A Possible Mechanism for Rail Dark Spot Defects

1998 ◽  
Vol 120 (2) ◽  
pp. 304-309 ◽  
Author(s):  
M. Kaneta ◽  
K. Matsuda ◽  
K. Murakami ◽  
H. Nishikawa
Keyword(s):  
Fracture Mechanics ◽  
Fatigue Failure ◽  
High Speed ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Traction Force ◽  
Rolling Contact ◽  
Dark Spot ◽  
A Posteriori ◽  
Direction Opposite

Rail dark spot defect, also termed squat failure or shelling, which is a kind of rolling contact fatigue failure and occurs frequently on running surfaces of railway rails carrying high speed traffic, is one of the most dangerous rail failures. The dark spot crack is characterized by a principal crack propagating in the direction of traffic and a second crack growing in the direction opposite to traffic. By using a newly developed two-disk machine, the authors have succeeded in reproducing very similar dark spot cracks to those which appear in actual rails. It is found that the dark spot defects are caused by frequent repetitions of dry and wet runnings, and that the traction force plays an important role for the occurrence of the cracks. The principal crack may occur from a tiny pit formed a posteriori on the contacting surface and after that, the second crack is formed by cracks branched from the extended principal crack. It has also been proved experimentally that water is capable of entering the tip of the crack. Furthermore, a possible mechanism for the dark spot cracking has been proposed on the basis of the fracture mechanics approach.

Modelling of Rolling Contact Fatigue of Rails

2006 ◽  
Vol 324-325 ◽  
pp. 987-990 ◽  
Author(s):  
Gorazd Fajdiga ◽  
Matjaž Šraml ◽  
Janez Kramar
Keyword(s):  
Fatigue Crack ◽  
Computational Model ◽  
Fatigue Failure ◽  
High Speed ◽  
Rolling Contact Fatigue ◽  
Fatigue Crack Initiation ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Dark Spot ◽  
Probable Number

Rail dark spot defect, also termed as squat failure or shelling, is a rolling contact fatigue failure which occurs frequently on the high speed traffic railway rails. The main goal of this study is to develop a computational model for simulation of the squat phenomena on rails in rail-wheel contact. The proposed computational model consists of two parts: (i) Contact Fatigue Crack Initiation (CFCI) and (ii) Contact Fatigue Crack Propagation (CFCP). The results of proposed unified model enable a computational prediction of a probable number of loading cycles that a wheel-rail system can sustain before development of the initial crack in the rail, as well as the number of loading cycles required for a crack to propagate from initial to critical length, when the final fatigue failure (squat) can be expected to occur.

scholarly journals Analytical Modeling of an Oblique Edge Crack in Rolling Contact Fatigue

2018 ◽  
Vol 2018 ◽  
pp. 1-12
Author(s):  
Francesca Di Puccio
Keyword(s):  
Fracture Mechanics ◽  
Edge Crack ◽  
General Procedure ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Traction Force ◽  
Rolling Contact ◽  
Test Case ◽  
Linear Elastic ◽  
Variable Approach

Surface cracks represent a frequent cause of damage and even failure in rolling contacts, observed in gears, cams, rails, and so on. In the literature, different approaches have been applied to describe the crack behaviour by means of Fracture Mechanics parameters, such as the stress intensity factors (SIFs) and the J-integral. In this paper, a general procedure for dealing with plane problems is presented, which is based on Linear Elastic Fracture Mechanics hypotheses. It combines the Weight Function Method for evaluating the SIFs in a loading cycle with the Kolosov-Muskhelishvili complex variable approach for estimating the nominal stress field. In this way, a completely analytical procedure can be applied for a general loading condition, assuming that the real geometry can be simplified in a half-plane with an oblique edge crack. As test case, a travelling load has been considered representing a combination of three contributions: Hertzian pressure distribution, traction force due to friction, and pressurization of the crack faces. A comparison with literature results proved that the proposed approach can be an efficient tool for SIFs estimation and crack growth description.

Evaluation of Surface Defects of Wheel and Rail for Korean High-Speed Railway

2010 ◽  
Vol 654-656 ◽  
pp. 2499-2502 ◽  
Author(s):  
Chan Woo Lee ◽  
Seok Jin Kwon
Keyword(s):  
High Speed ◽  
Surface Defects ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Railway Vehicle ◽  
High Speed Railway ◽  
Main Research ◽  
Rail Systems ◽  
Micro Cracks

Wheels of the railway vehicle play the important role for driving train through wheel-rail interaction. Especially wheel profile is one of the most important design factors to rule the running stability and safety of train. Accordingly, the control of rolling contact fatigue-related defects is an ongoing concern for both safety and cost reasons. This process is referred to as ratcheting. Wear of wheel and rail surfaces occur due to a mixture of adhesive, abrasive and corrosive processes. In wheel/rail systems with little wear, such failure is manifested by the appearance of closely spaced micro-cracks. In the present paper, a evaluation of surface defects of wheel and rail for Korean high-speed railway. The main research application is the wheel-rail maintenance of Korea high-speed train.

Theory of Lubrication and Failure of Rolling Contacts

1961 ◽  
Vol 83 (2) ◽  
pp. 213-222 ◽  
Author(s):  
B. Sternlicht ◽  
P. Lewis ◽  
P. Flynn
Keyword(s):  
Fatigue Life ◽  
Contact Zone ◽  
High Speed ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Fatigue Tests ◽  
Rolling Contact ◽  
Inlet Temperature ◽  
Fluid Properties ◽  
Contact Fatigue Life

The fatigue life of rolling-element bearings has been the subject of numerous investigations. Most recently the influence of the lubricant on fatigue failure has been given added emphasis. This paper presents the results of an investigation which was undertaken in order to gain a better understanding of fluid behavior in the contact zone and to determine the influence of the lubricant on rolling contact fatigue life. The investigation had three distinct facets: (a) An analysis was performed on pressure and temperature distribution within the contact zone of rolling disks. In the analysis Reynolds, energy, and elasticity equations were solved simultaneously and fluid properties, such as viscosity dependence on temperature and pressure were included. (b) Dynamic stresses in two contacting cylindrical bodies were measured by means of photoelastic techniques. These measurements were used to test the validity of the analytically predicted stress distribution. (c) High-speed ball-bearing fatigue tests were conducted with two specially blended oils which had the same viscosity at the bearing inlet temperature, but widely different pressure viscosity characteristics. The physical characteristics of the oils were the same as those considered in the analysis. The paper summarizes the work and presents a hypothesis for the failure mechanism.

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