Device and method for measuring dimensional stability of material based on white light interferometer

Abstract

The invention discloses a device and a method for measuring the dimensional stability of a material based on a white light interferometer, belongs to the field of physical property measurement of the material, and aims to solve the problems of high error and low precision in the existing measurement of the dimensional stability of the material. The device for measuring the dimensional stability of the material based on the white light interferometer comprises a rack, a linear guide rail, an electric sample platform, the white light interferometer, a data acquisition and processing system and a standard sample block, according to the device and the measurement method, the size change of the sample is measured through the white light interferometer, and compared with the traditional method for evaluating the size stability through thermal cycling by adopting a thermal expansion instrument, the measurement precision is higher. The relative height delta H is used as final measurement data, interference caused by the initial size difference of the sample can be eliminated, the influence of system errors in the measurement process is reduced, meanwhile, the relative height delta H can highlight the small change of the size, and the corresponding rule of the size stability of the material can be analyzed more conveniently.

Description

Technical Field

[0001] This invention belongs to the field of physical property determination of materials, specifically relating to an apparatus and method for measuring the dimensional stability of materials based on a white light interferometer. Background Technology

[0002] In high-precision components such as inertial instruments and optical mirrors, the dimensional stability of materials is directly related to the accuracy and reliability of the components. Under no-load conditions, current methods for evaluating dimensional stability mainly include: ① X-ray measurement of macroscopic residual stress; however, due to the limited penetration of X-rays, it can only reflect the surface or near-surface state of the sample, and the results are difficult to reflect the overall internal dimensional changes. ② The circular ring method for measuring residual stress; although it can measure the internal state, it is a destructive test and can only reflect the final result, unable to obtain the entire process of sample size changes with the environment in real time. ③ The method of real-time detection of sample size changes by thermal cycling; although it can continuously monitor dimensional response characteristics in a controlled temperature field and has good intuitiveness, existing systems are mostly single-sample tests, inefficient, costly, and the measurement methods are mostly contact methods (such as measuring absolute length with a push rod), which are prone to introducing systematic and instrumental errors, and it is difficult to achieve high-precision evaluation.

[0003] The literature "Thermal expansion behavior of SiC / Al composites under cyclic heating" (Ceramics International, 2022) points out that dimensional changes caused by thermal cycling mainly stem from the release of thermal stress and residual stress. However, existing thermal expansion meters can only test single samples and are costly. The thermal expansion measurement report in ASTM STP379 also shows that the measurement accuracy of the traditional strain gauge method decreases significantly after multiple cycles. However, these studies do not address high-precision, low-error online, parallel evaluation methods for dimensional changes. On the other hand, although patents such as US5624505A propose subjecting metal matrix composites to multiple thermal cycles to optimize stability, their focus is on material composition optimization, rather than real-time, parallel, and high-precision monitoring of dimensional changes using measuring devices or methods. In summary, existing technologies for evaluating the dimensional stability of metals and metal matrix composites under temperature cycling conditions still face two major problems:

[0004] (1) Low detection efficiency: Most tests are single-sample tests, which cannot meet the needs of batch evaluation.

[0005] (2) Outdated data acquisition and processing methods: The measurement methods are mostly contact methods, with large systematic errors, low degree of automation, and difficulty in achieving high resolution and parallel processing of multiple samples;

[0006] Therefore, there is an urgent need to develop a novel dimensional stability testing device and method with low error, ultra-high precision, and the ability to perform parallel testing of multiple samples. Summary of the Invention

[0007] To address the problems of high error and low accuracy in existing material dimensional stability measurements, this invention proposes a device and method for measuring material dimensional stability based on a white light interferometer. Based on the principle of online temperature cycling detection, this invention can monitor material dimensional changes at high resolution and rapidly and accurately evaluate their dimensional stability in a controlled temperature field, thus providing reliable data support for the application of metals and metal-based composite materials in high-precision components.

[0008] The device for measuring the dimensional stability of materials based on a white light interferometer includes a frame, a linear guide rail, an electric sample platform, a white light interferometer, a data acquisition and processing system, and a standard sample block. The linear guide rail is fixed at the bottom of the frame along the Z-axis, and the electric sample platform is mounted on the upper end of the linear guide rail. The white light interferometer is fixed above the frame and includes a white light interferometry module and an imaging acquisition system. The data acquisition and processing system is connected to the white light interferometer. The standard sample block is placed on the upper surface of the electric sample platform.

[0009] The present invention provides a method for measuring the dimensional stability of materials using a device based on a white light interferometer, comprising the following steps:

[0010] 1. Process the material to be tested into a test sample;

[0011] 2. Preheat the white light interferometer and adjust the imaging conjugate between the camera and objective lens of the white light interferometer; adjust the motorized sample platform so that the surface of the standard sample block is imaged in the camera of the white light interferometer, and use the white light interferometer to scan and obtain the height of the standard sample block;

[0012] 3. Place the test sample next to the standard sample block and use a white light interferometer to scan and obtain the initial height of the test sample; use the surface of the standard sample block as the initial reference plane to scan and obtain the initial height difference between the test sample and the standard sample block.

[0013] IV. Perform hot and cold cycling treatment on the test sample;

[0014] 5. Place the test sample next to the standard sample block, and use a white light interferometer to scan and obtain the difference in height between the test sample and the standard sample block to obtain the relative height;

[0015] 6. Repeat steps four and five to obtain the relative height after multiple cold and hot cycles, and create a curve showing the relationship between the length deformation rate and the number of cycles.

[0016] The present invention has the following beneficial effects:

[0017] 1. The present invention provides a device and method for measuring the dimensional stability of materials based on a white light interferometer. By measuring the changes in sample size using a white light interferometer, the measurement accuracy is higher compared with the traditional method of evaluating dimensional stability by thermal expansion meter through thermal cycling.

[0018] 2. The electric sample platform in the device of the present invention is made of single-crystal silicon, which can achieve nanoscale surface roughness and significantly reduce the influence of instrument surface roughness on measurement results.

[0019] 3. This invention measures the height difference of samples using a standard sample block, which can unify the indicators and enhance the comparability of results from multiple samples or groups of experiments.

[0020] 4. This invention uses relative height as the final measurement data, which can eliminate the interference caused by the initial size difference of the sample, reduce the influence of systematic errors during the measurement process, and at the same time, the relative height ΔH can highlight the small changes in size, making it easier to analyze the corresponding laws of material size stability.

[0021] 5. This invention does not require the use of environmentally harmful chemical reagents, is energy-saving and environmentally friendly, has lower costs, and is easy to industrialize and apply.

[0022] 6. The operation and measurement methods of the device of the present invention are simple and easy for operators to master. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the device for measuring the dimensional stability of materials based on a white light interferometer in Example 1, where a is the sample to be tested;

[0024] Figure 2 The curve showing the relationship between the length deformation rate and the number of cycles obtained in Example 1 is shown. Detailed Implementation

[0025] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any reasonable combination of the specific embodiments.

[0026] Specific Implementation Method 1: The device for measuring the dimensional stability of materials based on a white light interferometer includes a frame 1, a linear guide rail 2, an electric sample platform 3, a white light interferometer 4, a data acquisition and processing system 5, and a standard sample block 6. The linear guide rail 2 is fixed at the bottom of the frame 1 along the Z-axis, and the electric sample platform 3 is installed at the upper end of the linear guide rail 2. The white light interferometer 4 is fixed above the frame 1 and is equipped with a white light interferometer module and an imaging acquisition system. The data acquisition and processing system 5 is connected to the white light interferometer 4. The standard sample block 6 is placed on the upper surface of the electric sample platform 3.

[0027] This embodiment has the following beneficial effects:

[0028] 1. The device for measuring the dimensional stability of materials based on the white light interferometer in this embodiment measures the change in sample size using the white light interferometer 4. Compared with the traditional method of using a thermal expansion meter to evaluate dimensional stability through thermal cycling, the measurement accuracy is higher.

[0029] 2. The electric sample platform 3 in this embodiment is made of single-crystal silicon, which can achieve nanoscale surface roughness and significantly reduce the influence of instrument surface roughness on measurement results.

[0030] 3. This implementation method measures the height difference of samples using standard sample block 6, which can unify the indicators and enhance the comparability between multiple samples or multiple sets of experimental results.

[0031] 4. This implementation method does not require the use of environmentally harmful chemical reagents, is energy-saving and environmentally friendly, has lower costs, and is easy to achieve industrial production and application;

[0032] Specific Implementation Method Two: This implementation method for measuring material dimensional stability using a device based on a white light interferometer is carried out according to the following steps:

[0033] 1. Process the material to be tested into a test sample;

[0034] 2. Preheat the white light interferometer 4 and adjust the imaging conjugate of the camera and objective lens of the white light interferometer 4; adjust the motorized sample platform 3 so that the surface of the standard sample block 6 is imaged in the camera of the white light interferometer 4, and use the white light interferometer to scan and obtain the height of the standard sample block 6.

[0035] 3. Place the test sample next to the standard sample block 6 and use a white light interferometer to scan and obtain the initial height of the test sample; use the surface of the standard sample block 6 as the initial reference plane to scan and obtain the initial height difference between the test sample and the standard sample block 6.

[0036] IV. Perform hot and cold cycling treatment on the test sample;

[0037] 5. Place the test sample next to the standard sample block 6, and use the white light interferometer 4 to scan and obtain the difference in height between the test sample and the standard sample block 6 to obtain the relative height;

[0038] 6. Repeat steps four and five to obtain the relative height after multiple cold and hot cycles, and create a curve showing the relationship between the length deformation rate and the number of cycles.

[0039] 1. In this embodiment, the sample size change is measured by a white light interferometer 4, which has higher measurement accuracy compared with the traditional method of using a thermal expansion meter to evaluate the size stability by thermal cycling.

[0040] 2. The electric sample platform 3 in this embodiment is made of single-crystal silicon, which can achieve nanoscale surface roughness and significantly reduce the influence of instrument surface roughness on measurement results.

[0041] 3. This implementation method measures the height difference of samples using standard sample block 6, which can unify the indicators and enhance the comparability between multiple samples or multiple sets of experimental results.

[0042] 4. This implementation method uses relative height as the final measurement data, which can eliminate the interference caused by the initial size difference of the sample, reduce the influence of systematic errors during the measurement process, and at the same time, the relative height ΔH can highlight the small changes in size, making it easier to analyze the corresponding laws of material size stability.

[0043] 5. This implementation method does not require the use of environmentally harmful chemical reagents, is energy-saving and environmentally friendly, has lower costs, and is easy to achieve industrial production and application;

[0044] 6. The operation and measurement methods of the device in this embodiment are simple and easy for operators to master.

[0045] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method Two in that the material to be tested in step one includes metallic materials, metal-based composite materials, or inorganic non-metallic materials. The metallic materials are aluminum, magnesium, etc.

[0046] Specific Implementation Method Four: This implementation method differs from Specific Implementation Method Two in that: the test sample in step one is cylindrical or cuboid in shape; the roughness of the upper and lower surfaces of the test sample is lower than Ra0.4 and the parallelism is lower than 0.05μm.

[0047] Specific Implementation Method 5: This implementation method differs from Specific Implementation Method 2 in that the preheating time of the white light interferometer 4 in step 2 is 10~30 minutes to achieve optimal spectral stability.

[0048] Specific Implementation Method Six: This implementation method differs from Specific Implementation Method Two in that the hot and cold cycle treatment process in step four includes atmospheric conditions, heating rate, cycle temperature, and holding time. After the treatment is completed, the sample to be tested is placed in a constant temperature drying oven for drying. The atmospheric conditions are nitrogen atmosphere or argon atmosphere.

[0049] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Method Six in that: the measurement accuracy of the white light interferometer 4 is 1~2nm; the standard sample block 6 is made of zirconium oxide ceramic and has a height of 5~30mm; and the electric sample platform 3 is made of single-crystal silicon.

[0050] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Method Six in that the heating rate is 0.5~5℃ / min.

[0051] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Method Six in that the circulating temperature includes the peak temperature during heating and the minimum temperature during cooling, with the peak temperature being 20~250℃ and the minimum temperature being -196~20℃.

[0052] Specific Implementation Method 10: This implementation method differs from Specific Implementation Method 6 in that the heat preservation time is the holding time at the peak temperature and the lowest temperature, and the heat preservation time is 0~48h.

[0053] Example 1:

[0054] This embodiment of the device for measuring the dimensional stability of materials based on a white light interferometer includes a frame 1, a linear guide rail 2, an electric sample platform 3, a white light interferometer 4, a data acquisition and processing system 5, and a standard sample block 6. The linear guide rail 2 is fixed at the bottom of the frame 1 along the Z-axis. The electric sample platform 3 is mounted on the upper end of the linear guide rail 2. The electric sample platform 3 can achieve linear movement in the Z-direction through the linear guide rail 2. At the same time, the electric sample platform 3 itself can also achieve movement in the X and Y directions, allowing for adjustment of the position and height of the sample to be tested. The white light interferometer 4 is fixed above the frame 1. The white light interferometer 4 is equipped with a white light interferometer module and an imaging acquisition system for ultra-high precision measurement of sample height. The data acquisition and processing system 5 is connected to the white light interferometer 4 to realize real-time storage and rapid processing of test data. The standard sample block 6 is placed on the upper surface of the electric sample platform 3 for device calibration and comparative measurement of sample height, ensuring the stability and accuracy of the measurement results.

[0055] This embodiment utilizes a device based on a white light interferometer to measure the dimensional stability of materials, and the method for measuring material dimensional stability is performed according to the following steps:

[0056] I. Precision machining of the test sample

[0057] The material to be tested is processed into a test sample, ensuring that the roughness and parallelism of the upper and lower surfaces of the test sample are within the test requirements.

[0058] The material to be tested in step one is a SiC / pure Al composite material;

[0059] The test sample described in step one is a cylindrical sample with a diameter of 6 mm and a height of 25 mm ± 0.1 mm.

[0060] The surface roughness of the upper and lower surfaces of the sample to be tested in step one is Ra0.2;

[0061] The parallelism between the upper and lower surfaces of the sample to be tested in step one is 0.025 μm;

[0062] II. Instrument Preparation and Placement of Standard Sample Block 6

[0063] Turn on the white light interferometer 4 and preheat it to stabilize the interference fringes. Adjust the imaging conjugate of the camera and objective lens of the white light interferometer 4 to ensure that the interference fringes are clearly visible. Place the standard sample block 6 on the motorized sample platform 3 and adjust the motorized sample platform 3 so that the surface of the standard sample block 6 is clearly imaged in the camera of the white light interferometer 4. Use the white light interferometer to scan the Z-axis of the standard sample block 6 to obtain the height value H of the standard sample block 6.

[0064] The measurement accuracy of the white light interferometer 4 described in step two is 2 nm;

[0065] The white light interferometer 4 described in step two is preheated for 20 minutes to achieve optimal spectral stability.

[0066] The standard sample block 6 mentioned in step two is made of zirconia ceramic and has a height of 25mm; zirconia ceramic has a low coefficient of thermal expansion and is stable over a long period of time.

[0067] The electric sample platform 3 described in step two is made of single-crystal silicon, which can achieve nanoscale surface roughness.

[0068] III. Measurement of initial sample height H0 and initial relative height ΔH0

[0069] Place the test sample next to the standard sample block 6 on the electric sample platform 3, adjust the sample stage and scan the Z-axis of the test sample using a white light interferometer, repeat the measurement 5 times, and take the average value to obtain the initial height H0 of the test sample; take the surface of the standard sample block 6 as the initial reference surface, scan the Z-axis of the test sample again, repeat the measurement 3 to 5 times, and take the average value to obtain the initial height difference ΔH0 between the test sample and the standard sample block 6.

[0070] IV. Perform hot and cold cycling treatment on the test sample.

[0071] Set the atmospheric conditions, heating rate, cycling temperature and holding time for the hot and cold cycle treatment, and then carry out the hot and cold cycle treatment. After the treatment is completed, put the test sample into a constant temperature drying oven.

[0072] The atmosphere described in step four is a nitrogen atmosphere, the purpose of which is to prevent oxygen in the atmosphere from oxidizing the material during the hot and cold cycling process.

[0073] The heating rate described in step four is 1℃ / min;

[0074] The cycle temperature mentioned in step four includes the peak temperature during heating and the minimum temperature during cooling, with the peak temperature being 80°C and the minimum temperature being -40°C.

[0075] The heat preservation time mentioned in step four refers to the time spent at the peak temperature and the lowest temperature, and the heat preservation time is 30 minutes.

[0076] The temperature of the constant temperature drying oven described in step four is 20℃;

[0077] V. Sample Placement and Relative Height Measurement:

[0078] Take the test sample out of the constant temperature drying oven and place it next to the standard sample block 6. Use the white light interferometer 4 to scan the Z-axis of the test sample to obtain the difference between the height H of the test sample and the standard sample block 6. Repeat the measurement 5 times and take the average value of the measurement results to obtain the relative height ΔH1.

[0079] VI. Multiple Loops and Data Processing:

[0080] Repeat steps four and five to perform multiple hot and cold cycles, and obtain the relative height ΔH after multiple hot and cold cycles. x And a curve showing the relationship between length deformation rate and number of cycles was generated;

[0081] In step six, X represents the number of iterations, and X is 10.

[0082] The length deformation rate described in step six is ​​ΔH x The ratio to H0;

[0083] The measurement principle in this embodiment is as follows:

[0084] The optical path difference of white light is Δ = 2ndcosθ, where n is the refractive index of the sample or medium; d is the geometric thickness corresponding to the optical path difference; and θ is the angle of incidence. When Δ satisfies the interference condition, light of different wavelengths will produce coherent enhancement or attenuation at different positions, forming colored interference fringes. Since white light contains multiple wavelengths, clear interference fringes will only appear in regions where the optical path difference is zero or close to zero. This characteristic can be used to determine the position on the sample surface.

[0085] When the reference mirror of the interferometer moves or the height of the sample surface changes, the relationship between the optical path difference and the sample height is: Δ=2nh, where h is the height of a point on the sample surface; n is the air refractive index, which is approximately 1; and θ is the perpendicular incidence of the incident light, which is θ=0.

[0086] When the optical path difference Δ is exactly zero (i.e., the optical path of the reference mirror is equal to that of the sample), the interference signal intensity reaches its maximum value (the center position of the white light interference fringes). Therefore, by determining the reference mirror position corresponding to the peak value of the interference envelope at each measurement point, the height distribution of the sample surface can be obtained.

[0087] During the measurement process, the standard sample block 6 serves as a height reference standard. The light source of the white light interferometer 4 emits white light, which is split into two beams by a beam splitter. One beam illuminates the surface of the sample to be tested and is reflected, while the other beam illuminates the standard sample block 6 and is reflected. The two beams coincide in the interferometer and are received by the detector, forming an interference signal. The focal plane of the reference mirror or scanning objective lens is adjusted to record the change in interference intensity of each pixel with the scanning position. By analyzing the position of the peak value of the interference signal envelope, the optical path difference from the sample surface to the reference surface is calculated, thereby obtaining the height information of the sample.

[0088] Figure 1 This is a schematic diagram of the device for measuring material dimensional stability based on a white light interferometer in Example 1; Figure 2 This is a curve showing the relationship between the length deformation rate and the number of cycles measured in Example 1. From... Figure 2 The dimensional change trend of SiC / pure Al composite material after thermal cycling reveals that the length deformation rate of the composite material continuously increases with the number of cycles, and the deformation scale is on the micrometer level (10). -6 Compared with the traditional method of using a thermal expansion meter to evaluate dimensional stability through thermal cycling, Example 1 has higher measurement accuracy, reaching nanometer-level precision. By measuring the height difference, Example 1 can simply and effectively reflect the dimensional change per unit length of the material, and more intuitively show the corresponding laws of material dimensional stability.

Claims

1. A device for measuring the dimensional stability of materials based on a white light interferometer, characterized in that: The device for measuring the dimensional stability of materials based on white light interferometer includes a frame (1), a linear guide rail (2), an electric sample platform (3), a white light interferometer (4), a data acquisition and processing system (5), and a standard sample block (6). The linear guide rail (2) is fixed at the bottom of the frame (1) along the Z-axis, and the electric sample platform (3) is installed at the upper end of the linear guide rail (2). The white light interferometer (4) is fixed above the frame (1), and the white light interferometer (4) is equipped with a white light interferometer module and an imaging acquisition system. The data acquisition and processing system (5) is connected to the white light interferometer (4). The standard sample block (6) is set on the upper surface of the electric sample platform (3).

2. A method for measuring the dimensional stability of materials using the apparatus for measuring material dimensional stability based on a white light interferometer as described in claim 1, characterized in that: This method is performed in the following steps:

1. Process the material to be tested into a test sample; 2. Preheat the white light interferometer (4), adjust the camera and objective lens imaging conjugate of the white light interferometer (4); adjust the electric sample platform (3) so that the surface of the standard sample block (6) is imaged in the camera of the white light interferometer (4), and use the white light interferometer to scan to obtain the height of the standard sample block (6); 3. Place the test sample next to the standard sample block (6) and use a white light interferometer to scan and obtain the initial height of the test sample; The initial height difference between the test sample and the standard sample block (6) is obtained by scanning with the surface of the standard sample block (6) as the initial reference surface; IV. Perform hot and cold cycling treatment on the test sample; 5. Place the test sample next to the standard sample block (6), and use a white light interferometer (4) to scan and obtain the difference in height between the test sample and the standard sample block (6) to obtain the relative height; 6. Repeat steps four and five to obtain the relative height after multiple cold and hot cycles, and create a curve showing the relationship between the length deformation rate and the number of cycles.

3. The method according to claim 2, characterized in that: The material to be tested in step one includes metallic materials, metal-based composite materials, or inorganic non-metallic materials.

4. The method according to claim 2, characterized in that: The test sample in step one is cylindrical or cuboid in shape; the roughness of the upper and lower surfaces of the test sample is less than Ra0.4 and the parallelism is less than 0.05μm.

5. The method according to claim 2, characterized in that: The white light interferometer (4) described in step two has a preheating time of 10~30 min to achieve optimal spectral stability.

6. The method according to claim 2, characterized in that: The process of hot and cold cycling in step four includes atmospheric conditions, heating rate, cycling temperature and holding time. After the process is completed, the sample to be tested is placed in a constant temperature drying oven for drying. The atmospheric conditions are nitrogen atmosphere or argon atmosphere.

7. The method according to claim 2, characterized in that: The white light interferometer (4) has a measurement accuracy of 1~2nm; the standard sample block (6) is made of zirconium oxide ceramic and has a height of 5~30mm; the electric sample platform (3) is made of single crystal silicon.

8. The method according to claim 6, characterized in that: The heating rate is 0.5~5℃ / min.

9. The method according to claim 6, characterized in that: The cycle temperature includes the peak temperature during heating and the minimum temperature during cooling, with the peak temperature being 20~250℃ and the minimum temperature being -196~20℃.

10. The method according to claim 6, characterized in that: The heat preservation time refers to the time spent at the peak temperature and the lowest temperature, and the heat preservation time is 0~48h.

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