Analysis of limit speed impact on import needle bearing fatigue life

First of all, reasonable structure design and equipped with advanced, just can have a long needle roller bearing life. Imported bearing manufacturing generally go through forging, heat treatment, cutting, grinding and assembly, and multi-channel processing operations. The rationality of the processing technology, advanced, stability will also affect the service life of bearing. Which affects the quality of finished product TIMKEN bearing heat treatment and grinding process, tend to have a more direct relationship with bearing failure. In recent years the study of metamorphic layer of bearings working surface show that the grinding process and is close to the surface quality of the bearing. Bearing materials of metallurgical quality were the main factors influencing the premature failure of the rolling bearing. As metallurgy technology, For example, the bearing steel vacuum degassing, etc. ) Progress, raw material quality is improved. Raw material quality factor in the bearing failure analysis share has declined obviously, but it is still one of the main influence factors of bearing failure. Select material adequacy is still bearing failure analysis factors must be considered. The main task of the bearing failure analysis, which is based on a lot of background material, analyze data and failure forms, find out the main factors of bearing failure, so that the improvement measures are put forward, extend import bearings, avoid needle bearing sudden early failure. ( 1) And the influencing factors of the bearing fatigue life very much, can't all be estimated or through standard test conditions and to eliminate, this causes the bearing fatigue life has a great deal of actual discreteness, therefore, the fatigue life of bearing express parameters for rated L10 life, the meaning of the L10 in ISO standard of R281 clearly stipulated as follows: 'a batch of bearing enough on the same amount, the rated life L10 revolution ( Or the number of hours in at constant speed, 90% of this batch of bearing in the fatigue spalling occurring before can reach or exceed the number of revolutions ( Or hours) ”。 So far, all countries in the world to follow the rules. In some countries such as America, still use the concept of value in life. Median life LM refers to a group of bearing the same values in life and means that 50% of the bearing before fatigue spalling can reach or exceed the total number of turns, or under a certain speed from time to time, the median life LM arithmetic mean is not a batch of needle roller bearing life. Generally the median life LM is 5 times of the rated life. ( 2) , rated life concept is only applicable to enough of a batch of TIMKEN bearings, and does not apply to individual bearing. For example article 40 sets of 6204 bearing according to their use is its rated life is 1000 h without fatigue damage occurs, the rest 4 sets may be less than 1000 h would appear fatigue failure of bearing, rated the significance of fatigue life on behalf of this batch of imported bearings in normal use their life material potential can be expected. So in most cases, the user in selecting the bearing still first as the fatigue life calculation, according to the actual failure categories, such as wear life, take the results in a smaller value for the calculation of bearing life. Imported bearing high speed will make the friction surface to produce high temperature, affect the function of lubricant, oil film, which can lead to move body temper or element agglutination failure. Bearing limit rotational speed is refers to the bearing under the precondition of work, can bear highest speed value of the thermal equilibrium temperature. Bearing work speed should be lower than the speed limit. TIMKEN bearing function of the limit speed values are given in the table under the precondition of grease lubrication and oil lubrication, and only used for the level 0 tolerance, lubrication cooling normal, cooperate with rigid bearing and shaft, bearing load P 0 or less. 1 c ( C for bearing the basic dynamic load rating, only by centripetal bearing radial load, thrust bearing only by axial load) The bearings. When the bearing load P> 0. When the 1 c, the contact stress will increase; Imported bearing joint load, the load to move body will increase, this will increase the friction between the bearing contact surface, the lubrication state go bad. At this point, the limit speed value should be corrected.