## 1 Introduction
For example, in [8], the modelling of the vibration damper (mainly its valves) is discussed. Numerical simulations were validated on the basis of results of the experiment. The results of tests on shock absorbers with respect to temperature aspects can be found in literature [9; 10; 11; 12], as well as their influence on the driving comfort [13]. The paper [14] presents tests on shock absorbers filled with different fluids. Heating characteristics were performed for them at constant sinusoidal excitation parameters. Such tests make it possible to determine the magnitude of the heat transfer between the damper and the ambient air. This is important in terms of preventing shock absorbers from overheating and adversely altering their damping characteristics. The evaluation of the technical condition of dampers installed in a vehicle was made on the basis of their temperature changes throughout the movement of the vehicle [15]. In the paper [16], the authors attempted to use the Eusama method to determine the effect of temperature on the damping properties. Research was conducted for temperatures \(-5\)\({}^{\circ}\)C and \(20\)\({}^{\circ}\)C for various kinds of cars. Tests performed at a diagnostic station showed a reduction in shock absorber effectiveness of between \(5\) and \(25\%\) for the warmer shock absorbers. The principles of the Eusama method and its modifications are presented in the paper [17]. In [18], the authors presented the results of tests on a truck shock absorber over a wide range of temperatures (between \(-40\)\({}^{\circ}\)C and \(100\)\({}^{\circ}\)C). A significant effect of the temperature on the damping forces was demonstrated. However, the tests were performed for a limited range of shock absorber piston velocities (up to approximately \(60\) mm/s). Changes in characteristics caused by temperature changes are also being analysed in shock absorbers used in aviation technology. In the paper [19], the changes in the damping characteristics of the shock absorber and the viscosity of the aviation hydraulic oil were presented (at temperature range from \(-25\)\({}^{\circ}\)C to \(50\)\({}^{\circ}\)C). In the positive temperature range, a near-linearity decrease in viscosity along with the temperature was observed. At sub-zerotemperatures, viscosity increased rapidly. This directly affects the damping coefficient of the shock absorber. The impact of temperature is also assessed for dampers with adjustable damping characteristics. Paper [20] describes the influence of temperature on the characteristics of a damper with a magnetorheological fluid. Heating up the shock absorber changes the viscosity of the oil; however, it also changes the resistance of the control coils. These two factors change the values of the shock absorber resistance forces. Corresponding results were reported by the authors in [21]. The presented test results were obtained for temperatures ranging from 25 \({}^{\circ}\)C to 70 \({}^{\circ}\)C.  
The literature includes analytical papers [22; 23; 24]. In [23], the authors presented a thermodynamic model of a shock absorber. The model allows determination of the steady-state temperatures and heat transfer to the environment. The simulation results were compared with experimental results. Similar considerations are presented in paper [22]. The effects of the heating of a shock absorber during its operation have been correlated to the durability of the seals and their resistance to elevated temperatures. There are also studies in which simulations are conducted with the application of sophisticated software, fluids flowing through valves, and their effect on resistance forces. For example, in [24], numerical investigation of the orifice nearfield flow development in oleo-pneumatic shock absorbers was presented.