DEVELOPMENT OF INITIAL DATA FOR ESTIMATES REMAINING LIFE OF RAILS

ABSTRACT

Methods for developing preliminary data for estimating the remaining life of rails are presented. Determining and estimating the remaining life of rails is of great importance in the development of preliminary data.

АННОТАЦИЯ

Представлены методы получения исходных данных для оценки остаточного ресурса рельсов. Определение и оценка остаточного ресурса рельсов имеет большое значение при разработке исходных данных.

Keywords: rail, initial data, diagnostics, cracks and spalls, vertical wear, lateral wear, wavy wear

Ключевые слова: рельс, исходные данных, диагностика, трещины и выкрашивания, вертикальный износ, боковой износ, волнообразный износ.

Introduction. It is necessary to have a single generalized database that allows predicting the process of changes in the technical condition of rails. In addition, without such information, the economic-mathematical model cannot work. During the operation of the railway, which is determined by the working time of the transferred tonnage, measured in million gross tons, the processes of corrosion, wrinkling, decay, fatigue, etc. inevitably occur on the rails. Under the influence of these factors, various defects are formed. A rail defect is usually understood as a deviation from its geometrical parameters or specified standards of strength, failure to comply with which leads to a loss of performance under specified operating conditions [1-4].

Based on the results of track monitoring, preliminary data is collected to estimate the remaining life of the rails. As mentioned above, it is based on the data carried out by the "126-diagnostic laboratory" of the "Railway monitoring and diagnostics".

Object of research. Statistics on rail defects were obtained from the Tashkent Railway. The total distance of the Tashkent railway is 265 km, of which 73 km are single-track and 123 km are double-track.

Development initial data. In 2021, the number of defective rails on the railway in the distance of the Tashkent railway is presented in Fig. 1. The most common rail defects include cracks and chipping, as well as vertical, lateral and wavy wear. Damaged rails are generally divided into defective and acutely defective, depending on the degree of danger. On the basis of data from various sources, the average correlations of the development of defects in the missed tonnage were constructed. Cracks and chipping of the metal on the surface of the rail head usually occur after the warranty tonnage is exceeded due to the accumulation of local non-metallic strength or the lack of fatigue strength of the ferrous metal.

Figure 1. Number of defective rails

One of the factors affecting the development of defects on the rails, taking into account the tonnage of this section, the initial data is taken from the section between Saryogoch - Keles stations. Because the tonnage of this section is large. It is known that the import and export goods of Uzbekistan to China and South Korea pass through this section by rail. In addition, transit cargo from China and South Korea to Central Asia is delivered to the Keles station in Uzbekistan via the Saryogoch station in Kazakhstan [5, 6]. Another factor affecting the development of rail defects is the curvature and slope of the railway tracks. 200 mln. to service the new R65 rail made at the factory. ton. marked as gross. If we analyze the development of rail defects in European and US countries, 1100-1400 mln. ton. we see that it serves up to gross [7-11].

Figure 1. shows the average curve of the development of cracks and metal crushing, depending on the tonnage transferred on a flat section of the railway.

Figure 2 shows that the curve steepens after passing around 100 million tons of gross cargo. This graph confirms the constant growth of individual contact fatigue cracks in the rail during operation until reaching threshold values, which depends on the initial stiffness of the rails and increases with its decrease. It should be considered that the greatest danger is the merging of several inclined cracks, which can later form a single longitudinal crack proportional to the width of the railhead. A newly formed crack can change its direction of development and lead to the formation of a transverse fatigue crack.

Figure 2. The average dependence of the development of cracks and crushing on the transferred tonnage (on a flat part of the railway track)

Vertical wear occurs when the strength of the railhead metal does not match the conditions of the pressure exerted on it by the wheels of the rolling stock. In the metal, significant corrosion damage cracks appear, which can then become a catalyst for the formation of longitudinal vertical cracks.

Figure 3 shows the average curve of the development of the vertical erosion of the railhead as a function of the missed tonnage. Figure 3 shows that the vertical erosion developed more slowly in the straight sections of the rail.

Figure 3 shows that the smaller the radius of the curve, the stronger the development of this defect. The reasons for the appearance of lateral erosion are due to the increase in the angles of the wheel ridges on the side of the rails (due to the violation of the normal compliance of the wheel moving to the curved sections of the railway track), as well as the low erosion resistance of the iron metal of the rail ridges. In addition, due to insufficient distribution of the side face of the railhead, side erosion may occur.

Figure 3. The average dependence of the development of the vertical deflection of the rail head on the transferred tonnage (on a flat part of the railway track)

Figure 4 shows that on straight sections of the railway line, thrusts are generated that increase as the tonnage passed increases. In addition, the smaller the radius of the curve, the stronger the development of this defect. Figure 4 shows the average curve of the development of the side erosion of the railhead as a function of the tonnage missed.

Figure 4. The average dependence of the development of side erosion of the railhead on the transferred tonnage (on a flat part of the railway track)

In some sections of the railway, undulating erosion occurs frequently and is usually formed on curves. The reason for this defect is the displacement of locomotive wheels (for example, on curves due to different lengths of outer and inner threads). In addition, the cause of the defect may be a factory defect caused by vibration in the railway straightening machines.

Figure 5 shows the average curve of the dependence of the development of the undulating erosion of the railhead on the transferred tonnage in one section of the railway track (on a straight section of the railway).

Figure 5. The average dependence of the development of wave-shaped deformation of the railhead on the tonnage missed (on a straight section of the railway)

Conclusions

1. The creation of predictive models and therefore the values of indicators of the remaining life of rails is based on two types of data:

1) based on monitoring results only;

2) in addition to the measurement results, the opinions of experts qualified in this field are used in the diagnostic wagon.

2. The analysis shows that the curvature of the road is of great importance for the development of wear on the rails. The smaller the radius of curvature, the greater the intensity of the development of wear on the rail. In curves, lateral erosion develops faster than vertical erosion.

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