What are hydrodynamic lubricants?
Hydrodynamic lubrication is a term that defines a situation in which two rubbing surfaces are separated by a thin film of a lubricant. This situation is often beneficial and lubrication is used to reduce friction and/or wear of rubbing solids with the aid of liquid (or semi-solid) lubricant.
What is hydrostatic and hydrodynamic lubrication?
Hydrostatic lubrication depends on the inlet pressure of lube oil and clearance between the metal surfaces, whereas in hydrodynamic lubrication it depends on the relative speed between the surfaces, oil viscosity, load on the surfaces, and clearance between the moving surfaces.
What is hydrodynamic friction?
friction produced by the viscosity of a liquid in motion.
What is the difference between boundary lubrication and hydrodynamic?
In boundary lubrication, friction force is independent of speed. In hydrodynamic lubrication, the viscous friction force increases with increasing speed. The fluid pumping torque usually increases with speed squared.
What is the difference between hydrodynamic and hydrostatic?
Per definition, hydrostatic pressure is the “pressure exerted by, or existing within, a liquid at rest with respect to adjacent bodies [1],” while hydrodynamic pressure is the pressure generated by the motion of a liquid relative to adjacent bodies.
What causes friction in hydrodynamic lubrication?
High rotation speed at relatively low bearing loads results in hydrodynamic friction, which is characterized by stable squeeze film (oil film) between the rubbing surfaces. No contact between the surfaces occurs in hydrodynamic lubrication.
What is hydrodynamic lubrication?
Hydrodynamic lubrication: The tool and the workpiece are separated by a liquid lubricant which is thick enough to avoid any direct contact between their surfaces.
Can a hydrodynamic bearing come into contact with the shaft?
Although a hydrodynamic bearing is separated by a lubricant film, there will inevitably be occasions when the shaft and the bearing bushing surfaces come into direct contact.
What is the purpose of lubricant in the Journal of bearings?
•As lubricant is carried around the bearing it encounters the step that causes an increased pressure at the top of the journal inducing a stabilizing force onto the journal which forces the shaft into the bottom half of the bearing. ⇨ •This bearing has a high load capacity and is a common correction for machine designs susceptible to oil whirl.
How long do hydrodynamic bearings last?
When properly installed and lubricated, hydrodynamic bearings are considered to have infinite life. They are designed to operate within a certain speed range, and too high or too low a speed will upset the film lubrication.