Rail Thickness Research Articles

Study on the Prediction of Launcher Efficiency of Electromagnetic Launcher Based on Particle Swarm Optimization-Improved BP Neural Network

Launcher efficiency is an important index for evaluating the performance of the electromagnetic launcher, and it reflects the ability of the launcher to convert input electrical energy into kinetic energy of the armature. In this paper, the launcher efficiency is taken as the objective function of bore parameter optimization, and particle swarm optimization is used to optimize the initial parameters of the BP neural network to improve the accuracy of the neural network in predicting launcher efficiency. The results show the following: (1) The predicted efficiency of the launcher shows the same trend as the experimental results. When the ratio of rail separation and rail height is greater than 1.75, the rate of change in the launcher efficiency curve decreases as the rail separation increases. (2) The weight of the influence of each parameter on the launcher efficiency follows the following law: convex arc height > rail separation > rail height > rail thickness. (3) The mean absolute error of the BP neural network prediction is 0.70%; after optimization by PSO, the mean absolute error is reduced to 0.28% and the mean relative accuracy is improved from 0.9774 to 0.9910, which indicates the feasibility of the PSO-BP neural network for the prediction of the launcher efficiency of an electromagnetic launcher.

Analysis of Application the Device with Non-standart Scanner Installation for Rail Condition Monitoring

In this work, the possibility of application the device with a non-standard (side) piezoelectric sensor installation for rail condition monitoring is considered. The aim of this device application is reducing the risks of using single-strand flaw detectors on railway tracks with fixation system on the rail in the form of two rebords. Also, the application of this device allows you to obtain a new qualification criterion for the integrity of the rail, which is located in the railroad groundwork. This criterion is the presence of a signal from the opposite face of the rail head, which, in addition to the possible detection of a 30В.1-2 defect (DG) or 113 also allows you to record developed defects of the rail neck, passing into its head and implemented by sounding the rail head of the linear section of the track in the transverse direction (from the working to the non-working face). The study of round ultrasonic transducers of different frequencies was carried out. It has shown impossibility of using 10 MHz transducers. The results of statistical estimation of rail thickness and corresponding amplification levels are presented. The presence of statistically significant differences in the monitoring of different frequencies sensors and different sensors of the same frequency (which is relevant only for 5 MHz) was found. The difference between the maximum and minimum average in the test group of measured values of rail thickness was 0.06 mm, and between amplification levels — 17 dB.

Research on mechanism of eddy current in rail of maglev and optimum design of electromagnet

Aim: Due to the movement of medium-low speed maglev vehicles, eddy current is generated in the rail, leading to reduced levitation force. This detrimental effect becomes more prominent with increasing velocity. In order to reduce the influence of eddy current effect, the electromagnet is optimized to meet the requirement of vehicle speeding up from 100km/h to 160km/h.
 Methods: To maintain a constant levitation force, the current must also increase accordingly resulting in higher power consumption and heat generation. In this paper, a mathematical model is established by analytical method, focusing on the mechanism and influencing factors of eddy current. Three-dimensional transient magnetic field magnet model is analyzed by the ANSYS electromagnetic simulation software Maxwell.
 Results: The levitation force is related to five parameters, such as speed, length of the electromagnet, rail height, rail thickness and air gap. According to the finite element simulation results, when the train speed is 160 km/h, the levitation force of the end electromagnet is reduced by about 21.9 %. The levitation force of optimized electromagnet increases by 27 % under the same current, which can compensate for the drop of levitation force caused by eddy current .The levitation force is 41.4 kN at the speed of 160 km/h, which is slightly larger than the 39.6 kN of the former electromagnet static levitation force, which can meet the requirements.
 Conclusion: The result confirms that optimization methods proposed above are valid and effective.

Electromechanical Coupled Parametric Vibrations for Electromagnetic Railgun

In the rail gun system, the current fluctuation occurs which causes the changes of the electromagnetic stiffness and forms disturbance to the dynamics system. It may lead to disturbances of the projectile trajectory. This is an electromechanical-coupled parametric vibration problem and should be investigated. Rails in electromagnetic railgun are assumed to be elastic foundation beams. The current flowing through the rail causes an electromagnetic repulsive force between the two rails. The fluctuation of rail current causes mechanical vibration and stiffness change of the rails. The wave current is assumed to vary in the cosine function. Considering the current fluctuation in the railgun system, an electromechanical-coupled parametric vibration equation is proposed. Using Poincare method, the coupled parameter vibration equation is resolved. As the dynamic current amplitude, the static current, and distance of the armature to the entrance of the gun increase, the unstable region of the railgun system vibrations increases. As the distance between the two rails, the rail thickness and the rail width, and the stiffness of the elastic foundation increases, the unstable region of the railgun system vibrations decreases. In this paper, the unstable regions of the railgun system are determined and their changes as the function of the system parameters are analyzed. Results can be used to increase the stability of electromagnetic railgun.

Electromechanical coupled nonlinear dynamics of euler beam rails for electromagnetic railgun

The electromagnetic field can cause an essential change of the dynamic behavior of the railgun. The evaluation of the dynamics performance of railgun is a mandatory task. Here, a nonlinear electromagnetic force equation of the railgun is given in which the clearance, the thickness and the width of the rail are considered. Based on it, the nonlinear electromechanical coupled dynamics equations of Euler beam rails for the railgun are proposed. Using the equations, the nonlinear free vibration frequency of the railgun is investigated and the effects of the system parameters on the frequency are analyzed. The nonlinear forced responses of the rail to the electromagnetic excitation are investigated as well. The results show that as the nonlinearity of the railgun system is considered, the vibration frequencies of the railgun system increase; as the current in the rail increases, the difference between the natural frequencies and the nonlinear vibration frequencies increases significantly; the nonlinearity of the railgun system is more obvious for smaller distance between the two rails, smaller rail thickness, and smaller stiffness of the elastic foundation; the unstable dynamics state of the rail system occurs when the armature runs to the exit of the railgun. The results are useful for design and application of the railgun system.

Approximate Field Scaling of Railgun Launcher Under the Condition of Matching Projectile Dynamic Parameters

The results and experiences gained from the subscale railgun launcher's test can be extremely valuable to succeed with the full-scale railgun. This paper proposes an approximate field scaling method of the electromagnetic railgun launcher under the conditions of matching projectile dynamic parameters. A detailed derivation and numerical validation are presented in this paper. According to the results of the analytical derivation, the magnetic and temperature fields between two scales of railgun launchers can be matched if the time scaling factor is equal to the square of the geometric scaling factor in the rail thickness direction and if the linear current density remains equal between two scales. However, the stress field cannot be matched as long as the scaling method is desirous of using the same material in two scales and to match the magnetic and temperature fields as well. Numerical simulations are then conducted to assess the scaling performance. Simulation results show that profiles of projectile velocity are identical in two scales under the specific conditions. The magnetic and temperature fields can be matched well, but they are not exact images, which means that the field scaling method is an approximate scaling method. The stress field in the simulation cannot be matched between subscale and full scales, which validates the analytical derivation results. The results can be used to provide guidance for the suitable subscale tests of electromagnetic railgun.

Novel Study of the Rail’s Geometry in the Electromagnetic Launcher

This paper proposed a railgun with sector of circular rails. The center of the sector of circular rails is located at the outside of the railgun bore. The distance between the sectors of two circles is s , opening angle facing outward θ, the inner and outer radius are also assumed to be R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> and R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> , respectively. The influence of internal curvature of the rails, the rail thickness and the distance between rails on the current density, magnetic flux density, and inductance gradient (L') have been studied and analyzed using finite-element method. First of all, the different values of θ, s, R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> , and R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> are calculated for various values of the area of the railgun bore (S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> ) and cross section of the rails (S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</sub> ). The current density, magnetic flux density, and L' have been calculated for different values. The area of the railgun bore is assumed to be 9 and 10 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and the area of rails are assumed to be 9, 6, 3, and 1 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . In next section, L' is found as a function of s, R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> , and R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> for θ =90°, 120°, 150°, and 180°. Finally, L' is compute for rail thickness equals to one-tenth of bore size and θ on the interval [180°, 360°]. According to the achieved results it can be observed the behavior of L' in terms of railgun dimensions changes and it is compared with other geometries.

Bending moment capacity of simple and haunched mortise and tenon furniture joints under tension and compression loads

A study was conducted to examine the effects of tenon geometry on the bending moment capacity of simple and haunched mortise and tenon joints under the action of both compressive and tensile loads. The effects of tenon width (25, 37.5, and 50 mm), tenon thickness (7.5, 10, and 15 mm), and tenon length (20, 25, and 30 mm) were examined. All of the joints were constructed of Turkish beech (Fagus orientalis Lipsky) and were assembled with a 40% solid-content polyvinyl acetate. Optimum results were obtained with joints constructed with 10-mm-thick tenons that were 37.5 mm wide by 30 mm long. Tenon length was found to have the greatest effect on joint capacity, whereas tenon width was found to have a much smaller effect. Joints constructed with 37.5-mm-wide haunched tenons had essentially the same moment capacity as joints constructed with 37.5-mm simple tenons. Optimum tenon width was 10 mm (1/3 of rail thickness); joints constructed with 10-mm-thick tenons had greater capacity than joints constructed with either 7.5- or 15-mm thick tenons.

Analyzing the Near and Far Field Using Finite Difference and Finite Element Method

In this paper, the railgun is assumed to be an antenna and simulated with the finite element method (FEM) and the finite difference time domain (FDTD) method. For FEM analysis, the caliber of the railgun is 10 × 10 mm, rail thickness is 10 mm, and rail length is 400 mm. At first, the H-field on the cross section of the rails is computed. Next, power radiation and the maximum value of the E-field in the near and far field are obtained as a function of frequency. Polar radiation patterns versus frequency (1 kHz-1 MHz) in the near and far-field regions are calculated as a function of the angle. For FDTD, we assume that the railgun operates in the far-field region, and radiation patterns are computed in this region. The caliber of the railgun is 15 × 19 mm, rail thickness is 10 mm, and length is 1000 mm. Directivity has been computed versus frequency (100 Hz-1 MHz) in the far-field region. The H-field is calculated versus frequency and the energy is computed as a function of time. For both methods, the railgun included copper rails and an aluminum projectile.

An Analytic Expression of Inductance Gradient for Rail-Type Electromagnetic Launcher

The rail-type electromagnetic launcher (EML) has good development and applied prospects for military and civilian dual purpose. The inductance gradient is an important parameter to design the EML structure and evaluate the system performance. Based on the Biot-Savart law and current skin-effect behavior, we derive an analytic formula to predict the EML inductance gradient, which expands Batteh's formula by introducing rail thickness <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">w</i> and skin depth δ. Our expression is more accurate because the geometrical parameters of both rails and armature are considered in this paper. We investigate the inductance gradient change as a function of the ratio of bore width to height <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</i> / <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">h</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</sub> , rail thickness <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">w</i> , and two-rail interval <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</i> . Finally, our results at different scales are compared with those of other formulas of the inductance gradient. This paper could be used directly to design and optimize the rail-type EML.

Influences of Moisture Expansion on Motion Errors of Granite Hydrostatic Guideways

Granite is a kind of high damping material with low thermal expansion, so it is widely used in aerostatic guideways. However, moisture expansion may occur when the granite works in a moist environment, so the applicability of granite to oil hydrostatic guideways is investigated in this paper. By error modeling for a typical closed hydrostatic guideway with four pads, it is shown that the motion errors are mainly determined by geometric errors of the rails when film stiffness of each pads are equal. Experiments on rails of Jinan Dark Green granite are carried out, and the results show the rail straightness variation by the moisture expansion may be less than 1μm/300mm. According to the previous analysis on the error averaging mechanism of hydrostatic guideways, the motion straightness variation may be less than 0.1μm/300mm. In addition, the thickness variation may be less than one ten-thousandth of the rail thickness and the viscosity of liquid has little influence on the moisture expansion.

Development of a New Guardrail System

The W-beam guardrail system has been the standard in the United States since the late 1950s and has proved to perform reasonably well under most impact conditions. However, in recent years the vehicle fleet has changed to include a relatively large percentage of light trucks, such as pickups, vans, and sport-utility vehicles. These vehicles have a higher center of mass and bumper mounting height than conventional automobiles and have been shown to have higher rollover and injury rates during guardrail accidents than conventional automobiles. Standard W-beam guardrails were not designed to capture the bumper of many of these vehicles. In recognition of the potential safety problems associated with light-truck accidents, safety performance standards were recently changed with the publication of NCHRP Report 350, Recommended Procedures for the Safety Performance Evaluation of Highway Features. These performance standards require all new safety hardware to be tested with a full-size three-quarter-ton pickup to ensure acceptable performance for most vehicles in the light-truck category. In recognition of this, a guardrail system capable of capturing and redirecting a larger range of vehicle types and sizes was developed. A new guardrail system, called the Buffalo Rail, was designed with a new cross-sectional shape with an effective depth of 311 mm (compared to 194 mm for the W-beam), a rail thickness of 13 gauge, and a post spacing of 2500 mm. The safety performance of the Buffalo Rail was found to be acceptable according to the procedures and criteria recommended for the three-quarter-ton pickup truck at Test Level 3 in NCHRP Report 350.

Analysis of speed characteristics of attracting magnet for magnetic levitation of vehicles

Theoretical analysis was made of the magnetic field in the air gap between the attracting magnet and the rail for the electromagnetic levitation of vehicles. Eddy current induced by the magnetic field in the rail weakens the field, particularly near the leading end of the magnet, and decreases the attracting force as the magnet speed becomes higher. Eddy current also generates drag. Analytical solutions of the field equations were derived and formulas for calculating forces were obtained. Magnetic field distribution within the air gap was calculated to show how the excited field is weakened by the eddy current in the rail. Speed characteristics of the magnet, such as attracting force versus speed curves, drag versus speed curves, lift/drag ratio versus speed curves, were calculated, and are compared with some experimental curves. These curves show that speed-characteristics of the attracting magnet can be very superior in a very wide speed range, if it is designed properly. It is shown how parameters, such as magnet length, rail thickness, etc., affect the speed characteristics of the magnet.