Self-locking anti-backlash and segmental loading coating scratch testing device and self-locking anti-backlash and segmental loading coating scratch testing method

Abstract

The invention discloses a self-locking anti-backlash and segmented loading coating scratch testing device, comprising: a transmission mechanism mounted on a frame and used for providing rotation power and realizing self-locking; the loading mechanism is connected with the output end of the transmission mechanism and is used for converting the rotary motion into linear pressing motion and providing a linearly changing load for the pressing head; the measuring module is integrated on the loading mechanism and is used for detecting a normal load and a tangential shear force applied to the pressure head in real time; and the moving platform is used for bearing the sample. The transmission mechanism comprises a servo motor and a double-lead worm and gear pair driven by the servo motor. The loading mechanism comprises a cam shaft, a linear cam and a plane follower, and the working end of the plane follower is kept in contact with the contour curved surface of the linear cam. According to the invention, the dual-lead worm and gear transmission with a self-locking anti-backlash function is combined with the linear cam loading mechanism with segmented profile curves, so that the load control accuracy and the loading linearity are ensured, and the coating scratch test precision is improved.

Description

Technical Field

[0001] This invention belongs to the field of planar coating adhesion testing technology, and particularly relates to a coating scratch testing device and method with self-locking gap elimination and segmented loading. Background Technology

[0002] The scratch method is a common method for evaluating the bonding strength between a coating and a substrate. It involves scraping the coating surface with an indenter under a vertically increasing load, and the critical load at which the coating peels off is used to characterize the bonding force. Current technologies mainly rely on servo motors driving ball screws or ordinary screw-lever mechanisms for loading. While the former can dynamically apply pressure, the ball screw cannot self-lock and requires additional braking; the cantilever mounting of the indenter can easily lead to uneven force distribution and axis deflection. The latter applies pressure through a lever principle, has a simple structure but suffers from non-linear loading rates, low control precision, and backlash between the screw and nut causing idle strokes during unloading. Furthermore, the indenter is prone to lateral displacement due to shear force in the initial scratching stage. Figure 1 As shown in the figure, insufficient lifting after the scratching process can easily cause secondary scratch damage. Both methods have shortcomings in achieving high-precision linear loading, transmission self-locking backlash elimination, and suppressing indenter runout, which reduces the test accuracy and reliability. Summary of the Invention

[0003] Purpose of the invention: In order to overcome the shortcomings of the existing technology, the present invention provides a coating scratch testing device and method with self-locking backlash elimination and segmented loading. By combining a double-lead worm gear transmission with self-locking backlash elimination with a linear cam loading mechanism with segmented contour curves, the accuracy of load control and loading linearity are ensured, thereby improving the accuracy of coating scratch testing.

[0004] Technical solution: To achieve the above objectives, the present invention provides a self-locking gap-eliminating and segmented loading coating scratch testing device, comprising:

[0005] frame;

[0006] A transmission mechanism, mounted on the frame, is used to provide rotational power and achieve self-locking;

[0007] A loading mechanism, connected to the output end of the transmission mechanism, is used to convert the rotational motion into a linear downward pressing motion and to provide a linearly varying load to the pressure head fixedly connected to its end.

[0008] The measurement module, integrated into the loading mechanism, is used to detect the normal load and tangential shear force applied to the pressure head in real time.

[0009] A mobile platform is used to carry the specimen and move the specimen on it by translation.

[0010] Furthermore, the transmission mechanism includes a servo motor and a dual-lead worm gear pair driven by the servo motor.

[0011] Furthermore, the loading mechanism includes:

[0012] The camshaft is coaxially fixed with the worm wheel of the double-lead worm gear pair;

[0013] A linear cam is fixedly sleeved on the camshaft;

[0014] A planar follower, the working end of which remains in contact with the contour surface of the linear cam;

[0015] The linear cam can drive the planar follower to achieve linear motion with a total displacement range of 0-10mm.

[0016] Furthermore, the profile surface of the linear cam is constructed such that it can drive the planar follower to sequentially perform a first-stage buffered acceleration downward motion and a second-stage uniform linear downward motion.

[0017] Furthermore, in the first stage, the total downward displacement of the planar follower is 0-2mm; in the second stage, the total downward displacement of the planar follower is 0-8mm.

[0018] Furthermore, the planar follower is slidably mounted on the frame in a vertical direction, the working end of the planar follower is the top plane that contacts the linear cam, and the bottom of the planar follower is fixedly connected to the pressure head; an elastic element that provides a restoring force is provided between the planar follower and the frame.

[0019] Furthermore, the measurement module includes a group of strain gauges disposed on the planar follower for sensing the deformation caused by the force.

[0020] Furthermore, the planar follower is slidably connected to the frame via a linear guide pair.

[0021] Furthermore, the transmission ratio of the dual-lead worm gear pair is 14 to 40.

[0022] A method for testing the adhesion of a planar coating using a self-locking gap-eliminating and segmented loading coating scratch testing device, comprising the following steps:

[0023] Step S1: Control the transmission mechanism to drive the loading mechanism, so that the indenter descends to contact the coating surface of the sample to be tested and loads a preset initial contact load; at the same time, control the moving platform to move the sample horizontally so that the indenter is positioned above the starting point of the scratch trajectory relative to the sample.

[0024] Step S2: Control the servo motor to rotate at a constant speed, and drive the linear cam to rotate at a constant speed through the double-lead worm gear pair;

[0025] The linear cam, based on its contour surface, drives the planar follower and the pressure head to sequentially perform a first-stage motion and a second-stage motion, applying a continuously increasing load to the sample surface; wherein, the first-stage motion is a buffered and accelerated downward pressing motion, and the second-stage motion is a uniform linear downward pressing motion that is linearly related to the rotation angle of the linear cam.

[0026] During the loading process, the synchronous control moving platform drives the sample to move at a constant speed in the horizontal direction, so that the indenter scratches the coating surface from shallow to deep.

[0027] Step S3: Throughout the entire process of step S2, the instantaneous signals of the normal load and tangential shear force on the indenter are acquired in real time through the measurement module, and the relationship between the normal load, tangential shear force and the displacement or time of the indenter is recorded simultaneously.

[0028] Step S4: Analyze the changes obtained in Step S3, identify the critical points where the tangential shear force increases or decreases sharply with displacement or time, and determine the instantaneous normal load corresponding to the critical point. The critical value of the normal load is determined as the adhesion force of the coating.

[0029] Beneficial Effects: This invention achieves backlash-free transmission and self-locking upon stopping through a double-lead worm gear pair, avoiding complex external braking mechanisms and improving transmission accuracy and reliability. A linear cam directly drives the planar follower, converting rotational motion into precise linear motion. Through the buffering of the cam profile and the linear segmented design, a smooth transition of initial impact during loading and a linear load increase in the main working section are achieved, ensuring the control accuracy and stability of the loading rate. The planar follower is constrained by a linear guide rail, ensuring it moves only in the vertical direction. Combined with the strain gauge array integrated on it for direct force measurement, it suppresses the horizontal deviation of the indenter under shear force, ensuring the directional accuracy of shear force measurement. The coating adhesion test results show good repeatability and high accuracy. Attached Figure Description

[0030] Figure 1 This is a schematic diagram illustrating the situation where the scratch has shifted.

[0031] Figure 2 Schematic diagram of the overall structure of the coating scratch testing device Figure 1 ;

[0032] Figure 3 Schematic diagram of the overall structure of the coating scratch testing device Figure 2 ;

[0033] Figure 4 This is a schematic diagram of a linear cam. Detailed Implementation

[0034] The invention will now be further described with reference to the accompanying drawings.

[0035] like Figure 2 and Figure 3 As shown, a coating scratch testing device with self-locking gap elimination and segmented loading includes: a frame; a transmission mechanism 2, mounted on the frame, for providing rotational power and achieving self-locking; a loading mechanism 3, connected to the output end of the transmission mechanism 2, for converting rotational motion into linear downward pressing motion and providing a linearly varying load to the indenter 4 fixedly connected to its end; a measurement module, integrated into the loading mechanism 3, for real-time detection of the normal load and tangential shear force applied to the indenter 4; and a moving platform 6, for carrying the sample 7 and driving the sample 7 to translate on it. The frame provides a rigid support foundation for the entire device. The transmission mechanism 2 is responsible for providing controllable rotational power and has self-locking capability. The loading mechanism 3 accurately converts the rotational motion output by the transmission mechanism 2 into the vertical linear motion of the indenter 4, thereby applying a controllable load to the surface of the sample 7. The measurement module 5) is tightly integrated into the force transmission chain of the loading mechanism 3 and can directly sense the normal (vertical) force and tangential (horizontal) friction force experienced by the indenter 4 during the scratching process. The moving platform 6 independently provides the horizontal uniform motion of the sample 7, which, in conjunction with the vertical loading motion of the indenter 4, forms scratches on the coating surface.

[0036] like Figure 3 As shown, the transmission mechanism 2 includes a servo motor 21 and a double-lead worm gear pair 22 driven by the servo motor 21. More specifically, the double-lead worm gear pair 22 includes a worm 22a and a worm wheel 22b, and the drive shaft of the servo motor 21 is connected to the worm 22a via a coupling 2.1. The technical principle of the double-lead worm gear pair 22 used in this invention is as follows: the lead of the left tooth surface of the worm 22a is designed to be unequal to the lead of the right tooth surface, and the tooth thickness of the worm wheel 22b meshing with it changes continuously along the axial direction. By adjusting the position of the worm 22a axially during assembly, the worm wheel 22b and the worm 22a can achieve a backlash-free tight meshing state at a predetermined position. Therefore, the inherent single-stage large transmission ratio of the worm gear achieves significant speed reduction and torque amplification of the motor, reducing the requirements for the dynamic accuracy and torque of the motor itself. Furthermore, this transmission pair has a reverse self-locking characteristic; that is, the worm 22a can drive the worm wheel 22b, but the worm wheel 22b can hardly drive the worm 22a in the reverse direction. This ensures that the position of the pressure head 4 can be firmly locked during the stopping or holding phase, eliminating the need for an additional brake. In addition, the double-lead design completely eliminates transmission backlash, ensuring a strict correspondence between the motor rotation angle and the worm wheel output angle. This solves the problems of initial idle stroke and nonlinearity in dynamic response caused by backlash in traditional lead screws or ordinary worm gear pairs, laying a transmission foundation for high-precision displacement and load control.

[0037] In this invention, as a preferred embodiment, the transmission ratio of the dual-lead worm gear pair 22 is between 14 and 40. Within this range: on the one hand, a sufficiently large transmission ratio, such as greater than or equal to 14, can reduce the impact of speed fluctuations of the servo motor 21 on the output end, making the rotation of the worm gear 22b smoother and more stable, which is crucial for achieving precise micro-displacement loading of the pressure head; at the same time, the amplified torque allows the mechanism to output sufficient load. On the other hand, the transmission ratio should not be too large, such as less than or equal to 40, as an excessively large transmission ratio will lead to an increase in the size of the worm gear, a less compact mechanism, and consequently affect the dynamic response speed of the transmission system. Therefore, a transmission ratio range of 14-40 is more suitable for planar coating scratch testing.

[0038] The loading mechanism 3 of this invention realizes the conversion from rotational motion to precise linear loading motion. More specifically, as... Figure 3 As shown, the loading mechanism 3 includes: a camshaft 31, coaxially fixed with the worm gear 22b of the double-lead worm gear pair 22; a linear cam 32, fixedly sleeved on the camshaft 31; and a planar follower 33, the working end of which maintains contact with the contour surface of the linear cam 32. The camshaft 31 and the worm gear 22b are coaxially fixed, directly achieving backlash-free rotational motion. The linear cam 32 is fixed on this shaft, and its contour surface is pre-machined. The working end (i.e., the top plane) of the planar follower 33 always maintains contact with the cam surface under the action of spring force. When the linear cam 32 rotates, the different radial changes at various points on its contour surface are directly converted into the vertical displacement of the planar follower 33.

[0039] It is worth noting that the method by which the linear cam 32 of the present invention directly drives the planar follower 33 has the following advantages:

[0040] Advantage 1: Direct motion conversion and simple transmission of driving force, without intermediate links such as levers and connecting rods, avoiding errors introduced by hinge gaps and elastic deformation.

[0041] Advantage 2: The load is transmitted through the centerline of the camshaft, and the force is centered, so no additional bending moment will be generated that would cause the pressure head to deflect.

[0042] Thirdly, once the profile curve of the cam is machined, its driving motion law is definite and repeatable, which does not rely on complex real-time closed-loop control algorithms and has high reliability.

[0043] The linear cam 32 can drive the planar follower 33 to achieve linear motion with a total displacement range of 0-10mm, which covers the loading process from initial contact to complete coating peeling.

[0044] like Figure 4As shown, the profile surface of the linear cam 32 is constructed to drive the planar follower 33 to sequentially perform a first-stage buffered acceleration downward motion and a second-stage uniform linear downward motion. The profile surface of the linear cam 32 is specially segmented. In the first stage, the total downward displacement of the planar follower 33 is 0-2mm; in the second stage, the total downward displacement of the planar follower 33 is 0-8mm. In the first stage, corresponding to the initial segment of the cam rotation angle, a motion law similar to a modified sine wave is adopted, with the acceleration smoothly changing from zero without abrupt changes. This ensures that when the planar follower 33 and the pressure head 4 begin to press down from a stationary state, the speed increases steadily, achieving buffered acceleration. This solves the impact problem caused by excessive acceleration when the pressure head 4 contacts the sample 7, avoiding damage to the initial coating and interference with the high-sensitivity strain signal, and ensuring the stability of the initial stage of the test. In the second stage, the Archimedes spiral motion law is adopted, and the lift (i.e., the displacement of the planar follower 33) is linearly proportional to the cam rotation angle. When the servo motor 21 drives at a constant speed, the planar follower 33 will perform a uniform linear downward pressure in this stage, thereby applying a linearly increasing (constant slope) load to the sample 7, with good linearity. The slope can preferably be 2 mm / rad.

[0045] The planar follower 33 is slidably mounted on the frame in the vertical direction. More specifically, the planar follower 33 is slidably connected to the frame via a linear guide pair. When the indenter 4 is subjected to tangential shear force generated by the uneven resistance of the sample 7 surface, the linear guide pair can effectively suppress any offset or deflection tendency of the planar follower 33 and the indenter 4 in the horizontal plane, ensuring that the axis of the indenter 4 is always perpendicular to the surface of the sample 7, thereby making the measured shear force direction accurate and the scratch trajectory straight.

[0046] The working end of the planar follower 33 is the top plane that contacts the linear cam 32, and the bottom of the planar follower 33 is fixedly connected to the pressure head 4.

[0047] An elastic element, preferably a spring, is provided between the planar follower 33 and the frame to provide a restoring force. This spring consistently applies an upward restoring force to the planar follower 33. This elastic force achieves two functions: first, it ensures that regardless of the angle to which the linear cam 32 rotates, the top plane of the planar follower 33 remains in close contact with the cam's contour surface, maintaining reliable contact; second, at the end of the test, when the linear cam 32 returns to the contour section with a smaller lift, the elastic force actively lifts the indenter 4, reliably separating it from the surface of the sample 7, effectively preventing secondary contact and damage to the scratch morphology caused by the indenter 4 not being fully lifted after the scratching process.

[0048] The measurement module includes a group of strain gauges mounted on the planar follower 33 to sense its deformation caused by force. When the indenter 4 is subjected to normal load and tangential shear force, these forces are transmitted to the planar follower 33, causing it to undergo slight elastic deformation. The strain gauges deform accordingly, and their resistance values ​​change accordingly. The bridge circuit outputs an electrical signal proportional to the force value. The strain gauges sense the direct result of the force on the indenter 4, without the need for additional force sensors or complex force transmission links. This improves the response speed of the measurement signal while avoiding the added weight of external sensors.

[0049] A method for testing the adhesion of a planar coating using a self-locking gap-eliminating and segmented loading coating scratch testing device, comprising the following steps:

[0050] Step S1: Control the transmission mechanism 2 to drive the loading mechanism 3 so that the pressure head 4 descends to contact the coating surface of the test sample 7 and is loaded with a preset initial contact load; at the same time, control the moving platform 6 to move the sample 7 horizontally so that the pressure head 4 is positioned above the starting point of the scratch trajectory relative to the sample 7.

[0051] Step S2: Control the servo motor 21 to rotate at a constant speed, and drive the linear cam 32 to rotate at a constant speed through the double-lead worm gear pair 22.

[0052] The linear cam 32 drives the planar follower 33 and the pressure head 4 to perform the first stage motion and the second stage motion in sequence according to its contour surface, applying a continuously increasing load to the surface of the sample 7; wherein, the first stage motion is a buffered and accelerated downward pressing motion, and the second stage motion is a uniform linear downward pressing motion that is linearly related to the rotation angle of the linear cam 32.

[0053] During the loading process, the synchronous control moving platform 6 drives the sample 7 to move at a uniform speed in the horizontal direction, so that the pressure head 4 scratches the coating surface from shallow to deep.

[0054] Step S3: Throughout the entire process of step S2, the instantaneous signals of the normal load and tangential shear force on the pressure head 4 are collected in real time by the measurement module, and the relationship between the changes in normal load, tangential shear force and displacement or time of the pressure head 4 is recorded simultaneously.

[0055] Step S4: Analyze the changes obtained in Step S3, identify the critical points where the tangential shear force increases or decreases sharply with displacement or time, and determine the instantaneous normal load corresponding to the critical point. The critical value of the normal load is determined as the adhesion force of the coating.

[0056] In summary, this invention achieves backlash-free transmission and self-locking upon stopping through a double-lead worm gear pair, avoiding complex external braking mechanisms and improving transmission accuracy and reliability. A linear cam directly drives the planar follower, converting rotational motion into precise linear motion. Through the buffering of the cam profile and the linear segmented design, a smooth transition of initial impact during loading and a linear load increase in the main working section are achieved, ensuring the control accuracy and stability of the loading rate. The planar follower is constrained by a linear guide rail, ensuring it moves only in the vertical direction. Combined with the strain gauge array integrated on it for direct force measurement, the horizontal deviation of the indenter under shear force is suppressed, ensuring the directional accuracy of the shear force measurement. The coating adhesion test results show good repeatability and high accuracy.

[0057] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A coating scratch testing device with self-locking gap elimination and segmented loading, characterized in that: include: frame; The transmission mechanism (2) is mounted on the frame and is used to provide rotational power and achieve self-locking; The loading mechanism (3), connected to the output end of the transmission mechanism (2), is used to convert the rotational motion into a linear downward motion and to provide a linearly varying load to the pressure head (4) fixedly connected to its end; The measurement module, integrated into the loading mechanism (3), is used to detect the normal load and tangential shear force applied to the pressure head (4) in real time; The moving platform (6) is used to carry the specimen (7) and move the specimen (7) on it.

2. The coating scratch testing device with self-locking gap elimination and segmented loading according to claim 1, characterized in that: The transmission mechanism (2) includes a servo motor (21) and a double-lead worm gear pair (22) driven by the servo motor (21).

3. The coating scratch testing device with self-locking gap elimination and segmented loading according to claim 2, characterized in that: The loading mechanism (3) includes: The camshaft (31) is coaxially fixed with the worm wheel (22b) of the double-lead worm gear pair (22); A linear cam (32) is fixedly sleeved on the camshaft (31); The planar follower (33) has its working end in contact with the contour surface of the linear cam (32); The linear cam (32) can drive the planar follower (33) to achieve linear motion with a total displacement range of 0-10mm.

4. The coating scratch testing device with self-locking gap elimination and segmented loading according to claim 3, characterized in that: The profile surface of the linear cam (32) is constructed such that it can drive the planar follower (33) to perform a first-stage buffered acceleration downward motion and a second-stage uniform linear downward motion in sequence.

5. The coating scratch testing device with self-locking gap elimination and segmented loading according to claim 4, characterized in that: In the first stage, the total downward displacement of the planar follower (33) is 0-2 mm; In the second stage, the total downward displacement of the planar follower (33) is 0-8 mm.

6. The coating scratch testing device with self-locking gap elimination and segmented loading according to claim 3, characterized in that: The planar follower (33) is slidably mounted on the frame in the vertical direction. The working end of the planar follower (33) is the top plane that contacts the linear cam (32). The bottom of the planar follower (33) is fixedly connected to the pressure head (4). An elastic element that provides a restoring force is provided between the planar follower (33) and the frame.

7. The coating scratch testing device with self-locking gap elimination and segmented loading according to claim 6, characterized in that: The measurement module includes a strain gauge group disposed on the planar follower (33) for sensing the deformation caused by the force.

8. The coating scratch testing device with self-locking gap elimination and segmented loading according to claim 6, characterized in that: The planar follower (33) is slidably connected to the frame via a linear guide pair.

9. The coating scratch testing device with self-locking gap elimination and segmented loading according to claim 2, characterized in that: The transmission ratio of the dual-lead worm gear pair (22) is 14 to 40.

10. The planar coating adhesion test method of the self-locking gap-eliminating and segmented loading coating scratch test device according to claim 4, characterized in that: Includes the following steps: Step S1: Control the transmission mechanism (2) to drive the loading mechanism (3) so that the pressure head (4) descends to contact the coating surface of the test sample (7) and is loaded with a preset initial contact load; at the same time, control the moving platform (6) to carry the sample (7) to move horizontally so that the pressure head (4) is located above the starting point of the scratch trajectory relative to the sample (7). Step S2: Control the servo motor (21) to rotate at a constant speed, and drive the linear cam (32) to rotate at a constant speed through the double-lead worm gear pair (22); The linear cam (32) drives the planar follower (33) and the pressure head (4) to perform the first stage motion and the second stage motion in sequence according to its contour surface, applying a continuously increasing load to the surface of the sample (7); wherein, the first stage motion is a buffered and accelerated pressing motion, and the second stage motion is a uniform linear pressing motion that is linearly related to the rotation angle of the linear cam (32); During the loading process, the synchronous control moving platform (6) drives the sample (7) to move at a constant speed in the horizontal direction, so that the pressure head (4) scratches from shallow to deep on the coating surface; Step S3: Throughout the entire process of step S2, the instantaneous signals of the normal load and tangential shear force on the pressure head (4) are collected in real time by the measurement module, and the relationship between the normal load, tangential shear force and the displacement or time of the pressure head (4) is recorded simultaneously. Step S4: Analyze the changes obtained in Step S3, identify the critical points where the tangential shear force increases or decreases sharply with displacement or time, and determine the instantaneous normal load corresponding to the critical point. The critical value of the normal load is determined as the adhesion force of the coating.

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