A temperature field and deformation field synchronous measurement method and system thereof

Abstract

This invention relates to a system and method for synchronously measuring temperature and deformation fields based on laser speckle DIC and temperature field algorithms. The system includes a 3CCD color camera, a lens, a three-band filter, a monochromatic light source, a mechanical support adjustment platform, a tripod, and a computer. It utilizes a blue laser to actively illuminate the test specimen, and the 3CCD color camera acquires color images of the high-temperature specimen surface before and after deformation, containing sub-images of red, green, and blue channels. The temperature field on the specimen surface is calculated by analyzing the sub-images of the R and G channels after deformation using a temperature field algorithm. The strain field on the specimen surface is obtained by analyzing the sub-images of the B channel before and after deformation using digital image correlation methods, thus achieving synchronous measurement of the temperature and deformation fields of the specimen surface. This invention features a simple principle, a compact system structure, and temperature field measurement unaffected by speckle interference. It enables non-contact, high-precision, and synchronous measurement of the deformation and temperature fields of materials under force and thermal loads.

Description

Technical Field

[0001] This invention relates to a measurement method and system, and more particularly to a method and system for simultaneous measurement of temperature field and deformation field based on laser speckle DIC and temperature field algorithm, belonging to the fields of optical mechanics, high-temperature object surface deformation testing, and high-temperature mechanical property testing technology of materials. Background Technology

[0002] Hypersonic vehicles have become a key strategic development focus for major spacefaring nations worldwide. With the significant increase in designed flight speeds, the operational environment for hypersonic vehicles is becoming increasingly harsh, posing new challenges to their safe operation. Therefore, there is an urgent need to increase investment in ground-based testing capabilities for hypersonic vehicles and continuously advance basic research and technology development in extreme environments. Currently, accurately characterizing the high-temperature resistant materials and structural mechanical properties of hypersonic vehicles under extreme high-temperature environments remains a difficult problem in ground-based testing. Traditional contact deformation and temperature measurement methods, such as high-temperature strain gauges and thermocouples, can only measure the deformation and temperature at certain points on the specimen surface. Furthermore, temperature and deformation sensors attached to the specimen surface can interfere with the true temperature and deformation distribution, causing the measured values ​​to fail to reflect the actual parameter distribution. Meanwhile, non-contact deformation and temperature measurement methods developed in recent years, such as three-dimensional digital correlation technology and infrared thermometry, suffer from mutual interference problems. Therefore, in laboratory testing of materials or structures for hypersonic vehicles, there is an urgent need to develop a high-precision non-contact measurement method that can simultaneously measure high-temperature deformation fields and temperature fields. This would provide richer and more comprehensive real experimental data for ground-based aerodynamic thermal environment simulation tests.

[0003] When using digital image correlation (DIR) methods for deformation measurement, high-precision image matching requires obtaining a stable, high-quality image sequence of the specimen surface during the experiment. However, in high-temperature deformation measurements, the images acquired by the camera gradually saturate due to the significant increase in thermal radiation from the specimen surface. When the temperature exceeds 600 degrees Celsius, randomly distributed features in the acquired images weaken or even disappear, leading to a decorrelation effect during DIR matching.

[0004] To perform deformation measurements using digital image correlation (DIR) methods at temperatures exceeding 600°C, Pan et al. invented a DIR method combining monochromatic blue light active imaging. This method effectively isolates most of the thermal radiation from the specimen surface from the imaging, thus ensuring the acquisition of high-quality image sequences under high-temperature conditions. Based on this method, Pan et al. achieved high-quality speckle image acquisition and deformation field measurement at 1200°C.

[0005] Based on existing high-temperature full-field deformation and temperature measurement techniques, various methods for simultaneous measurement of high-temperature full-field temperature and deformation have been developed in recent years. In 2014, R Montanini et al. proposed and discussed a new method for determining the coefficient of thermal expansion of rigid solid materials, known as Infrared Image Correlation (IIC), which is based on performing DIC between thermal images obtained by an infrared camera at different temperatures. In 2021, Guo et al. proposed a new calibration method to calibrate the intrinsic and extrinsic parameters of infrared and visible light cameras, measuring and reconstructing the temperature and strain fields on the sample surface. However, all of the above studies require the fabrication of randomly distributed high-temperature speckles on the sample surface. Due to the difference in emissivity between the high-temperature speckle material and the sample material, the measured temperature has a significant error. Summary of the Invention

[0006] To address the problem that existing technologies cannot simultaneously measure the temperature and deformation fields of materials under high-temperature conditions due to thermo-mechanical coupling deformation, this invention proposes a method for simultaneous measurement of temperature and deformation fields based on laser speckle DIC and temperature field algorithms. This method enables non-contact, high-precision, and simultaneous measurement of the deformation and temperature fields of materials under force and thermal loads. It has advantages such as wide applicability, convenient use of the measurement system, high measurement accuracy, and simple and compact system structure.

[0007] The technical solution adopted by the present invention to solve its technical problem is as follows: a synchronous measurement system for temperature field deformation field based on laser speckle DIC and temperature field algorithm includes a 3CCD color camera, lens, three-band filter, monochromatic light source, mechanical support adjustment platform, tripod and computer;

[0008] The 3CCD color camera is used to acquire clear images of the test specimen surface under high temperature conditions and transmits the acquired images to the computer in real time.

[0009] The three-band filter is used to filter light into three narrow bands: R, G, and B, which are then captured by the three channels of the 3CCD color camera.

[0010] The monochromatic light source is a blue laser light source, and the laser beam is expanded and collimated before irradiating the surface of the object being measured.

[0011] The mechanical support platform is used to support the 3CCD color camera. By adjusting the mechanical support platform, six degrees of freedom can be achieved in three directions and three angles in space, thereby adjusting the optical axis of the 3CCD color camera to be perpendicular to the region of interest on the surface of the test piece, and obtaining an image of the test piece.

[0012] The tripod is used to support the 3CCD color camera and can also be used to coarsely adjust the height of the 3CCD color camera.

[0013] The computer is used to process image data acquired by a 3CCD color camera to obtain strain and temperature data on the surface of the test piece.

[0014] This invention also discloses a method for simultaneous measurement of temperature field and deformation field based on laser speckle DIC and temperature field algorithm.

[0015] 1) Place the test piece directly in front of the test system;

[0016] 2) Install a three-band filter in front of the lens, use a blue laser light source to actively illuminate the test piece, and adjust the 3CCD color camera to make the image clear;

[0017] 3) Use a 3CCD color camera to acquire digital images of the test piece surface before and after deformation, containing sub-images of the R, G, and B channels;

[0018] 4) The sub-images of the R, G, and B channels are transmitted to the computer. The temperature field of the test specimen surface can be calculated by analyzing the sub-images of the R and G channels after deformation using the temperature field algorithm. The strain field of the test specimen surface can be obtained by analyzing the sub-images of the B channel before and after deformation using the digital image correlation method, thereby realizing the synchronous measurement of the temperature field and deformation field of the test specimen surface.

[0019] Beneficial effects

[0020] 1. A three-band filter is used in conjunction with a 3CCD color camera to acquire sub-images of the R, G, and B channels of the test piece surface before and after deformation. The three-band filter only allows light of specific wavelengths to enter the camera, and the RGB response spectrum of the camera does not overlap between the three channels, thus effectively avoiding crosstalk between the channels.

[0021] 2. The sub-images of the three channels of the 3CCD color camera are acquired at the same time. The temperature field of the test specimen surface can be calculated by analyzing the sub-images of the R and G channels after deformation using the temperature field algorithm. The strain field of the test specimen surface can be obtained by analyzing the sub-images of the B channel before and after deformation using the digital image correlation method. Therefore, the temperature field and strain field data of the test specimen at the same time can be measured using only one 3CCD color camera.

[0022] 3. Since there is no need to create artificial speckles on the sample surface, the interference of speckles on non-contact temperature measurement is avoided, thus improving the accuracy of temperature measurement. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the system structure of the present invention;

[0024] Figure 2 The diagram shows the filtration efficiency of a three-band filter at different wavelengths. The three-band filter only allows light of a specific wavelength to enter the camera, and the RGB response spectrum of the camera does not overlap between the three channels, thus effectively avoiding crosstalk between the channels.

[0025] Figure 3 The diagram illustrates the implementation process of this invention. Blue laser is used to irradiate the sample surface to generate speckle, avoiding the influence of artificial speckle. The sub-images of the three channels of the 3CCD color camera are acquired at the same time. The temperature field of the test piece surface can be calculated by analyzing the sub-images of the R and G channels after deformation using the temperature field algorithm. The strain field of the sample surface can be obtained by analyzing the sub-images of the B channel before and after deformation using the digital image correlation method. Therefore, only one 3CCD color camera is needed to measure the temperature field and strain field data of the test piece at the same time.

[0026] In the diagram: 1. 3CCD color camera; 2. Lens; 3. Three-band filter; 4. Blue laser light source; 5. Mechanical support and adjustment platform; 6. Tripod; 7. Computer. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0028] like Figure 1As shown, the present invention performs synchronous measurement of temperature field and deformation field based on laser speckle DIC and temperature field algorithm. The system consists of a 3CCD color camera (1); lens (2); three-band filter (3); monochromatic light source (4); mechanical support adjustment platform (5); tripod (6) and computer (7). A 3CCD color camera (1) is used to acquire clear images of the test specimen surface under high temperature conditions and transmit the acquired images to the computer (7) in real time; a three-band filter (2) is used to filter light into three bands, which are acquired by the three channels of the 3CCD color camera (1); a monochromatic light source (4) is a blue laser light source; a mechanical support platform (5) is used to support the 3CCD color camera (1), and by adjusting the mechanical support platform (5), six degrees of freedom in three directions and three angles in space can be achieved, thereby adjusting the optical axis of the 3CCD color camera (1) to be perpendicular to the region of interest on the test specimen surface and obtaining an image of the test specimen; a tripod (6) is used to support the 3CCD color camera (1), and can also coarsely adjust the height of the 3CCD color camera (1); a computer (7) is used to process the image data acquired by the 3CCD color camera (1) to obtain real-time high-precision strain and temperature data of the test specimen.

[0029] Example 1

[0030] A synchronous measurement system for temperature field deformation field based on laser speckle DIC and temperature field algorithm includes a 3CCD color camera (1), a lens (2), a three-band filter (3), a monochromatic light source (4), a mechanical support adjustment platform (5), a tripod (6), and a computer (7).

[0031] The 3CCD color camera (1) is used to acquire clear images of the surface of the test piece under high temperature conditions and transmit the acquired images to the computer (7) in real time.

[0032] The three-band filter (2) is used to filter light into three bands, which are then collected by the three channels of the 3CCD color camera (1).

[0033] The monochromatic light source (4) is a blue laser light source.

[0034] The mechanical support platform (5) is used to support the 3CCD color camera (1). By adjusting the mechanical support platform (5), six degrees of freedom can be achieved in three directions and three angles in space, thereby adjusting the optical axis of the 3CCD color camera (1) to be perpendicular to the region of interest on the surface of the test piece, and obtaining an image of the test piece.

[0035] The tripod (6) is used to support the 3CCD color camera (1) and can also be used to coarsely adjust the height of the 3CCD color camera (1).

[0036] The computer (7) is used to process the image data acquired by the 3CCD color camera (1) to obtain real-time high-precision strain and temperature data of the test piece.

[0037] Example 2

[0038] A method for simultaneous measurement of temperature and deformation fields based on laser speckle DIC and temperature field algorithm, which is based on the temperature and deformation field simultaneous measurement system described in Example 1, includes the following steps:

[0039] 1) Place the high-temperature test piece to be tested directly in front of the testing system;

[0040] 2) Install a three-band filter (3) in front of the lens (2), use a monochromatic light source (4) to actively illuminate the test piece, and adjust the 3CCD color camera (1) to make the image clear;

[0041] 3) Use a 3CCD color camera (1) to acquire sub-images of the R, G, and B channels of the test piece surface before and after deformation;

[0042] 4) The sub-images of the R, G, and B channels are transmitted to the computer. The temperature field of the test specimen surface can be calculated by analyzing the sub-images of the R and G channels after deformation using the temperature field algorithm. The strain field of the test specimen surface can be obtained by analyzing the sub-images of the B channel before and after deformation using the digital image correlation method.

[0043] The temperature field algorithm includes the following: The temperature field algorithm determines the temperature of the object to be measured by measuring the spectral radiometry ratio of the wavelengths corresponding to the R and G channels of the 3CCD color camera (1);

[0044] The relationship between the spectral radiant exitance M0 of an object and its wavelength λ and temperature T is given by the following formula:

[0045]

[0046] Where C1 = 3.742 × 10 -16 W·m 2 The first radiation constant is C2 = 1.4388 × 10⁻⁶. -2 m·K is the second radiation constant, and e is the natural constant, with a value of approximately 2.718281828459045.

[0047] The spectral radiance M of a gray body with emissivity ε(λ) on a 3CCD camera sensor ccd for:

[0048]

[0049] Where τ a τ(λ) and τ0(λ) are the spectral transmittance of the atmosphere and the optical system, respectively, D is the aperture of the optical system, and f' is the focal length of the optical system.

[0050] The relationship between the gray level U measured by the camera and the received spectral radiant exitance is as follows:

[0051] U=R(λ)AM ccd (λ)

[0052] Where R(λ) is the grayscale response coefficient of the camera sensor, and A is the area of ​​the camera sensor.

[0053] Therefore, the grayscale ratio K(T) of the corresponding wavelengths of the R and G channels of the 3CCD color camera (1) can be obtained as follows:

[0054]

[0055] Assuming the experimental object is a gray body, i.e., ε(λ) is a constant, and because the optical path is short during the temperature measurement experiment, the atmospheric spectral transmittance τ... a (λ) can be approximated as 1.

[0056] After simplification, the ratio K(T) of the two-wavelength signals is:

[0057]

[0058] in, It is only related to the 3CCD color camera and can be obtained through blackbody furnace calibration. After the system is calibrated, the temperature of the object to be measured can be obtained by measuring the grayscale ratio of the R and G channels of the 3CCD color camera (1).

[0059] The principle of the digital image correlation method is as follows: After acquiring digital images of the sample surface before and after deformation in the B channel of the 3CCD color camera, in order to obtain the image displacement of a certain calculation point, it is first necessary to select a square reference image sub-region centered at the calculation point in the reference image, and search for the deformation image sub-region in the deformed image that has the greatest similarity to its grayscale distribution.

[0060] To quantitatively calculate the similarity between a reference image sub-region and its corresponding deformed image sub-region, a suitable objective function is defined. The objective function used is the zero-mean normalized sum of squared difference (ZNSSD) function. For a reference image sub-region centered at point (x0, y0), its objective function can be written as:

[0061]

[0062] Where: f(x,y) represents the gray value at the midpoint (x,y) of the sub-region of the reference image, and g(x',y') represents the gray value at the midpoint (x',y') of the sub-region of the deformed image. and It is the average gray value of the reference and deformed image sub-regions; p = (u, u x ,u y ,v,v x ,v y ) T Let be the deformation parameter vector of the point to be calculated. Assuming that the coordinates (x, y) in the reference image sub-region and the position (x', y') in the deformed image sub-region are described by first-order shape functions, then:

[0063]

[0064] Here: u, v are the displacements of the image sub-region center in the x, y directions, and Δx, Δy are the distances from point (x, y) to the image sub-region center point (x0, y0). x ,u y ,v x ,v y This represents the first-order displacement gradient.

[0065] Using algorithms to calculate C ZNSSD (p) The minimum value of p is the actual displacement of the calculation point. After obtaining the total displacement, the total strain can be obtained by difference. In this invention, a blue laser light source is used to irradiate the surface to generate speckle, avoiding the influence of artificial speckle on the sample. The three-band filter used in this invention only allows light of specific wavelengths to enter the camera, and the RGB response spectrum of the camera does not overlap between the three channels, thus effectively avoiding crosstalk between channels and improving the accuracy of temperature measurement. In this invention, the sub-images of the three channels of the 3CCD color camera are acquired at the same time. The temperature field of the test piece surface can be calculated by analyzing the sub-images of the R and G channels after deformation using the temperature field algorithm. The strain field of the test piece surface can be obtained by analyzing the sub-images of the B channel before and after deformation using the digital image correlation method. Therefore, only one 3CCD color camera is needed to measure the temperature field and strain field data of the test piece at the same time, reducing experimental costs and avoiding the problem of synchronous matching of temperature and displacement fields when measuring with multiple cameras.

[0066] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A synchronous measurement system for temperature field and deformation field, which is a synchronous measurement system for temperature field and deformation field based on laser speckle DIC and temperature field algorithm, characterized in that: It includes a 3CCD color camera (1), a lens (2), a three-band filter (3), a monochromatic light source (4), a mechanical support adjustment platform (5), a tripod (6), and a computer (7); The 3CCD color camera (1) is used to acquire clear images of the surface of the test piece under high temperature conditions and transmit the acquired images to the computer (7) in real time. The three-band filter (3) is used to filter light into three narrow bands of light, R, G and B, which are collected by the three channels of the 3CCD color camera (1). The monochromatic light source (4) is a blue laser light source. After beam expansion and collimation, the laser is irradiated onto the surface of the object being measured to generate laser speckle that can be acquired by the B channel of the 3CCD color camera (1). The mechanical support adjustment platform (5) is used to support the 3CCD color camera (1). By adjusting the mechanical support adjustment platform (5), the adjustment of six degrees of freedom in three directions and three angles in space can be achieved, thereby adjusting the optical axis of the 3CCD color camera (1) to be perpendicular to the region of interest on the surface of the test piece, and obtaining the image of the test piece. The tripod (6) is used to support the 3CCD color camera (1) and can also be used to coarsely adjust the height of the 3CCD color camera (1). The computer (7) is used to process the image data acquired by the 3CCD color camera (1) to obtain strain and temperature data on the surface of the test piece; Furthermore, when the system is in use, the blue laser light source irradiates the natural surface of the object under test to generate subjective laser speckle, eliminating the need to create artificial speckle on the surface of the test piece; the three-band filter (3) ensures that the spectral responses of the R, G, and B channels of the 3CCD color camera (1) do not overlap; the R and G channels of the 3CCD color camera (1) collect the spectral information of the thermal radiation of the high-temperature test piece itself, which is used to calculate the temperature field of the test piece surface through the temperature field algorithm; the B channel of the 3CCD color camera (1) collects the laser speckle image generated by the blue laser light source irradiation, which is used to calculate the deformation field of the test piece surface through the digital image correlation method, thereby realizing the synchronous measurement of the temperature field and the deformation field at the same time.

2. A method for simultaneous measurement of temperature and deformation fields based on laser speckle DIC and temperature field algorithm, the method being based on the simultaneous measurement system of temperature and deformation fields described in claim 1, characterized in that... Includes the following steps: 1) Place the test piece directly in front of the test system; 2) Install a three-band filter (3) in front of the lens (2), use a blue laser light source to actively illuminate the test piece, and adjust the 3CCD color camera (1) to make the image clear; 3) Use a 3CCD color camera (1) to acquire digital images of the test piece surface containing three channels (R, G, B) before and after deformation; 4) The sub-images of the R, G, and B channels are transmitted to the computer. The temperature field of the test specimen surface can be calculated by analyzing the sub-images of the R and G channels after deformation using the temperature field algorithm. The strain field of the test specimen surface can be obtained by analyzing the sub-images of the B channel before and after deformation using the digital image correlation method, thereby realizing the synchronous measurement of the temperature field and deformation field of the test specimen surface.

3. The method for synchronous measurement of temperature field and deformation field based on laser speckle DIC and temperature field algorithm as described in claim 2, characterized in that: The temperature field algorithm includes the following: the temperature of the object to be measured is determined by measuring the spectral irradiance ratio of the wavelengths corresponding to the R and G channels of the 3CCD color camera (1); Based on the spectral radiative exitance of the object With wavelength The relationship between temperature T and temperature is given by the formula: ； wherein is a first radiation constant; is a second radiation constant, e is the natural constant having a value of approximately 2.718281828459045; Spectral radiance on the 3CCD camera photosensitive element of a grey body with emissivity ε(λ) is: ； in and Here, represents the spectral transmittance of the atmosphere and the optical system, respectively, and D represents the aperture of the optical system. The focal length of the optical system; The relationship between the gray level U measured by the camera and the received spectral radiant exitance is as follows: ； Where R(λ) is the grayscale response coefficient of the camera sensor, and A is the area of ​​the camera sensor; The grayscale ratio K(T) of the R and G channels of the 3CCD color camera is obtained as follows: ； Assuming the experimental object is a gray body, i.e., ε(λ) is a constant, and because the optical path is short during the temperature measurement experiment, the atmospheric spectral transmittance is... It can be approximated as 1; After simplification, the ratio K(T) of the two-wavelength signals is: ； in, It is only related to the 3CCD color camera and is obtained through blackbody furnace calibration. After the system is calibrated, the temperature of the object to be measured can be obtained by measuring the grayscale ratio of the R and G channels of the 3CCD color camera (1).

4. The temperature field and deformation field synchronous measurement method based on laser speckle DIC and temperature field algorithm temperature measurement according to claim 2, characterized in that: The digital image correlation method is as follows: After acquiring digital images of the sample surface before and after deformation of the B channel of the 3CCD color camera, in order to obtain the image displacement of a certain calculation point, it is first necessary to select a square reference image sub-region centered at the calculation point in the reference image, and search for the deformation image sub-region with the greatest similarity to its grayscale distribution in the deformed image. To quantitatively calculate the similarity between a sub-region of the reference image and its corresponding deformed sub-region, a suitable objective function is defined; the objective function used is the zero-mean normalized sum of squared difference (ZNSSD) function; for a sub-region of the reference image, the objective function is defined as a point... For the reference image sub-region centered at the center, the objective function is written as: ； in: This represents the gray value at the midpoint (x, y) of a sub-region of the reference image. This represents the gray value at the midpoint (x', y') of the deformed image sub-region. and It is the average gray value of the reference and deformed image sub-regions; Let be the deformation parameter vector of the point to be calculated. Assuming that the coordinates (x, y) in the reference image sub-region and the position (x', y') in the deformed image sub-region are described by first-order shape functions, then: ； here: Is the center of the image sub-region in Displacement in direction, For point To the center point of the image sub-region distance, This represents the first-order displacement gradient; Using algorithms to calculate Take the minimum value This is the actual displacement of the calculation point. After obtaining the total displacement, the total strain can be obtained by difference.

5. A non-volatile storage medium, characterized by, The non-volatile storage medium includes a stored program, wherein the program, when executed, controls the device where the non-volatile storage medium is located to perform the method described in any one of claims 2-4.

6. An electronic device, comprising: It includes a processor and a memory; the memory stores computer-readable instructions, and the processor is configured to execute the computer-readable instructions, wherein the computer-readable instructions, when executed, perform the method according to any one of claims 2-4.

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