A method, system, device and storage medium for evaluating performance of a threaded joint

Abstract

The application discloses a threaded joint performance evaluation method, system, device and medium, the method comprises the steps of: determining J2-J3 anisotropy model and determining A-F follow-up reinforcement model respectively; according to the elastic-plastic flow law, based on the forward Euler explicit integration algorithm, using J2-J3 anisotropy model and A-F follow-up reinforcement model, an anisotropic follow-up elastic-plastic reinforcement constitutive model is constructed, and a finite element analysis model of the threaded joint to be evaluated is established; according to the actual service working condition of the threaded joint to be evaluated, the finite element analysis model of the threaded joint to be evaluated is used, and the threaded joint performance evaluation result is calculated through elastic-plastic finite element numerical simulation; the application realizes accurate evaluation of the structure and sealing performance of the threaded joint by simultaneously considering material anisotropy and Bauschinger effect, the service performance evolution of the threaded joint is clear, and the application provides a basis for safety evaluation and service life prediction of the oil and gas well pipe string joint.

Description

Technical Field

[0001] This invention belongs to the technical field of performance evaluation of special threaded joints for oil well pipes, and specifically relates to a method, system, equipment and storage medium for evaluating the performance of threaded joints. Background Technology

[0002] With the deepening exploration and development of oil and gas resources, oil and gas wells are trending towards greater depths and higher pressures, leading to increasingly harsh service conditions for well tubing strings. The tubing string pressure system, composed of numerous threaded joints, faces significant challenges to its structural and sealing integrity under the combined cyclic loading of tension, compression, internal pressure, and external pressure. Among these challenges, the threaded joints are the weakest link in the tubing string integrity system, exhibiting a high probability of leakage, disengagement, and fracture. Data shows that in recent years, the failure rate of complex deep well tubing strings has ranged from 10% to 20%, with over 60% of tubing string failures occurring at the threaded joints. Special threaded joints used in high-pressure deep wells are subjected to even more complex axial tensile and compressive cyclic loads, as well as internal and external pressure cyclic loads, during oil and gas well production enhancement operations and long-term production, exacerbating structural and sealing failure problems at the threaded joints. Therefore, it is urgent to reveal the deformation patterns of special threaded joints in oil well tubing under harsh service conditions to provide a basis for predicting and assessing the service safety of oil well tubing threaded joints.

[0003] Existing performance evaluation of oil well pipe threaded joints mainly relies on the ISO13679 standard, which involves conducting full-scale cyclic load tests. Although the evaluation process is highly reliable, the test cycle is long and costly. Furthermore, it is difficult to detect parameters such as joint sealing contact during the actual test process, making it impossible to understand the evolution mechanism of joint service performance. Therefore, the experimental understanding is insufficient to guide the optimization of threaded joint design, manufacturing, and maintenance procedures.

[0004] Currently, the performance evaluation method for oil well pipe threaded joints based on the finite element method has been included in the appendix of the ISO 13679 standard as a useful supplement to physical experiments, playing a role in the pre-evaluation of the performance of threaded joints. However, the current finite element evaluation method for oil well pipe threaded joints does not consider the significant anisotropy of hot-rolled oil well pipe materials, and does not accurately describe the forward hardening and reverse softening behaviors of metal materials under cyclic composite loads during downhole service, which seriously affects the accuracy of the finite element evaluation of threaded joints. Summary of the Invention

[0005] To address the technical problems existing in the prior art, this invention provides a method, system, equipment, and medium for evaluating the performance of threaded joints, thereby solving the technical problem that existing oil well pipe threaded joint performance evaluation methods cannot identify the service performance evolution stimuli of threaded joints and have low evaluation accuracy.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] This invention provides a method for evaluating the performance of threaded joints, comprising the following steps:

[0008] Based on the CB J2-J3 anisotropic yield criterion of the threaded joint material to be evaluated, the J2-J3 anisotropic model is determined; based on the Bauschinger effect of the threaded joint material to be evaluated, the AF kinematic hardening model is determined.

[0009] Based on the elastoplastic flow law, and using the forward Euler explicit integration algorithm, an anisotropic elastoplastic strengthening constitutive model is constructed by employing the J2-J3 anisotropic model and the AF kinematic strengthening model.

[0010] A finite element analysis model of the threaded joint to be evaluated is established based on the anisotropic follower elastoplastic strengthening constitutive model.

[0011] Based on the actual service conditions of the threaded joint to be evaluated, the performance evaluation results of the threaded joint are calculated by using the finite element analysis model of the threaded joint to be evaluated and through elastoplastic finite element numerical simulation.

[0012] Furthermore, based on the CB J2-J3 anisotropic yield criterion of the threaded joint material to be evaluated, in the process of determining the J2-J3 anisotropic model, a three-dimensional representative volume element model of the threaded joint to be evaluated is established based on the actual microstructure information of the threaded joint to be evaluated. Combined with the crystal plastic finite element method based on the dislocation physical slip mechanism, the dynamic evolution parameters of the J2-J3 anisotropic model are obtained.

[0013] Furthermore, based on the actual microstructure information of the threaded joint to be evaluated, a three-dimensional representative volume element model of the threaded joint to be evaluated is established. Combined with the crystal plastic finite element method based on the dislocation physical slip mechanism, the dynamic evolution parameters of the J2-J3 anisotropic model are obtained, as detailed below:

[0014] Based on the actual microstructure information of the threaded joint to be evaluated, a three-dimensional representative volume element model of the threaded joint to be evaluated is established.

[0015] The crystal shaping finite element method based on dislocation physical slip mechanism is used to apply different preset deformation modes to the three-dimensional representative volume element model of the threaded joint to be evaluated. Among them, different boundary conditions are applied to the crystal shaping finite element method based on dislocation physical slip mechanism to obtain the relationship between stress response and non-uniform deformation under different preset deformation modes.

[0016] Using the minimum square difference optimization function, the relationship between stress response and non-uniform deformation under different preset deformation modes is analyzed and processed to obtain the dynamic evolution parameters of the J2-J3 anisotropic model.

[0017] The preset deformation modes include uniaxial tension, uniaxial compression, pure shear, and plane strain under different strain rates and deformation conditions.

[0018] Furthermore, in the process of determining the AF follow-up strengthening model based on the Bauschinger effect of the threaded joint material to be evaluated, the Bauschinger effect parameters of the threaded joint material to be evaluated are obtained through cyclic loading mechanical tests, that is, the dynamic evolution parameters of the AF follow-up strengthening model are obtained.

[0019] Furthermore, in obtaining the Singer effect parameters of the material package of the threaded joint to be evaluated through cyclic loading mechanical testing, the specific process of cyclic loading mechanical testing is as follows:

[0020] The threaded joint to be evaluated is pre-stretched until the deformation reaches 0.7%, then unloaded.

[0021] The threaded joint to be evaluated after pre-stretch deformation was subjected to positive loading, and unloaded when the deformation reached 1.4%.

[0022] The threaded joint to be evaluated after positive loading is subjected to reverse loading until yielding.

[0023] Furthermore, the J2-J3 anisotropy model is as follows:

[0024]

[0025]

[0026]

[0027] Where f(σ) is the J2-J3 anisotropic model; J2 is the second invariant of the deviatoric stress tensor in the shear yield stress term; J3 is the third invariant of the deviatoric stress tensor in the shear yield stress term; For reference yield stress; a i ,i=1,2…10 are 10 anisotropic parameters;

[0028] In the AF kinematic hardening model, the evolution equation of the back stress is as follows:

[0029]

[0030] Where α is the back stress, i.e., the vector formed by the subsequent yield surface relative to the initial yield surface; dε P dε represents the plastic strain increment. -P Equivalent plastic strain increment; C and γ are both material constants; ε P For plastic strain; ε -P This is the equivalent plastic strain.

[0031] Furthermore, based on the actual service conditions of the threaded joint to be evaluated, the finite element analysis model of the threaded joint to be evaluated is used to calculate the performance evaluation result of the threaded joint through elastoplastic finite element numerical simulation. The deformation amount and sealing contact strength within the allowable load range are used as evaluation conditions to obtain the performance evaluation result of the threaded joint.

[0032] Among them, the deformation Δε within the allowable load condition range is less than or equal to 0.1;

[0033] Sealing contact strength is defined as the integral of the contact stress on the sealing surface over the effective contact length, which satisfies:

[0034] F s =∫σ c dx>200N / mm

[0035] Among them, F s For sealing contact strength; σ c This refers to the contact stress on the sealing surface.

[0036] The present invention also provides a threaded joint performance evaluation system, comprising:

[0037] The first model module is used to determine the J2-J3 anisotropic model based on the CB J2-J3 anisotropic yield criterion of the threaded joint material to be evaluated; and to determine the AF kinematic hardening model based on the Bauschinger effect of the threaded joint material to be evaluated.

[0038] The second model module is used to construct an anisotropic elastoplastic strengthening constitutive model based on the elastoplastic flow law, the forward Euler explicit integration algorithm, the J2-J3 anisotropic model, and the AF kinematic strengthening model.

[0039] The third model module is used to establish a finite element analysis model of the threaded joint to be evaluated based on the anisotropic follower elastoplastic strengthening constitutive model.

[0040] The evaluation and analysis module is used to calculate the performance evaluation results of the threaded joint based on the actual service conditions of the threaded joint under evaluation, using the finite element analysis model of the threaded joint under evaluation, and through elastoplastic finite element numerical simulation.

[0041] The present invention also provides a threaded joint performance evaluation device, comprising:

[0042] Memory, used to store computer programs;

[0043] A processor is used to implement the steps of the threaded joint performance evaluation method when executing the computer program.

[0044] The present invention also provides a computer-readable storage medium, characterized in that the computer-readable storage medium stores a computer program, characterized in that the computer program, when executed by a processor, implements the steps of the threaded joint performance evaluation method.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] This invention provides a method for evaluating the performance of threaded joints. By comprehensively considering the anisotropy of CB J2-J3 (tensile-compression asymmetry) and the AF (follow-up strengthening model), a finite element analysis model of the threaded joint to be evaluated is established. Using the finite element analysis model of the threaded joint to be evaluated, the threaded joint is calculated and analyzed through elastoplastic finite element numerical simulation, which clearly reveals the deformation law of the oil well pipe threaded joint under the action of composite cyclic load. By simultaneously considering material anisotropy and Bauschinger effect, the structural and sealing performance of the threaded joint is accurately evaluated, and the service performance evolution excitation of the threaded joint is clearly shown, providing a basis for the safety assessment and service life prediction of oil and gas well pipe joints.

[0047] Furthermore, by using a three-dimensional representative volume element model based on the true microstructure of the material, combined with the crystal plasticity finite element method based on the dislocation physical slip mechanism, the dynamic evolution parameters of the J2-J3 anisotropic model were accurately determined. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of a three-dimensional RVE model based on the actual material structure in the embodiment;

[0049] Figure 2 This is a schematic diagram of the Bauschinger effect of the special threaded joint material for oil well pipes in the embodiment;

[0050] Figure 3 This is a flowchart illustrating the constitutive relation analysis and calculation process for elastoplastic materials in the embodiments.

[0051] Figure 4 The simulation results of the special threaded joint of the oil well pipe under cyclic load conditions are shown in the embodiment. Detailed Implementation

[0052] To make the technical problems solved by the present invention, the technical solutions, and the beneficial effects clearer, the following specific embodiments provide a further detailed description of the present invention. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of the invention.

[0053] This invention provides a method for evaluating the performance of threaded joints, comprising the following steps:

[0054] Step 1: Based on the CB J2-J3 anisotropic yield criterion of the threaded joint material to be evaluated, determine the J2-J3 anisotropic model. Specifically, a three-dimensional representative volume element model of the threaded joint to be evaluated is established based on the actual microstructure information of the material. Combined with the crystal plastic finite element method based on the dislocation physical slip mechanism, the dynamic evolution parameters of the J2-J3 anisotropic model are obtained. The specific process is as follows:

[0055] Based on the actual microstructure information of the threaded joint to be evaluated, a three-dimensional representative volume element model of the threaded joint to be evaluated is established.

[0056] The crystal shaping finite element method based on dislocation physical slip mechanism is used to apply different preset deformation modes to the three-dimensional representative volume element model of the threaded joint to be evaluated. Among them, different boundary conditions are applied to the crystal shaping finite element method based on dislocation physical slip mechanism to obtain the relationship between stress response and non-uniform deformation under different preset deformation modes.

[0057] Using the minimum squared difference optimization function, the relationship between stress response and non-uniform deformation under different preset deformation modes is analyzed and processed to obtain the dynamic evolution parameters of the J2-J3 anisotropic model; wherein, the different preset deformation modes include uniaxial tension, uniaxial compression, pure shear and plane strain under different strain rates and deformation amounts.

[0058] Step 2: Determine the AF (Alternating Field) dynamic strengthening model based on the Bauschinger effect of the threaded joint material to be evaluated; wherein, the Bauschinger effect parameters of the threaded joint material to be evaluated are obtained through cyclic loading mechanical tests, that is, the dynamic evolution parameters of the AF dynamic strengthening model are obtained; wherein, the specific process of the cyclic loading mechanical test is as follows:

[0059] The threaded joint to be evaluated is pre-stretched until the deformation reaches 0.7%, then unloaded.

[0060] The threaded joint to be evaluated after pre-stretch deformation was subjected to positive loading, and unloaded when the deformation reached 1.4%.

[0061] The threaded joint to be evaluated after positive loading is subjected to reverse loading until yielding.

[0062] Step 3: Based on the elastoplastic flow law and using the forward Euler explicit integration algorithm, an anisotropic kinematic elastoplastic strengthening constitutive model is constructed using the J2-J3 anisotropic model and the AF kinematic strengthening model; wherein, the J2-J3 anisotropic model is as follows:

[0063]

[0064]

[0065]

[0066] Where f(σ) is the J2-J3 anisotropic model; J2 is the second invariant of the deviatoric stress tensor in the shear yield stress term; J3 is the third invariant of the deviatoric stress tensor in the shear yield stress term; For reference yield stress; a i ,i=1,2…10 are 10 anisotropic parameters.

[0067] In the AF kinematic hardening model, the evolution equation of the back stress is as follows:

[0068]

[0069] Where α is the back stress, i.e., the vector formed by the subsequent yield surface relative to the initial yield surface; dε P dε represents the plastic strain increment. -P Equivalent plastic strain increment; C and γ are both material constants; ε P For plastic strain; ε -P This is the equivalent plastic strain.

[0070] Step 4: Based on the anisotropic follower elastoplastic strengthening constitutive model, establish the finite element analysis model of the threaded joint to be evaluated.

[0071] Step 5: Based on the actual service conditions of the threaded joint to be evaluated, the performance evaluation results of the threaded joint are calculated by using the finite element analysis model of the threaded joint to be evaluated through elastoplastic finite element numerical simulation. Specifically, the deformation amount and sealing contact strength within the allowable load range are used as evaluation conditions to obtain the performance evaluation results of the threaded joint.

[0072] Among them, the deformation Δε within the allowable load condition range is less than or equal to 0.1; the sealing contact strength is defined as the integral of the contact stress on the sealing surface over the effective contact length, that is, satisfying:

[0073] F s =∫σ c dx>200N / mm

[0074] Among them, F s For sealing contact strength; σ c This refers to the contact stress on the sealing surface.

[0075] The present invention also provides a threaded joint performance evaluation system, including a first model module, a second model module, a third model module, and an evaluation and analysis module.

[0076] The first model module is used to determine the J2-J3 anisotropic model based on the CB J2-J3 anisotropic yield criterion of the threaded joint material to be evaluated; and to determine the AF kinematic hardening model based on the Bauschinger effect of the threaded joint material to be evaluated. The second model module is used to construct an anisotropic kinematic elastoplastic hardening constitutive model based on the elastoplastic flow law and the forward Euler explicit integration algorithm, using the J2-J3 anisotropic model and the AF kinematic hardening model. The third model module is used to establish a finite element analysis model of the threaded joint to be evaluated based on the anisotropic kinematic elastoplastic hardening constitutive model. The evaluation and analysis module is used to calculate the performance evaluation results of the threaded joint based on the actual service conditions of the threaded joint to be evaluated, using the finite element analysis model of the threaded joint to be evaluated, through elastoplastic finite element numerical simulation.

[0077] The present invention also provides a threaded joint performance evaluation device, comprising: a memory for storing a computer program; and a processor for executing the computer program to implement the steps of the threaded joint performance evaluation method.

[0078] When the processor executes the computer program, it implements the steps of the above-mentioned threaded joint performance evaluation method, for example: determining the J2-J3 anisotropic model based on the CB J2-J3 anisotropic yield criterion of the threaded joint material to be evaluated; determining the AF kinematic hardening model based on the Bauschinger effect of the threaded joint material to be evaluated; constructing an anisotropic kinematic elastoplastic hardening constitutive model based on the elastoplastic flow law and the forward Euler explicit integration algorithm, using the J2-J3 anisotropic model and the AF kinematic hardening model; establishing a finite element analysis model of the threaded joint to be evaluated based on the anisotropic kinematic elastoplastic hardening constitutive model; and calculating the threaded joint performance evaluation result by using the finite element analysis model of the threaded joint to be evaluated through elastoplastic finite element numerical simulation, based on the actual service conditions of the threaded joint to be evaluated.

[0079] Alternatively, when the processor executes the computer program, it implements the functions of each module in the above system. For example: a first model module is used to determine the J2-J3 anisotropic model based on the CB J2-J3 anisotropic yield criterion of the threaded joint material to be evaluated; and to determine the AF kinematic hardening model based on the Bauschinger effect of the threaded joint material to be evaluated; a second model module is used to construct an anisotropic kinematic elastoplastic hardening constitutive model based on the elastoplastic flow law and the forward Euler explicit integration algorithm, using the J2-J3 anisotropic model and the AF kinematic hardening model; a third model module is used to establish a finite element analysis model of the threaded joint to be evaluated based on the anisotropic kinematic elastoplastic hardening constitutive model; and an evaluation and analysis module is used to calculate the performance evaluation result of the threaded joint by using the finite element analysis model of the threaded joint to be evaluated and the actual service conditions of the threaded joint to be evaluated through elastoplastic finite element numerical simulation.

[0080] For example, the computer program may be divided into one or more modules / units, which are stored in the memory and executed by the processor to complete the present invention. The one or more modules / units may be a series of computer program instruction segments capable of performing preset functions, the instruction segments describing the execution process of the computer program in the threaded joint performance evaluation device.

[0081] For example, the computer program can be divided into: a first model module, a second model module, a third model module, and an analysis and evaluation module; the specific functions of each module are as follows: the first model module is used to determine the J2-J3 anisotropic model based on the CB J2-J3 anisotropic yield criterion of the threaded joint material to be evaluated; and to determine the AF kinematic strengthening model based on the Bauschinger effect of the threaded joint material to be evaluated.

[0082] The second model module is used to construct an anisotropic follower elastoplastic strengthening constitutive model based on the elastoplastic flow law, the forward Euler explicit integration algorithm, the J2-J3 anisotropic model, and the AF follower strengthening model.

[0083] The third model module is used to establish a finite element analysis model of the threaded joint to be evaluated based on the anisotropic follower elastoplastic strengthening constitutive model.

[0084] The evaluation and analysis module is used to calculate the performance evaluation results of the threaded joint based on the actual service conditions of the threaded joint under evaluation, using the finite element analysis model of the threaded joint under evaluation, and through elastoplastic finite element numerical simulation.

[0085] The threaded joint performance evaluation device can be a desktop computer, laptop, handheld computer, or cloud server, etc. The threaded joint performance evaluation device may include, but is not limited to, processors and memory. Those skilled in the art will understand that the above are merely examples of threaded joint performance evaluation devices and do not constitute a limitation on the threaded joint performance evaluation device. It may include more components than described above, or combine certain components, or different components. For example, the threaded joint performance evaluation device may also include input / output devices, network access devices, buses, etc.

[0086] The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor, or any conventional processor. The processor is the control center of the threaded joint performance evaluation equipment, connecting all parts of the equipment via various interfaces and lines.

[0087] The memory can be used to store the computer program and / or modules. The processor implements various functions of the threaded joint performance evaluation device by running or executing the computer program and / or modules stored in the memory and calling the data stored in the memory.

[0088] The memory may primarily include a program storage area and a data storage area. The program storage area may store the operating system and at least one application program required for a given function (such as sound playback or image playback). The data storage area may store data created based on the use of the phone (such as audio data or a phonebook). Furthermore, the memory may include high-speed random access memory (RAM) and non-volatile memory, such as hard disks, RAM, plug-in hard disks, SmartMediaCards (SMC), Secure Digital (SD) cards, flash cards, at least one disk storage device, flash memory device, or other volatile solid-state storage devices.

[0089] The present invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the threaded joint performance evaluation method.

[0090] If the modules / units integrated in the threaded joint performance evaluation system are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium.

[0091] Based on this understanding, the present invention can implement all or part of the processes in the above-described threaded joint performance evaluation method, or it can be accomplished by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the above-described threaded joint performance evaluation method. The computer program includes computer program code, which can be in the form of source code, object code, executable file, or a preset intermediate form, etc.

[0092] The computer-readable storage medium may include: any entity or device capable of carrying the computer program code, recording media, USB flash drive, portable hard drive, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium, etc.

[0093] It should be noted that the content contained in the computer-readable storage medium may be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable storage medium does not include electrical carrier signals and telecommunication signals.

[0094] The threaded joint performance evaluation method of this invention considers both material anisotropy and the Bauschinger effect. It establishes an anisotropic, elastoplastic, and stiffening constitutive model that considers both anisotropy and the Bauschinger effect under cyclic loading. Specifically, based on the three-dimensional representative volume element (RVE) of the actual microstructure of the special threaded connection material, the dynamic evolution parameters of the J2-J3 anisotropic model are determined using the crystal plastic finite element method (CPFEM). Simultaneously, through cyclic loading mechanical tests, the Bauschinger effect parameters of the threaded joint to be evaluated are obtained, thus determining the dynamic evolution parameters of the AF elastoplastic stiffening model.

[0095] In this invention, the anisotropic yield criterion CB(CB)J2-J3 considering tensile / compression asymmetry and the Armstrong-Frederick (AF) kinematic hardening model are combined. Based on the elastoplastic flow law, stress updates are achieved using the forward Euler explicit integration algorithm, resulting in an anisotropic kinematic elastoplastic hardening constitutive model. Using this anisotropic kinematic elastoplastic hardening constitutive model, a finite element analysis model of the threaded joint to be evaluated is established, forming a performance evaluation method for special threaded joints in oil well tubing. This method reveals the deformation law of special threaded connections in oil well tubing under composite cyclic loads, accurately evaluates the structure and sealing performance of special threaded joints in oil well tubing, and is of great significance for optimizing the design, manufacturing, and maintenance procedures of special threaded joints in oil well tubing.

[0096] Example

[0097] Taking the performance evaluation process of a special threaded joint in an oil well pipe as an example, this embodiment provides a method for evaluating the performance of threaded joints, which specifically includes the following steps:

[0098] Step 1: Determine the J2-J3 anisotropic model based on the Cazacu-Barlat (CB) J2-J3 anisotropic yield criterion for the threaded joint material to be evaluated; determine the Armstrong-Frederick (AF) kinematic hardening model based on the Bauschinger effect of the threaded joint material to be evaluated.

[0099] Step 2: Using the actual microstructure information of the threaded joint in the oil well to be evaluated, a three-dimensional representative volume element model of the threaded joint is established. Combined with the crystal plastic finite element method based on the dislocation physical slip mechanism, the dynamic evolution parameters of the J2-J3 anisotropic model are obtained. The specific process is as follows:

[0100] Based on the actual microstructure information of the threaded pipe joint in the oil well to be evaluated, a three-dimensional representative volume element (RVE) model of the threaded pipe joint in the oil well to be evaluated was established; as attached. Figure 1 As shown, in this embodiment, the three-dimensional representative volume element (RVE) model of the oil well pipe thread joint to be evaluated has an RVE element size of 60. 3 μm 3 The number of RVE meshes is 20×20×20=8000, and the mesh type is a three-dimensional eight-node hexahedral reduced integral element (C3D8R).

[0101] Each grid represents a grain of metallic material, with a grain size close to that of the actual observed microstructure. Each grain is assigned a different grain orientation, which can be determined by Euler angles φ1, φ2, and φ3; these orientations are derived from electron backscatter diffraction (EBSD) experimental data of special threaded connection materials.

[0102] Combining the crystal plasticity finite element method based on the physical slip mechanism of metallic dislocations, different deformation modes were applied to the RVE. These different deformation modes included uniaxial tension along the x, y, and z axes; uniaxial compression along the x, y, and z axes; pure shear along the xy, yz, and zx directions; and plane strain along the xy, yz, and zx directions. The strain rate was, for example, 0.00033 s⁻¹. -1 0.001s -1 and 0.003s -1 ; and different preset deformation amounts, to obtain the dynamic evolution parameters of the J2-J3 anisotropic model.

[0103] The Crystal Shaping Finite Element Method (CPFEM) based on dislocation physical slip mechanism is used to apply different preset deformation modes to the three-dimensional representative volume element model of the threaded joint to be evaluated. Among them, different boundary conditions are applied to the Crystal Shaping Finite Element Method based on dislocation physical slip mechanism to obtain the relationship between stress response and non-uniform deformation under different preset deformation modes.

[0104] Using the minimum square difference optimization function, the relationship between stress response and non-uniform deformation under different preset deformation modes is analyzed and processed to obtain the dynamic evolution parameters of the J2-J3 anisotropic model.

[0105] The preset deformation modes include uniaxial tension, uniaxial compression, pure shear, and plane strain under different strain rates and deformation conditions.

[0106] By applying different boundary conditions to the CPFEM, the relationship between stress response and non-uniform deformation under different deformation modes was obtained. Anisotropic parameters were obtained by minimizing the squared difference optimization function, thereby determining the dynamic evolution parameters of the constitutive model. The anisotropic parameters obtained by this method change continuously with material deformation, and the calculation results are consistent with actual conditions; see attached. Figure 1 As shown in Table 1, examples of material anisotropy parameters under different deformation amounts are given.

[0107] Table 1 Examples of material anisotropy parameters under different deformation amounts

[0108]

[0109] Step 3: Evaluate the Bauschinger effect of the threaded joint to be evaluated by conducting cyclic loading mechanical property tests on the threaded joint material to be evaluated, and determine the Bauschinger effect parameters of the threaded joint material to be evaluated, that is, obtain the dynamic evolution parameters of the AF follow-up strengthening model; wherein, the Bauschinger effect parameters include the material constant C and the material constant γ; wherein, Appendix Table 2 provides examples of physically meaningful dynamic evolution parameters of the AF follow-up strengthening model.

[0110] Table 2 Examples of physically meaningful dynamic evolution parameters for the AF servo-enhancing model

[0111]

[0112] In this embodiment, the specific process of obtaining the Singhe effect parameters of the material package of the threaded joint to be evaluated through cyclic loading mechanical testing is as follows:

[0113] The threaded joint to be evaluated is pre-stretched until the deformation reaches 0.7%, then unloaded.

[0114] The threaded joint to be evaluated after pre-stretch deformation was subjected to positive loading, and unloaded when the deformation reached 1.4%.

[0115] The threaded joint to be evaluated after positive loading is subjected to reverse loading until yielding.

[0116] In this embodiment, a designed cyclic loading test was used to obtain the following results: the yield strength of the special threaded connection material of the oil well tubing to be evaluated was 780 MPa during the initial tensile test; after reaching the yield point, the stress continued to increase with further loading; when the deformation was 0.7%, unloading and then reloading forward resulted in a stress value of 820 MPa before a new yielding occurred; loading continued until the deformation reached 1.4%, at which point unloading was performed, followed by reloading in the reverse direction until yielding; the results showed that the material yielded in the reverse direction when the stress value was 690 MPa; the 110Ksi grade steel material of the special threaded connection of the oil well tubing, after being subjected to pre-applied plastic tensile strain, showed an increase in yield stress during reloading forward and a decrease in yield stress during unloading and reloading in the reverse direction, exhibiting a significant Bauschinger effect, as shown in the attached figure. Figure 2 As shown.

[0117] Step 4: For the J2-J3 anisotropic model and the AF kinematic hardening model, based on the elastoplastic flow law, and using the forward Euler explicit integration algorithm to update stress, an anisotropic kinematic elastoplastic hardening constitutive model is constructed; the flowchart of the analysis and calculation of the anisotropic kinematic elastoplastic hardening constitutive model is attached. Figure 3 As shown.

[0118] The J2-J3 anisotropy model is as follows:

[0119]

[0120]

[0121]

[0122] Where f(σ) is the J2-J3 anisotropic model; J2 is the second invariant of the deviatoric stress tensor in the shear yield stress term; J3 is the third invariant of the deviatoric stress tensor in the shear yield stress term; For reference yield stress; a i ,i=1,2…10 are 10 anisotropic parameters.

[0123] In this embodiment, the Cazacu-Barlat J2-J3 yield criterion, which considers the asymmetry of tensile and compressive stress, is associated with the Armstrong-Frederick (AF) kinematic hardening model. Based on the elastoplastic flow law, stress updates are achieved using the forward Euler explicit integration algorithm. This results in a CB-AF material constitutive model that can consider both material anisotropy and reflect the Bauschinger effect under cyclic loading.

[0124] The dynamic evolution parameters of the AF kinematic hardening model were determined by nonlinear fitting of the back stress-plastic strain curve. Under uniaxial loading, the evolution equation of the back stress in the AF kinematic hardening model is as follows:

[0125]

[0126] Where α is the back stress, i.e., the vector formed by the subsequent yield surface relative to the initial yield surface; dε P dε represents the plastic strain increment. -P Equivalent plastic strain increment; C and γ are both material constants; ε P For plastic strain; ε -P This is the equivalent plastic strain.

[0127] Integrating the back stress evolution equation, we obtain the formula for calculating the back stress α:

[0128]

[0129] Where α is the back stress.

[0130] In this embodiment, the true stress-strain curve obtained from the cyclic loading experiment is processed by removing the elastic part. The true stress at this time represents the change in the subsequent yield stress relative to the initial yield stress surface, and the true strain is the plastic strain. By performing nonlinear fitting on the back stress α, the dynamic evolution parameters of the AF kinematic hardening model can be determined.

[0131] Step 5: Based on the anisotropic kinematic elastoplastic strengthening constitutive model, establish the finite element analysis model of the oil well pipe threaded joint to be evaluated; wherein, the simulation results of the special threaded joint of the oil well pipe under cyclic loading conditions in this embodiment are shown in the attached figure. Figure 4 As shown.

[0132] Step 6: Starting from the actual service conditions of the oil well pipe threaded joint to be evaluated, the finite element analysis model of the oil well pipe threaded joint to be evaluated is used to perform elastoplastic finite element numerical simulation calculation to obtain the performance evaluation results of the threaded joint; the deformation law of the special threaded joint of the oil well pipe under the combined loads such as cyclic internal pressure and cyclic tension / compression is revealed through elastoplastic finite element numerical simulation, so as to accurately evaluate the structure and sealing performance of the special threaded joint of the oil well pipe.

[0133] Specifically, the deformation and sealing contact strength within the allowable load range are used as evaluation conditions to obtain the performance evaluation results of the threaded joint.

[0134] Among them, the deformation Δε within the allowable load condition range is less than or equal to 0.1; the sealing contact strength is defined as the integral of the contact stress on the sealing surface over the effective contact length, that is, satisfying:

[0135] F s =∫σ c dx>200N / mm

[0136] Among them, F s For sealing contact strength; σ c This refers to the contact stress on the sealing surface.

[0137] As shown in Appendix 3, Appendix 3 provides the structural and sealing performance evaluation data of the threaded joint to be evaluated in this embodiment.

[0138] Table 3. Structural and sealing performance evaluation data of the threaded joint to be evaluated.

[0139]

[0140] In this embodiment, starting from the actual service conditions of the special threaded joint of the oil pipe, the deformation law of the special threaded joint of the oil pipe under the action of composite cyclic load is revealed through finite element numerical simulation, and the extreme values ​​of local strain and contact strength of sealing surface of the threaded joint are obtained. The evaluation results show that: internal pressure is the main reason for the high contact stress peak and plastic deformation accumulation of the sealing structure of the special threaded joint. The Bauschinger effect caused by the cyclic pressure inside the oil pipe has a significant impact on the deformation of the special threaded joint of the oil pipe. The Bauschinger effect significantly affects the deformation of the special threaded joint of the oil pipe in the low cycle process. The decrease in sealing contact strength caused by the Bauschinger effect within 50 load cycles does not significantly affect the sealing integrity of the joint. As the number of cycles increases, the decrease in the sealing performance of the joint needs to be carefully evaluated.

[0141] The threaded joint performance evaluation method described in this invention aims to reveal the deformation law of special threaded connections of oil tubing under harsh service environments and complex cyclic loads, accurately evaluate the structure and sealing integrity of special threaded joints, provide a basis for safety evaluation and service life prediction of oil and gas well tubing joints, and achieve high accuracy in evaluation results by starting from practical issues such as the anisotropy of hot-rolled oil well tubing materials and the cyclic composite loads it withstands during service.

[0142] In this invention, the Bauschinger effect of a special threaded joint material is evaluated based on cyclic loading experiments, and the parameters of the Bauschinger effect are determined. A constitutive model considering tensile-compressive asymmetry and AF kinematic strengthening is adopted based on the Bauschinger effect and the combined cyclic loading. A three-dimensional representative volume element (RVE) model is constructed based on the actual microstructure information of the special threaded joint material. Combined with the crystal plasticity finite element method (CPFEM) based on the physical slip mechanism of metal dislocations, the dynamics of the constitutive model are obtained by applying different deformation modes, strain rates, and deformation amounts to the RVE. Evolution parameters; combining the J2-J3 anisotropic yield criterion and the AF kinematic strengthening model, and based on the elastoplastic flow law, stress updates are achieved using the forward Euler explicit integration algorithm, and an anisotropic kinematic strengthening elastoplastic constitutive model is established; finally, starting from the actual service conditions of the special threaded joint of the oil well pipe, the established anisotropic kinematic strengthening elastoplastic constitutive model is used to reveal the deformation law of the special threaded joint of the oil well pipe under the combined loads of cyclic internal pressure, cyclic tension / compression, etc., through elastoplastic finite element numerical simulation, and accurately evaluate the structural and sealing performance of the special threaded joint of the oil well pipe.

[0143] The evaluation method described in this invention combines the anisotropy of CB J2-J3 considering tensile-compressive asymmetry with the AF kinematic strengthening constitutive model considering the Bauschinger effect, which can accurately describe the anisotropic deformation behavior of materials under cyclic loading. By using a three-dimensional representative volume element (RVE) model with true material microstructure information, combined with the crystal plasticity finite element method (CPFEM) based on dislocation physical slip mechanism, the dynamic evolution of constitutive model parameters is determined. It can accurately and efficiently evaluate the special threaded joint structure and sealing performance that simultaneously considers material anisotropy and the Bauschinger effect under combined cyclic loading.

[0144] The above embodiments are merely one of the implementation methods for achieving the technical solution of the present invention. The scope of protection claimed by the present invention is not limited to this embodiment, but also includes any variations, substitutions and other implementation methods that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention.

Claims

1. A method for evaluating the performance of threaded joints, characterized in that, Includes the following steps: Based on the CB J2-J3 anisotropic yield criterion of the threaded joint material to be evaluated, the J2-J3 anisotropic model is determined; based on the Bauschinger effect of the threaded joint material to be evaluated, the AF kinematic hardening model is determined. Based on the elastoplastic flow law, and using the forward Euler explicit integration algorithm, an anisotropic elastoplastic strengthening constitutive model is constructed by employing the J2-J3 anisotropic model and the AF kinematic strengthening model. A finite element analysis model of the threaded joint to be evaluated is established based on the anisotropic follower elastoplastic strengthening constitutive model. Based on the actual service conditions of the threaded joint to be evaluated, the performance evaluation results of the threaded joint are calculated by using the finite element analysis model of the threaded joint to be evaluated and through elastic-plastic finite element numerical simulation. The J2-J3 anisotropic model is as follows: in, The model is J2-J3 anisotropic. It is the second invariant of the deviatoric stress tensor in the shear yield stress term; It is the third invariant of the deviatoric stress tensor in the shear yield stress term; The reference yield stress; There are 10 anisotropic parameters; In the AF kinematic hardening model, the evolution equation of the back stress is as follows: in, The back stress is the vector formed by the subsequent yield surface relative to the initial yield surface. This represents the increment of plastic strain. This represents the equivalent plastic strain increment; and All are material constants; Plastic strain; This is the equivalent plastic strain.

2. The method for evaluating the performance of a threaded joint according to claim 1, characterized in that, Based on the CB J2-J3 anisotropic yield criterion of the threaded joint material to be evaluated, in the process of determining the J2-J3 anisotropic model, a three-dimensional representative volume element model of the threaded joint to be evaluated is established based on the actual microstructure information of the threaded joint to be evaluated. Combined with the crystal plastic finite element method of dislocation physical slip mechanism, the dynamic evolution parameters of the J2-J3 anisotropic model are obtained.

3. The method for evaluating the performance of a threaded joint according to claim 2, characterized in that, Based on the actual microstructure information of the threaded joint to be evaluated, a three-dimensional representative volume element model of the threaded joint to be evaluated is established. Combined with the crystal plastic finite element method based on the dislocation physical slip mechanism, the dynamic evolution parameters of the J2-J3 anisotropic model are obtained as follows: Based on the actual microstructure information of the threaded joint to be evaluated, a three-dimensional representative volume element model of the threaded joint to be evaluated is established. The crystal shaping finite element method based on dislocation physical slip mechanism is used to apply different preset deformation modes to the three-dimensional representative volume element model of the threaded joint to be evaluated. Among them, different boundary conditions are applied to the crystal shaping finite element method based on dislocation physical slip mechanism to obtain the relationship between stress response and non-uniform deformation under different preset deformation modes. Using the minimum square difference optimization function, the relationship between stress response and non-uniform deformation under different preset deformation modes is analyzed and processed to obtain the dynamic evolution parameters of the J2-J3 anisotropic model. The preset deformation modes include uniaxial tension, uniaxial compression, pure shear, and plane strain under different strain rates and deformation conditions.

4. The method for evaluating the performance of a threaded joint according to claim 1, characterized in that, Based on the Bauschinger effect of the threaded joint material to be evaluated, in the process of determining the AF follow-up strengthening model, the Bauschinger effect parameters of the threaded joint material to be evaluated are obtained through cyclic loading mechanical tests, that is, the dynamic evolution parameters of the AF follow-up strengthening model are obtained.

5. The method for evaluating the performance of a threaded joint according to claim 4, characterized in that, The specific process of obtaining the Singhe effect parameters of the material package of the threaded joint to be evaluated through cyclic loading mechanical testing is as follows: The threaded joint to be evaluated is pre-stretched until the deformation reaches 0.7%, then unloaded. The threaded joint to be evaluated after pre-stretch deformation was subjected to positive loading, and unloaded when the deformation reached 1.4%. The threaded joint to be evaluated after positive loading is subjected to reverse loading until yielding.

6. The method for evaluating the performance of a threaded joint according to claim 1, characterized in that, Based on the actual service conditions of the threaded joint to be evaluated, the finite element analysis model of the threaded joint to be evaluated is used to calculate the performance evaluation result of the threaded joint through elastoplastic finite element numerical simulation. The deformation amount and sealing contact strength within the allowable load range are used as evaluation conditions to obtain the performance evaluation result of the threaded joint. Among them, the deformation within the allowable load condition range Less than or equal to 0.1; Sealing contact strength is defined as the integral of the contact stress on the sealing surface over the effective contact length, which satisfies: in, For sealing contact strength; This refers to the contact stress on the sealing surface.

7. A threaded joint performance evaluation system, characterized in that, include: The first model module is used to determine the J2-J3 anisotropic model based on the CB J2-J3 anisotropic yield criterion of the threaded joint material to be evaluated; and to determine the AF kinematic hardening model based on the Bauschinger effect of the threaded joint material to be evaluated. The second model module is used to construct an anisotropic elastoplastic strengthening constitutive model based on the elastoplastic flow law, the forward Euler explicit integration algorithm, the J2-J3 anisotropic model, and the AF kinematic strengthening model. The third model module is used to establish a finite element analysis model of the threaded joint to be evaluated based on the anisotropic follower elastoplastic strengthening constitutive model. The evaluation and analysis module is used to calculate the performance evaluation results of the threaded joint based on the actual service conditions of the threaded joint under evaluation, using the finite element analysis model of the threaded joint under evaluation, through elastic-plastic finite element numerical simulation. The J2-J3 anisotropic model is as follows: in, The model is J2-J3 anisotropic. It is the second invariant of the deviatoric stress tensor in the shear yield stress term; It is the third invariant of the deviatoric stress tensor in the shear yield stress term; The reference yield stress; There are 10 anisotropic parameters; In the AF kinematic hardening model, the evolution equation of the back stress is as follows: in, The back stress is the vector formed by the subsequent yield surface relative to the initial yield surface. This represents the increment of plastic strain. This represents the equivalent plastic strain increment; and All are material constants; Plastic strain; This is the equivalent plastic strain.

8. A threaded joint performance evaluation device, characterized in that, include: Memory, used to store computer programs; A processor, configured to implement the steps of the threaded joint performance evaluation method as described in any one of claims 1-6 when executing the computer program.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, characterized in that, when the computer program is executed by a processor, it implements the steps of the threaded joint performance evaluation method as described in any one of claims 1-6.

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