In hydraulic pumped storage turbine runners, accidents due to cyclic loading often occur, that caused by residual stress at time of welding repair of a cavitation eroded part. In this study, for the aim of more fatigue property improvement of the welding materials JIS YS410,YS309, and bending fatigue tests were carried out , clarify fatigue properties and fracture mechanism of welding materials applied Ultrasonic Shot Peening (USP) treatment. The test result are summarized as follows: (1)The S-N curves of material YS410 used in this study have wide scatter since fatigue crack initiation is welding defect of mostly blowhole, on the other hand material YS309 have narrow scatter. (2)The bending fatigue limit at 107 cycles with ultrasonic shot peening materials improved by 10%(YS410),25%(YS309) in comparison with untreated material. The fatigue life of USP treated welding materials has longer 10 times than un USP treatment material. The high stress amplitude below bending fatigue limit at 107 cycles even if that repeats , he compression residual stress does not release. (3) It is possible to evaluate the fatigue life of welding materials by using the defect size √area and the initial stress intensity factor range calculated by defect size. The value of the threshold stress intensity factor range ΔKi obtained in this study were 3.06 MPa·m1/2, and ΔKi+R considering the compressive residual stress can suppress fatigue crack growth because it is less than ΔKi.
This paper describes the elucidation about the removal of surface oxidation layer of oxygen free copper after heating processing using NaCl-electrolyzed oxidizing water (It abbreviates as NaCl EO water). First, the etching characteristics of NaCl EO water against the surface of oxygen free copper was clarified using chemicals of HCl solution for comparative immersion experiments. The comparative study showed that as for the etching efficiency on oxygen free copper, NaCl EO water was superior to HCl solution, and the etching speed on the test pieces which has been processed in the heating compared with the material is high. As for the relationship between immersion time and etching speed, NaCl EO water is same as HCl solution, and become proportional connection. Next, by the observation using SEM image, the influence of EO water on the surface of oxygen free copper was clarified. The results indicated that when doing an immersion to NaCl EO water, the surface of the test pieces which has been processed in the heating becomes smooth but in the surface of the material, the etching appears remarkably. Lastly, as for the test pieces after heating processing, it did the surface oxidation layer removal experiment by the immersion. The results show that NaCl EO water can remove the surface oxidation layer like HCl solution.
In this study, the thermal fatigue life of substrate with Cu through-hole is evaluated by considering the mechanical properties of Cu thin film and glass fiber cloths structure. We first conducted tensile tests of Cu thin film and found that the rate-dependence of inelastic property varies abruptly with temperature. An inelastic constitutive model for Cu thin film is then proposed by combining both rate-independent and rate-dependent models. The proposed inelastic constitutive model is introduced in a Finite Element Method based analysis of glass epoxy substrate with Cu through-hole. Moreover, low cycle tests of Cu thin film are carried out by using repeated 4-point bending to evaluate its isothermal fatigue properties. Through our analysis we verified the capability of the proposed model to predict thermal fatigue life of Cu through-hole using the isothermal fatigue properties. The results show that the glass fiber cloths structure of the substrate needs to be considered in order to successfully predict the thermal fatigue life of the Cu through-hole.
This study aims to synthesize the bio-carbon with electro conductive properties by using graphitization catalyst synthesize from the woody carbon. In order to obtain the new functional bio-carbon, we prepared two initial powders. The two powdered samples (<Ⅰ>,<Ⅱ>) of cypress with different micro-structure were used for carbonization at 550～850°C and Fe-catalyzed carbonization at 850°C. The samples <Ⅰ> was prepared by pulverization of cypress chips with a wet cutter mill, which retained a micro-structure of coniferous wood . The sample <Ⅱ> was prepared by crushing the solid substance after drying the woody paste obtained by grinding the samples <Ⅰ> with a wet disk mill into ultra finely cellulose- fibrils. The carbon yield in carbonization and specific surface area were measured and XRD analysis was carried out for the carbonized products (chars) of both samples. The carbon yield for the sample <Ⅱ> was higher, and the specific surface area of the chars was considerably low compared with those for the samples <Ⅰ> and the chars. In Fe-catalyzed carbonization, it was confirmed that loaded Fe catalyst reacted with carbon atoms to form quantitatively Fe3C during carbonization and the crystallite size of char increased with increasing of amount of Fe loading up to 5 wt.%, but no definite difference in crystal structure between the chars of sample<Ⅰ> and <Ⅱ> was found. Fe3C contained in char could be easily removed by acid treatment. Specific surface area measured for the removed chars of sample <Ⅱ> was considerably high compared with that of carbonization without use of catalyst.
The objective of this study is to establish a methodology for high-speed fatigue testing, especially for resin materials, which includes fiber reinforced composites. To exert periodic stress on a material at a frequency of more than 200 Hz, a specimen was fixed as a cantilever to an electromagnetic vibrator and vibrated in its resonant frequency of the 1st bending mode by using a resonance tracking control. The shape of a specimen made of glass fiber-epoxy laminate was designed with finite element vibration analysis to obtain a resonant frequency of more than 200 Hz and a desired strain distribution for inducing fatigue damage under a certain stress level. A rise of temperature during the fatigue testing due to damping loss was estimated with a heat transfer theory and suppressed by external cooling to keep the specimen at a normal temperature. To confirm the validity of the high-speed testing, a completely reversed bending test at 1 Hz with identical specimens was also performed. Results both from testing at 230 Hz and 1 Hz were plotted on a single power-law curve in an S-N plot, which is a well-known fitting for fiber reinforced composites. This result suggests that we can evaluate fatigue strength in the high- or giga-cycle region for resin and composites in a very short time if temperature is controlled appropriately.
Effects of the cylinder wake in a freestream on joint velocity statistics of a turbulent boundary layer over a flat plate are investigated by means of wind tunnel experiments. The cylinder is set horizontally over the flat plate and the interactions between its wake and the zero-pressure-gradient turbulent boundary layer are investigated. The locations of the cylinder are varied in total 9 cases. The unit Reynolds number is Re = U0 / v = 7.38 × 105m-1 and the Reynolds number based on the momentum thickness at the measuring location is Reθ = 3,140, where U0 is the uniform inlet velocity and v is the kinematic viscosity. Instantaneous two component velocities are measured using hot-wire anemometry with an X-probe. The results show that the streamwise and vertical rms velocities and the Reynolds streeses are suppressed by the cylinder wake for all the cases. The decrease in vertical rms velocity is less significant in comparison with that in streamwise rms velocity. The four-quadrant analysis of the Reynolds shows that the Reynolds stresses in the 2nd and 4th quadrants are decreases by the cylinder wake, whereas changes in the 1st and 3rd quadrants are very small. The cospectra of fluctuating velocity components, u and v, are suppressed in the entire frequency region by the cylinder wake.
A mathematical model of rotor motion and an analysis model on mixed lubrication between the rotor and the spherical valve plate for a swash plate type piston pump have been presented in order to evaluate lubrication characteristics in the sliding part. The analysis on the mixed lubrication consists of Average-Flow-Model by Patir-Cheng and the contact theory by Greenwood-Tripp. The numerical calculations have been carried out under operating conditions and specifications of the spherical surface. It is found that (1) the torque efficiency in the sliding part can estimate with using nRSVCS/PD under each radius and radial clearance of the spherical surface, (2) the reduction rate of the torque efficiency with large spherical radius and radial clearance is smaller than that in other conditions, so that it is possible to obtain the torque efficiency substantially constant under a wide range of conditions, (3) asperity contact force and the friction torque decrease due to squeeze film effect for high pressure of the pump, and (4) the minimum film thickness and the torque efficiency decrease when the rotor motion is stabilized with increasing the rotation of the pump.
Inside of fuel cells, heat exchanger, chemical reactors, and other industrial devices, the fluid flow comes into the inlet chamber and streams into many branch passages. A uniform flow distribution requirement is a common issue in those devices. In this study, the flow rate in branch channels and the pressure loss of multiple passage are investigated experimentally. As the first step, four kinds of multiple-passage channels are investigated from the view point of flow uniformity and pressure loss. Experiments are performed for the Reynolds number based on the bulk velocity and channel width at the main channel from 6.0×102 to 2.0×103. The wall static pressure is measured, and the pressure loss and flow rate are evaluated. It becomes clear that the characteristic of a reverse flow passage has the highest performance for the flow rate distribution. In the second step, the dielectric barrier discharge plasma actuator (DBD-PA) is used for the reverse flow passage. The wave form with voltage of 5 kV and frequency of 2.5 kHz is applied to the electrode of actuator, and the position in which the actuator is installed is changed in four positions of the outside wall at inlet manifold. The velocity profiles are measured by a PIV system to clarify change of the velocity field with and without PA actuation. The results show that the pressure loss decreases and the flow rate in each branch passage improves by the effect of induced flow with PA. The effect becomes remarkable when PA is installed near the first branch channel. The flow uniformity and low pressure loss are related to the reduction of the recirculation region which exists at the inlet manifold.
This paper describes inner-water circulation DMFC (Direct Methanol Fuel Cell) system with low water cross-over MEA (Membrane Electrode Assembly). Water permeation controlled layer which has lower permeability (K~10 -14 m 2) than conventional micro porous layer (K~10 -13 m 2) was sandwiched between anode gas diffusion layer and anode catalyst layer. This layer blocks liquid water permeation from anode gas diffusion layer to anode catalyst layer and enhances water diffusion from cathode to anode. Water flux through the membrane can be changed from anode to cathode or cathode to anode based on operation parameters (air flow rate, cell temperature, fuel pump flow rate, anode circulation pump flow rate). The effect of operation parameters for water, methanol transport through the membrane and performance were examined experimentally. With these result, system operation method to control anode methanol concentration and solution volume by manipulating flux through the membrane was analyzed. As a result, the method to control methanol concentration by fuel pump flow rate and the method to control solution volume by air pump flow rate was established. This system enabled not only to achieve higher water and methanol utilization efficiency but also increased power efficiency without extra devices for cathode water condensation and recycling. DMFC total system volume was reduced for portable uses.
This study experimentally investigated combustion and emission characteristics with hydrogen added to both diesel fuel spray and emulsion fuel spray. The water percentage of 5 vol% in W/O emulsion fuel was used. For experimental setup, a burner equipped with a twin fluid atomizer was used. Hydrogen was supplied near the flame base. Results show that the height and luminosity of flame increased with hydrogen fraction for both spray combustion of diesel fuel and emulsion fuel. The amounts of CO and THC emissions decreased by increasing hydrogen fractions with both fuels. However, flame luminosity with emulsion fuel was lower than that with diesel fuel alone even if hydrogen was added. The lower flame luminosity is caused by smaller amount of soot with emulsion fuel due to water gas shift reaction and by lower combustion temperature. The combustion temperature was decreased by increased sensible heat and latent heat by the presence of water in emulsion fuel. Also, the lower temperature decreased the amount of NO emissions in comparison with the case with diesel fuel alone.
In daily life, there are many bottlenecks such as narrow passages, gaps between objects and entrances to rooms. At the bottlenecks, some deadlocks must occur so that mobile robots cannot move to their goals safely and efficiently. In order to solve this problem, it is necessary for robots working in daily life to give way to the others as humans do. The purpose of this research is to propose a new model for the mobile robot navigation in which the pedestrian intention is modeled with the probabilistic approach and show how important the give-way behavior is for the mobile robot navigation. In this research, we extend the Social Force Model with the intention vector to represent the intention change of the pedestrian and develop a new method to estimate others' intention. By modeling the pedestrian intention with probabilistic appoach, the proposed model solve the deadlocks at the bottleneck and realize the safe and efficient move of mobile robots.
This paper deals with the quenching problem of electromagnetic vibration of the motor stator with imperfections at the resonant frequency using a pair of dynamic absorbers. The iron stator of motor is modeled by a circular ring with single or two imperfect masses, and dynamic absorbers are installed on the outside of the circular ring to quench the forced vibration caused by the rotating distributed electromagnetic force. The solutions of forced vibration are obtained by the theoretical analysis. The following were made clear; (1) As imperfect mass reduces the natural frequency of the motor stator, resonant frequency becomes low. (2) In the case where the weight of two imperfect masses are heavy, the closer the angle at which two imperfect masses forms, is close to the angle between the loop and node of the mode that is to be quenched, the resonant amplitude is reduced. (3) By installing single dynamic absorber and single imperfect mass, and by setting an angle between the loop and node of the mode to be quenched, quenching is possible. (4) Even if imperfections exist, installing a pair of dynamic absorbers that make an angle equal to the one between the loop and node of the mode to be quenched, makes the motor stator quenched perfectly.
Riding on an electric skateboard needs rider's skill because it is difficult to keep standing. We should study how to move the skateboard to aid the postural control of human standing. To examine it theoretically, it requires a model of the human body and the system parameters. The purpose of this study is to estimate the postural control parameters of the model precisely when some disturbances act on the support surface. The structure of the model is regarded as a simple rigid-body and the torque for the postural control is assumed to be generated by muscle groups. We assume that the torque is determined by delayed feedback in terms of the angle and the angular velocity of the body. To estimate the feedback gains and the delay time of the postural control, we implemented impulse response tests. Center of mass (COM) and center of pressure (COP) were measured by motion capture and load measuring devices respectively. In this study, we propose a method which compares characteristic equations to estimate the postural control parameters. While variations in the estimated parameters generally appears, the presented method enables us to reduce the variations. The estimated parameters indicated that the parameters do not vary according to amplitude of the impulse. The validity of the estimated parameters were verified by comparing the equation of motion and experimental results.
This paper describes position control in consideration of tuning of passive compliance characteristic of the antagonistic drive system using rubberless artificial muscle. The rubberless artificial muscle is a pneumatic actuator similar to McKibben artificial muscle. The antagonistic drive system using pneumatic artificial muscle can control antagonistic position. In addition, it has a passive compliance characteristic vary with inner pressure. Therefore, this system has a possibility to control antagonistic position with adjusting passive compliance characteristic. In this paper, we confirm the rubberless artificial muscle has a variable stiffness characteristic experimentally. And we derive an equation model that shows the relation between passive stiffness characteristic and antagonistic force of this system. Next, we explain the contraction displacement linearization system (CDLS). This system decides the inner pressure based on the contraction displacement and contraction force. This system also performs linearization of the nonlinear characteristics of contraction displacement. We confirmed a possibility to realize the antagonistic position control with adjusting passive stiffness of the antagonistic drive system by using this system experimentally.
In this study, the replica of the metal processing surface was manufactured using the transparent silicone. Set for the new method for measurement using the transparence replica, it can get various characteristics by a processing method. The result was summarized in the following. The characteristic various patterns were provided by passing light in a transparence replica. Those patterns were able to be classified in a point pattern, a circle pattern, an oval pattern, four patterns of the diffraction pattern. It is possible that these patterns estimate the shape of the reflection plane, namely shape and processing method of the machined surface. The surface roughness by the diffraction was equal to the maximum height roughness by the tracer In the last paper, the empirical formula that showed the biggest height coarseness and the relations of the radius of gyration was provided in a circulation pattern and an oval pattern. This report makes a specimen of the end mill processing that is used a lot as a general processing method and shows the reliability as the measurement system of the assay by the transparence replica method.
We have theoretically investigated the properties of the stress wave propagation which is caused by a longitudinal impact of a cylindrical bar by a one-dimensional model. In the present study, the effects of the boundary condition and material nonlinearity of the bar are taken into account. An exponential function is chosen as the constitutive equation in order to realize that the one-dimensional model possesses some useful properties for the analysis. A governing equation which describes the behaviors of the stress wave is derived from the one-dimensional model. Since the governing equation is complicated, some mathematical techniques are applied in order to analyze the behaviors of the stress wave. As a result, it is shown that the stress wave, which can propagate through the cylindrical bar of semi-infinite length and that of finite length, is derived exactly from the governing equation. Moreover, the behaviors of the stress wave are shown analytically.
Many kinds of defects occurring at winding process such as telescoping and starring have been recognized. Their main cause is internal stress of a wound roll. Thus, understanding internal stress of a wound roll is necessary to prevent these defects. In the field of web handling, analytical models have been developed to figure out radial and circumferential stress of a wound roll. So far, models have been built based on an assumption that web has uniform thickness. However, actual web thickness is not uniform. We have faced defects caused by non-uniform thickness across widthwise direction. We use modified Hakiel's model with air entrainment effects. As the non-uniform web is wound, radius across widthwise direction also becomes non-uniform. The main characteristic of this model is that it distributes the winding tension across widthwise direction based on non-uniform radius. The model has a problem that it does not consider the radial compression of a wound roll when the most outer layer is added. Because of this, the tension applied to the thick web area tends to be higher at the time of tension distribution. Experimental coefficient is applied to the tension to correct this effect. Experimental verification has been performed on this model. Quantitative agreement between the calculated and measured results is confirmed. We explain both theoretical concept and experimental method of its verification.
Load is an important factor which has an influence to life cycle and performance in rolling bearing. The life cycle becomes shorter, and the sound and vibration intend to increase when a large load is applied. On the other hand, too small load causes a rotational instability and a shortage of rigidity. For a large load, dynamic and static rated loads are regulated, then applicable load is basically set. However, there are no regulations for the minimum load to stabilize the rotation of bearing. Therefore, in this research, the authors considered experimentally the necessary minimum combined (radial and axial) load for small ball bearing, with a parameter of increment in revolving skid of rolling element. As a result, it was clarified that the revolving skid of rolling element did not increase and stable rotation could be persisted when the dynamic equivalent load is almost 1% of the dynamic rated load.
Fuel cell cogeneration is one of promising energy-saving technologies in pursuit of a sustainable society. However, it is unpredictable how many fuel cell cogeneration systems will be diffused since there are many future uncertainties, such as people's lifestyles and national energy policies. As an approach to tackling with this problem, this paper proposes a method for describing scenarios to analyze the diffusion of residential energy systems, such as fuel cell cogeneration systems. We develop a simulation model for estimating the diffusion of residential energy systems, in which conjoint analysis is undertaken to analyze consumers' preferences. In a case study, several scenarios are described for analyzing the diffusion of solid oxide fuel cell (SOFC) cogeneration systems for apartment houses, where the region of interest is Kansai Area, Japan from 2013-2030. The described scenarios differ in terms of nuclear energy policies. The results show that the number of fuel cell cogeneration systems in 2030 reaches 147-157 thousands depending on the share of nuclear power. In addition, it is revealed that monthly utility cost has a much larger impact on SOFC diffusion than CO2 emissions. Future work includes further what-if analyses of the scenarios to identify factors that would give a significant influence on SOFC diffusion.
This paper proposes a practical approach to evaluating form deviation of surface of revolution based on the coordinate measurement data of discrete points. In this approach, the generating line of a surface of revolution to be inspected is represented approximately by the combination of straight line and circular arc segments under the condition of satisfying the pre-specified approximation accuracy. The form deviation of a measured point is calculated relative to its corresponding straight line or circular arc segment along the approximate generating line, and thus no specific calculation to compensate the influence of probe radius to the measured data is necessary. The localization errors of the inspected contour surface are evaluated using the minimum zone criterion or the least squares criterion to achieve the correct form deviation of the whole contour. Because it is guaranteed that the difference between the deviation definitions for a measured point, one relative to the original contour and the other to the approximate contour, is not larger than the value of the approximate accuracy pre-specified in the restructure operation of the generating line, the evaluation precision of the form deviation for the contour surface is sufficiently reliable. The effectiveness and the efficiency of the approach are verified with a practical evaluation example to a surface of revolution. Moreover, a weighting calculation taking into consideration of the distribution density of measured points is introduced for the least squares criterion in order to obtain a rational evaluation result for the measured points with non-uniform distribution on the inspected surface.
In this paper, we present a parameter-free free-form optimization method for the strength design problem of a shell structure. The maximum von Mises stress is minimized under a given volume constraint condition. The optimum design problem is formulated under the assumptions that a shell is varied in the out-of-plane direction to the surface and the thickness is constant. The issue of non-differentiability inherent in this min-max problem is avoided by transforming the singular local measure to a smooth differentiable integral functional by using the Kreisselmeier-Steinhauser function. The shape gradient function and optimality conditions theoretically derived are applied to the free-form optimization method for shells. With this method, the smooth optimal free-form of a shell structure is determined without any shape design parameterization, while minimizing the objective functional. Design examples are presented to demonstrate the validity of this free-form optimization method for minimizing the maximum stress of a shell structure.
In pharyngeal cancer surgery, an arc-shaped forceps is used for operations in the curved narrow working space of the throat. A flexible endoscope is also used because the affected portion is not visible directly. Due to the difference between the direction of the endoscopic view and that of the forceps handle, control of the forceps is not intuitive and the surgeons are required of high manipulation skills. In this paper, we propose a 3-DOF mechanical motion converter, which converts the backward and forward input motion to the rotating motion about the arc center of the forceps in order to prevent collision between the forceps and the organs during insertion. In addition, up and down, and right and left input motions are transmitted to the arc-shaped forceps. These motion conversion and transmission allow intuitive manipulation as if the surgeon manipulated a linear forceps. The proposed mechanism performs the motion conversion and transmission only through mechanical links without any actuators. Thus, it is safe and inexpensive, and its early introduction to practice can be expected. The experimental results demonstrate that the proposed mechanism can convert and transmit the input motions, and the front end of the arc-shaped forceps can move inside a pharynx mockup as expected.
Badminton shuttlecock is constructed of 16 goose feathers from a waterfowl with a hemispherical cork. The shuttlecock is light in mass (approximately 5.2g), with a highly specific air resistance. For professional badminton players, the highest initial speed of the shuttlecock by a smash shot exceeds over 80m/s, which is the fastest speed in all ball sports. Generally, it is extremely difficult to get the shuttlecock to speeds of over 30m/s with a launching machine without breaking the waterfowl feathers. In this study, a shuttlecock launching machine using two turn rollers for badminton exercises has been developed with a new launcher mechanism that includes an advanced holder device and a high rotational speed motor installed. In addition, a continuous launcher system which is able to discharge the 12 (maximum 96) shuttlecocks continuously at intervals of 1.5 seconds was designed. The results of the launching experiments using the two roller-type badminton machine show that the machine can launch the shuttlecock at mean initial speeds of up to 81.8m/s, with a maximum flight distance of over 11m. The standard deviation of the shot and lateral directions are approximately 0.34m and 0.12m, respectively. The launching performance of the badminton machine developed here has a performance far exceeding almost any commercial one, so the badminton machine can be used for harder practice by professional badminton players.
Falls are a major reason for elderly people to require nursing care. Prevention of falls requires evaluation of standing balance ability of human. Thus various measurements were performed and the relation between the results and occurrence of falls was considered. Although these measurements were mainly done under stable upright posture, the measurements of balance ability should be done under near falling. However, from a viewpoint of safety of subjects, the occurrences of falls which may inflict damage on them must be avoided during the measurements. This study, thus, develops a device that can measure standing balance of subjects until falls. The device consists of a three degree of freedom (3DOF) wire driven parallel mechanism, the output link of which is attached to a subject. The device can control 3DOF rotational motion of the output link by wires. Each wire has strain-gages to detect the forces applied to the output link and judge the falling moment. Furthermore, a force-plate is set on the base to measure the center of pressure (COP) of a subject. The device can guide subjects in specified direction at the measurement and support them safely at falling. We measured the COP at the fall moment and the body sways on tilting posture by the proposed device. As a result, it is found that the differences between subjects become clearer as their postures tilt closer to fall moment.
In this study, compactification (improvement of the light receiving density) and reduction of the directivity (dependence property for the sun position) are tried to improve the efficiency of the photovoltaics using Light Received Analysis Algorithm of a Plant Shoot (LAPS). The LAPS is a method of analysis to check the form of a plant shoot that has high light receiving density by numerical analysis using GA. A big scale plant needs big energy for maintenance and growth. A characteristic of the big scale plant is to have a branch structure. Thus, it means that a branch structure is necessary to get big energy by the solar cell module simulating a plant shoot. However, conventional LAPS was not able to express the branch structure so far. Therefore L-system is applied to LAPS. The purpose of this paper is to elucidate the influence that the branch structure gives to light receiving density. The analysis is carried out under sunshine condition of the summer solstice and the winter solstice in Sapporo, Hokkaido, and used a ginkgo for the shape of the leaf. As results, solar cell modules with the branch structure of a plant shoot optimized for sunshine condition of the summer solstice and the winter solstice were obtained. As the number of leaves increased, the solar cell module with the branch structure of a plant shoot came to have higher light receiving density than that of the solar cell module without the branch structure of a plant shoot. From this, it is confirmed that the branch structure increases the light receiving density of a plant with many leaves.
In recent years, much dynamic analysis and structural analysis have been done while considering abnormalities, such as derailment and collisions with foreign objects. In such situations, longitudinal force that exceeds design load may be applied to the car body and the ultimate load, also known as the buckling load and the crippling load, are more important than the design load that stipulates elastic strength. This is because a buckling load is the maximum load that a structure can sustain its soundness in the event of an accident. In this paper, the longitudinal strength of a railway vehicle is evaluated in consideration of plastic deformation. First in order to evaluate the strength of the railway vehicle body experimentally and validate the finite element (FE) model for the numerical simulations, the full scale crash test is conducted. Next the numerical simulations were conducted to investigate the relationship between the ultimate load and the design load, and effects on the buckling locations caused by load conditions such as dynamics and load path. As a result, it is clarified that existing vehicle structures have much larger longitudinal ultimate strength than elastic strength as defined in standards. Finally the ratios of the ultimate load to the design load are clarified, quantitatively.
A unique shield system has been developed utilizing electrostatic force to remove dust breaking into bearings and mechanical seals of equipment used for space exploration. Because the performance of the former system was not satisfactory for mitigating dust intrusion, we added wire electrodes above the former system to improve the performance. As the result, approximately 95 % of dust was repelled from the gap. Moreover, we developed a numerical calculation algorithm using distinct element method for decreasing calculation load without decreasing calculation accuracy. It was predicted by the developed numerical method that the shield performance of the electrostatic dust shield system would be great on the Moon and Mars environment if dust would be charged strongly. This technology is expected to increase the reliability of equipment used in long-term manned and unmanned activities on the Lunar and Martian surface.
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