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How to calculate the service life of bearings and when to replace bearings

Abstract: bearings, which are essential for the smooth operation of machinery, also have service life. However, bearings designed based on standards and manufactured with high quality can calculate the rated service life by applying standards. When should the bearings be replaced

about the service life of the bearing

even if the bearing is installed and lubricated normally under the correct load, the bearing surface and rolling elements will constantly exert constant compressive stress. The force is usually concentrated on the shallow part of the surface. As a result, scale cracking (spalling) due to material fatigue will eventually occur on the surface

bearing life refers to the state of use under normal conditions, which peels off due to repeated forces and cannot continue to be used

there are "life span", "functional life", "lubrication life", "acoustic life" and other ways to capture life

when the boundary jitter and rotation speed of the functional life exceed the specified value, the lubricant that makes the boundary exceed the specified value of the noise level is degraded. The elastic boundary lubrication life will not exert the lubrication performance. Each constant it tells you until you do not meet the standard

among them, let's take a closer look at "rating life", which is one of the most important ways of thinking, that is, bearing life calculation

bearing rated life

rated life, when moving a group of the same bearings alone under the same conditions, is defined, which can rotate at 90% of the total number of revolutions of the bearing without causing the peeling of the material or at a constant rotation speed, I will

high quality bearings manufactured according to JIS and other standards related to bearings can calculate the rated life or rated load by applying JIS and ISO standards

lifelong calculation formula

l 10 [rev] = (C/P) P × 10 6

L 10 h [h] =（C/P）p × 16667/n

l10: basic rated life

c: basic dynamic rated load [n]

p: dynamic equivalent radial load [n]

p: index ⇒ ball bearing: P = 3, roller bearing: P = 10/3

basic dynamic rated load (c)

basic amount in function according to national specifications, wood-based panel testing machines have multi-function experimental purposes. The fixed dynamic load is a constant radial load, The bearing is allowed to bear the basic rated life of 1million revolutions

refers to radial bearing. Under the condition that the outer ring is fixed and the inner ring rotates, in the case of thrust bearing, it is still the rotation of the other bearing ring of the raceway ring. For example, one of the rated life is 10000 revolutions, "load without changing direction and size" is called the basic dynamic load rating

dynamic equivalent load (P)

dynamic equivalent load is defined as the load that does not change the size and direction, and obtains "the same life as the actual load and rotation conditions"

p = XF R + YF a [n]

f R: radial load [n]

f A: axial load [n]

x: radial coefficient

y: axial coefficient

basic static load rating (CO)

basic static load rating. Most of them receive large loads. Add the bearing ring of rolling elements. The center of the permanently deformed contact part of the permanent deformation of the static load, such as rolling becomes 0.0001 times the diameter of the main body, which is defined as

correct the rated life

the basic rated life, that is, it is considered to be 90% of the bearing. For this point, please refer to the standard · linear grating ruler or resistance strain gauge in detail: the reliability during the 3-point zigzag test is obtained through the above formula. However, depending on the application, the expected life of the bearing is sometimes required, and the reliability is higher than 90%. Moreover, depending on the material to be used, manufacturing method or service conditions, the service life of the bearing will change. Taking these points into account, the service life of the basic rated life correction is called the corrected rated life. The calculation formula is as follows

l Na = a 1 · a 2 · a 3 · L 10

l Na: corrected rated life 106 revolutions

a 1: reliability coefficient

a 2: bearing characteristic coefficient

a 3: service condition coefficient

for reliability of 90% or higher, the value of reliability coefficient a 1 is as follows

when the reliability is 90%, the L 10 reliability coefficient is 1.00

when the reliability is 95%, the L 5 reliability coefficient is 1 0.62

when the reliability is 96%, the L 4 reliability coefficient is 1 0.53

when the reliability is 97%, the L 3 reliability coefficient is 1 0.44

when the reliability is 98%, the L 2 reliability coefficient is 1 0.33

when the reliability is 99%, L 1 reliability coefficient is 1 0.21

the final test report is completed once

bearing characteristic coefficient

if the type and quality of bearing materials, manufacturing methods and other special, the bearing characteristics that affect the service life will change. In these cases, the bearing characteristic coefficient a 2 is used to correct the service life coefficient. Usually, set 2 = 1

service condition coefficient

coefficient a 3 can correct service conditions, especially when lubrication affects the service life of bearings. Usually, for good lubrication, 3 = 1. In addition, it may be 31 for other bearings with good lubrication conditions and in other cases. However, in the operating temperature of such as "low rotation speed special", "bearing is high", "in bearing", "foreign matter and water mixed into lubricant", the low kinematic viscosity of lubricating oil is used at temperature, 3 which will be one

nowadays, the materials used for bearings and the manufacturing technology of bearings have been greatly improved. Under the good lubrication condition without errors or foreign matters during installation, sometimes the service life can be several times longer than the normal calculation, that is, the rated service life

bearings, which are essential for the smooth operation of machinery, also have service life. However, bearings designed based on standards and manufactured with high quality can calculate the rated service life by applying standards. Here, we have a method to capture the expected life of bearings and summarize how to calculate each bearing. Please help us understand the service life of bearings

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