Rail Geometries Research Articles

Investigations on Armature Jerk for Different Current Pulse and Rail Geometries in an Electromagnetic Railgun

Investigations on Armature Jerk for Different Current Pulse and Rail Geometries in an Electromagnetic Railgun

Inductance gradient and current density distribution for T-shaped convex and concave rail cross-sections

Rectangular rail was the most widely used cross section shape for the rail gun electromagnetic launching (EML) system. Based on sector assimilation, the rail gun key parameter especially current density (J) and inductance gradient (L’) greatly affected. J decides the efficiency of EML and L’ decides the force acting on the projectile of EML. So, it is mandatory to look upon the sector assimilation of rails. In this paper T shape convex and concave shape rail cross section is proposed and rail gun key design parameters are calculated by varying its dimensions using Ansoft Maxwell 2-D eddy current solver which uses finite element analysis technique to calculate these parameters. The performance of rail gun discussed using the obtained values and it has been observed and that the compared with other considered rail geometries, the T-shaped concave model shows more impact on inductance value which causes uniform current density distribution over the rails.

Analysis of Contact Stresses of Theoretical and Worn Profile by Using Computer Simulation

The wear of rails and rail wheels is important problem in rail traffic. The change of the shape of the wheel profile has not only a great influence on the dynamic properties of the vehicle (like stability, safety by passing curved tracks, etc.), but also affects the ride comfort of passengers and environmental insults. In extreme cases it can cause rail derailment, which is unwanted status. For these and other reasons, great effort is brought to create a software, which would be capable to compute the wear of a rail wheel profile. The presented article demonstrates how the change of the rail profile influences the resulting contact stresses. The wheel and rail geometries were created by using the CAD software CATIA. For the creation of the rail profile, the PYTHON programming language was used, because the imported .step file caused inaccuracies during import. The contact stresses were computed by using the commercial FEM software ABAQUS, and the results were compared with other methods which are used to calculate contact stresses.

Effects of coupling anisotropic yield functions with the optimization process of extruded aluminum front rail geometries in crashworthiness

Using advanced constitutive models in simulation tools can improve predictive capabilities of automotive structures in crashworthiness applications. This work presents the influences of coupling anisotropic yield functions into the size optimization of extruded front rails to maximize energy absorption characteristics. Finite element simulations of the extrusion crush response are performed using the von Mises (1913), Hosford (1972) and Barlat et al. (2005) Yld2004-18p yield functions. Each yield function is implemented into a 2-dimensional plane stress and 3-dimensional element formulation to highlight the modeling differences prior to optimization. The simulations are also compared to the experimental dynamic crush response of the extrusion. The response surface methodology (RSM) with the artificial neural network (ANN) metamodeling technique is coupled with the genetic algorithm (GA) optimization scheme to improve the specific energy absorption (SEA) through maximizing energy absorption and minimizing mass. A constrained and unconstrained mass optimization study is performed to identify the sensitivity of global optimization to yield surface choice. Analytical models are derived to explain the influence of the yield surface on the convergence of optimization. The results highlight the importance of incorporating anisotropic yield functions into the optimization process.

Generation and verification of QFix kVue Calypso-compatible couch top model for a dedicated stereotactic linear accelerator with FFF beams.

This study details the generation, verification, and implementation of a treatment planning system (TPS) couch top model for patient support system used in conjunction with a dedicated stereotactic linear accelerator. Couch top model was created within the TPS using CT simulation images of the kVue Calpyso‐compatible couchtop (with rails). Verification measurements were compared to TPS dose prediction for different energies (6 MV FFF and 10 MV FFF) and rail configurations (rails in and rails out) using: 1) central axis point‐dose measurements with pinpoint chamber in water‐equivalent phantom at 42 gantry angles for various field sizes (2×2 cm2,4×4 cm2,10×10 cm2); and 2) Gafchromic EBT3 film parallel to beam in acrylic slab to assess changes in surface and percent depth doses in PA geometry. To assess sensitivity of delivered dose to variations in patient lateral position, measurements at central axis using the pinpoint chamber geometry were taken at lateral couch displacements of 2, 5, and 10 mm for 6 MV FFF. The maximum percent difference for point‐dose measurements was 3.24% (6 MV FFF) and 2.30% (10 MV FFF). The average percent difference for point‐dose measurements was less than 1.10% for all beam energies and rail geometries. The maximum percent difference between calculated and measured dose can be as large as 13.0% if no couch model is used for dose calculation. The presence of the couch structures also impacts surface dose and PDD, which was evaluated with Gafchromic film measurements. The upstream shift in the depth of dose maximum (dmax) was found to be 10.5 mm for 6 MV FFF and 5.5 mm for 10 MV FFF for ‘Rails In’ configuration. Transmission of the treatment beam through the couch results in an increase in surface dose (absolute percentage) of approximately 50% for both photon energies (6 MV FFF and 10 MV FFF). The largest sensitivity to lateral shifts occurred at the lateral boundary of the rail structures. The mean magnitude (standard deviation) of the deviation between shifted and centered measurements over all field sizes tested was 0.61% (0.61%) for 2 mm shifts, 0.46% (0.67%) for 5 mm shifts, and 0.86% (1.46%) for 10 mm shifts.PACS numbers: 87.56.‐v, 87.56.Da, 87.56.Fc

Dynamics of plasma channel in a parallel-plate plasma gun

Lumped parameter models for describing dynamics of the plasma channel in a parallel-plate plasma gun are compared with the experimental results obtained from two plasma guns with different rail geometries. Comparison between the experiments and the numerical calculations reveals that the lumped parameter models can be utilized to describe the dynamic motion of the plasma channel quite well. Parametric study shows that minimizing the line inductance and increasing the charging voltage on a capacitor as well as minimizing the gas injection time for reducing the mass of the plasma channel are the key factors to increase the flow velocity of the plasma jet ejected from the plasma gun.

트랙좌표계를 이용한 철도차량의 동역학 해석에 관한 연구

Rail geometries such as cant, grade and curvature can be easily represented by means of a track coordinate system. In this analysis, in order to derive a dynamic and constraint equation of a wheelset, the track coordinate system is used as an intermediate stage. Dynamic and constraint equations of railway vehicle bodies except the wheelset are written in the Cartesian coordinate system as a conventional method. Therefore, whole dynamic equations of a railway vehicle are derived by combining wheelset dynamic equations and dynamic equations of railway vehicle bodies. Constraint equations and constraint Jacobians are newly derived for the track coordinate system. A process for numerical analysis is suggested for the derived dynamic and constraint equations of a railway vehicle. The proposed dynamic analysis of a railway vehicle is validated by comparison against results obtained from VI-RAIL analysis.

ANSYS Simulation Based Comparative Study between Different Actuators and Guide-ways used in DC Electromagnetic Suspension Systems

Magnetic levitation is a popular topic of research over the years throughout the world due to its wide range of industrial applications. In any DC attraction type suspension system, actuator and guide-way (rail) plays most important role. In this manuscript FEM based analysis of different structures of actuator and rail (guide-way) has been carried out utilizing ANSYS software. Input power to lift power ratio and lift power magnet weight ratio are two major factors for designing actuator and rail in electromagnetic levitation system (EMLS) (1). These factors are dependent on the magnet dimensions, required gap flux and hence the required current density in the winding. The magnet configurations chosen on the basis of required pole-face area and necessary window area to house the excitation coils. There are various magnet and rail geometries; i.e. magnet with I, U and E profiles and various winding arrangements with flat and U-profile rail. A FEM analysis utilizing ANSYS software has done to find out the flux pattern, working flux density, field intensity, force etc. for different single actuator based levitation system at different operating conditions. Different aspects of rail and actuator have been described based on the ANSYS simulation results. The main objective is to propose a suitable configuration of actuator and guide-rail for a specific DC electromagnetic levitation system.

Impact of Bridge Rail Geometry on Floodplain Analysis

This paper describes a method for incorporating the hydraulics of various bridge rail geometries on a bridge structure to determine the impacts on the surrounding floodplain during extreme flood events. Typical floodplain analysis either does not include the geometry of the bridge rails or simply increases the thickness of the bridge roadway deck to account for the bridge rails. These methods either underpredict or overpredict, respectively, the impact of the bridge rails and do not account for open space in the rails. The use of a previously developed rail rating curve and submergence model can be incorporated in floodplain mapping software such as HEC-RAS. The rail rating curve model can be used to determine the upstream specific energy as a function of the flow rate passing over the rail. Floodplain analysis software typically models flow over bridge structures using the weir equation. Therefore, the weir coefficient is altered such that the weir equation and rail rating curve model result in the same upstream specific energy. This method results in an iterative approach for incorporating the hydraulics of various bridge railing systems into floodplain analysis software. The method is outlined and a simple single bridge example is provided.

Bridge Rail Rating Curves and Submergence Characteristics

This paper describes a three-parameter model used for determining the hydraulic performance of bridge rails during extreme flood events as well as two submergence models. Typically the geometry of the bridge rails is not considered when conducting floodplain analysis. The use of certain bridge rails with large height or minimal open space may adversely impact the surrounding floodplain. Therefore, a mathematical model used to characterize the hydraulic performance of bridge rails has been developed in order to understand how different bridge rail systems may impact a floodplain. Physical modeling experiments are conducted in order to determine rating curves for various rail geometries that describe the upstream specific energy as a function of the flow rate passing over the rail. In addition, the effects of the submergence of bridge rails by an increase in downstream water surface elevation are also evaluated, as well as the submergence effects of two bridge rails in series. Two different mathematical models are used to approximate and characterize the effects of rail submergence.

The dynamics of European two-axle railway freight wagons with UIC standard suspension

The dynamics of two-axle railway freight wagons with the UIC standard suspension is investigated theoretically and the dynamic behaviour is explained. Fully nonlinear models are considered. The hysteresis from dry friction and the effect of impacts between elements of the suspension are included. Different wheel–rail geometries are investigated and the results commented. Bifurcation diagrams are used to describe the eigen-dynamics of the wagons.

Midwest Guardrail System W-Beam-to-Thrie-Beam Transition

For longitudinal barriers, it is common practice to use a standard W-beam guardrail along the required highway segments and to use a stiffened thrie-beam guardrail in a transition region near the end of a bridge. As a result of the differences in rail geometries, a W-beam-to-thrie-beam transition element is typically used to connect and provide continuity between the two rail sections. However, the W-beam-to-thrie-beam transition element has not been evaluated according to current impact safety standards. Therefore, an approach guardrail transition system, including a W-beam-to-thrie-beam transition element, was constructed and crash tested. The transition system was attached to Missouri's thrie-beam and channel bridge railing system.

Influence of bore and rail geometry on an electromagnetic naval railgun system

A large-scale railgun is being considered by the U.S. Navy as a future long-range (>200 nm) naval weapon system. The notional concept includes a 15 kg projectile with a 2.5 km/s muzzle velocity. The choice of bore and rail geometry for such a weapon can influence key aspects of the total system design. This study explored a range of bore and rail geometries and looked at their effects on key railgun system parameters such as parasitic mass, inductance gradient, linear current density, required pulse forming network (PFN) size, and barrel mass. Preliminary solid modeling and structural analysis of the integrated launch package was performed in order to quantify parasitic mass. Inductance gradient calculations were based on a current density distribution analysis. A PFN/launcher numerical simulation model was then used to determine linear current density and PFN size. Finally, barrel mass was estimated by structural analysis based on calculated rail repulsive forces. Trends and sensitivities of the different parameters to changes in the bore and rail geometries are presented and conclusions are given.