Multiple choice questions:
which one is a mechanism of failure
overheating
vibration
fatigue
These bearings operate by the following principle:
high lubricant density
roughness generates pressure
physical wedge
which of the following did Archard propose?
ΔT=µPV
Q=KWL/H
F=µW
Which of the following are true?
Kinematic viscosity is dynamic viscosity divided by the
density
The life of dry bearings is influenced by µPV because oils have
low viscosity at high temperatures
Mineral oils are denser than distilled water
The viscosity term in the Reynolds equation is the dynamic
viscosity
Elastohydrodynamic lubrication occurs when:
The lubricant exhibits elastic behaviour
The lubricant behaves like an elastomer
Pressures in the lubricant cause the surfaces to elastically
deform
Air bearings are commonly found in:
jet engines
wheel bearings of cars
dentists' drills
For a plane inclined slider bearing, to obtain pressure, p, the
value of dp/dx in the 1-D Reynolds is replaced by dp/dh
because:
dh/dx is a constant
h is a constant
p does not depend on h
The maximum load-carrying capacity of a hydrodynamic bearing
reduces at high speeds because:
heat generated reduces the viscosity of the lubricant which
produces thicker films
the lubricant viscosity decreases because of heat generation and
this reduces the minimum film thickness, which means that the load
capacity must be reduced to maintain adequate film thickness
the minimum film thickness becomes too small because the mean
velocity reduces with an increasing mean radius
The depth of wear in an artificial hip joint consisting of
stainless steel, spherical ball in a high-density polyethene cup,
will be larger:
if the ball radius is decreased
if the ball radius is increased
Which of the following are true?
Rolling element bearings in space can be lubricated with grease
provided it is very thick
Couette flow is caused by a negative pressure gradient
Large, hydrodynamic bearings in power generation units are often
started up by jacking up the journal with hydrostatic action
Adhesive wear can be reduced if surfaces are hardened
Reynolds equation is derived on the principle of no-slip at the
opposing surfaces
Third-body abrasive wear can occur in hydrodynamic bearings when
hard contaminants are in the lubricant
