This article details the static load rating and dynamic load rating of bearings, as well as the relationship between them.
Keywords: bearings; static load rating; dynamic load rating
Usually when we look up bearing models, we often see two options: Cr and Cor. What do these two sets of letters represent? Let me tell you now, Cr refers to the rated dynamic load of the bearing, and Cor refers to the rated static load of the bearing. So what are the static load rating and dynamic load rating of bearings? What is the relationship and difference between the two? Based on my understanding, I would like to share as follows:
The three basic parameters often used in rolling bearings in design are: the basic rated dynamic load Cr (radial) or Ca (axial) that meets certain fatigue life requirements; the basic rated static strength Cor (radial) that meets certain static strength requirements. direction) or Coa (axial direction) and the limit speed No. that controls bearing wear.
What is the static load rating of bearings?
The basic static load rating of a rolling bearing (radial Cor, axial Coa) refers to the phantom radial load or central axial static load equivalent to the maximum load of the bearing when the contact center between the rolling elements and the raceway causes a certain contact stress. The rated static load is determined under assumed load conditions. For radial bearings, the rated static load refers to the radial load. For radial thrust bearings (angular contact ball bearings), it refers to the load that loads the half-circle raceway in the bearing. The radial component of the thrust bearing refers to the central axial load. That is to say, the radial basic static load rating and axial basic static load rating of the bearing refer to the maximum load that the bearing can bear when static or rotating. The load-bearing capacity of deep groove ball bearings when stationary or slowly rotating (speed n≤10r/min) is the rated static load.
What is the dynamic load rating of bearings?
The rated dynamic load of the bearing refers to the constant radial load (constant axial load) that the rolling bearing can theoretically withstand. The basic rated life under this load is 100W revolutions. The basic dynamic load rating of the bearing reflects the rolling fatigue resistance of the bearing. Ability. The basic dynamic load ratings of radial bearings and thrust bearings are respectively called the radial basic dynamic load rating and the axial basic dynamic load rating, represented by Cr and Ca. The load-bearing capacity of groove ball bearings when rotating (speed n>10r/mim) is the basic dynamic load rating.
Why is the rated dynamic load of the bearing greater than the rated static load?
The rated dynamic load refers to the load borne by the bearing when the rated life is 1 million revolutions. The rated static load refers to the contact point between the rolling element and the ring raceway that is most loaded when the bearing is under the load. The sum of the permanent deformation of the rolling element and the ring raceway is one ten thousandth of the diameter of the rolling element. . There is a certain relationship between the service life of the bearing and the rated load of the bearing. So under what circumstances do we select bearings based on the rated load of the bearing? The main points are as follows: Note: In some cases, the size of the bearing should be selected based on the static load rating (for convenience of description, the definition code is Co) instead of calculating the bearing life. 1. Under the action of continuous or intermittent impact load, the bearing is stationary. 2. Under load, the bearing only makes slow reciprocating swing or adjustment movement. 3. Under load, the bearing speed is very low (less than 10 revolutions per minute) and requires only a short life. In particular, in this case, for a given equivalent load P, the required basic dynamic load rating C will be very low according to the life formula, so the selected bearing may be severely overloaded in actual operation. 4. In addition to the normal working load, it also has to bear heavy impact loads, and the bearings rotate. In the above cases, the load that the bearing can withstand does not depend on the fatigue of the material, but on the degree of permanent deformation caused by the load on the raceway.
