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The most common reason of the fatigue crack appearance is the presence of stresses in the rail. The process of stress strain state simulation for the R65 rail is presented in the paper. Values of residual stresses were modeled and chosen to be maximum allowed by GOST (State Standard): -77 MPa in the rail head, -125 MPa in the web and 106 MPa in rail foot. These stresses match the value-77 MPa measured by the acoustoelastic method from the center of the rolling surface of the rail. The influence of the crack at the highest level of the stress strain state was studied in cases of the maximum train load and its absence. According to results of modeling, stresses in the sharp edge of the crack can exceed the lowest acceptable by GOST (State Standard) value of the yield strength by more than 5 times in case of the presence of the train load. In case of the absence of the train load, the crack does not have a significant influence on the stress strain state. The modelling process was also used to study the influence of the installation temperature difference on the operational lifetime of the rail. The paper presents the description of the influence between the installation temperature difference and the crack initiation. According to modeling results and the rail defect catalogue, rails with the lowest acceptable mechanical characteristics are prohibited to be used after 300∙109 kg and higher tonnage.

High values of residual stresses is one of the most common reason of breaking lots of metal constructions, including rails. These stresses can reach values of flow limit, especially in the area of faults. Estimation of residual stresses values allows to get information about technical condition of the rail and also allow to avoid abnormal situations So, the aim of the research is creating the model of stress-strain state of the rail, which was hardened in its top and bottom, and to compare modeling results with experimental measurements of stresses and discrepancy of the housing.For creating the model and making evaluations by finite element method we used a program COMSOL. Forces on the top and bottom of the rail cause tension stresses, forces on the web of the rail cause tensile stresses. We compared calculated values of stresses with discrepancy of the housing. The discrepancy of the housing is informative characteristic for estimating the residual stresses according to standards. For experimental measurements we used an acoustic structuroscope SEMA. This structuroscope uses the acoustoelastic phenomenon for measurements. We made measurements of the five rails.According to the calculation results of the model, critical discrepancy of the housing in 2 mm corresponded to the following values of maximum stresses: –54 MPa in the top of the rail, 86 MPa in the web and –62 MPa in the bottom of the rail. Experimental measurements are the following: from –48 MPa to – 64 MPa in the top of the rail, 54 MPa to 93 MPa in the web of the rail, and –59 MPA to –74 MPa in the bottom of the rail. Absolute error was ±5 MPa.Thus we created the model, which allowed to analyze strain-stress state and compare real values of stresses with discrepancy of the housing. Results of the modeling showed coincidence with structure of distribution of residual stresses in five probes of rails.

Одной из наиболее часто встречающихся причин разрушения рельсов является высокое значение остаточных напряжений. В процессе производства рельсов остаточные напряжения могут возникать в процессе прокатки, термообработки, правки и рихтовки. В настоящее время приемо-сдаточные испытания включают в себя контроль по измерению расхождения паза рельса после прорезания шейки рельса на глубину 600 мм, а также измерение остаточных напряжений в подошве рельса до и после вырезки темплета с наклеенным тензодатчиком. В данной работе рассмотрен вопрос о связи значений расхождения паза и напряжения в подошве с остаточными напряжениями в отдельных элементах рельса, полученных методом акустической тензометрии. Для выявления данной зависимости было выполнено разрезание рельса на отдельные элементы (головка, шейка, подошва), после чего в каждом элементе было проведено измерение напряжений методом акустической тензометрии. Моделирование проводилось методом конечных элементов в программной среде Comsol Multiphysics. По результатам моделирования и экспериментальных исследований предлагается браковочный критерий для контроля остаточных напряжений в случае прозвучивания сечения рельса со стороны поверхности катания: полученные значения сжимающих напряжений должны находиться в пределах σ int = -52…-80 МПа.

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