A leveling device and method for Vickers hardness testing of high-hardness ceramic materials

Abstract

This invention provides a leveling device and method for Vickers hardness testing of high-hardness ceramic materials. The device aims to solve the problems of irregular indentations, inaccurate data, and indenter damage caused by insufficient machining precision leading to non-parallelism of the upper and lower surfaces in Vickers hardness testing. The device includes a base plate for fixing to the original sample stage of the hardness tester, a floating plate connected above the base plate via a ball joint assembly, and three leveling knobs arranged in a triangle, screwed into the floating plate with their lower ends resting against positioning holes in the base plate. By adjusting the leveling knobs, the floating plate can be driven to make omnidirectional micro-motion around the center of the ball joint, thereby directly adjusting the pitch and deflection angles of the sample to be tested, which is fixed to the upper surface of the floating plate. This invention has a compact and low-profile structure, does not interfere with the original function of the hardness tester, and ensures strict parallelism between the test surface and the indenter by "directly leveling the upper surface of the sample," significantly improving testing accuracy and reliability.

Description

Technical Field

[0001] This invention relates to Vickers hardness testing in materials mechanics, and more specifically to a leveling device and method for Vickers hardness testing of high-hardness ceramic materials. Background Technology

[0002] Vickers hardness testing is a key method for evaluating the mechanical properties of ceramic materials, especially high-hardness ceramics such as boron carbide. The principle involves pressing a diamond square pyramid indenter under a specific load into the sample surface, and calculating the hardness value by measuring the diagonal length of the indentation. For high-hardness materials, even the slightest misalignment between the sample surface and the indenter axis will result in an asymmetrical indentation with blurred boundaries, introducing measurement errors and subjecting the indenter to asymmetrical loads, increasing the risk of chipping.

[0003] Currently, commercial Vickers hardness testers are equipped with XY moving sample stages, but they lack precise pitch and yaw (i.e., rotation around the X and Y axes) leveling functions. Operators typically rely on fine machining to achieve parallelism between the upper and lower surfaces of the sample and the indenter. For samples with insufficient machining precision, rough leveling is achieved by visually and empirically placing hard clay under the sample. This method suffers from poor accuracy, low efficiency, and unreliable repeatability, failing to meet the requirements for precise testing of high-hardness materials.

[0004] Therefore, there is an urgent need in the field for a dedicated device that is compatible with existing hardness testers, easy to operate, and capable of directly and precisely leveling the upper surface of the sample. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a leveling device and method for Vickers hardness testing of high-hardness ceramic materials. This invention solves the problems of irregular Vickers hardness indentations, inaccurate data, and indenter damage caused by the non-parallelism of the upper and lower surfaces of high-hardness ceramic samples due to insufficient processing precision. The device can directly ensure that the sample test surface is parallel to the indenter without affecting the normal measurement function of the hardness tester.

[0006] The objective of this invention is achieved by the following technical solution:

[0007] A leveling device for Vickers hardness testing of high-hardness ceramic materials includes a base plate, a floating plate, a universal joint connector, and at least three leveling screws. The base plate is fixed to the original sample stage of the hardness tester, and its upper surface is provided with positioning holes adapted to the leveling screws. The upper side of the floating plate is equipped with a sample bearing surface for fixing the sample to be tested, and its lower side is connected to the base plate through the universal joint connector. The floating plate can pitch and yaw relative to the base plate through the universal joint connector. The leveling screws are threadedly connected to the floating plate, and their lower ends act in the positioning holes of the base plate. By adjusting the screw depth of each leveling screw, the floating plate is driven to make a fixed-point micro-motion around the center of the universal joint connector.

[0008] Preferably, the universal joint is a ball joint assembly, including a ball cup fixed to the upper surface of the substrate and a ball head fixed to the lower surface of the floating plate.

[0009] Preferably, the ball head is fixed to the center of the lower surface of the floating plate by threaded connection or adhesive bonding.

[0010] Preferably, the axes of the leveling screws are all perpendicular to the plane of the substrate.

[0011] Preferably, the leveling screws are evenly distributed around the center of the universal joint.

[0012] Preferably, there are three leveling screws, which are arranged in an equilateral triangle around the center of the universal joint.

[0013] Preferably, it also includes a universal bubble level, which is placed directly on the upper surface of the sample to be tested during the leveling process to indicate its levelness.

[0014] Preferably, both the substrate and the floating plate are circular metal plates with their centers on the same axis, and the diameter of the floating plate is smaller than the diameter of the substrate.

[0015] Preferably, the lower surface of the substrate is fixed to the original sample stage of the hardness tester by a magnet.

[0016] The working principle of the device is as follows: The ultrahard ceramic sample to be tested is fixed on the upper surface of the floating plate. A universal level is placed on the upper surface of the sample. By screwing in or out the three leveling screws, the tilt angle of the floating plate relative to the substrate can be changed. Since the sample is fixed on the floating plate, this operation directly changes the orientation of the sample's upper surface. When the bubble in the level is centered, it indicates that the sample's upper surface is level and perpendicular to the indenter axis. The level is then removed, and the entire device is moved together with the sample using the original XY motion platform of the hardness tester, allowing for accurate hardness testing.

[0017] A method for Vickers hardness testing of high-hardness ceramic materials, employing the aforementioned leveling device, includes:

[0018] Step 1: Fix the sample to be tested onto the sample bearing surface of the floating plate;

[0019] Step 2: Place the level directly on the upper surface of the sample to be tested;

[0020] Step 3: Adjust the leveling screws to make the level indicator indicate that the instrument is level.

[0021] Step 4: Remove the level and use the original sample stage of the hardness tester to move the sample test point under the indenter for hardness testing.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] Direct and precise leveling: Innovatively, the upper surface of the sample is directly leveled through the three-point support principle, which fundamentally eliminates all errors caused by uneven sample thickness, uneven lower surface, or non-parallel pads, achieving a precision of micro-radian level.

[0024] Perfectly compatible with the host unit: Designed as a low-profile device, it directly utilizes the original XY platform of the hardness tester without adding any additional motion axes. The compact structure completely avoids motion interference with the indenter and its support.

[0025] The operation is intuitive and simple: the leveling process is logically clear, and the operator only needs to observe the level and adjust three screws, which greatly reduces the reliance on the operator's experience and improves the testing efficiency.

[0026] Excellent protection and repeatability: The regular indentation effectively protects the expensive diamond indenter, while significantly reducing the dispersion of test data, ensuring the scientific validity and repeatability of the results. Attached Figure Description

[0027] Figure 1 This is a three-axis schematic diagram of the leveling device described in this invention. Figure 1 (a) in the diagram is a schematic diagram of the overall leveling device. Figure 1 (b) is a schematic diagram of the base plate of the leveling device. Figure 1 (a) in the figure is a schematic diagram of the floating plate of the leveling device.

[0028] Figure 2 This is a schematic cross-sectional view of the leveling device described in this invention.

[0029] Figure 3 This is a schematic diagram showing the usage state of the present invention installed on the original platform of the hardness tester.

[0030] Explanation of the labels in the diagram:

[0031] 1: Substrate; 2: Floating plate; 21: Sample bearing surface; 3: Ball joint assembly; 31: Ball cup; 32: Ball head; 4: Leveling screws (three in total); 5: Sample to be tested (e.g., B4C ceramic); 6: Universal bubble level; 100: Original sample stage for hardness tester; 200: Hardness tester indenter. Detailed Implementation

[0032] The following is combined Figures 1 to 3 The present invention will be described in a non-limiting manner according to a preferred embodiment.

[0033] like Figure 1 and Figure 2As shown, the device of this invention mainly consists of a base plate 1, a floating plate 2, a ball joint assembly 3, and a leveling screw 4. The base plate is a flat plate structure used to fix it to the upper surface of the original sample stage of the hardness tester via a connector. The floating plate is a flat plate located above the base plate, and its upper surface serves as a sample-bearing platform. The ball joint assembly includes a ball cup fixed to the base plate and a ball head fixed to the lower surface of the floating plate. The ball head and ball cup cooperate to form the universal rotation fulcrum of the floating plate. This device aims to solve the problems of irregular Vickers hardness indentations, inaccurate data, and indenter damage caused by insufficient processing precision and non-parallelism of the upper and lower surfaces of high-hardness ceramic samples.

[0034] The substrate 1 shown is a circular metal plate, the lower surface of which is fixed to the original sample stage 100 of the hardness tester by a strong magnet. The floating plate 2 is also a circular metal plate, but its diameter is smaller than that of the substrate 1, and it is located directly above the substrate 1. The upper surface of the floating plate 2 is precision ground to form a smooth sample bearing surface 21.

[0035] The ball joint assembly 3's ball cup 31 is pressed into the hole in the center of the base plate 1 by an interference fit. The ball head 32 is fixed to the center of the lower surface of the floating plate 2 by a threaded connection or adhesive bonding. The ball head 32 sits inside the ball cup 31, and the two fit together precisely, allowing the floating plate 2 to rotate freely around the ball center while withstanding pressure from above.

[0036] The three leveling screws 4 are micron-level precision fine-thread screws. The axes of the three screws are all perpendicular to the plane of the substrate. They are screwed vertically into the threaded holes on the edge of the floating plate 2 from above, and the centers of these three threaded holes form an equilateral triangle. After the lower end of the leveling screw 4 passes through the threaded hole, its tip directly rests in the positioning hole of the substrate 1. By rotating the leveling screw 4, its extension length can be precisely controlled, thereby raising or lowering the corresponding side of the floating plate 2 to achieve precise leveling.

[0037] The device also includes an independent universal bubble level 6, which is used to place directly on the upper surface of the sample to be tested during the leveling process to indicate its levelness.

[0038] The hardness testing method using the leveling device is as follows:

[0039] Combination Figure 3 Secure the entire apparatus to the original sample stage 100 of the hardness tester. Fix the B4C ceramic sample 5 to be tested onto the sample bearing surface 21 of the floating plate 2. Place the independent universal bubble level 6 directly on the upper surface of the sample 5. Observe the bubble in the level 6 and finely adjust the three leveling screws 4 sequentially until the bubble is precisely centered. At this point, the upper surface of the sample 5 is level. Carefully remove the level 6. Operate the hardness tester, using the XY movement function of the original sample stage 100, to move the sample test point directly below the indenter 200 for Vickers hardness testing.

[0040] The formula for calculating Vickers hardness (HV) is:

[0041]

[0042] Where F is the load (N) and d is the arithmetic mean of the lengths of the two diagonals (mm).

[0043] When the sample surface is at an angle to the indenter axis The formula for calculating the relative error between the measured and calculated values ​​is as follows:

[0044] .

[0045] By adjusting the leveling knob, the floating plate can be driven to make omnidirectional micro-movements around the center of the ball joint, thereby directly adjusting the pitch and deflection angles of the sample to be tested, which is fixed on the upper surface of the floating plate. This invention has a compact and low-profile structure, does not interfere with the original function of the hardness tester, and ensures strict parallelism between the test surface and the indenter by "directly leveling the upper surface of the sample," significantly improving testing accuracy and reliability.

[0046] Next, the measurement effect of the device of the present invention will be verified through experiments.

[0047] Experiment 1

[0048] This experiment provides a method for using a Vickers hardness leveling device for high-hardness ceramic materials, as follows:

[0049] (1) Fix the entire adapter to the original sample stage of the hardness tester;

[0050] (2) Fix a B4C ceramic sample with a parallelism error of 0.5° on its upper and lower surfaces onto the floating plate sample bearing surface;

[0051] (3) Place the universal bubble level directly on the upper surface of the sample, observe the bubble in the level, and finely adjust the three leveling screws in turn until the bubble is precisely centered;

[0052] (4) Carefully remove the level, adjust the original sample stage, move the sample test point to the center of the field of view, set a load of 1kg, hold pressure for 10s, and then perform at least 10 Vickers hardness tests.

[0053] (5) After the test, remove the leveling device and fix the same sample directly on the original sample stage. Perform Vickers hardness test no less than 10 times under the same load.

[0054] The Vickers hardness test results are shown in Table 1.

[0055] Table 1 Vickers hardness test results

[0056] Test conditions Average Vickers hardness (HV1) Hardness standard deviation (HV1) Indentation shape evaluation 0.5° parallelism error 2954 ±580 The indentations are irregular, with large differences in diagonal lengths. The boundaries are unclear, making measurement difficult and resulting in extremely high data dispersion. Use a leveling device 3382 ±122 The indentations are regular squares with clear boundaries and high repeatability.

[0057] As can be seen from the table, when the sample itself has a parallelism error of 0.5°, the systematic deviation and dispersion of the test data are significantly smaller when using the leveling device of the present invention compared with the direct placement test. This indicates that the present invention can transform the "unqualified" test sample into a "qualified" test state.

[0058] Experiment 2

[0059] The method of using a Vickers hardness leveling device for high-hardness ceramic materials is as follows:

[0060] (1) Fix the entire adapter to the original sample stage of the hardness tester;

[0061] (2) Fix a B4C ceramic sample with a parallelism error of 0.5° on its upper and lower surfaces onto the floating plate sample bearing surface;

[0062] (3) Place the universal bubble level directly on the upper surface of the sample, observe the bubble in the level, and finely adjust the three leveling screws in turn until the bubble is precisely centered;

[0063] (4) Carefully remove the level, adjust the original sample stage, move the sample test point to the center of the field of view, set a load of 1kg, hold pressure for 10s, and then perform at least 10 Vickers hardness tests.

[0064] (5) After the test, remove the leveling device and use the traditional method to insert a small number of shims into the same sample and the original sample stage to level them. Perform Vickers hardness test no less than 10 times under the same load.

[0065] The Vickers hardness test results are shown in Table 2.

[0066] Table 2 Vickers hardness test results

[0067] Test conditions Average Vickers hardness (HV1) Hardness standard deviation (HV1) Indentation shape evaluation Traditional shim leveling 3127 ±280 Most of the indentations are irregular quadrilaterals, some of which have broken boundaries, resulting in significant data dispersion. Use a leveling device 3382 ±122 The indentations are regular squares with clear boundaries and high repeatability.

[0068] As can be seen from Table 2, the standard deviation of sample hardness using the present invention is smaller than that of the traditional pad method, and the data repeatability is significantly improved. This indicates that the present invention transforms an unreliable testing method that relies on personal experience into a more convenient, efficient, stable and reliable testing method.

[0069] Experiment 3

[0070] The method of using a Vickers hardness leveling device for high-hardness ceramic materials is as follows:

[0071] (1) Fix the entire adapter to the original sample stage of the hardness tester;

[0072] (2) Fix a B4C ceramic sample with a parallelism error of 0.5° on its upper and lower surfaces onto the floating plate sample bearing surface;

[0073] (3) Place the universal bubble level directly on the upper surface of the sample, observe the bubble in the level, and finely adjust the three leveling screws in turn until the bubble is precisely centered;

[0074] (4) Carefully remove the level, adjust the original sample stage, move the sample test point to the center of the field of view, set a load of 1kg, hold pressure for 10s, and then perform at least 10 Vickers hardness tests.

[0075] (5) After the test, remove the leveling device and perform Vickers hardness tests on B4C ceramic samples of the same material and batch with parallel upper and lower surfaces under the same load for no less than 10 times.

[0076] The Vickers hardness test results are shown in Table 3.

[0077] Table 3 Vickers Hardness Test Results

[0078] Test conditions Average Vickers hardness (HV1) Hardness standard deviation (HV1) Indentation shape evaluation The upper and lower surfaces are parallel 3397 ±135 The indentations are regular, the boundaries are clear, and the repeatability is high. Use a leveling device 3382 ±122 The indentations are regular, the boundaries are clear, and the repeatability is high.

[0079] As shown in Table 3, when the sample itself has a parallelism error of 0.5°, the leveling device of this invention can achieve measurement accuracy and repeatability comparable to that of an ideal sample with "parallel upper and lower surfaces". Furthermore, even when testing ideal samples, this invention can avoid random tilting caused by simple placement, thus improving test quality.

[0080] In summary, Tables 1, 2, and 3 provide a data comparison of the sample hardness test values ​​under different test conditions, which strongly demonstrates that the leveling device of the present invention can not only solve the testing problem of "problem samples", but also generally improve the accuracy and repeatability of Vickers hardness testing, ensuring the reliability of test results and providing support for material evaluation and quality control.

[0081] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0082] Obviously, those skilled in the art can make various modifications and variations to the embodiments of the present invention without departing from the spirit and scope of the embodiments of the present invention. Thus, if these modifications and variations to the embodiments of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention also intends to include these modifications and variations.

Claims

1. A leveling device for Vickers hardness testing of high-hardness ceramic materials, characterized in that, The device includes a base plate, a floating plate, a universal joint connector, and at least three leveling screws. The base plate is fixed to the original sample stage of the hardness tester, and its upper surface is provided with positioning holes adapted to the leveling screws. The upper side of the floating plate is equipped with a sample bearing surface for fixing the sample to be tested, and its lower side is connected to the base plate through the universal joint connector. The floating plate can pitch and yaw relative to the base plate through the universal joint connector. The leveling screws are threaded to the floating plate, and their lower ends act in the positioning holes of the base plate. By adjusting the screw depth of each leveling screw, the floating plate is driven to make a fixed-point micro-motion around the center of the universal joint connector.

2. The leveling device according to claim 1, characterized in that, The universal rotating connector is a ball joint assembly, including a ball cup fixed to the upper surface of the base plate and a ball head fixed to the lower surface of the floating plate.

3. The leveling device according to claim 2, characterized in that, The ball head is fixed to the center of the lower surface of the floating plate by threaded connection or adhesive bonding.

4. The leveling device according to claim 1, characterized in that, The axes of the leveling screws are all perpendicular to the plane of the substrate.

5. The leveling device according to claim 4, characterized in that, The leveling screws are evenly distributed around the center of the universal joint.

6. The leveling device according to claim 5, characterized in that, There are three leveling screws, which are arranged in an equilateral triangle around the center of the universal joint.

7. The leveling device according to claim 1, characterized in that, It also includes a universal bubble level, which is placed directly on the upper surface of the sample to be tested during the leveling process to indicate its levelness.

8. The leveling device according to claim 1, characterized in that, Both the substrate and the floating plate are circular metal plates with their centers on the same axis, and the diameter of the floating plate is smaller than that of the substrate.

9. The leveling device according to claim 1, characterized in that, The lower surface of the substrate is fixed to the original sample stage of the hardness tester by a magnet.

10. A method for testing the Vickers hardness of high-hardness ceramic materials, characterized in that, The leveling device according to any one of claims 1-9 comprises: Step 1: Fix the sample to be tested onto the sample bearing surface of the floating plate; Step 2: Place the level directly on the upper surface of the sample to be tested; Step 3: Adjust the leveling screws to make the level indicator indicate that the instrument is level. Step 4: Remove the level and use the original sample stage of the hardness tester to move the sample test point under the indenter for hardness testing.

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