A new method of forming boss on a Magnesium alloy sheet has been developed by utilizing a friction stir technology. This new technology enables the press-forming of Mg alloys at room temperature without external heating devices. Rolled and extruded sheets of AZ31 Mg alloys the thicknesses of which are from 0.8 to 2mm were used as work-pieces. Forming a boss the size of which shall be from φ 3×4 to φ 7×5mm on the Mg sheet has been made by pressing a tool rotating on the sheet. We believe that this new forming technology for Mg alloys must be used in many fields of applications.
For the stabilization of insulation performance in the resin-molded insulators, strong adhesion between the resin and metal is required. In this paper, influence of surface roughness for interfacial strength between the resin and metal was investigated. Test pieces were made by covering Cu and SUS cylinders, which have some values of surface roughness, with epoxy resin. The interfacial strength was evaluated with shearing tests of these test pieces. The effective adhesive surfaces of those cylinders were evaluated from surface observation with a laser microscope. The interfacial strength increased with surface roughness. The adhesion-strength index (μ+B), which had been proposed in previous paper, were calculated with the effective adhesive surface and the interfacial strength. The adhesion-strength index gave a constant value with various surface roughnesses for each metal. We also discussed the multi-scale connection between nano-scale adhesion by using the molecular-dynamics method and macro-scale interface strength. We showed that our proposed interfacial fracture energy (mode I) is effective in determining the adhesion strength of two kinds of interfaces between epoxy resin and metals (Cu and SUS).
This paper introduce CAE design tool to calculate the singular values by FEM stress results near singularities. This tool made by Excel VBA. First, create a line graph of any direction after reading a stress results file based on FEM analysis. Second, calculate the stress singularities of each line from the profile of the stress distribution. From the values and the direction, we can evaluate the fracture strength and fracture direction at stress singularity field.
The present study describes applicability of local surface deformation process consisted from burnishing and shot preening for surface finish on tribological properties of copper based alloy containing sulfide fine particles sintered on a steel plate. The shot peening was carried out with a developed apparatus possible to eject fine particle with a low flow rate. A roller burnishing process installed to a conventional lathe was applied to truncate after the peening process. A ring on disc type testing apparatus was used to evaluate tribological properties with a hardened carbon steel ring as a mating specimen with a mirror finished surface in lubricated condition. Results showed that the application of the truncation was effective to reduce the friction resistance at the initial stage of the friction experiment and it was found that the combined surface deformation process is available to fabricate the surface texture for tribological interface.
The present study describes an applicability of fine particle peening to improve yield rate of semi-conductor materials during breaking process. A sapphire wafer and fine alumina beads with 5, 10, 30 μm in diameter were used for the specimen and the impact media. A developed apparatus possible to eject low flow rate was used for the fine particle peening. The crack growth was evaluated with an indentation fracture method using Vickers hardness apparatus. It was found that the increase in the surface roughness resulted in fine particle peening was small. Results of the indentation experiment showed that the radial crack length grown from the impression corner becomes smaller with the application of the fine particle peening and that significant growth of the lateral crack occurred along the boundary of the peened area. Therefore, it is estimated that partial application of the fine particle peening is effective for control the root of the crack pass during the breaking process of semi-conductor materials.
The present study describes effects of iron oxide dispersion on friction properties of a low carbon steel interface. The iron oxide was dispersed onto the groove fabricated with cutting. The friction and wear property was evaluated with a lathe incorporated to a friction measurement system in dry condition. The experiment was carried out at 3.4m/s of sliding speed and at 200 N of an applied load with interval contact condition. Results showed that the friction coefficient of the surface containing ferrite oxide layer penetrated into the spiral groove was higher than that of the nominal surface. It was also found that the surface morphology including color quality resulted in the oxidation was different depending on the nominal surface condition.
Gels are expected as the biomaterial of the human body such as our cartilages because of the improvement of the mechanical strength and their extremely low friction coefficient. The friction behavior of gels is different from hard and dry materials like metals, plastics and ceramics. In this study, we focus on the dynamic frictional interface of hydrogels and aim to develop a new apparatus with a polarization microscope for observation. The comparison between direct observation and measurement of friction coefficient will become a foothold to elucidate distinctive frictional phenomena that can be seen in soft and wet materials.
Gels have superior features such as high water content, materials permeability, extremely low friction, and biocompatibility, which are not found in the hard and dry materials, because these features are due to their soft and wet features. Now artificial gels have become similar to natural gels of the human body: the articular cartilage of our knee has both several MPa of mechanical strength and about 0.01 of surface frictional coefficient. In this study, we aim to develop an original apparatus for evaluating surface mechanical properties of gels such as surface friction and the stick-slip phenomenon of the high-strength gels.
There is an urgent demand to enhance the energy efficiency of various instruments. Carbon fiber-containing aluminum composites are expected to improve the ability of heat dissipation of heat exchanger, and heat sink. Especially, both carbon nanotube (CNT) and vapor-grown carbon fiber (VGCF), which is a kind of carbon fiber, have high thermal conductivities in the axial direction, because of its high aspect ratio. Therefore, alignment of carbon fibers is a key factor to fabricate high thermal conductive composites using CNT and VGCF. In this study, macro- and micro-channels were successfully fabricated and the possibility to control the alignments of VGCF using the contraction of the water flow in the channels was confirmed. The method may have a benefit to fabricate high thermal conductive composites containing CNT and VGCF.
Advanced lapping tools have been required to raise the yield rate of silicon wafer. Silicon is brittle material because the fracture toughness of monocrystalline silicon is 0.8 MPam^<1/2>. Therefore, to lap silicon wafer in the ductile mode, it is important to ensure the microscopic incision below 0.1 μm. The present authors propose Partial Functionally Graded Ceramics (PFGC) as an advanced lapping tool. PFGC can make microscopic surface asperity with polishing substances because there is stiffness distribution formed by partial electron beam irradiation in the surface of PFGC. To determine the most suitable distribution of surface-hardened layer, FEM analyses on microscopic surface asperity between PFGC and silicon were conducted with two parameters; the width of electron beam irradiation and the distance of surface-hardened layer. Microscopic surface asperity formed by PFGC was evaluated to be much smaller than the above microscopic incision. So it was found that the most suitable distribution depends on the angle and the number of microscopic surface asperity. The most suitable distribution of surface-hardened layer was evaluated that the width of electron beam irradiation is nearly 0 μm and the distance of electron beam irradiation is 20 μm.
A process of high-strength Carbon-fiber-reinforced SiC matrix (C/SiC) composite materials with a rapid and low-cost manufacturing method was examined in this study. In this process, the space between fibers in a 2D carbon fiber preform was impregnated with SiC powder slurry by pressure or vacuum assisted infiltration before the polymer infiltration and pyrolysis (PIP) or the melt infiltration (MI) process. The bulk density of the powder-filled preform achieved 1.3 g/cm^3. Then, the powder-filled preform was further densified by the PIP method or the MI method. Through these experiments, SiC powder infiltration behavior during the pressure or the vacuum assisted slurry infiltration process was discussed, and basic mechanical properties of C/SiC composites fabricated by these processes were evaluated.
ZrB_2-SiC-ZrC (ZSZ) ceramics were oxidized by two different methods to evaluate their oxidation mechanism and oxidation resistance at ultra high temperature region. Firstly, ZSZs were oxidized at 1700℃ by IR image furnace. Experimental results revealed that the glass formed on specimens with ZrB_2 rich composition was flown during oxidation and removed from the surface by the airflow. These results lead to the depletion of oxidation resistance because it is attribute to formation of the glass,. In addition, ZSZs were also oxidized continuously up to 1700℃ using a zirconia ultra high temperature furnace. The result showed that the ZSZs formed oxide scale, and the specimen after the experiment still had unoxidized area. These results imply that ZSZs have resistance of the active oxidation of the SiC. The results of two oxidation tests predict that ZSZs have optimal composition, and that the oxidation mechanism at ultra high temperature region should be taken into account to determine the optimal composition.
Soft tissues in the human body are almost in soft and wet gel-like state, containing 50-80 % amounts of water. In the scene of developing medical devices and materials, the importance of characterizing the structure and mechanical properties of gels is rising. However, the frozen inhomogeneities in gels make it difficult to observe the structure of gels by scattering method. To solve this difficulty, scanning microscopic light scattering (SMILS) was originally developed. Here our aim is improvement of SMILS to visualize the data. We tried to develop a new apparatus and implement original software to the Visual-SMILS. A pinhole was added to the Visual-SMILS to detect the scattered light at the angle exactly and to suppress the excess of the scattered light. We succeeded in reducing experimental errors and converting the analysis data to the image simply for the size distribution with the visual-SMILS.
An artificial muscle, which has properties of compact, lightweight and flexible, avaliable as wearable rehabilitation device has been developed using shape memory alloy (SMA) wires. To this end, firstly its mechanical performance and its optimal geometric shape as the SMA artificial muscle are investigated experimentally and discussed using finite element analysis. It was found that the wave shaped SMA wire extends to 25〜30% strain that is nearly equivalent to that of human muscle. It was also shown that recovery force and maximum local strain were changed with geometric shape and combination of SMA wire. It is therefore believed that the designed SMA artificial muscle is applicable to wearable rehabilitation device.
This paper describes output voltage characteristic and output power characteristic of the metal-core piezoelectric ceramic fiber/aluminum composite. As the metal-core piezoelectric fiber is very fragile, the interphase forming/bonding (IF/B) method proposed by Asanuma was used for embedding it in an aluminum matrix without fracturing it. In this study, thin patch type devices developed by using the IF/B method were evaluated with the oscillation test equipment. As the results, 1) the output voltages from the device were found to be proportional to their strains, 2) the output power generated by the specimen increases with increasing the square of its strain.
In recent years, green composites have been attracting attention from the viewpoint of prevention of global warming. Green composites which are reinforced by continuous natural yarns are mainly formed by stampable forming. During the forming process, it is known that the continuous natural yarns can move in the matrix and the movement of yarns may affect the strength of product. In this study, the kinetic behavior of continuous yarns during thermoforming process and the effect of lamination are investigated in three-point bending test for single and double layered green composites. As a result, the kinetic behavior of yarns has an influence on the bending strength of green composite. Additionally, it is estimated that the volume fraction of yarns and the test temperature affect the kinetic behavior of yarns. Finally, it is concluded that the adequate volume fraction of yarns and the test temperature are necessary to keep and improve the strength of product.
FeSi_2 thermoelectric elements are expected for high temperature applications because of its low cost, nontoxic and superior oxidation resistance. The thermoelectric conversion module was manufactured using a FeSi_2 thermoelectric conversion element produced by spark plasma sintering. In addition, the thermoelectric conversion characteristic and internal resistance was examined by using the thermoelectric conversion module. The thermoelectric conversion characteristic of p-n module joined with a silver solder was voltage of 70mV and internal resistance of 320 Ω at temperature difference of 250K. Moreover, p-Ag-n module was produced by spark plasma sinter-joining method. Thermoelectric conversion characteristic of sinter-joined p-Ag-n module was voltage of 81mV and internal resistance of 6.5 Ω at temperature difference of 250K. It was clarified that the sinter-joined p-Ag-n module indicated low internal resistance than the p-n module joined with a silver solder.