PECULIARITIES OF BENCH TESTS OF HYDRAULIC DAMPER OF RAILWAY PASSENGER CAR

The studies are devoted to the scientific problem connected with the significant differences in the piston stroke values during testing of the same type of hydraulic damper by the use of different test benches and methods. The damper manufacturer uses the mechanical test bench ЛИИЖТ, the design of which was created back in Soviet times. This test bench has certain design limitations regarding the amplitude of harmonic vibrations of the drive mechanism, and therefore the dampers are tested at short piston strokes, which are 4 %; 8 %; 16 %, respectively, as a percentage of the maximum stroke of the piston. The passenger car depot, as a consumer of absorbers, conducts their tests at the more modern universal stand ИГK-90.1, which differs from the mechanical stand of the manufacturer of absorbers, both in design and in the method of testing absorbers. The purpose of the research is to confirm or deny the presence of influence of the value of the piston stroke on the expert assessment of the technical condition of the hydraulic damper. To solve this problem, the modern universal test bench ИГК-90.1 carried out experimental studies with different volumes of damping fluid in the slave cylinder of the КВЗ-ЛИИЖТ 45.30.045M type. A comparative analysis of the protocols showed that in the “compression” mode, the nature of the obtained dependences of the force and resistance parameters with an increase in the piston’s moving speed changes depending on the volume of the damping fluid in the damper’s working cylinder. The authors believe that testing the absorbers during the piston stroke of at least 80% of the maximum piston stroke allows the presence of deformations of the guide rod and the insufficient amount of damping fluid (the presence of air) in the absorber’s working cylinder. Deformation of the stem can lead to jamming in operation. The presence of air in the working cylinder of the damper is generally unacceptable since such damper is not able to absorb the vertical and horizontal vibrations of the car body in a curved section of the railway track with the height difference of the railheads 150 mm.