Wheel-rail Contact Conditions Research Articles

Disc machine testing to assess the life of surface-damaged railway track

Wheel-rail contacts operate in an arduous and contaminated environment. Railway track running surfaces can become damaged either prior to or during operation. This work is aimed at understanding how that surface damage can affect the life of railway track. Pre-damaged surfaces and track damaged by the entrainment of solid contaminants are considered under both oil and water lubrication. A series of small-scale laboratory experiments has been carried out on a twin-disc rolling-sliding test machine. The test discs are artificially indented and run under typical wheel-rail contact conditions. The experimental results revealed that artificial dents only reduce the fatigue life of the contact under oil, but not water lubrication. With oil lubrication the fatigue failure initiates close to the location of the surface defect. However, with water as the lubricant the whole of the surface undergoes cracking with the defect having no preferential effect. Studies have also been carried out to investigate the damage caused by the entrainment of solid particles into the wheel-rail contact. This kind of damage can accelerate surface fatigue and also lead to excessive wear. An attempt has been made to quantify the wear process and develop a simple empirical model.

Effects of wheel-rail contact geometry on wheel set steering forces

Adverse wheel-rail contact geometry and flange lubrication have been implicated in a number of recent gage widening and rail rollover derailments. The underlying derailment mechanism is shown to be a loss of wheel set steering due to a reduction in wheel set rolling radius difference, leading to shear deformation of the truck and the generation of large lateral gage spreading forces. A series of theoretical analyses and field experiments have been conducted that demonstrate the loss of steering caused by the following wheel-rail contact conditions: 1. 1. strong two-point contact between flanging wheels and rails; 2. 2. hollow wom wheel treads; 3. 3. heavy gage corner grinding on the rail; 4. 4. high rail gage face lubrication; 5. 5. dry railheads. Studies conducted at several gage widening and rail rollover derailment sites have shown that these conditions are not uncommon on North American railroads.

Quasi Static Derailment of a Railway Vehicle, Comparison Between Experimental and Simulation Results

SUMMARY This paper describes an ORE B55 derailment test of a CORAIL passenger coach of the SNCF network, equipped with measurement wheelsets. This low speed test is simulated with the VOCO code. Experiments and simulations were executed for a co-operation between SNCF and INRETS-LTN, to evaluate the Dynamic Railway code VOCO, especially about wheel-rail contact conditions.

Rolling contact fatigue in railway wheels under high axle loads

Rolling contact fatigue defects are encountered in railway wheels used under high axle load conditions, in which substantial reductions in rail and wheel wear rates have been obtained through the previous introduction of higher strength materials and modified wheel and rail profiles. The metallurgical characteristics associated with defect initiation and growth are described. A fatigue initiation criterion based on exceedence of shakedown limits for the two wheel materials concerned has been assumed. An analysis of wheel-rail contact conditions in curved and tangent track was undertaken to identify which combinations of wheel load, wheel and rail profiles and vehicle dynamics result in stress levels which exceed shakedown limits. This analysis is supported by full-scale tests involving continuous monitoring of wheel-rail contact. Extreme dynamic loads, leading to the initiation of isolated defects, are more likely to occur on tangent track, while curved track conditions will favour fatigue crack growth, when contact geometry and vehicle tracking combine to concentrate higher stress cycles in the initiation zone. Additional field tests, using an instrumented vehicle, will be carried out to confirm these findings and allow appropriate remedial action to be identified.