This study aims to clarify the effects of the ballast renewal work at low temperature on the inward rail displacements and the axial rail forces of continuous welded rails on sharp curve. The authors measure the inward rail displacements and the changes in the axial rail forces caused by the ballast renewal works on the track having 400 m curvature radius and examine the effects of the work on the measurements. As a result, it becomes clear that the rail displacements occur by the two-day ballast renewal works with a total length of 16 m, even though the curve adjusting is performed after the works. The maximum value of rail displacement is 13 mm across the two-day works. The changes in the axial rail forces across the two-day works are -0.37 to 0.24 ℃ converted into the changes in the neutral temperature. The axial rail forces do not tend to be changed markedly in the compressive direction across the ballast renewal area due to the inward rail displacements. The changes in the neutral temperature due to the ballast renewal works are sufficiently smaller than the changes in that due to the rail creeps or the track maintenance which require the realignment of the axial rail forces or the reinforcement of the lateral ballast resistance.
This study focuses on the formation process of plate shock in an underexpanded jet impinging on a flat plate. The jet discharged from a convergent nozzle is underexpanded when the pressure ratio across the nozzle exceeds the critical value. When the jet impinges on a flat plate perpendicularly, a shock wave called ‘plate shock’ is formed in the jet. In such flow filed the impinging jet violently oscillates, which leads to a complicated flow field with a noise of high sound pressure level. In application of the jet to industrial use, careful attention should be paid to the behavior of jet with noise emission, in particular, the behavior of the plate shock. In this study, the nozzle-plate distance was changed, and the flow field was experimentally observed with attention to the formation of plate shock. Shadowgraph method was used to visualize the flow field and a structure of the jet was examined. As a result two weak shocks were observed upstream of the flat plate and these were found to play an important role in formation and disappearance on the plate shock.
The reduction of aerodynamic noise emitted from a circular cylinder was investigated experimentally by attaching the cylindrical rings arranged in the axial direction of the cylinder. The Reynolds number based on the cylinder diameter d was ranged from Re = (2.0 to 3.9) × 104. The sound pressure level was reduced up to 14 dB by attaching the rings of the diameter Dr/d = 1.3 and the width W/d = 1.0, which was arranged at the spanwise pitch P/d = 4. At this configuration, a 1/3 octave band analysis showed a reduction of the sound pressure up to 26 dB at the frequency band of the vortex shedding from a circular cylinder. The result of the PIV measurements showed that the reduction of the sound pressure is related to the reduction of the Reynolds stress in the wake, which is mainly caused by the suppression of the periodic vortex shedding.
This paper presents a detailed experimental study on the dispersion behaviour of a horizontal water jet with atomization. The study mainly focuses on flow structure of the water jet such as a spread angle and a flying distance. The experiments were conducted by using a flow visualization method. Dimensionless numbers (Reynolds number and Weber number) were introduced to determine evaluation condition on a map of the jet flow pattern. The experimental results were compared with existing theoretical model. The jet spread angle was increased by the atomization at the interface between the water jet and surrounding air, and its angle were correlated with non-dimensional numbers. It was also found that the experimental data of the jet flying distance agree with the theoretical model under the low velocity condition. However, the experimental data showed shorter flying distance compared with the theoretical model due to the atomization under the high velocity condition.
The backward-facing step channel flow in which the Reynolds number is 1080 is calculated to investigate the control effect by a DBD plasma actuator which is activated with continuous drive or burst modulation. The plasma actuator is located on the edge of the backward-facing step. The conditions for the actuator are 3, 5, 8, and 10 m/s of the surface velocity and 50, 100, 150, and 200 Hz of the burst frequency. When the actuator is activated with the continuous drive, the more the reattachment point moves upstream, the more the induced flow by the actuator is strong. When the burst modulation for the actuator is used, the smaller burst frequency makes the reattachment point move further upstream generally. The reattachment point could travel upstream if a huge vortex has a negative vorticity is generated by merging two vortices near the step. This is because that the huge vortex flows downward with the mainstream flow, on the other hands, if this combining two vortices is not appeared, the reattachment point is little changed. In addition, the mechanism for moving upstream for the reattachment point by the actuator is different for using the continuous drive or the burst modulation. In the continuous drive, the strong enough induced flow by the actuator becomes unstable near the step and flows downward with the mainstream flow, but in the burst modulation, the merged vortex from the mainstream flow appears near the step because a certain period by the burst modulation is introduced in the mainstream flow.
A new method to measure the distribution of specific surface area (total projection area of particles in a unit volume) is derived theoretically. The distribution of specific surface area is reconstructed from the intensity of light scattered in the direction of 90 degrees to the travelling direction of the light sheet irradiated on the spray. It is a feature of this method that the specific surface area distribution can be measured quantitatively by taking into account the extinction of the light through the spray. In order to confirm the validity of this method, the specific surface area of the sprays injected from two air blast nozzles arranged in parallel was measured by this method. In addition, the results were compared with the results measured by a light extinction method combined with CT process. The distribution of the specific surface area measured by this method agreed with that by the light extinction method. Furthermore, a method to measure the specific surface area instantaneously in an arbitrary two-dimensional cross section is proposed. In this method, the specific surface area is calculated from the ratio of the light intensities scattered in the directions of 90 and -90 degrees to the travelling direction of two parallel laser sheets. However the verification of this method with actual spray is a future task.
The prechamber combustion characteristics were studied using a constant volume combustion chamber to improve the efficiency of cogeneration natural gas engines. The torch flames generated by a prechamber were used to investigate the effect that a prechamber has on the main combustion. In our previous study, we observed the correlation between the torch flame and the main flame (which is a so-called “prechamber combustion”) as well as the knocking phenomena for various prechamber configurations using a rapid compression and expansion machine (RCEM). In this study, we have investigated the effect of prechamber combustion on main chamber combustion characteristics using a constant volume combustion chamber, especially to study the ignitability of the main chamber.
Flow Accelerated Corrosion (FAC) is a pipe wall thinning phenomenon to be monitored and managed in the power plants with high priority. Its management has been conducted with conservative evaluation of the thinning rate and the residual lifetime of the piping based on the wall thickness measurements. However, noticeable case of the wall thinning was occurred in branch and junction piping (tee tube). It is a problem to manage the section beneath the reinforcing plate of the tee tube; the region where measurement is difficult to conduct with ordinary ultrasonic testing device. In this study, numerical analysis for the tee tube was conducted, and the wall thinning profile due to the FAC was evaluated by calculating the mass transfer coefficient. In the case of the union flow, local wall thinning profile was found near the junction where is covered by the reinforcing plate. This profile showed the tendency of increase in association with increasing of the flow amount from the branch pipe. And, the profiles also have smooth decay tendency from the junction to downstream of the main pipe. Therefore, the amount of the wall thinning beneath the reinforcing plate can be predicted from the location where is deviated from the plate.
The temperature calculation of a practical hydrogen storage tank filled with a metal hydride under development was carried out. The metal hydride was a nano-stractured FeTi (n-FeTi) by mechanical alloying, which has low particle decay and low price. The governing equations used in the calculation were the unsteady two-dimensional heat conduction equations. Expansion and contraction of metal hydride due to hydrogen storage and release were considered as changes in porosity and changes in thermal properties. The change in porosity was treated as the change in energy generated per unit volume. For changes in thermal properties, the empirical formulas based on our experiments were used for the changes in effective thermal conductivity and effective thermal diffusivity due to hydrogenation. A hydrogen storage tank was actually manufactured, and the experimental and calculated results were compared. From the results, it is considered that the use of empirical formulas is important for improving the reliability of calculation results because the change in thermal properties of the packed bed of hydrogen storage alloy due to hydrogenation affects the temperature distribution. In addition, the effect of the presence or absence of heat transfer enhancement fins was evaluated by the calculation. As a result, this calculation can be used to design the heat transfer enhancement fins for hydrogen storage tanks.
The effects of the traveling sound wave generated by the speaker on diffusion flame were investigated experimentally. The sound frequency was varied from 50 to 1000 Hz using two sizes of loudspeakers, whose peak frequency showing the maximum sound pressure amplitude is nearly identical. A spirit lamp was used as the reference (diffusion) flame. Having irradiation of sound, the flame was inclined and stretched toward the traveling direction under specific range of the exposed frequencies and importantly, the effective range of the frequency was found to be quite different in two speakers used in this study. Precisely speaking, the deformed flame length reached its maximum value under the condition of 200 to 400 Hz for small speaker and 50 to 200 Hz for large speaker, respectively. In addition, the velocity distribution around the speaker was measured to reveal that the variation of flame length with respect to frequency, and it was found that the response against the applied frequency was rather close to that of flow velocity, not that of the acoustic pressure amplitude. Further investigation of flow field nearby the speaker clearly showed that the pump-like flow acceleration was induced by the periodic motion of the membrane of the speaker. From the above results obtained, it was confirmed that the effect of acoustic sound on the flame shall be come not only from pure acoustic wave feature but also from the factors depending on the hardware. Without the eliminating the latter effect, nature of acoustic-flame interaction behavior by using acoustic characters (e.g., frequency or acoustic pressure) is not readily available.
Cart control requires propulsion and steering simultaneously. It will impose the user a hard workload in crowded environment. To overcome this problem, we design a safe auto-steering wheeled mobile system. In this paper, the steering is controlled by an attractor controller that entrains the cart to the reference trajectory based on vector field. The trajectory and vector field are designed under non-holonomic constraints, and the controller is designed by functional approximation with an averaging method of the vector field. A cart system is designed and prototyped. The experimental results show that the propulsion force obtained from the user confirms the safety against collision with pedestrian.
As an alternative to the paralyzed arm of hemiplegics, if there is a robot arm and hand that is the same size as a human arm and hand, can grasp daily necessities and work cooperatively with the user’s healthy arm, it would help hemiplegics lives. If the weak force on the grasped object and how the grasped object is pulled can be detected on the robot's finger surface, the robot can grasp objects of various hardness with appropriate forces according to the work, prevent dropping the objects and estimate the user’s handling intention to the objects. The purpose of this study is to propose and develop a small and thin tactile force sensor and a calibration method for correcting nonlinearity to realize the measurement of force and its center position on the robot's finger surface irrespective of the loading area and pressure distribution, and to confirm the usefulness through an evaluation experiment. Measuring force regardless of the shape of the object is difficult for conventional sensors because they are affected by the loading area and pressure distribution. Therefore, we developed a small and thin sensor whose contact surface is a single plate unaffected by the object shape. And this sensor has a structure that the capacitance distributions in the sensor are uniquely determined from the applied pressure distribution to calculate the force and its center position. Additionally, we developed its calibration method to correcting uncertain elements due to the nonlinear property. Through the evaluation experiment, we confirmed that the developed sensor can measure the force and its center position. In conclusion, we confirmed that the proposed method can realize a small and thin tactile force sensor capable of measuring force and its center position irrespective of the loading area and pressure distribution.
This paper describes a new robust controller based on Model Predictive Control (MPC). MPC is one of the useful control methods because it enables to design time response intuitively and to consider the constraint of state and input. However, MPC does not have robustness against modeling errors and disturbances due to the use of a predictive model without considering these uncertainties. Robust Model Predictive Control (RMPC) by using a Linear Matrix Inequality (LMI) or H-infinity control theory has been proposed to improve the robust performance. The theoretical complexity loses the characteristics of the MPC, such as the intuitive design of a controller. On the other hand, Sliding Mode Control (SMC), which is a simple theory, has high robustness compared to H-infinity control theory and RMPC when a system satisfies a matching condition. In addition, the Integral Sliding Mode Control (ISMC) that developed from SMC can constrain the system to the reference model and the response of the target can be made approximate to the response of the ideal system even under the influence of modeling errors and disturbances. It is noted that a controller based on SMC should restrain chattering of control input when applying the controller to a real system. We propose the extended MPC (EMPC) that utilize a matching condition to have robustness against uncertainties. The feature of the proposed control method is not only robustness but only easy tuning of the controller. The effectiveness of the proposed control system is verified by numerical simulation in comparison with the conventional controllers that are PID, ISMC, and MPC.
Tandem control is the control to drive one load with multiple motors. Its basic method is a common torque method. The common torque method is that the position signal and the rate signal from the motor 1 feedbacks to obtain the torque reference value of the motor 1, and the same torque reference value as the motor 1 is given to the motor 2.This method does not cause a motor current difference, but we found the vibration when a disturbance is applied is significant. In this paper, we propose a method that halves the vibration settling time when a disturbance is applied and does not cause steady-state current difference. The method is the average rate feedback method. The position feedback signal is the average position of each motor, and the rate feedback signal is the average angular velocity of each motor. The signal obtained by multiplying the rate difference between the motors by the rate difference control gain is passed through a high-pass filter, and the torque of each motor is corrected using this signal. As a result, in the average rate feedback method, the response of the rigid body mode can be tuned by the rate control gain, and the damping of natural vibration can be improved by the rate difference gain. The response and the damping of the natural vibration can be tuned separately. With the feedback of the rate difference through the high-pass filter, the steady-state current can be made equal between the motors. As another comparison, we also examined an individual rate feedback method that feedbacks angular velocity signals individually. In the individual rate feedback method, the response of the rigid body mode and the damping of natural vibration can be simultaneously improved by the rate control gain. However, current difference occurs between the motors. It is not good because one motor reaches the current limit first due to the current difference.
Vibrational energy harvesting by application of stochastic resonance is receiving more and more attentions at the international level in recent years. However, the vibrational power conversion efficiency is still limited due to small excitation amplitude of the traditional bistable vibration model, and how to develop a high-efficient vibration energy harvester has been become an important research topic. Therefore, this study proposed a diagonally supported spring-mass system as a novel bistable vibration energy harvester using a piezoelectric element. In this system, the ordinary elastic spring has been replaced by an elastic bending plate with a spring; furthermore, the piezoelectric element is attached on the surface of the elastic bending plate to harvest vibration power. On the basis of a comprehensively theoretical analysis, Runge-Kutta method is adopted to propose a numerical analysis method, and the vibrational analysis results are consistent with the measuring results. With the procedure of experimental study, as a result vibrational response amplitude was greatly amplified under the occurrence of stochastic resonance phenomenon.
Acoustic properties of sound-absorbing poroelastic media such as sound absorption coefficient are affected by microscopic structures. However, the design method for microscopic structures of sound-absorbing poroelastic media has not been established and the trial and error approach based on prototypes is required. In this study, a parametric optimization method to design microscopic structures of sound-absorbing poroelastic media is proposed. First, various models of microscopic structure of sound-absorbing material are generated by some sets of microscopic parameters and homogenized macroscopic properties, such as air flow resistivity and equivalent density and bulk modulus, are calculated by the homogenization method. Then, Biot’s parameters are identified for each microscopic structure of sound-absorbing poroelastic material by using non-linear least square method, and the functions that link between Biot’s parameters and the microscopic parameters, such as fiber diameter and pore radius, are derived. Finally, the microscopic parameters of poroelastic materials are optimized by using genetic algorithm (GA) to maximize sound absorption coefficient at prescribed target frequencies. In the verification of the proposed design method, the microscopic structures of fibrous porous material and foamed poroelastic material are optimized.
A vibration power generator produce electricity using environmental vibration, such as floor vibration caused by people walking, vibration caused by cars and trains, and factory piping vibrations. Electric power generated by the vibration power generator is expected to be an alternative to a power source (a battery or the like) used in IoT sensor or the like. There are various types of vibration power generation such as electromagnetic induction type, magnetostriction type, piezoelectric type and electrostatic type. We are paying attention to electromagnetic induction type among them. There have been many studies on electromagnetic induction type vibration power generators, and it can be expected that the generated power will increase depending on each application. However, there are few studies to increase the generated power in the simple configuration of the vibration generator, that is, the configuration using the one-degree-of-freedom oscillator consisting of the magnetic circuit and the spring. Therefore, we constructed a mathematical model that formulated the effect of the magnetic parameters of a vibration generator using a one-degree-of-freedom oscillator on the generated power, and obtained design guidelines for a magnetic circuit for increasing the generated power. Furthermore, the validity of the model was evaluated by comparing the power generation performance test using the prototype and the calculation.
This research presents the evaluation method of contact-type failure level based on nonlinear wave modulation. It is difficult to detect contact-type failures using a linear ultrasonic inspection. The detection method based on nonlinear wave modulation has been proposed to detect the contact-type failure. Nonlinear wave modulation is the phenomenon, which is explained by contact acoustic nonlinearity (CAN) of ultrasonic caused by low-frequency vibration. The SDOF model for nonlinear wave modulation consists of modal mass, modal damping and modal stiffness which coefficient fluctuates caused by CAN of ultrasonic vibration. This model is described by time-varying linear model when the frequency ratio of the frequency of low-frequency vibration to frequency of ultrasonic vibration is sufficiently small. When the fluctuation frequency of coefficient of modal stiffness caused by low-frequency vibration is sufficiently smaller than the frequency of ultrasonic vibration, the instantaneous natural frequency of ultrasonic vibration fluctuates in synchronization with fluctuation of time-varying coefficient of modal stiffness. Therefore, the fluctuation of natural frequency can be used as a novel index for evaluation of failure level independent of viscous damping. In this paper, the estimation method of fluctuation of the natural frequency is proposed and verified using time response analysis. Firstly, the linear time-varying model of nonlinear wave modulation is introduced. The mechanism of fluctuation of natural frequency is explained by introduced model. Secondly, the estimation method of fluctuation of natural frequency based on the linear time-varying model is proposed. The phase fluctuation occurs as the result of the fluctuation of natural frequency. Finally, it is confirmed that the fluctuation of natural frequency can be estimated from time-invariant transfer function and phase modulation. The fluctuation range of natural frequency is the failure index.
This paper deals with the entrainment phenomenon by forced displacement excitation in vortex induced vibration of structures. This phenomenon can occur when a long-period earthquake occurs in a super high-rise structure that may have vortex induced vibration and can occur also when an offshore floating wind turbine is affected by wind and swell simultaneously. Moreover, it is important to examine this phenomenon from the viewpoint of the multi-degree-of-freedom forced self-excited system. By the experiment using wind tunnel and the numerical analysis using shooting method and ordinally numerical integration, following was made clear: (1) Entrainment phenomenon was confirmed in the excitation frequency region including the natural frequency . (2) There is the case that the entrainment region is wider at the higher wind speed than at the wind speed with the largest amplitude by vortex excitation. (3) Regarding the resonance amplitude in entrainment region, there is the case that its amplitude is slightly larger at the higher wind speed than that at the wind speed when the amplitude by the vortex excitation is the largest. (4) The largest vibration amplitude at entrainment is a value almost close to the sum of the largest amplitude at the time of only the vortex excitation and that at the time of only the forced displacement excitation. (5) The experimental results and the numerical analysis results mentioned above were almost qualitatively consistent.
We suggested a novel method to maintain a machined surface quality of a curved surface shape by synchronous motion between two linear axes and a rotary axis with the five-axis machining center. It was demonstrated that the proposed method made it feasible to prevent a machined error due to the quadrant glitch caused by friction of the ball screw and linear guide of feed drive system by the method. Moreover, in the previous report, we discussed the influence of servo characteristic difference between linear axis and rotary axis on the machined shape error to improve machined surface quality and suggested a method to reduce shape error of machined workpiece with an advanced control. However, we have not discussed the errors that influence the shape with this method and suggested an improved method based on non-machining motion. In the present report, we focused on using this method to develop a motion for cutting a circular shape, including approach path during actual machining. First, we developed a model formula for the shape error based on the predicted causes of error. Second, we validated our model based on NC data from an actual end-mill tool. We then determined the most appropriate processing method by comparing cutting results. The causes of error were identified as a circle radius decrement due to the circular interpolation motion of the two linear axes, relative angle difference between the linear and rotary axes, and eccentricity of the circular interpolation motion of the two linear axes because of the outside approach path of the machining tool. Finally, we confirmed an effect on reducing the shape error of the machined workpiece considering differences in the servo characteristics of the three axes by monitoring the cutting force with a wireless tool holder during machining. The results showed that the proposed method greatly decreased the shape error.
When a large earthquake occurs, a boiling water reactor is automatically shutdown through the insertion of control rods among fuel assemblies. A fuel assembly can vibrate in-plane when two seismic waves act on it in directions at right angles to each other in a horizontal plane. Although the state of contact between a control rod and fuel assembly is different from that with one directional input, the effect of the difference on scram time is not clear. In this study, we evaluated control rod insertability under bi-directional excitation inputs using a dynamic insertion model of control rod. Sine waves were used as input waves, and their frequency corresponds to the first natural frequency of a fuel assembly. By changing the amplitude and phase difference of the input wave, we simulated the behaviors of the fuel assembly, such as vibration direction and whirling under bi-directional excitation inputs. As a result, we concluded that a comparatively long scram time was obtained when the fuel assembly vibrated in the direction orthogonal to the surface of the control rod blade. Additionally, as the phase difference between two horizontal inputs increased, there was increase in the scram time because the number of contacts between the control rod and the fuel assembly increased.
A novel structural synthesis of a mechanism based on the multibody kinematics is proposed in this paper. Instead of the degree-of-freedom analysis by the Grubler’s equation, numbers of the generalized coordinates and those of the constraint¨ equations are introduced for the number synthesis of the mechanism. Sufficient and independent constraints which satisfy the number synthesis are described for the structural synthesis. The Jacobian matrix is derived by the derivative of the constraint equations with respect to time. By using the generalized coordinates, the proposed synthesis is widely applied for the lower degree analysis such as the three-dof planar mechanism, as well as the six-dof spatial mechanism without modifying the primary calculation method of the multibody kinematics. The lower degree analysis removes the redundant coordinates and over-constrained conditions, thus improves the complicated calculation, such as analyzing the planar mechanism using six-dof full spatial analysis. The proposed method is applied to the synthesis of the two-dof differential screw mechanism. The differential screw is comprised of two screw-nut mechanisms, each of them has two mechanical elements. The differential screw mechanisms are divided into two types; The coaxial serial-type differential screw mechanism in which one of the end of each non-driven mechanical element is directory connected to each other, and the parallel-type in which the non-driven mechanical element is connected via mechanical pairs. The rotational pair and the sliding pair are treated as the zero lead and the infinity lead of the screw pair as well as the general helix screw pair. A total of eight generalized coordinates, six kinematic constraints and two driving constraints are set for the number analysis. By evaluating the singularity of the Jacobian matrix from the generalized input velocity and that of the output element, forty combinations of the parallel-type differential screw mechanisms and twenty-four combinations of the serial-type are derived.
In the past several decades, electro medical equipment has been developing to enhance surgical technologies. Using electro surgical knife is very common in everywhere of medical scene now a days. An electro surgical knife is consisted with power supply, metal tip and return electrode. In the case of using it to stop bleeding by coagulation mode, the tip surface is frequently covered by coagulated blood, then it is not able to discharge again. It means that the surgeons should replace it to new metal tip to continue surgical operation. In order to overcome this problem, some tips are covered by silicon type coating to prevent coagulated blood adhesion. However, it still has problems of continuous using, low heat invasiveness for human organs and how design such tip surface. In this study, three different type coating tips and a non-coated tip were prepared to compare temperature rising abilities and coagulated blood adhesion on the surface. As a result, fully surface coated types and blade’s edge uncovered type realized excellent prevention ability of blood coagulation adhesion onto surface. Especially for the side edge uncovered type, it exhibited low temperature rising ability after the temperature exceeded 100 degree C. This result indicated that side edge uncovered type is one of the suitable design to prevent exceed temperature rising.
There are many things to consider about the fatigue of drivers during long time driving, such as the driver’s driving posture. In order to confirm the degree of fatigue, many studies have been conducted on methods of measuring fatigue during driving. However, it takes time and effort. So, the simple measurement method was needed. Therefore, we focused on the blood lactate value used as a physical fatigue evaluation characteristic mainly for muscles. In this study, we defined the difference in blood lactate levels before and after driving as an increase amount and proposed objective evaluation of muscle fatigue. At first, we verified whether blood lactate levels changed by driving experiments for long time. Then, we verified whether there was a difference in the results of the proposed fatigue evaluation method with or without lumbar support. From these results, we showed that the blood lactate value evaluation method is effective for the muscle fatigue evaluation of the driver for a long time driving.
As the authority of the self-driving system becomes large, the driver’s contribution to the safety decreases involving drowsiness or inattention to the driving. A sudden disengagement of self-driving system may result in a critical incident. Therefore, a monitoring system of the driver’s condition is required for self-driving car of level 2 or 3. We analyzed the eye movement model of driver watching preceding vehicle aiming at the application to the estimation of attentional state. Input and output of the eye movement model are the position of the preceding vehicle and the eye movement, respectively. The eye movement models were identified through driving simulator experiments. The relations between the model parameters and the attention degree to the preceding vehicle, which was varied by subtask, were studied. Statistical analyses revealed that the steady gain of eye movement model correlates with the attention degree of driver. This correlation can be applied to the future estimation system of driver’s condition.
The dynamic behavior of railway vehicle is often tested by roller rig equipment and this test is very useful. However, it is known that contact condition on roller rig is different from the case that wheels run on rail. Wear test using roller rig equipment is also conducted and very few studies have studied on the effect of these difference on wear. To understand the wear phenomenon on roller rig strictly, it is necessary to grasp influence of difference in dynamic behavior on wear characteristics. In this paper, from a view point of multi body dynamics, wheelset / roller rig analysis model is constructed in consideration of the 3 dimensional contact geometry between wheel and rail. By conducting numerical analysis, differences of contact condition between the case wheel runs on rail and the case wheels runs on roller rig are compared and examined. As a result, when the wheelset has a yaw angle on roller rig, the wear depth on roller rig increases compared to the wear depth on rail because the longitudinal creepage increases and normal contact pressure also increase due to the decrease in the size of contact patch.
Railway bogie frames are commonly constructed by welding several components. For a frame design, it is vital that all its welded joints have satisfactory strength and durability during their service life. This paper focuses on as-weld joints. The objectives include clarifying the influence of experimental stress assessment methods and developing analytical tools which are applicable to the design of as-weld joints in bogie frames. Static load tests were conducted on cruciform as-weld joints and machined test specimens using three different strain gauge attachment positions; finite element analyses (FEA) were performed. The results clarified that a new stress assessment method where the edge of strain gauge is attached at the weld toe shows the smallest deviation and little dependency on toe curvature radius variations. This suggests that the edge type strain gauge attachment is the best out of the three methods for stress assessment of as-weld joints. Moreover, the analytical stresses calculated from the FEA results agreed well with the experiments using the displacement differences corresponding to the strain gauge length. Appropriate FEA model shape and mesh size for the weld toes are proposed to calculate the edge type gauge stresses for the design of as-weld joints in bogie frames.
Planning elevator installation in high-rise buildings, it is important to co-create with not only elevator specialists but also multiple stakeholders such as building owners and architects. Therefore, we should share current issues and find consensus on measures among the multiple stakeholders. Then, we also should prototype to solve the issues, and make effects visible. To co-create the planning effectively, we have developed a people flow simulator that enables us simulation of lining up behavior for elevator inside high-rise building. It simulates based on a condition, which include a building layout and traffic demands, defined by a planning. It shows an impact of changes in building conditions and elevator specifications with an easy-to-understand 3D animation. It allows us easily to find issues from the planning and discuss measures with multiple stakeholders. Additionally, we verified an accuracy of developed simulator comparing actual index which calculated from the logs and simulated index which calculated by the simulator. As a result of accuracy evaluation, we have concluded that the simulator has enough accuracy.
In vacuum chambers, such as those at a ground test facility, pressure is higher and the gas resident time is longer than in space because such chambers are surrounded by walls and vacuum pumps. Investigating gas flow near a vacuum pump that influences the gas flow can be useful for evaluating differences of dynamic pressure near a high-vacuum pump. A parallelepiped vacuum chamber was measured for this study using two rarefied dynamic pressure measuring devices with approximately 0.004 mPa dynamic pressure resolution. Measurement results and evaluation indicate that flow to the high vacuum pump occurs. The dynamic pressure at the measurement point near the vacuum pump is proportional to the solid angle prospected to the high vacuum pump. The vacuum chamber wall reflection influences the vacuum evacuation and flow. Results show that spacecraft devices and the system should be operated in a region with a small solid angle to the high vacuum pump to prevent any influence from vacuum evacuation. Flow measurement and evaluation near the chamber wall using this measuring device are expected to contribute to characterization of the vacuum pump performance. Moreover, more detailed evaluation of gas flows within the vacuum chamber using a more precise resolution-measuring device might be useful for research and development of vacuum test facilities.