LAS series ultra-low expansion microcrystalline glass thermal expansion coefficient ultrasonic detection method

Abstract

The application provides a LAS system ultralow expansion microcrystalline glass thermal expansion coefficient ultrasonic detection method, which comprises the following steps: performing CTE-longitudinal wave sound velocity theoretical relationship analysis and deduction, establishing a theoretical relationship between CTE and longitudinal wave sound velocity, designing LAS system ultralow expansion microcrystalline glass samples, measuring the longitudinal wave sound velocity of the samples, obtaining the longitudinal wave sound velocity value, calibrating the CTE of the samples, obtaining the CTE calibration value, establishing a CTE-longitudinal wave sound velocity experimental relationship model based on the theoretical relationship between CTE and longitudinal wave sound velocity, the longitudinal wave sound velocity value and the CTE calibration value, and realizing full-caliber ultrasonic detection of CTE. The application realizes full-caliber nondestructive detection of the thermal expansion coefficient of LAS system ultralow expansion microcrystalline glass, breaks through the limitation that traditional top rod type measurement must be destructive sampling, does not need temperature changing operation, can inversely calculate the average CTE in a wide temperature range by using room temperature sound velocity, has high detection efficiency and low cost, and provides technical support for uniformity control in the preparation process of large-size materials.

Description

Technical Field

[0001] This invention relates to the field of non-destructive testing technology for material properties, and in particular to an ultrasonic testing method for the coefficient of thermal expansion of LAS-based ultra-low expansion microcrystalline glass. Background Technology

[0002] LAS (lithium aluminum silicate, Li2O-Al2O3-SiO2) is an ultra-low expansion microcrystalline glass due to its near-zero CTE (10⁻¹⁰) in the temperature range of 0℃ to 50℃. -9 On the order of / ℃, 1×10 -9 (CTE = 1 ppb / ℃), widely used in the development of key components such as ground-based large-aperture optical telescopes, space optical remote sensing cameras, laser gyroscopes, photoelectric radars, theodolites, and extreme ultraviolet lithography systems. Currently, my country is strengthening research on the melting method for preparing large-size LAS-based ultra-low expansion microcrystalline glass materials. During the crystallization process, the uniformity of crystal phase distribution affects the uniformity of CTE distribution, thus significantly impacting the processing quality of the LAS-based ultra-low expansion microcrystalline glass matrix and its mirror imaging stability. Therefore, ensuring the uniformity of CTE across the entire aperture is paramount in the preparation of large-size and highly uniform LAS-based ultra-low expansion microcrystalline glass materials. Thus, conducting high-precision measurement research on the full-aperture CTE of large-size LAS-based ultra-low expansion microcrystalline glass materials is particularly crucial.

[0003] Due to their ultra-low CTE values, LAS-based ultra-low expansion glass-ceramics require high-precision measurement methods and devices for CTE measurement. Among these, the most influential research and device upgrades conducted by Schott in Germany for high-precision CTE measurement of Zerodur glass-ceramics are significant. This paper summarizes the current state of domestic and international research on high-precision CTE detection technology for Zerodur glass-ceramics and proposes three CTE measurement methods based on thermal dilatometers for full-diameter CTE and uniformity testing of LAS-based ultra-low expansion glass-ceramics: standard, improved, and advanced. These methods utilize a linear variable differential transformer, a laser interferometer, and a linear incremental encoder as displacement sensors, respectively, to measure the change in specimen length with temperature at different sampling locations, calculate the corresponding CTE value, and thus obtain the full-diameter CTE uniformity of large-size LAS-based ultra-low expansion glass-ceramics. However, all three measurement methods are rod-type measurement methods, which have some shortcomings, including the need for regular system calibration with the help of standard reference samples, which are destructive sampling measurements, with long measurement cycles and high manpower and material costs. They cannot meet the needs of rapid and non-destructive testing of CTE and uniformity of large-size LAS-based ultra-low expansion microcrystalline glass.

[0004] Ultrasonic testing, due to its speed and non-destructive nature, has demonstrated unique advantages in characterizing key material properties. Corning Incorporated and the Institute of Optoelectronics, Chinese Academy of Sciences, have established a relationship between Young's modulus, sound velocity, and coefficient of thermal expansion (CTE) using Young's modulus as an intermediate value. Based on this relationship, they have conducted full-aperture testing of the CTE and uniformity of large-size ultra-low expansion quartz glass using ultrasonic methods, demonstrating strong engineering application value. However, the application of ultrasonic methods to test the CTE and uniformity of large-size LAS-based ultra-low expansion microcrystalline glass has not yet been studied. Therefore, this paper proposes an ultrasonic testing method for the average CTE (0℃, 50℃) of LAS-based ultra-low expansion microcrystalline glass. This method overcomes the limitations of previous push-rod measurement methods, which require destructive sampling, have long measurement cycles, and are costly, meeting the need for rapid and non-destructive testing of the CTE and uniformity of LAS-based ultra-low expansion microcrystalline glass across the entire aperture. In conclusion, it is essential to design an ultrasonic testing method for the coefficient of thermal expansion (CTE) of LAS-based ultra-low expansion microcrystalline glass. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide an ultrasonic testing method for the thermal expansion coefficient of LAS-based ultra-low expansion microcrystalline glass.

[0006] To achieve the above objectives, the present invention provides the following solution: This invention provides an ultrasonic testing method for the thermal expansion coefficient of LAS-based ultra-low expansion microcrystalline glass, comprising: Step 1: Perform theoretical analysis and derivation of the CTE-longitudinal wave velocity relationship to establish the theoretical relationship between CTE and longitudinal wave velocity; Step 2: Design LAS-based ultra-low expansion microcrystalline glass samples and measure their longitudinal wave velocity to obtain the longitudinal wave velocity values; Step 3: Perform CTE calibration on the sample and obtain the CTE calibration value; Step 4: Based on the theoretical relationship between CTE and longitudinal wave velocity, the longitudinal wave velocity value and the CTE calibration value, establish an experimental relationship model between CTE and longitudinal wave velocity to realize full-diameter ultrasonic testing of CTE.

[0007] Preferably, in step 1, the theoretical relationship between CTE and P-wave velocity is analyzed and derived to establish the theoretical relationship between CTE and P-wave velocity, specifically as follows: Based on the relationship between thermal expansion of materials and Young's modulus, theoretical formulas for CTE and Young's modulus are derived. Based on the theory of elastic waves, the relationship between Young's modulus and the longitudinal wave velocity is derived. The theoretical relationship between CTE and P-wave velocity is established based on the theoretical formulas of CTE and Young's modulus and the relationship between Young's modulus and P-wave velocity.

[0008] Preferably, the theoretical formulas for CTE and Young's modulus are as follows: (1) In the formula, k 1 and k 2 represents a constant related to material properties. α m This represents the average CTE of the corresponding material within a specific temperature range. E This represents the Young's modulus of the corresponding material at a specific temperature.

[0009] Preferably, the relationship between Young's modulus and longitudinal wave velocity is as follows: (2) In the formula, k This represents the ratio constant between the transverse wave velocity and the longitudinal wave velocity. c L The longitudinal wave velocity in the material. c S Let be the transverse wave velocity in the material, which are respectively: (3) In the formula, u It is the Poisson's ratio of the material; r It refers to the density of the material.

[0010] Preferably, the theoretical relationship between CTE and longitudinal wave velocity is as follows: (4) In the formula, k 3. α 0 is a coefficient obtained by nonlinear fitting of the calibrated CTE and the measured longitudinal wave velocity.

[0011] Preferably, in step 2, the longitudinal wave velocity of the LAS-based ultra-low expansion microcrystalline glass sample is measured, specifically as follows: The longitudinal wave velocity of LAS-based ultra-low expansion microcrystalline glass samples was measured using the water immersion ultrasonic pulse echo method to obtain the longitudinal wave velocity value.

[0012] Preferably, in step 3, the sample is calibrated for CTE to obtain the CTE calibration value, specifically as follows: The sample was calibrated using an L75 laser interferometric thermal dilatometer to obtain the CTE calibration value.

[0013] Preferably, in step 4, based on the theoretical relationship between CTE and P-wave velocity, the P-wave velocity value, and the CTE calibration value, an experimental relationship model between CTE and P-wave velocity is established to achieve full-diameter ultrasonic testing of CTE, specifically as follows: A sample library of LAS-based ultra-low expansion microcrystalline glass with the same residual stress but different crystalline phase contents was established, and longitudinal wave velocity was measured under the same temperature conditions. Based on the theoretical relationship between CTE and longitudinal wave velocity, the obtained longitudinal wave velocity measurement values ​​were statistically fitted with the corresponding absolute CTE calibration values, thereby establishing an experimental relationship model of CTE-longitudinal wave velocity for LAS-based ultra-low expansion microcrystalline glass materials.

[0014] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects: This invention provides an ultrasonic testing method for the coefficient of thermal expansion (CTE) of LAS-based ultra-low expansion microcrystalline glass. The method includes: analyzing and deriving the theoretical relationship between CTE and longitudinal wave velocity; establishing the theoretical relationship between CTE and longitudinal wave velocity; designing an LAS-based ultra-low expansion microcrystalline glass sample and measuring its longitudinal wave velocity to obtain the value; calibrating the sample's CTE to obtain the calibration value; and establishing an experimental CTE-longitudinal wave velocity relationship model based on the theoretical relationship between CTE and longitudinal wave velocity, the longitudinal wave velocity value, and the CTE calibration value, thereby achieving full-aperture ultrasonic testing of CTE. The significant beneficial effects of this invention are reflected in multiple aspects: 1. This invention can achieve non-destructive testing of CTE across the entire aperture. The method establishes an experimental relationship model between CTE and longitudinal wave velocity. The probe can be moved to any point of the LAS-based ultra-low expansion microcrystalline glass through a relatively integrated water immersion sound velocity measurement system to obtain the sound velocity value at that point, and then the corresponding CTE can be inverted. This method does not damage the large-sized test material, so the CTE and its uniformity across the entire aperture of the large-sized LAS-based ultra-low expansion microcrystalline glass can be obtained completely non-destructively. 2. This invention improves detection efficiency, eliminating the need for temperature-changing operations on the sample. The average CTE of the sample in the range of 0℃~50℃ can be directly predicted from the longitudinal wave sound velocity at 25℃. Furthermore, in sound velocity measurement, an automatic detection method for ultrasonic signals based on feature point recognition and a cross-correlation method for transit time estimation are proposed. Combined with a relatively integrated water immersion sound velocity measurement system, the sound velocity values ​​of various points in LAS-based ultra-low expansion microcrystalline glass can be quickly and automatically obtained. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This diagram illustrates the relationship between CTE (Central Crystal Phase) type, content, and size, and longitudinal wave velocity. Figure 2This is a schematic diagram illustrating the principle of the water immersion ultrasonic pulse echo method. Figure 3 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] The purpose of this invention is to provide an ultrasonic testing method for the thermal expansion coefficient of LAS-based ultra-low expansion microcrystalline glass, which realizes non-destructive testing of the thermal expansion coefficient of LAS-based ultra-low expansion microcrystalline glass across the entire aperture. It breaks through the limitation of traditional push-rod type measurement, which requires destructive sampling. It does not require temperature change operation and can invert the average CTE over a wide temperature range using room temperature sound velocity. It has high testing efficiency and low cost, and provides technical support for uniformity control in the preparation process of large-size materials.

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] like Figure 3 As shown, this invention provides an ultrasonic testing method for the thermal expansion coefficient of LAS-based ultra-low expansion microcrystalline glass, comprising: Step 1: Perform theoretical analysis and derivation of the CTE-longitudinal wave velocity relationship to establish the theoretical relationship between CTE and longitudinal wave velocity; Step 2: Design LAS-based ultra-low expansion microcrystalline glass samples and measure their longitudinal wave velocity to obtain the longitudinal wave velocity values; Step 3: Perform CTE calibration on the sample and obtain the CTE calibration value; Step 4: Based on the theoretical relationship between CTE and longitudinal wave velocity, the longitudinal wave velocity value and the CTE calibration value, establish an experimental relationship model between CTE and longitudinal wave velocity to realize full-diameter ultrasonic testing of CTE.

[0021] In step 1, the theoretical relationship between CTE and P-wave velocity is analyzed and derived to establish the theoretical relationship between CTE and P-wave velocity, specifically as follows: Based on the relationship between thermal expansion of materials and Young's modulus, theoretical formulas for CTE and Young's modulus are derived. Based on the theory of elastic waves, the relationship between Young's modulus and the longitudinal wave velocity is derived. The theoretical relationship between CTE and P-wave velocity is established based on the theoretical formulas of CTE and Young's modulus and the relationship between Young's modulus and P-wave velocity.

[0022] Based on the relationship between thermal expansion and Young's modulus of materials, the theoretical formulas for CTE and Young's modulus are derived as follows: From a materials science perspective, based on the principle that the increase in interatomic distance due to temperature rise and the decrease in interatomic distance due to atomic vibration cancel each other out, materials with suitable atomic structures can be prepared using chemical methods to achieve zero thermal expansion. Therefore, the thermal expansion and Young's modulus of a material are essentially closely related to its crystal structure and interatomic forces, and thus there is an inherent connection between the two. Therefore, the theoretical formulas for CTE and Young's modulus can be obtained as follows: (1) In the formula, k 1 and k 2 represents a constant related to material properties. α m This represents the average CTE of the corresponding material within a specific temperature range. E This represents the Young's modulus of the corresponding material at a specific temperature.

[0023] Based on elastic wave theory, the relationship between Young's modulus and longitudinal wave velocity is derived as follows: Since the speed of sound is determined by the elastic wave vibration characteristics and material properties, the longitudinal wave speed in a material... c L and transverse wave speed of sound c S The relationships with the material's elastic constant and density are as follows: (2) In the formula, E It is the Young's modulus of the material; u It is the Poisson's ratio of the material; r It refers to the density of the material. The longitudinal wave velocity of a material is mainly related to... E , u and r Regarding LAS-based ultra-low expansion microcrystalline glass... E right c L Size plays a dominant role. Based on formula (2), the relationship between Young's modulus and longitudinal wave velocity is derived as follows: (3) In the formula, k This represents the ratio constant between the transverse wave velocity and the longitudinal wave velocity, typically taken as 0.5 to 0.7.

[0024] Based on the theoretical formulas of CTE and Young's modulus, and the relationship between Young's modulus and P-wave velocity, a theoretical relationship between CTE and P-wave velocity is established, specifically: Based on the type, content and size of the main crystal phase ( C The influence mechanism of CTE on LAS-based ultra-low expansion microcrystalline glass materials: a specific mapping relationship can be established between CTE and longitudinal wave velocity, such as... Figure 1 As shown; Combining formulas (1) and (3), we can further derive the material's properties within a certain temperature range. α m At a specific temperature c L The relationship between them is: (4) According to formula (4), α m and c L The mapping relationship between them is quite complex, consisting of coefficients. k , k 1. k 2 working together, although k , k 1. k Accurately obtaining 2 is difficult, but for the same type of LAS-based ultra-low expansion microcrystalline glass material, k , k 1. k 2 can be treated as a constant value, therefore equation (4) can be simplified to: (5) In the formula, k 3. α 0 is a coefficient obtained by nonlinear fitting of the calibrated CTE and the measured longitudinal wave velocity, which is fixed for the same LAS-based ultra-low expansion microcrystalline glass material; as can be seen from equation (5), for a certain narrow range of sound velocity variation, α m and c L They exhibit an approximately linear relationship.

[0025] In step 2, the longitudinal wave velocity of the LAS-based ultra-low expansion microcrystalline glass sample is measured, specifically as follows: Under the same temperature (25℃), several LAS-based ultra-low expansion microcrystalline glass samples with a relatively wide range of CTE (0±100ppb / ℃) were selected for longitudinal wave velocity measurement. The requirements for the test samples are as follows: (1) The sample shape is required to be cylindrical, with a thickness of 50 mm and a diameter greater than that of the probe chip. (2) In order to avoid the influence of component differences on the CTE of the sample, the samples were obtained under the same process formula but with different heat treatment regimes; (3) The sample was subjected to fine annealing to remove the internal residual thermal stress in order to achieve a low stress state (all <10nm / cm). The fine annealing process included heating from room temperature to 800℃ at a rate of 30℃ / h; holding at 800℃ for 50h; and cooling from 800℃ to room temperature at a rate of 25℃ / h. (4) To avoid the adverse effects of ultrasonic wave scattering and attenuation at the sample interface, the sample is finely ground and polished to achieve a flatness of 0.5. l The parallelism reaches 20µm.

[0026] Based on this, a fully integrated high-precision sound velocity measurement system was constructed to measure the longitudinal wave velocity in LAS-based ultra-low expansion microcrystalline glass using the water immersion ultrasonic pulse-echo method. This method typically involves time-domain analysis based on ultrasonic time of flight (TOF), where the longitudinal wave velocity is obtained by the ratio of material thickness to TOF.

[0027] Figure 2 The diagram illustrates the principle of the water immersion ultrasonic pulse-echo method. The pulse wave generated by the ultrasonic probe is incident perpendicularly onto the LAS-based ultra-low expansion microcrystalline glass sample via a coupling medium—water. Reflection and transmission occur on the upper surface of the sample. The reflected wave is received by the ultrasonic probe, i.e., the surface reflected wave S. F The transmitted wave continues to propagate to the lower surface of the LAS-based ultra-low expansion microcrystalline glass sample, and after reflection, reaches the upper surface of the LAS-based ultra-low expansion microcrystalline glass sample. Similarly, reflection and transmission will occur on the upper surface of the LAS-based ultra-low expansion microcrystalline glass sample. The wave generated by transmission is received by the ultrasonic probe, which is the first bottom surface wave B1. The other reflected wave is again received by the ultrasonic probe after bottom reflection and upper surface transmission, which is the second bottom surface wave B2.

[0028] S F Time difference Δ with B1 t 1. Time difference Δ between B1 and B2 t Both 2 can represent Time-of-Flight (TOF). Considering the high similarity between the TOF estimation accuracy of the cross-correlation method and the time-domain signals of B1 and B2, a method for automatic ultrasonic signal detection and transit time estimation based on feature point recognition and cross-correlation is proposed. First, the original ultrasonic signal of the material is obtained using the water immersion ultrasonic pulse-echo method. The original signal is downsampled to obtain a time-domain signal with a reduced sampling rate, which reduces the number of wavelet transform data points and the wavelet transform processing time. Further, a Morlet wavelet transform is performed on the downsampled time-domain signal to return the wavelet coefficients at each scale. Based on the energy map of the wavelet coefficients at each scale, the first surface reflection wave S can be determined. F The energy is at its maximum, so the location of the maximum energy is locked, and this point is transformed to the corresponding time domain location to achieve the time domain location of the surface reflection wave.

[0029] Then, based on the time-domain signals, the primary bottom wave B1 and the secondary bottom wave B2 are automatically located. Given the thickness of the LAS-based ultra-low expansion microcrystalline glass sample and the reference sound velocity, the reference time-of-flight (TOF) between B1 and B2 can be determined. Furthermore, the interval between the primary bottom wave and the primary surface reflection wave is equal to the interval between the primary bottom wave and the secondary bottom wave. Therefore, based on the reference TOF and the time-domain position of the primary surface reflection wave, the time-domain position of B1 is determined; then, based on the time-domain position of B1 and the reference TOF, the time-domain position of B2 is determined, completing the automatic location of B1 and B2. After determining the time-domain positions of B1 and B2, based on the time-domain characteristics of the signal peaks and valleys, feature points of these two sets of signals are automatically identified and extracted, and digital cross-correlation is used to calculate the actual TOF between B1 and B2.

[0030] Therefore, the material thickness is known. d And TOF, by c L =2 d / (Δ t 1)=2 d / (Δ t 2) Obtain the longitudinal wave velocity to achieve rapid and automatic detection of the ultrasonic longitudinal wave velocity of LAS-based ultra-low expansion microcrystalline glass samples.

[0031] In step 3, the sample is calibrated using CTE, and the CTE calibration value is obtained, specifically as follows: This invention employs an L75 laser interferometric dilatometer to calibrate the CTE of LAS-based ultra-low expansion microcrystalline glass samples. This dilatometer performs high-precision CTE measurements based on the laser-Michelson interferometry principle. The preparation requirements for the test samples are as follows: (1) The specimens are subjected to the same fine annealing treatment as the longitudinal wave sound velocity measurement specimens to achieve the same stress state. (2) The sample shape is required to be cylindrical, with dimensions of Φ6±0.5mm and a thickness of 50mm, to ensure the correspondence between the sound velocity and the CTE calibration value; (3) The upper and lower surfaces of the sample are flat and parallel to each other, with a flatness of 0.5. l Parallelism reaches 2′, and surface roughness is 1nm~3nm; (4) The roundness and taper of the sample are controlled according to general standards, and the perpendicularity of the end face reaches 1′.

[0032] The length change of the LAS-based ultra-low expansion microcrystalline glass sample due to temperature change Δ L = L 0 α m ( T 2- T 1) =L 0 α m Δ T The laser Michelson interferometer in the L75 laser thermal expansion meter can achieve ∆ L High-precision measurement, by recording changes in optical path difference and Δ T The sample can then be determined. α m The value is: (6) In the formula, Δ N It is a change in the number of dry cleaning stripes; l It is the wavelength of the laser. l =632.8nm. It should be noted that currently, this laser thermal dilatometer only allows for two sample lengths for CTE testing (20mm and 50mm). Based on the formula for the length change caused by temperature variations in LAS-based ultra-low expansion microcrystalline glass samples, the initial sample length... L The longer the length of the 0, the higher the uncertainty level of the CTE test. Therefore, a 50mm long LAS-based ultra-low expansion microcrystalline glass sample should be used for CTE calibration.

[0033] Based on room temperature (20℃), LAS-based ultra-low expansion microcrystalline glass samples α m The target temperature range (0~50℃) was used to set experimental parameters. The starting temperature of the CTE calibration process was set to 0℃, the ending temperature to 52℃, and the heating rate to ≤1℃ / min. After determining the experimental parameters, CTE calibration was performed. The specific steps included: (1) First, the sample to be tested is dried and cleaned, and the initial length L0 of the sample is measured at room temperature (20℃); (2) Place the sample into the DIL and let the measuring system stand for 30 minutes; (3) Cool the sample to the measurement start temperature (0℃) using liquid nitrogen and keep it at that temperature for 10 min. Then heat the sample to the measurement end temperature (52℃) at a heating rate of ≤1℃ / min. (4) Record the linear expansion rate data of these samples within the measurement temperature range; Expansion rate (Δ) from 0 to 50°C L / L 0) - Temperature ( T Data processing and calculation α m (0℃, 50℃).

[0034] In step 4, based on the theoretical relationship between CTE and P-wave velocity, the P-wave velocity value, and the CTE calibration value, an experimental relationship model between CTE and P-wave velocity is established to realize full-diameter ultrasonic testing of CTE. Specifically: A sample library of LAS-based ultra-low expansion microcrystalline glass with the same residual stress (near-zero stress level) but different crystalline phase contents was established, covering samples with a range of 0±100 ppb / ℃. α m (0℃, 50℃), and P-wave velocity was measured under the same temperature condition (25℃). Based on the aforementioned CTE-P-wave velocity theoretical model, the obtained P-wave velocity measurements were... c L With the corresponding absolute CTE calibration value α m Statistical data fitting was performed to establish an experimental model of the CTE-longitudinal wave sound velocity relationship for LAS-based ultra-low expansion microcrystalline glass materials. The results were... α m and c L The fitting equation between them is α m = k 4 c L + k 5. In the formula k 4. k 5 represents the coefficients obtained by performing a least-squares linear fit between the calibrated CTE and the measured P-wave velocity, where k 4 is a negative value, approximately -8.4 ppb / ℃ / m / s. k A positive value of 5 indicates the CTE corresponding to zero longitudinal wave velocity, approximately 54485 ppb / ℃.

[0035] This CTE-longitudinal wave sound velocity experimental relationship model, combined with a relatively integrated water immersion sound velocity measurement system, enables non-destructive testing of the entire aperture of LAS-based ultra-low expansion glass using CTE.

[0036] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0037] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. An ultrasonic testing method for the coefficient of thermal expansion of LAS-based ultra-low expansion microcrystalline glass, characterized in that, include: Step 1: Perform theoretical analysis and derivation of the CTE-longitudinal wave velocity relationship to establish the theoretical relationship between CTE and longitudinal wave velocity; Step 2: Design LAS-based ultra-low expansion microcrystalline glass samples and measure their longitudinal wave velocity to obtain the longitudinal wave velocity values; Step 3: Perform CTE calibration on the sample and obtain the CTE calibration value; Step 4: Based on the theoretical relationship between CTE and longitudinal wave velocity, the longitudinal wave velocity value and the CTE calibration value, establish an experimental relationship model between CTE and longitudinal wave velocity to realize full-diameter ultrasonic testing of CTE.

2. The method according to claim 1, characterized in that, In step 1, the theoretical relationship between CTE and P-wave velocity is analyzed and derived to establish the theoretical relationship between CTE and P-wave velocity, specifically as follows: Based on the relationship between thermal expansion of materials and Young's modulus, theoretical formulas for CTE and Young's modulus are derived. Based on the theory of elastic waves, the relationship between Young's modulus and the longitudinal wave velocity is derived. The theoretical relationship between CTE and P-wave velocity is established based on the theoretical formulas of CTE and Young's modulus and the relationship between Young's modulus and P-wave velocity.

3. The method according to claim 2, characterized in that, The theoretical formulas for CTE and Young's modulus are as follows: （1） In the formula, k 1 and k 2 represents a constant related to material properties. α m This represents the average CTE of the corresponding material within a specific temperature range. E This represents the Young's modulus of the corresponding material at a specific temperature.

4. The method according to claim 3, characterized in that, The specific relationship between Young's modulus and longitudinal wave velocity is as follows: （2） In the formula, k This represents the ratio constant between the transverse wave velocity and the longitudinal wave velocity. c L The longitudinal wave velocity in the material. c S Let be the transverse wave velocity in the material, which are respectively: （3） In the formula, υ It is the Poisson's ratio of the material; ρ It refers to the density of the material.

5. The method according to claim 4, characterized in that, The theoretical relationship between CTE and longitudinal wave velocity is as follows: （4） In the formula, k 3. α 0 is a coefficient obtained by nonlinear fitting of the calibrated CTE and the measured longitudinal wave velocity.

6. The method according to claim 5, characterized in that, In step 2, the longitudinal wave velocity of the LAS-based ultra-low expansion microcrystalline glass sample is measured, specifically as follows: The longitudinal wave velocity of LAS-based ultra-low expansion microcrystalline glass samples was measured using the water immersion ultrasonic pulse echo method to obtain the longitudinal wave velocity value.

7. The method according to claim 6, characterized in that, In step 3, the sample is calibrated using CTE, and the CTE calibration value is obtained, specifically as follows: The sample was calibrated using an L75 laser interferometric thermal dilatometer to obtain the CTE calibration value.

8. The method according to claim 7, characterized in that, In step 4, based on the theoretical relationship between CTE and P-wave velocity, the P-wave velocity value, and the CTE calibration value, an experimental relationship model between CTE and P-wave velocity is established to realize full-diameter ultrasonic testing of CTE. Specifically: A sample library of LAS-based ultra-low expansion microcrystalline glass with the same residual stress but different crystalline phase contents was established, and longitudinal wave velocity was measured under the same temperature conditions. Based on the theoretical relationship between CTE and longitudinal wave velocity, the obtained longitudinal wave velocity measurement values ​​were statistically fitted with the corresponding absolute CTE calibration values, thereby establishing an experimental relationship model of CTE-longitudinal wave velocity for LAS-based ultra-low expansion microcrystalline glass materials.

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