Kiyoshi Sogabe

Dynamics of track/wheel systems on high-speed vehicles

For high speed railway vehicles, we consider a vibiation of flexible track/wheel system It is very important to deal with the complex phenomena of high-speed vehicles that can be occurred in the vertical vibration of the system From a viewpoint of multibody dynamics, this kind of problem needs accurate analysis because the system includes mutual dynamic behaviors of rigid body and flexible body The simulation technique for the complex problems is also discussed We consider the high-speed translation, rail elasticity, elastic supports under the rail and contact rigidity Eigen value analysis is also completed to verify the mechanism of the coupled vertical vibration of the system

Numerical and Experimental Approaches on the Motion of a Tethered System With Large Deformation, Rotation and Translation

In this paper, we discuss the motion of a tethered system. In general, a tether is a cable or wire rope, and a tethered system consists of a tether and attached equipment. A tethered subsatellite in space is an example of this system. We consider 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. Using this method, the motion of a flexible body with large deformation, rotation and translation can be expressed with the accuracy of rigid body motion. The combination of flexible body motion and rigid body motion is performed and the interaction between them is discussed. We also performed experiments to investigate the fundamental motion of the tethered system and to evaluate the validity of the numerical formulation. The first experiments were conducted using a steel tether and rubber tether in gravity space. We also conducted experiment of the motion of the tethered system with a rigid body in microgravity space. The numerical solutions using the proposed methods for the modeling and formulation for the tethered system are in good agreement with the experimental results.Copyright

Seismic response analysis models of an oil storage tank with a floating roof

Purpose – The purpose of this paper is to investigate the effects of the finite element models on the response of a free surface or a floating roof, which is important for safety assessment of oil storage tanks.Design/methodology/approach – Structural analyses of shell structures using the three‐dimensional finite element method (FEM), potential flow analyses by FEM, and fluid‐structure interaction analyses by strong coupling of the structural and fluid analyses were performed. In‐house software was utilized for computations shown in this paper except the solver for non‐symmetric sparse matrix.Findings – A model with a rigid tank and an elastic roof was confirmed to be able to perform the seismic response analysis most effectively from the viewpoint of computational cost with no reduction in accuracy.Research limitations/implications – The stress distribution on the floating roof will be evaluated to assess the safety of oil storage tanks subjected to seismic waves in the future research.Originality/value...

Analysis on Wheel Load Variation in Coupled Motion Between Running Wheel and Track with Irregularity

The decrease of wheel load variation is effective in enhancing stability, safety of high-speed train. In this paper, we conduct the simulation analysis on wheel load variation in order to figure out the mechanism of wheel load variation in consideration of track irregularity such as sine wave and to investigate the influence of the relation between unsprung mass and static wheel load. As a result, we figured out as follows : The wheel load variation at high speed increases according as the wheel speed because the vertical inertia force of wheel increases widely by high-speed running along the flexible rail with irregularity. If sleeper passing frequency and the irregularity passing frequency is close to the primary natural frequency of the wheel/rail system, the wheel load variation becomes larger. The decrease of wheel mass is very effective in decreasing the wheel load variation in comparison with the decrease of static wheel load.

Motion of a Tethered System Under Attitude Control With Large Deformation, Rotation and Translation

In this paper, we discuss about the motion of a system consisting of a very flexible body and rigid bodies at its end under attitude control to the end body. A tethered subsatellite in space is known as an example of this system. We consider two mathematical models for flexible body. First, the flexible body motion in a plane is described by using Finite Element Method formulation. Second, the flexible body in planer motion is described by using Absolute Nodal Coordinate formulation. In this method, it is easy to describe the motion of the flexible body with large deformation, rotation and translation displacement. We can consider interaction between the deflection of the flexible body and the motion of the rigid bodies in these methods. Furthermore we attempt to control the attitude of the end body using a reaction wheel. The flexible body motion is influenced on the motion of the rigid bodies under attitude control of end body. The control technique consists of an attitude control by the reaction wheel and a control by the reaction wheel with the joint torque control to cancel accumulation of angular momentum. First, eigenvalue analysis is carried out where control gain changes. Second, the motion under controlled system is discussed under free vibration. We compared these results. Furthermore we treat large deformation problem. The end of flexible body moves horizontally. As a result, we confirm the interaction between flexible body and rigid body under the attitude control.Copyright

Steady-State Response of the System which Consists of Shear Loading Rubber Isolators and a Mass

In order to find the mechanism of the steady-state response of a system which consists of shear loading rubber isolators and a mass, experiments for the steady-state frequency response of the system and dynamic tests for the rubber vibration isolators are conducted under the various conditions of ambient temperature and strain amplitude, and the results are considered and discussed. As a result, it is found that the amplitude and temperature response of the system interact via the temperature-dependent dynamic properties and the internal heat-generation rate of the vibrating rubber isolator. On the basis of this result, a new method for the analysis of the steady-state response of the system is presented. Using this method, the influence of system parameters on the response is also discussed.

Steady-State Response of the System which Consists of Shear Loading Rubber Isolators and a Mass.

A torsional dynamic vibration absorber for a crankshaft, which consist of a vibroisolating rubber component and a moment of inertia, is used at relatively high temperature and frequency. It is important to analyze the steady-state response of such a system. The most simplified model consists of shear loading rubber isolator and a mass. We have already suggested an analytical method of the system for which mechanical nonlinearity and heat generation have been taken into consideration. The validity of it has been examined by comparing analytical results directly with experimental ones. In this paper, we give more detailed consideration and clarify the mechanism of the response. The system can be characterized as a system which couples the mechanical nonlinearity, depending on temperature and internal heat generation. As a result, we can derive again the analytical method in the previous report.