The tensile test of die-cast aluminum alloy were carried out in 1.0% sodium chloride solution at room temperature, and the stress, strain and open-circuit potential were measured during the test. As a result, it was found that the stiffness of the as-cast specimen was lower than that of the casting specimen in the elastic region, but the stress-strain relationship was almost same in the plastic region. In addition, compared to the as-cast specimen, the polished specimen was susceptible to corrosion and it became clear that the damage of the film was early.

We have addressed the mechanism of fatigue crack initiation in cast aluminum alloys. To numerically simulate the actual mechanical condition around the crack initiation site, the finite element model has to include a lot of inclusions along with micro and macro pores and material surface. We are trying to realize this kind of large-scale image-based finite element analysis by using the synchrotron CT and voxel finite element techniques. The finite element model of AC4CH-T6 cast aluminum alloy was constructed and its fatigue simulation of ten cycles loading was carried out. From the comparison of the experiment and the simulation, we found that the silicon particle in the crack initiation site underwent a high stress concentration and a low geometrical constraint leading to a gradual increase in the stress.

In recent years, collapse of large structures has occurred because of aging. Displacement measurement is important for maintenance. There are various methods in the vertical and horizontal directions for displacement measurement of distant objects using optical method. However, there are few methods to measure displacement for a camera direction. In this paper, the authors propose and demonstrate a method to generate a fringe pattern along the depth direction using three-beam interferometry in combination with fringe power analysis. In three-beam interferometry, the fringe pattern along the depth direction appears by superimposing each two-beam interference fringe. Therefore, the power distribution of the fringe pattern appears along the depth direction. This method enables us to directly obtain the three-dimensional (3D) shape and displacement using the fringe pattern along the depth direction. Our method intended for wide application with 3D shape measurements and out-of-plane displacement measurements for the inspection and maintenance of large constructions. As the first step of developing a device for 3D shape and displacement measurement, in this paper, simulation and an experiment were used to confirm that depth directional patterns appeared.

TiAl alloy has a good creep rupture specific strength. A θ projection method proposed by Evans et al. is a method that draw creep curve mathematically. This method can draw creep curve including tertiary creep by four parameters. Many researchers have studied on mechanical properties of TiAl alloy. However, there is few research report on TiAl alloy applied to θ projection method. This paper discusses the θ projection analysis method in order to investigate the creep properties of TiAl alloys. We evaluate the creep curve drawn by θ projection method. Experimental creep curves obtained at four stress levels were used. The creep curve and creep strain rate curve was redrawn exactly with the data until time to rupture time ratio as 0.9. The predicted minimum creep strain rate using estimated θ parameters showed a good agreement with the experimental data. Using Monkman-Grant rule, we lead to rupture time prediction expression. We predict creep rupture time with predicted minimum creep strain rate. Predicted creep rupture time show good approximation with experimental data. We concluded that creep rupture time prediction is possible by calculating minimum creep strain rate from estimated θ parameters.

Copper has been applied to the TSV interconnection structure used in microelectronic devices because of its excellent electrical and mechanical properties. However, the physical properties of copper thin film interconnections were found to vary drastically depending on their micro texture and this serious degradation of physical properties was caused by its high-volume ratio of porous grain boundaries and fine columnar grains. Thus, the long-term reliability of products cannot be guaranteed and it is largely dominated by the strength of grain boundaries. In this study, a highly-reliable evaluation method of the strength of a grain and a grain boundary in polycrystalline copper thin films was used to determine a relationship between the crystallinity and their effective strength by using EBSD (Electron Back-scattered Diffraction) analysis and micro tensile test system. The crystallinity of a grain and a grain boundary was quantitatively evaluated by using IQ (Image Quality) value calculated from the Kikuchi pattern obtained from the EBSD analysis. And the strength of a grain and a grain boundary in polycrystalline copper thin films was evaluated by using the developed micro tensile test. Finally, it was found that there was a strong crystallinity dependence of the strength of a copper grain in electroplated copper thin films. In particular, the critical resolved shear stress (CRSS) of a grain significantly decreased with the increase of the IQ value at the grain boundary.

In this study, fine particle bombarding treatment (FPB) was applied to SCM435 chromium molybdenum steel and A5052 aluminum alloy. The effects of various FPB conditions on mechanical properties and microstructures were examined. In the result, the grain refinement layer observed, the maximum thicknesses were respectively about 30μm for SCM435 and about 15μm for A5052 in sufficiently bombarding. In this layer, two types of microstructures were formed, the ultrafine grained microstructures, and the lamellar structures. In the ultrafine grained microstructures grains were refined into the size of several hundred nanometers. On the other hand lamellar structures involved fragments of shot materials and the grain size was several ten nanometers. The ultrafine grained microstructures have a lot of dislocations, but the lamellar structures were little. The lamellar structure occupied 50% of the FPB treated surface. In accordance with Hall-Petch relationship, the hardness of the FPB treated surface was increased with grain size.

Recently, a volcanic eruption has been attracted attention. If Mt. Fuji is exploded, many gas turbines (GTs) located along Tokyo bay would be exposed to a threat of volcanic ash. The volcanic ash could be deposited on the turbine blade, and it is expected to cause a degradation of nickel-based superalloy as the substrate of turbine blade. In this study, a high-temperature exposure test was conducted for volcanic ash deposited IN738LC sample, and its degradation of microstructure was discussed by SEM observation and EDX analysis. As a result, it was found that oxide formation was controlled under shorter exposure time condition, because volcanic ash deposition interrupted supply of oxygen. On the other hand, the oxide layer brought about enough time for Al diffusing toward the surface under longer exposure time condition, which led to disappearing of γ′ phase beneath the surface. The dissipation of γ′ phase also affected Vickers hardness distribution in comparison with the bared sample. Thus, it was revealed that volcanic ash deposition reduces mechanical strength of IN738LC due to collapse of microstructure.

Heat transfer in media is generally characterized by the empirical heat conduction law which had been proposed by Fourier. However, the application of this empirical law to the problem of fast transient heat transfer such as a pulsed laser heat is not available, because Fourier's law leads to an infinite velocity of heat propagation since the resulting diffusion equation is parabolic form. It has to be imposed that the heat propagates with a finite velocity from the restriction of relativistic concept. A lot of models have been suggested to overcome this difficulty. In this study, one dimensional thermal wave analysis was conducted based upon coupling with relativistic heat conduction equation formulated by Load and Shulamn and dynamic theory of thermo-elasticity. In some reports related with this problem, the relativistic heat conduction equation was linearized by eliminating a higher order term. In this study, influence of nonlinear term in the relativistic equation on thermal wave propagation was discussed strictly.

The Japanese sword uses the unique quenching method. The swordsmith pasts the clay as called "YAKIBATSUTI" on the surface of sword to control the heat transfer coefficient. Therefore, the cooling speed can be controlled at the hasaki and the other part. Then, the edge part transforms to the martensitic structure. The residual stress also changes from the phase transformation. In this study, the effect of the quenching condition on the residual stress distribution for the Japanese sword was investigated by the numerical simulation. Therefore, the setting area of heat transfer coefficient at the edge part was changed. First, the setting area of the high heat transfer coefficient was expanded. As the result, the residual stress at the center part was changed close to tensile stress from high compressive stress in the cross section. Second, focusing on the cooling temperature, the rapid cooling area was expanded because of change the area of heat transfer coefficient. Therefore, the martensitic area was also expanded. To summarize these results, the martensitic ratio was expanded by the changing the area of heat transfer coefficient. Residual stress was changed close to tensile stress from high compressive stress, because of expanding the martensitic area at the edge part.

In recent years, high-strength steel sheets are used in production of vehicle bodies to reduce weight. As a result, it is known that fuel efficiency can be improved. The resistance spot welding is a primary joining method used for the manufacturing of vehicle bodies. However, the fatigue strength of the high-strength steel sheets joints does not increase with the increase in the strength of the base material. Therefore, it is necessary to increase the fatigue strength and a post-heating treatment is used to do this. Tempering treatment is one post-heating method. The application of a postheating method improves the fatigue strength of resistance spot welded high-strength steel sheets. This is caused by controlling properties of spot welds such as residual stress and nugget hardness distribution. However, very few studies have been reported on the individual effects in the spot welds on fatigue strength. In this study, the effects of residual stress and hardness distribution on fatigue strength was investigated using 980 MPa class high-strength steel sheets was investigated by experiment and numerical simulation. First, in order to investigate the effect of tempering treatment on the spot welds Vickers hardness was confirmed. The results show that the nuggets of resistance spot welded joints were softened by tempering treatment. Second, Fatigue tests were conducted under shear load in order to investigate the effect of tempering treatment on fatigue life. The results show that the fatigue life was improved by tempering treatment. Finally, the stress was calculated in the spot welds using the numerical simulation by changing the hardness distribution and residual stress in the nugget. The results of numerical simulation showed that the stress decreased near sheet separation by tempering treatment. The amount of decrease in stress was larger when changing the hardness distribution rather than changing the residual stress.

Recently, SiC power devices are expected to replace conventional Si devices. In the semiconductor field, the local stresses and strains affecting these device performance and reliability are very important. In this study, stress/strain measurements of 4H-SiC was carried out by Raman microspectroscopy with submicron spatial resolution. First, the Raman scattering intensity of the A₁ and E₂ vibration modes in single crystal SiC was theoretically obtained. These results for each vibration mode were good agreement with those obtained from the polarization intensity measurements in single crystal SiC, the polarization condition to decompose the double degeneracy of SiC were determined. Next, the relations between the change in Raman shift and the strain components were theoretically derived based on the energy change under the mechanical loading. These equations include three unknown parameters. The three potential parameters included in these equations were determined from the relationships between Raman shift and strain by various loading test, and then the possibility of measurement of stress/strain components in SiC devices were clarified.

The Mechanoluminescence materials to use in this study consists of SrAl₂O₄ : Eu (Strontium aluminate added with europium). It has peak wavelength of about 520 [nm], and has high luminance to deformation and stress. The europium at the center of luminescence emit light by the piezoelectric effect which is caused when crystal is deformed. Therefore we produce an inspection method which can visualize stress inside the material using the theory of elasticity. We derive a general solution for many circular cylindrical holes that are free boundary to an elastic medium (matrix) of infinite extent under in-plane problem. These many holes have different radii and different central points. When there are many holes in the matrix, we consider the matrix as a poroelastic matrix. The matrix is subjected to arbitrary loading, for example, by uniform stresses. Using these solutions, we observe the graph of brightness and maximum principal stress around the holes from mechanoluminescence materials, general solution of elasticity and numerical solution of FEM. In this study we present several numerical examples graphically.

This paper describes the progression of anisotropy in the yield surface formed during the process of applying a large simple shear. In our previous studies, the yield phenomenon has been investigated by using the test pieces, which are applied the simple shear in the reverse direction after large simple shear in the forward direction. Then, the shape of yield surfaces has been estimated on the basis of the slope of tangent in the deviatoric stress and deviatoric strain curve, which is represented by using the Natural Strain. Consequentially, since the anisotropy appears on the reverse shear side, it is revealed that the anisotropy is newly formed during the process of applying a reverse shear. In the present study, in order to examine the developing process of anisotropy more in detail, the transitions of yield stress on the forward shear side and the reverse shear side are investigated by changing the size of pre-deformation in the reverse shear side variously.

Cancer is one of the three major causes of death in Japan. The 90% of patients with cancer dies from metastasis. Therefore, it is essential to do the cancer treatment properly, in which the metastasis should be prevented or the place should be predicted where the cancer cells are going to spread to. However, the mechanical mechanism of metastasis is still under research. We attempt to develop a pressure sensor array that can continuously measure the force of nN order generated by the cancer cells in a distributed manner. The requirements that a pressure sensor array need to meet are as follows: the pressure sensor array must adhere to the surface of a cancer cell via many points, besides, it could measure the magnitude of the force (nN). The zinc oxide (ZnO) thin film, as the piezoelectric material, offers a desirable approach to fulfilling the need for measurement of the mechanical field generated by the cancer cells. In our research, we fabricated a set of plural sensors (Size: 100 μm×100 μm, Thickness: 1 μm) on a substrate by using the methods of sputtering and photolithography. In other words, we developed a multi-point pressure sensor array. The main purpose of this study is to evaluate the sensitivity of the sensor, we used Au or Cr buffer layers, on which the ZnO thin film was formed, to find out the influence of the sensitivity of the sensor. Moreover, we measured the output voltage as a function of the load by using the sensor. In summary, the result of experiments shows that the sensitivity of the sensor is 5.31 mV/N.

In recent years, various nanostructure materials such as nanowires, nanorods and nanobelts have been studied widely due to their excellent properties. Especially, much attention was paid by researchers in the preparation of oxide nanostructure materials due to their good optical and electrical properties. Numerous oxide nanostructure materials were synthesized so far, among which SnO₂ is considered to be an important one, because it is a typical n-type semiconductor. Particularly, SnO₂ nanobelts exhibited extensive optoelectronic and gas-sensitive properties which make them being excellent candidates for a wide range of applications such as gas sensors and transparent conductive film. SnO₂ nanobelt is generally synthesized by thermal evaporation method, but it is difficult to control the shape, size and density of SnO₂ nanobelts in the thermal evaporation process. However, since the elastic modulus and conductivity of the nanobelt depend on its shape and size, it is important to control shape and size of nanobelt. Hence, in this study, we adjusted experimental parameters such as pressure during heating and concentrations of gold nanoparticle solution to control the shape and size of nanobelts. From the scanning electron microscope image, we found that the aspect ratio of cross-section was controlled by pressure during heating. The results show that we succeeded in controlling the aspect ratio of cross-section and density of the SnO₂ nanobelts. From the above, it is expected that the improvement of flexibility and transparency of a transparent conductive film could be realized.

In recent years, the development of a transparent conductive film using metal nanowires (NW) as a dispersing material has been carried out. Recent studies have reported many methods for fabricating transparent conductive films using Ag NW. However, Ag is a rare metal and there is a problem that the price is susceptible to market fluctuations. In order to utilize inexpensive Al NW as a new dispersing material, we developed a single crystal Al NW array fabrication method. The present method utilizes atomic diffusion to convert Al atoms to NW shape. Compressive stress and stress gradient in the Al thin film which is generated due to the difference in linear expansion coefficient between Al and Si when heating the Al / Si substrate. The atomic diffusion phenomenon caused by such stress is called stress migration (SM). It is a major feature of this method that NW generation is possible with two simple steps, film formation and heating. However, this method has a problem that the generation density of Al NW is low. In this research, we tried to increase the stress gradient by partial etching of Al film and introduce adhesion intermediate layer, and tried to improve generation density. As a result, we could get high density of Al NW with etching depth 10 nm and Cr film thickness 1.5 nm.

It is well-known that traditional fossil energy sources such as oil are limited. Hydrogen is attracting the attention of the world because it is renewable, plentiful in supply, clean and non-toxic. Cu₂O is a promising material for solar water splitting because it has an impressive performance as photocathode. It is a p-type semiconductor and with a band gap of 2.0 eV, which could theoretically deliver a solar to hydrogen conversion efficiency of 18% for water splitting. In this research, we use tube furnace to fabricate Cu₂O nanowire (NW) by thermal oxidation and reduction process of thin copper plate. Different experimental conditions (temperature, time and gas flow rate) were investigated to find out the best parameters for nanowire synthesis (diameter, length, and number density of NW) which is better for the photoelectrochemical system.

In order to clarify the influence of stress concentration on the tensile strength of nanowire, we developed an experimental method to perform a tensile test for nanowire under field emission scanning electron microscope (FESEM) observation and evaluated mechanical properties of two types of aluminum nanowire specimens: one was a smooth nanowire and the other was a notched nanowire. A notch was introduced by using focused helium ion beam. As a result of the tensile test with the developed experimental method, the relationship between load and displacement, and the FESEM image during the test was acquired. Young's modulus of the notched specimen was equal to that of the smooth specimen. On the other hand, the values of yield stress, ultimate tensile strength, and total elongation of the notched specimen were, respectively, less than those of the smooth specimen, indicating the sensitivity to the presence of a notch. Fracture location of the notched specimen was at a notch. These results suggest that stress concentration dominants fracture.

Electromigration (EM) technique is a growth method of metallic micro/nanowires. In general, EM deteriorates the metallic interconnects in integrated circuits by forming micro/nanoscale structures referred to as voids and hillocks. Voids and hillocks are generated by the depletion and accumulation of atoms, respectively. Recently, the EM technique for fabricating metallic micro/nanowires was reported, and the fabrication of Al microwires was demonstrated. The EM technique can fabricate Al micro/nanowires with high-aspect ratio, higher purity, and single crystal resulting in higher mechanical strength. The passivation constraining the deformation of metallic interconnect due to accumulation of atoms and the artificial hole through which metallic atoms are extruded are key factors. Rigid passivation generates the higher localized stress field in the metallic interconnect with accumulation of atoms. This higher stress field can push atoms out through the hole and the extruded metallic atoms becomes to grow a wire. This work reports the effect of the passivation thickness on fabrication performance. Two samples with different passivation thickness was used. The growth rate was experimentally measured to evaluate the performance. X-ray diffraction system was used to obtain the values of residual stress in passivation, showing that higher absolute value of compressive residual stress resulted in lower growth rate of an Al microwire. As a result, the lower absolute value of compressive residual stress increases the fabrication performance and can decrease the delamination risk of topmost passivation deposited by sputtering. On the other hand, the too thinner passivation resulting in lower absolute value of compressive stress increases the risk of passivation crack due to accumulation of atoms by EM. The optimized thickness of passivation can be determined based on this finding.

Micro/nano materials are utilized for various industrial products due to characteristic physical properties, such as high surface to volume ratio, high aspect ratio and so on. Among them, metal micro/nano materials especially have good workability and low-cost production. Metal micro/nano materials are expected to be used as next-generation materials in the future. Thus, the various fabrication techniques have been studied. Recently, the fabrication technique of metal micro/nano materials using electromigration (EM) has been reported. EM is a physical phenomenon of the atomic diffusion in a metal line with the high-density electron flow. It was reported that the metal micro/nano materials fabricated by EM have the single crystal structure and the strong mechanical strength. The previous study reported that the fabrication of Al micro/nano materials grown in a horizontal direction was realized and the difference of the sample structure resulted in the different shapes of Al micro/nano materials. It was well known that the current density caused by the sample structure was contributed to the shape of fabricated materials. On the other hand, the current density in a metal line could not be measured and it is difficult to predict the shape of fabricated materials. This paper shows the value of current density calculated by finite element analysis on the sample structure. The shape of micro/nano materials by EM can be predicted by using current density based on this result.

Electrochemical migration (ECM) is known as a cause of threating the reliability of electronic devices by generating metal or its compound deposits. ECM is a kind of electrochemical phenomenon consisting of dissolution of anodic metal into water as ions, migration of ions between electrodes caused by electrical field and deposition of metals at cathode. The occurrence condition relates with water or high humidity and voltage-applied metal electrodes, and inhibition research has been mainly performed conventionally. In recent years, some researchers are trying to utilize ECM for environmentally friendly and simple fabrication of micro/nanomaterials because the deposits take various fine structures and they can be made by just water and metal without any other chemicals. In this study, we attempted to take ECM deposits apart using physical force of ultrasonic wave in dispersion medium to obtain micro/nanomaterial dispersion. A 100-fold dilution kitchen detergent in the amount of 0.1 ml was added as a dispersion medium to deposits of 0.5 mg, and ultrasonic wave of 40 kHz was applied for 60 seconds. As a result, the deposits were taken apart and dispersed to medium. For observation with a scanning electron microscope, the dispersion was spin-coated on a copper plate. Through the observation, the presence of wire-like materials was confirmed.

The optimum positions of three circle-type bone plates for bone valve fixation were estimated by the static calculations and FEM simulations in this study. Although the stresses generated in the plates without notches were quite good agreement with the results in the static calculations, the maximum stress was strongly affected by the position of the notch in the plate and the gap between the skull and the bone valve. Then after the bone plate with the largest stress were moved and/or rotated avoiding the coincidence of positions between the notch and the gap, the maximum stresses were reduced. Finally the positions of screws for plate fixation were changed. In the case that two screws used on the bone valve (the remaining one screw was used on the skull), the maximum stressed were reduced in all bone plates, because the displacement of the bone valve were fairly suppressed.

In this study, the deformation behaviors and stress distributions in a vertbra with bone screw were calculated by FEM, whrere the vertebral model was constracted from μCT image with a 3D modeler software considering the bone density and the vertical loading to the screw axis was applied to the top of the screw. Then the loading test were performed experimentally for a vertebra with bone screw to confirm the validty of FE simulation. In the first approach in the loading tests, the rotation of vertebra was confirmed through the digital image coliration (DIC) method, then the fixation of the vertebra was modfied. The loading value was extrimly higher in FE analysis than in the experiment. In FE analysis, the stress around screw tip was slightly smaller in the model with the pilot hole than without it because of the decrease in the the contact area between the screw and the bone.

The purpose of this study is to investigate the mechanical property of catheter made of soft nylon resin reinforced with thin stainless wires. In our previous study, the yield stresses under combined loads for tension and torsion have been examined with changing those ratios and with two types of different deformation speeds. As the way to determine the yield stress, the method that the point where a curve obtained in the viscoelastic region and a curve in plastic region intersects will be regarded as the yield stress is adopted. Since not only Young's modulus reduces for containing water but also stainless wires are peeled from matrix with an increase of load, it is predicted that the value of yield stress decrease. In the present study, the yield phenomenon is examined by using the test pieces, which have already been contained water, in consideration of actual usage. Then, the relation between the occurrence region of yield stress in water content condition and the occurrence region of yield stress in non-water content condition is revealed by performing the combined loading tests with various directions in the stress space.

Recently, various resin materials are used widely in engineering. MC nylon of thermoplastics is used as many mechanical structures such as gear and bearing. In this study, the mechanical properties of MC nylon (Polyamide 6) were investigated due to design of mechanical parts with this material. The uni-axial tensile, uni-axial compressive and simple torsion test was carried out. The strain rate dependency on the mechanical properties of MC nylon is important. Therefore, the experiments under various strain rate were carried out by using multi-loading mechanical tester (Autograph AG-G20kN ; Shimadzu corporation). The strain rate was 5.0×10^-5 s^-1~5.0×10^-2 s^-1. This mechanical tester can apply axial load and torque to specimen. Normal stress and shear stress of each test was calculated from force and torque measured by load cell, respectively. Strain was measured with strain gauge. As a result, the strain rate dependency of MC nylon under all loading conditions was clear. The shear stress at 2 % strain was lower than the normal stress regardless of strain rate. The shear strength of MC nylon with the simple torsion was the lowest and the compressive strength was the highest. Therefore, the shear loading for MC nylon parts will result in the risk of the strength degradation.

The impact strength of acrylic resin board has been evaluated by three- point bending impact test in our laboratory,. The relationship between the minimum kinetic energy required for breaking the acrylic resin plate specimen and the mass of the impactor was researched. As a result, with low mass impactor, the kinetic energy increased with increasing mass. On the other hand, with high mass impactor, the kinetic energy decreased with increasing mass. The purpose of this study is to clarify the reason why the kinetic energy decreases as the mass increases in the experiments using high mass impactors.In the impact three-point bending test by the high-mass impactor, the impact load was given by free fall of the impactor. It is predicted that the load method of impact load is the cause. Therefore, the experiment was conducted with the impact load direction in the horizontal direction, and compared with the result obtained by the free fall loading experiment. As a result, when the impact load was applied in the horizontal direction, the kinetic energy of the impactor showed a substantially constant value regardless of the impactor mass. The bending stresses in each loading method were evaluated. For the horizontal load, the stresses were calculated by the kinetic energy of the impactor. On the other hand, at the free falli load, the bending stresses were calculated considering the kinetic energy of the impactor and the mass of the impactor. Both bending stresses were almost equal. Therefore, as the mass of the impactor increases, the static stress due to the mass increases, so it is considered that the kinetic energy required for breaking of the specimen decreases.

Recently, Soft robot and actuator are attracted interest in robotics field. The battery used for those applications are heavy and stiff. However, using such a heavy and stiff battery for soft robot and actuator prevent those unique movement, so in requiring flexible and light weight, organic solar cells can make that device very thin around several micrometers. Then it can have realized property of flexibility and lightweight because to reduce the thickness of the structure itself can reduce bending stiffness and limit bending radius. Therefore, it can attach complicated surface like soft robot body. But they have several issues in previous studies, for example, thermal stability, fabrication process and so on. In order to these problems, we tried optimizing fabrication process of organic solar cells with using 1.3μm-thick transparent because to deposit such a very thin film as a substrate and then peel off the devices from support glass is quite difficult. The devices performance shows Power conversion efficiency (PCE): 6.28%, current density(J_SC): 12.3 mA cm^-2, open circuit voltage (V_OC): 0.723 V, fill factor (FF) : 0.704. In conclusion, here we succeeded in developing fabrication process for ultra-thin organic solar cells which are highly resisted compression. As a flexible, lightweight, compatible and more environment stable power source device, our developing ultrathin organic solar cells are expected to use practically.

GFRP is expected to be used as automotive components because it has high specific strength and failure strain, and its cost is lower than CFRP. We fabricated GFRP cylinders by a filament winding method and the drop weight impact test was carried out. As a result, the specific energy absorption capability of GFRP cylinders using a high strength glass fiber was almost same values of CFRP cylinders. In this study, in order to investigate the effect of lamination constitution of GFRP cylinders on energy absorption property, GFRP cylinders with the first layer and the second layer wound at different angles were fabricated and the drop weight impact test was carried out. The test results showed that the specific energy absorption capability of specimens with different angles were higher than those of specimens with same angles.

In this study, mechanical properties of FW-hybrid FRP shafts using glass fiber and carbon fiber were investigated. Two kinds of FW-hybrid FRP shafts were fabricated by a filament winding apparatus. One was the HGF/CF hybrid shaft using high strength glass fiber (HME-Glass) and carbon fiber (T700SC-24K), and the other was the EGF/CF hybrid shaft using general-purpose glass fiber (E-glass) and carbon fiber (T700SC-24K). The experimental results revealed that shear strength of HGF/CF hybrid shafts were higher than that of EGF/CF hybrid shafts. The experimental behavior of the EGF/CF hybrid shafts was compared with numerical results. As a result, the numerical results in the linear region of torsional torque and twist angle curves are good agree with experimental results.

FRP sandwitch structure is used in aerospace and automotive industries because of it has high specific bending modulus and strength. In this study, a GFRTP sandwich panel using in situ polymerization polyamide 6 (in situ PA6) as metrix was fabricated by VaRTM method. In order to confirm its mechanical properties, three-point bending and impact tests were carrid out. As a result, the bending strength and specific energy absorption capability of the GFRTP sandwich were almost same values of the GFRP sandwitch using epoxy resin as materix.

We considered the axisymmetric contact problem of multi-elastic layer with different elastic constants bonded on elastic semi-infinite substrate indented by a rigid flat-ended cylindrical indenter. In this study, the information of each elastic layers can be sorted by using transfer matrix method and dual integral equations were reduced to an infinite system of simultaneous equations by expressing a normal contact stress at the surface elastic layer as an appropriate series. Numerical results were obtained to demonstrate the effects of the elastic constants of each elastic layers and semi-infinite elastic substrate on the radial distribution of normal contact stress and normal displacement of free surface of elastic layer, stress singularity factor at the edge of cylindrical indenter, and applied load of rigid indenter which needed to penetrate to a constant depth into multi-layered materials. The present results of applied load were good agreement with the results of the previous other studies. Numerical results were given for several combinations of the shear modulus of each elastic layers and substrate, and Poisson's ratio of both each elastic layers and substrate was fixed as 0.3 throughout present study. These results give us great contribution to the establishment of the indentation tests on composite materials as well as the guideline for design of appropriate mechanical properties of layered materials.

Carbon fiber reinforced plastic composite (CFRP) exhibits very complex interactive failure mechanisms because it includes fiber–matrix interfaces and interlaminar interfaces. Modeling fibers, matrix and interfaces in detail is required to conduct progressive damage analysis of CFRP accurately, but the model becomes large scale. Therefore, we have developed finite element analysis (FEA) software that could simulate failure of large-scale CFRP models including interfaces, based on open-source large-scale parallel FEA program FrontISTR. We implemented cohesive element into FrontISTR to model interfaces. We evaluated mesh size effects on interfacial damage analysis simulating double cantilever beam (DCB) experiments for measuring interlaminar strength. We conducted the simulation with 5 different element sizes by using supercomputer system. The simulation results showed that the maximum test force converges to a certain value as the mesh size decreases. In addition, we found that the software could analyze progressive damage of large-scale model with more than 70 million degrees of freedom.

Hydrogen permeability membrane with high temperature dependence is available to produce hydrogen from ammonia that be used as the hydrogen carrier in an energy system because the membrane could control that hydrogen absorption and desorption with temperature. First, we measure a hydrogen permeability coefficient of some candidate materials by the equipment that had been designed in this laboratory. Second, the temperature dependences of the hydrogen permeability coefficient of the single layer membrane Polyimide (PI), Ni and SUS304 were evaluated. Third, the composite membrane PI/Pd that was produced by vacuum evaporation and then we measured the dependence. Since PI has a higher heat-resistant even in plastic, it was used the base of the composite membrane. The temperature dependence of the permeability of PI was the almost same as the results of other research. That of PI/Pd had also more dependence of the former materials at the same temperature range and the drastic change especially in the range from 384 K to 423 K because of its logarithmic variability. This PI/Pd composite might be available for the membrane of new hydrogen carrier energy system because can control hydrogen absorption and desorption by temperature.

As a monitoring instrument of the mechanical conditions at composite/metal shear fastener joints, a "Smart bolt" embedded optical fiber sensor was proposed. In addition, it was shown that, by applying Smart bolt to the single-row fastener joint specimens, the mechanical behaviors and the early stage of damage of composite around the bolt hole can be monitored. In this study, Smart bolt was applied to the composite/metal multiple-row joint specimen of in-line array and the tensile tests of the joint specimen with looseness of one fastening bolt were conducted. Through the test results, it was demonstrated that the mechanical behaviors at fastener joint are successfully monitored also in the multiple-row fastener joint and the loosing case of fastening bolt around Smart bolt can be detected.

Recently, reduction in weight of automobiles is required to solve environmental issue. In case of clamped parts made of lightweight material such as Magnesium or resin for bolted joints, creep deformation occurs in a high temperature environment, and the axial bolt tension decrease. Conventionally, a plain washer has been used as one of the methods for preventing from the deformation of contact surface. In this study, investigated the method of suppressing axial bolt tension reduction due to creep with a plain washer in a bolted joint been investigated by experiment and FEM analysis. In the case of using a plain washer, the residual rate of axial bolt tension and residual axial bolt tension was improved. The plain washer dimension was changed. Increasing the outer diameter of plain washer, the residual axial bolt tension was improved and axial bolt tension reduction increased. Increasing the thickness of plain washer, the progression of deformation at contact surface could be suppressed. Contact surface deformation by creep is considered to be related to contact surface stress distribution and stress inside the bolted joint. It was found that when the contact surface stress is large at the outer diameter side of the contact surface, the stress near the bolt hole inside the bolted joint decreases and the creep strain decreases. From these results, it was possible to grasp the influence of the plain washer in the bolted joint causing creep deformation and to define the design guidelines.

The subloading-friction model will be improved based on the hyperelastic-based plasticity in this section. It is capable of describing exactly the finite sliding behavior under the finite rotation of contact surface without the cumbersome time-integration of corotational contact stress rate by relating the contact stress directly to the elastic sliding displacement by the hyperelastic equation. Further, it is extended to be applicable to the general case that the contact surface undergoes the rotation and the deformation.

A simple and exact closed form solution for a rotating cylinder is presented. The cylinder is inserted in a bored dissimilar elastic solid. The exact form of the absolute acceleration and the Coulomb's rule for the friction on the circular interface are employed. After discussing the resonant frequency/velocity, numerical computations are carried out for all stress components in the cylinder. It is found that the hoop stress on the cylinder edge changes its nature from extensive to compressive as the rigidity of the surrounding solid increases. The torque and power to keep the cylinder rotation is also discussed, briefly.

In order to develop a new method for evaluating the wear properties of ceramic thin film with high wear resistance, the cyclic sphere indentation tests were carried out with changing the tilting angle of the specimen (indentation angle θ), and the effects of the indentation angle θ on the wear behaviors of ceramic thin film were investigated. The tests were carried out for two types of specimen, TiAlN coated specimen and DLC coated specimen, under θ = 0°, 6°, 12°, 18°. Silicon nitride ball with 5.96mm diameter was used for the sphere indenter. These tests were carried out by using electromagnetic exciter. The sinusoidal cyclic contact load (maximum load=1.0kN, minimum load=0.1kN) was applied to the specimen through the sphere indenter. The loading frequency was 200Hz. By the conventional cyclic sphere indentation test under the indentation angle θ =0°, wear was not observed for both TiAlN film and DLC film even at cyclic number N = 2.0×10⁷. However, by tilting the specimen, wear was observed at much lower cyclic number. It was found that the wear of these films were accelerated by the indentation angle θ, and the wear rate increased with increasing θ. By measuring the cross-sectional shape of wear part by confocal microscope, the cross-sectional area of wear was evaluated, and the wear rate was calculated from the relationship between “the cross-sectional area of wear” and “the number of cycles”. By using the wear rate obtained by this method, it was possible to compare the wear property of TiAlN film and DLC film quantitatively.

Multi-material structures are constructed by screw bolts in addition to welding and adhesion. However, the interfacial stiffness of the bolted joints is often lower than that of the welding part etc. and varied by the clamping force of the bolt and the nut, because the micro asperities formed on the interfaces just contact each other. The contact analysis by using the surface texture of the interfaces in microscale is one of the accurate estimations. However, the estimation method of the interfacial stiffness in macroscale is also necessary for the in-situ evaluation. This study has proposed an evaluation method of the interfacial stiffness from the natural frequency of the structure in macroscale. The hammering test was performed by using the specimen which consisted of the aluminum alloy plate and the steel plate joined by the bolts and the nuts. Moreover, the finite element method (FEM) in microscale simulated the contact of the asperities formed on the interfaces. The interfacial stiffness estimated by the proposed method agreed with that by the microscale FEM.

In recent years, weight saving of car body is required in automobile industry to solve the issue of global warming. Aluminum alloy is one of the light materials to replace steel. ADC12, which is Al-Si_10.4-Cu_1.74 alloy (mass%), is widely used for the die casting alloy. However, ADC12 alloy has a problem due to the low strength compared to that for the steel. In this research, the microstructure of ADC12 alloy die casting was controlled by two new methods to increase the mechanical properties: (i) Precipitation strengthening because of CuAl2. In this process, aging treatment at low temperature (175 °C) was applied to the die casting samples; (ii) Microstructure refinement and spheroidizing by the addition of appropriate amount of Na. In general, it is difficult and dangerous to use Na caused by active material. In this study, an attempt was made to employ NaHCO3. From the examination of microstructural characteristics on the mechanical properties, high hardness was obtained for ADC12 alloy die casting after heating at 175 °C for 3 h. Furthermore, the α-Al + Si eutectic structure of ADC12 alloy die casting became fine and spherical with 0.1% Na. With these microstructure control, the Vickers hardness improved by about 15% and the tensile strength increased by about 40%.

Additive manufacturing AM of metallic components is an attractive method for medical implants and aviation components, as it is easy to make porous implants and to reduces weight of the components by nearly free design without consideration of machining. However, fatigue strength of AM metals is relatively weak due to surface roughness and tensile residual stress. Mechanical surface treatment such as shot peening and other shotless peening can improve the fatigue strength of AM metals. In order to demonstrate the improvement of AM metal by mechanical surface treatment, fatigue specimen made of titanium alloy Ti6Al4V manufactured by electron beam melting was treated by shot peening, cavitation peening and laser peening, then tested by a plate bending fatigue test. In the present treatment, recirculating shots accelerated by a water jet was used as shot peening, submerged laser peening with 1,064 nm in wave length was applied as laser peening, and a submerged water jet with 30 MPa of injection pressure was used for cavitation peening. It was concluded that the fatigue strength of the titanium alloy Ti6Al4V manufactured by electron beam melting was improved by 2 times by laser peening, 1.8 times by cavitation peening and 1.7 times by shot peening, comparing with the fatigue strength of as-built specimen, whose fatigue strength was 221 ± 11 MPa.

The double integrity is recently focused on to improve the structure integrity of the large container ships. In addition to material performance to arrest a propagating brittle crack, structural factors are expected to enhance the double integrity. Such structural design is called as crack arrester, and in large container ships, so called “structural crack arrest design” utilizing welded joint has been recently used as the crack arrester. Although such design is already applied to commercial ships, the mechanism of crack arrest in such design has not been clear because crack behavior in the joint is 3D and hard to measure by conventional methods. Therefore, in order to clarify crack arrest mechanism in structural crack arrest design, 3D rapid crack propagation and arrest behavior was observed in T-joint-like structures made of transparent elastic material by using high speed camera. The experiments were carried out for three kinds of specimen, whose flange thickness were different. The experiments showed that the crack was likely to be arrested in the thicker flange. The observation using high speed camera showed that the crack front shape was significantly important to consider crack arrest mechanism because the semi-elliptical-like crack front shape in flange plates caused reduction of SIF and crack arrest. Such crack front shape was easily kept in the thicker flange specimen, so the crack was arrested.

The purpose of this study is to clarify the effects of surface oxide layer on fracture toughness of approximately 500-nm-thick freestanding copper nano-films. Freestanding film specimens with thermal oxide layer (oxide layer thickness: ~3 nm and ~6 nm) were prepared by thermal treatment in dry air. Specimens without oxide layer were prepared by removing the surface oxide layer by means of argon ion sputtering. In situ field emission scanning electron microscope fracture toughness experiments confirmed that a crack initiated at the notch root by applying a tensile load. The effects of surface oxide layer on the critical crack tip opening displacement of the specimens with native/thermal oxide layer were not clearly observed. On the other hand, the critical crack tip opening displacement of the specimens without oxide layer was clearly higher than that of the specimens with native/thermal oxide layer.

Thermal barrier coatings (TBCs), consisting of a ceramic insulating top coat (TC) and metal bond coat, have been widely used in gas turbines to protect hot section metal alloy components. In general, TC is deposited by atmospheric plasma spraying (APS) method or by electron beam physical vapor deposition (EB-PVD) one . APS method provides a porous TC which has lower thermal conductivity compared with EB-PVD TBC. On the other hand, EB-PVD TBC has columnar microstructure resulting in higher resistant to thermal shock than APS TBC. Suspension plasma spraying (SPS), as a newly emerged technique, is used to deposit coatings with enhanced characteristics utilizing suspensions containing submicron spray particles. However, there are few reports of damage behavior of SPSed TBC system. In this study, the high temperature oxidation test and thermal cycle fatigue test were carried out on SPSed TBC and damage behavior was investigated comparing with APSed TBC. It was revealed form the experimental results that there were differences in the thermally grown oxide (TGO) growth behavior and damage behavior between both coatings. In particular, the TGO growth behavior suggested the superiority of coating life of SPSed TBC.