Method and device for measuring crack propagation of notched sample in situ by direct-current potentiometry

Abstract

The invention provides a method and a device for in-situ measurement of crack propagation of a notched sample by a direct-current potentiometry, and belongs to the technical field of crack propagation detection. The method comprises the following steps: providing a measurement sample; setting a detection position on the measurement sample, and measuring the detection position; providing a measurement analysis formula; and combining the measurement data of the detection position with the measurement analytic expression to measure the crack length of the measurement sample. According to the method and the device applying the method, rapid detection of the crack length of the notch sample can be realized, and the accuracy of crack length detection can be improved.

Description

Technical Field

[0001] This disclosure relates to the field of crack propagation detection technology, and more specifically, to a method and apparatus for in-situ measurement of crack propagation in notched specimens using the DC potential method. Background Technology

[0002] High-temperature alloys are widely used in key hot-end components such as aero engines and gas turbines due to their excellent high-temperature strength, oxidation resistance and creep resistance. However, under high-temperature cyclic loading, cracks are prone to initiation and propagation inside the material, leading to fatigue failure. Therefore, closely monitoring crack propagation at stress concentration points is crucial to ensuring the safety and reliability of hot-end components.

[0003] In related technologies, methods such as optical microscopy and replica methods are used to monitor crack length. However, these conventional methods are difficult to implement in high-temperature, oxidizing, or vibrating environments, rely on manual operation, and are prone to subjective errors. Further research has shown that some related technologies use the DC potential method to monitor crack length in standard samples. Due to its excellent crack sensitivity, crack monitoring stability, and low labor costs, the DC potential method can effectively achieve online crack monitoring, making it the most efficient crack monitoring method currently available. However, the DC potential method also has some drawbacks. For example, the potential signal is weak at the crack initiation stage in notched samples, and the DC potential method system is susceptible to interference from temperature drift and changes in contact resistance, leading to insufficient measurement accuracy. Furthermore, notched samples come in various forms, and crack monitoring of notches with different geometric sizes presents numerous inconveniences.

[0004] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this disclosure is to overcome the shortcomings of the prior art and provide a method and apparatus for in-situ measurement of crack propagation in notched specimens using the DC potentiometric method. This facilitates crack monitoring of notched specimens of different specifications and also improves the accuracy of crack detection on hot-end components.

[0006] According to one aspect of this disclosure, a method for in-situ measurement of crack propagation in a notched specimen using a DC potentiometric method is provided, the method comprising: Provide measurement samples; A detection position is set on the measurement sample, and the detection position is measured. Provide measurement analytical expressions; The measurement data at the detection location is combined with the measurement analytical formula to determine the crack length of the measured sample.

[0007] According to one embodiment of this disclosure, the measurement analytical formula includes: Prepare the notched specimen; A detection position is set on the notched sample; First data is generated by detecting a first parameter of the detection location, second data is generated by detecting a second parameter of the detection location, and third data is generated by detecting a third parameter of the detection location. The optimal detection point is obtained by combining the first data, the second data, and the third data. The potential difference at the optimal detection point was measured; The potential difference at the optimal detection point is combined with the first analytical expression to obtain the second analytical expression, and the second analytical expression is optimized to form the measurement analytical expression, until the measurement analytical expression can solve for the crack length of the notched sample.

[0008] According to one embodiment of this disclosure, when a detection position is set on the notched sample and the detection position is measured, The detection location includes a group of detection points symmetrically arranged along the width direction of the center position of the notched sample. The group of detection points includes voltage detection points and current loading points arranged sequentially along the length direction of the notched sample.

[0009] According to one embodiment of this disclosure, the detection point group further includes a reference potential difference detection point; The reference potential difference detection point is located between the voltage detection point and the current loading point.

[0010] According to one embodiment of this disclosure, when detecting a first parameter of the detection location to form first data, detecting a second parameter of the detection location to form second data, and detecting a third parameter of the detection location to form third data, and combining the first data, the second data, and the third data to obtain the optimal detection point, The first parameter includes the relationship between the potential difference at the detection location and the crack length; The second parameter includes the relationship between the potential difference at the detection location and the notch distance on the notched sample; The third parameter includes the relationship between the sensitivity of the potential difference at the detection location and the crack length.

[0011] According to one embodiment of this disclosure, a second analytical expression is obtained by combining the potential difference at the optimal detection point with a first analytical expression, and the second analytical expression is optimized to form the measurement analytical expression, until the measurement analytical expression can be used to determine the crack length of the notched sample. The first analytical expression is:

[0012] The second analytical expression is:

[0013] Wherein, U(a) is the potential difference between the optimal detection points; U a0 U represents the potential difference corresponding to a0; a Let be the potential difference value corresponding to 'a'; 'a' is the crack length corresponding to the potential difference at the optimal detection point; 'a0' is the initial crack length; 'C' is a constant; 'W' is the width of the notched sample; 'y' is half the distance between the symmetrically arranged optimal detection points; cosh -1 and cosh are both trigonometric functions; π is the value of a circle.

[0014] According to one embodiment of this disclosure, a second analytical expression is obtained by combining the potential difference at the optimal detection point with a first analytical expression, and the second analytical expression is optimized to form a measurement analytical expression until the measurement analytical expression can be used to determine the crack length of the notched specimen. The measurement analytical expression is:

[0015] Among them, U a0 U represents the potential difference corresponding to a0; a Here, π is the potential difference value corresponding to 'a'; 'a' is the crack length corresponding to the potential difference at the optimal detection point; π is pi; cos, cos -1 ,cosh,cosh -1 All are trigonometric functions; W is the width of the notched sample; y is half the distance around the notch from the optimal detection point; X is related to the shape of the notched sample; Y is the width of the notch along the notch in the notched sample; Z is the error correction factor.

[0016] According to one embodiment of this disclosure, the method further includes: Prepare a crack propagation specimen; The potential difference data of the crack propagation specimen is measured, and the crack length of the crack propagation specimen is measured according to the measurement analytical formula. The crack length measured according to the analytical formula will be compared with the actual crack length of the crack propagation specimen.

[0017] According to one embodiment of this disclosure, when constructing a crack propagation specimen... A first crack and a second crack are set on the crack propagation specimen. The length of the first crack is set to a fixed value. The length of the second crack increases sequentially within the range of 0.1 to 1.0 mm.

[0018] According to one aspect of this disclosure, an apparatus for in-situ measurement of crack propagation in a notched specimen using a DC potential method is provided. The apparatus includes a specimen processing module, a potential detection module, a loading control module, a data processing module, a displacement adjustment module, a microscopic imaging module, and a measurement and analysis module. The loading control module is configured to apply pressure to the notched specimen to create a crack; The sample processing module is configured to set the detection location; The potential detection module is configured to detect the potential at the detection location; The data processing module is configured to determine the crack length based on the measurement analytical expression; The microscopic imaging module is connected to the adjustment displacement module, and the microscopic imaging module is used to observe the cracks on the notched sample; The displacement adjustment module is used to drive the microscopic imaging module to move; The measurement and analysis module is connected to the microscopic imaging module and is used to measure the cracks on the notched sample in real time.

[0019] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0020] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0021] Figure 1 This is a schematic diagram illustrating the steps of a method for measuring crack propagation in a notched specimen according to one embodiment of the present disclosure.

[0022] Figure 2 This is a schematic diagram of step S3 in one embodiment of the present disclosure.

[0023] Figure 3 This is a schematic diagram of step S32 in one embodiment of the present disclosure.

[0024] Figure 4 This is a schematic diagram showing the distribution of detection locations for a notched sample with a triangular notch shape, according to one embodiment of this disclosure.

[0025] Figure 5 This is a schematic diagram showing the distribution of detection positions for a notched sample with a semi-circular notch shape, according to one embodiment of this disclosure.

[0026] Figure 6 This is a schematic diagram showing the distribution of detection locations for a notched sample with a triangular notch shape, according to one embodiment of this disclosure.

[0027] Figure 7 This is a schematic diagram of the detection position distribution where the notch shape is semi-circular, according to one embodiment of this disclosure.

[0028] Figure 8 This disclosure presents eight mapping relationships for a notched specimen with a triangular notch shape, as described in one embodiment.

[0029] Figure 9 This disclosure presents eight mapping diagrams for a notched specimen with a semi-circular notch shape, as described in one embodiment.

[0030] Figure 10 This is a schematic diagram of the parameters of a notched sample with a triangular notch shape, according to one embodiment of the present disclosure.

[0031] Figure 11 This is a schematic diagram of the result of unequal-length cracks in one embodiment of the present disclosure. Figure 1 .

[0032] Figure 12 This is a schematic diagram of the result of unequal-length cracks in one embodiment of the present disclosure. Figure 2 .

[0033] Figure 13 This is a schematic diagram illustrating the steps of a method for measuring crack propagation in a notched specimen according to one embodiment of the present disclosure.

[0034] Figure 14 This is a schematic diagram of step S5 in one embodiment of the present disclosure.

[0035] Figure 15 In one embodiment of this disclosure, a comparison curve is obtained by measuring the crack length using an analytical formula and comparing it with the actual crack length measured by an optical microscope.

[0036] Figure 16 This is a schematic diagram of the sample processing module in one embodiment of the present disclosure.

[0037] Figure 17 This is a schematic diagram of a potential detection module, a loading control module, and a data processing module in one embodiment of the present disclosure.

[0038] Explanation of reference numerals in the attached figures: 1. Notched specimen; 11. Detection point group; 111. Voltage detection point; 112. Current loading point; 113. Reference potential difference detection point; 12. First crack; 13. Second crack; 14. Notch; 2. Specimen processing module; 21. Processing fixture; 22. Welding gun; 23. Welding machine; 24. Nickel-based wire; 3. Potential detection module; 4. Loading control module; 41. Fatigue testing machine; 5. Data processing module; 51. Measurement and analysis module. Detailed Implementation

[0039] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore detailed descriptions of them will be omitted. Furthermore, the drawings are merely illustrative of this disclosure and are not necessarily drawn to scale.

[0040] Although relative terms such as "up" and "down" are used in this specification to describe the relative relationship of one component of an icon to another, these terms are used only for convenience, such as according to the orientation of the examples shown in the accompanying drawings. It is understood that if the device of the icon is flipped upside down, the component described as "up" will become the component described as "down." When a structure is "up" of another structure, it may mean that the structure is integrally formed on the other structure, or that the structure is "directly" mounted on the other structure, or that the structure is "indirectly" mounted on the other structure through another structure.

[0041] High-temperature alloys are widely used in key hot-end components such as aero engines and gas turbines due to their excellent high-temperature strength, oxidation resistance and creep resistance. However, under high-temperature cyclic loading, cracks are prone to initiation and propagation inside the material, leading to fatigue failure. Therefore, closely monitoring crack propagation at stress concentration points is crucial to ensuring the safety and reliability of hot-end components.

[0042] Currently, the length of cracks on notches is commonly detected using optical direct reading methods such as microscopy, compliance methods, and film coating methods. However, all three methods have drawbacks: optical direct reading methods require continuous observation, which is labor-intensive; compliance methods are simple to operate, but due to the small size of the notch, it is difficult to measure the true displacement using an extensometer; and the film coating method measures the crack propagation length based on a thin film applied to the sample surface, which makes it difficult to guarantee that the measured crack length is the true crack length. Furthermore, the film coating method requires stopping the test and removing the film for observation, which can also affect the crack propagation rate.

[0043] Based on this, the present disclosure provides a method and apparatus for in-situ measurement of crack propagation in a notched specimen using a DC potentiometric method. Using this method and apparatus can improve the efficiency and accuracy of crack detection.

[0044] The method for measuring cracks in notched specimens in this application is applicable to the measurement of cracks in notched specimen 1; it is understood that it is also applicable to the detection of crack lengths in notches 14 of different specifications (e.g., semi-circular notches and triangular notches), which will not be elaborated in this application.

[0045] See Figure 1 The crack measurement method for notched specimen 1 is described in detail below: S1: Provide the measurement sample.

[0046] S2: Set the detection position on the test sample and measure the detection position.

[0047] S3: Provides measurement analytical expressions.

[0048] S4: Combine the measurement data of the detection location with the measurement analytical formula to determine the crack length of notched sample 1.

[0049] In this embodiment, when it is necessary to detect the length of the crack on the notch 14, a detection position is first set on the sample, and then relevant parameters at the detection position are measured. These parameters are then substituted into the measurement analytical formula to calculate the crack length of the sample. This measurement method can quickly and accurately measure the crack length of the sample.

[0050] In some embodiments described herein, see Figure 2 In step S3, providing the measurement analytical expression includes: S31: Prepare notched specimen 1.

[0051] Specifically, the notched specimen 1 has two notches 14 at its center, and the two notches 14 are symmetrically arranged along the length of the notched specimen 1.

[0052] Further, see Figure 4 , Figure 5 Cracks can be constructed in the notches 14 using the Seam module. Corresponding to the two notches 14 are the first crack 12 and the second crack 13. The length direction of the first crack 12 is the same as that of the second crack 13, that is, the first crack 12 and the second crack 13 are located on the same horizontal line.

[0053] In some embodiments, the notch 14 can be a semi-circular notch. Of course, the notch 14 can also be other shapes, such as a triangular notch. This application does not impose any specific limitations on this.

[0054] S32: Set the detection position on the notched sample 1.

[0055] In some embodiments of this disclosure, see Figure 3 , Figure 4 , Figure 5 When setting the detection position on the notched sample 1, the following steps are included: S321: The detection position includes a detection point group 11 symmetrically arranged along the width direction of the center position of the notched sample 1. The detection point group 11 includes a voltage detection point 111 and a current loading point 112 arranged sequentially along the length direction of the notched sample 1.

[0056] In this embodiment, the voltage detection point 111 and the current loading point 112 are located on the central axis of the notched sample 1.

[0057] As an example, a current of 5A can be applied at the current application point 112. It should be noted that in other embodiments, a current of 10A can also be applied at the current application point 112, and this application does not limit this.

[0058] As another example, see Figure 6 , Figure 7 The detection point group 11 also includes a reference potential difference detection point 113; wherein, the reference potential difference detection point 113 is located between the voltage detection point 111 and the current loading point 112. In this example, the voltage detection point 111, the potential difference detection point, and the current loading point 112 are all located on the central axis of the notched sample 1.

[0059] It should be noted that the reference potential difference detection point 113 set in this embodiment can eliminate the influence of the external environment (temperature, humidity, electromagnetic interference, etc.). By monitoring the changes in the reference potential difference detection point 113, the system stability can be ensured and measurement errors caused by environmental changes can be avoided.

[0060] S33: Detect the first parameter of the detection position to form first data, detect the second parameter of the detection position to form second data, detect the third parameter of the detection position to form third data, and combine the first data, second data and third data to obtain the optimal detection point.

[0061] In some embodiments of this disclosure, when detecting a first parameter of the detection location to form first data, detecting a second parameter of the detection location to form second data, and detecting a third parameter of the detection location to form third data, and combining the first data, second data, and third data to obtain the optimal detection point, the first parameter includes the relationship between the potential difference at the detection location and the crack length; the second parameter includes the relationship between the potential difference at the detection location and the notch distance on the notched sample 1; and the third parameter includes the relationship between the sensitivity of the potential difference at the detection location and the crack length. The optimal detection point can be obtained by combining the first data formed by the first parameter, the second data formed by the second parameter, and the third data formed by the third parameter.

[0062] S34: Measure the potential difference at the optimal detection point.

[0063] S35: The potential difference at the optimal detection point is combined with the first analytical expression to obtain the second analytical expression, and the second analytical expression is optimized to form the measurement analytical expression until the measurement analytical expression can solve for the crack length of the notched sample 1.

[0064] In some embodiments of this disclosure, a second analytical expression is obtained by combining the potential difference at the optimal detection point with a first analytical expression, and the second analytical expression is optimized to form a measurement analytical expression, until the measurement analytical expression can be used to determine the crack length of the notched sample. The first analytical expression is:

[0065] The second analytical expression is: ; Where U(a) is the potential difference between the optimal detection points; U a0 U represents the potential difference corresponding to a0; a Let be the potential difference value corresponding to 'a'; 'a' is the crack length corresponding to the potential difference at the optimal detection point; 'a0' is the initial crack length; 'C' is a constant; 'W' is the width of the notched sample; 'y' is half the distance between the symmetrically set optimal detection points; cosh -1 and cosh are both trigonometric functions; π is the value of a circle.

[0066] It is understood that the first analytical expression is the Johnson formula, which is applicable to specimens with a central crack. The embodiments disclosed herein are based on the first analytical expression to construct the measurement analytical expression. Specifically, considering the structural similarity between specimens with a central crack and specimens with a notch, a corresponding mapping relationship can be established.

[0067] The first analytical expression is applicable to the center crack test, and its dimensionless expression is: ; The inverse function a~U relation of the above dimensionless expression is: ; Based on this relationship, it can be seen that there are three parameters affecting the crack length: a0, y, and W (U, where U0 is only related to the optimal detection point). Therefore, the dimensionless analytical formula under the mapping relationship is: ; Further, see Figure 8 , Figure 10 By controlling variables, a mapping relationship can be established to show the specific manifestation of each mapping parameter in the notched specimen.

[0068] As an example, when the notch in notched specimen 1 is a triangular notch, the mapping relationship is as follows:

[0069] As another example, see Figure 9 When the notch in notched sample 1 is a semi-circular notch, the mapping relationship is as follows:

[0070] Using the above mapping relationships (including the mapping relationships for the triangular notch and the semi-circular notch), the dimensionless expression is corrected, and the measurement analytical expression is obtained as follows:

[0071] Among them, U a0 U represents the potential difference corresponding to a0; a Here, π represents the potential difference value corresponding to 'a'; 'a' is the crack length corresponding to the potential difference at the optimal detection point; π is pi; cos, cos -1 ,cosh,cosh -1 All are trigonometric functions; W is the width of the notched sample; y is half the distance around the notch from the optimal detection point; X is related to the shape of the notched sample; Y is the width of the notch along the notch in the notched sample; Z is the error correction factor.

[0072] It is understandable that when the notch 14 of notched sample 1 is a triangular notch, X=cb / 2, Y=h, Z=0.042 (it is understandable that this parameter is only applicable when the side length of the triangular notch is 0.5mm, but when the side length of the triangular notch is other, this parameter needs to be corrected again, which will not be elaborated here), where b is the length of the base of the triangle, c is the side length of the triangle, and h is the height of the base of the triangle.

[0073] When the notch 14 of notched sample 1 is a semi-circular notch, X=D(π / 2-1) / 2, Y=D / 2, Z=0.058 (it can be understood that this parameter is only applicable to the semi-circular diameter D=0.5mm, but when the semi-circular notch is of other diameters, this parameter needs to be corrected), where D is the semi-circular diameter.

[0074] Furthermore, the above cracks are based on the case where the first crack 12 and the second crack 13 have the same length. However, in some embodiments, the lengths of the first crack 12 and the second crack 13 may be different. Therefore, it is necessary to verify the type of crack length measured by the measurement formula (for example, it is necessary to clarify whether the measurement formula measures the length of the first crack 12 or the length of the second crack 13, provided that the first crack 12 and the second crack 13 are not of equal length).

[0075] Based on this, to verify the crack type of the measured analytical formula, see [reference needed]. Figure 11 , Figure 12 , Figure 13 , Figure 14 In some embodiments of this disclosure, the following method is employed: S5: Prepare a crack propagation specimen.

[0076] S51: First crack 12 and second crack 13 are set on the crack propagation specimen (see...) Figures 4-7 The length of the first crack 12 is set to a fixed value; the length of the second crack 13 increases sequentially within the range of 0.1~1.0 mm.

[0077] It is understood that, in one implementation, the length of the first crack 12 can be 0.3 mm, and correspondingly, the length of the second crack 13 can be 0.1 mm, 0.2 mm, 0.3 mm...1.0 mm.

[0078] In another embodiment, the length of the first crack 12 can be 0.4 mm, and the corresponding length of the second crack 13 can be 0.1 mm, 0.2 mm, 0.3 mm...1.0 mm.

[0079] S6: Measure the potential difference data of the crack propagation specimen, and determine the crack length of the crack propagation specimen according to the analytical formula. Specifically, obtain the potential difference data under unequal crack lengths, and calculate the crack length according to the analytical formula.

[0080] The table below illustrates the length of the cracks measured using analytical formulas when the length of the first crack 12 is fixed and the length of the second crack 13 increases sequentially within the range of 0.1 to 1.0 mm.

[0081]

[0082] As can be seen from the above, see Figure 11 , Figure 12 The diagram illustrates the calculation results of the measurement analytical formula (71 represents the changing crack in the asymmetric crack in the finite element simulation; 72 represents the unchanged crack in the asymmetric crack in the finite element simulation; 73 represents the crack length calculated by the measurement analytical formula). From the table above, it can be seen that the crack length measured by the measurement analytical formula is close to half of the sum of the first crack 12 and the second crack 13.

[0083] S7: The crack length measured according to the analytical formula will be compared with the actual crack length of the crack propagation specimen. In this way, the accuracy of the analytical formula can be verified by comparing the crack length measured by the analytical formula with the actual crack length (which can be detected by electron microscopy).

[0084] See Figure 15 The diagram illustrates the test results of the crack length test of notched specimen 1. The results show that the accuracy of measuring the crack length of notched specimen 1 using analytical measurement is comparable to that of microscopic optical measurement.

[0085] See Figure 16 , Figure 17 This disclosure also provides an apparatus for in-situ measurement of crack propagation in notched specimens using the DC potential method.

[0086] The device provided above will be described in detail below: The measuring device includes a sample processing module 2, a potential detection module 3, a loading control module 4, a data processing module 5, a displacement adjustment module (not shown in the accompanying drawings), a microscopic imaging module (not shown in the accompanying drawings), and a measurement analysis module 51. The loading control module 4 is configured to apply pressure to the notched sample 1 (it is understood that the pressure here can refer to at least one or more forces such as tension and shear force, which will not be elaborated in this embodiment) to create a crack. As an example, the loading control module 4 can be a fatigue testing machine 41 equipped with a notched sample 1 fixture, through which a crack can be created on the notched sample 1. The sample processing module 2 is configured to set the detection position. As an example, the sample processing module 2 can be a welding machine 23, a welding gun 22, and a processing fixture 21. When setting the detection position, the nickel-based wire 24 can be fixed on the notched sample 1 using the processing fixture 21. After precise positioning, the nickel-based wire 24 is welded to the notched sample 1 using the welding gun 22. Potential detection module 3 is configured to detect the potential at the detection location. As an example, potential detection module 3 can be a voltage measuring device, which can accurately detect the voltage between relatively optimal detection points. Data processing module 5 is configured to determine the crack length based on a measurement formula. As an example, data processing module 5 can be a device with a measurement formula program (e.g., a laptop computer) and can generate an aN curve. Microscopic imaging module 6 is connected to the adjustment displacement module and is used to observe the crack on the notched specimen 1. As an example, the microscopic imaging module (not shown in this application) can be an electron microscope. The adjustment displacement module (not shown in this application) is used to drive the microscopic imaging module to move. Measurement analysis module 51 is connected to the microscopic imaging module and is used to measure the crack on the notched specimen 1 in real time.

[0087] As an example, the diameter of the nickel-based wire 24 can be selected between 0.2 and 0.5 mm. It is understood that in other embodiments, the material and diameter of the wire used are not limited to this.

[0088] As another example, the adjustment displacement module is a mechanical displacement stage with a displacement accuracy of ±0.01mm, which will not be described in detail here.

[0089] This disclosure also provides a computer-readable storage medium having a computer program that can perform the measurement methods described above.

[0090] Furthermore, this disclosure also provides an electronic device including a memory and a processor; The memory is configured to store executable instructions for the processor; the processor is configured to perform the measurement method described above by executing executable quality.

[0091] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the appended claims.

Claims

1. A method for in-situ measurement of crack propagation in a notched specimen using DC potential method, characterized in that, The method includes: Provide measurement samples; A detection position is set on the measurement sample, and the detection position is measured. Provide measurement analytical expressions; The measurement data at the detection location is combined with the measurement analytical formula to determine the crack length of the measured sample.

2. The method for in-situ measurement of crack propagation in a notched specimen using the DC potential method according to claim 1, characterized in that, The analytical expressions provided for measurement include: Prepare the notched specimen; A detection position is set on the notched sample; First data is generated by detecting a first parameter of the detection location, second data is generated by detecting a second parameter of the detection location, and third data is generated by detecting a third parameter of the detection location. The optimal detection point is obtained by combining the first data, the second data, and the third data. The potential difference at the optimal detection point was measured; The potential difference at the optimal detection point is combined with the first analytical expression to obtain the second analytical expression, and the second analytical expression is optimized to form the measurement analytical expression, until the measurement analytical expression can solve for the crack length of the notched sample.

3. The method for in-situ measurement of crack propagation in a notched specimen using the DC potential method according to claim 2, characterized in that, When a detection position is set on the notched sample and the detection position is measured, The detection location includes a group of detection points symmetrically arranged along the width direction of the center position of the notched sample. The group of detection points includes voltage detection points and current loading points arranged sequentially along the length direction of the notched sample.

4. The method for in-situ measurement of crack propagation in a notched specimen using the DC potential method according to claim 3, characterized in that, The detection point group also includes a reference potential difference detection point; The reference potential difference detection point is located between the voltage detection point and the current loading point.

5. The method for in-situ measurement of crack propagation in a notched specimen using the DC potential method according to claim 2, characterized in that, When detecting a first parameter at the detection location to form first data, detecting a second parameter at the detection location to form second data, and detecting a third parameter at the detection location to form third data, and combining the first data, the second data, and the third data to obtain the optimal detection point, The first parameter includes the relationship between the potential difference at the detection location and the crack length; The second parameter includes the relationship between the potential difference at the detection location and the notch distance on the notched sample; The third parameter includes the relationship between the sensitivity of the potential difference at the detection location and the crack length.

6. The method for in-situ measurement of crack propagation in a notched specimen using the DC potential method according to claim 4, characterized in that, The potential difference at the optimal detection point is combined with the first analytical expression to obtain a second analytical expression. This second analytical expression is then optimized to form the measurement analytical expression, until the measurement analytical expression can determine the crack length of the notched specimen. The first analytical expression is: The second analytical expression is: Wherein, U(a) is the potential difference between the optimal detection points; U a0 U represents the potential difference corresponding to a0; a Let be the potential difference value corresponding to 'a'; 'a' is the crack length corresponding to the potential difference at the optimal detection point; 'a0' is the initial crack length; 'C' is a constant; 'W' is the width of the notched sample; 'y' is half the distance between the symmetrically arranged optimal detection points; cosh -1 Both cosθ and cosh are trigonometric functions; π is the mathematical constant pi.

7. The method for in-situ measurement of crack propagation in a notched specimen using the DC potential method according to claim 4, characterized in that, The potential difference at the optimal detection point is combined with the first analytical expression to obtain a second analytical expression. This second analytical expression is then optimized to form a measurement analytical expression, until the measurement analytical expression can be used to determine the crack length of the notched specimen. The analytical expression for the measurement is: Among them, U a0 U represents the potential difference corresponding to a0; a Here, π is the potential difference value corresponding to 'a'; 'a' is the crack length corresponding to the potential difference at the optimal detection point; π is pi; cos, cos -1 ,cosh,cosh -1 All are trigonometric functions; W is the width of the notched sample; y is half the distance around the notch from the optimal detection point; X is related to the shape of the notched sample; Y is the width of the notch along the notch in the notched sample; Z is the error correction factor.

8. The method for in-situ measurement of crack propagation in a notched specimen using the DC potential method according to claim 1, characterized in that, The method further includes: Prepare a crack propagation specimen; The potential difference data of the crack propagation specimen is measured, and the crack length of the crack propagation specimen is measured according to the measurement analytical formula. The crack length measured according to the analytical formula will be compared with the actual crack length of the crack propagation specimen.

9. The method for in-situ measurement of crack propagation in a notched specimen using the DC potential method according to claim 8, characterized in that, When preparing a crack propagation specimen A first crack and a second crack are set on the crack propagation specimen. The length of the first crack is set to a fixed value. The length of the second crack increases sequentially within the range of 0.1 to 1.0 mm.

10. A device for in-situ measurement of crack propagation in a notched specimen using a DC potentiometric method, characterized in that, The device includes a sample processing module, a potential detection module, a loading control module, a data processing module, a displacement adjustment module, a microscopic imaging module, and a measurement and analysis module. The loading control module is configured to apply pressure to the notched specimen to create a crack; The sample processing module is configured to set the detection location; The potential detection module is configured to detect the potential at the detection location; The data processing module is configured to determine the crack length based on the measurement analytical expression; The microscopic imaging module is connected to the adjustment displacement module, and the microscopic imaging module is used to observe the cracks on the notched sample; The displacement adjustment module is used to drive the microscopic imaging module to move; The measurement and analysis module is connected to the microscopic imaging module and is used to measure the cracks on the notched sample in real time.

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