This study aim to develop a method to estimate stress distribution within forearm muscles using electromyography computed tomography (EMG-CT) method. Three subjects performed gripping tasks using three hand grips, while EMG signals around the forearm were measured. An EMG conduction model was constructed using an outline of the subject's forearm geometry. Distribution of muscle activity within the forearm was calculated using EMG-CT method. To obtain the stress, we calculated the trend of the relationship by linear regression. As a result, stress level within the forearm muscles was presented in a tomographic image. The highest stress increased from 0.08±0.01 to 0.18±0.02 MPa when gripping force increased from 77 to 242 N. This study provides a novel method of measuring stress in forearm muscles.

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The 'H-Gait' is a wearable sensor based gait analysis system intended for evaluating the walking ability of a person. The work reported here proposes to advance the 'H-Gait' system by addressing some key features of usability and investigating the effects of walkways on gait. First, the usability issue has been addressed by developing a bespoke GUI for 'H-Gait'. This GUI was capable of showing a step by step gait measurement operation manual through graphic illustrations and presenting the result of the gait analysis by a moving 3D wire frame model in addition to gait parameters. Second, the walkway effects were investigated by comparing the kinematic and spatio-temporal parameters obtained from 'H-Gait' system of normal overground, treadmill and snow road walking. It was found that treadmill walking decreased the stride by 2.2% and increased the cadence by 3.0% when compared with those of overground. The result of regression analysis of each lower joint angle between overground and treadmill walking showed more than 0.89 correlation coefficient and more than 0.95 coefficient of determination. This means there were no significant difference between overground and treadmill walking. It was found that snow road walking increased ankle dorsi-flexion angle at toe-off by 20% and hip flexion angles' mean absolute difference by 10deg.

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This study performed an usability test under the gait conditions of 70.0[kg] loading level and 2.0[s] cyclic loading period with the testing equipment which reproduced a motion walk based on strength testing method (ISO22675) of the prosthetic foot part in a walk period. I evaluated the influence that the combination of prosthetic foot part and Stable/Unstable shoes gave in walk properties using three-dimensional Rollover Shape. As a result, I clarified the following characteristics than dynamic Rollover properties of the combination of prosthetic foot part and Stable/Unstable shoes. 1) By the Stable shoes wearing, I can relax a shock to occur at the time of heel grounding and can maintain the walk function of the prosthetic foot part. 2) Because three-dimensional Rollover Shape is an arc shape with both aspects by the unstable shoes wearing, a flexible center of gravity can move to not only the anteroposterior direction but also the inside and outside direction.

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A cause of thigh pain after cementless THA is still uncertain. The final goal of this study is clear up the cause for thigh pain and the development of painless cementless stem. For that, the objective of this paper is to make the animal model of thigh pain and to establish the method of evaluating the pain. We made special pin that pushes from the inside and expands the rat bone. The rat that the pin was implanted was bred with the cage. The loadcells were arranged on four corners of the cage in order to calculate rat's dynamics parameters, namely, rat's position, stay rate, total movement distance, crosspoint and errorpoint. There is the resulting rat grimace scale score (RGS score) as an index that evaluates the pain that the rat feels. RGS score is a method of evaluating the pain from the rat's facial expression. On the other hand, the method of the proposal in this study is a method of evaluating the pain from the activity of the rat. This new index shall be designated as "the resulting rat activity scale score (RAS score)". RAS is more objective and more quantitative.

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Solder joints under temperature changes are destroyed by low cycle fatigue. So, it is important that evaluations of thermal fatigue life of the lead-free solder joints are performed. Evaluations of thermal fatigue life of the solder joints are done by next process. First, low cycle fatigue properties of the solder are got by conducting mechanical fatigue examinations. Second, equivalent inelastic strain range is got by conducting the FE structural analysis of the solder joints. At last, the fatigue life of lead-free solder joints is got from the properties and the equivalent inelastic strain range. Therefore, when we estimate the fatigue life of solder joints, we have to get accurate low cycle fatigue properties of the solder. There, the size effects, the interface influences and direction of stress on solder joints have to be considered. Therefore, in this study, an acquisition way of inelastic strain range by lead-free solder lap joint type shear specimen was proposed. Next, we conducted a tension-compressive test using Sn3.5Ag0.5Cu0.07Ni0.01Ge lead-free solder lap joint type shear specimen and got equivalent inelastic strain range for the low cycle fatigue properties actually.

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Most of tests to grasp fatigue characteristics have been performed under normal stress in rotating bending tests or axial loading fatigue tests. It is also important to clarify fatigue strength characteristics under shear stress from design aspect. So, we have developed a multiple-high-speed torsion fatigue testing machine which has a rotating-reciprocating-swinging conversion mechanism. The developed testing machine is a displacement control type in which an electric motor as a driving source. Therefore, the stress amplitude condition range must be set at less than the rated torque of the motor. It is necessary to modify the test stress range depending on the fatigue strength of the evaluation material, it is convenient to correspond with the specimen geometry changes. Although specimen geometry design is generally performed by using a finite element method, in the present study was conducted shape designed using the formula of material mechanics. As a result, it becomes possible to easily design the specimen geometry for evaluating materials given test stress range and the motor rated torque as the specified value.

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Now, aging is progressing all over the world. Therefore, prevention of bone fracture is required. In order to do it, it is necessary to analyze deformation behavior of bone when a person falls down. However, the mechanical properties of bone have not been investigated when impact load acts on it. This study focuses on impact tension property of bone and constructs impact tension test equipment as a purpose. The theory of the split Hopkinson stick method was applied to the impact tension test. But various problems have occurred on the impact tension test equipment. The fixed method of lead wires produced a wave problem at Gauge 2 and this problem was improved by using straws. The biggest problem is occurred at Gauge 1, which is unstable output from Gauge 1. But the confirmation of this problem is difficult by experimental method. So, the relationship between the incident stress and the influence of collision of leaned striker with Flange were clarified by numerical analysis.

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Indentation technique is used as one of the evaluation methods of material on microscopic region. But this method shows the shallower the indenter presses, the harder the result of a measurement. This is called as size effect of hardness. The strain gradient theory is studied on this problem. In this study, observation by EBSD(Electron Back Scatter Diffraction) were done around several sized indentations and crystal orientations were measured. The direction of expanse of the plastic region was different and it was found that the slip direction affects it. And it was found that the relative plastic region size to the maximum indentation depth decreased when the maximum indentation depth became extremely small and when the tip of indenter was dull. Provided that the strain near the indentation is same, the strain gradient increase if the plastic deformation region decrease. So, many GN dislocations, which prevent atoms from moving, occur and material becomes harder.

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The techniques to heal fatigue damage by electric current have been studied. However, these mechanism was not investigated in detail. In this study, we observed dislocation motion by transmission electron microscope (TEM) before and after applying electric current in a sample cut out from fatigue specimen. The dislocation motion that depended on the current direction was confirmed from different plane orientations.

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The digital image correlation (DIG) method can be used to determine the surface deformation of an object by comparing digital images taken before and after the deformation. However, when taken from the vehicle moving images at high speed, the camera position occurred shift in-plane direction and out-of-plane direction. In this case, it is difficult to carry out the displacement measured by DIG using one camera. In order to apply the DIG method to the health monitoring of over bridges, a method for correcting the depth direction displacement of the image was proposed in this study. First, the deflection distributions of a steel beam in a three-point bending test were measured by using the previous DIG method with a camera moving. An error correction was performed by using the coordinates of each point in each image. The deflection distributions were measured using the new DIG method. The results showed that the effect of the camera movement in could be corrected using the proposed method. This method could ensure accurate measurements for a displacement of approximately 3%.

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In this study, we aim to develop an active infrared thermographic non-destructive inspection system for structures located 10-20 m from observers. In order to achieve the aim, we are developing a remote heating lamp for heating test objects efficiently, and studying some data processing techniques for the temperature data to improve defect detectability. In the present paper, we report a prototype of the remote heating lamp and a data processing technique to reduce non-uniform heating in the temperature images which disturbs detection of defects. It was found from experiments that the developed heating lamp could heat a concrete specimen located 15m from the heater, and an artificial defect in the specimen could be detected in the observed temperature images. It was also found that the non-uniform heating, which was mainly caused by configuration of the heating lamp, could be reduced by using phase images obtained by applying Fourier transformation to the temperature data. These findings will contribute to the developing infrared thermographic remote non-destructive inspection system.

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Carbon fiber reinforced plastic (CFRP) is recently used in a lot of fields, and efficient non-destructive inspection (NDI) techniques for the CFRPs are also required with increasing the use of CFRPs. Infrared thermography is one of a convenient NDI method which features early and non-contact inspection. However, a disadvantage of the thermographic method is that its defect detectability is not enough for the practical applications. One of techniques to improving the defect detectability is using phase images obtained by applying Fourier transformation to the temperature data. In this study, we tried to apply various image filters to further improve the defect detectability in the phase images by reducing shot noise appears in the temperature images. Analytical and experimental studies revealed that applying median or moving average filter reduce the noise in temperature-time data, and the reduction of the temperature noise also lead to improve the defect detectability in the phase images.

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Gasket stresses in flanged joints decrease due to creep deformation of gaskets. Prediction of long-term viscoelastic properties of a gasket is important to ensure the tightness of flange joint for a long-term use, especially in elevated temperature applications. Nanoindentation creep test was carried out using TMA with Berkovich indenter to evaluate the viscoelastic characteristics of a PTFE based sheet gasket. The time-temperature superposition principle using W.L.F equation was applied to obtain the master curve of the creep compliance of gasket material at elevated temperature. The elastic-viscoelastic correspondence principle was also applied to estimate the gasket creep strain in the flanges from the master curve of the creep compliance. It is improved the repeatability of the test result by the pre-processed specimens. It is necessary to perform the pre-processing at the test temperature. Each creep compliance overlaps when applying time-temperature superposition to the results obtained from the pre-processed specimens. Creep strain predictive expression is useful for estimating the long-term creep modification in a flange with a high temperature.

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This study examined the effect of surface condition and plastic strain on eddy current signals of austenite stainless steel. Round bar test piece with 6mm in diameter and plate test piece with 30mm square were prepared. The surface of the test pieces were ground using emery paper. Eddy current testing was carried out by using eddy current testing equipment. Eddy current signal, which is output of the eddy current instrument, were measured. Grinding on the surface of the test piece showed effect on the eddy current signal. Difference in the eddy current signal by the surface roughness could be distinguished, but it is smaller than the difference with the specimen which was applied plastic deformation. It is suggested that the eddy current method can be detect not only the difference of the surface roughness but also metallurgical change of the test piece. The shape of the test piece showed slight effect on the eddy current signal.

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A tensile test of a magnesium alloy (AZ31B) was performed in various temperature environments, and the change of the mechanical characteristics of the magnesium alloy with temperature was examined. A creep test of the magnesium alloy was performed, and the relation between creep damage and the acoustic emission (AE) occurrence behavior under high temperature conditions was investigated. In the tensile test, when temperature rise in more than 150℃, the 0.2% proof stress and tensile strength of the magnesium alloy (AZ31B) became small, and the elongation of it increased. In the creep test, although AE event count increased in the transient creep stage just after loading, it decreased in the stationary creep stage and increased again in the accelerating creep stage. Since the relation between AE occurrence and each stage of the creep deformation was observed clearly, it was confirmed that the acoustic emission method was available in creep damage evaluation of the magnesium alloy.

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Small fatigue crack closure is observed as a thing with a possibility that the influence of change of the stress level and a stress ratio, etc. to the crack growth behavior can be explained, and until now various researches have been done. Although there is a method using the strain gage as the dynamic measurement method required for the elucidation of a minute fatigue crack, in respect of generating of minute fatigue cracks being directly contacted to a measuring object thing, and there is a problem in durability or measurement of the crack growth behavior, it may not necessarily be effective. Then, its attention was paid to the magnetostriction effect which is one of the magnetic actions of a ferromagnetic substance. Measurement of the opening stress of the minute fatigue crack under dynamic load and crack length performed by measuring the magnetic field change by the magnetostriction effect, without needing the contact to an object with simple equipment. Moreover, it measured by having changed cross-sectional shape of the specimen. Resulting in, opening stress of the minute fatigue crack opening stress was able to measure about specimen regardless of the cross-sectional shape of the specimen. However, at this stage, it is possible to perform a crack length measurement can only specimen having a circular cross-section.

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Wooden materials and biodegradable polymers have attracted much attention as promising materials to achieve carbon neutrality and biodegradability. To ensure the quality of wooden materials, nondestructive evaluation techniques need to be developed. On the other hand, the films made of poly-L-lactic acid, as one of biodegradable polymers, are expected to be employed in the human-machine interface devices. For safe operation of applications using these materials, the electroelastic field inside the material must be elucidated. From a mesoscopic viewpoint, both materials are considered to have D_∞ symmetry. In this study, we analyze the electroelastic field in a body with D_∞ symmetry. As an example, we treat a semi-infinite body subjected to locally distributed surface electric loading and free from traction The electroelastic field quantities are obtained by applying the potential function method derived by us and Fourier transform techniques. By numerical calculation, the field quantities are investigated qualitatively and quantitatively.

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The present paper deals with a one-dimensional elastodynamic problem of a functionally graded piezoelectric material (FGPM) thin film. It is assumed that one surface of the thin film is fixed to a flat rigid body and the other surface is suddenly subjected to a uniform impact pressure and that variation of material properties is given by exponential functions of the spatial variable. The analytical solution is derived by employing techniques of the spatial variable transformation and the Laplace transform. It is seen from obtained numerical results that a complicated stress oscillation is induced in the thin film and it can be suppressed by applying an appropriate voltage.

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Micromechanics is one of the effective methods to analyze the macroscopic fields induced in composite materials due to their microscopic structures. It can also be adopted to the problems of electric fields in addition to those of elastic fields. In this study, micromechanical analyses of the macroscopic dielectric constants and dielectric loss tangents of composite materials under the alternative electric field are performed by using the equivalent inclusion method. In modeling of the composite materials, the two-dimensional random distribution in three-dimensional space, which can be covered from the unidirectional distribution to the three-dimensional random one, is used for the zenith angle distribution of reinforcements. As a result, effects of the orientation distribution and the shape of reinforcements on the macroscopic dielectric properties of the composite materials will be clarified.

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The micro-columnar-structure in alumina was controlled by the process which consist of unidirectional solidification, freeze-drying and sintering of alumina-slurry. In particular, the effect of additives in the alumina slurry on the formation of columnar-structure was investigated. In the sample made from the slurry containing sodium chloride, the direction of columnar-structure of alumina was randomly arranged, while the columnar-structure was unidirectionally arranged in the sample obtained from the slurry without additives. On the other hand, the alumina sample obtained from the slurry containing ethylene glycol shows the micro-cell structure. The mechanical property in micro-columnar-structured alumina / unsaturated polyester composites was strongly depended on the width and spacing of columnar-structured alumina.

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Nanoscale hybrids attract much attention of researchers nowadays. Rebar graphene is one of such hybrids. It means polycrystalline graphene which is reinforced by carbon nanotubes laid across its grain boundaries. In this paper, the tensile properties of rebar graphene are investigated by means of molecular-dynamics. Simulation models consist of rectangular twinning graphene and carbon nanotubes. The effects of the number and length of reinforcing carbon nanotubes on the strength of rebar graphene are examined.

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Gum metal (one kind of titanium alloy, also called gum titanium) with higher elastic deformability and comparatively lower elastic modulus are intrested in this study for implant applications. Meshed gum metal plates with excellent 3-demensional flexibility and light-weight performance compared to usual palates are designed parametrically using 3D CAD tools for hernia of intervertebral disk applications. Mechanical properties like tensile/compression and bending stiffness and volume densities of sample meshed gum titanium plates are evaluated through experimenatal approaches with respect to different design parameters like basic mesh shape, mesh line width etc.

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Tensile test of high-density polyethylene (HDPE) was performed on the stage of digital holographic microscope (DHM) using plate specimen. The surface height of the order of nano meter was evaluated during tensile test and its change was discussed. Microscopic undulations were observed at small load and the undulations became larger at higher load or displacement. As the height distribution in observation area was similar throughout the tensile test, it seemed that the microscopic deformation was predictable from the surface undulation under small loadings.

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Polymer materials are light-weight, good corrosive-resistance, high heat insulating properties, and high erstic insulation quality. Thus, polymer materials are adopted by many products and engineering materials as one candidate for replacement of metals. Thereby, on polymer materials, creep properties are needed to investigation for design. In this study, stress-relaxation tests of POM and PTFE were conducted at 55 ℃, 85 ℃ and 115 ℃. At these tests, we used Instron 8513 type testing machine. Next, we analyzed these properties by Norton's law and also proposed compatibility for FE technology. Then, we analyzed the conducted material tests using the proposed technology and compered FE analysis results with experimental test data to examine the validity of the proposed technology. As a result, it was confirmed that analytical results were in good agreements with the experimental ones.

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The purpose of this study is to investigate the mechanical properties of wood plastic composites (WPC). The target of this study was the wood particles of 1-100 um which were fabricated by wet milling. In this paper, the mechanical properties of WPC were evaluated by the tensile test. Wood flour obtained from thinnings was fabricated by using a planetary ball mill. The average particle size of wood particles was controlled by changing the milling times. The particle size was measured by a laser diffraction / scattering particle size distribution analyzer. Then maleic anhydride-modified polypropylene (MAPP) which enhances adherence strength between wood flour and polypropylene was employed in order to fabricate the compounds. The specimens of the tensile test were fabricated by injection molding. As a result, the tensile elastic modulus and strength decrease as the average particle size becomes smaller. Experimental results indicate it is important to consider particle size dependence for WPC.

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In this study, effect of thermal fatigue on tensile property of plain woven jute fiber reinforced PLA was investigated. As a condition of thermal fatigue test, a range of temperature was from 35°C to 55°C. The maximum number of cycle was 200 cycles. The quasi-static tensile test was conducted after thermal fatigue test. Fracture surface of composite was observed by scanning electron microscope. As a result, tensile strength and Young's modulus of composite at 200 cycles decreased 22% and 14% compared with those of virgin material, respectively. Tensile strength and Young's modulus of PLA resin almost did not change until 200 cycles. From fracture surface observation of composite, the length of fiber pull out in fracture surface of composite at 200 cycles was larger than that of virgin material. Therefore, the tensile property of composite after thermal fatigue was probably decreased due to the decrease of interfacial adhesion between fiber and resin.

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In this paper, we discuss the buckling stress relation expression of the box beams representing the automobile body frame which is composed of thin plates under axial compression load and torsional torque. First, it is shown that the well-known buckling stress relation expressions of the rectangular plate under combined stress have similarities, and they are related by one coefficient. Based on these well-known expressions, the buckling stress relation expression of the box beams is proposed. And the accuracy of this expression is validated by comparison with the results of the finite element method (FEM). As the results, it is shown that the proposed expression of the box beams under compression and shear stresses are sufficiently useful.

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In this paper, deformations and stresses of a hook bolt, anchoring railroad track on a railway bridge, are analyzed both experimentally and theoretically. When a train passes through on a railway, dynamic load act on the hook bolts which are settled to fix a rail to a sleeper. Thus, repeated passing of the train may cause fatigue fracture of the hook bolt. Therefore, analyzing the deformations and the stresses of the hook bolt under the dynamic loading, caused by the train, is crucially important for the security of the train operation. In our study, by using the bending strains along the straight part of the hook bolt, we present a new method for estimating the axial force acting on the hook bolt when it is fastened. And performing both the deformation analysis based on the Castigliano's theorem and the 3D-FEM analysis, we clarify the stress distribution of the bolt. The experimental results are compared with the theoretical ones and the validity of the present approach are demonstrated.

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Bellows is a metal pipe with stretch and flexibility. Bellows is used in various environments as expansion joints of piping equipment to absorb vibration and thermal expansion. 60% of bellows failure is caused by fatigue and low cycle fatigue failure occurs on bellows because the bellows are used in plastic region. This study intends to elucidate the mechanical properties of the bellows with elasto-plastic analysis. Then manufacturing the bellows, the shape of bellows is formed by extruding from the inside of a pipe. Therefore thickness of the bellows is not uniform and the thickness of the crown becomes thinner than the root. Analysis models considering thickness distribution are constructed in order to elucidate the influence of the thickness distribution. As a result, maximum equivalent stress is higher in U-type than n-type. Then, number of cycle to failure of U-type is about 30-40% less than fi-type, so ft-type has mechanical superiority than U-type. Also life of the bellows is reduced by considering the thickness distribution. Therefore, it is necessary to consider the thickness distribution in order to evaluate the life of bellows in safe side.

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The safe performance of current helmet for American football is evaluated by the standard of NOCSAE, National Operating Committee on Standards for Athletic Equipment. However the evaluation does not consider that head injury is developed by repeated impacts and a risk of shortened protection performance by the aged deterioration of buffer materials. Therefore, final objective of this study is to establish a new standard considering the influence of them. However in evaluation of helmet, a dummy head which can get acceleration is necessary. Accordingly, this paper intends to create it which indicates the acceleration reply like a conventional dummy head and to evaluate it by drop test. Self-making dummy head is made of urethane foam because it is easy to work and mold. As a result of drop test, the buffering performance of self-making dummy head is not suitable for the evaluation of head injury. Then it is necessary to ensure the buffering performance by changing physical property of urethane foam. From compression test for urethane foam, it is found that young's modulus and yield point are correlated to density. Therefore, after this, it is necessary to inspect the density that is suitable for dummy head under impact load.

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A unified theory of the size effect on the yield stress of un-notched, notched and cracked specimens is developed on the basis of the yield zone growth curve, that shows the relation between the yield zone size and the applied stress (they are normalized by the adequately selected size parameter and the yield strength of material, respectively). The yield zone growth curve of the cracked specimen can be described by Dugdale model, and that of the un-notched specimen can be done by partially/fully plastic solution. However, the yield zone growth curve of the notched specimen has not been clear in spite of many studies. So, in the present report, an adequate size parameter for normalizing the yield zone growing at the notch root is considered, and Notch Root Yield Zone (NRYZ) model is devised and verified by elastic plastic FEM analyses. As a result, the yield zone growth curve of the notched specimen can be formulated from NRYZ model. The basic equation on size effect is derived from each yield zone growth curve of geometric similitude notch condition, and the size effect criterion is constituted based on the equation of geometric dissimilitude notch condition that is selected particularly for replacement, such as an hour-glass type notch (in place of an un-notch case), a spherical notch/small drill hole, a crack-like notch, etc.

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This paper presents the theoretical solution of a two-dimensional isotropic elastic medium (matrix) with eccentric two circular inclusions (ring model) under the in-plane problems. Inner inclusion is perfectly bonded to the outer inclusion. These inclusions have different elastic moduli, radii and central points. The matrix is infinite extent and subjected to arbitrary in-plane loading, for example, uniform stresses at infinity, as well as a concentrated force at an arbitrary point. These inclusion problems have many applications in disciplines such as engineering. The purpose of the present study is to apply the reflection principle and produces a general solution. Using these solutions, several numerical examples are presented with graphs.

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We suppose the disturbances for many circular those voids are free boundaries to an elastic medium (matrix) of infinite extent under the in-plane problem. The matrix is subjected to arbitrary loading, for example, by uniform stresses. From past studies, we derived these general solutions for the theory of elasticity. We observed the stresses around the voids from this solution and analysis of FEM (ANSYS). We focused on the disturbances of the stresses due to the span between the circular voids, size of the voids and arrangement. In this paper, several numerical examples are presented with graphs. From the graphs, we consider validity of the theoretical solution of the theory for elasticity.

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The subloading surface model has been formulated and applied to the prediction of cyclic loading behavior of metals. Furthermore, the return-mapping for the subloading surface model has been formulated and used in order to obtain high calculation efficiency in the whole loading state. In this article, the return-mapping in cutting-plane projection is extended so as to describe the cyclic stagnation of isotropic hardening to make the accurate prediction of the cyclic loading behavior. Then, the validity and efficiency of this algorithm for the description of cyclic loading behavior of ductile cast iron are verified by comparison with the test data.

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This study describes an estimation method of the structural failure probability based on an efficient simulation, where a structural failure probability is formulated by using a radial variable and a directional variable and sampling of these variables are generated by using mixed variance reduction techniques. Executing specified numbers of directional simulations preliminarily, and the conditional Mure probabilities in the sampled directions are evaluated by calculating the respective radial distances from the origin to the Mure surfaces and determine the minimum of the radial distances. A virtual hypersphere having a radius of the minimum radial distance-0.5 is formed, and referred as a pseudo β hypersphere. Radial variable samples are generated from a truncated chi-square probability densities defined outside the pseudo β hypersphere based on the concept of partition of the region. A limited directional region formed by the sampled directions with the radial distances smaller than the minimum radial distance+3, is considered to have effective contributions to the structural failure probability. Directional importance sampling probability densities are constructed by using the respective the conditional failure probabilities generated in this Umited directional region. By using the directional vector samples generated from the directional importance sampling probability densities constructed in the limited directional region and radial variable samples generated from the truncated chi-square probability densities defined outside the pseudo β hypersphere, simulations are executed within the limited directional region and outside the β pseudo hypersphere region to estimate the structural failure probability. A numerical example to estimate the failure probability of a structure with multiple limit state functions is presented to illustrate that the proposed method gives an accurate estimation of structural failure probability effectively.

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An area-type shear difference method, which has been previously developed by one of the authors, can analyze stresses in a member of structures using photoelastic data (principal stress differences and principal stress directions) obtained from photoelastic experiments. The method uses an approximate equation for a directly integrated stress equation of equilibrium between two points in any direction. In this study, most of the procedures in the stress analysis using the method were automated, and the stress analysis method was applied to photoelastic data obtained from an experiment on a circular disk subjected to diametric compression. The results indicated that the stress components obtained by the method were in good agreement with those obtained theoretically.

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The subloading surface model has been formulated and applied to the prediction of cyclic loading behavior of metals. In this article, the return-mapping in the fully implicit algorithm based on the extended subloading surface model is formulated aiming at obtaining accurate solutions in a high efficiency in the whole loading state. It is incorporated into the implicit finite element program Abaqus through the User-subroutine UMAT. Simulation result by the fully implicit algorithm is compared to the forward Euler algorithm about the accuracy and the convergence property under the cyclic loading.

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The failure mode so called local failure could occur at structure discontinuities. Local failure is caused from Von Misses stress and hydrostatic stress. So the triaxiality factor considering hydrostatic stress has been introduced to evaluate local failure based on Misses type criteria. However the mechanism of local failure has not been clarified. For this reason it is not easy to say that triaxiality factor is properly applied to evaluate local failure. Thus the purpose of this study is to clarify the relation of local failure and triaxiality factor with tensile tests of notched bars and FEM simulation. As a result, it is clarified that triaxiality factor doesn't always indicate difficulty occurs of plastic deformation. Furthermore it is clarified the relation of local failure and triaxiality factor by introducing the Von Misses stress - hydrostatic stress plane and fracture curve.

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Titanium alloys with beta-stabilizing elements have excellent characteristics such as high specific strength, good plastic formability and good corrosion resistance. However, the deformation behaviors of those alloys under biaxial loadings are still not clarified. In this study, uniaxial and biaxial compression tests of binary titanium-niobium alloys (Ti-Nb alloys) of different niobium contents were performed. The influences of niobium contents upon the compressive deformation behavior were then investigated. It was found that the primary plastic deformation mechanism changed with the niobium content and with deformation pattern. As a consequence of that, the different type of anisotropic hardening appeared. The niobium content dependency of constitutive relation of Ti-Nb alloys was then discussed using equivalent stress variation based on an anisotropic yield function and plastic work.

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The purpose of this study is to investigate the temperature condition for distributing the residual moment efficiently along the irradiation direction in a thin metal plate when a laser beam is irradiated to the surface of the plate with cooling its back side. In our previous study, it was revealed that the residual moment cannot be distributed largely and widely only by conducting the first multi-point irradiation. Therefore, it is necessary to examine overlapping irradiation that is performed by irradiating once again after conducted the first multi-point irradiation. Especially, the distributions of the residual moment generated under the overlapping irradiation are examined by changing the conditions of irradiation temperature and irradiation distance. Then, the effect of temperature condition on the distribution of the residual moment is revealed in this research.

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The behavior of ultraviolet (UV) curable resin in the initial stage of curing was investigated using a particle image velocimetry (PIV) technique. The specimen consisted of a mold and UV curing resin in liquid form with acrylic powder. The mold consisted of glass and acrylic plates. The specimen was illuminated with UV rays downwards from the upper side of the specimen. The images of the resin during curing process were then captured at a constant time interval using a digital camera. The results indicated that the behavior of uncured resin during initial curing occurred in the upper part of the resin, and the behavior of the uncured resin in the initial cured stage determined the behavior of the resin after the initial stage.

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In this paper, residual strength of poly-p-phenylene benzobisoxazole (PBO) fiber with kinking damage under ultraviolet irradiation was investigated in monofilament tests. Kinking damages was created on surface of virgin fiber by winding bundle fibers to steel rod. Diameter of steel rod was set to 5, 2.5, 1.25 and 0.65 mm. Kink damage density was defined to evaluate occurrence of kinking damage. UV irradiation time was 1 and 10 h, the irradiation intensity was 8 W/m^2. It was found that the residual strength of fiber with kink damage decreased with increasing kink damage density. When the PBO fiber with kink damage was subjected to ultraviolet light, the residual strength is greatly reduced due to the auto-oxidation generated in the kink damaged region.

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Residual stress that is mainly caused by heat treatment is one of the important factors in mechanical products such as internal combustion engines, since it affects the maintenance of peak performance and operational durability in competitive scenarios. In past, a phase transformation analysis method, in which volume fraction of 4 phases (Ferrite, Pearlite, Bainite and Martensite) during heat treatment process can be individually taken into account, was constructed for the prediction of residual stress caused by heat treatment such as induction hardening. In this paper, elasto-plastic analysis combines with this and applies to prediction of residual stress of S50C steel crankshaft to verify the validity of this method.

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Bellows is an elastic tube that can be expanded when pressure is applied to the inside of the tube, or compressed under vacuum. The tubes are manufactured using sheet metal forming process that includes a vacriety of deep drawing. Residual stress can exist in the manufacture process of bellows. If the bellows are affected by the stress, their properties will be decreased, that is a reason of unexpected deterioration of the bellows. To estimate characteristics of the bellows with residual stress, numerical analysis method will be performed in this study. The residual stress, which is existed by manufacturing process of the tubes, will be evaluated quantitatively. The numerical analysis supposes deformation of stainless material when forming bellows shape. However, it is difficult to estimate the residual stress that will appear on bellows in actual deformation by its forming process, thus three point bending deformation with a stainless steel plate, which is raw material for bellows, was selected for the first application to simulate the manufacturing process. And the bending test by FEM analysis will be compared with those by experiment to verify results of them.

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In recent years, it was experienced in laboratory that a highly concentrated moving carbon dioxide gas laser beam applied to the surface of a soda glass plate causes a continuous peeling of the material surface. That is, as if a peeler for vegetables, there is a possibility that a damaged surface of the glass plate can be removed by laser beam if the mechanical background of this phenomenon is fully understood. In the present study, in order to grasp the characteristics of thermal stress distribution, a quasi-stationary thermoelastic analysis near the moving heat applied along the surface of the semi-infinite plate was carried out.

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Pulse laser produces two kinds of shock wave related to laser abrasion and bubble collapse. In the case of laser peening, the shock wave induced by laser abrasion in water was normally used. However, the shock wave induced bubble collapse can be also used for the mechanical surface treatment. In the present paper, it was revealed that the noise corresponding to the shock wave by bubble collapse produced by pulse laser was stronger than that of laser abrasion and we demonstrated that the pulse laser at the present condition can be applied for the mechanical surface treatment.

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In order to investigate the effects of new surface modification method "Laser quenching after coating" on the rolling contact fatigue strength of ceramic coated steels, CrAIN coated steel specimens and TiAIN coated steel specimens were processed by this method and the thrust type rolling contact fatigue tests were carried out for these specimens. In the process of the laser quenching after coating, laser irradiation was carried out under various laser power conditions. The delamination initiation life of CrAIN coated specimen increased with the heat input, however the excessive heat input decreased the delamination initiation life. The adhesive strength of CrAIN coated specimen showed similar variation for the increase of the heat input, and a good correlation was recognized between the delamination initiation life and the adhesive strength. It was considered that the delamination initiation life of CrAIN coated specimen was strongly affected by the adhesive strength. For TiAIN coated specimen, the delamination initiation life once increased and then decreased with increasing the heat input, although the adhesive strength increased monotonously. The hardness of TiAlN film decreased from the heat input at which the delamination initiation life began to decrease. By laser irradiation, the film hardness of TiAIN decreased more easily than that of CrAIN, because the oxidation temperature of TiAIN was lower than CrAIN. The decrease of the delamination initiation life of TiAIN coated specimen laser-irradiated under the high heat input condition could be explained by the decrease of the film hardness. The delamination initiation life of TiAIN coated specimen was strongly affected by the decrease of the film hardness caused by laser irradiation.

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It is unknown about the relationship between hardness of DLC film and fatigue strength in detail, though hard film coating method is applied everywhere. When hard film coating method is applied for industrial products, it's desirable to clarify the relationship between film and fatigue strength in terms of safety and strength. In the present study, we conducted to clarify a relationship between fatigue strength and DLC (diamond-like carbon)'s adhesion by using the DLC coating method that can control deposition condition, i.e. gas species, power and intermediate layer during deposition influenced on the property of DLC film. The specimens consisted of 4 steps; machining, polishing, applying a solution treatment, and DLC coating. We used INSTRON 8800 which is a servo hydraulic fatigue testing machine in fatigue testing. Fatigue testing was conducted under the condition of stress ratio: R=-1, repetition frequencies: f=7 Hz, at a room temperature. Based on the results of the fatigue testing, fatigue strength of the DLC-coated test pieces was 71% higher than that of solution treated specimens. Therefore, it can be expected that fatigue strength improves if highly-adhesive DLC is applied. It suggests that highly-adhesive film is effective to improve fatigue strength of substrate.

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