CN1645103A - Microfriction testers - Google Patents

Abstract

A micro-friction test device, the two-dimensional force sensor fixed on the two-dimensional displacement platform adopts a cantilever structure, and the horizontal bending beam and the vertical bending beam perpendicular to each other are fixed together by connecting blocks, and the horizontal bending beam and the vertical bending beam are composed of two Composed of parallel elastic bodies, one end of the cantilever is fixed, and the measured cylinder and friction head are fixed on the front end of the cantilever at the other end. The probe of the non-contact displacement sensor directly above the measured cylinder is fixed on the two-dimensional mobile platform by a rigid cantilever. Strain gauges are pasted on the vertical bending beam to measure friction, and the load is measured indirectly through displacement sensors. The invention can simultaneously measure micronewton-level load and frictional force, realize high-resolution loading of load without using a high-precision micro-displacement platform, and ensure force measurement accuracy at the same time.

Description

Micro friction test device

technical field

The invention relates to a micro-friction test device, in particular to a ball-on-disk type micro-friction test device for evaluating the tribological properties of various surface nano-lubricating films (or coatings).

Background technique

With the increasing application of micro-electromechanical systems (MEMS), the problems of friction and wear are becoming more and more prominent. Controlling and improving the surface characteristics of micromachines is an effective way to improve their microtribological properties. Surface nanofilms (or coatings) can greatly reduce the occurrence of wear and adhesion, thereby improving the service life of micromachines. Microfriction testing is of great significance for evaluating the tribological properties of lubricating films on these surfaces. However, the existing friction and wear test equipment, such as pin-on-disk friction and wear testing machine, four-ball friction and wear testing machine, etc. generally work above the Newton level, and none of them can reach the millinew level precision required for micro-friction testing. Literature [Yang Mingchu, Luo Jianbin, Wen Shizhu. Development of Magnetic Recording Microscopic Tribological Performance Tester. Journal of Tsinghua University (Natural Science Edition), 2000, 40(8): 36-40] and [Li Haiwen, Jia Hongguang, Wu Yihui, etc. Micro friction tester force sensor research. Optical precision engineering, 2002, 10 (4), 388-391] mentioned in the micro friction tester are all used to paste strain gauges on the elastic body, using the resistance strain effect to The elastic body strain caused by the load and friction is converted into a change in resistance, and then further converted into a voltage signal through the bridge, thereby indirectly measuring the magnitude of the load and friction. In these test devices, the loading of the load is achieved by changing the strain of the elastic body. However, due to the extremely small strain of the elastic body, it is necessary to use an expensive high-precision micron-scale displacement platform to obtain a high load loading resolution. , such as the use of piezoelectric ceramic telescopic tubes to achieve micro-displacement, which increases the cost; in addition, the level of the motion platform needs to be very high, so as to avoid the change of the load amplitude in the micro-friction test from being too large.

Contents of the invention

The purpose of the present invention is to solve the above problems and provide an economical and practical micro-friction testing device, which can not only measure the friction force and normal load of piconew level at the same time, but also has a higher load loading resolution.

In order to achieve such a purpose, the technical solution adopted in the present invention is: a two-dimensional force sensor adopting a cantilever structure is fixed on the two-dimensional displacement platform, and in the two-dimensional force sensor, the horizontal bending beam and the vertical bending beam perpendicular to each other pass through The connecting blocks are fixed together. Both the horizontal bending beam and the vertical bending beam are composed of two parallel elastic bodies. One end of the cantilever is fixed, and the other end is the front end of the cantilever. The measured cylinder and the friction head are fixed on the front end of the cantilever. The probe of the non-contact displacement sensor is installed directly above the measured cylinder, which is fixed on the two-dimensional mobile platform by a rigid suspension beam. Strain gauges are pasted on the vertical bending beam to measure friction, and the load is measured indirectly through displacement sensors.

In the present invention, a two-dimensional force measuring sensor can be fixed on the two-dimensional displacement platform capable of realizing micro-displacement in the horizontal direction and the vertical direction. The two-dimensional force sensor adopts an elastic cantilever structure, including a cantilever composed of a horizontal bending beam, a connecting block, a vertical bending beam, a rigid cantilever directly above the cantilever, and a displacement sensor probe. The vertical curved beam and the horizontal curved beam are respectively composed of two parallel elastic bodies, and the cube connection block connects the vertical curved beam and the horizontal curved beam perpendicular to each other in the length direction to form the main structure of the cantilever. Four pieces of strain gauges are symmetrically pasted on the front and back of any elastic body of the vertical bending beam, and form a full-bridge circuit, and the position is close to the two-dimensional mobile platform. The cantilever end is connected to the horizontal bending beam as the free end of the cantilever. A friction ball is fixed at the bottom of the cantilever end, and the measured cylinder at the top serves as the reference measured surface of the displacement sensor probe above it. The displacement sensor probe is located at one end of the rigid suspension beam, and the other end of the rigid suspension beam is fixed on the two-dimensional mobile platform. The sample stage connected coaxially with the speed-regulating motor is used to place friction test samples.

During the friction test, the speed-regulating motor drives the sample table to perform ball-on-disk frictional motion. Adjusting the vertical fine-tuning knob of the two-dimensional mobile platform can change the strain of the horizontal bending beam on the cantilever, thereby changing the load on the sample to be tested. . The friction ball is under the simultaneous action of load and friction, both the vertical bending beam and the horizontal bending beam are strained and deformed, and the distance between the displacement sensor probe and the measured cylinder also changes, and the vertical bending beam is only strained by friction Deformation, the distance between the displacement sensor probe and the measured cylinder is only related to the load. Use the resistance strain effect to convert the elastic strain gauge strain caused by friction into the resistance change of the strain gauge, and then further convert it into a voltage signal through the bridge, so as to indirectly measure the magnitude of the load and friction force; use the non-contact displacement sensor probe to the measured The distance between the cylindrical end faces can indirectly obtain the magnitude of the load.

The invention uses a non-contact displacement sensor to measure the size of the load, can realize high-resolution loading of the load without using a high-precision micro-displacement platform, and simultaneously ensures the force measurement accuracy. The two-dimensional load cell is fixed on the two-dimensional mobile platform, and the load size and the position of the friction contact point can be changed through the horizontal and vertical fine-tuning knobs on the two-dimensional mobile platform. It has a high load loading resolution.

The invention has the advantages of simple structure, good reliability and low cost, and can be widely used in evaluation tests of micro-friction properties of various thin films (or coatings).

Description of drawings

Fig. 1 is a schematic diagram of the structure of the present invention.

In Figure 1, 1. Horizontal fine-tuning knob, 2. Two-dimensional displacement platform, 3. Vertical fine-tuning knob, 4. Rigid suspension beam, 5. Displacement sensor probe, 6. Sample, 7. Sample stage, 8. Speed-regulating motor, 13. Horizontal curved beam, 14. Connecting block, 15. Vertical curved beam.

Fig. 2 is a schematic diagram of the three-dimensional structure of the two-dimensional load cell of the present invention.

In Fig. 2, 4. rigid cantilever beam, 5. displacement sensor probe, 9. fixed end, 10. measured cylinder, 11. friction ball, 12. cantilever end, 13. horizontal bending beam, 14. connection block, 15. Vertical bending beam, 16. Strain gauge

Detailed ways

The present invention will be further described below in conjunction with accompanying drawing.

The structural principle of the present invention is shown in Figure 1, the two-dimensional displacement platform 2 realizes micro-displacement in the horizontal direction and the vertical direction through the horizontal fine-tuning knob 1 on the lower left and the vertical fine-tuning knob 3 on the top, and one side of the two-dimensional displacement platform 2 is fixed Two-dimensional load cell. The structure of the two-dimensional force sensor includes a cantilever composed of a horizontal bending beam 13, a connecting block 14, a vertical bending beam 15, and a rigid cantilever 4 directly above the cantilever and a displacement sensor probe 5. One end of the rigid suspension beam 4 is fixed on the two-dimensional mobile platform, and the displacement sensor probe 5 is placed on the other end. The friction test sample 6 is placed on the sample stage 7 coaxially connected with the speed regulating motor 8 .

In the present invention, the two-dimensional load cell adopts an elastic body cantilever structure, as shown in FIG. 2 . The vertical curved beam 15 and the horizontal curved beam 13 are respectively composed of two parallel elastic bodies, and the cube connection block 14 connects the vertical curved beam 15 and the horizontal curved beam 13 perpendicular to each other in the length direction to form a cantilever main structure. Four strain gauges 16 are symmetrically pasted on the front and back of any elastic body of the vertical bending beam 15 to form a full-bridge circuit, and the position is close to the fixed end 9 connected to the two-dimensional mobile platform 2 . The cantilever end 12 is connected with the horizontal bending beam 13 as the free end of the cantilever. A friction ball 11 is fixed at the bottom of the cantilever end 12 , and the measured cylinder 10 at the top serves as a reference measured surface of the displacement sensor probe 5 above it. The displacement sensor probe 5 is located at one end of the rigid suspension beam 4, and the other end of the rigid suspension beam 4 is fixed on a two-dimensional mobile platform.

The working principle of the micro-friction testing device of the present invention is given below.

The friction test sample 6 is placed on the sample stage 7 coaxially connected with the speed regulating motor 8 . The speed-regulating motor 8 drives the sample table 7 to perform a ball-on-disc frictional motion, and adjusting the vertical fine-tuning knob 3 of the two-dimensional mobile platform 2 can change the strain of the horizontal bending beam 13 on the cantilever 9, thereby changing the effect on the sample 6 to be tested. load size. The change of the distance between the non-contact displacement sensor probe 5 and the measured cylinder 10 reflects the change of the load. During the friction test, the friction ball 11 is subjected to the simultaneous action of load and friction force, the vertical bending beam 15 and the horizontal bending beam 13 both undergo strain deformation, and the distance between the displacement sensor probe 5 and the measured cylinder 10 also changes, and the vertical bending beam 15 also changes. The bending beam 15 is only deformed by friction, and the distance between the displacement sensor probe 5 and the measured cylinder 10 is only related to the magnitude of the load. This means that a certain frictional force corresponds to a certain strain of the vertical bending beam 15 ; a certain load corresponds to a certain distance between the displacement sensor probe 5 and the measured cylinder 10 . Therefore, the resistance strain effect can be used to convert the strain of the elastic strain gauge 16 caused by friction into the resistance change of the strain gauge, and then further converted into a voltage signal through the electric bridge, thereby indirectly measuring the magnitude of the load and friction force; using a non-contact displacement sensor The distance from the probe 5 to the end face of the measured cylinder 10 can indirectly obtain the magnitude of the load.

In one embodiment of the present invention, the vertical curved beam 15 is composed of two parallel elastic bodies with a length of 40mm, a width of 10mm, and a thickness of 0.34mm, and the distance between the two parallel elastic bodies is 2mm; the horizontal curved beam 13 is composed of a length of 30mm and a width of 10mm , two parallel elastic bodies with a thickness of 0.1 mm, and the distance between the two parallel elastic bodies is 2 mm. The side length of the square connection block 14 connecting vertical curved beams 15 and horizontal curved beams 13 perpendicular to each other is 10 mm, and the model of the non-contact displacement sensor probe 5 is ST-1-05 produced by Beijing Hongjidian Technology Development Co., Ltd. Located 1.5mm directly above the measured cylinder 10. The ST-1-05 displacement sensor has a large linear distance of 1.5mm, that is, the load is from zero to the maximum, and the vertical displacement of the two-dimensional displacement platform 12 can reach 1.5mm. Using an ordinary displacement platform, a high-resolution load can be achieved load.

Claims (1)

1. A micro-friction test device, characterized in that the two-dimensional displacement platform (2) realizes micro-displacement in the horizontal direction and the vertical direction through the horizontal fine-tuning knob (1) and the vertical fine-tuning knob (3), and the two-dimensional displacement platform (2 ) in the two-dimensional load cell fixed on one side, the cube connecting block (14) connects vertical bending beams (15) and horizontal bending beams (13) perpendicular to each other in the length direction to form the main structure of the cantilever, and the vertical bending beam (15) and the horizontal bending beam (13) are respectively composed of two parallel elastic bodies, and four strain gauges (16) are symmetrically pasted on the positive and negative sides of any elastic body of the vertical bending beam (15), and form a full-bridge circuit, The position is close to the two-dimensional mobile platform (2), and the cantilever end (12) is connected with the horizontal bending beam (13) as the free end of the cantilever. The bottom of the cantilever end (12) is fixed with a friction ball (11), and the cantilever end (12 ) is fixed on the top of the measured cylinder (10), the displacement sensor probe (5) directly above the measured cylinder (10) is located at one end of the rigid suspension beam (4), and the other end of the rigid suspension beam (4) is fixed on the two-dimensional mobile platform , the friction test sample (6) is placed on the sample stage (7) coaxially connected with the speed regulating motor (8).

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