A method for establishing a constitutive model of the post-weld heat affected zone of high-strength steel based on simulation

Abstract

The present invention belongs to the field of steel structure welding in civil engineering and construction, and specifically relates to a method for establishing a constitutive model of the heat-affected zone after welding of high-strength steel based on simulation. It includes: conducting standard material property tests on steel materials and welding materials to obtain the true stress-true strain relationship curve before material necking; then fitting the parameters in the improved power-law form constitutive model proposed by the present invention; obtaining the constitutive models of steel materials and welding materials through finite element simulation technology; then conducting axial tensile tests on the butt welds of high-strength steel; establishing a finite element model with the same dimensions as the butt welds, and making the comparison between the test and the finite element within the error range by modifying the constitutive model parameters of the heat-affected zone, so as to obtain the constitutive model of the heat-affected zone material. In the present invention, by means of finite element simulation technology, the method of comparing the load-displacement curves obtained by tests and finite element simulations can be used to establish the constitutive model of the relatively narrow heat-affected zone that appears after welding of high-strength steel.

Description

Technical Field

[0001] The present invention belongs to the field of steel structure welding in civil engineering and construction, and particularly relates to a method for establishing a constitutive model of the heat-affected zone after welding of high-strength steel based on simulation. Background Art

[0002] High-strength structural steel (steel with a nominal yield strength standard value not less than 460 MPa, hereinafter referred to as "high-strength steel") has the characteristics of light weight and high strength, which can effectively reduce the cross-sectional size of components, increase the usable space of buildings, reduce the welding workload and lower the processing and manufacturing cost, etc. The alloying elements and carbon content of high-strength steel increase, and there are significant differences in the production process from ordinary steel, which will have an obvious impact on the weldability and mechanical properties after welding of the steel. In the research on high-strength steel weld connections, it is found that there is a unique softening phenomenon in the heat-affected zone. The degree of softening and the range of the softened zone are related to the welding process, which in turn affects the static strength and fatigue strength of the welded joint.

[0003] The constitutive model of a material is a mathematical expression used to describe the mechanical properties of the material (such as the stress-strain relationship). With the development of finite element simulation technology, by inputting the constitutive model of the material into the finite element model, the mechanical properties of the material under external loads can be analyzed through numerical analysis, greatly saving the cost of experiments and the time cost.

[0004] Tensile test is a test method for determining the material properties under axial tensile load, and it is the basic test method for obtaining the constitutive model of the material. The data obtained from the tensile test can be used to determine the elastic limit, elongation, elastic modulus, proportional limit, reduction of area, tensile strength, yield point, yield strength and other tensile property indexes of the material.

[0005] Generally, the constitutive models of steel and welding materials can be obtained through tensile tests in combination with finite element simulation technology. However, for the constitutive model of the heat-affected zone after welding of high-strength steel, due to the too narrow heat-affected zone, it is difficult to machine specimens for tensile tests, so it cannot be obtained through experiments. However, the constitutive model of the heat-affected zone has a significant impact on the mechanical properties of high-strength steel weld connections. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above-mentioned disadvantages of the prior art and provide a method for establishing a constitutive model of the heat-affected zone after welding of high-strength steel based on simulation. This method can establish the constitutive model of the relatively narrow heat-affected zone that appears after welding of high-strength steel.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is: a method for establishing a constitutive model of the heat-affected zone after welding of high-strength steel based on simulation, including the following steps:

[0008] S1. Conduct monotonic tensile tests on standard material specimens of steel and welding materials to obtain the load F and displacement Δ data of the steel and welding materials during the entire loading stage;

[0009] S2. Obtain the true stress-true strain relationship curves of the steel and welding materials before necking based on the load and displacement data in step S1;

[0010] S3. Propose an improved power-law constitutive model for high-strength steel, such as formula (1). Use the true stress-true strain data before necking in step S2 to fit the parameters in formula (1) to obtain the initial values of the constitutive model parameters (n and K);

[0011]

[0012] In the formula, and σ 0 are the plastic strain and true stress corresponding to the end of the yield plateau on the stress-strain relationship curve. If the material does not have a yield plateau, the point is the intersection of the experimental plastic stress-true strain curve and the curve σ = Eε p , where E is the elastic modulus; σ is the true stress; ε p is the plastic strain; σ y is the yield stress; K is a constant; n is the strain hardening index.

[0013] It should be noted that the constitutive model of a material is a mathematical expression used to describe the mechanical properties of the material (such as the stress-strain relationship). The constitutive model established in the present invention refers to a mathematical model that describes the relationship between the plastic strain ε p and the true stress σ of the material.

[0014] It should be noted that the plastic strain ε p in the present invention represents the true plastic strain, which is the difference between the true strain and the elastic strain. Since the elastic strain is the ratio of the true stress σ to the elastic modulus E, the relationship between the plastic strain and the true stress given in the present invention is equivalent to giving the relationship between the true strain and the true stress.

[0015] It should be noted that the values of the parameters σ 0 , ε p , σ y and E can be obtained from the load-displacement curve obtained in step S1 and the nominal stress-nominal strain relationship curve obtained in step S2. The value-taking method refers to the standard "Metallic materials - Tensile testing - Part 1: Method of test at room temperature GB / T 228.1 - 2010".

[0016] It should be noted that in the present invention, the term "constitutive model parameter" specifically refers to the parameters n and K.

[0017] S4. Establish a finite element model with the same dimensions as the standard material property specimen in step S1, input the constitutive models of the steel and welding materials obtained in step S3 as the material property models of the corresponding materials into the finite element model, and obtain the load-displacement relationship curve of the standard material property specimen through finite element simulation technology;

[0018] S5. Compare the load-displacement curve obtained by finite element simulation technology in step S4 with the load-displacement curve obtained by the test in step S1, specify an error range, and by fine-tuning the values of the constitutive model parameters n and K, repeat steps S4 and S5 to make the comparison between the load-displacement curve obtained by finite element and the load-displacement curve obtained by the test within the error range. Finally, substitute the adjusted values of the parameters n and K into formula (1) to obtain the constitutive models of the steel and welding materials;

[0019] S6. Measure the hardness values, yield strength values, and tensile strength values of several high-strength steels, high-strength steels after heating and cooling, and welding materials, and establish a prediction model for the relationship between the tensile strength and hardness of the materials, as well as a prediction model for the relationship between the yield strength and hardness in each region. The prediction models are as follows:

[0020] The relationship model between the material hardness and tensile strength is:

[0021] σ u = aH + b (2)

[0022] The relationship model between the material hardness and yield strength is:

[0023] σ y = cH + d (3)

[0024] In the formula, σ u is the tensile strength, σ y is the yield strength, H is the hardness, and a, b, c, and d are fitting parameters obtained by the least squares method.

[0025] Then, measure the hardness of the high-strength steel and the heat-affected zone after welding of the high-strength steel. According to the linear positive correlation relationship between the hardness and strength, assuming that the constitutive model of the heat-affected zone still conforms to the relationship of formula (1), and the parameters σ 0 , ε p , σ y and E take the same values as those of the steel, the initial values of the constitutive model parameters n and K of the heat-affected zone can be obtained through formula (4).

[0026] n HAZ = n b

[0027]

[0028] In the formula, n HAZ and n b are respectively the strain hardening indexes of the heat affected zone and the steel; K HAZ and K b are respectively the material constants of the heat affected zone and the steel; H HAZ and H b are respectively the hardnesses of the heat affected zone and the steel.

[0029] S7. Axial tensile tests are carried out on high-strength steel butt weld specimens to obtain load-displacement curves;

[0030] S8. A finite element model of the butt weld with the same dimensions as that in step S7 is established. By comparing the results of the load-displacement curves obtained by the test and the finite element simulation technology, and by correcting the constitutive model parameters n and K of the heat affected zone in step S6 so that the comparison of the two load-displacement curves is within the error range, the constitutive model of the material in the heat affected zone can be obtained.

[0031] In a preferred embodiment of the present invention, the welding materials in step S1 are not limited by the strength grade. The matching methods in which the strength of the weld material in the weld connection is higher than, equal to, and lower than the strength of the steel are respectively called over-strength matching, equal-strength matching, and under-strength matching. Over-strength matching, equal-strength matching, and under-strength matching welding materials can be selected in step S1.

[0032] In a preferred embodiment of the present invention, the load-displacement curve in step S1 must include a descending section, and preferably a complete load-displacement curve until the specimen fails is obtained to obtain a more accurate constitutive model.

[0033] In a preferred embodiment of the present invention, the finite element model in step S4 can be a numerical model established by using ABAQUS software or ANSYS software.

[0034] In a preferred embodiment of the present invention, the hardness in step S6 can be Brinell hardness, Rockwell hardness, or Vickers hardness.

[0035] In a preferred embodiment of the present invention, the finite element model in step S8 can be a numerical model established by using ABAQUS software or ANSYS software.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The present invention discloses a method for establishing a constitutive model of the heat affected zone after welding of high-strength steel based on simulation. The present invention compares the load-displacement curve obtained by means of finite element simulation technology with the load-displacement curve obtained by experiments, and by modifying the material constitutive model input into the finite element simulation technology, the coincidence degree between the load-displacement curve obtained by the finite element simulation technology and the load-displacement curve obtained by experiments is within the error range, so as to obtain the constitutive models of steel, welding materials and heat affected zone materials. The present invention firstly provides a method capable of obtaining a constitutive model with high precision, and at the same time solves the problem that it is difficult to establish a constitutive model of a narrow heat affected zone through experiments, and can realize the establishment of a constitutive model of a narrow heat affected zone that appears after welding of high-strength steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a flowchart of a preferred embodiment of the present invention.

[0039] Figure 2 It is a schematic diagram (after acid etching) of the area near the weld of a high-strength steel butt weld specimen which is a preferred embodiment of the present invention.

[0040] Figure 3 a is a schematic diagram of a standard monotonic tensile specimen of steel, where R in the figure is the radius of the arc of the transition section.

[0041] Figure 3 b is a schematic diagram of a standard round bar monotonic tensile specimen of welding material, where R in the figure is the radius of the arc of the transition section.

[0042] Figure 4 a is the load-displacement curve of a standard monotonic tensile specimen of steel Q690.

[0043] Figure 4 b is the load-displacement curve of a standard monotonic tensile specimen of welding material ER50-6.

[0044] Figure 5 a is the stress-strain curve of a standard monotonic tensile specimen of steel Q690.

[0045] Figure 5 b is the stress-strain curve of a standard monotonic tensile specimen of welding material ER50-6.

[0046] Figure 6 a is the constitutive model of steel Q690 (plastic strain-true stress curve).

[0047] Figure 6 b is the constitutive model of welding material ER50-6 (plastic strain-true stress curve).

[0048] Figure 7a is the comparison of the load-displacement curves obtained from the test and those obtained from the full-scale finite element model (steel Q690).

[0049] Figure 7 b is the comparison of the load-displacement curves obtained from the test and those obtained from the full-scale finite element model (welding material ER50-6).

[0050] Figure 8 It is the plastic strain-true stress relationship diagram of steel Q690 and welding material ER50-6.

[0051] Figure 9 a is the relationship between the tensile strength and hardness of the high-strength steel, the high-strength steel after heating and cooling, and the welding material obtained in the embodiment. The abscissa represents the Vickers hardness of the material, and the ordinate represents the tensile strength of the material, with the unit of MPa.

[0052] Figure 9 b is the relationship between the yield strength and hardness of the high-strength steel, the high-strength steel after heating and cooling, and the welding material obtained in the embodiment. The abscissa represents the Vickers hardness of the material, and the ordinate represents the yield strength of the material, with the unit of MPa.

[0053] Figure 10 It is the Vickers hardness distribution diagram of the area near the butt weld composed of steel Q690 and welding material ER50-6.

[0054] Figure 11 It is a schematic diagram of the standard monotonic tensile specimen of the high-strength steel butt weld. In the figure, R is the radius of the arc of the transition section.

[0055] Figure 12 It is the comparison of the load-displacement curves obtained from the test and those obtained from the full-scale finite element model (butt weld).

[0056] Figure 13 It is the finite element model of the butt weld including the heat-affected zone.

[0057] Figure 14 It is the constitutive model of the material in the heat-affected zone in the embodiment. Detailed implementation manners

[0058] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0059] For the convenience of understanding the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. The preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present invention more thorough and comprehensive.

[0060] The present invention will now be further described in detail with reference to the accompanying drawings and embodiments. These drawings are all simplified schematic diagrams, only showing the basic structure of the present invention in a schematic manner, so they only show the components related to the present invention.

[0061] See Figure 1 , the present invention provides a method for establishing a constitutive model of the heat-affected zone after welding of high-strength steel based on simulation. As in Figure 2 the specific engineering case shown, in this embodiment, the strength grade of the steel is Q690 (yield strength not less than 690 MPa), and the strength grade of the welding material is ER50-6 (ultimate strength not less than 500 MPa). The relationship between the welding material and the steel belongs to under-strength matching.

[0062] It should be noted that Figure 2 is a fracture etching picture of an actual butt weld joint area of high-strength steel. After grinding and polishing the weld joint area, the fracture etching picture is obtained by soaking the specimen in a nitric acid alcohol solution with a concentration of about 4% for about 5 seconds. Through the different light and dark degrees in the etching picture, it can be clearly seen that the area near the high-strength steel weld is divided into three regions: namely, the base metal area (steel), the weld area (welding material), and the heat-affected zone.

[0063] A method for establishing a constitutive model of the heat-affected zone after welding of high-strength steel based on simulation includes the following steps:

[0064] S1. Conduct a monotonic tensile test on standard material property specimens of the steel and the welding material to obtain the load F and displacement Δ data of the steel and the welding material during the entire loading stage. Design, process, and load the standard specimens of the steel and the welding material according to the methods of the specifications "Metallic materials - Tensile testing - Part 1: Method of test at room temperature GB / T 228.1-2010" and "Methods for tensile testing of welds and deposited metals GB / T 2652-2008". The detailed dimensions are shown in Figure 3 a and Figure 3 b. In the figure, R is the radius of the transition section arc, D is the diameter of the cylindrical part. The measured load-displacement curves of the steel and the welding material are shown in Figure 4 a and Figure 4 b respectively.

[0065] S2. According to the load and displacement data in step S1, use formulas (5) and (6) to obtain the nominal strain and nominal stress of the steel and the welding material. Further, through the correlation between the true stress and true strain before necking and the nominal stress and nominal strain, as shown in formulas (7) and (8), obtain the true strain-true stress relationship curve of the steel and the welding material before necking, as in Figure 5 shown.

[0066]

[0067]

[0068] ε = ln(1 + ε N ) (7)

[0069] σ = σ N ·(1 + ε N ) (8)

[0070] Where Δ is the displacement of the measured gauge length section, F is the measured load, L0 and A0 are the initial length and initial cross-sectional area of the gauge length section, ε N and ε are the nominal strain and true strain, σ N and σ are the nominal stress and true stress.

[0071] It should be noted that Figure 5 a and Figure 5 Although the blue dotted line in b is calculated by formulas (7) and (8), after the specimen undergoes necking, the cross-sectional area of the specimen is no longer uniform, and there is a circumferential stress in addition to the axial stress at the necking. Formulas (7) and (8) are no longer applicable, that is, the stress and strain calculated after necking are not the true stress and true strain of the material.

[0072] S3. Propose a constitutive model in the form of a power exponent for high-strength steel materials, such as formula (10). Convert the true strain-true stress relationship curve before necking obtained in step S2 into a plastic strain-true stress relationship curve, as shown in formula (9), and then fit it with the constitutive model of formula (10). Using the least squares method theory, obtain approximate values K1 and n1 of the parameters K and n in the constitutive model.

[0073]

[0074]

[0075] It should be noted that the parameters σ 0 , ε p , σ y and E can be obtained from the load-displacement curve obtained in step S1 and the nominal stress-nominal strain relationship curve obtained in step S2. The value-taking method refers to the standard "Metallic materials - Tensile testing - Part 1: Method of test at room temperature GB / T 228.1 - 2010".

[0076] It should be noted that during the tensile test of the standard material property specimens of steel or welding materials in step S1, at the moment of the peak load of the specimen's bearing capacity, according to the physical relationship between stress and strain, the true stress at this time is equal to the slope of the true stress-true strain curve, as shown in formula (11). According to formulas (10) and (11), another set of approximate values of K and n can be obtained through formulas (12) and (13), denoted as K2 and n2.

[0077]

[0078]

[0079]

[0080] It should be noted that the first set of values (K1, n1) of the parameters K and n is obtained by numerical fitting based on the true stress-true strain curve before necking obtained in step S2. It ensures that the constitutive model curve (10) conforms to the actual true stress-true strain curve before the peak load (i.e., before necking) in terms of shape; the second set of values (K2, n2) of the parameters K and n is obtained by formulas (12) and (13), which is derived from the physical relationship between stress and strain, and it provides more physically meaningful values of K and n. In the present invention, the initial values (K2, n2) of K and n obtained by formulas (12) and (13) are used as the starting points defined in the least squares fitting. The upper and lower limits of the fitting data are respectively within ±5% of the starting point. This not only ensures the consistency of the fitting curve with the original curve in terms of shape but also ensures that the values of K and n have clear physical meanings. The obtained values (K0, n0) of K and n are used as the initial values of K and n. The values of K and n for steel Q690 and welding material ER50-6 are shown in the following table

[0081] Table 1

[0082]

[0083] S4. Establish a finite element model with the same dimensions as the standard material property specimens in step S1, and input the plastic strain-true stress relationship curves of the steel and welding materials obtained in step S3 into the finite element model as the material property models of the corresponding materials, where the initial values of K and n are taken as (K0, n0) in step S3. Obtain the load-displacement relationship curve of the standard material property specimens through finite element simulation technology;

[0084] S5. Compare the load-displacement curve obtained by the finite element simulation technology in step S4 with the load-displacement curve obtained from the test in step S1. Given an error range, by finely adjusting the values of parameters K and n, repeat steps S4 and S5 until the comparison between the load-displacement curve obtained by the finite element method and the load-displacement curve obtained from the test is within the error range. Finally, substitute the adjusted values of parameters K and n into formula (1) to obtain the constitutive model of the steel and welding materials. Figure 7 The comparison between the test data points and the load-displacement curve obtained by substituting the corrected constitutive model curve into the finite element model is given. It can be seen that the constitutive model of the steel and welding materials obtained by this method (including before and after necking) is relatively accurate. The corrected constitutive model parameters are shown in Table 2 below, and the constitutive model curves of the steel and welding materials are as Figure 8 shown.

[0085] Table 2

[0086]

[0087] S6. Measure the hardness values, yield strength values, and tensile strength values of several high-strength steels, high-strength steels after heating and cooling, and welding materials, and establish a prediction model for the relationship between the tensile strength and hardness of the materials, as well as a prediction model for the relationship between the yield strength and hardness in each region. The prediction models are as follows:

[0088] The relationship model between the material hardness and tensile strength is:

[0089] σ u = aH + b (14)

[0090] The relationship model between the material hardness and yield strength is:

[0091] σ y = cH + d (15)

[0092] Figure 9 The measured tensile strength, yield strength, and Vickers hardness values of the above-mentioned several materials are given. It can be seen that there is a linear positive correlation between the material strength and hardness. The values of parameters a, b, c, and d in formulas (14) and (15) obtained by the least squares method are 2.948, 43.77, 3.391, and -127.8 respectively. In the figure, R2 represents the correlation coefficient between the result fitted by the least squares method and the actual relationship between strength and hardness. The value of R2 varies from 0 to 1.0. The closer it is to 1.0, the better the fitting result. In the present invention, the correlation coefficients of the fitting curves of the relationship between the tensile strength and hardness and the relationship between the yield strength and hardness are both higher than 0.9, indicating that the correlation between the fitting result and the actual result is good.

[0093] Then, the hardness of high-strength steel and the heat-affected zone after welding of high-strength steel is measured. According to the linear positive correlation between hardness and strength, assuming that the constitutive model of the heat-affected zone still conforms to the relationship of formula (1), the parameters σ 0 , ε p , σ y and E take the same values as those of the steel, and the initial values of the parameters K and n can be obtained through formula (16). Figure 10 The hardness distribution near the weld zone is given. The hardness measurement points are arranged according to the red dots in Figure 2 . The measurement points are sparse at the weld and on the steel, and dense in the heat-affected zone, especially at the junction of the zones. Through statistical analysis, the average hardness of steel Q690 is 277, the average hardness of welding material ER50-6 is 230, and the average hardness of the heat-affected zone is 188. Therefore, the initial values of K and n in the heat-affected zone are (679, 0.036).

[0094] n HAZ = n b

[0095]

[0096] S7. An axial tensile test is carried out on the butt weld specimen of high-strength steel to obtain the load-displacement curve. The specimen size is as shown in Figure 11 . The unit of the dimension in the figure is mm, the specimen thickness is 10 mm, where R represents the curvature radius of the chamfer. The load-displacement curve measured in the test is shown in Figure 12 .

[0097] S8. A finite element model of the butt weld with the same dimensions as in step S7 is established, as shown in Figure 13 . By comparing the results of the load-displacement curves obtained from the test and the finite element simulation technology, and by modifying the constitutive model parameters of the heat-affected zone in step S6 so that the comparison of the two load-displacement curves is within the error range, the constitutive model of the material in the heat-affected zone can be obtained. Figure 7 The test data points of the butt joint specimen shown in Figure 2 and the comparison of the load-displacement curves obtained by substituting the corrected constitutive model curves of the steel, welding material, and heat-affected zone material into the finite element model are given. It can be seen that the constitutive model of the heat-affected zone material obtained by this method is relatively accurate. The constitutive model parameters of the heat-affected zone are shown in Table 2, and the constitutive model curve of the heat-affected zone is as shown in Figure 14 .

[0098] It should be noted that in this embodiment, a finite element model is established by borrowing the numerical simulation software ABAQUS (see Figure 13) According to the symmetry of the specimen in the x and y directions, only a 1 / 4 model is established for finite element analysis, and the eight-node hexahedron quadratic reduced integration element (C3D8R) is used. Due to the symmetry of the model in both directions, the normal displacements are constrained on the symmetry planes. On the loading surface, the degrees of freedom in the other five directions except the loading direction are constrained. The nodes on the loading surface are bonded to a reference point for axial displacement control loading.

[0099] Based on the ideal embodiments of the present invention as inspiration, through the above description, relevant personnel can completely make various changes and modifications without departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the content in the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. A method for establishing a constitutive model of the post-weld heat affected zone of high-strength steel based on simulation, characterized in that, It includes the following steps: S1. Conduct standard material property tests on steel materials and welding materials to obtain the load and displacement data of the materials; S2. Obtain the true stress-true strain relationship curve before necking of the steel materials and welding materials based on the load and displacement data in step S1; S3. Propose an improved constitutive model in the form of a power exponent, and fit the initial values of the parameters in the constitutive model with the data in steps S1 and S2; In the formula, and σ 0 are the plastic strain and the true stress corresponding to the end of the yield plateau on the stress-strain relationship curve. If the material does not have a yield plateau, the point is the intersection point of the plastic strain-true stress curve of the test and the curve σ = Eε p , where E is the elastic modulus; σ is the true stress; ε p is the plastic strain; σ y is the yield stress; K is a constant; n is the strain hardening exponent; S4. Establish a finite element model with the same dimensions as the standard material property test specimens in step S1, input the constitutive model of the materials obtained in step S3 into the finite element model, and obtain the load-displacement relationship curve of the standard material property test specimens through finite element simulation technology; S5. Compare the load-displacement curve obtained by finite element simulation technology in step S4 with the load-displacement curve obtained by the test in step S1, given an error range, by fine-tuning the values of n and K in the constitutive model parameters, repeat steps S4 and S5 to make the comparison between the load-displacement curve obtained by finite element and the load-displacement curve obtained by the test within the error range, and finally substitute the adjusted values of the parameters n and K into the constitutive model to obtain the constitutive model of the materials; S6. Measure the hardness values, yield strength values, and tensile strength values of several high-strength steels, high-strength steels after heating and cooling, and welding materials, establish a prediction model for the relationship between the tensile strength and hardness of the materials, and a prediction model for the relationship between the yield strength and hardness in each region; then measure the hardness of the steel materials and the materials in the heat-affected zone, and obtain the initial values of the parameters of the constitutive model of the materials in the heat-affected zone according to the linear positive correlation relationship between hardness and strength; S7. Conduct an axial tensile test on the high-strength steel butt weld specimens to obtain the load-displacement curve; S8. Establish a finite element model of the butt weld with the same dimensions as in step S7, compare the results of the load-displacement curves obtained by the test and finite element simulation technology, and correct the values of the parameters n and K of the constitutive model of the heat-affected zone in step S6 to make the comparison between the two load-displacement curves within the error range, and then the constitutive model of the materials in the heat-affected zone can be obtained.

2. The method for establishing a constitutive model of the post-weld heat-affected zone of high-strength steel based on simulation according to claim 1, wherein The relationship model between the material hardness and the tensile strength in step S6 is: σ u = aH + b (2) The relationship model between the material hardness and the yield strength is: σ y = cH + d (3) where σ u is the tensile strength, σ y is the yield strength, H is the hardness, and a, b, c, and d are fitting parameters obtained by the least squares method.

3. The method for establishing a constitutive model of the post-weld heat affected zone of high-strength steel based on simulation according to claim 1, characterized in that, The method for taking the initial values of the parameters of the constitutive model of the materials in the heat-affected zone proposed in step S6 is: Where n HAZ and n b are the strain hardening indices of the heat affected zone and the steel respectively; K HAZ and K b are the material constants of the heat affected zone and the steel respectively; H HAZ and H b are the hardnesses of the heat affected zone and the steel respectively.

4. The method for establishing a constitutive model of the heat-affected zone after welding of high-strength steel based on simulation according to claim 1, wherein The finite element model modeling software in steps S4 and S8 includes software such as BAQUS software or ANSYS software.

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