Effect of Railcar Wheel Tire Profiles on the Contact Stress Level in Subway Rails
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EFFECT OF RAILCAR WHEEL TIRE PROFILES ON THE CONTACT STRESS LEVEL IN SUBWAY RAILS V. V. Kosarchuk, É. I. Danilenko, and A. V. Agarkov
UDC 625.1.032.3
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The statistical analysis performed on the defectiveness of rails in the Kiev subway railway shows that the main cause of the occurrence of most defects is the contact fatigue of the rail material. The paper presents modern concepts of crack growth in the railhead. It has been found that one of the most promising directions of studying the stress-strain state of rails and the crack growth process is a numerical simulation, which results on the contact interaction between rails and subway rolling stock wheels are presented. During the simulation, the problem was solved in an elastic formulation. We considered R50, R65, and UIC60 rail profiles, standard railway wheels, and wheels whose tire profile was developed by the Minetek closed joint-stock company. The conditions for the rail–wheel interaction corresponded to train movement on the straight section of the track without slipping. The effect of the wheel tire profile on the contact stress level in rails of different types has been assessed. Comparison of the maximum equivalent stress levels for a different combination of rail and wheel types shows that the best combination (in terms of reducing the contact stress level) for the straight sections of the subway track is an R50 rail with a gradient of 1 in 20 and 1 in 10 taper wheel, whose profile corresponds to GOST 9036-88. When wheels with the profile developed by the Minetek company are used, the maximum equivalent stress level in the contact zone is over 1000 MPa for all rail types. It is higher than the yield strength of rail steel, which will accelerate wear and give rise to low-cycle fatigue cracks with subsequent formation of contact fatigue defects. Keywords: railway rails, contact stresses, wheel profile, contact fatigue defects, finite element method. Introduction and Problem Statement. During operation, the subway track structures are exposed to tens of millions of force impacts of rolling stock wheels. As a result, fatigue damages as microcracks accumulate in the rail material under the action of fluctuating stresses. Their further development (increase in size, coalescence, change in growth direction) gives rise to so-called contact fatigue defects in rails. It is known that almost 80% of the damages of railway rails are associated with the occurrence of defects of just this type [1–3]. In many countries, systems of defect classification for railway rails by external signs and the causes of the occurrence of defects have been developed. In [4], all types of defects are coded with a three-digit number: the first digit denotes the type of defect and the site of its occurrence; the second digit denotes the kind of defect, taking into account the main cause of its initiation and development; the third digit denotes the defect location along the rail. A statistical analysis of the defectiveness of Kiev subway rails performed during 12 years (from 2002 to 2
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