Derailment and Dynamic Analysis of Tilting Railway Vehicles Moving Over Irregular Tracks Under Environment Forces

Utilizing a nonlinear creep model, the dynamic behavior of tilting railway vehicles moving over curved tracks with rail irregularities and under earthquakes and wind loads is studied. The car model adopted consists of 28 degrees of freedom, capable of simulating the lateral, vertical, roll and yaw motions for the wheelsets, truck frames and car body. The derailment quotient is investigated to analyze the running safety of a tilting railway vehicle using the linear and nonlinear creep models, while considering the rail irregularities and environmental forces for various tilting angles. Generally, the derailment risk of the tilting railway vehicle is higher than that of non-tilting railway vehicle with or without rail irregularities and environmental forces. The derailment quotients calculated by the linear creep model are underestimated for a tilting railway vehicle. In addition, the derailment quotients evaluated for rough rails and under environmental forces are higher than those obtained for smooth rails with no environmental forces. It is confirmed that rail irregularities and each type of environmental forces have decisive effects on derailment quotients. They are compared and ranked according to their significance.

Simulation of Active Suspension System Based on Optimal Control

A 7-DOFs vehicle dynamics model which includes active suspension system (ASS) is established, and a LQR controller for active suspension system was designed based on optimal control theory. The simulation models for active suspension system and passive suspension system were built, and a simulation experiment was carried out with MATLAB/Simulink Software. The simulation results show that the optimal control of active suspension system can reduce vertical, roll and pitch accelerations of sprung mass, and the vehicle ride comfort and handling stability were improved effectively.

FEM Simulation of the Slab Edge Rolling in Unsteady Rolling Stage

According to characteristics of adjusting width by vertical roll at a certain steel corporation, unsteady deformation of head and tail of slab during edge rolling was analyzed by FEM simulation on base of a commercial software. The effect of several process conditions on the cross-section deformation and width loss of slab were also analyzed.

Finite Element Simulation of Residual Stress in Heavy Rail

The test here is to simulate the process of flat and vertical roll from Baogang heavy rail using the finite element, which analyzes the steel, the high strings, the initial stress and straightening process effect on residual stress. It is concluded that the discipline among the steel, the high strings, the initial stress, straightening process and residual stress.

Effect of Aluminum Content on Mechanical Properties of Cast Magnesium Alloy Sheets Fabricated by Twin-Roll Casting

This paper describes the twin-roll casting technology of magnesium alloys that contain relatively high weight ratios of aluminum, such as AM60, AZ91 and AZ121. The magnesium alloy sheets were cast by a vertical roll caster to manufacture relatively high-strength Mg alloys with high aluminum content. The influences of such process parameters as roll materials, casting temperature, and roll speed were ascertained. A simple method of predicting the convection heat transfer coefficient between casting rolls and molten metal is introduced. The microstructures of cast magnesium alloy sheets are microscopically observed to investigate the effects of roll-casting conditions on crystal growth in the cast products. It was found that Mg alloys with high aluminum content can be fabricated at a roll speed of 90m/min with a vertical-roll caster. The grain size of the manufactured wrought magnesium alloy sheet was about 30 micrometers due to rapid solidification in the proposed process.

Control of Spatial Orientation of the Angular Vestibuloocular Reflex by the Nodulus and Uvula

Wearne, Susan, Theodore Raphan, and Bernard Cohen. Control of spatial orientation of the angular vestibuloocular reflex by the nodulus and uvula. J. Neurophysiol. 79: 2690–2715, 1998. Spatial orientation of the angular vestibuloocular reflex (aVOR) was studied in rhesus monkeys after complete and partial ablation of the nodulus and ventral uvula. Horizontal, vertical, and torsional components of slow phases of nystagmus were analyzed to determine the axes of eye rotation, the time constants (Tcs) of velocity storage, and its orientation vectors. The gravito-inertial acceleration vector (GIA) was tilted relative to the head during optokinetic afternystagmus (OKAN), centrifugation, and reorientation of the head during postrotatory nystagmus. When the GIA was tilted relative to the head in normal animals, horizontal Tcs decreased, vertical and/or roll time constants (Tcvert/roll) lengthened according to the orientation of the GIA, and vertical and/or roll eye velocity components appeared (cross-coupling). This shifted the axis of eye rotation toward alignment with the tilted GIA. Horizontal and vertical/roll Tcs varied inversely, with Tchor being longest and Tcvert/roll shortest when monkeys were upright, and the reverse when stimuli were around the vertical or roll axes. Vertical or roll Tcs were longest when the axes of eye rotation were aligned with the spatial vertical, respectively. After complete nodulo-uvulectomy, Tchor became longer, and periodic alternating nystagmus (PAN) developed in darkness. Tchor could not be shortened in any of paradigms tested. In addition, yaw-to-vertical/roll cross-coupling was lost, and the axes of eye rotation remained fixed during nystagmus, regardless of the tilt of the GIA with respect to the head. After central portions of the nodulus and uvula were ablated, leaving lateral portions of the nodulus intact, yaw-to-vertical/roll cross-coupling and control of Tcvert/roll was lost or greatly reduced. However, control of Tchor was maintained, and Tchor continued to vary as a function of the tilted GIA. Despite this, the eye velocity vector remained aligned with the head during yaw axis stimulation after partial nodulo-uvulectomy, regardless of GIA orientation to the head. The data were related to a three-dimensional model of the aVOR, which simulated the experimental results. The model provides a basis for understanding how the nodulus and uvula control processing within the vestibular nuclei responsible for spatial orientation of the aVOR. We conclude that the three-dimensional dynamics of the velocity storage system are determined in the nodulus and ventral uvula. We propose that the horizontal and vertical/roll Tcs are separately controlled in the nodulus and uvula with the dynamic characteristics of vertical/roll components modulated in central portions and the horizontal components laterally, presumably in a semicircular canal-based coordinate frame.

Wheelset Mechanics During Wheelclimb Derailment

An analysis of the mechanics and dynamics of a railroad vehicle wheelset during flange contact and wheelclimb derailment is presented. The theoretical model includes wheelset lateral, vertical, roll, yaw, and axle rotation degrees of freedom, plus lateral displacement of the truck frame. The equations of motion are based on the kinematics and dynamics of the wheelset subject to constraints imposed by wheel/rail contact geometry. These constraints are used to compute creepages and normal forces at the wheel/rail contact points, needed as inputs to the Kalker Simplified Theory of rolling contact. Computational methods for simulation of the nonlinear dynamic model are discussed. Results of the simulation demonstrate the significance of the various degrees of freedom on wheelset motion and on predicted values of the derailment quotient (Q/P).