Nonlinear Wheelset Forces in Flange Contact—Part 1: Steady State Analysis and Numerical Results

1979 ◽  
Vol 101 (3) ◽  
pp. 238-246 ◽  
Author(s):  
L. M. Sweet ◽  
J. A. Sivak
Keyword(s):  
Steady State ◽  
Contact Point ◽  
Lateral Force ◽  
Lateral Position ◽  
Geometric Constraints ◽  
Curving Performance ◽  
Yaw Angle ◽  
Nonlinear Geometric ◽  
Force Displacement ◽  
Yaw Moment

A theoretical model for steady-state wheelset force/displacement relations in tread and flange contact is presented. The analysis includes nonlinear geometric constraints that characterize wheel/rail contact, creep forces in the contact plane due to wheel/rail differential velocities, limits on adhesion at each contact point, and equilibrium conditions applied to the wheelset body forces. Results are summarized as the resultant lateral force and yaw moment acting on the wheelset as functions of lateral position and yaw angle. The results of this analysis, verified experimentally in Part 2 of this paper, are important to the analysis of wheelset response to track inputs, curving performance, and wheelclimb derailment.

Nonlinear Wheelset Forces in Flange Contact—Part 2: Measurements Using Dynamically Scaled Models

1979 ◽  
Vol 101 (3) ◽  
pp. 247-255 ◽  
Author(s):  
L. M. Sweet ◽  
J. A. Sivak ◽  
W. F. Putman
Keyword(s):  
Lateral Force ◽  
Contact Forces ◽  
Scale Model ◽  
Rail Vehicle Dynamics ◽  
Curving Performance ◽  
Lateral Displacements ◽  
Scaled Models ◽  
Force Displacement ◽  
Yaw Moment ◽  
Contact Part

This paper presents new experimental methods for the study of rail vehicle dynamics through the use of scaled models on tangent track, and the application of these techniques to the measurement of nonlinear wheelset force/displacement relations in steady-state. These relations are important to the analysis of wheelset response to track inputs, curving performance of trucks, and wheelclimb derailment. A one-fifth scale model instrumented wheelset with new wheel profiles is used, with similitude scaling of the contact forces achieved through use of a polycarbonate resin for the contact surfaces. Data are presented for wheelset lateral force and yaw moment for the nonlinear range of wheelset lateral displacements and yaw angles, including flange contact. The measured data validate the analytical model presented in Part 1 of this paper, based on nonlinear wheel/rail contact geometry, creep forces with adhesion limits, and wheelset kinematics. A criterion for wheelclimb derailment is presented and verified experimentally.

scholarly journals Effect of the Longitudinal Contact Location on Vehicle Dynamics Simulation

2016 ◽  
Vol 2016 ◽  
pp. 1-6 ◽  
Author(s):  
N. Burgelman ◽  
Z. Li ◽  
R. Dollevoet
Keyword(s):  
Dynamic Simulation ◽  
Contact Point ◽  
Vertical Plane ◽  
Numerical Approach ◽  
Dynamics Simulation ◽  
Vehicle Dynamic ◽  
Dynamic Simulations ◽  
Vehicle Dynamic Simulation ◽  
Yaw Angle ◽  
Yaw Moment

This paper investigates the effect of the calculation of the longitudinal location of a wheel rail contact point on the wheelset’s motion in a vehicle dynamic simulation. All current vehicle dynamic software programs assume that the contact between wheel and rail takes place in the vertical plane through the wheelset’s rolling axis. However, when the yaw angle of the wheelset is nonzero, the contact point is situated up to 10 mm from that plane. This difference causes a difference in the yaw moment on the wheelset which is used in the vehicle dynamic simulation. To such an end, an existing analytical method to determine the longitudinal method was validated using a numerical approach. Then vehicle dynamic simulations with both the classic and the new contact location were performed, concluding that using a more accurate contact point location results in a smaller wheelset yaw angle in a vehicle dynamic simulation, although the effect is small.

Computer Modeling of a Tire under Cornering Loads

1989 ◽  
Vol 17 (2) ◽  
pp. 86-99 ◽  
Author(s):  
I. Gardner ◽  
M. Theves
Keyword(s):  
Finite Element Analysis ◽  
Geometric Approach ◽  
Lateral Force ◽  
Slip Angle ◽  
Element Analysis ◽  
Pressure Distributions ◽  
Slip Effects ◽  
Improved Accuracy ◽  
Nonlinear Geometric ◽  
Good Agreement

Abstract During a cornering maneuver by a vehicle, high forces are exerted on the tire's footprint and in the contact zone between the tire and the rim. To optimize the design of these components, a method is presented whereby the forces at the tire-rim interface and between the tire and roadway may be predicted using finite element analysis. The cornering tire is modeled quasi-statically using a nonlinear geometric approach, with a lateral force and a slip angle applied to the spindle of the wheel to simulate the cornering loads. These values were obtained experimentally from a force and moment machine. This procedure avoids the need for a costly dynamic analysis. Good agreement was obtained with experimental results for self-aligning torque, giving confidence in the results obtained in the tire footprint and at the rim. The model allows prediction of the geometry and of the pressure distributions in the footprint, since friction and slip effects in this area were considered. The model lends itself to further refinement for improved accuracy and additional applications.

scholarly journals Camera-based measurement of cyclist motion

2018 ◽  
Vol 233 (7) ◽  
pp. 1793-1805 ◽  
Author(s):  
Chris Eddy ◽  
Christopher de Saxe ◽  
David Cebon
Keyword(s):  
Contact Point ◽  
Ground Plane ◽  
Blind Spot ◽  
Geometric Constraints ◽  
Average Error ◽  
Camera System ◽  
Position Data ◽  
Close Range ◽  
Heavy Goods Vehicles ◽  
Full Scale Tests

Heavy goods vehicles are overrepresented in cyclist fatality statistics in the United Kingdom relative to their proportion of total traffic volume. In particular, the statistics highlight a problem for vehicles turning left across the path of a cyclist on their inside. In this article, we present a camera-based system to detect and track cyclists in the blind spot. The system uses boosted classifiers and geometric constraints to detect cyclist wheels, and Canny edge detection to locate the ground contact point. The locations of these points are mapped into physical coordinates using a calibration system based on the ground plane. A Kalman Filter is used to track and predict the future motion of the cyclist. Full-scale tests were conducted using a construction vehicle fitted with two cameras, and the results compared with measurements from an ultrasonic-sensor system. Errors were comparable to the ultrasonic system, with average error standard deviation of 4.3 cm when the cyclist was 1.5 m from the heavy goods vehicles, and 7.1 cm at a distance of 1 m. When results were compared to manually extracted cyclist position data, errors were less than 4 cm at separations of 1.5 and 1 m. Compared to the ultrasonic system, the camera system requires simple hardware and can easily differentiate cyclists from stationary or moving background objects such as parked cars or roadside furniture. However, the cameras suffer from reduced robustness and accuracy at close range and cannot operate in low-light conditions.

scholarly journals Improving the FLORIS wind plant model for compatibility with gradient-based optimization

2017 ◽  
Vol 41 (5) ◽  
pp. 313-329 ◽  
Author(s):  
Jared J Thomas ◽  
Pieter MO Gebraad ◽  
Andrew Ning
Keyword(s):  
Steady State ◽  
Wind Turbine ◽  
Case Studies ◽  
Wind Farm ◽  
Optimization Problems ◽  
Algorithmic Differentiation ◽  
Function Calls ◽  
Gradient Based ◽  
Wake Model ◽  
Yaw Angle

The FLORIS (FLOw Redirection and Induction in Steady-state) model, a parametric wind turbine wake model that predicts steady-state wake characteristics based on wind turbine position and yaw angle, was developed for optimization of control settings and turbine locations. This article provides details on changes made to the FLORIS model to make the model more suitable for gradient-based optimization. Changes to the FLORIS model were made to remove discontinuities and add curvature to regions of non-physical zero gradient. Exact gradients for the FLORIS model were obtained using algorithmic differentiation. A set of three case studies demonstrate that using exact gradients with gradient-based optimization reduces the number of function calls by several orders of magnitude. The case studies also show that adding curvature improves convergence behavior, allowing gradient-based optimization algorithms used with the FLORIS model to more reliably find better solutions to wind farm optimization problems.

Cross-Sensitivity Characteristics of Instrumented Wheelset Associated With Longitudinal Force and Lateral Contact Position

2021 ◽  
Author(s):  
Takatoshi Hondo ◽  
Takayuki Tanaka ◽  
Shoya Kuniyuki ◽  
Mitsugi Suzuki
Keyword(s):  
Measurement Accuracy ◽  
Contact Point ◽  
Fem Analysis ◽  
Longitudinal Force ◽  
Lateral Position ◽  
Contact Forces ◽  
Load Test ◽  
Static Load Test ◽  
Cross Sensitivity ◽  
The Cross

Abstract It is crucial to grasp wheel-rail contact forces in the evaluation of running safety and curving performance of railway vehicles. To measure the wheel-rail contact forces, instrumented wheelset, which has the strain gauges on the wheel surface, is widely used. The purpose of this research is to increase the measurement accuracy of the wheel-rail contact forces by understanding the detailed characteristics of the instrumented wheelset. Although the various researches on the instrumented wheelset have been carried out to increase the measurement accuracy of wheel-rail contact forces, there are few works considering the longitudinal force and the lateral shift of the wheel-rail contact point. However, sometimes the longitudinal force has a non-negligible influence on the measurement accuracy on the instrumented wheelset. In this paper, the authors clarify the cross-sensitivity characteristics of the instrumented wheelset when the longitudinal force is applied to the various lateral position on the wheel tread through the FEM analysis and the static load test. The authors also propose a method to approximate the cross-sensitivity as an analytical function of the lateral and circumferential contact positions.

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