Method for testing metal hydrogen absorption and hydrogen diffusion parameters in stress field

Abstract

The invention belongs to the technical field of material performance testing, and provides a method for testing metal hydrogen absorption and hydrogen diffusion parameters in a stress field, which comprises the following steps: extracting and dehydrogenating, processing into a sample, compressing and loading, carrying out gas-phase hydrogen charging, controlling the hydrogen concentration, carrying out short-time and long-time heat preservation diffusion in stages, and testing the sample. Hydrogen distribution at the beginning before hydrogen charging, after hydrogen charging and after short-time and long-time heat preservation is measured in sequence, stress distribution of the self-loading sample is analyzed through a finite element method, hydrogen absorption rates at different stress positions are calculated, a relation expression that the hydrogen absorption rates change along with parameters such as stress is fitted, and the relation between hydrogen chemical potential and stress is established; a finite element model is constructed, distribution after hydrogen filling is used as an initial state, a flux equation is adopted, stress-related diffusion coefficients are adjusted in an iterative mode, simulated short-time diffusion distribution is matched with actual test data, and the change rule of a diffusion system along with stress is determined. The application can meet the requirements of high-temperature testing, simultaneous testing of various stresses and the like.

Description

Technical Field

[0001] The present application belongs to the technical field of material performance testing, and in particular relates to a method for testing metal hydrogen absorption and hydrogen diffusion parameters under a stress field. Background Art

[0002] Zirconium alloys and metals with similar hydrogen absorption properties (such as titanium and yttrium, hereinafter collectively referred to as zirconium-like alloys) easily absorb hydrogen at higher temperatures. Hydrogen-induced delayed cracking is one of the key failure mechanisms of zirconium-like alloys. Stress has a significant influence on the material's hydrogen absorption, hydrogen diffusion, and hydrogen redistribution (approximately the distribution of hydrogen chemical potential). Therefore, it is very important to accurately measure parameters such as hydrogen absorption, hydrogen diffusion, and hydrogen chemical potential of metal materials under stress.

[0003] Currently, the main method for this test is to apply a uniform stress field to the material area to be tested, then test various hydrogen permeation parameters using the double electrolytic cell method, and finally determine the influence of stress on these parameters. There are several problems with the existing method:

[0004] First, the test temperature of the double-electrolytic cell method usually does not exceed 95°C, which is difficult to meet the needs of high-temperature testing and cannot test zirconium-like alloys that diffuse extremely slowly at low temperatures.

[0005] Second, one test only targets one stress, which is less efficient.

[0006] Third, it is impossible to test the hydrogen chemical potential under different stress conditions, making it difficult to apply to actual devices with complex stresses. Summary of the Invention

[0007] The purpose of this application is to overcome the defects of the existing technology and thus provide a method for testing metal hydrogen absorption and hydrogen diffusion parameters under a stress field to meet the needs of high temperature testing, simultaneous testing of multiple stresses, etc.

[0008] In order to achieve the above objectives, this application provides the following technical solutions:

[0009] A method for testing metal hydrogen absorption and hydrogen diffusion parameters under a stress field, comprising:

[0010] Step 1: The sample is processed into a specimen after vacuum heat extraction and dehydrogenation, compressed and loaded, and gas-phase hydrogen is charged and the hydrogen concentration is controlled. Short-term and long-term heat preservation diffusion are carried out in stages;

[0011] Step 2: Test the sample and measure the hydrogen distribution before hydrogen charging, after hydrogen charging, and after short and long time holding;

[0012] Step 3: Analyze the stress distribution of the self-loaded specimen using the finite element method, calculate the hydrogen absorption rate at different stresses, and fit the relationship between the hydrogen absorption rate and parameters such as stress; establish the relationship between hydrogen chemical potential and stress based on the steady-state hydrogen concentration distribution; by constructing a finite element model, using the distribution after hydrogen charging as the initial state, using the flux equation, iteratively adjust the stress-related diffusion coefficient D, so that the simulated short-term diffusion distribution matches the actual test data, and determine the change pattern of D with stress.

[0013] In some embodiments, in step 1, the sample is processed into a U-shaped or C-shaped specimen.

[0014] In some embodiments, in step 1, the short time is when the average diffusion distance is about 1 / 4 of the sample thickness d, and the long time is when the average diffusion distance is twice the sample extension length L.

[0015] In some embodiments, step 1 specifically includes:

[0016] Step 1.1: Use vacuum heat extraction to remove hydrogen from the raw material. Process it into a self-loading U-shaped or C-shaped specimen. Compress the specimen in a universal testing machine and record the pressure at a specific position. After unloading, reload it with bolts to compress it to the same position.

[0017] Step 1.2: Use a gas phase hydrogen charging device to charge the loaded sample with hydrogen. Before charging, calculate the maximum chargeable hydrogen volume and the corresponding maximum charging pressure based on the solubility of hydrogen in the material. The average hydrogen concentration should be no less than 5ppm. The surface oxide film of the hydrogen-charged sample should be fully removed, and the sample should be loaded under the protection of inert gas.

[0018] Step 1.3: Short-term heat preservation diffusion, the heat preservation diffusion is carried out directly in the air environment, and the average diffusion distance of the short-term heat preservation diffusion is 1 / 4 of the sample thickness d;

[0019] Step 1.4: Long-term heat preservation diffusion. The average diffusion distance of long-term heat preservation diffusion is twice the sample extension length L.

[0020] In some embodiments, in step 2, a hydrogen concentration distribution test is performed after gas-phase hydrogen charging to obtain the hydrogen content distribution of the sample after gas-phase hydrogen charging, and the hydrogen absorption rate is calculated based on this.

[0021] In some embodiments, in step 2, a hydrogen concentration distribution test after short-time heat preservation is performed to obtain the hydrogen content distribution of the sample after short-time heat preservation and diffusion.

[0022] In some embodiments, in step 2, a hydrogen concentration distribution test after long-term heat preservation is performed to obtain the hydrogen content distribution of the sample after long-term heat preservation and diffusion to calculate the hydrogen chemical potential.

[0023] In some embodiments, in step 3, the hydrogen absorption rate at different stresses is calculated based on the pressure drop curve during the hydrogen charging process, the hydrogen concentration distribution after gas-phase hydrogen charging, and the initial hydrogen concentration distribution, and the relationship between the hydrogen absorption rate and parameters such as stress is fitted.

[0024] In some embodiments, in step 3, after a long period of heat preservation, the hydrogen concentration distribution reaches a steady state, and the hydrogen chemical potential gradient is the sum of the hydrogen concentration gradient and the chemical potential gradient caused by stress. When reaching a steady state, the chemical potential gradient caused by stress is equal to the concentration gradient in magnitude and opposite in direction, and the formula is:

[0025]

[0026] Where M is the proportional coefficient, D is the diffusion coefficient, is the stress-induced hydrogen chemical potential gradient, is the concentration gradient.

[0027] In some embodiments, in step 3, diffusion parameter calculation is performed. When the hydrogen concentration is low, it is assumed that the diffusion coefficient does not change with the change of hydrogen concentration. A finite element diffusion model is established, and the hydrogen concentration distribution after gas phase hydrogenation is used as the initial state of diffusion. The diffusion flux equation is:

[0028]

[0029] When u=-c is used to obtain the law of change of u with stress, let M=D, first assume a function of change of D value with stress, substitute the time of short-time insulation, calculate the hydrogen concentration distribution after diffusion, and compare it with the actual hydrogen concentration distribution after short-time insulation. Then, gradually adjust the function of change of D value with stress until the two are consistent, and finally obtain the function of change of D value with stress.

[0030] Compared with the existing technology, the method for testing metal hydrogen absorption and hydrogen diffusion parameters under stress field provided by this application has the following beneficial effects:

[0031] 1. This application adopts the method of gas phase hydrogen charging and heat preservation diffusion, which has a wider applicable temperature range and can be higher than 95°C;

[0032] 2. One test can obtain the influence rules of various stress states from compressive stress to tensile stress;

[0033] 3. This application can obtain the quantitative influence of stress on the gas-phase hydrogen absorption rate of materials;

[0034] 4. This application can obtain the quantitative influence of stress on the chemical potential of hydrogen in materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solution of this application, the following is a brief introduction to the drawings required for the technical description.

[0036] Figure 1 Flowchart of the method for testing metal hydrogen absorption and hydrogen diffusion parameters under stress field provided in this application;

[0037] Figure 2 Schematic diagram of the test and calculation process of metal hydrogen absorption and hydrogen diffusion parameters under stress field provided in this application;

[0038] Figure 3 A front view of the Type C specimen provided for this application;

[0039] Figure 4 Side view of the C-type specimen provided for this application. DETAILED DESCRIPTION

[0040] The following is further explained in detail through specific implementation methods.

[0041] like Figure 1 and Figure 2 The present application provides a method for testing metal hydrogen absorption and hydrogen diffusion parameters under a stress field, comprising:

[0042] Step 1: Sample processing. After vacuum heat extraction and dehydrogenation, the sample is processed into a U-shaped or C-shaped specimen. Compression loading is performed, and the sample is loaded under inert gas protection. Gas-phase hydrogenation is performed and the hydrogen concentration is controlled. Subsequently, short-term and long-term heat diffusion are carried out in stages to optimize hydrogen distribution.

[0043] Step 2: Sample testing. Neutron scattering (with a control sample) or multi-point sampling is used to measure the hydrogen distribution before and after hydrogenation, and after short and long holding times. This is used for background subtraction, hydrogen uptake rate calculation, diffusion coefficient determination, and chemical potential analysis.

[0044] Step 3: Parameter calculation. Calculate stress distribution, hydrogen absorption parameters, hydrogen chemical potential, and diffusion parameters. Analyze the stress distribution of the self-loaded specimen using the finite element method, calculate the hydrogen absorption rate of each stress zone by combining the hydrogen charging pressure drop curve with the concentration distribution difference, and establish a mathematical model of its relationship with stress and hydrogen pressure. Based on the steady-state hydrogen concentration distribution, establish the relationship between hydrogen chemical potential and stress. By constructing a finite element model, taking the hydrogen distribution after hydrogenation as the initial state, using the diffusion equation, iteratively adjust the stress-related diffusion coefficient D (such as a polynomial function) to match the simulated short-term diffusion distribution with the actual test data, and finally determine the change pattern of D with stress.

[0045] Step 1 specifically includes:

[0046] Step 1.1: Sample preparation, including raw material processing, sample processing, and loading. The raw materials should contain as little hydrogen as possible. If the raw materials have a high hydrogen content, vacuum heat extraction can be used to remove it, that is, placing the material in a high vacuum chamber (usually the pressure can be less than 4×10 -6 Pa), and then heated to a higher temperature where the structure does not change, so that the hydrogen in it is released. Then refer to GB / T15970.3 and GB / T15970.5 to process it into a self-loaded U-shaped or C-shaped specimen, such as Figure 3 and Figure 4 As shown in the figure, L is the length direction, w is the width direction, and d is the thickness direction. A is the location of maximum tensile stress, B is the location of maximum compressive stress, and C is the approximately stress-free location. The specimen was compressed in a universal testing machine, and the pressure at a specific compression point was recorded. After unloading, the specimen was loaded with bolts to compress to the same position. The force applied to the specimen now matched the previous compressor pressure. To prevent the bolts from affecting the diffusion of hydrogen absorbed by the specimen, ceramic gaskets were used between the bolts and the specimen.

[0047] Step 1.2: Gas-phase hydrogenation. A gas-phase hydrogenation device is used to charge the loaded sample with hydrogen. Before hydrogenation, the maximum chargeable hydrogen amount and the corresponding maximum hydrogenation pressure should be calculated based on the solubility of hydrogen in the material at the test temperature. The actual hydrogenation pressure should be lower than the maximum hydrogenation pressure. At the same time, taking into account the accuracy of subsequent tests, the average hydrogen concentration used in this embodiment is not less than 5ppm (mass fraction). The hydrogenation temperature can be flexibly selected according to the actual service temperature of the material or the accelerated test temperature, but should not exceed the stress relief temperature of the material. Under the protection of inert gas, use fine sandpaper to gently polish the inner and outer surfaces of the sample to remove the oxide film (the oxide film on the side of the sample is retained to avoid side hydrogen absorption), and load the sample to minimize the obstruction of the oxide film on the inner and outer surfaces to hydrogen absorption and increase the hydrogen absorption rate. The hydrogenation time should be short, and the average diffusion distance should not exceed 1 / 20 of the sample thickness d to reduce internal diffusion.

[0048] Step 1.3: Short-term heat-insulating diffusion. The hydrogen equilibrium partial pressure of zirconium-like alloys at relatively low temperatures (below the stress relief temperature) is extremely low, so there is no need to consider releasing hydrogen into the air. At the same time, heating in air will quickly form an oxide film on the surface. Under the action of the oxide film, there is no need to consider absorbing hydrogen from the air. Therefore, heat-insulating diffusion can be carried out directly in an air environment. For short-term heat-insulating diffusion, the average diffusion distance d1 should be approximately 1 / 4 of the sample thickness d. The diffusion time calculation formula is as follows:

[0049]

[0050] Where t is the holding diffusion time, d1 is the average diffusion distance, and D is the diffusion coefficient (the diffusion coefficient under no stress can be used here).

[0051] Step 1.4: Long-term diffusion. For long-term diffusion, the average diffusion distance should be approximately twice the specimen extension length, L. The diffusion time is calculated using the same method as above. Based on this and the acceptable duration, the size of the U-shaped specimen can be reversely designed.

[0052] In step 2, the hydrogen distribution test is carried out by neutron scattering method in the direction perpendicular to the U-shaped surface (i.e., in the direction of width w) (due to the presence of an oxide film on the side of the sample, it can be assumed that the side does not absorb hydrogen, and only the inner and outer surfaces absorb hydrogen. Therefore, it is reasonable to assume that the distribution of hydrogen in the w direction is uniform, and the subsequent hydrogen absorption and diffusion model can also be simplified to a two-dimensional model). When testing by neutron scattering method, samples of the same material, width and different hydrogen concentrations (which can be prepared by gas phase absorption method) can be placed at the same time as calibration samples to improve the test accuracy. When there are no neutron scattering test conditions, a multi-point sampling test method is adopted (specific test methods include vacuum heat extraction-mass spectrometry, inert gas melting-thermal conductivity method, etc.). Since the latter is a destructive test method, multiple samples need to be prepared, and at least one sample is taken for sampling test in each step.

[0053] In step 2, an initial hydrogen distribution test is performed to obtain the hydrogen content distribution of the sample before gas-phase hydrogenation, which serves as a background to be considered in subsequent calculations.

[0054] In step 2, a hydrogen concentration distribution test is performed after gas-phase hydrogen charging. The hydrogen content distribution of the sample after gas-phase hydrogen charging is obtained, and the difference between the hydrogen content distribution and the initial hydrogen content distribution is the absorbed hydrogen content, which is used to calculate the hydrogen absorption rate.

[0055] In step 2, a hydrogen concentration distribution test is performed after a short-term heat preservation. The hydrogen content distribution of the sample after a short-term heat preservation diffusion is obtained and used for the calculation of the diffusion coefficient.

[0056] In step 2, a hydrogen concentration distribution test is performed after a long period of heat preservation. The hydrogen content distribution of the sample after long-term heat preservation and diffusion is obtained and used for hydrogen chemical potential calculation.

[0057] In step 3, the stress distribution is calculated using the finite element method (FEM) to calculate the stress distribution in the self-loaded sample.

[0058] In step 3, the hydrogen absorption parameters are calculated. Based on the pressure drop curve during the hydrogen charging process, the hydrogen concentration distribution after gas-phase hydrogen charging, and the initial hydrogen concentration distribution, the hydrogen absorption rate at different stresses is calculated (when the total amount of hydrogen absorbed is small, it is reasonable to assume that the ratio of hydrogen absorption rates at different locations remains unchanged throughout the hydrogen absorption process). The relationship between the hydrogen absorption rate and parameters such as stress and upstream pressure is fitted.

[0059] In step 3, the hydrogen chemical potential is calculated. After a long period of heat preservation, the hydrogen concentration distribution reaches a steady state, that is, the hydrogen chemical potential at different locations reaches equilibrium, and the hydrogen chemical potential gradient is the sum of the hydrogen concentration gradient and the chemical potential gradient caused by stress. That is, when the steady state is finally reached, the chemical potential gradient caused by stress at different locations is equal to the concentration gradient in magnitude but opposite in direction. The formula is:

[0060]

[0061] Where M is the proportional coefficient, i.e. the generalized diffusion coefficient, and D is the diffusion coefficient. is the stress-induced hydrogen chemical potential gradient, is the concentration gradient.

[0062] Therefore, the relationship between the stress-induced hydrogen chemical potential and stress is calculated based on the stress and hydrogen concentration at different locations. If only the effect of the two on diffusion is considered, without considering the dimension difference and only considering the numerical value, and setting M = D, it can also be simplified to the following formula:

[0063] u＝ -c (Formula 2)

[0064] Where u is the stress-induced hydrogen chemical potential and c is the hydrogen concentration.

[0065] In step 3, the diffusion parameters are calculated. When the hydrogen concentration is low, it is reasonable to assume that the diffusion coefficient does not change with the change of hydrogen concentration. First, a finite element diffusion model is established, and the hydrogen concentration distribution after gas phase hydrogenation is used as the initial state of diffusion. The diffusion flux equation is:

[0066]

[0067] When using Formula 2 to obtain the law of change of u with stress, M=D can be set. First, a function of change of D value with stress is assumed (the greater the tensile stress, the faster the diffusion, for example, a polynomial function can be taken), and the time of short-time insulation is substituted. The hydrogen concentration distribution after diffusion is calculated and compared with the actual hydrogen concentration distribution after short-time insulation. Then, the function of change of D value with stress is gradually adjusted until the two are in good agreement, and finally the function of change of D value with stress is obtained.

[0068] Therefore, the method for testing metal hydrogen absorption and hydrogen diffusion parameters under stress field provided in this application mainly includes sample preparation, gas phase hydrogen charging, thermal insulation diffusion, hydrogen distribution testing, calculation, etc.

[0069] (1) Sample preparation. Self-loading specimens such as U-shaped or C-shaped specimens are used. The specific preparation methods can be referred to GB / T15970.3 and GB / T15970.5.

[0070] (2) Gas-phase hydrogen charging. Use a gas-phase hydrogen charging device to charge the loaded sample with hydrogen. The hydrogen charging time should be short to reduce internal diffusion. The hydrogen charging temperature can be flexibly selected based on the actual service temperature of the material or the accelerated test temperature, but it should not exceed the stress relief temperature of the material.

[0071] (3) Thermal diffusion. The hydrogen-charged sample is thermally diffused to allow the hydrogen in it to diffuse freely and redistribute. The thermal insulation temperature can be flexibly selected according to the actual service temperature of the material or the accelerated test temperature, but it should not exceed the stress relief temperature of the material. There are many options for thermal insulation time: when the time is long enough (i.e., hydrogen diffuses to a steady state), the hydrogen distribution is related to the chemical potential; when the thermal insulation time is relatively short, the hydrogen distribution is related to the hydrogen diffusion process.

[0072] (4) Hydrogen distribution test. When there is a standard sample with the same material and thickness as the sample, the neutron scattering method is preferred; other methods include multiple local sampling tests and then fitting the hydrogen concentration distribution based on the multi-point concentration.

[0073] (5) Calculation. It mainly includes stress distribution calculation, hydrogen absorption parameter calculation, hydrogen chemical potential calculation and hydrogen diffusion calculation. The stress distribution is calculated by the finite element method through the mechanical properties parameters, size, loading parameters and test temperature of the sample. The hydrogen absorption parameter is calculated as a function of stress. First, the hydrogen absorption rate ratio at different positions is obtained by the hydrogen distribution after hydrogenation (assuming that the ratio remains unchanged during the hydrogenation process), and then it is calculated based on the curve of the change of gas pressure with time during the hydrogenation process. The function of hydrogen chemical potential changing with stress can be calculated based on the hydrogen distribution in the sample with a sufficiently long holding time (the hydrogen concentration is proportional to the absolute value of hydrogen chemical potential). The method for calculating the function of hydrogen diffusion coefficient changing with stress is as follows: calculate the hydrogen distribution at the end of holding according to the hydrogen distribution after gas phase hydrogenation (i.e. the initial state of diffusion), the function of hydrogen diffusion coefficient changing with stress (first assume, then gradually optimize), the function of hydrogen chemical potential changing with stress, holding temperature and diffusion time, and compare it with the hydrogen distribution test results, and gradually optimize the function of hydrogen diffusion coefficient changing with stress until the calculated hydrogen distribution is consistent with the test results.

[0074] Through the above tests and calculations, the variation functions of hydrogen absorption parameters, hydrogen chemical potential and diffusion coefficient of zirconium-like alloys with stress can be obtained.

[0075] The above description is only a specific implementation method of the present application, but the scope of protection of the present application is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed in this application should be covered by the scope of protection of the present application.

Claims

1. A method for testing metal hydrogen absorption and hydrogen diffusion parameters under stress field, characterized in that: include: Step 1: The sample is processed into a specimen after vacuum heat extraction and dehydrogenation, compressed and loaded, and gas-phase hydrogen is charged and the hydrogen concentration is controlled. Short-term and long-term heat preservation diffusion are carried out in stages; Step 2: Test the sample and measure the hydrogen distribution before hydrogen charging, after hydrogen charging, and after short and long time holding; Step 3: Analyze the stress distribution of the self-loaded specimen using the finite element method, calculate the hydrogen absorption rate at different stresses, and fit the relationship between the hydrogen absorption rate and the parameters; based on the steady-state hydrogen concentration distribution, establish the relationship between hydrogen chemical potential and stress; By constructing a finite element model, taking the distribution after hydrogen charging as the initial state, and using the flux equation, the stress-related diffusion coefficient D is iteratively adjusted to match the simulated short-time diffusion distribution with the actual test data, and the change pattern of D with stress is determined.

2. The method for testing metal hydrogen absorption and hydrogen diffusion parameters under stress field according to claim 1, characterized in that: In step 1, the sample is processed into a U-shaped or C-shaped specimen.

3. The method for testing metal hydrogen absorption and hydrogen diffusion parameters under stress field according to claim 1, characterized in that: In step 1, the average diffusion distance in the short term is about 1 / 4 of the sample thickness d, and the average diffusion distance in the long term is twice the sample extension length L.

4. The method for testing metal hydrogen absorption and hydrogen diffusion parameters under stress field according to claim 1, characterized in that: Step 1 specifically includes: Step 1.1: Use vacuum heat extraction to remove hydrogen from the raw material. Process it into a self-loading U-shaped or C-shaped specimen. Compress the specimen in a universal testing machine and record the pressure at a specific position. After unloading, reload it with bolts to compress it to the same position. Step 1.2: Use a gas phase hydrogen charging device to charge the loaded sample with hydrogen. Before charging, calculate the maximum chargeable hydrogen volume and the corresponding maximum charging pressure based on the solubility of hydrogen in the material. The average hydrogen concentration should be no less than 5ppm. The surface oxide film of the hydrogen-charged sample should be fully removed, and the sample should be loaded under the protection of inert gas. Step 1.3: Short-term heat preservation diffusion, the heat preservation diffusion is carried out directly in the air environment, and the average diffusion distance of the short-term heat preservation diffusion is 1 / 4 of the sample thickness d; Step 1.4: Long-term heat preservation diffusion. The average diffusion distance of long-term heat preservation diffusion is twice the sample extension length L.

5. The method for testing metal hydrogen absorption and hydrogen diffusion parameters under stress field according to claim 1, characterized in that: In step 2, a hydrogen concentration distribution test is performed after gas-phase hydrogen charging to obtain the hydrogen content distribution of the sample after gas-phase hydrogen charging, and the hydrogen absorption rate is calculated based on this.

6. The method for testing metal hydrogen absorption and hydrogen diffusion parameters under stress field according to claim 1, characterized in that: In step 2, a hydrogen concentration distribution test after short-time heat preservation is performed to obtain the hydrogen content distribution of the sample after short-time heat preservation and diffusion.

7. The method for testing metal hydrogen absorption and hydrogen diffusion parameters under stress field according to claim 1, characterized in that: In step 2, a hydrogen concentration distribution test after long-term heat preservation is performed to obtain the hydrogen content distribution of the sample after long-term heat preservation and diffusion to calculate the hydrogen chemical potential.

8. The method for testing metal hydrogen absorption and hydrogen diffusion parameters under stress field according to claim 1, characterized in that: In step 3, the hydrogen absorption rate at different stresses is calculated based on the pressure drop curve during the hydrogen charging process, the hydrogen concentration distribution after gas-phase hydrogen charging, and the initial hydrogen concentration distribution, and the relationship between the hydrogen absorption rate and the parameters is fitted.

9. The method for testing metal hydrogen absorption and hydrogen diffusion parameters under stress field according to claim 1, characterized in that: In step 3, after a long period of heat preservation, the hydrogen concentration distribution reaches a steady state. The hydrogen chemical potential gradient is the sum of the hydrogen concentration gradient and the chemical potential gradient caused by stress. When the steady state is reached, the chemical potential gradient caused by stress is equal to the concentration gradient in magnitude and opposite in direction. The formula is: Where M is the proportional coefficient, D is the diffusion coefficient, is the stress-induced hydrogen chemical potential gradient, is the concentration gradient.

10. The method for testing metal hydrogen absorption and hydrogen diffusion parameters under stress field according to claim 1, characterized in that: In step 3, the diffusion parameters are calculated. When the hydrogen concentration is low, it is assumed that the diffusion coefficient does not change with the change of hydrogen concentration. A finite element diffusion model is established. The hydrogen concentration distribution after gas phase hydrogenation is used as the initial state of diffusion. The diffusion flux equation is: When u=-c is used to obtain the law of change of u with stress, let M=D, first assume a function of change of D value with stress, substitute the time of short-time insulation, calculate the hydrogen concentration distribution after diffusion, and compare it with the actual hydrogen concentration distribution after short-time insulation. Then, gradually adjust the function of change of D value with stress until the two are consistent, and finally obtain the function of change of D value with stress.

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