Working principle of bearing; It is to minimize the friction of machine parts that behave separately, such as two different speeds, opposite directions or fixed surfaces and rotating surfaces.
Even though it is not perceived by the eye, the roller or balls in the bearing undergo a deformation at the micron level, this is revealed by determining their hardness according to a certain speed and a certain load. Normally, balls and rollers that exert linear or point pressure, together with these forces, create friction by spreading to a larger surface, that is, a certain area, instead of a linear, point contact on the shaft of the bearing together with the ring, thus causing the balls to rotate inside the bearing. All bearings must be operated by applying a little force.
There is no specific rule about bearing selection, each designer can use different bearings on the same machines. The important thing is to meet the need.
In this catalogue;
Axial and radial load
working cycle
Operation time
Bearing life
Lubrication method
Selection of sealing elements
Operating temperature
amount of sound
Vibration during operation
Main features, such as the mounting method, should be considered.
Most designers and engineers in our country choose bearings according to inner diameter, outer diameter and load. This causes big errors. Instead of calculating values such as load calculation, life, temperature, it is now possible to find these values ready in the catalog of every company.
EQUIVALENT DYNAMIC LOAD (P)
The resultant force created by radial and axial loads is the main factor that determines the bearing life.
The resultant force is called “Equivalent dynamic load (P) in the bearing literature and its formula is P(N)= Fr *cos β+ Fa * sinβ.
The sinβ and cos β values vary according to the type and size of the bearing, and these are given as X and Y coefficients in the bearing catalogue. Like this;
It becomes P=X* Fr + Y* Fa.
If F is below a certain magnitude, the second term is accepted as 0 and the formula reverts to P=X*Fr .
Whether the Fa value will be taken into account is determined by the "e" coefficient given in the catalog.
If Fa/Fr > e, then P=X* Fr + Y* Fa formula is used
If F Fr < e> P=X* Fr formula is used
Here Fr: Radial load (N)
Fa: Axial load (N)
Determined Equivalent dynamic load (P) is the main parameter used in calculating the life of the bearing.
L10= (C/P)p
L10 : Bearing life in millions of revolutions
C : Dynamic load number in Newtons
P : Dynamic equivalent load in Newtons
p : This value is always 3 for ball bearings and 10/3 for roller bearings.
The sinβ and cos β values vary according to the type and size of the bearing, and these are given as X and Y coefficients in the bearing catalogue. Like this;
It becomes P=X* Fr + Y* Fa.
If F is below a certain magnitude, the second term is accepted as 0 and the formula reverts to P=X*Fr .
Whether the Fa value will be taken into account is determined by the "e" coefficient given in the catalog.
If Fa/Fr > e, then P=X* Fr + Y* Fa formula is used
If F Fr < e> P=X* Fr formula is used
Here Fr: Radial load (N)
Fa: Axial load (N)
Determined Equivalent dynamic load (P) is the main parameter used in calculating the life of the bearing.
L10= (C/P)p
L10 : Bearing life in millions of revolutions
C : Dynamic load number in Newtons
P : Dynamic equivalent load in Newtons
p : This value is always 3 for ball bearings and 10/3 for roller bearings.
EQUIVALENT STATIC LOAD (P0)
The "dynamic load number (C)" used in the life calculation is taken from the table of the relevant bearing in the catalog. In the tables, a "static load number (C0)" is given next to C.
Static load number (C0) is taken into account in cases where the bearing speed is very low, in slow oscillating movements, under load while stationary, and most importantly in cases where it will be exposed to shock impacts. In these cases, not fatigue but permanent deformation caused by static load is effective in determining bearing performance. This deformation causes increased noise, vibration and friction in bearings. Static equivalent load P0 (N) is used in calculations by calculating the following formula in order to ensure that the bearing works without reaching the low performance limit.
P0 = X0*Fr+Y0*Fa
C0 = s0*P0, s0 = C0 / P0
C0: the static load number is taken from the relevant bearing catalogue.
s0 :static safety factor
X0 , Y0 It is given on the relevant pages of the bearing catalogue. Static load number C0, how much the equivalent static load P0 ratio should be, is given in the s0 static safety factor table. (This ratio is less than one for ball bearings if there are no shock loads.) If the calculated S0 value is less than the S0 value found in the table, a bearing with a larger C0 value should be selected.