CN101178345B - Twisting or micro-moving frictional wear test device - Google Patents

Abstract

The invention relates to a torsional fretting friction wear test method, the method is that: an upper testing part is clamped in an upper clamp, a lower clamp is fixed with a high-precision low-speed rotation table by a thread, a vertical central line of a holding cavity of the lower clamp is aligned with a rotating shaft of the high-precision low-speed rotation table, a spherical lower testing part is clamped by the lower clamp; the upper clamp is controlled for up and down movements by a data collection control system, the upper and lower testing parts are contacted and are exerted by a setload, at the same time, the lower clamp and the lower testing part clamped by the lower clamp are controlled by the data collection control system to carry out a plurality of times of reciprocating rotations by a set rotation speed and a rotation angle; at the same time, the friction torque is measured by a six-dimension force/torque sensor which is connected with the upper clamp and is sent to the data collection control system, and a torque-angular displacement curve under the set rotation speed and the load conditions can be obtained by analysis. The method can conveniently allow the materials to generate the small angle torsional fretting friction wear, the degree of the automation is high, the precision of the control and the test is high and the reproducibility of the test data is good.

Description

A torsion fretting friction and wear test device

technical field

The invention belongs to the field of friction technology research, in particular to a fretting friction test method and a test device thereof.

Background technique

Fretting (Fretting) refers to the relative motion with extremely small amplitude between contact surfaces under the action of alternating loads such as mechanical vibration, fatigue load, electromagnetic vibration or thermal cycle. These contact surfaces are usually static in name, that is, fretting occurs In mechanical parts that are "tightly" fitted. Fretting tribology is a branch of disciplines that studies the mechanism of fretting, damage, testing, monitoring, and prevention. Electrical Engineering etc. Fretting is a friction method with a small relative motion range, and the material damage caused by it is usually manifested in two forms, namely: (1) Wear caused by fretting: fretting can cause surface wear between contact surfaces, resulting in material damage. Losses and changes in component dimensions, causing component seizure, loosening, power loss, increased noise, or source of contamination. (2) Fatigue caused by fretting: fretting can accelerate the initiation and expansion of cracks, greatly reducing the fatigue life of components, and the fretting fatigue limit can even be lower than 1/3 of the ordinary fatigue limit. Often this form of injury is more dangerous, resulting in some catastrophic accidents.

Under the condition of ball-plane contact, fretting can be divided into four basic fretting modes: tangential, radial, rolling and torsion. Both tangential fretting and radial fretting are the linear motions of the grinding pair with small displacement on the contact surface under the action of normal load. The difference is that the normal load direction of tangential fretting is perpendicular to its motion direction. , the radial fretting normal load direction is consistent with the motion direction. Rolling fretting and torsion fretting are the rotating movements of the grinding pair on the contact surface at a small angle under the action of the normal load. The difference is that the rotation axis of the rolling fretting is parallel to the contact plane, such as a wheel Friction with the ground; the axis of rotation of the twisting fretting is perpendicular to the contact surface, such as the friction between the hip joint and the hip joint disc.

Torsional fretting is the relative movement of slight torsion between contact pairs under alternating loads. Twisting and fretting phenomena exist in a large number of mechanical equipment and equipment, such as the steering process of the steering ball joint of the steering mechanism of the front wheel of the automobile, the friction of the center disc connected between the bogie and the car body of the locomotive when the locomotive is turning, and the human body implant The friction between the valve shaft and the shaft seat of the artificial heart valve in the device, the fretting that occurs in the club-like contact area of the hip joint and the knee joint, etc. Twisting and fretting friction have brought great losses and troubles to production and life. Due to the difficulty in reproducing or simulating artificial control, the related research work on twisting and fretting has been carried out less. The research and development of new methods and devices for torsion and fretting tests is very important for reducing the problems of torsion and fretting wear in engineering, improving the related design of mechanical and biological engineering, improving the performance and life of equipment and instruments, and saving energy. meaning.

Contents of the invention

The purpose of the present invention is to provide a test method for twisting and fretting friction and wear, which can easily cause small-angle twisting and fretting friction and wear of materials, and has a high degree of automation, high precision of control and testing, and test data The reproducibility is good.

The technical scheme that the present invention adopts to solve its technical problem is: a kind of torsion fretting friction and wear test method, and its practice is:

a. Clamp the upper specimen on the upper fixture, and then fix the lower fixture and the high-precision low-speed turntable through threads, and the vertical centerline of the clamping cavity of the lower fixture is aligned with the rotation axis of the high-precision low-speed turntable, Clamp the spherical lower test piece with the lower clamp;

b. Control the up and down movement of the upper fixture through the data acquisition control system, so that the upper and lower specimens contact and apply the set load P, and at the same time, through the control of the data acquisition control system, the lower fixture and the lower specimen held by it are set at the same time. Reciprocating rotation at a fixed speed ω, rotation angle θ, and reciprocating times N to achieve torsional and fretting friction between the upper and lower specimens;

c. While twisting and fretting friction occurs on the upper and lower test pieces, the friction torque is measured through the six-dimensional force/torque sensor connected to the upper fixture, and sent to the data acquisition and control system. The data acquisition and control system analyzes and obtains the design Torque-angular displacement curves under constant speed and load conditions to characterize the dynamics of torsional fretting friction.

Compared with prior art, the beneficial effect of the present invention is:

1. Since the vertical centerline of the clamping chamber of the lower fixture is aligned with the rotation axis of the high-precision low-speed turntable, the vertical centerline of the spherical specimen held by the lower fixture and its rotation axis can be guaranteed when the high-precision low-speed turntable rotates The overlapping makes the vertical apex of the spherical specimen not change in the horizontal position during rotation, that is, the pin-disk wear phenomenon when the two axes do not coincide, so that the twisting and fretting can be realized. 2. Through the control of the data acquisition control system, the adjustment of the position of the upper fixture and the loading of the set load can be accurately realized, and the reciprocating rotation of the lower fixture and its lower test piece at a given speed and angle can also be accurately realized. So as to accurately realize the torsion fretting friction and wear test under the condition of given parameters. 3. Through the six-dimensional force/torque sensor connected to the upper fixture, the friction torque during twisting and fretting is measured, and sent to the data acquisition and processing system for processing, and the torque-angular displacement curve under the set conditions is obtained, which can accurately characterize the torque The dynamic characteristics of dynamic fretting; and other related wear analysis can be carried out on the tested material.

In a word, this test method can conveniently cause accurate small-angle torsion and fretting friction and wear of the material. The test is directly controlled by the data acquisition control system to set the corresponding test parameters, and use it for automatic analysis and processing. The degree of automation is high, and the control and control The accuracy of the test is high, and the reproducibility of the test data is good.

Another object of the present invention is to provide a kind of test device that implements above-mentioned torsion fretting friction and wear test method, this device structure is simple, can realize this test method conveniently, can carry out the test of the material of different operating conditions and specification, Experimental parameters can be precisely controlled.

The technical solution adopted by the present invention to realize the object of the invention is: a test device for a twisting and fretting friction and wear test method, including upper and lower clamps, and a support for installing the upper and lower clamps. Its structural characteristics are:

The specific structure of the lower fixture installed on the machine base is as follows: the lower fixture is a fixture for clamping a spherical test piece, the lower fixture and the high-precision low-speed rotating table are fixed by threads, and the vertical centerline of the clamping chamber of the lower fixture is Align with the rotating shaft of the high-precision low-speed turntable; the high-precision low-speed turntable is installed on the bottom plate of the machine base;

The specific structure of the upper fixture installed on the machine base is as follows: the upper end of the upper fixture is connected to the six-dimensional force/torque sensor, the six-dimensional force/torque sensor is connected to the two-dimensional mobile platform capable of horizontal and vertical movement, and the two-dimensional mobile platform fixed on the middle and upper part of the frame;

The high-precision low-speed rotary table, the two-dimensional mobile table, and the six-dimensional force/torque sensor are all electrically connected to the data acquisition and control system.

The use method and working process of this device are:

Fix the upper sample on the upper fixture, fix the lower sample on the lower fixture, and control the movement of the two-dimensional mobile platform through the data acquisition and control system to adjust the position of the upper sample in the horizontal and vertical directions so that it is in line with the lower sample. The specimen is contacted and given a set load. Through the control of the data acquisition and control system, the high-precision and low-speed rotary table is controlled to make the lower sample rotate reciprocatingly according to the set parameters, and then the six-dimensional force/torque sensor is used to monitor the torque during the twisting and micro-movement in real time, and send it to the data acquisition and control system for further testing. processing to obtain the torque-angular displacement curve.

Given different parameters, the torsional fretting friction and wear test under different working conditions can be carried out. For lower specimens of different sizes, the test can be completed by using lower fixtures of corresponding sizes.

It can be seen that by using the above device, the test method of the present invention can be conveniently implemented, the test of materials with different working conditions and specifications can be carried out, the test parameters can be precisely controlled, and the structure of the device is simple.

The composition of the above-mentioned two-dimensional mobile platform is as follows: the vertical motor is fixed on the top plate on the upper part of the machine base, the vertical motor shaft is connected with the vertical screw rod, the vertical screw rod cooperates with the internal thread of the moving block, and the slide on the inner side of the moving block The groove is matched with the guide rail on the vertical plate, and the outer side of the moving block is fixedly connected with the beam; the slide rail at the lower part of the beam is matched with the chute at the upper part of the moving plate, and the horizontal motor is fixed on the vertical plate at the side of the machine base, and the shaft of the horizontal motor is connected with the horizontal The screw rod is connected, the horizontal screw rod cooperates with the inner thread of the motion board, and the lower part of the motion board is connected with the six-dimensional force/torque sensor.

The motor drives the screw mechanism and the slide rail and chute mechanism to realize the horizontal and vertical movement. These mechanisms are simple in structure and reliable in operation; and the motor is controlled by a data acquisition control system, so that its position adjustment is accurate and convenient.

The specific method of connecting the above-mentioned motion board to the six-dimensional force/torque sensor is: the lower part of the motion board is screwed to the connection block, and the lower part of the connection block is connected to the six-dimensional force/torque sensor.

In this way, the sensor can be installed on the sports board more stably and firmly, and it is also very convenient to replace.

The above-mentioned vertical plate is provided with a guide bearing, and the lower part of the vertical screw rod passes through the guide bearing.

This makes the vertical stability of the two-dimensional mobile station better.

The composition of the above-mentioned high-precision low-speed rotary table is as follows: the bracket is installed on the bottom plate of the machine base, the high-precision low-speed motor is vertically fixed on the bracket, the output shaft of the high-precision low-speed motor is fixed on the rotating table, and the screw on the rotating table is used to fix the lower fixture.

In this way, the structure of the high-precision low-speed rotary table is simple, the transmission is direct, and the control is precise.

There is an arc surface in the middle of the bottom of the clamping chamber of the lower fixture, the radius of curvature of the arc surface is the same as the radius of the spherical lower test piece, and a positioning through hole is opened in the center of the arc surface; the pressure plate of the lower fixture has a The radius of curvature of the arc-shaped through hole is also the same as that of the spherical lower test piece, and the centerlines of the positioning through hole, the arc surface of the clamping cavity of the lower fixture and the arc-shaped through hole of the pressure plate of the lower fixture coincide.

This can ensure that the vertical centerline of the spherical specimen clamped by the lower fixture overlaps with its rotation axis during rotation, so that the vertical apex of the spherical specimen does not change in the horizontal position during rotation, so that twisting and fretting wear can be accurately realized and avoid Pin-disk wear occurs.

The above-mentioned high-precision low-speed turntable has a minimum rotation angle θ of 0.05° for torsional motion, and a range of rotation speed ω of 0.01-5°/s.

The above-mentioned six-dimensional force/moment sensor has a normal load measurement range of 1-580N; a tangential force measurement range of 1-180N in both lateral and longitudinal directions, a torque measurement range of 1-10000N mm, and a measurement accuracy of 1N· mm.

In this way, the device of the present invention can realize a high-precision small-angle torsion fretting friction and wear test, and the test result is accurate and reliable.

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Description of drawings

Fig. 1 is a front structural schematic diagram of a test device according to an embodiment of the present invention.

Fig. 2 is a right side view of Fig. 1 .

Fig. 3 is a test device according to an embodiment of the present invention, a cross-sectional enlarged schematic diagram of the lower fixture and the rotating table when the lower test piece is not clamped.

Fig. 4a is a torque-angular displacement (T-θ) curve obtained by testing a specific specimen material with the test device of the embodiment of the present invention and the method of the present invention. The upper test piece of the test is LZ50 axle steel test block of 20mm×10mm×10mm, the lower test piece is GCr15 steel ball of Φ40mm, the test parameters are: normal load P=50N, reciprocating rotation (torsion) angular velocity ω=0.2°/ s, the rotation angle θ is 0.5°, and the number of reciprocating cycles is N=10 ³ .

Figure 4b is the torque-angular displacement curve obtained by using the same test device and specimen material as Figure 4a, and the test parameters are basically the same, except that the rotation angle θ is changed to 2°.

Fig. 5a is a topography diagram of the wear scar after the test of the upper specimen of Fig. 4a.

Fig. 5b is a topography diagram of the wear scars of the upper specimen in Fig. 4b after the test.

Fig. 6a is the X-ray energy spectrogram (EDX) of wear scars and debris after the test of the upper specimen in Fig. 4a, where the abscissa is: energy/kev (energy/kev); the ordinate is: counts.

Detailed ways

Example

A kind of specific embodiment of the present invention is, a kind of torsion fretting friction and wear test method, and its practice is:

a. Clamp the upper specimen on the upper fixture, and then fix the lower fixture and the high-precision low-speed turntable through threads, and the vertical centerline of the clamping cavity of the lower fixture is aligned with the rotation axis of the high-precision low-speed turntable, Clamp the spherical lower test piece with the lower clamp;

b. Control the up and down movement of the upper fixture through the data acquisition control system, so that the upper and lower specimens are in contact with and apply the set load P, and at the same time, through the control of the data acquisition control system, the lower fixture and the lower specimen held by it are controlled by the data acquisition control system. The reciprocating rotation of the set speed ω, rotation angle θ and reciprocating times N realizes the torsional and fretting friction between the upper and lower specimens;

c. While twisting and fretting friction occurs on the upper and lower test pieces, the friction torque is measured through the six-dimensional force/torque sensor connected to the upper fixture, and sent to the data acquisition and control system. The data acquisition and control system analyzes and obtains the design Torque-angular displacement curves under constant speed and load conditions to characterize the dynamics of torsional fretting friction.

In order to realize the above test method more conveniently and quickly, the specific composition of the test device used in this example is as follows.

Fig. 1, 2 shows, realizes the test device of twisting fretting friction test method of the present invention, comprises upper and lower clamp 15,19, and the support 1 of upper and lower clamp is installed.

The specific structure that the lower clamp 19 is installed on the machine base 1 is as follows: the lower clamp 19 is a clamp for clamping a spherical test piece, the lower clamp 19 and the high-precision low-speed rotating table are fixed by threads, and the vertical direction of the clamping chamber of the lower clamp 19 is The center line is aligned with the rotating shaft of the high-precision low-speed turntable; the high-precision low-speed turntable is installed on the bottom plate 24 of the machine base 1 .

The specific structure of the upper fixture 15 installed on the base 1 is as follows: the upper end of the upper fixture 15 is connected to the six-dimensional force/torque sensor 13, and the six-dimensional force/torque sensor 13 is connected to a two-dimensional mobile platform capable of horizontal and vertical movement , the two-dimensional mobile platform is fixed on the middle and upper part of the base.

The high-precision low-speed rotary table, the two-dimensional mobile table, and the six-dimensional force/torque sensor 13 are all electrically connected to the data acquisition and control system.

The composition of above two-dimensional mobile station is: vertical motor 3 is fixed on the top plate of support 1 top, and vertical motor shaft is connected with vertical screw mandrel 5, and vertical screw mandrel 5 cooperates with the internal thread of motion block 25, The chute on the inside of the moving block 25 cooperates with the guide rail 6 on the vertical plate 2, and the outside of the moving block 25 is fixedly connected with the crossbeam 7; On the side vertical plate 2 of the machine base 1, the horizontal motor shaft is connected with the horizontal screw mandrel 9, and the horizontal screw mandrel 9 cooperates with the internal thread of the motion board 11, and the bottom of the motion board 11 is connected with the six-dimensional force/torque sensor 13.

The specific way of connecting the above moving board 11 to the six-dimensional force/torque sensor 13 is: the lower part of the moving board 11 is screwed to the connecting block 12, and the lower part of the connecting block 12 is connected to the six-dimensional force/torque sensor 13.

The vertical plate of support is also provided with guide bearing 26, and the bottom of vertical screw mandrel 5 passes this guide bearing 26.

The composition of the above high-precision low-speed rotary table is as follows: the bracket 23 is installed on the base plate 24 of the machine base, the high-precision low-speed motor 22 is vertically fixed on the bracket 23, and the output shaft 21 of the high-precision low-speed motor 22 is fixed on the rotary table 20, The lower clamp 19 is screwed on the rotating table top 20 .

Fig. 3 shows, there is an arc surface 31 in the middle of the bottom of the clamping chamber of the lower fixture 19, the radius of curvature of the arc surface 31 is the same as the radius of the spherical lower test piece 17, and a positioning channel is opened at the center of the arc surface. Holes 32; the lower fixture pressing plate 18 has an arc-shaped through hole 30, the radius of curvature of which is also the same as that of the spherical lower test piece 17, and the positioning through hole 32, the arc surface 31 of the clamping cavity of the lower fixture 19 and the lower fixture pressing plate 18 The arc-shaped through-holes 30 of the three are coincident with each other. In this way, after the lower test piece 17 can be ensured to be placed in the clamping chamber and the lower fixture pressing plate 18 is pressed, the vertical diameter of the clamped lower test piece 17 overlaps with the vertical centerline of the clamping chamber, that is, it is in line with the height of the clamping chamber. The axes of rotation of the precision low-speed turntable overlap.

The minimum rotation angle θ of the torsional motion of the high-precision low-speed turntable used in this example is 0.05°, and the range of the rotational speed ω is 0.01-5°/s. That is, the minimum output rotation angle of the high-precision low-speed motor 22 is 0.05°, and the rotation speed range is 0.01-5°/s.

The normal load measurement range of the six-dimensional force/torque sensor 13 adopted in this example is 1-580N; It is 1N·mm.

The results of two concrete tests that adopt the above device of the present invention and test method thereof to carry out are as follows:

The test materials are: the upper test piece is LZ50 axle steel test block of 20mm×10mm×10mm, and the lower test piece is GCr15 steel ball of Φ40mm. Test conditions: load P=50N, angular velocity ω=0.2°/s, rotation angle θ of 0.5°, 2°, reciprocating times N=1000. The two tests differ only in the angle of rotation θ, the angle θ of the first one is 0.5°, and the angle of rotation θ of the second is 2°.

Fig. 4a is the torque-angular displacement curve of LZ50 steel under torsional fretting condition obtained from the first (small angle, θ=0.5°) test. The shape of the curve is elliptical, and it can be judged that it belongs to the partial slip state of fretting. This is consistent with the experimental characteristics of tangential fretting friction.

Figure 4b shows the parallelogram-shaped T-θ curve obtained from the second (large angle, θ=2°) test, which can be judged to be a complete slip state of fretting; it is also the experimental feature of tangential fretting friction unanimous.

Figure 5a shows the wear scar morphology of LZ50 steel after the first test above. The figure shows that when the part slips, the center of the wear scar on the upper specimen adheres and is slightly damaged; the outer side is slightly slipped, that is, relative slip, and the wear is serious. It shows that a partial slip has occurred, which is also consistent with the judgment in Figure 4a.

Figure 5b shows the wear scar morphology of LZ50 steel after the second test above. It can be seen from the figure that the contact area has completely slipped, and all contact areas have serious wear scar damage, which is also consistent with the judgment in Figure 4b. It is also consistent with the experimental characteristics of tangential fretting wear.

Figure 6a shows the EDX results of the reddish-brown wear debris on the surface of LZ50 steel after the first test above. It is found that the oxygen content after wear increases significantly, indicating that torsional fretting wear occurs on the contact surface.

Obviously, the upper fixture 15 and the two-dimensional mobile platform of the present invention, the lower fixture 19 and the high-precision low-speed rotary platform can be symmetrically interchanged, that is, the upper fixture and the two-dimensional mobile platform are rotated 180 degrees and installed on the bottom of the machine base 1; The lower fixture 19 and the high-precision low-speed rotary table are installed on the upper part of the machine base 1 by rotating 180 degrees; they belong to the simple equivalent replacement of the test device of the present invention.

Claims (7)

1. a twisting and fretting friction and wear test device, comprising upper and lower clamps (15,19), installing the support (1) of upper and lower clamps (15,19), characterized in that: The specific structure that the described lower clamp (19) is installed on the machine base (1) is: the lower clamp (19) is a clamp for clamping the spherical lower test piece (17), and the lower clamp (19) and the high-precision low-speed rotation The table is fixed by threads, and the vertical centerline of the clamping cavity of the lower fixture (19) is aligned with the rotation axis of the high-precision low-speed turntable; the high-precision low-speed turntable is installed on the base plate (24) of the machine base (1); The specific structure that the upper clamp (15) is installed on the machine base (1) is as follows: the upper end of the upper clamp (15) is connected with the six-dimensional force/torque sensor (13), and the six-dimensional force/torque sensor (13) is connected to the horizontal It is connected with the vertically moving two-dimensional mobile platform, and the two-dimensional mobile platform is fixed on the middle and upper part of the base (1); The composition of described two-dimensional mobile station is: vertical motor (3) is fixed on the top plate of support (1) top, and the shaft of vertical motor (3) is connected with vertical screw mandrel (5), and vertical screw The rod (5) cooperates with the internal thread of the moving block (25), the chute on the inside of the moving block (25) cooperates with the guide rail (6) on the vertical plate (2), and the outer side of the moving block (25) matches the crossbeam (7) Fixed connection; the slide rail (10) on the bottom of the beam (7) cooperates with the chute on the top of the motion plate (11), the horizontal motor (8) is fixed on the vertical plate (2) of the support (1), and the horizontal motor (8 ) is connected with the horizontal screw mandrel (9), the horizontal screw mandrel (9) cooperates with the internal thread of the motion plate (11), and the bottom of the motion plate (11) is connected with the six-dimensional force/torque sensor (13); The high-precision low-speed rotary table, the two-dimensional mobile table, and the six-dimensional force/torque sensor (13) are all electrically connected with the data acquisition control system. 2. A kind of test device according to claim 1, characterized in that, the concrete mode that described motion board (11) is connected with six-dimensional force/moment sensor (13) is: the bottom of motion board (11) and The connecting block (12) is threaded, and the bottom of the connecting block (12) is connected with the six-dimensional force/torque sensor (13). 3. A kind of test device according to claim 1, characterized in that, a guide bearing (26) is provided on the vertical plate (2) of the described machine base (1), and the bottom of the vertical screw mandrel (5) Pass through the guide bearing (26). 4. A kind of test device according to claim 1, characterized in that: the high-precision low-speed turntable is composed of: the support (23) is installed on the base plate (24) of the machine base (1), and the high-precision low-speed The motor (22) is vertically fixed on the support (23), and the output shaft (21) of the high-precision low-speed motor (22) fixes the rotary table (20), and the screw thread on the rotary table (20) fixes the lower clamp (19). 5. A kind of test device according to claim 1, characterized in that: an arc surface (31) is formed in the middle of the bottom of the clamping cavity of the lower clamp (19), and the curvature of the arc surface (31) is The radius is the same as the radius of the spherical lower test piece (17), and a positioning through hole (32) is arranged at the center of the arc surface (31); The radius of curvature is also identical with the radius of the lower test piece (17) of the spherical shape; the arc-shaped through hole ( 30), the center lines of the three coincide. 6. A test device according to claim 1, characterized in that: the minimum rotational angle θ of the torsional motion of the high-precision low-speed turntable is 0.05°, and the range of the rotational speed ω is 0.01-5°/s. 7. A kind of testing device according to claim 1, characterized in that: the normal load measuring range of the six-dimensional force/moment sensor (13) is 1-580N; The force measurement range is 1-180N, the torque measurement range is 1-10000N·mm, and the measurement accuracy is 1N·mm.

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