Terumichi Yoshiaki

The decrease of wheel load variation is one of the most important issues which must be solved in railway dynamics. The purpose of this study is to make clear the mechanism of wheel load variation by the numerical simulation by the analytical model which is based on the concept of the multibody dynamics. In this study, we were able to figure out the in-depth mechanism of the wheel load variation, particularly, concerning the phenomenon that the wheel load variation suddenly decreases with more than wheel velocity at which the 1^<st> natural frequency of system consists with the irregularity passing frequency.

In this paper, from a view point of multibody dynamics, the modeling and the formulation for rocking motion of a rigid body system considering contact geometry are proposed. The rigid body system is composed of three rigid bodies. The bottom rigid body has restriction of contact geometry between a support. The formulation for the rigid body that has the constraint is completed by augment method. The formulations for the other rigid bodies are completed by Lagrange equation. When the support is given oscillation disturbance in a horizontal direction, we note the vibration and the rocking motion of the rigid body system. In this case, we discuss an influence of the disturbance and the stiffness between rigid bodies.

The characteristic of vibration on railway system is that due to multipule wheels continuously passing on railway track and interactions between the wheels influence contact force. Contact force is thought to influence ride comfort and safety of high speed trains. In this paper, from a view point of multibody dynamics, the modeling and the formulation are proposed and we carried out numerical simulation on contact force fluctuation of high speed train in order to investigate the effect of the interactions between the wheels. As a result, it can be pointed out that natural frequency of the wheel/rail system and phase difference of contact point displacement on influence contact force fluctuation.

The rammer is used in order to firm the ground. Then the vibration of its handle causes the poor circulation to the hand, and lead to the Raynaud's disease. We consider attaching the multi-particle collision damper in the rammer to attenuate the vibration of the handle. Vertical vibration and the torsional vibration are generated on the handle. Since the handle rotated by the movement of rammer, we focused to the torsional vibration. In this study, the characteristic of this damper to torsional vibration examined through experiments and simulation. A number of particles were put in the cylindrical vessel. In addition, the division plate was installed to colliding the particles. As a result, it turned out that the torsional vibration decreases if the particle of a suitable particle diameter and filling ration of particle for the vessel was filled.

In this paper, from a view point of multibody dynamics, the modeling and the formulation for development of corrugation on the elastic rail under the motion of wheel with contact rigidity is proposed. The formulation for the rail motion is completed by A.N.C.F. We discuss about the effect of contact rigidity and elastic support on the contact force fluctuation. It is confirmed that the contact rigidity and the elastic support influence on the vibration mode of this system. This leads the fundamental knowledge of the prevention of the corrugation development.

This paper deals with the experimental study of the growing process of the corrugation on a flexible truck. The flexible track/wheel corrugation simulator was made in the laboratory. A rolling wheel driven with constant velocity runs around on the track. From an experiment results it is clarified that the wave length of the corrugation with the natural frequency of the system depends on the position of the disturbance on the track. It is also pointed out that the contact rigidity, flexible track and a little slip should be considered as the main factor of the corrugation development.

In this paper, the modeling and the formulation is proposed to analyze three dimensions behavior of the elastic rolling disc precisely, and is inspected its validity. The proposed model in this paper consists of a rigid body and some particles of mass that have voigt elements for the local part deformation. This model can grasp both the shape of the elastic rolling disc and the local part deformation in the contact area.

In this paper we discuss the motion of a tethered system. We considered the tethered system consisting of a very flexible body (the tether) and rigid bodies at one end as our analytical model. A flexible body in planer motion is described using the Absolute Nodal Coordinate Formulation. The combination of flexible body motion and rigid body motion is performed and interaction between them is discussed. We performed experiments to investigate the fundamental motion of the tethered system and to evaluate the validity of the numerical formulation. We conducted experiment of the motion of the tethered system with a rigid body in microgravity space. The numerical solutions using the proposed methods for modeling and formulation for the tethered system are in good agreement with the experimental results.

From a viewpoint of multibody dynamics, we propose modeling and formulation for such a motion of the rolling disks, and discuss about the mechanism of corrugation development based on the result of the numerical simulation. The unilateral contact between two rolling disks is expressed as a constraint condition on contact point and its surface profile changes with time due to wear development. In particular, we focus on the self-excited vibration with time lag for two disks with rolling contact. In this system, a phase difference between the corrugation profile and the contact force fluctuation influences corrugation development.

In this paper, the experimental study of corrugation development on a flexible track is discussed. The flexible track / wheel corrugation simulator was made in the laboratory. A rolling wheel driven with constant velocity runs around on the track. We take note on the vertical vibration of the system, which is consisted of wheel, contact rigidity and flexible track. The vertical disturbance is also given on the track surface to give a little slip. Using the experimental results, we discuss about the characteristics and the mechanism of the corrugation development on the flexible track.

Various mechanisms in mechanical systems have rolling contact. It is known that the wavy surface caused by wear, called corrugation, generates and develops due to the rolling contact of two disks under a certain condition. In this paper we focus on fluctuation of slip and contact force between two rolling disks. It is expressed as a restraint condition on the contact point that unilateral contact and the surface shape changes with time due to its wear. Modeling and formulation for such like a problem are proposed. Using the numerical results, we discuss about the characteristics of this closed loop system and the mechanism of corrugation development on the disk surface from a viewpoint of the phase shift between the contact force fluctuation and the worn surface profile.

In this paper, a motion of a rolling wheel on a elastic rail supported elastically with contact rigidity and slip is discussed. The accurate numerical simulation technique for the interaction between the wheel motion and the rail motion is required because of the difficulty of the experiment in practical systems. This motion analysis also includes the contact problem and the flexible multibody dynamics problem. In the system motion with high speed, the amplitude of lateral vibration of the rail increases comparing with the ordinary speed. We pay attention to the motion of the contact point between the wheel and the rail. The effect of the coupled motions between the rotation and the rail vibration, the elastic contact and the rail vibration and so on are clarified quantitatively.

The purpose of this paper is to discuss about how to model and formulate of the nonstationary vibration of a string with time-varying length using finite elements. The string is hung vertically and excited sinusoidally by a horizontal displacement at its upper end. It is modeled and formulated, using the method of multiple scales with a nonlinear scale. In the case that the string moves with the passage through the resonance, the numerical results using the proposed method is compared with the analytical approximate ones and its validity is confirmed.

In motion analysis of vehicles, dynamic behavior of a tire is an important factor. Therefore, many models expressing the dynamic characteristic of a tire have been proposed. They are modeled considering the static characteristic of a tire and express the steady state characteristics with sufficient accuracy. However, It is important to investigate the transitional dynamic characteristic of a tire with sufficient accuracy, because it affects the vehicles motion during especially curving, accelerating or breaking. In this paper, the tire model that can express the static, the steady state and the dynamic characteristics with sufficient accuracy is proposed.

We have examined the behavior of the particles in a two dimensional system by using the rotary barrel with round section and the particle with round section up to now, for the examination about the factor of the segregation in the barrel which rotates around the horizontal axis. Then, we have demonstrated that the segregation occurred depending on the relation between the diameter and the mass of two kinds of particles. In this study, we have examined the behavior of the particles with square section, which were filled into the rotary barrel with the round section through the experiment and the simulation using Discrete Element Method (DEM). As a result, we don't found the segregation in our experiment and simulation.

In this study, we propose the modeling and the formulation for the motion of an elastic rail/wheel system with contact rigidity and flexible track. In numerical approach, the treatment for the system running with high speed requires circumspection. We clarify the calculation condition using A.N.C Formulation and constraint of the contact between a wheel and a flexible rail. Some numerical results for the effect of high speed on the vertical vibration of the rail/wheel system are also discussed.

In this study, we attempt to propose the modeling and the formulation for the motion of two wheels with contact rigidity on the elastic rail with support spring. The formulation for the rail motion is completed by A.N.C. formulation. The coupled motion between the wheel and rail is expressed, considering the contact force and the rail deformation. We discuss about the effect of contact rigidity, support spring and elasticity of the rail from a viewpoint of repeated passage of wheels.

While operating the contact rotating systems, a periodic polygonal deformation pattern is formed on the peripheral surface of a roll. Such phenomena is called the pattern formation phenomena. The occurrence mechanism of pattern formation phenomena for some contact rotating systems was clarified by regarding the cause of phenomena as the unstable vibration generated in a time delay system. Linear analysis is sufficiently effective in order to estimate the occurrence region of the unstable vibration. However, it is not possible to know behavior of large vibration, because the effect of the nonlinearity increases as the vibration grows. In this report, the authors add the adequate nonlinearity to cylindrical grinding systems and analyze the vibration behavior of the system. The harmonic balance method is used to calculate the periodic steady-state vibration approximately. In addition, the stability analyses of the periodic steady-state vibration are carried out from the characteristic exponents obtained from the variational equation. Furthermore, influence of initial condition and nonlinearity upon the vibration behavior was in vestigated.

In the field of surface treatment, barrel polishing is an extremely efficient processing method for the surface smoothing treatment of a large number of workpieces. However, workpieces and grinding materials may separate depending on the conditions. In this study, two kinds of particles of different materials and sizes were filled into the planetary barrel that simultasneously rotates around the horizontal axis and revolves around the vertical axis, and the behavior of these particles was examind through experiments and simulations using the discrete element method (DEM). The rotary barrel with the cross section of a regular polygon was used. As a result, it was demonstrated that the distribution of two kinds of particles in segregation might be inverted by the difference between the cross-sectional shape of the rotary barrel, even if the same combination of two kinds of particles was filled.

In this paper we discuss about motion of a system consisting of a string and rigid bodies at its end. A tethered subsatellite in space is known as an example of this system. The string in planar motion is described by using Absolute NodaI Coordinate method. In this method, it is easy to describe the motion of the string with a large deformation, rotation and translation displacement. The string motion influences the motion of the rigid bodies. In other words, the connection point is constrained by the end of the string. Therefore the motion of the system is calculated using differential algebraic equations. First, the motion of the string with a large deformation, rotation and translation displacement is simulated for a simple case. The numerical results agreed with the experimental results qualitatively. Second,the simulations for the some cases of a string with rigid bodies, a string that doesn't have deflection with rigid bodies, and a string with a simple mass are performed. In these cases, an end of the string moves horizontally. As a result, the mechanism of the interaction between the string deflection and the rigid bodies rotation is made clear numerically.

This paper introduces experimental set-up for corrugation development on the flexible rail. The wheel drives on the track, which have flexible rail in part of track with longitudinal slip. There is the ruggedness at the center of flexible rail to generate the longitudinal slip. This experimental equipment also can generate the longitudinal slip by the slip generator that gives difference between wheel rotation and wheel velocity. So corrugation develops on the flexible rail gradually. We measured the corrugation profile by laser displacement sensor.

In this study, we attempt to propose the modeling and the formulation for the motion of wheel on the flexible rail with contact rigidity and slip. The formulation for the rail motion is completed by A.N.C formulation. The coupled motion between the wheel and rail is expressed, using the contact force and the rail deformation. Due to the translation of the wheel, Coliori's inertia is taken into account. Moreover we switch the equations of motion to solve for the state of slip and non-slip motion. We discuss about the effect of slip, contact rigidity and flexibility of the rail on the system motion.

This study is focused on dynamic behavior of rolling elastic disc in collision and understanding its mechanism. The analytical model and formulation is proposed for the state of contact of rolling disc with considering the effect of sliding, friction, local elasticity and velocities. The local elasticity shows the vertical and rotational displacement and the difference between the center of gravity and the contact point. The velocities are horizontal, vertical and rotational velocity. As the result, in comparing of the numerical results and the experimental results in collision, we can obtain the good agreement.

In this paper, we discuss growing process of the self-excited vibration in cylindrical grinding that is caused by the regenerative effect analytically. It is reported that frequency follows the variation of work speed experimentally. We formulate a model that is a system with 2 degree of freedom, and simulate in time domain by using it. Transit amplitude chatter vibration simulated is in good agreement with experimental result. As a result, it is shown that are variation of band of speed and the rate of speed affect growing process of the self-excited vibration.

The investigation of the cause of the segregation that arises during barrel finishing is desired, because the workpiece is not mixed with abrasives. Fundamentally, the motion of the workpiece and abrasives is equal to the motion of the discontinuous objects in the rotary barrel. Therefore, if the motion of the particles in the rotary barrel and characteristics of the segregation are known in various conditions, that knowledge can be used in order to investigate the cause of the segregation and the optimum machining condition. In this study, the bahavior of the particles in the planetary barrel which rotate about its horizontal axis and revolve around its vertical axis was examined through experiment and analysis using DEM (Discrete Element Method). As a result, it was demonstrated that the segregation was not generated by the relationship between length and inside diameter of the rotary barrel.

Barrel polishing used in surface finishing is a very efficient processing method. However, the workpiece may have separated from the abrasive depending on the processing conditions. Though the machining condition has been determined based on experiment and experience in the expert, it is expected that the numerical simulation of the behavior of workpiece and abrasive examine it. In the barrel, compressive forces, shearing force and frictional force, etc. affect workpieces, abrasive and wall. Therefore, it is important to know the motion states of abrasive and workpieces, etc. in order to examine machining condition and cause of the segregation. In this study, the behavior of two kinds of particles in which material or diameter differ in the rotary barrel was examined both experimentally and numerically by discrete element method (DEM). To begin with, the behavior of particles in the rotary barrel that rotates about its horizontal axis in a two-dimensional system was fundamentally examined in order to specify the generation factor of the segregation. Secondary, the behavior of particles in a three-dimensional planetary barrel was examined. Then, the figure for the condition of the segregation of filled particles is shown, examining distribution rate of particles. As a result, it was demonstrated that the segregation is the combination of diameter and mass of the filled particles in both motion forms.

We consider about motion of a rolling wheel with contact rigidity, slip and interaction with the rail motion. Railway systems, elevators, transport systems in the factory and so on are mentioned as good examples of practical problems. For simplicity of analysis, moving load or moving mass-spring system on rail is often adopted as wheel/rail system. Such simple models for calculation give useful results for many cases. However, there are some problems that need the more detailed models for wheel/rail systems in order to discuss the contact force fluctuation. In the study, we propose the approach for the slip motion of the wheel, using the distance between the center of the wheel and the contact point as an index for the elastic contact. We also attempt to formulate the constraint conditions for the coupled motion of the wheel and rail with dynamic load. Furthermore, it is shown that the rail motion and the contact rigidity influence on the slip motion.

In this paper we discuss about dynamic response of a tethered system under attitude control of end body. The system in consideration is composed of a string and rigid bodies attached at its end. We formulate the motion of the string taking into its flexibility. We attempt to control the attitude of the end body. The control technique is consists of attitude control by the reaction wheel, attitude control by the joint torque, and attitude control by the reaction wheel with the joint torque control to cancel accumulation of angular momentum of reaction wheel. First eigenvalue analyses were carried out for these cases where control gain changes. Second the motions of the controlled system are discussed under the free vibration and forced vibration.

Various mechanisms with rolling contact are used in mechanical systems .In this paper we focus on fractuation of contact force between rail and wheel. The following assumptions are considered; Motion of the wheel is constrained in planar plane. The rail and wheel are constantly in contact. We switch the equations of motion to solve for the conditions of slip and constraint. In those equations, the effect of slip and contact rigidity is taken into account. Some numerical results for the wheel motion with slip are shown, comparing with friction force and tangential force.

While operating the contact rotating systems, a periodic polygonal deformation pattern is formed on the peripheral surface of a roll. Such phenomena is called the pattern formation phenomena. The occurrence mechanism of pattern formation phenomena for some contact rotating systems was clarified by regarding the cause of phenomena as the unstable vibration generated in a time delay system. Linear analysis is sufficiently effective in order to estimate the occurrence region of the unstable vibration. However, it is not possible to know behavior of large vibration, because the effect of the nonlinearity increases as the vibration grows. In this report, the authors add the adequate nonlinearity to some contact rotating systems and analyze the vibration behavior of the system. The harmonic balance method is used to calculate the periodic steady-state vibration approximately. In addition, the stability analyses of the periodic steady-state vibration are carried out from the characteristic exponents obtained from the variational equation. As typical examples, the nonlinear vibration phenomena in a viscoelastic system and a grinding system are investigated from the numerical computational results.

In this paper, we discuss the dynamics of a rolling wheel with contact rigidity and slip. We propose the approach for formulation, using the distance between the center of the wheel and the contact point as an index to the elastic contact for this problem. We discussed about the generation and disappearance condition of slip with dynamic load and initial vertical displacement, using some results for simple cases. It is shown that contact rigidity influences on the time when slip generates or disappears and duration time of slip.

In this paper we discuss about motion and vibration of a tethered system. The system in consideration is composed of a string and rigid bodies attached at its end. We formulate the motion of the string taking into account large deformation, rotation and translation. The numerical simulations for the some cases of a string with rigid bodies and a string with a simple mass are performed. It is shown that we have to notice the interaction between the string deflection and the rigid bodies rotation.

The elucidation of the segregation that arises in the barrel finishing is desired. This study concerns the planet barrel with rotation of the horizontal and vertical axis circumference. The barrel was filled with two groups of objects of differing material and diameter, and the behavior of objects was examined by experiment and simulation using DEM (Discrete Element Method). Then, the cause of the segregation was examined in comparison with experimental and simulation result. As the result, experiment and simulation by DEM showed the good coincidence, and two groups of objects segregated for running direction of the barrel in front and rear.

This paper presents study on mechanism of corrugation development with longitudinal slips. To investigate the mechanism of corrugation, the authors built corrugation simulator which could reproduce corrugation phenomenon. In previous study, the effect of steady state longitudinal slip on corrugation development is cleared in experiments. In this paper, this mechanism of corrugation development was considered by numerical analysis. It was found how the longitudinal slip effects on corrugation development.

It is known that there are some problems about the mechanical system with both collision and rolling contact. But they haven't been discussed widely to solve more general cases with elasticity such as rubber tires of vehicles. So this study is focused on dynamic behavior of rolling elastic body in collision and understanding its mechanism. Then, the formulation is proposed for the state of contact of rolling ball in collision with considering the effect of sliding, friction and elasticity, in order to accomplish the numerical simulations for such a system. As the result, it is shown that there are some differences in the displacement and rolling speed after collision between the methods with elasticity and without it.

The formulation for motion of a string with large rotation and large displacement is discussed. It is assumed that the tension acting on a string is uniform and the gravity force acting on a string is ignored. The shape of the string in the planar motion is described by acting on a string is small by using Finite Element Method formulation on absolute nodal coordinate. Numerical simulation results in the two cases. One is the case that the string motion is coupled with large deformation and longitudinal vibration. Another one is the case that the end of the string is moved with large displacement.

Application of a system with a string has various possibilities for the engineering in the extreme environment. The system under consideration in this report is composed of a string and rigid bodies attached at its end. The purpose of this report is to understand a dynamic behavior of the system. It is investigated that the natural frequencies of the linear system with a rigid body change with a string length. The steady state response for forced oscillations and the nonlinearity governing the motion of the system is examined.

Analytical model for Rail/Wheel system is composed of a wheel and a flexible beam fixed at the both ends in this study. The expression of constraints of constraints for elastic body in rolling contact coupled with the motion and vibration of beam is proposed. The following the assumptions are considered; Motion of the wheel is constrained in x-y plane. Slip of a wheel is ignored. The rotation of the wheel, the linear contact stiffness between the wheel and the rail and the large rotation and deformation of the beam are considered. Elastic body in rolling contact is expressed using the distance between the contact points and the gravity center of the wheel, which is function of the time.

It is generally accepted that self-excited vibration in cylindrical grinding is caused by the regenerative effect. In this paper, the stability of the system with the rotation speed of the work is discussed analytically and numerically. The stability boundaries are examined by using the characteristic equation. Each number of polygons, natural frequency, has the unstable region with the rotation speed of the workd. The amplitude and number shift of the convex polygon of the work in steady state is determined using the averaging method with the nonlinearity of the damping force taken into consideration. The effect of the work speed on the self-excited vibration is also discussed analytically and numerically.