Hydrogen induced cracking threshold value testing method and system based on notched round rod tensile sample

Abstract

The invention belongs to the field of material testing, and discloses a method and a system for testing a hydrogen-induced cracking threshold value based on a notched round rod tensile sample, the testing method comprises the following steps: in a hydrogen environment and an inert gas environment, respectively carrying out a slow strain rate tensile test on the notched round rod tensile sample to obtain test data and two elongation rates; the hydrogen embrittlement sensitivity index of the material is obtained through the two elongation rates; acquiring elastic-plastic parameters by using the hydrogen embrittlement sensitivity index of the material and test data; when the elastic-plastic parameter is greater than 3.5, acquiring a hydrogen induced cracking threshold value by adopting an elastic-plastic crack propagation mechanism; and when the elastic-plastic parameter is not greater than 3.5, a hydrogen induced cracking threshold value is obtained by adopting a linear elastic crack propagation mechanism. The test method is short in period, high in efficiency and high in universality.

Description

Technical Field

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

[0002] Hydrogen transport by pipeline is currently the main method of hydrogen energy transmission, but hydrogen can damage pipeline materials, thereby restricting the improvement of material performance and endangering the safe and stable operation of equipment. Among them, hydrogen induced cracking (HIC) is particularly significant. Hydrogen induced cracking refers to the initiation of microcracks inside the material due to the penetration and aggregation of hydrogen atoms under stress below the conventional strength limit in a hydrogen environment. These cracks gradually expand under continuous stress and eventually lead to the overall fracture of the material. This phenomenon is difficult to predict, and the material performance degrades sharply during the fracture process, posing a major 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 material failure. 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 extend 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 test cycles (for pipeline steel, it often takes weeks to months for cracks to stop expanding), and large differences in test results between different laboratories, which limits repeatability. Summary of the invention

[0005] In view of the defects of the prior art, the purpose of this application is to provide a method and system for testing the hydrogen-induced cracking threshold value based on a notched round rod tensile specimen, 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 test method for the hydrogen-induced cracking threshold value of a notched round bar tensile specimen, comprising: 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, first maximum displacement, engineering stress and engineering strain, and a first elongation is obtained by 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 same notched round bar tensile specimen to obtain a second maximum displacement, and a second elongation is obtained by using the second maximum displacement and the original length; S2 uses the first elongation and the second elongation to obtain a material hydrogen embrittlement sensitivity index; uses the material hydrogen embrittlement sensitivity index, the yield strength and the tensile strength to obtain elastic-plastic parameters; S3 determines whether the elastic-plastic parameter R is greater than 3.5. If so, the hydrogen-induced cracking threshold value is obtained based on the elastic-plastic crack growth mechanism; if not, the hydrogen-induced cracking threshold value is obtained based on the linear elastic crack growth mechanism.

[0007] Further, in step S2, the formula for obtaining the material hydrogen embrittlement sensitivity index is expressed as:

[0008] in, I HE is the material hydrogen embrittlement sensitivity index, δ H is the first elongation, δ 0 is the second elongation.

[0009] Furthermore, the notch stress concentration coefficient of the notched round bar tensile specimen is greater than or equal to 3.

[0010] Furthermore, in step S2, the formula for obtaining the elastic-plastic parameters is expressed as:

[0011] 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.

[0012] Furthermore, in step S3, the elastic-plastic parameter R When it is not greater than 3.5, the hydrogen-induced cracking threshold is obtained using the following formula:

[0013] in, KIH 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.

[0014] Furthermore, the first geometric function is obtained by the following formula:

[0015] 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.

[0016] Furthermore, in step S3, the elastic-plastic parameter R When it is greater than 3.5, the corresponding hydrogen-induced cracking threshold is obtained using the following formula:

[0017] 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.

[0018] Furthermore, the calculation formula of the hydrogen-induced cracking J integral value is:

[0019] 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.

[0020] Furthermore, the calculation formula of the second geometric function is:

[0021] in, F2 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.

[0022] Furthermore, the hydrogen-induced cracking critical load is obtained. 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 the 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 .

[0023] Furthermore, in step S301, the formula for obtaining the true stress is:

[0024] in, is the engineering stress, For engineering strain, T is the true stress; And / or, in step S301, the formula for obtaining the true strain is:

[0025] in, For real strain; And / or, in step S302, fitting the test data into a fifth-order polynomial; And / or, in step S303, obtaining the actual strain The method is: differentiate the fitted test data and draw The curve diagram, where , the strain hardening rate = 0 is taken as the true strain .

[0026] According to another aspect of the present application, a test system is provided for implementing the test method as described in any one of the above items, and the test system includes: A test data acquisition module is used 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, 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 extension mechanism; if not, it is also used to obtain the hydrogen-induced cracking threshold value based on the linear elastic crack extension mechanism.

[0027] Compared with the prior art, the above technical solution conceived by this application has the following beneficial effects: 1. Compared with traditional methods, the test method provided in this application is more convenient and flexible, with fewer restrictions and a short test cycle, and 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, and has the advantages of high material utilization, low material cost, simple specimen processing and easy implementation of the test method.

[0028] 2. The test method provided in this application is based on a slow strain rate tensile test to explore the fracture mechanics properties. By performing a slow strain rate tensile test on the same notched round bar tensile specimen under two environments, the test data is obtained to calculate the hydrogen-induced cracking threshold value, which significantly shortens the test cycle. In addition, notches are designed in specific areas of the notched round bar tensile specimen, so that narrow areas such as the weld and heat-affected zone of the welded joint can be accurately studied. The obtained test data can also effectively evaluate the hydrogen embrittlement sensitivity of the material, calculate the elastoplastic parameters based on the hydrogen embrittlement sensitivity index of the material, and then use the elastoplastic parameters to obtain the hydrogen-induced cracking threshold value, and the calculation results are more accurate.

[0029] 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, with high repeatability and greater universal applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a flow chart of the testing method provided in the embodiment of the present application.

[0031] 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.

[0032] Figure 3 is the θ-ε provided in the embodiment of the present application T Graph.

[0033] Figure 4 This is a comparison chart of hydrogen-induced cracking threshold values ​​of different test methods provided in the embodiments of the present application. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0035] In the description of the present application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the feature. In the description of the present application, "plurality" means two or more, unless otherwise clearly and specifically defined.

[0036] In addition, references throughout this specification to "one embodiment"; "one embodiment", "an example" or similar language indicate that a particular feature, structure, or characteristic described in conjunction 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.

[0037] The present application embodiment provides a method for testing the hydrogen-induced cracking threshold value based on a notched round bar tensile specimen, such as Figure 1 As shown, the test method includes the following steps: S1 In 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, and the first elongation is obtained by using the first maximum displacement and the original length of the notched round bar tensile specimen; In an inert gas environment, a slow strain rate tensile test is performed on a notched round bar tensile specimen to obtain a second maximum displacement, and the second elongation is obtained by 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, yield strength and tensile strength to obtain elastic-plastic parameters R ; 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.

[0038] 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 20mm, the gauge section of the specimen needs to be measured with an extensometer, and the specimen needs to be placed in a hydrogen environment for 2 hours at the beginning of the test.

[0039] In step S2, the formula for obtaining the material hydrogen embrittlement sensitivity index is expressed as: (1) in, I HE is the material hydrogen embrittlement sensitivity index, δ H is the first elongation, δ 0 is the second elongation.

[0040] The formula for obtaining elastic-plastic parameters is expressed as: (2) in, R is the elastic-plastic parameter, is the yield strength, in MPa, and is defined as the elongation strength when the non-proportional elongation is 0.2%; is the tensile strength, in MPa; I HE It is the material hydrogen embrittlement sensitivity index.

[0041] 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: (3) 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.

[0042] The calculation formula of the aforementioned first geometric function is: (4) 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 ; In step S3, when the elastic-plastic parameter R When it is greater than 3.5, it is an elastic-plastic crack extension mechanism, and the formula for calculating the hydrogen-induced cracking threshold is: (5) 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 0.3 for metal materials.

[0043] The calculation formula for the aforementioned hydrogen-induced cracking J integral value is: (6) J IH is 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.

[0044] The second geometric function F 2 The calculation formula is: (7) 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.

[0045] Under the two mechanisms in step S3, the specific steps of obtaining the aforementioned hydrogen-induced cracking critical load include: S301 uses engineering stress and engineering strain to obtain the true strain and true stress of notched round bar tensile specimens; S302 draws a true stress-true strain curve based on the true strain and the 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 of hydrogen-induced cracking.

[0046] In step S301, the formula for obtaining the true stress is: (8) in, is the engineering stress, For engineering strain, T is the true stress; The formula for obtaining the true strain is: (9) in, For real strain.

[0047] In step S302, the test data is fitted into a fifth-order polynomial. Specifically, the true stress-true strain curve is drawn by using the origin software, and then the polynomial is fitted to the experimental data. The order of the fitted polynomial is 5th order.

[0048] In step S303, the real strain is obtained The method is to differentiate the fitted test data and plot it using the origin software 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 .

[0049] In a more preferred embodiment, the aforementioned steps S1-S3 may be repeated at least three times to obtain at least three groups of hydrogen-induced cracking threshold values, and the average value of the multiple groups of hydrogen-induced cracking threshold values ​​is calculated as the final hydrogen-induced cracking threshold value.

[0050] The following comparative tests are conducted using the test method of the present invention and the conventional compliance unloading test method, respectively, with X65 pipeline steel as the test object.

[0051] Sample processing drawings of X65 pipeline steel are as follows Figure 2 As shown, the yield strength of the welded joint is 464 MPa, the tensile strength is 540 MPa, and multiple specimens are obtained.

[0052] The corresponding samples were tested at 25℃ and 5 different atmospheres using the traditional flexibility unloading test method and the slow strain rate tensile method (SSRT) respectively, and 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 the present application IH(SSRT) The aforementioned atmosphere is pure N 2 atmosphere, and 4 different component ratios of N 2 and H 2 The mixed atmosphere, the hydrogen content of the mixed atmosphere is 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.

[0053] Table 1 Hydrogen induced cracking threshold Test results

[0054] Figure 3 Indicates the θ-ε obtained using the test method of this application T The curve diagram shows that the true strain corresponding to the strain hardening rate of 0 is obtained in this diagram, 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 by 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.

[0055] Another embodiment of the present application further provides a test system for implementing any of the above test methods, the test system comprising: A test data acquisition module is used 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 elastic-plastic parameters using the material hydrogen embrittlement sensitivity index, yield strength and tensile strength; 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.

[0056] It can be understood that the detailed functional implementation of each of the above-mentioned units / modules can be found in the introduction of the aforementioned method embodiment, and will not be repeated here.

[0057] 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, its implementation principle and technical effect are similar to the description in the above-mentioned method. The working process of the device can refer to the corresponding process in the above-mentioned method, which will not be repeated here.

[0058] Based on the method in the above embodiment, an embodiment of the present application provides 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 program stored in the memory is executed, the processor is used to execute the method described in the above embodiment.

[0059] 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.

[0060] 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.

[0061] It is understandable that the processor in the embodiment of the present application may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or 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.

[0062] 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, and the software modules 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, mobile 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 a component of the processor. The processor and the storage medium can be located in an ASIC.

[0063] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on the computer, the process or function according to the embodiment of the present application is 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 through a computer-readable storage medium. The computer instructions can be transmitted from a website site, a computer, a server or a data center to another website site, a computer, a server or a data center by 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 a computer can access or a data storage device such as a server or a data center that includes one or more available media integrated. The available medium can be a magnetic medium (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., a solid-state drive (SSD)), etc.

[0064] It should be understood that the various numerical numbers involved in the embodiments of the present application are only used for the convenience of description and are not used to limit the scope of the embodiments of the present application.

[0065] It will be easily understood by those skilled in the art that the above description 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 shall be included in the scope of protection of the present application.

Claims

1. A test method for the hydrogen-induced cracking threshold value based on 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, first maximum displacement, engineering stress and engineering strain, and a first elongation is obtained by 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 same notched round bar tensile specimen to obtain a second maximum displacement, and a second elongation is obtained by using the second maximum displacement and the original length; S2: obtaining a material hydrogen embrittlement sensitivity index using the first elongation and the second elongation; and obtaining an elastic-plastic parameter R using the material hydrogen embrittlement sensitivity index, the yield strength and the tensile strength; S3 determines whether the elastic-plastic parameter R is greater than 3.

5. If so, the hydrogen-induced cracking threshold value is obtained based on the elastic-plastic crack growth mechanism; if not, the hydrogen-induced cracking threshold value is obtained based on 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, characterized in that: 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; And / or, the notch stress concentration factor of the notched round bar tensile specimen is greater than or equal to 3.

3. The method for testing the hydrogen-induced cracking threshold value based on a notched round bar tensile specimen according to claim 1, characterized in that: In step S2, the elastic-plastic parameters are obtained. R The formula is expressed as: 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.

4. The method for testing the hydrogen-induced cracking threshold value based on a notched round bar tensile specimen according to claim 1, characterized in that: In step S3, when the elastic-plastic parameter R is not greater than 3.5, the 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, F 1 is the first geometric function under the linear elastic crack growth mechanism.

5. The method for testing the hydrogen-induced cracking threshold value based on a notched round bar tensile specimen according to claim 4, characterized in that: 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.

6. The method for testing the hydrogen-induced cracking threshold value based on a notched round bar tensile specimen according to claim 1, characterized in that: 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: 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.

7. The method for testing the hydrogen-induced cracking threshold value based on a notched round bar tensile specimen according to claim 6, characterized in that: 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.

8. The method for testing the hydrogen-induced cracking threshold value based on the notched round bar tensile specimen according to claim 7, characterized in that: 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.

9. The method for testing the hydrogen-induced cracking threshold value based on a notched round bar tensile specimen according to claim 4 or 7, characterized in that: 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 the 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 ; And / or, in step S301, the formula for obtaining the true stress is: in, is the engineering stress, For engineering strain, T is the true stress; And / or, in step S301, the formula for obtaining the true strain is: in, For real strain; And / or, in step S302, fitting the test data into a fifth-order polynomial; And / or, in step S303, obtaining the actual strain The method is: differentiate the fitted test data and draw The curve diagram, where , the strain hardening rate = 0 is taken as the true strain .

10. A testing system, characterized in that: Used to implement the test method according to any one of claims 1 to 9, the test system comprises: A test data acquisition module is used 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, 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 extension mechanism; if not, it is also used to obtain the hydrogen-induced cracking threshold value based on the linear elastic crack extension mechanism.

Images