An Investigation of the Influence of Temperature and Technical Condition on the Hydraulic Shock Absorber Characteristics

The paper presents issues related to the operation of hydraulic shock absorbers. The primary objective was to determine the influence of temperature and the technical condition on the damping properties of a twin-tube hydraulic shock absorber. Three units (one new and two used) of the same type of a shock absorber were used for testing. During the tests, the shock absorber was subjected to sinusoidal excitation at fixed values of frequency and displacement amplitudes. There are few low-temperature tests of shock absorbers available in the literature; thus, great emphasis was placed on this aspect of the study. The characteristics of the shock absorbers were determined from a temperature of −30 °C until a steady-state temperature was reached at a given excitation. The resistance force at this temperature is about 2.5 times higher than at 20 °C. The study shows that such high forces can lead to the failure of shock absorber components (especially the valves). The amount of energy dissipated in a single operating cycle of a shock absorber decreases non-linearly with the increase of the temperature. Understanding the temperature dependence of the shock absorber in combination with the cooling curve allows for the steady-state temperature to be estimated at a given excitation. The study also shows that the installation of used shock absorbers in vehicles is not acceptable. Although there are no external signs of wear, their characteristics can differ significantly from those of new shock absorbers.