Aluminum foil cups are used as food trays and kitchen accessories with superior strength and high rigidity generated by wrinkles on the cup wall and flange parts. Deep aluminum foil cups are also demanded in food and other industries. In this study, it aims to enhance the formability of circular cup with acceptable wrinkles drawn by using local heating and cooling deep drawing technique, so-called warm deep drawing, which can prevent fracture at punch shoulder. Specific experimental equipment was utilized and the warm deep drawing experiments under constant blank holder force method and constant gap method are conducted. Compared to the deep drawing test results at room temperature, it is seen that limiting drawing ratio (LDR) decreases in the case of constant blank holder force method. However, LDR is improved in the case of constant gap method. Consequently, it is shown that the formability of aluminum foil cups with wrinkles could be improved by using warm deep drawing technique.

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The magnesium alloy used here attracts attention as one of the most light-weight metals in practical use. However, the magnesium alloy has strong anisotropy due to crystal structure itself and shows specialized mechanical properties because of the texture formed by plastic working processes such as rolling and extrusion. In this study, we investigated the plastic deformation of the fine grained AZ61 magnesium alloy which obtained by severe strain processing with rolling after multi-axial alternating forging. In particular, to evaluate plastic work formability of these materials, mechanical properties at high temperature under uni-axial tensile test and bi-axial deformation behaviors in the punch stretch test by the method of Nakajima were examined. It was possible to determine the temperature dependence of the forming limit diagram in a different stress state of AZ61 fine grained magnesium material. Comparing the results of the FEM formability analysis based on experimental stress-strain curves, Predicted numerical and experimental results of formability were in good agreement.

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Magnesium alloys can be used for reducing the weight of various structural products. They have attracted considerable attention as materials with a reduced environmental load, since they help to save both resources and energy. In order to use Mg alloys for manufacturing vehicles, it is important to investigate the tensile properties, thermal stability and formability. The tensile properties and formability of high strength of Mg alloy and 6N01 aluminum alloy was examined. High strength in A6N01 alloy rolled sheet decreases monotonically annealing temperature rise to the static recrystallization temperature, but in the flame retardant Mg alloy without significantly reduced for compounds to suppress the grain growth of Ma phase, flame retardant Mg alloy was maintained high strength between 200 and 400℃. In flame resistance Mg alloy, an examination of the drawability revealed that drawing of the alloy at 100℃ and room temperature was not possible, and the conical cup value (CCV) was higher than that of the AZ31 magnesium alloy. However, the drawability improved remarkably for tests at 150 to 250℃, with corresponding good CCVs.

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In this study, the tensile properties and crystal structure by the addition of Ca with subsequent cast of AZX311 magnesium alloy which subjected to a multi-axis forging (MAF) process and rolled process were investigated. The yield stress and ultimate tensile strength of the cast of AZX311 magnesium alloy were 65 MPa and 119 MPa respectively, and elongation was 5%. The result of observation of the crystal structure, the average grain size of 480 μm in the coarse grains, dendrite structure had spread to network shape. The forged of AZX311 magnesium alloy which has been subjected to forging into cast material, the yield stress and ultimate tensile strength were 214 MPa similar, and elongation was 2.6%. Cause of the decrease in ductility is due to the insufficient broken and dispersion of the intermetallic (Al_2Ca) compounds by the MAF. The rolled of AZX311 magnesium alloy which has been subjected to rolling into forged material, the yield stress and ultimate tensile strength were 340 MPa and 351 MPa respectively, and elongation was 6%. The result of observation of the crystal structure, Al_2Ca compound was fine-dispersed in a lamellae shape by plastic flow. Therefore, strength and ductility is improved. From these, the found that as a strengthening mechanism of AZX311 magnesium alloy, Al_2Ca compound is an important factor.

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Die-cast magnesium alloy (AZ91D) contains intermetallic compound of Mg_<17>Al_<12>, which may affect the macroscopic mechanical properties. Here, we investigated the mechanical properties of Mg_<17>Al_<12> phase by using micro indentation testing. In this method, uni-axial stress and strain curve can be derived based on reverse analysis. Micro indentation tests were carried out for both β-Mg_<17>Al_<12> phase and a-Mg matrix at room temperature. It is found that the yield stress and flow stress of Mg_<17>Al_<12> phase were much larger than Mg matrix. In particular, the yield stress achieves more than 300 MPa, which is twice larger than Mg matrix. Thus, the intermetallic compound of Mg_<17>Al_<12> may affect macroscopic properties of AZ91D alloy.

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Application of CFRP tubes for torque transmission shafts is expected to improve driving performance and natural frequency as well as fuel efficiency. CFRP tubes manufactured by modified simultaneous multi ply winding method have less voids and fiber waviness compared with conventional CFRP tubes manufactured by filament winding method, and the modified CFRP tubes showed 20% improvement of the static torsional strength. We investigated the fracture mechanisms of CFRP tubes by modified simultaneous multi ply winding method. As a result, a delamination from the prepreg end occurred at the innermost layer and it progressed through ±45° interlayer just before the failure of the specimen. In order to apply CFRP tubes to torque transmission shafts, it is expected to design the stacking sequence appropriately for preventing the delamination from the prepreg end in terms of long-time reliability. Thus in this study, we investigated an influence of the stacking sequence of CFRP tubes on their torsional strength. According to static torsional tests, it was revealed that the specimen with less lamination angle differences caused less delamination due to relaxation of interlaminar shear stress. Moreover, torsional strength was improved moderately mainly because the small lamination angle differences delayed the initiation of the delamination.

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Generally, Fiber Reinforced Plastics (FRP) have been regarded to have same mechanical properties if reinforcing fibers, reinforcement configurations, matrix resins, surface treatment and volume fraction of fibers are same regardless of molding method. However, it is considered that interface properties are changed by impregnating process among hand lay-up method and VaRTM method. In this study, effects of difference in molding method on mechanical properties and fatigue properties of FRP were investigated. As a result, static tensile properties, low-cycle fatigue properties and interlaminar fracture toughness were changed by molding process.

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Carbon nanotubes (CNTs) are highly expected as a reinforcement material for polymer composites because of their excellent mechanical properties. However, it is difficult to disperse CNTs in polymer matrix because CNTs tend to aggregate by Van der Waals force. In this study, CNT/epoxy composite was prepared using discharge dispersion method which is completely different from the conventional methods. Micro shock waves caused by discharge disperse CNTs, and furthermore, electrostatic repulsion decreases the reaggregation of CNTs. This discharge dispersion method is able to disperse CNTs in a short time and requires no special chemical agents. The dispersion state was observed using digital microscope and mechanical properties were studied by flexural tests. Although monodispersed CNTs were observed, CNT aggregates of ten-plus micro meter were also observed. The flexural modulus was increased by CNT dispersion. Compared to 0.00 wt %, flexural modulus was increased about 34 % when CNT content was 0.01 wt %.

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Carbon nanotubes (CNTs) grafted on the fiber surface improves fiber/matrix interfacial adhesion, and form the CNT-resin local composite around each fiber. This study reports the fabrication method of CNT-grafted unidirectional glass fiber reinforced plastics (GFRP) and their mechanical properties. In this study, CNTs were grafted on the T-glass fiber surface using thermal chemical vapor deposition (CVD) at 750℃. First, quality of grafted CNTs and the mechanical properties of T-glass fiber were evaluated. From the results of investigations and analyses, CNTs grafted onto the fiber surface had relatively-many defects, but were uniform and dense. Moreover, mechanical properties of CNT-grafted T-glass fiber decreased drastically compared with as-received fiber. This degradation was caused by the relaxation of thermal residual stress at fiber surface. Finally, static tensile test were performed to investigate the tensile properties of GFRP. According to static tensile test, it was revealed that fracture strain of CNT-grafted GFRP was decreased by 80% compared with as-received one, and it showed brittle fracture. This fracture was mainly due to the degradation of fiber strength and the improvement of fiber/matrix adhesion.

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The fracture toughness of the nano-silica particulate-reinforced epoxy composites with different crosslinking densities were investigated experimentally to consider the interaction effects between the nano-particles and the network structure in matrix resin. The composite materials were prepared by adding silica particles of 240 nm in diameter to the bisphenol A type epoxy resins with the particle volume fraction of 0.2. The neat epoxy resins and the matrix resin in the composite were cured non-stoichiometrically to change the crosslinking densities of the resins. Although the fracture toughness decreased monotonously from the one of the stoichiometrically cured resin as the crosslinking density decreased, the fracture toughness of the composite was largest at little lower crosslinking density than 2740 mol/m^3: the stoichiometric condition. The fracture toughness and the bending strength were improved for higher crosslinking density than 2000 mol/m^3 with by adding the particles. At lower crosslinking density, the particles worked against the mechanical properties as defects in the matrix resins.

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Ultra thin fiber reinforced plastic plates, with around l0μm thickness, were fabricated using the uni-directionally aligned carbon nanotube (CNT) sheet. The CNT sheets are drawn wound around the bobbin from the CNT array developed on the silica glass base plate. The CNT used in this study was multi-walled CNT with diameter of around 40 nm. The CNT/epoxy resin prepreg was created by heating the CNT sheet put on the epoxy resin sheet at the temperature of 100℃ for 3 minutes using a hotpress. The CNT/epoxy resin composite material is laminated on the symmetrical cross ply lamination ([90/0]s). To minimize the content of epoxy resin to have thinner thickness, the CNT sheet with out resin were used to 0° layers and the prepreg to 90° layers. The total thickness of the composite became around 40 μm with high volume fraction of &ap; 30 to 50 %. However, the modulus and strength of the composites in tensile test became low. The low modulus attributes from the ply thickness un-uniformity where 0° ply thickness became about 1.5 times larger than 90° ply. Because of this thickness un-uniformity, CNT volume fraction in 0° plies became small to make tensile modulus low To improve mechanical properties of thin CNT composite film, process optimization to have thinner and uniform ply thickness were required as a future work.

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Purpose of this study is to improve the inter-laminar fracture properties of the carbon fiber reinforced plastic laminates by addition of fine particle to brittle matrix resin. In this study, vinyl ester resin was used for the CFRP matrix and two types of particle, alumina and silicon rubber were used for the modifier. Tensile test and three point bending test was conducted to investigate the effect of mechanical properties of the particles on the mechanical properties of the laminates. The mechanism of the difference in fracture behavior for these particle modified laminates was discussed on the bases of in-situ observation during the test.

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This study focus on the effect of long-term exposure to high temperature atmosphere on physical properties of carbon fiber reinforced plastic (CFRP) laminates. The unidirectional laminate of carbon fiber/ polycyanate CFRP was employed on isothermal aging at 180℃ in air up to 4000 hours. The strength test was conducted and the effect of isothermal aging on mechanical properties was also investigated.

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The effects of direction dependent interfacial fracture toughness on the tensile strength of CFRP / thin titanium films hybrid laminates are evaluated by tensile and fracture toughness tests. In tesile tests, the fiber-metal laminates which have the 90° ply-titanium interface shows lower tensile strength compared to the CFRP laminates, because the 90° ply-titanium interfacial delamination occurs. It is interesting to note that the FML which has no 90° ply-titanium interface shows higher tensile strength as well as the CFRP laminates, this may be because there are no interfacial delamination. In three-point bending tests, two types of the interfacial fracture toughness which are 0° ply-titanium interface and 90° ply-titanium interface are evaluted. As a result, the 0° ply-titanium interface shows a higher interfacial fracture toughness than that of the 90° ply-titanium interface. Thus, it is possible to suppress delamination by inserting titanium films in adjacent with the 0° plies, results in improved tensile strength.

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Tensile tests are conducted on open-hole specimens of these laminates that consist of CFRP and thin titanium films. The effects of three different patterns with various stacking sequence on mechanical behavior are evaluated by tensile tests. The hybrid laminates in which inner 0° layers are sandwiched by the titanium films have the highest tensile strength. From observations of just before fracture, the initiation and growth of cracks are found to be suppressed in the hybrid laminates where inner 0° plies are sandwiched by the titanium films compared to the other two hybrid specimens that have different stacking sequence. It has been found that the titanium layers that are inserted inner side of the laminate receive the tensile load as bridging effect then results in the suppressed crack initiation.

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In the automotive industry, reducing vehicle body weight is one of the most effective ways to increase fuel economies. Fiber Reinforced Thermoplastics (FRTP) have several advantages over FRP or thermoplastics such as high specific strength and stiflBiess, high moldability. Fiber reinforced polyamide is one of FRTP and in engine parts (e.g. cylinder head covers, intake manifolds) . However, its applications for structural materials or energy absorption ones are limited due to the strict design standards. Therefore, it is necessary to evaluate impact properties of the material. The objective of this paper is to investigate strain rate effects on flexural properties of glass fiber reinforced polyamide. Reinforcement morphology of the materials were two types, twill weave (TWGF) and short fiber (SGF) . Drop weight impact test was used to determine impact flexural properties. The results showed that both TWGF and SGF had strain rate dependencies on flexural properties. SGF had higher strain rate dependency on flexural modulus owing to its higher viscoelastic property, while TWGF had higher one on flexural strength and specific absorbed strain energy owing to its superior tensile property. Furthermore, it was revealed that both TWGF and SGF had high impact absorption properties.

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Effect of calcium carbonate fine particle dispersion on the mechanical properties of polypropylene/montmorillonite(MMT) composites was investigated by tensile tests. The results showed that calcium carbonate fine particle dispersion improved the organized MMT dispersion, resulting the improvement of elongation at break by the reduction of local stress concentration during tensile loading.

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Recently, the application of composite materials such as carbon fiber reinforced plastic (CFRP) is widely adopted to aircraft structures. Because of lower electrical and thermal conductivity of CFRP compared to metal materials, CFRP structure can be severely damaged by lightning without any protection systems. In this study, understanding the principal lightning damage mechanisms of CFRP, artificial lightning test with coupon specimen was conducted and the damage process was visualized with high-speed camera observation. The obtained highspeed-imaging revealed that ply-lift of surface layer along fiber direction was occurred subsequent to gasification reaction of epoxy resin expanded towards orthogonal to the surface fiber direction. In order to simulate the damage behavior of CFRP laminate, coupled thermal-electrical analysis was conducted. In order to simulate the early phase gasification reaction of epoxy resin, the analysis model considering electrical property change due to insulation breakdown of CFRP is newly applied. The analysis result with newly proposed analysis model can predict the temperature rising orthogonal to the surface fiber direction; the area is well correlated with resin deterioration area observed in the experiments. It is confirmed that the major factor of early phase gasification reaction is electrical property change associated with insulation break down of CFRP in thickness direction.

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Reduction effect of thin foam films on impact forces was considered experimentally by using a fall ball testing. The specimens were acrylic foam films having thicknesses of 700 to 200 μm and density of 0.5 to 0.3 mg/mm3 on polyethylene terephthalate substrate with a thickness of 38 or 25 μm. The stainless steel sphere dropped onto the specimen on the flat end of a steel circular bar to generate the impact load. The impact loads were measured from the strain histories of the steel bar. The maximum impact force for the foam film of mere 200 μm thick was 60% smaller than the one for no foam film with increasing the duration of the impact load. Therefore, the acrylic foam films were found to have enough strength and noticeable effect on the reduction of the impact force.

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Bioactive Ti alloy for implant application has been developed by producing thin hydroxyl-apatite (HAp) film on its surface. The interfacial strength between the base metal and the HAp film has to be evaluated to ensure the reliability of the implant, but the method of evaluation is not yet established. In this paper, tensile load is applied to the HAp film on Ti-6Al-4V alloy substrate nominal to its thickness by using a specimen bonded with adhesives. We improve accuracy of this method by preventing adhesive overflow from bonded surface by applying surface active agent thus avoid coverage of the interface between Ti-6Al-4V substrate and HAp film. As a result, fracture occurs at interface between Ti alloy and HAp. It means this method is useful for evaluating interfacial strength between Ti alloy and HAp.

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The purpose of this research is to discuss the effect of Simulated body fluid immersion one the adhesive strength for hydroxyapatite (HAp) coating using the four-point bending test with a slit coated specimen. During testing, AE signals were recorded and delamination behavior from the edges of HAp coating was observed. In air condition specimens, stresses when AE signals were firstly detected were in a narrow range from 120 MPa to 130 MPa, which can demonstrate the effectiveness of AE signals in order to detect an initiation of delaminations of HAp coatings. However, after SBF immersion, a stress when AE detected shifted stronger region, which indicated AE characteristics during immersion would change, which requires the measurement of 4points-bending testing to tune the AE measurement conditions in order to successfully detect the initiations of HAp delaminations.

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Chromium is a relatively abundant metallic element in the Earth's crust and is a useful beta stabilizer for Ti. With this in mind, we developed a new Ti-13Cr-1Fe-3Al (mass%) alloy as a low-cost beta titanium alloy. Alloys of Ti and V, such as Ti-22V-4Al and Ti-6Al-4V, are the most common commercially produced Ti alloys. If Ti-Cr-V-Al alloys were developed, scrap Ti-13Cr-1Fe-3A and Ti-V system alloys in factories could be usefully recycled. Therefore, the influence of partial substitution of V with Cr on the phase constitution and heat treatment behavior of Ti-Cr-V-Al alloys was investigated by electrical resistivity and Vickers hardness measurements, X-ray diffraction and tensile tests. For all of the as-quenched specimens, only the beta phase was identified by XRD. In the as-quenched state, resistivities at both temperatures increased with Cr content except for the case of 3Cr alloy, although the Vickers hardness was constant at about 300 HV. Isothermal aging was found to produce only the alpha phase in the specimens, and no omega phase was present. TiCr2 precipitation was found in 7Cr and 11Cr alloys aged at 773K, and no that intermetallic compound was precipitated in 1Cr and 3Cr alloy on 773K aging up to 3000ks.

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A novel β-type titanium alloy (Ti-29Nb-l 3 Ta-4.6Zr, TNTZ) has been developed as a candidate for biomedical applications. In this study, the effect of high-pressure torsion (HPT) on the corrosion behaviors of TNTZ after cold rolling (CR) and aging treatment (AT) was investigated under in-vitro conditions by potentiodynamic polarization technique (PDS). It was found that After HPT processing, TNTZ having single β phase is more resistant to corrosion than the others in Ringer's solution. However the current density and the minimum current density are very high in aged TNTZ after HPT processing.

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