scholarly journals Analysis on mechanical characteristics of welded joint with a new reinforced device in high-speed railway

2020 ◽  
Vol 12 (10) ◽  
pp. 168781402096720
Author(s):  
Hong Xiao ◽  
Dongwei Yan ◽  
Guangpeng Liu ◽  
Haoyu Wang
Keyword(s):  
Service Life ◽  
High Speed ◽  
Mechanical Characteristics ◽  
Welded Joint ◽  
Lateral Displacement ◽  
Three Dimensional ◽  
Coupling Model ◽  
Lateral Acceleration ◽  
Track Structure ◽  
Train Speed

High-speed railways adopt continuous welded rail to maintain the smoothness and continuity of the rail surface. However, the welded joint became one of the weakest parts. In order to clear the characteristics and mechanical properties of the new reinforced device, a dynamic three-dimensional vehicle-reinforced device-track coupling model is established. The mechanical characteristics of the track structure under high-speed train load were simulated and analyzed. After installing the new reinforced device, the dynamic response and service life of the track structure are obviously improved compared with the unreinforced rail. When the train speed is 300 km/h, the dynamic bending stress at the bottom of rail is reduced by 26.90%, the vertical and lateral acceleration of the rail are reduced by 42.78% and 21.56%, the vertical and lateral displacement of the rail are reduced by 6.36% and 8.67%, and the theoretical service life of the rail is greatly extended.

scholarly journals Modeling of Coupling Mechanism between Ballast Bed and Track Structure of High-Speed Railway

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Xuejun Wang ◽  
Jianghua Pu ◽  
Peng Wu ◽  
Mingfang Chen
Keyword(s):  
Contact Force ◽  
High Speed ◽  
Three Dimensional ◽  
Coupling Model ◽  
Strength Increase ◽  
Track Structure ◽  
Coupling Mechanism ◽  
Scanning Method ◽  
Driving Speed ◽  
Coupling Algorithm

In this paper, a discrete and continuous body coupling algorithm is used to study the dynamic contact characteristics between ballasts and between ballasts and track structures. Firstly, the three-dimensional fine modeling of ballast particles is realized based on the three-dimensional laser scanning method, and then through the discrete and continuum coupling algorithm from the micro-macro point of view, a multiscale and unified particle-track structure coupling model is established. Based on the coupling model, the macro- and microdynamic characteristics of the ballast bed and the mechanical characteristics of the track structure under the dynamic load of high-speed trains with different driving speeds are studied. It is shown that the cumulative settlement of the ballast bed is directly proportional to the contact force and rotation speed of the ballast, and the faster the driving speed is, the greater the cumulative deposition speed and cumulative settlement of the ballast are. The contact force between the ballast and sleeper mainly comes from the bottom of the sleeper, and its contact force and contact strength increase with the increase of driving speed.

scholarly journals A computational simulation study on the dynamic response of high-speed wheel–rail system in rolling contact

2018 ◽  
Vol 10 (11) ◽  
pp. 168781401880921 ◽  
Author(s):  
Xiaoqi Ma ◽  
Lin Jing ◽  
Liangliang Han
Keyword(s):  
High Speed ◽  
Lateral Displacement ◽  
Equivalent Stress ◽  
Contact Process ◽  
Contact Forces ◽  
Rolling Contact ◽  
Initial Contact ◽  
Vertical Acceleration ◽  
Rail System ◽  
Train Speed

The dynamic wheel–rail responses during the rolling contact process for high-speed trains were investigated using the explicit finite element code LS-DYNA 971. The influence of train speed on the wheel–rail contact forces (including the vertical, longitudinal, and lateral forces), von Mises equivalent stress, equivalent plastic strain, vertical acceleration of the axle, and the lateral displacement of the initial contact point on the tread, were examined and discussed. Simulation results show that the lateral and longitudinal wheel–rail contact forces are very smaller than the corresponding vertical contact forces, and they seem to be insensitive to train speed. The peak value of dynamic vertical wheel–rail contact force is approximately 2.66 times larger than the average quasi-static value. The elliptical wheel–rail contact patches have multiple stress extreme points due to the plastic deformation of the wheel tread and top surface of the rail. The vertical acceleration value of the axle in the steady condition is around ±5 m/s2 for the perfected wheel–rail system with the running speed below 300 km/h.

scholarly journals Levitation Characteristics of a Transport Installation with an Electrodynamic Suspension During a Longitudinal Joint with Road Track

2019 ◽  
Vol 5 (2) ◽  
pp. 70-82
Author(s):  
Konstantin E. Voevodskii ◽  
Vladimir M. Strepetov ◽  
Gennadiy E. Sereda
Keyword(s):  
Mathematical Model ◽  
Cross Section ◽  
High Speed ◽  
Lateral Displacement ◽  
Rectangular Cross Section ◽  
New Method ◽  
Technical Solution ◽  
Track Structure ◽  
Longitudinal Joint ◽  
Electrodynamic Suspension

Aim:to propose a technical solution to ensure the lateral stabilization of the vehicle with an electrodynamic suspension. Development of a method for calculating the levitation characteristics of a transport installation with an electrodynamic suspension in the presence of a longitudinal joint in the track. Analysis of the results of theoretical studies. Мaterials and methods: The article used the methods of the electromagnetic field theory, generalized functions, Fourier transform, analytical and numerical methods for determining quadratures. The program for PC was developed in the Fortran language. Result: to ensure lateral stabilization of the vehicle with an electrodynamic suspension, it was proposed to introduce a longitudinal insulating joint into the structure of the track bed. A mathematical model is proposed for this system of electrodynamic suspension in approximation of an infinitely wide track structure of rectangular cross section. A mathematical model is proposed for this system of electrodynamic suspension in approximation of an infinitely wide track structure of rectangular cross section. Numerical integration of these equations was performed by applying the Gauss formula and the Philo method. The results of the calculations allowed us to obtain a number of graphical dependencies of the levitation characteristics on the magnitude of the lateral displacement of the carriage electromagnet from a relatively symmetrical position. Conclusion: thus, the obtained results of the study fully meet the goal of determining the parameters of the side stabilization of the vehicle with an electrodynamic suspension with a track, containing a longitudinal joint under the assumptions made. Comparison of the proposed method with other proposed stabilization methods does not reveal the decisive advantages or disadvantages of the new method. In most cases, its most serious drawback is its low levitation quality. However, it is significantly reduced if the movement of the high speed ground transportation vehicle occurs predominantly at high speed, at which the force of aerodynamic drag prevails over the force of electrodynamic braking. Same relative is and the dignity of the system-high lateral rigidity. The reason for this is that the demands on the lateral stiffness can be quantified only formulated in relation to a particular track HSGT taking into account the timetable and other factors. In fact, the main destabilizing influences in sideways are inertia at motion on component and crosswind. Its role in choosing the stabilization system could play and other tasks the system subsystems HSGT. For example, installing additional stabilizing magnets can make it difficult to escape the passenger compartment from the magnetic field. Plays a role also principle and system design of traction. From the above it is clear that the final choice of the lateral stabilization of the research at this stage would be premature. Proposed and studied in this article a new way to stabilize should be regarded as another possible along with the preceding. The answer to the question on the competitiveness of the new method must be bound to the characteristics of specific trails HSGT. Necessary and further refinement of results associated with the more strict account of edge effect, as well as consideration of the case of uninsulated interface.

scholarly journals Mechanistic Insights Into Posterior Mitral Leaflet Inter-Scallop Malcoaptation During Acute Ischemic Mitral Regurgitation

Circulation ◽  
2002 ◽  
Vol 106 (12_suppl_1) ◽  
Author(s):  
David T. Lai ◽  
Frederick A. Tibayan ◽  
Truls Myrmel ◽  
Tomasz A. Timek ◽  
Paul Dagum ◽  
...  
Keyword(s):  
Mitral Regurgitation ◽  
High Speed ◽  
Lateral Displacement ◽  
Three Dimensional ◽  
Mitral Annulus ◽  
Left Ventricular ◽  
Ischemic Mitral Regurgitation ◽  
Posterior Leaflet ◽  
Mitral Leaflet ◽  
Posterior Mitral Leaflet

Background Three-dimensional dynamics of the 3 individual scallops within the posterior mitral leaflet during acute ischemic mitral regurgitations have not been previously measured. Methods Radiopaque markers were sutured to the mitral annulus, papillary muscle tips, and leaflet edges in 13 sheep. Immediately postoperatively, under open-chest conditions, 3-D marker coordinates were obtained using high-speed biplane videofluoroscopy before and during echocardiographically verified acute ischemic mitral regurgitation produced by occlusion of the left circumflex coronary artery. Results During acute ischemic mitral regurgitation, at end systole, the anterolateral edge of the central scallop was displaced 0.8±0.9 mm laterally and 0.9±0.6 mm apically away from the anterolateral scallop; such displacement correlated with lateral displacement of the lateral annulus (R 2 =0.7, SEE=0.7 mm, P <0.001) and movement of the right lateral annulus away from the nonischemic anterior papillary tip (R 2 =0.6, SEE=0.8 mm, P =0.002), respectively. End-systolic displacement of the posteromedial edge of the central scallop was 1.4±0.9 mm anteriorly and 0.9±0.6 mm laterally away from the posteromedial scallop, corresponding to anterior displacement of the mid-lateral annulus (R 2 =0.5, SEE=1.0 mm, P <0.001). Conclusions Malcoaptation of the scallops within the posterior leaflet during acute left ventricular ischemia is a novel observation. The primary geometric mechanism underlying scallop malcoaptation in acute ischemic mitral regurgitation was annular dilatation, which hindered leaflet coaptation by drawing the individual scallops apart. These findings support the use of annular reduction in the repair of ischemic mitral regurgitation and also suture closure of prominent subcommissures between posterior leaflet scallops.

INVESTIGATION INTO THE CALCULATION OF SUPERELEVATION DEFECTS ON CONVENTIONAL RAIL LINES

Transport ◽  
2012 ◽  
Vol 27 (3) ◽  
pp. 229-236 ◽  
Author(s):  
Inesa Gailienė
Keyword(s):  
High Speed ◽  
Great Influence ◽  
Railway Track ◽  
Lateral Acceleration ◽  
Essential Factor ◽  
Railway Line ◽  
Passenger Transportation ◽  
Heavy Haul ◽  
Train Speed ◽  
Conventional Rail

Railway curves have influence on train speed on a curve and/or wheel/rail interface. Additional forces that have to be compensated appear in the curves. The purpose of superelevation is to compensate acceleration emerging in the curve thus assuring comfortable passenger transportation and equal wearing of both rails. However, it is very difficult to calculate superelevation when designing and maintaining a railway track, because the estimation of actual train speed on the curves is very complicated. As we know, railway lines can be divided into conventional, high speed and heavy haul ones. As these lines are absolutely different, requirements for the installation and maintenance of the track may also differ. Conventional rail lines are the object of research discussed in this article. The speed of freight and passenger trains is different on conventional rail lines, which is an essential factor in determining superelevation. On the ground of scientific researches, the article analyzes and evaluates the factors influencing wheel/rail interface on the curves. The paper also deals with railway line curves, superelevation and uncompensated lateral acceleration. The article presents the method used in Lithuania for calculating superelevation in the railway curves and analyzes calculation defects. For research purposes, analytical and statistical methods have been used. The obtained results have shown that actual superelevation in the researched curves does not match the calculated one. The calculations and obtained results of superelevation depend on how average train speed in the curves is estimated and used for calculations. As most of the results show that even small variations in the curve have a great influence on track/vehicle behaviour, it is necessary to find more precise methods for calculating superelevation, evaluating actual train speed and considering permissible uncompensated lateral acceleration in the curves.

Dynamic Responses Analysis of Vehicle and Track Based on Different Train Speed

2013 ◽  
Vol 706-708 ◽  
pp. 1314-1318
Author(s):  
Hong Mei Shi ◽  
Zu Jun Yu
Keyword(s):  
High Speed ◽  
Rapid Development ◽  
Coupling Model ◽  
Dynamic Responses ◽  
High Speed Railway ◽  
Vertical Coupling ◽  
Railway Infrastructure ◽  
Train Operation ◽  
Vibration Responses ◽  
Train Speed

With the rapid development of high-speed railway, dynamic interaction between vehicles and track is correspondingly strengthened. Therefore, dynamic responses analysis of the high-speed vehicles and track become more and more important to the train operation safety, riding comfort as well as the maintenance of railway infrastructure. In this paper, vehicle and track vibration equations are separately established based on the vehicle track vertical coupling model. Taking the CRH vehicle running on the existing line as an example, the random vibration responses of the vehicle and track under different running speed are analyzed in time domain through numerical integral method and MATLAB program. According to the results, the velocity of train has more influence on the vibration property of rail and wheelsets than bogie and carbody.

A three-dimensional coupled dynamics model of the air spring of a high-speed electric multiple unit train

2016 ◽  
Vol 231 (1) ◽  
pp. 3-18 ◽  
Author(s):  
Zhuang Qi ◽  
Fu Li ◽  
Dalian Yu
Keyword(s):  
High Speed ◽  
Ride Comfort ◽  
Lateral Displacement ◽  
Three Dimensional ◽  
Coupled Model ◽  
Nonlinear Behaviour ◽  
Dynamics Model ◽  
Air Spring ◽  
Coupled Dynamics ◽  
Multiple Unit

Although air springs are widely applied on high-speed electric multiple unit (EMU) trains, there is no accepted method to model the dynamics of these air springs. In this paper, a three-dimensional (3D)-coupled dynamics model of an air spring used on a high-speed EMU train was created through the derivation of thermodynamics equations and using a curve-fitting method. Experimental and simulated stiffness tests were performed to verify the accuracy of the 3D-coupled model, which was then implemented in the MBS vehicle dynamics model. The influence of the nonlinear behaviour of the air spring on the vehicle’s dynamic performance was analyzed by a dual-simulation approach using the 3D-coupled model of the air spring and the dynamics model of the vehicle. From the results, it can be concluded that the air spring can improve the vehicle’s vertical ride comfort, due to its ability to adjust the vertical stiffness and damping based on the level of vibration. However, the vehicle’s ability to negotiate curves is reduced due to an increase in the air spring’s lateral and longitudinal stiffness, a result of the lateral displacement of the car body. Furthermore, the operation of the leveling valve in the 3D-coupled model can slightly reduce the vehicle’s overturning coefficient, which is a phenomenon that the normal air spring models cannot simulate. Finally, the 3D-coupled model was applied to simulate a leakage process, which is a complex series of chain reactions, in the air spring system. The calculation results indicate that, even though the ride comfort is severely degraded by the leakage, the vehicle’s running safety can still be guaranteed.

scholarly journals Three-Dimensional Dynamic Analyses of Track-Embankment-Ground System Subjected to High Speed Train Loads

2014 ◽  
Vol 2014 ◽  
pp. 1-19 ◽  
Author(s):  
Qiang Fu ◽  
Changjie Zheng
Keyword(s):  
Dynamic Response ◽  
High Speed ◽  
Concrete Slab ◽  
Three Dimensional ◽  
Element Model ◽  
Moving Loads ◽  
Infinite Elements ◽  
Ground System ◽  
High Speed Trains ◽  
Train Speed

A three-dimensional finite element model was developed to investigate dynamic response of track-embankment-ground system subjected to moving loads caused by high speed trains. The track-embankment-ground systems such as the sleepers, the ballast, the embankment, and the ground are represented by 8-noded solid elements. The infinite elements are used to represent the infinite boundary condition to absorb vibration waves induced by the passing of train load at the boundary. The loads were applied on the rails directly to simulate the real moving loads of trains. The effects of train speed on dynamic response of the system are considered. The effect of material parameters, especially the modulus changes of ballast and embankment, is taken into account to demonstrate the effectiveness of strengthening the ballast, embankment, and ground for mitigating system vibration in detail. The numerical results show that the model is reliable for predicting the amplitude of vibrations produced in the track-embankment-ground system by high-speed trains. Stiffening of fill under the embankment can reduce the vibration level, on the other hand, it can be realized by installing a concrete slab under the embankment. The influence of axle load on the vibration of the system is obviously lower than that of train speed.

scholarly journals Study of the Vibration-Energy Properties of the CRTS-III Track Based on the Power Flow Method

Symmetry ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 69 ◽  
Author(s):  
Hanwen Jiang ◽  
Liang Gao
Keyword(s):  
High Speed ◽  
Power Flow ◽  
Coupling Model ◽  
Vibration Energy ◽  
Track Structure ◽  
Severe Problem ◽  
Evaluation Indexes ◽  
Flow Method ◽  
New Perspective ◽  
Power Flow Method

The vibration induced by the high-speed railway (HSR) system has been a severe problem during the construction and operation period. To investigate the vibration-energy properties of the China Railways Track System (CRTS)-III track, a vehicle-track-subgrade coupling model is developed, in which the distribution of the tangent force is symmetrical according to the FASTSIM theory, and the power flow method is utilized. What’s more, the corresponding evaluation indexes of the power flow are proposed to analyze the vibration energy of the track structure. The results reveal that the vibration energy decreases from top to bottom of the track structure among the frequency considered, and the decreasing trend is obvious. The vibration energy of the track structure is sensitive to the stiffness of fasteners. Differently, the vibration energy of the composite slab and the base slab is more sensitive to the stiffness of rubber damping pads than that of the rail. To sum up, this paper can provide a new perspective and method to study the vibration-energy properties and select the reasonable stiffness of the fasteners and the rubber damping pads of the CRTS-III track, and the proposed values of the stiffness of the fasteners and the rubber damping pads for the case under this study are 40 kN/mm and 400 MPa/m, respectively.

Parameters Analysis of Train Running Performance on High-Speed Bridge during Earthquake

2010 ◽  
Vol 163-167 ◽  
pp. 4457-4463 ◽  
Author(s):  
Yu Sen Lin ◽  
Li Hua Xin ◽  
Min Xiang
Keyword(s):  
High Speed ◽  
Lateral Displacement ◽  
Damping Ratio ◽  
Dominant Frequency ◽  
Dynamic Responses ◽  
Natural Vibration Frequency ◽  
Wheel Load ◽  
Running Performance ◽  
Vehicle Acceleration ◽  
Train Speed

A model of coupled vehicle-bridge system excited by earthquake and irregular track is established for studying train running performance on high-speed bridge during earthquake, by the methods of bridge structure dynamics and vehicle dynamics. The results indicate that under Qian’an earthquake waves vehicle dynamical responses hardly vary with the increasing-height pier, but vehicle dynamical responses increase evidently while the height of pier is 18m, which the natural vibration frequency is approaching to dominant frequency of earthquake waves. Dynamic responses are linearly increasing with earthquake wave strength. Dynamic response of vehicles including lateral car body accelerations and every safety evaluation index all increase with train speed, so the influences of train speed must be taken into account in evaluating running safety of vehicles on bridge during earthquakes, but lateral displacement of bridge is varying irregularly. Dynamic responses and lateral displacement of bridge reduce under the higher dominant frequency of earthquake wave. Derailment coefficient, later wheel-rail force and lateral vehicle acceleration become small with increasing damping ratio. Vertical vehicle acceleration and reduction rate of wheel load are hardly varying with damping ratio.

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