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Relevance of the research topic. During operation rubber-cord couplings with a toroidal shell form may fail. For the period from 2019 to 2023 (5 years) such failures amounted to more than 58 cases. According to a visual inspection of a large number of failed rubber-cord couplings, it was found that the cause of failure was a rupture of the side surface. The aim of this scientific article is to determine the forces and moments acting on the rubber-cord coupling, as well as the displacements of the shafts connected by the rubber-cord coupling in axial, radial and angular deflections. To determine the properties of the material, single tensile and cyclic tests of fragments of rubber-cord couplings were carried out. Based on the test results, a mathematical model of the material was determined. In the environment of the FEM software, the test results were compared with models of elastomeric materials and the most suitable model of elastomeric material that most accurately corresponded to the test results was selected. The calculated forces and torque effects were simulated, and the effects of radial, axial and angular deflection and measured coupling deflections were simulated. The purpose of modelling is to identify dangerous operating modes and dangerous forms of the rubber-cord coupling loading during operation. [ABSTRACT FROM AUTHOR]

One of the main criteria for the quality of steels is the ability to resist brittle fracture. This ability is qualitatively expressed in the value of impact strength and toughness. According to the statistical data at AS "Pasažieru vilciens", at low temperatures, the number of failures of the M-24 bolts for fastening the rubber-cord coupling increases. In this regard, the urgent task is to reduce the number of failures during the winter. The article presents the results of tests of impact strength and toughness, as well as a metallographic analysis of two steel grades 41Cr4 and P355NL1. Also an experiment was carried out, on the basis of which the main conclusions were made on the mechanical properties of two grades of steel 41Cr4 and P355NL1. [ABSTRACT FROM AUTHOR]

One of the main defects in rail steel is a defect on the rolling surface of the rail head. A sign of the defect appearance is delamination and spalling of the metal on the rolling surface. The development of this type of defect to a length of more than 25 mm and a depth of more than 4 mm requires a decrease of the train speed up to 70 km·h-1, and with a depth of more than 8 mm - to 25 km·h-1. Reducing the speed significantly affects the quality of service and railway performance. As a result, there is a disruption in the accuracy of train traffic, which subsequently leads to material costs for restoring the movement of trains at set speeds. The primary task of the study presented in this article is the collection and analysis of statistical information on the Latvian Railway defective rails in the period from 2011 to 2021. A secondary task is to investigate the causes of the appearance of rail defects under code X 10.1. The research process included: detection of these defects on the Latvian Railway using a modern ultrasonic flaw detector of the "RDM-24" type, determination of the metal hardness (EN 13674-1:2011 standard 350-390 HB) in the rail head and on the rolling surface using a certified modern device "Tinius O Olsen" Firmware Version 1.07, FH - 31 Series as well as the study of the chemical composition of the rail head using the optical emission analyzer PMI - Master PRO and determination of the microstructure of the metal in the rail head. At the final stage, to compare the results obtained in an independent certified laboratory, based on the results of the research to draw conclusions about the causes of this type of defect. [ABSTRACT FROM AUTHOR]

For the first time at the Riga Technical University a study was carried out of a highly defective frog core of grade 1/9. In the course of the research an analysis of crossing piece defects on the Latvian railway was carried out in eight railway sections during years of 2015, 2016, 2017. The defect of the frog core of grade 1/9 (the 60 E1 DO 07 12 frog type) was considered according to the basic classification of the defects, and the analysis and research of the cause of its fracture were conducted from the bolt hole to the web and the base of the frog core. The research process consisted of four stages: - Stage 1: determination of metal hardness according to the Brinell scale with a modern device "Tinius O Olsen" Firmware Version 1.07, FH - 31 Series. The obtained results should be compared with the data of the manufacturer's factory - Dowlais Steel. - Stage 2: determination of the chemical composition of the rail steel of the frog core 1/9 (in the rail top, rail web, and rail base) using the ARC-MET 8000 Mobile Lab Optical Emission Spectometer Analyser. The obtained data should be compared with the manufacturer's data. - Stage 3: determination of the rail steel structure. Drawing of main conclusions about the quality of the rail steel of the frog core of grade 1/9. - Stage 4: drawing of main conclusions and summary of the cause and development of the fracture from the bolt hole of the frog core of grade 1/9. [ABSTRACT FROM AUTHOR]