We propose a novel relative-story displacement sensor for structural health monitoring. The sensor is composed of three pairs of position sensitive detector (PSD) units and light emitting diode (LED) arrays, and is capable of measuring both the local inclination angle of the PSD unit and the relative displacement between the PSD unit and the LED array. By immobilizing the LED arrays on the ceiling and the PSD units on the floor, we can accurately measure the relative-story displacement in real time. We have verified the measurement accuracy of the developed sensor using a shaking table and a θ stage, and the accuracy was evaluated to be approximately 0.15 mm in the displacement and 0.1 mrad in the local rotation angle. The results indicate that the developed sensor is applicable to the relative-story displacement measurement for the diagnostics of an actual building.

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Development of an early gas leak detection system is essential for safety of energy storage tank fields or chemical plants. Contact-type conventional gas sensors are not suitable for remote surveillance of gas leakage in wide area Infrared camera has been utilized for gas leak detection, however it is limited only for detecting particular gas. In this study a new gas leak identification system, which enables us to detect gas leakage and to identify gas type and density, is developed based on infrared spectmm imaging system utilizing low cost and compact microbolometer infrared camera. Feasibility of the proposed system was demonstrated by experimental results on identification of hydrofluorocarbon gas.

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For the design of mechanical structures, the fatigue limit is indispensable. Therefore, it has been developed the simple evaluation method with thermography. In this method, the temperature change can be measured for the specimen under cyclic load, and the fatigue limit is corresponding to the inflection point the temperature starts to rise rapidly. This method has been studied widely, the thermography system is used the lock-in type thermography which synchronize the signal with the cyclic load. However, it has a problem that the equipment is expensive. In this study, we performed the estimation of fatigue limit by using the non-lock-in type thermography for rotate bending fatigue testing, in particular, examines the following three points, i) the validity of applying the non-lock-in type thermography for rotate bending fatigue test, ii) determination of the inflection point in the stress-temperature change curve, iii) relationship between temperature and time.

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Evaluation of fatigue strength under cyclic loading is one of the most basic issues for the design of engineering products. Fatigue limit of materials is usually evaluated by the fatigue test using some standard test piece. However, evaluation of fatigue limit of real parts of products is demanded nowadays in order to ensure the safety of engineering products from more practical viewpoint. Unfortunately fatigue limit evaluation of such real parts by usual testing methods costs too much to conduct in practice. To reduce the cost for fatigue limit evaluation, a newly developed technique utilizing the temperature rise due to energy dissipation under cyclic loading is paid attention recently. In this paper, this technique is applied to fatigue limit evaluation of notched specimen in order to verify its applicability. As a result, it is verified that the fatigue limit predicted by this technique coincides very well with that determined by usual fatigue testing method.

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Evaluation of fatigue limit of every component is an important issue to ensure the safety of engineering products. However, determination of fatigue limit by traditional WOhler method is a time consuming task and costs too much. Recently a technique besed on the measurement of dissipated energy using infrared thennography is paid attention for rapid and convenient evaluation of fatigue limit. However, there have been few reports considering application of the technique to stress concentration parts. In this study, the technique is applied to a notched specimen made of stainless steel in order to verify its applicability to real engineering products.

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Thennoelastic stress analysis (TSA) has been developed as a technique for the direct measurement of stress distribution near crack tip in structural components. This technique provides full-field stress data on component surface subjected to a cyclic load. Stress intensity factor K can be calculated from stress distribution data around crack tip. Conventional techniques for K-value determination are based on the fitting of themioelastic data to Westergaard's equations using a least squares method. In these techniques, however, stress intensity factor was detenmned only from data extrapolation algorithm based on the 1st term of theoretical solution of stress distribution In this paper, K-value determination method based on the first three terms in Westergaard's equations is proposed. Accuracy improvement of K detennination is investigated by the new data ex(rapolation algorithm for K-value detennination.

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The present paper is about the improvement of the delamination identification of the CFRP structure by the electric potential method via the discriminant analyses. In general, the relation between the damage and measurement values is identified by solving an inverse problem. The inverse problem in damage identification is one of the optimization problems involving the minimization of estimation error, and is usually solved by common optimization tools such as neural network and genetic algorithm. However, trial and error processes are generally required to derive the optimum solution using these methods, and these processes demand much calculation and human cost. In the present paper, delamination identification of CFRP beam via discriminant analysis using Support Vector Machine is conducted. The present study adopts an electric potential method for monitoring the structural integrity of laminated composites. As a result, it was shox that this method is effective for identification of damages.

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Carbon Fiber Reinforced Polymer (CFRP) laminated structures are applied to many aerospace structures. Although the CFRP laminates have high specific strength and specific stiffness, delamination cracks are easily created and the delamination cracks are usually difficult to be detected by visual inspections. Recently, high toughness CFRP laminates are adopted to primary structures. The tough CFRP yields small fiber breakages hen delamination crack is made in many cases. This requires a detection system of fiber breakages at low cost for large structures. In the present study, Time Domain Reflectometry (TDR) is adopted. TDR uses an electrical pulse wave and observes the reflected wavefrom. The method is applied to a 2m CFRP strip specimen and notches are detected from the reflected pulse wavefonn.

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The present paper investigates Electrical Resistance Change Method (ERCM) for thick CFRP laminates with a dent The authors have proposed the damage identification method for CFRP using thc ERCM and confirmed its applicability for beams and thin plate-type specimens in the previous studies. However, the dent is made for thick CFRP and the dent causes electrical resistance decreases. In the present study, we focus on the dent and the electrical resistance decrease is adopted for monitoring delamination location. FEM analyses are used to obtain electrical resistance decrease distributions. Response surfaces are adopted to estimate the delamination location here. The results show good agreements with the experimental data.

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This paper describes the investigation of thermoelastic effect and damage process in carbon fiber reinforced thermoplastic composite laminates through thermoelastic stress analysis. Symmetrically orthotropic model laminate specimens having 4-layers of carbon fibers using spread tows and Nylon-6 were conducted to tension-tension fatigue tests. In order to estimate the thermal conduction effects due to thermoelastic effects generated in the sub-layer in a specimen under fatigue test, the measurement employed all of delayed phase emission via FFT processing the data recorded by Lock-in therrnograpy. Evidently, the processed thennoelastic images (TSA images) brought the information from the second or third layers. Thermoelastic damage analysis (TDA) between two TSA images, proposed by one of the authors, detected splitting and/or transverse matrix cracks in the notched root of a specimen and TDA information also showed a possible quantitative estimation of damage development.

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The contact stress distributions and permanent sets at the bearing surfaces in bolted joints in initial clamping state are analyzed using an elasto-plastic FEM when hexagon bolts with flanges are used. It is seen that the effect of the flange slope angle and the flange thickness are substantial on both of them. It is found that the difference in the contact stress distributions is larger between elastic analyses and elasto-plastic analyses when the bolt preload is higher. In the experiments, aluminum alloy specimens were compressed by the bolts with flanges and the permanent sets were measured. The permanent sets obtained from FEM are in a fairly good agreement with the measured results. In addition, the equivalent length for the bolt with flange is proposed.

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Bolted flange connections for wind power generations and chemical plants are subjected to repeated bending moments due to wind and earthquake loads. It is knou empirically that the bolt loosening in the bolted connections occur. Thus, it is necessary to examine the cause of the bolt loosening in the bolted flange connections under repeated bending moments. The objective of the present paper is to clarify the mechanism of bolt loosening in bolted flange connections subjected to repeated bending moments and to discuss on a solution for preventing the loosening of the bolted flange connections subjected to repeated bending moments, too. The loosening mechanism of the bolted flange connections is examined using the FEM calculations and the experiments. In the loosening experiments using the specified hexagon nuts, it is observed that the loosening of the bolts in the connection occurs due to the permanent-set of the bolts and the movement of the bearing surfaces in the flange due to the external repeated bending moment. In the FEM calculation, it is examined that the bolt loosening in the bolted flange connections qualitatively. In addition, it is found that as the bolt preload increases, the bolt loosening decreases. From the REM results and the experimental results, it is found that the most effective part for preventing the loosening of the bolted flange connection is the ecceninc nut.

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[in Japanese]

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Plastic region bolt tightening was applied to JPI 20-inch Class 300 lb flange joint by downsized bolt. Tightening test, Loading test of internal pressure, and evaluation of sealing performance were examined. Tightening characteristics of the bolt, behavior of axial bolt force subjected to the internal pressure, and sealing performance of the flange joint were demonstrated.

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This report measured the liquid leakage and gas leakage. Then it compared the liquid leakage to gas leakage. The examination sample used the compressed non-asbestos fiber sheet (V#6500). The experimental gas (Helium) leakage was 1×10^<-8> times or more as large as the experimental liquid (water) leakage. But when the experimental water and Helium volume leakage converted mass leakage, these values became near.

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A long-term life prediction method for a compressed fiber sheet gasket under an elevated temperature environment is studied. Non-asbestos compressed fiber sheet gaskets are now being used as a substitute for asbestos in the bolted flange joint. Consequently, there is a real need for a technology to predict the lifetime of non-asbestos compressed fiber sheet gaskets quantitatively. In this report, the facing surface of the gasket and flange is visualized with scanning acoustic tomography (SAT). Voids were observed on the facing surface of the gasket and increased with the increase in exposure time at elevated temperature. If a leak path for inner fluids is created by the increasing number of voids, the leak occurs on the facing surface of the gasket. The probability of a leak due to voids and the lifetime of this gasket are predicted by applying the percolation theory, which describes the connectedness of clusters.

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In this study, four cases of bending tests were conducted to evaluate the deformation behavior of bolted flanged joints. Experimental results showed that the evaluation method specified in "Seismic design code for high pressure gas facilities" was applicable to bolted flanged joint used in city gas pipeline network, such as the joints between valve and straight pipe. In addition, it was revealed that the buckling and leakage may occur at straight pipe before the leakage at bolted flanged joints.

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It has been well known that a scatter in axial bolt forces in pipe flange connections tightened by the torque control method is substantial. In practice, pipe flange connections with the larger nominal diameter tightened by the torque control method have been used in chemical industry, and so on. In some study, the characteristics of the connections with smaller nominal diameter (less than 8") have been examined. So, in an optimum design of pipe flange connections with gaskets, it is necessary to understand the characteristics of the pipe flange connections with large nominal diameter under internal pressure and the contact gasket distributions due to the scatter in axial bolt forces in the connections tightened by the torque control method. In this paper, the experimental and FE analyses were done to evaluate the effect of scatter in axial bolt force on the gasket stress distribution and the sealing performance of pipe flange connections with 20" nominal diameter. Two types of torque controlled assembling procedures and an effect of scatter in the axial bolt forces obtained from the above methods is examined. Then, the effect of scatter in the axial bolt forces on the sealing performance of the connection is evaluated. The contact stress distribution in the larger pipe flange connection with 20" nominal diameter under internal pressure is analyzed using FEM by taking into account a non-linearity and a hysteresis. The measured scatter in the axial bolt forces is applied in the FEM calculations.

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A Creep/relaxation occurs when gaskets for the flanged joints are used over extended periods. The Creep/relaxation of gaskets may causes leakage of an internal fluid from the flanged joints. A PTFE sheet gasket is easy to cause a creep strain of gasket and the stress relaxation of the flanged joints, and may causes leakage compared with compressed other gaskets. In the present study, the relationship between the sealing performance and the stress relaxation behavior is investigated in flanged joints using the gasket. The experiment is carried out using the PT Class 150, slip-on type and six-inch flanges and expanded PTFE sheet gasket, and the relaxation behavior of the bolts and leak rate of internal fluid is measured from the start time of the test to 240 hours at room temperature. The leak rate decreases with the decreasing relaxation behavior of the bolts. It is considered that ununiformly-distributed stress of test gasket right after the tightening relaxed with the time.

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Since an external bending moment affected the sealing performance of pipe flange connection, it was important to investigate this effect. This paper analyzed the contact gasket stress distribution of pipe flange connections and evaluated the effect of external bending moment on the sealing performance from the viewpoint of changes in contact gasket stress. The study included the FE analyses and the experimental leakage tests. The FE analyses revealed the large decrease of contact gasket stress at tension side and small increase at compression side. The difference in change in contact gasket stress was caused by the non-linear hysterics characteristics of stress-displacement curve of gasket. The FE analyses also revealed that the loading order, internal pressure and external bending moment, also affected the sealing performance due to the non-linear deformation characteristic of the gasket. The experimental leakage tests using helium (He) gas were analyzed by the finite element method and discussed. This paper also evaluated the stress distribution in the pipe flange under external bending moment. The results suggested that the hub stress dominated the flange structure and the most important factor in designing the flange.

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The authors have been evaluating the effects of the material properties of spiral wound gaskets(SWG) and the sealing performance of the pipe flange connections at thermal changes with numerical and experimental analysis. In this experiment we used 3" pipe flange connections and tightened by torque wrench. And then, we heated and measured leak volume. On the other hand we evaluated with the experimental leakage test and 3-D FE analysis in this study. Considering the circumstances mentioned above, we inspected stress analysis under scatter on bolt preloads and thermal changes.

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In order to develop a brain spatula or a brain retractor made of a shape memory alloy (SMA), the bending fatigue characteristics of the brain spatula of TINi SMA made by the precision casting were discussed. The results obtained can be summarized as follows. (1) At the room temperature, the fatigue life in pulsating-plane bending is longer than that in alternating-plane bending. (2) Relationship between dissipated work W_d and number of cycles to failure N_f can be expressed by one power function for alternating- and pulsating-plane bendings. (3) The above mentioned characteristics of the SMA-brain spatula obtained in this study can be substantially applied to the development not only for the brain spatula but also for other retractors and instruments used in other surgery operations.

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In order to develop the new function of the shape memory materials, the shape memory composite (SMC) with the shape memory alloy (SMA) and the shape memory polymer (SMP) was fabricated, and the three-way bending motion and recovery force were investigated. The results obtained can be summarized as follows. (1) Two kinds of SMA tapes which show the shape memory effect (SME) and superelasticity (SE) were heat-treated to memorize the round shape. The shape-memorized round SMA tapes were arranged facing in the opposite directions and were sandwiched between the SMP sheets. The SMC belt can be fabricated by using the appropriate factors: the number of SMP sheets, the pressing force, the heating temperature and the holding time. (2) The three-way bending movement in the fabricated SMC belt is observed based on the SME and SE of the SMA tapes and the glass transition of the SMP sheet during heating and cooling. (3) If the SMC belt is heated and cooled by keeping the bent form, the recovery force increases during heating and decreases during cooling based on the three-way properties of the SMC. (4) The development and application of high-functional SMCs are expected by the combination of the SMA and the SMP with various kinds of phase transformation temperatures, volume fractions, configurations and heating-cooling rates.

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To obtain the two-way shape memory effect, a shot-peening treatment was applied. The shot-peening region works as a bias spring. In the previous report, it s showl that more than 0.2 % two-way strain could be obtained by this treatment. In this paper, fatigue property was examined. To this end, a fatigue machine was made, there specimens were immersed in hot and cold liquid alternately and cyclically. The results showed that the two-way strain reduced in the first several cycles but after the cycles the strain remained until at least 10,000 cycles.

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This study describes the effect of temperature on critical stress for slip of Ti-Ni shape memory alloy. The yield stress of general metals represents the critical stress for slip. However, in shape memory alloy, stress loading causes martensite variant rearrangement in the martensitic phase and stress-induced martensitic phase transformation followed by martensite variant rearrangement in parent phase, so that it is difficult to determine the critical stress for slip of shape memory alloys. Consequently, the critical stress for slip in the mixtures of the martensitic and parent phases has not been clarified yet. To investigate the effect of temperature on critical stress for slip of Ti-Ni shape memory alloy, this study has carried tensile loading-unloading tests using Ti-50.3at%Ni in the temperature range from 193K to 423K. In the temperature range from 273K to 373K, the critical stress for slip in the mixtures of the martensitic and parent phases increases with increasing temperature.

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To demonstrate the ability of the coristitutive model which was developed by the authors, example calculations are conducted for the transformation behavior of shape memory alloys. The problem calculated here is described as below. The polycrystalline Ti-Ni shape memory alloy with austenitic phase is first set to be under the stress free condition. The material is cooled down below the martensite finish temperature to occur the martensite phase transformation. The orientations of martensite variants are randomly distributed in the space so as to accomplish the state of the material free from the macroscopic strain. Then uniaxial tensile loading is applied to cause martensite variant reorientation. The material shows the inelastic stress-strain curve during this loading path. Then the load is removed where the residual strain of transformation remains at the stress free state. Next, the material is heated up to above the reverse transformation finish temperature. The residual strain disappears during this process and the shape memory effect is realized. Computational results by the constitutive model for these loading paths are revealed to be reasonable in comparing with experimental observations.

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Molecular dynamics simulations are carried out to clarify the mechanism of the deformation and shape- recovery in a shape memory alloys. An embedded-atom-method (EAM) potential for Ni-Al alloy are applied, and a series of thermo-mechanical condition, consisting of loading by an external shear force, unloading, heating and cooling processes, are imposed. Consequently, the shape memory behavior associated with deformation and phase transformation is successfully demonstrated. As an example of the simulation, a result obtained for a polycrystalline model is demonstrated in this paper, while various arrangement of crystal grains have been investigated. The resultant stress-strain curve showing a hysteresis loop is also exhibited, and the future study is noted as the concluding remarks.

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Super-elastic shape memory alloy (SE-SMA) has unique properties such as the stress saturation by stress-induced martensitic transformation, the recoverable strain over 6% and the huge hysteretic damping. By using those properties, its application to shock absorbing device is expected. In order to put it in a practical use, modeling of the SE-SMA under high strain rate deformation is required. In this paper, a constitutive model of the SE-SMA that takes account of the strain rate dependence of the transformation stress is proposed. The strain rate dependence of the transformation stress is formulated by applying the model of the thermally activated motion of dislocations incorporated with a thermomechanical model of polyciystalline SE-SMA proposed by Ikeda et al. The simulated results are compared with the experimental results to verify the validity of the proposed model.

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A polycrystalline finite element method is presented for the analysis of three-dimensional deformation behavior of shape memory alloys under thennomechanical loading. The presented method is developed based on the theory of crystal plasticity. Transformation conditions are assumed to be dependent only on the local stress and temperature state. Numerical results show good agreement with experimental tests.

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An Ion beam sputtering device and segment type TiJNi target were used in order to fabricate Ti/Ni thin film. After sputtering, vacuum annealing treatment was performed in order to obtain the crystallized Ti-Ni thin film. The microstructure and composition of the film was analyzed by X-ray diffractmeter and energy dispersive X-ray spectrometry. Furthermore, the mechanical and tribological characteristics of the film were investigated. As the results, it was confirmed that the thin crystallized Ti-Ni fthn can be obtained by the method. Also, the microstructure and composition of the film is nearly equal to these values of ordinaiy Ti-Ni shape memory alloy. In addition, the film shows a high hardness and low frictional coefficient and superior peel resistance.

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Internal friction (IF) in the martensite phase of a Ti-base shape memory alloy, Ti-24mol%Nb-3mol%Al, with a strong texture was investigated by a dynamic mechanical analyser (DMA) in a tensile mode. The IF in the martensite (C-orthorhombic) phase, tanδ=0.01〜0.05, was much higher than that of the parent phase in all the test conditions. In addition to high IF-background, IF peak of tanδ-0.1 appeared in the martensite phase at around 153K. The IF-peak height clearly depended on the stress amplitude and the IF peak In addition, a threshold stress for the appearance of the IF peak existed in the DMA test and it was in good agreement with the yield stress (0.2% proof stress) in a tensile test at 153K. These results mean that a long-range motion of twin-boundaries is necessary for the appearance of the IF peak.

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Effects of single- and multi-step aging on mechanical properties and shape memory properties of Ti-6Mo-8A1 (mol%) biomedical shape memory alloy were studied using tensile tests at room temperature. As for the single-step aging, (1) pseudoelastic shape recovery by unloading was observed after aging at 623K, (2) the alloy became brittle after aging at 773K due to a) embrifflement, and (3) strength was improved with small shape memory effect by aging at 1023K. On the other hand, after a multistep aging at 773K-1023K-1123K, the alloy was strengthened and showed perfect shape recovery.

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SMAs has been put to first practical use in toy as shape recoverable wire and are now highly-popularized in wide range of areas such as cars and. electlical goods. Medical application has been expanded with increasing the minimally invasive therapy. SMAs have been consolidating core materials of medical devices such as guide wire, stent and so on. But many applications necessitate an extension of usual definition of fatigue And they are depend on surface condition of elements. In the case of Shape memory alloys, surface finishing are texture control, mechanical and chemical polishing. In specially, medical devices retained in the body should hanve good properties to the kink-resistance.

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Since a solid-state heat engine using a shape memory alloy (SMA) works at the temperature difference of several ten degrees, the development of the SMA-heat engine to use the low-temperature thermal energy below 373 K is greatly expected from a view-point of global warming prevention. The working principle of the SMA-heat engine is discussed based on the recovery stress of the SMA. The working principle and traveling speed of a solar-powered car using a simple pulley SMA-heat engine are investigated.

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It is useful to recover various waste heat in power plants. So we have proposed a heat engine using shape memory alloy wires which work at cyclic supplying hot/cold water. The purpose of this study is to measure the output of the engine under various conditions (cyclic rate, cooling temperature, load torque) and to clarify the best working conditions of the newly developed heat engine. As a result, output power increases with an increase of cyclic rate in the limited test conditions. Total work obtained during working life of SMA of the heat engine becomes maximum when output power becomes maximum.

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For the physically impaired, it can be said that assistive devices are an important part of their body. Therefore, assistive devices are required to be user friendly, safe, and rehable for the person who uses them. As well, there are variety of demands including good appearance, no noise, and ease of wearing it. Shpae memory alloy's super-elastic property and shape memory property are beneficial in fitting to the human body movement. They have been already applied to various products including catheters, stents, and intramedullary nails, and are expected to be widely utilized for assistive devices for the physically impaired. Focusing on assistive devices for the hand, which especially delicate movement is required by the human body, we challenged for development of a power-assested glove using shape-memory alloy and successfully created a more silent, compact and lightweight device compared to conventional products. This device can be operated by heating the shape-memory alloy electrically. Also, adopting electric control as the method of controlling allows the device to be controlled by acomputer.

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If we develop a novel self-repairing product, which can always return to its original shape after it was damaged, the product can be used repeatedly and contribute toward solving environmental problems today. The purpose of this study is to create self-repairing materials by using shape-memory gels. However the previous shape-memory gels are always weak, so that we tried to add hydroxypropyl cellulose (HPC) as a liquid crystalline polymer into the gels with the aim of improving mechanical properties of the gels. Our idea is that the order structure of the gels is enhanced by the addition of the HPC and makes it possible to improve the mechanical strength. Our experimental results showed that the maximum stress and the maximum strain of the shape-memory gels are increased when an appropriate amount of the HPC is added to the gels.

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Above their glass transition temperatures (T_g), shape-memory polymers (SIVIPs) can be deformed by applying a small load. They maintain their shape after they have been cooled below Tg, and then return to a predefmed shape when next heated above T_g. The reversible change in the elastic modulus between the glassy and rubbery states of SMPs can be of the order of 100 to 1000 times. Exploiting these characteristics, this study seeks to evaluate the application of SMPs to low energy position keeping of a robot ann. Prototypes of a SMP-based position keeping module were fabricated, together with a prototype hybrid McKibben actuator using a SMP. When the SMP is heated above T_g it softens and the prototypes can deform upon the application of a small load. After the robot aim attains a desired length, the SMP is cooled to below T_g and it is fixed in a rigid state. This state is maintained without the need for any electric power, air supply or control system. The enhanced versatility of this application of SMP to position keeping of a robot is shown through a series of experiments conducted on the prototypes.

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The aim of present study is to investigate the mechanism of deformation for single crystal NiMnGa foil. Firstly, we prepare two types of NiMnGa specimen. One is as-received single crystal NiMnGa foil and the other is trained one after cyclic thermo mechanical loadings. Then, we attempt to measure macroscopic stress-strain curve and local strain distribution under uniaxial tensile loading for single crystal NiMnGa. At this time, we use the in-house measurement system on the basis of digital image correlation to measure local deformation behavior, and also use the laser speckle extensometer to measure strain from point to point in a part of specimen.

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The purpose of this study is to investigate fatigue characteristics of Cu-Al-Mn superelastic alloy for lumbago prevent apron and assistance tools for grape faming. The specimen was made from five Cu-Al-Mn superelastic wires of 1.7mm in diameter and 400mm in length. Specimens were made by Furukawa Techno Material Co., Ltd. The apparatus generated the power to use superelastic component. The transformation temperatures were measured by differential scanning calorimetry (DSC). The bending fatigue characteristics of superelastic components were investigated by fatigue tester. The maximum strain ration of bending fatigue test was about 3.4%. Fatigue lives of the superelastic components were about 1,300 times.

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This experimental study presents validity of limit load analysis for pipes with multiple circumferential flaws. We performed quasi-static four-point bending tests on Type 304 stainless steel pipes with single, double or triple circumferential flaws. Maximum loads measured in these tests were estimated by limit load analysis for pipes with multiple circumferential flaws. All estimation results using flow stress (2.7S_m) defined by the JSME S NA-l-2008 show conservatism against test results. Estimation results using flow stresses obtained from tests for the pipe with the single flaw show in quantitative agreement with test results.

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Evaluation methods of leak and collapse loads using material properties were developed for pipes th multiple circumferential flaws. We performed quasi-static four-point bending tests on Type 304 stainless steel pipes th single, double or triple circumferential flaws. In these examinatioos, peak loads were measured at the flaw penetration and the crack propagition from penetrated flaw. Evaluation methods of leak and collapse loads for pipes th the single flaw led to evaluation methods for pipe with multiple circumferential flaws. Evaluation results using material properties obtained by the pipe specimen show in good agreement with experimental resultx

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In order to evaluate the integrity of the cracked pipes for general case, a limit load estimation method has been proposed by authors considering a circumferential surface crack with arbitrary shape. In this paper, the proposed method was verified by comparing with experimental results. Four-point bending experiments were carried out for full scale stainless steel pipes with a symmetrical or asymmetrical circumferential crack. Estimated failure bending moments by the proposed method were found to be in good agreement with the experimental results, and the proposed method was confirmed to be effective for evaluating bending failure of pipes with crack.

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The magnitude of Niigata-ken Chuetsu-Oki earthquake in 2007 was beyond the assumed one provided in seismic design. Therefore it becomes an important issue to evaluate the crack growth behaviors due to the cyclic overload like large earthquake. Fatigue crack growth is usually evaluated by Paris's law using the range of stress intensity factor (ΔK). However, ΔKis inappropriate in a loading condition beyond small scale yielding. In this study, the crack growth behaviors for piping materials were investigated based on an elastic-plastic fracture mechanics parameter, J-integral. It was indicated that the crack growth due to the cyclic overload beyond small scale yielding could be the sum of fatigue and ductile crack growth. The retardation effect of excessive loading on the crack growth was observed after the loading. The modified Wheeler model using J-integral has been proposed for the prediction of retardation effect Finally, an evaluation method for crack growth behaviors due to the cyclic overload was suggested.

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This paper describes fracture assessment method of a pipe with a circumferential flaw subjected to seismic loading. The theoretical and analytical examination for fracture behavior of the nozzle, the elbow and the tee, which are the typical components of the piping system, was performed.

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For the purpose of establishing fracture evaluation method of Alloy 600 weld of nuclear power plants, fracture tests using pipe model(8B and 14B) with alloy 600 weld joint have been perfonned at RT and 325℃. Predicted loads calculated by limit load evaluation method using measured and code regulated flow stresses were compared with the maximum test loads. And the predicted loads of the pipe at 325℃(8B and 14B) and at RT(8B), the initial crack depth of which is 75% of the pipe thickness, were in good agreement with the maximum test loads.

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"Rules on Fitness-for-Service for Nuclear Power Plants" is published by The Japan Society of Mechanical Engineers. It provides flaw evaluation methods to assess the effect of detected flaws on the structural integrity. To realize reliable flaw evaluation, the arrangement of mechanical property database is essential as well as the improvement of the flaw evaluation methods. In this paper, tensile properties of typical Class 1 fenitic piping materials were systematically formulated. The effect of temperature on fracture strength was then examined.

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The fracture toughness Master Curve gives a universal relationship between the median of fracture toughness and temperature in the ductile-brittle transition temperature region of ferritic steels such as reactor pressure vessel (RPV) steels. Considering the possible application of the Master Curve method coexistent with the present surveillance program for operating RPVs, the utilization of miniature specimens is quite important for efficient determination of the Master Curve from limited volume of the materials of concern. In this study, fracture toughness tests were conducted for typical Japanese RPV steels using the miniature C(I') specimens with the thickness of 4 mm following the procedure of the ASTM standard. The results showed that the differences in test temperature, evaluation method, and specimen size did not affect the Master Curves, and the fracture toughness indexed by the reference temperature, T_o, obtained from miniature C(T) specimens were consistent with those obtained from standard and larger C(f) specimens.

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Fluid temperature fluctuates at an incomplete mixing area of high and low temperature fluids in nuclear components. Temperature stratified layer tends to appear at cooled stagnant branch pipe. To prevent thermal fatigue due to above thermal loads, the JSME guideline is adopted. Development of knowledgebase and sophisticated method for thermal fatigue was planned to validate and justify the above guideline which was not revised. This paper describes the objectives and the plan for thermal fatigue issue.

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