Lightbulbs for automobiles breaks after shipment from a factory at a certain probability. The breaking of the lightbulbs is thought to be caused by residual stress in the lightbulbs. The residual stress of lightbulbs has, however, not been measured because of the difficulty to measure residual stress in glass. The present study measures the residual stress of lightbulbs for automobiles by phase-shifting photoelasticity.

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Solid-oxide fuel cells(SOFC) are expected to be one of the most effective and clean energy sources because of their highest efficiency and simple system, SOFC is consisted of three layered structures: anode, electrolyte and cathode. In order to guarantee their long-term durability, it is important to comprehend stress state in the cell. In this study, the residual stress is evaluated by using X-ray diffraction and also a method of resonant ultrasound spectroscopy (RUS). The residual stress in the electrolyte of the anode-supported cell measured by X-ray diffraction was a compressive stress of about 675MPa. Based on the results, the residual stress distribution in the cell was simulated using the finite element method, followed by the modal analysis. The natural frequency of the cell decreased by 0.84 % when the simulated compressive stress in the electrolyte increased to about 526 MPa, which could suggest a validity of the RUS for evaluating the residual stress in the cell.

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We have developed the Mach-Zehnder interferometer type optical fiber AE sensor that has portability by adhering the optical fiber to a polycarbonate block. The aim of this research is to improve the sensitivity and the directivity of the sensor. It is demonstrated that by increasing the number of sensing regions, the difference of the sensitivity against the directions tends to disappear. It is also found that the absolute sensitivity of the sensor is described by the sinusoidal function.

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The composite hardness, the hardness obtained from indentation tests on film/substrate system, is evaluated from elastic-plastic analysis with a FEM program, on the combinations of the film and substrate materials that show relatively closer hardness values. From the computational results, we can conclude that the composite hardness in the film/substrate indentation cannot always be expressed by a monotonic function that changes from the film hardness to the substrate hardness. If we choose two materials with similar hardness but different plastic properties, we can expect a strange behavior, either an overshoot or undershoot of the composite hardness.

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The influences of hydrogen on nano-indentation of STPG370 steel were investigated. The results obtained are as follows. (1) The "pop-in" was observed in the hydrogen uncharged specimen. (2) The "pop-in" was observed in the specimen which charged with hydrogen after heat treated at 200℃/1h. (3)The "pop-in" was not observed in the specimen whitch charged with hydrogen after mechanical and electrolytically pollished. (4) The "pop-in" was observed in the specimen which charged with hydrogen after the heat treatment at 200℃/1h.

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The objectives of this paper are to obtain the axial compressive strength of PBO fiber. Direct compressive tests were performed to investigate the compressive strength of the fiber. The compressive test pieces were manufactured by using photolithography technology. Finite element analysis was performed to describe internal stress distribution. It was found that the compressive strength of PBO fiber was well represented by normal distribution. However, the scatter of compressive strength was large. This is attributed to compressive failure occurred in nonuniformly-distributed stress region.

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Recently, the eutectic solder alloys have been replaced by the lead-free solder alloys because of the environmental pollution problems. In this study, temperature dependency and strain rate dependency on plastic behavior of Sn-37Pb and Sn-3.5Ag-0.75Cu solder alloys under biaxial loading with sudden change in strain rate and in stress relaxation at several temperature are investigated experimentally and theoretically based on the overstress theory. The overstress constitutive model is found predict the inelastic deformation behaviors of eutectic and lead-free solder alloys precisely, including relaxation behavior.

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A two-surface cyclic plasticity model which enables precise prediction of inelastic behaviors of cyclically loaded metallic materials under non-isothermal conditions is presented. A concept of generic stress-strain relation, which is generated from monotonic and cyclic stable stress-strain curves, is introduced in the model to represent cyclic hardening. Temperature dependent material properties are taken into account in the rate form constitutive equation. The functional capability of the model is verified through its application to basic uniaxial material tests with/without varying temperature.

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Polymeric material is essential in daily life. Especially Polypropylene has superior character in many filed. In this study, characterizing Polypropylene's material behavior consider to inverse analysis on load-depth curve measured by microindentation tests. First define polypropylene's constitutive equations, and consider strain rate dependence is represented by yield stress, and calculate strain rate 10^<-5>〜10 from extrapolation method. Using defined constitutive equations considered strain rate dependence, as a result inverse analysis is useful to characterize elastic-visco-plastic properties of Polypropylene.

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Indentation technique was applied to evaluate the viscoelastic characteristic of a polymeric material. In the present study, load controlled indentation test with a Berkovich indenter was performed on Polypropylene (PP). The results showed that the measured penetration depth exhibits typical creep behavior of viscoelastic materials. The viscoelastic and plastic deformation can be separated from the measured penetration depth through the shape measurement of impression by using AFM. Creep compliances estimated by the viscoelastic deformation are in good agreement with that obtained by tensile creep test. Moreover, the master curves evaluated by indentation and tensile creep test were corresponding over a wide range of the reduced time. These facts mean that indentation is an useful technique for the measurement of viscoelastic characteristics of polymeric materials.

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In this study, a numerical method of the identification of mechanical parameters of thin films such as Young's modulus is developed. The identification is based on the minimization of a cost functional using a gradient descent algorithm. The main result is the computation of the gradient of the contact problem using a direct differentiation technique. The efficiency of the method is illustrated in the identification of the Young's moduli of thin films.

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In this study, a new and convenient mechanical testing method is provided for measuring the Young's modulus in a flexible material. The method is based on a nonlinear deformation theory that takes into account large deformation behaviors of the flexible material. By means of measuring the horizontal displacement or the vertical displacement, the Young's modulus can be easily obtained for various thin and long flexible materials. Measurements were carried out on a Piano wire (SWPA). The results confirm that the new method is suitable for flexible materials.

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It is well known that the crack propagation in a structure is a serious problem from the structural integrity point of view. In order to prevent serious crack propagation, a circular hole is using as a crack arrester. This paper describes the application of a hierarchical neural network to the estimation of a crack arrester position in a solid with the FEM. We solve the 2D crack propagation problem in three point bending model. NN is used as a method of asking for a crack arrester position. It was shown that NN is very effective in prediction of crack arrester position.

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This paper was reported deformation of press forming die and mould with rib attachment. At producing the body panels of an automobile, stamping die press process is mainly used. When the press machine produces its, the hitting of upper and lower die is caused by deformation of the press machine and the dies. Dies are processing by the skillful workers, because these errors differ for each press machine. In order to reduce this working, in this study, we made the small press model, and examined the effect of rib attachments in Dies, the effect of the die and mold that processed the bottoming. As a result, the displacement of die and press machine decreases by rib attachments. The displacement can be adjusted by adjusting the position and amount of them.

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In this paper, experimental results for anisotropy of the fracture toughness for the rolled steel are discussed. A rolled steel (SM490A) with thiclmess of 70mm was used in this experiment. Six kind of compact tension specimens were processed from this material for fracture toughness test. Each specimen has different crack plane orientations. The fracture toughness tests were carried out by these specimens. From these tests, anisotropy of the fracture toughness was confirmed. The fracture toughness values depended on the crack plane orientations of the specimens. When the crack plane was parallel to the rolled surface, the specimen showed the minimum fracture toughness value. On the other hand, the specimen of which crack plane was normal to the rolled surface showed high fracture toughness value. The anisotropy of fracture toughness can be explained by distribution of inclusions contained in the rolled steel.

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[in Japanese]

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Cracking and delamination of brittle coating under equi-biaxial tension are investigated using the ring-on-ring test apparatus. As the specimen, brittle paint (stress-analysis paint) was coated on the surface of the substrate of PMMA (polymethyl methacrylate). The in-plane and the interface strengths of the brittle coating were changed by drying temperature of the paint. After the ring-on-ring test, the total length of the cracking and the delamination area were measured. In the coating dried at 30℃, both delamination and cracking increase with the strain. However, in the coating dried at 60℃, delamination is predominant and the spread of cracking with the strain is little when the applied equi-biaxial strain is not small (over 1500 microstrain). Furthennore, scale-like cracking pattern was observed in the coating dried at 60℃.

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Thermal stress field around contact faces was analyzed by FEM to understand the crack propagation across contact faces. Stress singularities disappear when the crack tip reaches to the contact face. For the continuous growth, new edge crack must be created at the opposite face. Frictional forces acting on the contact faces restrain the crack creation until the propagating crack tip reaches the face. Then the frictional forces act oppositely to increase the normal stress acting parallel to the face at the crossing point. Suitable situation is achieved for the crack creation at the opposite face. Experimentally, cracking was observed at the contacting faces against continuous face and separated faces. Crack timing and position were well in accord with the analysis.

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A ductile fracture locus formulated in the space of the equivalent plastic strain to fracture and the stress triaxiality for the polypropylene (PP) blended with ethylene-propylene (EPR) and talc fillers is obtained at the intermediate strain rate by using a combined experimental-numerical approach. Biaxial loading tests on the flat butterfly specimens are carried out to characterize fracture behaviors under pure shear, combined shear and tension, pure tensile loading conditions at various loading velocities. Corresponding fmite element analysis is performed to determine the evolution of stress, strain and strain rate states. It is found that the material ductility strongly depends on the stress triaxiality for the present PP/EPR/talc blend. The obtained fracture locus covers a wide range of the stress triaxiality. It would be applicable to the fracture analysis of real automotive components under various impact loading conditions.

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The influence of strain rate on the compressive strength and the absorbed energy of polylactic acid resin foam which is low environmental load plant-derived plastic was experimentally studied by conducting compression tests at strain rates from 10^<-3> to 170 s^<-1>. It was found that the flow stress of polylactic acid resin foam during deformation and the absorbed energy up to the strain of 0.6 increased with the increase of strain rates. The compressive strength of the foam was also strongly dependent on the density of specimen, despite the same material.

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Fracture toughness K_<IC> or J_<IC> is generally used as criterion for safety design. These criteria are defined under plane sirain condition. Shear lips on crack surface is caused in case of thin plates fracture. Therefore, fracture mechanism in thin plates is not clarified. And some of these fracture behavior depends on loading speed. In this study, three point bending fracture experiments are demonstrated to gain basic data for elastic plastic fracture in thin plates. The specimens are consists of aluminum alloy. Pure mode I and mixed mode fracture experiments are done under quasi-static loading and dynamic loading. Roughness on crack surfaces are evaluated using laser focus displacement meter. Fracture path, crack surface trend and surface roughness are depended on loading speed.

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The goal of the present study is to reveal the coupling of large-amplitude (including plastic deformation) flexural waves and precursor waves in water-filled, thin-wall tubes. The flexural waves are generated by stress waves in the water propagating along the tube axis. The maximum hoop strain with mild-steel tubes was observed just below the bottom surface of the buffer as a bulge with 25% hoop strain. Hoop and longitudinal strains indicate a steep elastic front followed by a gradual plastic deformation. Since the plastic deformation wave travels much slower than the elastic waves, the initial flexural wave fronts propagate at 1350 m/s and are close to the wave speed of the Korteweg's elastic theory of water hammer. Measured wave speeds with CFRP tubes are consistent with effective modulus models of layered composite materials. The failure mechanisms of the CFRP tube wound at 45° resemble that of ductile materials, whereas the mechanisms for the tubes wound at 60° resemble those of brittle materials.

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We present an analysis of the pressure distribution in a bucket due to an incident water jet. The pressure distribution on a semispherical bucket resulting from momentum variation in ajet of known velocity distribution was evaluated as the sum of two components: jet impact on the bucket, and flow along the surface of the bucket following collision. The distribution of the pressure had a high plateau region concerning the potential core in the central region local to the jet with a singularity at its central point. To confirm the validity of the theoretical results, the experiment was conducted. Theoretical calculations were found to agree with experimental results from measurement of force on an aluminum alloy semispherical bucket.

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[in Japanese]

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A numerical simulation based on FEM is undertaken in order to clarify the influence of the axial impact velocity V_0 on the crushing behavior of cylindrical tubes subjected to an axial impact. In general, the initial peak stress u1 for a tube of a strain rate sensitive material is higher than that of a stain rate insensitive material. It is found that the initial peak stress σ_l for a strain rate sensitive material can be predicted from that for a strain rate insensitive material by taking into account of the modified yield stress σ_Y and the plastic hardening coefficient E '_h. Here, σ_Y and E'_h can be calculated using the the strain rate ε|_l at the apex of a wrinkle when σ_l generates.Also, the strain rate ε|_l is a function of a ratio of V_0 and tube radius R, and based on numerical results, an approximate technique for evaluating ε|_l and σ_l is proposed and checked the effectiveness of the approximation.

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Solid particle erosion is affected by many factors such as the impact velocity, the impact angle, the particle size, mechanical properties of the particle and the target. The computer simulation is effective to clarify the erosion mechanism. However, the simulation of erosion is troublesome, because the local surface roughness continuously changes during the process. In this paper, the Extended Distinct Element Method (EDEM) was applied to simulate solid particle erosion. The EDEM is a kind of the mesh-less method and it seems to be effective to simulate a dynamic process like erosion by the EDEM By obtaining the numerical results, the effectiveness of the EDEM for solid particle erosion was examined. The influence of the impact angle of solid particles on erosion was also shown.

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This paper describes that dissimilar metal weld for pressure boundary of class 1 components is to be defined based on the extent of stress intensity generated by difference of thermal expansion dependant on materials. This study was performed to provide a background for the introduction of questions and answers on an interpretation of dissimilar metal weld in Japan Electric Association Code (JEAC) 4205 into Japan Society of Mechanical Engineers (JSME) Fitness-for-Service Code.

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To develop the failure assessment procedure of Ni-based alloy, the fracture tests of flat plate specimens with a rectangular flaw were conducted at 302℃ in temperature. The flat plate specimens were base metal plates, NCF600 and butt weld joints, whose weld metal are Alloy 182 with 25 mm in thickness. Since the ratios of maximum loads at 302℃ to those at room temperature of both NCF600 and Alloy 182 are coincide with the ratio of flaw stress defined as the average of 0.2% proof strength σ_<0.2> and ultimate tensile strength σ_u, in tensile tests, it is judged that the fractures of Ni-based alloy are governed by the plastic collapse at both room temperature and 302℃. The maximum load at 302℃ could be estimated by the limit load analysis (LLA) and twice elastic slope (TES) method with fmite element analysis. In addition, the difference between maximum load obtained by the fracture tests and estimations by LLA and TES method became smaller with increasing the flaw area. The net stress at the maximum load depends on the flaw depth and this tendency in Ni-based alloy at 302℃ is almost the same as the Hasegawa's experimental proposal obtained by the fracture tests of austenitic stainless steel.

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[in Japanese]

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Finite element modeling of welding residual stress has been experimmentally validated for dissimilar metal welds. And applicability of stress intensity factor solutions for simple geometry, available in fracture mechanics handobooks to realistic and geometrically-complex components has been studied.

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The Sm value is the one of the most important value for the design of machine and structure of nuclear power plants. The values are defined in the Code. The values are defined the lowest value using yield stress and tensilestrength of materials. Thus it is useful for the design. However, it is not so useful for the aseismatic evaluation of the real plants, such as nuclear power plants and chemical plants, because the materials strength is quite higher than that defined by Code. If the Sm defined in Code were used for the evaluation, the results will be quite conservative.

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This paper describes applicability of the 2 parameter assessment method for cracked pipes in NPP's subjected to displacement controlled seismic load from the viewpoint of reliability and proposes a method of fracture assessment which treated seismic load for JSME fitness for service (FFS) codes.

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Tri-axial shake table tests on the piping system with wall thinning were conducted to clarify the effect of wall thinning on vibration characteristics and failure modes of the piping system. The test results show that the predominant frequency and the maximum response acceleration would be reduced due to the existence of wall thinning. Nondestructive inspection methods would be useful for detecting the damage before the failure caused by the seismic load.

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Hybrid test have been conducted incorporating a seismic response analysis of piping system as a whole model with a static loading test of wall thinning elbow model. The failure mode of wall thinning elbow under seismic loadings had been clarified and effectiveness of this evaluation method has been demonstrated.

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Low cycle fatigue tests were conducted using 100A elbow specimens of STPT410 with local wall thinning. Local wall thinning was machined on the inside of elbow specimens in order to simulate erosion/corrosion metal loss. The local wall thinning areas were located at three different areas, called extrados, crown and intrados. The elbow specimens were subjected to cyclic in-plane bending under displacement control with or without 3MPa inner pressure. The effects of eroded conditions, such as eroded ratio, eroded angle and position, on the low cycle fatigue behavior and fatigue life were discussed. Three-dimensional elasto-plastic analyses were also carried out using the finite element method. Prediction result for the location of crack initiation and the crack growth direction were discussed.

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This study was conducted to examine the effect of aging after cold-rolling on microstructure and mechanical properties of β-type titanium alloy Ti-20V-4Al-1Sn. Aging was carried out at 473 K after cold-rolling of 30% reduction. The results showed that not only age-hardening was accelerated by cold-rolling but also the maximum hardness and static strength of the alloy were greatly increased. TEM micrographs suggested that the above phenomena were because a lot of dislocations which were introduced through cold-rolling gave preferential sites for phase precipitation so that the phase was densely precipitated.

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In this study the hybrid effect on the orientation dependence of the composite strength of an aluminum cast alloy reinforced by AL_2O_3 whiskers and SiC particles is studied experimentally and numerically. The monotonic strength is higher when the hybrid MMCs is subjected to the external load parallel to the random whisker orientation in plane than those when the load is perpendicular to the whisker orientation. The whisker orientation dependence of composite strength in the hybrid composite is weaker than the one in the whisker reinforced composite. On the fracture surface of the specimen loaded along parallel direction to the random whisker orientation in plane broken whiskers are the majority while a lot of de-bonded interfaces between whisker and matrix are observed on the fracture surface of the specimen loaded along perpendicular direction to whisker orientation. To characterize the hybrid effect on the whisker orientation dependence of composite strength, a three-dimensional hybrid composite unit cell model including whiskers and particles is developed using finite element method.

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The study focused on the tensile properties of TiB whiskers reinforced β21S Ti matrix composites prepared by spark plasma sintering. TiB whiskers are synthesized by reaction sintering of TiB_2with Ti. The effect of the volume fraction of TiB whiskers on the tensile properties and morphology were studied at processing temperatures ranging from 900℃ and 1100℃. The microstructure and morphology of the in-situ TiB whiskers in the matrix were observed by scanning electron microscopy (SEM). Tensile properties, such as elevated temperature tensile strength and Young's modulus, were investigated.

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We report the mechanical properties of multi-walled carbon nanotube (MWCNT)/alumina composites made with a pristine MWCNT and an acid-treated version that have nanoscale defects on their surfaces from the acid treatment. Microstructural observations revealed that a homogeneous distribution of MWCNTs in the alumina matrix was achieved by a novel processing approach based on the precursor method for the synthesis of alumina and acid-treated MWCNTs. An interesting geometric structure was observed between individual MWCNT and alumina matrix. The nanodefect on the acid-treated MWCNT was filled up with alumina crystal, wiuich may be intruding into the nanodefect during grain growth The addition of only 0.9 voL% acid-treated MWCNTs to alumina resulted in 27% and 25% simultaneous increases in bending strength (689.6 ± 29.1 MPa) and fracture toughness (5.90 ± 0.27 MPam^<1/2>), respectively.

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It is thought that the content and placement of inclusion in composite materials have a great influence on the mechanical characteristic such as strength. However there is no an effective technique to estimate characteristic of all models. In this research, a technique to obtain an optimum composite material under a constant content cavity rate is proposed by using CellularAutomaton (CA), Genetic Algorithm (GA) and Finite Element Method (FEM).

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Functionally graded materials (FGMs) are those whose composition and hence the properties vary gradually as a function of position. As the materials that the body surface and difference of temperature with the inside can bear a severe condition of 1,000 degrees Celsius, the use is expected to strong in heat and mechanics, in the field of aerospace that a concept of FGMs. However, The space mission using space shuttle heavily relies on the perfonnance of FGMs, since space shuttle is protected by FGM panels. Its vely important to understand fracture behavior of FGM Up to now; the evaluation technique has not been developed, due to many complex behaviors of FGMs. In this paper, simulation technique of fracture path prediction in functionally graded materials was successfully developed.

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Recent experimental observations have demonstrated that silica-filled rubber has network like gel-structure between silica particles in rubber matrix. This study examined the effect of the inter-particle networks on the viscoelastic deformation behavior of silica-fliled rubber based on molecular chain network theory and homogenization method. The series of simulation clarified that the increase of stress in the later stage of stretch observed in the experimental results was successfully reproduced by the new model. This suggested that the role of inter particle network like structure formed by adding bonding agent to control the surface of silica particles plays an additional role in controlling the mechanical characteristics of silica filled rubber.

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To construct a design methodology for porous titanium mechanical parts, the linearity limit in the load vs. displacement curve has been predicted by the inner microscopic stress calculated by the micro-CT image-based modelling and finite element mesh superposition method. Two L-shaped specimen of porous titanium with different pore diameter, l8Ojsm and 90jim, have been tested. The strain measurement from macroscopic viewpoint by an optical instrument implied that the macroscopic strain/stress fails to predict the linearity limit. In the proposed numerical method, the homogenized macroscopic properties agreed well with the experimental results, and a consistent criterion to predict the linearity limit has been determined for the above two types of porous titanium parts.

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Darrieus wind turbine is a windmill with the blade parallel to the axis of rotation, and with many advantages such as no control on the direction of the wind turbine. This wind turbine is exposed to a large centrifugal force throughout the blade. Therefore, it will be necessary to evaluate the strength of the blade. In this study, we evaluate the strength of both experiment and calculation for the blade of the Darrieus wind turbine made of CFRP.

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A non-contact strain field measurement method using advanced digital images correlation technique has been developed by modification of the classical grating method. In this study, the strain mapping method has been applied to quantify 3D deformations of the surface of woven fabric composites subjected to a tensile loading. The out-of-plane deformation was locally developed by weave pattem in a single layer woven composite. Higher strains was also located in the matrix areas between the longitudinal fiber and transverse fiber bundles and in the area occupied by the transverse fiber bundles. It was obvious that the output of this method gives us detailed information on the unit cell level of textile composites, necessary to understand their deformation behavior, stress concentrations and damage occurrence. To conclude strain filed measurement technique is very useful for understanding the failure mechanism for geometrical defects in textile based composites.

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