A system and method for eliminating thermal distortion during high-temperature deformation measurement

Abstract

This invention discloses a system and method for eliminating thermal distortion during high-temperature deformation measurement, belonging to the field of optical measurement technology. The system includes an environmental signal acquisition module, a dual-band image information acquisition module, and a calculation module. The method includes a calibration stage and a measurement stage. In the calibration stage, the environmental signal acquisition module measures the state of the ambient air near the camera lens, the dual-band image information acquisition module acquires the initial speckle image of a specific dual-band light, and the calculation module calculates the refractive index of the specific dual-band light. In the measurement stage, the dual-band image information acquisition module acquires the speckle image of the specific dual-band light under high-temperature conditions, derives the thermal distortion elimination formula, and calculates the displacement field after eliminating thermal distortion. This invention can fundamentally and completely eliminate thermal distortion, has better accuracy in high-temperature displacement field measurement, and has a wider range of applications and a larger measurable temperature range.

Description

Technical Field

[0001] This invention relates to the field of optical measurement technology, and more specifically, to a system and method for eliminating thermal distortion during high-temperature deformation measurement. Background Technology

[0002] Non-contact deformation measurement under high-temperature conditions is of great significance in aerospace, machinery manufacturing, and nuclear energy fields. Therefore, advanced optical deformation measurement methods under high-temperature conditions are crucial for promoting the development of these fields and are also essential for exploring the high-temperature mechanical properties of materials. Currently, due to the special high-temperature conditions, traditional optical deformation measurement methods directly yield the sum of the specimen's own thermal deformation and the thermal distortion deformation caused by hot air disturbance in the high-temperature environment. The influence of thermal distortion introduces significant measurement errors to accurately measure the specimen's own thermal deformation.

[0003] Existing methods for eliminating thermal distortion only address distortion caused by lens temperature, lens optical component errors, or assembly errors. For example, Chinese Patent Application No. 202310510096.5, filed on May 8, 2023, discloses a method for temperature estimation and thermal distortion correction in structured light reconstruction. This method acquires a target speckle image from a structured light lens and matches it with a first preset speckle image to obtain a first set of speckle spots with the same name. The first preset speckle image represents speckle on a flat surface at a first preset temperature. The image is processed using a preset speckle temperature sequence relationship. Based on a first set of speckles with the same name, the average temperature of the structured light lens is calculated. Based on the average temperature, the speckle offset of the first preset speckle image is determined. Based on the speckle offset, the first preset speckle image is offset to obtain a calibrated speckle image on a flat surface. This algorithm compensates for the deficiencies at the physical hardware level by using a speckle image of a flat surface that is independent of the actual situation to calibrate and complete the image to a speckle image of a flat surface with a temperature closer to the actual situation. This facilitates more accurate matching of speckle pairs and improves the accuracy of speckle structured light measurement. However, this method only characterizes and eliminates lens temperature distortion. It eliminates distortion caused by temperature (mainly lens deformation caused by camera heat after a period of operation, or lens distortion caused by high ambient temperature), which leads to distortion in the acquired image. It cannot eliminate thermal distortion caused by spurious deformation due to hot air.

[0004] While some researchers have proposed methods such as using air knives and high-speed, multiple-sample averaging techniques to reduce the impact of thermal distortion, these methods and techniques can only mitigate the effects of thermal distortion under specific conditions, limiting their application. Eliminating thermal distortion under conditions such as open environments with high temperatures and high-speed loading is difficult. Therefore, there is currently no universally applicable method to fundamentally eliminate thermal distortion.

[0005] Therefore, providing a universal system and method that can completely eliminate thermal distortion and accurately measure high-temperature deformation fields, applicable to eliminating thermal distortion during high-temperature deformation measurement, is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the present invention provides a system and method for eliminating thermal distortion during high-temperature deformation measurement, in order to solve the problem that the thermal distortion correction methods in the prior art cannot eliminate the thermal distortion caused by false deformation due to high-temperature hot air, and thus do not fundamentally eliminate thermal distortion, resulting in low measurement accuracy.

[0007] This invention discloses a system for eliminating thermal distortion during high-temperature deformation measurement, comprising: an environmental signal acquisition module, a dual-band image information acquisition module, and a calculation module; the environmental signal acquisition module and the dual-band image information acquisition module are electrically connected to the calculation module respectively; wherein,

[0008] The environmental signal acquisition module includes:

[0009] A thermometer, used to obtain the ambient temperature T near the camera lens;

[0010] A hygrometer is used to obtain the ambient humidity e near the camera lens;

[0011] A barometer is used to obtain the atmospheric pressure P near the camera lens;

[0012] The dual-band image information acquisition module includes:

[0013] Special light source, used to provide specific dual-band light;

[0014] A camera used to acquire initial speckle images of specific dual-band light and high-temperature deformed speckle images of specific dual-band light;

[0015] The dual-band image information acquisition module is used to acquire the initial speckle pattern of the test piece under specific dual-band light, which are respectively denoted as the first initial speckle image of the first band and the second initial speckle image of the second band; the position matching relationship between the first initial speckle image and the second initial speckle image is calculated based on the digital image correlation method; the dual-band image information acquisition module is also used to acquire the high-temperature deformation speckle pattern of the test piece under specific dual-band light, which are respectively denoted as the third high-temperature deformation speckle image of the first band and the fourth high-temperature deformation speckle image of the second band;

[0016] The calculation module is used to substitute ambient temperature T, ambient humidity e, and ambient atmospheric pressure P into the formula. The refractive indices n1 and n2 of a specific dual-band light are calculated; where n1 is the refractive index of the light corresponding to the first band in the specific dual-band light, n2 is the refractive index of the light corresponding to the second band in the specific dual-band light, and λ is the known center wavelength of the corresponding band light in the specific dual-band light.

[0017] The calculation module is also used to calculate the data of the initial speckle image of a specific dual-band light and the high-temperature deformed speckle image of a specific dual-band light to obtain the actual displacement field that eliminates thermal distortion.

[0018] The calculation module performs digital image correlation calculations on the first initial speckle image and the third high-temperature deformed speckle image of the first band to obtain the total displacement field ΔS1′ with thermal distortion.

[0019] The calculation module performs digital image correlation calculations on the second initial speckle image and the fourth high-temperature deformed speckle image of the second band to obtain the total displacement field ΔS2′ with thermal distortion.

[0020] At this time, ΔS1′=ΔS0+ΔS1, ΔS2′=ΔS0+ΔS2, where ΔS0 is the actual displacement field of the test piece, and ΔS1 and ΔS2 are the thermal distortion displacement of the first band and the thermal distortion displacement of the second band, respectively.

[0021] Based on formula The displacement formula for eliminating thermal distortion is derived. Substituting n1, n2, ΔS1′, and ΔS2′ into the displacement formula for eliminating thermal distortion, the actual displacement field ΔS0 of the test piece after eliminating thermal distortion is calculated.

[0022] Optionally, when the experimental temperature exceeds 600℃, the specific dual-band light includes any two bands of blue light, violet light, and ultraviolet light; when the experimental temperature is below 600℃, the specific dual-band light includes any two bands of violet light, blue light, green light, and red light.

[0023] Optionally, a camera refers to a multispectral camera whose response band includes specific dual-band light; or, a camera refers to a combination of a single camera and a beam-splitting filter; or, a camera refers to a combination of two cameras and a beam-splitting filter.

[0024] Optionally, the special light source may include a polychromatic light source; or, the special light source may include two independent monochromatic light sources.

[0025] Based on the same inventive concept, this invention also discloses a method for eliminating thermal distortion during high-temperature deformation measurement, comprising:

[0026] Provide the test piece;

[0027] The calibration stage is performed before the test piece is heated;

[0028] The measurement phase is performed while the test piece is being heated;

[0029] The calibration phase includes:

[0030] The environmental parameters near the camera lens are measured. Before the test piece is heated, the environmental signal acquisition module collects data on the ambient temperature, ambient humidity and ambient atmospheric pressure near the camera lens. The calculation module is used to obtain the refractive indices n1 and n2 of specific dual-band light in the measurement environment.

[0031] Lens distortion calibration: Lens distortion is calibrated and removed using a dual-band image information acquisition module;

[0032] Dual-band image position coordinate matching: The initial speckle pattern of a specific dual-band light on the test piece is acquired using a dual-band image information acquisition module and denoted as the first initial speckle image of the first band and the second initial speckle image of the second band, respectively; the position matching relationship between the first initial speckle image and the second initial speckle image is calculated based on the digital image correlation method.

[0033] The measurement phase includes:

[0034] When the test piece is heated, the high-temperature deformation speckle pattern of the test piece under specific dual-band light is acquired using the dual-band image information acquisition module, and is recorded as the third high-temperature deformation speckle image of the first band and the fourth high-temperature deformation speckle image of the second band.

[0035] The calculation module is used to perform digital image correlation calculations on the first initial speckle image and the third high-temperature deformed speckle image of the first band to obtain the total displacement field ΔS1′ with thermal distortion.

[0036] The calculation module is used to perform digital image correlation calculations on the second initial speckle image and the fourth high-temperature deformed speckle image of the second band to obtain the total displacement field ΔS2′ with thermal distortion.

[0037] At this time, ΔS1′=ΔS0+ΔS1, ΔS2′=ΔS0+ΔS2, where ΔS0 is the actual displacement field of the test piece, and ΔS1 and ΔS2 are the thermal distortion displacement of the first band and the thermal distortion displacement of the second band, respectively.

[0038] Based on formula The displacement formula for eliminating thermal distortion is derived. Substituting n1, n2, ΔS1′, and ΔS2′ into the displacement formula for eliminating thermal distortion, the actual displacement field ΔS0 of the test piece after eliminating thermal distortion is calculated.

[0039] Optionally, before heating the test piece, a special light source simultaneously illuminates it to obtain an initial speckle pattern. Then, a camera separates the first initial speckle image of the first band and the second initial speckle image of the second band; wherein,

[0040] The camera refers to a multispectral camera whose response band includes specific dual-band light; or,

[0041] A camera refers to a combination of a single camera and a beam splitter / filtering optical path; or,

[0042] The camera refers to a combination of dual cameras and a beam splitter filter.

[0043] Optionally, while the test piece is heated, a special light source simultaneously illuminates it to obtain a high-temperature deformation speckle pattern. Then, a camera is used to separate a third high-temperature deformation speckle image in the first band and a fourth high-temperature deformation speckle image in the second band; wherein,

[0044] The camera refers to a multispectral camera whose response band includes specific dual-band light; or,

[0045] A camera refers to a combination of a single camera and a beam splitter / filtering optical path; or,

[0046] The camera refers to a combination of dual cameras and a beam splitter filter.

[0047] Optional, according to the formula The refractive indices n1 and n2 of a specific dual-band light are calculated; where T is the ambient temperature near the camera lens, n is the refractive index to be measured for the corresponding band light, P is the atmospheric pressure near the camera lens, e is the ambient air humidity, and λ is the known center wavelength of the corresponding band light.

[0048] Further optional, according to the formula The refractive indices n1 and n2 of a specific dual-band light were calculated, including:

[0049] A specific dual-band light includes a first-band light and a second-band light. The center wavelength of the first-band light is λ1, according to the formula... The refractive index n1 of the first wavelength band was calculated.

[0050] The center wavelength of the second band of light is λ2, according to the formula The refractive index n2 of the second band of light was calculated.

[0051] Compared with the prior art, the system and method for eliminating thermal distortion during high-temperature deformation measurement provided by the present invention achieves at least the following beneficial effects:

[0052] The system and method for eliminating thermal distortion during high-temperature deformation measurement provided by this invention have universal applicability. They are suitable for both enclosed heating environments (like furnaces) and open heating environments, as well as static heating environments and dynamic high-speed heating environments involving impact and thermal vibration. Therefore, they are applicable to a wider range of loading conditions and scenarios. The special light source of this invention can provide different specific dual-band light depending on the experimental temperature. It can target different experimental temperature ranges by selectively choosing different specific band light sources and filtering optical paths, thus making it suitable for high-temperature and ultra-high-temperature environments and providing a wider measurable temperature range. This invention uses formulas to calculate the refractive index of the specific dual-band light and can also use a calculation module to directly calculate the actual displacement field of the test piece itself after eliminating thermal distortion, i.e., the thermal deformation of the test piece itself. This quantitative and qualitative elimination of thermal distortion makes the elimination more thorough, providing wide applicability and fundamentally eliminating thermal distortion completely, resulting in higher measurement accuracy. The system and method for eliminating thermal distortion during high-temperature deformation measurement based on specific dual-band image information provided by this invention can fundamentally and completely eliminate thermal distortion, have better accuracy in high-temperature displacement field measurement, and are applicable to various high-temperature load conditions such as static heating, thermal vibration, and open heating environments. Therefore, it has a wider range of application scenarios and a larger measurable temperature range.

[0053] Of course, any product implementing this invention does not necessarily need to achieve all of the technical effects described above at the same time.

[0054] Other features and advantages of the invention will become clear from the following detailed description of exemplary embodiments of the invention with reference to the accompanying drawings. Attached Figure Description

[0055] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the invention and, together with their description, serve to explain the principles of the invention.

[0056] Figure 1 This is a schematic diagram of the structure of a system for eliminating thermal distortion during high-temperature deformation measurement provided in an embodiment of the present invention;

[0057] Figure 2 This is a flowchart of a method for eliminating thermal distortion during high-temperature deformation measurement provided in an embodiment of the present invention;

[0058] Figure 3 This is a schematic diagram showing the test piece placed in the measurement environment and able to be imaged by a camera when using the method provided in this embodiment for measurement. Detailed Implementation

[0059] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention.

[0060] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0061] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0062] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0063] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0064] Example 1

[0065] Please refer to Figure 1 , Figure 1 This is a schematic diagram of a system for eliminating thermal distortion during high-temperature deformation measurement according to an embodiment of the present invention. The system 000 provided in this embodiment includes: an environmental signal acquisition module 10, a dual-band image information acquisition module 20, and a calculation module 30; the environmental signal acquisition module 10 and the dual-band image information acquisition module 20 are electrically connected to the calculation module 30 respectively; wherein,

[0066] The environmental signal acquisition module 10 includes:

[0067] Thermometer 101 is used to obtain the ambient temperature T near the camera lens;

[0068] Hygrometer 102 is used to obtain the ambient humidity e near the camera lens;

[0069] Barometer 103 is used to obtain the atmospheric pressure P near the camera lens;

[0070] The dual-band image information acquisition module 20 includes:

[0071] Special light source, used to provide specific dual-band light;

[0072] Camera 201 is used to acquire an initial speckle image of a specific dual-band light and a high-temperature deformed speckle image of a specific dual-band light.

[0073] Calculation module 30 is used to substitute ambient temperature T, ambient humidity e, and ambient atmospheric pressure P into the formula. The refractive index of a specific dual-band light is calculated; where n is the refractive index of the corresponding band light in the specific dual-band light, and λ is the known center wavelength of the corresponding band light in the specific dual-band light.

[0074] The calculation module 30 is also used to calculate the data of the initial speckle image of the specific dual-band light and the high-temperature deformed speckle image of the specific dual-band light to obtain the actual displacement field that eliminates thermal distortion.

[0075] During the optical measurement of test piece deformation under high-temperature conditions, the measurements include both the thermal deformation of the test piece itself and the thermal distortion caused by spurious deformation due to hot air. The thermal distortion caused by spurious deformation due to hot air can affect the measurement accuracy. Therefore, the system for eliminating thermal distortion during high-temperature deformation measurement provided in this embodiment can be used in optical measurements to eliminate the impact of thermal distortion on measurement accuracy, thereby improving the accuracy of measuring the true deformation of the test piece.

[0076] Specifically, the system for eliminating thermal distortion during high-temperature deformation measurement provided in this embodiment may include at least an environmental signal acquisition module 10, a dual-band image information acquisition module 20, and a calculation module 30. The environmental signal acquisition module 10 and the dual-band image information acquisition module 20 can be electrically connected to the calculation module 30, which can be a computer or other device with data collection, processing, and organization functions. The environmental signal acquisition module 10 is used to acquire environmental parameters near the camera lens, such as temperature, humidity, and air pressure, under the measurement environment. For example, the environmental signal acquisition module 10 may include a thermometer 101 for detecting and obtaining the ambient temperature T, a hygrometer 102 for detecting and obtaining the ambient humidity e, and a barometer 103 for detecting and obtaining the ambient atmospheric pressure P, to obtain environmental parameter values ​​that may affect measurement accuracy under the measurement environment. It is understood that this embodiment does not limit the model or structure of the thermometer 101, hygrometer 102, and barometer 103; they can be selected according to actual measurement needs during specific implementation. This embodiment does not limit the types of devices included in the environmental signal acquisition module 10. In specific implementations, the environmental signal acquisition module 10 may include a thermometer 101, a hygrometer 102, and a barometer 103, but is not limited to these. It may also include other devices capable of detecting environmental parameters, which will not be elaborated in this embodiment. The thermometer 101, hygrometer 102, and barometer 103 included in the environmental signal acquisition module 10 of this embodiment are used after detecting the ambient temperature T, ambient humidity e, and ambient atmospheric pressure P near the camera lens.

[0077] The dual-band image information acquisition module 20 of this embodiment includes a special light source (not shown in the figure, but can be understood as a light source illuminating the test piece). The special light source can be understood as a light source emitter used to emit special light, that is, to provide specific dual-band light for measurement. Optionally, the special light source includes a polychromatic light source; or, the special light source includes two independent monochromatic light sources. Since the thermal distortion elimination system provided in this embodiment requires two bands, i.e., dual-band, the special light source needs to be two monochromatic light sources or one polychromatic light source to provide specific dual-band light for measurement. The dual-band image information acquisition module 20 also includes a camera 201, which is used to acquire the initial speckle image of the specific dual-band light and the high-temperature deformation speckle image of the specific dual-band light. It is understood that the camera 201 in this embodiment may not be an ordinary camera used in daily life. The camera 201 may refer to a multispectral camera whose response band includes specific dual-band light; or, the camera 201 may refer to a combination structure of a single camera combined with a beam splitting and filtering optical path; or, the camera 201 may refer to a combination structure of a dual camera combined with a beam splitting and filtering optical path. In this way, after acquiring the initial speckle image of specific dual-band light, it can be separated to obtain the initial speckle image under different band light. Similarly, after acquiring the high-temperature deformation speckle image of specific dual-band light, it can be separated to obtain the high-temperature deformation speckle image under different band light, which is convenient for subsequent data calculation.

[0078] The special light source in this embodiment is used to provide specific dual-band light for measurement. This specific dual-band light can be selected according to different experimental temperatures. For example, when the experimental temperature is a high temperature or ultra-high temperature exceeding 600°C, the specific dual-band light provided by the special light source includes any two bands of blue light, violet light, violet light, and ultraviolet light; when the experimental temperature is below 600°C, the specific dual-band light provided by the special light source includes any two bands of violet light, blue light, green light, and red light. Thus, different specific dual-band light can be provided according to different experimental temperatures to achieve better measurement results.

[0079] In this embodiment, the calculation module 30 is used to substitute the ambient temperature T, ambient humidity e, and ambient atmospheric pressure P detected by the environmental signal acquisition module 10 under the measurement environment into the formula. The refractive index of the specific dual-band light is calculated. Assuming the specific dual-band light includes blue and violet light, with the center wavelength of the blue band being λ1 and the center wavelength of the violet band being λ2, the ambient temperature T, ambient humidity e, and ambient atmospheric pressure P detected by the environmental signal acquisition module 10, along with the center wavelength of the blue band λ1 (as λ), are substituted into the formula. The refractive index n1 of the blue band in the specific dual-band light can be calculated from n1 in the formula. Similarly, the ambient temperature T, ambient humidity e, ambient atmospheric pressure P detected by the environmental signal acquisition module 10, and the center wavelength λ2 of the violet band (as λ) are substituted into the formula. The refractive index n2 of the violet band in the specific dual-band light can be calculated from the formula. Therefore, the calculation module 30 can calculate the refractive indices n1 and n2 of the specific dual-band light by collecting and processing the parameters detected by the environmental signal acquisition module 10 and the center wavelength of the specific dual-band light provided by the special light source. It can be understood that the refractive indices n1 and n2 of this specific dual-band light can be interpreted as the refractive indices of different specific dual-band lights under different measurement environments.

[0080] The calculation module 30 in this embodiment is also used to calculate the data of the initial speckle image of the specific dual-band light and the high-temperature deformation speckle image of the specific dual-band light. The initial speckle image of the specific dual-band light can be acquired and separated by the camera 201 included in the dual-band image information acquisition module 20 before the experiment, i.e. before the test piece is heated. The high-temperature deformation speckle image of the specific dual-band light can be acquired and separated by the camera 201 included in the dual-band image information acquisition module 20 during the experiment, i.e. when the test piece is heated. After collecting the above data, the calculation module 30 performs data calculation on the initial speckle image of the specific dual-band light and the high-temperature deformation speckle image of the specific dual-band light. Finally, through the calculation of the calculation module 30, the actual displacement field of the test piece after eliminating thermal distortion is obtained, i.e., the amount of thermal deformation of the test piece itself after eliminating the false deformation caused by hot air.

[0081] The system for eliminating thermal distortion during high-temperature deformation measurement provided in this embodiment has universal applicability. It is suitable for both closed heating environments (like furnaces) and open heating environments, as well as static heating environments and dynamic high-speed heating environments involving impact and thermal vibration. Therefore, it is applicable to a wider range of loading conditions and scenarios. The special light source in this embodiment can provide different specific dual-band light depending on the experimental temperature. It can target different experimental temperature ranges by selectively choosing different specific band light sources and filtering optical paths, thus making it suitable for high-temperature and ultra-high-temperature environments and providing a wider measurable temperature range. This embodiment uses formulas to calculate the refractive index of the specific dual-band light and can also use the calculation module 30 to directly calculate the actual displacement field of the test piece after eliminating thermal distortion, i.e., the thermal deformation of the test piece itself. This quantitative and qualitative elimination of thermal distortion makes the elimination more thorough, providing wide applicability and fundamentally eliminating thermal distortion completely, resulting in higher measurement accuracy. The system provided in this embodiment, which eliminates thermal distortion during high-temperature deformation measurement based on specific dual-band image information, can fundamentally and completely eliminate thermal distortion, has better accuracy in high-temperature displacement field measurement, and is suitable for various high-temperature load conditions such as static heating, thermal vibration, and open heating environments. Therefore, it has a wider range of application scenarios and a larger measurable temperature range.

[0082] In the system for eliminating thermal distortion during high-temperature deformation measurement in this embodiment, the dual-band image information acquisition module 20 includes a camera 201 for acquiring an initial speckle image of specific dual-band light and a high-temperature deformation speckle image of specific dual-band light. During the measurement process, before the test piece is heated, the camera 201 can acquire and separate the initial speckle image of the test piece under specific dual-band light to obtain a first initial speckle image of the first band and a second initial speckle image of the second band. Optionally, the calculation module 30 can calculate the positional matching relationship between the first and second initial speckle images based on a digital image correlation method. During the measurement process, when the test piece is heated, the camera 201 can acquire and separate the high-temperature deformation speckle image of the test piece under specific dual-band light to obtain a third high-temperature deformation speckle image of the first band and a fourth high-temperature deformation speckle image of the second band. Optionally, the calculation module 30 can calculate the positional matching relationship between the third and fourth high-temperature deformation speckle images based on a digital image correlation method. Understandably, Digital Image Correlation (DIC) is a three-dimensional, full-field, non-contact optical measurement system for measuring the contours, displacements, vibrations, and strains of any material object. This technology can be used for a variety of tests, including static and dynamic applications involving tension, torsion, bending, and combined loading.

[0083] Since the calculation module 30 needs to calculate the pixel correspondence of the two speckle images one by one when calculating the initial speckle image of the specific dual-band light and the high-temperature deformed speckle image of the specific dual-band light, position matching is required, which is also a prerequisite for subsequent corresponding calculations. At this time, the position matching relationship of the calibration stage is continued.

[0084] The calculation module 30 in this embodiment is also used to calculate the data of the initial speckle image and the high-temperature deformed speckle image of the specific dual-band light to obtain the actual displacement field with thermal distortion eliminated. Specifically, the calculation module 30 needs to perform digital image correlation (DIC) calculations on the first initial speckle image and the third high-temperature deformed speckle image of the first band to obtain the total displacement field ΔS1′ with thermal distortion in the first band; and perform DIC calculations on the second initial speckle image and the fourth high-temperature deformed speckle image of the second band to obtain the total displacement field ΔS2′ with thermal distortion in the second band. At this time, ΔS1′=ΔS0+ΔS1, ΔS2′=ΔS0+ΔS2, where ΔS0 is the actual displacement field of the test piece, and ΔS1 and ΔS2 are the thermal distortion displacements of the first band and the second band, respectively. Based on the formula... The displacement formula for eliminating thermal distortion can be derived. Therefore, the refractive indices n1 and n2 of the specific dual-band light, the total displacement field ΔS1′ with thermal distortion in the first band, and the total displacement field ΔS2′ with thermal distortion in the second band, calculated by the calculation module 30 through collecting and organizing the parameters detected by the environmental signal acquisition module 10 and the center wavelength of the specific dual-band light provided by the special light source, are substituted into the displacement formula for eliminating thermal distortion. The calculation module 30 can calculate the actual displacement field ΔS0 of the test piece after eliminating thermal distortion, that is, the amount of thermal deformation of the test piece itself after eliminating the spurious deformation caused by hot air.

[0085] This embodiment is based on the theoretical formula for eliminating thermal distortion using specific dual-band image information. The calculation module 30 collects and organizes the parameters detected by the environmental signal acquisition module 10 and the center wavelength of the specific dual-band light provided by the special light source. The refractive indices n1 and n2 of the specific dual-band light, the total displacement field ΔS1′ of the first band with thermal distortion, and the total displacement field ΔS2′ of the second band with thermal distortion are calculated and substituted into the displacement formula for eliminating thermal distortion. The thermal deformation of the test piece itself can be directly calculated to eliminate thermal distortion. This can completely and thoroughly eliminate thermal distortion, resulting in higher measurement accuracy. Furthermore, the quantitative elimination of thermal distortion makes the elimination of thermal distortion more thorough and has wide applicability.

[0086] Example 2

[0087] Please refer to the reference. Figure 1and Figure 2 , Figure 2 This is a flowchart illustrating a method for eliminating thermal distortion during high-temperature deformation measurement according to an embodiment of the present invention. It is understood that the system for eliminating thermal distortion during high-temperature deformation measurement provided in the above embodiment can be used to perform measurements using the method of this embodiment, thereby eliminating the impact of thermal distortion on measurement accuracy. The method for eliminating thermal distortion during high-temperature deformation measurement provided in this embodiment includes:

[0088] S11: Provide the test piece;

[0089] S12: Calibration stage before heating the test piece;

[0090] S13: Measurement stage performed while the test piece is heated;

[0091] The calibration phase includes:

[0092] S121: Measurement of environmental parameters near the camera lens. Before the test piece is heated, the environmental signal acquisition module collects data on the ambient temperature, ambient humidity and ambient atmospheric pressure near the camera lens. The calculation module is used to obtain the refractive indices n1 and n2 of specific dual-band light in the measurement environment.

[0093] S122: Lens distortion calibration, using a dual-band image information acquisition module to calibrate and remove lens distortion;

[0094] S123: Dual-band image position coordinate matching. The initial speckle pattern of a specific dual-band light on the test piece is acquired using the dual-band image information acquisition module and denoted as the first initial speckle image of the first band and the second initial speckle image of the second band, respectively. The position matching relationship between the first initial speckle image and the second initial speckle image is calculated based on the digital image correlation method.

[0095] The measurement phase includes:

[0096] S131: When the test piece is heated, the high-temperature deformation speckle pattern of the test piece under specific dual-band light is acquired using the dual-band image information acquisition module, and is recorded as the third high-temperature deformation speckle image of the first band and the fourth high-temperature deformation speckle image of the second band, respectively.

[0097] S132: Using the calculation module, the actual displacement field of the test piece after eliminating thermal distortion is calculated from the first initial speckle image, the third high-temperature deformed speckle image, the second initial speckle image, and the fourth high-temperature deformed speckle image.

[0098] This embodiment provides a method for eliminating thermal distortion during high-temperature deformation measurement. Figure 1 The system in this embodiment can use this method to perform measurements, eliminating the impact of thermal distortion on measurement accuracy. Specifically,

[0099] The method for eliminating thermal distortion during high-temperature deformation measurement provided in this embodiment includes providing a test piece 40, such as... Figure 3 As shown, Figure 3 This is a schematic diagram showing the test piece placed in the measurement environment and able to be imaged by a camera when using the method provided in this embodiment for measurement. Figure 3 The following example uses the test piece 40 as a substrate. A calibration stage is performed before heating the test piece 40.

[0100] The calibration stage includes measuring environmental parameters near the camera lens. Before the test piece is heated, the environmental signal acquisition module 10 collects data on ambient temperature T, ambient humidity e, and ambient atmospheric pressure P. The calculation module 30 is used to obtain the refractive indices n1 and n2 of specific dual-band light in the measurement environment.

[0101] Optionally, the formula can be pre-entered in the calculation module 30. The refractive indices n1 and n2 of a specific dual-band light are calculated; where T is the ambient temperature, n is the refractive index to be measured for the corresponding band light, P is the atmospheric pressure, e is the ambient air humidity, and λ is the known center wavelength of the corresponding band light. For example, a specific dual-band light includes a first band light and a second band light, with the center wavelength of the first band light being λ1, according to the formula... The refractive index n1 of the first band of light is calculated; the center wavelength of the second band of light is λ2, according to the formula... The refractive index n2 of the second band of light was calculated.

[0102] The calibration stage also includes lens distortion calibration, which uses the dual-band image information acquisition module 20 to calibrate and remove lens distortion in order to eliminate the problem of inaccurate measurement accuracy caused by lens distortion.

[0103] The calibration stage also includes dual-band image position coordinate matching. The dual-band image information acquisition module 20 acquires the initial speckle image of the specific dual-band light of the test piece 40, which is recorded as the first initial speckle image of the first band and the second initial speckle image of the second band, respectively. The position matching relationship between the first initial speckle image and the second initial speckle image is calculated based on the digital image correlation method.

[0104] Optionally, before heating the test piece 40, a special light source simultaneously illuminates it to obtain an initial speckle pattern. Then, camera 201 separates the first initial speckle image of the first band and the second initial speckle image of the second band. Here, camera 201 refers to a multispectral camera whose response band includes specific dual-band light; or, camera 201 refers to a combination structure of a single camera combined with a beam-splitting filter; or, camera 201 refers to a combination structure of two cameras combined with a beam-splitting filter. This allows for the separation of initial speckle images under different bands of light after acquiring the initial speckle image of the specific dual-band light, facilitating subsequent data calculation. At this time, calculation module 30 can also calculate the positional matching relationship between the first and second initial speckle images based on digital image correlation methods. Since calculation module 30 needs to calculate the pixel-to-pixel correspondence between the two speckle images when calculating the data of the initial speckle image of the specific dual-band light and the high-temperature deformation speckle image of the specific dual-band light, positional matching is necessary and is a prerequisite for subsequent corresponding calculations. The positional matching relationship obtained by calculating the first and second initial speckle images during the calibration phase remains applicable during the measurement phase.

[0105] The measurement phase is performed while the test piece 40 is heated;

[0106] First, when the test piece 40 is heated, the dual-band image information acquisition module 20 acquires high-temperature deformation speckle images of the test piece 40 under specific dual-band light, which are respectively denoted as the third high-temperature deformation speckle image of the first band and the fourth high-temperature deformation speckle image of the second band. Based on the digital image correlation method, the first initial speckle image, the third high-temperature deformation speckle image, the second initial speckle image, and the fourth high-temperature deformation speckle image are calculated to obtain the true thermal deformation field that eliminates thermal distortion.

[0107] Optionally, while the test piece 40 is heated, a special light source simultaneously illuminates it to obtain a high-temperature deformation speckle image. Then, the camera 201 separates the third high-temperature deformation speckle image of the first band and the fourth high-temperature deformation speckle image of the second band. Here, camera 201 refers to a multispectral camera whose response band includes specific dual-band light; or, camera 201 refers to a combination structure of a single camera combined with a beam-splitting filter; or, camera 201 refers to a combination structure of a dual camera combined with a beam-splitting filter. This allows for the separation of high-temperature deformation speckle images under different bands of light after acquiring the high-temperature deformation speckle image of the specific dual-band light, facilitating subsequent data calculation. It is understood that the position matching relationship obtained in the calibration stage through the calculation of the first and second initial speckle images is still applicable in the measurement stage of this embodiment. Therefore, there is no need to recalculate the position matching relationship; only the position matching relationship obtained in the calibration stage needs to be used, which is beneficial for improving efficiency.

[0108] Finally, the actual displacement field of the test piece 40 after eliminating thermal distortion can be calculated using the calculation module 30 from the first initial speckle image, the third high-temperature deformed speckle image, the second initial speckle image, and the fourth high-temperature deformed speckle image.

[0109] Optionally, the calculation module 30 uses the first initial speckle image, the third high-temperature deformed speckle image, the second initial speckle image, and the fourth high-temperature deformed speckle image to calculate the actual displacement field of the test piece 40 after eliminating thermal distortion. This includes performing digital image correlation (DIC) calculations on the first initial speckle image and the third high-temperature deformed speckle image of the first band to obtain the total displacement field ΔS1′ with thermal distortion in the first band; and performing DIC calculations on the second initial speckle image and the fourth high-temperature deformed speckle image of the second band to obtain the total displacement field ΔS2′ with thermal distortion in the second band. At this time, ΔS1′=ΔS0+ΔS1, ΔS2′=ΔS0+ΔS2, where ΔS0 is the actual displacement field of the test piece, and ΔS1 and ΔS2 are the thermal distortion displacements of the first and second bands, respectively; based on the formula... The displacement formula for eliminating thermal distortion can be derived. The calculation module 30, by collecting and processing the parameters detected by the environmental signal acquisition module 10 and the center wavelength of the specific dual-band light provided by the special light source, calculates the refractive indices n1 and n2 of the specific dual-band light, the total displacement field ΔS1′ of the first band with thermal distortion, and the total displacement field ΔS2′ of the second band with thermal distortion. These values ​​are then substituted into the displacement formula for eliminating thermal distortion. The calculation module 30 can calculate the actual displacement field ΔS0 of the test piece after eliminating thermal distortion, that is, the amount of thermal deformation of the test piece itself after eliminating the spurious deformation caused by hot air.

[0110] The method for eliminating thermal distortion during high-temperature deformation measurement provided in this embodiment has universal applicability. It is suitable for both closed heating environments (like furnaces) and open heating environments, as well as static heating environments and dynamic high-speed heating environments involving impact and thermal vibration. Therefore, it is applicable to a wider range of loading conditions and scenarios. The special light source in this embodiment can provide different specific dual-band light depending on the experimental temperature. It can target different experimental temperature ranges by selectively choosing different specific band light sources and filtering optical paths, thus making it applicable to high-temperature and ultra-high-temperature environments and providing a wider measurable temperature range. This embodiment uses formulas to calculate the refractive index of the specific dual-band light and can also use the calculation module 30 to directly calculate the actual displacement field of the test piece after eliminating thermal distortion, i.e., the thermal deformation of the test piece itself. This quantitative and qualitative elimination of thermal distortion makes the elimination more thorough, providing wide applicability and fundamentally eliminating thermal distortion completely, resulting in higher measurement accuracy. The method for eliminating thermal distortion during high-temperature deformation measurement provided in this embodiment is based on the theoretical formula for eliminating thermal distortion using specific dual-band image information. The calculation module 30 collects and organizes the parameters detected by the environmental signal acquisition module 10 and the center wavelength of the specific dual-band light provided by the special light source. The refractive indices n1 and n2 of the specific dual-band light, the total displacement field ΔS1′ of the first band with thermal distortion, and the total displacement field ΔS2′ of the second band with thermal distortion are calculated and substituted into the displacement formula for eliminating thermal distortion. The thermal deformation of the test piece itself can be directly calculated, thus eliminating thermal distortion completely and thoroughly, resulting in higher measurement accuracy.

[0111] As can be seen from the above embodiments, the system and method for eliminating thermal distortion during high-temperature deformation measurement provided by the present invention achieves at least the following beneficial effects:

[0112] The system and method for eliminating thermal distortion during high-temperature deformation measurement provided by this invention have universal applicability. They are suitable for both enclosed heating environments (like furnaces) and open heating environments, as well as static heating environments and dynamic high-speed heating environments involving impact and thermal vibration. Therefore, they are applicable to a wider range of loading conditions and scenarios. The special light source of this invention can provide different specific dual-band light depending on the experimental temperature. It can target different experimental temperature ranges by selectively choosing different specific band light sources and filtering optical paths, thus making it suitable for high-temperature and ultra-high-temperature environments and providing a wider measurable temperature range. This invention uses formulas to calculate the refractive index of the specific dual-band light and can also use a calculation module to directly calculate the actual displacement field of the test piece itself after eliminating thermal distortion, i.e., the thermal deformation of the test piece itself. This quantitative and qualitative elimination of thermal distortion makes the elimination more thorough, providing wide applicability and fundamentally eliminating thermal distortion completely, resulting in higher measurement accuracy. The system and method for eliminating thermal distortion during high-temperature deformation measurement based on specific dual-band image information provided by this invention can fundamentally and completely eliminate thermal distortion, have better accuracy in high-temperature displacement field measurement, and are applicable to various high-temperature load conditions such as static heating, thermal vibration, and open heating environments. Therefore, it has a wider range of application scenarios and a larger measurable temperature range.

[0113] While specific embodiments of the invention have been described in detail by way of examples, those skilled in the art should understand that the examples are for illustrative purposes only and not intended to limit the scope of the invention. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.

Claims

1. A system for eliminating thermal distortion during high-temperature deformation measurement, characterized in that, include: Environmental signal acquisition module, dual-band image information acquisition module, and computing module; The environmental signal acquisition module and the dual-band image information acquisition module are electrically connected to the computing module, respectively; wherein... The environmental signal acquisition module includes: A thermometer is used to obtain the ambient temperature T near the camera lens; A hygrometer is used to obtain the ambient humidity e near the camera lens; A barometer is used to obtain the atmospheric pressure P in the vicinity of a camera lens; The dual-band image information acquisition module includes: Special light source, used to provide specific dual-band light; A camera is used to acquire an initial speckle image of the specific dual-band light and a high-temperature deformed speckle image of the specific dual-band light. The dual-band image information acquisition module is used to acquire the initial speckle pattern of the test piece under specific dual-band light, which are respectively denoted as the first initial speckle image of the first band and the second initial speckle image of the second band; the position matching relationship between the first initial speckle image and the second initial speckle image is calculated based on the digital image correlation method; the dual-band image information acquisition module is also used to acquire the high-temperature deformation speckle pattern of the test piece under specific dual-band light, which are respectively denoted as the third high-temperature deformation speckle image of the first band and the fourth high-temperature deformation speckle image of the second band. The calculation module is used to substitute the ambient temperature T, the ambient humidity e, and the ambient atmospheric pressure P into the formula. The refractive indices n1 and n2 of the specific dual-band light are calculated; where n1 is the refractive index of the light corresponding to the first band in the specific dual-band light, n2 is the refractive index of the light corresponding to the second band in the specific dual-band light, and λ is the known center wavelength of the corresponding band light in the specific dual-band light. The calculation module is also used to calculate the data of the initial speckle image of the specific dual-band light and the high-temperature deformed speckle image of the specific dual-band light to obtain the actual displacement field that eliminates thermal distortion. The calculation module performs digital image correlation calculations on the first initial speckle image and the third high-temperature deformed speckle image of the first band to obtain the total displacement field ΔS1′ with thermal distortion. The calculation module performs digital image correlation calculations on the second initial speckle image and the fourth high-temperature deformed speckle image of the second band to obtain the total displacement field ΔS2′ with thermal distortion. At this time, ΔS1′=ΔS0+ΔS1, ΔS2′=ΔS0+ΔS2, where ΔS0 is the actual displacement field of the test piece, and ΔS1 and ΔS2 are the thermal distortion displacement of the first band and the thermal distortion displacement of the second band, respectively. Based on formula The displacement formula for eliminating thermal distortion is derived. Substituting n1, n2, ΔS1′, and ΔS2′ into the displacement formula for eliminating thermal distortion, the actual displacement field ΔS0 of the test piece with eliminated thermal distortion is calculated.

2. The system for eliminating thermal distortion during high-temperature deformation measurement according to claim 1, characterized in that, When the experimental temperature exceeds 600℃, the specific dual-band light includes any two bands of blue light, violet light, and ultraviolet light. When the experimental temperature is below 600℃, the specific dual-band includes any two bands of violet, blue, green and red light.

3. The system for eliminating thermal distortion during high-temperature deformation measurement according to claim 1, characterized in that, The camera refers to a multispectral camera whose response band includes the specific dual-band light; or... The camera referred to here is a combination of a single camera and a beam-splitting filter optical path; or... The camera referred to here is a combination of dual cameras and a beam splitting and filtering optical path.

4. The system for eliminating thermal distortion during high-temperature deformation measurement according to claim 1, characterized in that, The special light source includes a polychromatic light source; or, The special light source includes two independent monochromatic light sources.

5. A method for eliminating thermal distortion during high-temperature deformation measurement, characterized in that, include: Provide the test piece; A calibration phase is performed before the test piece is heated; The measurement phase is performed while the test piece is being heated; The calibration phase includes: The environmental parameters near the camera lens are measured. Before the test piece is heated, the environmental signal acquisition module collects data on the ambient temperature, ambient humidity and ambient atmospheric pressure near the camera lens. The calculation module is used to obtain the refractive indices n1 and n2 of specific dual-band light in the measurement environment. Lens distortion calibration: Lens distortion is calibrated and removed using a dual-band image information acquisition module; Dual-band image position coordinate matching: The dual-band image information acquisition module acquires the initial speckle pattern of a specific dual-band light on the test piece, which is denoted as the first initial speckle image of the first band and the second initial speckle image of the second band, respectively; the position matching relationship between the first initial speckle image and the second initial speckle image is calculated based on the digital image correlation method. The measurement phase includes: When the test piece is heated, the dual-band image information acquisition module is used to acquire the high-temperature deformation speckle pattern of the test piece under the specific dual-band light, which are respectively recorded as the third high-temperature deformation speckle image of the first band and the fourth high-temperature deformation speckle image of the second band. The calculation module is used to perform digital image correlation calculations on the first initial speckle image and the third high-temperature deformed speckle image of the first band to obtain the total displacement field ΔS1′ with thermal distortion. The calculation module is used to perform digital image correlation calculations on the second initial speckle image and the fourth high-temperature deformed speckle image of the second band to obtain the total displacement field ΔS2′ with thermal distortion. At this time, ΔS1′=ΔS0+ΔS1, ΔS2′=ΔS0+ΔS2, where ΔS0 is the actual displacement field of the test piece, and ΔS1 and ΔS2 are the thermal distortion displacement of the first band and the thermal distortion displacement of the second band, respectively. Based on formula The displacement formula for eliminating thermal distortion is derived. Substituting n1, n2, ΔS1′, and ΔS2′ into the displacement formula for eliminating thermal distortion, the actual displacement field ΔS0 of the test piece after eliminating thermal distortion is calculated.

6. The method for eliminating thermal distortion during high-temperature deformation measurement according to claim 5, characterized in that, Before the test piece is heated, it is simultaneously illuminated by a special light source to obtain an initial speckle pattern. Then, a camera separates the first initial speckle image in the first band and the second initial speckle image in the second band; wherein, The camera refers to a multispectral camera whose response band includes the specific dual-band light; or... The camera referred to here is a combination of a single camera and a beam-splitting filter optical path; or... The camera referred to here is a combination of dual cameras and a beam splitting and filtering optical path.

7. The method for eliminating thermal distortion during high-temperature deformation measurement according to claim 6, characterized in that, When the test piece is heated, the special light source simultaneously illuminates it, obtaining a high-temperature deformation speckle pattern. Then, the camera separates the third high-temperature deformation speckle image in the first band and the fourth high-temperature deformation speckle image in the second band; wherein, The camera refers to a multispectral camera whose response band includes the specific dual-band light; or... The camera referred to here is a combination of a single camera and a beam-splitting filter optical path; or... The camera referred to here is a combination of dual cameras and a beam splitting and filtering optical path.

8. The method for eliminating thermal distortion during high-temperature deformation measurement according to claim 5, characterized in that, According to the formula The refractive indices n1 and n2 of the specific dual-band light are calculated; where T is the ambient temperature near the camera lens, n is the refractive index to be measured for the corresponding band light, P is the atmospheric pressure near the camera lens, e is the air humidity near the camera lens, and λ is the known center wavelength of the corresponding band light.

9. The method for eliminating thermal distortion during high-temperature deformation measurement according to claim 8, characterized in that, According to the formula The refractive indices n1 and n2 of the specific dual-band light are calculated, including: The specific dual-band light includes a first-band light and a second-band light, wherein the center wavelength of the first-band light is λ1, according to the formula... The refractive index n1 of the first wavelength band light is calculated; The center wavelength of the second band of light is λ2, according to the formula The refractive index n2 of the second band of light was calculated.

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