Full-field strain quantitative measurement method based on DIC auxiliary stress luminescence

Abstract

The invention relates to the technical field of strain measurement, in particular to a full-field strain quantitative measurement method based on DIC auxiliary stress luminescence, which comprises the following steps: (1) preparing a stress luminescence film metal test piece; (2) carrying out tensile test and optical acquisition through a measuring system; (3) data extraction and picture processing; (4) establishing a quantitative calibration relationship between the stress luminescence light intensity and the DIC effective strain; finally, the quantitative calibration relation y = 0.25 x + 3.59 of the stress luminescence light intensity and the DIC effective strain is obtained, x represents light intensity data, y represents strain data, a quantitative strain visualization cloud picture of the test piece is drawn, and quantitative full-field strain measurement based on DIC auxiliary stress luminescence can be achieved. According to the method, stress luminescence detection and DIC strain measurement have good compatibility in the aspect of data acquisition and processing, and direct conversion from a stress luminescence intensity field to a physical strain field is realized, so that the method can be popularized and applied to quantitative analysis of mechanical response characteristics of various stress luminescence material systems.

Description

Technical Field

[0001] This invention relates to the field of strain measurement technology, and in particular to a full-field quantitative strain measurement method based on DIC-assisted stress luminescence. Background Technology

[0002] In critical fields such as aerospace, automotive engineering, and large-scale new energy infrastructure, structural components continuously endure complex dynamic loads under multi-field coupling environments during their service life. The reliability of their mechanical properties directly affects not only the overall operational efficiency of the equipment system but also the safety of personnel. Therefore, achieving accurate real-time monitoring of the stress state and deformation behavior of key components is of significant engineering value for preventing structural failure and extending service life. Among these, strain, as a key mechanical parameter characterizing the local deformation and damage evolution of materials, has become an indispensable technical indicator in structural health monitoring systems due to its precise measurement.

[0003] Traditional strain measurement techniques (resistance strain gauges, fiber optic strain sensors, etc.) can accurately measure the strain distribution of structures, but they suffer from drawbacks such as single-point measurement, cumbersome wiring, requirement for external power supply, high cost of demodulation equipment, and difficulty in directly sensing structural damage. Stress luminescence (ML) is a phenomenon where materials convert mechanical energy into light energy when subjected to mechanical stimuli such as pressure or impact, thus emitting light. Currently, stress luminescence thin-film sensors are widely used in structural health monitoring fields such as structural stress-strain visualization, micro-crack detection, and structural damage identification due to their advantages of self-powered operation, non-contact operation, and visualization. Although stress luminescence thin-film sensors have made some progress in qualitative monitoring of structural strain, they still face significant challenges in high-precision quantitative measurement of structural strain. Specifically, how to achieve a direct quantitative conversion from the stress luminescence intensity field to the physical strain field, thereby enabling high-precision quantitative measurement of the actual strain distribution by stress luminescence thin-film sensors, remains a pressing issue. Summary of the Invention

[0004] In order to overcome the shortcomings of existing stress luminescence sensing technology, which only achieves qualitative strain measurement, this invention proposes a quantitative full-field strain measurement method based on DIC-assisted stress luminescence.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: 1. A quantitative full-field strain measurement method based on DIC-assisted stress luminescence, comprising the following steps: (1) Preparation of stress-luminescent thin film metal specimens: Weigh an appropriate amount of stress-luminescent powder SrAl2O4:Eu 2+ Dy 3+(SAOED) and epoxy resin are thoroughly mixed to form a uniform solution. Then, a curing agent is added and stirred to ensure that each component is evenly dispersed in the solution. The uniformly stirred composite solution is then slowly poured into a polytetrafluoroethylene mold, and excess solution is gently scraped off along the edge of the mold with a scraper to make the film thickness uniform. Finally, the polytetrafluoroethylene mold is placed in an oven to form a stress-luminescent film of a certain thickness. To ensure good adhesion between the stress-luminescent film and the metal specimen surface, the specimen surface needs to be pretreated. First, the specimen surface is sanded with sandpaper, then thoroughly cleaned with alcohol and acetone to remove any residual oil, dust, and other impurities. After cleaning and drying, the stress-luminescent film is adhered to the metal specimen surface using transparent epoxy adhesive and cured at room temperature for a certain period of time. Random speckle patterns are then sprayed onto the back of the specimen, thus completing the preparation of the stress-luminescent film metal specimen. (2) Tensile testing and optical data acquisition are performed using a measurement system: The measurement system comprises a tensile testing machine, a data processing device, a CCD camera, and a three-dimensional DIC strain testing system. The three-dimensional DIC strain testing system includes two DIC cameras (left and right), a central blue light source, and a tripod platform. The data processing device is connected to the CCD cameras and the three-dimensional DIC strain testing system. The CCD cameras are positioned on the front of the tensile testing machine, and the three-dimensional DIC strain testing system is positioned on the back of the tensile testing machine. A light-shielding plate is placed in the middle of the tensile testing machine to prevent the blue light from the three-dimensional DIC strain testing system from affecting the stress emission acquisition.

[0006] The stress-luminescent thin film metal specimen obtained in step 1 is mounted on the tensile fixture of the tensile testing machine, ensuring that the stress-luminescent thin film metal specimen is axially aligned; before the test, the stress-luminescent thin film is continuously excited by an ultraviolet light source until its luminescence reaches saturation; then it is left to stand under no load to reduce the influence of stress-free photoluminescence attenuation on the stress luminescence intensity. A stress-luminescent thin film is pasted on the front of the metal specimen for stress-luminescence detection, and a random speckle pattern is sprayed on the back of the specimen for DIC strain measurement. A light shield is set around the tensile testing machine to completely isolate ambient light and ensure the accuracy of data acquisition. During the tensile testing process, the CCD camera collects the luminescence intensity of the stress-luminescent film. The optical axis of the CCD camera is perpendicular to the stress-luminescent film, and a certain distance is maintained between the lens and the surface of the stress-luminescent film. At the same time, the three-dimensional DIC system monitors the full-field strain distribution on the surface of the stress-luminescent film metal specimen in real time at the same sampling frequency to ensure the temporal consistency between the stress luminescence signal and the strain data. (3) Data extraction and image processing: A CCD camera was used to acquire stress luminescence images, and a DIC camera was used to acquire DIC speckle images. Because the stress luminescence images and DIC speckle images rely on different imaging systems (a CCD camera was used for stress luminescence image acquisition, while a DIC camera was used for DIC speckle images), their image coordinate systems are inconsistent, making direct spatial registration impossible. It is necessary to ensure that the selected data points are located on the same physical reference line to guarantee correspondence and accuracy. Therefore, physical scale calibration is introduced into the stress luminescence images and DIC speckle images to transform their respective image coordinates to the physical space coordinate system of the specimen, thereby achieving cross-system data correspondence matching and joint analysis. To quantitatively characterize the evolution of stress-luminescence response during tensile testing, an image processing program based on the Python platform was developed to extract light intensity data of the stress-luminescence film on the front side of the specimen at different loading times. This image processing program mainly achieves its purpose through the following three core processing steps: 1) Calculation of average background light intensity: Since the stress-emitting film exhibits a certain degree of self-emission in the unloaded state, the background light intensity needs to be corrected to ensure data accuracy. The program first extracts the grayscale image of the specified region of interest (ROI) from the initial frame image and calculates the average grayscale value within that region as the average background light intensity. ( x , y ), used for background removal in subsequent images; 2) Background subtraction: For each frame of the image, extract its grayscale data within the same ROI range. I raw ( x , y And perform background removal according to the following formula:

[0007] To obtain image grayscale data containing only the stress-induced luminescence enhancement portion. I * ( x , y That is, the image grayscale data after removing the stress-luminescent background light intensity grayscale matrix. x and y Represents the coordinates of image pixels; max represents the maximum value operator. 3) Visualization processing: The grayscale data of each frame after removing the background light intensity is visualized in the form of a pseudo-color image, which facilitates the analysis of the stress luminescence intensity distribution and its variation with load evolution. 4) The effective strain distribution within the same ROI on the back of the specimen is directly calculated using the 3D DIC strain testing system software. This information is used as a reference for the stress luminescence image data and is subsequently used to establish and analyze the stress luminescence intensity-effective strain mapping relationship. (4) Establish the quantitative calibration relationship between stress emission intensity and effective strain of DIC: Stress emission intensity and effective strain data of DIC were extracted from the upper two-thirds of the region along the vertical centerline of the specimen (corresponding to the longitudinal range of the ROI region, with a height of 60 mm), and linear regression analysis was performed to obtain the quantitative calibration relationship between stress emission intensity and effective strain of DIC. , x Represents light intensity data. y By representing strain data, quantitative full-field strain measurement based on DIC-assisted stress luminescence can be achieved.

[0008] To solve the above-mentioned technical problems, the present invention adopts a further technical solution as follows: In step (1): stress luminescent powder SrAl2O4:Eu is weighed at a mass ratio of 5:1-1:1. 2+ Dy 3+ (SAOED) and epoxy resin.

[0009] To solve the above-mentioned technical problems, the present invention adopts a further technical solution as follows: In step (1), a curing agent is added at a mass ratio of 5:1, and a magnetic stirrer is used to stir at a speed of 500 rpm for 15 minutes to ensure that each component is evenly dispersed in the solution.

[0010] To solve the above-mentioned technical problems, the present invention adopts a further technical solution as follows: In step (1): the polytetrafluoroethylene mold is placed in an oven and cured at 80°C for 1 hour to form a stress-luminescent film with a thickness of 0.4 mm.

[0011] To solve the above-mentioned technical problems, the present invention adopts a further technical solution as follows: In step (1): a transparent epoxy adhesive is used to attach the stress luminescent film to the surface of the specimen and cure it at room temperature for 12 hours.

[0012] To solve the above-mentioned technical problems, the present invention adopts a further technical solution as follows: in step (2): the tensile testing machine is set to a constant loading rate of 6 mm / min.

[0013] To solve the above-mentioned technical problems, the present invention adopts a further technical solution as follows: In step (2): before the test, a 10W ultraviolet light source (wavelength range 350-450nm) is used to continuously excite the stress luminescent film for 2 minutes to make its luminescence reach saturation; then, it is left to stand for 3 minutes under no load to reduce the influence of stress-free photoluminescence decay on stress luminescence intensity.

[0014] In order to solve the above technical problems, the present invention adopts a further technical solution as follows: In step (2): during the tensile testing machine, the CCD camera collects the luminescence intensity of the stress luminescent film at a speed of 5fps, the optical axis of the CCD camera is perpendicular to the stress luminescent film, and a fixed distance of 25cm is maintained between the lens and the surface of the stress luminescent film.

[0015] The advantages of this invention are: 1) This invention enables stress luminescence detection and DIC strain measurement to have good compatibility in data acquisition and processing, making the method of this invention applicable to the quantitative analysis of the mechanical response characteristics of various stress luminescence material systems.

[0016] 2) This invention realizes the direct conversion from stress-luminescent light intensity field to physical strain field while preserving the spatial resolution of the original image, providing a feasible path for stress-luminescent strain perception to move from qualitative observation to quantitative measurement. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the measurement system in this invention.

[0018] Figure 2 This is a comparison of the front stress luminescence cloud map and the back DIC effective strain cloud map of the stress luminescence thin film metal specimen in this invention.

[0019] Figure 2 (a) Stress-luminescence image of the specimen when unloaded; (b) Stress-luminescence image of the specimen under load from the front. (c) Effective strain cloud diagram of DIC on the back side of the specimen under load.

[0020] Figure 3 This is a graph showing the linear calibration relationship between stress luminescence intensity and effective strain of DIC in this invention.

[0021] Figure 4 A comparison diagram of stress luminescence, DIC, and finite element method in this invention. Detailed Implementation

[0022] The specific content of the present invention will now be described in conjunction with the accompanying drawings and specific embodiments.

[0023] Example: A quantitative full-field strain measurement method based on DIC-assisted stress luminescence includes the following steps: (1) Preparation of stress-luminescent thin film metal specimens: Weigh out stress-luminescent powder SrAl2O4:Eu at a mass ratio of 1:1. 2+ Dy 3+(SAOED) and epoxy resin are thoroughly mixed to form a homogeneous solution. Curing agent is added at a mass ratio of 5:1, and the mixture is stirred at 500 rpm for 15 minutes using a magnetic stirrer to ensure that each component is evenly dispersed in the solution. The homogeneous composite solution is then slowly poured into a polytetrafluoroethylene mold, and excess solution is gently scraped off along the edge of the mold with a scraper to ensure uniform film thickness. Finally, the polytetrafluoroethylene mold is placed in an oven and cured at 80°C for 1 hour to form a stress-luminescent film with a thickness of 0.4 mm. To ensure good adhesion between the stress-luminescent film and the metal specimen surface, the specimen surface needs to be pretreated. First, the specimen surface is sanded with sandpaper, then thoroughly cleaned with alcohol and acetone to remove any residual oil, dust, and other impurities. After cleaning and drying, the stress-luminescent film is adhered to the metal specimen surface using transparent epoxy adhesive and cured at room temperature for 12 hours. Random speckle patterns are then sprayed onto the back of the specimen, thus completing the preparation of the stress-luminescent film metal specimen. (2) Tensile testing and optical data acquisition are performed using a measurement system: like Figure 1 As shown, the structure of the measurement system includes: a tensile testing machine, a data processing device, a CCD camera, and a three-dimensional DIC strain testing system. The three-dimensional DIC strain testing system includes two DIC cameras on the left and right, a blue light source in the middle, and a tripod platform. The data processing device is connected to the CCD camera and the three-dimensional DIC strain testing system. The CCD camera is set on the front of the tensile testing machine, and the three-dimensional DIC strain testing system is set on the back of the tensile testing machine. A light shield is set in the middle of the tensile testing machine. The stress-luminescent thin film metal specimen obtained in step 1 is mounted on the tensile fixture of the tensile testing machine, ensuring that the stress-luminescent thin film metal specimen is axially aligned. The tensile testing machine is set to a constant loading rate of 6 mm / min. Before the test, the stress-luminescent thin film is continuously excited for 2 minutes using a 10W ultraviolet light source (wavelength range 350-450nm) to saturate its luminescence. Then, it is left to stand for 3 minutes under no-load conditions to reduce the influence of stress-free photoluminescence decay on the stress luminescence intensity. A stress-luminescent thin film is pasted on the front of the metal specimen for stress-luminescence detection, and a random speckle pattern is sprayed on the back of the specimen for DIC strain measurement. A light shield is set around the tensile testing machine to completely isolate ambient light and ensure the accuracy of data acquisition. During the tensile testing process, the CCD camera acquires the luminescence intensity of the stress-luminescent film at a speed of 5fps. The optical axis of the CCD camera is perpendicular to the stress-luminescent film, and a fixed distance of 25cm is maintained between the lens and the surface of the stress-luminescent film. At the same time, the three-dimensional DIC system monitors the full-field strain distribution on the surface of the stress-luminescent film metal specimen in real time at the same sampling frequency to ensure the temporal consistency between the stress luminescence signal and the strain data. (3) Data extraction and image processing: A CCD camera was used to acquire stress luminescence images, and a DIC camera was used to acquire DIC speckle images. Because the stress luminescence images and DIC speckle images rely on different imaging systems (a CCD camera was used for stress luminescence image acquisition, while a DIC camera was used for DIC speckle images), their image coordinate systems are inconsistent, making direct spatial registration impossible. It is necessary to ensure that the selected data points are located on the same physical reference line to guarantee correspondence and accuracy. Therefore, physical scale calibration is introduced into the stress luminescence images and DIC speckle images to transform their respective image coordinates to the physical space coordinate system of the specimen, thereby achieving cross-system data correspondence matching and joint analysis. To quantitatively characterize the evolution of stress-luminescence response during tensile testing, an image processing program based on the Python platform was developed to extract light intensity data of the stress-luminescence film on the front side of the specimen at different loading times. This image processing program mainly achieves its purpose through the following three core processing steps: 1) Calculation of average background light intensity: Since the stress-emitting film exhibits a certain degree of self-emission in the unloaded state, the background light intensity needs to be corrected to ensure data accuracy. The program first extracts the grayscale image of the specified region of interest (ROI) from the initial frame image and calculates the average grayscale value within that region as the average background light intensity. ( x , y ), used for background removal in subsequent images; 2) Background subtraction: For each frame of the image, extract its grayscale data within the same ROI range. I raw ( x , y And perform background removal according to the following formula:

[0024] To obtain image grayscale data containing only the stress-induced luminescence enhancement portion. I * ( x , y That is, the image grayscale data after removing the stress-luminescent background light intensity grayscale matrix. x and yRepresents the coordinates of image pixels; max represents the maximum value operator. 3) Visualization processing: The grayscale data of each frame after removing the background light intensity is visualized in the form of a pseudo-color image, which facilitates the analysis of the stress luminescence intensity distribution and its variation with load evolution. 4) The effective strain distribution within the same ROI on the back of the specimen is directly calculated using the 3D DIC strain testing system software. This information is used as a reference for the stress luminescence image data and is subsequently used to establish and analyze the stress luminescence intensity-effective strain mapping relationship. (4) Establish the quantitative calibration relationship between stress emission intensity and effective strain of DIC: like Figure 2 As shown, Figure 2 This is a comparison of the front stress luminescence cloud map and the back DIC effective strain cloud map of the stress luminescence thin film metal specimen in this invention; Figure 2 (a) Stress-luminescence image of the specimen when unloaded; (b) Stress-luminescence image of the specimen under load from the front; (c) Effective strain cloud map of the DIC on the back of the specimen under load. Stress-induced emission intensity and effective strain data of DIC were extracted from the upper two-thirds of the region along the vertical centerline of the specimen (corresponding to the longitudinal range of the ROI region, with a height of 60 mm), and linear regression analysis was performed to obtain the quantitative calibration relationship between stress-induced emission intensity and effective strain of DIC. , x Represents light intensity data. y Representing strain data, such as Figure 3 As shown, quantitative full-field strain measurement based on DIC-assisted stress luminescence can be realized.

[0025] To verify the applicability of the linear calibration relationship of the present invention under different stress states, the present invention designed a metal specimen with an artificial notch (7 mm × 2 mm) for axial tensile testing. Similarly, a stress luminescent film was pasted on the front of the notched specimen, and a random speckle pattern was sprayed on the back.

[0026] like Figure 4 As shown, Figure 4 The system displays various types of image data obtained in the experiment; Figure 4 a is a reference image of the front stress-luminescent thin film of the specimen before and after optical excitation; Figure 4 b is the luminescence intensity cloud map of the front stress of the notched specimen corresponding to the tensile elastic stage; according to Figure 4 The light intensity data of each pixel in the ROI region of b is used with a linear calibration relationship. The calculated strain values ​​for each pixel are used to create a quantitative strain visualization cloud map of the specimen, as shown below. Figure 4 As shown in c.

[0027] As a comparative verification, an image of the back side of the notched specimen with sprayed speckles was obtained to acquire a DIC reference image (e.g., Figure 4 As shown in d), the effective strain distribution diagram was calculated using DIC software (as shown in d). Figure 4 As shown in e), the theoretical strain distribution map of the surface near the notch is obtained through finite element analysis (FEA) (e.g. Figure 4 (as shown in f).

[0028] from Figure 4 (c) Figure 4 (e) Figure 4 It is not difficult to see in (f) that after substituting the light intensity data of the stress emission cloud map into the linear calibration relationship, the effective strain distribution reconstructed by the stress emission image is in high agreement with the effective strain field measured by DIC and the effective strain field simulated by finite element method. In particular, it still maintains good morphological consistency in high strain concentration areas such as crack tip, which fully verifies that the calibration relationship can still maintain high quantitative measurement accuracy in local high strain areas.

[0029] This invention enables good compatibility between stress luminescence detection and DIC strain measurement in terms of data acquisition and processing, allowing the method to be extended to the quantitative analysis of the mechanical response characteristics of various stress luminescence material systems.

[0030] The above embodiments describe 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 only illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from the spirit and scope of the invention, and all such changes and modifications should fall within the scope of the present invention as claimed.

Claims

1. A quantitative full-field strain measurement method based on DIC-assisted stress luminescence, characterized in that: Includes the following steps: (1) Preparation of stress-luminescent thin film metal specimens: Weigh an appropriate amount of stress-luminescent powder SrAl2O4:Eu 2+ Dy 3+ (SAOED) and epoxy resin are thoroughly mixed to form a uniform solution. Then, a curing agent is added and stirred to ensure that each component is evenly dispersed in the solution. The uniformly stirred composite solution is then slowly poured into a polytetrafluoroethylene mold, and excess solution is gently scraped off along the edge of the mold with a scraper to make the film thickness uniform. Finally, the polytetrafluoroethylene mold is placed in an oven to form a stress-luminescent film of a certain thickness. The surface of the specimen is pretreated by first sanding it with sandpaper, then thoroughly cleaning it with alcohol and acetone to remove any residual oil, dust and other impurities. After cleaning, the specimen is dried, and the stress luminescent film is adhered to the surface of the metal specimen with transparent epoxy adhesive and cured at room temperature for a certain period of time. Random speckle patterns are then sprayed on the back of the specimen to complete the preparation of the stress luminescent film metal specimen. (2) Tensile testing and optical data acquisition are performed using a measurement system: The measurement system comprises a tensile testing machine, a data processing device, a CCD camera, and a three-dimensional DIC strain testing system. The three-dimensional DIC strain testing system includes two DIC cameras (left and right), a central blue light source, and a tripod platform. The data processing device is connected to the CCD cameras and the three-dimensional DIC strain testing system. The CCD cameras are positioned on the front of the tensile testing machine, and the three-dimensional DIC strain testing system is positioned on the back of the tensile testing machine. A light-shielding plate is placed in the middle of the tensile testing machine to prevent the blue light from the three-dimensional DIC strain testing system from affecting the stress emission acquisition. The stress-luminescent thin film metal specimen obtained in step 1 is mounted on the tensile fixture of the tensile testing machine, ensuring that the stress-luminescent thin film metal specimen is axially aligned; before the test, the stress-luminescent thin film is continuously excited by an ultraviolet light source until its luminescence reaches saturation; then it is left to stand under no load to reduce the influence of stress-free photoluminescence attenuation on the stress luminescence intensity. A stress-luminescent thin film is pasted on the front of the metal specimen for stress-luminescence detection, and a random speckle pattern is sprayed on the back of the specimen for DIC strain measurement. A light shield is set around the tensile testing machine to completely isolate ambient light and ensure the accuracy of data acquisition. During the tensile testing process, the CCD camera collects the luminescence intensity of the stress-luminescent film. The optical axis of the CCD camera is perpendicular to the stress-luminescent film, and a certain distance is maintained between the lens and the surface of the stress-luminescent film. At the same time, the three-dimensional DIC system monitors the full-field strain distribution on the surface of the stress-luminescent film metal specimen in real time at the same sampling frequency to ensure the temporal consistency between the stress luminescence signal and the strain data. (3) Data extraction and image processing: A CCD camera is used to acquire stress luminescence images, and a DIC camera is used to acquire DIC speckle images. Physical scale calibration is introduced into the stress luminescence images and DIC images, and the image coordinates of the two are transformed to the physical space coordinate system of the specimen, thereby realizing the correspondence matching and joint analysis of cross-system data. To quantitatively characterize the evolution of stress-luminescence response during tensile testing, an image processing program based on the Python platform was developed to extract light intensity data of the stress-luminescence film on the front side of the specimen at different loading times. This image processing program mainly achieves its purpose through the following three core processing steps: 1) Calculation of average background light intensity: Since the stress-emitting film exhibits a certain degree of self-emission in the unloaded state, the background light intensity needs to be corrected to ensure data accuracy. The program first extracts the grayscale image of the specified region of interest (ROI) from the initial frame image and calculates the average grayscale value within that region as the average background light intensity. ( x , y ), used for background removal in subsequent images; 2) Background subtraction: For each frame of the image, extract its grayscale data within the same ROI range. I raw ( x , y And perform background removal according to the following formula: To obtain image grayscale data containing only the stress-induced luminescence enhancement portion. I * ( x , y That is, the image grayscale data after removing the stress-luminescent background light intensity grayscale matrix. x and y Represents the coordinates of image pixels; max represents the maximum value operator. 3) Visualization processing: The grayscale data of each frame after removing the background light intensity is visualized in the form of a pseudo-color image, which facilitates the analysis of the stress luminescence intensity distribution and its variation with load evolution. 4) The effective strain distribution within the same ROI on the back of the specimen is directly calculated using the 3D DIC strain testing system software. This information is used as a reference for the stress luminescence image data and is subsequently used to establish and analyze the stress luminescence intensity-effective strain mapping relationship. (4) Establish the quantitative calibration relationship between stress emission intensity and effective strain of DIC: Stress emission intensity and effective strain data of DIC were extracted from the upper two-thirds of the region along the vertical centerline of the specimen (corresponding to the longitudinal range of the ROI region, with a height of 60 mm), and linear regression analysis was performed to obtain the quantitative calibration relationship between stress emission intensity and effective strain of DIC. , x Represents light intensity data. y By representing strain data, quantitative full-field strain measurement based on DIC-assisted stress luminescence can be achieved.

2. The quantitative full-field strain measurement method based on DIC-assisted stress luminescence according to claim 1, characterized in that: In step (1): the stress luminescent powder SrAl2O4:Eu is weighed at a mass ratio of 5:1-1:

1. 2+ Dy 3+ (SAOED) and epoxy resin.

3. The quantitative full-field strain measurement method based on DIC-assisted stress luminescence according to claim 1, characterized in that: In step (1): the curing agent is added at a mass ratio of 5:1, and a magnetic stirrer is used to stir at a speed of 500 rpm for 15 minutes to ensure that each component is evenly dispersed in the solution.

4. A quantitative full-field strain measurement method based on DIC-assisted stress luminescence according to claim 1, characterized in that: In step (1): the polytetrafluoroethylene mold is placed in an oven and cured at 80°C for 1 hour to form a stress-luminescent film with a thickness of 0.4 mm.

5. A quantitative full-field strain measurement method based on DIC-assisted stress luminescence according to claim 1, characterized in that: In step (1): a stress-luminescent film is attached to the surface of the specimen using transparent epoxy adhesive and cured at room temperature for 12 hours.

6. A quantitative full-field strain measurement method based on DIC-assisted stress luminescence according to claim 1, characterized in that: In step (2): the tensile testing machine is set to a constant loading rate of 6 mm / min.

7. A quantitative full-field strain measurement method based on DIC-assisted stress luminescence according to claim 1, characterized in that: In step (2): before the test, a 10W ultraviolet light source (wavelength range 350-450nm) was used to continuously excite the stress luminescent film for 2 minutes to make its luminescence saturate; then it was left to stand for 3 minutes under no load to reduce the influence of stress-free photoluminescence decay on stress luminescence intensity.

8. A quantitative full-field strain measurement method based on DIC-assisted stress luminescence according to claim 1, characterized in that: In step (2): during the tensile testing process, the CCD camera collects the luminescence intensity of the stress luminescent film at a speed of 5fps. The optical axis of the CCD camera is perpendicular to the stress luminescent film, and a fixed distance of 25cm is maintained between the lens and the surface of the stress luminescent film.

Images