scholarly journals Effects of Differential Subgrade Settlement on Slab Track Deformation Based on a DEM-FDM Coupled Approach

2021 ◽  
Vol 11 (4) ◽  
pp. 1384
Author(s):  
Xuhao Cui ◽  
Rui Zhou ◽  
Gaoran Guo ◽  
Bowen Du ◽  
Hanlin Liu
Keyword(s):  
Contact Force ◽  
Three Dimensional ◽  
Coupled Model ◽  
Contact Forces ◽  
Railway Track ◽  
Slab Track ◽  
Maximum Value ◽  
Track System ◽  
Track Deformation ◽  
Maximum Contact

Slab track structures become deformed under the effects of differential subgrade settlement. According to the properties of the China Railway Track System (CRTS) II slab track on a subgrade, a three-dimensional (3D) coupled model based on both the discrete element method (DEM) and finite difference method (FDM) was developed. The slab track and subgrade were simulated using the FDM and DEM, respectively. The coupled model was verified. The deformation of the slab track and contact forces of gravel grains in the surface layer of the subgrade were studied under differential subgrade settlement. The effects of settlement wavelength, settlement amplitude, and other types of settlements were also discussed. The results demonstrate that the settlement amplitude and settlement wavelength of the subgrade have significant effects on track deformation. The deformation amplitude of the slab track increases nonlinearly with an increasing settlement amplitude of the subgrade. Increases in the settlement wavelength and amplitude of the subgrade significantly increase the maximum value of the contact force of the gravel grains in the subgrade. The maximum contact force of gravel grains near the boundaries of the settlement section can reach two to three times that of the unsettled condition, which makes it easy to accelerate the plastic settlement of the subgrade.

Rail vehicle model motion analysis on curved track with vertical irregularity

2020 ◽  
Vol 130 ◽  
pp. 75-84
Author(s):  
Mirosław Dusza
Keyword(s):  
Contact Forces ◽  
Railway Track ◽  
Temperature Changes ◽  
Track System ◽  
Standards And Regulations ◽  
Vehicle Motion ◽  
Track Irregularity ◽  
Atmospheric Phenomena ◽  
The Impact ◽  
Track Deformation

The properties of a classic railway track largely depend on the properties of the sub-grade, which is most often a natural creation. Atmospheric phenomena (e.g. temperature changes, heavy rainfall) can locally reduce the elasticity of the subgrade and create conditions conducive to permanent track deformation. One of the most common forms of a track fragment destruction is the loss of foundation support (one or several neighbouring sleepers) resulting from the indentation of the ballast material in the subgrade. The pressure of a vehicle passing through a damaged section of the track causes the so-called dynamic track irregularity. The impact of dynamic track vertical irregularity on the values of wheel-rail contact forces of a passing vehicle was investigated. The model of the passenger wagon-track system was created using the VI-Rail tool. The vehicle motion on curves with different values of track radius and superelevations was investigated. Vertical track irregularities occur on the internal rail only. The lengths of the track irregularity correspond to one, two or three sleepers unsupported on one side. The test results are presented in the form of diagrams and referred to applicable standards and regulations.

The Effect of Body Position and Number of Supports on Wall Reaction Forces in Rock Climbing

1997 ◽  
Vol 13 (1) ◽  
pp. 14-23 ◽  
Author(s):  
Franck Quaine ◽  
Luc Martin ◽  
Jean-Pierre Blanchi
Keyword(s):  
Body Weight ◽  
Contact Force ◽  
Body Position ◽  
Three Dimensional ◽  
Rock Climbing ◽  
Contact Forces ◽  
Vertical Posture ◽  
Reaction Forces ◽  
Force Data ◽  
Lower Contact

This manuscript describes three-dimensional force data collected during postural shifts performed by individuals simulating rock-climbing skills. Starting from a quadrupedal vertical posture, 6 expert climbers had to release their right-hand holds and maintain the tripedal posture for a few seconds. The vertical and contact forces (lateral and anteroposterior forces) applied on the holds were analyzed in two positions: an “imposed” position (the trunk far from the supporting wall) and an “optimized” position (the trunk close to the wall and lower contact forces at the holds). The tripedal postures performed in the two positions were achieved by the same pattern of vertical and contact forces exerted by the limbs on the holds. In the optimized position, the transfer of the forces was less extensive than in the imposed position, so that the forces were exerted primarily on the ipsilateral hold. Moreover, a link between the contact force values and the couple due to body weight with respect to the feet was shown.

Finite Element Analysis of a Fishplate Rail Joint in Extreme Environment Condition

2020 ◽  
Vol 12 (5) ◽  
Author(s):  
Sunil Kumar Sharma ◽  
Jaesun Lee
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Element Model ◽  
Extreme Environment ◽  
High Rate ◽  
Railway Track ◽  
Element Analysis ◽  
Track System ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

Railways are very efficient mode of transportation. Speed limits of the railways and loads they carry are increasing rapidly. Due to some advantages, the insulated rail joints are still the part of a rail-track system. However, a high rate of failure of joints puts the railway track at risk. Therefore, a detailed study of these joints is required. In this paper, a three-dimensional finite element model of rail-fishplate joint is created using Abaqus - a finite element method-based software. Stresses in fishplate and bolts due to wheel impact are analysed by coupling implicit and explicit methods. It is found that bolts are a critical part of a joint due to stresses and vibrations to which they are subjected. The large number of stresses and vibration can result into loosening of bolts.

Robust contact force estimation for robot manipulators in three-dimensional space

2006 ◽  
Vol 220 (9) ◽  
pp. 1317-1327 ◽  
Author(s):  
J Jung ◽  
J Lee ◽  
K Huh
Keyword(s):  
Contact Force ◽  
Robot Manipulator ◽  
Robot Manipulators ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Contact Forces ◽  
Robust Estimator ◽  
Force Sensors ◽  
Force Estimation ◽  
Estimation Algorithms

Information on contact forces in robot manipulators is indispensable for fast and accurate force control. Instead of expensive force sensors, estimation algorithms for contact forces have been widely developed. However, it is not easy to obtain the accurate values due to uncertainties. In this article, a new robust estimator is proposed to estimate three-dimensional contact forces acting on a three-link robot manipulator. The estimator is based on the extended Kalman filter (EKF) structure combined with a Lyapunov-based adaptation law for estimating the contact force. In contrast to the conventional EKF the new estimator is designed such that it is robust to the deterministic uncertainties such as the modelling error and the sensing bias. The performance of the proposed estimator is evaluated through simulations of a robot manipulator and demonstrates robustness in estimating the contact force. The estimation results show that it can be potentially used to replace the expensive force sensors in robot applications.

scholarly journals Contact Loss beneath Track Slab Caused by Deteriorated Cement Emulsified Asphalt Mortar: Dynamic Characteristics of Vehicle-Slab Track System and Prototype Experiment

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Dan Liu ◽  
Yu-feng Liu ◽  
Juan-juan Ren ◽  
Rong-shan Yang ◽  
Xue-yi Liu
Keyword(s):  
Dynamic Characteristics ◽  
Railway Track ◽  
Fem Model ◽  
Slab Track ◽  
Operation Speed ◽  
Track System ◽  
Emulsified Asphalt ◽  
Ca Mortar ◽  
Asphalt Mortar ◽  
Track Slab

The contact loss beneath track slab caused by deteriorated cement emulsified asphalt mortar (CA mortar) has been one of the main diseases occurring in the CRTS- (China Railway Track System-) I Slab Track of high-speed railway in China. Based on the slab track design theory and the vehicle-track coupling vibration theory, a vehicle-track vertical coupling dynamic FEM model was established to analyze the influence of the contact loss length on the dynamic characteristics of vehicle and track subsystems at different train speeds. A prototype dynamic characteristic experimental test of CRTS-I Slab Track with CA mortar contact loss was conducted to verify the FEM model results. The train load was generated by the customized ZSS50 excitation car. The results showed that when the operation speed is less than 300 km/h, the contact loss with length smaller than 2.0 m barely affects the running smoothness ride safety of vehicle. The contact loss length effect on the dynamic characteristics of track subsystem is pronounced, especially on the track slab. Once the contact loss beneath the track slab occurs, the vibration displacement and the acceleration of the track slab increase rapidly, while it has little influence on the displacement and acceleration of the concrete roadbed.

Optimal Contact Force Distribution for Multi-Limbed Robots

2005 ◽  
Vol 128 (3) ◽  
pp. 566-573 ◽  
Author(s):  
Dennis W. Hong ◽  
Raymond J. Cipra
Keyword(s):  
Contact Force ◽  
Dimensional Space ◽  
Contact Point ◽  
Three Dimensional ◽  
Optimal Solution ◽  
Solution Space ◽  
Contact Forces ◽  
Force Distribution ◽  
New Strategy ◽  
Contact Force Distribution

One of the inherent problems of multi-limbed mobile robotic systems is the problem of multi-contact force distribution; the contact forces and moments at the feet required to support it and those required by its tasks are indeterminate. A new strategy for choosing an optimal solution for the contact force distribution of multi-limbed robots with three feet in contact with the environment in three-dimensional space is presented. The incremental strategy of opening up the friction cones is aided by using the “force space graph” which indicates where the solution is positioned in the solution space to give insight into the quality of the chosen solution and to provide robustness against disturbances. The “margin against slip with contact point priority” approach is also presented which finds an optimal solution with different priorities given to each foot contact point. Examples are presented to illustrate certain aspects of the method and ideas for other optimization criteria are discussed.

Coupling OCREC Contact Code With ADAMS: Simulations of One Coach at 130mph

2009 ◽  
Author(s):  
J. P. Pascal ◽  
J. Berger ◽  
F. Bondon ◽  
C. Clerc ◽  
S. Teppe
Keyword(s):  
High Speed ◽  
Model Updating ◽  
Contact Forces ◽  
Railway Track ◽  
Frenet Frame ◽  
Time Step ◽  
Space Curves ◽  
Track System ◽  
Curvature Measurements ◽  
Multi Body

This paper presents the Online Calculation of Railway Elastic Contacts (OCREC), a dynamic railway calculation tool based on an advanced contact kernel, and its coupling with the MSC ADAMS multi-body commercial software. The OCREC contact kernel is used as a subroutine of multi-body codes in order to calculate contact forces between wheelsets and rails. The OCREC method is “online” as it not only redefines new contact parameters at each time step but also determines all simultaneous contacts on each wheel as allowed by Hertz Elasticity theory. From the normal forces and relative velocities given by the Hertz theory, Tangential Forces are calculated using Kalker’s FASTSIM (modified for elliptical pressure distribution). After a description of the OCREC theory, the paper presents the linkage between OCREC and MSC ADAMS software. OCREC calculates contact forces within a Frenet frame (oxyz) following the track layout where ox is tangent to the track; oy is horizontal and oz normal to oxy. As ADAMS calculates inside a different frame, and as it has no built-in track system, it was necessary to develop a program capable of connecting 3 different frames: the ‘dummy’ track frame, the Frenet frame and the fixed ADAMS frame. Note that the ‘dummy’ frame is directly calculated from railway track curvature measurements recorded in so-called ‘space curves’. The OCREC ADAMS link is first validated by a bogie rolling on a dummy track. With the equations of the OCRECYM code established directly within the “dummy” frame, the OCREC-ADAMS results are compared to a specific OCRECYM validation code. Then, the results from an actual railway case are presented: behavior of one coach is calculated on a real measured track including curves and defaults. During the following step, the OCREC-ADAMS results are compared to OCRECYM results. After some model updating for adjustment to physical properties of elastic joints (helicoidal springs), a good correlation is obtained between the codes. The analysis of the different force and displacement components proves this kind of numerical tool’s capabilities of assessing the railway vehicle’s dynamic behavior. Especially, the Y/Q safety ratio is well calculated. Thus, the OCREC contact kernel, which is powerful for complex contact topologies such as conformal contacts, and necessary for high speed safety calculation, can be used as a subroutine of standard multi-body software, giving it high capabilities for dynamic railway calculation.

Dynamic characteristic difference of steel-spring floating slab track between single-carriage and multi-carriage models

2021 ◽  
pp. 095745652199986
Author(s):  
Wenhao Chang ◽  
Xiaopei Cai ◽  
Qihao Wang
Keyword(s):  
Coupling Effect ◽  
Three Dimensional ◽  
Coupled Model ◽  
Measured Data ◽  
Dynamic Responses ◽  
Theoretical Research ◽  
Maximum Displacement ◽  
Steel Spring ◽  
Slab Track ◽  
Computation Efficiency

The steel-spring floating slab track (SSFST) is a low-stiffness structure, sensitive to the vehicle loads. Due to the coupling effect of the superposition of adjacent bogies, it is difficult for conventional single-carriage models to meet the simulation requirements. To find a balance between computation efficiency and authenticity of analytical model results, the influence of carriage number on SSFST should be studied. Based on the finite element method and multi-body dynamics, a refined three-dimensional coupled model of multi-carriage-SSFST-tunnel was established. The difference in the dynamic response of the SSFST between single-carriage and multi-carriage models was analyzed and compared with the measured data. The field test results show that structural displacements and accelerations under the two-carriage model are much closer to the measured data. The dynamic model analysis results show that the maximum displacement of the rail and SSFST in the midspan of the slab increase by 0.48 mm and 0.34 mm under the multi-carriage model, and the vibration reduction effectiveness increases by 1.4–2.0 dB. Dynamic responses of the rail and SSFST show minor differences under the two-carriage and three-carriage models. The article is expected to provide a reference for the theoretical research, design, and layout optimization of subway SSFST.

scholarly journals Performance of railway track system under harmonic loading by finite element method

2018 ◽  
Vol 162 ◽  
pp. 01043
Author(s):  
Ammar Shuber ◽  
Mohammed Hamood ◽  
Walaa Jawad
Keyword(s):  
Soil Structure ◽  
Theoretical Models ◽  
Contact Forces ◽  
Railway Track ◽  
Ansys Software ◽  
Applied Loading ◽  
High Speeds ◽  
Track System ◽  
European Code ◽  
Real Behavior

The performance of railway track under dynamic loading depends on many parameters such as type of sleepers, ballast, soil - structure interaction and the relation of contact forces between the track and railway. The rail track classified as low and high speeds, where speed is a very important factor in design. Many theoretical models were derived and some developed for dynamic analysis of railway track system with assumptions that simplified or matched actually the real behavior especially the support of sleepers as linear or nonlinear and the contact between railway and track. In the present paper, a Finite Elements Approach is one of the numerical analysis by ANSYS software that adopted here to study the performance of harmonic analysis of railway track system. Harmonic ranges were applied with constant applied loading based on the European code for the steel rail.

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