Determination of Creep Force, Moment, and Work Distribution in Rolling Contact With Slip

1989 ◽  
Vol 111 (4) ◽  
pp. 711-718 ◽  
Author(s):  
Bor-Tsuen Wang ◽  
Robert H. Fries
Keyword(s):  
Rolling Contact ◽  
Wear Model ◽  
Contact Patch ◽  
Rail Wear ◽  
Work Distribution ◽  
Force Moment ◽  
Creep Force ◽  
Rigid Body Motions ◽  
Work Done

Investigators interested in the wear of wheels and rails frequently use a wear model that postulates wear is proportional to the work done in the contact patch. Most investigators compute the work using the rigid body motions of the wheel and the total creepage at the contact patch. Such an approach gives an overall or integrated measure of the wear in the contact patch. In previous wheel/rail wear work, we have assumed the wear to be distributed parabolically across the contact patch. In order to check this assumption and to permit refinement of our wear modeling technique, we desired to know the distribution of work within the contact patch. In order to compute the work distribution within the contact patch, we must be able to compute the distributions of both the creep force and the creepage. This paper describes a method of computing lateral and longitudinal creep force and creep moment distributions within the contact patch for combined rolling and slip conditions. It also describes the computations of creep distributions within the contact patch. The work distribution is computed from the dot product of force and creepage. The method uses Kalker’s simplified theory to determine the force and creepage distributions. The actual computations are made using a modification of Kalker’s program FASTSIM. A by-product of the work is the determination of the adhesion and slip regions for arbitrary creepage conditions.

Numerical analysis of the effect of track parameters on the wear of turnout rails in high-speed railways

2016 ◽  
Vol 232 (3) ◽  
pp. 709-721 ◽  
Author(s):  
Jingmang Xu ◽  
Ping Wang ◽  
Jian Wang ◽  
Boyang An ◽  
Rong Chen
Keyword(s):  
Friction Coefficient ◽  
Wear Rate ◽  
High Speed ◽  
Numerical Procedure ◽  
Dynamic Interaction ◽  
Operating Conditions ◽  
Rolling Contact ◽  
Wear Model ◽  
Rail Wear ◽  
Railway Turnout

In this study, a numerical procedure is developed to predict the wear of turnout rails, and the effect of track parameters is investigated. The procedure includes simulation of the dynamic interaction between the train and the turnout, the rolling contact analysis, and the wear model. The dynamic interaction is simulated with the validated commercial software Simpack that uses a space-dependent model of a railway turnout. To reproduce the actual operating conditions of a railway turnout, stochastic variations in the input parameters are considered in the simulation of the dynamic interaction. The rolling contact is analyzed with the semi-Hertzian method and improved FASTSIM algorithm, which enable the contact model to deal with situations of multipoint contact and nonelliptic contact. Based on the Archard’s wear law, the wear model requires the calculation of normal/tangential stresses and a relative slide on the contact patches. The numerical procedure is performed for the selected sections of the vehicle, which runs through the railway turnout in the diverging route. By using the numerical procedure, the effect of track parameters (track gage, rail inclination, and friction coefficient) on the wear of turnout rails is analyzed. The results show that the wear of the front wheelset is more serious than the wear of the rear wheelset for a single vehicle. The degree of wear of switch rails is more severe than that of the stock rails and the difference is more obvious for the front wheelset of the switch rails. The wear of switch rails is mainly concentrated on the rail gage corner, while the wear of stock rails is mainly concentrated on the rail crown. For the analysed CN60-1100-1:18 turnout and the high-speed vehicle CRH2 in China, the rail wear rate could be slowed down by increasing the track gage and decreasing the rail inclination. Alternatively, the rail wear rate could be slowed by decreasing the friction coefficient; however, the variation of wear depth is quite small for friction coefficients that are larger than 0.3.

Numerical and Experiment Analysis of Rail Wear

2011 ◽  
Vol 189-193 ◽  
pp. 697-702 ◽  
Author(s):  
Cai Yun Wang ◽  
Peng Shen ◽  
Wen Zhong ◽  
Qi Yue Liu
Keyword(s):  
Simulation Experiment ◽  
Static Condition ◽  
Rolling Contact ◽  
Wear Behaviour ◽  
Growth Speed ◽  
Stick Slip ◽  
Severe Problem ◽  
Rail Wear ◽  
Creep Force ◽  
Curve Radius

The rolling contact wear is a severe problem and meets with much widespread interest in the world. This paper describes an numerical method and simulation experiment investigation on the rail wear affected by the curve radius and axle load etc. The creep force ,stick/slip areas of contact particles, and friction work of wheel/rail in static condition are analyzed by kalker’s program CONTACT. The effect of curve radius and axle load on rolling wear behaviour of rail is investigated by simulation experiment. The results of numerical and experiment indicates that with the decreasing of curve radius and the increasing of axle load, the wear value of rail increase nonlinearly, especially in the condition of the curve radius is less than 1200m,the wear value of rail increase rapidly. And with the decrease of curve radius, the maximum slippage decrease gradually, and the stick areas decrease while the slip areas increase. The growth speed of friction work of wheel/rail in the condition of smaller curve radius and heavier axle load is faster than in the condition of larger curve radius (straigth line) and lighter axle load.

Is it necessary to calculate Young’s modulus in AFM nanoindentation experiments regarding biological samples?

2020 ◽  
Vol 12 ◽  
Author(s):  
S.V. Kontomaris ◽  
A. Malamou ◽  
A. Stylianou
Keyword(s):  
Young’S Modulus ◽  
Biological Samples ◽  
Young's Modulus ◽  
Reference Sample ◽  
Nonlinear Behavior ◽  
Accurate Method ◽  
Accurate Solution ◽  
Hertz Model ◽  
Work Done

Background: The determination of the mechanical properties of biological samples using Atomic Force Microscopy (AFM) at the nanoscale is usually performed using basic models arising from the contact mechanics theory. In particular, the Hertz model is the most frequently used theoretical tool for data processing. However, the Hertz model requires several assumptions such as homogeneous and isotropic samples and indenters with perfectly spherical or conical shapes. As it is widely known, none of these requirements are 100 % fulfilled for the case of indentation experiments at the nanoscale. As a result, significant errors arise in the Young’s modulus calculation. At the same time, an analytical model that could account complexities of soft biomaterials, such as nonlinear behavior, anisotropy, and heterogeneity, may be far-reaching. In addition, this hypothetical model would be ‘too difficult’ to be applied in real clinical activities since it would require very heavy workload and highly specialized personnel. Objective: In this paper a simple solution is provided to the aforementioned dead-end. A new approach is introduced in order to provide a simple and accurate method for the mechanical characterization at the nanoscale. Method: The ratio of the work done by the indenter on the sample of interest to the work done by the indenter on a reference sample is introduced as a new physical quantity that does not require homogeneous, isotropic samples or perfect indenters. Results: The proposed approach, not only provides an accurate solution from a physical perspective but also a simpler solution which does not require activities such as the determination of the cantilever’s spring constant and the dimensions of the AFM tip. Conclusion: The proposed, by this opinion paper, solution aims to provide a significant opportunity to overcome the existing limitations provided by Hertzian mechanics and apply AFM techniques in real clinical activities.

scholarly journals Influence of Induction Hardening on Wear Resistance in Case of Rolling Contact

2016 ◽  
Vol 66 (1) ◽  
pp. 17-26 ◽  
Author(s):  
Michal Šofer ◽  
Rostislav Fajkoš ◽  
Radim Halama
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Induction Hardening ◽  
Rolling Contact ◽  
Isotropic Hardening ◽  
Wear Model ◽  
Wear Rates ◽  
C Programming Language ◽  
Hardening Rule ◽  
C Programming

AbstractThe main aim of the presented paper is to show how heat treatment, in our case the induction hardening, will affect the wear rates as well as the ratcheting evolution process beneath the contact surface in the field of line rolling contact. Used wear model is based on shear band cracking mechanism [1] and non-linear kinematic and isotropic hardening rule of Chaboche and Lemaitre. The entire numerical simulations have been realized in the C# programming language. Results from numerical simulations are subsequently compared with experimental data.

Analytic Determination of Slip and Efficiencies of Rolling Contact C.V.T.’s With Experimental Verifications

1986 ◽  
Vol 108 (1) ◽  
pp. 72-76 ◽  
Author(s):  
J. Modrey ◽  
Y. K. Younes
Keyword(s):  
Computer Simulation ◽  
Rolling Contact ◽  
Analytic Determination ◽  
Continuously Variable Transmissions ◽  
Fluid Properties ◽  
Good Guide ◽  
Parallel Tests

Rolling contact continuously variable transmissions (C.V.T.) transmit forces through a highly viscous spot between rolling-slipping contacts. The mechanics of the spot are characterized by complex elastohydrodynamic conditions and fluid properties only partially determinable at the extreme pressures of operation. A computer simulation of the spot mechanics based on extensions of research in less complex elastohydrodynamic situations was developed. Comparisons with parallel tests on a commercial C. V. T. verify that the simulation described in a good guide to design of this class of transmissions.

Parametric Simulation of Rolling Contact Fatigue

2008 ◽  
Author(s):  
Scott M. Cummings ◽  
Patricia Schreiber ◽  
Harry M. Tournay
Keyword(s):  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Wear Model ◽  
Primary Methods ◽  
Vehicle Performance ◽  
Track Geometry ◽  
Advantages And Disadvantages ◽  
Defect Prevention ◽  
Design Speed

Simulations of dynamic vehicle performance were used by the Wheel Defect Prevention Research Consortium (WDPRC) to explore which track and vehicle variables affect wheel fatigue life. A NUCARS® model was used to efficiently examine the effects of a multitude of parameters including wheel/rail profiles, wheel/rail lubrication, truck type, curvature, speed, and track geometry. Results from over 1,000 simulations of a loaded 1,272 kN (286,000-pound) hopper car are summarized. Rolling contact fatigue (RCF) is one way that wheels can develop treads defects. Thermal mechanical shelling (TMS) is a subset of wheel shelling in which the heat from tread braking reduces a wheel’s fatigue resistance. RCF and TMS together are estimated to account for approximately half of the total wheel tread damage problem [1]. Other types of tread damage can result from wheel slides. The work described in this paper concerns pure RCF, without regard to temperature effects or wheel slide events. Much work has been conducted in the past decade in an attempt to model the occurrence of RCF on wheels and rails. The two primary methods that have gained popularity are shakedown theory and wear model. The choice of which model to use is somewhat dependent on the type of data available, as each model has advantages and disadvantages. The wear model was selected for use in this analysis because it can account for the effect of wear on the contacting surfaces and is easily applied to simulation data in which the creep and creep force are available. The findings of the NUCARS simulations in relation to the wear model include the following: • Degree of curvature is the single most important factor in determining the amount of RCF damage to wheels; • The use of trucks (hereafter referred to as M-976) that have met the Association of American Railroads’ (AAR) M-976 Specification with properly maintained wheel and rail profiles should produce better wheel RCF life on typical routes than standard trucks; • In most curves, the low-rail wheel of the leading wheelset in each truck is most prone to RCF damage; • While the use of flange lubricators (with or without top of rail (TOR) friction control applied equally to both rails) can be beneficial in some scenarios, it should not be considered a cure-all for wheel RCF problems, and may in fact exacerbate RCF problems for AAR M-976 trucks in some instances; • Avoiding superelevation excess (operating slower than curve design speed) provides RCF benefits for wheels in cars with standard three-piece trucks; • Small track perturbations reduce the overall RCF damage to a wheel negotiating a curve.

Determination of aerobic work and power on a rope-braked cycle ergometer by direct measurement

2006 ◽  
Vol 31 (4) ◽  
pp. 392-397 ◽  
Author(s):  
Rae S. Gordon ◽  
Kathryn L. Franklin ◽  
Julien S. Baker ◽  
Bruce Davies
Keyword(s):  
Direct Measurement ◽  
Power Estimation ◽  
Cycle Ergometer ◽  
Mean Power ◽  
Physiological Assessment ◽  
Brake Force ◽  
The Mean ◽  
The Difference ◽  
Work Done

The purpose of this study was to compare the power and work outputs of a cycle ergometer using the manufacturer’s guidelines, with calculations using direct flywheel velocity and brake torque. A further aim was to compare the values obtained with those supplied by the manufacturer. A group of 10 male participants were asked to pedal a Monark 824E ergometer at a constant cadence of 60 r/min for a period of 3 min against a resistive mass of 3 kg. The flywheel velocity was measured using a tachometer. The brake force was determined by measuring the tension in the rope on either side of the flywheel. The calculated mean power was 147.45 ± 6.5 W compared with the Monark value of 183 ± 3.7 W. The difference between the methods for power estimation was 18% and was statistically significant (p < 0.01). The mean work done by the participants during the 3 min period was found to be 26 460 ± 1145 J compared with the Monark value of 33 067 ± 648 J (p < 0.01). The Monark formulae currently used to determine the power and work done by a participant overestimates the actual values required to overcome the resistance. There findings have far-reaching implications in the physiological assessment of athletic, sedentary, and diseased populations.

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