hydraulic bearing w pressure control
hydraulic bearing w pressure control
(OP)
Hi,
A long cylindrical ram which is making axial alternating movement, and bending mostly due to its own weight. The ram is supported by two hydraulic bearings with pressure control and a slide joke at the drive side. The vertical vibration of the ram often causes problems at certain speeds.
We think of doing a modal analysis on the system, but there are very limited information on the dynamics of a hydraulic bearing to input into FE. How exactly does a hydraulic bearing work?
Does anybody have any information on how to handle such problem? Any infos are appreciated. Thanks.
GSC
A long cylindrical ram which is making axial alternating movement, and bending mostly due to its own weight. The ram is supported by two hydraulic bearings with pressure control and a slide joke at the drive side. The vertical vibration of the ram often causes problems at certain speeds.
We think of doing a modal analysis on the system, but there are very limited information on the dynamics of a hydraulic bearing to input into FE. How exactly does a hydraulic bearing work?
Does anybody have any information on how to handle such problem? Any infos are appreciated. Thanks.
GSC





RE: hydraulic bearing w pressure control
Correctly designed hydrostatic bearings are usually very stiff (easily a million pounds/inch). The linearized stiffness calculation is quite straight forward. If you want I can FAX the pages (about 20 ) to you.
sreid@dac-intl.com
RE: hydraulic bearing w pressure control
I assume that the stiffness of the bushing against rotation/bending of the shaft would also derive from the bearing stiffness, right?
GSC
RE: hydraulic bearing w pressure control
Bearing stiffness might need to be included in a mode analysis. The hydrostatic bearings would appear as very stiff springs supporting you ram. You could get a measure of the bearing stiffness by applying a force close to the bearing and measuring the shaft movement with a dial indicator.
If your ram moves fast it is possible to have the bearings oil starve-the oil shear from velocity counteracts to oil flow through the bearing gap at the leading edge.