Correction method for temperature and rating life of basic load rating of seated bearing
When the seated rolling bearing is used at high temperature, the structure of the bearing material will change and the hardness will decrease, so the basic dynamic load rating of the bearing will be less than when used at room temperature. Once the structure of the bearing material changes, it will not recover even if the temperature returns to normal temperature. Therefore, when using a seated rolling bearing above 150°C, the basic dynamic load rating in the bearing size table must be temperature corrected, that is, multiplied by the temperature coefficient in Table 4.1. Table 4.1 Temperature coefficient bearing temperature, ℃ 125 150 175 200 250 Temperature coefficient 1 1 0.95 0.9 0.75 Modified rating life: The basic rating life (L10) expressed by formula (4.1) is the fatigue life of the bearing with 90% reliability, but according to Depending on the application, a high reliability life with a reliability higher than 90% is sometimes required. In addition, the use of special materials can sometimes extend the life of the bearing, and even the difference in use conditions (such as lubrication, etc.) will also affect the life of the bearing. The basic rating life considering the above factors is called the modified rating life, which can be calculated by equation (4.6). In the above formula, Lna: modified rating life, 106 revolutions, after taking into account bearing characteristics and service conditions, the reliability is 100-n% (that is, the damage probability is n%) life. L10: Basic rating life, 106 revolutions. 90% reliability life a1: Reliability coefficient refer to (1) item a2: Bearing characteristic coefficient refer to (2) item a3: Use condition factor refer to (3) item. Reliability coefficient a1 When calculating the modified rated life with reliability not less than 90% (that is, the damage probability is not higher than 10%), select the reliability coefficient a1 according to Table 4.2. Table 4.2 Reliability factor a1Lna a190 L10a 195 L5a 0.6296 L4a 0.5397 L3a 0.4498 L2a 0.3399 L1a 0.21 Bearing characteristic coefficient a2 Depending on the bearing material (steel type, material), design and manufacturing process, bearing characteristics related to life may change. At this time, the bearing characteristic coefficient a2 is used to modify the basic rating life of the bearing. The ball bearing for rolling bearing with seat adopts high-quality vacuum deoxidized bearing steel as the standard bearing material. The test results show that it has a considerable life extension effect. Bearing characteristic coefficient a2u003d1 for ball bearings for rolling bearings with seats. In addition, when using special materials for prolonging fatigue life, a2>1 may be adopted. Use condition factor a3 When the operating conditions of the bearing (especially whether lubrication is adequate) have a direct impact on the life, use the factor a3 to modify the basic rating life. When the lubrication conditions are normal, a3u003d1 can be taken, and when the lubrication conditions are particularly good, a3>1 can be taken. But for the following conditions, take a3<1. ① When the kinematic viscosity of the lubricant is low during operation, the ball bearing is less than 13 mm2/s and the roller bearing is less than 20 mm2/s. ② When the speed is particularly low, dmn is less than 10 000. . ③ Even if special material a2>1 is used when impurities are mixed into the lubricant, if the lubrication conditions are not suitable, a2×a3>1 will not be achieved. Therefore, when a3<1, it is generally considered that a2≤1.