Modal characteristics of rollers immersed in different fluids: experimental and numerical analysis

Abstract

The immersed roller is very common in the roll-to-roll industry, such as hot dip galvanizing, electroplating, roll coating. In these applications, the strip is developing thinner and wider, and its flexibility is also strengthening. The vibration of the sinking roller has an increasingly significant impact on its product quality. A theoretical model was established to study the sink roller immersed in fluids, and modal tests and corresponding finite element simulations were carried out to study the sink roller's characteristics. The effects of roller density, wall thickness, fluid density, viscosity, and constraint conditions on modal characteristics were investigated. The results were well-validated, and the modal tests in air with and without a rod have high consistency, proving the reliability. The first six peak values of FRF curves are clear when immersed in water and hydraulic oil, but only the first three are evident in glycerin. It is observed that the viscosity of glycerin has a minor effect on natural frequencies, but the added damping factor grows when viscosity increases. The added mass factor rises linearly with the growth of wall thickness or liquid density while decreasing when the structure's density increases. The added mass factors of the (1,2)th and (2,2)th modes are more significant than the bending modes. A rigid-body displacement occurs at the constrained end journal of bending mode for rollers in liquids. Liquid density is the main factor affecting natural frequencies, especially for aluminum rollers. The maximum frequency growth rates under the constrained state of the steel and aluminum rollers in water are 5.7% and 20.4%, respectively, on the (2,2)th mode. Moreover, it increases with the increase of liquid density and viscosity, which leads to higher resonance probability. It can provide a basis for the dynamics research of similar systems.