Basic concept of bearing life

According to the latest rolling bearing fatigue life theory, a good design, excellent material, excellent manufacture and install the correct bearing, if the bearing load easily enough (not more than the bearing corresponding a endurance limit load value), the bearing materials will never produce fatigue damage. Therefore, as long as the working environment of the bearing temperature is appropriate and did not significantly change, absolutely no solid dust, harmful gases and moisture ingress bearing, bearing lubrication fully and proper lubricant is absolutely pure without impurities and does not deteriorate... , then the bearing will run indefinitely..

The significance of the theory lies in not only the it provides a than the ISO life equation is more reliable prediction of modern bearing life of tools, but also lies in the fact that it shows all of the fatigue life of rolling bearings have a considerable potential of development, and shows the way to develop this potential, thus bearing product development, quality management and application technology has a profound impact.

But bearing of infinite only under laboratory conditions will it be possible to achieve, and such conditions for under certain condition field use of the bearing, not only difficult to is too expensive.

Field use of the bearing, the work load is often greater than the corresponding fatigue limit load and lasting, at work to after a certain period of time, or later or sooner due to the material itself up to call the fatigue limit and fatigue spalling and is unable to continue to use. Even some bearing the work load is lower than that of the corresponding endurance limit load, due to the difficult to eradicate the bearing problem of pollution and wear failure. In a word, using live bearing more or less of the total can not fully equipped with the laboratory with those conditions, which either condition slightly less than, shorter bearing available period, which produced the life of bearings.

In general, rolling bearing life refers to the rolling bearing in the actual service conditions, including working conditions, environmental conditions and the maintenance and maintenance conditions, can continue to maintain meet requested the working performance and accuracy of specialty services to the deadline.

Two, can calculate the bearing life category

Rolling bearing failure forms of diversity. However, most of the failure forms so far there is no available method for calculating the life, only a fatigue life, wear life, lubrication life and fretting fatigue life can be evaluated by quantitative calculation method.

1, fatigue life in the lubrication fully and other conditions of use normal, rolling bearing is often caused by fatigue spalling failure. The term fatigue life can sample check relevant data, according to the provisions of the formula and the computer program to the reliability of the calculated.

2, wear service life of the machine tool spindle bearing large diameter to ensure its high stiffness, the distribution of bearing size is large, in the far end to the fatigue limit before, often due to wear and loss of precision that can not continue to use, of this kind of bearings must wear life to showing partiality to the possibility of the period of service. In fact, the use of the bearing mostly due to excessive wear and tear, so we must also consider the wear life issues.

3, the lubrication life mainly for the double seal grease grease, once filled with grease, then the bearing life will depend on the service life of grease.

4, fretting wear life winch, cantilever on micro machine and gearbox and automobile clutch bearing in the non operating state under vibration load produced by the fretting wear damage. Tend to develop into the dominant cause of bearing failure, of this kind of mechanism of bearing, sometimes need to calculate the fretting wear life.

Four kinds of life categories and their calculation methods are introduced respectively..

Fatigue life of a rolling bearing

1. Basic concept of fatigue life of bearings

General meaning of bearing fatigue life is refers to certain technical conditions (structure, state of the art, fit, install, clearance and lubrication state and) rolling bearings, run in a host of practical use until rolling surface fatigue and the host can not meet the requirements of bearing, the outer ring (shaft, a seat) relative rotation number value, total number of revolutions. When bearing turns more or less constant or is known, fatigue life can be used with the total number of revolutions corresponding total working hours number said that in addition, it should also be noted:

Factors influence the fatigue life of bearing is very large, not all of them estimates or the standard test conditions and to be eliminated. As a result, the actual bearing fatigue life has a lot of discrete, so expression parameters of the fatigue life of the bearing rated life L10, the ISO recommended standard R281 the meaning of L10 clearly defined as follows:

"A large enough number the same batch of bearings and the rated life of L10 use Revolution (or when the speed is constant with the number of hours said, the number of bearing is 90% in before the fatigue spalling can reach or exceed the speed (or hours). So far, the world has complied with the above provisions.

In the United States and other countries, the concept of median life. Median life LM is refers to a group of bearing the same median life, refers to which 50% of bearing in front of the fatigue spalling can reach or exceed the total number of revolutions, or in a certain speed work from time to time number and median life LM is not a group of bearing life of arithmetic average value. Average median life LM is about 5 times the rated life of the.

2, the rated life concept applies only to a number of sufficient number of bearings, and not for individual bearings.