Seiji Komiya

Computational model of a Shinkansen train running on the railway structure and the industrial applications

Abstract In this paper, an efficient numerical model for the dynamic interaction analysis of a Shinkansen train (bullet train) and railway structure is given. The motion of a Shinkansen train is modeled in multibody dynamics with nonlinear springs and dampers employed. A simple and efficient mechanical model for interaction between wheel and rail is described. The railway structure including the track is modeled with various finite elements. A nonlinear spring element based on a trilinear elastic–plastic material model is devised to express the elastic–plastic behavior of parts in the structure effectively for practical problems. Combined transient dynamic response of the train and railway structure is obtained by solving the nonlinear equations of motion using a modal method. A computer program DIASTARS has been developed for the interaction analysis of a Shinkansen train and the railway structure. The visualization program has been developed to visualize the combined dynamic behavior of the train and railway structure. Applications to industrial problems are demonstrated.

Simulation and visualization of a high-speed Shinkansen train on the railway structure

The equation of the combined motion of a Shinkansen train (bullet train), rail, and the railway structure is described, and an efficient numerical method to solve the combined response is discussed. Mechanical models for the train with as many as 16 vehicles connected and for the interaction between wheel and rail are described. A computer program for the simulation of a Shinkansen train running on the railway structure at high speed has been developed. A visualization program, VIS, for the animation of dynamic motion of the train and railway structure has been developed. Numerical examples are demonstrated.

Ultrasonic Wave Propagation Analysis for In-Process Monitoring of Stamping

The servo press has high potential for producing high precision mechanical parts. However, small gaps between dies and workpieces tend to exist even in servo press stamping, and the potential of the servo press has not yet been fully utilized. The reason for this is conventional presses do not have feedback control systems, and the lack of a suitable method of sensing contact information in real time causes deterioration in the accuracy of products. If slide motion could be controlled by contact information, the small gaps could be removed. To solve this problem, the authors have developed a method of monitoring the contact states between dies and workpieces during the stamping process. The method uses ultrasonic wave reflection and transmission at the contact surfaces and was proved to be able to monitor contact pressure by using a simple geometry experimental die apparatus. Finite-difference time-domain (FDTD) numerical simulation was conducted in this study to obtain better understanding of wave propagation through dies and workpieces. The results obtained from this FDTD simulation visualized wave propagation that could not be experimentally measured. Some of the major results obtained are as follows. 1) When a thin metal sheet is pressed between dies that have inclined stamping surfaces, ultrasonic elastic waves are reflected and transmitted multiple times. 2) Modal conversion occurs at the die-workpiece boundary in such a way that normal waves with an inclined incident angle are transformed into normal and shear waves. 3) Elastic waves sent out from an ultrasonic transducer are mixtures of normal waves with flat wave fronts along the propagation path axis, normal waves with circular or spherical wave fronts expanding from both sides of the transducer, and shear waves. These results brought about much useful information for setting ultrasonic transducers and analyzing collected signals.