scholarly journals Effect of the vertical relative motion of stock/switch rails on wheel–rail contact mechanics in switch panel of railway turnout

2018 ◽  
Vol 10 (7) ◽  
pp. 168781401879065 ◽  
Author(s):  
Xiaochuan Ma ◽  
Ping Wang ◽  
Jingmang Xu ◽  
Rong Chen
Keyword(s):  
Contact Mechanics ◽  
Relative Motion ◽  
Contact Forces ◽  
Actual Contact ◽  
Numerical Example ◽  
Line Method ◽  
Contact Points ◽  
Trace Line ◽  
Railway Turnout

In order to enable the vehicle to change among the tracks, the stock and switch rails are separated and provided with different rail resilience levels on the baseplate in the railway turnout switch panel. Therefore, there will be vertical relative motion between stock/switch rails under wheel loads, and the relative motion will change the combined profile of stock/switch rails and consequently affect the wheel–rail contact mechanics. A method is developed in this article to investigate the effect of the relative motion of stock/switch rails on the wheel–rail contact mechanics along the railway turnout switch panel. First, the possible rigid wheel–rail contact points, called primary and secondary stock/switch rail contact points, are calculated based on the trace line method; second, the actual contact points are determined by the presented equations; finally, the distribution of wheel–rail contact forces on the stock/switch rails is obtained based on the continuity of interface displacements and forces. A numerical example is presented in order to investigate the effect of the relative motion of stock/switch rails on the wheel–rail contact points, stresses, and forces, and the results are presented and discussed.

Wedge Damper Modeling and Forced Response Prediction of Frictionally Constrained Blades

2007 ◽  
Author(s):  
Ender Cigeroglu ◽  
Ning An ◽  
Chia-Hsiang Menq
Keyword(s):  
Rigid Body ◽  
Relative Motion ◽  
Harmonic Balance ◽  
Contact Stiffness ◽  
Contact Point ◽  
Harmonic Balance Method ◽  
Forced Response ◽  
Contact Forces ◽  
Contact Points ◽  
Contact Surfaces

In this paper, an improved wedge damper model is presented, based on which the effects of wedge dampers on the forced response of frictionally constrained blades are investigated. In the analysis, while the blade is modeled as a constrained structure, the damper is considered as an unconstrained structure. The model of the damper includes six rigid body modes and several elastic modes, the number of which depends on the excitation frequency. In other words, the motion of the damper is not artificially constrained. When modeling the contact surfaces of the wedge damper, discrete contact points along with contact stiffness are evenly distributed on the two contact surfaces. At each contact point, contact stiffness is determined and employed in order to take into account the effects of higher frequency modes that are omitted in the dynamic analysis. Depending on the engine rpm, quasi-static contact analysis is initially employed to determine the contact area as well as the initial preload or gap at each contact point due to the centrifugal force. A friction model is employed to determine the three-dimensional nonlinear contact forces and the relationship between the contact forces and the relative motion is utilized by the Harmonic Balance method. As the relative motion is expressed as a modal superposition, the unknown variables, and thus the resulting nonlinear algebraic equations, in the Harmonic Balance method is in proportion to the number of modes employed, and therefore the number of contact points used is irrelevant. The developed method is applied to tuned bladed disk system and the effects of normal load on the rigid body motion of the damper are investigated. It is shown that, the effect of rotational motion is significant, particularly for the in-phase vibration modes.

scholarly journals Slipping–rolling transitions of a body with two contact points

2021 ◽  
Author(s):  
Mate Antali ◽  
Gabor Stepan
Keyword(s):  
Rigid Body ◽  
Contact Point ◽  
Static Friction ◽  
Rigid Body Dynamics ◽  
Contact Forces ◽  
Friction Forces ◽  
Contact Points ◽  
Body Dynamics ◽  
Coulomb Model ◽  
Rigid Surfaces

AbstractIn this paper, the general kinematics and dynamics of a rigid body is analysed, which is in contact with two rigid surfaces in the presence of dry friction. Due to the rolling or slipping state at each contact point, four kinematic scenarios occur. In the two-point rolling case, the contact forces are undetermined; consequently, the condition of the static friction forces cannot be checked from the Coulomb model to decide whether two-point rolling is possible. However, this issue can be resolved within the scope of rigid body dynamics by analysing the nonsmooth vector field of the system at the possible transitions between slipping and rolling. Based on the concept of limit directions of codimension-2 discontinuities, a method is presented to determine the conditions when the two-point rolling is realizable without slipping.

Periodic Response of a Link Coupling With Clearance

1989 ◽  
Vol 111 (2) ◽  
pp. 253-259 ◽  
Author(s):  
Y. S. Choi ◽  
S. T. Noah
Keyword(s):  
Steady State ◽  
Boundary Conditions ◽  
Solution Procedure ◽  
Contact Forces ◽  
Steady State Response ◽  
Algebraic Equations ◽  
State Response ◽  
Contact Points ◽  
Integration Schemes ◽  
Nonlinear Algebraic Equations

The nonlinear, steady-state response of a displacement-forced link coupling with clearance with finite stiffness is determined. The solution procedure is derived from satisfying the boundary conditions at the contact points and then solving the resulting nonlinear algebraic equations by setting the duration of contact as a parameter. This direct approach to determining periodic solutions for systems with clearances with finite stiffness is substantially more efficient than numerical integration schemes. Results in terms of contact forces and durations of contact are pertinent to fatigue and wear studies. Parametric relations are presented for effects of the variation of damping, stiffness, exciting displacement, and gap length on the dynamic behavior of the link pair.

Estimation of Graphite Dust Production in a Pebble-Bed Type Nuclear Reflector

2014 ◽  
Author(s):  
Ji-Ho Kang ◽  
Eung Seon Kim ◽  
Seungyon Cho
Keyword(s):  
Adhesive Wear ◽  
Cell Model ◽  
Estimation Method ◽  
Unit Cell ◽  
Contact Forces ◽  
Dust Explosion ◽  
Dust Production ◽  
Pebble Bed ◽  
Normal Contact ◽  
Contact Points

In this study, an estimation method of graphite dust production in the pebble-bed type reflector region of Korean HCSB (Helium-Cooled Solid Breeder) TBM (Test Blanket Module) in the ITER (International Thermonuclear Experimental Reactor) project using FEM (Finite Element Method) was proposed and the amount of dust production was calculated. A unit-cell model of uniformly arranged pebbles was defined with appropriate thermal and mechanical loadings. A commercial FEM program, Abaqus V6.10 was used to model and solve the stress field under multiple contact constraints between pebbles in the unit-cell. Resulting normal contact forces and slip distances on contact points were applied into the Archard adhesive wear equation to calculate the amount of graphite dust. The friction effect on contact points was investigated. The calculation result showed that the amount of graphite dust production was estimated to 2.22∼3.67e−4 g/m3 which was almost linearly proportional to the friction coefficient. The analysis results will be used as the basis data for the consecutive study of dust explosion.

scholarly journals Repeatability Analysis of Overconstrained Kinematic Coupling Using a Parallel-Mechanism-Equivalent Model

2020 ◽  
Author(s):  
Jianzhong Ding ◽  
Xueao Liu ◽  
chunjie wang
Keyword(s):  
Parallel Mechanism ◽  
Sampling Method ◽  
Contact Forces ◽  
Equivalent Model ◽  
Parallel Mechanisms ◽  
Kinematic Coupling ◽  
Contact Points ◽  
Prismatic Joints ◽  
Type Coupling ◽  
Additional Support

Abstract A novel method for repeatability analysis of overconstrained kinematic coupling using a parallel-mechanism-equivalent-model is proposed. An overconstrained Kelvin-type coupling with one additional support is introduced and used for method illustration. Contact forces of the overconstrained coupling under preload are computed with Moore-Penrose inverse and the deformations are obtained using the Hertz theory. The couping is equivalently modeled as a 7-SPS parallel mechanism, spherical joints of which represent the centers of the supporting balls and the contact points, respectively, and prismatic joints are used to simulate the deformations. Therefore, pose error of the coupling arisen from preload is analyzed using the well-appraised incremental method for forward kinematics analysis of parallel mechanisms. The uncertainties of the preload are discussed and a boundary-sampling method is proposed for repeatability analysis. The main contribution of this study lies in that the proposed parallel-mechanism-equivalent-model and the boundary-sampling method greatly simplify the repeatability analysis of overconstrained kinematic couplings. Finally, the proposed methods are validated by case study.

Calculation of Contact Forces of Large-Scale Heavy Forging Manipulator Grippers

2009 ◽  
Vol 419-420 ◽  
pp. 645-648 ◽  
Author(s):  
Qun Ming Li ◽  
Dan Gao ◽  
Hua Deng
Keyword(s):  
Large Scale ◽  
Optimization Method ◽  
Contact Forces ◽  
Robotic Hand ◽  
Closure Condition ◽  
Contact Points ◽  
Robot Hands ◽  
Calculation Results ◽  
Forging Manipulator ◽  
Gripping Force

Different from dexterous robotic hands, the gripper of heavy forging manipulator is an underconstrained mechanism whose tongs are free in a small wiggling range. However, for both a dexterous robotic hand and a heavy gripper, the force closure condition: the force and the torque equilibrium, must be satisfied without exception to maintain the grasping/gripping stability. This paper presents a gripping model for the heavy forging gripper with equivalent friction points, which is similar to a grasp model of multifingered robot hands including four contact points. A gripping force optimization method is proposed for the calculation of contact forces between gripper tongs and forged object. The comparison between the calculation results and the experimental results demonstrates the effectiveness of the proposed calculation method.

Modeling of a Finger-Follower Cam System With Verification in Contact Forces

1993 ◽  
Author(s):  
Wensyang Hsu ◽  
Albert P. Pisano
Keyword(s):  
Constraint Equation ◽  
Contact Forces ◽  
Valve Train ◽  
Dynamic Responses ◽  
Valve Lift ◽  
Distributed Parameter ◽  
Contact Points ◽  
Frictional Forces ◽  
Contact Position ◽  
Force Data

Abstract A lumped/distributed-parameter, dynamic model is developed to investigate the dynamic responses of a finger-follower valve train with the effects of an oscillating pivot, frictional forces between sliding surfaces, and a hydraulic lash adjuster. Based on the measured force data at low speed, an algorithm is derived to determine the dynamic Coulomb friction coefficients around maximum valve lift simultaneously at three contact points. A constraint equation is formulated to find the contact position between the cam and the follower kinematically. This makes it possible for the model to simulate the dynamic response of the cam system when the pivot is moving. A hydraulic lash adjuster acting as the pivot of the follower is also modeled with the effects of oil compressibility and oil refill mechanism. The model is numerically integrated and shown to have good agreement between simulation results and experimental data of contact forces at three different speeds. The maximum operating speed is limited by valve toss, loss contact between components. The model predicts toss between the hydraulic lash adjuster and the follower at 2535 rpm, and experiment indicates toss starting at 2520 rpm of camshaft speed.

scholarly journals Wheelset/rail geometric characteristics and contact forces assessment with regard to angle of attack

2019 ◽  
Vol 254 ◽  
pp. 01014 ◽  
Author(s):  
Tomáš Lack ◽  
Juraj Gerlici ◽  
Pavol Šťastniak
Keyword(s):  
Gamma Function ◽  
Geometric Characteristic ◽  
Angle Of Attack ◽  
Contact Forces ◽  
Geometric Characteristics ◽  
Contact Points ◽  
Current State ◽  
Geometric Relation ◽  
Equivalent Conicity

The geometric relation between a wheelset and a rail is assessed with the help of geometric characteristics. Geometric characteristics are: equivalent conicity function, delta r function placement of contact points of a wheelset and a rail, tangent gamma function and effective conicity. It turned out that these characteristics are at present the most important not only for the judgment of ride characteristics of a vehicle on the rail but also for the wearing of wheel treads and rail heads, i.e., for the assessment of the track and vehicles in order to find out the current state and for the assessment of changes of the wheels and rails profile shapes in order to improve the current state too. The process of geometric characteristic assessment of a wheelset and rail with regard to angle of attack, as well as contact forces are analysed in the article.

Stability Analysis of High-Speed Railway Vehicle Based on Multibody Dynamics Analysis

2013 ◽  
Vol 392 ◽  
pp. 156-160
Author(s):  
Ju Seok Kang
Keyword(s):  
Stability Analysis ◽  
Multibody Dynamics ◽  
High Speed ◽  
Equations Of Motion ◽  
Contact Forces ◽  
Design Parameters ◽  
Railway Vehicle ◽  
Dynamics Analysis ◽  
Contact Points ◽  
The Stability

Multibody dynamics analysis is advantageous in that it uses real dimensions and design parameters. In this study, the stability analysis of a railway vehicle based on multibody dynamics analysis is presented. The equations for the contact points and contact forces between the wheel and the rail are derived using a wheelset model. The dynamics equations of the wheelset are combined with the dynamics equations of the other parts of the railway vehicle, which are obtained by general multibody dynamics analysis. The equations of motion of the railway vehicle are linearized by using the perturbation method. The eigenvalues of these linear dynamics equations are calculated and the critical speed is found.

The Development of a Roller Rig for Experimental Evaluation of Contact Mechanics for Railway Vehicles

2015 ◽  
Author(s):  
Sajjad Z. Meymand ◽  
Milad Hosseinipour ◽  
Mehdi Ahmadian
Keyword(s):  
Data Acquisition ◽  
Contact Mechanics ◽  
State Of The Art ◽  
Lateral Displacement ◽  
Data Acquisition System ◽  
Operating Conditions ◽  
Contact Forces ◽  
Acquisition System ◽  
Design Solution ◽  
Roller Rig

This paper discusses the development of a state of the art single-wheel roller rig for studying contact mechanics and dynamics in railroad applications. The use of indoor-based simulation tools has become a mainstay in vehicle testing for the automotive and railroad industries. In contrast to field-testing, roller rigs offer a controlled laboratory environment that can provide a successful path for obtaining data on the mechanics and dynamics of railway systems for a variety of operating conditions. The idea to develop a laboratory test rig started from the observation that there is a need for better-developed testing fixtures capable of accurately explaining the relatively unknown physics of the wheel-rail contact mechanics and dynamics. Developing a better understanding of such physics would assist with designing faster, safer, and more efficient railroad systems. A review of the existing roller rigs indicated that many desired functional requirements for studying contact mechanics are not readily available. The Virginia Tech Railway Technologies Laboratory (RTL) has embarked on a mission to develop a state-of-the-art testing facility that will allow experimental testing for contact mechanics in a dynamic, controlled, and consistent manner. The VT roller rig is intended to allow for actively controlling all the wheel-rail interface degrees of freedom: cant angle, angle of attack, and lateral displacement. Two AC synchronous servomotors, accompanied with proper gearheads, accurately drive the rotating wheels. A novel force measurement system, suitable for steel on steel contact, is configured to precisely measure the contact forces and torques. The control architecture is developed based on the SynqNet data acquisition system offered by Kollmorgen, the drive-motor and actuator supplier. The Synqnet provides a unified communication protocol between actuators, drives, and data acquisition system; therefore eliminating any difficulty with data conversion among these units. Other auxiliary sensors and measurement systems are implemented to help with characterizing the contact mechanics and contact geometry. This paper will describe the main steps in the design process of the VT roller rig and the final design solution selected. It will also present the testing capabilities of the rig. The design analysis indicates that the rig can successfully meet the set requirements: additional accuracy in measurements, and better control on the design of experiments.

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