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Bearing Capacities
Static Bearing Capacity
In rolling bearing technology we talk about
the static bearing capacity when the ball
bearing is loaded while stationary or during
slow swinging movements. The calculations
are made according to DIN ISO 76.
Basic Static Radial Load Rating C or
The basic static radial load rating is the static
radial load which corresponds to a calculated
contact stress of 4200 MPa at the centre of
the most heavily loaded rolling element /
raceway contact.
Static Equivalent Radial Load P or
The static equivalent radial load is the static
radial load which would cause the same
contact stress at the centre of the most
heavily loaded rolling element / raceway
contact that occurs under the actual load
conditions.
Calculating the static equivalent radial load:
P or =X o · F r + Y o · F a
X o = 0.6
Y o = 0.5
F r = greatest radial load occurring [N]
F a =greatest axial load occurring [N]
If the calculation gives a value, P or < F r ,
P or = F r should be set.
Permanent Deformation
Permanent deformation on raceways and
rolling elements even occurs when a
stationary ball bearing is only loaded
moderately.
Experience shows that a deformation of
0.0001 x rolling element diameter on the
most highly loaded point of contact between
raceway and rolling element will not
noticeably effect the function of the ball
bearing.
Even greater deformation is justifiable if the
ball bearing is running at low speed and the
requirements for noise are not high. On the
other hand only slight permanent deformation
is allowed if the noise and friction
requirements are particularly stringent.
Dynamic Bearing Capacity
The dynamic bearing capacity is the stress on
a rotating ball bearing. The additional term
“dynamic” indicates the operating condition
of the bearing not the effect of the load.
The calculations are made according to
DIN ISO 281.
Basic Dynamic Radial Load Rating C r
The basic dynamic radial load rating for radial
ball bearings is that constant radial load
which a sufficiently large number of
apparently identical ball bearings could
theoretically endure for a basic rating life of
one million revolutions.
Dynamic Equivalent Radial Load P r
The dynamic equivalent radial load for radial
ball bearings is that constant radial load
under the influence of which a rolling bearing
would have the same life as it will attain
under the actual load conditions.
The DIN load ratings are given in the ball
bearing tables. The actual load ratings can
deviate depending on the ball bearing type.
The load ratings are approx. 30% lower for
hybrid ball bearings than for comparable steel
ball bearings.
Please ask our technical support for the exact
load ratings.
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