A device and method for testing subsurface stress and distributed contact state of a three-point contact ball bearing based on fiber grating

Abstract

The application relates to a three-point contact ball bearing subsurface stress testing and distributed contact state testing device and method based on fiber optical gratings, and belongs to the technical field of rolling bearing testing and experiment. The device comprises a main shaft device, a bearing subsurface stress testing device, a radial loading device, a bearing box, a bending moment loading device and an axial loading device; a fiber optical grating measuring point group is arranged at a subsurface stress sensitive position of an outer ring and two half inner rings of a bearing to be tested, each group comprising three measuring points of the outer ring and two measuring points of the inner ring. One or more static loads of an axial load, a radial load and a bending moment are applied to obtain strain responses of the measuring points, and the differential responses of the corresponding measuring points of the same rolling body are used to judge contact area deviation and a distributed contact state. The application can realize synchronous testing of local subsurface stresses of the inner and outer rings and contact state testing under composite static loads.

Description

Technical Field

[0001] This invention belongs to the field of rolling bearing testing technology, specifically relating to a device and method for testing the subsurface stress and distributed contact state of a three-point contact ball bearing based on a fiber Bragg grating. In particular, it relates to a testing device and method for testing the local subsurface stress of the bearing rings under one or more combined static loads of axial load, radial load, and bending moment in a three-point contact ball bearing, and for determining the distributed contact state between the rolling elements and the inner and outer rings based on the measured subsurface stress response. Background Technology

[0002] Three-point contact ball bearings typically employ a structure with a double inner ring and an outer ring raceway. This structure includes an outer ring, a first inner ring, a second inner ring, and rolling elements positioned between the outer ring and the two inner rings. Each rolling element forms a contact point with the outer ring and another contact point with both the first and second inner rings, thus creating a three-point contact relationship: one point of contact on the outer ring and two points of contact on the inner ring.

[0003] Due to its contact structure, three-point contact ball bearings can withstand axial loads, radial loads, and bending moments, making them suitable for applications involving combined forces such as slewing bearings, robot joints, and turntable supports. Under no-load conditions, the contact relationship between the rolling elements and the raceways in a double-inner-ring type three-point contact ball bearing is typically defined: the rolling elements form a single-point contact with the outer ring and a single-point contact with each of the two inner ring halves. This contact relationship can serve as a baseline for analyzing changes in the contact state of a three-point contact ball bearing under load.

[0004] However, when a three-point contact ball bearing is subjected to one or more of the following loads: axial load, radial load, and bending moment, especially when multiple loads work together to form a composite static load, the actual contact area between the rolling elements and the inner and outer rings will change relative to the unloaded reference state, and the stress distribution of the subsurface layer of the rings corresponding to the corresponding contact area will also change accordingly.

[0005] Specifically, under combined static loads, the peak position of subsurface stress, the intensity of stress response, and the distribution of the circumferential bearing area corresponding to the single contact area of ​​the outer ring and the double contact areas of the first and second inner rings may all change. Different combinations of axial loads, radial loads, and bending moments may also cause the contact area to shift in different directions, so that the original reference contact area no longer corresponds to the actual maximum contact response area.

[0006] Because the aforementioned changes are simultaneously influenced by factors such as the magnitude and direction of external loads, the three-point contact relationship, and bearing structural parameters, it is difficult to directly determine the actual contact area, contact area offset direction, main load-bearing area, and maximum contact response location of the rolling elements and inner and outer rings after loading based solely on the axial load, radial load, and bending moment conditions applied to the outside of the bearing. Therefore, it is necessary to test the actual distributed contact state of the three-point contact ball bearing by using the local subsurface stress response, which can reflect the load transmission state between the rolling elements and the raceway.

[0007] In the existing technology, there are already technical solutions for applying fiber optic grating sensing technology to the condition testing of bearings or similar support structures. For example, existing technologies can embed fiber optic grating sensing units in structures such as bearing bushes to monitor parameters such as load, temperature, or stress; there are also solutions that place fiber optic grating sensors in different directions on the outer ring of a spherical bearing to test the temperature and strain state of the spherical bearing.

[0008] However, the aforementioned test objects differ significantly from three-point contact ball bearings. Firstly, the contact patterns, load-bearing paths, and contact state change mechanisms of water-lubricated bearings and spherical plain bearings differ from those of rolling contact three-point contact ball bearings. Secondly, existing fiber optic grating bearing testing technologies primarily test the overall temperature, strain, load, or health status of the bearing, without setting corresponding local subsurface stress measurement points for the specific contact relationship where each rolling element forms three contact points with the outer ring, the first half of the inner ring, and the second half of the inner ring.

[0009] Especially under the combined static load of axial load, radial load and bending moment, how to simultaneously obtain the local subsurface stress response of the single contact area of ​​the outer ring and the two half contact areas of the inner ring corresponding to the same rolling element, and use the response difference between different measuring points to deduce the actual contact area offset direction and the relative bearing state of the two contact areas of the inner ring, the existing technology still lacks corresponding dedicated testing devices and testing methods.

[0010] Therefore, it is necessary to provide a device and method for testing the subsurface stress and distributed contact state of a three-point contact ball bearing based on a fiber Bragg grating, so as to realize the synchronous testing of the local subsurface stress of the inner and outer rings of the three-point contact ball bearing, and further determine the distributed contact state of the three-point contact ball bearing under the action of composite static load based on the test results. Summary of the Invention

[0011] The purpose of this invention is to address the problem that existing technologies cannot directly test the actual contact area and distributed contact state of three-point contact ball bearings under combined static loads, and to provide a device and method for testing the subsurface stress and distributed contact state of three-point contact ball bearings based on fiber Bragg gratings.

[0012] This invention involves creating grooves at the subsurface stress-sensitive locations of the outer ring, the first half-inner ring, and the second half-inner ring of a three-point contact ball bearing, and grouping fiber optic grating sensors according to the number and circumferential position of the rolling elements. This ensures that each rolling element corresponds to three measuring points on the outer ring and two measuring points on the inner ring. By applying one or more loads, including axial load, radial load, and bending moment, the local subsurface stress-related strain response of each measuring point is obtained. Furthermore, by comparing the differences between different measuring points corresponding to the same rolling element, the offset direction of the outer ring contact area and the relative response state of the two half-inner ring contact areas are determined, thereby testing the actual distributed contact state of the three-point contact ball bearing.

[0013] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a device for testing the subsurface stress and distributed contact state of a three-point contact ball bearing based on a fiber Bragg grating, comprising a spindle device 1, a bearing subsurface stress testing device 2, a radial loading device 3, a bearing housing 4, a bending moment loading device 5, and an axial loading device 6.

[0014] The bearing subsurface stress testing device 2 is installed inside the bearing housing 4 and is used to install the test bearing 23 and obtain the local subsurface stress response of the test bearing 23 under the corresponding load conditions.

[0015] The test bearing 23 is a three-point contact ball bearing, preferably a double-half-inner-ring type three-point contact ball bearing. The test bearing 23 includes an outer ring 231, an inner ring 234, and a plurality of rolling elements 233, wherein the inner ring 234 includes a first half-inner ring and a second half-inner ring.

[0016] Each rolling element 233 forms three contact points with the outer ring 231, the first inner ring, and the second inner ring, respectively. These three contact points correspond to different contact load transmission paths. This invention tests the distributed contact state of a three-point contact ball bearing under combined static loads by measuring the local strain response in the stress-sensitive area of ​​the subsurface layer of the bearing rings near the three contact points.

[0017] Grooves for mounting fiber optic grating sensors are made in the subsurface stress-sensitive areas corresponding to the outer ring 231, the first half of the inner ring, and the second half of the inner ring of the bearing.

[0018] Grooves are made at the subsurface stress-sensitive locations corresponding to the reference contact area of ​​the bearing outer ring 231 and the subsurface stress-sensitive locations corresponding to the possible offset paths on both sides of the reference contact area; grooves are also made at the subsurface stress-sensitive locations corresponding to the first half-inner ring contact area and the second half-inner ring contact area.

[0019] Fiber Bragg grating sensors are arranged in each trench to obtain the local strain response at the corresponding location.

[0020] There is residual wall thickness between the bottom of the groove and the corresponding raceway profile. h The remaining wall thickness h The determination is based on the possible offset range of the contact area, the sensitivity of the subsurface stress response, the installation space of the fiber Bragg grating sensor, and the safety requirements for the strength of the collar.

[0021] Specifically, it can be first determined based on the axial load of the tested bearing 23. radial load and bending moment M The potential displacement range of the contact area under action and the subsurface stress concentration area are used to determine the trench opening area and the fiber Bragg grating sensor placement area; then, based on the sensitivity requirements of the local subsurface stress-related strain response at the bottom of the trench to changes in the contact state, the remaining wall thickness is determined. h The maximum allowable value is determined to enable the fiber Bragg grating sensor to obtain a strain response that reflects changes in contact state; simultaneously, the remaining wall thickness is determined based on the strength and fatigue safety requirements of the bearing rings. h The minimum allowable value is determined to avoid excessive impact on the bearing capacity of the raceway due to excessively deep trenches; the target remaining wall thickness is determined while simultaneously meeting the requirements for subsurface stress testing sensitivity and raceway structural safety. h .

[0022] The fiber optic grating sensors are grouped and arranged according to the number and circumferential position of the rolling elements 233 in the bearing under test 23.

[0023] Suppose that the bearing under test 23 has n rolling elements 233 arranged circumferentially, then n sets of fiber optic grating measurement points are arranged circumferentially, and the measurement point group corresponding to the i-th rolling element 233 is denoted as . ,in: i =1,2,..., n .

[0024] Each measuring point group It includes five measuring points, consisting of three outer ring measuring points located on the outer ring 231 of the bearing and two inner ring measuring points located on the inner ring 234 of the bearing.

[0025] For the i-th rolling element 233, the three outer ring measuring points are respectively denoted as the first outer ring measuring point. Outer ring reference measuring points Second outer ring measuring point .

[0026] First outer ring measuring point Second outer ring measuring point The subsurface stress-sensitive locations corresponding to the possible offset paths of the contact areas on both sides of the outer ring reference contact area; outer ring reference measuring points. The stress-sensitive location is set at the subsurface layer corresponding to the outer ring reference contact area.

[0027] By comparing the measuring points of the first outer ring With the second outer ring measuring point The change in response before and after loading can be used to determine the offset direction of the actual contact area between the i-th rolling element 233 and the outer ring 231 of the bearing relative to the reference contact area.

[0028] The two inner circle measuring points are respectively referred to as the first inner circle measuring point. Second inner circle measuring point .

[0029] First inner circle measuring point The second inner ring measuring point is located at the subsurface stress-sensitive position corresponding to the contact area of ​​the first inner ring. Located at the subsurface stress-sensitive location corresponding to the contact area of ​​the second inner ring.

[0030] By comparing the measuring points of the first inner circle Second inner circle measuring point The response changes can determine the relative response strength of the two inner ring contact areas, and thus determine the offset state of the inner ring side contact area.

[0031] Therefore, for the same rolling element 233, the corresponding first outer ring measuring point... Outer ring reference measuring points Second outer ring measuring point First inner circle measuring point Second inner circle measuring point This constitutes a five-point measurement group. This allows for the correlation testing of the single contact area of ​​the outer ring and the contact areas of the two semi-inner rings corresponding to the same rolling element.

[0032] Furthermore, the grooves used to set the above five measuring points include an outer ring first side groove 23a, an outer ring reference groove 23b, an outer ring second side groove 23c, a first half inner ring groove 23d, and a second half inner ring groove 23e.

[0033] The first side groove 23a of the outer ring is used to set the first outer ring measuring point. The outer ring reference groove 23b is used to set the outer ring reference measuring points. The second outer ring groove 23c is used to set the second outer ring measuring point. The first inner ring groove 23d is used to set the first inner ring measuring point. The second inner ring groove 23e is used to set the second inner ring measuring point. .

[0034] By placing the fiber Bragg grating sensor in the aforementioned groove, the fiber Bragg grating sensor is positioned close to the contact load transfer area between the rolling element 233 and the corresponding collar, thereby improving the response sensitivity of the fiber Bragg grating sensor to changes in subsurface stress in the local contact area.

[0035] Furthermore, the bearing subsurface stress testing device 2 includes a bearing outer ring cover 21, a fiber optic grating wiring structure 22, a bearing under test 23, a loading bearing seat 24, a shaft end cover 25, a loading plate 26, and a fiber optic rotary connector 27.

[0036] The outer ring 231 of the test bearing 23 is fixed inside the loading bearing housing 24, and the axial position of the outer ring 231 is restricted by the bearing outer ring cover 21.

[0037] The inner ring 234 of the test bearing 23 is mounted on the spindle of the spindle assembly 1 and is limited by the shaft end cover 25.

[0038] Loading plate 26 is used to transfer the loading force applied by bending moment loading device 5. and the axial load applied by the axial loading device 6 .

[0039] Furthermore, the fiber optic grating routing structure 22 includes an outer ring fiber guide groove 221, a first inner ring fiber guide groove 222, a second inner ring fiber guide groove 223, and an optical fiber bus 224.

[0040] The fiber optic cable on the outer ring side corresponding to the fiber optic grating sensor located on the outer ring 231 of the bearing is led out through the outer ring fiber guide groove 221.

[0041] The fiber optic cables on the inner ring side corresponding to the fiber optic grating sensors located in the first and second inner rings are led out through the first inner ring fiber guide groove 222 and the second inner ring fiber guide groove 223, respectively.

[0042] The first inner ring fiber guide groove 222 and the second inner ring fiber guide groove 223 extend along the main shaft axially and are arranged along the main shaft circumferentially to accommodate the fiber led out from the inner ring side and reduce the possibility of the fiber being squeezed, worn, tangled or twisted when the main shaft is rotated for positioning.

[0043] When the bearing inner ring remains stationary or the spindle is only positioned in small-angle steps during the test, the optical fiber on the inner ring side can be led out through the first inner ring fiber guide groove 222 and the second inner ring fiber guide groove 223.

[0044] When the spindle device 1 needs to drive the inner ring of the bearing to rotate to different circumferential test angle positions, the fiber optic cable on the inner ring side is connected to the rotating end of the fiber optic rotary connector 27, and the stationary end of the fiber optic rotary connector 27 is connected to the fiber optic bus 224, so as to stably transmit the signal of the fiber optic grating sensor on the inner ring side during the spindle rotation positioning process.

[0045] The outer ring optical fiber can be directly led out to the external optical fiber demodulation equipment through the outer ring fiber guide groove 221.

[0046] Furthermore, the spindle device 1 is used to adjust the bearing under test 23 to the set test angle position, so that the target rolling element 233 is aligned with the corresponding measuring point group. Establish a circumferential correspondence.

[0047] The radial loading device 3 is disposed in the radial direction of the bearing under test 23 and is used to apply a radial load to the bearing under test 23. The radial loading device 3 includes a radial loading actuator 31 and a radial force transmission element 32.

[0048] The bending moment loading device 5 is used to apply a loading force to the bearing under test 23 through the loading plate 26. The bending moment loading device 5 includes a bending moment loading rod 51 and a bending moment transmission connector 52.

[0049] Loading force A bending moment is generated on the tested bearing 23 by lever arm S. M Bending moment M satisfy: ; in, The loading force applied by the moment loading device 5, where S is the loading force. The lever arm relative to the tested bearing 23.

[0050] Axial loading device 6 is arranged along the spindle axis and is used to apply axial load to the test bearing 23. The axial loading device 6 includes an axial loading rod 61 and an axial force transmission connector 62.

[0051] By applying load individually or in combination to the radial loading device 3, the bending moment loading device 5, and the axial loading device 6, the tested bearing 23 can be subjected to axial load. radial load and bending moment M A static test state in which one or more of the following functions work together.

[0052] The present invention also provides a method for testing the subsurface stress and distributed contact state of a three-point contact ball bearing based on the above-mentioned testing device, comprising the following steps.

[0053] S1. Layout of measuring points.

[0054] Based on the structure of the test bearing 23 and the possible displacement range of the contact area under combined static load, the subsurface stress sensitive positions on the outer ring 231, the first half inner ring and the second half inner ring of the bearing are determined, and grooves are opened at the corresponding positions.

[0055] First outer ring measuring points are arranged at the subsurface stress-sensitive positions corresponding to the reference contact area of ​​the bearing outer ring 231 and at the subsurface stress-sensitive positions corresponding to the possible offset paths of the contact areas on both sides. Outer ring reference measuring points Second outer ring measuring point .

[0056] Measuring points of the first inner ring are respectively arranged at the subsurface stress-sensitive locations corresponding to the contact areas of the first and second inner rings. Second inner circle measuring point .

[0057] Make the first outer ring measuring point corresponding to the same rolling element 233 Outer ring reference measuring points Second outer ring measuring point First inner circle measuring point Second inner circle measuring point Form a measuring point group .

[0058] Set up corresponding measuring point groups according to the number and circumferential position of the rolling elements 233 in the tested bearing 23. This makes the rolling element 233 and the measuring point group... Establish a circumferential correspondence.

[0059] S2, Baseline State Test.

[0060] The bearing under test 23, after being grooved and fitted with a fiber optic grating sensor, is installed in the composite loading test apparatus.

[0061] The bearing 23 under test is adjusted to the set test angle position by the spindle device 1, so that the target rolling element 233 is aligned with the corresponding measuring point group. Establish a predetermined circumferential correspondence.

[0062] The reference strain response of each measuring point was collected under no-load conditions.

[0063] Let the first i Group of measuring points The reference strain response of the k-th measuring point under no-load condition is: ,in: .

[0064] S3, Static Loading and Response Acquisition.

[0065] Radial load is applied to the bearing under test 23 by one or more of the radial loading device 3, bending moment loading device 5, and axial loading device 6. Bending moment M and axial load One or more static loads in the process.

[0066] After the load reaches the set state and remains stable, the static wavelength drift signal of each fiber grating measuring point is collected, and the strain response of each measuring point after loading stabilization is obtained based on the collected static wavelength drift signal. .

[0067] S4. Calculation of subsurface stress response.

[0068] For the i-th measurement point group The k-th measuring point is used to determine the strain response after loading stabilizes. and the reference strain response under no-load conditions Determine the effective load strain response at this measuring point. : ;in, i Indicates the first i The circumferential measuring point group corresponding to each rolling element 233 .

[0069] The effective load strain response It is used to characterize the local subsurface stress-related strain increment near the corresponding measuring point after loading due to changes in contact state.

[0070] Furthermore, the i-th measurement point group Effective load strain response at the k-th measuring point Convert to the corresponding subsurface stress characterization value : ;in, For the i-th measurement point group The groove structure correction coefficient corresponding to the kth measuring point is E, where E is the elastic modulus of the 23 ring material of the tested bearing.

[0071] Trench structure correction factor It can be obtained through finite element simulation or calibration test, and is used to consider the influence of the grooved ring structure on the relationship between the local strain at the measuring point and the actual subsurface stress response.

[0072] S5. Distributed contact state discrimination.

[0073] First, based on the difference in effective load strain response between the outer ring measuring points corresponding to the same rolling element 233, the offset direction of the contact area between the rolling element 233 and the bearing outer ring 231 is determined.

[0074] For the i For each rolling element 233, define the outer ring subsurface stress offset discrimination value at its corresponding position. for: ; in, Indicates the second outer ring measuring point The effective load strain response, Indicates the first outer ring measuring point The effective load strain response.

[0075] when: At that time, it indicates the second outer ring measuring point The subsurface stress-related response on the side relative to the first outer ring measuring point The side that is stronger is determined by the first. i The contact area between the rolling element 233 and the outer ring 231 of the bearing extends towards the measuring point on the second outer ring. Offset on the side where it is located.

[0076] when: At that time, it indicates the first outer ring measuring point The subsurface stress-related response on the side relative to the second outer ring measuring point The side that is stronger is determined by the first. i The contact area between the rolling element 233 and the outer ring 231 of the bearing extends towards the measuring point of the first outer ring. Offset on the side where it is located.

[0077] when: At that time, determine the first outer ring measuring point. Second outer ring measuring point The difference in response between the two sides did not reach the set discrimination level. i The contact area between the rolling element 233 and the outer ring 231 of the bearing is not significantly offset.

[0078] in, The threshold for determining the offset of the outer contact area can be determined based on finite element simulation results or calibration loading tests.

[0079] Furthermore, based on the difference in effective load strain response between the two inner ring measuring points corresponding to the same rolling element 233, the relative response state of the corresponding contact areas of the first half inner ring and the second half inner ring is determined.

[0080] Definition of the first i Stress discrimination value of the inner ring subsurface layer at the corresponding position of each rolling element 233 for: ; in, For the first inner circle measuring point The corresponding effective load strain response, For the second inner circle measuring point The corresponding effective load strain response.

[0081] when: At that time, the second inner circle measuring point The response of the corresponding second inner ring contact area is stronger than that of the first inner ring measuring point. The corresponding first half of the inner ring contact area is determined to be the entire contact area towards the second inner ring measuring point. Offset on the side where it is located.

[0082] when: At that time, the first inner circle measuring point The response of the first half of the inner ring contact area is stronger than that of the second inner ring measuring point. The corresponding second half of the inner ring contact area is determined to be in the direction of the entire contact area towards the first inner ring measuring point. Offset on the side where it is located.

[0083] when: When the response difference between the two contact areas of the first and second inner rings is not significant, the inner ring contact area shift is not significant or is in a near-equilibrium state.

[0084] in, The threshold for determining the offset of the inner ring contact area can be determined through finite element simulation or calibration loading test.

[0085] Different sets of measuring points were obtained sequentially along the circumference of the bearing. Corresponding outer ring subsurface stress offset discrimination quantity and inner ring subsurface stress discrimination quantity It is possible to obtain the changes in contact response at different circumferential positions of the rolling element 233.

[0086] Further combining the subsurface stress characterization values ​​corresponding to each measuring point This allows us to determine the response strength, main load-bearing area, and maximum contact response location at different circumferential positions, thereby obtaining the axial load. radial load and bending moment M The distributed contact state of a three-point contact ball bearing under one or more combined static loads.

[0087] The beneficial effects of this invention are as follows: (1) In view of the unique relationship between the outer ring and the inner ring of the three-point contact ball bearing, the present invention establishes a five-point grouping structure consisting of three measuring points on the outer ring and two measuring points on the inner ring at the corresponding position of the same rolling element, so that the local subsurface stress response of the single contact area of ​​the outer ring and the two half contact areas of the inner ring can be correlated and tested, thereby realizing the synchronous testing of the local subsurface stress of the inner and outer rings of the three-point contact ball bearing.

[0088] (2) Based on the stress sensitivity of the subsurface layer under the combined static load of the three-point contact ball bearing, grooves are made at the corresponding stress-sensitive positions of the bearing rings, and the remaining wall thickness is retained between the bottom of the groove and the raceway profile.h While ensuring test sensitivity, the structural strength and fatigue safety requirements of the bearing rings are also taken into account, enabling the fiber optic grating sensor to effectively sense the local subsurface stress-related strain changes caused by contact load transmission.

[0089] (3) The first outer ring measuring point Second outer ring measuring point Possible offset paths are set on both sides of the outer ring reference contact area, and the offset direction of the outer ring contact area is determined by differential comparison of the responses of the measuring points on both sides; simultaneously, the offset direction of the outer ring contact area is determined by the first inner ring measuring point. Second inner circle measuring point The differential comparison determines the relative response state of the two semi-inner ring contact areas, thus enabling the actual distribution contact state of the bearing under combined static load to be deduced from the measured local response.

[0090] (4) The present invention is equipped with a radial loading device, a bending moment loading device and an axial loading device, which can apply one or more of radial load, bending moment and axial load to the bearing under test, so as to realize the test of subsurface stress and distribution contact state of three-point contact ball bearing under different composite static load conditions.

[0091] (5) The present invention provides a fiber optic grating routing structure and a fiber optic rotary connector, so that the optical fibers set in the two semi-inner rings can maintain stable signal transmission when the main shaft is adjusted and positioned at different test angles, reducing the possibility of the optical fibers getting tangled, twisted or damaged during the corner positioning process.

[0092] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0093] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1(a) shows the three-point contact ball bearing model under axial load. =1 kN, radial load Schematic diagram of the circumferential distribution of subsurface stress-related response under the combined action of 2 kN; Figure 1(b) shows the three-point contact ball bearing model under axial load. =1 kN, radial load =2 kN, bending moment M Schematic diagram of the circumferential distribution of subsurface stress-related response under the combined action of 10 N·m; Figure 2(a) is a schematic diagram of the arrangement of the measuring points for a single rolling element corresponding to five measuring points in this invention, and the remaining wall thickness of the groove. h A magnified view of a portion of the image; Figure 2(b) is a schematic diagram of the circumferential distribution relationship between the n sets of measuring points in the full circumference and each rolling element in this invention. Figure 2(c) is a schematic diagram of the cross-sectional structure of the inner and outer rings of the tested three-point contact ball bearing after the groove modification in this invention; Figure 3(a) is a partial cross-sectional schematic diagram of the bearing subsurface stress testing device and fiber optic grating trace structure in this invention. Figure 3(b) is a schematic diagram of the outer ring fiber guide groove structure set at the position adjacent to the load bearing seat or the outer ring cover of the bearing in this invention; Figure 4 This is a schematic diagram of the overall structure of the three-point contact ball bearing composite loading test device based on fiber Bragg grating of the present invention.

[0094] Reference numerals: 1. Spindle assembly; 2. Bearing subsurface stress testing device; 3. Radial loading device; 31. Radial loading actuator; 32. Radial force transmission component; 4. Bearing housing; 5. Bending moment loading device; 51. Bending moment loading rod; 52. Bending moment force transmission connector; 6. Axial loading device; 61. Axial loading rod; 62. Axial force transmission connector; 21. Bearing outer ring cover; 22. Fiber optic grating wiring structure; 23. Bearing under test; 24. Loading bearing housing; 25. Shaft 26. End cap; 27. Loading plate; 28. Fiber optic rotary connector; 221. Outer ring fiber guide groove; 222. First inner ring fiber guide groove; 223. Second inner ring fiber guide groove; 224. Fiber optic bus; 231. Bearing outer ring; 232. Subsurface stress characterization measurement point; 233. Rolling element; 234. Bearing inner ring; 23a. Outer ring first side groove; 23b. Outer ring reference groove; 23c. Outer ring second side groove; 23d. First half inner ring groove; 23e. Second half inner ring groove. Detailed Implementation

[0095] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0096] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0097] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0098] Example 1: Structure of stress measuring points on the secondary surface of a three-point contact ball bearing In this embodiment, a double-half-inner-ring type three-point contact ball bearing is used as the test bearing 23.

[0099] The test bearing 23 includes an outer ring 231, a first inner ring, a second inner ring, and a plurality of rolling elements 233 disposed between the outer ring 231 and the two inner rings. Each rolling element 233 forms an outer ring contact point with the outer ring 231, and simultaneously forms two inner ring contact points with the first and second inner rings respectively, thus constituting a three-point contact relationship.

[0100] As shown in Figures 1(a) and 1(b), the distribution of contact stress-related responses along the circumferential direction of each raceway in a three-point contact ball bearing differs under different combined static load conditions.

[0101] Figure 1(a) shows the axial load. =1 kN and radial load The circumferential distribution of the contact response of the first half inner raceway, the second half inner raceway, and the outer raceway when 2 kN are applied together.

[0102] Figure 1(b) shows the further application of bending moment. M Circumferential distribution of contact response after 10 N·m.

[0103] Comparing Figure 1(a) and Figure 1(b), it can be seen that the addition of bending moment causes changes in the peak response position, response amplitude, and circumferential bearing area of ​​the first half inner ring raceway, the second half inner ring raceway, and the outer ring raceway. This indicates that under the action of combined static load, the actual contact area of ​​the three-point contact ball bearing can shift relative to the original reference contact area.

[0104] Therefore, this embodiment does not directly infer the contact state from the external load itself, but instead infers the distributed contact state by measuring the local subsurface stress response of the collar near the three contact points.

[0105] As shown in Figure 2(a), grooves are formed on the outer ring 231, the first half-inner ring, and the second half-inner ring of the bearing under test 23, and fiber optic grating sensors are arranged in each groove. Indicates the first i Each rolling element corresponds to the first outer ring measuring point in the measuring point group; Indicates the first i Each rolling element corresponds to the outer ring reference measuring point in the measuring point group; Indicates the first i Each rolling element corresponds to the second outer ring measuring point in the measuring point group; Indicates the first i Each rolling element corresponds to the first inner ring measuring point in the measuring point group; Indicates the first i The second inner ring measuring point in the measuring point group corresponding to each rolling element; h This indicates the remaining wall thickness between the bottom of the groove and the raceway profile.

[0106] With the first i Taking a rolling element 233 as an example, a set of measuring points is set at its corresponding position. .

[0107] measuring point group Including the first outer ring measuring points Outer ring reference measuring points Second outer ring measuring point First inner circle measuring point Second inner circle measuring point .

[0108] Among them, the outer ring reference measuring points The stress-sensitive position is located at the subsurface layer corresponding to the reference contact area of ​​the bearing outer ring 231.

[0109] First outer ring measuring point Second outer ring measuring point They are respectively set at the outer ring reference measuring points Both sides, and respectively corresponding to the subsurface stress-sensitive areas that the contact area may pass through when it shifts to both sides.

[0110] Therefore, when the actual contact area between the rolling element 233 and the bearing outer ring 231 shifts relative to the reference contact area, the first outer ring measuring point... Second outer ring measuring point It can produce varying degrees of local strain response changes.

[0111] First inner circle measuring point It is located at the subsurface stress-sensitive position corresponding to the contact area of ​​the first half inner ring.

[0112] Second inner circle measuring point It is located at the subsurface stress-sensitive position corresponding to the contact area of ​​the second half inner ring.

[0113] Due to the i Each rolling element 233 forms two contact points with the first and second inner rings, respectively. When the contact load corresponding to the two contact points changes, the stress-related strain response of the subsurface layer in the vicinity also changes accordingly. Therefore, this can be observed through the measuring point on the first inner ring. Second inner circle measuring point The response difference between the two inner rings characterizes the relative load-bearing state between the two inner ring contact points.

[0114] As shown in the enlarged area in Figure 2(a), the remaining wall thickness is retained between the bottom of the groove and the corresponding raceway profile. h .

[0115] For the remaining wall thickness h The determination of the remaining wall thickness, on the one hand, is based on the fact that... h If the thickness is too large, the local strain response generated when the contact load between the rolling element and the raceway is transferred to the bottom of the groove may be weak, which is not conducive to the fiber optic grating sensor accurately acquiring changes in the contact state; on the other hand, if the remaining wall thickness is too large... h If it is too small, it may weaken the local structural strength of the ring.

[0116] Therefore, this embodiment is first based on the test bearing 23 under axial load. radial load and bending moment M The trench layout area is determined by the contact area offset range under action and the subsurface stress-sensitive area, and then the remaining wall thickness is determined by combining the subsurface stress test sensitivity. h The maximum allowable value is determined, and the remaining wall thickness is determined in conjunction with the ring strength and fatigue safety requirements. h The minimum allowable value is used to determine the remaining wall thickness of the target within a range that simultaneously meets the requirements of test sensitivity and structural safety. h .

[0117] As shown in Figure 2(b), when the tested bearing 23 has nWhen there are 233 rolling elements, they are set accordingly along the circumferential direction. n Group of measuring points This ensures that each rolling element 233 corresponds to a set of measuring points. .

[0118] Therefore, different sets of measuring points distributed along the circumference of the bearing can be used. The local subsurface stress response at the circumferential position of each rolling element 233 is obtained, thereby further obtaining the load distribution and contact state variation law of the entire bearing along the circumferential direction.

[0119] As shown in Figure 2(c), corresponding to the first outer ring measuring point Outer ring reference measuring points Second outer ring measuring point The outer ring first side groove 23a, the outer ring reference groove 23b, and the outer ring second side groove 23c are respectively set; corresponding to the measuring points of the first inner ring. Second inner circle measuring point The first half of the inner ring groove 23d and the second half of the inner ring groove 23e are respectively set.

[0120] The fiber Bragg grating sensor is attached to the corresponding groove so that the fiber Bragg grating sensor is close to the area where the corresponding contact load is transferred.

[0121] Example 2: Fiber Bragg grating routing and composite loading test device As shown in Figure 3(a), the bearing subsurface stress testing device 2 includes a bearing outer ring cover 21, a fiber optic grating wiring structure 22, a bearing under test 23, a loading bearing seat 24, a shaft end cover 25, a loading plate 26, and a fiber optic rotary connector 27.

[0122] The outer ring 231 of the test bearing 23 is installed in the loading bearing housing 24 and is axially limited by the bearing outer ring cover 21.

[0123] The inner ring 234 of the test bearing 23 is mounted on the spindle of the spindle assembly 1 and is limited by the shaft end cover 25.

[0124] Since the outer ring 231 of the test bearing 23 remains stationary relative to the load bearing housing 24 during the test, the optical fiber set on the outer ring 231 can be directly led out through the outer ring fiber guide groove 221.

[0125] As shown in Figure 3(b), the outer ring fiber guide groove 221 is located adjacent to the load bearing seat 24 and the bearing outer ring cover 21, and avoids the pressing area and end cover mating area of ​​the bearing outer ring 231, so that the optical fiber on the outer ring side can be led out from near the bearing outer ring 231 to the outside, while reducing the possibility of the optical fiber being squeezed, bent or worn during assembly, pressing and loading.

[0126] For the fiber optic grating sensors located in the first and second inner rings, their corresponding optical fibers are led out through the first inner ring fiber guide groove 222 and the second inner ring fiber guide groove 223, respectively.

[0127] The first inner ring fiber guide groove 222 and the second inner ring fiber guide groove 223 extend along the main shaft axial direction.

[0128] When the spindle is adjusted to different circumferential test angle positions, the inner ring side fiber is connected to the rotating end of the fiber optic rotary connector 27. The stationary end of the fiber optic rotary connector 27 is connected to the external fiber optic demodulation equipment through the fiber optic bus 224, thereby avoiding continuous entanglement or twisting of the inner ring side fiber during the spindle rotation.

[0129] like Figure 4 As shown, Indicates axial load; Indicates radial load; This indicates the loading force applied by the moment loading device; S The lever arm is indicated. The composite loading test device in this embodiment includes a main shaft device 1, a bearing subsurface stress testing device 2, a radial loading device 3, a bearing housing 4, a bending moment loading device 5, and an axial loading device 6.

[0130] The spindle assembly 1 is used to support the inner ring 234 of the bearing under test 23 and to adjust the bearing under test 23 to different set test angle positions.

[0131] The radial loading device 3 is disposed in the radial direction of the bearing under test 23, and includes a radial loading actuator 31 and a radial force transmission element 32, for applying radial load to the bearing under test 23. .

[0132] The bending moment loading device 5 includes a bending moment loading rod 51 and a bending moment force transmission connector 52, which applies a loading force to the tested bearing 23 through the loading plate 26. .

[0133] Loading force A lever arm S is present relative to the bearing under test 23, thereby creating a bending moment on the bearing under test 23. M ,Right now: .

[0134] The axial loading device 6 is arranged along the axial direction of the main shaft and includes an axial loading rod 61 and an axial force transmission connector 62, used to apply axial load to the test bearing 23. .

[0135] Therefore, the radial loading device 3, the bending moment loading device 5, and the axial loading device 6 can be controlled separately according to the combined stress condition to be simulated, so that the bearing under test 23 is subjected to radial load. Bending moment Mand axial load Static loading states that function individually or in combination.

[0136] Example 3: Subsurface Stress and Distribution Contact State Test The structures described in Examples 1 and 2 were used for testing.

[0137] First, the bearing under test 23 is installed in the bearing subsurface stress testing device 2, and the circumferential angular position of the bearing under test 23 is adjusted by the spindle device 1 so that the target rolling element 233 is aligned with the predetermined measuring point group. A corresponding relationship is formed.

[0138] Without applying an external load, the measurement points were collected separately. The first outer circle measuring point Outer ring reference measuring points Second outer ring measuring point First inner circle measuring point Second inner circle measuring point The reference strain response.

[0139] No. i The reference strain response of the k-th measuring point in the set of measuring points is denoted as . .

[0140] Subsequently, an axial load was applied to the test bearing 23 according to the test conditions. radial load and bending moment M One or more of them.

[0141] After the load reaches the predetermined state and remains stable, the static wavelength drift signal at each measuring point is acquired using fiber Bragg grating sensors to obtain the strain response at each measuring point after the load has stabilized. .

[0142] Calculate the first i The first measurement point group k Effective load strain response at each measuring point : .

[0143] Therefore, the existing initial strain response at the corresponding measuring point under no-load conditions can be eliminated using the reference value, making... It is used to characterize the local subsurface stress-related strain changes near the corresponding measuring point after loading, caused by changes in contact state.

[0144] Based on the elastic modulus of the ring material E and the i In the group of measuring points, the first k Correction coefficient for trench structure at each measuring point The subsurface stress characterization values ​​at the corresponding measuring points were obtained. : .

[0145] Among them, the trench structure correction coefficient The specific trench structure and measuring point location are determined through finite element simulation or calibration tests.

[0146] For bearing outer ring 231, calculate the stress offset discrimination factor of the subsurface layer of the outer ring: .

[0147] like Then the second outer ring measuring point The response relative to the first outer ring measuring point More powerful, determining the contact area between the rolling element 233 and the bearing outer ring 231 towards the second outer ring measuring point. Offset on the side where it is located.

[0148] like Then the first outer ring measuring point The response relative to the second outer ring measuring point More powerful, determining the contact area between the rolling element 233 and the bearing outer ring 231 towards the first outer ring measuring point. Offset on the side where it is located.

[0149] like If the outer contact area is not significantly shifted to either side, then it can be determined that the shift is not obvious.

[0150] For the first and second halves of the inner ring, calculate the subsurface stress discrimination factor of the inner ring: .

[0151] like Then the second inner circle measuring point The response of the corresponding contact area is stronger than that of the first inner ring measuring point. Based on the response of the corresponding contact area, it is determined that the entire inner ring contact area is directed towards the second inner ring measuring point. Offset on the side where it is located.

[0152] like Then the first inner circle measuring point The response of the corresponding contact area is stronger than that of the second inner ring measuring point. Based on the response of the corresponding contact area, it is determined that the entire inner ring contact area is directed towards the first inner ring measuring point. Offset on the side where it is located.

[0153] like If the response difference between the two inner ring contact areas is not significant, it can be determined that the inner ring contact area shift is not significant or is in a state of near equilibrium.

[0154] Among them, the outer contact area offset discrimination threshold and the threshold for judging the offset of the inner contact area. It can be determined through finite element simulation or calibration loading test, respectively.

[0155] The above method was used to set up each measuring point group along the circumference of the bearing. By performing response analysis sequentially, the offset state of the outer ring contact area corresponding to the circumferential position of different rolling elements 233 and the relative response state of the contact areas of the first half inner ring and the second half inner ring can be obtained.

[0156] By further combining the subsurface stress characterization values ​​corresponding to each measuring point, the intensity of the subsurface stress response, the main load-bearing area, and the location of the maximum contact response at each circumferential position can be obtained, thereby reflecting the test bearing 23 under the current axial load. radial load and bending moment M Actual distributed contact state under combined conditions.

[0157] When changing axial load radial load Or bending moment M After one or more of these steps, the above-mentioned no-load reference acquisition, static loading, response acquisition, and distributed contact state discrimination processes can be repeated to obtain the variation law of contact area offset and circumferential load distribution of the three-point contact ball bearing under different composite static load conditions.

[0158] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A device for testing the subsurface stress and distributed contact state of a three-point contact ball bearing based on a fiber Bragg grating, characterized in that, It includes a spindle assembly, a bearing subsurface stress testing device, a radial loading device, a bearing housing, a bending moment loading device, and an axial loading device; The bearing subsurface stress testing device includes a test bearing, which is a three-point contact ball bearing, including an outer ring, a first half-inner ring, a second half-inner ring, and a plurality of rolling elements disposed between the outer ring and the first half-inner ring and the second half-inner ring, wherein a single rolling element forms contact with the outer ring, the first half-inner ring, and the second half-inner ring respectively. The outer ring, the first semi-inner ring, and the second semi-inner ring are each provided with grooves for arranging fiber Bragg grating sensors. The fiber Bragg grating sensors are grouped according to the number and circumferential position of the rolling elements. The bearing under test is provided with [number of sensors] circumferentially. n For each scrolling element, set the corresponding value. n Group of measuring points , i =1, 2, ..., n ; Each of the aforementioned measurement point groups Including the first outer ring measuring point set on the outer ring. Outer ring reference measuring points Second outer ring measuring point And measuring points on the first inner ring respectively set on the first half of the inner ring and the second half of the inner ring. Second inner circle measuring point The first outer ring measuring point Second outer ring measuring point The outer ring reference measuring points are located at the subsurface stress-sensitive positions corresponding to the possible offset paths of the contact areas on both sides of the outer ring reference contact area. The first inner ring measuring point is located at the subsurface stress-sensitive position corresponding to the outer ring reference contact area. Second inner circle measuring point The subsurface stress-sensitive locations are respectively located in the contact areas of the first and second inner rings. The spindle device is used to adjust the bearing under test to a set test angle position, so that the target rolling element is aligned with the corresponding test point group. Establish circumferential correspondence; The radial loading device is used to apply a radial load to the bearing under test. The axial loading device is used to apply an axial load to the bearing under test. The bending moment loading device is used to apply a bending moment to the bearing under test. M So that the tested bearing is subjected to axial load. radial load and bending moment M Static test state under one or more of the following effects; Each of the fiber optic grating sensors is used to acquire the strain response at the corresponding subsurface stress-sensitive location, so as to measure the strain at the first outer ring measuring point corresponding to the same rolling element. Outer ring reference measuring points Second outer ring measuring point First inner circle measuring point Second inner circle measuring point The strain response determines the distributed contact state between the rolling element and the outer ring, the first half of the inner ring, and the second half of the inner ring.

2. The device for testing the subsurface stress and distributed contact state of a three-point contact ball bearing based on a fiber Bragg grating according to claim 1, characterized in that, The groove includes an outer ring first side groove, an outer ring reference groove and an outer ring second side groove disposed on the outer ring, as well as a first half inner ring groove and a second half inner ring groove disposed on the first half inner ring and the second half inner ring respectively. First outer ring measuring point Outer ring reference measuring points Second outer ring measuring point The measuring points of the first inner ring are respectively set in the first side groove of the outer ring, the reference groove of the outer ring, and the second side groove of the outer ring. Second inner circle measuring point They are respectively disposed in the first half of the inner ring groove and the second half of the inner ring groove; The bottom of the groove has residual wall thickness between it and the corresponding raceway profile. h The remaining wall thickness h The determination is based on the possible offset range of the contact area, the sensitivity of the subsurface stress response, the installation space of the fiber Bragg grating sensor, and the safety requirements for the strength of the collar.

3. The device for testing the subsurface stress and distributed contact state of a three-point contact ball bearing based on a fiber Bragg grating according to claim 1, characterized in that, The bearing subsurface stress testing device also includes a bearing outer ring cover, a fiber optic grating wiring structure, a loading bearing housing, a shaft end cover, a loading plate, and a fiber optic rotary connector. The outer ring of the bearing under test is fixed in the bearing housing and is axially limited by the bearing outer ring cover. The first and second inner rings of the bearing under test are mounted on the spindle of the spindle assembly and are limited by the shaft end cover. The loading plate is used to transmit the loading force applied by the bending moment loading device and the axial load applied by the axial loading device.

4. The device for testing the subsurface stress and distributed contact state of a three-point contact ball bearing based on a fiber Bragg grating according to claim 3, characterized in that, The fiber grating routing structure includes an outer ring fiber guide groove, a first inner ring fiber guide groove, a second inner ring fiber guide groove, and a fiber bus. The fiber optic cable of the fiber optic grating sensor located on the outer ring is led out through the outer ring fiber guide groove. The fiber optic cables of the fiber optic grating sensors located on the first and second inner rings are led out through the first and second inner ring fiber guide grooves respectively and connected to the rotating end of the fiber optic rotary connector. The stationary end of the fiber optic rotary connector is connected to the fiber optic bus to transmit the signal of the inner ring fiber optic grating sensor when the spindle device is adjusting the angle and positioning.

5. The device for testing the subsurface stress and distributed contact state of a three-point contact ball bearing based on a fiber Bragg grating according to claim 3, characterized in that, The bending moment loading device applies a loading force to the bearing under test through the loading plate. The loading force The position of action has a lever arm with respect to the bearing under test. S To form a satisfactory shape on the tested bearing. bending moment M .

6. A method for testing the subsurface stress and distributed contact state of a three-point contact ball bearing based on a fiber Bragg grating, characterized in that, Includes the following steps: S1. Grooves are made in the outer ring, the first half of the inner ring, and the second half of the inner ring of the tested three-point contact ball bearing. Measurement points of the first outer ring are arranged at the subsurface stress-sensitive positions corresponding to the reference contact area of ​​the outer ring and the subsurface stress-sensitive positions corresponding to the possible offset paths of the contact areas on both sides. Outer ring reference measuring points Second outer ring measuring point Measurement points for the first inner ring are arranged at the subsurface stress-sensitive locations corresponding to the contact areas of the first and second inner rings. Second inner circle measuring point The first outer ring measuring point corresponding to the same rolling element Outer ring reference measuring points Second outer ring measuring point First inner circle measuring point Second inner circle measuring point Form a measuring point group ; S2. Install the tested three-point contact ball bearing in the composite loading test device, and adjust the target rolling element to the corresponding test point group through the spindle device. The corresponding test angle positions were set, and the measurement point group was collected under no-load conditions. The reference strain response at each measuring point; S3. Apply an axial load to the tested three-point contact ball bearing. radial load and bending moment M One or more static loads are applied. After the load stabilizes, the static wavelength drift signal of the fiber optic grating at each measuring point is collected, and the strain response of each measuring point after loading stabilizes is obtained based on the static wavelength drift signal. S4. Obtain the effective load strain response of each measuring point based on the strain response after loading and stabilization and the corresponding reference strain response, and obtain the subsurface stress characterization value corresponding to each measuring point based on the effective load strain response. S5. Perform differential comparison of the effective load strain response at different measuring points on the outer ring corresponding to the same rolling element to determine the offset direction of the contact area between the rolling element and the outer ring, and perform differential comparison on the first inner ring measuring point. Second inner circle measuring point The effective load strain response is differentially compared to determine the relative contact response state between the rolling element and the first half inner ring and the second half inner ring. Based on the offset direction of the contact area and the relative contact response state, the distributed contact state of the three-point contact ball bearing under the combined static load is determined.

7. The method for testing the subsurface stress and distributed contact state of a three-point contact ball bearing based on a fiber Bragg grating according to claim 6, characterized in that, In S4, let the first... i Group of measuring points The first in k The reference strain response of each measuring point under no-load condition is as follows: The strain response after loading and stabilization is Then the first k Effective load strain response at each measuring point for: in, ; The first k Subsurface stress characterization values ​​at each measuring point for: in, For the first i Group of measuring points The Middle k The trench structure correction coefficients corresponding to each measuring point are obtained through finite element simulation or calibration tests. E The elastic modulus is the material of the three-point contact ball bearing rings of the test subject.

8. The method for testing the subsurface stress and distributed contact state of a three-point contact ball bearing based on a fiber Bragg grating according to claim 6 or 7, characterized in that, In S5, the first is defined i Discrimination of outer ring subsurface stress offset at corresponding position of each rolling element for: when At that time, the judgment of the first i The contact area between the rolling element and the outer ring extends towards the second outer ring measuring point. Offset on the side; when At that time, the judgment of the first i The contact area between the rolling element and the outer ring is measured towards the first outer ring point. Offset on the side; when At that time, the judgment of the first i The offset of the contact area between the rolling element and the outer ring is not obvious; in, The threshold for determining the offset of the outer contact area.

9. The method for testing the subsurface stress and distributed contact state of a three-point contact ball bearing based on a fiber optic grating according to claim 6 or 7, characterized in that, In S5, the first is defined i Discrimination of subsurface stress at the corresponding position of each rolling element on the inner ring for: when At that time, determine the second inner circle measuring point. The response of the corresponding second inner ring contact area is stronger than that of the first inner ring measuring point. The corresponding first half of the inner ring contact area, the contact area towards the second inner ring measuring point Offset on the side; when At that time, determine the first inner circle measuring point. The response of the first half of the inner ring contact area is stronger than that of the second inner ring measuring point. The corresponding second half of the inner ring contact area, the contact area towards the first inner ring measuring point Offset on the side; when When the response difference between the first half inner ring contact area and the second half inner ring contact area is not obvious, the contact area offset is not obvious or is in an approximately balanced state. in, The threshold for determining the offset of the inner contact area.

10. The method for testing the subsurface stress and distributed contact state of a three-point contact ball bearing based on a fiber Bragg grating according to claim 9, characterized in that, The outer ring contact area offset discrimination threshold And the inner ring contact area offset discrimination threshold The parameters, load conditions, and measuring point locations of the tested three-point contact ball bearings were determined through finite element simulation or calibration loading tests.

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