JB/T 7381-1994 Determination of PV value of powder metallurgy oil-containing bearings
Some standard content:
Mechanical Industry Standard of the People's Republic of China
JB/T7381-94
Determination of pV value of powder metallurgy oil-containing bearings
Published on July 26, 1994
Ministry of Machinery Industry of the People's Republic of China
Implementation on July 1, 1995
Mechanical Industry Standard of the People's Republic of China
Determination of V value of powder metallurgy oil-containing bearings
1 Subject content and scope of application
This standard specifies the determination method of the value of powder metallurgy oil-containing bearings. JB/T7381-94
This standard is applicable to the evaluation limit u value of powder metallurgy oil-containing bearings (hereinafter referred to as bearings) with iron base, copper base and other bases. 2 Reference standards
GB2688 Technical conditions for sliding bearings and powder metallurgy bearings 3 Terms
3.1 Bearing u value
The ability of a bearing to withstand external friction conditions (pressure and sliding linear velocity) is expressed by multiplying the force, which is called the value. 3.2 Bearing limit value
The limit value of pressure (p) that a bearing can withstand under a certain sliding linear velocity (), or the limit value of sliding linear velocity that a bearing can withstand under a certain pressure. The value at this time is called the limit u value. 4 Test equipment
The evaluation value requires the use of a sliding bearing tester with the following structure and performance. 4.1 The transmission system can ensure that the pair (steel shaft) rotates at any given speed, and the speed error is no more than 10r/min when the empty load is measured. The radial runout of the shaft at the pair installation position is no more than 0.01mm. 4.2 The loading system can apply any given stable radial load to the specimen, and the load indication error should not exceed ±2% of the maximum load of each level.
4.3 Measure and record the friction torque. The error of the friction indication is ±3% from 10% of the maximum load of each scale. The allowable error of the pointer returning to zero is 1 grid.
4.4 Measure and record the friction temperature rise. Use a thermistor or armored thermocouple to measure the temperature and an electronic potentiometer to record it. The measurement accuracy is ±2℃.
4.5. The roller bearing part of the measuring head must be kept clean and the accuracy of the part must be maintained. 5 Test
5.1 Test specification
5.1.1 This standard selects the test method of constant speed and variable load, constant speed, step-by-step loading, until the friction torque or friction temperature exceeds the damage mark. Generally, it is selected according to the recommended value of the allowable load specified in GB2688. The test speed and loading level difference are shown in Table 1. It can also be selected according to actual use requirements.
Approved by the Ministry of Machinery Industry on July 26, 1994
Implemented on July 1, 1995
Speed n
Linear speed√
Loading difference each time
JB/T 7381--94
5.1.2 Before the test, run-in shall be carried out, and the limit load (the limit load is determined by experimental exploration) of 20% to 30% radial load shall be applied at the selected sliding linear speed. The formal test shall be carried out after 30 minutes of running-in. 5.1.3 The time interval between each loading test is generally 10 minutes. When the friction temperature or friction torque is unstable, the time can be appropriately extended, and the maximum time shall not exceed 30 minutes. Due to different test materials, the load size and time interval shall be adjusted according to the specific situation. 5.1.4 The clearance between the specimen and the pair is generally selected as 0.015d to 0.020d (d is the inner diameter of the test bearing). 5.1.5 The test is carried out continuously under self-lubricating conditions, without adding lubricant, and naturally cooled. The test environment temperature is required to be Basically consistent, with no obvious air flow.
5.2 Specimen damage signs
When measuring the bearing V value, in order to judge the test results, the bearing damage signs are specified as the friction coefficient not less than 0.15 and the friction temperature not less than 110°C. When the bearing is damaged during the test, both rise sharply, so as long as one of them reaches the specified value, it is considered damaged and the test will not be continued.
6 Specimens and pairs
6.1 If a shaft sleeve with an inner surface as the friction surface is used as the specimen, the specimen dimensions are shown in Figure 1. The $2 hole on the end face of the specimen is used to insert a thermistor or armored thermocouple for measuring the friction temperature, and its size is not greater than 20~25js12(±0.125)
Figure 1 Specimen dimensions
6.2 Pair The material is 45 steel or 40Cr steel, the hardness after heat treatment is 40~45HRC, and the surface roughness parameter R is 0.4μm. The inner hole of the dual is a 1:7 cone. The cone must be machined with a special tapered shaft and measured with a special tapered plug gauge. The dual dimensions are shown in Figure 2. After the dual is installed on the spindle, the radial runout is no more than 0.01mm. JB/T738194
42js12(±0.125)
Dual dimensions
7Operation steps
1×45°
88988#
Rubber corner example pure
40~45HRC
7.1 Before the test, the composition, mechanical and physical properties, oil content, metallographic structure and lubricating oil brand of the sample are known. Sample Weigh with a measurement accuracy of 0.1g, and then install it in the bearing seat. When the inner diameter of the specimen shrinks after being pressed into the seat hole, the hole can be expanded by a non-cutting method using an optical axis, a steel ball, a toothless reamer, or a toothless pusher, and the inner diameter size can be measured with a measurement accuracy of 0.01mm. The couple is installed on the main shaft of the testing machine, and the radial runout is measured to be no more than 0.01mm. The assembly combination of the specimen and the couple is shown in Figure 3. Insert the temperature probe into the end hole of the specimen. Torque lever
External test group sleeve
Test sleeve
Lock nut
Temperature probe
Roller seat
Sound diagram
7.2 Run-in
JB/T7381-94
7.3 Remove oil stains from the surface of the specimen and the couple after running-in. Ultrasonic cleaning is recommended as the cleaning method, and the original lubricating oil is used as the cleaning agent. Wipe the surface clean and reassemble it. During assembly, be careful to avoid scratching the already run-in surface. 7.4 Adjust the spindle speed to the test speed, and load step by step from zero. The loading difference refers to Table 1. 7.5 After the load is increased to a fixed value, if the friction force or the friction temperature rises sharply and reaches the damage index, it is considered to have ended its life. 7.6 After the test, remove the sample from the spindle, record the state of the friction surface, and measure and record the changes in the size of the sample and the pair after the test.
7.7 If any abnormal phenomenon occurs during the test, such as discoloration, odor, smoke, shaking, jamming, sound, pipe oil, and fluctuations in friction temperature and friction force, etc., keep a record to use as a basis for result analysis. 8 Result calculation
Generally, there should be no less than five pairs of samples and pairs for each measurement, and then the average value is taken. 8.1
8.2 The ultimate pressure is calculated according to formula (1)
wherein: p——ultimate pressure, MPa;bzxZ.net
W. Ultimate load, N;
L-test bearing length, mm;
d-test bearing inner diameter, mm. The ultimate load is determined based on the previous load when the friction force or friction temperature rises sharply, plus the breaking load. The breaking load is determined by the number of minutes when the bearing appears. If it appears within minutes, the previous load is the ultimate load: if it appears within two minutes, the ultimate load is the sum of the previous load plus 1/10 of the loading level difference. The ultimate load is calculated by analogy for failures occurring at other times.
8.3 The sliding line speed of the test bearing is calculated according to formula (2), element Dn
60×1000
In the formula: ---- sliding line speed.m/s;
D-dual outer diameter, mm;
----spindle speed, r/min.
8.4p multiplied by v is the limit value of the test bearing. 8.5 The arithmetic mean of the measured sample number·v value is calculated according to formula (3), and the standard deviation value is calculated according to formula (4): In the formula: - value arithmetic mean;
\. The value measured for each sample;
Number of samples.
In the formula: S---value standard deviation,
8.6 Friction coefficient is calculated according to formula (5):
·（3）
In the formula: H Friction coefficient at a certain load level
JB/T7381-94
Friction torque, N·cm: It includes the friction torque M measured by the pressure sensor and the torque WR consumed to overcome the friction of the roller bearing.
Friction temperature rise is calculated according to formula (6):
AT=T,-T. =1/K,(K,Apo)
In the formula: AT
Friction temperature rise, ℃;
Friction temperature at a certain load level, ℃;
T. —Test environment temperature, ℃;
K, —Mechanical heat dissipation of the shaft and bearing seat; K2——The heat dissipation of the bearing itself.
8.8u value, calculated to two significant figures. 9
Test report
(6)
According to the different requirements for evaluating the y value of the material, different test result curves can be made: u-curve, Tu curve and -v curve.
The test report also includes the following contents:
Test bearing material, brand, preparation process, standard number, sample number; bearing density, hardness, metallographic structure, surface roughness, dimensional accuracy and other properties; mating material, hardness, surface roughness, dimensional accuracy; the gap between the bearing and the mating;
Test environment temperature, lubrication method:
Test details that may affect the results during the test; test unit, personnel, date.
JB/T7381-94
Appendix A
Calculation of bearing friction coefficient
(Supplement)
This standard recommends the use of MPV-1500 sliding bearing tester as a device for determining the p value of powder metallurgy oil-containing bearings. From the structure of the tester, it can be seen that the indicated value on the pressure sensor is the difference between the actual friction force of the sample and the friction force required to overcome the rotation of the rolling bearing. Therefore, when the MPV-1500 measures the value, its friction torque must be increased by a correction value to ensure the accuracy of the friction coefficient calculation. AI test bearing friction calculation
The test bearing friction calculation method is as follows: As shown in Figure A1, the magnitude of the friction force indicated on the pressure sensor is determined by the displacement of the outer sample sleeve along the rotation direction of the main shaft. This displacement is determined by the difference between the friction force generated by the relative sliding of the sample and the pair after overcoming the static friction of the roller. The static friction of the roller will affect the actual measured value of the sample.
The actual friction force M of the sample consists of two parts, namely, one part is M\ measured by the pressure sensor, and the other part is the torque consumed by the friction of the roller bearing, that is, aWR,
M=M+oWR
Where: M\-torque measured by the pressure sensor, N·cm; 8-static friction coefficient of roller:
R--the distance from the center of the spindle to the center of the roller.cm; u--friction coefficient of the test bearing;
C-correction coefficient (i.e. aR/d), for a given structure, the C value of the u test machine is a constant. In order to ensure the accuracy of the test results, it is necessary to calibrate regularly. A2 Static friction coefficient of rolling bearing
Static friction coefficient of rolling bearing? Calibration method: Install an equal-weight code disc on each side of the roller, and the base code disc is 11 and 2 away from the center line of the spindle, respectively, to form a roller static friction coefficient measurement device, see Figure A1. Clean the roller, roller and roller seat before measurement, and drip some lubricating oil. Measurement steps: a. When no weight is added to the left or right, adjust the counterweight to make it balanced; b. Gradually add the basic weight on the left (or right) until the device shows micro-movement, and record the weight of the left (or right) weight at this time. Repeat this step more than three times and take the average value;
From the moment balance, it is known that the critical state is expressed by formula (A1): LW=GR
Where: LW-
. (A1)
Where: LW-.—The torque required to make the roller bearing show micro-movement. This value is the average of 6 tests for the left and right (L is the lever arm and W is the base weight);
..Left lever length, cm;
1.---Right lever length, cm;
WLeft weight g
-Number of measurements on the left;
6-Number of measurements on the right;
JB/T7381-94
G-Total weight of the test bearing seat (including rollers, lever arms, counterweights, etc.), g; 8-Static friction coefficient of roller bearing, =LW/(NR). Substitute it into R/d to get the correction coefficient C, which is used to calculate the correction friction coefficient μ. Lever rod
Pressure sensor
Additional instructions:
Roller bearing friction calibration diagram
This standard is proposed and managed by Beijing Powder Metallurgy Research Institute. This standard is drafted by Beijing Powder Metallurgy Research Institute. The main drafter of this standard is Ma Huanong.
External test sleeve (ferry)
Pair (spindle)
Liquid column bearing
Roller seat
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