Abstract
Introduction . The paper is devoted to the evaluation of cracking of white layers formed on the surface of the rail while in operation. Cracks are detected in the white layer of rail steel after one thousand test cycles. This is due to tensile and shear stresses on the surface of the wheel-rail contact spot. The paper presents the study results of the morphological characteristics of the white layer on the rail surface. Materials and Methods . The object of study (rail surface after operation) was examined under a microscope. Then, a two-dimensional model of finite elements of the plane deformation was developed to simulate the dynamic characteristics of the white layer cracking. Mathematical models describing crack propagation are proposed. For this, we applied the criterion of the elastic plastic fracture mechanics, the J -integral method. The SYSWELD program performed numerical modeling of the formation of a white layer and the distribution of residual stresses. Results . Optical images of the microstructure of the cross section of a white layer on the rail surface after operation are presented. Two different types of cracks were fixed at the trailing edge of the white layer of the samples studied. The SYSWELD program visualized fragments of simulating the mechanism of the white layer formation with the distribution of residual stresses, compression, and tension. The calculation results show that the values of the J -integral for all three cracks slightly decrease if the crack length reaches 10-50 gm. Discussion and Conclusions . The results obtained are applicable to assess the wear resistance of rail steels and predict the direction of crack growth. Comparisons of J -integral maxima have shown that under identical load conditions, crack no. 1 is likely to grow faster than cracks nos. 2 and 3. With an increase in the length of the crack, the maxima of the J -integral of all three cracks decreased.
Highlights
The paper is devoted to the evaluation of cracking of white layers formed on the surface of the rail while in operation
Cracks are detected in the white layer of rail steel after one thousand test cycles
A two-dimensional model of finite elements of the plane deformation was developed to simulate the dynamic characteristics of the white layer cracking
Summary
ФГБОУ ВО «Иркутский национальный исследовательский технический университет» (г. Иркутск, Российская Федерация). Трещины в белом слое рельсовой стали обнаруживаются уже после 1 тыс. В работе представлены результаты исследований морфологических характеристик белого слоя на поверхности рельса. В программе SYSWELD выполнено численное моделирование образования белого слоя и распределения остаточных напряжений. Представлены оптические снимки микроструктуры поперечного сечения белого слоя на поверхности рельса после эксплуатации. В программе SYSWELD визуализированы фрагменты моделирования механизма образования белого слоя с распределением остаточных напряжения, сжатия и растяжения. Результаты расчетов показывают, что значения J-интеграла для всех трех трещин немного уменьшаются, если длина трещины достигает 10–50 мкм. Полученные результаты применимы для оценки износостойкости рельсовых сталей и прогнозирования направления роста трещины. С увеличением длины трещины максимумы J-интеграла всех трех трещин уменьшались. Ключевые слова: рельсовая сталь, белый слой, трещина, упругое пластическое разрушение, метод J-интеграла распределением остаточных напряжений. Ю. Исследование распространения трещины в поверхностном белом слое рельсовой стали / А.
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