Method and device for testing wear resistance of self-lubricating gasket and method for optimizing assembly stress of self-lubricating joint bearing

Abstract

The invention provides a method and a device for testing the wear resistance of a self-lubricating gasket and a method for optimizing the assembly stress of a self-lubricating knuckle bearing. The method for testing the wear resistance of the self-lubricating gasket comprises the following steps: attaching the self-lubricating gasket to the surface of a substrate; a pressure load is applied to the surface of the base body attached with the self-lubricating gasket, the pressure load is determined based on preset pressure stress and the area of the surface of the base body attached with the self-lubricating gasket, and the preset pressure stress is set according to the assembly stress of the self-lubricating knuckle bearing installed on the bearing seat; and carrying out friction test on the self-lubricating gasket after the pressure load is applied, and evaluating the wear resistance of the self-lubricating gasket. According to the method, the stress condition of the self-lubricating gasket in the actual service process after the self-lubricating joint bearing is mounted on the bearing race in an interference manner can be simulated without using a finished bearing, and the influence of the assembly stress of the self-lubricating joint bearing on the wear resistance of the self-lubricating gasket can be accurately evaluated; and guidance is provided for optimization of installation and fixing process parameters and service parameters of the self-lubricating bearing.

Description

Technical Field

[0001] The present invention relates to the technical field of friction testing, and particularly to a method and device for testing the wear resistance of a self-lubricating gasket, and a method for optimizing the assembly stress of a self-lubricating spherical plain bearing. Background Art

[0002] A self-lubricating spherical plain bearing consists of an outer ring, an inner ring and a self-lubricating gasket, and can bear high loads, with good self-lubrication and impact resistance, and is widely used in the industrial field. Compared with traditional bearings, self-lubricating bearings rely on their self-lubricating gaskets, without the need for additional lubricants, reducing the risk of oil leakage and improving environmental performance. The self-lubricating gasket is composed of woven fibers and a resin matrix, and its friction performance is affected by various factors, and the combined effect of these factors determines the service safety and service life of the bearing.

[0003] At present, many studies have explored the friction performance of gaskets in different environments, including high temperature, vacuum and underwater environments. These studies have found that when the bearing is in service, the friction performance of the self-lubricating gasket therein will change with different environmental conditions. Therefore, it is very necessary to test the friction performance of the self-lubricating gasket according to the actual service conditions. However, in addition to the influence of environmental conditions, when the self-lubricating spherical plain bearing is installed on the bearing seat ring, an interference fit is usually used to ensure safety and reliability. This installation method will cause compressive stress to be generated on the outer ring of the bearing, and this compressive stress will be transmitted to the self-lubricating gasket through the outer ring of the bearing, affecting the fiber structure and the state and distribution of the resin matrix of the gasket, and further affecting its subsequent self-lubricating ability, that is, the friction performance under actual service conditions.

[0004] In the laboratory, the pin-on-disc and ball-on-disc devices in the ASTM G99-23 standard are usually used to conduct friction tests on materials. These two test methods are usually carried out under non-abrasive conditions. By pressing a pin or ball with a specific material and shape on the surface of the material to be tested, and testing under specific load, speed and time conditions, the friction and wear behavior of the material to be tested can be evaluated. In these two standard friction test methods, the test conditions can be precisely controlled, but there are differences between the laboratory environment and the actual application scenario, and in the existing studies, it is impossible to directly test the wear resistance of the self-lubricating gasket after being subjected to the compressive stress during the assembly process by this method.

[0005] According to the SAE AS 81820 standard, the bearing swing friction and wear test is usually used to test the wear resistance of self-lubricating pads for bearings. The test sample used in this test device is a complete bearing sample, which is installed on the bearing housing and the axial and radial load values corresponding to the bearings of the corresponding specifications are applied. After 25,000 cycles of ±25° swing, the wear amount of the test pad is measured to evaluate its wear resistance. This bearing swing friction and wear test actually simulates the influence of the working load received under the bearing service conditions on the friction performance of the pad. However, since the test specimen required for this test device is the finished product of the bearing, if it is used to test the influence of the assembly process compressive stress on the wear resistance of the pad, it will cause more material waste. Summary of the Invention

[0006] The purpose of the present invention is to provide a test method and device for the wear resistance of self-lubricating pads, and an optimization method for the assembly stress of self-lubricating spherical bearings, without using finished bearings to solve the above problems. In other words, the present invention can simulate the stress situation of the self-lubricating pad during actual service after the self-lubricating spherical bearing is press-fitted onto the bearing seat ring, accurately evaluate the influence of the assembly stress of the self-lubricating spherical bearing on the wear resistance of the self-lubricating pad, and provide guidance for the optimization of the installation and fixing process parameters and service parameters of the self-lubricating bearing.

[0007] The present invention provides a test method for the wear resistance of a self-lubricating pad, the self-lubricating pad being used for a self-lubricating spherical bearing, comprising the following steps:

[0008] Attach the self-lubricating pad to the surface of the substrate.

[0009] Apply a pressure load to the surface of the substrate attached with the self-lubricating pad, the pressure load being determined based on a preset compressive stress and the area of the surface of the substrate attached with the self-lubricating pad, the preset compressive stress being set according to the assembly stress when the self-lubricating spherical bearing is installed on the bearing housing.

[0010] Perform a friction test on the self-lubricating pad after the pressure load is applied, and evaluate the wear resistance of the self-lubricating pad.

[0011] In one embodiment, the performing a friction test on the self-lubricating pad after the pressure load is applied and evaluating the wear resistance of the self-lubricating pad specifically includes:

[0012] Apply a friction load perpendicular to the surface of the self-lubricating pad to the self-lubricating pad after the pressure load is applied, and set the friction speed and friction time.

[0013] Measure the real-time shear force on the self-lubricating pad during the friction process.

[0014] Calculate the friction coefficient of the self-lubricating pad based on the shear force and the friction load. The smaller the friction coefficient, the better the wear resistance of the self-lubricating pad.

[0015] In one embodiment, the self-lubricating gasket is adhered to the surface of the substrate by a resin adhesive.

[0016] In one embodiment, before applying a pressure load to the surface of the substrate with the self-lubricating gasket attached, the self-lubricating gasket attached to the surface of the substrate is heated and press-cured. The parameters of the heating and press-curing are determined according to the resin components of the self-lubricating gasket and the type of the resin adhesive. The parameters of the heating and curing include the curing temperature, the curing time, and the curing pressure.

[0017] In one embodiment, the surface of the substrate with the self-lubricating gasket attached is a plane, and the method of applying a pressure load to the surface of the substrate with the self-lubricating gasket attached is flat die compression;

[0018] The pressure load is the product of a preset compressive stress and the area of the surface of the substrate with the self-lubricating gasket attached.

[0019] In one embodiment, self-lubricating gaskets are respectively attached to two opposite surfaces of the substrate.

[0020] In one embodiment, the self-lubricating gasket is circular. When performing a friction test on the self-lubricating gasket after applying a pressure load, the friction is along the circumference at a radius from the center of the self-lubricating gasket radius.

[0021] The present invention also provides an optimization method for the assembly stress of a self-lubricating spherical plain bearing, including the following steps:

[0022] Design a plurality of different preset compressive stresses, and the preset compressive stresses are determined according to the assembly stress when the self-lubricating spherical plain bearing is installed on the bearing seat;

[0023] Adopt the above-mentioned test method for the wear resistance of the self-lubricating gasket to respectively test the wear resistance of the self-lubricating gasket under each preset compressive stress;

[0024] Determine the optimal assembly stress for installing the self-lubricating spherical plain bearing on the bearing seat based on the wear resistance of the self-lubricating gasket under each preset compressive stress.

[0025] The present invention also provides a test device for the wear resistance of a self-lubricating gasket, which is used to implement the above-mentioned test method for the wear resistance of the self-lubricating gasket, and includes:

[0026] A substrate for attaching the self-lubricating gasket;

[0027] A pressure application component for applying a pressure load to the surface of the substrate with the self-lubricating gasket attached;

[0028] Friction assembly, including a carrier table, a friction head and a friction controller, the base body is detachably connected to the carrier table, the friction head is arranged perpendicular to the carrier table, and the friction controller is connected to the friction head to control the friction load, friction speed and / or friction time of the friction head;

[0029] Shearing force sensor, connected to the friction head, to measure the real-time shearing force of the friction head on the self-lubricating gasket during the friction process.

[0030] In one embodiment, the base body is made of metal material;

[0031] The base body includes a disc and a plurality of lugs, the number of the lugs is not less than 3, the lugs are evenly distributed along the circumference of the disc, and the height of the lugs is the same as that of the disc.

[0032] In one embodiment, the pressure application assembly includes a first flat die pressing plate, a second flat die pressing plate and a pressure controller;

[0033] The first flat die pressing plate and the second flat die pressing plate are arranged relatively parallel;

[0034] The pressure controller is used to control the pressure load between the first flat die pressing plate and the second flat die pressing plate.

[0035] Compared with the prior art, the beneficial effects of the test method and device for the wear resistance of the self-lubricating gasket and the optimization method for the assembly stress of the self-lubricating spherical plain bearing of the present invention are as follows:

[0036] 1) The test method for the wear resistance of the self-lubricating gasket of the present invention applies a pressure load to the self-lubricating gasket before testing its wear resistance. Without using the finished bearing, it can simulate the stress condition of the self-lubricating gasket during actual service after the self-lubricating spherical plain bearing is press-fitted into the bearing housing ring, and can accurately evaluate the influence of the assembly stress of the self-lubricating spherical plain bearing on the wear resistance of the self-lubricating gasket.

[0037] 2) The test method for the wear resistance of the self-lubricating gasket of the present invention only needs to use the self-lubricating gasket without using the finished bearing, and the test cost is low.

[0038] 3) By testing the friction performance of the self-lubricating gasket under different compressive stresses, it is possible to understand the change in the wear resistance of the gasket after being subjected to different compressive stresses during the process of installing and fixing the self-lubricating spherical plain bearing to the bearing housing, so as to guide the optimization of the assembly process of installing the self-lubricating spherical plain bearing to the bearing housing ring. On the premise of meeting the assembly pressure required for safety and reliability, select the assembly pressure that makes the friction performance of the self-lubricating gasket optimal. Description of the Drawings

[0039] Figure 1Schematic flow chart of the test method for the wear resistance of the self-lubricating liner according to an embodiment of the present invention;

[0040] Figure 2 Schematic diagram of the operation of the test device for the wear resistance of the self-lubricating liner according to an embodiment of the present invention;

[0041] Figure 3a Top view of the base in the test device for the wear resistance of the self-lubricating liner according to an embodiment of the present invention;

[0042] Figure 3b is Figure 3a front view of the base in

[0043] Figure 4 Test curve graph of the friction coefficient of the self-lubricating liner under each preset compressive stress according to an embodiment of the present invention.

[0044] Reference numerals

[0045] 1. Base; 11. Disc; 12. Lug; 21. First flat die pressing plate; 22. Second flat die pressing plate; 31. Bearing table; 32. Friction head. Detailed implementation manners

[0046] To make the objectives, technical solutions and advantages of the present invention more comprehensible, the present invention will be further described in detail below with reference to the accompanying drawings of the specification and specific embodiments. It should be noted here that many specific details are set forth in the following description to facilitate a thorough understanding of the present invention. However, the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar generalizations without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0047] Secondly, the present invention will be described in detail with reference to the schematic diagrams. When detailing the embodiments of the present invention, for the sake of convenience of description, the cross-sectional views showing the device structure may be enlarged locally out of the general proportion, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention herein. In addition, in actual production, three-dimensional spatial dimensions including length, width and depth should be included.

[0048] Thirdly, "an embodiment" or "a kind of embodiment" in the present application refers to specific features, structures or characteristics that can be included in at least one implementation manner of the present invention. The phrases "in an embodiment" and "a kind of embodiment" appearing in different places in this specification do not necessarily refer to the same embodiment, nor are they separate or selectively exclusive embodiments from other embodiments. The terms "including" and "comprising" indicate the presence of the claimed features, but do not exclude the presence of one or more other features. The phrase "and / or" used in the present application includes any and all combinations of one or more of the related listed items.

[0049] The present invention provides a test method for the wear resistance of a self-lubricating gasket, which is used for a self-lubricating spherical plain bearing. Refer to Figure 1 , and it includes the following steps:

[0050] Step S1: Attach the self-lubricating gasket to the surface of the substrate.

[0051] Step S2: Apply a pressure load to the surface of the substrate with the self-lubricating gasket attached (hereinafter simply referred to as the "test workpiece"). The pressure load is determined based on a preset compressive stress and the area of the surface of the substrate with the self-lubricating gasket attached. The preset compressive stress is set according to the assembly stress when the self-lubricating spherical plain bearing is installed on the bearing housing.

[0052] Step S3: Conduct a friction test on the self-lubricating gasket after the pressure load is applied to evaluate the wear resistance of the self-lubricating gasket.

[0053] Among them, "attachment" means that the self-lubricating gasket is tightly combined with the substrate, and there is a certain interaction force between their contact surfaces, making them not easily separated.

[0054] In step S3 of an embodiment of the present invention, a friction test is conducted on the self-lubricating gasket after the pressure load is applied to evaluate the wear resistance of the self-lubricating gasket. Specifically, it includes:

[0055] Apply a friction load perpendicular to the surface of the self-lubricating gasket to the self-lubricating gasket after the pressure load is applied, and set the friction speed and friction time.

[0056] Measure the real-time shear force on the self-lubricating gasket during the friction process.

[0057] Calculate the friction coefficient of the self-lubricating gasket based on the shear force and the friction load. The smaller the friction coefficient, the better the wear resistance of the self-lubricating gasket.

[0058] Specifically, the coefficient of friction is the ratio of the shear force to the frictional load. The measured shear force is a curve that changes with time, and the calculated coefficient of friction is also a curve that changes with time. The coefficient of friction of the self-lubricating gasket takes the value in the stable stage of the coefficient-of-friction curve. In the wear resistance test of the self-lubricating gasket, the friction of the self-lubricating gasket will go through three stages: the running-in wear stage, the stable wear stage, and the rapid wear stage. The measured coefficient-of-friction curve also has obvious three-stage characteristics. Among them, the running-in wear stage is relatively short, and the duration of this stage varies due to different test conditions. Therefore, the time for taking the value of the coefficient of friction cannot be quantitatively described. Regarding the setting of the frictional load and the frictional speed, the GJB10850-2022 specification stipulates the bearing performance verification conditions. Usually, the test conditions used in the wear resistance test method of the self-lubricating gasket should be as consistent as possible with the bearing test environment, that is, the experimental PV value (the product of the frictional load P and the frictional speed V) should be consistent with the requirements of GJB 10850-2022. Regarding the frictional time, it needs to be determined according to the time when the self-lubricating gasket enters the stable wear stage.

[0059] The self-lubricating gasket of an embodiment of the present invention is adhered to the surface of the substrate through a resin adhesive. Of course, in addition to the pasting method, the effect of attaching the self-lubricating gasket to the substrate can also be achieved through various other methods such as adsorption and fitting.

[0060] Before applying a pressure load to the surface of the substrate with the self-lubricating gasket attached in step S2 of an embodiment of the present invention, the self-lubricating gasket attached to the surface of the substrate will also be heated and pressure-cured to ensure that the self-lubricating gasket is firmly attached to the substrate and prevent it from shifting or falling off during the friction test. The parameters of the heating and pressure curing are determined according to the resin components of the self-lubricating gasket and the type of the resin adhesive. The parameters of the heating curing include the curing temperature, the curing time, the curing pressure, etc. For example, if the resin component of the self-lubricating gasket is phenolic resin and the phenolic resin adhesive is also selected as the resin adhesive, the heating parameters can be set to heat at about 135 °C for 8 hours. It should be noted that the curing pressure is much lower than the pressure load applied to the surface of the substrate with the self-lubricating gasket attached. The curing pressure only cures the resin adhesive to ensure that the self-lubricating gasket is firmly attached to the substrate and hardly affects the structure and performance of the self-lubricating gasket; while the pressure load applied to the surface of the substrate with the self-lubricating gasket attached will change the state and distribution of the fiber structure and resin components in the gasket to simulate the compressive stress from the bearing outer ring received by the self-lubricating gasket during actual service.

[0061] In step S2 of an embodiment of the present invention, when applying a pressure load to the surface of the substrate with a self-lubricating gasket attached, the press load stops when it reaches the required value. This is because in this process, a compression test of the test workpiece is carried out with a relatively large tonnage of pressure to achieve the purpose of deforming the self-lubricating gasket. Since the self-lubricating gasket is attached to the substrate, at the moment of force application, the substrate will drive the self-lubricating gasket to deform, and no additional pressure holding is required.

[0062] The surface of the substrate with a self-lubricating gasket attached in an embodiment of the present invention is a plane, and the method of applying a pressure load to the surface of the substrate with a self-lubricating gasket attached is flat die compression. Flat die compression refers to an operation method of compressing materials using a flat die. Under the flat die compression method, the value of the pressure load is the product of the preset compressive stress and the area of the surface of the substrate with a self-lubricating gasket attached.

[0063] In an embodiment of the present invention, one self-lubricating gasket is attached to each of the two opposite surfaces of the substrate. This is to ensure that the surface of the self-lubricating gasket can be subjected to uniform stress during subsequent application of compressive stress.

[0064] The self-lubricating gasket in an embodiment of the present invention is circular. When performing a friction test on the self-lubricating gasket after applying a pressure load, the circumferential friction is along the circumference at a radius from the center of the self-lubricating gasket Friction can also be tested at other positions, but it is necessary to keep a certain distance from the edge of the specimen to avoid damaging the edge structure during specimen cutting and affecting the accuracy of the friction test results.

[0065] The present invention also proposes an optimization method for the assembly stress of a self-lubricating spherical plain bearing, including the following steps:

[0066] Step S100: Design multiple different preset compressive stresses, which are determined according to the assembly stress when the self-lubricating spherical plain bearing is installed on the bearing seat. Generally, there should be at least 3 groups of preset compressive stresses;

[0067] Step S200: Use the above-mentioned test method for the wear resistance of the self-lubricating gasket to test the wear resistance of the self-lubricating gasket under each preset compressive stress respectively;

[0068] Step S300: Determine the optimal assembly stress for installing the self-lubricating spherical plain bearing on the bearing seat based on the wear resistance of the self-lubricating gasket under each preset compressive stress. Specifically, under the condition of meeting the assembly stress required for the service safety and reliability of the self-lubricating spherical plain bearing, select the assembly stress that makes the wear resistance of the self-lubricating gasket better.

[0069] For each self-lubricating liner under a preset compressive stress, at least three wear resistance tests need to be carried out, and the average value is taken as the wear resistance test result of the self-lubricating liner under the preset compressive stress. The wear resistance can be characterized by the friction coefficient. The smaller the friction coefficient, the better the wear resistance of the self-lubricating liner. Of course, it can also be characterized by other parameters such as wear rate and wear amount.

[0070] When determining the optimal assembly stress for installing the self-lubricating spherical plain bearing into the bearing housing, in addition to the wear resistance, factors such as the stability and reliability of its operation after assembly also need to be considered. The optimization method for the assembly stress of the self-lubricating spherical plain bearing of the present invention is to incorporate the wear resistance of the self-lubricating liner into the consideration range for determining the assembly stress of the self-lubricating spherical plain bearing.

[0071] The present invention also proposes a test device for the wear resistance of the self-lubricating liner, which is used to implement the test method for the wear resistance of the self-lubricating liner as described above. Refer to Figure 2 , the test device includes a base 1, a pressure application component, a friction component, and a shear force sensor. The base 1 is used to attach the self-lubricating liner. The pressure application component is used to apply a pressure load to the surface of the base attached with the self-lubricating liner. The friction component is used to conduct a friction test on the self-lubricating liner, including a bearing table 31, a friction head 32, and a friction controller. The base 1 is detachably connected to the bearing table 31. The friction head 32 is arranged perpendicular to the surface of the bearing table 31. The friction controller is connected to the friction head 32 and controls the friction load, friction speed, and / or friction time of the friction head 32 during the friction test. The shear force sensor is connected to the friction head 32 and is used to measure the real-time shear force of the friction head 32 on the self-lubricating liner during the friction process. Among them, various commercial friction test instruments such as a pin-on-disk friction testing machine can be used for the friction component to simulate the frictional force received by the self-lubricating liner during use.

[0072] Before applying a pressure load to the self-lubricating liner attached to the surface of the base, it needs to be heated and pressure-cured. The implementation method of heating and pressure-curing can be to use a pressing iron or the like for heating and pressure-curing, or to heat and cure after applying a curing pressure to the base attached with the self-lubricating liner in various heaters with a closed space (such as a heating furnace).

[0073] In one embodiment of the present invention, the substrate 1 is made of a metal material, preferably the same as the material of the bearing outer ring, such as common materials for bearing outer rings like steel, aluminum, copper, titanium, etc. The substrate 1 includes a disc 11 and a plurality of lugs 12. The number of lugs 12 is not less than 3, and the lugs 12 are preferably evenly distributed along the circumference of the disc 11. The height of the lugs 12 is the same as that of the disc 11. During the subsequent application of the pressure load, the lugs 12 can bear the applied stress, preventing the bulging effect of some metals of the disc 11, and the same height of the lugs 12 and the disc 11 can prevent the lugs 12 from warping during the compression process. In addition, the design of the lugs 12 can, in the subsequent friction test, fix the test workpiece (the substrate with a self-lubricating liner attached) to the bearing table 31 of the friction assembly without damaging the main body of the test workpiece by drilling holes in the lugs 12 or pressing down on the lugs 12. As shown in Figure 3, it is a schematic diagram of a substrate in an embodiment, with four lugs evenly distributed around the disc, and the free ends of the lugs being semi-circular. Among them, the disc radius / substrate height / lug position / lug radius are respectively R / H / L / r (disc diameter / lug diameter is D / d). The ratio of the disc radius to the height R / H should be not less than 2 to maintain the stability when applying the pressure load to the test workpiece. If the value of R / H is too small, it is prone to rebound and warp after being compressed, affecting subsequent tests. The ratio of the lug position to the disc radius L / R should be not less than 1. The size of the lug radius r needs to be reasonably designed according to the number n of the lugs.

[0074] The pressure application assembly in one embodiment of the present invention includes a first flat die pressing plate 21, a second flat die pressing plate 22, and a pressure controller. The first flat die pressing plate 21 and the second flat die pressing plate 22 are arranged relatively parallel, and the pressure controller is used to control the pressure load between the first flat die pressing plate 21 and the second flat die pressing plate 22, and stops when the pressure load reaches the required value during the compression process. The pressure application assembly can select various commercial pressing instruments, such as a hydraulic tablet press, an electric press, etc.

[0075] When testing the wear resistance of the self-lubricating liner using the wear resistance testing device of the present invention, refer to Figure 2 , and the operation steps are as follows:

[0076] 1) Material preparation:

[0077] Select the substrate material for attaching the self-lubricating liner and process it into the above specific shape according to the specific dimensional requirements of the disc radius / substrate height / lug position / lug radius;

[0078] Preferably, use the laser cutting method to cut the self-lubricating liner according to the end face size of the disc of the substrate.

[0079] 2) Preparation of the test workpiece:

[0080] Under normal temperature conditions, a resin adhesive is evenly coated on the end face of the disc of the substrate, and the cut self-lubricating gasket is pasted onto the end face of the disc of the substrate. In order to ensure that the surface of the self-lubricating gasket can be subjected to uniform stress when subsequent compressive stress is applied, a self-lubricating gasket is pasted on both the upper and lower end faces of the substrate.

[0081] 3) Heat and press the test workpiece for curing:

[0082] Install the workpiece with the self-lubricating gasket pasted thereon onto the pressurized curing fixture and then place it in a heating furnace. Set the curing temperature, curing time, and curing pressure according to the resin components in the self-lubricating gasket and the type of resin adhesive until the binder and the resin in the self-lubricating gasket are completely cured. After the temperature of the heating furnace returns to room temperature, remove the pressurized curing fixture.

[0083] 4) Apply compressive stress:

[0084] Place the cured test workpiece between two flat die platens, set the pressure load and the pressure application duration to ensure that the state of the self-lubricating gasket after applying the pressure load can accurately simulate the state of the self-lubricating gasket subjected to the compressive stress from the outer ring of the bearing during actual service. The value of the pressure load F is the product of the preset compressive stress σ and the area S of the surface of the substrate with the self-lubricating gasket attached, i.e., F = σ·S.

[0085] 5) Drill a circular through-hole at the end of each lug of the test workpiece after compression, and the radius of the through-hole should be smaller than the radius of the lug.

[0086] 6) Machine threaded holes on the bearing platform of the friction assembly according to the positions and sizes of the respective through-holes, and the radius of the threaded holes should be slightly smaller than the radius of the through-holes.

[0087] 7) Wear resistance test:

[0088] Connect and fix the test workpiece and the bearing platform with bolts, adjust the friction head to be vertically in contact with the surface of the self-lubricating gasket, and the contact position is at the radius of the gasket surface. Connect the friction head to a shear force sensor, set the friction load F N , the friction speed (rotation speed of the friction head), and the friction time, conduct a wear resistance test on the test workpiece, and use the shear force sensor to record the shear force F τ .

[0089] 8) Wear resistance evaluation:

[0090] Combine the shear force F τ that changes with time obtained after the test with the applied friction load F N , and according to the friction coefficient formula μ = F τ / F NThe variation curve of the friction coefficient μ of the self-lubricating pad with time during the friction test is calculated, and the friction coefficient of the self-lubricating pad can be obtained by taking the stable section of the friction coefficient curve.

[0091] The following details the process of applying the test method for the wear resistance of the self-lubricating pad to the optimization of the assembly stress of the self-lubricating spherical plain bearing through specific embodiments:

[0092] First step: Select 05Cr17Ni4Cu4Nb stainless steel, which is commonly used for the outer ring of the bearing, as the base material. Its yield strength at room temperature is approximately 1000 MPa. Machine it according to the specific dimensional requirements of disk radius / base height / lug position / lug radius, which are 15 mm / 7 mm / 25 mm / 4 mm.

[0093] Second step: Select the self-lubricating pad commonly used for self-lubricating spherical plain bearings: phenolic resin-based PTFE / Nomex (polytetrafluoroethylene / aramid) woven composite material as the test object. The single-layer thickness ranges from 0.35 to 0.38 mm. Use laser cutting to cut the self-lubricating pad into a size of 30 mm, which is the same as the diameter of the disk end face of the base, and use phenolic resin adhesive to paste it on the upper and lower surfaces of the disk of the base.

[0094] Third step: Clamp the workpiece with the self-lubricating pad pasted on it with an upper and lower disk clamping tool with four bolts to provide curing pressure for the pad, and place it in a heating furnace. Take it out after heating to about 135 °C and curing for 8 hours.

[0095] Fourth step: Measure the key dimensions of the test workpiece, including the outer diameter and height of the test workpiece. Measure three times with a vernier caliper and take the average value. The specific values are 30 mm and 7.7 mm respectively.

[0096] Fifth step: Apply compressive stress to the test workpiece under the clamping of two flat die platens: Design 5 groups of compressive stresses not higher than the yield strength of the base, specifically 0 MPa / 288 MPa / 371 MPa / 554 MPa / 680 MPa. Calculate the specific contact area between the test workpiece and the flat die platen, that is, the area of the surface of the base attached with the self-lubricating pad. The specific calculation formula is: The total area S is the sum of the disk end face area S 1 = πD 2 / 4 and the area S 2 = n(πd 2 / 4 + Ld - Dd / 2), and S = S 1 + S 2 . According to the calculated specific contact area of 1094 mm 2, calculate the required pressure loads, specifically 0 kN / 315 kN / 406 kN / 606 kN / 744 kN, as shown in Table 1. Each group of compressive stresses is repeated 3 times. Under 5 groups of different pressure load conditions, the self-lubricating gasket deforms to varying degrees along with the metal matrix.

[0097] Step 6: After compression, drill a through-hole with a radius of 2.5 mm at the lug end of the workpiece to be tested, and machine an M5 threaded hole at a distance of 25 mm from the center point on the bearing platform of the friction assembly.

[0098] Step 7: Use four M5 bolts to connect the workpiece to be tested with the bearing platform of the friction assembly to complete the fixation of the workpiece to be tested. Connect a shear force sensor at the friction head, set the required friction load of 30 N, the friction head rotation speed of 200 r / min, and the friction time of 8000 s, and conduct wear resistance tests on the self-lubricating gasket.

[0099] Step 8: According to the data of the shear force changing with time obtained, calculate and obtain the friction coefficient curve, as Figure 4 shown.

[0100] Step 9: Take the values in the stable stage of the friction coefficient curve, calculate the average value, and obtain that the friction coefficients after 3 repeated tests under 5 groups of compressive stresses are 0.124 / 0.128 / 0.130 / 0.125 / 0.131 respectively. Combining with Figure 4 the friction coefficient curve diagrams under different assembly stresses in [reference], it can be seen that appropriate assembly stress (554 MPa) can improve the wear resistance of the gasket. Therefore, taking this as the goal, optimize the process parameters of the bearing assembly process.

[0101] Table 1 Compressive stress, corresponding pressure load and friction coefficient test results of each group of workpieces to be tested

[0102] Serial number Compressive stress (MPa) Pressure load (kN) Coefficient of friction 1 0 0 0.124 2 288 315 0.128 3 371 406 0.130 4 554 606 0.125 5 680 744 0.131

[0103] It should be noted that the orientation or positional relationship indicated by terms such as "upper" and "lower" is all based on the orientation or positional relationship shown in the drawings. Such expressions are only for making the description of the present invention simpler and more convenient, rather than indicating or implying that the indicated components must have a specific orientation or be constructed and operated in a specific orientation.

[0104] In addition, in this application, unless otherwise clearly specified and defined, similar terms such as "connection" and "installation" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can also be the communication inside two components. Those skilled in the art can understand the specific meanings of the above terms in this application according to specific situations. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0105] The present invention has the following beneficial effects:

[0106] 1) Before testing the wear resistance of the self-lubricating gasket of the present invention, a pressure load is applied to it. Without using the finished bearing, it can simulate the stress situation of the self-lubricating gasket during actual service after the self-lubricating spherical plain bearing is press-fitted onto the bearing housing ring, and can accurately evaluate the influence of the assembly stress of the self-lubricating spherical plain bearing on the wear resistance of the self-lubricating gasket.

[0107] 2) The test method for the wear resistance of the self-lubricating gasket of the present invention only needs to use the self-lubricating gasket without using the finished bearing, and the test cost is low.

[0108] 3) By testing the friction performance of the self-lubricating gasket under different compressive stresses, it is possible to understand the change in the wear resistance of the gasket after being subjected to different compressive stresses during the process of installing and fixing the self-lubricating spherical plain bearing to the bearing housing, so as to guide the optimization of the assembly process of installing the self-lubricating spherical plain bearing onto the bearing housing ring, and select the assembly pressure that makes the friction performance of the self-lubricating gasket optimal on the premise of meeting the assembly pressure required for safety and reliability.

[0109] Although the above methods are illustrated and described as a series of actions for simplicity of explanation, it should be understood and appreciated that these methods are not limited by the order of the actions, because according to one or more embodiments, some actions may occur in a different order and / or concurrently with other actions shown and described herein or not shown and described herein but understood by those skilled in the art.

[0110] The construction and arrangement of the present application shown in various different exemplary embodiments are merely illustrative. Although only a few embodiments are described in detail in this disclosure, those who refer to this disclosure should readily understand that many modifications are possible without materially departing from the novel teachings and advantages of the subject matter described in this application (e.g., dimensions, structures, shapes and proportions, as well as parameter values, installation arrangements, use of materials, etc.). For example, elements shown as integrally formed may be composed of multiple parts or elements, the positions of the elements may be inverted or otherwise changed, and the nature or number or position of discrete elements may be altered or changed. Accordingly, all such modifications are intended to be included within the scope of the present invention. The order or sequence of any process or method steps may be altered or re-ordered according to alternative embodiments. In the claims, any clause of "means-plus-function" is intended to cover the structures that perform the recited function described herein, and not only structural equivalents but also equivalent structures. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding modifications and changes according to the present invention, but these corresponding modifications and changes should all fall within the protection scope of the present invention.

Claims

1. A method for testing the wear resistance of a self-lubricating liner, wherein the self-lubricating liner is used for a self-lubricating spherical bearing, characterized in that: The steps include: attaching a self-lubricating liner to the surface of a substrate; Applying a pressure load to the surface of the substrate to which the self-lubricating pad is attached, wherein the pressure load is determined based on a preset compressive stress and an area of ​​the surface of the substrate to which the self-lubricating pad is attached, wherein the preset compressive stress is set according to an assembly stress of the self-lubricating spherical plain bearing mounted on the bearing seat; The friction test was carried out on the self-lubricating pad after applying pressure load to evaluate the wear resistance of the self-lubricating pad.

2. The method for testing the wear resistance of the self-lubricating pad according to claim 1, characterized in that: The friction test of the self-lubricating liner after applying the pressure load is performed to evaluate the wear resistance of the self-lubricating liner, specifically including: Apply a friction load perpendicular to the surface of the self-lubricating pad to the self-lubricating pad after the pressure load is applied, and set the friction speed and friction time; Measure the real-time shear force on the self-lubricating pad during the friction process; The friction coefficient of the self-lubricating pad is calculated based on the shear force and the friction load. The smaller the friction coefficient, the better the wear resistance of the self-lubricating pad.

3. The method for testing the wear resistance of the self-lubricating pad according to claim 1, characterized in that: The self-lubricating liner is adhered to the surface of the substrate by means of a resin adhesive.

4. The method for testing the wear resistance of the self-lubricating liner according to claim 3, characterized in that: Before applying a pressure load to the surface of the substrate to which the self-lubricating pad is attached, the self-lubricating pad attached to the surface of the substrate is also heated and pressurized for curing. The parameters of the heating and pressurizing curing are determined according to the resin component of the self-lubricating pad and the type of resin adhesive. The heating and curing parameters include curing temperature, curing time, and curing pressure.

5. The method for testing the wear resistance of the self-lubricating pad according to claim 1, characterized in that: The surface of the substrate to which the self-lubricating pad is attached is a plane, and the method of applying a pressure load to the surface of the substrate to which the self-lubricating pad is attached is flat die compression; The pressure load is the product of the preset compressive stress and the area of ​​the substrate surface to which the self-lubricating pad is attached.

6. The method for testing the wear resistance of the self-lubricating pad according to claim 1, characterized in that: Self-lubricating pads are respectively attached to two opposite surfaces of the base.

7. The method for testing the wear resistance of the self-lubricating pad according to claim 1, characterized in that: The self-lubricating pad is circular, and when the self-lubricating pad is subjected to a friction test after a pressure load is applied, the distance from the center of the self-lubricating pad is Circumferential friction at the radius.

8. A method for optimizing the assembly stress of a self-lubricating spherical plain bearing, characterized in that: The steps include: Designing a plurality of different preset compressive stresses, wherein the preset compressive stresses are determined according to the assembly stress of the self-lubricating spherical plain bearing when it is installed on the bearing seat; The wear resistance of the self-lubricating liner under each preset compressive stress is tested by using the test method for the wear resistance of the self-lubricating liner as described in any one of claims 1 to 7; The optimal assembly stress for installing the self-lubricating spherical plain bearing into the bearing seat is determined based on the wear resistance of the self-lubricating liner under various preset compressive stresses.

9. A test device for the wear resistance of a self-lubricating liner, characterized in that: A method for testing the wear resistance of a self-lubricating liner according to any one of claims 1 to 7, comprising: A substrate for attaching a self-lubricating liner; A pressure applying assembly applies a pressure load to a surface of a substrate to which a self-lubricating pad is attached; The friction assembly comprises a bearing platform, a friction head and a friction controller, wherein the base is detachably connected to the bearing platform, the friction head is arranged perpendicular to the bearing platform, and the friction controller is connected to the friction head to control the friction load, friction speed and / or friction time of the friction head; The shear force sensor is connected to the friction head and measures the real-time shear force of the friction head on the self-lubricating liner during the friction process.

10. The wear resistance testing device of the self-lubricating pad according to claim 9, characterized in that: The substrate is made of metal; The base includes a disc and a plurality of lugs, the number of the lugs is not less than 3, the lugs are evenly distributed along the circumference of the disc, and the height of the lugs is the same as that of the disc.

11. The wear resistance testing device of the self-lubricating pad according to claim 9, characterized in that: The pressure applying assembly includes a first flat die platen, a second flat die platen and a pressure controller; The first flat die pressing plate and the second flat die pressing plate are arranged relatively parallel to each other; The pressure controller is used to control the pressure load between the first flat die platen and the second flat die platen.

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