Construction and simulation optimization method for drill collar taper thread finite element model

Abstract

The invention provides a drill collar taper thread finite element model construction and simulation optimization method, which remarkably improves the modeling efficiency and precision and reduces the simulation cost through a parameterized modeling technology, and comprises the following steps: constructing an initial finite element model, dividing the initial finite element model according to radial, axial and circumferential directions to form a three-dimensional cylindrical mesh model, and constructing a three-dimensional cylindrical mesh model; the widths of radial grids X of the cylindrical grid model are sequentially reduced from the drill collar body to the tooth crest; meanwhile, extracting number information of each grid node of the initial finite element model and coordinate information corresponding to the node; constructing a standard drill collar taper thread model based on parameterized features of an API standard thread series; and the node number information and the coordinate information of the initial meta-model are imported into a standard drill collar taper thread model, the node positions of the nodes of the cylinder grid model are changed node by node according to parameterized features, and a drill collar taper thread contour grid is generated.

Description

Technical Field

[0001] The invention relates to the field of drill collar taper thread design, and in particular to a drill collar taper thread finite element model construction and simulation optimization method. Background Art

[0002] Drill collars are key tools in the oil drilling process, and the reliability of their threaded connections directly affects the safety and efficiency of drilling. In the past, the analysis of drill collar threads mainly relied on physical tests and two-dimensional model simulations. Physical tests are costly, long, and destructive, which limits the number of tests and sample size. Although two-dimensional model simulations are low-cost, they are difficult to fully reflect the three-dimensional mechanical behavior of threaded connections, limiting the accuracy and practicality of the simulation results. At present, three-dimensional finite element simulation technology can simulate the mechanical behavior of drill collar threads more accurately, but due to the complexity of the drill collar thread structure, traditional three-dimensional modeling methods face problems such as low parameterization, low modeling efficiency, and difficulty in automation, which limits the application of three-dimensional finite element simulation in drill collar thread analysis. Summary of the invention

[0003] The object of the present invention is to provide a method for constructing a finite element model of a drill collar cone thread, which can quickly refer to the parametric features of the API standard thread series to achieve fast and accurate parametric modeling of the finite element model.

[0004] Another object of the present invention is to provide a simulation optimization method for a drill collar taper thread finite element model, which can optimize the input parameters of the drill collar taper thread finite element model, thereby further improving the high precision and high reliability of the drill collar taper thread finite element model.

[0005] The embodiment of the present invention is achieved as follows:

[0006] A method for constructing a finite element model of a drill collar taper thread comprises the following steps:

[0007] An initial finite element model is constructed. The initial finite element model is divided into a three-dimensional cylindrical mesh model according to radial, axial and circumferential directions. The width of the radial mesh X of the cylindrical mesh model decreases from the distance between the drill collar body and the tooth top. The height of the axial mesh Y of the cylindrical mesh model is equally spaced from top to bottom. The circumferential nodes Z of the cylindrical mesh model are equally divided nodes distributed in a circular array. At the same time, the number information of each mesh node of the initial finite element model and the coordinate information corresponding to the node are extracted.

[0008] Construct a standard drill collar taper thread model based on the parametric features of the API standard thread series;

[0009] The node numbering information and coordinate information of the initial meta-model are imported into the standard drill collar cone thread model. The nodes of the cylindrical mesh model change their node positions node by node according to the parametric features to generate the drill collar cone thread contour mesh.

[0010] In a preferred embodiment of the present invention, the parametric features of the above-mentioned standard drill collar taper thread model include pitch P, bolt nominal diameter d, tooth height h, taper Taper, tooth top width fc, tooth root width fr, tooth side angle θ, tooth profile radius Rho, back-off groove pitch Pg, and stress relief groove radius r1.

[0011] In a preferred embodiment of the present invention, the method for changing the node positions of the nodes of the cylindrical mesh model node by node according to the parameterized features comprises:

[0012] Read standard drill collar taper thread model;

[0013] The flank angle of the corresponding thread interface is obtained at each changing node, and the thread interface is assumed to be on the XOY plane, and the flank angle is calculated according to the position of the node;

[0014] When the change node is located in the first quadrant of the thread interface, θ-ini=atan(Coord-Y / Coord-X); when the change node is located in the second or third quadrant of the thread interface, θ-ini=π+atan(Coord-Y / Coord-X); when the change node is located in the fourth quadrant of the thread interface, θ-ini=2*π+atan(Coord-Y / Coord-X), where Coord-X is the X coordinate and Coord-Y is the Y coordinate;

[0015] Calculate the node flank angle increment θ-add caused by the change in thread interface height;

[0016] Calculate the true flank angle θ of the node according to the flank angle increment of the node, where θ=θ-ini+θ-add. When the true flank angle θ exceeds 2π, perform a modulus operation on the true flank angle θ.

[0017] The circumferential node Z is modified layer by layer from the innermost layer according to the actual tooth flank angle θ.

[0018] In a preferred embodiment of the present invention, the method of modifying the circumferential node Z layer by layer from the innermost layer according to the real tooth flank angle θ comprises:

[0019] Determine whether the axial node Z is in the normal thread part according to the width of the radial grid X;

[0020] If the axial node Z is located in the normal thread part, when [0≤θ≤θ1], r=d / 2-Coord-Z / 2 / Tapper; when (θ1<θ<θ2), r=d / 2+fc-H / π*θ-Coord-Z / 2 / Tapper; when [θ2<θ≤π], r=d / 2-H+fc+2*Rho-sqrt(Rho 2 -(π-θ) 2 / (4*π 2 )*p 2 )-Coord-Z / 2 / Tapper; when (π≤θ≤θ3), r=d / 2-H+fc+2*Rho-sqrt(Rho 2 -(θ-π) 2 / (4*π 2 )*p 2 )-Coord-Z / 2 / Tapper; when [θ3≤θ≤θ4], r=d / 2-2*H+fc+θ / π*H-Coord-Z / 2 / Tapper; when the actual tooth side angle θ is not within any of the above-mentioned tooth side angle ranges, r=d / 2-Coord-Z / 2 / Tapper.

[0021] In a preferred embodiment of the present invention, the above-mentioned θ1=π*fc / H; θ2=(1-sqrt(3) / P*Rho)*π; θ3=(1+sqrt(3) / P*Rho)*π; θ4=(2-fc / H)*π.

[0022] In a preferred embodiment of the present invention, the method of modifying the circumferential nodes Z layer by layer from the innermost layer according to the real tooth flank angle θ further includes: when the axial nodes Z are located in the undercut portion, the mesh nodes are changed one by one according to the undercut position, and the modification method is:

[0023] When Coord-Z>=-2^0.5 / 2*r1 and Coord-Z<=0, r=d / 2+Coord-Z;

[0024] When Coord-Z>=-2^0.5*r1 and Coord-Z<=-2^0.5 / 2*r1, r=d / 2-(r1^2-(2^0.5*r1+Coord-Z)^2)^0.5;

[0025] When Coord-Z>=-4Pg+r1 and Coord-Z<=-2^0.5*r1, r=d / 2-r1;

[0026] When Coord-Z>=-4Pg and Coord-Z<=-4Pg+r1,

[0027] r=d / 2-(r1^2-(-4Pg+r1-Coord-Z)^2)^0.5;

[0028] When Coord-Z <= -4Pg, r = 60;

[0029] When Coord-Z>100, r=50,

[0030] Where Pg is the pitch of the backing groove and r1 is the inner diameter of the stress relief groove.

[0031] In a preferred embodiment of the present invention, the nodes of the cylindrical mesh model change their node positions node by node according to the parameterized features, and the method for generating the drill collar cone thread profile mesh further includes:

[0032] Calculate the radial distance from the unmodified node to the origin;

[0033] The true radial distance from the outer grid to the origin is calculated by a linear interpolation algorithm;

[0034] Calculate Cartesian coordinates from radial and angular coordinates of nodes;

[0035] The modified node information is stored in a new matrix, and the modified mesh node distribution is drawn to obtain the drill collar cone thread profile mesh.

[0036] In a preferred embodiment of the present invention, the generation process of the standard drill collar cone thread profile mesh is performed in MATLAB. After generation, the standard drill collar cone thread profile mesh is converted into a file format that can be processed by HyperMesh software, and finally a drill collar cone thread finite element model is obtained.

[0037] In a preferred embodiment of the present invention, the width of the radial grid X of the cylindrical grid model decreases from the drill collar body to the tooth top, and the spacing of the radial network within the tooth root optimization range decreases from the tooth root to the tooth top.

[0038] A simulation optimization method for a drill collar taper thread finite element model, using any of the above-mentioned fine modeling methods for the drill collar taper thread finite element model to construct a drill collar taper thread finite element model, and optimizing the input parameters of the drill collar taper thread finite element model by simulating the working state of the drill collar.

[0039] The beneficial effects of the embodiments of the present invention are:

[0040] 1. For the large-size and tapered threads used in drill collars for oil drilling, the parametric generation program of the thread finite element model is written using the MATLAB language, and the parametric features of the API standard thread series are referred to to achieve fast and accurate parametric modeling of the finite element model.

[0041] 2. The drill collar taper thread finite element model construction method significantly improves modeling efficiency and reduces simulation costs, while ensuring high accuracy and reliability of simulation results, which can meet the urgent needs of the oil drilling industry for drill collar thread analysis;

[0042] 3. By simulating and optimizing the finite element model of the drill collar taper thread, the working state of the drill collar taper thread under the action of composite load is obtained, which is conducive to obtaining the optimized input parameters and feeding the above parameters back to the finite element model of the drill collar taper thread, greatly shortening the research and development cycle and test expenses of the drill collar thread. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0044] Figure 1 It is a flow chart of a method for constructing a finite element model of a drill collar taper thread according to an embodiment of the present invention;

[0045] Figure 2 Schematic diagram of radial grid X of a cylindrical grid model according to an embodiment of the present invention;

[0046] Figure 3 The mesh schematic diagram of the drill collar cone thread profile obtained by the modified mesh node distribution of the embodiment of the present invention;

[0047] Figure 4 It is a schematic diagram of the first finite element simulation result of the finite element model of the drill collar taper thread profile according to an embodiment of the present invention;

[0048] Figure 5 It is a schematic diagram of the results of the second finite element simulation of the drill collar taper thread profile finite element model according to the embodiment of the present invention after being modified according to the optimization suggestions of the first finite element simulation;

[0049] Figure 6 The present invention is a flowchart of a method for automatically constructing a drill collar cone thread profile network according to an embodiment of the present invention. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0051] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0053] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this application will be more comprehensive and complete and fully convey the concept of example embodiments to those skilled in the art.

[0054] In addition, described feature, structure or characteristic can be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present application. However, those skilled in the art will appreciate that the technical scheme of the present application can be put into practice without one or more of the specific details, or other methods, components, devices, steps, etc. can be adopted. In other cases, known methods, devices, realizations or operations are not shown or described in detail to avoid blurring the various aspects of the application.

[0055] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities may be implemented in software form, or in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or microcontroller devices.

[0056] The flowcharts shown in the accompanying drawings are only exemplary and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps can be decomposed, and some operations / steps can be combined or partially combined, so the actual execution order may change according to actual conditions.

[0057] This embodiment provides a method for establishing a refined three-dimensional finite element model of a drill collar thread, which aims to significantly improve modeling efficiency and reduce simulation costs through parametric modeling technology, while ensuring high accuracy and high reliability of simulation results to meet the urgent needs of the oil drilling industry for drill collar thread analysis.

[0058] First embodiment

[0059] See also Figure 1 This embodiment provides a method for constructing a finite element model of a drill collar taper thread, comprising the following steps:

[0060] S1: Construct an initial finite element model. Construct a basic cylindrical mesh model in the HyperMesh software and use the cylindrical mesh model as the initial finite element model. The initial finite element model is divided into a three-dimensional cylindrical mesh model according to radial, axial and circumferential directions.

[0061] As the basis for subsequent thread mesh generation, the cylindrical mesh model needs to ensure that its geometry and mesh properties can meet the requirements of subsequent processing, such as key parameters such as the number of mesh layers and density.

[0062] The width of the radial grid X of the cylindrical grid model is preset according to the thread type of the drill collar cone, so that the distance from the drill collar body to the tooth top becomes smaller in sequence. Figure 2 The purpose is to use fine meshing in the threaded section and sparse meshing in other parts to improve the calculation accuracy and efficiency. Furthermore, the width of the radial mesh X of the cylindrical mesh model decreases from the drill collar body to the tooth top, and the spacing of the radial network in the tooth root optimization range decreases from the tooth root to the tooth top.

[0063] The height of the axial grid Y of the cylindrical grid model is evenly spaced from top to bottom, and the circumferential nodes Z of the cylindrical grid model are equally divided nodes distributed in a circular array; and the numbering information of each grid node of the initial finite element model and the coordinate information corresponding to the node are extracted at the same time.

[0064] These coordinate information are key input data in the mesh transformation process, and their accuracy directly affects the quality of the final thread mesh. Equally important as the coordinate information is the node number information of the mesh. These numbers are the unique identifiers for identifying and locating each mesh node, which is crucial for subsequent mesh transformation and processing.

[0065] S2: A standard drill collar thread model is constructed based on the parametric features of the API standard thread series. After obtaining the number information of each mesh node and the coordinate information corresponding to the node in S1, the above information is sorted and input into the MATLAB drill collar thread three-dimensional finite element mesh modeling program. The node number information and coordinate information of the initial finite element model are imported into the standard drill collar thread model. The nodes of the cylindrical mesh model change the node position node by node according to the parametric features, and finally the drill collar thread contour mesh is generated.

[0066] This step provides a method for generating a drill collar thread profile network based on MATLAB. As the core step of this technical solution, by writing a three-dimensional finite element mesh modeling program for drill collar threads, the model can integrate the parametric features of the main model of drill collar threads, the API standard thread series, into the mathematical equation, and then automatically generate a mathematical model of the drill collar thread outer contour by inputting key thread parameters. The introduction of these parameters enables the program to automatically construct an accurate drill collar thread profile network. For specific calculation methods, please refer to Figure 6 .

[0067] S21: Based on the parametric features of the API standard thread series, polar coordinate angle sample points, polar coordinate radius sample points, nominal diameter lines, internal thread contour lines, marking and drawing are initially performed on the cylindrical mesh model.

[0068] S22: Parametric features and input parameters of API standard thread series are processed one by one on the finite element mesh nodes.

[0069] In various models, whether the model is simple or complex, accurate or rough, to obtain the correct results, it is of utmost importance to obtain correct and accurate model parameters. The input parameters in this embodiment combine the parameters of API standard threads, which at least include pitch P, bolt nominal diameter d, tooth height h, taper Taper, tooth top width fc, tooth root width fr, tooth side angle θ, tooth profile radius Rho, undercut pitch Pg, stress relief groove radius r1. The specific processing steps of finite element mesh nodes are as follows:

[0070] S221: Read the initial mesh nodes of the initial finite element model, calculate the total number of mesh nodes and draw the initial mesh node distribution;

[0071] S222: Modify the node coordinates one by one in a circular manner, and store the modified node coordinates. The specific method is:

[0072] S2221: Obtain the flank angle of the corresponding thread interface at each changing node, and assume that the thread interface is on the XOY plane, and calculate the real flank angle of the corresponding node according to the position of the node; when the changing node is located in the first quadrant of the thread interface, θ-ini=atan(Coord-Y / Coord-X); when the changing node is located in the second or third quadrant of the thread interface, θ-ini=π+atan(Coord-Y / Coord-X); when the changing node is located in the fourth quadrant of the thread interface, θ-ini=2*π+atan(Coord-Y / Coord-X), where Coord-X is the X coordinate and Coord-Y is the Y coordinate;

[0073] Calculate the node flank angle increment θ-add caused by the change in thread interface height, θ-add = mod(2*π*(Coord-Z / P), 2*π);

[0074] Calculate the true flank angle θ of the node according to the flank angle increment of the node, where θ=θ-ini+θ-add. When the true flank angle θ exceeds 2π, perform the remainder operation of the true flank angle θ=mod(θ,2*π);

[0075] S2222: Modify the circumferential node Z layer by layer starting from the innermost layer according to the actual tooth flank angle θ.

[0076] First, determine whether the axial node Z is in the normal thread part according to the width of the radial grid X;

[0077] If the axial node Z is located in the normal thread part:

[0078] When [0≤θ≤θ1], r=d / 2-Coord-Z / 2 / Tapper;

[0079] When (θ1<θ<θ2), r=d / 2+fc-H / π*θ-Coord-Z / 2 / Tapper;

[0080] When [θ2<θ≤π], r=d / 2-H+fc+2*Rho-sqrt(Rho 2 -(π-θ) 2 / (4*π 2 )*p 2 )-Coord-Z / 2 / Tapper;

[0081] When (π≤θ≤θ3), r=d / 2-H+fc+2*Rho-sqrt(Rho 2 -(θ-π) 2 / (4*π 2 )*p 2 )-Coord-Z / 2 / Tapper;

[0082] When [θ3≤θ≤θ4], r=d / 2-2*H+fc+θ / π*H-Coord-Z / 2 / Tapper;

[0083] When the actual flank angle θ is not within any of the above flank angle ranges, r=d / 2-Coord-Z / 2 / Tapper.

[0084] Among them, the calculation method of θ1, θ2, θ3 and θ4 is:

[0085] θ1=π*fc / H;

[0086] θ2=(1-sqrt(3) / P*Rho)*π;

[0087] θ3=(1+sqrt(3) / P*Rho)*π;

[0088] θ4=(2-fc / H)*π.

[0089] If the axial node Z is not in the normal thread part, but in the undercut part, the specific calculation method is as follows:

[0090] When Coord-Z>=-2^0.5 / 2*r1 and Coord-Z<=0, r=d / 2+Coord-Z;

[0091] When Coord-Z>=-2^0.5*r1 and Coord-Z<=-2^0.5 / 2*r1, r=d / 2-(r1^2-(2^0.5*r1+Coord-Z)^2)^0.5;

[0092] When Coord-Z>=-4Pg+r1 and Coord-Z<=-2^0.5*r1, r=d / 2-r1;

[0093] When Coord-Z>=-4Pg and Coord-Z<=-4Pg+r1,

[0094] r=d / 2-(r1^2-(-4Pg+r1-Coord-Z)^2)^0.5;

[0095] When Coord-Z <= -4Pg, r = 60;

[0096] When Coord-Z>100, r=50,

[0097] Where Pg is the pitch of the backing groove and r1 is the inner diameter of the stress relief groove.

[0098] S23: Calculate the radial distance from the unmodified node to the origin; calculate the true radial distance from the outer grid to the origin by linear interpolation algorithm; calculate the Cartesian coordinates according to the radial coordinates and angular coordinates of the node; store the modified node information in a new matrix;

[0099] S24: Draw the modified mesh node distribution to obtain the drill collar thread profile mesh, see Figure 3 , and store.

[0100] S 3: Import the node coordinates and node numbers of the drill collar thread profile mesh after node transformation into HyperMesh, and finally generate a three-dimensional finite element mesh model with rich details and accurate reflection of the complex geometric characteristics of the drill collar thread. The generation process of the standard drill collar thread profile mesh is carried out in MATLAB. After generation, the standard drill collar thread profile mesh is converted into a file format that can be processed by HyperMesh software, such as an INP file, and finally the drill collar thread finite element model is obtained.

[0101] The advantage of the drill collar cone thread finite element model construction method provided in this embodiment is that the coordinate information and node number of the basic cylindrical mesh are imported into the thread mesh node change program. The program exists independently as an external plug-in. The program will automatically execute a complex coordinate transformation algorithm to convert the original cylindrical mesh points into coordinates that accurately match the drill collar thread shape, thereby generating a highly customized and parameterized thread profile mesh. The transformed thread mesh node coordinates are then imported into HyperMesh again, and finally a three-dimensional finite element mesh model with rich details that accurately reflects the complex geometric characteristics of the thread is generated.

[0102] Mainly for the large-size, tapered threads used on drill collars for oil drilling, the parametric generation program of the thread finite element model is written using the MATLAB language, and the parametric features of the API standard thread series are referred to to achieve fast and accurate parametric modeling of the finite element model. The drill collar tapered thread finite element model construction method significantly improves modeling efficiency, reduces simulation costs, and ensures high accuracy and reliability of simulation results, which can meet the urgent needs of the oil drilling industry for drill collar thread analysis.

[0103] Second embodiment

[0104] The present embodiment provides a finite element simulation method for a drill collar taper thread. A finite element model of a drill collar taper thread is constructed using the drill collar taper thread finite element model construction method in the first embodiment. The finite element model is applied to the finite element simulation of the drill collar taper thread. The mechanical properties of the drill collar taper thread under different working conditions are analyzed by simulation. Subsequently, parameters such as thread taper, thread flank angle, and pitch can be optimized, and the optimized parameters can be fed back to the finite element model of the drill collar taper thread, which is conducive to outputting a more optimized drill collar connection thread.

[0105] For example, the thread profile of NC46 threaded buckle in API SPEC 7-2 standard is V-038R. The maximum stress of the first buckle of the external thread under the make-up torque of 50KN*m is 552MPa. From the finite element simulation results, we can see that Figure 4:The maximum stress occurs at the root of the thread. The root radius of the V-038R thread is 0.97. It is planned to optimize the thread tooth structure, increase the root radius of the thread, and improve the force distribution of the thread. However, the root radius of the thread cannot be increased infinitely. As the root radius of the thread increases, the meshing area of ​​the thread also decreases. Therefore, the root radius of the thread is selected as 1.2. The maximum stress of the first thread of the external thread is 502MPa. The thread stress is reduced by 10% under the same make-up torque. Please refer to Figure 5 Compared with traditional tests, the drill collar thread finite element simulation method can greatly shorten the thread development cycle and test costs.

[0106] The method for establishing and simulating a refined three-dimensional finite element model of drill collar threads proposed in the present invention uses a thread mesh node change program to accurately integrate the parametric features of the drill collar threads into the mathematical model, and automatically converts the basic cylindrical mesh into a refined drill collar thread mesh. This technology significantly improves modeling efficiency, quickly responds to design changes, and effectively shortens the design cycle. At the same time, the automated coordinate transformation process reduces human errors and reduces simulation costs. The generated mesh model accurately captures the complex geometric characteristics of the thread with high quality, significantly improving the accuracy of the simulation.

[0107] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in terms of function in the above description. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0108] In the several embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, or it can be an electrical, mechanical or other form of connection.

[0109] The units described as separate components may or may not be physically separated. As a unit, it can be appreciated by those skilled in the art that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in terms of function in the above description. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0110] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0111] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions for a computer device (which can be a personal computer, a server, or a grid device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0112] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for constructing a finite element model of a drill collar taper thread, characterized in that: The steps include: Constructing an initial finite element model, wherein the initial finite element model is divided into a three-dimensional cylindrical mesh model according to radial, axial and circumferential directions, wherein the width of the radial mesh X of the cylindrical mesh model decreases from the drill collar body to the tooth top, the height of the axial mesh Y of the cylindrical mesh model is equally spaced from top to bottom, and the circumferential nodes Z of the cylindrical mesh model are equally divided nodes distributed in a circular array; and simultaneously extracting the number information of each mesh node of the initial finite element model and the coordinate information corresponding to the node; A standard drill collar cone thread model is constructed based on the parametric features of the API standard thread series, and the node numbering information and coordinate information of the initial metamodel are imported into the standard drill collar cone thread model. The nodes of the cylindrical mesh model change the node positions node by node according to the parametric features to generate a drill collar cone thread profile mesh.

2. The fine modeling method of the drill collar taper thread finite element model according to claim 1 is characterized in that: The parametric features of the standard drill collar taper thread model include pitch P, bolt nominal diameter d, tooth height h, taper Taper, tooth top width fc, tooth root width fr, tooth side angle θ, tooth profile radius Rho, back-off groove pitch Pg, and stress relief groove radius r1.

3. The fine modeling method of the drill collar taper thread finite element model according to claim 2 is characterized in that: The method for changing the node positions of the nodes of the cylindrical mesh model node by node according to the parameterized features comprises: Reading the standard drill collar taper thread model; Obtain the flank angle of the corresponding thread interface at each changing node, assume that the thread interface is on the XOY plane, and calculate the flank angle according to the position of the node; When the change node is located in the first quadrant of the thread interface, θ-ini=atan(Coord-Y / Coord-X); when the change node is located in the second or third quadrant of the thread interface, θ-ini=π+atan(Coord-Y / Coord-X); when the change node is located in the fourth quadrant of the thread interface, θ-ini=2*π+atan(Coord-Y / Coord-X), where Coord-X is the X coordinate and Coord-Y is the Y coordinate; Calculate the node flank angle increment θ-add caused by the change in thread interface height; Calculate the true flank angle θ of the node according to the flank angle increment of the node, where θ=θ-ini+θ-add, and when the true flank angle θ exceeds 2π, perform a modulus operation on the true flank angle θ; The circumferential node Z is modified layer by layer from the innermost layer according to the actual tooth flank angle θ.

4. The fine modeling method of the drill collar taper thread finite element model according to claim 2 is characterized in that: The method of modifying the circumferential node Z layer by layer from the innermost layer according to the real tooth flank angle θ comprises: Determine whether the axial node Z is in the normal thread part according to the width of the radial grid X; If the axial node Z is located in the normal thread part, when [0≤θ≤θ1], r=d / 2-Coord-Z / 2 / Tapper; when (θ1<θ<θ2), r=d / 2+fc-H / π*θ-Coord-Z / 2 / Tapper; when [θ2<θ≤π], r=d / 2-H+fc+2*Rho-sqrt(Rho 2 -(π-θ) 2 / (4*π 2 )*p 2 )-Coord-Z / 2 / Tapper; when (π≤θ≤θ3), r=d / 2-H+fc+2*Rho-sqrt(Rho 2 -(θ-π) 2 / (4*π 2 )*p 2 )-Coord-Z / 2 / Tapper; when [θ3≤θ≤θ4], r=d / 2-2*H+fc+θ / π*H-Coord-Z / 2 / Tapper; when the actual tooth side angle θ is not within any of the above-mentioned tooth side angle ranges, r=d / 2-Coord-Z / 2 / Tapper.

5. The fine modeling method of the drill collar taper thread finite element model according to claim 4 is characterized in that: The θ1=π*fc / H; θ2=(1-sqrt(3) / P*Rho)*π; θ3=(1+sqrt(3) / P*Rho)*π; θ4=(2-fc / H)*π.

6. The fine modeling method of the drill collar taper thread finite element model according to claim 3 is characterized in that: The method of modifying the circumferential nodes Z layer by layer from the innermost layer according to the real tooth flank angle θ also includes: when the axial nodes Z are located in the undercut portion, the mesh nodes are changed one by one according to the undercut position, and the modification method is: When Coord-Z>=-2^0.5 / 2*r1 and Coord-Z<=0, r=d / 2+Coord-Z; When Coord-Z>=-2^0.5*r1 and Coord-Z<=-2^0.5 / 2*r1, r=d / 2-(r1^2-(2^0.5*r1+Coord-Z)^2)^0.5; When Coord-Z>=-4Pg+r1 and Coord-Z<=-2^0.5*r1, r=d / 2-r1; When Coord-Z>=-4Pg and Coord-Z<=-4Pg+r1, r=d / 2-(r1^2-(-4Pg+r1-Coord-Z)^2)^0.5; When Coord-Z <= -4Pg, r = 60; When Coord-Z>100, r=50, Where Pg is the pitch of the backing groove and r1 is the inner diameter of the stress relief groove.

7. The fine modeling method of the drill collar taper thread finite element model according to any one of claims 1 to 6, characterized in that: The method of generating a drill collar cone thread profile mesh by changing the node positions of the nodes of the cylindrical mesh model node by node according to the parameterized features further includes: Calculate the radial distance from the unmodified node to the origin; The true radial distance from the outer grid to the origin is calculated by a linear interpolation algorithm; Calculate Cartesian coordinates from radial and angular coordinates of nodes; The modified node information is stored in a new matrix, and the modified mesh node distribution is drawn to obtain the drill collar cone thread profile mesh.

8. The fine modeling method of the drill collar taper thread finite element model according to any one of claims 1 to 6, characterized in that: The generation process of the standard drill collar cone thread profile mesh is carried out in MATLAB. After generation, the standard drill collar cone thread profile mesh is converted into a file format that can be processed by HyperMesh software, and finally the drill collar cone thread finite element model is obtained.

9. The fine modeling method of the drill collar taper thread finite element model according to any one of claims 1 to 6, characterized in that: The width of the radial grid X of the cylindrical grid model decreases from the distance between the drill collar body and the tooth top, and the distance between the radial grids in the tooth root optimization range decreases from the tooth root to the tooth top.

10. A simulation optimization method for a drill collar taper thread finite element model, characterized in that: A finite element model of a drill collar taper thread is constructed using the fine modeling method of the drill collar taper thread finite element model described in any one of claims 1 to 9, and the input parameters of the finite element model of the drill collar taper thread are optimized by simulating the working state of the drill collar.

Images