Hydrogen embrittlement of steel was caused due to hydrogen accumulation in the material. And the hydrogen distribution in material depends on the distribution of hydrostatic stress. Furthermore, since actual structures have the three dimensional shapes, each component will be under the local multiaxial. Therefore, concerning stress induced hydrogen diffusion under local stress field, the hydrogen distribution depends on the multiaxial stress. In this study, hydrogen distributions around a notch tip under fatigue condition were obtained by numerical analysis for a two dimensional plane stress model and a three dimensional axial symmetric model. Concerning hydrogen diffusion analysis in structural component, FEM (finite element method) - FDM (finite difference method) coupled method was applied for this numerical analysis. And the effect of multiaxial stress on hydrogen diffusion behavior was investigated. Hydrogen concentration behaviors were found to be dominated by local multi-axial stress in structure.

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Today, CFRP composite vessels are used as fuel containers of CNG (Compressed Natural Gas) vehicles and fuel-cell vehicles. It is known that material property and fatigue life of CFRP composite vessels are seriously reduced by out-of-plane loading. Also, autofrettage treatment for the improvement of the fatigue life is conducted on composite vessels. The main objective of this study is to evaluate effects of autofrettage on damage behavior subjected to impact loading. Composite vessels used in this study consisted of aluminum liner fully wrapped by carbon/epoxy, which were fabricated by filament winding method. Impact tests and damage observation were performed on the composite vessels with and without autofrettage. Internal pressure test were also conducted after impact tests, and to investigate residual strength. As a result, absorbed energy of composite vessels with autofrettage became smaller than composite vessels without autofrettage. In composite vessels with autofrettage, delamination was suppressed, and residual burst strength became larger. It was clarified that CFRP composite vessels with autofrettage were superior in the impact resistance.

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For popularization of hydrogen fuel cell vehicles, adequate amount of hydrogen refueling stations is indispensable. Accumulators are regarded as important parts for the stations, and have to be made with low cost and enough reliabilities. Conventional steel accumulators have problems of manufacturing such as heat treatment of heavy-walled vessels to cope with holding higher pressure than before. That is the reason why Type3 CFRP pressure vessels are commonly used at the stations. The CFRP pressure vessels have been manufactured by trial and error manner, since it is difficult to make up accurate model of dome part where helical winding CFRP layers are layered complicatedly. We have developed a computer software to describe the complex layered structure accurately for finite element analysis. We demonstrate its validity in problem of better understanding the results of cyclic pressure tests of the Type3 CFRP pressure vessels.

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We have developed a rational strength evaluation methodology with meso-scopic model based on fiber bundle and resin system for filament wound CFRP pressure vessel. Our developed software adequately generates model data of varying filament winding pattern. The validity of meso-scale simulation is exemplified with strain concentrations near fiber bundle crossover of helical winding vessel.

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Strength limited design of carbon fiber reinforced plastic (CFRP) is very important for hydrogen pressure vessel to reduce the cost with reliability. Authors have approached to evaluate a test piece sized model representing CFRP in the vessel. The model is analyzed by a meso-scale finite element model, where mesoscopic structure of carbon fiber bundle and matrix resin is explicitly handled. The actual test pieces are examined by quasi-biaxial tensile test. As for macroscopic load-strain relationship, the finite element analyses yield good agreement with the experiments. We reveal strain concentration in the vicinity of fiber bundle crossover, which causes burst pressure reduction of the vessels.

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This paper investigated the influence of chemical damage of polymer electrolyte membrane (Nafion^[○!R]) on fracture strength in Polymer Electrolyte Fuel Cell. Nafion^[○!R] NR211 was damaged for 24 h by using a Fenton's accelerated aging experiment. The fracture strength of Nafion^[○!R] was evaluated by essential work of fracture (EWF). EWF was derived by using double edge notched tensile (DENT) test. DENT test was conducted for fresh and damaged Nafion^[○!R] under four conditions: 30℃ 50 %RH, 30℃ 100 %RH, 80℃ 50 %RH and 80℃ 100 %RH. The fracture surface was observed by using Scanning Electron Microscope (SEM). The results showed that the fracture strength of Nafion^[○!R] was decreased by chemical attack; decreasing rate was about 41 % at room temperature and normal humidity, about 79 % at high temperature and normal humidity, about 87 % at high temperature and high humidity. Moreover, the fracture surface revealed that the brittle fracture with crazing was occurred on the damaged Nafion^[○!R] at normal temperature and high humidity.

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Various forms of life need oxygen, and the unmanned diving machine also needs oxygen. However, it is limited under water in the present situation because of a capacity of oxygen cylinders. In nature, there are some special insects, which utilize superhydrophobic hair structures as physical gills, semipermanently living in water. We focused on this physical gill of the plastron and prepared artificial plastrons by using self-organized honeycomb-patterned films. In this paper, we showed the preparation of artificial plastrons and measurements of oxygen permeability in water. As results, durable honeycomb-patterned films resisting water pressure were obtained, and oxygen was transferred from water to inside of the bottles though the films. This phenomenon suggested the honeycomb-patterned films showed possibility of use as artificial plastrons.

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In order to improve fuel consumption and collision safety of a car, application of ultra-light porous metals having high specific rigidity and good impact energy absorption to various car parts are hopeful. Generally, it is thought that the applicable porous metals include closed cells and their relative density is less than 0.3. Especially, metallic hollow sphere (MHS) structure is comparatively homogeneous and has high reliability to apply it to the car parts. However, production cost, insufficient controllability of performance and weak tensile strength have been problems yet. To solve these problems, we propose a ball-chain type MHS structure. Many strings of metallic hollow spheres are precisely produced from thin metal sheets by plastic working with dies and then the strings are consolidated. Since the neighboring hollow spheres are connected by a bridge, the tensile strength may be improved. In this paper, the fabrication method and results of simple compression, simple tension and 3-point bending tests of the structure are reported.

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Porous aluminum has lightweight and high energy absorption properties. In this study, impact test of functionally graded porous aluminum by varying pore structures was carried out. Functionally graded porous aluminum was manufactured by heating the precursor that was made by precursor without a blowing agent addition and with a blowing agent addition. It was shown that deformation of functionally graded porous aluminum changed from the high porosity layer to the low porosity layer. This result shows that functionally graded porous aluminum has two characteristics of a low porosity layer and a high porosity layer under the compression.

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In this paper, easy casting method of the ingot with through holes is shown. Core-bar-pulling method is proposed to improve the disadvantages of the lotus type porous metal. The through holes were formed by pulling core-bars from the semisolid ingot. The holes with diameters ranging from 0.5 mm to 5 mm and 50 mm length was made in the Al-Si alloy ingots. Relationship between temperature and formability of holes were investigated using the eutectic Al-Si alloys. The pulling of core-bars and the forming of the holes were easy, in the condition that the Si content was less than 6 mass%. This means that the forming of the holes in the Al-Si alloys was easy at Si content with which the flow ability at semisolid condition becomes worse.

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Porous metals, which contain large amount of pores inside, exhibit various unique physical and mechanical properties, such as low bulk density and high strain energy absorbing capability. In this presentation, a novel processing method (reactive precursor method) to synthesize high-melting point porous metals and an attempt to control the cell structure are discussed. A precursor is made by blending two or more kinds of elemental powders. The precursor is then heated to ignite an exothermic reaction between the elemental powders. The closed-cell porous structure is obtained when the maximum temperature during the reaction exceeds the melting point of the reaction product, and open-cell porous structure is obtained when the maximum temperature is below the melting point. Therefore, if the optimum porous structure is the closed cell, then an additive powder (exothermic agent powder) which releases large amount of heat of reaction should be additionally blended. By blending additive powders in the precursor, the maximum temperature can be controlled. Aside from the additive powders, replication powders are also used to extend the diversity of cell morphology. Closed, flat, open, bimodal-sized and high-porosity open pores are currently achieved by the reactive precursor process.

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Titanium and its alloys of low elastic modulus have been required as materials for the implants. Porous materials have been considered as a way to respond to the request, so the conflicting problem of mechanical strength and porosity has been challenged. By the way, production of porous materials by capsule-free hot isostatic pressing (HP) has been said to be able to control the porosity and mechanical strength simultaneously, hi this study, commercial titanium powders were compacted by several uniaxial loads (4.9-24.5 kN) in a die having a diameter of 15 mm, and the green compactions were sintered by a capsule-free HIP method under an argon gas atmosphere at a holding temperature of 1523 K, a holding time of 1 hour. Porosity of the sintered body was, however, not so high with an average relative density of 72 %. Results showed that characteristic improvement of porous titanium sintered compacts was expected by homogenization of the green compacts, optimization of the HIP pressure and so on.

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Compression behavior of a porous aluminum made by the friction stir processing was investigated through the finite element analysis. The finite element model was automatically constructed by the image-based modeling using a micro-focus X-ray CT. The voxel modeling was employed to robustly and quickly generate the finite element mesh. To examine the validity of finite element simulation, the nominal stress and nominal strain relationship was compared between the finite element analysis and the experiment. The simulation result overestimated the total stiffness and nominal stress due to mainly the inadequate approximation of contact boundary condition with the compressing plate. However, the error in plateau stress was about thirty percent, and it may be reduced by the rigorous contact analysis and the refinement of finite element mesh.

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Porous aluminum (Al) was fabricated by a tool traversing friction powder sintering process. In this process, a mixture of Al powder and sodium chloride (NaCl) powder as spacer particles was used as a starting material. The powder mixture was placed in a mold, compaction and sintering of the mixture was conducted only by the traversing of a rotating tool as in friction stir welding. In this study, functionally graded porous aluminum was fabricated by a tool traversing friction powder sintering process which had different range of porosity of 60%, 70% and 80%. By X-ray computing tomography observation, it was found that the fabricated functionally graded porous Al had uniform pore distribution in each porosity range. By a compression test, it was shown that the plateau stress was decreased with the increased in porosity. Consequently, it was shown that functionally graded porous Al can be fabricated by changing of NaCl mixing rate and tool traversing friction powder sintering process.

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This study investigates the compressive deformation behavior of a low-density polymeric foam. The present polymer material has micron-sized pores with a closed cell structure. The porosity is about 94 %. After a uni-axial compressive test, the macroscopic stress - strain curve indicates a plateau region during plastic deformation. Finite Element Method (FEM) simulation was carried out, in which the yield criterion considered both components of Mises stress and hydrostatic stress. By using the present FEM and experimental data, we established a computational model for the plastic deformation behavior of porous material. To verify our model, several indentation experiments with different indenters (spherical indentation and wedge indentation) were carried out to generate various tri-axial stress states. From the series of experiments and computations, we observed good agreement between the experimental data and that generated by the computational model. Therefore, the present computational model can predict the plastic deformation behavior of porous material subjected to uni-axial compression and indentation loadings.

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Sintering experiments of cylindrical compacts of metallic hollow spheres are conducted under partial uniaxial pressure at some elevated temperatures, and the state of contact between spheres is examined. The cylindrical compact is made by pouring iron hollow spheres into a stainless steel container. An aluminum weight is put on the inner part of the upper surface of the compact, and the outer part is covered by a stainless plate with or without empty space. Vertical cross sections of the fired compacts are observed to examine the degree of contact between spheres. The increase in contact area with the reduction in height of compacts is small in the outer region compared with the inner region. In the case of covering with empty space, the spheres tend to move out of pressure by the weight, and the reduction in height and the contact area vary widely. When the compact is covered without empty space and compressed enough, the contact areas between spheres become large.

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To produce aluminum foams with complicated shape, an additive process of aluminum foam is proposed. Experiments of producing aluminum foam by extruding and foaming of precursor from heated die are conduced to deposit aluminum foam on a stage for the additive process. The precursor is made by hot powder extrusion of A6061 and TiH_2. The speed and the die temperature in the extruding and foaming of precursor are examined. The experimental results show the density distribution within the aluminum foam.

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To fabricate aluminum foam having nonporous surface layer (sandwich structure), the selective laser sintering (SLS) was applied to fill surface pores of a commercial closed-cell type aluminum foam (ALPORAS) with nylon (polyamide). A nylon powder with an average diameter of about 10 μm was supplied in the surface pores of the aluminum foam, while a nylon sheet with a thickness of 0.3 mm or 0.8 mm was set on the surface pores of the aluminum foam. The nylon powder or sheet was continuously melted and solidified in the surface pores of the aluminum foam by irradiating with a Nd:YAG laser with an average power of 10 J/mm^2. As a result, the aluminum foam having nylon surface layer was successfully fabricated.

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Aluminum foam composite of aluminum alloy die casting ADC12 coated by pure aluminum A1050 was fabricated by friction stir welding (FSW) route precursor foaming method. Moreover, weight drop impact compression tests of the aluminum foam composites were carried out. We attempt to estimate the plateau stress of the aluminum foam composite based on the mean compressive stress on a maximum-porosity cross section perpendicular to the direction of compressive loading. Through the comparison of impact compression test results with the estimated results, it was expected that the plateau stress of the aluminum foam composite can be evaluated when the equivalent diameter of pores in ADC12 region is approximately equal to that of ADC12 uniform porous aluminum.

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Porous metals are one of promising super-light materials. However, there are currently few applications of porous metals. Advanced porous metals must be developed based on their specific characteristics. In the present work, new horizon of porous metals is discussed from the viewpoint of microarchitecture. Weigh reduction is one of main targets for porous metals, but it cannot be attained only by replacement of conventional materials with porous metals and special use of porous metals is required for weight reduction. For special use, important is microarchitecture control such as pore refinement. Also, an artificial bone requires microarchitecture control of the pore size of about 200 μm and the low elastic modulus fitting a living body. Besides, the importance of microarchitecture control is shown for an acoustic absorbent material and a microchannel.

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Porous aluminum (Al) is a lightweight with high energy absorption properties and expected as structural materials. In this study, static compression tests of porous Al core filled in SUS304 pipe composite material (porous core pipe) with slits fabricated by friction welding were carried out. Precursor of porous Al was fabricated by friction stir processing (FSP) route. Precursor was put into the SUS304 pipe, and rotating tool was pressed into the precursor. Then,, bonding between Al precursor and SUS304 pipe can be conducted. The slit parts are formed by notching the porous core pipe. From the compression tests, it was suggested that the slits are effective to control the compressive deformation behavior.

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In this research, we present the model of the hydrogen storage microcapsule that is constructed with carbon-based materials wrapped in the hydrogen permeable membrane that is produced by a multilayer of transition metals and a substrate. Since carbon-based materials more adsorb hydrogen at low temperature, it is presented that the steps of hydrogen storage in the microcapsule are as follows. First, the microcapsule is introduced hydrogen which permeates through the membrane at high temperature. Second, the carbon-based materials adsorb hydrogen and then the membrane prevents from releasing hydrogen at low temperature. Third, the carbon-based materials and then the microcapsule release hydrogen due to raising temperature and we can use the hydrogen in more safety and efficiently. For such a membrane of the microcapsule, Stainless/Ti/Ni/Ti multilayer is prepared with Pulsed Laser Deposition method and evaluated amount of hydrogen storage against temperature with Pressure-Composition-Temperature curve measurement. The maximum hydrogen contents of the multilayer are 0.0838wt.% at room temperature and 0.573wt.% at 200℃ and those of the stainless film without Ti and Ni layer are 0.193wt.% at room and 0.504wt.% at 200℃. The hydrogen contents of the multilayer are rarely different from the stainless film and it is possible that the membrane can be evaluated hydrogen permeation against temperature with polymeric membrane as its substrate and determination test of gas transmission rate defined in JIS K 7126-1.

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In order to bond the aluminum foams by foaming bonding, the oxide film on the surfaces of the foams has to be removed. A flux is widely used for the aluminum brazing-bonding to remove the oxide film. In this study, the effect of the surface treatment by the flux on the bonding strength of the specimen bonded by the foaming bonding is investigated. A commercial flux was applied to bonding surfaces of two aluminum foams. An aluminum precursor with low melting point was put between the aluminum foams and it was heating and foaming. The bonding strength of the bonded specimen was evaluated by using 4 point bending test. The bonding strength of the bonded specimen with flux applied is 30 % higher than that without flux applied. However, the bending strength of the bonded specimen varies widely. This is because that a part of the cell wall of the aluminum foams was melted and broken.

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The objects of this paper are numerical prediction of the distortion that is induced after a machining process under the residual stress field, and new method to measure the residual stress distribution. In this work, the residual stress field caused by plastic forming is numerically evaluated by using a commercial FEM code ABAQUS. Residual stresses induced by machining are limited in a region with a maximum depth of 0.2mm. For this reason, a machining process can be seen as a simple stress redistribution process due to material removal. Numerical results have been compared to experimental distortion measurements. The results show the redistribution of the residual stresses is the major factor of the distortion at machining process under the residual stress field. In order to measure the residual stress distribution in thickness direction of about 10 mm thick plate, this paper propose the new measurement method that combines drilling-method and machining.

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In recent years, flexible materials with very high performance are widely used and large deformation analyses of these materials have attracted considerable attention. However, there is not sufficient analysis for problems of practical interest such as large deformation of a cable within a channel (or a pipe), or of a drill within a hole in rock engineering and petroleum production, or of a catheter within a blood vessel, and so on. When a lightweight, flexible material must be pushed through the narrow space, it is possible for the materials to buckle since the leading edge of the material strikes an obstacle (or a barrier) and cannot proceed any further. The postbuckled configuration, namely large deformation, will be thus of great concern in handling these flexible materials. This paper deals with the postbuckling behavior of a flexible elastic beam contained within rigid, parallel walls with friction under the action of axial compressive forces at each end.

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The shape memory effect (SME) in Fe-Mn-Si based alloy is associated with γ&elarr;ε martensitic transformation which is caused by motion of the Shockley partial dislocation. The variants in Fe-Mn-Si based alloy could appear the four orientations according to Shouji-Nishiyama (S-N) relation in the austenite phase (A-phase) to the martensitic phase (M-phase). It was reported that the variant formed the single orientation under stress induced transformation and that is the advantage for SME in the variant selection behavior. In this study, the variant selection of Fe-Mn-Si based alloy under stress applied is investigated on the basis of crystallography in the SME with Electron Backscatter Diffraction (EBSD). The amount of shape recovery was quantified by means of bending test and the best recovery ratio was revealed about 83% for the specimen annealed 600[℃]. The SME in improved by not only the increase of A-phase but also the promotion of the single orientation under stress induced transformation. Most of A-phase formed the single orientation with Schmid's factor during the stress-induced martensitic transformation.

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Mechanical properties of metal materials depend in a large part of their microstructures. Metal materials having periodic microstructures consist of coarse grains (core) surrounded by fine grains (shell) show high strength and ductility; however, the reason is not fully understood. Such microstructures are so-called "harmonic"-type. In this study, crystal plasticity analysis of unidirectional tensile tests was conducted, using some simple geometric models of harmonic-type bimodal microstructures with different grain sizes of the core and shell. The results showed that the difference of yield points between the core and shell makes difference of slip strain; it results in piling up of geometrically necessary dislocations (GNDs) within the core. High density of GNDs makes the mean free path of dislocations short, and the SSDs also accumulated in high density within the core. In the initial deformation, it suggests the accumulation of GNDs strongly influences work hardening of the metal materials with harmonic-type bimodal microstructures.

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Dislocations in ferrite lamella in pearlite microstructure and stress-strain response of the pearlite are examined by a strain gradient crystal plasticity analysis. Obtained results show that difference of initial friction stress in the ferrite lamella and stepped section of cementite lamella arise dislocation bowing. While the dislocation bowing from low initial friction stress area disappeared with increase of plastic deformation, the dislocation loop from stepped section of the layer keeps bowing. However, presence or absence of dislocation bowing has an insignificant effect on the stress-strain response of the pearlite. One of major factor to influence the mechanical response of a layered metal is a mean free path of dislocation.

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Honeycomb structures made from thin aluminum or other material sheets are usually utilized as panel cores with faces and taking their light-weight performances for construction applications. Design parameters such as cell size, height, foil thickness etc. of honeycomb structures will affect the compression performance of honeycomb structures and also the panel constructions. In this study, relationships between the compression performances of honeycomb structures with respect to different design variables like honeycomb foil thickness; cell size and height were experimentally evaluated and reported here.

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Honeycomb sandwich structures are constructed by bonding two stiffer skins with one honeycomb core, which are called composite panel structures with light-weight and high-strength performances. Sandwich-structured composite panels are normally used for secondary and tertiary functions like aircraft flooring or Rotor blades etc. and sometime used by bending member. In this study, the relationship between bending flexural rigidity and bending elastic modulus performances of honeycomb sandwich composite panels with design parameters like skin thicknesses, honeycomb cell size and height etc. are experimentally and analytical evaluated through the four point bending flexural test.

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The dynamic behavior of the cushioning material underlying a sealed air is estimated by numerical simulation using the air bag analysis function of the general-purpose finite element code LS-DYNA. A black natural rubber with hardness of 65 is used for the mother material of the cushioning material. It is because easy to obtain. First, the dynamic compression characteristics of the black natural rubber is obtained by drop weight tests using a test piece of a cube shape. Then, assuming that the cushioning material has planar arranged sealed spheres in a lattice shape inside, a simulation model with a virtual airbag on the inside of the sphere is created. With this model, the influence of the pneumatic shock absorbing effects are estimated by numerical simulation for drop weight impact loading. The numerical simulation is carried out by changing the air pressure inside the sphere and by changing the rigidity of the natural rubber.

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Heat treatment is ordinarily conducted to reduce residual stress caused by plastic work. Also to improve physical properties of steel, such as tensile strength, heat treatment is conducted. For example, an appropriate way of quenching leads to compressive stress to improve of fatigue strength. To obtain an optical condition of the heat treatment, it is important to understand the phase transformation during the heat treatment. In the case of large forging, especially, the scale effect induces temperature difference inside the steel and it makes difficult to consider the phase transformation due to the heat treatment. Therefore a method to quantitatively evaluate the residual stress after hear treatment of large forging steal is required. In this paper, in the aim at reduction of heat treatment processes of a large size forged steel, finite element method (FEM) is conducted to find an optical condition of the heat treatment. The analysis considers the effects of both transformation plasticity and creep deformation. Furthermore, the transformation plastic deformation are also considered. Finite element analysis software ANSYS14.5 is used with user subroutine "Usermat".

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To evaluate the strength reliability of the electronic substrate accurately, the deformation behavior, especially, the creep deformation of the solder joint should be estimated in-situ. The indentation creep test is one of the effective test to evaluate the creep deformation in the microscopic region. However, this test has the problem that the stress is overestimated by employing the contact area between the indenter and the specimen as the reference of the stress evaluation. To solve the problem, methods to determine the suitable area for the indentation test and to evaluate the creep deformation by using the suitable area were numerically proposed by the authors. In the proposed method, the principal stress plane approximated by the spherical surface is defined as the reference area to calculate the stress assuming that the specimen is homogeneous. In this paper, the indentation process is simulated by using the inhomogeneous model of the specimen to confirm that the principal stress plane is assumed as the spherical surface. The actual indentation test with a constant depth process is also conducted using Sn-3.0Ag-0.5Cu solder specimens to verify the applicability of the proposed method to the actual indentation test.

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The elasto-plastic deformation behaviors of an IF steel sheet during stress path changes were investigated by performing nonproportional tension-compression tests. To evaluate the developed constitutive models in describing nonproportional deformation behaviors, numerical simulations of stress-strain responses were conducted for the same stress paths as the experiments. From the comparisons of experiment and calculations, it was found that the proposed constitutive model can describe well every deformation behaviors of an IF steel sheet during stress path changes.

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The authors have proposed a parameter of "creep strain amplitude" as an alternative to the inelastic strain amplitude to estimate the fatigue life of solder alloys. To evaluate the fatigue strength of the solder joints using the creep strain amplitude, a constitutive model which can accurately predict the creep deformation under cyclic loadings is needed to conduct the FEA of the solder joints. Especially, the model must be able to describe the recovery behavior of the creep strain hardening due to the stress variation under cyclic loadings. However, such a model for solder alloys has not been proposed because of the lack of the information about the recovery behavior. Then, in this work, we investigated the behavior by conducting creep tests including stress variation process using Sn-3.0Ag-0.5Cu (SAC) solder. In the tests, the stress was maintained constant at 20 MPa for 1000 s at first (Stage I), and then the stress was decreased to a lower level and maintained constant at the level for a time period. Five kinds of stress levels were chosen for the lower stress, and five kinds of time periods were used for the stress maintenance at each stress level. After the process, the stress was increased to 20 MPa and maintained constant again for 1000 s (Stage II). The recovery behavior of the creep strain hardening was discussed by comparing the creep curve and the creep strain rate between the Stage I and the Stage II.

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In the previous work, the authors proposed a method to estimate the tensile characteristics of the Cu/Sn intermetallic compounds (IMCs) of Cu_6Sn_5 and Cu_3Sn. The method provided two new findings. One is that the breaking elongation of the Cu/Sn IMCs is approximately 1%. The other is that the stress-strain relation of the Cu/Sn IMCs shows non-linearity. Since the Cu/Sn IMCs have been regarded as elastic materials for a long time, the latter finding needs to be verified in some way. Then, in this study, we conducted finite element analyses (FEAs) which simulated the shear tests using the copper-solder joint specimen whose solder joint includes the Cu/Sn IMCs layer. The FEA for a loading condition was conducted in two different ways. Namely, two different constitutive models of elastic model and elasto-plastic model were employed to describe the deformation behavior of the IMCs for a loading condition. The real shear tests were also conducted in the same loading conditions as the FEAs. Comparing the results of FEAs with those of the real tests, we discuss the presence or absence of the material nonlinearity of the Cu/Sn IMCs. The discussion result suggests that the Cu/Sn IMCs have non-linear stress-strain curves.

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In order to evaluate quantitatively the strain rate dependence of the dynamic flow stress at each strain, decrement strain rate tests are performed at strains of about 0.152, 0.195, 0.243, 0.292, 0.342, 0.394 and 0.436, respectively at the strain rate of about 10000/sec. The reduction ratio caused by the collision between an impact bar and a decelerator is 0.586 of the strain rate before reduction. The flow stress drop caused by the rate reduction was assumed to be a response to an instantaneous strain rate. An activation volume is determined from the relation of a thermal activation process and the amount of the flow stress drop obtained from the reduction tests. The results indicate that the activation volume decreases slightly with strain.

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Many reports on the high strength and grain refinement of the flame-resistance Mg alloy has been obtained in thin rolled sheet, but there is little report of rolled plate (thickness of 3 mm) the fabrication process in order to achieve both high strength and large elongation. In development of high strength magnesium alloys with large elongation for medium plate, effect of calcium containing of magnesium alloy and rolling process on mechanical properties of rolled Mg-Al-Zn-Ca alloys with thickness of 3 mm were investigated used by rapid cooling cast materials. In this study, to prepare a flame-resistance Mg-Al-Zn-Ca cast material, have been developed in the sheet thickness 3 mm with strength of 340 MPa and large elongation of 11.1% by hot rolling process. The cast material crystal structure is coarse as a starting material, to a total reduction in thickness about 60% strength is significantly improved, but also to further increase the reduction in thickness was strength slightly increased. The hot rolled sheet shows intensively deformed band or shear band structures, as well as finely and crushed Al_2Ca compounds during rolling process.

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High tensile steel must be used in automobiles to reduce weight of components. Although the strength of high tensile steel is known to be extremely high, its workability is not good. Therefore, "texture control procedures" using industrial lasers were applied to high tensile steel in this study. Results show increased bending workability attributable to y-fiber in ND plate. Bending workability was examined based on various mechanical properties assessed in several experimental tests such as sectional observation, micro-Vicker's hardness, SEM-EBSD (crystal orientation), and 90° and 30° bending. This high tensile steel was found to have excellent workability and a no-crack surface.

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When aluminum is bent, a crack occurs in the range of the bend according to the crystal orientation and material strength. Recent reports have described improved processability of a cube orientation ({001}<100>) with bending. To increase the bending workability of pure aluminum and aluminum alloy and their application to brass, the respective relations between crystallographic orientations and microstructures were examined along with their bending and mechanical properties. The texture distribution was also analyzed. Bending workability was assessed based on various mechanical properties investigated using experimental tests such as SEM-EBSD (crystal orientation), and 30° bending and hemming. Some analytical results related to crystal direction maps, inverse pole figures, and textures were obtained from electron backscatter diffraction (EBSD) analyses. Pure aluminum and aluminum alloy were found to have excellent workability and a no-crack surface. Brass was found to have a wrinkled surface after high-temperature laser irradiation.

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To improve the attenuation coefficient of the GFRP, it was considered a way to complex with rubber which has high attenuation coefficient. Although the attenuation coefficient is improved by sandwiching the rubber sheet to the GFRP, the strength is lowered. Also, there is a problem in the adhesion between the rubber sheet and the GFRP. In order to solve these problems, it was thought that the holes in the rubber sheet. Test pieces which have different diameters of holes and the width of the rubber were made. And, test pieces were resonated by the vibrator in order to determine the attenuation coefficient by a half-width method. The results of the experiment, to improve adhesion by drilling, it was found to suppress the decrease in strength. Also, when the rubber was sandwiched in GFRP, attenuation coefficient was improved. The diameter of the hole drilled in the rubber changing the vibration damping property.

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When producing plastic products, considerable corrosion and wear on the plasticizing parts (barrels, nozzle, and screw) of injection molding machine. Corrosion gas environment resulted from molten plastic chemically reacts with surface of metals. Furthermore, wear damages are made by friction between glass-filled polymers and plasticizing parts. It is important to increase corrosion resistant and control wear damages of plasticizing parts for qualitative improvement of plastic products. Especially about corrosion, a few test methods like a immersion test by reagents are being conducted to evaluate corrosion resistance. However, in these tests it is difficult to evaluate corrosion and wear damages simultaneously. In this study, the anodic polarization test have been conducted to monitor the effect of plastic dissolved in 30wt.% H_2SO_4. And we also conducted corrosion wear test with ball on disk test. As test samples, SKD61 metal for injection molding machine and PA66+GF25% an engineering plastic are used. As a result, the regenerative faculty of oxide film on SKD61 was decreased.

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The author proposed a new criterion of micro-crack nucleation, which was deduced theoretically by shock wave theory, based on a new concept whereby micro-crack nucleation is caused by a jump in the wave velocity along the intersection line between two different stationary discontinuity bands characterized by the vanishing velocity of an acceleration wave. Successively, in order to consider the crystal orientation dependence of the ductile fracture progress, algorithm of the proposed criterion was incorporated into the finite element crystal plasticity model. In the present paper, the new micro-crack evolution equations are derived based on the previously proposed evolution equation. The new evolution equation deduces the strain jump being infinite within finite time which corresponds occurrence of the displacement jump: macro-crack/void. Simulations of ductile fracture progress of FCC single crystal notched plates with different crystal orientations to the loading direction and also qualitative comparisons of simulated results with experimental observations are performed. Based on the simulations and the new evolution equations it is concluded that the strain gradient dominates the ductile fracture progress from micro-crack nucleation to macro-crack growth and fracture/collapse.

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Float glass is widely used for many applications such as windows of buildings and cars due to its properties of transparency and corrosion resistance. The float glass is usually brittle material so that it might fracture, scatter on impact loading in some accidents and damage human bodies. There is one of the ways to reduce the risk that the installing window films to the float glass and that is a reasonable way to prevent scattering and also suggests that the glass plate installed the films might enhance the strength with the increase of the adhesive force between the film and the glass. Although the strength of the glass plate is qualitatively evaluated according to JIS R 3212, we measured the strain of the impact loading during the test. On the other experiment the adhesive forces were determined for JIS A 5759 with the days and it was investigated that the more adhesive force affects the surface strain and then the strength of the float glass. The results show that the increase of the adhesive force decreases the maximum strain and also improves the gross strength of the glass plates.

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Thin polyimide (PI) films have been widely used for spacecraft polymeric materials. In the use in low earth orbit environment; however, small defects often initiate at the surface of PI films by the erosion of atomic oxygen. Mechanical strength of PI films are significantly reduced by the crack propagation from these defects; therefore, to evaluate fracture toughness in the direction of film thickness is important. This paper conducted tensile tests of 125-μm-thick PI films with two types of surface pre-cracks having the depth of 20μm and 40μm, and estimated fracture toughness J_<in> and CTOD_<in>. As a result, J_<in> of the specimen with the pre-crack of 40μm depth (40μm pre-crack specimen) was larger than that of 20μm depth (20μm pre-crack specimen). In contrast, CTOD_<in> showed almost same values regardless of the depth of pre-cracks. Thus, CTOD_<Ic> can be considered as elastic-plastic fracture toughness CTOD_<Ic>. J_<Ic> was estimated from the CTOA_<Ic> based on the commonly-used relationship between J and CTOD. Then, J_<in> of 20μm pre-crack specimen was same as J_<Ic> with an error of 12%. Therefore, J_<in> of 20μm pre-crack specimen was approximately considered as J_<Ic>.

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Biaxial loading of a variety of stress ration are carried out for GFRP plates with circular hole and this study is to investigate effect of stress ration and fiber placement on stress concentration and strain around circular hole. In addition to general GFRP plates, GFRP whose fibers were not cut with circular hole by placing fiber around the hole in order to decrease stress concentration were used as improved GFRP plates. Vertical and horizontal strain around circular hole and strain apart from the hole was measured in biaxial loading whose stress ration increased from 0% to 100% by 10 points. When a vertical loading is 100% and a horizontal loading ration was varied, variation of vertical strain around circular hole of improved GFRP is 2.4 times more than general GFRP, and horizontal strain of general GFRP is 0 at 30 % stress ration, but one of improved GFRP is 0 at 40% stress ration. Vertical strain around circular hole of improved GFRP in equi-biaxial loading is non-linear against loading.

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This paper presents the mechanical property of Aluminum based composites containing of carbon fibers (CF), carbon nano-tubes and graphite. Recently there are many researches on the reinforcement using these fibers from the view point of saving energy and resource because of their remarkable strength and thermal performances; thermal conductivity, tensile strength, specific strength, and so on. Especially, aluminum based composites of carbon fibers are expected to be applied to heat exchangers and heat sink, for example. To reveal the strength properties of the composite materials, tensile tests are conducted. The results show that Graphite makes composite brittle, CF makes Young's modulus of composite a little bit higher if the volume fraction of CF is from 30 to 50 vol%.

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The non-direction ultrasonic sensor is developed for the purpose of the high-speed non-destructive test of a structure. First, the ultrasonic sensor using the electromagnetic Acoustic Transducer has been developed as a non-contact sensor. This paper has reported three transmitting and receiving system. Three of the transmitting and receiving system is incomplete. There is a need for further improvement.

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The residual thickness measurement of a pipe line has been requested for a long time. However, there has been no conventional measurement system nondestructively. We then tried to develop a measurement system to measure the residual thickness of a pipe using a guide wave that travels to a circumferential direction. In this report, the research priciple and preliminary experimental results are shown.

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Underground storage tanks have passed for many years after they were installed. Therefore, corrosion progresses occur on the wall of tanks and cause leak accidents. These tanks are generally monitored and checked by pressure tests or observation tests. However, it is difficult to detect the corrosion before tank leakage occurred at present. We employ the acoustic emission (AE) method to monitor the corrosion by detecting breakage and exfoliation of the rust. Immersion-type sensor for monitoring underground storage tank was developed using optical fiber sensor and rectangular sensor box. In this study, elastic wave propagated in underground storage tank composed of gas-liquid phase portion and outer wall was simulated by using the fmite-difference time-domain (FDTD) method. The sensor shape was determined by using the result of simulation. It was considered that optical fiber sensor should be mounted on the upper and lower parts of the sensor box to detect signals from side wall of the tank, and on the bottom parts of sensor box to detect signals below the sensor.

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