Pneumatic soft actuators have high potential to be applied to medical devices, because they are safe mechanically, light weight and low cost. We have developed several pneumatic soft actuators which are configured with rubber materials. In this paper two of them for medical devices are reported. One is the rubber tube actuator for colonoscopy. This actuator is tube shape and is wound around an endoscope. Then by the actuator, the endoscope can have self-propellant function. Experimentally the effectiveness of the actuator have been confirmed using the colon phantom. The other is the balloon actuator for stomach X-ray examination. The actuator is used for pushing the abdomen for taking clear x-ray images. Actually the actuator was used in X-ray mass examination in a hospital. The number of the examinee was 56, and in 40 cases clearer x-images were able to be obtained by the actuator compared with the conventional method.

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With developments of stronger permanent magnets, the application field of magnetic coupling is spreading in recent years. Since the magnetic couplings can transmit power by non-contact, it can add physical isolation to a transmission shaft, and it also can transmit driving power through a partition. Adding to these benefit of magnetic coupling, a magnetic gear can also removed the wear and noise from mechanical contact, which are main problems in mechanical gear. However, since torque transmitted by conventional magnetic gears is extremely low compared with mechanical type of same size so far, it has only used in limited application area. To solve this problem, a magnetic gear which is eaual to a mechanical gear for 750W industrial motors was developed. In this paper, design criteria and measurement results of the prototype magnetic gear is described.

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Traditional engineering has focused its attention and efforts on achieving excellent functions of a final product. Engineers thought the better functions are, the more they would satisfy their customers. But with the increasing diversification, customers would like to have products that will break in better to their use conditions so that they can enjoy using the machines and products. In other words, we have to develop a new way to customize our products. In order to achieve this goal, we have to develop a new way to control degradation so that the machines and products degrade in such a way that we can enjoy using them as much as we like. The new technology of digital material might help to achieve this goal and modular design which separates parts into functional ones and emotional ones is expected to be very effective for this purpose.

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Mechanical twinning governs the plastic deformation in ceramic materials at low temperatures. However, its mechanism is not well known because of lack of direct observations during twinning. We investigated dynamic behavior of mechanical twinning in sapphire (α-Al_2O_3) by in situ nanoindentation in a transmission electron microscope. Our in situ observations revealed that slip motion of many strain contrasts on a twin plane. This suggests that the mechanical twinning occurs by slip of twinning dislocations. However, the observed behavior of twinning dislocations may not be consistent with the double cross-slip mechanism, which is the mainstream twinning mechanism in sapphire.

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The Nano Indentation has measurement error which caused by the Pile-Up and the Sink-In. Because it is difficult to interpret the existence of the Pile-Up and the Sink-In using the Nano Indentation test results. Recently, it is possible to observe the Pile-Up and the Sink-In using simultaneous measurement the Nano indentation test and SEM observation. This technique could be applied to in-situ observation of the nano structure crushing by the Nano Indentation. In this study, we showed the availability of the In-SEM indenter technique for nano structure.

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The observation of nano-scale deformation in real time is a significant step toward understanding the mechanisms of friction and lubrication. Our experimental setup of a micromachine combined with a transmission electron microscope allowed us to measure the deformation, force and cross-sectional area of a single Ag asperity. The experimental results provided insight into one of the parameters that determines the frictional coefficient. Furthermore, we have demonstrated that the energy loss associated with a shear fracture event is strongly correlated with the increase in total surface energy of the two surfaces formed here after the fracture of the nanocontact.

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In this paper, we consider a one dimensional L-C transmission line as a serial chain of L-C circuits with holonomic constraints and we propose a variational integrator for such an interconnected system by the discrete Lagrange-d' Alembert principle. We show how to formulate the discrete Lagrangian system for the L-C transmission line by introducing the extended Lagrangian and we finally show the numerical validity of our theory for evaluating energy errors in a long-time numerical integrations by comparing with the case by the 4-th order Runge-Kutta method.

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Graphene grown on substrates ordinarily have defects in its structure. Such defects affect the electronic properties of graphene. In this report, the atomic structures of graphene having a monovacancy or a multivacancy are equilibrated using first-principles calculations. The formation energies and bandgaps of the equilibrated structures are compared with each other. It is shown that the formation energy ofa 555-777 divacancy is the lowest, and that graphene with some kinds of defects can have nonzero bandgaps.

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The effect of 0-velocity inlet and free-out outlet boundary condition used in the free energy based LBM with large density ratio was investigated in this paper. A static water droplet in the quiescent gas in a gas channel was simulated with both the 0-velocity inlet and free-out outlet boundary condition and the periodic boundary conditions along Z direction of the computational domain. The total mass loss was observed while using the 0-velocity and free-out outlet boundary condition. By comparing with results from the periodic boundary condition, it was proved that both the velocity inlet and the free-out outlet can be the sources of mass un-conservation; the difference of the simulation results between the two types of boundary conditions are small, both boundary conditions can be used in the target simulation.

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Lithium ion battery is generally used in mobile devices for its advantages such as easy downsizing and weight saving due to high energy density. If there is the short circuit point in the battery, the abnormal heating occurs because of the high energy density. Therefore, it is necessary to identify the short circuit part in Lithium ion battery. However, it is difficult to clarify the micro abnormal part in the battery by diagnosis imaging such as X-ray inspection. In this study, a new technique of nondestructive detection of short circuit part has been developed by using inverse analysis of the magnetic field around the battery. This technique enables detection of the short circuit part by estimating the current density in the battery from data of the magnetic field around the battery. To verify the effectiveness of the technique, numerical simulations were carried out for specimen models with several slit modeled short circuits. The result shows that the technique could detect the internal short circuit of the battery.

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The purpose of study is to identify the defect occurrence function of injection molded magnesium alloy products by using numerical simulation and to demonstrate its validity for practical application. The casting defects were classified into four types now line, crack, shrinkage and penetration, and its occurrence was investigated by using 38 types of actual casting products. The numerical simulation was also conducted to actual products previously mentioned to identify the defect occurrence function. The estimated defect occurrence function was applied to predict the casting defect of practical casting product. Test result showed that the good agreement between estimated defect occurrence function was also utilized to modify the casting mold for prevent the casting defects. Finally this paper proposed an effective concept to design the casting mold by using defect occurrence function.

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In high-rize builiding or large-scale commercial buliding, waiting time of elevator-arrival tend to be long cause of large number of floors and passengers. As the solution, increasing number of shafts is effective, though it results in reduction of space of the buliding, there is a limit to increasing number of shaft. For the reason, some systems which have somne independent elevators within one shaft are presented. One of the latest system is one-shaft-twin-car-elevator developped in Germany. This systems is actually running in some buildings. Tough this system has the disadvatage that each car can't overtake each other. For soloving this problems, we proposed one-shaft-multi-car-elevator including one special car movable between two shafts, which are driven by common ropes and each car can overtake each other. In this paper, we evaluate the passenger transportation capacity of this system using numerical simulation.

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The swimming motion of Tuna type fishes has excellent ability for its speed and efficiency. In the former studies, we made 1/1 scale model of Blue Fin Tuna body and caudal fin. The body resistance in the water flow are measured, and the lift and drag force of caudal fin are also measured. By using these data, this paper shows a design example of fish type robot which can swim maximum 2m/s speed.

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Recently, Impingement problem of femoral component and polyethylene insert after total knee replacement (TKR) has been brought to light by contact pressure analysis using the knee joint simulator. Therefore, adequate motion analysis is important for estimating the impingement between components and improving postoperative exercise. The purpose of this paper is to analyze the impingement of TKR components during stair climbing activity in vivo. Nine patients (Ten knees) with posterior-stabilized (PS) TKR and Ten patients (Twelve knees) with cruciate-retaining (CR) TKR were examined in stair climbing activity. The 3-D position and orientation of the implant components were determined using image matching technique. Kinetic relation between the femoral component and polyethylene insert and between the intercondylar notch and tibial eminence was calculated, and then their impingement was analyzed. In the CR subjects, the femoral intercondylar notch was considered impinging the tibial eminence in hyperextension of stair claiming activity, but there was no such case. In the PS subjects, impingement of the femoral intercondylar notch and the anterior tibial post were observed in hyperextension of stair claiming activity. In addition, it was observed that femoral cam impinge the posterior tibial post in deep flexion or external rotation. This study helps the surgeon be more aware about impingement between components under some conditions and is useful to improve the design of artificial knee joint.

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Laser Induced Liquid Jet (LILJ) is investigated about novel medical treatment device. LILJ uses liquid on dissection or removal of tissue with preserved vessel. Medical anxieties are dissemination and droplet infection with splash interacting between tissue and liquid. In this study, numerical simulation was attempted that estimation of range on droplet with worst case. And, LILJ and high-speed camera were used for validation of result on numerical simulation. Numerical simulation was not convergence with real boundary conditions. Experimental result clarified that droplet was not occurred when nozzle tip was in liquid on the target surface.

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This paper proposes a novel method for estimating the knee joint center of rotation (CoR) using inertial sensors. The inertial sensors used in this work contain tri-axial accelerometers and gyroscopes. The inertial sensors are attached to the femur and tibia segments of the leg and are capable of measuring the acceleration and angular in all 3 axes simultaneously. The angular velocity data was used to calculate the rotation angle around the CoR and the centrifugal acceleration was used to calculate the distance from the inertial sensor to the CoR. Experiments were carried out in two stages: preliminary pendulum experiment and measuring the flexion-extension motion of the human knee. In both experiments the accuracy of the sensor's distance to the CoR was evaluated. The preliminary pendulum experiment showed correlation coefficient (CC) of over 0.99 whereas the human flexion-extension motion showed lower CC and the average absolute error was about 5.1 cm. Improvements such as a countermeasure for attachment errors/skin motion and consideration for other rotational motions such as internal-external rotation and varus-valgus rotation should be considered to further increase the accuracy of the proposed method.

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In this study, an experimental system has been developed to evaluate the efficacy of the implant which is implanted at the first molar position to support the mastication force acting on the cantilever type partial denture and to reduce the mechanical loads suffered by the abutment tooth. By using the established system, the effect of direct connection between the dental implant and the partial denture was examined. Results indicated that the tested implant had a certain effect to reduce the mechanical loadings on the abutment. However, the intense lateral loading on the abutment tooth could not be suppressed sufficiently by only one implant at the first molar position, especially when the mastication force was applied on the denture not only vertically but also laterally.

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Neurofilaments (NFs) are a major constituent of nerve cell axons where they form a spacious network that aids in axonal transport and provides a structural scaffold within the long projections. NFs assemble from three subunit proteins of low (NFL), medium (NFM), and high (NFH) molecular weight into a semi flexible rod with radiating sidearms to form a bottlebrush-like structure. The sidearms of NFs have been proposed to be highly disordered, leading to entropically and electrostatically based interactions that play a key role in mediating interfilament spacing. Here, to investigate the mechanical behaviors of two interacting neurofilament sidearms, we performed molecular dynamics simulations using one bead represented one amino acid coarse graining model. We then measured the electrostatic interactions between the sidearms based on Debye-Huckel model. As a result, the repulsive interactions based on negative charges generate between NFLs, indicating that they form large interfilament spacing. On the other hand, the attractive interactions generate between NFMs. In comparison with recent experiments investigating condensed and expanded gel states, our results demonstrated that the local interactions between NF sidearms could regulate the network structure of NFs.

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Ti-based bulk metallic glasses are reported to have high strength, low Young's modulus and high corrosion resistance, indicating their potentials in biomedical applications. However a specific in vivo evaluation of its biocompatibilities has not been conducted yet. In this study, we implanted bars of Ti-based bulk metallic glass in rats' femoral bones and evaluated the tissue reaction and its component ions' diffusion in local area and whole body twelve weeks after the implantation. It showed that the Ti-based BMG (Ti40Zr10Cu34Pd14Sn2) alloy has a good biocompatibility and bone bonding ability that is equal to Ti implant, component ion diffusion was not detected in study period.

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Slip deformation in tri-crystal models subjected to cyclic deformation is investigated by a finite element crystal plasticity analysis code. Accumulation of geometrically necessary dislocations (GNDs) and statistically stored dislocations (SSDs) are studied in detail. Results of the analysis shown that non-uniform deformation and the high density of GNDs accumulated in the form of band around the grain boundary triple junction, SSDs accumulated in the form of band during cyclic deformation. Mechanism of dislocation pattern formation is discussed from the viewpoint of influence of strain and stress amplitude.

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In this study, the effect of plastic deformation on microscopic structure and anisotropy of elastic modulus in SPCC (Steel Plate Cold Commercial) is investigated. Various plastic strains (0%, 2.5%, 5%, 7.5%, 10%) are applied to annealed SPCC plates, then, specimens for tensile tests are cut out from them. The elastic modulus of 0° and 90° directions are measured by tensile tests. Cyclic loading tests are performed to investigate the influence of the internal frictions caused by movable dislocations in elastic deformation Movable dislocations are quantified by the boundary tracking for TEM micrographs. As a result, the elastic modulus of the maximum principal strain direction (0° direction) and the minimum principal strain direction (90° direction) decrease more than 10% as 10% pre-strain applied. On the other hand, the elastic modulus shows recovery behavior after strain aging and annealing. The internal frictions increase by movable dislocations after plastic deformation. Remarkable anisotropy is not observed in the elastic modulus and the internal frictions. From the above, it is considered the movable dislocations affect the elastic modulus strongly.

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Transformation of conventional energy systems to renewable energy can limit the climate change to a safe level. Among the sources of renewable energy, solar energy is more convenient and easy to access. However, high cost of silicon wafer is a problem for photovoltaic solar cells. Therefore, manufacturers need to the development of solar cells made of thinner crystalline silicon wafer as a way to reduce costs. Silicon is brittle, and thinner silicon is easier to break due to residual stress induced during soldering process under high temperature. The solar cell conductive film (CF) can bonds the solar cell with metal ribbon at lower temperature than soldering. After the manufacturing process when the solar panel is subsequently exposed to sunlight for its operation, the temperature distribution redistributes the residual stress. Therefore, it is necessary to know how silicon wafers of different thicknesses are deformed for the two bonding materials, solder and CF in order to find out a reliable bonding option for thinner silicon. This study used the finite element method (FEM) to analyze the thermal deformation during the manufacturing and using processes of solar cells with different thicknesses of silicon wafer. It was found that varying the thickness of silicon wafer has long term effects on the deformation and residual stress. Sn-3.5Ag solder and CF were employed as the bonding interface to carry out a comparison of the thermal deformation characteristics.

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This paper describes the estimation-method for the shape of yield surface generated after applying the large pre-deformation. In a series of our previous reports, using a test piece applying the large pre-deformation of combined loading of tension and shear, the shape of yield surface has been estimated based on the Natural Strain theory by investigating the tangent modulus of the deviatoric stress-deviatoric strain curve, which is obtained by performing the experiments of proportional loading tests of tension and torsion. Since the shape of the yield surface becomes convex in the direction of the pre-deformation, the existence of anisotropy in yield surface has been confirmed from the results of our previous experiments. In this paper, another type of pre-deformation is chosen as the subject of this study. In particular, the deformation history of uni-axial tension after simple shear is examined in this report.

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Machine structure under elevated temperature generally causes not only static stress but multiaxial cyclic stress. It is common to be subjected cyclic stress simultaneously with mean stress. It is necessary to accumulate not only experimental data, such as creep and fatigue, but also the experiment data of fatigue-creep interaction in designing these structures. However, there are very little studies of inelastic deformation under multiaxial cyclic stresses. The purposes of this research are to obtain of the experimental data with reliability under multiaxial cyclic stresses, and to construct of the constitutive equation. It carried out a tension-torsion cyclic tests using triangular stress wave and the tension-torsion cyclic experimental result was compared with the multi-axis cyclic creep constructive equation of two internal variables at 180℃. As the result, the constitutive model and the experimentalresult are well in agreement.

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The compressive deformation behavior in micro areas of industrial pure titanium was investigated, by using a new method in which the deformation constraints from the neighboring areas were reduced by fabricating micro parallel grooves or V-shaped cross-section grooves, by focused ion beam machining. Uniaxial compression test was performed in the direction parallel to the grooves, and the deformation behavior in the areas between the grooves was observed by scanning electron microscopy. The parallel grooves were fabricated to across the deformation twin that appeared by pre-compression, and then the influence of deformation constraint on twinning was discussed. Meanwhile, the V-shaped cross-section grooves were fabricated on several grains to examine the crystal orientation dependency of the deformation of the micro areas. In both cases, the possibility was found to change the primary deformation mechanism in the areas by fabricating micro grooves.

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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 waz also applied to estimate the gasket creep strain in the flanges from the master curve of the creep compliance. It was able to obtain equally prediction equation with results of HPIS Z 105 test by taking into account the pre-strain. In order to obtain a creep strain predictive expression, it is necessary to consider the prestrain. Creep strain predictive expression is useful for estimating the long-term creep modification in a flange with a high temperature.

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For the purpose of a verification of an estimation method that material plasticity parameters are identified by using indentation test and FE analysis, experimental tests are carried out by the Rockwell testing machine on metal materials. First, the P-h curves of the indentation are determined by experimental test. Second, FE analysis of the indentation test assuming plastic hardening behavior is specified by the stress-strain curve. Comparing the P-h curve obtained from the experiment test and FE analysis, the process of loading characteristics has almost the same curve. The material parameters can be identified based on the curve fit using the polynomial function consisting of material parameters. The best solution is determined by using the response surface methodology. Comparing the identified parameters obtained from the tensile and compress test, the elastic and plastic material parameters on several metal materials are matched within the allowable range of practical values.

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This study proposed a method to evaluate the residual stress and plastic strain of stainless steel using Berkovich indentation test. This method deals with austenitic stainless steel, SUS316L that obeys the Ludwik work hardening law and involves in-plane equi-biaxial residual stress. Numerical experiment with finite element method (FEM) was carried out in order to simulate Berkovich indentation test for SUS316L having various plastic strain (pre-strain) and residual stress. It was found that indentation force increases with the increasing in pre-strain as well as compressive residual stress. Next, parametric FEM study by changing of residual stress σ_<res> and pre-strain ε_<pre> was conducted in order to deduce relationship between indentation curve and materials parameter of ε_<pre> and σ_<res> (Which was employed for the FEM study). This relationship can be expressed by dimensionless function with simple formulae. Thus, the present method can estimate both ε_<pre> and σ_<res> from an indentation curve of SUS316L. In addition, micro indentation test was conducted for several SUS316L steels including as-received, cold rolled steel, and shot peened steel. It is found that the proposed method can estimate the values of ε_<pre> and σ_<res> acculately.

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The stress-strain curves for carbide cermets which are typical sprayed coatings have been identifled by using the elasto-viscoplastic damage constitutive equation with twelve material constants based on continuum damage mechanics. Locally-coupled approach has been applied to the elasto-viscoplastic damage analysis of a beam with sprayed coating under three-point bending to show the validity of the present material and computational modeling.

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The present study newly attempts the numerical simulation of mechanical sensors using IPMCs (ionic polymer-metal composites). The generated electric potential of mechanical sensing mode is very much smaller than the supplied electric potential of actuating mode with respect to the same displacement and structure. Furthermore, the mechanical sensors show the relaxation and time lag of reaction force and electric potential, The non-invertible and time-dependent behaviors of the mechanical sensors are numerically modeled with a set of basic equations with multi-fields such as solid stress, fluid pressure, ion concentration and electric potential. The basic equations consist of Biot poroelastic model, layered Timoshenko beam model and Poisson-Nernst-Plank model. Instantaneous pore pressure is estimated on undrained condition, Poisson effect of pore pressure on uniaxial condition is added, and the significant changes of volume and mechanical stiffness due to hydration are considered with water uptake. The related models are integrated and simplified into numerical simulation, and the numerical results are compared with experimental results.

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In this study, a method for identifying the material characteristics of bi-material from measured displacements is proposed. The virtual fields method is employed for determining the material characteristics of bi-material. Three-point bending test and tensile test are performed for verification of the proposed principle. Specimen is obtained by bonding the polycarbonate and acrylic resin. Displacement distributions on a specimen surface are measured using digital image correlation. Special virtual displacements capable of reducing the measurement error of the strain are used as an input values. Then, the inverse analysis of material characteristics from the displacements under various loads is carried out. Result of the bending test occurred an error between the experimental value and correct value. However, the accurate identification result can be obtained in the tensile test. On the other hand, the result of this time, there was no effect on the results due to differences in the number of elements.

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Brittle failure of the structure such as a bridge, large tank and warship sometimes can be caused by the cracks. In the past century, many human life were lost and physical damages were caused in these accidents. To explain brittle failure phenomena, linear fracture mechanics are established by Irwin et al. based on brittle failure theory proposed by Griffith. In fracture mechanics, new parameters named 'Stress Intensity Factors (SIFs)' were introduced since that parameters are nearly constant if different size pieces are broken by any loadings. For the isotropic materials with cracks, SIFs are obtained by many researchers, and Tada summarized these analytical solutions. In this paper, SIFs for Cylinder with cracks subjected any loadings, for example, splitting force, on the lateral side of a cylinder are derived by using constraint release technique and some numerical examples are shown graphically. It is assumed that a cylinder behaved as anisotropic elastic body.

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This paper presents general solutions for piezoelectric materials and anisotropic materials subjected to arbitrary loads at the boundary. General solutions are provided by using complex functions based on Lekhnitskii formalism. In the analysis, similarities of fundamental equation between piezoelectric materials and anisotropic materials are shown. By defining new similarity-based complex functions, expressions of mechanical and electrical quantities are derived by analogous form. It is shown that expression forms of electric displacement in piezoelectric materials are corresponding to those of out-of-plane share stress in anisotropic materials. And stress distribution, electric displacement distribution and coupling effect are shown by graphical representation from several analysis results.

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Various models are proposed to the composite materials including clusters of reinforcements. In such models, the concentration of reinforcements in the cluster is generally very high or low compared to the outside region of the cluster. However, in realistic composite materials, the difference of concentrations inside and outside of the cluster is relatively small. In the present study, such a low-level clustering of reinforcements is modeled by replacing the cluster with the mixed double inclusion of the first kind by focusing on some reinforcement and smearing out of its surrounding, and by addition of the reinforcements in the matrix region outside of the clusters. As a result, the total internal stress occuring in the reinforcement is different in magnitude inside and outside of the cluster and also that in the matrix is so.

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This study describes an efficient directional importance sampling method for the simulation-based estimation of the structural failure probability. The proposed method is composed of two-stage procedures. In the first stage, executing specified numbers of directional simulations, the conditional failure probabilities on various random directions are determined by calculating the radial distances from the origin to the failure surfaces. When the basic random variables are subject to the normal distributions, the conditional failure probabilities on the respective random directions are evaluated by using the upper probabilities of the chi-square distribution. Random directional vectors with the radial distances smaller than the minimum radial distance+3 are considered to have effective contributions to the structural failure probability, while random directions with the radial distances larger than minimum radial distance+3 are considered to be ineffective to the structural failure probability. It is proposed that by using random directions with the effective radial distances only, a directional importance sampling probability density is constructed on the basis of the respective upper probability of the chi-square distribution per unit hypersurrace area. In the second stage, a directional importance sampling simulation is executed to estimate the structural failure probability by using the directional vector samples generated from the directional importance sampling probability density constructed in the first stage. Numerical emples to estimate the failure probability of structure with multiple failure surfaces and structure with nonlinear limit state function are presented to illustrate that the proposed method gives accurate estimations effectively.

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Plain washers are used to increase the area of the bearing surfaces in bolted joints. It was investigated that even if the average contact stress between a washer and a clamped part was the same, a thinner washer showed larger plastic deformation at the bearing surfaces after the bolt tightening. It is thought that this is because the real contact area decreases due to the warp of the plain washer. In this paper, mean permanent sets w^^- at the bearing surfaces are calculated based on elasto-plastic FEM analyses for several bolt sizes of the hexagon head bolted joints with plain washers. The deflection parameter k_w is proposed to introduce as a equation for calculating the mean permanent set by hand easily, and it is shown that the proposed method is effective to determine appropriate thickness of a plain washer.

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In this study, we investigated the loosening behavior of screw rotation under transverse cyclic loads using 3D-FEM analyses. Tightening and loosening tests were carried out for validation of the FEM analyses. It was confirmed that the loosening of screw rotation occurs due to accumulation and release of elastic torsional force during cyclic loading. FEM analyses provided that the improved formula considering elastic torsion would be helpful to evaluate the loosening of screw rotation.

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Stress concentration occurs in the root of threads in the threaded cover structure of the pressure vessel. The internal pressure causes unequal load distribution of threads and stress concentration in the root of threads, Then, it is necessary to consider the fatigue fracture because of the stress concentration. In this study, the improvement of the load distribution and unequal stress distribution in the threaded portion of the pressure vessel is considered by using a FEA, The effect of stress values of the root of the first thread by make a circumference groove in the cover and changing the depth of groove is considered. Results of the FEA shows that the stress value of the root of the first thread reduces by make a groove in the cover and changing depth of groove. Therefore, make a groove in the cover is shown to be useful for improving the stress concentration for the root of the first thread.

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Structural integrity of reactor pressure vessel (RPV) is evaluated according to the Japan Electric Association Code JEAC4206 "Method of Verification Tests of the Fracture Toughness for Nuclear Plant Components" in Japan. In the current code, the fracture toughness curve for evaluation against pressurized thermal shock (PTS) phenomenon shall be constructed for each plant so that it envelopes all the fracture toughness data obtained from surveillance tests and adjusted to the end of plant operation term. Through this activity, a large number of irradiated fracture toughness data have been accumulated for Japanese RPV materials. In this study, fracture toughness curves for Japanese RPV materials depending on product form that employ master curve concept are developed. The curves are intended to represent 5% lower tolerance bound of fracture toughness trend with incorporating fracture toughness variation of each product form.

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This research aims to find nondestructive and noncontact technique to detect the degree of pipe wall thinning. Microwaves, which have high sensitivity and resolution, are expected to be able to detect and evaluate pipe wall thinning. A microwave vector network analyzer to generate microwave signals and a waveguide sensor to transmit and receive were employed in this experiment where the frequency was swept in K-band (18 to 26 GHz). By analyzing the frequency domain response of the signals and extracting the shift of resonance frequency that corresponds to the pipe wall thickness reduction, evaluation of the pipe wall thinning degrees was realized. It was confirmed that the results obtained by this experiment are good agreement with the results obtained by our previous method. It was found that there is a liner relationship between a resonance frequency and wall thinning volumes. Our results demonstrate the importance and plausibility of microwave-based detection technique for remote monitoring wall thinning in metal pipeline in industry.

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