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Bearing life adjustment factors allow OEMs to better predict the actual service life and reliability of the bearings you select and install in your equipment. The adjusted L10 rated life is calculated using the following formula:

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Radial cylindrical roller bearings with opposing flanges on the inner and outer rings have a limited ability to withstand thrust loads over the length of the rollers. Acceptable thrust loads are those using roller ends and flanges for intermittent thrust and positioning purposes. Since any thrust loads will be perpendicular to the radial loads and different bearing contact surfaces will be used, thrust loads along the roller length are not a factor in bearing life calculations.

Equipment manufacturers need to improve the reliability of selected bearings to predict longer service times. The a1 factor shown below is used to increase the reliability value. If the L10 value calculated using the a1 factor is unacceptably low, a bearing with a greater dynamic load capacity will need to be selected.(Citation from JIS B 1518:2013)

In some applications, bearings are subject to very high radial and thrust loads. For applications subject to both types of loading, a better design is to provide separate bearings for radial or thrust loads. If this is the case, the machine designer must be careful to ensure that the radial bearings only carry radial loads and the thrust bearings only carry thrust loads. A good way to achieve this is to use a cylindrical roller bearing with a straight race in the “radial” position, since this bearing cannot handle any thrust forces. A pair of angular contact bearings or large angle tapered roller bearings are usually good choices for carrying thrust loads, but they must be protected from any radial loads. One way to achieve this is to make the outer ring fit very loosely into the housing: typically 0.5mm/0.020in. to 1.0 mm/0.040 in.

This equation shows that these bearings as a system have a shorter rated life than bearings with shorter lifespans. This fact is important in estimating bearing service life in applications where two or bearings are used.

All ball bearings and roller bearings can withstand large axial thrust loads. When combined radial and axial loads occur, the “equivalent bearing load” P used in the rating life formula needs to be calculated. This calculation can be somewhat complex as it depends on the relative magnitudes of the radial and thrust loads to each other and the contact angle created by the bearing. It would be too difficult to demonstrate the calculation of P for all bearing types shown. For tapered roller bearings, the “K” thrust coefficient is used. For any rating life calculations requiring a combination of radial and thrust loads, please contact Aubearing.

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[example]When a shaft is supported by two roller bearings with service lives of 50 000 hours and 30 000 hours respectively, the rated life of the bearing system supporting the shaft is calculated as follows: Formula (1-11):

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If solid particles from contaminated lubricant become trapped between the raceways and rolling elements, indentations may form on one or both of the raceways and rolling elements. These indentations will cause localized pressure increases, thus shortening life. The shortened life due to lubricant contamination can be calculated according to the degree of contamination, that is, the contamination coefficient ec. Shown in the Dpw table is the pitch circle diameter of the ball/roller set, simply expressed as < /span>: inner diameter) Relevant special For details such as lubrication conditions or detailed investigation, please contact JTEKT. d: outer diameter, D)/2. (d＝(D＋pwD

Based on the rated dynamic load being a pure radial load of constant direction and constant magnitude (for radial bearings) or a central axial load (for thrust bearings), a basic rated life of 1 million revolutions can be obtained in this case. The value of this important bearing parameter C is shown in every bearing table except for crane hook bearings. The basic dynamic load rating indicates the bearing’s ability to withstand rolling fatigue and is specified as the basic dynamic radial load rating (< a i=3>Cr) for radial bearings, and the basic dynamic axial load rating (Ca) for thrust bearings. These values have been defined by associations such as the American Bearing Manufacturers Association (ABMA) and the International Organization for Standardization (ISO) to calculate dynamic loads on bearings. Bearing dynamic loading is used to predict the rating life of each bearing at its expected load and speed. Generally speaking, a bearing can only withstand a maximum operating load equal to half of its bearing dynamic load capacity.

The various effects on bearing life are interdependent. The systematic method of calculating corrected life has been evaluated as a practical method for determining the life correction factor αISO (see Figure 5-1). The life correction coefficient αISO is calculated by the following formula. There are diagrams for each bearing type (radial ball bearings, radial roller bearings, thrust ball bearings and thrust roller bearings). (Each figure (Figures 5-2 to 5-5) is quoted from JIS B 1518≤50. ISOαNote that in actual use, this is set to the lifetime modification factor: 2013.)

Since a longer service life does not always contribute to economical operation, the most suitable service life for each application and operating conditions should be determined. For reference, the empirically determined recommended service life based on application is described in the table below.

For reference only, the values of fn, fh and L10h can be easily obtained by using the nomogram attached to this catalog as a simplified method.

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Bearing static capacity Co is the maximum load that can be safely applied to a non-rotating bearing without causing damage to subsequent bearing operation. It is based on the calculated contact stress at the center of the most heavily loaded rolling element in contact with the inner ring. The stress levels for the three types of bearings are:

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The basic rating life L10 refers to the usage conditions of high-quality manufacturing bearings with a service life of 90% reliability in normal use. The inside of the bearing is made of bearing steel materials specified by JIS or a standard design made of equivalent materials. The relationship between basic dynamic load rating and dynamic load. The equivalent load and basic rating life of the bearing can be expressed by equation (5-1). This life calculation formula is not applicable to bearings C0 that are affected by factors such as plastic deformation of the raceway and rolling element contact surfaces due to extremely high load conditions (when P exceeds the basic static load rating) (refer to the basic static load rating and static equivalent load) or 0.5C) or conversely, for bearing load conditions affected by factors such as raceway contact surfaces and rolling elements sliding due to extremely low slip. This is the time that a set of apparently identical bearings will go through or exceed before fatigue spalling develops. The basic formula for calculating the rated life of bearing L10 is (1-1):

Therefore, the dynamic equivalent load is P and the rotational speed is n; then you can refer to the bearing specification table to select the bearing size most suitable for the specific purpose. C can calculate the basic dynamic load rating formula (1-4); the recommended service life of the bearing varies depending on the machine using the bearing, as shown in Table 1-5 Recommended service life of the bearing (reference) .

Most machines use two or bearings on one shaft, and often have two or shafts. All bearings in a machine are considered a bearing system. For business purposes, it is important for manufacturers to understand the reliability of their machines or system longevity. This evaluation process considers the important factor of combining the L10 life of all bearings in the system to answer the question: “How long will the machine run with ninety percent reliability?” “Simply put, the system L10 reliability will be lower than the lowest individual L10 rated life. The calculation formula of the system rated life is as follows: