3 Mins To know Bearing Life Test

July 29, 2026

Bearing Life

The total number of revolutions of any element in a single rolling bearing before fatigue pitting or the number of hours of working at a certain speed is called the bearing life.

Basic rated life L10: the total number of revolutions(millionrevolutions) that 90% of the bearings can run before fatigue pitting or the number of working hours at a certain speed(failureprobability10%) when the same batch of bearings work under the same working conditions.Calculation formula of bearing life.

Purpose of life test

To find out the defects of the bearing itself and provide data support for further improving the service life of the bearing, because the design, manufacturing and applied materials of the product will affect the service life of the bearing. The factors affecting the service life of the bearing can be divided into two categories:

Class I: bearing itself, such as material, machining accuracy, heat treatment, etc.

Class II: application itself, such as incorrect installation, bad working conditions (speed, working temperature, environment, etc.).

To check the fatigue life of the bearing and obtain the reliability level of the relevant life of the bearing;
To provide direction for bearing R&D and improvement, and provide document data support for procurement.

Test Method

Complete test: a group of bearing samples shall be tested to failure under the same test conditions.

Censored test: a group of bearing samples are partially tested to failure under the same test conditions.

Internal Structure Principle of Test Equipment

The structural schematic diagram of the testing machine includes frame components, test unit, driving system,radial loading system, axial loading system, lubrication system, cooling system, high temperature generation system, measurement and control system and other components.

The test unit consists of a test chamber and a test head. The test chamber is fixed on the flat plate in the frame components;

The test head is installed in the test chamber and is mainly composed of end load body.

Test

Generally, the test equipment shall operate continuously to monitor the whole process of the test (load, speed, vibration, current, temperature and temperature rise). The parameters of the equipment shall be controlled within the required range. The test equipment and test bearing shall be protected to prevent accidental damage to the equipment during the test. The failure of the bearing can also be controlled in the initial stage, which is conducive to the failure cause analysis and put forward the improvement direction.

bearing life test4 During the test, the relevant parameters are monitored through the speed, load, temperature, vibration and current sensors, which are transmitted to the monitoring software for summary display.

Under the working conditions requiring thermal insulation test, the corresponding heater needs to be added (the “heating strip” of grease lubricated bearing is added to the test unit for heating, and the purpose of oil lubrication test is achieved by heating the lubricating oil).

Recording the changes of working conditions of the bearing in the test one by one, such as the change trend of rotating speed n, radial load GR and axial load GA at each time point, so as to ensure the accuracy and stability of the test conditions.

Record the vibration of the whole test tooling and the vibration value at each time. The vibration trend change in the whole test can track the state of the bearing in the whole process, whether there is abnormality and abnormal trend change, and analyze which stage of the bearing in the test begins to be abnormal and whether there is slip & etc.

Monitor the current status, current change trend, whether there is overload & etc. in the whole test process.

During the test, monitor the temperature and temperature rise of each set of bearings one by one, record the temperature condition of each set of bearings at each time point in detail, and form a trend for the temperature change of the whole test, whether there is abnormal high temperature, etc.

Test Article Analysis

Reliability Assessment

Reliability refers to the ability of the product to complete the predetermined function within the specified time and under the specified conditions, including the safety, applicability and durability of the structure.

Best Linear Invariant Estimate

A) Complete Test B) Censored Test

When \(r = n\), it is a complete test;
Estimate the basic rated life test values of L10t,L50t

bearing life test11

Data of L10t and Re are generally accurate to two significant digits;
L10t/L10h ≥ Z is qualified, including ball bearing z = 1.4, roller bearing and self‑aligning ball bearing z = 1.2;
According to the quality requirements, the conformity assessment shall be carried out as follows. During the long‑life test, the value reaching the qualified multiple shall also be given in the test report.

Verification test: if the qualified service life is reached, the verification test is qualified;

Qualification test: the qualification test is qualified when the qualified service life is 3 times.

(Excerpted from CHIPRO)