Engineering ceramics have high stiffness, excellent thermostability and relatively low density, but their brittleness impedes their use as structural materials. Incorporating carbon nanotubes (CNTs) into a brittle ceramic might be expected to produce CNT/ceramic composites with both high toughness and high temperature stability. Until now, however, materials fabrication difficulties have limited research on CNT/ceramic composites. The mechanical failure of CNT/ceramic composites reported previously is primarily attributed to poor CNTs-matrix connectivity and severe phase segregation. The connectivity with, and uniform distribution within the matrix are essential structural requirements for the stronger and tougher CNT/ceramic composites. Here we show that a novel processing approach based on the precursor method for synthesis of Al₂O₃ and acid-treated multi-walled carbon nanotubes (MWCNTs) can diminish the phase segregation, and render MWCNT/Al₂O₃ composites highly homogeneous. Combined with mechanical interlock induced by the chemically modified MWCNTs, this approach leads to improved mechanical properties. Direct toughness measurements, using the single edge notched beam method, reveal that only 0.9 vol.% acid-treated MWCNT addition results in 25% increases in fracture toughness (5.90±0.27 MPa·m^1/2).

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Quantitative detection of microcracks during fracture process of alumina was carried out by AE source characterization, which enables the quantitative characterization of the size, nucleation velocity and fracture mode, as well as nucleation time and location of individual microcracks. Fracture toughness tests of SENB specimens of two types of alumina with different grain size and purity were carried out in air and water. AE signals emitted from microcrackings were detected by piezoelectric transducers. The combined response function of the specimen and measurement system was experimentally determined using a pencil lead breaking as a simulated source. Then AE source function which describes the nature of microcrack nucleation was determined by the inverse calculation using obtained response function and detected signal. Consequently, it was clarified that the size of microcrack in water was larger than that in air for both alumina and larger microcracks nucleated in water resulted in the degradation of fracture resistance.

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In this paper, an exact distribution of fracture strength was derived from extreme value statistics for an initial distribution of flaw size, via conversion to an exact distribution of largest flaw size. Gamma distribution was shown as a better function to approximate the initial distribution data measured by immersion liquid technique. The exact distribution of fracture strength was obtained as a function of the number of links in the weakest link theory. With increasing the number of links, the exact distribution gradually became linear on Weibull plot, and almost coincided to Weibull distribution at the number of links larger than 1000. Compared to actual distributions of fracture strength, the number of links in the specimens was estimated to be in the range from 10⁴ to 10⁵. The above discussion showed a verification of this theory.

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The microstructural influence of martensitic carbon steel on torsional fatigue endurance was investigated, taking into consideration the application of high strength steel electric resistance welded (ERW) tubes to automotive structural parts. The chemical composition of the base steel alloy was 0.1-0.2%C-0.2-1.5%Si-1.3-1.9%Mn-0.01%P-0.001%S-(Cr, Mo, Ti, Nb, B). Laboratory vacuum-fused ingots were hot-rolled, heated to 1023 or 1223 K in a salt bath, and then water-quenched and tempered at 473 K. Consequently, three types of microstructure, martensite (M), martensite and ferrite (M+F), and ferrite and pearlite (F+P), were prepared. Fully reversed torsional fatigue testing was conducted with 6 mm diameter round bar specimens. Torsional fatigue endurance was found to monotonously increase with increases in the tensile strength of the specimen from 540 to 1380 MPa. The martensitic single structure and the M+F dual-phase structure showed a similar level of fatigue endurance at a tensile strength of approximately 950 MPa. However, fatigue micro-crack morphology varied slightly between them. At the surface of the M+F specimen, many small cracks were observed in addition to the main crack. Conversely, in the martensitic specimen, these small cracks were rarely observed. ΔK decreasing/increasing crack growth testing with compact tension (CT)-type specimens was also conducted. Based on these experimental results, the effect of microstructure and stress level on the initiation/propagation cycle ratio is discussed. In addition to fatigue properties, some practical properties, such as low-temperature toughness and hydrogen embrittlement resistance, were also evaluated in view of actual applications for automotive structural parts.

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Aluminum matrix composites (70vol%SiC/Al, 55vol%SiC/Al, 60vol%Al₂O₃/Al, 70vol%AlN/Al, and 30vol%SiC/Al) were prepared by the infiltration and the casting methods. The internal friction and the microplasticity of these composites were measured with a Föppel-Pertz torsion pendulum apparatus over the temperature range of 303 to 853 K and the strain range of 3×10^-5 to 3×10^-3. The internal friction of these composites increases with increasing temperature and increases rapidly over 600 to 800 K, while their shear modulus gradually decrease and rapidly decrease over 600 to 800 K. The internal friction of the composites at elevated temperatures is caused by relaxations due to the interfacial diffusion between a reinforcement phase and Al and due to the plastic flow at grain boundaries. The activation energy of the interfacial diffusion is 40.7-56.7 kJ/mol for SiC/Al, 62.1 kJ/mol for Al₂O₃/Al, and 27.7 kJ/mol for AlN/Al, respectively. The activation energy of the plastic flow is 42.3-119 kJ/mol. The internal friction of the infiltration composites remarkably depends on strain amplitude rather than that of the casting composites. The Granato-Lücke plots of the composites show a linear relationship, indicating that the increase in internal friction with increasing shear strain is caused by the vibration energy loss due to the dislocation damping mechanism. The dislocation mobility of the infiltration composites is larger than that of the casting composites. The specific damping capacity and Young's modulus of 70vol%SiC are higher than those of 70vol%AlN.

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The behavior of transverse crack growth and delamination growth under high-cycle fatigue loadings was investigated with cross-ply CFRP laminates, [0/90₂]_s and [0/90₆]_s, and quasi-isotropic CFRP laminates, [45/0/-45/90]_s. As a result, it was observed that the behavior of damage growth was different depending on the applied stress level. The growth of local or edge delamination was exacerbated under the test conditions of a low applied stress level and high-cycle loadings, because the areas of stress concentration were applied with high-cyclic loadings. On the other hand, when the fatigue tests were conducted under the applied stress level of 40% of the transverse crack initiation, the growth of transverse cracks was hardly observed until 10⁸ cycles with [0/90₂]_s, [0/90₆]_s and [45/0/-45/90]_s laminates.

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This paper presents the thermal actuation capabilities of the SiC continuous fiber/aluminum active composite plates fabricated by laminating a unidirectional fiber-reinforced layer and an unreinforced one. In this study, the effects of the fiber spacing and the number of thermal cycles on the curvature change of the composite during the thermal cycles between room temperature and 712 K up to three times were examined, and it was found that the curvature changes during the thermal cycles become almost repeatable after a couple of cycles, but the curvatures slightly increase with increasing the number of thermal cycles. It was also found that the room temperature curvatures can be maximized by the optimized heat treatment at 833 K, and the maximized one becomes repeatable even after the thermal cycle up to the higher temperature of 833 K. Therefore, the optimally heat treated composite can be used as a stabilized thermal actuator. As the maximized room temperature curvature can be recovered by the same optimum heat treatment even after a severe plastic deformation, this remarkable shape recovering capability of the active composite can be regarded as a newly developed function.

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This report describes the application of magnetic compound fluid (MCF) rubber as a material for microwave heating. MCF rubber is one of several new composite materials utilizing MCF as a newly developed magnetic responsive fluid developed by Shimada. The temperature of water in a PP container enveloped by MCF rubber in a microwave oven was measured at various mass concentrations of magnetic particles in the MCF rubber. The measurements were compared to those of MCF rubber in a microwave oven. The results showed an optimum mass concentration in relationship to the increase or decrease of the water temperature. At less than about 50 wt% and more than about 90 wt% of the magnetic particles in the MCF rubber, changes in the water temperature were small but those of the MCF rubber were large. However, in the range of about 60-80 wt%, changes in the water temperature were large but those of the MCF rubber were small. To explain the experimental data, we derived a simple microwave heating theory and measured experimental data for the complex permittivity and permeability of the MCF rubber. This could partly explain the experimental results qualitatively. We also found in the present study that iron particles are better for the MCF rubber in microwave heating than copper or nickel particles. In conclusion, the MCF rubber is a useful material for microwave heating in a microwave oven.

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Metal flow and strain distribution in the flat rolling of Sn-Pb alloy powder are experimentally analyzed by the modified visioplasticity method. The alloy powder is packed in a container of 10mm square made of aluminum foil and rolled up to 80% reduction in height. After the interruption of rolling, distorted shapes of the powder particles are measured experimentally. It is observed that the difference of reduction has considerable influence on the flow and strain distribution. As a result, it is made clear that the deformation of powder particles can be classified into three areas; (A) pore decreasing area, (B) particle bonding area and (C) plate forming area.

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In this paper, the synthesis of WC-Co alloy was investigated. Especially the formation of WC phase during the solid-phase sintering was discussed. The chemical composition of WC-Co was chosen to be WC-20vol%Co. The powder mixture of stoichiometric quantities of elemental powders was mechanical alloyed by using low-energy ball mill under an Ar atmosphere. After 1800ks milling, the X-ray diffraction profile showed only elemental W phase. At DTA runs, W₂C and Co₆W₆C phase formed about 1140K and then transformed to WC and W₃Co₃C with increasing temperature. Therefore, it is considered that the WC phase synthesized at the sintering process, not milling stage like other investigations. 1800ks milled powder was consolidated by using pulse current sintering method at the temperature of 1373K. The compact consisted mainly of WC with Co and W₃Co₃C phases. The hardness of the compact was 1648HV and 91.8HRA. The 3-point bending strength was about 2GPa.

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This paper describes the effect of the friction welding condition on the joining phenomena and tensile strength of friction welded joint between pure copper (OFC) and low carbon steel (LCS). When the joint was made at friction pressure of 30 MPa with friction speed of 27.5 s^-1, OFC transferred to the half radius region of the weld interface on the LCS side, and then transferred toward the entire weld interface. The temperatures at the centerline, half radius and periphery portions on the weld interface of the LCS side were almost the same after the initial peak. When the joint was made at a friction time of 2.4 s, i.e. the friction torque was close to the initial peak, that had obtained approximately 40% joint efficiency and fractured from the weld interface with a little OFC adhering to the weld interface on the LCS side. The joint efficiency increased with increasing forge pressure, and it reached approximately 80% at a forge pressure of 180 MPa. This joint fractured at the softened OFC region adjacent to the weld interface. On the other hand, OFC transferred to the peripheral region of the weld interface on the LCS side when the joint was made at friction pressure of 90 MPa with friction speed of 27.5 s^-1. However, OFC transfer was not obtained at the central region because the temperature at the periphery portion was higher than that of the other portions. The joint efficiency increased with increasing friction time, and it obtained approximately 74% at a friction time of 1.2 s. Moreover, all joints fractured between the OFC side and the weld interface, although the joints were made with higher forge pressure. To obtain higher joint efficiency and fracture in the OFC side, the joint should be made with low friction pressure and high forge pressure, and with the friction time at which the friction torque reaches the initial peak.

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Thermal barrier coating (TBC) systems which are used for insulating the substrates of gas turbine blades from high temperature can be made by thermal spraying. The TBC system has residual stresses because of high temperature deposition and the thermal expansion mismatch in the system. In this study, how the residual stress occurs in TBC system was examined by both experimental measurement and FEM analysis. The Yttria-stabilized zirconia (YSZ) top coating was deposited by atmospheric plasma spraying (APS). CoNiCrAlY bond coatings were deposited by high velocity oxygen-fuel (HVOF) spraying and APS. The temperatures of YSZ, CoNiCrAlYs and substrates were measured during thermal spraying. The temperature of YSZ was the highest and that of CoNiCrAlY(HVOF) was the lowest among the three types of spray processes. The residual stresses were elastically calculated by FEM based on the measured temperature histories. The residual stress of YSZ and CoNiCrAlYs on two types of substrates were also measured by X-ray diffraction method. It was confirmed from FEM analysis that residual stress consisted of primary quench stress and secondary thermal mismatch stress. The quench stress was caused by the quenching of coating particles during deposition which occurs due to the huge thermal capacity of the substrate. The thermal mismatch stress was caused by the difference in linear expansion coefficients between coating and substrate. It was found that not only these two mechanisms but also microcrack formation caused by quench played an important role in the residual stress. The temperatures at which residual stresses might begin to occur in the coatings were shown based on the stress relaxation by microcrack formation. It was also found that peening effect played an important role in the residual stress of HVOF sprayed coating.

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Titanium dioxide (TiO₂) is a promising material for photocatalyst coating. However, it was difficult to fabricate TiO₂ coatings which have excellent photocatalytic property by thermal spray processes. Because anatase phase of TiO₂ transforms into rutile phase under high temperature i.e. the photocatalytic property of TiO₂ declines by heating. In this study, TiO₂ photocatalyst coatings were fabricated by cold spray process. Agglomerated TiO₂ powder with 100% anatase phase was injected into helium gas stream and deposit onto steel substrate. It was possible to fabricate TiO₂ coatings with anatase phase. The deposition efficiency was increased with working gas temperature. The photocatalytic property of the coatings was evaluated by NOx elimination test. From the results, it became clear that cold sprayed TiO₂ coatings have outstanding photocatalytic property.

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Hydrogenerated boron nitride (BN:H) films were deposited by nanopulse plasma chemical vapor deposition (CVD) using borane-ammonia complex as a source gas. Fourier transform infrared (FTIR) spectroscopy, glancing angle x-ray diffraction (XRD) and atomic force microscopy indicated that the BN films had a smooth surface and amorphous structure. Surface roughness (Ra) value of these films was under 0.5 nm. The films deposited at room temperature had high adhesion strength, as determined by scratch tests. Ball-on-disk tests were carried out to evaluate the tribological properties of the deposited films against the SUJ2 ball. The friction coefficients of BN:H films deposited at 300°C and 400°C were very high, exceeding 1.0. The specific wear rate of these BN:H films was as low and of the order of 10^-7 mm³/Nm which is close to that of DLC. Annealing tests on the deposited BN:H films were performed in order to evaluate their thermal stability. It was found that the deposited BN:H films had higher thermal stability than DLC films at 500°C in air.

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The feasibility of recycling machining grindings of aluminum alloys by the semisolid process has been investigated. Machining grindings of A2011 aluminum alloy produced experimentally by lathe machining were used. The material is put into a metal mold and compressed up to 90% of the true density at room temperature. The metal mold with the compressed machining grindings is heated to a specified temperature. Afterwards, the metal mold is set into the extrusion container, and extrusion in the hot and semisolid range is carried out. In this experimental study, extrusion load, internal structure and mechanical properties (tensile strength, elongation, hardness) of the product are assessed. It was proven that (1) semisolid extrusion has about 40% less extrusion load compared with that of hot extrusion, (2) the shape of the machining grindings remained in the hot extrusion products and (3) the semisolid extrusion products at extrusion ratios exceeding 10 have an excellent elongation property comparable to that of the commercialized product.

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Dieless drawing technique, which can achieve a large reduction in the area of metal tubes in a single pass by local heating and cooling, is a flexible metal drawing process without dies. In this study, we suggested the effective drawing path control in the early drawing stage to restrain the unstable deformation, which leads to fracture. The actual deformation limit of the material is evaluated by coupled thermo-mechanical finite element analysis and experiments of the dieless drawing. The metal tubular materials used in the experiment are SUS304 alloy tubes of 2mm outer diameter. A high-frequency induction heating apparatus with a water-cooling box is used for the dieless drawing. Results show that effective drawing speed control enhances the forming limit in the dieless drawing. Moreover, the effect of heating length, which affects the temperature distribution, on the deformation behavior is investigated in the use of effective drawing speed control under the condition of avoiding the fracture by unstable deformation in the early drawing stage. It is found that the forming limit slightly improves with increasing heating length. Consequently, we clarified that it is possible to make the dieless drawing process successfully even if the local heating is not always realized.

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This study summarizes the characteristics of blanking behavior with a negative clearance. Several experiments were performed for two aluminum sheets over a wide range of clearances including negative values. Blanking with negatively large clearances was found to produce fine cut edges with less roll-over and no fracture zone even for a brittle material. Corresponding simulations were performed using the Ayada's criterion for predicting ductile fracture initiation. Each zone of blanked part edges such as roll-over and fractured zone agreed well with that obtained in the experiments except a few cases accompanied by secondary shear. The reason for prevention of fracture by using negative clearances was explained with the change of the damage value during the process; the damage value was kept low throughout the blanking operation since the mean stress dominating the damage value became compressive around the die edge. Influences of blanking parameters on load-stroke curves were also investigated. The curves for negative clearances showed gradual increase in load toward the end of stroke. The earlier fracture initiated, the earlier the load reached a peak. Simulated curves showed the same tendency and in good agreement with the experimental ones quantitatively.

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An extruded or rolled material such as a bar and a tube naturally possesses plastic anisotropy like a sheet. The property influences the metal flow in bulk forming as well as in sheet metal forming. In this paper, some examples of the anisotropic bulk deformations in a cube- and a ring-compression test were demonstrated. The cube with the edges of 1 mm long, which was cut out of a round bar or a tube, was compressed in z-axis under a well-lubricated condition by applying beef-tallow. After the compression test, the strain ratios of ε_y to ε_x were 0.83 and 0.76 for A1050 and A6063 respectively. They showed normal anisotropy, because the ratios of ε_y/ε_x keep unity if they are isotropic materials. Furthermore, friction also affects the metal flow for the anisotropic material. The ratios of ε_y/ε_x changed when the cubes were compressed under different frictional conditions by using some lubricants such as beef-tallow, VG460, VG100, castor oil, and no lubrication. The anisotropic deformation was restrained by the higher-frictional die-surface. Also the ring-compression test, as another example, was investigated, which is a well-established test to determine the friction coefficients by measuring the change in the inner diameter. Plastic anisotropy and friction influenced the reduction in the inner diameter, so the coefficient of friction must be decided with appropriate diagrams that consider the plastic anisotropy of the material.

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A simple and effective method for generation and detection of a guided wave in a pipe was proposed using an iron hose-fixing belt as a reflector of the guided wave. The reflector is located (2n+1)λ/4 (n=1,2,3,,,) apart from a guided wave sensor in axial direction for the effective generation or detection in the magneto-strictive transduction. The reflector setting is determined under the consideration to the distance between the sensor and the reflector as well as phase inversion at the reflector. In above reflector setting, large amplitude is obtained because multiple-reflection between the reflector and the sensor occurs under phase matching conditions. In this paper, the principle of the method was first described. Experiments were carried out with the non-dispersive T(0,1) mode to verify the principle in comparison to a simple theory.

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We quantitatively estimated the location and area fraction of a model blockage inside a pipe utilizing guided waves propagating in a liquid inside a pipe. The guided wave was excited and detected by film-type PZT elements wounded around an external pipe surface. Location of the blockage can be estimated from an arrival time of the wave reflected by the blockage and measured propagation velocity. The blocking ratio can be also estimated by comparing the measured amplitude to the predicted one when the profile of the blockage was roughly evaluated prior to the measurement. We also discussed the effect of the flow rate on the amplitude of the reflected wave.

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The effect of strain rate on compressive properties of starch-based biodegradable plastics (Nihon Cornstarch Co., CPR-M2) was examined. Dynamic stress-strain curves of starch-based biodegradable plastics were measured over a wide range of strain rates from 10^-5 s^-1 to 10⁴ s^-1, using a quasi-static compression testing machine and a split Hopkinson pressure bar (SHPB) system. The strain rate slightly affected Young's modulus and considerably increased 7% flow stress. Empirical equation for 7% flow stress was derived for the strain rates from 10^-5 s^-1 to 10⁴ s^-1. In addition, the effect of temperature on Young's modulus and flow stress was also examined in a range from 4°C to 63°C. A master curve of 7% flow stress, reduced to 24°C, was made. The values of activation energies related to the α and β relaxation processes were respectively estimated from the master curve of 7% flow stress and from the best fit of equations based on Ree-Eyring theory and Bauwens' treatment. Temperature measurement of specimens was also made using thermocouples during dynamic compression.

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In order to obtain precise and correct dynamic stress-strain behavior for steel plate, the split Hopkinson (Kolsky) bar method or the one bar method has been adopted as a testing method. In these two methods, a dynamic load transducer is the thin steel bar (s). On the input and output bars, typically two or four strain gages are adhered at the same distance from the end of the bars to detect elastic strains of the bars as dynamic load signal. The bars are usually mounted on simple supports, allowing a little axial elongation of the bars. Then, ball bearings or polytetrafluoroethylene parts are frequently installed between the bars and supports, because the friction between them will affect the quality of the dynamic load signal. On the other hand, only for the one bar method, it is reported that a relatively tight support, neighboring the loading end of the output bar, is effective to reduce an extraordinarily-high initial stress peak on dynamic stress-strain curve. In this paper, some trials have been carried out to find the optimum supporting condition for the output bar loading end in the one bar method. An assembly for a steel plate specimen is connected to an impact block. The other end of the assembly is an extension of the output bar. Usually, from the end of gage length of the specimen plate, there is no output bar support within approximately 650mm, for the present apparatus. This situation is designated as “no support”. At a location of 60mm from the end of the gage length, a simple output bar support is introduced additionally. This situation is called as “simple support”, because the output bar is left on the V-shaped top of the support. Additional upper supporting parts can be installed to the simple support condition. After the installation, a square hole is formed on the top of the support. The output bar touches four sides of the hole. This situation is called as “surrounding support”. In addition, specimen assembly types are also included in experimental conditions. Shapes of obtained stress-strain curves in each experimental condition are mutually compared. Also they are compared with that of a reference curve which has the quality of interchangeable with the curves obtained by the split Hopkison bar method. Two experimental conditions are recommended to detect acceptable stress-strain relationships for steel plate.

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A new in-situ technique to observe the behavior of lubricant molecules on a metal surface during friction has been developed by combining a two-dimensional fast imaging ATR-FTIR (attenuated total reflection-Fourier transform infrared) spectrometer with temperature-controlled friction apparatus containing a lubricating agent. Using this new system, the chemical and/or physical changes of lubricant molecules have been successfully detected. In this paper, the chemical reaction of ZnDTP during friction is reported with detailed information on time-dependent 2D images of the spatial distribution on a sliding metal surface.

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Thin-wall injection molded products with micro-scale surface features of polycarbonate (PC) were produced using precision injection compression molding (ICM) to analyze effects of molding conditions on replication of surface patterns and higher-order structural development of products. The molded parts' flow length using ICM was greater than using injection molding. The compression delay time in ICM, the start time after molten resin injection, was the most important factor for improving flow lengths. Residual strain inside the parts was influenced by compression conditions: it increased concomitantly with increased compression delay time. Compression conditions also influenced optical retardation. Particularly, retardation was decreased at longer delay times because molded parts started solidification inside the cavity at this condition. The replication ratio was higher than by injection molding. Compression conditions influenced the ratio, which decreased drastically at longer delay times. The replication ratio near the flow end was lower than at any other position. The ratio was especially lower for the surface pattern with the high aspect ratio of 2.

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In order to improve the adhesion strength of the DLC coating, Fine Particle Peening (FPP) treatment was employed as pretreatment for DLC coatings. FPP treatment was performed using SiC shot particles, and then the AISI316L steel was DLC-coated. The FPP treatment increased the surface roughness of the specimen, and a Si-rich layer was formed on the surface because of the mechanical mixing of SiC shot particles into the steel substrate. Reciprocating sliding wear tests were conducted to measure the friction coefficient. While the non-pretreated (only DLC-coated) specimens showed a sudden increase in friction coefficient resulting from delamination of the DLC coating, the pre-FPP-treated specimens maintained a low friction coefficient during the wear tests. This indicates the strong adhesion of the DLC coating of the pre-FPP-treated specimen caused by the increase in surface roughness and the presence of Si on the surface.

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Relationship between mechanical properties of DLC film prepared by UBM method and bonding structure of carbon atoms in film has been revealed by Raman spectrum analysis. Four types of DLC films with different hydrogen content were prepared by UBM method. Increase in hydrogen content in DLC film results in deterioration of hardness. Increase of hardness seems to result in shift of G-peak position toward shorter wavelengths in Raman spectra. Increase in hydrogen content in DLC film leads to deterioration of friction coefficient, but correlation between G-peak position and friction coefficient was not as high as correlation between G-peak position and hardness. So friction coefficient has no stronger relationship with bonding structure than does hardness. In order to clear mechanism of appearance of low friction coefficient of DLC film, changes in sp² and sp³ bonding components are analyzed using AES-EELFS spectra measured before and after applying sliding friction. Decrease in amount of sp² bonding component or disordering of sp² bond has been confirmed. Content of sp² bond component in film decreases mainly through migration of graphite component to counter material, so that graphite contents in DLC film and counter material reach equilibrium. This is considered to be one of factors of appearance of low frictional coefficient.

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Various surface coating technologies have been applied to improve the tribological and mechanical properties of thin films. For the use of surface modified tools and parts under severe conditions, thin films with high adhesion strength are required. To quantitatively measure the adhesion of coating films on substrates a new method for the measurement of hard coating film was developed which consists of an indentation and an AE (Acoustic Emission) system. TiN coatings were deposited onto substrates using arc ion plating PVD. Indentation tests were conducted on substrates with different film thicknesses of 3, 5, and 7 μm. Two specific loads, denoted the “Critical load”, and the “Fracture load” were defined. The critical load and fracture load correlate to the initiation of delamination and film fracture. The critical load was calculated a finite element calculation and SEM observation.

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Diamond-like carbon (DLC) has remarkable mechanical and tribological properties. Besides those mechanical properties, it has been clarified that DLC shows high biocompatibility in recent years. DLC coating can give high strength, abrasion resistance, and biocompatibility for surface of substrates. Hence DLC is a candidate for the coating material for medical devices such as artificial organ, joint, catheter, etc. The objective of this study is to develop safety protection films for implantable medical polymer devices utilizing segment-structured DLC (S-DLC) coatings. S-DLC and continuous-structured DLC were deposited on polyurethane and nylon sheet for balloon catheters. As a result, friction coefficient of DLC coated polyurethane sheet was approximately one-sixth of that of pristine polyurethane sheet, and S-DLC showed very low friction coefficient of μ=0.1-0.15. DLC coating can prevent polyurethane sheet from worn out. The puncture-resistance of nylon sheets increased 0.2MPa on average by DLC coatings regardless of the film structure. It was confirmed that DLC inhibits adsorption of blood coagulation factor. In conclusion, we succeed to verify that these DLC films can improve tribological property, abrasion-resistance, puncture-resistance, and anti-thrombogenicity of polymer catheters. Moreover, segment-structured DLC films exhibits high performance for protection of polymer material for polymer catheters.

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A nanostructured surface was designed and created by synthesizing Carbon Nanotubes (CNTs) on a plane substrate. Multi-walled carbon nanotubes (MWNTs) were synthesized on a Si/SiO2 substrate by alcohol catalytic chemical vapor deposition (ACCVD). The MWNTs were vertically synthesized on the surface, and the structure and characteristics of the surface, such as wettability, were evaluated. The surface with the MWNTs was also treated by coating with Au and subsequent plasma irradiation, in order to change the wettability from hydrophobic to hydrophilic. The results of wettability tests show that the surface with the MWNT film behaved as a super-hydrophobic surface before coating with Au and plasma irradiation, but behaved as a super-hydrophilic surface after coating with Au and plasma irradiation. Furthermore, experiments using water droplets on the MWNTs and subsequent drying was carried out, and the resulting changes in the structure and characteristics of the MWNTs were evaluated using scanning electron microscopy (SEM). The MWNTs subjected to plasma irradiation were found to clump together forming bundles after dropping water and drying; we found that the CNTs moved after the water was dropped on them. These results show that highly dense CNTs with self-assembled structures can be realized for potential applications as microreactors.

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In this study, the effect of tool asperity and the lubrication condition on tribological behavior, inner surface characteristics and deformation limit of metallic microtube in flaring test were investigated experimentally. The microtube used in this experiment is stainless steel (SUS 316L) and has a 500 μm outer diameter and 50 μm thickness. The flaring tests of the microtube using a conical tool were conducted under dry and two kinds of lubricated-contact conditions as well as different tool surface roughnesses. As a result, it is found that the flaring load and deformation limit of the microtube increase when using a rougher tool. In addition, a spray-type fluorocarbon resin, as a solid lubricant, decreases the above characteristics, but lubrication oil, as a liquid lubricant, exhibits different behavior. Meanwhile, the surface roughnesses of the inner surface of the microtube along axial and circumferential directions reduce when using a rougher tool. From these results, the surface smoothing mechanism of the microtube in the flaring test and the influencing parameters on tribological behavior are discussed.

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Palladium based thin film metallic glasses were plastically bent by laser forming process. Thin films of Pd₇₇Cu₆Si₁₇ with a thickness of 0.028mm and Pd₄₀Ni₄₀P₂₀ with a thickness of 0.017mm were used for specimen. A 50W YAG laser was employed for forming. Variation of bending angle was investigated by changing working conditions such as laser power, laser operation mode (continuous wave and Q-switch pulsed modes), Q-sw frequency, scanning velocity and scanning number. From the experimental results, both thin films of Pd₇₇Cu₆Si₁₇ and Pd₄₀Ni₄₀P₂₀ were successfully bent for more than 85°. The formed thin films did not crystallize but were amorphous. As scanning number increased, bending angle also increased but increasing rate decreased. When laser power and scanning velocity were changed, bending angle had a peak. When Q-sw frequency was changed, bending angle had a broad peak in Pd₇₇Cu₆Si₁₇ case, but that was larger as frequency was smaller in Pd₄₀Ni₄₀P₂₀ case.

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In the miniaturization of dimensions for sheet metal forming, the relative ratio of the surface asperities of tools and blanks to the outside dimensions becomes larger than that in the case of the conventional macroscale process. This means that the surface asperities may affect frictional behavior, so that it would also affect processing characteristics and accuracy of products. In this report, micro-deep drawing for producing cups of 700μm diameter and 20μm thickness is conducted using microtools and stainless steel foils with different surface conditions. To evaluate the effects of surface properties on micro-formability and micro-forming accuracy, punch force, surface accuracy, and the thickness strain distribution of microcups are experimentally investigated. Additionally, using a finite element (FE) model that considers surface roughness, the effect of surface roughness on formability is analyzed under different tool and material surface conditions. Results show that the global forming behavior in microforming is subjected much more intensely to tribological contact behavior, which is caused by the difference of surface asperities, than that in the case of the macroscale region. Moreover, it is shown that predominant factor over this local tribological behavior is the interaction of both tool/material surface asperities that depends on the normal load condition.

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Direct joint of dissimilar materials between SUS304 stainless steel and plastics, PET (Polyethylene Terephthalate) or PC (Polycarbonate), was studied by using pulse YAG laser. Welding configuration was lap joint. Weldability and shear-tensile strength were investigated for the joints. It was possible to make a joint for both combination of materials, SUS304/PET and SUS304/PC. Weldable condition range was wider in case of SUS304/PET joint compared to that in case of SUS304/PC joint. The difference in the weldability may be due to difference in glass transition temperature of the plastics. Pores were observed in plastics near the interface of the joint for both combinations of the materials when the joint welded with higher heat input. Sear-tensile test was carried out for the joints. SUS304/PET joint shows higher strength compared to SUS304/PC joint. Higher strength was observed for the joint which includes pores near the interface in plastics. However, if large size and number of pores are existing near the interface in plastics, the pores play as a defect and causes degradation of the strength.

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X-ray radiographic imaging technique has found applications in various fields. However, it is not enough to get clear X-ray images of samples with low absorbance, such as biological soft tissues. To resolve this problem, we proposed a method using an X-ray Talbot interferometer of X-ray phase imaging. In this X-ray Talbot interferometer, X-ray gratings were required to have a fine, high accuracy, high aspect ratio structure. Then, we have developed and succeeded high aspect ratio X-ray gratings with a pitch of 5.3 μm and a height of 30 μm using X-ray lithography technique. We discuss that the X-ray gratings having a large effective area in order to obtain imaging size of practical use in medical application. In currently study, we have fabricated the X-ray gratings with a large effective area of 60 mm×60 mm. And, we conducted X-ray phase tomography of mouse at the chest and abdominal using X-ray Talbot interferometer. As a result, we successfully observed soft tissues and high density tissues. With the aim of broadening a field of view, we try to fabricate X-ray gratings that have a pitch of below 5.3 μm and larger area of 100 mm square. This result suggests that X-ray Talbot interferometer is a novel and simple method for phase sensitive X-ray radiography.

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