Vibration Protection Systems

Design and deploy advanced vibration protection systems based on elastic composites under post-buckling, with this essential reference. Methods for designing vibration protection systems with negative and quasi-zero stiffness are formulated, explained, and demonstrated in practice. All key steps of the system design are covered, including the type and number synthesis, modelling and studying of stress-strain state under post-buckling of elastic composite designs, chaotic dynamics and stability conditions, real-time dimensioning, and active motion control. In addition to coverage of underlying theory, the use in helicopters, buses, railroad vehicles, construction equipment and agricultural machinery are included. An excellent reference for researchers and practicing engineers, as well as a tutorial for university students and professors with an interest in study, development and application of alternative methods of vibration protection anywhere.

Designing High-Voltage and Large-Capacity Battery Packs for Fuel-Cell Hybrid Railroad Propulsion System

Due to the problem of global warming caused by greenhouse gas emissions, internal combustion engines in a lot of transportation systems are being electrified. For the railroad propulsion system, it is essential to apply a high-voltage/large-capacity energy source in order to ensure that the system operates properly. Thus, fuel-cell and rechargeable battery systems are being considered nowadays. The battery system can receive and store all regenerative energy to improve energy efficiency. In addition, since the battery pack of a propulsion system utilizing a hydrogen fuel-cell requires continuous charging/discharging, regardless of the railroad vehicle’s driving profile, the battery pack is designed to ensure its stable use and to minimize maintenance costs. Consideration should be given to the characteristics of railroad vehicles. In this research, a hydrogen fuel-cell hybrid railroad vehicle propulsion system specification, which has been studied recently, was applied to study the considerations in the design of high-voltage/large-capacity battery packs for railroad vehicles. In particular, the passive and active cell-balancing circuit and an algorithm for the stable management of battery packs for hybrid railroad vehicles in which a continuous charging/discharging operation is repeated are proposed and verified through experiments.

Impact monitoring characteristics of piezoelectric paint sensor by thermal fatigue analysis for railroad vehicle applications

The strong aerodynamic drag under a railroad vehicle in motion causes the track ballast to fly up and around. The flying ballast can collide with the underside of the coach, damaging the electronics installed there. There are even cases wherein the aerodynamics of fast-moving train causes the gravel to hit the side of the coach and break the windows. Extensive and numerous studies are underway to reduce the damage caused by such phenomena. In this study, a “smart paint sensor” for impact monitoring was fabricated using piezoelectric nano powder and commercial paint for railroad vehicles, and the application of impact monitoring to railroad vehicles was analyzed. The process was simplified because the use of commercial paint eliminated the need to apply an additional layer of functionalized paint. Furthermore, the fact that the paint can be evenly sprayed on a large surface made it suitable for use on large and intricate objects such as a railroad vehicle bogie. Because railroad vehicles are exposed to thermal stress for a long period of time, a thermal fatigue test was conducted in order to figure out the stability of the polymer-based material, which is relatively vulnerable to temperature variations. The test results were used to analyze the impact sensitivity of the piezoelectric paint sensor. For the analysis, a full-size mock-up of the railroad vehicle bogie and an impact monitoring system with piezoelectric paint sensor were implemented in order to visualize the impact signals from differently shaped objects with large surfaces.

Experimental Study on Track-Bridge Interactions for Direct Fixation Track on Long-Span Railway Bridge

The rail and track girder of the direct fixation track (DFT) system on the Yeongjong Grand Bridge (YGB) in Korea exhibit integrated behavior. Therefore, unlike the DFT system in general concrete tracks, the track support stiffness (TSS) of the DFT system on the YGB cannot be evaluated with only the displacement of the rail. The actual TSS of the DFT system supported by the flexible track girders was lower than that of the DFT system supported by the general substructure. For this reason, field measurements and a finite element analysis that reflects the actual operating speed of railroad vehicles on the YGB (i.e., Airport Railroad Express (AREX), nonstop Airport Railroad Express (AREX Express), and Korea Train Express (KTX)) were conducted in this study to determine the interactions between the rail and the track girder. The results indicated that the DFT system on the YGB is supported by track girders that exhibit relatively flexible behavior. As a result, the TSS is directly influenced by the bending stiffness of the track girder.

Analysis of Tank Car Deformations Using Multibody Systems and Finite Element Algorithms

This investigation demonstrates the effect of the tank flexibility and plate thickness on the wheel/rail contact and the nonlinear dynamic behavior of railroad vehicles. To this end, a flexible tank is modeled using the finite element (FE) floating frame of reference formulation (FFR). The tank car finite element model is integrated with a three-dimensional railroad vehicle using computational non-linear multibody system (MBS) framework in which the wheel/rail interaction is formulated using a three-dimensional elastic contact formulation that allows for the wheel/rail separation. A triangular shell element is used to build the tank car and describe its deformation, The effect of the coupling between different modes of displacements is demonstrated by comparing the results of the simulations of the flexible and rigid tank car models. It is shown that there is a strong dynamic coupling between different modes of displacements of the tank car, the plate thickness, and the wheel/rail contact parameters. The effect of the flexibility and plate thickness of the tank car on the vehicle critical speed and dynamic characteristics are also examined.