Recently, a term of "Security and Safety" has been widely used instead of a single term of "Safety" not only in mechanical fields but also in various fields in Japan. In this study, a fundamental concept of the paradigm shift from safety to security & saf

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Experimental technique using area detectors is very important for the stress measurements of welding parts and materials with large grains. In this presentation, the direct method, which is a new stress analysis using an area detector, is proposed. The di

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Saint-Venant's principle is generally interpreted as the rapid decay of end effects, but we know some systems where the local stress decays slowly. The whole stress field of an elastic body can be expressed as superposition of stress fields, which corresp

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Fatigue strength diagrams are characterized and formulated as a function of an equivalent cyclic stress ratio (symbolized as R_<EQ>), which was proposed as a parameter for the correspondence between cyclic stress conditions of notched and un-notched speci

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This paper presents residual strength property of ceramics after static loading. First, a residual strength prediction model was proposed on the basis of the slow crack growth (SCG) concept. Second, the residual strengths in soda glass and alumina ceramic

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We investigate the mechanical characteristics of S45C/Cu/Si_3N_4 structures subjected to thermal loadings. First, thermal loading tests are conducted under various heat conditions. Next, four-point bending tests are conducted to evaluate the stress-strain curves and residual strength. The results reveal that thermal loadings cause fatigue damage to the Cu interlayers and its amount increase with increases in the cycle number and temperature range of thermal loading. The increases in the cycle number and temperature range promote reductions of fracture ductility, Young's modulus and residual strength for S45C/Cu/Si_3N_4 structures. It is found that the reductions of the mechanical characteristics of the S45C/Cu/Si_3N_4 structures are affected by the fatigue damage of the Cu interlayers.

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Transition to the Yayoi period from the Jomon period means change to rice-farming culture from hunting and gathering culture. It has been supposed that transition of culture was resulted in change of the earthenware style to Yayoi pottery from Jomon pottery. The history of a rice-farming start is going back by archaeological discovery. The transition of culture and the change of an earthenware style are not being in agreement. The authors considered that the change of an earthenware style was aimed the strength and toughness increase of Jomon pottery material. Jomon people also added mica intentionally into the pottery material. Present study clarifies the effect of the addition of mica on strength and fracture toughness of the pottery material. For the purpose, we performed 4-point bending and fracture toughness tests on Jomon pottery material imitation.

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According to the recent remarkable development of bend-insensitive optical fibers, silica optical fibers are beginning to be used with small bending radii for many applications. However the radical decrease of the bending radius may cause delayed failure of the fibers when they are used in harsh environment, because the conventional theories to estimate the mechanical reliability of the bent portion are not applicable to such a case. Though one of the authors has driven an enhanced equation applicable to the fibers at high temperature and/or high humidity, calculations with the equation are not so easy because numerical integration must be done. We now propose another simpler equation that we have driven from commonly-used conventional equations. Calculations for specific conditions were carried out with the parameters extracted from an empirical formula in other paper. By comparing the calculation result with that of the former precise equation, the calculation error was found to be sufficiently small.

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Filler ropes of IWRC (Independent Wire Rope Core) are used as derricking and hoisting ropes in mobile cranes in order to prevent wire ropes from flattening. Although the load which affects a wire rope in mobile cranes is extremely changed, a loading history of the wire rope is not considered and the damage of a wire rope is evaluated by the number of breaking wire on the surface. In this study, S type bending fatigue tests under the different wire rope tensions were carried out in order to investigate the effect of wire rope tension on fatigue damage in IWRC wire ropes. Fatigue tests were finished when a visible breaking wire was observed and then the number of internal breaking wire was evaluated. The number of internal breaking wire varied in inversely proportion to wire rope tension, even though the fatigue lives of wire ropes decreased in proportion to rope tension.

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Corrosion test and pre-corrosion fatigue test of the friction stir welded 2024-T3 aluminum alloy and base material are conducted in order to evaluate the corrosion resistance and the effect of corrosion damage on the fatigue life. Corrosion test reveals that the apparent corrosion pits are observed around the weld edge and near center of the weld line of the FSW specimen. The fatigue test result indicates that the fatigue life of the FSW specimen is several times shorter than that of the base material. The fracture origin of the FSW specimen is several corrosion pits on the weld line in most cases. It is considered that the FSW joint is more sensitive to corrosion than the base material and then additional care might be necessary for usage.

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Titanium alloys are one of the main metallic materials for biomedical applications. It is important to clarify the crack growth mechanism under corrosion environment, such as bio-environment. Under corrosive condition, hydrogen embrittlement also may be caused due to hydrogen origination by anodic dissolvent reaction. Therefore, the mechanism of fracture under corrosive condition is complicate because anodic dissolvent and hydrogen embrittlement mechanism are competitively involved. However, the load frequency effect on the crack growth under the corrosive environment for a titanium alloy has not yet been clarified. In this study, the corrosion fatigue crack growth tests of Ti-6Al-4V alloy were conducted, and the load frequency effect on corrosion fatigue crack growth rate was investigated.

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Low cycle fatigue tests were conducted at high temperature. The tests included those cases with and without a strain hold process. The test results were evaluated based on the inelastic behavior around the center hole of the specimens, where the most serious inelastic strain occurred, obtained by the finite element analysis that took into account the inelastic anisotropy of material properties. The number of crack initiation cycles of the tests without a strain hold process and with a compressive hold process correlated with the maximum tensile stress around the hole, while that of all the tests correlated with the frequency-modified strain energy.

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Effects of redox cycling on the mechanical properties of the Ni-YSZ cermets were investigated by using an in-situ small punch (SP) testing method as a function of porosity, and influence of the redox cycling on the volume expansion of Ni-YSZ cermets was examined by using a thermo-mechanical analysis (TMA) as a function of porosity and Ni/YSZ volume ratio. Experimental results obtained from the in-situ SP tests demonstrated that ductile-like fracture took place under the reducing environment at 800℃. It was shown that mechanical degradation due to redox cycling was mitigated for the Ni-YSZ cermets with higher porosities greater than 30 vol. %. Higher porosities and lower Ni content were useful to maintain the dimensional stability of the Ni-YSZ cermets. Based on the experimental results, a quantitative correlation was proposed which predict the volume expansion from porosity volume and Ni content.

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Rolled metallic materials have anisotropy of mechanical properties due to the shape of the crystal grain. We have carried out experimental studies focusing on the fracture strength anisotropy of rolled metallic materials. This paper reported anisotropy of fracture toughness of two kinds of rolled steels (SM490A and SS400). SM490A steel shows a property of ductile fracture in the fracture toughness test. On the other hand, SS400 shows a property of brittle fracture. Six kinds of different compact tension specimens of the crack plane orientation were made by these materials. The fracture toughness tests were carried out by these specimens and the fracture toughness values were evaluated. As a result SM490A showed anisotropy clearly. In addition, the fracture surface was different in each direction. The direction relations of rolled plane and crack plane influenced a fracture toughness value. SS400 showed anisotropy, but the tendency was different from that of SM490A. The anisotropy of this material cannot be explained by the relation of two planes.

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The purpose of this study is to investigate the tensile properties of super rapid tempering steel treated by high frequency induction heating method. In order to discuss the effect of tempering time on tensile properties, two types of specimens in which tempering time was different were prepared. Super rapid tempering specimen (IHT steel) was tempered for 0.35 sec by induction heating, and conventional tempering specimen (FT steel) was tempered for 3.6 Ksec by furnace tempering. While both of specimens were quenched by induction heating .These specimens were evaluated at room temperature. As a result, the both steel had almost same tensile strength. However the true stress of fracture of IHT steel was higher than that of FT steel. This result was explained by the reduction of area of IHT steel was higher than that of FT steel. The toughness of both specimens was also evaluated by the measuring area of nominal stress-nominal strain diagram. The toughness of IHT steel was 30% higher than that of FT steel. SEM observation suggested that the cementite particle of IHT steel was smaller and more finely dispersed compared to FT steel.

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The effect of hydrogen on the tensile properties of SUS316 stainless steel are investigated. 0, 5 and 10% pre-strained specimens are exposed to hydrogen atmosphere of 100MPa in pressure at 393K for 400h. It is observed that the tensile strength does not vary but the reduction of area reduces by performing hydrogen exposure. Cup-and-cone fracture occurs in the unexposed specimens. Fracture surface of hydrogen exposed specimens is quasi-cleavage fracture surface in the region from the specimen surface to 200μm. In the inside of the quasi-cleavage fracture area, the fracture surface is covered by dimples. Slip bands are seen in the side surface of unexposed specimens, and many cracks of 300-500μm in length are found in the side surface of hydrogen exposed specimens.

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Wood is made from the early part which is soft and the late part which is hard. It is important to measure mechanical properties of the each part, in order to use woods. Therefore in this paper, we investigate an indentation method to measure the Young's modulus of the early part and the late part of the flat grain face of wood material. It is difficult to confirm measured material constant of wood, since the values of those properties are unknown. Thus, we investigate layered specimen of the rubber and the acrylic resin as a wood specimen model. By comparing relationship between load and displacement from experiment and FEM simulation, it is confirmed to give the Young' modulus of the early part and the late part of wood. By an indentation for the wood specimen, the possibility to measure Young's modulus of early and late part is confirmed.

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The elastic velocities of nano-polycrystalline diamond were measured by an ultrasound pulse method and resonance method in high pressure and high temperature. Both sound velocities for longitudinal and transverse waves of samples can be obtained from sound signals waves both with QE mode 100 MHz fundamental frequency and with S mode 50 MHz frequency LiNbO_3 transducers. Elastic constants of bulk modulus, rigidity, Young's modulus, Poisson's number and elastic constants of C_<11>,C_<12> are derived from these velocities data. Elastic constants of sphere-nano polycrystalline diamond were measured by resonance method in helium gas. Velocities of sphere samples of nano-polycrystalline diamond were compered with cylindrical nano-polycrystalline diamond and sintered diamond samples.

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In this study the temperature change of piano wires according to the load stress was measured using infrared stress measurement method. Piano wires used six sizes (0.1mm, 0.2mm, 0.4mm, 0.8mm, 1.0mm and 1.5mm). I used a fatigue testing machine for the three experiments. First of all, conduct an experiment to break the piano wires, and prepares stress-strain diagram for next experiments. Next experiment measured when the change in temperature of strain control was multiplied by the square wave. At this time, change in temperature was measured using infrared thermography. The change in temperature for all piano wire was proportional to the load stress. Therefore the effect of thermo elasticity consists. The third experiment was to measure the response of the change in temperature. As a result of the thin piano wires returned immediately for the change in temperature, but thick piano wires were hard to return to the original temperature after that.

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A strain rate effect on load-displacement relation by instrumented a sharp indentation was investigated for pure Aluminum which has high strain rate dependence of strength. When micro-indentation tests were carried out by using a sharp indenter (Berkovich type) at a loading rate of 07-70mN/s the indentation load rose with the loading rate. Finite Element Method was used for the indentation analysis in comparison with experiment. The load increase behavior could be simulated by dynamic FEM with the Cowper-Simonds constitutive equation which includes the strain rate dependence of strength. The FE simulation showed the strain rate under the indenter reaches dynamic range and it caused the load increase. The strain rate under the indenter depends on not only the loading rate but also the indenter angle. If the relationship between the load increase and the indentation test condition is constructed, the strain rate dependence of strength may be evaluated by indentation test.

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Both in laboratories and in the field, explosives are usually utilized as energy sources in order to produce impact-induced fracture of solids. However, it is not simple to detonate explosives in urban areas. In this study, instead of explosives, Q-switched Nd:YAG laser pulses are used as energy sources to perform laboratory fracture experiments: Laser pulses can be more safely and digitally handled. Crack extension patterns in acrylic sheets produced by laser pulses are compared with those generated by detonating explosives. Like in detonation-produced fractures, not only the "crush zone" in the vicinity of the energy source but also the radial cracks can be recognized in laser-induced fracture patterns, but the cracks develop rather quasi-statically upon irradiation of laser pulses.

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In this paper, distributions of tensile and compressive strength of PBO fibers were investigated in tensile test and compression test. Two types of PBO fibers were used in the experiment. One is conventional type of fiber. Another is high modulus type of fiber, and its crystal orientation is higher than conventional type of the fiber. Weibull analysis was performed to compare distribution of tensile strength and compressive strength. It was found that tensile strength and compressive strength of each type PBO fibers were well fitted the Weibull distribution function with 2 parameters regardless of degree of crystallization. Then, in tensile strength, shape parameter of HM type PBO fiber was lower than that of AS type PBO fiber. Also, in compressive strength, shape parameter of HM type PBO fiber was a little higher than that of AS type PBO fiber.

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Adhesive joint is increasingly used for products, because it is possible to apply the joint to various materials and to joint of different materials. Because of plastic adhesives, it is predicted that the significant decrease of strength of the adhesive joint happens depending on the environmental conditions such as high-temperature or high-humidity conditions. Therefore, it is needed to evaluate strength deterioration appropriately on each environmental condition. In this study, the strength deterioration tests of silicon glue on high-humidity conditions are conducted for the purpose of predicting strength deterioration caused by humidity. As the result, it is predicted that it takes about 50000 hours for the strength of the silicon glue to become 0.9 times as much as initial strength on 50℃ and 100% RH condition.

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Recently,acrylic resin plate is expected to be used as a replacement for glass windows of automobile and so on. In such a use, a small particle collides repeatedly to the plate. However, impact fatigue strength of acrylic resin plate isn't evaluating yet. In this paper, evaluation method of impact fatigue strength of acrylic resin plate was suggested. The resin plate thickness of 2mm, 3mm and 5mm were used in this study. Rectangular specimens were made from the resin plate. Test equipment is based on the principle of free fall. A weight repeatedly collides to the specimen that is supporting simply both ends. A kinematic energy of the weight and the collision number of until the fracture of specimen were recorded. The relations of both resembled the S-N curve of the fatigue test. For the evaluation of the impact fatigue strength of acrylic resin plate, the kinematic energy of the collision weight is effective.

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The failure behavior of poly(methyl metahcrylate)(PMMA) was investigated under pure shear state of stress both in ethanol and in air environments at room temperature. The craze (crack) formation was identified under pure shear not only in ethanol but also in air. The critical crazing (cracking) stress in ethanol was greatly less than that in air.

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In this paper, the influence of spot welding location on fatigue strength of two spot welded joints under tensile shear was investigated. The nominal structural stresses σ_<ns> which is a fatigue life evaluation parameter of spot welded structure were calculated and the fatigue test of two spot welded specimen were conducted. The main results were as follows. The nominal structural stress of parallel two spot welded joints is smaller than one of joints with two spot welds arranged in series. The information obtained was verified by the experimental results of fatigue test. The rate of fatigue life was calculated using the nominal structural stress showed a better trend compared with fatigue test result. Fatigue life of series two spot welded joints is not greatly affected by variation of spot welding location. However, fatigue life of parallel two spot welded joints received up to 35% at the maximum the effect of variation of spot welding location.

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We proposed a method for analyzing the sensitivity of the nugget diameter to the nominal structural stress, and conducted a fatigue test to verify the results of the sensitivity analysis. The proposed method was confirmed to provide a good solution. The nugget diameter sensitivity S_d differs according to the general load components. The nugget diameter sensitivity S_<Nde> to fatigue life showed a good correlation with the estimated value of the standard deviation of the logarithm of the fatigue life, and it was demonstrated that the fluctuations in fatigue life resulting from variations of the nugget diameter can be assessed using S_<Nde>.

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Welding is widely used in construction of structures. Residual stress is generated near the bead because of locally given heat. Tensile residual stress degrades fatigue strength. The authors have proposed a new methods for reduction of residual stress. In this method, vibration is applied during welding. For mold and die, welding is used for repair. Thick plates are used as specimens. It is found that tensile residual stresses are reduced when specimens are welded applying ultrasonic vibrations during welding. In this paper, simulation of welding by heating is examined. Specimens are heated by high frequency heating machine.and ultrasonic vibration is applied during heating. Residual stresses induced by heating are similar to those by welding. Tensile residual stresses are reduced when ultrasonic vibration is applied during heating.

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In this paper, the residual stress distributions of Electron Beam Welding (EBW) for the mock-up of the core barrel in the pressurized water reactor are described. The mock-up was fabricated from type 304 stainless steel and has a thickness of 51 mm. Strain gauge method was applied to the measurement. The finite element analysis was also applied in order to validate the effectiveness of residual stress analysis for EBW. In the result, the residual stress distribution obtained by finite element analysis was in good agreement with measurement data. In this way, the effectiveness of finite element analysis for EBW is validated.

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In this study, we present anneal effect of internal strain in steel material with laser welding by using synchrotron radiation white X-rays in SPring-8. Internal strain distributions were measured by the strain scanning method based on X-ray diffraction technique. A strong compressive strain appeared in the region of affected laser welding directly in welding material before annealing, and a weak compressive strain remained in the same region after annealing. We think that this cause is remained plastic strain generated by slip.

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Small crack growth behavior at edge of partial electrode in poled lead zirconate titanate was investigated under cyclic electric loading. The crack grew along the electrode boundary immediately after the loading. However, the propagation rate decreased suddenly and the crack arrested. The length of the non-propagating crack was affected by amplitude and bias levels of the electric loading. In the case of high-amplitude loading or negative biased loading, the crack propagating rate varied considerably because of domain switching. The testing environments also affect the crack propagating behavior. The higher temperature increased propagating rates. Finite element analysis of a three-dimensional permeable crack showed that the mode III stress intensity factor range is independent of crack length, but it decreases as a result of the frictional force of a positive electric field.

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The effect of the shot-peening on rolling contact fatigue of Si_3N_4 was investigated. Additionally we tried to clarify damage mechanism of rolling contact fatigue. By shot-peening, high compressive residual stress -8500MPa can be introduced near the surface. The residual stress can improve apparent fracture toughness K_<IC> and Vickers hardness HV of Si_3N_4 by approximately 73% and 8%, respectively. As a result, bending strength of pre-cracked specimen was improved 27〜46% by shot-peening. The delamination damage was inhibited by shot-peening, and as a result rolling contact fatigue of the Si_3N_4 was improved. These results are achieved by the compressive residual stress which is introduced by shot-peening. These results indicate that shot-peening is effective method to make use of ceramics as a rolling contact member.

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Effect of shot peening on the critical stress for crack-healing of Si_3N_4/SiC composite ceramics was investigated. Shot peening was carried out on the Si_3N_4/SiC composite with a surface crack by Yittorium stabilized Zirconia beads. Peend specimens were healed at 1100 ℃ for 5 hours under tensile stress σ_<app>&le; ranging from 0 to 500 MPa. The result clearly showed that peend specimens could heal the surface crack completely under the σ_<app>&le;450 MPa. Thus, critical stress of the specimens was determined to be σ^C_<app>=450 MPa. This σ^C_<app> was 2.3 times higher than that of un-peened specimen. Furthermore, the σ^C_<app> of both specimens showed the proportional relationship to bending strength of cracked specimen σ_c(σ^C_<app> &ap; 0.64σ_c). Therefore, it can be concluded that the improved σ^C_<app> of the peened specimen is due to the compressive residual stress and, consequently, increment of σ_c.

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In this study, we proposed the creation of surface modification layer by ultra-fine particle peening process in order to achieve the development of high strength aluminum alloy. Therefore, we aim to clarify the effect of impact energy and surface modification by ultra-fine particle peening process. The analysis of collision energy was used for finite element analysis software LS-DYNA. Analysis conditions were set was particle of high speed steel and work of aluminum alloy. Results of the analysis, in the case with a constant amount of projection, the impact energy increases as the material is a small projection of the particle size was revealed

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Fiber-Metal laminates that consist of carbon fiber composites and thin titanium films are applied to bolted joint to improve damage behavior of composite laminates. Tensile tests for bolted joints in the CFRP laminates and the hybrid laminates with five thin titanium films inserted to the CFRP plates are conducted. It is shown that load drop point in load-displacement curves represents damage onset in the laminates. In the CFRP laminate the micro-buckling of the carbon fiber in 0 degree direction layer (fiber kinking) occurs first and then matrix shear cracks in adjacent layers are induced by fiber kinking. On the other hand, matrix shear cracks that follow after the fiber kinking are found to be suppressed by the thin titanium films in the hybrid laminates. In particular, the laminate with the titanium films inserted to form sandwich with inner 0 degree direction layer showed low damage level compared to other hybrid specimen.

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In the present study, we propose a system for monitoring cure process of FRP prepregs during hot-press molding using dual light sources, FBG sensors and refractive-index measurement. The optical system is composed of a 1310 nm narrow-band FP-LD light, a 1510nm broad-band SLD light, 1300/1500 WDM couplers, a spectrum recorder and an optical power meter. The FBG sensors have a distal end at which Fresnel's reflection between glass and resin occurs. The reflected 1310nm light form the distal end and the FBG reflection (about 1550nm) were divided into two individual paths by a WDM coupler. The power of 1310nm light was measured by an optical power meter and used for calculating refractive index of matrix resin. Spectra of the FBG light were recorded by a spectrum analyzer. In this study, GFRP prepregs were used for the experiments. From the results in the present paper, it was found that the monitoring system monitor both cure index and strain during molding quantitatively. In addition, it appeared that the system can be used for monitoring existence of air voids.

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In this research, effects of the multi-walled carbon nanotubes (MWCNTs) addition on mechanical properties and microstructures of spark plasma-sintered MWCNT/alumina composites were investigated by using four types of MWCNTs that were annealed at different temperatures. The annealing temperatures were 1200, 1800, 2200 and 2600℃. Experimental results showed that bending strength of the composites was increased up to 1800℃, and they were decreased gradually with increasing annealing temperature of MWCNTs. According to the fracture surface observation, dispersibility of the MWCNTs tended to decrease with increasing the annealing temperature of the MWCNTs, and fracture toughness of the composites corresponded to the dispersibility of the MWCNTs. The present study implies that the effectiveness of the use of MWCNTs having a higher load carrying capacity and dispersibility for preparation of stronger and tougher ceramic composites.

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Carbon nanotubes (CNTs) offer a new class of material as reinforcements for the development of ceramic composites, due to their intrinsic mechanical and other functional properties. In previous studies, pressure-assisted sintering methods such as spark plasma sintering (SPS) and hot pressing (HP) are the two techniques that have been commonly employed to prepare CNT/ceramic composites. In this research, in order to evaluate the effects of the sintering method on the mechanical properties and microstructures of the composites, alumina ceramics reinforced with multi-walled CNTs (MWCNTs) were prepared by pressureless sintering and SPS. Resultant composites containing 1.9 vol.% MWCNTs prepared by the pressureless sintering and SPS had relative density as high as 97% and 99%, respectively. Fracture toughness of the composites prepared by the pressureless sintering was almost the same as that obtained for the composites prepared by SPS. Scanning electron microscope observations indicated that the MWCNTs, rather than pulling out from the alumina matrix, failed by clean break. For the design of tougher ceramics with MWCNTs, appropriate modification of fiber/matrix interface will be one of important factors.

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To clarify the generating mechanism of the wrinkles on the surface of the test piece in a rotary draw bending forming, the processing experiment and the simulation analysis using finite element method (FEM) were done. The result of obtaining is as follows: the wrinkle is generated by not only curved part but also the straight run of the original pipe as the processing progresses; the frictional force between the pipe and bending die generates the wrinkle, and promotes the wrinkle generated in addition; the occurrence condition of the wrinkle depends on parameters other than frictional properties, because the wrinkle is generated even when the frictional force between the pipe and the die is disregarded.

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Recently, electric is used by many tools and toys as a driving source. On the other hand, tools and toys are usually applied with an external force when we are using these equipments. If we can use these force to generate a power, we can use these tools without battery. Therefore, we invent a power generation equipment with the small size by using these force. We use piezoelectric element which can generated voltage by the applied force. We invent the cantilever with a hinge to efficiently convey the applied force. The output voltage is measured when the uniform stress fluctuation is applied to this cantilever. We invent the cantilever with a hinge to efficiently convey the applied force. The relationship between the structure of the cantilever and the voltage is investigated. Higher output voltage is observed for the cantilever with hinge comparing to the cantilever without hinge. The output voltage is increasing with decreasing the height of the hinge. Moreover, the experimental value and the theoretical value are in qualitatively agreement.

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Capsule-Chuck is a support part used in order to grip the core of a continuation medium. In order to satisfy the needs to diversify, new product are expected. However, the deformation properties of Capsule-Chuck is not yet clarified. To solve this problem, analyzing by a simulation is useful. In this research, Capsule-Chuck was modeled using finite element analysis. Simulation was performed for contact of a capsule and a core. It compared with the experimental result about surface contact stress and contact length to verify about the validity of the models. The contact pressure result of simulation was different from experimental result in the area of edge. It is required to improvement the model in the area of edge.

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Recently, the mechanical joint of the steel pipe pile for foundation construction has studied to decrease work time and keep reliability. In this study, the mechanical joint changed the lap length and the mechanical joint without pins were analyzed by a finite element method. These simulations were performed under the bending load. From the simulations, it is confirmed that the change of lapping part's length do not have the effect on its bending characteristics in the case that the joint has pins.

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The effect of notch geometries on the tensile strength of notched FRP plates was investigated. The material was a short-jute-fiber-reinforced polypropylene (JF/PP). The JF/PP plate was made by injection molding. The plate contains 30 % jute fiber by weight. The notch-root radius was 0.5, 1 and 2 mm. In addition, notch depth ranged from 2 to 4 mm. Tension test was performed by an Instron-type testing machine at a constant cross-head speed of 0.5 mm/min in a temperature controlled room at 22 ℃. The experiment shows that the maximum elastic stress at fracture for notched JF/PP plate is governed by the notch-root radius, and it is independent of notch depth. The experimental results can be clearly explained on the basis of the concept of severity near the notch root. It was shown that a fracture criterion based on the severity near the notch root is effective in the JF/PP plate.

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The effect of CFRP chip content on the tensile strength and fracture toughness of polypropylene composites with CFRP chips has been investigated. Polypropylene composite with CFRP chip content from 0% to 20% were prepared using twin-screw extruders and small injection molding machine. Tensile strength of polypropylene composites with CFRP chip content of 5% was higher than that of 0%. However, tensile strength of polypropylene composites with CFRP chip decreased with increasing CFRP chip content. Fracture toughness of polypropylene composites did not change with CFRP chip content up to 15%. However, Fracture toughness of polypropylene composites with CFRP chip content of 20% decreased to 30% of that of not reinforced polypropylene.

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This study focused on the effect of patch bonding on mechanical property of damaged Carbon Fiber Reinforced Thermo Plastics (CFRTP). In this study, CFRTP in which matrix was made of PA6 was fabricated to investigate the bending properties. The 0.1mm thick of PA6 sheet and plain woven CF was stacked and pressed under 240℃, 2.5 MPa for 3 min to fabricate the prepreg. The prepreg was stacked with quasi-isotropic laminate configuration of [0-90/-±45]_<5s>. The fabricated CFRTP was cut into 70×10×2.5 mm of strip specimen. The damage morphology of CFRTP was studied under four-point bending load. The observation of side view of specimen during bending test suggested that the local delamination was appeared when the 2.0% of bending strain was applied. According to the increment of bending strain, the damage was initiated from compression side to the tension side. The effect of patch bonding on bending strength and modulus was evaluated. Test result showed that the damaged specimen would be repaired when appropriate layer of patch was bonded. The bending modulus of repaired specimen was predicted by calculated model. Calculated result suggested that the effect of patch bonding on bonding modulus was simply estimated by laminated beam theory.

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In this study, effects of water absorption and freezing on mode I interlaminar fracture toughness of CFRP were investigated. Water absorption test was conducted at 90℃ for 24, 100, 250 and 500 hours. After water absorption, the specimens were kept in the -15℃ environment for 24 hours. Static three-point bending and double cantilever beam (DCB) tests were conducted after water absorption and freezing. As a result, the water absorption rate at 500 hour was 1.5%. Bending strength and mode I interlaminar fracture toughness G_<IC> were decreased with increasing water absorption time. Bending modulus of CFRP did not change after water absorption and freezing. And bending strength and mode I interlaminar fracture toughness G_<IC> in frozen CFRP were lower than that of water absorbed CFRP. These result implied that interfacial adhesion of CFRP was decreased by water absorption.

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In this paper, we derive a general solution for an isotropic elastic medium (matrix) with nonconcentric multilayered circular inclusions. Inner inclusions are perfectly bonded to the outer inclusions and matrix that is infinite extent under anti-plane deformation. The inclusions have different elasticity, radii and central points. The matrix is subjected to arbitrary loading, for examples, by uniform anti-plane shear stresses at infinity, as well as a concentrated force or screw dislocation at an arbitrary point. The solution is obtained through iterations of the Mebius transformation as a series with an explicit general term involving the complex potential of the corresponding homogeneous problems. The procedure is referred to as heterogenization. Using there solutions, several numerical examples are presented graphically.

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The fracture of ductile metallic material is caused by the voids in the material which grow and unite with each other when stress is applied to the material. The linking and cracking processes of neighboring voids in a thin sheet metal are investigated in detail to get quantitative information about the deformation behavior of voids in a ductile deformation. And the damage tensor show the damage of the material which includes voids. In this study , The deformation behavior of voids and the change of damage tensor in two dimensional model with five voids under the uniaxial tensile load were investigated by experiment. As results of this study, it is shown that the array of holes have an influence on the interference between holes.

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The buckling stress relational formula under the combined stress of compression and shear is derived concerning a rectangle thin shell which constitutes the frame structure of a car body. The approximate buckling stress relational formula is shown by deriving the exact formula of the combined buckling stress based on the energy method, and by simplifying that formula. The accuracy of this approximate formula is confirmed as compared with the conventional relational formula. As the result, it is found that the exact solution can be expressed accurately by the derived formula here than the conventional formula.

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Constitutive modeling is studied for the homogenized elastic-viscoplastic behavior of pore-pressurized anisotropic open-porous bodies made of metallic solids. For this, by describing micro-macro relations relevant to periodic unit cells of anisotropic open-porous bodies subjected to pore pressure, constitutive features are discussed for the viscoplastic macro-strain rate in steady states. On the basis of the constitutive features found, the viscoplastic macro-strain rate is represented as an anisotropic function of Terzaghi's effective stress, which is shown using Hill's macro-homogeneity condition. The resulting homogenized equation is used to simulate the homogenized elastic-visco plastic behavior of an ultrafine plate-fin structure under uniaxial and biaxial loading conditions combined with pore pressure. The corresponding finite element homogenization analysis is also performed for comparison. It is demonstrated that the developed homogenized constitutive equation simulates well the anisotropic effect of pore pressure.

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