PSI - Issue 30

N.A. Makhutov et al. / Procedia Structural Integrity 30 (2020) 87–92 N.A. Makhutov et al. / Structural Integrity Procedia 00 (2020) 000–000

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• Resistance to elastic and plastic deformations under a static loading and accumulated deformations under a cyclic loading with a possible form change of parts • Resistance to a failure according to mechanism of ductile fracture or mechanism of brittle fracture • Fatigue strength (low-, high- and ultra high-cycle one) • Resistance to buckling and vibrations • Resistance to corrosion and wear To work in conditions of Siberia, the Far North and the Arctic, the criteria for cold resistance are additionally taken into account. Bench tests at standard climatic temperatures (20 °C) are supplemented by laboratory tests of standard specimens at low temperatures (up to -70 °C). 3. Actual damage cases The statistics of failures of side frames (Fig. 1) of freight wagon bogies (10–20 per year) during their operation, ruptures of automatic coupler casting (50–60 annually) in trains, occurring mainly in winter, definitely shows the influence of ambient temperature on the probability of emergency and catastrophic situations and indicates the necessity to improve the cold resistance of steels of welded and cast parts by Oganyan et al. (2013), Kossov et al. (2016) and Protopopov et al. (2019). Calculations have shown that the service lifetime of such parts (the operation time before a crack initiation) and the crack growth life (the period of a crack growth until the loss of a bearing capacity – failure) strongly depend on technological and operational factors, as a result of which defects can develop (until a crack reaches a part section surface) for 8–10 years or more or very quickly, for 1.5–2 years. And if they have a small design safety factor of fatigue strength, within 1.20–1.35, then it is not able to compensate for a negative impact of technological and operational defects (Table 1). As can be seen in the table 1, breakdowns of bogie side frames occur mainly along the inner radius R55 of the jaw opening (approximately 80 % of failure cases). And this is not a coincidence. According to results of calculations and tests, this point turns out to be the most stressed one under both vertical and lateral static and dynamic loads. These areas are sensitive to the casting quality, to the technical state of a bogie, operation conditions and modes, negative ambient temperatures. a b

Fig. 1. Fractures of bogie side frames with derailments of freight wagons.

Table 1. Reasons for the fracture of side frames of freight wagon bogies in the area of the inner angle of the pedestal jaw opening. Year of frame manufacture Fracture reason 2010 Casting defect in the area of the radius R55 of the pedestal jaw opening in the area invisible to wagon inspectors 2010 Casting defect in the area of the radius R55 of the pedestal jaw opening in the area invisible to wagon inspectors 2010 Casting defect in the area of the radius R55 of the pedestal jaw opening 2011 Casting defect 3,5 × 4,0 mm in size