It is important to understand characteristics of rocking vibration related to overturning small structures inside buildings. In order to understand the overturning of the structure due to rocking vibration by numerical analysis, numerical analysis considering energy loss in a collision and duration of collision is performed by using a quadrilateral hysteresis loop characteristics in which repulsive force is a function of speed. In case that the restitution coefficient is constant and sine wave is used as an input wave, it is good agreement between experiment and numerical analysis response waveforms of rocking vibration in stationary process. However, it is not good agreement in nonstationary process. And it is not good agreement between experiment and numerical analysis response waveforms of rocking vibration using seismic ground motion as an input wave. On the other hand, in case that the restitution coefficient is considering energy loss in a collision and duration of collision, sine wave is used as an input wave, it is good agreement between experiment and numerical analysis response waveforms of rocking vibration in nonstationary process. Also it is good agreement using seismic ground motion as an input wave. From these results, numerical analysis for rocking vibration considering energy loss in a collision and duration of collision is effective using a quadrilateral hysteresis loop characteristics in which repulsive force is a function of speed. And it is effective for this model to understand overturning behavior of small structures in earthquake.
This paper describes the result of a tangential force measurement experiment by means of test wheels which is 500mm in diameter in order to investigate the relation between the size of the contact-patch and the tangential force characteristics. In the previous study on the tangential force characteristics of the wheel/rail, it had been sometimes indicated that the experimental results are a little bit smaller than those derived from the Kalker’s theory. Therefore, with a focus on the contact-patch of the wheel/rail, contact-patches of various sizes are set by means of changing the vertical load from 5kN to 35kN, and the tangential force coefficient and creep coefficient of contact-patch of various sizes are evaluated in terms of comparison with the Kalker’s theoretical value under the same criteria. As a result, we confirmed that the creep coefficient is 60% to 90% compared with the theoretical value under the same experimental conditions, because the ambient humidity of the test wheel is high and the contact-patch changes a little due to wear and plastic deformation. On the other hand, it has been clarified that the tangential force coefficient under large slip ratio condition in this study is saturated without falling like the Kalker’ theory.
In the assembly of micro components, a slight impact during assembly affects product performance. This work focuses on the assembly of parts including magnetized components. In the assembly of such parts, the attractive force acting between the parts causes a difficulty of assembly without collision. For this reason, such a work is conducted by skilled workers. However, the lack of successors has become a problem. Therefore, a bilateral operation system is developed for training such successors. A bilateral control is installed using two devices including a voice coil motor, a leaf spring and a sensor. The slave device is controlled to follow the motion of the master device. The force applied to the slave device is estimated with a full order observer to reflect the force on the master device. It is confirmed experimentally that the slave device can follow the master device and that the force applied by the slave device can be presented to the master device. In addition, assembling experiments are conducted using the bilateral operation system. The displacement of each device and the applied external force to slave device are obtained. It is demonstrated that the assembling technique could be evaluated quantitatively.
In recent years, PMVs (Personal Mobility Vehicles) have been attracting attention as a new means of transportation. We focus on the three-wheeled PMV which has two front-wheel and one rear-caster. They are environmentally friendly without exhausting harmful gases. These vehicle bodies are relatively smaller than cars, so they have a high affinity for pedestrian space. However, depending on the specifications of the vehicle, there is a possibility that wheel lifts during turning because the weight of the vehicle is low. In this study, we proposed the model of the three-wheeled PMV with two front-wheel and one rear-caster. We discussed the validity of the modeling by comparing the numerical simulation and the experiments. In terms of the driving force of the front wheels, the modeling was generally valid when the velocity of the vehicle is low and the turning radius is large. However, in the opposite case, the centrifugal force of the driver during the turning becomes larger and the moment around the front wheels axle center point is generated. Then it is expected that more detailed analysis will be possible by considering the relationship between the centrifugal force received by the driver and the driving force of the motor in consideration of the driver’s behavior. From the parametric study, it was found that the normal forces of the wheels greatly changed depending on the riding position of the driver. The area of the risk of falling was shown.
The rotation of a deforming body is usually evaluated using the antisymmetric tensor W (W-spin) constructed from displacement incremental gradient tensor L. On the analysis (Nagtegaal and de Jong, 1982) in which W-spin was applied to the torsion test of a circular tube, the phenomenon appeared where the stress was oscillating. Various studies have been made to find out the cause of the oscillating, but it hasn’t yet been obtained sufficiently. In-plane rotation of a line element on a coordinate plane depends on its orientation. The W-spin represents the average value of the rotation, but does not always correspond to the in-plane rotation of the coordinate axes. Then, taking place of W-spin, in this paper we used pseudo spin which takes especially the in-plane rotation of coordinate axes into consideration, and applied to the torsion test. The oscillating of the stress value was completely disappeared.
In order to estimate the fatigue strength of used rail of railway, bending fatigue test of actual rail and plane bending of element specimen are conducted. In this paper, we discussed difference of results on each test methods from the viewpoint of fracture mechanics. Also, we proposed a simple method for estimating fatigue limit considering surface roughness of rust surface and residual stress. These results are as follows;(1) As a result of conducting bending fatigue test of actual rails, plane bending and uniform tensile fatigue test of element specimens, it was confirmed that respective fatigue strengths were different. (2) √ area and surface irregularities formed by rust on bottom of used rail were measured. As a result of estimating stress intensity factor with these parameters considering stress generated in each fatigue test, it was confirmed that the stress intensity factor differs depending on each fatigue test method, and that affects the fatigue strength. (3) It was shown that the difference in the dimensions of actual rail and element test piece affects the residual stress and size of corrosion hole existing in each test piece, which in turn affects the fatigue limit. (4) We proposed a simple method for predicting the fatigue limit of used rails, considering the residual stress and the estimation result of extreme value statistical analysis for maximum roughness Rz.
A binding energy, EB, and the number of trap sites, NX, of hydrogen trapped in cold-rolled austenitic stainless and quenched-tempered low alloy steels exposed in high-pressure hydrogen gas were determined from a linear relationship between the concentration of the trapped hydrogen, NHX, and the trap-site occupancy, θX, which is a function of EB and NX, being calculated from the Oriani’s local equilibrium theory. The determinations identified that EB = 28 kJ/mol and NX = 2.12×1025 /m3 for 30% cold-rolled SUS316L (heat of B); EB = 28 kJ/mol and NX = 3.83×1025 /m3 for 60% cold-rolled SUS316L (heat of B); EB = 24 kJ/mol and NX = 2.29×1025 /m3 for 30% cold-rolled SUS304 (heat of B); EB = 43 kJ/mol and NX = 2.68×1024 /m3 for SCM435 (heat JL); EB = 42 kJ/mol and NX = 2.80×1024 /m3 for SCM435 (heat KL); EB = 42 kJ/mol and NX = 2.20×1024 /m3 for SNCM439 (heat BL); EB = 42 kJ/mol and NX = 2.42×1024 /m3 for SNCM439 (heat GL). From binding energies reported in existing literatures and the size of dislocation cores, the trapped hydrogen in cold-rolled austenitic stainless and quenched-tempered low alloy steels was mainly trapped by dislocation cores. For the low alloy steels, furthermore, hydrogen-induced degradations (HIDs) of various fracture characteristics were linearly proportional to θX and the following values of EB were obtained: EB = 44 kJ/mol for fatigue crack growth characteristics in hydrogen gas at pressures, p, of 0.1 ~ 95 MPa and temperatures, T, of 25 ~ 95℃ for SCM435 (heat TS); EB = 44 kJ/mol for fracture toughness characteristics in hydrogen gas at p = 0.7 ~ 115 MPa and T = 25℃ for SCM435 (heat of KL); EB = 43 ~ 46 kJ/mol for slow strain rate tensile characteristics in hydrogen gas at p = 115 MPa and T = −45 ~ 120℃ for SCM435 (heats JL and KL) and SNCM439 (heats BL and GL). The values of EB obtained from the strength characteristics were nearly equal to those from the hydrogen-diffusion. A series of analyses implied that the hydrogen-diffusion characteristics and the HIDs of various facture characteristics were dominated by the interaction of hydrogen and dislocation cores; then, the characteristics under various combinations of p and T could be predicted by the unified parameter, θX.
Internal delamination is often the point of origin for CFRP structural damage, and as a result, the mechanism of this internal CFRP damage was studied in detail. However, obtaining surface damage information is also essential to better understand CFRP structural damage. In this report, fluorescent penetrant testing was used as the method for observing the formation process of fatigue damage on the surface. This particular method allowed for the rapid and clear observation of microscopic damages, such as transverse cracks, splitting, and delamination. Observations showed the progression of splitting demonstrating saw-like patterns of damage on the woven CFRP surface. Penetrant testing allowed for easy observation of the entire structure, readily identifying cracks in cross sections as well as the surface.
The effect of the installation position of serrated tabs on the flow characteristics of a rectangular jet was studied experimentally. The serrated tabs, i.e. flat tabs of delta configuration, were placed on the short, long or both sides of a 2:1 rectangular nozzle. Measurements of mean and fluctuating velocities were made with cross– and single–wire probes for Reynolds number based on the height of nozzle of 9,000. In the case of the rectangular jet with tabs placed on the short sides, the y–axis spread of jet increases more than the z–axis spread of jet, and the intersection point of axis–switching get closer to the nozzle exit than the jet without tabs. On the other hand, in the case of the rectangular jet with tabs placed on the long sides, the y–axis spread of jet decreases less than the z–axis spread of jet, and the intersection point of axis–switching moves farther from the nozzle exit than the jet without tabs. Moreover, in the case of the rectangular jet with tabs in both sides, the intersection point of axis–switching moves between that of jet with tabs placed on both short and tabs placed long sides. Therefore, the installation position of serrated tabs at a 2:1rectangular nozzle exit significantly affects the development of rectangular jet.
Aerodynamic drag on several types of road cones was measured by wind tunnel experiments purposing improvement of anti-fall-down functions against lateral wind blowing. By opening holes on the side surface of cones, drag coefficient decreased so that maximum endurable wind speed increased over 30 m/s in the best case. This finding contributes to three benefits in road safety; reducing the weight of the cone for workers at roads, cost cutting by manufacturers for the synthetic resin material, and also for security aspects by internal visibility preventing from hidden matters. We also found different aerodynamic characteristics due to bottom plate condition of the cones. That is, when the bottom plate opened to the inner space of the cone, small angle of inclination intensified a recovery moment that pulls back the cone to the standing attitude. This effect significantly improved the maximum endurable wind speed and was explained by the flow allowed inside the cone when the side holes were provided. Such a fluid-structure interaction was analyzed theoretically to clarify the endurance mechanism.
This paper reports the quantitative method of vapor concentration in unsteady evaporating gasoline type spray with Laser Induced Exciplex Fluorescence（LIEF）. The LIEF is an exciplex fluorescence method developed by Melton to visualize the liquid and vapor phases separately. In this study, iso-octane（92 vol%）, benzene（4 vol%）, and triethylamine（4 vol%） were used as a fluorescent agent that emit excited complex fluorescence that can optically separate fluorescence from the liquid phase and the vapor phase respectively. We tested the dependence of the fluorescence characteristics on the vapor concentration, ambient pressure, and ambient temperature when quantifying the vapor concentration. The relationship between the vapor concentration and the fluorescence intensity ratio was similar to the theoretical relationship. Furthermore, the relationship between the fluorescence intensity ratio and each parameter could be considered as a function of only its parameter. Since the fluorescence intensity is proportional to the laser incident light intensity and the emitted laser light has a Gaussian intensity distribution, the intensity distribution of the laser sheet light could be predicted, and the captured image could be corrected. For quantitative measurement, we used the image analysis method of vapor concentration quantification measurement of direct injection diesel spray developed by Senda et al. The quantitative distribution of vapor concentration was measured by applying the method to the results of simultaneous measurement of Mie scattering, exciplex fluorescence, and monomer fluorescence.
The vanadium redox flow battery (VRFB) is expected as a large-capacity battery for leveling output fluctuation of variable renewable energy because of its characteristics: flexible design of charging and discharging capacities, superior responsiveness and safety, and other advantageous characteristics. In the previous research, the authors investigated the cell performance and the current density distribution in various operation conditions experimentally, and developed analysis models which can evaluate the effects of structure and operation conditions, based on the experimental results. The objective of this study is to propose an evaluation method of these effects on various overpotentials. First, electrochemical impedance spectroscopy was applied and it was shown that our conventional method are useful to evaluate the overpotentials during discharging where the method can divide measured overpotential into activation and concentration overpotentials with satisfactory accuracy. The analysis models were also developed using the experimental results. Then, two major parameters were introduced based on simple evaluation equations to calculate discharge performance under very low current density operations. The two major parameters summarize the effects of structure and operation conditions on the cell performance: one represents a ratio of through-plane ionic and electric resistances of porous electrode to activation overpotential effects, and the other represents a ratio of concentration overpotential effects at the electrode surface to in the electrolyte flow. This study showed that the major parameters and further introduced two dimensionless diagrams make it possible to evaluate various overpotentials visually even in high current density operations. Finally, the experimental validation of the proposed evaluation method was conducted, and the effectiveness for efficient design of the optimal structure and operation conditions to achieve high performance was demonstrated by showing some examples: evaluation of the effects of electrode thickness on the activation overpotential and the effects of SOC on the concentration overpotential.
The purpose of this research is to develop a VR simulator that can safely train wheelie, which is a stepping technique for manual wheelchair users. The equation of motion of the wheelchair was shown, and the actual wheelchair motion was compared with the simulation results. A wheelchair simulator that moves using this equation of motion was constructed. The effectiveness of the simulator in wheelie training was evaluated by experiments. In the experiment, 20 subjects were divided into two groups of 10 subjects, and one group trained using a wheelchair simulator and did not practice the other group. After that, Subjects tried wheelie in a real wheelchair and we calculated the success rates. As a result, the average success rate of the group using the wheelchair simulator increased by about 48 points compared to the unused group. From the results, it was shown that the simulator developed in this study is effective for learning the wheelie motion.
The uniform support motion (USM) method is generally used for multiply supported nuclear piping system. This method uses a uniform response spectrum (URS) which envelopes all of the individual response spectra and can result in considerable overestimation of seismic responses. An alternate method is the independent support motion (ISM) approach. This approach can also result in overestimation when the maximum responses by multiple excitations are combined by the absolute sum rule, while this may result in underestimation when the maximum responses by the multiple excitations are combined by the square root of sum of squares rule. Then authors have developed a new method of the ISM approach named SATH (Spectrum Method Assisted by Time History Analysis) to achieve a more realistic combination of the maximum responses by the multiple excitations. In the SATH method, both of floor response spectra and floor acceleration time histories are used as seismic input data. The maximum modal responses by the multiple excitations are combined with the effect of correlation coefficients. In order to account for the correlation coefficients, the time history analysis of an oscillator having each of modal frequencies of the piping system is performed using each of the floor acceleration time histories. The correlation coefficients are calculated from the covariance and the standard deviations of time history responses of the oscillators. In this paper, the necessity of taking the effects of the correlation coefficients into account in the ISM approach is discussed, and then the advantage and the applicability of the SATH method to an actual design is confirmed.
To investigate the failure behaviors of piping systems under extremely large seismic loads, which should be considered in beyond design basis events (BDBE), a new experimental procedure was proposed that used pipes made of a simulation material. In the proposed procedure, destructive experiments were carried out with the use of pure lead (Pb) as the simulation material, owing to its considerably low strength compared with that of steel. As the first step of the structural experiment, shaking table tests on simple piping system models, which included an elbow pipe made of Pb were conducted. Then, through excitation tests using various sinusoidal inputs, failure modes such as “ratchet and subsequent collapse,” “excessive deformation by one cycle,” and “no failure after considerable large number of inputs” were obtained. The failure modes appeared to be affected by steady loads such as self-weight, input seismic load, and the relation between input motion’s frequency and specimen’s natural frequency. The proposed procedures seemed to be effective for studying mechanical failure behaviors with large plasticity under excessive seismic load, which is difficult to achieve by experiments on steel pipes.
In order to clarify the effect of Ta (tantalum) content on the friction and wear characteristics of the ta-CNx (tetrahedral amorphous carbon nitride) coating, an IBA-FAD (Ion Beam Assisted Filtered Arc Deposition method) was applied to generate hard carbonaceous coating to achieve low friction coefficient in ambient air. Following research works clarified that Ta containing carbon nitride (CNx:Ta) showed friction coefficient lower than 0.05 in ambient air, however, the coating only had around 10 GPa hardness which was assumed to be soft in industrial fields. To confirm Ta containing to the ta-CNx coating on friction and wear properties, ta-CNx:Ta coating was synthesized by IBA-FAD and an arc plasma gun which supplied different amount of Ta by using pulse discharge technique (100 or 200 pulse/min.). The hardness of ta-CNx was approximately 54 GPa, then the hardness of Ta containing ta-CNx became softer than ta-CNx such as approximately 33 GPa (ta-CNx:Ta200). After the ball-on-disk friction test between those coatings and SUJ2 disk, a specific wear rate of those coatings did not along with its hardness. From the XPS (x-ray photoelectron spectroscopy) analysis, oxygen/carbon ratio of the topmost coating surface decreased by containing Ta. Those results implied that Ta in the coating may have a possibility to prevent oxidation of carbonaceous coating. The friction coefficient of ta-CNx, ta-CNx:Ta100 and ta-CNx:Ta200 showed around 0.15 during friction test. To confirm the importance of Ta transformed layer on low friction property, friction test between ta-CNx coating and thin Ta coated SUJ2 disk was conducted. The friction coefficient of the pair became the lowest among them which value was approximately 0.08.
In this study, we intended to make the prediction method of the transient characteristics of the flooded lubrication tilting pad bearings, and we developed the high speed calculation method with reasonable accuracies assuming the use by designers. Instead of solving the Reynolds equation and the energy equation simultaneously such as THL analysis, a method of simply calculating the oil film reaction force and temperature by using a database was employed. Based on this method, the average temperature of the shaft, pad, and housing in the time step is calculated every moment, and finally the changes over time in the bearing gap and oil film temperature can be obtained in seconds. In addition, we measured the bearing temperature with a test bearing bored 100 mm in diameter under conditions where the transient temperature exceeds the steady temperature to validate the analysis. In the transient state, the bearing gap decreases remarkably just after starting, and then gradually increases toward convergence. We considered it as a factor that the temperature rise of the shaft and pad with small heat capacity is large and their outer diameter and thickness change rapidly due to thermal expansion, while the temperature rise of the housing with large heat capacity is small and its inner diameter change gradually. We considered those mechanizm in the analysis. Also, the thermal expansion of the housing is considered to be suppressed by the casing or something, thus the deformation is multiplied by the hot clearance coefficient. When the value was set to 0.4, though the errors between the measured and the analyzed tempreratures at steady and maximus points increase as the mean pressure increases, both errors are minimized and they are within 5 deg. C under the test conditions. Although the sensitivity of the mean pressure is high, the analysis can predict the transient temperature with reasonable accuracy in short calculation time.
During cervical lateral bending, cervical axial rotation occurs simultaneously; this phenomenon is known as coupled motion. To date, many studies have been conducted on coupled motion. However, it remains unknown how protagonists of cervical lateral bending affect lateral bending and coupled axial rotation. Therefore, in this study, we aim to construct a multibody model of the neck comprising the bones, muscles, and ligaments (including the intervertebral disc) and to analyze its effects on lateral bending and coupled axial rotation when one of the main protagonists is removed. The bone model, which included cervical vertebrae C1 to C7, was bound by 11 types of ligament models and intervertebral disc models constructed from 12 spring models. The sternocleidomastoid (SC), anterior scalene (AS), and levator scapulae (LS) were set as protagonist muscles of the right lateral bending of the neck, and the trapezius was set as the antagonist muscle. The condition under which all muscle models operate was set as the normal condition, and the condition under which one protagonist was removed was set as the removal condition. Under the normal condition, the right lateral bending angle was more than 30° and coupled axial rotation angle was 2.1° on right rotation. Compared with the normal condition, no changes were observed in the right lateral bending angle under the SC removal condition and AS removal condition, whereas the right lateral bending angle markedly decreased under the LS removal condition. Under the SC removal condition, coupled axial rotation resulted in a right rotation of 17.7° and right axial rotation markedly increased. However, under the LS removal condition, coupled axial rotation resulted in a left rotation of 11.2°, which showed a change to left axial rotation. These results indicate that the LS plays a key role in cervical lateral bending, whereas the SC and AS play ancillary roles. Furthermore, the SC and AS inhibited right coupled axial rotation and the LS inhibited left coupled axial rotation.
Noise generated from Shinkansen trains mainly consists of wheel/rail noise, bridge noise and aerodynamic noise. Generally rolling noise and structure-borne noise from a viaduct increase in proportional to the second to third power of the train speed, whereas the aerodynamic noise increases in proportional to the sixth power of the train speed. Past studies showed that the aerodynamic noise becomes dominant at above 300km/h, and the main sources of the aerodynamic noise are the pantographs and bogies. In particular, aerodynamic bogie noise is important even if noise barriers are installed since the number of bogies are much larger than pantographs. This study focuses on the aerodynamic bogie noise for high-speed trains. A new measurement method is proposed to identify the source of the aerodynamic bogie noise precisely in wind tunnel test by using a porous plate. A part of the ground under a bogie is replaced by a porous plate which lets the sound wave propagates pass through while blocking off the air flow. This measurement method makes it possible to determine the sound source of the bogie in detail. It is found that traction motors and gear unit, which are located downstream in the bogie section, are dominant sound sources. Based on this knowledge, two mitigation measures for aerodynamic bogie noise are proposed. It is found that both of them reduce the aerodynamic bogie noise about 5dB in the frequency range of 250 to 315Hz.