Scaled Roller Rig to Assess the Influence of Active Wheelset Steering on Wheel-Rail Contact Forces

2020 ◽  
pp. 82-89
Author(s):  
Jan Kalivoda ◽  
Petr Bauer
Keyword(s):  
Contact Forces ◽  
Roller Rig

Evaluating the Effect of Natural Third Body Layers on Friction Using the Virginia Tech Roller Rig

2019 ◽  
Author(s):  
Ahmad Radmehr ◽  
Karan Kothari ◽  
Mehdi Ahmadian
Keyword(s):  
Virginia Tech ◽  
Contact Forces ◽  
Third Body ◽  
Traction Coefficient ◽  
The Coefficient Of Friction ◽  
Creep Force ◽  
Series Of Experiments ◽  
Roller Rig ◽  
Friction Reducer ◽  
Material Wear

In this study, the effect of natural third body layers on the coefficient of friction and contact forces is evaluated using the Virginia Tech-Federal Railroad Administration (VT-FRA) roller rig facility. The test rig allows us to precisely control the contacting surfaces to study its effect on the wheel-rail interface forces and moments. Experiments have shown while running the tests, a slight amount of wear occurs at the running surfaces. The worn material deposits at the surface and behaves like a “natural” third-body layer at the contact, resulting in changes in traction coefficient and creep forces. The material wear and its accumulation on the running surfaces change with wheel longitudinal load and creepage. A series of organized time-based experiments have been conducted with the running surfaces cleaned at the beginning of the test to study the effect of material wear accumulation on selected parameters including traction coefficient and creep forces over time. In order to highlight the effect of the natural third body layer on the wheel-rail contact forces, a series of experiments were conducted, in which the wheel and roller surfaces were cleaned in one case and left uncleaned in another. The results of the experiments are quite revealing. They indicate that when the running surfaces are cleaned after each test, the maximum creep force (or adhesion) is far lower than when the running surfaces are not cleaned, i.e., the natural third-body layer is allowed to accumulate at the surfaces. The results indicate that the wear debris act as a friction enhancer rather than a friction reducer.

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.

Virginia Tech-Federal Railroad Administration Roller Rig Measurement Capabilities and Baseline Measurements

2019 ◽  
Author(s):  
Ahmad Radmehr ◽  
Ali Tajaddini ◽  
Brian Marquis ◽  
Mehdi Ahmadian
Keyword(s):  
Virginia Tech ◽  
Contact Forces ◽  
Precise Control ◽  
The Past ◽  
Rail Industry ◽  
Roller Rig ◽  
The One ◽  
High Degree ◽  
Lateral Positioning ◽  
Measurement Capabilities

A detailed description of the Virginia Tech-Federal Railroad Administration (VT-FRA) Roller Rig measurement capabilities, along with the efforts in establishing the accuracy, repeatability, and integrity of the results are presented. The results of a series of baseline tests are also documented in an effort to provide an indication of the type of experiments that can be achieved on the rig. The one-fourth scaled rig is intended to be used for evaluating wheel-rail contact mechanics and dynamics with a high degree of precision. The rail is represented by a roller with a diameter that is five times larger than the wheel, in order to maintain the contact ellipse distortion to less than 10 percent. The primary point of differentiation between this rig and others that have been used in the past or are presently in use is that it is able to measure the wheel-rail contact forces with far greater precision than achieved in the past. The rig is also designed such that it provides a high degree of repeatability in testing, often needed for performing design of experiments accurately. The VT-FRA rig is capable of precisely controlling the lateral positioning of the wheel and rail, rail cant angle, the wheel-rail angle of attack, and the speed of the roller and wheel independently. The latter is intended to provide precise control of the relative speed of the wheel and roller, which amounts to precisely controlling creepage. Beyond presenting the rig’s capabilities, the paper provides a discussion of the initial results from the commissioning of the rig. It is concluded that the rig is ready to be commissioned for studies that are of interest to the practitioners in the rail industry and scientists in the research community.

scholarly journals A Novel Analytical Method to Calculate Wheel-Rail Tangential Forces and Validation on a Scaled Roller-Rig

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Nicola Bosso ◽  
Nicolò Zampieri
Keyword(s):  
Contact Problem ◽  
Analytical Method ◽  
Efficient Algorithm ◽  
Experimental Tests ◽  
Dynamical Behaviour ◽  
Contact Forces ◽  
Strongly Nonlinear ◽  
Fast Solution ◽  
Tangential Forces ◽  
Roller Rig

The study of railway dynamic strongly depends on the estimation of the tangential forces acting between wheel and rail. Simulation of the dynamical behaviour of railway vehicles is often performed using multibody codes, and the calculation of the contact forces must be efficient and accurate, even if the contact problem is strongly nonlinear. Therefore, the contact problem is still of great interest for researchers. This work proposes an analytical and efficient algorithm to calculate wheel-rail tangential forces. The proposed method is compared with the most commonly used algorithms under different conditions. In addition, experimental tests are performed on a scaled prototype on roller-rig to demonstrate that the method can be easily adjusted using experimental results. The benefit of the proposed method is to provide an analytical and fast solution, able to obtain accurate results and to allow corrections based on empirical evidence.

Modeling of Tread Block Contact Mechanics Using Linear Viscoelastic Theory3

2008 ◽  
Vol 36 (3) ◽  
pp. 211-226 ◽  
Author(s):  
F. Liu ◽  
M. P. F. Sutcliffe ◽  
W. R. Graham
Keyword(s):  
High Speed ◽  
Slip Rate ◽  
Material Model ◽  
Contact Forces ◽  
Block Modeling ◽  
Rate Dependent ◽  
Linear Viscoelastic Material ◽  
Linear Viscoelastic ◽  
The Impact ◽  
Good Agreement

Abstract In an effort to understand the dynamic hub forces on road vehicles, an advanced free-rolling tire-model is being developed in which the tread blocks and tire belt are modeled separately. This paper presents the interim results for the tread block modeling. The finite element code ABAQUS/Explicit is used to predict the contact forces on the tread blocks based on a linear viscoelastic material model. Special attention is paid to investigating the forces on the tread blocks during the impact and release motions. A pressure and slip-rate-dependent frictional law is applied in the analysis. A simplified numerical model is also proposed where the tread blocks are discretized into linear viscoelastic spring elements. The results from both models are validated via experiments in a high-speed rolling test rig and found to be in good agreement.

Modeling Vibration-Induced Tire-Pavement Interaction Noise in the Mid-frequency Range

2020 ◽  
Author(s):  
Sterling McBride ◽  
Ricardo Burdisso ◽  
Corina Sandu
Keyword(s):  
Sound Intensity ◽  
Element Model ◽  
Dominant Frequency ◽  
Contact Forces ◽  
Surface Velocity ◽  
New Wave ◽  
Normal Surface ◽  
Radiated Noise ◽  
Physical Effects ◽  
Effects Of Rotation

ABSTRACT Tire-pavement interaction noise (TPIN) is one of the main sources of exterior noise produced by vehicles traveling at greater than 50 kph. The dominant frequency content is typically within 500–1500 Hz. Structural tire vibrations are among the principal TPIN mechanisms. In this work, the structure of the tire is modeled and a new wave propagation solution to find its response is proposed. Multiple physical effects are accounted for in the formulation. In an effort to analyze the effects of curvature, a flat plate and a cylindrical shell model are presented. Orthotropic and nonuniform structural properties along the tire's transversal direction are included to account for differences between its sidewalls and belt. Finally, the effects of rotation and inflation pressure are also included in the formulation. Modeled frequency response functions are analyzed and validated. In addition, a new frequency-domain formulation is presented for the computation of input tread pattern contact forces. Finally, the rolling tire's normal surface velocity response is coupled with a boundary element model to demonstrate the radiated noise at the leading and trailing edge locations. These results are then compared with experimental data measured with an on-board sound intensity system.

OLIN C197

Alloy Digest ◽  
1999 ◽  
Vol 48 (1) ◽  
Keyword(s):  
Thermal Conductivity ◽  
Wear Resistance ◽  
Physical Properties ◽  
Tensile Properties ◽  
High Performance ◽  
Corrosion And Wear ◽  
Contact Forces ◽  
High Current ◽  
Lower Strength ◽  
Current Carrying Capability

Abstract Olin C197 is a second-generation high performance alloy developed by Olin Brass. It has a strength and bend formability similar to C194 (see Alloy Digest Cu-360, September 1978), but with 25% higher electrical and thermal conductivity. High conductivity allows C197 to replace brasses and bronzes in applications where high current-carrying capability is required. Also, the strength of C197 provides higher contact forces when substituted for many lower strength coppers. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion and wear resistance as well as forming and joining. Filing Code: CU-627. Producer or source: Olin Brass.

scholarly journals Design and Calibration of a Force/Tactile Sensor for Dexterous Manipulation

Sensors ◽  
2019 ◽  
Vol 19 (4) ◽  
pp. 966 ◽  
Author(s):  
Marco Costanzo ◽  
Giuseppe De Maria ◽  
Ciro Natale ◽  
Salvatore Pirozzi
Keyword(s):  
Experimental Validation ◽  
Sensory System ◽  
Tactile Sensor ◽  
Contact Forces ◽  
Dexterous Manipulation ◽  
Soft Contact ◽  
Grasping Force ◽  
Sense Of Touch ◽  
Human Sense ◽  
Robotic Applications

This paper presents the design and calibration of a new force/tactile sensor for robotic applications. The sensor is suitably designed to provide the robotic grasping device with a sensory system mimicking the human sense of touch, namely, a device sensitive to contact forces, object slip and object geometry. This type of perception information is of paramount importance not only in dexterous manipulation but even in simple grasping tasks, especially when objects are fragile, such that only a minimum amount of grasping force can be applied to hold the object without damaging it. Moreover, sensing only forces and not moments can be very limiting to securely grasp an object when it is grasped far from its center of gravity. Therefore, the perception of torsional moments is a key requirement of the designed sensor. Furthermore, the sensor is also the mechanical interface between the gripper and the manipulated object, therefore its design should consider also the requirements for a correct holding of the object. The most relevant of such requirements is the necessity to hold a torsional moment, therefore a soft distributed contact is necessary. The presence of a soft contact poses a number of challenges in the calibration of the sensor, and that is another contribution of this work. Experimental validation is provided in real grasping tasks with two sensors mounted on an industrial gripper.

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.

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