Nanometer cutting depth high-speed single-point scratch test device and test method thereof

Abstract

A nanometer cutting depth high-speed single-point scratch test device includes a workbench, an air-bearing turntable, a test piece fixture, a test piece, a Z-direction feeding device, a nano positioning stage, a force sensor and a scratch tool. A micro convex structure with controllable length and height is machined in a position of the test piece to be scratched.

Claims

1. A scratch test device, comprising: a base; a horizontally arranged workbench fixedly installed on a top surface of the base; a vertically arranged air-bearing turntable fixedly installed on the workbench; a test piece fixture installed on an end face of a top portion of the air-bearing turntable and coaxially arranged with the air-bearing turntable, wherein, the air-bearing turntable drives the test piece fixture to rotate and the test piece fixture is a vacuum chuck, a magnetic chuck, or a mechanical structure fixture; a test piece installed on the test piece fixture; a Z-direction feeding device installed on a top surface of the workbench and configured to feed in a rotational axial direction of the air-bearing turntable; a nano positioning stage installed to the Z-direction feeding device through a nano positioning stage connection piece; a force sensor affixed to the nano-positioning stage through a force sensor connection piece, wherein the force sensor is configured to measure a normal force in a Z-direction and a tangential force in a X-direction; and a scratch tool affixed to the force sensor through a scratch tool connection piece, wherein a micro convex structure with controllable length and height is machined in a position of the test piece to be scratched, and a scratch length L.sub.x along a scratch direction of the micro convex structure corresponding to a scratch depth d satisfies the following relation: $L_X\ge \frac{\mathrm{vq}}{f}$ wherein v is a scratch speed required for the test; q is a quantity of force signal points required for the test in an effective scratch area; and f is a sampling frequency set by the force sensor; a length L.sub.y of the micro convex structure along a radial direction is no less than a feeding step length l.sub.y of the scratch tool along a Y direction in a scratch process; a maximum height H of the micro convex structure along the Z direction is larger than a maximum cutting depth d.sub.max required for the test; and a Y-section shape of the micro convex structure is arc-shaped or polyline-shaped, and an arc radius or a straight slope is selected according to the scratch speed, the scratch depth, and the scratch length set by the scratch test.

2. The scratch test device according to claim 1, wherein the air-bearing turntable is driven by a servo motor installed on a bottom surface of the workbench, and the air-bearing turntable is connected to the servo motor through a belt; the air-bearing turntable is an air bearing mechanical air-bearing turntable; an end face runout and a radial runout of the air-bearing turntable are both less than 0.5 μm; and relative positions of the air-bearing turntable, the test piece fixture and the test piece are fixed in the Z direction.

3. The scratch test device according to claim 1, wherein a shape of the test piece is centrosymmetry about the Z axis, the micro convex structure is machined in the position of the test piece to be scratched, and is affixed to the air-bearing turntable through the test piece fixture, and a centrosymmetry axis of the test piece coincides with a rotational axis of the air-bearing turntable.

4. The scratch test device according to claim 1, wherein the shape of the test piece is centrosymmetry about the Z axis and a thickness of the test piece is less than 1 mm, an elastic film having a length of no less than 5 mm, a width of no less than 1 mm, and a height of no less than 10 mm is pasted on a back of the test piece, and the magnetic chuck or the vacuum chuck having a flat surface is used for clamping, during a clamping process, the flat surface of the vacuum chuck/magnetic chuck and the elastic film are used to elastically deform a surface of the test piece through vacuum adsorption/magnetic adsorption to form the micro convex structure, and the centrosymmetry axis of the test piece coincides with a rotational axis of the air-bearing turntable.

5. The scratch test device according to claim 1, wherein the test piece is a block test piece having an irregular shape, and is clamped on an end face of the air-bearing turntable through the test piece fixture in order to ensure a dynamic balance of the end face of the air-bearing turntable in a rotary motion, a balancing block is additionally installed on the test piece fixture and a gravity center of the balancing block and a gravity center of the test piece are centrosymmetric about a rotational axis of the air-bearing turntable.

6. The scratch test device according to claim 1, wherein the scratch tool comprises a single-point tool and a fixed seat, and is made of a material that is diamond, cubic boron nitride, or ceramic; and the single-point tool is affixed to a top end of the fixed seat through bonding, brazing, or electroplating.

7. The scratch test device according to claim 1, wherein the nano positioning stage is a nanometer linear displacement platform, which realizes a linear displacement in the Z direction and the Y direction, the nanometer linear displacement platform is affixed to the Z-direction feeding device through the nano positioning stage connection piece, a precision of a Z-direction closed-loop linear motion is better than 10 nm, a stroke of the Z-direction closed-loop linear motion is no less than 10 μm, a precision of a Y-direction closed-loop linear motion is better than 100 nm, and a stroke of the Y-direction closed-loop linear motion is no less than 100 μm.

8. The scratch test device according to claim 1, wherein the nano positioning stage is a nano linear stage, which realizes linear displacement with a nanometer precision in the Z direction and a deflection motion around an X axis, and indirectly realizes a micro feed in the Y direction and the Z direction) of the air-bearing turntable by adjusting a deflection radius; a precision of a Z-direction closed-loop linear motion is better than 10 nm, a stroke of the Z-direction closed-loop motion is no less than 10 μm, a precision of an X-direction closed-loop deflection motion is better than 1 μrad, and a stroke of the X-direction closed-loop deflection motion is no less than ±0.5 mrad.

9. A test method of a scratch test device, comprising: A. clamping a test piece selecting a mode for clamping the test piece according to a shape of the test piece, when the test piece is an axisymmetric shape, performing step A1, and when the test piece is a block test piece of an irregular shape, performing step A2; A1. for the test piece of the axisymmetric shape, machining a micro convex structure having a controllable length and height in a position of the test piece to be scratched, and fixedly installing the micro convex structure on an air-bearing turntable through a test piece fixture; then performing step B; A2. for the block test piece of the irregular shape, machining the micro convex structure in the position of the test piece to be scratched, clamping the test piece on an end face of the air-bearing turntable through the test piece fixture, and installing a corresponding balancing block to ensure a dynamic balance of the end face of the air-bearing turntable in a high-speed rotary motion, wherein a gravity center of the balancing block and a gravity center of the test piece are centrosymmetric about a rotational axis of the air-bearing turntable; B. controlling a scratch tool to approach a surface of the test piece through a Z-direction feeding device; rotating the air-bearing turntable so that the micro convex structure on a surface of the test piece to be scratched is located directly below the scratch tool; pasting a protective film with a thickness of T on the micro convex structure of the test piece, controlling the scratch tool to move to a negative limit position of a nano positioning stage in a radial direction, and controlling the Z-direction feeding device to enable the scratch tool to rapidly approach the micro convex structure of the test piece by using an online micro-observation system; C. adjusting tool C1. opening a locking mechanism of the Z-direction feeding device; C2. controlling the scratch tool to step toward the test piece at a step length smaller than the thickness T of an elastic film in the Z direction through the nano positioning stage; C31. when a force sensor detects a significant increase in force signals, that is, the scratch tool contacts the protective film adhered to the micro convex structure of the test piece, performing step C6; otherwise, performing step C32; C32. when the nano positioning stage steps toward the negative limit position in the Z direction, performing step C4; otherwise, performing step C2; C4. unlocking the locking mechanism of the Z-direction feeding device, and controlling the nano positioning stage to lift to a positive limit position in the Z direction; C5. controlling the Z-direction feeding device to feed a specified distance in a direction of the test piece, wherein the distance does not exceed a difference value between a stroke limit of the nano positioning stage in the Z direction and the positioning precision of the Z-direction feeding device; then performing step C1; C6. stopping the feeding of the nano positioning stage in the Z direction, removing the protective film, and completing the step of adjusting tool; D. scratching the test piece starting the air-bearing turntable, and calculating and setting a rotation speed n of the air-bearing turntable (3) according to the following formula, with the unit of rpm: $n=\frac{30v}{\pi R}$ wherein, R is a rotation radius of the end face of the air-bearing turntable where the micro convex structure is located, v is a scratch speed required for a scratch test, and the test piece is clamped on the test piece fixture and rotates with the air-bearing turntable according to the set rotation speed n; controlling the nano positioning stage and the Z-direction feeding device to implement an alternative scratch feeding strategy, wherein the alternative scratch feeding strategy comprises the following feeding motions of: D1. opening the locking mechanism of the Z-direction feeding device; D2. controlling the scratch tool to step feed to the test piece at a step length of 10 to 1000 nm through the nano positioning stage, wherein the stepping feed is decomposed into the feed in a negative Z direction and the feed in a negative Y direction; in the case of single scratch of the same residual imprint, performing step D21; and in the case of multiple scratches of the same residual imprint, performing step D22; D21. for the single scratch of the same residual imprint, driving the test piece to rotate every one revolution by the air-bearing turntable, a component f.sub.z of the step length of the stepping feed of the scratch tool in the Z direction is no less than a minimum cutting depth d.sub.min required for the scratch test and no more than a maximum cutting depth d.sub.max required for the scratch test, i.e., d.sub.min≤f.sub.z≤d.sub.max; and a component f.sub.y of the step length of the stepping feed of the scratch tool in a radial direction (i.e. the Y direction) of the end surface of the air-bearing turntable is no less than 10 μm, so that scratches distributed in the Y direction with gradually changed cutting depths are independent of each other and do not interfere with each other; performing step D3; D22. for the multiple scratches of the same residual imprint, after one step is completed in the stepping feed motion of the scratch tool, staying for a residence time t, until a quantity s of scratches required for the test is reached, and continuing to feed to the test piece step by step, wherein the residence time t satisfies s/n≤t<(s+1)/n; a component f.sub.z of the step length of the stepping feed of the scratch tool in the Z direction is no less than a minimum cutting depth d.sub.min required for the scratch test and no more than a maximum cutting depth d.sub.max required for the scratch test, i.e., d.sub.min≤f.sub.z≤d.sub.max; and a component f.sub.y of the step length of the stepping feed of the scratch tool in a radial direction (i.e. the Y direction) of the end face of the air-bearing turntable is no less than 10 μm, so that scratches distributed in the Y direction with gradually changed cutting depths are independent of each other and do not interfere with each other; D3. when a cumulative displacement of the stepping feed in the Z direction exceeds the maximum cutting depth required for the test, or the nano positioning stage moves to a negative limit position in the Y direction, or the cumulative displacement of the stepping feed in the Z direction reaches a negative limit position in Z direction of the nano positioning stage, stopping the stepping feed, and performing step D31; otherwise, performing step D2; D31. analyzing the force signals collected by the force sensor during feed, when the scratch force signals are detected, indicating the high-speed scratch conducted by the scratch tool on the surface of the micro convex structure of the test piece, and performing step D5; otherwise, performing step D32; D32. when the nano positioning stage has reached the negative limit position in the Y direction, controlling the nano positioning stage to move to a positive limit position in the Y direction, and performing step D2; otherwise, performing step D33; D33. when the nano positioning stage has reached the negative limit position in the Z direction, performing step D4; otherwise, performing step D2; D4. unlocking the locking mechanism of the Z-direction feeding device, and controlling the scratch tool to feed to the surface of the test piece through the Z-direction feeding device, so that the scratch tool further approaches the surface of the test piece; in order to avoid the scratch tool coming into contact with the micro convex structure in the approaching process, a feeding amount of the Z-direction feeding device does not exceed a difference value between a stroke of the nano positioning stage in the Z direction and a positioning precision of the Z-direction feeding device, and controlling the nano positioning stage to move to the positive limit position in the Z direction; and performing step D1; and D5. unlocking the locking mechanism of the Z-direction feeding device , controlling the scratch tool to lift up through the Z-direction feeding device, stopping the air-bearing turntable, and completing the scratch test.

10. The test method according to claim 9, wherein, when a thickness of the test piece of axisymmetric shape in step A2 is less than 1 mm, an elastic having a length no less than 5 mm, a width no less than 1 mm, and a height no less than 10 μm is pasted on a back of the test piece, a magnetic chuck or a vacuum chuck with a flat surface is used for clamping, in the clamping process, the flat surface of the vacuum chuck/magnetic chuck and the elastic film are used to elastically deform the surface of the test piece through vacuum adsorption/magnetic adsorption to form the micro convex structure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates a front view of a test device according to the present disclosure.

(2) FIG. 2 illustrates a top view of FIG. 1.

(3) FIG. 3 illustrates a diagram of a micro convex structure of a workpiece.

(4) FIG. 4 illustrates an A-A section view of FIG. 3.

(5) FIG. 5 illustrates a flow chart of a test method according to the present disclosure.

(6) In the drawings: 1—base; 2—workbench; 3—air-bearing turntable; 4—test piece fixture; 5—test piece; 6—scratch tool; 7—scratch tool connection piece; 8—force sensor; 9—force sensor connection piece; 10—nano positioning stage; 11—nano positioning stage connection piece; 12—Z-direction feeding device; 13—elastic film; and 14—micro convex structure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) The present disclosure is further described hereinafter with reference to the drawings. As shown in FIGS. 1 to 4, a nanometer cutting depth high-speed single-point scratch test device comprises:

(8) a base 1;

(9) a horizontally arranged workbench 2 fixedly installed on a top surface of the base 1;

(10) a vertically arranged air-bearing turntable 3 fixedly installed on the workbench 2;

(11) a test piece fixture 4 that is installed on an end face of a top portion of the air-bearing turntable 3 and is coaxial with the air-bearing turntable 3, the air-bearing turntable 3 drives the test piece fixture 4 to rotate, and the test piece fixture 4 is vacuum chuck, magnetic chuck or mechanical structure fixture;

(12) a test piece 5 installed on the test piece fixture 4;

(13) a Z-direction feeding device 12 that is installed on a top surface of the workbench 2 and feeds in a rotation axis direction of the air-bearing turntable 3; the Z-direction feeding device 12 is installed on the top surface of the workbench 2 through threaded connection, with a positioning precision better than 5 μm;

(14) a nano positioning stage 10 installed to the Z-direction feeding device 12 through a nano positioning stage connection piece 11;

(15) a force sensor 8 installed to the nano positioning stage 10 through a force sensor connection piece 9; the force sensor 8 has a function of measuring normal force and tangential force, and normal direction is Z direction, and tangential direction is an X direction; and

(16) a scratch tool 6 installed to the force sensor 8 through a scratch tool connection piece 7;

(17) wherein the test piece 5 is non-ferrous metal, ferrous metal or hard brittle material, a micro convex structure 14 with controllable length and height is machined in a position of the test piece 5 to be scratched, and a length L.sub.x along a scratch of the micro convex structure 14 corresponding to a scratch depth d satisfies the following formula:

(18) $L_X\ge \frac{\mathrm{vq}}{f}$

(19) wherein, v is a scratch speed required for the test, m/s; q is a quantity of force signal points required for the test in an effective scratch area; and f is a sampling frequency set by the force sensor 8, Hz;

(20) a length L.sub.y of the micro convex structure 14 along a radial direction is no less than a feeding step length l.sub.y of the scratch tool 6 in a Y direction in a scratch process;

(21) a maximum height H of the micro convex structure 14 along the Z direction is larger than a maximum cutting depth d.sub.max required for the test; and

(22) a Y-section shape of the micro convex structure 14 is arc-shaped or polyline-shaped, and an arc radius or a straight slope is selected according to the scratch speed, scratch depth and scratch length set by the scratch test.

(23) Further, the air-bearing turntable 3 is driven by a servo motor, the servo motor is installed on a bottom surface of the workbench 2, and the air-bearing turntable 3 is connected to the servo motor through a belt; the air-bearing turntable 3 is an air bearing mechanical air-bearing turntable 3; an end face runout and a radial runout of the air-bearing turntable 3 are both less than 0.5 μm; and relative positions of the air-bearing turntable 3, the test piece fixture 4 and the test piece 5 are fixed in the Z direction.

(24) Further, a shape of the test piece 5 is centrosymmetry about Z axis, the micro convex structure 14 with controllable length and height is machined in the position of the test piece 5 to be scratched, and is fixedly installed to the air-bearing turntable 3 through the test piece fixture 4, and a centrosymmetry axis of the test piece 5 coincides with a rotation axis of the turntable.

(25) Further, the shape of the test piece 5 is centrosymmetry about Z axis and a thickness of the test piece 5 is less than 1 mm, an elastic film 13 with a length no less than 5 mm, a width no less than 1 mm and a height no less than 10 mm is pasted on a back of the test piece 5, and a magnetic chuck or a vacuum chuck with a flat surface is used for clamping, during a clamping process, the flat surface of the vacuum chuck/magnetic chuck and the elastic film 13 are used to elastically deform a surface of the test piece 5 through vacuum adsorption/magnetic adsorption to form the micro convex structure 14 with controllable length, width and height, and the central centrosymmetry axis of the test piece 5 coincides with the rotation axis of the air-bearing turntable 3.

(26) Further, the test piece 5 is a block test piece 5 with irregular shape, and the micro convex structure 14 with controllable length and height is machined in the position of the test piece 5 to be scratched; the test piece 5 is clamped on an end face of the air-bearing turntable 3 through the test piece fixture 4; in order to ensure a dynamic balance of the end face of the air-bearing turntable 3 in a high-speed rotary motion, a balancing block is additionally installed on the test piece fixture 4, and a gravity center of the balancing block and a gravity center of the test piece 5 are centrosymmetric about the rotation axis of the air-bearing turntable 3.

(27) Further, the scratch tool 6 comprises a single-point tool and a fixed seat of single-point tool, and the material of the single-point tool is the material with higher hardness than that of the test piece 5 and has the characteristic of machining a sharp point of micron/submicron curvature radius, comprising diamond, cubic boron nitride or ceramic; and the single-point tool is fixed on a top end of the fixed seat through bonding, brazing or electroplating.

(28) Further, the nano positioning stage 10 is a nanometer linear displacement platform, which realizes linear displacement with nanometer precision in a vertical direction (i.e. the Z direction) and a radial direction of the end face of the air-bearing turntable 3 (i.e. the Y direction); the nanometer linear displacement platform is installed to the Z-direction feeding device 12 through the nano positioning stage connection piece 11, the precision of a Z-direction closed-loop linear motion is better than 10 nm, a stroke of the Z-direction closed-loop linear motion is no less than 10 μm, the precision of a Y-direction closed-loop linear motion is better than 100 nm, and the stroke of the Y-direction closed-loop linear motion is no less than 100 μm.

(29) Further, the nano positioning stage 10 is a nano linear stage, which realizes linear displacement with nanometer precision in a vertical direction (i.e. the Z direction), and realizes deflection motion around an X axis, and indirectly realizes micro feed in a radial direction (i.e. the Y direction) and a vertical direction (i.e. the Z direction) of the air-bearing turntable 3 through adjusting a deflection radius; the precision of a Z-direction closed-loop linear motion is better than 10 nm, a stroke of the Z-direction closed-loop motion is no less than 10 μm, the precision of an X-direction closed-loop deflection motion is better than 1 μrad, and a stroke of the X-direction closed-loop deflection motion is no less than ±0.5 mrad.

(30) As shown in FIGS. 1 to 5, a test method of a nanometer cutting depth high-speed single-point scratch test device comprises the following steps of:

(31) A. clamping a test piece 5;

(32) selecting a mode for clamping the test piece 5 according to a shape of the test piece 5, if the test piece 5 is an axisymmetric shape, performing step A1, and if the test piece 5 is a block test piece of an irregular shape, performing step A2;

(33) A1. for the test piece of the axisymmetric shape, machining a micro convex structure 14 with controllable length and height in a position of the test piece 5 to be scratched, and fixedly installing the micro convex structure 14 to an air-bearing turntable 3 through a test piece fixture 4; performing step B;

(34) A2. for the block test piece of the irregular shape, machining the micro convex structure 14 with controllable length and height in the position of the test piece 5 to be scratched, clamping the test piece 5 on an end face of the air-bearing turntable 3 through the test piece fixture 4, and installing a corresponding balancing block to ensure a dynamic balance of the end face of the air-bearing turntable 3 in high-speed rotary motion, wherein a gravity center of the balancing block and a gravity center of the test piece 5 are centrosymmetric about a rotation axis of the air-bearing turntable 3;

(35) B. controlling a scratch tool 6 to approach a surface of the test piece 5 through a Z-direction feeding device 12;

(36) rotating the air-bearing turntable 3 so that the micro convex structure 14 on a surface of the test piece 5 to be scratched is located directly below the scratch tool 6;

(37) pasting a protective film with a thickness of T on the micro convex structure 14 of the test piece 5, controlling the scratch tool 6 to move to a negative limit position of the nano positioning stage 10 in a radial direction, and controlling the Z-direction feeding device 12 to enable the scratch tool 6 to rapidly approach the micro convex structure 14 of the test piece 5 by using an online micro-observation system;

(38) C. adjusting tool

(39) C1. opening a locking mechanism of the Z-direction feeding device 12;

(40) C2. controlling the scratch tool 6 to step toward the test piece 5 according to a step length smaller than the thickness T of an elastic film 13 in the Z direction through the nano positioning stage 10;

(41) C31. if a force sensor 8 detects a significant increase in force signals, that is, the scratch tool 6 contacts the protective film adhered to the micro convex structure 14 of the test piece 5, performing step C6; otherwise, performing step C32;

(42) C32. if the nano positioning stage 10 steps toward the negative limit position in the Z direction, performing step C4; otherwise, performing step C2;

(43) C4. unlocking the locking mechanism of the Z-direction feeding device 12, and controlling the nano positioning stage 10 to lift to a positive limit position in the Z direction;

(44) C5. controlling the Z-direction feeding device 12 to feed a specified distance in a direction of the test piece 5, wherein the distance does not exceed a difference value between a stroke limit of the nano positioning stage 10 in the Z direction and the positioning precision of the Z-direction feeding device 12; and performing step C1;

(45) C6. stopping the feeding of the nano positioning stage 10 in the Z direction, removing the protective film, and completing the step of adjusting tool;

(46) D. scratching the test piece 5

(47) starting the air-bearing turntable 3, and calculating and setting a rotation speed n of the air-bearing turntable 3 according to the following formula, with the unit of rpm:

(48) $n=\frac{30v}{\pi R}$

(49) wherein, R is a rotation radius of the end face of the air-bearing turntable 3 where the micro convex structure 14 is located, m; v is a scratch speed required for a scratch test, m/s; and the test piece 5 is clamped on the test piece fixture 4 and rotates with the air-bearing turntable 3 according to the set rotation speed n;

(50) controlling the nano positioning stage 10 and the Z-direction feeding device 12 to implement an alternative scratch feeding strategy, wherein the alternative scratch feeding strategy comprises the following feeding motions of:

(51) D1. opening the locking mechanism of the Z-direction feeding device 12;

(52) D2. controlling the scratch tool 6 to step feed to the test piece 5 according to the step length of 10 to 1000 nm through the nano positioning stage 10, wherein the stepping feed is decomposed into the feed in a negative Z direction and the feed in a negative Y direction; in the case of single scratch of the same residual imprint, performing step D21; and in the case of multiple scratches of the same residual imprint, performing step D22;

(53) D21. for the single scratch of the same residual imprint, driving the test piece 5 to rotate every one revolution by the air-bearing turntable 3, a component f.sub.z of the step length of the stepping feed of the scratch tool 6 in the Z direction is no less than a minimum cutting depth d.sub.min required for the scratch test and no more than a maximum cutting depth d.sub.max required for the scratch test, i.e., d.sub.min≤f.sub.z≤d.sub.max; and a component f.sub.y of the step length of the stepping feed of the scratch tool 6 in a radial direction (i.e. the Y direction) of the end face of the air-bearing turntable 3 is no less than 10 μm, so that scratches distributed in the Y direction with gradually changed cutting depths are independent of each other and do not interfere with each other; and performing step D3;

(54) D22. for the multiple scratches of the same residual imprint, after one step is completed in the stepping feed motion of the scratch tool 6, staying for time t until a quantity s of scratches required for the test is reached, and continuing to feed to the test piece 5 step by step, wherein the residence time satisfies s/n≤t<(s+1)/n; a component f.sub.z of the step length of the stepping feed of the scratch tool 6 in the Z direction is no less than a minimum cutting depth d.sub.min required for the scratch test and no more than a maximum cutting depth d.sub.max required for the scratch test, i.e., d.sub.min≤f.sub.z≤d.sub.max; and a component f.sub.y of the step length of the stepping feed of the scratch tool 6 in a radial direction (i.e. the Y direction) of the end surface of the air-bearing turntable 3 is no less than 10 μm, so that scratches distributed in the Y direction with gradually changed cutting depths are independent of each other and do not interfere with each other;

(55) D3. if the cumulative displacement of the stepping feed in the Z direction exceeds the maximum cutting depth required for the test, or the nano positioning stage 10 moves to a negative limit position in the Y direction, or the cumulative displacement of the stepping feed in the Z direction reaches a negative limit position in Z direction of the nano positioning stage 10, stopping the stepping feed, and performing step D31; otherwise, performing step D2;

(56) D31. analyzing the force signals collected by the force sensor 8 during feed, if the scratch force signals are detected, indicating the high-speed scratch conducted by the scratch tool 6 on the surface of the micro convex structure 14 of the test piece 5, and performing step D5; otherwise, performing step D32;

(57) D32. if the nano positioning stage 10 has reached the negative limit position in the Y direction, controlling the nano positioning stage 10 to move to a positive limit position in the Y direction, and performing step D2; otherwise, performing step D33;

(58) D33. if the nano positioning stage 10 has reached the negative limit position in the Z direction, performing step D4; otherwise, performing step D2;

(59) D4. unlocking the locking mechanism of the Z-direction feeding device 12, and controlling the scratch tool 6 to feed to the surface of the test piece 5 through the Z-direction feeding device 12, so that the scratch tool 6 further approaches the surface of the test piece 5; in order to avoid the scratch tool 6 coming into contact with the micro convex structure 14 in the approaching process, a feeding amount of the Z-direction feeding device 12 does not exceed a difference value between a stroke of the nano positioning stage 10 in the Z direction and a positioning precision of the Z-direction feeding device 12, and controlling the nano positioning stage 10 to move to the positive limit position in the Z direction; and performing step D1; and

(60) D5. unlocking the locking mechanism of the Z-direction feeding device 12, controlling the scratch tool 6 to lift up through the Z-direction feeding device 12, stopping the air-bearing turntable 3, and completing the scratch test.

(61) Further, when a thickness of the test piece 5 of axisymmetric shape in step A2 is less than 1 mm, an elastic film 13 with a length no less than 5 mm, a width no less than 1 mm and a height no less than 10 μm is pasted on a back of the test piece 5, a magnetic chuck or a vacuum chuck with a flat surface is used for clamping, in the clamping process, the flat surface of the vacuum chuck/magnetic chuck and the elastic film 13 are used to elastically deform the surface of the test piece 5 through vacuum adsorption/magnetic adsorption to form the micro convex structure 14 with controllable length, width and height.

(62) The present disclosure is not limited to the embodiments, and any equivalent concept or change within the technical scope disclosed by the present disclosure is listed as the protection scope of the present disclosure.