. And also, in order to improve deposition efficiency and control coating hardness of cold-sprayed high carbon steel, high carbon and mild steel mixed powder and its mechanical milled powder were developed and were optimized. By using the cold-spray technique, particle deposition of a high carbon steel was successful. Moreover, by applying mixed and mechanical milled powders, the porosity ratio was decreased and deposition efficiency was improved. Furthermore, using these powders, it is possible to control the hardness value. Especially, when using mechanical milled powder, it is very difficult to identify the interface between the coating and the substrate. The bonding between the coating and the substrate is thus considered to be excellent.

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Ultrasonic welding is an attractive joining method, because bonding is quickly obtained without extra heat or welding metal. Thus far, there have been several researches about the bonded interface structure and process of the ultrasonic welding. However, atomic structure analysis of the bonded interface was limited and sometimes controversial results were obtained. Besides, there were only few studies about application of the ultrasonic welding to Al/Glass substrates and detailed bonding mechanism was unclear. In this report, the ultrasonic bonded interface between an Al wire and a Mo coated glass substrate was observed by high resolution transmission electron microscopy and the bonding mechanism was discussed. The bonded sample was cut perpendicular to the interface and, the atomic structure and chemical composition of the cross-section of the sample were analyzed. Grains in a Mo layer on the glass observed before bonding extended perpendicular to the glass substrate and terminated with nano sized pyramids. Structure of Mo grains remained unchanged after the bonding. Around the interface between Al and Mo, several dislocations and Al sub-grains were produced in Al and no intermetallic compounds were observed. Al and Mo lattices were directly connected at the interface. This indicates that dislocations generated at the interface moved to form low angle grain boundaries during a recovery process without intermetallic formation. During the ultrasonic welding process, the pyramids of Mo surface were considered to work effectively to break a native oxide and produce the bonded interface.

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Clinching is an attractive joining method as one of alternatives meeting the recent significant demand for joining low-weldability materials and dissimilar materials. Because it has many advantages in terms of productivity, cost, recyclability, and no requirements for specific surface conditions of materials. However, application of clinching is restricted by its low joint-strength and the difficulty to join low-ductile materials. Hence, to overcome this problem, we developed a novel clinching process in which ultrasonic vibrations were applied perpendicularly to the materials by the clinching tools. In this paper, the effects of ultrasonic assists on clinching for aluminum sheets in two types of vibration modes were investigated. In one mode, work pieces were located on the maximum-displacement-amplitude position, and in the other mode, materials were located on the maximum-stress-amplitude position. As the results, the application of ultrasonic vibrations in the maximum-displacement-amplitude mode showed no prospective results. Because the applicable vibration amplitudes were restricted by generation of cracks due to the high-cycle bending load. On the other hand, the application of ultrasonic vibrations in the maximum-stress-amplitude mode showed unique vortical flows in the applied material. These vortical flows led to a stirring phenomenon in the material, and the aluminum sheets were unified. Due to the unification by the stirring phenomenon, the cross-tensile strength was increased up to 60 % and the joining pressure was reduced up to 80 %. And a grain refinement effect was also observed. Finally we discussed about the potentials of the stirring phenomenon for joining dissimilar materials and a new grain-size refinement method.

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Surface rolling experiments and surface durability tests were carried out using powder metallurgy (P/M) gears made of 1.5Cr-0.2Mo single-press single-sinter (1P1S) high density (7.55×10³ kg/m³) sintered steel. The fundamental densification properties of this P/M material were first examined using P/M rollers. A high precision form rolling machine of two roller-dies transverse type was employed. The porosity became nearly zero from the surface down to a depth of at least 0.5 mm when the amount of decrease in the roller radius was more than 0.15 mm. Next, the gear tooth profile analysis was done by finite element simulation (FE-simulation) to optimize some shape parameters of a modified convex tooth profile of P/M spur gears before rolling. Simulation results agree well with the experimental data and gears with good tooth profile accuracy and a fully densified surface layer of about 0.5 mm in depth on the gear flank could be obtained. The gear running tests were finally conducted using a power re-circulating type gear testing rig with a counter pinion gear made of Ni-Cr-Mo wrought steel. Both P/M gears and counter pinions were case-carburized and finished by grinding under the same conditions. The test results confirmed that high density 1.5Cr-0.2Mo P/M gears had sufficiently high load bearing capacity as an automotive power transmission gear and those surface durability tended to increase by surface rolling.

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Thin liquid layer exists between bone and bone in joint of human body, and also, thin tear film covers cornea. These thin liquid layers contain biopolymer such as hyaluronic acid and mucin. These thin liquids make it possible that smooth movement of the joints and smooth blinks. In this research, effects of polymer in thin liquid layer are studied by using flowing soap films. Soap films consist of about 4 µm thickness water layer inside and surfactant mono-layer in the surface. Interference patterns of the soap films are affected by the thickness of the water layer. Thus the interference pattern reflects the behavior of the water layer. In this study, turbulence was made in flowing soap films, the effects of long flexible polymer Polyethylene oxide (PEO, M_w=4x10⁶) to the turbulence was observed by the interference pattern. This technique is proposed as Film Interference Flow Imaging method (FIFI). Thickness and velocity information of the turbulence were observed by FIFI. Inner structure of the soap solution containing PEO was observed by Scanning Microscopic Light Scattering (SMILS) which is a light scattering system specialized for analyzing microscopic structures. For some applications, investigations of the polymer effects in thin liquid layer are useful for the development of polymer drag for joint pain or dry eyes.

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This paper describes the effect of the friction welding condition and the weld faying surface properties on the tensile strength of the friction welded joint between pure titanium (Ti) and pure copper (OFC). The joint strength of the joint, which was made with the weld faying surface of the Ti side specimen finished with a surface grinding machine, was investigated. The joint did not have 100% efficiency and OFC side fracture regardless of the friction welding conditions. When the joint was made with a friction pressure of 75 MPa, the joint efficiency was approximately 64% regardless of the forge pressures, and all joints fractured at the weld interface, although that efficiency exceeded that of the joints made with other friction pressures. To improve the joint efficiency, one was made with a Ti side specimen whose weld faying surface was finished by buff polishing. The joint efficiency was increased to approximately 85%, although the joint fractured at the weld interface. Moreover, a joint at a friction pressure of 75 MPa with a forge pressure of 270 MPa or higher was obtained with an OFC side fracture, although it did not achieve 100% efficiency. The fact that the joint did not fracture at the OFC base metal was due to the mechanically mixed layer at the weld interface that depended on the maximum height of the Ti side weld faying surface. To clarify the reason why the joint did not achieve 100% joint efficiency, the tensile strength of the OFC base metal with the addition of various compressive stresses was investigated. When the compressive stress was higher than the yield stress of the OFC base metal, its tensile strength was lower than that without a compressive load. Moreover, the tensile strength along the radial direction of the OFC base metal was also slightly lower than that of the longitudinal direction. Hence, the fact that the joint did not also achieve 100% efficiency was due to the decrease in the tensile strength of the OFC base metal by the Bauschinger effect and the difference of the anisotropic property with as-manufactured condition.

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Alumina matrix composites reinforced by carbon nanofibers (CNFs) of 0, 5, 10, 20 vol% were fabricated using a spark plasma sintering (SPS) technique. In this study, to disperse CNFs uniformly in ceramic matrix, an electrostatic adsorption technique was used to fabricate the mixed powder. The open porosity of the specimen increased and the mechanical properties decreased with the increase in CNF content. It might be resulted from the insufficient interfacial shear strength and CNFs worked as flaws in composites. In order to improve the interfacial shear strength, SiC particles were added into the interfacial phase between CNF and matrix so that the thermal mismatch and bonding between CNF and matrix were controlled. Consequently, it was demonstrated that mechanical properties were enhanced and the pull-out length decreased for the specimens with SiC addition. It was then suggested that the interfacial shear strength was successfully improved due to SiC addition.

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A series of three-point bending tests for granite consisting of quartz, plagioclase, alkali feldspar and biotite was carried out at quasi-static and dynamic rates to examine the relation between its mechanical properties and electromagnetic phenomena during fracture. The output of ferrite-core antenna, which was located close to the specimen in a shielding box made of Permalloy plates, was measured through a band-pass filter. The dynamic bending strength was larger than the static one, i.e. the positive strain-rate dependence was observed in the strength of granite. It was also found that the intensity of electromagnetic waves measured in dynamic tests was much greater than that observed in static tests. This means that the electromagnetic phenomenon strongly depends on the loading rate, too.

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Metallic cellular materials containing a polymer were fabricated by the polymer penetrating into cells of the metallic cellular material. The stainless steel cellular materials were selected for use as the cellular material and polyurethane resin was selected as the penetrated polymer. The mechanical properties of this material were measured. The results of the compressive tests showed that the stainless steel cellular material containing the polyurethane has different stress-strain curves from that without any polymer. These results also showed that the stainless cellular material containing polyurethane has a high-energy absorption. The shock absorbability of this material is higher than that of the polymer and lower than that of the stainless steel cellular material.

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Segment-structured diamond-like carbon (S-DLC) film, which is separated DLC films into small segments using metal mask, has been developed in order to improve its tribological property or accomplish multi-functionalized surface. Meanwhile, the S-DLC deposition by conventional methods using metal mesh as masks is difficult to apply to the three-dimensional substrates which have complicate curves. The purpose of this study is to develop coating methods for S-DLC deposition on the three-dimensional substrates like an aspect of the cylinder and a ball surface. In this study, we report the coating method using a robot employing six degrees of freedom (MOTOMAN-MH6: Yaskawa electric corporation) and a micro ink jet system (IJHB-1000 and IJHB-30: Microjet corporation). By adjusting the parameters applied to the piezoelectric element, the ink droplet was stable discharged. Then, small grid patterns were drawn on the plate. The substrate temperature is also controlled in order to make the drawn line thinner, because the resin ink is thermosetting material. Then, the DLC film was deposited onto the ink drawn substrate by a micro-pulse plasma CVD method using acetylene gas for 40 minutes. After the liftoff and the Raman spectroscopy measurement, we found that the resin ink could play a role as a mask material. Finally, grid patterns were successfully drawn on the aspect of the cylinder and a ball surface. In conclusion, it could be thought that this masking method could be used to various shape by complicating the robot programming in the future.

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Small surface intergranular cracks similar to those detected in the heat affected zone of the welded components of primary water recirculation loop for boiling water reactor (BWR) were introduced on the surface of sensitized SUS304 stainless steel by using a fretting fatigue technique, where multiple parallel small surface cracks in the localized fretting slip region were nucleated. Constant load tests at various initial stress intensity factors (K_i) were then carried out in 288°C, 7.3MPa pure water, which is the operating condition for BWR, to investigate failure behavior of this material under constant load condition. From the results, it was speculated that the K_ISCC for small surface crack was lower than 4.7MPa·m^1/2, which was significantly low compared to that of long crack (10-20 MPa·m^1/2).

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Japanese lantern that is made and used in Kyoto is called “Kyo-Chouchin”, which is one of traditional crafts in Kyoto. Kyo-Chouchin is made by craftsman one by one and made of bamboo framework and Japanese paper. In fabricating process, there is “Hone-tame” process that craftsman applies load to a bunch of bamboo circles. In this study, in order to investigate the influence of Hone-tame process to bamboo properties, mechanical test and form measurement of bamboo were performed. Specimens treated in Hone-tame process different amount of time were prepared. As a result, the Hone-tame process has effects which tensile strength of bamboo beam is evened up and bamboo hoop become true circle.

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Influences of loading rates on the stress-strain relations of cured adhesive were experimentally investigated. A brittle epoxy adhesive and a ductile epoxy adhesive modified with rubber particles were examined. Concave specimens of the cured adhesives were made, and strain gages for very large strain were bonded on the specimens. The specimens were tested in static conditions with a material testing machine and in dynamic condition with a drop-weight impact testing machine. The influences of loading rates on the stress-strain relations of the adhesives were identified. For the brittle adhesive, the modulus was constant in both the static and dynamic conditions, and the tensile strength and total strain increased with the increase of loading rates. For the ductile adhesive, large plastic deformation occurred in the static condition, and the tensile strength was 37 MPa and the total strain was 14%. In contrast, in the condition of high loading rate, the ductile adhesive became brittle, and the ultimate stress increased and the maximum strain decreased.

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Pd₇₇Cu₆Si₁₇ thin film metallic glasses of which thicknesses were 10, 20 and 28 µm were bent by laser forming. The working conditions were changed and crystallization of thin films was investigated. When the laser power was changed under fixing the scanning velocity to 40 mm/s and the Q-switch frequency to 3 kHz, crystallization was observed at laser irradiated surface and/or the reverse side to the laser irradiation. In a case of changing the scanning velocity under fixing the Q-switch frequency to 3 kHz and the laser power to 2.0 W for the film thickness of 20 µm and 3.0 W for the film thickness of 28 µm, the working conditions without crystallization were found at high scanning velocity. When the Q-switch frequency was changed under fixing the scanning velocity to 40 mm/s and the laser power to 2.0 W for the film thickness of 20 µm and 3.0 W for the film thickness of 28 µm, the working conditions without crystallization were found at low Q-switch frequency.

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Diamond-like carbon (DLC) films have many excellent characteristics such as low friction coefficient, wear resistance, gas barrier property and biocompatibility. These many positive characteristics enable DLC coatings to be applied to a lot of fields from metallic materials to polymer materials for overcoatings. However, usual DLC film has a lot of micro-pores or pinholes, and those defects become problems as DLC film is not able to make the best use of abrasion resistance effectively due to the substrate corrosion. In addition, the DLC films deposited directly on the steel substrates often encountered the problem of poor adhesion. It has been attempted to overcome the negative effect by means of multilayer structure using metal and ceramic layers. In this study, we aim to deposit DLC films satisfied with both antiwear and anticorrosion characteristics. This time, we attempted to improve those properties by enhancing adhesion strength between DLC film and substrate. Interlayers used were a Si modified DLC (Si-C:H) interlayer deposited by using Si(CH₃)₄ gas and a Cr interlayer deposited with magnetron sputtering method. These interlayered DLC films were deposited on austenite stainless steel substrates. DLC films with Si-C:H and/or Cr interlayer were deposited by a pulse plasma CVD method using C₂H₂ gas. Three kinds of coatings: (1) substrate/Si-C:H/DLC, (2) substrate/Cr/DLC and (3) substrate/Cr/Si-C:H/DLC had been done. As fundamental tests, Raman spectroscopy, nano indentation, X-ray reflectometer analysis and rutherford back scattering spectrometry/elastic recoil detection analysis were carried out to reveal both mechanical and anticorrosion characteristics. Then, ball-on-disk tests and electrochemical measurements also had been running. These results lead us to conclusion that the effects of the DLC coating had been confirmed and an optimal structure to improve both tribological property and anticorrosion property was substrate/Si-C:H/DLC. Moreover, in the case of emphasizing tribological property, substrate/Cr/Si-C:H/DLC structure was recommended.

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In this study, the jute fiber and glass fiber were used as reinforcements in polypropylene (PP) to fabricate the jute/PP and glass/PP pellets by the long fiber pellet technique. Those two long fiber pellets were used to mold both dispersed and sandwich dumbbell specimens by injection molding. The effects of jute/glass fiber hybridization and sandwich structure on mechanical properties of the hybrid composites were investigated related to “Green degree”. When adding about 12.5 wt. % of glass fiber into natural fiber composite as in hybrid dispersed composite, the mechanical properties as comparing with jute/PP composite were significantly improved due to the high mechanical properties of the added glass fiber. Moreover, the glass fiber hybridization also improved the better fiber orientation and distribution of jute fiber based on the SEM observation on the fracture surface after tensile test. Regarding natural fiber sandwich structure, the jute/PP core sandwich composite with relative higher jute fiber content shows higher tensile modulus than the jute/PP skin sandwich composite but a decreased bending modulus conversely. The addition of glass fiber in the core layer or skin layer can significantly improve both tensile and bending modulus of sandwich composite comparable to the jute/PP composite and dispersed jute/glass fiber hybrid composite. Moreover, it can be seen that the hybrid core layer sandwich composite shows higher tensile and bending strength than the hybrid skin layer sandwich composite. In a word, with appropriate designed sandwich structure in both core and skin layers, jute/glass fiber hybrid composite with higher green degree and desired mechanical properties can be achieved.

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The combination of laser displacement sensor and strain gauge method is newly devised to measure the elastic deformation of the tool-workpiece interface in cold forging. A deep hole is bored close to the inside surface of the die container. A steel pin is placed in the hole to detect the minute displacement near the die-workpiece interface. The movement of the pin is measured by laser displacement sensor. The displacement of the installation position of the laser sensor is measured simultaneously by the strain gauge method to adjust the measurement obtained from the laser sensor. This method is applied to the measurement of die deformation in the backward extrusion process. The displacement distribution over the die-workpiece interface under various conditions is obtained. It is proved that the newly developed method is effective for the measurement of die deformation in forging.

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Coal ash and aluminum sludge are industrial wastes discharged in large amounts by electric power plants and aluminum sash factories. In this study, aluminum sludge was heat treated at a temperature of 1573K for 2 hours to change the α-alumina crystal structure. The silica (SiO₂) contained in coal ash and the alumina (Al₂O₃) contained in aluminum sludge were combined to synthesize mullite by using a spark plasma sintering apparatus. While varying the composition ratio of the fly ash and α-alumina sludge, the mechanical properties were investigated. As a result, the bending strength of the composite material (composition weight ratio of coal ash and α-alumina sludge 2:3) showed an extremely high value of 270MPa at a sintering temperature of 1573K and holding pressure of 40MPa. Using X-ray analysis, the existence of mullite crystal structures in this material was confirmed.

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A Finite element (FE) model considering mesoscopic material inhomogeneity due to a different flow stress for each crystal grain to predict free surface roughening is proposed. The effect of the standard deviation of the material inhomogeneity and grain size was investigated by the 2D FE model. In addition, to verify the model considering material inhomogeneity, the free surface roughening behavior is predicted under a bi-axial tension state using the 3D FE model. Furthermore, by comparison with experimental results, the validity of the FE model considering material inhomogeneity and its determination method is discussed. The standard deviation σ_sd of the material inhomogeneity parameter α in the model has a strong correlation with the rate of increase in the surface roughness, which increases with increasing grain size, is agreement with the conventional empirical equation. The surface roughness under bi-axial tension state is larger than that under uni-axial tension state. In addition, the experimental results are in good agreement with the simulation results. From these findings, we can verify the fundamental behavior and the validity of this model considering material inhomogeneity for the prediction of free surface roughening.

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For the fabrication of MEMS or devices in micro scale, joining of small parts is a critical issue. In this study, thin metal foils were welded using electron beam welding to investigate the weldability of the foils. In the welding of thin foils, the heat-affected zone and welding state are strongly dependent on the energy density of the irradiation beam, and size effects, such as heat capacity and stiffness, are important as the thickness of the material becomes small. Two materials, stainless steel and titanium with thickness values of 10 µm and 20 µm, were used as workpieces. An electron beam with several incident energies was applied, and the surfaces and cross-sections of the weld zones of the workpieces were examined. The experimental results show that the weldability of foil welding strongly depends on the material properties and the thickness of the workpieces, and it becomes more difficult to weld two overlapping foils with smaller thickness and lower thermal conductivity.

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In order to understand the splat formation process of individual splat deposited by thermal spraying, commercially available Nickel powders with diameter of several tens micrometers were thermally sprayed onto mirror polished AISI304 substrate surface. The deposited splat shows transition phenomenon from splash type to disk one in flattening on collision onto substrate surface according to both substrate temperature and ambient pressure change. That is, transition temperature, Tt and transition pressure, Pt can be defined as critical values for the transitions. The three-dimensional map was set up to control the thermal spraying process. The observation on the bottom surface morphology on single splat indicates that the initial solidification may induce the splashing occurrence. Moreover, as the simulation of the real thermal spraying process, free falling experiment was conducted in this study. The thermal history of the free falling Cu droplet onto AISI304 substrate was investigated, indicating the flattening pattern is decided just after collision onto solid surface, which is enough earlier to finalization of the flattening.

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Double network (DN) gels are anomalously robust but soft and wet materials, whose maximum stress in compression reaches 30MPa and surface friction coefficient reaches 0.001 simultaneously. The DN gels also have shock absorbency, permeability, and biocompatibility. Thus it is expected that the DN gels will be applied to artificial joints, artificial cartilages, and artificial blood vessels. In this study we focused on both high transparency and large transformation of the DN gels, and we tried to develop novel optical devices. Our purpose is to apply it to a deformable lens system. Indeed, we succeed to make an artificial gel lens, which is nontoxic and have biocompatibility. The value of strain of the gel lens can achieve more than 2, and Young's moduli of our two kinds of DN gels show 0.45MPa and 0.46×10^-1MPa, which is enough higher than human lens. We will realize further miniaturization and simplification of various optical products containing the gel lens.

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For the future construction of the large scale space platform on the earth orbit, the high specific strength and modulus engineering materials will be required to braze in space. In this research, the combination of carbon/carbon composites and titanium is chosen and it is investigated that the effect of the cross-ply angle to the brazing interface to the shear strength and the microstructure at the brazing interface. A 2-D laminated C/C composites plates with cross-ply angle of [0°/90°]S, [+45°/-45°]S and [30°/-60°]S were prepared. They were brazed to pure titanium tablet in the vacuum using the active brazing filler of Ag-32.25Cu-1.75Ti at 830°C for 300s. The shear strength of the brazed joint was measured by the tensile shear rupture test. All of the obtained joints were fractured at the bulk C/C composites. On the case of [0°/90°] cross-ply laminated C/C composites, the shear strength reached to the maximum value up to 24 MPa.

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Two kinds of roll casters to cast the aluminum alloy clad strip were invented. One was a vertical tandem type twin roll caster and the other was an unequal diameter type roll caster. Three layers of clad strips were able to be cast by these roll casters. The three layers clad strip, of which the temperature of the liquidus line of the base strip was higher than that of the overlay strip, could be cast by the vertical tandem type roll caster. When the temperature of the liquidus line of the base strip was lower than that of the overlay strip, the unequal diameter type roll caster was used to cast the three layers clad strip. The interfaces between the strips were clear and the layer of the diffusion of the element was very thin. The clad strip was not peeled off at the interface by the bending and the cold rolling. The strips were connected strictly. The casting of the strip and the cladding of the strips could be operated simultaneously by one caster.

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To establish the shearing delamination strength evaluation method of thin coating layer with high strength, thermal sprayed coatings were tested by newly proposed torsion pin test method with tension. In this study, delamination strength of WC-12Co thermal sprayed coating is investigated experimentally and analytically. Stress distributions at crack tip singular point on delaminated surfaces are analyzed by FEM and is approximated by the expression σ=Kr^-λ where K means a size of the field of singular stress. The critical combinations of shear stress intensity factor (Ks) with tensile stress intensity factor (Ka) which means delamination criteria of coating under combined shear and tensile loadings can be obtained for various pin clearance. These combinations were found to be independent of pin clearance.

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A new direct joining method for dissimilar materials between a metal and a plastic by using friction stir heating technique is introduced. A5052 and polyethylene terephthalate (PET) were used as materials used in this study. The joining strength was evaluated under tensile shear loading condition. The fracture surface and the cross section of the joined specimens were observed in order to understand characteristics of the joints. The results show that A5052 and PET were successfully welded by the present joining method. Similar strength of the joints was obtained regardless of the joining conditions. Melting and softening behaviors of PET and formation of bubbles observed in welded area might affect the joining strength.

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Dieless drawing offers several advantages not only lack of the expensive dies and lubricant but also the ability to draw difficult material since the process is carried out at elevated temperature. However dimensional stability and accuracy is still unsolved issue. A finite element method (FEM) is utilized to examine a valid deformation behavior. As the result, a correction function is formulated from deformation sequence of dieless drawing to predict elongation of desired profile. A new approach to control desired profile of dieless drawing parts using a fuzzy model and correction function is presented in this paper. The result shows that by applying fuzzy control and correction function model, dimensional accuracy of drawn tube profile increases significantly.

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Magnesium alloy is the lightest in practical metals, and it is used for small home appliance products and automobile parts. It is also expected to be a new material for medical stents, because of its possibility of systemic absorption. But, it is known that the processing of magnesium alloy is very difficult and many magnesium alloys are hot-worked. Therefore, surface quality and strength of products and processing cost are the points when cold-plastic working of magnesium alloy is carried out. The purpose of this study is fabrication of a tube of magnesium alloy to improve stent strength and to reduce processing cost. Fineness, thinness, adequate strength and high-quality surface are required for stents of the medical tube. Therefore, firstly, plug drawing was carried out, because it was thought to be one of the methods for satisfying the requirements. But, it proved to be impossible to apply this method, because magnesium alloy is too brittle for plug drawing. Secondly, soft-metal mandrel drawing was tried. Drawing was possible, but it was difficult to extract the mandrel, because there is a possibility that the tube might break due to its high drawing stress. So, fluid-mandrel, a new method for mandrel drawing, was carried out. As a result, the fabrication of a fine and thin-walled tube for a stent became possible. And it was found that the wall-thickness of the tube was as thin as existing medical tubes. In fluid-mandrel drawing, fluid is used as mandrel. So, it is easy to extract mandrel after drawing. And it is possible to prevent tube break during drawing, because drawing stress is lower than that of soft-metal mandrel drawing.

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