The paper describes the observed occurrence of hysteresis of the characteristic curve of a shock absorber valve. The phenomenon has an impact on the asymmetry of the damping force characteristic and should be taken into account when modelling the valve operation. The aim of the investigations was to determine the factors generating the phenomenon and establish the relationships between these factors and the hysteresis size. Tests were carried out on a stand intended for valve measurements in isolated conditions. A strongly coupled Fluid-Structure Interaction numerical model was also created to simulate the valve operation in selected conditions. The results indicate that the hysteresis loop occurrence is mainly due to the conditions of the valve disc stack preload in the process of its composition and, consequently, to the friction between the valve elements. Having an impact on the contact between discs and on the disc stack overall structure, they affect the hysteresis field significantly. The testing results confirm the supposition that hysteresis is not due to the phenomena related to the conditions of the flow through the valve.

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