Method and system for testing hydrogen-induced cracking threshold based on notched round bar tensile specimens

Abstract

This application belongs to the field of materials testing and discloses a method and system for testing the hydrogen-induced cracking threshold value based on notched round bar tensile specimens. The testing method comprises: performing slow strain rate tensile tests on notched round bar tensile specimens in a hydrogen environment and an inert gas environment, respectively, to obtain test data and two elongations; using the two elongations to obtain the material's hydrogen embrittlement sensitivity index; using the material's hydrogen embrittlement sensitivity index and the test data to obtain elastic-plastic parameters; when the elastic-plastic parameter is greater than 3.5, the hydrogen-induced cracking threshold value is obtained using an elastic-plastic crack propagation mechanism; when the elastic-plastic parameter is not greater than 3.5, the hydrogen-induced cracking threshold value is obtained using a linear elastic crack propagation mechanism. This testing method has a short cycle time, high efficiency, and strong universality.

Description

Technical Field

[0001] The present application belongs to the field of material testing technology, and specifically relates to a method and system for testing the hydrogen-induced cracking threshold value based on a notched round bar tensile specimen. Background Art

[0002] Hydrogen pipeline transport is currently the primary method of hydrogen energy transmission. However, hydrogen damages pipeline materials, hindering material performance and jeopardizing the safe and stable operation of equipment. Hydrogen-induced cracking (HIC) is particularly significant. In a hydrogen environment, hydrogen atoms penetrate and accumulate in metals or alloys under stresses below their conventional strength limit, leading to the initiation of microcracks within the material. These cracks gradually expand under continued stress, ultimately causing the material to fracture. This phenomenon is difficult to predict, and the material's performance degrades rapidly during the fracture process, posing a significant threat to the safe operation of industrial equipment.

[0003] In the study of hydrogen-induced cracking, the stress intensity factor threshold value K IH It is a key parameter for evaluating the crack resistance of materials. The stress intensity factor K is a physical quantity that measures the stress concentration at the crack tip and reflects the driving force of crack propagation. IH It represents the minimum stress intensity factor required for the material to resist hydrogen-induced cracking under specific conditions. Once the stress intensity factor at the crack tip exceeds K IH , the crack will expand and cause the material to fail. Therefore, K IH It is crucial to ensure the safety of hydrogen energy transportation equipment.

[0004] Traditional measurement K IH The methods include constant load method, slow strain rate method and constant displacement method, among which double cantilever beam (DCB) and wedge opening loading (WOL) are more commonly used. The DCB method uses a specimen with a specific geometry to generate the necessary stress intensity factor to initiate and propagate cracks and measure the stress intensity factor threshold value K. IH However, the above methods have many limitations: they require a large amount of experimental data accumulation, long testing cycles (for pipeline steel, it often takes weeks to months for cracks to stop growing), and large differences in test results between different laboratories, limiting repeatability. Summary of the Invention

[0005] In response to the defects of the existing technology, the purpose of this application is to provide a method and system for testing the hydrogen-induced cracking threshold value based on notched round bar tensile specimens, aiming to solve the problems of low test efficiency and poor repeatability of the existing test methods for measuring the hydrogen-induced cracking threshold value.

[0006] To achieve the above objectives, the present application provides a method for testing the hydrogen-induced cracking threshold value of a notched round bar tensile specimen, comprising:

[0007] S1: Under a hydrogen environment, a slow strain rate tensile test is performed on a notched round bar tensile specimen to obtain test data, wherein the test data includes yield strength, tensile strength, a first maximum displacement, engineering stress, and engineering strain, and a first elongation is obtained using the first maximum displacement and an original length of the notched round bar tensile specimen; under an inert gas environment, a slow strain rate tensile test is performed on the same notched round bar tensile specimen to obtain a second maximum displacement, and a second elongation is obtained using the second maximum displacement and the original length;

[0008] S2 obtains a hydrogen embrittlement sensitivity index of the material using the first elongation and the second elongation; and obtains elastic-plastic parameters using the hydrogen embrittlement sensitivity index of the material, the yield strength, and the tensile strength;

[0009] S3 determines whether the elastic-plastic parameter R is greater than 3.5. If so, a hydrogen-induced cracking threshold value is obtained based on an elastic-plastic crack growth mechanism; if not, a hydrogen-induced cracking threshold value is obtained based on a linear elastic crack growth mechanism.

[0010] Furthermore, in step S2, the formula for obtaining the material hydrogen embrittlement sensitivity index is expressed as:

[0011]

[0012] in, I HE is the material hydrogen embrittlement sensitivity index, δ H is the first elongation, δ 0 is the second elongation.

[0013] Furthermore, the notch stress concentration coefficient of the notched round bar tensile specimen is greater than or equal to 3.

[0014] Furthermore, in step S2, the formula for obtaining the elastic-plastic parameters is expressed as:

[0015]

[0016] in, R is the elastic-plastic parameter, is the yield strength, is the tensile strength, I HE It is the material hydrogen embrittlement sensitivity index.

[0017] Furthermore, in step S3, the elastic-plastic parameters R When it is not greater than 3.5, the hydrogen-induced cracking threshold is obtained using the following formula:

[0018]

[0019] in, K IH is the hydrogen-induced cracking threshold, in MPa·m 0.5 , P IH is the critical load for hydrogen-induced cracking, F 1 is the first geometric function under the linear elastic crack growth mechanism.

[0020] Furthermore, the first geometric function is obtained by the following formula:

[0021]

[0022] in, D is the original diameter of the notched round bar tensile specimen; d is the notch diameter of the notched round bar tensile specimen.

[0023] Furthermore, in step S3, the elastic-plastic parameters R When it is greater than 3.5, the corresponding hydrogen-induced cracking threshold is obtained using the following formula:

[0024]

[0025] in, K IH is the hydrogen-induced cracking threshold, in MPa·m 0.5 , J IH is the J integral value of hydrogen-induced cracking, E Y is the elastic modulus of the material, v is Poisson's ratio.

[0026] Furthermore, the calculation formula of the hydrogen-induced cracking J integral value is:

[0027]

[0028] in, J IH is the J integral value of hydrogen-induced cracking, l 0 is the original length of the notched round bar tensile specimen; r 0 is the original radius of the notched round bar tensile specimen, F 2 is the second geometric function, P IH is the critical load for hydrogen-induced cracking, ∆l is the first maximum displacement.

[0029] Furthermore, the calculation formula of the second geometric function is:

[0030]

[0031] in, F 2 is the second geometric function under the elastic-plastic crack growth mechanism, where r is the notch radius of the notched round bar tensile specimen.

[0032] Furthermore, the hydrogen-induced cracking critical load is obtained. P IH The steps include:

[0033] S301 uses the engineering stress and engineering strain to obtain the true strain and true stress of the notched round bar tensile specimen;

[0034] S302: drawing a true stress-true strain curve based on the true strain and true stress to fit the test data;

[0035] S303 Based on the fitted test data, the actual strain corresponding to the strain hardening rate of 0 is obtained. , the actual strain The corresponding load is taken as the critical load for hydrogen-induced cracking P IH .

[0036] Furthermore, in step S301, the formula for obtaining the true stress is:

[0037]

[0038] in, is the engineering stress, For engineering strain, T is the true stress;

[0039] And / or, in step S301, the formula for obtaining the true strain is:

[0040]

[0041] in, For real strain;

[0042] and / or, in step S302, fitting the test data to a fifth-order polynomial;

[0043] And / or, in step S303, obtain the actual strain The method is: differentiate the fitted test data and draw curve graph, where , the strain hardening rate = 0 is taken as the true strain .

[0044] According to another aspect of the present application, a test system is provided for implementing any of the above test methods, the test system comprising:

[0045] a test data acquisition module, configured to acquire test data after a slow strain rate tensile test is performed on a notched round bar tensile specimen in a hydrogen environment, the test data including yield strength, tensile strength, first maximum displacement, engineering stress, and engineering strain, and to acquire a first elongation using the first maximum displacement and the original length of the notched round bar tensile specimen; and to acquire a second maximum displacement corresponding to a slow strain rate tensile test performed on the same notched round bar tensile specimen in an inert gas environment, and to acquire a second elongation using the second maximum displacement and the original length;

[0046] A sample parameter acquisition module is used to obtain a material hydrogen embrittlement sensitivity index using the first elongation and the second elongation; and to obtain an elastic-plastic parameter R using the material hydrogen embrittlement sensitivity index, the yield strength, and the tensile strength;

[0047] The hydrogen-induced cracking threshold value acquisition module is used to determine whether the elastic-plastic parameter R is greater than 3.5. If so, it is also used to obtain the hydrogen-induced cracking threshold value based on the elastic-plastic crack growth mechanism; if not, it is also used to obtain the hydrogen-induced cracking threshold value based on the linear elastic crack growth mechanism.

[0048] The above technical solutions conceived by this application have the following beneficial effects compared with the existing technology:

[0049] 1. Compared with traditional methods, the test method provided in this application is more convenient and flexible, has fewer restrictions, and a short test cycle. It is very suitable for the testing needs of metal materials such as pipeline steel. At the same time, this test method simultaneously conducts slow strain rate tensile tests on notched round bar tensile specimens under two environments, which has the advantages of high material utilization, low material cost, simple specimen processing and easy implementation of the test method.

[0050] 2. The test method provided in this application uses slow strain rate tensile testing to explore fracture mechanics properties. By conducting slow strain rate tensile tests on identical notched round bar tensile specimens under two different conditions, the test data is used to calculate the hydrogen-induced cracking threshold, significantly shortening the test cycle. Furthermore, notches are designed in specific areas of the notched round bar tensile specimens, enabling accurate study of narrow areas such as welds and heat-affected zones of welded joints. The resulting test data can also effectively assess the hydrogen embrittlement sensitivity of the material. Elastoplastic parameters are calculated based on the material's hydrogen embrittlement sensitivity index, and the hydrogen-induced cracking threshold is then calculated using these elastic-plastic parameters, resulting in a more accurate calculation result.

[0051] 3. The test method provided in this application is not limited by the test environment and can be applied to the calculation of hydrogen-induced cracking threshold values under various conditions. It has high repeatability and greater universal applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is a flow chart of the testing method provided in the embodiment of the present application.

[0053] Figure 2 This is a processing drawing of a notched slow strain rate tensile test of X65 pipeline steel provided in an embodiment of the present application.

[0054] Figure 3 is the θ-ε provided in the embodiment of this application T curve chart.

[0055] Figure 4 This is a comparison chart of hydrogen-induced cracking threshold values using different test methods provided in the examples of this application. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0057] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0058] Additionally, references throughout this specification to "one embodiment," "one embodiment," "an example," or similar language indicate that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present application. Thus, appearances of the phrase "in one embodiment," "in one embodiment," and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

[0059] The present invention provides a method for testing the hydrogen-induced cracking threshold value of a notched round bar tensile specimen. Figure 1 As shown, the test method includes the following steps:

[0060] S1: Under a hydrogen environment, a slow strain rate tensile test is performed on a notched round bar tensile specimen to obtain test data, including yield strength, tensile strength, first maximum displacement, engineering stress, and engineering strain. The first elongation is obtained using the first maximum displacement and the original length of the notched round bar tensile specimen. Under an inert gas environment, a slow strain rate tensile test is performed on the notched round bar tensile specimen to obtain a second maximum displacement. The second elongation is obtained using the second maximum displacement and the original length.

[0061] S2 uses the first elongation and the second elongation to obtain the hydrogen embrittlement sensitivity index of the material; uses the hydrogen embrittlement sensitivity index, yield strength and tensile strength of the material to obtain the elastic-plastic parameters R ;

[0062] S3 determines the elastic-plastic parameters R Is it greater than 3.5? If so, the hydrogen-induced cracking threshold is obtained based on the elastic-plastic crack growth mechanism; if not, the hydrogen-induced cracking threshold is obtained based on the linear elastic crack growth mechanism.

[0063] The metal material to be tested shall be Figure 2 The drawing shown in the figure is processed into a standard slow strain tensile notched round bar specimen (hereinafter referred to as the specimen), and the notch stress concentration factor of the specimen is greater than or equal to 3. In step S1, in a hydrogen environment, the strain rate during the test is 2×10 -6 s -1 The gauge length is 20 mm. The gauge length section of the specimen needs to be measured with an extensometer. At the beginning of the test, the specimen needs to be placed in a hydrogen environment for 2 h.

[0064] In step S2, the formula for obtaining the material hydrogen embrittlement sensitivity index is expressed as:

[0065] (1)

[0066] in, I HE is the material hydrogen embrittlement sensitivity index, δ H is the first elongation, δ 0 is the second elongation.

[0067] The formula for obtaining elastic-plastic parameters is expressed as:

[0068] (2)

[0069] in, R is the elastic-plastic parameter, is the yield strength, in MPa, which is defined as the elongation strength when the non-proportional elongation is 0.2%; is the tensile strength, in MPa; I HEIt is the material hydrogen embrittlement sensitivity index.

[0070] In step S3, when R When it is not greater than 3.5, the formula for obtaining the hydrogen-induced cracking threshold based on the linear elastic crack growth mechanism is:

[0071] (3)

[0072] in, K IH is the hydrogen-induced cracking threshold, in MPa·m 0.5 , P IH is the critical load for hydrogen-induced cracking, in units of kN , F 1 is the first geometric function under the linear elastic crack growth mechanism.

[0073] The calculation formula of the aforementioned first geometric function is:

[0074] (4)

[0075] in, F 1 is the first geometric function under the linear elastic crack growth mechanism, D is the original diameter of the notched round bar tensile specimen, in units of m ; d is the notch diameter of the notched round bar tensile specimen, in units of m ;

[0076] In step S3, when the elastic-plastic parameters R When it is greater than 3.5, it is an elastic-plastic crack growth mechanism, and the formula for calculating the hydrogen-induced cracking threshold is:

[0077] (5)

[0078] Among them, among them, K IH is the hydrogen-induced cracking threshold, in MPa·m 0.5 , J IH is the J integral value of hydrogen-induced cracking, E Y is the elastic modulus of the material, v is Poisson's ratio, which is generally taken as 0.3 for metal materials.

[0079] The calculation formula for the aforementioned hydrogen-induced cracking J integral value is:

[0080] (6)

[0081] J IHis the J integral value of hydrogen-induced cracking, in kJ / m 2 ,in r 0 is the original radius of the specimen, in m; E Y is the elastic modulus of the material, in MPa, P IH is the critical load for hydrogen-induced cracking.

[0082] The aforementioned second geometric function F The calculation formula for 2 is:

[0083] (7)

[0084] in, F 2 is the geometric function under the elastic-plastic crack growth mechanism, and its unit is m -2 ,in r is the notch radius of the notched round bar tensile specimen, in units of m，∆l is the first maximum displacement.

[0085] Under the two mechanisms in step S3, the specific steps of obtaining the aforementioned hydrogen-induced cracking critical load include:

[0086] S301 uses engineering stress and engineering strain to obtain the true strain and true stress of notched round bar tensile specimens;

[0087] S302 draws a true stress-true strain curve based on the true strain and true stress to fit the test data;

[0088] S303 Based on the fitted test data, the actual strain corresponding to the strain hardening rate of 0 is obtained. , the actual strain The corresponding load is taken as the critical load for hydrogen-induced cracking.

[0089] In step S301, the formula for obtaining the true stress is:

[0090] (8)

[0091] in, is the engineering stress, For engineering strain, T is the true stress;

[0092] The formula for obtaining the true strain is:

[0093] (9)

[0094] in, For real strain.

[0095] In step S302, the test data is fitted into a fifth-order polynomial. Specifically, the true stress-true strain curve is drawn using the origin software, and then the polynomial is fitted to the experimental data. The order of the fitted polynomial is 5th order.

[0096] In step S303, the real strain is obtained The method is to differentiate the fitted test data and draw the result using origin software. The curve diagram shows the strain hardening rate , strain hardening rate = 0 when the true strain is ,Pick The corresponding load is taken as the critical load for hydrogen-induced cracking P IH , the unit is kN .

[0097] In a more preferred embodiment, the aforementioned steps S1-S3 may be repeated at least three times to obtain at least three sets of hydrogen-induced cracking threshold values, and the average value of the multiple sets of hydrogen-induced cracking threshold values is calculated as the final hydrogen-induced cracking threshold value.

[0098] The following comparative tests are conducted using the test method of the present invention and the traditional compliance unloading test method, respectively, with X65 pipeline steel as the test object.

[0099] Sample processing drawings of X65 pipeline steel are as follows: Figure 2 As shown, the yield strength of the welded joint is 464 MPa and the tensile strength is 540 MPa, and multiple specimens are obtained.

[0100] The corresponding samples were tested at room temperature of 25℃ and five different atmospheres using the traditional flexibility unloading test method and the slow strain rate tensile method (SSRT). The hydrogen-induced cracking threshold values K under the traditional flexibility unloading test method were obtained. IH（J） And the hydrogen-induced cracking threshold value K under the slow strain rate stretching method of this application IH(SSRT) The aforementioned atmosphere is pure N2 atmosphere, and mixed atmospheres of N2 and H2 with four different component ratios. The hydrogen content of the mixed atmosphere is 1 HE When the slow strain rate tensile test was carried out on the specimen, at least 3 repeated tests were carried out in each environment. The test results are shown in Table 1. Figure 3 and Figure 4 shown.

[0101] Table 1 Hydrogen-induced cracking threshold Test results

[0102]

[0103] Figure 3 Indicates the θ-ε obtained using the test method of this application T The curve diagram is used to obtain the true strain corresponding to the strain hardening rate of 0, and the load corresponding to the true strain at this time is used as the critical load of hydrogen-induced cracking. The hydrogen-induced cracking threshold value K under different hydrogen doping ratio environments is obtained using the above calculation process. IH(SSRT) . Combining Table 1 and Figure 4 It can be seen that the hydrogen-induced cracking threshold value obtained using the test method of the present application is close to the result obtained by the traditional compliance unloading test method, which proves the accuracy of the test method of the present application and can replace the traditional test method to efficiently obtain the hydrogen-induced cracking threshold value.

[0104] Another embodiment of the present application further provides a testing system for implementing any of the above testing methods, the testing system comprising:

[0105] a test data acquisition module for acquiring test data after a slow strain rate tensile test is performed on a notched round bar tensile specimen in a hydrogen environment, the test data including yield strength, tensile strength, first maximum displacement, engineering stress, and engineering strain, and for acquiring a first elongation using the first maximum displacement and the original length of the notched round bar tensile specimen; and for acquiring a second maximum displacement corresponding to a slow strain rate tensile test performed on the same notched round bar tensile specimen in an inert gas environment, and for acquiring a second elongation using the second maximum displacement and the original length;

[0106] A sample parameter acquisition module is used to obtain the hydrogen embrittlement sensitivity index of the material using the first elongation and the second elongation; and to obtain elastic-plastic parameters using the hydrogen embrittlement sensitivity index, yield strength and tensile strength of the material;

[0107] The hydrogen-induced cracking threshold value acquisition module is used to obtain the hydrogen-induced cracking threshold value by adopting the linear elastic crack extension mechanism when the elastic-plastic parameter is not greater than 3.5; and is also used to obtain the hydrogen-induced cracking threshold value by adopting the elastic-plastic crack extension mechanism when the elastic-plastic parameter is greater than 3.5.

[0108] It is understandable that the detailed functional implementation of each of the above units / modules can be found in the introduction of the aforementioned method embodiment, and will not be repeated here.

[0109] It should be understood that the above-mentioned system is used to execute the method in the above-mentioned embodiment, and the corresponding program module in the device has an implementation principle and technical effects similar to those described in the above-mentioned method. The working process of the device can refer to the corresponding process in the above-mentioned method and will not be repeated here.

[0110] Based on the methods described in the above embodiments, embodiments of the present application provide an electronic device. The device may include: at least one memory for storing programs and at least one processor for executing the programs stored in the memory. When the programs stored in the memory are executed, the processor is configured to execute the methods described in the above embodiments.

[0111] Based on the method in the above embodiment, an embodiment of the present application provides a computer-readable storage medium, which stores a computer program. When the computer program runs on a processor, the processor executes the method in the above embodiment.

[0112] Based on the method in the above embodiment, an embodiment of the present application provides a computer program product. When the computer program product runs on a processor, the processor executes the method in the above embodiment.

[0113] It is understood that the processor in the embodiments of the present application may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA), other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. The general-purpose processor may be a microprocessor or any conventional processor.

[0114] The method steps in the embodiments of the present application can be implemented by hardware or by a processor executing software instructions. The software instructions can be composed of corresponding software modules, which can be stored in random access memory (RAM), flash memory, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disks, removable hard disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor so that the processor can read information from the storage medium and write information to the storage medium. Of course, the storage medium can also be an integral part of the processor. The processor and storage medium can be located in an ASIC.

[0115] The above embodiments can be implemented in whole or in part through software, hardware, firmware, or any combination thereof. When implemented using software, they can be implemented in whole or in part in the form of a computer program product. A computer program product comprises one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the processes or functions according to the embodiments of the present application are generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted via a computer-readable storage medium. The computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that can be accessed by a computer, or a data storage device such as a server or data center that integrates one or more available media. Available media can include magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., DVDs), or semiconductor media (e.g., solid-state drives (SSDs)).

[0116] It will be understood that the various numerical numbers involved in the embodiments of the present application are merely distinctions for the convenience of description and are not intended to limit the scope of the embodiments of the present application.

[0117] It is easy for those skilled in the art to understand that the above is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A method for testing the hydrogen-induced cracking threshold of a notched round bar tensile specimen, characterized in that: include: S1: Under a hydrogen environment, a slow strain rate tensile test is performed on a notched round bar tensile specimen to obtain test data, wherein the test data includes yield strength, tensile strength, a first maximum displacement, engineering stress, and engineering strain, and a first elongation is obtained using the first maximum displacement and an original length of the notched round bar tensile specimen; under an inert gas environment, a slow strain rate tensile test is performed on the same notched round bar tensile specimen to obtain a second maximum displacement, and a second elongation is obtained using the second maximum displacement and the original length; S2 uses the first elongation and the second elongation to obtain the material hydrogen embrittlement sensitivity index; uses the material hydrogen embrittlement sensitivity index, the yield strength and the tensile strength to obtain the elastic-plastic parameter R, and obtains the elastic-plastic parameter R The formula is: in, R is the elastic-plastic parameter, is the yield strength, is the tensile strength, I HE is the material hydrogen embrittlement sensitivity index; S3 determines whether the elastic-plastic parameter R is greater than 3.

5. If so, the corresponding hydrogen-induced cracking threshold is obtained using the following formula: in, K IH is the hydrogen-induced cracking threshold, in MPa·m 0.5 , J IH is the J integral value of hydrogen-induced cracking, E Y is the elastic modulus of the material, v is the Poisson's ratio; if not, the corresponding hydrogen-induced cracking threshold is obtained using the following formula: in, K IH is the hydrogen-induced cracking threshold, in MPa·m 0.5 , P IH is the critical load for hydrogen-induced cracking, D is the original diameter of the notched round bar tensile specimen, F 1 is the first geometric function under the linear elastic crack growth mechanism.

2. The method for testing the hydrogen-induced cracking threshold value based on a notched round bar tensile specimen according to claim 1, wherein: In step S2, the formula for obtaining the material hydrogen embrittlement sensitivity index is expressed as: in, I HE is the material hydrogen embrittlement sensitivity index, δ H is the first elongation, δ 0 is the second elongation.

3. The method for testing the hydrogen-induced cracking threshold value based on a notched round bar tensile specimen according to claim 1, wherein: The notch stress concentration coefficient of the notched round bar tensile specimen is greater than or equal to 3.

4. The method for testing the hydrogen-induced cracking threshold value based on a notched round bar tensile specimen according to claim 1, wherein: The first geometric function is obtained by the following formula: in, D is the original diameter of the notched round bar tensile specimen; d is the notch diameter of the notched round bar tensile specimen.

5. The method for testing the hydrogen-induced cracking threshold value based on a notched round bar tensile specimen according to claim 1, wherein: The calculation formula of the hydrogen-induced cracking J integral value is: in, J IH is the J integral value of hydrogen-induced cracking, l 0 is the original length of the notched round bar tensile specimen; r 0 is the original radius of the notched round bar tensile specimen, F 2 is the second geometric function, P IH is the critical load for hydrogen-induced cracking, ∆l is the first maximum displacement.

6. The method for testing the hydrogen-induced cracking threshold value based on a notched round bar tensile specimen according to claim 5, wherein: The calculation formula of the second geometric function is: in, F 2 is the second geometric function under the elastic-plastic crack growth mechanism, where r is the notch radius of the notched round bar tensile specimen.

7. The method for testing the hydrogen-induced cracking threshold value based on a notched round bar tensile specimen according to claim 1 or 5, wherein: Obtain the hydrogen-induced cracking critical load P IH The steps include: S301 uses the engineering stress and engineering strain to obtain the true strain and true stress of the notched round bar tensile specimen; S302: drawing a true stress-true strain curve based on the true strain and true stress to fit the test data; S303 Based on the fitted test data, the actual strain corresponding to the strain hardening rate of 0 is obtained. , the actual strain The corresponding load is taken as the critical load for hydrogen-induced cracking P IH .

8. The method for testing the hydrogen-induced cracking threshold value based on a notched round bar tensile specimen according to claim 7, wherein: In step S301, the formula for obtaining the true stress is: in, is the engineering stress, For engineering strain, T is the true stress; The formula for obtaining the true strain is: in, For real strain.

9. The method for testing the hydrogen-induced cracking threshold value based on a notched round bar tensile specimen according to claim 7, wherein: In step S302, the test data is fitted into a fifth-order polynomial.

10. The method for testing the hydrogen-induced cracking threshold value based on a notched round bar tensile specimen according to claim 7, wherein: In step S303, the actual strain is obtained The method is: differentiate the fitted test data and draw curve graph, where , the strain hardening rate = 0 is taken as the true strain .

11. A testing system, characterized in that: For implementing the test method according to any one of claims 1 to 10, the test system comprises: a test data acquisition module, configured to acquire test data after a slow strain rate tensile test is performed on a notched round bar tensile specimen in a hydrogen environment, the test data including yield strength, tensile strength, first maximum displacement, engineering stress, and engineering strain, and to acquire a first elongation using the first maximum displacement and the original length of the notched round bar tensile specimen; and to acquire a second maximum displacement corresponding to a slow strain rate tensile test performed on the same notched round bar tensile specimen in an inert gas environment, and to acquire a second elongation using the second maximum displacement and the original length; A sample parameter acquisition module is used to obtain a material hydrogen embrittlement sensitivity index using the first elongation and the second elongation; and to obtain an elastic-plastic parameter R using the material hydrogen embrittlement sensitivity index, the yield strength, and the tensile strength; The hydrogen-induced cracking threshold value acquisition module is used to determine whether the elastic-plastic parameter R is greater than 3.

5. If so, it is also used to obtain the hydrogen-induced cracking threshold value based on the elastic-plastic crack growth mechanism; if not, it is also used to obtain the hydrogen-induced cracking threshold value based on the linear elastic crack growth mechanism.

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