CN106248379B - A kind of bearing with solid lubricant accelerated life test loading spectrum design method - Google Patents

Abstract

The invention relates to a load spectrum design method for an accelerated life test of a solid lubricating bearing, which is characterized in that it comprises the following steps: 1) obtaining the on-orbit working section of the solid lubricating bearing; 2) converting the obtained load spectrum block into a typical load spectrum block ; 3) According to the failure mechanism and dynamic wear law of solid lubricated bearings, the load spectrum blocks are graded. On the premise of not changing the failure mechanism of the solid lubricating bearing, the accelerated life test of the solid lubricating bearing has a better acceleration effect.

Description

A Load Spectrum Design Method for Accelerated Life Test of Solid Lubricated Bearings

technical field

The invention belongs to the field of reliability of key components of an aerospace on-board transmission mechanism, and in particular relates to a method for obtaining a load spectrum of a solid lubricating bearing accelerated life test.

Background technique

According to the statistics of foreign satellites, the "stuck" of the on-board transmission mechanism due to poor lubrication is one of the main reasons for the failure of the satellite, and the friction and wear of the on-board transmission mechanism is an important reason for its performance degradation. Solid lubricated bearings are key components of spaceborne transmission mechanisms. Performance degradation and loss of precision caused by long-term operation are the key factors affecting the life of satellites in orbit. Therefore, their high reliability and long life are of great importance to the development and use of my country's spacecraft. important. Usually the life characteristics of products are obtained by doing life tests under normal conditions. However, for solid lubricated bearings, the design is precise, the weaving process is complex, the production cost is high, and the specificity is strong. Generally, mass production will not be carried out. less. With the development of design and manufacturing technology, and the use of new materials, the life of solid lubricated bearings for aerospace is getting longer and longer, so that the life test requires a long test time and a lot of test costs, and may even cause all The required test time is much longer than the development cycle, and it is difficult to complete the life evaluation and verification before putting it into use. Therefore, the accelerated life test of solid lubricated bearings has gradually attracted people's attention.

At present, in the industry, the constant stress accelerated life test method of electronic products is relatively mature, and there are complete test specifications and statistical methods to follow, but the required test sample size is large and the test time is long. Because the failure mechanism of mechanical products is more complicated than that of electronic products, standardized accelerated life test specifications have not yet been formed. As a precision mechanical component, solid lubricated bearings have many failure modes and severe stress coupling characteristics due to their unique lubrication method, working space environment and periodic stress profile, which lead to the traditional constant stress accelerated life test. The load spectrum and existing acceleration models are difficult to give accurate life assessment results. Therefore, how to deeply reveal the failure mechanism of solid lubricated bearings, extract the accelerated stress, and how to design the load spectrum of accelerated life tests based on the unique failure mechanism and working stress profile of solid lubricated bearings are the keys to breaking through the theory and statistical methods of accelerated life tests of solid lubricated bearings.

The accelerated life test is a method to predict the life characteristics of the product under normal stress in a short period of time by increasing the stress without changing the failure mechanism of the product. Not changing the failure mechanism is the premise of the accelerated life test, and strengthening the environmental stress or working stress of the product is a necessary means for the accelerated life test. The accelerated life test is to shorten the test time by strengthening the stress, but if the stress is too large and changes the failure mechanism of the product, the accelerated life test will lose its meaning. If the stress is too small, the shortening of the test time will not be obvious, and the accelerated life test cannot get the best results. The accelerated life test load spectrum refers to the relationship between the stress strengthened in the accelerated life test and the relative time period. How to combine the actual working conditions of the product to determine the accelerated life test load spectrum that does not change the failure mechanism of the product and can play a better accelerated role has always been a difficult problem for designers.

At present, the reference materials of accelerated life tests of foreign products can be retrieved, but most of them focus on the research of statistical methods, and there is very little content about load spectrum design. In view of the closed policy adopted by foreign countries on my country's related technologies, we have no way of knowing how to design the accelerated life test load spectrum of foreign aerospace solid lubricated bearings. The research on accelerated life tests of solid lubricated bearings in my country has just started. A load spectrum design method for accelerated life tests of solid lubricated bearings for engineering applications.

Contents of the invention

In order to solve the problem of achieving a better acceleration effect in the accelerated life test of solid lubricated bearings without changing the failure mechanism of solid lubricated bearings, the present invention proposes a load spectrum design method for comprehensive stress accelerated life tests of solid lubricated bearings. Solid lubricated bearings provide a load spectrum design method for accelerated life tests that does not change the failure mechanism and has a more obvious acceleration effect. This method is practical and operable, and is an effective accelerated method for evaluating the life of solid lubricated bearings.

A method for designing the load spectrum of a comprehensive stress accelerated life test for solid lubricated bearings proposed by the present invention, specifically:

Step 1: Obtain the on-orbit working section of the solid lubricating bearing.

The on-orbit working profile refers to a working status graph drawn by the component to complete the on-orbit flight task. The abscissa is time, and the ordinate is the load stress and working status corresponding to the corresponding task.

Step 2, converting the obtained load spectrum block into a typical load spectrum block.

The load spectrum is the corresponding relationship between the component's actual work, the load stress, the working condition and the time used for each gear. For example, the axial load on the bearing in this example, the corresponding relationship between the rotational speed of the bearing and the duration.

Typical load spectrum blocks are representative load spectra of different levels that can reflect actual working conditions.

Step 3, according to the failure mechanism and dynamic wear law of the solid lubricated bearing, classify the load spectrum blocks.

Specifically, the present invention achieves the above objects through the following solutions.

A method for designing a load spectrum for an accelerated life test of a solid lubricated bearing, comprising the following steps:

1) Obtain the on-orbit working profile of the solid lubricated bearing;

2) Convert the obtained load spectrum block into a typical load spectrum block;

3) According to the failure mechanism and dynamic wear law of solid lubricated bearings, the load spectrum blocks are graded.

According to the method described in the preceding scheme, it is characterized in that step 1) includes: by analyzing the wear and transfer of the lubricating film in the solid lubricating bearing, the relationship between the wear rate of the coating film and the transfer rate of the lubricating material of the cage and the applied stress is respectively given, The dynamic complex wear of solid lubricated bearings is obtained.

According to the method described in the aforementioned solution, it is characterized in that step 2) includes: converting the obtained load spectrum into a typical load spectrum block by direct interception.

According to the method described in the preceding scheme, it is characterized in that step 3) includes: for the case where the transfer rate of the cage is higher than the consumption rate of the channel coating, resulting in excessive lubrication film and/or the transfer rate of the cage is lower than the consumption of the channel coating The load spectrum blocks that caused the loss of lubricant film due to the velocity were merged.

According to the method described in the preceding scheme, it is characterized in that step 3) includes:

The dynamic compound wear of solid lubricated bearings is obtained by the following methods:

For the wear rate of the channel coating, the speed and time are introduced to characterize the sliding distance, and the wear amount formula is obtained as:

Among them, W ₁ is the wear amount of the channel coating, p ₁ is the pressure, v ₁ is the sliding velocity, t is the test time, and K ₁ , a, b, and c are all constants determined based on statistical data;

The relationship between the channel coating consumption rate and the accelerated stress is fitted by statistical data; considering that the commonly used accelerated stress of solid lubricated bearings is rotational speed and axial load, this relationship is expressed as:

I _off =F ₁ (V,P) (2)

Where I _off represents the channel coating consumption rate, V and P represent the magnitude of the rotational speed and axial load stress, respectively;

Based on the concavity of the wear scar of the cage in the shape of an elliptical parabola, the expression of the lubricant film transfer amount of the cage is obtained:

Among them, W ₂ is the amount of lubricating film transfer of the cage, p ₂ is the average Hertz contact force, D=v ₂ t is the sliding distance, K ₂ , j, m are constants determined based on statistical data, v ₂ is the relative sliding speed; The relationship between the migration rate of the lubricating material and the accelerated stress is:

I _br =F ₂ (V,P) (4)

Where I _br represents the transfer rate of the cage lubricating material;

Based on formulas (2) and (4), the volume of lubricating film W _off (t) consumed by wear on the inner and outer raceways and the volume of lubricating film W _br (t) transferred from the cage to the inner and outer raceways through the rolling elements are obtained, so that different stresses can be obtained The dynamic expression of lower lubricating film thickness:

Where δ is the thickness of the lubricating film, δ ₀ is the initial thickness of the trench coating, and A is the area of the trench coating. According to the method described in the preceding scheme, it is characterized in that step 3) includes:

The combined expression is:

Where N is the number of load spectrum blocks, △δ _i is the total lubricant film change corresponding to the i-th load spectrum block, and △δ _A is the lubricant film change corresponding to the accelerated load spectrum block.

Advantage and positive effect of the present invention are:

(1) Under the condition that the routine life test load spectrum is determined, the failure process of solid lubricated bearings can be accelerated to a large extent, and the speed of obtaining failure test samples can be accelerated;

(2) A load spectrum design method based on spectral block classification and equivalent damage is provided, which can better reflect the actual operating load profile of solid lubricated bearings;

(3) When designing the load spectrum of the accelerated life test of solid lubricated bearings, the failure mechanism of solid lubricated bearings is not changed by adjusting the stress amplitude and time.

Description of drawings

Figure 1 is a schematic diagram of the structure of a solid lubricated bearing and the transfer of a lubricating film;

Figure 2 is the design method of the load spectrum for the accelerated life test of solid lubricated bearings;

Figure 3 is the derivation process of the dynamic compound wear law of solid lubricated bearings;

Figure 4 is the elliptical contact area between the rolling element and the channel.

The accompanying drawings are schematic illustrations of the content of the present invention, and the content shown in the accompanying drawings is not used to specifically limit the content of the present invention.

Detailed ways

The method for designing the load spectrum of the accelerated life test of the solid lubricated bearing according to the present invention will be described in detail below in conjunction with the accompanying drawings and the embodiments.

Figure 1 is a schematic diagram of a solid lubricating bearing. A solid lubricating bearing usually adopts a structural form that combines the inner and outer rings of the bearing, the cage and the rolling elements. Among them, 1 is the outer ring, 2 is the inner ring, 3 is the cage, 4 is the lubricating film of the outer ring on the outer ring 1, 5 is the lubricating film of the inner ring on the inner ring 2, and 6 is the rolling element. The outer ring usually remains fixed, while the inner ring usually rotates with the shaft. In practical applications, the kinematic relationship between the two may also need to be changed, that is, the inner ring 2 may be fixed while the outer ring 1 rotates. When a relative movement occurs between the inner ring 1 and the outer ring 2, the rolling elements 6 rotate. The lubricating film 4 of the outer ring is located in the groove on the inner surface of the outer ring 1 , and the lubricating film 5 of the inner ring is located in the groove on the outer surface of the inner ring 2 . The most widely used material for the lubricating film is molybdenum disulfide. The lubricating film can be prepared by coating. Cage 3 is a self-lubricating cage made of "sacrificable" lubricating materials, the most commonly used materials being PI (polyimide) and MoS ₂ . During the operation of solid lubricated bearings, the channel coating acts as a lubricant; while the cage is designed to transfer its own lubricating material to the inner and outer channels through the rotation of the rolling elements at a controllable speed and method, thereby reducing the loss of the lubricating film. Supplementary effect to maintain the lubricating effect.

As shown in Figure 2, the method for designing the load spectrum of the accelerated life test is as follows:

Step 1: Obtain the on-orbit working section of the solid lubricating bearing. In the initial stage of operation, the channel coating is mainly used for lubrication. With the rotation of the rolling elements and the contact and collision between the rolling elements and the cage, the lubricating material of the cage is continuously transferred to the channel through the rotation of the rolling elements. During this process, the channel coating is gradually worn and consumed, and the channel coating Gradually transition to transfer film lubrication, and finally the transfer film plays the main role of lubrication, as shown in Figure 1. After the channel coating and the transfer film are consumed, the bearing gradually wears out until it fails. During actual operation, the transfer speed of lubricating material may also be too fast, resulting in the accumulation of lubricating material on the inner and outer channels. The friction torque is too large, which makes the bearing stalled or difficult to work smoothly, which leads to failure. Therefore, it is necessary to study the wear and transfer laws of the lubricating film in solid lubricated bearings, and give the relationship between the wear rate of the coating film and the transfer rate of the lubricating material of the cage and the applied stress, and obtain the dynamic compound wear law of the solid lubricated bearing, so as to facilitate the subsequent accelerated life. Design of test load spectrum.

The derivation process of the dynamic composite wear law of solid lubricated bearings is shown in Fig. 3. For the wear rate of the channel coating, the speed and time are introduced to characterize the sliding distance, and the wear amount formula is obtained as:

Where W ₁ is the wear amount of the channel coating, p ₁ is the pressure, v ₁ is the sliding velocity, t is the test time, K ₁ , a, b, and c are all constants determined based on statistical data.

The contact between the rolling elements and the inner and outer channels is a point contact. According to the Hertz contact theory, the stress distribution in the contact area can be obtained through the force analysis and the applied external load (ie accelerated stress). Based on the macroscopic wear theory, the relationship between the channel coating consumption rate and the accelerated stress can be fitted through statistical data. Considering that the acceleration stress commonly used in solid lubricated bearings is rotational speed and axial load, this relationship can be expressed as:

I _off =F ₁ (V,P) (8)

Among them, I _off represents the consumption rate of channel coating, and V and P represent the magnitude of rotational speed and axial load stress, respectively.

The transfer rate of the cage lubricating material can also be obtained based on tribological methods. Based on the concavity of the wear scar of the cage in the shape of an ellipse paraboloid, the expression of the amount of lubricating film transfer of the cage is given:

Where W ₂ is the transfer amount of lubricating film on the cage, p ₂ is the average Hertz contact force, D=v ₂ t is the sliding distance, K ₂ , j, m are constants determined based on statistical data, and v ₂ is the relative sliding speed. Also based on macro wear theory and Hertz contact theory. Using methods such as finite element analysis, the relationship between the transfer rate of the cage lubricating material and the accelerated stress can be obtained, which is characterized as:

I _br =F ₂ (V,P) (10)

Where I _br represents the transfer rate of the cage lubricating material. Combined with the actual load history, it can be divided into the lubricating film volume W _off (t) consumed by wear on the inner and outer raceways calculated based on (8) and (10) and the lubricating film volume transferred from the cage to the inner and outer raceways through the rolling elements W _br (t), and then the dynamic expression of the lubricating film thickness under different stresses can be given as:

Where δ is the thickness of the lubricating film, δ ₀ is the initial thickness of the trench coating, and A is the area of the trench coating. The above dynamic expression of lubricating film thickness represents the dynamic complex wear of solid lubricated bearings. According to the dynamic wear law and the failure threshold based on statistical data, the physical essence and coupling relationship of the failure mechanism of solid lubricated bearings under different stress levels can be obtained, which lays the foundation for the design of the load spectrum of the accelerated life test.

Step 2, converting the obtained load spectrum block into a typical load spectrum block. Because there are two commonly used acceleration stresses for solid lubricated bearings—rotational speed and axial load, and the actual solid lubricated bearings in orbit may bear a more complex phased load spectrum, so the obtained load spectrum can be transformed by direct interception is a typical load spectrum block.

Step 3. According to the failure mechanism and dynamic wear law of solid lubricated bearings, the load spectrum block is divided into four levels. Level I means that the transfer rate of the cage is too fast. Under this stress level, the solid lubricated bearing will soon be on the inner and outer grooves. Excessive lubricating film is formed, resulting in stall and rapid failure. This kind of load spectrum block generally does not appear in engineering practice, or it occupies a small proportion in the entire load spectrum, but it will quickly lead to bearing failure, so it belongs to the load spectrum block that changes the failure mechanism. When compiling the load spectrum should be retained. Level II indicates that the transfer rate of the cage is higher than the consumption rate of the channel coating, but it will not cause excessive lubrication film in a short period of time. In engineering practice, it is often reflected in the fact that the friction torque is too large, which will lead to failure after a long time. Class III indicates that the transfer rate of the cage is lower than the consumption rate of the channel coating, so the bearing will gradually consume the channel coating and transfer film, and eventually fail due to the lack of lubricating film. Class IV indicates that the cage transfer rate and channel coating consumption rate are very slow. In this case, the thickness of the bearing lubricant film remains almost constant, so the impact of this type of load spectrum on the performance degradation and life of solid lubricated bearings can be almost Neglected; for solid lubricated bearings running on orbit, this kind of load occupies a large proportion, and can usually be omitted when compiling the load spectrum.

For the above-mentioned level II and level III load spectrum blocks, a combined form is usually adopted when compiling the accelerated life test load spectrum. For solid lubricated bearings, the combined principle is the principle of equivalent damage (that is, the change in thickness of the equivalent lubricating film). The load spectrum block of level II corresponds to the fault of excessive transfer film, which corresponds to the increase of the thickness of the lubricating film. The principle of combination is:

Among them, N is the number of II-level load spectrum blocks, Δδ _i is the total lubricant film change corresponding to the i-th II-level load spectrum block, and Δδ _A is the lubricant film change corresponding to the accelerated load spectrum block. According to the calculated △δ _A , the acceleration stress V and P can be calculated by using the optimization method based on formula (11). The actual operation also needs to consider the engineering feasibility.

The third-level load spectrum block corresponds to the failure of the lack of lubrication film, corresponding to the decrease of the thickness of the lubrication film, and the combination principle is the same as that of the second-level load spectrum block.

Example:

Adopt the method of the present invention to the accelerated life test load spectrum design of certain space-borne solid lubricated bearing as follows:

Firstly, analyze the working environment and the stress of the solid lubricated bearing, and select the acceleration stress. Solid lubricating bearings are a basic spaceborne transmission component, widely used in various instruments and mechanisms of space vehicles. The environmental stresses suffered by solid lubricated bearings mainly include temperature, radiation, etc., and the main working stresses include rotational speed, radial load, axial load, etc.

In actual work, the failure of solid lubricated bearings is mostly caused by poor lubrication or wear. The solid lubricating film is gradually worn out, and the lubricating film is destroyed, resulting in increased bearing torque or vibration, which eventually leads to failure. In the accelerated life test of solid lubricated bearings, the rotational speed and axial load are mainly selected as the accelerated stress.

Table 1 shows the load history of a spaceborne solid lubricated bearing on orbit, and the total time of each cycle is 11 minutes. The load history shown in Table 1 is divided into six stages, corresponding to the corresponding on-orbit working conditions, that is, low-speed forward rotation, low-speed reverse rotation, high-speed forward rotation, and high-speed reverse rotation. Because there are two accelerated stresses commonly used in solid lubricated bearings, the obtained load spectrum block is transformed into a typical load spectrum block. According to the failure mechanism and dynamic wear law of solid lubricated bearings, its load spectrum block can be divided into four levels, among which the stages 1-5 in Table 1 can be intercepted as II and III spectrum blocks, and the sixth stage is I level spectrum piece.

Table 1 Load history of a spaceborne solid lubricated bearing in orbit

The solid lubricated bearings of spacecraft mechanisms generally work under light load and low speed conditions. For rolling element bearings, a certain axial preload is often applied to improve the stiffness and rotation accuracy of the bearing. In order to simplify the analysis and calculation, this paper makes the following two assumptions:

1) Under low speed conditions, the inertial load generated by the motion of the rolling elements is negligible.

2) In the space microgravity environment, the rolling element bearing only bears the preload.

When the bearing bears the central axial preload Fa, the contact load Q of each rolling element is the same, that is

In the formula, Z is the number of rolling elements, and α is the actual contact angle of the bearing. According to the Hertz theory of point contact, the contact area between the rolling element and the inner and outer channels is an ellipse. Establish a coordinate system s={o, x y z}, the origin o of the coordinate system s is set at the center of the ellipse, the x-axis is along the long axis of the ellipse, the y-axis points to the rolling direction of the rolling body along the short axis of the ellipse, and the z-axis is along the normal of the contact surface direction, as shown in Figure 4, the contact force at any point (x, y) in the ellipse contact area is:

In the formula, p ₀ is the maximum contact stress in the ellipse contact area, a and b are the major and minor semi-axes of the ellipse respectively. According to the calculation formula of the maximum Hertz contact stress, the maximum contact stress is obtained as:

In the formula, πe _a e _b is a constant, which can be obtained from the Hertz contact coefficient table, and ∑ρ ² is the sum of the principal curvatures of the contact object, where ε _E =1.

The kinematic analysis of rolling element bearings introduces the following assumptions:

1) The outer ring of the bearing is fixed and the inner ring rotates;

2) Under low-speed conditions, the contact angles of the inner and outer rings of the bearing are the same, and the gyroscopic motion of the rolling elements is not considered;

3) The rolling body only rolls in the outer ring channel of the bearing, while the inner ring channel has both rolling and spin.

4) The relative sliding speed v(x, y) between the rolling element and the inner ring channel at the point (x, y) of the elliptical contact area is the differential sliding speed v1(x, y) along the short axis of the ellipse at this point and Vector sum of spin-slip velocities v2(x, y), see Fig. 4.

The sliding velocity v(x, y) at point (x, y) is:

In the formula, ω is the absolute angular velocity of the inner ring of the bearing; g(x, y) is a function of the elliptical contact area x, y, which is related to the geometric characteristics of the bearing, working conditions (load), etc.

It can be seen from formula (7) that the linear wear rate of the solid lubricating film at any point (x, y) in the elliptical contact area between the rolling element and the raceway is:

As shown in Figure 4, a small area unit dxdy is taken at the point (x, y). It can be known from formula (4) that each rolling element has the same contact with the raceway, and integrating γ(x, y) in the elliptical contact area, the volume wear rate w of the solid lubricating film in the raceway of the inner ring of the bearing can be obtained as:

In the formula, Ω is the elliptical contact area between the rolling element and the inner raceway of the bearing. Substituting equations (14), (16) into equation (18) to get:

In the formula, a _{i and} b _i are the semi-major axis and semi-minor axis of the elliptical contact area between the rolling element and the inner raceway of the bearing, respectively, and the subscript i represents the inner ring.

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The parameter K ₃ is related to the shape of the elliptical contact area, the working condition of the bearing and the geometric characteristics of the bearing.

At this time, formula (19) can be expressed as:

In the stable wear stage, it can be considered that the volume wear rate _w1 of the solid lubricant film remains unchanged with time. At this time, the parameter c in formula (7)=1, K=K ₁ K ₃ =4.0×10 ⁻⁹ . To verify the wear failure model of solid lubricated bearings in a vacuum environment, it is necessary to obtain life test data in a vacuum environment, and obtain the corresponding parameters K ₁ , K ₃ , a, and b based on the life test data in a vacuum environment. Due to the experimental conditions However, the actual working condition of solid lubricated bearings on orbit is relatively complicated, and its accurate numerical value cannot be obtained locally. According to statistical data, a=0.127 and b=1.3849 are taken. In the same way, the transfer amount of the lubricating film of the cage can be obtained and can be expressed as:

Same as above, take K ₂ =1.2×10 ^-8 , j=0.103, m=1, then it can be obtained:

Among the load spectrum blocks corresponding to level II and level III, the change amount of the lubricating film of the i-th spectrum block is:

δ _i =W ₁ -W ₂ (23)

Intercept the first five stages corresponding to Table 1 into grade II and grade III spectral blocks,

Table 2 Interception of the first five stages of a certain space-borne solid lubricating bearing

Therefore, it can be obtained by the above formula (21) (22) (23):

δ ₁ =2.5069×10 ^-5 -3.0930×10 ^-5 =-5.8610×10 ^-6

δ ₃ =4.4105×10 ^-5 -3.1727×10 ^-5 =1.2379×10 ^-5

δ ₅ =0.0011-5.9539×10 ^-4 =4.5549×10 ^-4

According to the premise of not changing the failure mechanism of solid lubricated bearings, according to the actual working conditions, the II and III spectrum blocks are combined to make it have the best possible acceleration effect. Here we take the axial load of 20N and the rotational speed of 240rpm as its After the combined working condition, the acceleration time can be obtained according to formula (11)(21)(22):

t=253.5394s=4.2257min

The time to go through one cycle can be equivalent to 5.2257min. Finally, the accelerated life test spectrum of solid lubricated bearings is shown in Table 3 as follows:

Table 3 Accelerated life test spectrum of a spaceborne solid lubricated bearing

Through the above-mentioned accelerated life test load spectrum conversion method, without changing the failure mechanism of solid lubricating bearings, the load history of the original six stages of solid lubricating bearings on rail can be equivalent to the above two In the typical stage, the total time used for each cycle is also reduced from 11 minutes to 5.2257 minutes, and the acceleration effect is more obvious, which can accelerate the failure process of solid lubricated bearings to a greater extent, thus obtaining an effective accelerated life test load Spectrum.

Apparently, the above-mentioned embodiments are only examples for clearly illustrating the present invention, rather than limiting the implementation of the present invention. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. And these obvious changes or modifications derived from the spirit of the present invention are still within the protection scope of the present invention.

Claims (4)

1. A method for designing a load spectrum of a solid lubricated bearing accelerated life test, characterized in that, Include the following steps: 1) Obtain the on-orbit working section of the solid lubricated bearing; by analyzing the wear and transfer of the lubricating film in the solid lubricated bearing, the relationship between the wear rate of the coating film and the transfer rate of the lubricating material of the cage and the applied stress is respectively given, and the dynamic composite of the solid lubricated bearing is obtained. Wear pattern; 2) Convert the obtained load spectrum block into a typical load spectrum block; convert the obtained load spectrum block into a typical load spectrum block by direct interception; 3) According to the failure mechanism and dynamic compound wear law of the solid lubricated bearing, the typical load spectrum blocks are graded. 2. The method according to claim 1, characterized in that step 3) comprises: Load spectrum blocks were combined for cases where the cage transfer rate was higher than the channel coating wear rate resulting in excess lubricant film and/or the cage transfer rate was lower than the channel coating wear rate resulting in loss of lubricant film. 3. The method according to claim 1, characterized in that step 3) comprises: The dynamic composite wear law of solid lubricated bearings is obtained by the following methods: For the wear rate of the channel coating, the speed and time are introduced to characterize the sliding distance, and the wear amount formula is obtained as: Among them, W ₁ is the wear amount of the channel coating, p ₁ is the pressure, v ₁ is the sliding velocity, t is the test time, and K ₁ , a, b, and c are all constants determined based on statistical data; The relationship between the channel coating wear rate and the accelerated stress is fitted by statistical data; considering that the commonly used accelerated stress of solid lubricated bearings is the rotational speed and axial load, this relationship is expressed as: I _off =F ₁ (V,P) (2) where I _off represents the wear rate of the channel coating, and V and P represent the magnitude of the rotational speed and axial load stress, respectively; Based on the concavity of the wear scar of the cage in the shape of an elliptical parabola, the expression of the lubricant film transfer amount of the cage is obtained: Where W ₂ is the transfer amount of lubricating film on the cage, p ₂ is the average Hertzian contact force, D=v ₂ t is the sliding distance, K ₂ , j, m are constants determined based on statistical data, and v ₂ is the relative sliding speed; The relationship between the transfer rate of the cage lubricant material and the accelerated stress is: I _br =F ₂ (V,P) (4) Where I _br represents the transfer rate of the cage lubricating material; Based on formulas (2) and (4), the volume of lubricating film W _off (t) consumed by wear on the inner and outer raceways and the volume of lubricating film W _br (t) transferred from the cage to the inner and outer raceways through the rolling elements are obtained, so that different stresses can be obtained The dynamic expression of the thickness of the lubricating film is to characterize the dynamic compound wear law of the solid lubricated bearing: Where δ is the thickness of the lubricating film, δ ₀ is the initial thickness of the trench coating, and A is the area of the trench coating. 4. The method according to claim 2, characterized in that step 3) comprises: The combined expression is: Where N is the number of typical load spectrum blocks, Δδ _i is the total lubricant film change corresponding to the i-th typical load spectrum block, and Δδ _A is the lubricant film change corresponding to the accelerated load spectrum block.