Wheel-Rail Contact Patch Geometry Measurement and Shape Analysis Under Various Loading Conditions

2020 ◽  
Author(s):  
Ahmad Radmehr ◽  
Arash Hosseinian Ahangarnejad ◽  
Yu Pan ◽  
SayedMohammad Hosseini ◽  
Ali Tajaddini ◽  
...  
Keyword(s):  
Pressure Distribution ◽  
Wheel Load ◽  
Contact Patch ◽  
Pressure Sensitive ◽  
Sensitive Film ◽  
Consistent Method ◽  
Geometry Measurement ◽  
Static Conditions ◽  
The Relationship ◽  
Patch Geometry

Abstract This study evaluates the wheel-rail contact patch geometry of the VT-FRA roller rig, designed and commissioned at the Virginia Tech’s Railway Technologies Laboratory (RTL). Contact patch measurements are crucial for better analyzing the underlying factors that affect the wheel-rail interface (WRI) contact mechanics and dynamics. One of the challenges is in determining the size and pressure distribution at the contact patch, under various conditions. Although past studies have attempted to reach a method that can be used to make such measurements, more research is needed in reaching a practical and consistent method. This is particularly true for making the measurements under dynamic conditions. The use of pressure sensitive films was considered as the means for contact patch measurements on the VT-FRA rig, however, the thickness of the film influences the contact patch area and shape. This paper provides the results of the measurements with films with different range of pressure sensitivities. Three types of pressure-sensitive films are used under static conditions. The films are placed in between the wheel and roller in exact positions to enable comparing the test results for various wheel loads. The contact patch measured by the most sensitive film, which reacts to pressures as low as 0.5 MPa, provides the most accurate outline for the contact patch, although it does not provide the highest resolution for the pressure distribution. The other pressure-sensitive films that are used have a higher pressure range, with minimums of 49.0 MPa and 127.6 MPa. The relationship between the size of the contact patch and average contact pressure is evaluated as a function of the wheel load. The results indicate that with increasing wheel load, the size of the contact patch changes minimally, with the average pressure increasing in a nearly linear relationship to the wheel load as expected.

scholarly journals Feasibility Study for Real Time Measurement of Wheel-Rail Contact Using an Ultrasonic Array

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
R. S. Dwyer-Joyce ◽  
C. Yao ◽  
J. Zhang ◽  
R. Lewis ◽  
B. W. Drinkwater
Keyword(s):  
Real Time ◽  
Physical Phenomenon ◽  
High Stress ◽  
Measurement Procedure ◽  
Contact Patch ◽  
Line Scan ◽  
Pressure Sensitive ◽  
Array Transducer ◽  
Sensitive Film ◽  
Pressure Sensitive Film

Failure of a wheel-rail contact is usually by wear or fatigue of either component. Both mechanisms depend on the state of stress, which in turn depends on size and location of the contact patch. In this work, the feasibility of an ultrasonic approach for measuring the contact, real time on a rail, has been evaluated. The approach is based on the physical phenomenon of ultrasonic reflection at an interface. If the wheel and rail surfaces make contact, and are under high stress, they will transmit an ultrasonic pulse. However, if there is no contact, or the contact is under low stress, then the wave is completely or partially reflected. By measuring the proportion of the wave reflected, it is possible to deduce the extent of the contact area and also estimate the pressure distribution. In a previous work (Marshall, Lewis, Dwyer-Joyce, Olofsson, and Bjorklund, 2006, “Experimental Characterisation of Wheel-Rail Contact Patch Evolution,” ASME J. Tribol., 128(3), pp. 493–504), static wheel-rail contacts were scanned using a transducer to build up a two-dimensional (2D) map of the contact. The procedure was time consuming and could in no way be used for measurements online. In this work, a method is presented that could be used at line speeds, and so provide wheel-rail contact measurements in field trials. The scan is achieved by using an array transducer that performs a one dimensional electronic line scan. This, coupled with the speed of travel of the contact patch past the sensor location, enables a 2D map of the contact to be produced. Specimens were cut from wheel and rail sections and loaded together hydraulically in a biaxial frame. An array transducer was mounted beneath the rail specimen. The array transducer consisted of 64 ultrasonic elements that could be pulsed independently, simultaneously, or with controlled phase difference. The signals were reflected back from the contact to effectively produce a line scan. The transducer was physically moved to simulate the translation of the contact patch and so generate a series of 2D reflection profiles. Contacts under a range of normal and lateral loads have been measured and compared with some simple results using a pressure sensitive film. While the map produced by ultrasonic reflection is relatively coarse, the results agree well with measurements from the pressure sensitive film. The work concludes with a discussion of how this array measurement procedure might be implemented at full line speed, and what resolution could potentially be achieved.

A Modular Race Tire Model Concerning Thermal and Transient Behavior using a Simple Contact Patch Description

2013 ◽  
Vol 41 (4) ◽  
pp. 232-246
Author(s):  
Timo Völkl ◽  
Robert Lukesch ◽  
Martin Mühlmeier ◽  
Michael Graf ◽  
Hermann Winner
Keyword(s):  
Load Distribution ◽  
Thermal Condition ◽  
Transient Behavior ◽  
Wheel Load ◽  
Contact Patch ◽  
Fundamental Parameters ◽  
Dry Conditions ◽  
Simple Contact ◽  
Tire Forces ◽  
Descriptive Set

ABSTRACT The potential of a race tire strongly depends on its thermal condition, the load distribution in its contact patch, and the variation of wheel load. The approach described in this paper uses a modular structure consisting of elementary blocks for thermodynamics, transient excitation, and load distribution in the contact patch. The model provides conclusive tire characteristics by adopting the fundamental parameters of a simple mathematical force description. This then allows an isolated parameterization and examination of each block in order to subsequently analyze particular influences on the full model. For the characterization of the load distribution in the contact patch depending on inflation pressure, camber, and the present force state, a mathematical description of measured pressure distribution is used. This affects the tire's grip as well as the heat input to its surface and its casing. In order to determine the thermal condition, one-dimensional partial differential equations at discrete rings over the tire width solve the balance of energy. The resulting surface and rubber temperatures are used to determine the friction coefficient and stiffness of the rubber. The tire's transient behavior is modeled by a state selective filtering, which distinguishes between the dynamics of wheel load and slip. Simulation results for the range of occurring states at dry conditions show a sufficient correlation between the tire model's output and measured tire forces while requiring only a simplified and descriptive set of parameters.

The Use of Contact Biomechanics to Study the Intact, Proximal Row Carpectomy and Scaphoid Excision, Four Bone Fusion Wrist

2020 ◽  
Vol 16 (3) ◽  
pp. 189-193
Author(s):  
David H. Wei ◽  
Peter Tang
Keyword(s):  
Proximal Row Carpectomy ◽  
Scapholunate Ligament ◽  
Bone Fusion ◽  
Pressure Sensitive ◽  
Sensitive Film ◽  
Radiocarpal Joint ◽  
Pressure Sensitive Film ◽  
Number Of Authors

The study of contact biomechanics of the wrist is a challenge. This is partly due to the relatively small size of the joint as well as the lack of space in the radiocarpal joint which makes the delivery of investigative materials such as pressure sensitive film without causing artifact, difficult. Fortunately, a number of authors have studied the intact wrist, the scapholunate ligament injured wrist, the proximal row carpectomy and the scaphoid excision, four bone fusion. Despite some contrasting findings, there are some general concepts that we understand about wrist mechanics.

A Technique for Measuring Absolute Toe Pressures: Evaluation of Pressure-Sensitive Film Techniques

Foot & Ankle ◽  
1992 ◽  
Vol 13 (4) ◽  
pp. 220-223 ◽  
Author(s):  
Alan S. Tuckman ◽  
Frederick W. Werner ◽  
Maria D. Fortino ◽  
Joseph A. Spadaro
Keyword(s):  
Soft Tissues ◽  
Flat Surface ◽  
Imaging System ◽  
Accurate Method ◽  
Total Force ◽  
Confined Space ◽  
Pressure Sensitive ◽  
Sensitive Film ◽  
Pressure Sensitive Film ◽  
Deforming Forces

Although a number of pathologies of the forefoot in ballet dancers on pointe have been described, pressures and deforming forces have not been adequately measured. To evaluate the possible use of pressure-sensitive film (PSF) in measuring the pressures on the external soft tissues in such a confined space as the dancer's toe shoe, it was tested and calibrated with 20 cadaver toes. Each cadaver toe was internally stabilized and loaded longitudinally against PSF on a flat surface. The resultant films were analyzed with a video imaging system and the pressures and total forces were determined. Results showed that the linearity of the PSF to pressure had a regression value of 0.98. By using two sensitivity ranges of films, the total force measured by the PSF was found to be within 10% of the known applied force on each toe. The PSF, therefore, may very well be a useful and accurate method of measuring external soft tissue pressures on the forefoot.

Biomechanics of the wrist after proximal row carpectomy in cadavers

2009 ◽  
Vol 35 (1) ◽  
pp. 43-45 ◽  
Author(s):  
Y.-L. Zhu ◽  
Y.-Q. Xu ◽  
J. Ding ◽  
J. Li ◽  
B. Chen ◽  
...  
Keyword(s):  
Sharp Decrease ◽  
Material Testing ◽  
Testing System ◽  
Average Pressure ◽  
Proximal Row Carpectomy ◽  
Pressure Sensitive ◽  
Sensitive Film ◽  
Fresh Frozen ◽  
Pressure Sensitive Film ◽  
Lunate Fossa

We investigated the biomechanics of the radiocapitate joint after a proximal row carpectomy in six fresh-frozen cadaver wrists using super-low-pressure-sensitive film on a material testing system. The average pressure within the lunate fossa increased significantly from 23.2 to 136.4 N/cm2 with a sharp decrease in the contact area from 2.08 to 0.30 cm2 after a proximal row carpectomy. The cartilage of the proximal capitate had four sub-facets and therefore was not as smooth as the normal proximal lunate. We found that the wrist was overloaded after a proximal row carpectomy and the main cause was the anatomical mismatch of the radiocapitate articulation.

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