VIBTOOL 02.2009
30
What are shock pulses?
Shock pulses are short duration pressure pulses which are
generated by mechanical impacts. Mechanical impacts
occur in all rotating rolling bearings because of irregulari-
ties in the surfaces of the raceways and rolling elements.
The magnitude of the shock pulses depends on the impact
velocity and surface area.
Like random vibrations, shock pulses are encountered
relatively often in daily life. They can originate from widely
different releases of energy such as rough handling of
equipment. However, one thing which is noticeable with
shock pulses is the short duration. A simple shock pulse can
be defined as a transmission of kinetic energy to a system
which takes place in a relatively short period of time.
Where do shock pulses occur?
A common place where shock pulses are generated is in
bearings. Shock pulses are generated in the rolling inter-
face between the loaded rolling element and the raceway of
the bearing. The surface of the bearings is rough.
The rough surface gives rise to pressure variations in the
oil film which separates the moving surfaces, as well as
collisions between peaks in the surface. These factors result
in shock pulses which spread through the material of the
bearing, the bearing housing and any adjacent machine
parts.
Bearing diagnosis
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