Frequency response of hydraulic hoses

Hoses can be components of fluid power control systems. To determine the dynamic behaviour of such systems you need to know the dynamic properties of the components included. This investigation aims to develop a method to determine these properties of hoses. Nitrile-black-carbon is used in hydraulic hoses. A literature study gives that rubber is a very complex material. It is viscoelastic with a lot of non-linearities so it is not self-evident how to model the hose. Four different models are studied. One of them gives an idea of the static relation between the rubber tube and the reinforcing. Two of them take the dynamic properties of rubber into account. The fourth model is a second order black box model. Laboratory tests have been done. The relationship between pressure changes and volume changes in hydraulic hoses at different frequencies is measured. Two seated valves were used, one for increasing and one for decreasing the pressure in the hose. The volume of oil coming out from the hose was measured with a cylinder. Three different hoses are tested. The test results agree rather well with one of the dynamic rubber models and with the black box model, useful for control system analysis.QC 20150917