s modaresahmadi - department of mechanical Engineering, tarbiatmodares University tehran Iran
m ghazavi - department of mechanical Engineering, tarbiatmodares University tehran Iran
m sheikhzad saravani - department of mechanical Engineering, University of wollongong wollongong australia

Squeeze film dampers (SFDs) are often used in machines with high rotational speed to reduce nonperiodic behavior by creating external damping. There are some structural parameters which are ofgreat importance in designing these systems, such as oil film thickness and inner race mass of SFD.Moreover, there is a crucial parameter associated with manufacturing process, under the title of waviness. Geometric imperfections are often called waviness if its wavelength is much longer thanHertzian contact width. In this paper, a system of a flexible rotor and two ball bearings with squeezefilm dampers and centralizing springs and also consideration of waviness has been modeled and solved by a numerical integration method to investigate the system dynamic response. Results show that byincreasing the number of wave lobes, non-periodic and chaotic behavior increases. This reveals theimportance of manufacturing accuracy and necessity of taking this term into account in simulations. Moreover, by changing the oil film thickness, it is revealed that there is an optimal value for this parameter to provide maximum damping. In addition, with increasing the inner race mass of SFD, thedisc displacement amplitude increases. This reveals the importance of utilizing light materials in manufacturing the SFDs

Squeeze-film Damper , Waviness , Ball Bearing , Bifurcation ,