Підвищення надійності п’ятникових вузлів вантажних вагонів шляхом удосконалення технології їх відновлення

UKR: Дисертація присвячена розв’язанню актуального науково-прикладного завдання з підвищення міжремонтного ресурсу п’ятникових вузлів вантажних вагонів. Зокрема, у теоретичному аспекті розроблено модель і запропоновано вирази для визначення стану зносу п’ятникового вузла з прогнозуванням міжремонтного ресурсу, що на практиці дає змогу зменшити витрати на ремонт завдяки підвищенню міжремонтного ресурсу п’ятникових вузлів вантажних вагонів. Виконано теоретичне обґрунтування підвищення міжремонтного ресурсу п’ятникового вузла вантажних вагонів з використанням технологічних методів поліпшення фізико-механічних та триботехнічних властивостей сполучених поверхонь п’ятникового вузла. Водночас уперше отримано модель для оцінки величини зносу циліндричної поверхні підп’ятника, яка враховує фізико-механічні та триботехнічні властивості матеріалів, що взаємодіють у п’ятниковому вузлі, і сумарні сили, що діють у поперечному й поздовжньому напрямках. Також вперше запропоновано вирази для визначення зазору в з’єднанні «п’ятник – підп’ятник», які враховують геометричне положення поверхонь, що взаємодіють, а також зміну величини зносу п’ятникового вузла в процесі експлуатації вантажного вагона. Експлуатаційні дослідження з визначення міжремонтного ресурсу п’ятникових вузлів вантажних вагонів моделі 12-7023 підтвердили доцільність застосування контактного наварювання зносостійких композиційних стрічок.

ENG: The dissertation is devoted to solving the current scientific and applied problem of increasing the service life of the foot assemblies of freight cars. At the same time, in the theoretical aspect, a model has been developed and expressions have been proposed for determining the state of wear of the foot assembly with the forecast of the service life, which in practical terms allows reducing repair costs by increasing the service life of the foot assemblies of freight cars. In the first section, an analysis of the faults of freight cars that led to transport incidents was carried out. As a result, the need to increase the service life of the foot assembly of freight cars was identified. Therefore, technological methods for repairing and increasing the wear resistance of the foot assemblies were considered, as a result of applying the technical and economic criterion, it was established that the most attractive technological methods are laser and plasma surfacing, despite the high cost of these methods, they provide the highest value of the service life between repairs of foot assemblies. Taking into account the simplicity of application, it was proposed to use contact welding for repairing foot assemblies. This method does not require additional special equipment, that is, industrial transformers and other means of wagon repair enterprises can be used. In the second section, a study of the operational wear of foot assemblies and thrust washers of the spring beams of freight wagon bogies was carried out. As a result of the conducted studies of the operational wear of the thrust bearings and thrust bearings of the bogie beams of freight cars, it was established that the uncoupling for premature repair when forecasted for the ultimate wear of the thrust bearing occurs when the freight car has run for 174 thousand km, and for the wear of the thrust bearing, the forecasted service life is 320 thousand km. That is, the resource-intensive element of the freight car is the thrust bearing, which has an insufficient service life, and to achieve the service life of 300 thousand km, it is necessary to increase its wear resistance. The third section presents the results of theoretical studies of the service life of freight car bogies, in which the thrust bearing assembly is the resource-generating element. When considering the interaction of the elements of the pair "thrust bearing - thrust bearing" of a freight car at the moment of applying traction force, an expression for determining the gap is proposed. The use of composite strips for welding them onto the cylindrical surface of the thrust bearing is theoretically justified. It has been established that when using a composite tape during the repair of the freight car’s footrest assembly, the strength and wear-resistant properties of the cylindrical surface of the thrust bearing increase, i.e. during the operation of the repaired car, the wear value will also change, which is 2...2.7 times less than in the base version. The fourth section presents the results of the study of the physical, mechanical and tribotechnical properties of the restored surfaces of the piston assembly, which confirmed the theoretical prerequisites for increasing the service life of the piston assemblies. Bench studies have shown that the wear rate of repaired thrust bearings with welded composite strips is 2.7...5.6 times lower than the wear rate of thrust bearings repaired by surfacing and 1.6...4.3 times lower than the wear rate of thrust bearings with installed wear-resistant elements. The fifth section presents the results of operational studies to determine the service life between overhauls of thrust assemblies of freight cars of model 12-7023, which also confirmed the feasibility of using contact welding of wear-resistant composite strips. The predicted values of the service life between overhauls of the thrust bearing of the gondola car model 12-7023 in terms of wear are 660 thousand km and 680 thousand km of mileage, respectively, for the two cases. Forecasting the service life between overhauls based on the permissible wear of the diameters of the thrust bearings of the gondola car model 12-7023 showed that the mileage before repair for thrust bearings with welded composite strips Fe-Cr-Ni-Cr3C2 is about 1 million. km, and for thrust bearings with welded composite strips Fe-Cr-Ni-TiC – 740 thousand km. The overall economic effect of applying the proposed technology of restoring the thrust bearing by contact welding with a wear-resistant composite strip is 79991.85 UAH, and the payback period is 1.9 years.