Method for testing hydrogen induced cracking of material in high-pressure hydrogen environment

Abstract

The invention relates to the technical field of material testing, and discloses a method for testing hydrogen induced cracking of a material in a high-pressure hydrogen environment, which comprises the following steps: firstly, preparing an extended compact tensile sample based on size data of a standard wedge-shaped opening loading sample and a standard compact tensile sample; then carrying out fatigue crack prefabrication on the extended compact tensile sample through a fatigue testing machine, and carrying out shape conversion to obtain a standard wedge-shaped opening loading sample with fatigue cracks, and taking the standard wedge-shaped opening loading sample as a target wedge-shaped opening loading sample; applying a load to the tail end of the fatigue crack on the target wedge-shaped opening loading sample, and placing the target wedge-shaped opening loading sample in a high-pressure hydrogen environment to determine the length of the current hydrogen-induced crack; and finally, determining a stress intensity factor threshold value of the to-be-tested material according to the initial applied stress intensity factor, the current hydrogen-induced crack length and the standard value of the hydrogen-induced crack length. According to the method, not only can a more accurate hydrogen-induced delayed cracking stress intensity factor threshold value be obtained, but also the test cost can be effectively reduced.

Description

Technical Field

[0001] The present application relates to the technical field of material testing, and in particular to a method for testing hydrogen-induced cracking of materials in a high-pressure hydrogen environment. Background Art

[0002] Hydrogen-induced cracking (HIC) is a brittle fracture phenomenon in metallic materials caused by the adsorption, diffusion, and localized enrichment of hydrogen atoms in a hydrogen environment. Essentially, hydrogen reduces the fracture toughness of the material and promotes crack nucleation and propagation. In high-pressure hydrogen environments (such as hydrogen storage vessels and hydrogen pipelines), HIC has become a key risk factor for material failure in service.

[0003] The hydrogen-induced delayed cracking stress intensity factor threshold value is an important fracture mechanics performance parameter of hydrogen-resistant materials. This parameter can characterize the material's ability to resist hydrogen-induced cracking in a high-pressure hydrogen environment. It can be used as a basis for screening hydrogen-resistant materials and as basic data for calculating the fatigue life of hydrogen-resistant components based on fracture mechanics methods. In related technologies, a certain initial load is applied to a pre-cracked specimen, and then it is placed in a high-pressure hydrogen environment for testing. The hydrogen-induced delayed cracking stress intensity factor threshold value is obtained based on the test results. However, the accuracy of the hydrogen-induced delayed cracking stress intensity factor threshold value measured in related technologies needs to be improved. Therefore, it is urgent to propose a new testing method. Summary of the Invention

[0004] The present application provides a method for testing hydrogen-induced cracking of materials in a high-pressure hydrogen environment, which solves the technical problem in the related art that the accuracy of the stress intensity factor threshold value of hydrogen-induced delayed cracking needs to be improved, and achieves the technical effect of being able to obtain a more accurate stress intensity factor threshold value.

[0005] In order to achieve the above objectives, the main technical solutions adopted in this application include: The present invention provides a method for testing hydrogen-induced cracking of materials in a high-pressure hydrogen environment. The method comprises: Determining an expanded dimension that meets the installation requirements of a fatigue testing machine based on the dimensional data of a standard wedge-shaped open loading specimen and the dimensional data of a standard compact tensile specimen, and preparing an expanded compact tensile specimen of the material to be tested based on the expanded dimension; wherein the material to be tested is a material intended for use in a hydrogen storage container or a structural component of a hydrogen energy device in a high-pressure hydrogen environment; Prefabricate fatigue cracks on the expanded compact tensile specimen using the fatigue testing machine to obtain an expanded compact tensile specimen having fatigue cracks; Transforming the expanded compact tensile specimen with fatigue cracks to obtain a standard wedge-shaped open loading specimen with fatigue cracks as a target wedge-shaped open loading specimen; Applying a load to the end of a fatigue crack on the target wedge-shaped open-loaded specimen, and placing the loaded target wedge-shaped open-loaded specimen in a high-pressure hydrogen environment to determine a current hydrogen-induced crack length; wherein the load is an initially applied stress intensity factor, and the initially applied stress intensity factor is determined based on an estimated stress intensity factor threshold value; The stress intensity factor threshold value of the material to be tested is determined according to the initial applied stress intensity factor corresponding to the target wedge-shaped open loading specimen, the current hydrogen-induced crack length, and the standard value of the hydrogen-induced crack length.

[0006] Optionally, the initial applied stress intensity factor corresponding to the target wedge-shaped open-loaded specimen adopts the initial applied stress intensity factor of the target specimen group to which the target wedge-shaped open-loaded specimen belongs; and determining the stress intensity factor threshold value of the material to be tested based on the initial applied stress intensity factor corresponding to the target wedge-shaped open-loaded specimen, the current hydrogen-induced crack length, and the standard value of the hydrogen-induced crack length includes: If the target sample group is determined to meet the preset requirements based on the current hydrogen-induced crack length and the standard value of the hydrogen-induced crack length, a stress intensity factor threshold value of the material to be tested is determined based on the initial applied stress intensity factor corresponding to the target sample group.

[0007] Optionally, the target sample group includes a plurality of target wedge-shaped open loading samples; and whether the target sample group meets the preset requirement is determined by the following method: determining a current hydrogen-induced crack length of the target sample group based on the hydrogen-induced crack length of each target wedge-shaped open-loaded sample; The current hydrogen-induced crack length of the target sample group is compared with a standard value of the hydrogen-induced crack length, and based on the comparison result, it is determined that the target sample group meets the preset requirement.

[0008] Optionally, determining whether the target sample group meets the preset requirement based on the comparison result includes: When the current hydrogen-induced crack length is less than or equal to the standard value and the difference data between the current hydrogen-induced crack length and the standard value meets the preset difference requirement, it is determined that the target sample group meets the preset requirement.

[0009] Optionally, the target wedge-shaped open-loaded specimen belongs to a target specimen group, and the target specimen group corresponds to an initially applied stress intensity factor; applying a load to a fatigue crack end of the target wedge-shaped open-loaded specimen and placing the loaded target wedge-shaped open-loaded specimen in a high-pressure hydrogen environment comprises: According to the initial applied stress intensity factor corresponding to the target sample group, a load is applied to the fatigue crack end of each target wedge-shaped open-loaded sample in the target sample group, and each target wedge-shaped open-loaded sample with the applied load is placed in a high-pressure hydrogen environment to determine the current hydrogen-induced crack length corresponding to the target sample group.

[0010] Optionally, the initial applied stress intensity factor corresponding to the target wedge-shaped open-loaded specimen adopts the initial applied stress intensity factor of the target specimen group to which the target wedge-shaped open-loaded specimen belongs; the target specimen group is determined by: Providing a plurality of initial specimen groups; wherein each initial specimen group includes a plurality of target wedge-shaped open-loaded specimens having fatigue cracks; determining an initial applied stress intensity factor for any initial set of specimens between a first stress intensity factor threshold and a second stress intensity factor threshold; performing a hydrogen-induced cracking test on each target wedge-shaped open-loaded specimen in any of the initial specimen groups according to the initial applied stress intensity factor of any of the initial specimen groups, to obtain a current hydrogen-induced crack length corresponding to the any of the initial specimen groups; The target sample group is determined from the multiple initial sample groups according to the current hydrogen-induced crack length corresponding to any one of the initial sample groups and the standard value of the hydrogen-induced crack length.

[0011] Optionally, applying a load to the fatigue crack end of the target wedge-shaped open loading specimen includes: Obtaining a stress intensity factor threshold estimate value of the material to be tested; wherein the stress intensity factor threshold estimate value is used to characterize an estimation of a hydrogen-induced delayed cracking stress intensity factor threshold value; determining the initially applied stress intensity factor of the material to be tested; A constant displacement method is used to apply load to the fatigue crack end of the target wedge-shaped open loading specimen.

[0012] Optionally, obtaining a stress intensity factor threshold estimate value of the material to be tested includes: The stress intensity factor threshold value of the material to be tested is estimated according to the relationship between the yield strength of the material and the stress intensity factor threshold value to obtain the stress intensity factor threshold estimated value.

[0013] Optionally, the fatigue testing machine has a matching U-shaped clamp, and the fatigue crack prefabrication of the expanded compact tensile specimen by the fatigue testing machine to obtain the expanded compact tensile specimen with fatigue cracks includes: clamping the expanded compact tensile specimen using the U-shaped clamp; Adjusting the Young's modulus in a fatigue testing machine; wherein the fatigue testing machine before adjustment is used to perform fatigue crack prefabrication on a standard compact tensile specimen; Fatigue crack prefabrication is performed on the expanded compact tensile specimen by using the adjusted fatigue testing machine.

[0014] Optionally, the step of converting the extended compact tensile specimen with fatigue cracks to obtain a standard wedge-shaped open loading specimen with fatigue cracks as a target wedge-shaped open loading specimen comprises: The expanded compact tensile specimen with fatigue cracks is machined to adjust its length to a target length that meets the requirements of the standard wedge-shaped open loading specimen, and the flat pin holes and threaded holes required by the standard wedge-shaped open loading specimen are machined; wherein, during the machining of the threaded holes, a shock-absorbing component needs to be added at the machined cracks.

[0015] In the embodiment of the present application, first, based on the dimensional data of the standard wedge-shaped open loading specimen and the standard compact tensile specimen, the expanded size that meets the installation requirements of the fatigue testing machine is determined, and based on the expanded size, the expanded compact tensile specimen of the material to be tested is prepared, thereby realizing the use of the existing fatigue testing machine for prefabrication of fatigue cracks of the compact tensile specimen to prefabricate fatigue cracks. After the prefabrication is completed, the specimen is processed into the target wedge-shaped open loading specimen, and there is no need to introduce new equipment for prefabrication of fatigue cracks of the wedge-shaped open loading specimen. Compared with the three-point bending specimen used in the related art, the expanded compact tensile specimen can not only greatly reduce the fatigue cracks of the material to be tested, but also greatly reduce the fatigue cracks of the material to be tested. Consumption can also be reduced by using existing fatigue testing machines to prefabricate fatigue cracks, thereby effectively saving testing costs in two aspects; then, the load is determined according to the estimated value of the stress intensity factor threshold, and a load is applied to the fatigue crack end of the target wedge-shaped open-loaded specimen to perform a hydrogen-induced crack test. According to the initial applied stress intensity factor, the current hydrogen-induced crack length and the standard value of the hydrogen-induced crack length corresponding to the target wedge-shaped open-loaded specimen, the stress intensity factor threshold value of the material to be tested is determined. Compared with related technologies, determining the initial applied stress intensity factor based on the estimated value of the stress intensity factor threshold can obtain a more accurate stress intensity factor threshold value. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the specific implementation methods or the description of the prior art. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0017] Figure 1aA flow chart of a method for testing hydrogen-induced cracking of materials under high-pressure hydrogen conditions provided in an embodiment of this specification; Figure 1b A schematic diagram of the structure of a standard wedge-shaped open loading specimen provided in the embodiments of this specification; Figure 1c A schematic diagram of the structure of an extended compact tensile specimen provided in an embodiment of this specification; Figure 2 A flow chart of a method for testing hydrogen-induced cracking of materials under high-pressure hydrogen conditions provided in an embodiment of this specification; Figure 3 A flow chart of a method for testing hydrogen-induced cracking of materials under high-pressure hydrogen conditions provided in an embodiment of this specification; Figure 4 A flow chart of a method for testing hydrogen-induced cracking of materials under high-pressure hydrogen conditions provided in an embodiment of this specification; Figure 5 This is a flow chart of a method for testing hydrogen-induced cracking of materials in a high-pressure hydrogen environment provided in an embodiment of this specification. DETAILED DESCRIPTION

[0018] To make the purpose, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative efforts shall fall within the scope of protection of this application.

[0019] Hydrogen-induced cracking is one of the key risk factors that lead to service failure of materials. Therefore, when designing hydrogen containers, it is necessary to test the material's resistance to hydrogen embrittlement in a high-pressure hydrogen environment. The ASME BPVC KD10 standard stipulates that the material's suitability for hydrogen environments can be determined by testing the material's hydrogen-induced delayed cracking stress intensity factor threshold. The current common testing process is to apply a certain initial load to the wedge-shaped open loading (WOL) specimen, and then place it in a high-pressure hydrogen environment for a period of time. After reaching the specified test time, the specimen is removed and its crack extension is measured. The hydrogen-induced delayed cracking stress intensity factor threshold K of the material is determined by the crack extension. IH In the related art, fatigue cracks are first prefabricated using a three-point bending specimen, and then the three-point bending specimen is processed into a wedge-shaped open loading specimen. However, the initial processing of the three-point bending specimen requires the consumption of several times the material to be tested than the target specimen, resulting in high consumption of the material to be tested and high testing costs. Furthermore, the ASME BPVCKD10 standard only specifies the initial applied stress intensity factor (K IAPP ) can be set within the range, which means that any K selected within the defined range IAPPThe values ​​can be regarded as reasonable experimental conditions. For the same material and test environment, different people may obtain different K values ​​by setting different initial applied stress intensity factors. IH values, and the difference is large. However, K IH The ability of a material to resist hydrogen-induced cracking in a high-pressure hydrogen environment is inherent to the material and should not be altered by loading conditions. This artificial dependence seriously violates the theoretical framework of fracture mechanics and may mislead engineering material selection. For example, overestimating the suitability of high-strength steel in hydrogen environments may lead to potential structural failure risks.

[0020] Based on this, the present application provides a method for testing hydrogen-induced cracking of materials in a high-pressure hydrogen environment, the method comprising: first, determining the expanded dimensions that meet the installation requirements of the fatigue testing machine based on the dimensional data of the standard wedge-shaped open loading specimen and the dimensional data of the standard compact tensile specimen, and preparing an expanded compact tensile specimen of the material to be tested based on the expanded dimensions; then, performing fatigue crack prefabrication on the expanded compact tensile specimen through the fatigue testing machine to obtain an expanded compact tensile specimen with fatigue cracks; then, performing shape conversion on the expanded compact tensile specimen with fatigue cracks to obtain a standard wedge-shaped open loading specimen with fatigue cracks as the target wedge-shaped open loading specimen. By using the above method, compared with the related art, the consumption of the material to be tested can be significantly reduced, thereby reducing the testing cost.

[0021] Furthermore, when conducting hydrogen-induced cracking tests, first, multiple initial sample groups are provided; wherein each initial sample group includes multiple target wedge-shaped open-loaded samples with fatigue cracks; then, the initial applied stress intensity factor of any initial sample group is determined between a first stress intensity factor threshold and a second stress intensity factor threshold; then, a hydrogen-induced cracking test is performed on each target wedge-shaped open-loaded sample in any initial sample group according to the initial applied stress intensity factor of any initial sample group, and the current hydrogen-induced crack length corresponding to any initial sample group is obtained; finally, a target sample group is determined from the multiple initial sample groups according to the current hydrogen-induced crack length corresponding to any initial sample group and the standard value of the hydrogen-induced crack length, and the hydrogen-induced delayed cracking stress intensity factor threshold value of the material to be tested is determined according to the test data of the target sample group. Through the above method, the target sample group whose current hydrogen-induced crack length is closest to the standard value can be obtained, and the accurate hydrogen-induced delayed cracking stress intensity factor threshold value can be determined based on the initial applied stress intensity factor corresponding to the group, which effectively solves the problem that the accuracy of the potential hydrogen-induced delayed cracking stress intensity factor threshold value in the ASMEBPVC KD10 standard needs to be improved.

[0022] According to an embodiment of the present application, an embodiment of a method for testing hydrogen-induced cracking of materials in a high-pressure hydrogen environment is provided. It should be noted that although a logical sequence is shown in the flow chart, in some cases, the steps shown or described may be performed in an order different from that shown here.

[0023] This embodiment provides a method for testing hydrogen-induced cracking of materials in a high-pressure hydrogen environment. Figure 1a , the method comprising: S110. Determine an expanded dimension that meets the installation requirements of the fatigue testing machine based on the dimensional data of the standard wedge-shaped open loading specimen and the dimensional data of the standard compact tensile specimen, and prepare an expanded compact tensile specimen of the material to be tested based on the expanded dimension.

[0024] Among them, the dimensional data of the standard wedge-shaped open loading specimen may be the dimensional data specified in the ASTM E1681 standard. The dimensional data of the standard compact tensile specimen may be the dimensional data specified in the ASTM E399 standard. The expanded size may refer to the size of the standard wedge-shaped open loading specimen adjusted according to the standard compact tensile specimen dimensional data. The fatigue testing machine may be an MTS fatigue testing machine suitable for testing standard compact tensile specimens, which can perform fatigue crack prefabrication on standard compact tensile specimens according to the ASTM E399 standard, etc. It is a commonly used equipment for fatigue crack prefabrication, and there are many of them at present. The present application uses this equipment to achieve fatigue crack prefabrication of wedge-shaped open loading specimens, thereby eliminating the need to introduce new equipment for fatigue crack prefabrication of wedge-shaped open loading specimens. The material to be tested is a certain material intended for use in hydrogen storage containers or hydrogen energy equipment structural parts in a high-pressure hydrogen environment.

[0025] In some embodiments, see Figure 1b , Figure 1b The figure shows a standard wedge-shaped open loading specimen. The first direction in the figure is parallel to the machined crack, and the second direction is perpendicular to the first direction. The dimensional data of the standard wedge-shaped open loading specimen are: The width (from the center line of the screw hole to the back of the specimen) is W, and along the first direction, the error is ±0.005W; The distance from the center line of the screw hole to the end of the machining crack is a, along the first direction; The total width of the specimen is 1.255W, and along the first direction, the error is ±0.005W; The thickness B is 0.5W, and along the first direction, the error is ±0.01W; The distance from the crack center to the bottom of the specimen is 0.486W, and along the second direction, the error is ±0.005W; The distance from the center plane of the flat pin to the center plane of the crack is 0.1W, and along the second direction, the error is ±0.005W; The diameter of the flat pin hole is 0.25W, and the error is ±0.005W; The diameter of the screw hole is 0.25W; The side groove is a V-shaped groove structure with an opening angle of 53±2°, and the groove depth is precisely controlled within the range of 10±0.5% of the sample thickness.

[0026] It should be noted that when preparing the expanded compact tensile specimen, it is based on the above-mentioned dimensional data of the standard wedge-shaped open loading specimen, but does not include the data of the screw hole and the flat pin hole. In this case, there is no need to process the above-mentioned two holes. It should also be noted that the expanded size is the size expanded in the second direction, that is, the length direction of the standard wedge-shaped open loading specimen. The purpose is to have space on the specimen to process two symmetrical loading holes of the standard compact tensile specimen, so that fatigue cracks can be prefabricated on the expanded compact tensile specimen through a fatigue testing machine. The size of the loading hole is consistent with the dimensional data of the standard compact tensile specimen, and the distance from the center line of the loading hole to the end of the machined crack is a. For example, please refer to Figure 1c , Figure 1c This is an extended compact tensile specimen. The first direction in the figure is parallel to the machining crack, and the second direction is perpendicular to the first direction. The dimensional data are: The width (from the center line of the screw hole to the back of the specimen) is W, and along the first direction, the error is ±0.005W; The total width of the specimen is 1.255W, and along the first direction, the error is ±0.005W; The thickness B is 0.5W, and along the first direction, the error is ±0.01W; The distance from the center line of the loading hole to the end of the machined crack is a, along the first direction; The distance from the center line of the loading hole to the center plane of the crack is 0.714W, and along the second direction, the error is ±0.005W; The distance from the center plane of the extended crack to the bottom of the specimen is 0.942W, and along the second direction, the error is ±0.005W; The loading hole diameter is 0.25W.

[0027] It should be noted that, from the above-mentioned dimensional data, it can be concluded that the thickness and width of the test material used in the expanded compact tensile specimen are the same as those of the standard wedge-shaped open-loaded specimen, and the length is less than twice that of the standard wedge-shaped open-loaded specimen, that is, the material consumption is less than twice that of the standard wedge-shaped open-loaded specimen. Compared with the use of three-point bending specimens in related technologies, which requires several times more test materials than the standard wedge-shaped open-loaded specimen, the consumption of test materials is significantly reduced.

[0028] In some embodiments, when sampling from the material to be tested, the specimen should be oriented in the TL direction, i.e., the normal to the specimen fracture surface is oriented transversely for plate materials or circumferentially for tubular products, and the expected crack propagation direction is oriented in the direction of maximum grain flow, or longitudinally for the plate or tubular product. For weld metal and the heat-affected zone of welded joints, LT specimens may be used if TL specimens are unavailable from the material to be tested.

[0029] S120. Prefabricate fatigue cracks on the expanded compact tensile specimen using a fatigue testing machine to obtain an expanded compact tensile specimen having fatigue cracks.

[0030] In some embodiments, the surface of the expanded compact tensile specimen is first degreased and derusted, and the crack surface and side grooves are cleaned. Then, the specimen is clamped to a fatigue testing machine using a U-clamp, and fatigue cracks are preformed using a sinusoidal loading waveform with a stress ratio of 0.1 and 20 Hz. The ratio of the preformed initial crack length a0 (the distance from the fatigue crack terminal to the loading centerline) to the specimen width W, a0 / W, is controlled between 0.45 and 0.55.

[0031] Specifically, the stress intensity factor threshold of the material being tested is first estimated to obtain an estimated stress intensity factor threshold value. During fatigue crack prefabrication, the maximum stress intensity factor (Kmax) should be controlled to not exceed 80% of the estimated stress intensity factor threshold value. Furthermore, during the final 1 mm of fatigue pre-crack formation, the maximum stress intensity factor (Kmax) should not exceed 60% of the estimated stress intensity factor threshold value. Then, because the MTS fatigue testing machine uses force control, the maximum stress intensity factor (Kmax) needs to be converted into the force that the fatigue testing machine should apply, according to the formula for CT specimens in ASTM E399: Where B is the thickness of the expanded compact tensile specimen, B N is the net thickness of the side-grooved specimen (the distance between the lowest points of the grooves on either side), W is the specimen width, a is the distance from the centerline of the loading hole to the end of the machined crack (also known as the machined crack length), K is the stress intensity factor, and P is the force applied by the fatigue testing machine. The compliance method can be used to measure crack length during prefabrication.

[0032] It should be noted that before fatigue crack formation, the machined crack length must be checked using an MTS fatigue testing machine, and the Young's modulus of the material being tested must be adjusted to offset the effects of specimen lengthening. Specifically, an elastic tensile test can be performed by applying a small force to an expanded compact tensile specimen. The Young's modulus is then adjusted based on the machined crack length measured by the MTS fatigue testing machine, ensuring that the deviation between the manually measured value and the MTS fatigue testing machine value is less than 0.02 mm.

[0033] It should also be noted that the MTS fatigue testing machine is a commonly used device for prefabricating fatigue cracks in CT specimens and is easily available. In the related art, there is also a new type of equipment specifically used for prefabricating fatigue cracks in WOL specimens. Obviously, through the method of the embodiment of the present application, technicians in this field can use existing equipment to prefabricate fatigue cracks in WOL specimens without purchasing new dedicated equipment, thereby greatly reducing the testing cost.

[0034] S130. Transforming the extended compact tensile specimen with fatigue cracks to obtain a standard wedge-shaped open loading specimen with fatigue cracks as a target wedge-shaped open loading specimen.

[0035] Among them, the shape conversion can be to convert an extended compact tensile specimen that already has fatigue cracks into a standard wedge-shaped open loading specimen with fatigue cracks through physical processing.

[0036] In some embodiments, the expanded compact tensile specimen with fatigue crack is machined according to the drawing of the standard wedge-shaped open-load specimen in the ASTM E1681 standard, firstly the expanded portion is cut off, then a flat pin hole is machined, and finally a threaded hole is machined.

[0037] S140. Apply a load to the end of the fatigue crack on the target wedge-shaped open loaded specimen, and place the loaded target wedge-shaped open loaded specimen into a high-pressure hydrogen environment to determine the current hydrogen-induced crack length.

[0038] Wherein, load is the initial applied stress intensity factor, which is determined based on an estimated stress intensity factor threshold. The target wedge-shaped open-loaded specimen can be a standard wedge-shaped open-loaded specimen that has undergone fatigue crack preformation. The current hydrogen-induced crack length can be the crack propagation length of the target wedge-shaped open-loaded specimen when tested in a high-pressure hydrogen environment.

[0039] In some embodiments, first, the stress intensity factor threshold value K of the material to be tested is IHAn estimate of the stress intensity factor threshold is obtained. Then, using twice the estimated stress intensity factor threshold as the initial applied stress intensity factor, a load is applied to the fatigue crack tip of the target wedge-shaped open-loaded specimen using the constant displacement method.

[0040] Specifically, first, the initial applied stress intensity factor can be converted to the initial applied displacement using the following formula: Where Vm is the displacement, E is the Young's modulus of the material to be tested, a is the sum of the lengths of the machined crack and the fatigue pre-crack, W is the width of the specimen, and K is the stress intensity factor. Then, in an air environment, insert a flat pin into the flat pin hole of the target wedge-shaped open loading specimen, with the flat pin plane facing upward and forming an angle of 90±2° with the loading axis. Embed the extensometer into the cutting edge of the target wedge-shaped open loading specimen, screw the bolt into the bolt hole for constant displacement loading, pay attention to the extensometer reading during loading, and stop loading when the initial applied displacement is reached. Next, remove the extensometer and place the loaded target wedge-shaped open loading specimen in a high-pressure hydrogen environment for 1000 hours.

[0041] In some embodiments, after the test duration reaches 1000 hours, the unloaded target wedge-shaped open-loaded specimen undergoes thermal coloring to distinguish hydrogen-induced cracks from cracks caused by artificial brittle fracture. Specifically, this can be achieved by heating the specimen to 300°C in a high-temperature furnace for 30 minutes. The specimen is then broken, and the cross-sectional cracks are measured using an electron microscope using the nine-point method. The initial crack length a0 (the distance from the fatigue crack end to the loading centerline) and the final crack length a1 (the distance from the hydrogen-induced crack end to the loading centerline) before testing are calculated. The current hydrogen-induced crack length Δl = a1 - a0.

[0042] S150. Determine a stress intensity factor threshold value of the material to be tested according to the initial applied stress intensity factor, the current hydrogen-induced crack length, and the standard value of the hydrogen-induced crack length corresponding to the target wedge-shaped open loading specimen.

[0043] The standard value of hydrogen-induced crack length may be the maximum allowable hydrogen-induced crack length of 0.25 mm for a standard wedge-shaped open-loaded specimen specified in the ASME BPVC KD10 standard. The stress intensity factor threshold value is used to characterize the stress intensity factor threshold value of hydrogen-induced cracking.

[0044] In some embodiments, if the current hydrogen-induced crack length does not exceed the standard value of hydrogen-induced crack length of 0.25 mm, the stress intensity factor threshold value K of the material to be tested is determined. IHIt is half of the initial applied stress intensity factor. It should be noted that the stress intensity factor threshold value also needs to be tested for the validity of the basic plane strain: 2.5 (K IH / R p0.2 ) 2 must be smaller than B, a o and Wa o , where R p0.2 is the yield strength of the material to be tested. If the test passes, it means that the stress intensity factor threshold value has nothing to do with the thickness of the material to be tested and can be used as the stress intensity factor threshold value of the material to be tested; otherwise, it means that the stress intensity factor threshold value is related to the thickness of the material to be tested and cannot be used as the stress intensity factor threshold value of the material to be tested. It can be understood that if the current hydrogen-induced crack length exceeds the standard value of the hydrogen-induced crack length, a slightly smaller initial applied stress intensity factor can be tested to obtain an accurate stress intensity factor threshold value. This method can effectively solve the problem of selecting the initial applied stress intensity factor from the settable range in the ASMEBPVC KD10 standard. For the same material and test environment, different people may obtain different K values ​​due to setting different initial applied stress intensity factors. IH The value is large and the difference is large.

[0045] In the above embodiment, first, the expanded size that meets the installation requirements of the fatigue testing machine is determined based on the size data of the standard wedge-shaped open loading specimen and the standard compact tensile specimen, and the expanded compact tensile specimen of the material to be tested is prepared based on the expanded size, thereby realizing fatigue crack prefabrication using the existing fatigue testing machine for prefabrication of fatigue cracks on compact tensile specimens. After the prefabrication is completed, the specimen is processed into the target wedge-shaped open loading specimen, and there is no need to introduce a new type of equipment for prefabrication of fatigue cracks on wedge-shaped open loading specimens. Compared with the use of three-point bending specimens in related technologies, the expanded compact tensile specimen can not only greatly reduce the fatigue cracks of the material to be tested, but also greatly reduce the fatigue cracks of the material to be tested. Consumption, fatigue crack prefabrication can also be carried out using existing fatigue testing machines, which effectively saves testing costs from two aspects. Then, the load is determined according to the estimated value of the stress intensity factor threshold, and a load is applied to the fatigue crack end of the target wedge-shaped open-loaded specimen to perform a hydrogen-induced crack test. The stress intensity factor threshold value of the material to be tested is determined according to the initial applied stress intensity factor, the current hydrogen-induced crack length and the standard value of the hydrogen-induced crack length corresponding to the target wedge-shaped open-loaded specimen. Compared with related technologies, determining the initial applied stress intensity factor based on the estimated value of the stress intensity factor threshold can obtain a more accurate stress intensity factor threshold value.

[0046] In some embodiments, the initial applied stress intensity factor corresponding to the target wedge-shaped open-loaded specimen adopts the initial applied stress intensity factor of the target specimen group to which the target wedge-shaped open-loaded specimen belongs; and determining the stress intensity factor threshold value of the material to be tested based on the initial applied stress intensity factor corresponding to the target wedge-shaped open-loaded specimen, the current hydrogen-induced crack length, and the standard value of the hydrogen-induced crack length includes: If the target sample group is determined to meet the preset requirements based on the current hydrogen-induced crack length and the standard value of the hydrogen-induced crack length, the stress intensity factor threshold value of the material to be tested is determined based on the initial applied stress intensity factor corresponding to the target sample group.

[0047] The preset requirement may be that the current hydrogen-induced crack length does not exceed a standard value of the hydrogen-induced crack length. The target sample group may be a sample group consisting of a plurality of target wedge-shaped open loading samples.

[0048] In some embodiments, if the maximum value of the hydrogen-induced crack length of the target wedge-shaped open-loaded sample in the target sample group does not exceed the standard value of the hydrogen-induced crack length, the target sample group is determined to meet the preset requirements, and the initial applied stress intensity factor K corresponding to the target sample group is set to IAPP One half of the stress intensity factor threshold value K of the material to be tested IH It is understandable that the stress intensity factor threshold value needs to undergo a basic plane strain validity test before it can be finally determined whether it can be used as the stress intensity factor threshold value of the material to be tested.

[0049] In the above embodiment, by performing hydrogen-induced cracking testing on the target sample group, the randomness of the test data of a single sample can be avoided, the stability of the test data can be increased, and the accuracy of the stress intensity factor threshold value can be improved.

[0050] In some embodiments, the target sample group includes a plurality of target wedge-shaped open loading samples; and the target sample group is determined to meet the preset requirements by the following method: S310 , determining a current hydrogen-induced crack length of the target sample group based on the hydrogen-induced crack length of each target wedge-shaped open-loaded sample.

[0051] S320: Compare the current hydrogen-induced crack length of the target sample group with the standard value of the hydrogen-induced crack length, and determine whether the target sample group meets the preset requirements based on the comparison result.

[0052] The current hydrogen-induced crack length of the target sample group may be an average value of the hydrogen-induced crack lengths of all target wedge-shaped open-loaded samples in the target sample group.

[0053] In some embodiments, the average hydrogen-induced crack length of all target wedge-shaped open-loaded specimens in the target specimen group is determined as the current hydrogen-induced crack length of the target specimen group. If the current hydrogen-induced crack length of the target specimen group does not exceed the standard value of the hydrogen-induced crack length, the target specimen group is determined to meet the preset requirements.

[0054] In the above embodiment, the current hydrogen-induced crack length of the target sample group is first determined based on the hydrogen-induced crack length of each target wedge-shaped open-loaded sample. Then, the current hydrogen-induced crack length of the target sample group is compared with the standard value of the hydrogen-induced crack length. Based on the comparison result, it is determined that the target sample group meets the preset requirements. Compared with testing using a single sample, the sample group can reduce the impact of random errors, thereby improving the accuracy of the stress intensity factor threshold value.

[0055] In some embodiments, determining that the target sample group meets the preset requirements based on the comparison results includes: determining that the target sample group meets the preset requirements when the current hydrogen-induced crack length is less than or equal to the standard value and the difference data between the current hydrogen-induced crack length and the standard value meets the preset difference requirement.

[0056] The preset difference requirement may be that when there are multiple initial sample groups, the difference data between the current hydrogen-induced crack length of the target sample group and the standard value is the smallest among all the initial sample groups.

[0057] In some embodiments, there are multiple initial sample groups. After the hydrogen-induced crack test is completed, first, based on the nine-point method, an electron microscope is used to measure and calculate the hydrogen-induced crack length of all samples; then, the average value of the hydrogen-induced crack length of the initial sample group is calculated as its current hydrogen-induced crack length; then, the relationship between the current hydrogen-induced crack length and the standard value of each initial sample group is determined, and several initial sample groups whose current hydrogen-induced crack length is less than or equal to the standard value are screened out. Further, the group with the smallest difference data between the current hydrogen-induced crack length and the standard value is selected as the target sample group.

[0058] In the above embodiment, first, based on the current hydrogen-induced crack length being less than or equal to the standard value, a sample group that meets the ASME BPVC KD10 standard is determined. Then, based on whether the difference data between the current hydrogen-induced crack length and the standard value meets the preset difference requirement, it is determined whether the target sample group meets the preset requirement, thereby determining the target sample group that can test the most accurate hydrogen-induced delayed cracking stress intensity factor threshold value.

[0059] In some embodiments, the target wedge-shaped open-loaded specimen belongs to a target specimen group, and the target specimen group corresponds to an initially applied stress intensity factor; applying a load to a fatigue crack tip on the target wedge-shaped open-loaded specimen, and placing the loaded target wedge-shaped open-loaded specimen in a high-pressure hydrogen environment, comprises: According to the initial applied stress intensity factor corresponding to the target specimen group, a load is applied to the fatigue crack end of each target wedge-shaped open-loaded specimen in the target specimen group, and each loaded target wedge-shaped open-loaded specimen is placed in a high-pressure hydrogen environment to determine the current hydrogen-induced crack length corresponding to the target specimen group.

[0060] In some embodiments, a target specimen group includes multiple target wedge-shaped open-loaded specimens. Each of these target wedge-shaped open-loaded specimens requires applying the same load to the fatigue crack tip, i.e., the same initial applied stress intensity factor. For example, a constant displacement method is used to apply a load to the fatigue crack tip of each target wedge-shaped open-loaded specimen. First, the initial applied stress intensity factor can be converted to the initial applied displacement using the following formula: Where Vm is the displacement, E is the Young's modulus of the material to be tested, a is the sum of the lengths of the machined crack and the fatigue pre-crack, W is the width of the specimen, and K is the stress intensity factor. Then, in an air environment, insert a flat pin into the flat pin hole of the target wedge-shaped open loading specimen, with the flat pin plane facing upward and forming an angle of 90°±2° with the loading axis. Embed the extensometer into the cutting edge of the target wedge-shaped open loading specimen, screw the bolt into the bolt hole for constant displacement loading, pay attention to the extensometer reading during loading, and stop loading when the initial applied displacement is reached. Next, remove the extensometer and place the loaded target wedge-shaped open loading specimen in a high-pressure hydrogen environment for 1000 hours.

[0061] Furthermore, after the test time is reached, each target wedge-shaped open-loaded specimen in the target specimen group is unloaded and subjected to thermal coloring to distinguish hydrogen-induced cracks from cracks caused by artificial brittle fracture. Specifically, this can be achieved by heating the specimen to 300°C in a high-temperature furnace and holding the temperature for 30 minutes. The specimen is then broken, and the cross-sectional crack is measured using an electron microscope using the nine-point method. The initial crack length a0 (the distance from the fatigue crack end to the loading centerline) and the termination crack length a1 (the distance from the hydrogen-induced crack end to the loading centerline) of the specimen before the test are measured and calculated. The hydrogen-induced crack length Δl = a1-a0. Finally, the average hydrogen-induced crack length of the target specimen group is calculated as its current hydrogen-induced crack length.

[0062] In some embodiments, the initial applied stress intensity factor corresponding to the target wedge-shaped open-loaded specimen adopts the initial applied stress intensity factor of the target specimen group to which the target wedge-shaped open-loaded specimen belongs; the target specimen group is determined by: S610: Provide multiple initial sample groups.

[0063] S620: Determine an initial applied stress intensity factor for any initial sample group between a first stress intensity factor threshold and a second stress intensity factor threshold.

[0064] S630. Perform a hydrogen-induced cracking test on each target wedge-shaped open-loaded specimen in any initial specimen group according to the initial applied stress intensity factor of any initial specimen group to obtain a current hydrogen-induced crack length corresponding to any initial specimen group.

[0065] S640: Determine a target sample group from the multiple initial sample groups according to the current hydrogen-induced crack length and the standard value of the hydrogen-induced crack length corresponding to any initial sample group.

[0066] Each initial specimen group includes a plurality of target wedge-shaped open-load specimens having fatigue cracks. The first stress intensity factor threshold may be a minimum initially applied stress intensity factor. The second stress intensity factor threshold may be a maximum initially applied stress intensity factor.

[0067] In some embodiments, a stress intensity factor threshold estimated value K0 is first obtained, and then a first stress intensity factor threshold value is determined to be 1.6K0 and a second stress intensity factor threshold value is determined to be 2.2K0. Then, an initial applied stress intensity factor is set between the first stress intensity factor threshold value and the second stress intensity factor threshold value at intervals of 10-15% K0. For example, there are seven initial sample groups, and 1.6K0, 1.7K0, 1.8K0, 1.9K0, 2.0K0, 2.1K0, and 2.2K0 are set as the initial applied stress intensity factors, respectively.

[0068] Furthermore, in air, the constant displacement method was used to apply the initial applied stress intensity factor corresponding to the group to multiple target wedge-shaped open-loaded specimens of each initial specimen group. Then, all the overloaded initial specimen groups were placed in the same high-pressure hydrogen environment for hydrogen-induced cracking testing for a duration of 1000 h.

[0069] Furthermore, after the hydrogen-induced crack test is completed, first, based on the nine-point method, an electron microscope is used to measure and calculate the hydrogen-induced crack length of all samples; then the average value of the hydrogen-induced crack length of each initial sample group is calculated as its current hydrogen-induced crack length; then, the relationship between the current hydrogen-induced crack length and the standard value of each initial sample group is judged, and several initial sample groups with current hydrogen-induced crack lengths less than or equal to the standard value are screened out. Finally, the group with the smallest difference data between the current hydrogen-induced crack length and the standard value is selected as the target sample group.

[0070] It should be noted that, in this embodiment, if the current hydrogen-induced crack length is less than the standard value of 0.25 mm, the stress intensity factor threshold value is equal to half of the initially applied stress intensity factor. The stress intensity factor threshold value can be estimated based on the performance parameters of the material to be tested, such as based on the mapping relationship between the yield strength and the stress intensity factor threshold value. Therefore, this embodiment determines the first stress intensity factor threshold value and the second stress intensity factor threshold value on the left and right sides based on twice the estimated value of the stress intensity factor threshold, and determines multiple initially applied stress intensity factors between the above two thresholds for hydrogen-induced crack testing. The current hydrogen-induced crack length closest to the standard value is obtained by the clamping method, and then an accurate stress intensity factor threshold value can be obtained, which effectively solves the problem in the ASME BPVC KD10 standard that the initial applied stress intensity factor is selected from a settable range. For the same material and test environment, different people may obtain different K values ​​due to setting different initial applied stress intensity factors. IH The problem of large differences in values ​​is of vital importance to the design of hydrogen storage containers or pipelines.

[0071] In the above embodiment, a clamping method is used to first determine multiple initial applied stress intensity factors (SIFs) corresponding to multiple initial sample groups based on a first SIF threshold and a second SIF threshold. Hydrogen-induced cracking testing is then performed on these initial sample groups. Based on the current hydrogen-induced crack length and standard value of each group, a target sample group of the material to be tested is obtained. Furthermore, accurate SIF threshold values ​​can be obtained based on the initial applied SIFs corresponding to these target sample groups.

[0072] In some embodiments, applying a load to a fatigue crack tip on a target wedge-shaped open-loaded specimen includes: S710: Obtain an estimated value of a stress intensity factor threshold of the material to be tested.

[0073] S720. Determine the initial applied stress intensity factor of the material to be tested.

[0074] S730. Use the constant displacement method to apply load to the fatigue crack tip of the target wedge-shaped open-loaded specimen.

[0075] Among them, the stress intensity factor threshold estimated value is used to characterize the estimation of the stress intensity factor threshold value of hydrogen-induced delayed cracking.

[0076] In some embodiments, the stress intensity factor threshold estimate is obtained based on the tensile strength of the material, using the following formula: K IH =60×(R m / 950) Among them, R mIt is the tensile strength of the material, measured in MPa, and can be measured by a tensile test in air. is the stress intensity factor threshold value, unit: MPa·m 1 / 2 When the tensile strength of the material to be tested is known, the above formula can be used to obtain an estimated value of its stress intensity factor threshold.

[0077] Furthermore, the initial applied stress intensity factor of the material to be tested is determined to be multiple values ​​of approximately twice the estimated value of its stress intensity factor threshold. The initial applied stress intensity factor is then converted into displacement using the following formula. The constant displacement method is used to apply loads to the fatigue crack ends of multiple target wedge-shaped open-loaded specimens to conduct hydrogen-induced crack testing: Where Vm is the displacement, E is the Young's modulus of the material to be tested, a is the sum of the lengths of the machining crack and the fatigue pre-crack, W is the width of the specimen, and K is the stress intensity factor.

[0078] After the test time has elapsed, the specimen is unloaded and heat-tinted to distinguish hydrogen-induced cracks from artificial brittle fractures. Finally, the stress intensity factor threshold of the material under test is determined based on the initial applied stress intensity factor corresponding to the target wedge-shaped open-loaded specimen whose current hydrogen-induced crack length is closest to the standard value. This stress intensity factor threshold is half the initial applied stress intensity factor.

[0079] In some embodiments, obtaining a stress intensity factor threshold estimate value of the material to be tested includes: estimating the stress intensity factor threshold value of the material to be tested based on a relationship between the yield strength of the material and the stress intensity factor threshold value to obtain the stress intensity factor threshold estimate value.

[0080] In some embodiments, the stress intensity factor threshold value of the material to be tested is estimated according to the following formula: Among them, R p0.2 is the yield strength of the material, in MPa, is the stress intensity factor threshold value, unit: MPa·m 1 / 2 When the yield strength of the material to be tested is obtained through a tensile test, the above formula can be used to obtain an estimated value of the stress intensity factor threshold.

[0081] It should be noted that the formula and All of them are used to calculate the estimated threshold value of the stress intensity factor of the material to be tested. According to the experiment, the inventor found that the formula Effectively predicts within a specific intensity range However, when the tensile strength of the material exceeds a certain range, the predicted results of the formula deviate significantly from the experimental observations. Based on this, the inventors proposed the formula , the formula showed wider applicability and higher prediction accuracy in experiments.

[0082] In some embodiments, a fatigue testing machine is provided with a matching U-shaped clamp, and fatigue cracks are preformed on an expanded compact tensile specimen using the fatigue testing machine to obtain an expanded compact tensile specimen having a fatigue crack, including: S910. Use U-clamps to clamp the expanded compact tensile specimen.

[0083] S920. Adjust the Young's modulus in the fatigue testing machine. The fatigue testing machine before adjustment is used to perform fatigue crack prefabrication on standard compact tensile specimens.

[0084] S930, fatigue crack prefabrication of expanded compact tensile specimens using the adjusted fatigue testing machine.

[0085] The U-clip is a specially designed clamping tool that can be used to secure standard compact tensile specimens for fatigue crack prefabrication on a fatigue testing machine. However, it cannot be used to secure standard wedge-shaped open-load specimens. It should be noted that since the loading hole of the expanded compact tensile specimen is designed based on the standard compact tensile specimen, the U-clip can be used to secure the expanded compact tensile specimen in this application, allowing fatigue crack prefabrication using a fatigue testing machine.

[0086] In some embodiments, fatigue crack prefabrication is performed on an expanded compact tensile specimen using an MTS fatigue testing machine, which is used to prefabricate fatigue cracks on standard compact tensile specimens. First, the expanded compact tensile specimen is clamped using a U-shaped clamp. The machined crack length is then checked using the MTS fatigue testing machine, and the Young's modulus of the material is adjusted to offset the effects of specimen lengthening. Specifically, a tensile test can be performed by applying a small force to the expanded compact tensile specimen. The Young's modulus is adjusted based on the machined crack length measured by the MTS fatigue testing machine, ensuring that the deviation between the manually measured value and the value measured by the MTS fatigue testing machine is less than 0.02 mm.

[0087] Furthermore, fatigue crack prefabrication was performed on the extended compact tensile specimen using an adjusted fatigue testing machine with a sinusoidal loading waveform of a stress ratio of 0.1 and 20 Hz. The ratio of the initial crack length a0 to the specimen width W, a0 / W, was controlled between 0.45 and 0.55. Specifically, the stress intensity factor threshold value of the material to be tested was estimated to obtain a stress intensity factor threshold estimated value. During the fatigue crack prefabrication process, the maximum stress intensity factor (Kmax) should be controlled not to exceed 80% of the stress intensity factor threshold estimated value, and the maximum stress intensity factor (Kmax) in the last 1 mm stage of the fatigue pre-crack should not exceed 60% of the stress intensity factor threshold estimated value. Then, since the MTS fatigue testing machine adopts a force control method, the maximum stress intensity factor (Kmax) needs to be converted into the force that the fatigue testing machine should apply, according to the formula for CT specimens in ASTM E399: Where B is the thickness of the expanded compact tensile specimen, B N is the net thickness of the specimen with side grooves, W is the specimen width, a is the distance from the centerline of the loading hole to the end of the machined crack (also known as the machined crack length), K is the stress intensity factor, and P is the force applied by the fatigue testing machine. The compliance method can be used to measure crack length during prefabrication.

[0088] In some embodiments, an expanded compact tensile specimen with fatigue cracks is transformed into a standard wedge-shaped open loading specimen with fatigue cracks as a target wedge-shaped open loading specimen, including: machining the expanded compact tensile specimen with fatigue cracks, adjusting the length to a target length that meets the requirements of the standard wedge-shaped open loading specimen, and machining flat pin holes and threaded holes required by the standard wedge-shaped open loading specimen; wherein, during the machining of the threaded holes, it is necessary to add a shock-absorbing component at the machined cracks.

[0089] In some embodiments, an extended compact tension specimen with a fatigue crack is machined according to the drawing for a standard wedge-shaped open-load specimen in ASTM E1681. The extended portion is first removed, followed by machining to create a flat pin hole, and finally, a threaded hole. It should be noted that during the threaded hole machining, a 3 mm thick carbide gasket is installed in the center groove to isolate the impact of machining vibration on the pre-existing crack tip.

[0090] In some embodiments, the method for testing hydrogen-induced cracking of materials in a high-pressure hydrogen environment includes: S1001. Provide multiple initial sample groups.

[0091] Each initial specimen group includes a plurality of target wedge-shaped open loading specimens with fatigue cracks.

[0092] S1002. For any initial sample group, apply a load to the fatigue crack end of each target wedge-shaped open loaded sample in any initial sample group according to the initial applied stress intensity factor corresponding to any initial sample group, and place each target wedge-shaped open loaded sample with the applied load in a high-pressure hydrogen environment to determine the current hydrogen-induced crack length corresponding to any initial sample group.

[0093] In some embodiments, a stress intensity factor threshold estimated value K0 is first obtained, and then several values ​​are determined on and around 2K0 as an initial applied stress intensity factor set. Exemplarily, the initial applied stress intensity factor set consists of 1.6K0, 1.8K0, 2K0, 2.2K0, and 2.4K0, and each initial applied stress intensity factor in the set corresponds to an initial sample group.

[0094] Furthermore, in air, the constant displacement method was used to apply the initial applied stress intensity factor corresponding to the group to multiple target wedge-shaped open-loaded specimens of each initial specimen group. Then, all the overloaded initial specimen groups were placed in the same high-pressure hydrogen environment for hydrogen-induced cracking testing for a duration of 1000 h.

[0095] Furthermore, after the hydrogen-induced crack test is completed, first, the hydrogen-induced crack length of all samples is calculated based on the nine-point method using an electron microscope; then the average value of the hydrogen-induced crack lengths of multiple samples in each initial sample group is calculated as its current hydrogen-induced crack length.

[0096] S1003. Compare the current hydrogen-induced crack length corresponding to each initial sample group with the standard value of the hydrogen-induced crack length, so as to determine, among the multiple initial sample groups, a target sample group whose current hydrogen-induced crack length is less than or equal to the standard value and whose difference data with the standard value meets a preset requirement.

[0097] The preset requirement is that the difference between the current hydrogen-induced crack length of the target sample group and the standard value is the smallest among all groups.

[0098] In some embodiments, the relationship between the current hydrogen-induced crack length and the standard value of each initial sample group is determined, and several initial sample groups whose current hydrogen-induced crack length is less than or equal to the standard value are screened out. Finally, the group with the smallest difference data between the current hydrogen-induced crack length and the standard value is selected as the target sample group.

[0099] S1004: Determine a stress intensity factor threshold value of the material to be tested based on the initial applied stress intensity factor corresponding to the target sample group.

[0100] In some embodiments, half of the initially applied stress intensity factor corresponding to the target sample group is used as the stress intensity factor threshold value of the material to be tested.

[0101] It should be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, commodity, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or includes elements inherent to such process, method, commodity, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a..." does not exclude the presence of other identical elements in the process, method, commodity, or apparatus that includes the element.

[0102] The various embodiments in this specification are described in a progressive manner. Similar parts between the various embodiments can be referred to in conjunction with each other. Each embodiment focuses on the differences between the other embodiments. In particular, the system embodiments are generally similar to the method embodiments, so the description is relatively simple. For relevant parts, refer to the description of the method embodiments.

[0103] The foregoing is merely an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should all be included within the scope of the claims of the present application.

[0104] Although the embodiments of the present application have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present application, and such modifications and variations shall fall within the scope defined by the appended claims.

Claims

1. A method for testing hydrogen-induced cracking of materials under high-pressure hydrogen environment, characterized in that: The method comprises: Determining an expanded dimension that meets the installation requirements of a fatigue testing machine based on the dimensional data of a standard wedge-shaped open loading specimen and the dimensional data of a standard compact tensile specimen, and preparing an expanded compact tensile specimen of the material to be tested based on the expanded dimension; wherein the material to be tested is a material intended for use in a hydrogen storage container or a structural component of a hydrogen energy device in a high-pressure hydrogen environment; Prefabricate fatigue cracks on the expanded compact tensile specimen using the fatigue testing machine to obtain an expanded compact tensile specimen having fatigue cracks; Transforming the expanded compact tensile specimen with fatigue cracks to obtain a standard wedge-shaped open loading specimen with fatigue cracks as a target wedge-shaped open loading specimen; Applying a load to the end of a fatigue crack on the target wedge-shaped open-loaded specimen, and placing the loaded target wedge-shaped open-loaded specimen in a high-pressure hydrogen environment to determine a current hydrogen-induced crack length; wherein the load is an initially applied stress intensity factor, and the initially applied stress intensity factor is determined based on an estimated stress intensity factor threshold value; The stress intensity factor threshold value of the material to be tested is determined according to the initial applied stress intensity factor corresponding to the target wedge-shaped open loading specimen, the current hydrogen-induced crack length, and the standard value of the hydrogen-induced crack length.

2. The method according to claim 1, characterized in that The initial applied stress intensity factor corresponding to the target wedge-shaped open-loaded specimen adopts the initial applied stress intensity factor of the target specimen group to which the target wedge-shaped open-loaded specimen belongs; and determining the stress intensity factor threshold value of the material to be tested based on the initial applied stress intensity factor corresponding to the target wedge-shaped open-loaded specimen, the current hydrogen-induced crack length, and the standard value of the hydrogen-induced crack length, includes: If the target sample group is determined to meet the preset requirements based on the current hydrogen-induced crack length and the standard value of the hydrogen-induced crack length, a stress intensity factor threshold value of the material to be tested is determined based on the initial applied stress intensity factor corresponding to the target sample group.

3. The method according to claim 2, characterized in that The target sample group includes a plurality of target wedge-shaped open loading samples; and the target sample group is determined to meet the preset requirements by the following method: determining a current hydrogen-induced crack length of the target sample group based on the hydrogen-induced crack length of each target wedge-shaped open-loaded sample; The current hydrogen-induced crack length of the target sample group is compared with a standard value of the hydrogen-induced crack length, and based on the comparison result, it is determined that the target sample group meets the preset requirement.

4. The method according to claim 3, characterized in that The determining, based on the comparison result, that the target sample group meets the preset requirement includes: When the current hydrogen-induced crack length is less than or equal to the standard value and the difference data between the current hydrogen-induced crack length and the standard value meets the preset difference requirement, it is determined that the target sample group meets the preset requirement.

5. The method according to claim 1, wherein The target wedge-shaped open-loaded specimen belongs to a target specimen group, and the target specimen group corresponds to an initially applied stress intensity factor; applying a load to a fatigue crack end of the target wedge-shaped open-loaded specimen, and placing the loaded target wedge-shaped open-loaded specimen in a high-pressure hydrogen environment, comprises: According to the initial applied stress intensity factor corresponding to the target sample group, a load is applied to the fatigue crack end of each target wedge-shaped open-loaded sample in the target sample group, and each target wedge-shaped open-loaded sample with the applied load is placed in a high-pressure hydrogen environment to determine the current hydrogen-induced crack length corresponding to the target sample group.

6. The method according to claim 1, characterized in that The initial applied stress intensity factor corresponding to the target wedge-shaped open loading specimen adopts the initial applied stress intensity factor of the target specimen group to which the target wedge-shaped open loading specimen belongs; The target sample group is determined by: Providing a plurality of initial specimen groups; wherein each initial specimen group includes a plurality of target wedge-shaped open-loaded specimens having fatigue cracks; determining an initial applied stress intensity factor for any initial set of specimens between a first stress intensity factor threshold and a second stress intensity factor threshold; performing a hydrogen-induced cracking test on each target wedge-shaped open-loaded specimen in any of the initial specimen groups according to the initial applied stress intensity factor of any of the initial specimen groups, to obtain a current hydrogen-induced crack length corresponding to the any of the initial specimen groups; The target sample group is determined from the multiple initial sample groups according to the current hydrogen-induced crack length corresponding to any one of the initial sample groups and the standard value of the hydrogen-induced crack length.

7. The method according to claim 1, characterized in that The step of applying a load to the fatigue crack end of the target wedge-shaped open loading specimen comprises: Obtaining a stress intensity factor threshold estimate value of the material to be tested; wherein the stress intensity factor threshold estimate value is used to characterize an estimation of a hydrogen-induced delayed cracking stress intensity factor threshold value; determining the initially applied stress intensity factor of the material to be tested; A constant displacement method is used to apply load to the fatigue crack end of the target wedge-shaped open loading specimen.

8. The method according to claim 7, characterized in that The step of obtaining an estimated threshold value of the stress intensity factor of the material to be tested includes: The stress intensity factor threshold value of the material to be tested is estimated according to the relationship between the yield strength of the material and the stress intensity factor threshold value to obtain the stress intensity factor threshold estimated value.

9. The method according to claim 1, characterized in that The fatigue testing machine has a matching U-shaped clamp, and the fatigue crack prefabrication is performed on the expanded compact tensile specimen by the fatigue testing machine to obtain the expanded compact tensile specimen with fatigue cracks, including: clamping the expanded compact tensile specimen using the U-shaped clamp; Adjusting the Young's modulus in a fatigue testing machine; wherein the fatigue testing machine before adjustment is used to perform fatigue crack prefabrication on a standard compact tensile specimen; Fatigue crack prefabrication is performed on the expanded compact tensile specimen by using the adjusted fatigue testing machine.

10. The method according to claim 1, characterized in that The method of converting the expanded compact tensile specimen with fatigue cracks to obtain a standard wedge-shaped open loading specimen with fatigue cracks as a target wedge-shaped open loading specimen comprises: The expanded compact tensile specimen with fatigue cracks is machined to adjust its length to a target length that meets the requirements of the standard wedge-shaped open loading specimen, and the flat pin holes and threaded holes required by the standard wedge-shaped open loading specimen are machined; wherein, during the machining of the threaded holes, a shock-absorbing component needs to be added at the machined cracks.

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