Metal material performance evaluation method and system based on creep-fatigue interaction

Abstract

The present invention discloses a metal material performance evaluation method and system based on creep-fatigue interaction, which belongs to the technical field of metal material performance evaluation, including: based on the elastic-plastic performance data and creep performance data of the metal material, respectively calculating the monotonic crack tip opening displacement and cyclic crack tip opening displacement caused by plasticity or creep of the short crack under the far-field maximum stress and far-field cyclic stress; and obtaining the total monotonic crack tip opening displacement and cyclic crack tip opening displacement of the short crack under the combined action of creep-fatigue by linear superposition method, and evaluating the performance of the metal material by calculating the short crack growth rate of the metal material under the creep-fatigue interaction. The present invention solves the problems in the traditional method that the existing method relies on a large amount of crack growth test data and does not fully consider the creep-fatigue short crack effect.

Description

Technical Field

[0001] The present invention relates to the technical field of metal material performance evaluation, and in particular to a metal material performance evaluation method and system based on creep-fatigue interaction. Background Art

[0002] Energy equipment will generate creep-fatigue loads due to start-stop and power adjustment during operation. Different from single creep / fatigue loads, under creep-fatigue interaction, structural parts will fail faster, threatening the stable operation of energy unit structural parts. The calculation of creep-fatigue crack growth rate is of vital importance in the structural integrity assessment of high-temperature components of modern energy equipment.

[0003] The traditional method of calculating the creep-fatigue crack growth rate requires a large number of creep-fatigue crack growth tests to determine the corresponding material parameters. At the same time, due to the short crack effect, traditional fracture mechanics parameters cannot be used to calculate the creep-fatigue short crack growth rate. A large number of studies have shown that the short crack growth stage accounts for more than 70% of the material crack growth life. Therefore, it is urgent to develop a metal material performance evaluation technology based on creep-fatigue interaction, which can simply and efficiently evaluate the creep-fatigue performance of metal materials by calculating the short cracks of metal materials under creep-fatigue interaction. Summary of the invention

[0004] In order to solve the above problems, the purpose of the present invention is to provide a metal material performance evaluation technology based on creep-fatigue interaction, based on the evolution law of the plastic zone and creep zone at the tip of the short crack under creep-fatigue load, calculate the damage caused by creep and fatigue load through the dislocation model, and then determine the short crack growth rate model of the metal material under creep-fatigue interaction. The test data of this method are all derived from simple uniaxial test results, which solves the problems of existing methods relying on a large amount of crack growth test data and incomplete consideration of creep-fatigue short crack effects, and provides a theoretical basis for the structural integrity evaluation of high-temperature components of energy equipment serving under complex working conditions.

[0005] In order to achieve the above technical objectives, the present application provides a metal material performance evaluation method based on creep-fatigue interaction, comprising the following steps:

[0006] Based on the elastic-plastic performance data of metal materials and the evolution law of the crack tip plastic zone, the first monotonic crack tip opening displacement caused by the plasticity of the short crack under the far-field maximum stress and the first cyclic crack tip opening displacement caused by the plasticity under the far-field cyclic stress are obtained;

[0007] Based on the creep performance data of metal materials and the evolution law of the creep zone at the crack tip, the second monotonic crack tip opening displacement caused by the creep of short cracks under the far-field maximum stress and the second cyclic crack tip opening displacement caused by creep under the far-field cyclic stress are obtained through the dislocation model.

[0008] Based on the first monotonic crack tip opening displacement, the first cyclic crack tip opening displacement, the second monotonic crack tip opening displacement and the second cyclic crack tip opening displacement, the total monotonic crack tip opening displacement and the cyclic crack tip opening displacement of the short crack under the combined action of creep-fatigue are obtained, and the performance of the metal material is evaluated by calculating the short crack growth rate of the metal material under the interaction of creep-fatigue.

[0009] Preferably, in the process of obtaining the first monotonic crack tip opening displacement, the first monotonic crack tip opening displacement is obtained according to the yield strength, elastic modulus, Poisson's ratio, far-field maximum stress and short crack length of the metal material.

[0010] Preferably, in the process of obtaining the first cycle crack tip opening displacement, the first cycle crack tip opening displacement is generated by obtaining the load ratio based on the yield strength, elastic modulus, Poisson's ratio, far-field maximum stress and short crack length of the metal material.

[0011] Preferably, in the process of obtaining the second monotonic crack tip opening displacement, the second monotonic crack tip opening displacement is obtained by obtaining the equivalent creep yield strength of the metal material based on the yield strength, elastic modulus, Poisson's ratio, far-field maximum stress and short crack length of the metal material.

[0012] Preferably, in the process of obtaining the second cycle crack tip opening displacement, the second cycle crack tip opening displacement is generated by obtaining the load ratio and equivalent creep yield strength based on the yield strength, elastic modulus, Poisson's ratio, far-field maximum stress and short crack length of the metal material.

[0013] Preferably, in the process of obtaining the equivalent creep yield strength, the coplanar creep zone size related to the creep time is obtained, and the equivalent creep yield strength is obtained according to the short crack length and the far-field maximum stress.

[0014] Preferably, in the process of obtaining the coplanar creep zone size, the stress intensity factor of mode I crack, the creep stress index of the metal material, the sample thickness, the creep time and the correction parameters related to the creep stress index are obtained, and the coplanar creep zone size is obtained according to the elastic modulus of the metal material.

[0015] Preferably, in the process of acquiring the correction parameter, the correction parameter is acquired based on the creep stress index by acquiring material parameters related to the creep stress index.

[0016] Preferably, in the process of obtaining the total monotonic crack tip opening displacement and cyclic crack tip opening displacement of a short crack under the combined action of creep-fatigue, a linear superposition method is used to obtain the total monotonic crack tip opening displacement and cyclic crack tip opening displacement of a short crack under the combined action of creep-fatigue.

[0017] The present invention discloses a metal material performance evaluation system based on creep-fatigue interaction, comprising:

[0018] A first data calculation module is used to obtain the first monotonic crack tip opening displacement caused by the plasticity of the short crack under the far-field maximum stress and the first cyclic crack tip opening displacement caused by the plasticity under the far-field cyclic stress based on the elastic-plastic performance data of the metal material and the evolution law of the crack tip plastic zone;

[0019] The second data calculation module, based on the creep performance data of metal materials and combined with the evolution law of the creep zone at the crack tip, obtains the second monotonic crack tip opening displacement caused by the creep of the short crack under the far-field maximum stress, and the second cyclic crack tip opening displacement caused by the creep under the far-field cyclic stress through the dislocation model;

[0020] The evaluation module is used to obtain the total monotonic crack tip opening displacement and cyclic crack tip opening displacement of the short crack under the combined action of creep-fatigue based on the first monotonic crack tip opening displacement, the first cyclic crack tip opening displacement, the second monotonic crack tip opening displacement and the second cyclic crack tip opening displacement, and evaluate the performance of the metal material by calculating the short crack growth rate of the metal material under the interaction of creep-fatigue.

[0021] The present invention discloses the following technical effects:

[0022] The present invention takes into account the accelerating effect of creep-fatigue interaction on the short crack growth rate, solving the problem that the traditional method cannot accurately calculate the creep-fatigue short crack growth rate;

[0023] The present invention is a short crack growth rate calculation method based on uniaxial tension and creep test data, which solves the problem that the traditional method relies on a large amount of crack growth test data;

[0024] The method for calculating the short crack growth rate under creep-fatigue interaction proposed in the present invention can obtain a unified prediction result of the short crack growth rate under different creep times, thus solving the limitation of the creep holding time effect in the traditional method.

[0025] It has been verified that the present invention has good effect in calculating the creep-fatigue short crack growth rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 It is a schematic diagram of the method flow of the present invention;

[0028] Figure 2 It is a schematic diagram of parameter fitting of uniaxial creep test data of the present invention;

[0029] Figure 3 is a schematic diagram of parameter fitting of uniaxial tensile test data of the present invention;

[0030] Figure 4 It is a graph of calculation results of creep-fatigue short crack growth rate described in the present invention;

[0031] Figure 5 This is a graph of the calculation results of the creep-fatigue short crack growth rate using the traditional method based on test data described in the present invention. DETAILED DESCRIPTION

[0032] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme 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 only part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0033] like Figure 1-5As shown, the present invention provides a metal material performance evaluation technology based on creep-fatigue interaction, which simply and efficiently evaluates the creep-fatigue performance of metal materials by calculating short cracks of metal materials under creep-fatigue interaction, including the following steps: constructing a short crack growth rate calculation model under creep-fatigue interaction. The prediction model calculates the creep-fatigue short crack growth rate of the material using creep performance data based on uniaxial creep test and elastic-plastic performance data based on uniaxial tensile test; through the elastic-plastic performance data of the uniaxial tensile test, combined with the evolution law of the plastic zone at the crack tip, the monotonic crack tip opening displacement caused by the plasticity of the short crack under the far-field maximum stress is obtained through the dislocation model. and the cyclic crack tip opening displacement caused by plasticity under remote cyclic stress Through the creep performance data of the uniaxial creep test, combined with the evolution law of the creep zone at the crack tip, the monotonic crack tip opening displacement caused by the creep of the short crack under the maximum stress in the far field is obtained through the dislocation model. and the cyclic crack tip opening displacement caused by creep under remote cyclic stress The total monotonic crack tip opening displacement δ of a short crack under the combined action of creep and fatigue is calculated based on the monotonic / cyclic crack tip opening displacement caused by creep / fatigue. t and the cyclic crack tip opening displacement δ r ; Based on the acquired δ t and δ r The creep-fatigue short crack growth rate of the material is calculated through the short crack growth rate calculation model under creep-fatigue interaction. The invention solves the problems in the traditional method that the existing method relies on a large amount of crack growth test data and does not fully consider the creep-fatigue short crack effect.

[0034] The present invention provides a method for calculating short cracks in metal materials under creep-fatigue interaction, which specifically includes the following steps:

[0035] Step 1: Construct a calculation model for the short crack growth rate under creep-fatigue interaction. This prediction model uses creep performance data based on uniaxial creep tests and elastic-plastic performance data based on uniaxial tensile tests to calculate the creep-fatigue short crack growth rate of the material;

[0036] Step 2: Based on the elastic-plastic performance data of the uniaxial tensile test and the evolution law of the crack tip plastic zone, the monotonic crack tip opening displacement caused by the plasticity of the short crack under the far-field maximum stress is obtained through the dislocation model. and the cyclic crack tip opening displacement caused by plasticity under remote cyclic stress

[0037] Step 3: Based on the creep performance data of the uniaxial creep test and the evolution law of the creep zone at the crack tip, the monotonic crack tip opening displacement caused by the creep of the short crack under the far-field maximum stress is obtained through the dislocation model. and the cyclic crack tip opening displacement caused by creep under remote cyclic stress

[0038] Step 4: Calculate the total monotonic crack tip opening displacement of the short crack under the combined action of creep-fatigue based on the monotonic / cyclic crack tip opening displacement caused by creep / fatigue and cyclic crack tip opening displacement

[0039] Step 5: Based on the obtained δ t and δ r , the creep-fatigue short crack growth rate of the material is calculated through the short crack growth rate calculation model under creep-fatigue interaction.

[0040] When constructing the short crack growth rate calculation model under creep-fatigue interaction described in step 1, the crack growth rate is expressed as the crack extension amount per cycle: (dc) cycle

[0041] The expression used in constructing the short crack growth rate calculation model under creep-fatigue interaction described in step 1 is:

[0042] (dc) cycle =β(δ t δ r )α

[0043] Where β and α are the fitting parameters of the model.

[0044] Obtain the monotonic crack tip opening displacement caused by the plasticity of the short crack under the far-field maximum stress described in step 2 When , its expression is:

[0045]

[0046] Among them, σ y is the yield strength of the material, E is the elastic modulus of the material, ν is the Poisson's ratio of the material, σ peak is the far-field maximum stress, and c is the short crack length.

[0047] The cyclic crack tip opening displacement caused by the plasticity of the short crack under the remote cyclic stress described in step 2 is obtained. When , its expression is:

[0048]

[0049] Where R is the load ratio.

[0050] Obtain the monotonic crack tip opening displacement caused by creep of the short crack under the far-field maximum stress described in step 3 When , its expression is:

[0051]

[0052] Preferably, the equivalent creep yield strength of the material is obtained When , its expression is:

[0053]

[0054] Among them, ρ cr (t) is the coplanar creep zone size related to the creep time.

[0055] In obtaining the time-dependent coplanar creep zone size ρ cr (t), its expression is:

[0056]

[0057] Among them, K I is the stress intensity factor of mode I crack, m is the creep stress index of the material, W is the specimen thickness, t is the creep time, r m and ψ cr is a correction parameter related to the creep stress exponent m.

[0058] In obtaining the correction parameter r related to the creep stress exponent n m When , its expression is:

[0059]

[0060] Among them, η m is a material parameter related to the creep stress exponent m.

[0061] In obtaining the correction parameter η related to the creep stress exponent m m When , its value is determined by interpolation method based on Table 1.

[0062] Table 1

[0063] m 3 5 9 13 <![CDATA[η m ]]> 3.86 3.41 3.03 2.87

[0064] In obtaining the correction parameter ψ related to the creep stress exponent m cr When , its value is determined by interpolation method based on Table 2.

[0065] Table 2

[0066] m 3 5 13 <![CDATA[ψ cr ]]> 0.25 0.32 0.38

[0067] Obtain the total monotonic crack tip opening displacement δ of the short crack described in step 4 under the combined action of creep and fatigue t and the cyclic crack tip opening displacement δ c When the linear superposition method is used, the expression is:

[0068]

[0069] When predicting the creep-fatigue short crack growth rate of high-temperature components of energy equipment, the materials are heat-resistant martensitic steel and austenitic steel, and the service temperature is 500-700℃.

[0070] Example 1: Please refer to Figure 1 As shown, the present invention provides a method for calculating short cracks under creep-fatigue interaction of metal materials, including: a method for calculating the creep-fatigue short crack growth rate based on creep performance data of a uniaxial creep test and elastic-plastic performance data of a uniaxial tensile test.

[0071] In order to better illustrate the calculation method of short cracks under creep-fatigue interaction of metal materials in the present invention, a single-side notch specimen will be used for verification. The material used for verification is 316H heat-resistant steel, and uniaxial creep, uniaxial tension, and creep-fatigue short crack growth tests are carried out at 550°C. The load control method is used in the predicted creep-fatigue short crack growth rate test, which is maintained at the peak load and the waveform is a trapezoidal wave.

[0072] Step (1) is to use a nonlinear fitting method based on the steady-state creep rates at different stress levels obtained from the uniaxial creep test, such as Figure 2 As shown in the figure, the creep stress exponent m at 550°C is 11.31. Further, the correction parameter r related to the creep stress exponent m can be obtained. m and ψ cr The values ​​of are 1.01 and 0.3673 respectively.

[0073] Step (2), according to the tensile curve obtained by the uniaxial tensile test, such as Figure 3 As shown in Figure 2, the elastic-plastic properties at 550°C are obtained, including: elastic modulus E is 180 GPa; yield stress σ y The Poisson's ratio ν for metal materials is 0.3.

[0074] Step (3), based on the obtained elastic-plastic properties, obtain the monotonic crack tip opening displacement caused by the plasticity of the short crack under the far-field maximum stress and the cyclic crack tip opening displacement caused by plasticity under remote cyclic stress The expressions are:

[0075]

[0076]

[0077] Step (4), based on the obtained creep performance, obtain the time-dependent coplanar creep zone size ρ cr (t) and the equivalent creep yield strength of the material The expressions are:

[0078]

[0079]

[0080] Step (5), using the results obtained in step (4), obtain the monotonic crack tip opening displacement caused by creep of the short crack under the far-field maximum stress and the cyclic crack tip opening displacement caused by creep under remote cyclic stress The expressions are:

[0081]

[0082]

[0083] Step (6), using the monotonic / cyclic crack tip opening displacement caused by creep / fatigue determined in steps (3) and (4), calculate the total monotonic crack tip opening displacement δ of the short crack under the combined action of creep-fatigue t and the cyclic crack tip opening displacement δ c , whose expression is:

[0084]

[0085] Step (7), based on the obtained δ t and δ c , the creep-fatigue short crack growth rate of the material is calculated by the short crack growth rate calculation model under creep-fatigue interaction, and its expression is:

[0086] (dc) cycle =β(δ t δ r )α.

[0087] In order to verify the calculation method for short cracks in metal materials under creep-fatigue interaction proposed in this invention, the creep-fatigue short crack growth rate under 550°C calculated by this method is as follows: Figure 4As shown. For comparison, the traditional method based on experimental data to calculate the creep-fatigue short crack growth rate is shown in Figure 5 It can be seen that the calculation method for short cracks under creep-fatigue interaction of metal materials proposed in the present invention has good prediction results for creep-fatigue short crack growth rate under different holding times, which solves the limitations of traditional methods that cannot accurately describe short crack growth behavior and the prediction results have a correlation with the holding time.

[0088] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0089] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0090] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A metal material performance evaluation method based on creep-fatigue interaction, characterized in that: The following steps are involved: Based on the elastic-plastic performance data of metal materials and the evolution law of the crack tip plastic zone, the first monotonic crack tip opening displacement caused by the plasticity of the short crack under the far-field maximum stress and the first cyclic crack tip opening displacement caused by the plasticity under the far-field cyclic stress are obtained; Based on the creep performance data of metal materials and the evolution law of the creep zone at the crack tip, the second monotonic crack tip opening displacement caused by the creep of short cracks under the far-field maximum stress and the second cyclic crack tip opening displacement caused by creep under the far-field cyclic stress are obtained through the dislocation model. Based on the first monotonic crack tip opening displacement, the first cyclic crack tip opening displacement, the second monotonic crack tip opening displacement and the second cyclic crack tip opening displacement, the total monotonic crack tip opening displacement and the cyclic crack tip opening displacement of the short crack under the combined action of creep-fatigue are obtained, and the performance of the metal material is evaluated by calculating the short crack growth rate of the metal material under the interaction of creep-fatigue; In the process of obtaining the first monotonic crack tip opening displacement, the first monotonic crack tip opening displacement The expression is: Among them, σ y is the yield strength of the material, E is the elastic modulus of the material, ν is the Poisson's ratio of the material, σ peak is the far-field maximum stress, c is the short crack length; In the process of obtaining the first cycle crack tip opening displacement, the first cycle crack tip opening displacement The expression is: Where R is the load ratio; In the process of obtaining the second monotonic crack tip opening displacement, the second monotonic crack tip opening displacement The expression is: In obtaining the equivalent creep yield strength of the material When , its expression is: Among them, ρ cr (t) is the size of the coplanar creep zone related to the creep time; In obtaining the time-dependent coplanar creep zone size ρ cr (t), its expression is: Among them, K I is the stress intensity factor of mode I crack, m is the creep stress index of the material, W is the specimen thickness, t is the creep time, r m and ψ cr is the correction parameter related to the creep stress exponent m; In the process of obtaining the second cycle crack tip opening displacement, the second cycle crack tip opening displacement The expression is: In obtaining the correction parameter r related to the creep stress exponent n m When , its expression is: Among them, η m is a material parameter related to the creep stress exponent m.

2. The metal material performance evaluation method based on creep-fatigue interaction according to claim 1 is characterized in that: In the process of obtaining the total monotonic crack tip opening displacement and cyclic crack tip opening displacement of a short crack under the combined action of creep-fatigue, the linear superposition method is used to obtain the total monotonic crack tip opening displacement and cyclic crack tip opening displacement of a short crack under the combined action of creep-fatigue.

3. A metal material performance evaluation system based on creep-fatigue interaction, used to implement the metal material performance evaluation method based on creep-fatigue interaction as claimed in claim 1, characterized in that: include: A first data calculation module is used to obtain the first monotonic crack tip opening displacement caused by the plasticity of the short crack under the far-field maximum stress and the first cyclic crack tip opening displacement caused by the plasticity under the far-field cyclic stress based on the elastic-plastic performance data of the metal material and the evolution law of the crack tip plastic zone; The second data calculation module, based on the creep performance data of metal materials and combined with the evolution law of the creep zone at the crack tip, obtains the second monotonic crack tip opening displacement caused by the creep of the short crack under the far-field maximum stress, and the second cyclic crack tip opening displacement caused by the creep under the far-field cyclic stress through the dislocation model; An evaluation module is used to obtain the total monotonic crack tip opening displacement and the cyclic crack tip opening displacement of the short crack under the combined action of creep-fatigue based on the first monotonic crack tip opening displacement, the first cyclic crack tip opening displacement, the second monotonic crack tip opening displacement and the second cyclic crack tip opening displacement, and evaluate the performance of the metal material by calculating the short crack growth rate of the metal material under the interaction of creep-fatigue.

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