In-situ testing device and method for frictional characteristics of self-lubricating composite material after deformation

Abstract

The invention relates to an in-situ test device and method for friction characteristics of a self-lubricating composite material after deformation, and the in-situ test device comprises a power system, a pressure head, a female die, a friction test unit, a friction hydraulic unit, a rotation driving unit and a shearing force test unit which are used for enabling a metal plate matrix to deform, the pressure head is in contact with the metal plate matrix during working, and the power system is connected with the pressure head; a friction rod in the friction testing unit is in contact with the self-lubricating composite material, the bottom of the friction rod is connected with the rotary driving unit, and the shearing force testing unit is arranged between the friction unit and the rotary driving unit. By combining the forming pressure head and the rotary friction testing device, in-situ testing of the rotary friction performance of the composite material under different strain levels is achieved under the condition that the deformation stress state of the material is kept, and the device is particularly suitable for evaluating the friction performance of the self-lubricating composite material under the working conditions of simulating bearings, shaft sleeves and the like.

Description

Technical Field

[0001] The present invention relates to a technology in the field of machining, specifically an in-situ test device and method for the friction characteristics of a self-lubricating composite material after deformation. Background Art

[0002] Self-lubricating composite materials are applied to structural components in different scenarios. To meet the requirements of different structures, self-lubricating composite materials often undergo deformation during the manufacturing or assembly process of structural components. Characterizing the tribological properties of self-lubricating composite materials after deformation can provide an optimization direction for the research and development of self-lubricating composite materials. For the tribological property testing of self-lubricating composite materials, the existing public testing technologies do not consider the influence of the stress deformation of self-lubricating composite materials, and cannot truly reflect the deformation state of self-lubricating composite materials in components, resulting in significant differences between laboratory test results and actual service results. Therefore, it is urgent to develop an in-situ test device and method for the friction characteristics of self-lubricating composite materials after deformation. Summary of the Invention

[0003] Aiming at the above deficiencies of the existing technology, the present invention provides an in-situ test device and method for the friction characteristics of a self-lubricating composite material after deformation. By combining a forming punch and a rotary friction test device, under the condition of maintaining the deformation stress state of the material, the in-situ test of the rotary friction performance of the composite material at different strain levels is realized, which is particularly suitable for evaluating the friction performance of self-lubricating composite materials under working conditions such as bearings and bushings. The present invention realizes the integration of deformation and friction testing, avoids the influence brought by specimen loading and unloading and stress release, and can accurately reflect the friction performance of materials under different deformation degrees in actual applications.

[0004] The present invention is realized by the following technical solutions:

[0005] The present invention relates to an in-situ test device for the friction characteristics of a self-lubricating composite material after deformation, including: a power system for deforming a metal plate substrate, a punch and a die, a friction test unit, a friction hydraulic unit, a rotary drive unit, and a shear force test unit. Among them: the punch is in contact with the metal plate substrate during operation, the power system is connected to the punch, the friction rod in the friction test unit is in contact with the self-lubricating composite material, and the bottom is connected to the rotary drive unit. The shear force test unit is arranged between the friction unit and the rotary drive unit.

[0006] Between the punch and the power system, they are connected through an upper template, and an upper die backing plate is placed therein to play a role of pressure buffering to protect the punch.

[0007] The die is connected to the lower template, and a lower die backing plate is arranged in the middle to play a role of buffering to protect the die.

[0008] In the described deformation process, the blank holder is first pressed downward by the power system until it contacts the test workpiece, and then the punch is pressed downward to the required height and then stopped. The guiding function is realized by the guide pillar, guide sleeve and guide pillar spring.

[0009] The contact part between the lower end of the punch and the test workpiece is a spherical arc surface, which deforms the workpiece into a spherical curved surface. On this spherical curved surface, the equivalent strain at the same diameter is consistent, and different degrees of tensile strain are achieved by controlling the ejection stroke.

[0010] After the deformation is completed, the punch stops and does not withdraw, and the friction test is carried out. After the main functional components and the test workpiece are formed, the force states during the friction test are as shown in the figure.

[0011] The force states of the test workpiece during the friction test include: the pressure F_punch applied by the punch and the force F applied by the friction rod. Among them: F_punch is the magnitude of the force applied by the press that reaches the required height in the deformation step, that is, simulating the force condition under this strain state; F is the magnitude of the force applied at the contact point between the ball head of the friction rod and the convex curved surface of the workpiece. It can be perpendicular to the paper surface direction and decomposed into F_normal force and F_tangential force.

[0012] The described friction test device includes: a grooved semi-circular seat and an adjusting bolt arranged therein and a rotating shaft connected thereto. Among them: the friction rod is arranged in the semi-circular seat groove through a fixing bolt, and its position is adjusted by adjusting the length of its thread in the groove. The position of the friction rod is determined according to the distribution of the tensile strain degree of the test workpiece; the rotating shaft is connected to the rotation drive unit to realize the overall rotation of the friction test device and the friction rod.

[0013] The described hydraulic unit includes: two hydraulic cylinders and a force transmission component connected thereto. Among them: the force transmission component is a bushing with symmetric lugs, and a hydraulic cylinder is connected under each of the symmetric lugs at both ends. The upper part of the bushing is connected to the friction position adjusting device. The power is transmitted by the hydraulic system to start the two hydraulic cylinders at the same time, and its hydraulic pressure F is transmitted to the friction rod through the bushing and the magnitude of the force F is monitored in real time by the force sensor inside it. According to the slope k of the convex curved surface and the load F set for the friction test, the actual normal stress received by the woven composite material during friction is calculated

[0014] The described rotation drive unit includes: a motor, a reducer and a coupling connected in sequence. Among them: the motor drives the reducer to output an appropriate rotation speed, and the coupling connects the reducer shaft to the bottom rotating shaft of the friction test device to transmit the output rotational motion to the friction test device, thereby realizing the rotation of the friction rod.

[0015] The rotation speed v of the described rotation drive unit needs to be determined according to the tribological load and the pv value of the friction and wear test.

[0016] The described shear force test unit is a torque sensor, which is connected to the friction test device through a rotating shaft and measures the shear force F received by the friction rod during the working time. τ , combined with the normal stress F received by the test material N The friction coefficient μ = F can be calculated τ / F N . Technical effects

[0017] In the present invention, through the indenter with a spherical arc surface, the workpiece is deformed into a spherical curved surface, realizing the characteristic of consistent equivalent strain at the same diameter. Through the friction rod position adjustment mechanism, accurate positioning tests can be carried out for different strain regions on the workpiece. Compared with the prior art, the present invention can accurately reflect the friction performance of materials under different deformation degrees in actual applications, solves the problem that there are significant differences between laboratory test results and actual service results, is particularly suitable for evaluating the friction performance of self-lubricating composite materials under working conditions such as bearings and bushings, has higher practicability and pertinence, and can obtain friction characteristic data of materials under various deformation degrees in a single experiment, improving the test efficiency. Description of the drawings

[0018] Figure 1 is a schematic structural diagram of the present invention;

[0019] Figure 2 is a schematic diagram of the composition of the standard test workpiece of the present invention;

[0020] Figure 3 is a schematic diagram of the friction test and the force-receiving state of the workpiece;

[0021] Figure 4 is a schematic diagram of the friction test device;

[0022] Figure 5 is a schematic diagram of the hydraulic device;

[0023] Figure 6 is a schematic diagram of the rotation drive unit;

[0024] Figure 7 is a test result diagram of the sample in the embodiment. Specific implementation manners

[0025] Such as Figure 1As shown in the figure, this is an in-situ test device for the friction characteristics of a self-lubricating composite material after deformation according to this embodiment, including: a power system 101 for deforming the test workpiece 113, a punch 115 and a die 106, a friction test unit 240, a friction hydraulic unit 220, a rotary drive unit 210, and a shear force test unit 230, where: the test workpiece 113 is composed of a metal plate substrate 310 and a self-lubricating composite material 320 to be tested that are pasted together, and the front surface of the metal plate substrate 310 is bonded to the self-lubricating composite material 320, as Figure 2 shown. The punch 115 contacts the back surface of the metal plate substrate 310 in the test workpiece 113, and the power system 101 drives the punch 115 to move downward to the required height. The friction rod 241 in the friction test unit contacts the self-lubricating composite material 320 in the test workpiece 113 and is connected to the rotary drive unit 210 at the bottom. The shear force test unit 230 is arranged between the friction unit 240 and the rotary drive unit 210.

[0026] The punch 115 and the power system 101 are connected through an upper template 102 and an upper die backing plate 117.

[0027] The die 106 and the lower template 108 are connected through a lower die backing plate 107.

[0028] Guide columns 104, guide sleeves 103, and guide column springs 105 for guiding are provided between the upper template 102 and the lower template 108.

[0029] After the power system 101 presses the blank holder 114 downward until it contacts the test workpiece 113, it stops after pressing the punch 115 to the required height.

[0030] The contact part between the lower end of the punch 115 and the back surface of the test workpiece 113 is a spherical arc surface, which deforms the workpiece 113 into a spherical curved surface. On this spherical curved surface, the equivalent strain at the same diameter is the same, and different tensile strain degrees are achieved by controlling the ejection stroke.

[0031] After the deformation is completed, the punch 115 stops without being withdrawn for friction testing. After the main functional components and the test workpiece 113 are formed, the stress state during the friction testing is as Figure 3 shown.

[0032] During the friction testing of the test workpiece, it is subjected to the pressure F_punch applied by the punch 115 and the force F applied by the friction rod 241, where: F_punch is the magnitude of the force applied by the press that reaches the required height during the deformation step, that is, simulating the stress situation under this strain state, and F is the magnitude of the force applied at the contact point between the ball head of the friction rod and the convex curved surface of the workpiece. It can be perpendicular to the paper surface direction and decomposed into F_normal force and F_tangential force.

[0033] AsFigure 4 As shown in the figure, the friction test device 240 includes: a grooved semi-circular seat 243, an adjusting bolt 242 disposed therein, and a rotating shaft 244 connected thereto. Among them: the friction rod 241 is disposed in the semi-circular seat groove 243 through the fixing bolt 242, and the position of the friction rod 241 is adjusted by adjusting the length of its thread in the groove. The position of the friction rod 241 is determined according to the distribution of the tensile strain degree of the test workpiece 113; the rotating shaft 244 is connected to the rotation driving unit 210 to realize the overall rotation of the friction rod 241 of the friction test device 240.

[0034] As Figure 5 shown in the figure, the hydraulic unit 220 includes: two hydraulic cylinders 222, 223 and a force transmission member 221 connected thereto. Among them: the force transmission member 221 is a bushing with symmetric lugs, and a hydraulic cylinder 222, 223 is connected to each of the symmetric lugs at both ends, and the upper part of the bushing is connected to the friction position adjusting device. The power is transmitted through the hydraulic system to start the two hydraulic cylinders 222, 223 at the same time, and the hydraulic pressure F is transmitted to the friction rod 241 through the bushing, and the magnitude of the force F is monitored in real time through the force sensor inside it. According to the slope k of the protrusion surface and the load F set for the friction test, the normal stress actually received by the woven composite material during friction is calculated

[0035] As Figure 6 shown in the figure, the rotation driving unit 210 includes: a motor 211, a speed reducer 212 and a coupling 213 connected in sequence. Among them: the motor 211 drives the speed reducer 212 to output an appropriate rotation speed, and the coupling 213 connects the speed reducer shaft 212 to the bottom rotating shaft 244 of the friction test device 240, and transmits the output rotational motion to the friction test device 240, so as to realize the rotation of the friction rod 241.

[0036] The rotation speed v of the rotation driving unit 210 needs to be determined according to the tribological load and the pv value of the friction and wear test.

[0037] The shear force test unit 230 is a torque sensor, which is connected to the friction test device 240 through the rotating shaft 244 to measure the shear force F received by the friction rod 241 during the working time τ , combined with the normal stress F received by the test material N The friction coefficient μ = F can be calculated τ / F N .

[0038] This embodiment relates to an in-situ test method for the friction characteristics of a self-lubricating composite material after deformation based on the above device, including:

[0039] Step 1) Preparation of self-lubricating composite material specimens to be tested: Isotropic 45# steel is used as the metal matrix 310, with a circular plate shape, and its diameter / thickness are 100 mm / 1.6 mm respectively. The self-lubricating composite material 320 made of phenolic resin-based PTFE / Nomex fiber mixed weaving is cut into a circular disc with a diameter of 100 mm. After sandblasting the front surface of the metal plate, the self-lubricating composite material 320 to be tested is pasted, and then heated and cured to form the test workpiece 113. 10 test workpieces are prepared.

[0040] Step 2) Adjust the strain state of the composite sheet: It is necessary to simulate the influence of deformation on the friction performance when the phenolic resin-based PTFE / Nomex fiber mixed woven composite material is used as the self-lubricating component of a self-lubricating joint bearing. Therefore, it is necessary to simulate the friction performance under a strain of less than 20%. According to the above requirements, through finite element simulation, the deformation characteristics of the isotropic 45# steel metal plate in Table 1 are obtained. Therefore, the downward height of the indenter is set to 11 mm to deform the test workpiece.

[0041] Table 1

[0042] Step 3) Friction performance test: After the deformation is completed, the indenter is kept under pressure without being withdrawn. Two strain states of 4% / 10% are selected. Through the friction rod 241 with a 6-mm diameter spherical head and the front surface of the test workpiece 113, contact is made at a radius of 19.3 mm / 15 mm. The hydraulic mechanism 220 applies a load of 30 N to the friction rod. The contact width c is calculated to be approximately 0.3 mm. According to σv = 30000 MPa·mm / s, the friction rotation speeds shown in Table 2 are calculated. The driving mechanism 210 in this combined device sets the rotation speeds of the corresponding friction rod 241 to 114 rpm / 144 rpm. Measure the shear force F τ and the vertical stress F. Combining with the surface slope k, according to the formula calculate the normal stress F N received by the test workpiece 113 at two positions. Combining with the shear force F τ the friction coefficient can be calculated

[0043] As Figure 7 shown, it is the physical diagram of the test workpiece after tension and friction obtained by using this embodiment.

[0044] Table 2

[0045] Compared with the prior art, the device avoids the influence of stress release through the integrated design of deformation and friction tests, making the test results more consistent with the actual application scenarios; through the design of a spherical arc indenter, the equivalent strain is consistent at the same diameter, and the friction performance under multiple strain levels can be simulated in a single experiment; by maintaining the deformed state of the material through in-situ testing, the obtained friction coefficient is closer to the actual use conditions; through the friction rod position adjustment mechanism, precise positioning tests are achieved, multiple sets of data are obtained in a single experiment, and the R & D cycle is shortened. The present invention is particularly suitable for evaluating the friction performance of self-lubricating composite materials under working conditions such as bearings and bushings, and expands the application scope of the testing method.

[0046] The above specific embodiments can be locally adjusted in different ways by those skilled in the art without departing from the principles and purposes of the present invention. The protection scope of the present invention is subject to the claims and is not limited by the above specific embodiments, and all implementation solutions within its scope are subject to the present invention.

Claims

1. An in-situ testing device for the friction characteristics of a composite material after tensile deformation, characterized in that, Comprising: A power system, a punch, a die, a friction test unit, a friction hydraulic unit, a rotary drive unit, and a shear force test unit for deforming a metal plate substrate. Among them: The punch contacts the metal plate substrate during operation. The power system is connected to the punch. The friction rod in the friction test unit contacts the self-lubricating composite material and is connected to the rotary drive unit at the bottom. The shear force test unit is arranged between the friction unit and the rotary drive unit; During the friction test of the test workpiece, it is subjected to the pressure F_punch applied by the punch and the force F applied by the friction rod. Among them: F_punch is the magnitude of the force applied by the press that reaches the required height during the deformation step, that is, simulating the force condition under this strain state; F is the magnitude of the force applied at the contact point between the ball head of the friction rod and the convex curved surface of the workpiece. It can be in the direction perpendicular to the paper surface and is decomposed into F_normal force and F_tangential force.

2. The in-situ testing device for the friction characteristics after tensile deformation of the composite material according to claim 1, characterized in that, The punch and the power system are connected through an upper template and an upper die backing plate; the die is connected to the lower template through a lower die backing plate; guide columns, guide sleeves, and guide column springs for guiding are provided between the upper template and the lower template.

3. The in-situ testing device for the friction characteristics after tensile deformation of the composite material according to claim 1, characterized in that, The contact part between the lower end of the punch and the test workpiece is a spherical arc surface to deform the workpiece into a spherical curved surface; The equivalent strain at the same diameter on the spherical curved surface is the same, and different tensile strain degrees are achieved by controlling the ejection stroke.

4. The in-situ testing device for the friction characteristics after the tensile deformation of the composite material according to claim 1, characterized in that, The friction test device includes: a grooved semi-circular seat, an adjusting bolt arranged therein, and a rotary shaft connected thereto. Among them: The friction rod is arranged in the semi-circular seat groove through a fixing bolt, and its position is adjusted by adjusting the length of its thread in the groove. The rotary shaft is connected to the rotary drive unit to realize the overall rotation of the friction test device and the friction rod.

5. The in-situ testing device for the friction characteristics after tensile deformation of the composite material according to claim 1, wherein, The hydraulic unit described above includes: two hydraulic cylinders and a force transmission component connected thereto, where: the force transmission component is a bushing with symmetric lugs, and a hydraulic cylinder is connected below each of the symmetric lugs at both ends. The upper part of the bushing is connected to a friction position adjustment device. The two hydraulic cylinders are started simultaneously by transmitting power through a hydraulic system, and the hydraulic pressure F is transmitted to the friction rod through the bushing and the load F is monitored in real time by a force sensor; the actual normal stress received by the woven composite material during friction is calculated based on the slope k of the protrusion surface and the load F set for the friction test.

6. The in-situ testing device for the friction characteristics after the tensile deformation of the composite material according to claim 1, wherein, The rotary drive unit includes: a motor, a reducer, and a coupling connected in sequence. Among them: The motor drives the reducer to output an appropriate rotational speed. The coupling connects the reducer shaft to the rotary shaft at the bottom of the friction test device to transmit the output rotational motion to the friction test device, thereby realizing the rotation of the friction rod.

7. An in-situ test method for the friction characteristics of a self-lubricating composite material after deformation based on the device according to any one of claims 1-6, characterized in that, Comprising: Step 1) Preparation of the self-lubricating composite material sample to be tested: Use an isotropic circular sheet as the metal substrate. Paste the self-lubricating composite material of phenolic resin-based PTFE / Nomex fiber on the front surface of the metal substrate after sandblasting, and then heat and cure it to form a test workpiece; Step 2) Adjust the strain state of the composite sheet: Through finite element simulation, obtain the deformation characteristics of the isotropic metal plate, and set the punch to descend to deform the test workpiece; Step 3) Friction performance test: After the deformation is completed, the indenter keeps the pressure and does not withdraw. The friction rod with a ball head contacts the front surface of the test workpiece and applies a load, calculates the corresponding friction rotation speed and sets the rotation speed of the corresponding friction rod, and measures the shear force F τ and the vertical stress F, combines with the surface slope k, and calculates the normal stress received by the test workpiece at two positions Combined with the shear force F τ Obtain the friction coefficient

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