A strip specimen plane strain testing device and method for determining failure mode

Abstract

The application discloses a strip filling body damage mode plane strain testing device and method. The testing device comprises a container (10), a containing cavity (101) with an open end, and at least one end face of the container (10) is a transparent face; a test piece (20) provided with a speckle on the surface and arranged in the containing cavity (101); a loader (30) comprising a pressing column (31) and arranged at the open end of the container (10) and configured to apply a load to the test piece (20); and a digital speckle device (40) comprising a high-definition camera (41) arranged at the transparent face of the container (10) and configured to acquire deformation image information of the test piece (20), analyze and calculate the image information to obtain stress and strain values of the test piece (20), and combine the stress and strain values with the image to analyze and obtain a damage mode of the test piece (20).

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering backfilling technology, and in particular to a plane strain testing device and method for the failure mode of strip backfill bodies. Background Technology

[0002] Backfilling mining technology is a core technology for controlling surface subsidence and improving resource recovery rates. Especially under conditions of "three-under" mining (preventing surface subsidence), traditional methods are ineffective, while backfilling technology offers a possibility for releasing these valuable resources. Through long-term practice, those skilled in the art have found that for certain types of ore bodies or in areas with severe ground pressure, traditional full-area backfilling methods have significant drawbacks, such as high economic costs and unsatisfactory material consumption. Therefore, strip backfilling technology has emerged. Its basic idea is to construct strip-shaped cemented backfill bodies at intervals within the goaf, while the areas between the strips are filled with non-cemented backfill or left empty.

[0003] However, the strip backfilling technology currently used in mines still faces several unresolved technical challenges: First, the stability of the strips and the overall synergistic mechanism are unclear. Existing technologies treat the strips as isolated supports, neglecting the interactions between the strips and the surrounding rock, and between the strips and the roof and floor. For example, the constraint effect of the roof and floor on the strips is not fully recognized and utilized, making it impossible to fully leverage the material's performance through optimized structural design. Second, the strength design theory is incomplete. Currently, backfill mix design largely relies on empirical formulas and numerous experiments, lacking precise theoretical models and scientific basis based on the correlation between the microstructure and macroscopic mechanical properties of the backfill. This directly leads to either overly conservative strip designs, resulting in economic and resource waste. Third, the stress-strain relationship and failure mode criteria of the backfill under complex mining stress paths have not been accurately revealed. The interaction mechanism between the backfill and the surrounding rock, especially the instability criterion for the "artificial pillar" of the backfill, remains a "gray box." The lack of clarity regarding failure modes prevents us from performing precise limit state design, forcing us to rely on increasing the safety factor to ensure safety. This is a fundamental scientific challenge faced by all filling technologies. Therefore, there is an urgent need for a plane strain testing device and method for strip-filled bodies that can simulate plane strain conditions and monitor specimens using digital speckle technology. Summary of the Invention

[0004] This solution addresses the problems and needs raised above by proposing a plane strain testing device and method for the failure mode of strip-filled bodies. Due to the adoption of the following technical features, it can achieve the above-mentioned technical objectives and bring about several other technical effects.

[0005] One object of the present invention is to provide a plane strain testing device for the failure mode of strip-filled bodies, comprising: A container having an open end accommodating cavity, and at least one end face of the container being a transparent surface; The specimen has speckled markings on its surface and is located within the accommodating cavity; A loader, including a pressure column, is disposed at the open end of the container and configured to apply a load to the specimen; A digital speckle analyzer includes: a high-definition camera disposed on the transparent surface of the container, configured to acquire deformation image information of the specimen, analyze and calculate the stress and strain values ​​of the specimen based on the image information, and analyze the failure mode of the specimen based on the stress and strain values ​​combined with the image.

[0006] Furthermore, the plane strain testing device for the failure mode of strip-filled bodies according to the present invention may also have the following technical features: In one example of the invention, the accommodator includes: The base has a rough upper surface. The plate assembly is arranged sequentially along the circumferential direction of the base to form a receiving cavity with an open end, wherein the test piece is placed in the receiving cavity and the loader is placed at the open end.

[0007] In one example of the present invention, the plate assembly includes: Two parallel front panels and a back panel, and side panels located on both sides of the front and back panels; wherein the front, back, and side panels are connected by fasteners. The panel, side panel, and back panel are provided with a plurality of first positioning holes, second positioning holes, and third positioning holes in sequence, and the fasteners are provided through the first positioning holes, second positioning holes, and third positioning holes in sequence; wherein, the panel is a transparent part.

[0008] In one example of the present invention, the pressure column further includes a pressure plate connected to the lower end of the pressure column, configured to contact the specimen, and having a rough lower surface.

[0009] Another objective of this invention is to provide a speckle method for a plane strain testing device for the failure mode of strip-filled bodies as described above, comprising the following steps: S10: Apply black and white matte paint to the surface of the specimen to create speckles, and place it into the receiving cavity; S20: A high-definition digital camera is mounted on the front of the equipment. A lubricant made of a mixture of Teflon and silicone grease is applied to the glass panel and back plate on the side that contacts the specimen to eliminate friction, so as to meet the condition of no friction in the cross section corresponding to the mechanical model of plane strain. S30: The loader loads the specimen. After the specimen is damaged, the loader is removed and the plate assembly is disassembled. The specimen is taken out and all data are exported. S40: Extract the grayscale values ​​of the corresponding coordinates in all images, then calculate the relevant values ​​to obtain the coordinates of each point in the deformed image corresponding to the image before deformation, further calculate the displacement, and then perform differential operation on the displacement to obtain the strain data of the specimen. After obtaining the strain value, substitute it into the corresponding constitutive model to obtain the stress value. Thus, the stress and strain values ​​of the specimen are obtained. Combine them with the images for analysis and summary to obtain the failure mode of the specimen.

[0010] In one example of the present invention, in step S10, the process of spraying black and white matte paint onto the surface of the specimen to create speckles specifically includes the following steps: first, white matte paint is sprayed onto the surface of the specimen as a primer until it is completely covered and allowed to dry; then, black matte paint is sprayed onto the speckles and allowed to dry.

[0011] In one example of the present invention, in step S40, the grayscale values ​​of corresponding coordinates in all images are extracted, specifically including the following steps: When processing digital speckle images using the digital correlation method, a sub-region is first selected from the speckle image before deformation as a sample image, whose gray-level distribution is... Then, the target image is searched in the deformed speckle pattern, and its grayscale distribution is... ,in, It is an unknown quantity containing the displacement to be determined and its first and second derivatives. The position of maximum correlation is determined by using a correlation search algorithm.

[0012] In one example of the present invention, the calculation of the relevant value in step S40 specifically includes the following steps: The correlation between the sample image and the target image is calculated using the standardized covariance correlation function, where the specific expression of the standardized covariance correlation function is: In the formula, C is the correlation coefficient. and These represent the average grayscale values.

[0013] Using the variational method, the correlation coefficient C is expressed in a different form, with the unknown variable to be determined as the independent variable parameter. The specific expression is as follows: In the formula, S is the correlation factor, u is the displacement expression of the image in the x direction, and v is the unique expression of the image in the y direction.

[0014] In one example of the present invention, in step S40, the coordinates of each point in the deformed image corresponding to the image before deformation are obtained, and the displacement is further calculated, specifically including the following steps: First, the correlation factor S is a function of the displacement and strain we are looking for. The parameter that minimizes the value of S is the true displacement and strain of the sample. The horizontal and vertical displacements conform to the following polynomials: In the formula, and The coordinates of the sample in the image. and The displacement of the sample in the horizontal and vertical directions. The coefficients of the polynomial; Then, since the displacement values ​​obtained by searching for integer pixels are discrete, it is necessary to perform linear fitting on the displacement values ​​to obtain continuous displacement values ​​for the samples.

[0015] In one example of this invention, by differentiating the displacement, the specific expression for the strain data of the specimen is obtained as follows: In the formula, For the test specimen in Strain in direction, For the test specimen in Strain in the direction of movement; For point exist Displacement in the direction, For point exist Displacement in the direction; , These are the coordinates of the corresponding point.

[0016] Compared with the prior art, the present invention has the following beneficial effects: Clarify the failure modes of strip filling bodies: After conducting experiments and analyzing data through this device, the failure modes of strip filling bodies under different intensities can be summarized. This allows the determination of key design parameters (such as filling body ratio, exposed surface size, pillar spacing, etc.) to change from subjective judgment to objective calculation with theoretical support, fundamentally avoiding safety hazards caused by insufficient design.

[0017] The preferred embodiments of the invention will be described in more detail below with reference to the accompanying drawings, so as to facilitate an understanding of the features and advantages of the invention. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention will be briefly described below. The drawings are merely illustrative of some embodiments of the present invention and are not intended to limit the scope of the present invention to all embodiments.

[0019] Figure 1 This is a schematic diagram of the plane strain testing device for the failure mode of strip-filled bodies according to an embodiment of the present invention; Figure 2 This is a front view of the container according to an embodiment of the present invention; Figure 3 This is a side view of the container according to an embodiment of the present invention.

[0020] List of reference numerals in the attached diagram: Test device 100; Container 10; Base 11; Panel assembly 12; Panel 121; Back panel 122; Side panel 123; Limit plate 124; Fastener 125; Smooth surface 126; Receptacle 101; Specimen 20; Loader 30; Pressure column 31; Pressure plate 32; Rough surface 321; Digital speckle filter 40; High-definition camera 41. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The same reference numerals in the drawings represent the same components. It should be noted that the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0022] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains. The terms “first,” “second,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, “an” or “a” and similar terms do not necessarily indicate a quantity limitation. Terms such as “comprising” or “including” mean that the element or object preceding the word encompasses the element or object listed following the word and its equivalents, without excluding other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships; these relative positional relationships may change accordingly when the absolute position of the described object changes.

[0023] According to a second aspect of the present invention, a plane strain testing device 100 for the failure mode of a strip-filled body is provided, such as... Figures 1 to 3 As shown, it includes: The container 10 has an open end receiving cavity 101, and at least one end face of the container 10 is a transparent surface; The specimen 20 has speckled patterns on its surface and is located inside the accommodating cavity 101; The loader 30 includes a pressure column 31 disposed at the open end of the container 10 and configured to apply a load to the specimen 20; The digital speckle analyzer 40 includes a high-definition camera 41 disposed on the transparent surface of the container 10, configured to acquire deformation image information of the specimen 20, analyze and calculate the stress and strain values ​​of the specimen 20 based on the image information, and analyze the failure mode of the specimen 20 based on the stress and strain values ​​combined with the image.

[0024] The working principle of the device is as follows: black and white matte paint is sprayed onto the surface of the specimen 20 to create speckle patterns. A camera is set up on the front of the device. A lubricant made of a mixture of Teflon and silicone grease is applied to the sides of the glass panel 121 and the back plate 122 that are in contact with the specimen 20 to eliminate friction, so as to meet the condition of no friction in the cross section corresponding to the plane strain mechanical model. Then, the treated specimen 20 is correctly placed into the device, and the bolts and side limiting plates are firmly fixed to meet the condition of limiting the displacement in the corresponding direction in the plane strain mechanical model. After checking and ensuring that all parts are installed correctly and firmly, the pressure machine is used to apply load to the specimen 20. Personnel stay away during the experiment. After specimen 20 is damaged, the loader 30 is removed and the plate assembly 12 is disassembled. Specimen 20 is taken out, and various data are exported. The images in the camera are analyzed using software. The specific process is as follows: the gray values ​​of corresponding coordinates in all images are extracted, and then a series of calculations are performed on the relevant values ​​to obtain the coordinates of each point in the deformed image corresponding to the image before deformation. The displacement is further calculated, and then the displacement is differentiated to obtain the strain data of specimen 20. After obtaining the strain value, it is substituted into the corresponding constitutive model to obtain the stress value. Thus, the stress and strain values ​​of specimen 20 are obtained. They are combined with the images for analysis and summary to obtain the failure mode of specimen 20.

[0025] This device clarifies the failure modes of strip-filled bodies: by conducting experiments and analyzing data through this device, the failure modes of strip-filled bodies under different intensities can be summarized, making the determination of key design parameters (such as filler mix ratio, exposed surface size, pillar spacing, etc.) change from subjective judgment to objective calculation with theoretical support, fundamentally avoiding safety hazards caused by insufficient design.

[0026] This device improves strength design: it can test the design strength of the filling material to prevent the strength of the filling material from being too high or too low, ensuring that the strength, size and structural form of the filling material are perfectly matched with the actual load, maximizing performance utilization and reducing resource waste.

[0027] In one example of the present invention, the accommodator 10 includes: The base 11 has a rough surface on its upper surface; The plate assembly 12 is arranged sequentially along the circumferential direction of the base 11 to form a receiving cavity 101 with an open end, wherein the test piece 20 is disposed in the receiving cavity 101 and the loader 30 is disposed at the open end; In other words, the plate assembly 12 and the base 11 together form an open cavity 101, and the specimen 20 is placed into the cavity 101 from the open end. The loader 30 applies a load to the upper surface of the specimen 20 from the open end, and during the application of the load, the high-definition camera 41 acquires the deformation image information of the specimen 20 in the cavity 10.

[0028] In one example of the present invention, the plate assembly 12 includes: Two parallel front panels 121 and a back panel 122, and side panels 123 disposed on both sides of the front panels 121 and the back panel 122; wherein the front panels 121, the back panel 122, and the side panels 123 are connected by fasteners 125. The panel 121, side panel 123 and back panel 122 are provided with a plurality of first positioning holes, second positioning holes and third positioning holes in sequence, and the fastener 125 passes through the first positioning holes, second positioning holes and third positioning holes in sequence; wherein, the panel 121 is a transparent part; The plate assembly 12 can be reliably connected together by setting fastener 125, and the fastener 125 can facilitate the assembly and disassembly of the receiving cavity 101.

[0029] Preferably, a fastener 125 is provided near the open end, which can limit the open end between the panel 121 and the back panel 122. For example, a limit plate 124 is provided on the fastener 125, which can improve the reliability of the connection of the panel assembly 12.

[0030] In one example of the present invention, the pressure column 31 further includes a pressure plate 32, which is connected to the lower end of the pressure column 31, configured to contact the specimen 20, and its lower surface is rough. By setting the pressure plate 32, the contact area of ​​the pressure column 31 can be increased, thereby improving the stability and uniformity of applying external force to the specimen 20.

[0031] In one example of the present invention, the back plate 122 is a solid metal plate, the surface in contact with the specimen 20 is a smooth surface 126, and there are feet at the left and right ends of the bottom, so that it can be placed on the base 11. In one example of the present invention, the base 11 is a solid metal cuboid with grooves for placing the glass panel 121 and the back plate 122, and the upper surface is roughened. In one example of the present invention, the main body of the pressure column 31 is an I-shaped metal structure with a rough surface 321 on the lower surface.

[0032] Another objective of this invention is to provide a speckle method for the plane strain testing device 100 for the failure mode of the strip-filled body described above, comprising the following steps: S10: Apply black and white matte paint to the surface of specimen 20 to create speckles, and place it into the receiving cavity 101; S20: A high-definition digital camera is mounted on the front of the equipment. A lubricant made of a mixture of Teflon and silicone grease is applied to the glass panel 121 and the back plate 122 on the side that contacts the specimen 20 to eliminate friction, so as to meet the condition of no friction in the cross section corresponding to the plane strain mechanical model. Then, the treated specimen 20 is correctly placed into the equipment, and the bolts and side limiting plates are firmly fixed to meet the condition of limiting the displacement in the corresponding direction in the plane strain mechanical model. After checking and ensuring that all parts are installed correctly and firmly, the pressure machine is used to apply load to the specimen 20. Personnel should stay away during the experiment. S30: Loader 30 loads specimen 20. After specimen 20 is damaged, loader 30 is removed and plate assembly 12 is disassembled. Specimen 20 is taken out and all data are exported. S40: The software is used to analyze the images in the camera. The specific process is as follows: extract the gray values ​​of the corresponding coordinates in all images, and then perform a series of calculations on the relevant values ​​to obtain the coordinates of each point in the deformed image corresponding to the image before deformation. The displacement is further calculated, and then the displacement is differentiated to obtain the strain data of specimen 20. After obtaining the strain value, it is substituted into the corresponding constitutive model to obtain the stress value. Thus, the stress and strain values ​​of specimen 20 are obtained. Combined with the images for analysis and summary, the failure mode of specimen 20 is obtained.

[0033] This method clarifies the failure modes of strip-filled bodies: After conducting experiments and analyzing the data through this device, the failure modes of strip-filled bodies under different intensities can be summarized, so that the determination of key design parameters (such as filler ratio, exposed surface size, pillar spacing, etc.) changes from subjective judgment to objective calculation with theoretical support, fundamentally avoiding safety hazards caused by insufficient design.

[0034] This method improves strength design: the device can test the design strength of the filling material to prevent the strength of the filling material from being too high or too low, ensuring that the strength, size and structural form of the filling material are perfectly matched with the actual load, maximizing performance utilization and reducing resource waste.

[0035] In one example of the present invention, in step S10, the process of spraying black and white matte paint onto the surface of the specimen 20 to create speckles specifically includes the following steps: first, spraying white matte paint as a primer onto the surface of the specimen 20 until it is completely covered and allowing it to dry; then, spraying black matte paint onto the speckles and allowing it to dry; wherein, the speckle size is preferably 3-5 pixel units.

[0036] In one example of the present invention, in step S40, the grayscale values ​​of corresponding coordinates in all images are extracted, specifically including the following steps: When processing digital speckle images using the digital correlation method, a sub-region is first selected from the speckle image before deformation as a sample image, whose gray-level distribution is... Then, the target image is searched in the deformed speckle pattern, and its grayscale distribution is... ,in, It is an unknown quantity containing the displacement to be determined and its first and second derivatives. The position of maximum correlation is determined by using a correlation search algorithm.

[0037] In one example of the present invention, the calculation of the relevant value in step S40 specifically includes the following steps: The correlation between the sample image and the target image is calculated using the standardized covariance correlation function. The correlation coefficient is a mathematical indicator reflecting the degree of similarity between two images. The specific expression of the standardized covariance correlation function is as follows: In the formula, C is the correlation coefficient. and These represent the average grayscale values.

[0038] The formula normalizes the covariance correlation function using the mean square error of the two correlation functions, and the value of C ranges from 1 to 10. The value is 1 when the two functions are exactly the same; 0 when they are completely different; and -1 when they are completely opposite. A value of 1 indicates that the images have the highest correlation.

[0039] Using the variational method, the correlation coefficient C is expressed in a different form, with the unknown variable to be determined as the independent variable parameter. The specific expression is as follows: In the formula, S is the correlation factor, u is the expression for the image displacement in the x-direction, and v is the unique expression for the image in the y-direction. Here, S=0 indicates correlation, and S=1 indicates no correlation.

[0040] In one example of the present invention, in step S40, the coordinates of each point in the deformed image corresponding to the image before deformation are obtained, and the displacement is further calculated, specifically including the following steps: First, the correlation factor S is a function of the displacement and strain we are looking for. The parameter that minimizes the value of S is the true displacement and strain of the sample. The horizontal and vertical displacements conform to the following polynomials: In the formula, and The coordinates of the sample in the image. and The displacement of the sample in the horizontal and vertical directions. The coefficients of the polynomial; Then, since the displacement values ​​obtained by searching for integer pixels are discrete, it is necessary to perform linear fitting on the displacement values ​​to obtain continuous displacement values ​​for the samples.

[0041] In one example of the present invention, by differentiating the displacement, the specific expression for the strain data of specimen 20 is obtained as follows: In the formula, For the test specimen in Strain in direction, For the test specimen in Strain in the direction of movement; For point exist Displacement in the direction, For point exist Displacement in the direction; , These are the coordinates of the corresponding point.

[0042] The foregoing description, with reference to preferred embodiments, details exemplary implementations of the plane strain testing device 100 and method for the failure mode of strip-filled bodies proposed in this invention. However, those skilled in the art will understand that various modifications and alterations can be made to the above specific embodiments without departing from the concept of this invention, and various combinations can be made to the various technical features and structures proposed in this invention without exceeding the protection scope of this invention, which is determined by the appended claims.

Claims

1. A plane strain testing device for the failure mode of strip-filled bodies, characterized in that, include: The container (10) has an open end accommodating cavity (101), and at least one end face of the container (10) is a transparent surface; The specimen (20) has speckled patterns on its surface and is located inside the accommodating cavity (101); The loader (30) includes a pressure column (31) located at the open end of the container (10) and configured to apply a load to the specimen (20); The digital speckle generator (40) includes: a high-definition camera (41) disposed on the transparent surface of the container (10), configured to acquire deformation image information of the specimen (20), and to analyze and calculate the stress and strain values ​​of the specimen (20) based on the image information, and to analyze and obtain the failure mode of the specimen (20) based on the stress and strain values ​​combined with the image.

2. The plane strain testing device for the failure mode of strip-filled bodies according to claim 1, characterized in that, The container (10) includes: The base (11) has a rough surface on its upper surface; The plate assembly (12) is arranged in sequence along the circumferential direction of the base (11) to form a receiving cavity (101) with an open end, wherein the test piece (20) is disposed in the receiving cavity (101) and the loader (30) is disposed at the open end.

3. The plane strain testing device for the failure mode of strip-filled bodies according to claim 2, characterized in that, The plate assembly (12) includes: Two parallel panels (121) and a back panel (122), and side panels (123) located on both sides of the panels (121) and the back panel (122); wherein the panels (121), the back panel (122), and the side panels (123) are connected by fasteners (125): The panel (121), side panel (123) and back panel (122) are provided with a plurality of first positioning holes, second positioning holes and third positioning holes in sequence, and the fastener (125) passes through the first positioning holes, second positioning holes and third positioning holes in sequence; wherein, the panel (121) is a transparent part.

4. The plane strain testing device for the failure mode of strip-filled bodies according to claim 1, characterized in that, The pressure column (31) also includes a pressure plate (32), which is connected to the lower end of the pressure column (31), configured to contact the specimen (20), and its lower surface is rough.

5. A test method for a plane strain testing device for failure modes of strip-filled bodies as described in claims 1 to 4, characterized in that, Includes the following steps: S10: Apply black and white matte paint to the surface of the specimen (20) to create speckles, and place it into the receiving cavity (101); S20: A high-definition digital camera is mounted on the front of the equipment. A lubricant made of a mixture of Teflon and silicone grease is applied to the glass panel (121) and the back plate (122) on the side that contacts the specimen (20) to eliminate friction, so as to meet the condition of no friction in the cross section corresponding to the mechanical model of plane strain. S30: The loader (30) loads the specimen (20). After the specimen (20) is destroyed, the loader (30) is removed and the plate assembly (12) is disassembled. The specimen (20) is taken out and the data is exported. S40: Extract the gray values ​​of the corresponding coordinates in all images, and then calculate the relevant values ​​to obtain the coordinates of each point in the deformed image corresponding to the image before deformation. Further calculate the displacement, and then perform differential operation on the displacement to obtain the strain data of the specimen (20). After obtaining the strain value, substitute it into the corresponding constitutive model to obtain the stress value. Thus, the stress and strain values ​​of the specimen (20) are obtained. Combine them with the image for analysis and summary to obtain the failure mode of the specimen (20).

6. The test method of the plane strain testing device for the failure mode of strip-filled bodies according to claim 5, characterized in that, In step S10, the process of creating speckles by spraying black and white matte paint on the surface of the specimen (20) includes the following steps: first, use white matte paint as a primer to spray on the surface of the specimen (20) until it is completely covered and let it dry; then, use black matte paint to spray the speckles and let it dry.

7. The test method of the plane strain testing device for the failure mode of strip-filled bodies according to claim 5, characterized in that, In step S40, the grayscale values ​​of corresponding coordinates in all images are extracted, specifically including the following steps: When processing digital speckle images using the digital correlation method, a sub-region is first selected from the speckle image before deformation as a sample image, whose gray-level distribution is... Then, the target image is searched in the deformed speckle pattern, and its grayscale distribution is... ,in, It is an unknown quantity containing the displacement to be determined and its first and second derivatives. The position of maximum correlation is determined by using a correlation search algorithm.

8. The test method of the plane strain testing device for the failure mode of strip-filled bodies according to claim 5, characterized in that, In step S40, the relevant values ​​are calculated, specifically including the following steps: The correlation between the sample image and the target image is calculated using the standardized covariance correlation function, where the specific expression of the standardized covariance correlation function is: In the formula, C is the correlation coefficient. and These are the average grayscale values; Using the variational method, the correlation coefficient C is expressed in a different form, with the unknown variable to be determined as the independent variable parameter. The specific expression is as follows: In the formula, S is the correlation factor, u is the displacement expression of the image in the x direction, and v is the unique expression of the image in the y direction.

9. The test method of the plane strain testing device for the failure mode of strip-filled bodies according to claim 8, characterized in that, In step S40, the coordinates of each point in the deformed image corresponding to the original image are obtained, and the displacement is further calculated. Specifically, this includes the following steps: First, the correlation factor S is a function of the displacement and strain we are looking for. The parameter that minimizes the value of S is the true displacement and strain of the sample. The horizontal and vertical displacements conform to the following polynomials: In the formula, and The coordinates of the sample in the image. and The displacement of the sample in the horizontal and vertical directions. The coefficients of the polynomial; Then, since the displacement values ​​obtained by searching for integer pixels are discrete, it is necessary to perform linear fitting on the displacement values ​​to obtain continuous displacement values ​​for the samples.

10. The test method of the plane strain testing device for the failure mode of strip-filled bodies according to claim 5, characterized in that, By differentiating the displacement, the specific expression for the strain data of specimen (20) is obtained as follows: In the formula, For the test specimen in Strain in direction, For the test specimen in Strain in the direction of movement; For point exist Displacement in the direction, For point exist Displacement in the direction; , These are the coordinates of the corresponding point.

Images