The Research on the DEM Simulation of the Railway Ballast Tamping Process

2013 ◽  
Vol 724-725 ◽  
pp. 1723-1726
Author(s):  
Xue Jun Wang ◽  
Bin Hua ◽  
Bin Hu ◽  
Yi Lin Chi ◽  
Yan Fang Ding
Keyword(s):  
High Speed ◽  
Retaining Wall ◽  
Sphere Packing ◽  
Contact Dynamics ◽  
Railway Ballast ◽  
Dem Simulation ◽  
Polyhedral Particles ◽  
Long Time ◽  
Ballast Track ◽  
Packing Method

Ballast degradation and unrecoverable deformation are emerged on the railway ballast track under the loads of high-speed and heavy loading locomotive. With the change of tamping frequency, a better understanding of the physics of compactness degree is important for long-time stability of ballast. This paper presented a numerical investigation of the bulk materials dynamics and the transient impaction of a system of irregular polyhedral particles confined with a rectangular box with a retaining wall subjected to cyclic tamping loading. Sphere packing method was being used in this study to simulate typical full-sized ballast particles. This paper aimed to establish firm-soft coupling particle-flow tamping operation simulation numerical model based on contact dynamics theory. This study checked the validity of the model while different tamping working conditions and out-loads was being implemented. The study shows that discrete element method (DEM) is an efficient method to reveal the rearrangement rule of railway ballast after the process of tamping operation.

scholarly journals Research on Bogie Frame Lateral Instability of High-Speed Railway Vehicle

2018 ◽  
Vol 2018 ◽  
pp. 1-13
Author(s):  
Chen Wang ◽  
Shihui Luo ◽  
Ziqiang Xu ◽  
Chang Gao ◽  
Weihua Ma
Keyword(s):  
High Speed ◽  
Dynamics Simulation ◽  
Lateral Acceleration ◽  
Railway Vehicle ◽  
Lateral Instability ◽  
Bogie Frame ◽  
High Speed Railway ◽  
Long Time ◽  
Line Test ◽  
Equivalent Conicity

In order to find out the reason for the bogie frame instability alarm in the high-speed railway vehicle, the influence of wheel tread profile of the unstable vehicle was investigated. By means of wheel-rail contact analysis and dynamics simulation, the effect of tread wear on the bogie frame lateral stability was studied. The result indicates that the concave wear of tread is gradually aggravated with the increase of operation mileage; meanwhile the wheel-rail equivalent conicity also increases. For the rail which has not been grinded for a long time, the wear of gauge corner and wide-worn zone is relatively severe; the matching equivalent conicity is 0.31-0.4 between the worn rail and the concave-worn-tread wheel set. The equivalent conicity between the grinded rail and the concave-worn tread is below 0.25; the equivalent conicities are always below 0.1 between the reprofiled wheel set and various rails. The result of the line test indicates that the lateral acceleration of bogie frame corresponding to the worn wheel-rail can reach 8.5m/s2, and the acceleration after the grinding is reduced below 4.5m/s2. By dynamics simulation, it turns out that the unreasonable wheel-rail matching relationship is the major cause of the bogie frame lateral alarm. With the tread-concave wear being aggravated, the equivalent conicity of wheel-rail matching constantly increases, which leads to the bogie frame lateral instability and then the frame instability alarm.

scholarly journals Biaxial Shear Load Capacity of Anchor System for Quick-Hardening Track on Railway Bridges

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Kyoung Chan Lee ◽  
Il-Wha Lee ◽  
Seong-Cheol Lee
Keyword(s):  
High Speed ◽  
Ride Comfort ◽  
Load Capacity ◽  
Frictional Resistance ◽  
Shear Capacity ◽  
Railway Track ◽  
Railway Bridges ◽  
Anchor System ◽  
Ballast Track ◽  
Anchor Systems

Quick-hardening railway track was developed to rapidly convert old-style ballast track to slab track in order to improve its maintainability and ride comfort. On bridges, quick-hardening track is applied in a segmented structure to reduce the temperature constraint, and anchors at the centers of the segments securely couple the track to the bridge. In this study, an anchor system is proposed that facilitates fast construction, and two designs for the proposed anchor systems are provided along with experimental test results of the same. Two anchor system designs were developed to allow for the maximum possible longitudinal and transverse loads in high-speed railways while considering the frictional resistance between the track slab and bridge deck. The biaxial shear capacity of each design was investigated experimentally, and the structural capacity for biaxial shear loads was evaluated using an elliptical curve to represent the longitudinal and transverse shear capacities. The minimum friction coefficient was determined based on the results of the evaluation to minimize damage to the anchor. The results obtained from the experiments confirmed that the proposed anchor systems possess sufficient shear capacity for application on high-speed railway bridges.

Induced Flow Reciprocating Pump Theory Supported by New Performance Data

1972 ◽  
Vol 94 (4) ◽  
pp. 706-714 ◽  
Author(s):  
J. D. Burton ◽  
J. Lobo-Guerrero U.
Keyword(s):  
High Speed ◽  
Performance Data ◽  
Experimental Measurements ◽  
Long Time ◽  
Induced Flow ◽  
Hydraulic Accumulator ◽  
Reciprocating Pump

Reciprocating pumps have been employed in conjunction with air vessels and fluid accumulators for a long time in order to reduce maximum cylinder pressures and energy wastage in friction. More recently, diaphragm pumps, run at high speed, have been built utilizing a hydraulic accumulator or capacitance in conjunction with a hydraulic inductance, in order to greatly increase the flow output. Volumetric efficiencies of over 250 percent have been obtained. The present paper describes briefly this induced flow principle and then compares theoretical solutions with experimental measurements taken in the first commercially available pump of this type.

scholarly journals High speed internet development in Africa using 4G-LTE technology-a review

2019 ◽  
Vol 8 (2) ◽  
pp. 577-585
Author(s):  
Mohamed Njikam ◽  
Nanna S. ◽  
Shahrin S. ◽  
Mohd Fairuz Iskandar Othman
Keyword(s):  
High Speed ◽  
Telecommunication Networks ◽  
African Continent ◽  
African Countries ◽  
Lte Networks ◽  
Telecommunication Infrastructure ◽  
Long Time ◽  
Populated Region ◽  
4G Lte ◽  
Internet Development

The African continent is ranked second most populated region and has a huge amount of natural resources to be locally transformed or outsourced overseas. The traditional telecommunications system has helped connect people and enabled them to manage their businesses and trading in Africa for a long-time; many African countries have embarked early in changing their network and technology systems during the first years of the information age. Over a few decades ago, the introduction of new telecommunication methods and techniques have influenced much of African countries’ growth via different perspectives. The situation has triggered an enormous interest in people. They analyzed the factors supporting such changes, which in the case of this paper is all about the advent and adoption of LTE/4G-LTE technologies including its service commercialization in Africa. This review article attempts to provide an overview of 4G-LTE networks technologies and the internet; it includes the current evolution of telecommunication networks within and even beyond the African continent, assisted by the 4G-LTE expansion. An extended view is provided throughout this article’s development with respect to what could be expected (or is missing) for the sake of this continent’s telecommunication infrastructure enhancement and a better QoS to Africa’s dwellers.

An Analysis of Heave Added Mass and Damping of a Surface-Effect Ship

1981 ◽  
Vol 25 (01) ◽  
pp. 44-61
Author(s):  
C. H. Kim ◽  
S. Tsakonas
Keyword(s):  
Free Surface ◽  
High Speed ◽  
Surface Effect ◽  
Practical Method ◽  
Added Mass ◽  
Damping Coefficients ◽  
Calm Water ◽  
Surface Effect Ship ◽  
Long Time ◽  
Computational Procedures

The analysis presents a practical method for evaluating the added-mass and damping coefficients of a heaving surface-effect ship in uniform translation. The theoretical added-mass and damping coefficients and the heave response show fair agreement with the corresponding experimental values. Comparisons of the coupled aero-hydrodynamic and uncoupled analytical results with the experimental data prove that the uncoupled theory, dominant for a long time, that neglects the free-surface effects is an oversimplified procedure. The analysis also provides means of estimating the wave elevation of the free surface, the escape area at the stern and the volume which are induced by a heaving surface-effect ship in uniform translation in otherwise calm water. Computational procedures have been programmed in the FORTRAN IV language and adapted to the PDP-10 high-speed digital computer.

scholarly journals Interplanetary Response to Solar Long Time-Scale Phenomena

1980 ◽  
Vol 91 ◽  
pp. 105-125
Author(s):  
C. D'Uston ◽  
J. M. Bosqued
Keyword(s):  
Solar Wind ◽  
Time Scale ◽  
High Speed ◽  
Coronal Holes ◽  
Observational Evidence ◽  
Solar Wind Flow ◽  
Speed Solar Wind ◽  
Long Time ◽  
Outer Corona ◽  
High Speed Solar Wind

In this paper, we briefly review the experimental knowledge gained in the recent years on the interplanetary response to solar long-time scale phenomena such as the coronal magnetic structure and its evolution. Observational evidence that solar wind flow in the outer corona comes from the unipolar diverging magnetic regions of the photosphere is discussed along with relations to coronal holes. High-speed solar wind streams observed within the boundary of interplanetary magnetic sectors are associated with these structures. Their boundaries appear as very narrow velocity shears.

scholarly journals White Dwarf Pulsations

1980 ◽  
Vol 5 ◽  
pp. 469-472
Author(s):  
W. Dziembowski
Keyword(s):  
Effective Temperature ◽  
High Speed ◽  
White Dwarfs ◽  
Binary Systems ◽  
Early Suggestion ◽  
Nonradial Oscillation ◽  
High Speed Photometry ◽  
Long Time ◽  
Nuclear Burning ◽  
Radial Pulsations

It has been known for a long time that white dwarfs are pulsationally unstable if nuclear burning takes place in their envelopes. Perturbation of energy generation rate promotes pulsational instability and this effect is frequently referred to as ε-mechanism. In recent years, with the advent of high-speed photometry, many rapidly varying white dwarfs have been discovered. However, periods of variability were found to be significantly longer than the periods of radial pulsations which were the only type of oscillations considered before the discovery. Furthermore, the case of ε-mechanism as being responsible for the observed variability has never been made strong for any of the observed objects.Variable white dwarfs are found among: Io single DA-type objects in the effective temperature range 10000-15000K; 2o members of close, usually but not always, cataclysmic binary systems. Although, following an early suggestion by Warner and Robinson (1972), the excitation of nonradial oscillation is postulated in both cases, the two types represent very different physical situations and they will be discussed here separately.

The Effect of Oil Droplet on the Lubrication Performance

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Shengguang Zhang ◽  
Wenzhong Wang ◽  
Xinming Li ◽  
Feng Guo
Keyword(s):  
High Speed ◽  
Contact Region ◽  
Oil Droplet ◽  
Large Size ◽  
Lubrication Performance ◽  
Air Lubrication ◽  
Long Time ◽  
Base Radius ◽  
The One ◽  
Starvation Conditions

Oil–air lubrication is widely used in the high-speed rotary machines; the oil is usually in the form of discrete droplets. The lubrication behavior of the oil droplet is rarely investigated. This paper investigates the effect of the oil droplet on lubrication performance based on the developed transient lubrication model with consideration of starvation conditions. The oil droplet is modeled as spherical segment with different heights, base radius, and positions, which will change the inlet oil supply conditions. The results show that the oil droplet with large size can generate thick oil film which is close to the one in fully flooded condition and can remain long time; the position of the oil droplet entering the contact region also has significant effect on the lubrication performance.

Running Behavior of a High-Speed Spindle Using a Micro-Mist Lubrication System

2013 ◽  
Vol 773-774 ◽  
pp. 400-408
Author(s):  
Shen Yung Lin ◽  
Jheng Hua Li
Keyword(s):  
Temperature Rise ◽  
High Speed ◽  
Lubricating Oil ◽  
Lubrication System ◽  
Operation Performance ◽  
Response Measurement ◽  
Rotating Speed ◽  
Oil Supply ◽  
Analysis Measurement ◽  
Long Time

This work investigates the effect of lubrication parameter on the operation performance of a high-speed spindle using a micro-mist lubrication system. Experiments are conducted through a long-time spindle test under different combinations of oil-supply parameter and rotating speed for a micro-mist lubricated spindle. The correspondent relationships among temperature rise, vibration, oil-supply parameter and rotating speed are established through the experiments under moderate oil-supply. The results show that the better oil-supply parameter combinations exist under different spindle rotating speeds, which could ensure the sufficient and adequate lubricating oil film to be formed and a stable elasto-hydro-dynamic lubrication could be further created during the operation period. The minimization of the temperature rise in bearings may be attained. Increasing air pressure contributed to the reduction in bearing temperature, but saturation might be appeared after the pressure level reached to a certain extent. The dynamic response measurement shows that this prototype spindle has an overly large vibration and rotation unbalance on the radial plane, which highlights the unstable operation problem of the spindle. Therefore, it is necessary to improve the constructed procedures, such as design, manufacture, and assembly for further use, to enhance the operation performance of the spindle. The analysis, measurement and diagnosis procedures established in this study could be helpful to uplift the related techniques for precision machinery industry.

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