A method for detecting and evaluating the unsteady damage of rolling bearings

Abstract

The present invention relates to the technical field of unsteady damage detection of bearings, and particularly to a method for detecting and evaluating unsteady damage of rolling bearings. According to the conditions of rapid acceleration / deceleration and rapid load change under different unsteady service conditions, the present invention uses a single-ball rolling friction and wear testing machine to conduct variable-load and variable-speed tests on rolling bearings respectively, uses a reciprocating sliding friction and wear testing machine to test the friction and wear performance of materials under oil lubrication, uses a three-dimensional profiler to measure the wear scar area in the reciprocating sliding test, and then calculates the unsteady damage influence factor of the bearing material under rolling conditions based on the wear rate results, so as to detect and evaluate the unsteady damage of rolling bearings. The method of the present invention is reasonable and feasible, ingeniously designed, evaluates the damage behavior of bearings under unsteady service conditions, finds a suitable method for detecting and evaluating unsteady damage of rolling bearings, improves the bearing performance, and prolongs the bearing life.

Description

Technical Field

[0001] The present invention relates to the technical field of bearing unsteady damage detection, and particularly relates to a method for detecting and evaluating unsteady damage of rolling bearings. Background Art

[0002] During the service process of bearings, with the change of working conditions, unsteady service conditions with larger frequency amplitudes of rapid acceleration / deceleration and rapid load changes often occur, leading to premature bearing failure and even sudden accidents. In unsteady service environments such as rapid speed change and rapid load change, due to the large change rate of speed and load, the deformation of bearing materials and the dynamic response of the lubrication system are completely mismatched with the change rate of speed and load, resulting in local slip-roll phenomena in the bearings. Due to the occurrence of local sliding phenomena, the deterioration of bearing performance is aggravated and the bearing life is reduced. Therefore, it is necessary to study the sliding behavior under unsteady conditions. However, since the rolling-sliding state of bearings under rolling conditions is random, it is very difficult to monitor the transient slip-roll ratio of bearings under rolling conditions, and thus it is impossible to accurately evaluate the unsteady damage behavior of bearings.

[0003] Therefore, how to design a reasonable, feasible and ingenious method to evaluate the damage behavior of bearings under unsteady service conditions, find a suitable method for detecting and evaluating unsteady damage of rolling bearings, improve bearing performance and extend bearing life is a problem that needs to be solved at present. Summary of the Invention

[0004] In order to solve the technical problems of damage and failure mechanisms caused by unsteady service conditions such as rapid acceleration / deceleration and rapid load change during the service process of existing bearings, the present invention provides a method for detecting and evaluating unsteady damage of rolling bearings, which is of great significance for the high-reliability and long-life design of bearings.

[0005] The technical solution adopted by the present invention to solve the above technical problems is as follows: A method for detecting and evaluating the unsteady damage of a rolling bearing. Through a single-ball rolling friction and wear testing machine, a rolling test is carried out on the bearing material under unsteady service conditions. The unsteady service conditions include two situations: variable load conditions and variable speed conditions. Under variable load conditions, the load of the rolling bearing changes and the speed remains unchanged. Under variable speed conditions, the speed of the rolling bearing changes and the load remains unchanged. Through a reciprocating sliding friction and wear testing machine, a reciprocating sliding test is carried out on the same bearing material. The test load of the reciprocating sliding test is determined according to the load during the rolling test. The linear velocity difference between the driving wheel and the steel ball of the testing machine during the rolling test is used as the sliding speed of the reciprocating sliding test. According to the test load, sliding speed, set sliding test time, reciprocating sliding stroke during the reciprocating sliding test, and the wear scar area of the bearing material obtained from the test, the unsteady damage amount of the bearing material under unsteady conditions and the steady damage amount under steady conditions are calculated, so as to obtain the unsteady damage influence factor of the bearing. The unsteady damage situation of the rolling bearing is judged according to the unsteady damage influence factor of the bearing.

[0006] The above is the basic implementation mode of the present invention, and further improvements, perfection and limitations can be made on this basis: For example, the same oil lubrication conditions are adopted for the rolling test and the reciprocating sliding test.

[0007] The above is the basic implementation mode of the present invention, and further improvements, perfection and limitations can be made on this basis: When the unsteady service conditions adopt variable load conditions,

[0008] Set the rotational speed of the driving wheel of the single-ball rolling friction and wear testing machine to n 1 , n 1 is a fixed value, and the test load is set to P 1 . After running for a period of time, at a variable load rate of , the load is suddenly changed from P 1 to P t . When the load reaches P t , quickly change the load from P to P t at a variable load rate of 1 . Subsequently, run for a period of time under the conditions of load P 1 and rotational speed n 1 ;

[0009] Calculate the unsteady mutation time to be . At any moment t i during the unsteady mutation time t, the corresponding load is P i , and the linear velocity difference between the driving wheel and the steel ball is v i .

[0010] The above is the basic implementation mode of the present invention, and further improvements, refinements and limitations can be made on this basis: when the non-steady service condition adopts a variable-speed test,

[0011] set the test load to p, where p is a fixed value, and set the rotational speed of the driving wheel to n 1 , run for a period of time, and then at the variable-speed rate, change the rotational speed from n 1 suddenly to n t , when the rotational speed of the driving wheel reaches v t , quickly change the speed at the variable-load rate from n t suddenly to n 1 , and then run for a period of time under the rotational speed n 1 and the load p;

[0012] Calculate that the non-steady mutation time is , and at any moment t i during the non-steady mutation time t, the corresponding load is p, and the linear velocity difference between the driving wheel and the steel ball is v i .

[0013] The above is the basic implementation mode of the present invention, and further improvements, refinements and limitations can be made on this basis: if the contact stress between the driving wheel and the steel ball in the rolling test is calculated based on the load of the rolling test, and based on the fact that the contact stress between the driving wheel and the steel ball in the rolling test is the same as the contact stress between the ball and the surface in the reciprocating sliding test, calculate the test load of the reciprocating sliding test according to the contact stress between the ball and the surface in the reciprocating sliding test.

[0014] The above is the basic implementation mode of the present invention, and further improvements, refinements and limitations can be made on this basis: if the contact type between the driving wheel and the steel ball in the rolling test is a ball-ring type, the contact stress , where E * is the equivalent elastic modulus, and the calculation formula is , E 1 and E 2 are the elastic moduli of the steel ball and the driving wheel materials, μ 1 and μ 2 are the Poisson's ratios of the steel ball and the driving wheel materials, R 1 is the radius of the steel ball, R 2 is the radius of curvature of the driving wheel raceway; substitute the rolling test load P i into the above formula to calculate the contact stress s i between the driving wheel and the steel ball in the rolling test; in the reciprocating sliding test, it is a ball-surface contact type, and the contact stress , where E is the equivalent elastic modulus in the reciprocating sliding test, which is the same as E *Same, R is the radius of the reciprocating sliding test steel ball; according to the contact stress s i The test load F of the reciprocating sliding test is calculated i .

[0015] The above is the basic implementation mode of the present invention, and further improvements, perfection and limitations can be made on this basis: for example, the wear conditions of the bearing material under unsteady conditions and steady conditions are tested through the reciprocating sliding test, and the wear scar area A is measured by a three-dimensional profiler during the process i ; According to the volume wear rate calculation formula , the volume wear rate w of the material under unsteady conditions is calculated i , where w i represents the wear rate of the material at any moment t during the unsteady mutation time t i , A i is the wear scar area, v i is the linear velocity difference between the driving wheel and the steel ball, t 滑 is the reciprocating sliding test time, and L is the reciprocating sliding stroke; The volume wear rates w i during the unsteady mutation process are superimposed to obtain the unsteady damage amount of the bearing material ; The volume wear rate of the material at any moment t i under steady conditions is , where F 1 is the reciprocating sliding test load determined according to the load at the steady state in the rolling test, v 1 is the linear velocity difference between the driving wheel and the steel ball at the steady state in the rolling test, A 1 is the wear scar cross-sectional area corresponding to the test load F 1 and the sliding velocity v 1 under the conditions, and further the steady state damage amount is obtained as .

[0016] The above is the basic implementation mode of the present invention, and further improvements, perfection and limitations can be made on this basis: for example, the unsteady damage influence factor of the bearing material is calculated according to the unsteady damage amount of the bearing material under unsteady conditions and the steady state damage amount under steady conditions ; If , it indicates that the bearing changes from a stable lubrication state to an unstable lubrication state, the bearing damage is aggravated under unsteady service conditions, and the bearing life is reduced; , it indicates that the unsteady service conditions of the bearing do not affect the bearing damage; , it indicates that the bearing changes from an unstable lubrication state to a stable lubrication state, and the bearing damage is reduced under unsteady service conditions

[0017] Beneficial effects

[0018] According to the conditions of rapid acceleration / deceleration and rapid load change under different unsteady service conditions, the variable load and variable speed tests are respectively carried out on the rolling bearing materials by using a single-ball rolling friction and wear test machine. The instantaneous rotational speeds of the driving wheel and the driven wheel can be directly output by this test machine, so that the instantaneous slip-roll ratio of the bearing material can be obtained, and then the instantaneous linear velocity difference between the driving wheel and the steel ball can be obtained, which is the sliding velocity of the material. Then, the reciprocating sliding friction and wear test machine is used to test the friction and wear performance of the material under oil lubrication. The wear scar area in the sliding test is measured by using a three-dimensional profiler, and the unsteady damage influence factor of the bearing material under rolling conditions is calculated according to the wear rate result, so as to detect and evaluate the unsteady damage of the rolling bearing.

[0019] The method of the present invention is reasonable and feasible, and the design is ingenious. It evaluates the damage behavior of the bearing under unsteady service conditions, finds a suitable method for detecting and evaluating the unsteady damage of the rolling bearing, improves the bearing performance, and prolongs the bearing life. Brief Description of the Drawings

[0020] Figure 1 It is a schematic diagram of the single-ball rolling unsteady test of the bearing;

[0021] Figure 2 It is a schematic diagram of the reciprocating sliding test of the bearing material;

[0022] Figure 3 It is a schematic diagram of the load spectrum under unsteady conditions in the rolling test;

[0023] Figure 4 It is a schematic diagram of the linear velocity difference (sliding velocity) under unsteady conditions in the rolling test;

[0024] Figure 5 It is a schematic diagram of the test load in the sliding test;

[0025] Figure 6 It is a schematic diagram of the unsteady damage wear rate and steady damage wear rate of the material under rolling conditions;

[0026] Figure 7 It is a schematic diagram of the unsteady damage wear rate and steady damage wear rate of GCr15 steel under the rolling test conditions of No. 1;

[0027] Figure 8 It is a schematic diagram of the unsteady damage wear rate and steady damage wear rate of GCr15 steel under the rolling test conditions of No. 2;

[0028] Figure 9 It is a schematic diagram of the unsteady damage wear rate and steady damage wear rate of GCr15 steel under the rolling test conditions of No. 3. Detailed Embodiments

[0029] The following further elaborates on the specific implementation manners of the present invention in conjunction with the drawings and tables.

[0030] In actual application, for convenience of description, the bearing material in the following steps of the present invention adopts GCr15 steel.

[0031] As Figure 1 、 2 shown, a method for detecting and evaluating the unsteady damage of a rolling bearing conducts a rolling test on the bearing material under unsteady service conditions through a single-ball rolling friction and wear testing machine. The unsteady service conditions include two situations: variable load conditions and variable speed conditions. Under variable load conditions, the load of the rolling bearing changes and the rotational speed remains unchanged. Under variable speed conditions, the rotational speed of the rolling bearing changes and the load remains unchanged. A reciprocating sliding test is conducted on the same bearing material through a reciprocating sliding friction and wear testing machine. The test load of the reciprocating sliding test is determined according to the load during the rolling test. The linear velocity difference between the driving wheel and the steel ball of the testing machine during the rolling test is used as the sliding speed of the reciprocating sliding test. According to the test load, sliding speed, set sliding test time, reciprocating sliding stroke during the reciprocating sliding test, and the wear scar area of the bearing material obtained from the test, the unsteady damage amount under unsteady conditions and the steady damage amount under steady conditions of the bearing material are calculated, thereby obtaining the unsteady damage influence factor of the bearing. The unsteady damage situation of the rolling bearing is judged according to the unsteady damage influence factor of the bearing.

[0032] The rolling test and the reciprocating sliding test adopt the same oil lubrication conditions.

[0033] When the unsteady service conditions adopt variable load conditions, as Figure 3 、 4 shown, an unsteady test of the bearing material under oil lubrication is carried out using a single-ball rolling friction and wear testing machine. The rotational speed of the driving wheel of the single-ball rolling friction and wear testing machine is set to n 1 , n 1 is a fixed value, and the test load is set to P 1 . After running for a period of time, the load is suddenly changed from P to P 1 at a variable load rate of t . When the load reaches P t , the load is quickly changed from P to P t at a variable load rate of 1 . Subsequently, it runs for a period of time under the conditions of a load of P 1 and a rotational speed of n 1 ;

[0034] The unsteady mutation time is calculated to be . At any moment t i within the unsteady mutation time t, the corresponding load is Pi The linear velocity difference between the driving wheel and the steel ball is v i .

[0035] When the non-steady service condition adopts a variable-speed test,

[0036] Set the test load to p, where p is a constant value, and set the rotational speed of the driving wheel to n 1 , operate for a period of time, and then at The variable-speed rate of 1 Suddenly change the rotational speed from n t To n t , when the rotational speed of the driving wheel reaches v The variable-load rate of t Suddenly change from n 1 To n 1 , and then operate for a period of time under the rotational speed n

[0037] The calculated non-steady mutation time is , at any moment t i Of the non-steady mutation time t, the corresponding load is p, and the linear velocity difference between the driving wheel and the steel ball is v i .

[0038] Based on the load of the rolling test, calculate the contact stress between the driving wheel and the steel ball in the rolling test. Based on the fact that the contact stress between the driving wheel and the steel ball in the rolling test is the same as the contact stress between the ball and the surface in the reciprocating sliding test, calculate the test load of the reciprocating sliding test according to the contact stress between the ball and the surface in the reciprocating sliding test. The sliding speed in the reciprocating sliding test is the linear velocity difference v between the driving wheel and the steel ball in the rolling variable-load test i , the sliding test time in the reciprocating sliding test is t 滑 (constant value), and the reciprocating sliding stroke is L (constant value).

[0039] Figure 5 As shown, in the rolling test, the contact type between the driving wheel and the steel ball is ball-ring type, and the contact stress , where E * Is the equivalent elastic modulus, and the calculation formula is , E 1 And E 2 Are the elastic moduli of the steel ball and the driving wheel materials, μ 1 And μ 2 Are the Poisson's ratios of the steel ball and the driving wheel materials, R 1 Is the radius of the steel ball, R 2 Is the radius of curvature of the driving wheel raceway; Substitute the rolling test load P i Into the above formula to calculate the contact stress s between the driving wheel and the steel ball in the rolling test i ; In the reciprocating sliding test, it is a ball-surface contact type, and the contact stress , where E is the equivalent elastic modulus in the reciprocating sliding test, which is the same as E * ; R is the radius of the steel ball in the reciprocating sliding test; according to the contact stress s i , the test load F of the reciprocating sliding test is calculated i .

[0040] The wear of the bearing material under unsteady and steady conditions is tested through the reciprocating sliding test. As Figure 6 shown, the wear scar area A is measured by a 3D profilometer during the process i ; according to the volume wear rate calculation formula , the volume wear rate w of the material under unsteady conditions is calculated i , where w i represents the wear rate of the material at any moment t during the unsteady mutation time t i , A i is the wear scar area, v i is the linear velocity difference between the driving wheel and the steel ball, t 滑 is the reciprocating sliding test time, and L is the reciprocating sliding stroke; the volume wear rates w i during the unsteady mutation process are superimposed to obtain the unsteady damage amount of the bearing material ; the volume wear rate of the material at any moment t i under steady conditions is , where F 1 is the reciprocating sliding test load determined according to the load at steady state in the rolling test, v 1 is the linear velocity difference between the driving wheel and the steel ball at steady state in the rolling test, A 1 is the wear scar cross-sectional area corresponding to the test load F 1 and the sliding velocity v 1 under the conditions, and further the steady damage amount is obtained as .

[0041] The above is the basic implementation mode of the present invention, and further improvements, perfection and limitations can be made on this basis: for example, the unsteady damage influence factor of the bearing material is calculated according to the unsteady damage amount of the bearing material under unsteady conditions and the steady damage amount under steady conditions ; if , it indicates that the bearing changes from a stable lubrication state to an unstable lubrication state, the bearing damage is aggravated under unsteady service conditions, and the bearing life is reduced; , it indicates that the unsteady service conditions of the bearing do not affect the bearing damage; , it indicates that the bearing changes from an unstable lubrication state to a stable lubrication state, and the bearing damage is reduced under unsteady service conditions.

[0042] In the specific implementation process of the present invention, reference is made to Figures 7-9 , Figures 7-9 which are the non-steady-state damage wear rate diagrams and steady-state damage wear rate diagrams of GCr15 steel under different conditions. The overall gray area in the figure is the non-steady-state damage amount, and the hatched area is the steady-state damage amount. Among them, Figure 7 the rolling test conditions shown are set as follows: load 1 - 2.5 - 1 KN, rotational speed 1000 rpm, variable load rate 1 KN / min, and non-steady-state time 180 s (No. 1); Figure 8 the rolling test conditions shown are set as follows: load 1 - 2.5 - 1 KN, rotational speed 1000 rpm, variable load rate 1.5 KN / min, and non-steady-state time 120 s (No. 2); Figure 9 the rolling test conditions shown are set as follows: rotational speed 3000 - 1000 - 3000 rpm, load 1 KN, variable speed rate 400 rpm / s, and non-steady-state time 20 s (No. 3). In all rolling tests, the materials of the driving wheel, driven wheel, and steel balls are all GCr15 steel, and the elastic moduli E 1 and E 2 are both 210 GPa, the Poisson's ratios μ 1 and μ 2 are both 0.3, the diameters of the driving wheel and the driven wheel are both D = 60.404 mm, the radius R 1 of the steel ball is 8.731 mm, and the radius of curvature R 2 of the rolling track of the driving wheel is 8.99 mm; in all sliding tests, the material of the steel ball is GCr15 steel, the elastic modulus E is 210 GPa, the radius R of the steel ball is 3.175 mm, and the sliding test time is set as t 滑 = 10 min, and the reciprocating sliding stroke is set as L = 12 mm. The worn scar area A i of GCr15 steel in the sliding test is measured by a three-dimensional profiler. According to the volume wear rate calculation formula , the volume wear rate w i of the material under non-steady-state conditions and the volume wear rate w 稳态 of the material under steady-state conditions are calculated. The volume wear rate w i during the non-steady-state mutation process and the volume wear rate w i稳态 of the material under steady-state conditions are respectively superimposed to obtain the non-steady-state damage amount and the steady-state damage amount of , and the non-steady-state damage influence factor of the bearing material under rolling conditions is further calculated, as shown in Table 1.

[0043] Table 1 Non-steady-state damage influence factors of GCr15 steel under different non-steady-state conditions

[0044]

[0045] As can be seen from Table 1, the non-steady-state damage influence factors of No. 1 and No. 2 are both greater than 1, indicating that under these two service conditions, the bearing changes from a stable lubrication state to an unstable lubrication state, the material damage intensifies, and the bearing life decreases. And the value of the non-steady-state damage influence factor of No. 1 is less than that of No. 2, indicating that the bearing damage caused under the non-steady-state conditions of No. 2 is more serious. The non-steady-state damage influence factor of No. 3 is less than 1, indicating that the bearing changes from an unstable lubrication state to a stable lubrication state, and under the service conditions shown in No. 3, the material damage is reduced.

[0046] The method of the present invention is reasonable and feasible, with ingenious design. Evaluating the damage behavior of bearings under non-steady-state service conditions is of great significance for the high-reliability and long-life design of bearings.

[0047] The above has described in detail the preferred specific embodiments and examples of the present invention in conjunction with the diagrams. However, the present invention is not limited to the above embodiments and examples. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the concept of the present invention.

Claims

1. A rolling bearing non-steady-state damage detection and assessment method, characterized in that: The rolling test of the bearing material under non-steady-state service conditions is carried out by a single ball rolling friction and wear tester. The non-steady-state service conditions include variable load conditions and variable speed conditions. Under variable load conditions, the load of the rolling bearing changes but the speed remains unchanged. Under variable speed conditions, the speed of the rolling bearing changes but the load remains unchanged. A reciprocating sliding test is performed on the same bearing material by using a reciprocating sliding friction and wear testing machine, the test load of the reciprocating sliding test is determined according to the load during the rolling test, the linear velocity difference between the driving wheel of the rolling test machine and the steel ball during the rolling test is used as the sliding velocity of the reciprocating sliding test, and the non-steady-state damage amount of the bearing material under non-steady-state conditions and the steady-state damage amount under steady-state conditions are calculated according to the test load, sliding velocity, set sliding test time and reciprocating sliding stroke during the reciprocating sliding test, and the wear scar area of ​​the bearing material obtained in the test, so as to obtain the bearing non-steady-state damage influencing factor, and judge the non-steady-state damage condition of the rolling bearing according to the bearing non-steady-state damage influencing factor; The contact stress between the driving wheel and the steel ball in the rolling test is calculated based on the load of the rolling test. The contact stress between the driving wheel and the steel ball in the rolling test is the same as the contact stress between the ball and the surface in the reciprocating sliding test. The test load of the reciprocating sliding test is calculated based on the contact stress between the ball and the surface in the reciprocating sliding test. In the rolling test, the driving wheel and the steel ball are in ball-ring contact type, and the contact stress , where E * is the equivalent elastic modulus, and the calculation formula is , E1 and E2 are the elastic moduli of the steel ball and the driving wheel materials, μ1 and μ2 are the Poisson's ratios of the steel ball and the driving wheel materials, R1 is the radius of the steel ball, and R2 is the curvature radius of the driving wheel raceway; the rolling test load P i Substituting the above formula, the contact stress s between the driving wheel and the steel ball in the rolling test is calculated: i ; In the reciprocating sliding test, the contact type is spherical-surface type, and the contact stress , where E is the equivalent elastic modulus in the reciprocating sliding test, and E * Same, R is the radius of the reciprocating sliding test ball; according to the contact stress s i Calculate the test load F for the reciprocating sliding test i ; The wear of the bearing material under non-steady-state and steady-state conditions was tested by reciprocating sliding test. The wear scar area A was measured by a three-dimensional profiler during the process. i ; According to the volume wear rate calculation formula , calculate the volume wear rate w of the material under non-steady-state conditions i , where w i Represents any time t in the non-steady-state mutation time t i Wear rate of material, A i is the wear scar area, v i is the linear velocity difference between the driving wheel and the steel ball, t 滑 is the reciprocating sliding test time, L is the reciprocating sliding stroke; the volume wear rate w in the non-steady-state mutation process i Superposition to obtain the non-steady-state damage of the bearing material ; Under steady-state conditions, at any time t i The volume wear rate of the material is , where F1 is the reciprocating sliding test load determined according to the load when the rolling test reaches a steady state, v1 is the linear velocity difference between the driving wheel and the steel ball when the rolling test reaches a steady state, and A1 is the wear scar cross-sectional area corresponding to the test load F1 and sliding velocity v1 in the reciprocating sliding test. The steady-state damage amount is further obtained as ; The non-steady-state damage influencing factor of the bearing material is calculated based on the non-steady-state damage amount under non-steady-state conditions and the steady-state damage amount under steady-state conditions. ;like , indicating that the bearing changes from a stable lubrication state to an unstable lubrication state, and the bearing damage is aggravated under the non-steady-state service condition, and the bearing life is reduced; , indicating that the non-steady-state service condition of the bearing does not affect the bearing damage; , indicating that the bearing changes from an unstable lubrication state to a stable lubrication state, and the bearing damage is reduced under non-steady-state service conditions.

2. A rolling bearing non-steady-state damage detection and assessment method as claimed in claim 1, characterized in that: The rolling test and the reciprocating sliding test adopted the same oil lubrication condition.

3. A rolling bearing non-steady-state damage detection and assessment method as claimed in claim 1, characterized in that: When the non-steady-state service condition adopts the variable load condition, The single ball rolling friction and wear tester is set to drive wheel speed n1, n1 is a constant value, and the test load is set to P1. After running for a period of time, The load change rate changes from P1 to P t , when the load reaches P t When The load change rate is from P t It suddenly changes to P1, and then runs for a period of time under the conditions of load P1 and speed n1; The non-steady-state mutation time is calculated to be , at any time t of the non-steady-state mutation time t i The corresponding load is P i , the linear velocity difference between the driving wheel and the steel ball is v i .

4. A rolling bearing non-steady-state damage detection and assessment method as claimed in claim 1, characterized in that: When the non-steady-state service condition adopts the variable speed test, The test load is set to p, p is a constant value, the driving wheel speed is set to n1, and it runs for a period of time, and then The speed change rate changes the speed from n1 to n t , and wait until the driving wheel speed reaches v t When The load rate changes from n t It suddenly changes to n1, and then runs for a period of time under the conditions of speed n1 and load p; The non-steady-state mutation time is calculated to be , at any time t of the non-steady-state mutation time t i The corresponding load is p, and the linear velocity difference between the driving wheel and the steel ball is v i .

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