A method for simulating high-temperature tensile of a ferritic / austenitic dissimilar steel welded joint

Abstract

The present invention relates to a method for simulating high-temperature tensile of a ferritic / austenitic dissimilar steel welded joint, comprising: Step 1: Obtaining high-temperature tensile specimen data of ferritic steel, austenitic steel and ferritic / austenitic dissimilar steel welded joint; Step 2: Fitting the stress-strain in Step 1 according to a multi-linear model to obtain unknown parameters in the model, thereby obtaining the stress-strain constitutive relationship of the material; Step 3: Modeling according to the test model and boundary conditions, performing finite element simulation based on the stress-strain constitutive relationship, and saving the simulation results; Step 4: Post-processing the simulation results and outputting key data. Compared with the prior art, the present invention has the advantages of good simulation effect, high efficiency, low cost, etc.

Description

Technical Field

[0001] The present invention relates to the field of finite element simulation analysis, and particularly to a method for simulating high-temperature tension of a ferritic / austenitic dissimilar steel welded joint. Background Art

[0002] Dissimilar steel welded joints are widely used in industries such as electric power, shipbuilding, and chemical engineering. In thermal power plants, especially ultra-supercritical units, components operating in high-temperature and high-pressure environments, such as superheaters and reheaters, all use austenitic heat-resistant steels. Austenitic heat-resistant steels represented by HR3C, TP347H, and Super304H have characteristics such as high creep fracture strength, oxidation resistance, and the ability to serve for a long time; components such as boilers and heat exchangers working in environments with relatively low temperatures are made of cheaper martensitic heat-resistant steels. Martensitic heat-resistant steels represented by T / P91 and T / P92 have excellent thermal conductivity, low thermal expansion coefficient, and high creep fracture strength and other characteristics. Therefore, welding of different metals has to be carried out in the transition region, taking into account the characteristics of both heat-resistant steels. However, due to the different compositions, structures, and physical properties of the base materials, the failure time of dissimilar steel welded joints will be earlier than that of the base materials, especially in high-temperature and high-pressure environments. Therefore, the research on dissimilar steel welded joints is very important. A large number of scholars have studied dissimilar steel welded joints, mainly from two aspects: joint processing and manufacturing and joint service performance: (1) studying the effects of welding grooves, rotary friction welding, post-weld heat treatment, etc. on the microstructure and mechanical properties of dissimilar steel welded joints; (2) studying creep-fatigue performance, crack propagation law, the influence of oxide layers on material properties, and changes in the microstructure before and after joint service during the service process of the joint. There is less research on the tensile properties and constitutive models of dissimilar steels, and there is also less research using finite element simulation methods in this regard, mainly focusing on the simulation of material creep, fracture, and welding processes, etc.

[0003] Experiment is the most direct and accurate research method, but experiments require a certain amount of time, energy, and experimental costs. Some experiments are also dangerous, and improper operation will even lead to large errors or failures in the experiments. The simulation method well solves the above problems and shortens the research cycle. At the same time, simulation can also more intuitively display many experimental phenomena, or magnify some unobvious experimental phenomena. Some insignificant experimental phenomena may bring new ideas. Therefore, it is extremely necessary to find a finite element simulation method for high-temperature tension, which can be studied simply, conveniently, and efficiently. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for simulating high-temperature tension of a ferritic / austenitic dissimilar steel welded joint with good simulation effect, high efficiency, and low cost, in order to overcome the defects of the existing technologies described above.

[0005] The object of the present invention can be achieved by the following technical solutions:

[0006] A method for simulating high-temperature tension of a ferritic / austenitic dissimilar steel welded joint, the simulation method comprising:

[0007] Step 1: Obtain high-temperature tension test specimen data of ferritic steel, austenitic steel, and a ferritic / austenitic dissimilar steel welded joint;

[0008] Step 2: Fit the stress-strain in Step 1 according to a multi-linear model to obtain the unknown parameters in the model, thereby obtaining the stress-strain constitutive relationship of the material;

[0009] Step 3: Model according to the test model and boundary conditions, perform finite element simulation based on the stress-strain constitutive relationship, and save the simulation results;

[0010] Step 4: Post-process the simulation results and output key data.

[0011] Preferably, Step 1 is specifically:

[0012] Fabricate high-temperature tension test specimens of ferritic steel, austenitic steel, and a ferritic / austenitic dissimilar steel welded joint, perform high-temperature tension experiments on a high-temperature tension testing machine according to the actual working conditions required, and save the required data.

[0013] More preferably, the method for obtaining specimen data in Step 1 is specifically:

[0014] Step 1-1: Design tensile specimens according to the dimensions of the raw materials and the dimensions allowed to be clamped by the high-temperature tension testing machine, and process the specimens;

[0015] Step 1-2: Install the specimen on the high-temperature tension testing machine and clamp it, install an extensometer and adjust the extensometer, and close the high-temperature furnace;

[0016] Step 1-3: Set the parameters of the high-temperature tension testing machine;

[0017] Step 1-4: Release the load brought during the test, let the high-temperature furnace cool naturally, after the temperature of the high-temperature furnace and the specimen drops to room temperature, remove the extensometer and the specimen, reset the high-temperature tension testing machine and shut it down, end the test, and record the required sample data.

[0018] More preferably, Step 1-3 is specifically:

[0019] Set the test temperature, temperature gradient, heat preservation time, strain range, loading rate, and loading time of the high-temperature tension testing machine.

[0020] More preferably, the sample data includes: temperature, displacement, load force, strain, and time.

[0021] Preferably, step 2 is specifically as follows:

[0022] Step 2-1: Fit the true stress and true strain data according to a pre-selected model to obtain the unknown parameters in the model;

[0023] Step 2-2: Compare the fitted model curve with the true stress-true strain curve graph, and let the user judge whether it is reasonable. If it is reasonable, export it. If it is not reasonable, return to step 2-1 for re-fitting.

[0024] Preferably, step 3 is specifically as follows:

[0025] Step 3-1: Set the model parameters and import the stress-strain constitutive relationship obtained in step 2;

[0026] Step 3-2: Build the model and perform mesh division;

[0027] Step 3-3: Define the constraints and finite element analysis items, perform finite element analysis, and obtain the simulation results.

[0028] More preferably, the model parameters include model real constants, material elastic modulus, Poisson's ratio, and density.

[0029] Preferably, step 4 is specifically as follows:

[0030] Step 4-1: Obtain the Von Misses equivalent stress diagram, and save the equivalent stress point coordinates and node information;

[0031] Step 4-2: Obtain the radial displacement diagram, and save the maximum radial displacement point coordinates and node information;

[0032] Step 4-3: Obtain the stresses and radial displacements on the surface of the model;

[0033] Step 4-4: Obtain the variation information of the position of the maximum Von Misses equivalent stress in the model with time;

[0034] Step 4-5: Set several reference points and obtain the coordinate information and node information of the reference points.

[0035] More preferably, the stresses on the surface of the model in step 4-3 include:

[0036] The first principal stress, the second principal stress, the third principal stress, and the Von Misses equivalent stress.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. Good simulation effect: The high-temperature tensile simulation method for ferritic / austenitic dissimilar steel welded joints in the present invention can observe some phenomena that are difficult to measure during the test, such as the minute deformation on the surface of the specimen and the change in the position of the maximum stress point, etc.

[0039] 2. High efficiency and low cost: The high-temperature tensile simulation method for ferritic / austenitic dissimilar steel welded joints in the present invention is completed based on certain existing tests; and since the use of test equipment such as high-temperature furnaces is reduced, the danger of the test is lowered; at the same time, a large amount of test costs are saved to a certain extent, effectively reducing the simulation cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a schematic flow chart of the high-temperature tensile simulation method for ferritic / austenitic dissimilar steel welded joints in the present invention;

[0041] Figure 2 is the size and technical requirements of the machined specimen in the embodiment of the present invention;

[0042] Figure 3 is the Von Misses equivalent stress diagram of the T92 / HR3C dissimilar steel welded joint simulated according to the present invention;

[0043] Figure 4 is the radial displacement diagram of the T92 / HR3C dissimilar steel welded joint simulated according to the present invention;

[0044] Figure 5 is the diagram of the change of the coordinates of the maximum Von Misses equivalent stress point of the T92 / HR3C dissimilar steel welded joint with time simulated according to the present invention;

[0045] Figure 6 is the diagram of the first principal stress, second principal stress, third principal stress, Von Misses equivalent stress and stress triaxiality of each point on the outer surface of the T92 / HR3C dissimilar steel welded joint simulated according to the present invention;

[0046] Among them, Figure 6 (a) is the diagram of the first, second, third and Von Misses stresses on the outer surface, Figure 6 (b) is the stress triaxiality diagram;

[0047] Figure 7 is the diagram of the change of the radial displacement of the reference point of the T92 / HR3C dissimilar steel welded joint with time and the radial displacement diagram of each point on the outer surface of the specimen simulated according to the present invention;

[0048] Among them, Figure 7 (a) is the diagram of the change of the radial displacement of the reference point with time, Figure 7 (b) is the radial displacement diagram of the outer surface. Specific Embodiments

[0049] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0050] A high-temperature tensile simulation method for a ferritic / austenitic dissimilar steel welded joint, the process of which is as Figure 1 shown, including:

[0051] Step 1: Fabricate high-temperature tensile specimens of ferritic steel, austenitic steel, and ferritic / austenitic dissimilar steel welded joints, conduct high-temperature tensile experiments on a high-temperature tensile testing machine according to the actual working conditions required, and save the required data;

[0052] Step 1-1: Design tensile specimens according to the dimensions of the raw materials and the dimensions allowed for clamping by the high-temperature tensile testing machine, and process the specimens;

[0053] Step 1-2: Install the specimen on the high-temperature tensile testing machine and clamp it, install an extensometer and adjust the extensometer, and close the high-temperature furnace;

[0054] Step 1-3: Set the parameters of the high-temperature tensile testing machine, including test temperature, temperature gradient, holding time, strain range, loading rate, and loading time;

[0055] Step 1-4: Release the load brought during the test, let the high-temperature furnace cool naturally. After the temperature of the high-temperature furnace and the specimen drops to room temperature, remove the extensometer and the specimen, reset the high-temperature tensile testing machine and shut it down to end the test, and record the required sample data, including: temperature, displacement, load force, strain, and time;

[0056] Step 2: Fit the stress-strain in Step 1 according to the multi-linear model to obtain the unknown parameters in the model, and obtain the stress-strain constitutive relationship of the material;

[0057] Step 2-1: Fit the true stress and true strain data according to the pre-selected model to obtain the unknown parameters in the model;

[0058] Step 2-2: Compare the fitted model curve with the true stress-true strain curve graph, and judge whether it is reasonable by the user. If it is reasonable, export it. If it is unreasonable, return to Step 2-1 for re-fitting;

[0059] Step 3: Build a model according to the test model and boundary conditions, conduct finite element simulation based on the stress-strain constitutive relationship, and save the simulation results;

[0060] Step 3-1: Set the model parameters, including the model real constants, material elastic modulus, Poisson's ratio, and density, and import the stress-strain constitutive relationship obtained in Step 2.

[0061] Step 3-2: Build the model and perform mesh division.

[0062] Step 3-3: Define the constraints and finite element analysis items, perform finite element analysis, and obtain the simulation results.

[0063] Step 4: Post-process the simulation results and output the key data.

[0064] Step 4-1: Obtain the Von Misses equivalent stress diagram, and save the equivalent stress point coordinates and node information.

[0065] Step 4-2: Obtain the radial displacement diagram, and save the maximum radial displacement point coordinates and node information.

[0066] Step 4-3: Obtain the stresses and radial displacements on the model surface. The model surface stresses include the first principal stress, the second principal stress, the third principal stress, and the Von Misses equivalent stress.

[0067] Step 4-4: Obtain the information on the variation of the position of the maximum Von Misses equivalent stress in the model with time.

[0068] Step 4-5: Set several reference points and obtain the coordinate information and node information of the reference points.

[0069] The following provides a specific application example:

[0070] Step 1: Fabricate high-temperature tensile specimens of ferritic steel, austenitic steel, and ferritic / austenitic dissimilar steel welded joints, conduct high-temperature tensile experiments on a high-temperature tensile testing machine according to the actual required working conditions, and save the required data.

[0071] Step 2: Fit the unknown parameters in the model according to the stress-strain in Step 1 by the multi-linear model to obtain the stress-strain constitutive relationship of the material.

[0072] Step 3: Build a model in the finite element software according to the actual experimental model and boundary conditions, import the stress-strain constitutive relationship obtained in Step 3, set the parameters of the finite element simulation, conduct the simulation, and save the simulation results.

[0073] Step 4: Post-process the simulation results in the finite element simulation software and output the key data.

[0074] Step 1 specifically is:

[0075] Step 1-1: Design a tensile specimen according to the size of the raw material and the size allowed for clamping by the high-temperature tensile testing machine, and process the specimen. As Figure 2 shown;

[0076] Step 1-2: Install the specimen on the high-temperature tensile testing machine and clamp it, install an extensometer and adjust the extensometer, and close the high-temperature furnace;

[0077] Step 1-3: Set parameters on the high-temperature tensile testing machine. The test temperature is set to the service temperature of the joint, the temperature gradient is 3°C, and after reaching the set temperature, keep it warm for 30 minutes to ensure uniform temperature distribution of the specimen. The strain range is set to 1.5%, strain control is adopted, the loading rate is set to 10 -5 / s, the loading time is 1500 s, to avoid unstable test caused by too fast loading rate. Set the data to be recorded: temperature, displacement, load force, strain, time, etc.;

[0078] Step 1-4: Start the test after setting the parameters. Save the experimental data in time after the test ends, release the load brought during the test, let the high-temperature furnace cool naturally. After the temperature of the high-temperature furnace and the specimen drops to room temperature, remove the extensometer and the specimen, reset the high-temperature tensile testing machine and shut it down to end the test.

[0079] Step 2 is specifically as follows:

[0080] Step 2-1: Import the true stress and true strain data into the fitting software, set the required model for fitting to obtain the unknown parameters in the model;

[0081] Step 2-2: Compare the fitted model curve with the true stress-true strain curve to see if it is reasonable.

[0082] Step 3 is specifically as follows:

[0083] Step 3-1: Define the model real constants, material elastic modulus, Poisson's ratio and density, and import the stress-strain constitutive relationship obtained in Step 2;

[0084] Step 3-2: Build the model and perform mesh division. The mesh size parameter for the experimental part is set to 5, and the mesh size parameter for the non-experimental part is set to 10 to reduce the time and workload of the simulation process while ensuring accuracy;

[0085] Step 3-3: Define the constraints and finite element analysis items, perform finite element analysis, and obtain the simulation results.

[0086] The beam is constrained according to the actual conditions. In the finite analysis item time load step parameters, the specified load step is set to 100000, the maximum sub-step is set to 200000, the minimum sub-step is set to 5000, and the maximum equilibrium iteration number for non-linear analysis is set to 50. Then, finite element analysis is performed, and the simulation results are saved.

[0087] Step 4 is specifically as follows:

[0088] Step 4-1: Obtain the Von Misses equivalent stress diagram, and save the equivalent stress point coordinates and node information.

[0089] The Von Misses equivalent stress diagram of the T92 / HR3C dissimilar steel welded joint simulated according to the present invention is as Figure 3 shown;

[0090] Step 4-2: Obtain the radial displacement diagram, and save the maximum radial displacement point coordinates and node information.

[0091] The radial displacement diagram of the T92 / HR3C dissimilar steel welded joint simulated according to the present invention is as Figure 4 shown;

[0092] Step 4-3: Obtain the stresses and radial displacements on the model surface. The stresses include the first principal stress, the second principal stress, the third principal stress, and the Von Misses equivalent stress. Four points are taken on the working part of the model, and the line connected by them is defined as the path. Export the stress values and radial displacements of each point on the path and save them.

[0093] The diagrams of the first principal stress, the second principal stress, the third principal stress, the Von Misses equivalent stress, and the stress triaxiality of each point on the outer surface of the T92 / HR3C dissimilar steel welded joint simulated according to the present invention are as Figure 6 shown;

[0094] Step 4-4: Obtain the information about the change of the position of the maximum Von Misses equivalent stress in the model over time.

[0095] To obtain the change of the position of the maximum Von Misses equivalent stress in the model over time, a data table with 1500 rows and 2 columns is defined to store the X coordinate and Y coordinate values at each load step. Loop 1500 steps. In each step, find the point with the maximum Von Misses equivalent stress, output the coordinate information and store it in the data table. After the loop ends, output the data table.

[0096] The diagram of the change of the coordinates of the point with the maximum Von Misses equivalent stress in the T92 / HR3C dissimilar steel welded joint simulated according to the present invention over time is as Figure 5 shown;

[0097] Step 4-5: Set several reference points and obtain the coordinate information and node information of the reference points;

[0098] Step 4-6: To obtain the stress change of the Von Misses equivalent stress points of the reference points in the model, define a data table with 1500 rows and 1 column to store the Von Misses equivalent stress values of the reference points at each load step. Loop 1500 steps, output the Von Misses equivalent stress information at each step and store it in the data table. After the loop ends, output the data table;

[0099] Step 4-7: To obtain the radial displacement change of the reference points in the model, define a data table with 1500 rows and 1 column to store the radial displacement of the reference points at each load step. Loop 1500 steps, output the Von Misses equivalent stress information at each step and store it in the data table. After the loop ends, output the data table;

[0100] The graph of the radial displacement of the reference points of the T92 / HR3C dissimilar steel welded joint simulated according to the present invention changing with time and the graph of the radial displacement of each point on the outer surface of the specimen are as Figure 7 shown.

[0101] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A high-temperature tensile simulation method for a ferritic / austenitic dissimilar steel welded joint, characterized in that The described simulation method includes: Step 1: Obtain the high-temperature tensile test specimen data of ferritic steel, austenitic steel, and ferritic / austenitic dissimilar steel welded joints; Step 2: Fit the stress-strain in Step 1 according to the multi-linear model to obtain the unknown parameters in the model, and get the stress-strain constitutive relationship of the material; Step 3: Model according to the test model and boundary conditions, perform finite element simulation based on the stress-strain constitutive relationship, and save the simulation results; Step 4: Post-process the simulation results and output key data. Specifically: Step 4-1: Obtain the Von Misses equivalent stress diagram, and save the equivalent stress point coordinates and node information; Step 4-2: Obtain the radial displacement diagram, and save the maximum radial displacement point coordinates and node information; Step 4-3: Obtain the stresses and radial displacements on the surface of the model. The stresses include: the first principal stress, the second principal stress, the third principal stress, and the Von Misses equivalent stress. Take four points in the working part of the model, and the connected line is defined as the path. Export the stress values and radial displacements of each point on the path and save them; Step 4-4: Obtain the change information of the position of the maximum Von Misses equivalent stress in the model over time; Step 4-5: Set several reference points, and obtain the coordinate information and node information of the reference points; Step 4-6: Obtain the stress change of the Von Misses equivalent stress point of the reference points in the model; Step 4-7: Obtain the radial displacement change of the radial displacement of the reference points in the model.

2. The high-temperature tensile simulation method for a ferritic / austenitic dissimilar steel welded joint according to claim 1, characterized in that The specific content of the described Step 1 is: Fabricate high-temperature tensile test specimens of ferritic steel, austenitic steel, and ferritic / austenitic dissimilar steel welded joints, and conduct high-temperature tensile experiments on a high-temperature tensile testing machine according to the actual working conditions required, and save the required data.

3. A method for simulating high-temperature tensile of a ferritic / austenitic dissimilar steel welded joint according to claim 2, characterized in that, The specific method for obtaining specimen data in Step 1 is: Step 1-1: Design tensile specimens according to the dimensions of the raw materials and the dimensions allowed to be clamped by the high-temperature tensile testing machine, and process the specimens; Step 1-2: Install the specimen on the high-temperature tensile testing machine and clamp it, install the extensometer and adjust the extensometer, and close the high-temperature furnace; Step 1-3: Set the parameters of the high-temperature tensile testing machine; Step 1-4: Release the load brought during the test, let the high-temperature furnace cool naturally. After the temperature of the high-temperature furnace and the specimen drops to room temperature, remove the extensometer and the specimen, reset the high-temperature tensile testing machine and shut it down, end the test, and record the required sample data.

4. A method for simulating high-temperature tensile of a ferritic / austenitic dissimilar steel welded joint according to claim 3, characterized in that The specific content of the described Step 1-3 is: Set the test temperature, temperature gradient, holding time, strain range, loading rate, and loading time of the high-temperature tensile testing machine.

5. A method for simulating high-temperature tensile of a ferritic / austenitic dissimilar steel welded joint according to claim 3, characterized in that The sample data includes: temperature, displacement, load force, strain, and time.

6. A method for simulating high-temperature tensile of a ferritic / austenitic dissimilar steel welded joint according to claim 1, characterized in that, The specific content of the described Step 2 is: Step 2-1: Fit the true stress and true strain data according to the pre-selected model to obtain the unknown parameters in the model; Step 2-2: Compare the fitted model curve with the true stress-true strain curve diagram, and let the user judge whether it is reasonable. If it is reasonable, then export it. If it is not reasonable, then return to Step 2-1 for re-fitting.

7. A method for simulating high-temperature tensile of a ferritic / austenitic dissimilar steel welded joint according to claim 1, characterized in that The specific content of the described Step 3 is: Step 3-1: Set the model parameters and import the stress-strain constitutive relationship obtained in Step 2. Step 3-2: Build the model and perform mesh division. Step 3-3: Define the constraints and finite element analysis items, perform finite element analysis, and obtain the simulation results.

8. A method for simulating high-temperature tensile of a ferritic / austenitic dissimilar steel welded joint according to claim 7, characterized in that The model parameters include model real constants, material elastic modulus, Poisson's ratio, and density.

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