Evaluation method for service life of lubricating grease used for sliding friction pair in high and low temperature environments

Abstract

An evaluation method for the service life of a lubricating grease used for sliding friction pairs in high and low temperature environments, comprising the following steps: a first-stage test: adjusting a lubricating grease at a set temperature and operating same under a rated load to obtain first-stage test data, and, on the basis of the first-stage test data, determining whether the lubricating grease passes the first-stage test; and if the first-stage test is passed, further performing a second-stage test on the lubricating grease on the basis of the first-stage test: operating the lubricating grease under a load above the rated load to obtain second-stage test data, and determine the service life class of the lubricating grease on the basis of the second-stage test data. The evaluation method is used for testing the service life of a lubricating grease used for sliding friction pairs, can quickly test and accurately evaluate the service life of the lubricating grease used for sliding friction pairs, and also can be used in both high and low temperature environments, thereby expanding the application range for the service life evaluation method of lubricating greases.

Description

A method for evaluating the life of grease for sliding friction pairs under high and low temperature environments. Technical Field

[0001] This invention belongs to the field of grease life testing technology, specifically relating to a method for evaluating the life of grease used in sliding friction pairs under high and low temperature environments. Background Technology

[0002] Lubricants play an extremely important role in industrial production. They can reduce friction, thereby reducing unnecessary wear and energy loss, and protecting mechanical equipment and extending its service life.

[0003] In related technologies, the life evaluation of lubricating grease is generally carried out at room temperature, and the tests are mainly conducted on lubricating grease for rolling bearings. There is a lack of rapid and accurate evaluation methods for lubricating grease for sliding friction pairs. Summary of the Invention

[0004] The purpose of this invention is to propose a method for evaluating the life of grease for sliding friction pairs under high and low temperature environments, thereby solving the problem of the lack of a fast and accurate evaluation method for grease for sliding friction pairs in the prior art.

[0005] Therefore, the present invention provides a method for evaluating the life of grease for sliding friction pairs under high and low temperature environments, comprising the following steps: conducting a first-stage test on the grease on a sliding friction pair test bench: adjusting the grease at a set temperature, operating it under a rated load, obtaining the first-stage test data, and determining whether the first-stage test has been passed based on the first-stage test data;

[0006] If the grease passes the first stage test, a second stage test is conducted based on the first stage test results: the grease is operated under a load higher than the rated load to obtain the second stage test data, and the life rating of the grease is determined based on the second stage test data.

[0007] Preferably, the test data in the first stage includes the number of times the friction pair operates and the number of times abnormal noise occurs, the highest temperature, the coefficient of friction, and the noise level that occurs during operation. More preferably, it also includes the wear condition of the friction pair.

[0008] Preferably, in the first stage of testing, the number of operations under rated load does not exceed the maximum set number. The last few operations within the maximum set number range are used as auxiliary judgment counts.

[0009] Preferably, in the first stage of the test, if no abnormal noise occurs, or if no abnormal noise occurs after it has occurred, or if the number of consecutive abnormal noises exceeds a certain limit, the first stage of the test ends.

[0010] Preferably, the step of determining whether the first-stage test has passed based on the first-stage test data includes:

[0011] If the highest temperature and friction coefficient do not exceed the critical value, the first stage test is passed, and the fewer the number of abnormal noises during operation, the higher the evaluation level.

[0012] If the high temperature or friction coefficient exceeds the critical value, or if the abnormal noise persists even after the number of operation cycles exceeds the maximum set number, then the first stage test is deemed unsuccessful.

[0013] Preferably, the test data in the second stage includes the wear state of the friction pair, the number of times the friction pair operates, the maximum temperature, the coefficient of friction, and the abnormal noise values ​​that occur during operation.

[0014] Preferably, the operation above the rated load means operation at 1.05-2 times the rated load.

[0015] Preferably, in the second stage of the test, if the abnormal noise value, the highest temperature, or the coefficient of friction exceeds the critical value, the second stage of the test ends.

[0016] Preferably, in determining the life rating of the lubricating grease based on the second-stage test data, the higher the evaluation rating is, provided that the abnormal noise value, maximum temperature, and friction coefficient do not exceed the critical values, the more times the grease is run.

[0017] Preferably, the sliding friction pair test bench is placed inside an environmental chamber, which is used to regulate the ambient temperature of the friction pair test bench when testing the lubricating grease. Beneficial effects:

[0018] 1. This invention provides a method for evaluating the lifespan of grease used in sliding friction pairs under high and low temperature environments. The method tests the lifespan of grease used in sliding friction pairs. The first stage test allows the grease to pass through a stable wear stage, and the second stage test tests and evaluates the lifespan of the grease. The method provides fast and accurate evaluation of the lifespan of grease used in sliding friction pairs and can be used in both high and low temperature environments, thus expanding the applicability of the grease lifespan evaluation method.

[0019] 2. The second stage test of the present invention operates at 1.05-2 times the rated load to conduct accelerated wear tests without changing the failure mode of the friction pair, thereby reducing the test bench running time, improving the test bench running efficiency, and improving the accuracy of the second stage test of the lubricating grease.

[0020] 3. The sliding friction pair test bench in this invention is placed in an environmental chamber, which can provide an ambient temperature of -60℃ to 100℃. The life test and evaluation of the lubricating grease can be carried out at low or high temperatures, and the accuracy of the evaluation can be guaranteed. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 is a flowchart of a method for evaluating the life of grease for sliding friction pairs under high and low temperature environments according to the present invention.

[0023] Figure 2 is a friction life curve of a method for evaluating the life of grease for sliding friction pairs under high and low temperature environments according to the present invention.

[0024] Figure 3 is a schematic diagram of the sliding friction pair test bench of the method for evaluating the life of grease for sliding friction pairs under high and low temperature environments according to the present invention.

[0025] Figure 4 shows the wear condition of the friction pair of the prototype 1 of the method for evaluating the life of grease for sliding friction pairs under high and low temperature environments according to the present invention.

[0026] Figure 5 shows the wear condition of the friction pair of the prototype 2 in the method for evaluating the life of grease for sliding friction pairs under high and low temperature environments according to the present invention.

[0027] Figure 6 shows the wear condition of the friction pair in Example 2 of the method for evaluating the life of grease for sliding friction pairs under high and low temperature environments according to the present invention.

[0028] In the figure, 1-fixed seat, 2-pin, 21-injection channel, 3-shaft sleeve, 4-sealing ring, 5-thermocouple. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0030] The terms "first," "second," "third," "fourth," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be used interchangeably where appropriate. For example, without departing from the scope of this document, first information can also be referred to as second information, and similarly, second information can also be referred to as first information.

[0031] Depending on the context, the word "if" as used here can be interpreted as "when," "when," or "in response to determination."

[0032] Furthermore, as used herein, the singular forms “a,” “one,” and “the” are intended to also include the plural forms, unless the context indicates otherwise.

[0033] It should be further understood that the terms “comprising” or “including” indicate the presence of features, steps, operations, elements, components, items, kinds, and / or groups, but do not exclude the presence, occurrence, or addition of one or more other features, steps, operations, elements, components, items, kinds, and / or groups.

[0034] The terms “or” and “and / or” as used herein are interpreted as inclusive, or mean any one or any combination thereof. Therefore, “A, B, or C” or “A, B, and / or C” means “any one of the following: A; B; C; A and B; A and C; B and C; A, B, and C”. Exceptions to this definition occur only when combinations of elements, functions, steps, or operations are inherently mutually exclusive in some way.

[0035] Example 1:

[0036] A method for evaluating the life of grease for sliding friction pairs under high and low temperature environments, using a sliding friction pair test bench as shown in Figure 3, includes:

[0037] The system comprises a fixed base 1, a pin 2, and a bushing 3. Both ends of the pin 2 are fixedly connected to the fixed base 1. The bushing 3 is fitted onto the pin 2, and an external drive device is connected to the bushing 3 to achieve relative rotation with the pin 2, forming a sliding friction pair. The rotation angle is not less than 50°. A positive pressure is provided to apply a load to the sliding friction pair, with a maximum positive pressure of not less than 100 MPa, which can be adjusted arbitrarily within the range of 0 to the maximum positive pressure. One end of the pin 2 is provided with a flow channel 21, the outlet of which is located on the side wall of the pin 2, used to add grease between the pin 2 and the bushing 3. A sealing ring 4 is provided on the outside of the flow channel 21 to seal the grease. The other end of the pin 2 is provided with a thermocouple 5 for detecting the operating temperature.

[0038] The materials and specifications of pin 2 and bushing 3 can be selected according to the different working conditions and actual needs of the hinge points of the engineering machinery. When selecting a friction pair, its rated load needs to match the radial load that the sliding friction pair test bench can provide. For example, when the rated load of the friction pair is N, the sliding friction pair test bench should be able to provide a radial load of more than 2N.

[0039] The sliding friction pair test rig is set up inside an environmental chamber, which provides a sealed space and regulates the temperature to simulate working conditions under different environments.

[0040] As shown in Figure 2, based on the principles of tribology and wear curves, the friction pair will go through three stages in succession as the operating time increases: the break-in stage, the stable wear stage, and the severe wear stage. In addition, different wear stages will also show corresponding changes in noise, friction coefficient, and temperature.

[0041] During the break-in period, because the surfaces of the friction pairs are not perfectly smooth, a high coefficient of friction and a rapid increase in wear, sometimes accompanied by abnormal noise, occur in the initial stages of friction. Under specific friction pairs and with sufficient lubrication, the role of the tested grease is to form a stable and effective oil film and / or adsorption film on the friction surfaces, isolating them and thus achieving lubrication, reducing friction and wear, and eliminating early abnormal noise from the friction pairs. According to the wear curve, the wear of the friction pairs during the break-in period usually increases rapidly with the extension of operating time, accompanied by abnormal noise. After the introduction of grease, the friction and wear of the friction pairs usually decrease, and the duration of abnormal noise shortens. The disappearance of abnormal noise indicates the end of the break-in period or the beginning of the stable wear phase. The shorter the break-in period, the better the performance of the grease in the first stage test, i.e., the better it effectively reduces break-in wear.

[0042] After the friction pair enters the stable wear stage, in addition to evaluating the lubricating performance of the grease under the rated load of the friction pair, an accelerated testing method under a slightly excessive rated load can be used to quickly evaluate the anti-wear performance and service life of the grease. As the friction pair continues to operate, when the grease cannot form a complete oil film and / or adsorbed film on the friction pair surface, dry friction and wear will occur, possibly accompanied by abnormal noise. Simultaneously, the coefficient of friction increases rapidly, and the friction surface temperature rises rapidly, indicating that the grease has failed. The more times the friction pair operates stably, the longer the service life of the grease.

[0043] As shown in Figure 1, the method for evaluating the life of grease for sliding friction pairs under high and low temperature environments in this embodiment includes the following steps:

[0044] S1. Preparation before testing: Preparations should be made before testing the lifespan of the grease used in sliding friction pairs.

[0045] S11. Inject grease: Inject grease through the injection channel, rotate to the maximum angle, and inject grease again until grease is visible at the seal. Run unloaded for 0.01h-1h, then inject grease again until grease is visible at the seal, thereby achieving sufficient grease filling and adequate lubrication of the friction pair.

[0046] S12. Set temperature: Set the temperature of the ambient chamber according to the working conditions to keep the temperature of the sliding friction pair test bench constant at the actual working temperature. After injecting the grease, adjust it at the actual working temperature for at least 3 hours to allow the sliding friction pair test bench and the grease to adapt to the current ambient temperature.

[0047] S2. First-stage test: The first-stage test of the grease is carried out on the sliding friction pair test bench: the grease is adjusted at the set temperature and operated under the rated load to obtain the first-stage test data. The first-stage test data is used to determine whether the first-stage test is passed.

[0048] The first phase of test data includes the number of times the friction pair operates and the number of times abnormal noise occurs, the highest temperature, the coefficient of friction, and the noise level during operation. The first phase of test data also includes the wear condition of the friction pair, which can be tested according to actual needs. During the rotation of the bushing 3, the number of times the friction pair operates is recorded by a counting sensor, and the noise level during operation is measured by a decibel meter. When the noise level reaches the abnormal noise decibel level, the counting sensor records the number of abnormal noise operations. The highest temperature during operation is detected by thermocouple 5. The temperature can be detected using a center-drilled hole or a secondary interpolation method.

[0049] In the first phase of testing, the number of operations under rated load does not exceed the maximum set number. The last few operations within the maximum set number range are used as auxiliary judgment counts. In this embodiment, the maximum set number is 5000 operations, the minimum number of operations is 2000, and the maximum number is 5000. The 4000th to 5000th operations are auxiliary judgment counts. If no abnormal noise occurs, if abnormal noise does not reappear after it appears, or if continuous abnormal noise exceeds the limit, the first phase of testing ends. No new grease is injected during the test.

[0050] The steps to determine whether the first phase of testing has been passed based on the first phase test data include:

[0051] If the highest temperature and friction coefficient do not exceed the critical value, the first stage test is passed, and the fewer the number of abnormal noises during operation, the higher the evaluation level.

[0052] If the high temperature or friction coefficient exceeds the critical value, or if the abnormal noise persists even after the number of operation cycles exceeds the maximum set number, then the first stage test is deemed unsuccessful.

[0053] The evaluation results of the first stage test of the lubricating grease in this embodiment are shown in the table below:

[0054] S3. Second Stage Test: If the first stage test is passed, a second stage test is conducted on the grease based on the first stage test: the grease is operated under a load higher than the rated load to obtain the second stage test data, and the life grade of the grease is determined based on the second stage test data.

[0055] The second phase of test data includes the wear condition of the friction pair, the number of times the friction pair operates, the maximum temperature, the coefficient of friction, and the abnormal noise levels observed during operation. During the rotation of bushing 3, a counter records the number of times the friction pair operates, and a decibel meter measures the noise level. When the noise level reaches the abnormal noise decibel level, the counter records the number of abnormal noise operations. Thermocouple 5 is used to detect the maximum temperature during operation. Temperature can be detected using a center-drilled hole or a secondary interpolation method. No new grease is injected during the test.

[0056] In this embodiment, operation at a load higher than the rated load is performed at 1.1 times the rated load. If the abnormal noise value, the highest temperature, or the coefficient of friction exceeds the critical value, the second stage of testing ends.

[0057] Based on the second-stage test data, in determining the life rating of lubricating grease, the higher the number of operations, the higher the rating, provided that the abnormal noise value, maximum temperature, and coefficient of friction do not exceed the critical values.

[0058] The evaluation results of the second-stage test of the lubricating grease in this embodiment are shown in the table below:

[0059] Example 2:

[0060] In this embodiment, the sliding friction pair uses a 40Cr pin 2 and a powder metallurgy bushing 3, and the grease to be tested is molybdenum disulfide grease.

[0061] The grease in this embodiment was tested for its actual service life under real-world conditions. It was used in machinery at a sand pit and a quarry in Guangxi to verify the grease's service life.

[0062] Under normal grease application conditions, prototype 1 operated continuously in the sand pit for 1500 hours without any abnormal noise feedback, and the average wear of pin 2 was 0.06 mm, and the average wear of bushing was 0.08 mm. The wear condition of the friction pair is shown in Figure 4.

[0063] Under normal grease conditions, prototype 2 operated continuously for 1500 hours in the quarry without any abnormal noise feedback, and the average wear of pin 2 was 0.02 mm, and the average wear of bushing was 0.07 mm. The wear condition of the friction pair is shown in Figure 5.

[0064] Prototype 1 and Prototype 2 operate 100 times per hour, and over 120,000 times in total over 1,500 hours of continuous operation.

[0065] The life evaluation method of this disclosure uses the lubricant.

[0066] The first stage test of the lubricating grease was conducted on a sliding friction pair test bench: the lubricating grease was adjusted at a set temperature and operated under rated load. After more than 3000 cycles, no abnormal noise appeared in the friction pair consisting of pin 2 and bushing 3. The maximum operating temperature was 60℃, and the maximum coefficient of friction was 0.12. The first stage test was rated as excellent, and further second stage testing can be carried out.

[0067] The second-stage test, based on the first-stage test, was conducted under 1.1 times the rated load without the addition of grease. The data for the second-stage test was obtained after more than 120,000 cycles without any abnormal noise. The maximum temperature reached 65°C, and the maximum coefficient of friction was 0.12. The test concluded at this point. According to the evaluation method of this embodiment, the grease's lifespan is rated as C (preferred). At this time, the average wear of pin 2 was 0.057 mm, and the average wear of the bushing was 0.235 mm. The wear condition of the friction pair is shown in Figure 6.

[0068] In summary, the grease rated C as a preferred grade in the life evaluation of this patent can operate without abnormal noise after 1500 hours under actual machine conditions, and the maximum wear of the friction pairs will not exceed the wear after 120,000 cycles under the grease life evaluation method disclosed herein. This verifies that the grease life evaluation method disclosed herein accurately reflects the actual service life under real working conditions.

[0069] The test items are shown in the table below:

[0070] The experimental results are shown in the table below:

[0071] Example 3:

[0072] In this embodiment, the friction pair consists of a pin 2 and a bushing 3, using a 40Cr pin and a figure-eight channel steel bushing. An axial blind hole is machined at the center of the other end face of the oil filling hole on the pin 2. The end of the hole is about 50mm away from the end of the oil filling hole of pin 2, and this hole serves as a temperature measuring point.

[0073] The ambient temperature was set to a constant 25°C, and the test bench was allowed 3 hours to adjust before the test.

[0074] The test will be terminated if the temperature exceeds 70℃, the coefficient of friction is greater than 0.3, or the abnormal noise exceeds 81dB.

[0075] Six types of grease were tested, each corresponding to a brand new friction pair.

[0076] The test items are shown in the table below:

[0077] The test results are shown in the table below:

[0078] Example 4:

[0079] In this embodiment, the friction pair consists of a pin 2 and a bushing 3, using a 40Cr pin and a figure-eight channel steel bushing. An axial blind hole is machined at the center of the other end face of the oil filling hole on the pin 2. The end of the hole is about 50mm away from the end of the oil filling hole of pin 2, and this hole serves as a temperature measuring point.

[0080] This embodiment was tested in a high-temperature environment. The ambient temperature was set to a constant 50°C, and the test bench was allowed 3 hours to adjust before the test.

[0081] The test will be terminated if the temperature exceeds 70℃, the coefficient of friction is greater than 0.3, or the abnormal noise exceeds 81dB.

[0082] One type of grease was tested.

[0083] The test items are shown in the table below:

[0084] The test results are shown in the table below:

[0085] Example 5:

[0086] In this embodiment, the pin 2 and bushing 3 are made of 40Cr metallurgical material. An axial blind hole is machined at the center of the other end face of the oil filling hole of the pin 2. The end of the hole is about 50mm away from the end of the oil filling hole of pin 2, and this hole serves as a temperature measuring point.

[0087] This embodiment was tested in a low-temperature environment, with the ambient temperature set at a constant -20°C. The test bench was allowed 3 hours to adjust before the test.

[0088] The test will be terminated if the temperature exceeds 70℃, the coefficient of friction is greater than 0.3, or the abnormal noise exceeds 81dB.

[0089] One type of grease was tested.

[0090] The test items are shown in the table below:

[0091] The test results are shown in the table below:

[0092] The grease life evaluation method for sliding friction pairs in this embodiment can be used to evaluate the life of different greases. Through continuous first-stage and second-stage tests, the life of the grease can be accurately evaluated. It can be used in both high-temperature and low-temperature environments, thus expanding the applicability of the grease life evaluation method.

[0093] It should be understood that although the steps in the flowcharts of the above embodiments are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some of the steps in the figures may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the sub-steps or stages of other steps.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for evaluating the lifespan of lubricating grease for sliding friction pairs under high and low temperature environments, characterized in that, Includes the following steps: The first stage test of the grease was carried out on the sliding friction pair test bench: the grease was adjusted at the set temperature and operated under the rated load to obtain the first stage test data. The first stage test data was used to determine whether the first stage test was passed. If the grease passes the first stage test, a second stage test is conducted based on the first stage test results: the grease is operated under a load higher than the rated load to obtain the second stage test data, and the life rating of the grease is determined based on the second stage test data.

2. The method for evaluating the life of lubricating grease for sliding friction pairs under high and low temperature environments according to claim 1, characterized in that, The test data for the first phase includes the number of times the friction pair operates and the number of times abnormal noise occurs, the highest temperature, the coefficient of friction, and the noise level that occurs during operation.

3. The method for evaluating the life of lubricating grease for sliding friction pairs under high and low temperature environments according to claim 2, characterized in that, In the first phase of testing, the number of operations under rated load does not exceed the maximum set number.

4. The method for evaluating the life of lubricating grease for sliding friction pairs under high and low temperature environments according to claim 3, characterized in that, In the first phase of testing, if no abnormal noise occurs, or if an abnormal noise does not recur after it has occurred, or if the number of consecutive abnormal noises exceeds the limit, the first phase of testing ends.

5. The method for evaluating the life of lubricating grease for sliding friction pairs under high and low temperature environments according to claim 4, characterized in that, The steps for determining whether the first-stage test has been passed based on the first-stage test data include: If the highest temperature and friction coefficient do not exceed the critical value, the first stage test is passed, and the fewer the number of abnormal noises during operation, the higher the evaluation level. If the highest temperature or friction coefficient exceeds the critical value, or if the abnormal noise persists even after the number of operation cycles exceeds the maximum set number, then the first stage test is deemed unsuccessful.

6. The method for evaluating the life of lubricating grease for sliding friction pairs under high and low temperature environments according to claim 1, characterized in that, The second phase of test data includes the wear condition of the friction pair, the number of times the friction pair operates, the maximum temperature, the coefficient of friction, and the abnormal noise values ​​that occur during operation.

7. The method for evaluating the life of lubricating grease for sliding friction pairs under high and low temperature environments according to claim 6, characterized in that, The operation above the rated load means operation at 1.05-2 times the rated load.

8. The method for evaluating the life of lubricating grease for sliding friction pairs under high and low temperature environments according to claim 7, characterized in that, In the second stage of the test, if the abnormal noise value, the highest temperature, or the coefficient of friction exceeds the critical value, the second stage of the test will end.

9. The method for evaluating the life of lubricating grease for sliding friction pairs under high and low temperature environments according to claim 8, characterized in that, In determining the life rating of lubricating grease based on the second-stage test data, the higher the evaluation rating is, provided that the abnormal noise value, maximum temperature, and friction coefficient do not exceed the critical values, the more times the grease is run.

10. The method for evaluating the life of lubricating grease for sliding friction pairs under high and low temperature environments according to claim 1, characterized in that, The sliding friction pair test bench is placed inside an environmental chamber, which is used to regulate the ambient temperature of the friction pair test bench when testing lubricating grease.

Images