A method for analyzing the strength of a nail connection structure

Abstract

The application discloses a nail connection structure strength analysis method, comprising the following steps: establishing a three-dimensional model, establishing a mesh division structure and defining a contact relationship and a boundary condition; establishing a one-dimensional beam element model of a connecting piece, generating and outputting element and node information of the connecting piece; layered connection: dividing the one-dimensional beam element model in the length direction according to the number of connected pieces and the local connection thickness, each layer of the beam element being consistent with the local connected piece thickness; generating a model and performing analysis. The analysis method disclosed by the application models the connecting piece as a one-dimensional beam element, supports the connection of the connecting piece with or without an opening, automatically processes the one-dimensional beam element according to the local connected size, has high operation efficiency for large-scale nail connection structures and can more accurately simulate the actual nail connection relationship, ensures the accuracy of analysis in the case of improving the modeling and calculation efficiency, and the nail and nail hole connection stiffness data can be upgraded.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of finite element simulation, in particular to a nail connecting structure strength analysis method. BACKGROUND

[0002] Finite element simulation analysis is a step of verifying the strength of a structure by grid processing a three-dimensional entity structure and simulating the operating condition through load application. At present, the analysis process for connecting member positions, such as bolt and rivet structures, removes the connecting member structure and simulates a point rigidly connected with the surrounding hole at the center position of the connecting member to form an approximate connecting effect. However, for an aircraft connecting structure with high precision and complex structure, the fatigue damage risk from the nail hole connecting position is high, and more accurate simulation calculation of the connecting member is required. Accurate acquisition of the connecting nail load and the bypass load of the connected member is the basis for accurate analysis. At the same time, the real aircraft structure has a large number of connecting members, which not only has high model processing workload and low efficiency, but also has a large number of contact analyses between the inner wall of the connecting member, the hole wall and the connected member, which affects the calculation efficiency and the convergence of the calculation, and it is difficult to realize accurate strength analysis of the connecting member position.

[0003] Therefore, how to improve the finite element analysis efficiency and analysis accuracy of the connecting member position is a technical problem to be solved by those skilled in the art. SUMMARY

[0004] The present application provides a nail connecting structure strength analysis method to improve the finite element analysis efficiency and analysis accuracy of the connecting member position.

[0005] In order to achieve the above purpose, the present application provides the following technical scheme:

[0006] A nail connecting structure strength analysis method, comprising:

[0007] Establishing a three-dimensional model: establishing a grid division structure of a three-dimensional entity unit for a structure to be analyzed, defining the contact relationship between the connected members and the boundary conditions for subsequent simulation calculation according to the analysis needs, and outputting;

[0008] Establishing a one-dimensional beam element model of the connecting member: establishing a finite element model of the connecting member according to the position, size and material information of the connecting member, and outputting the element and node information of the connecting member;

[0009] Layered connection: layering the one-dimensional beam element model of the connecting member in the length direction according to the number of connected members and the local connection thickness size, for the connected members with a hole structure, subsequently constraining the hole wall by geometry, and for the connected members without a hole structure, identifying the connection area through the size information of the beam element; and performing displacement constraint and stiffness constraint on the newly generated segmented beam element nodes according to the requirements;

[0010] The model is generated and analyzed, and a one-dimensional beam element and a connecting element are connected according to the layered situation to output the connection model and the node constraint information. The generated layered connection model is imported into a general analysis software, and a selected finite element solver is called to complete the simulation analysis of the nail connection structure.

[0011] Preferably, in the nail connection structure strength analysis method, in the step of establishing the one-dimensional beam element model of the connecting element, the two ends of the one-dimensional beam element model in the length direction exceed the surface of the connected element; in the step of layered connection, the beam element protruding from the surface of the connected element is truncated.

[0012] Preferably, in the nail connection structure strength analysis method, the two layered regions located at the two ends of the connecting element are offset to the middle region from the constraint center point of the connected element.

[0013] Preferably, in the nail connection structure strength analysis method, the outermost one-dimensional beam element model and the connected element are connected by stiffness displacement constraint and flexible constraint; the surface nodes are simultaneously provided with axial constraint, and the region between the connected elements and the connecting element is simultaneously provided with shear constraint to simulate the axial constraint of the bolt head or nut and the shearing condition of the screw rod.

[0014] Preferably, in the nail connection structure strength analysis method, the stiffness displacement constraint and the flexible constraint are connected by a spring element simulating the shear stiffness of the bolt.

[0015] Preferably, in the nail connection structure strength analysis method, in the radial direction of the connecting element, three nodes are arranged at the same position of the layered beam element, which are flexible element (RBE3), spring element and rigid element (RBE2), respectively. The flexible element at the surface constrains the axial direction and three rotational directions, and the spring element is located at the middle position.

[0016] Preferably, in the nail connection structure strength analysis method, the number of layers of the one-dimensional beam element in the middle region is equal to the number of the connected elements, and the single-layer layering is consistent with and aligned with the thickness of the connected element corresponding thereto.

[0017] Preferably, in the nail connection structure strength analysis method, in the step of establishing the one-dimensional beam element model of the connecting element, the generated and output element and node information of the connecting element at least includes the number, size, position of the connecting element, and the material of the connecting element to reflect the geometric information and stiffness information of the connecting element.

[0018] Preferably, in the nail connection structure strength analysis method, in the three-dimensional model establishing step, the three-dimensional model has three-dimensional unit filling at the opening position of the connector, and in the layered connection step, the one-dimensional beam element model of the connector directly passes through the three-dimensional unit filling at the opening position.

[0019] Preferably, in the nail connection structure strength analysis method, in the layered connection step, the one-dimensional beam element model is layered to output the layer number and thickness information of the beam element, the node position information, and the connection region information of each layered region and the connected component.

[0020] As can be seen from the above technical solutions, the nail connection structure strength analysis method provided by the application performs one-dimensional beam element modeling on the connector, so that there is a solid grid connection between the connector and the connected component, rather than a simple rigid constraint. With the one-dimensional beam element modeling of the connector, it can be applied to a three-dimensional model of a connected component with an opening structure or a three-dimensional model of a connected component with a closed structure. Only the setting position of the connector needs to be determined. For a connected component with an opening structure, the subsequent geometric constraint hole wall and the outer wall of the connector are determined. For a connected component without an opening structure, the connection region, i.e. the outer wall region of the connector, is identified through the size information of the beam element, and a new constraint relationship between the outer wall region of the connector and the surrounding connected component is established. The above method does not need to perform excessive processing on the grid structure of the connected component. Only the connection position of the connector needs to be identified, and the one-dimensional beam element modeling of the connector is performed to pass through the grid model of the connected component. On an aircraft model with a multi-hole structure, the modeling efficiency of the connection structure strength analysis process can be significantly improved. On this basis, the one-dimensional beam element model is layered in the length direction. Specifically, the connected component is layered according to the number of connected components and the local connection thickness size. For a two-layer or multi-layer connected component, each layer has a connection component layered node corresponding to the thickness. For a single-layer connected component, the single-layer connected component is connected to the corresponding layered node, displacement constraints and stiffness constraints are set, and the connector can form two or more simulated constraint connection structures with the connected component. Compared with the simple point constraint in the prior art, the connector has a more detailed constraint connection structure, which is closer to the fixed state of the nail connection structure under actual working conditions, so that more accurate strength analysis results can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to make the technical solutions in the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced below. Obviously, the accompanying drawings in the following description only show some examples or embodiments of the present application, and for those skilled in the art, other drawings can be obtained from the provided drawings without any creative effort, and the present application can also be applied to other similar scenarios according to the provided drawings. Unless it is obvious from the language environment or otherwise stated, the same reference numbers in the drawings represent the same structure or operation.

[0022] Figure 1 is a schematic diagram of the entity connection structure of the connecting piece and the connected piece provided by the embodiments of the present application;

[0023] Figure 2 is a schematic diagram of the constraint structure of the connecting piece and the connected piece;

[0024] Figure 3 is a schematic diagram of the layered connection of the one-dimensional beam unit of the connecting piece and the grid structure of the connected piece;

[0025] Figure 4 is a front view of the contact structure of two connected pieces;

[0026] Figure 5 is a schematic diagram of marking the connection position on the connected piece;

[0027] Figure 6 is a schematic diagram of the grid structure of the connecting piece and the connected piece of the entity structure;

[0028] Figure 7 is a top view of Figure 6 ;

[0029] Figure 8 is a schematic diagram of the grid structure of the connecting piece and the connected piece of the one-dimensional beam unit model provided by the embodiments of the present application;

[0030] Figure 9 is a top view of Figure 8 ;

[0031] Figure 10 is a schematic diagram of the grid structure of the layered constraint of the connecting piece after the opening of the connected piece;

[0032] Figure 11 is a top view of Figure 10 ;

[0033] Figure 12 is a flowchart of the strength analysis method of the nail connection structure provided by the embodiments of the present application.

[0034] Wherein: 10-connector; 20-connected piece; 310-flexible unit; 320-rigid unit; 330-spring constraint. DETAILED DESCRIPTION

[0035] The core of the present application is to disclose a nail connection structure strength analysis method to improve the finite element analysis efficiency and analysis accuracy of the connector position.

[0036] In order to make the person in the technical field better understand the present application scheme, the following refers to the drawings of the present application embodiment, and in addition, the following shown embodiment does not have any limiting effect on the invention content recorded in the claims. In addition, the constitution represented by the following embodiment is not limited to the solution necessary for the invention recorded in the claims.

[0037] Reference Figures 1-12 The nail connection structure strength analysis method disclosed in the embodiment of the present application is used for the structure connected by the connector 10 such as bolt, rivet, etc. to realize the connection of skin, frame structure and beam structure, etc. to carry out more accurate strength analysis at the setting position of the connector 10. Specifically, as Figure 12 The nail connection structure strength analysis method at least includes the following steps:

[0038] S01: Establish a three-dimensional model.

[0039] The establishment of the three-dimensional model structure is the basis of strength analysis. First, the grid division structure of the three-dimensional entity unit is established for the analyzed structure, and the contact relationship between the connected pieces 20 is defined according to the analysis needs, such as face-face contact, face-line contact, etc. At the same time, the boundary adjustment for subsequent simulation calculation is determined according to the analysis needs, that is, the fixed end, free end and outside force condition of the connected piece 20 based on the actual working condition, so that the model is closer to the actual operation condition, and provides a reliable basis for subsequent analysis.

[0040] After the above information is determined, it is output, and it needs to be explained that in step S01, the connected piece 20 does not consider the hole problem, that is, it does not need to consider the installation structure of the connector 10, but only the modeling and grid division of the connected piece 20; At the same time, according to the complexity of the structure and the analysis accuracy requirement, the suitable grid type and density are selected.

[0041] On the basis of the above structure, the connected piece 20 is not further processed such as hole digging in step S01, so as to reduce the model processing difficulty under the working condition of a large number of connectors 10. Therefore, the position of the connector 10 needs to be identified in step S01, so as to clearly define the relative position relationship between the connector and the connected piece 20 on the connected piece 20, and provide an accurate reference for the establishment of the connector 10 model. At the same time, as Figure 4 and Figure 5As shown, the position markers of the connecting member 10 can be positioned by coordinate positioning, geometric feature positioning, etc. to ensure the accuracy of the connecting position.

[0042] S02: Establishing a one-dimensional beam element model of the connecting member.

[0043] Unlike the common hole grab point simulation connection of the connecting position in the prior art, in the embodiments of the present disclosure, the connecting member 10 is established as a one-dimensional beam element model based on its setting position, selected size, material information, etc., and the one-dimensional beam element model of the connecting member 10 is set through the model of the connected member 20 according to the connecting position marked in step S01. It should be noted that the one-dimensional beam element model is a model widely used in structural analysis, which can effectively simulate the mechanical behavior of the connecting member 10. After the one-dimensional beam element model is set through the connected member 20, the element and node information of the connecting member 10 is output at the same time, i.e. the numbering, node coordinates and element length of the connecting element formed by each connecting member 10 and the surrounding structure, etc. information, and the element and node information is recorded.

[0044] It should be noted that in step S02, after the one-dimensional beam element model is set through the connected member 20, a stiffness information database can also be generated according to the thickness of the connected member 20, i.e. the sandwich thickness, the type of the connecting member 10, such as rivet, bolt, etc. The connecting stiffness to provide more comprehensive and accurate data support for subsequent review and analysis.

[0045] S03: Layered connection.

[0046] Specifically, in step S03, as shown, Figure 3 the one-dimensional beam element model of the connecting member 10 is layered according to the number of the connected member 20 and the local connection thickness size. The number of the connected member 20 and the local connection thickness size information has been output in advance, and the one-dimensional beam element of the connecting member 10 is automatically layered to form the corresponding number of layers based on the above information, and each layer of the structure region is only connected with the corresponding connected member 20 region flush with it. At the same time, in the connection process, the connecting element is centered and constrained in the axis of the connecting member 10 to ensure the stability of the connection and avoid additional stress and deformation caused by eccentric connection.

[0047] It should be noted that the newly generated segmented beam element node on the connecting piece 10 is subjected to displacement constraint and stiffness constraint according to requirements, that is, the MPC (multi-point constraint) connection is performed on the newly generated segmented beam element on the connecting piece 10. It should be noted that the MPC connection is a method commonly used in finite element analysis process to simulate physical phenomena such as rigid connection and load transmission by establishing coupling relationship between different node degrees of freedom. Its popular explanation is Multipoint constraint, that is, in the present disclosure, appropriate multi-point constraints are established between each node of the beam element and the nodes near the connected piece 20, and the multi-point connection considering stiffness is established considering different layer thicknesses, bolt diameters and other information, so as to more comprehensively simulate the interaction between the connecting piece 10 and the connected piece 20.

[0048] That is, for the connecting piece 10, the locking to the connected piece 20 is realized by the area through which the connecting piece 10 passes the connected piece 20, and the pressure and torsion limiting action of the surrounding connected piece 20, and each part of the structure of the connecting piece 10 passing through the area of the connected piece 20 generates stress action with the surrounding connected piece 20. However, the commonly used rigid connection simulation is mostly simulated by connecting the single point located at the center of the connecting piece 10 with the surrounding connected piece 20, which has a large difference from the actual working condition. The layering of the one-dimensional beam element model of the connecting piece 10 in the embodiment of the present disclosure can realize more refined connection simulation of the area of the connecting piece 10 passing through the connected piece 20. Each layer of the connected piece 20 has a corresponding beam element structure with the same thickness, so that the constraint connection between each layer of the connected piece 20 and the corresponding beam element is realized, and the constraint connection is centered on the axis of the connecting piece 10. The connecting piece 10 is divided into several connection regions, and the internal stress of the multiple connection regions is maintained due to the one-dimensional beam element model. The outside of the multiple connection regions can simulate the stress with the connected piece 20 region contacted, and does not act with the misaligned connected piece 20 region, so as to accurately refine the stress of the connecting piece 10. It should be noted that through the layering of the connecting piece 10, the stress condition and deformation behavior of the connecting piece 10 at different positions can be more accurately simulated, thereby providing more detailed and accurate data support for subsequent strength analysis.

[0049] It should be noted that in step S03, the analyst can input the single-layer thickness of the connecting piece 10 to manually adjust locally on the basis of the automatic layering of the connecting piece 10 according to requirements, and realize more refined layering structure of multiple connecting pieces 10.

[0050] It needs to be further explained that in step S03, only the setting position of the connecting piece 10 needs to be determined, without considering the opening state of the connected piece 20. In fact, for the connected piece 20 with an opening structure, the subsequent geometric constraint hole wall and the outer wall of the connecting piece 10 are established, and for the connected piece 20 without an opening structure, the connecting area, i.e. the outer wall area of the connecting piece 10, is identified through the size information of the beam unit, and a new constraint relationship between the outer wall area of the connecting piece 10 and the surrounding connected piece 20 is established. The above method does not need to perform excessive processing on the grid structure of the connected piece 20, only the connection position identification of the connecting piece 10 is needed, and the one-dimensional beam unit modeling of the connecting piece 10 is set through the grid model of the connected piece 20. On the aircraft model with a multi-hole structure, the modeling efficiency of the connection structure strength analysis process can be significantly improved.

[0051] S04: Generate a model and analyze.

[0052] According to the layered situation, the connection model of the one-dimensional beam unit and the connected piece 20 and the node constraint information are output, and the generated layered connection model is imported into a general commercial analysis software to call a selected finite element solver to complete static analysis, dynamic analysis, fatigue analysis and the like of the connection structure. The finite element solver calculates mechanical parameters such as stress, strain and displacement of the connection structure according to the above information, thereby providing a reliable strength evaluation basis for further design. The layered connection model imported into the analysis software can store and view the MPC connection information of the segmented beam unit on the connecting piece 10 in the foregoing steps, as well as related node and coordinate information.

[0053] In order to further improve the simulation accuracy of the connection unit, in some embodiments of the present disclosure, the one-dimensional beam unit model is extended beyond the surface of the connected piece 20 at both ends in the length direction, to simulate the working condition that both ends of the connecting piece 10 usually extend beyond the surface of the connected piece 20, thereby more truly reflecting the stress condition of the connecting piece 10 in actual engineering. In step S03, the beam unit structure of the connecting piece 10 extending out of the surface of the connected piece 20 is truncated, so that the connecting piece 10 maintains the same thickness as the connected piece 20, thereby realizing more accurate butt joint between the two, and ensuring the stiffness effect of the connected piece 20. For the vertical support effect of the bolt and nut, vertical stiffness constraints are set at the corresponding nodes to realize the vertical support effect.

[0054] It should be noted that in other embodiments, the beam element structure of the connecting piece 10 extending out of the surface of the connected piece 20 is not processed, and the structures such as bolt heads, nuts and the like that exceed the surface of the connected piece 20 are also simulated. It should be noted that for the beam element structure of the connecting piece 10 extending out of the surface of the connected piece 20, the area of the connecting piece 10 exceeding the connected piece 20 at both ends can not only bear the load, but also have a certain influence on the strength of the layered structure at the position of both ends of the connecting piece 10. By simulating the structure of the surface of the connected piece 20 exceeding the connected piece 20 through the one-dimensional beam element model, the problem that the simulation of the stress condition of the area at both ends of the connecting piece 10 is not accurate enough due to the fact that the both ends of the connecting piece 10 are flush with the surface of the connected piece 20 is avoided, and the influence of the end area of the connecting piece 10 on the strength and load distribution of the connecting unit can be more accurately simulated, thereby improving the structural strength analysis precision of the entire connecting unit position.

[0055] On the basis of the above embodiments, the area of the connecting piece 10 exceeding the connected piece 20 at both ends will form an asymmetric mechanical relationship structure with the connected piece 20 after layering, and for the layered structure at both ends, the area exceeding the surface of the connected piece 20 at both sides, and the area exceeding the surface of the connecting piece 10 at both sides does not produce a connecting effect or only produces a small connecting force between the connecting piece 10 and the surrounding connected piece 20 during the connecting process of the connecting piece 10. At this time, the central constraint of the single-layer structure on the axis of the connecting piece 10 will lead to differences between the simulated state and the actual operating condition, and therefore in some embodiments of the present disclosure, for the beam element structure of the connecting piece 10 extending out of the surface of the connected piece 20, the two layered areas at the position of both ends of the connecting piece 10 are biased towards the central area in the axial direction of the connecting piece 10 from the constraint center point of the connected piece 20, so that the layered areas at both ends of the connecting piece 10 are within the range of the connected piece 20, and the structure simulation bearing a small connecting force in the area exceeding the connected piece 20 can more accurately reflect the actual mechanical interaction between the connecting piece 10 and the connected piece 20, thereby improving the analysis precision and reliability.

[0056] It should be further noted that for the outermost side of the one-dimensional beam element model of the connecting piece 10, the stiffness displacement constraint and the flexible constraint are adopted between the connecting piece 10 and the connected piece 20, and the shear constraint is also provided between the contact area of the connected piece 20 and the connecting piece 10, that is, the locking effect of the connecting piece 10 on the connected piece 20 is considered, and the shear effect of the contact surface on the connecting piece 10 when the different connected pieces 20 are under different stress, and the axial constraint of the actual structure bolt head or nut and the shear condition of the screw rod are simulated, thereby providing a more accurate model basis for subsequent strength calculation.

[0057] For the connector 10 in the one-dimensional beam element model, the connection between it and the connected component 20 is rigid. However, when the connector 10 is subjected to stress to the yield limit, it will undergo a certain degree of deformation before failure, while maintaining the connection effect. To more accurately simulate the complex mechanical relationships in the above structure, such as... Figure 2 As shown, in some embodiments of this disclosure, in steps S02 and S03, the outermost part of the one-dimensional beam element model, i.e., the outer wall region of the connector 10, is constrained by flexible elements 310 with the connected component 20. In the region near the central axis of the connector 10, the one-dimensional beam element model is constrained by rigid elements 320. Furthermore, based on the above embodiments, the flexible elements 310 and the rigid elements 320 are connected by spring constraints 330. It should be noted that during the simulation, the flexible element 310 constraint can better simulate the possible gap between the connector 10 and the connected component 20, as well as the relative deformation effect after contact. The parameter settings of the flexible element 310 are adjusted according to actual mechanical requirements and material properties. The rigid element 320 constraint in the axial region of the one-dimensional beam element model can simulate the internal force of the connector 10, ensuring the rigid transmission of force. Meanwhile, the spring constraint 330 is used to realize the transmission of force between the flexible unit 310 and the rigid unit 320. The spring constraint 330 has both flexible and rigid effects. For the contact deformation area on the connector 10 and the stiffness area of ​​the axis, the connection between the two through the spring constraint 330 can better simulate the transition structure between the stress deformation area and the rigid support area on the connector 10 under actual working conditions. Similarly, the spring constraint 330 can be set with different stiffness parameters according to actual needs, thereby simulating different degrees of transition connection.

[0058] During the layered connection process, the one-dimensional beam element model of the connector 10 is layered along its length. Each layered region is connected to the corresponding connected component 20. Each layered region and the connected component 20 are connected from the outside to the inside through the constraints of flexible element 310, spring constraint 330 and rigid element 320, thereby achieving a more accurate simulation of the working condition of the connector 10.

[0059] Further, based on the one-dimensional beam element model structure with the coexistence of the flexible unit 310 and the rigid unit 320, in some embodiments of the present disclosure, the flexible unit 310 is aggregated and arranged towards the axis of the one-dimensional beam element model, it is to be noted that the arrangement of the flexible unit 310 needs to be aggregated into one rigid action point, that is, the outer wall area of the connecting piece 10 still needs to form a rigid action point to realize the contact state simulation of the connecting piece 10 and the connected piece 20 while performing a certain degree of deformation simulation, so as to avoid the simulation deviation caused by the disordered deformation of the flexible unit 310; and for the rigid unit 320 close to the axis area of the connecting piece 10, it is constrained in the radial direction of the one-dimensional beam element model, after the aggregation of the action force on the outer wall of the connecting piece 10 by the flexible unit 310, the rigid unit 320 needs to realize the parallel transmission of the action force, that is, through the radial size of the connecting piece 10, the strength resisting the action force on the connecting piece 10 is reached, and the radial parallel constraint of the rigid unit 320 along the one-dimensional beam element model can ensure the parallel transmission of the action force, so that each position of the connecting piece 10 can bear the action force, and the local area of the connecting piece 10 will not be forced too much due to the excessive aggregation of the action force, and the local fracture problem in the simulation process will not occur.

[0060] It is to be noted that for the layered structure of the one-dimensional beam element, the number of layers is preferably equal to the number of connected pieces 20, that is, each connected piece 20 has a corresponding layered node, and the corresponding layered node is equal to the thickness of the connected piece 20, which improves the accuracy of the model simulation process. Similarly, in another embodiment of the present disclosure, the layered structure of the one-dimensional beam element can also be more subdivided, so that a single connected piece 20 corresponds to two or more layered nodes in the thickness direction, and only the two sides of the connected piece 20 in the thickness direction need to be aligned with the layered nodes.

[0061] Further, in the nail connection structure strength analysis method provided in the embodiments of the present disclosure, step S03 is essentially to finely segment the one-dimensional beam element model of the connecting piece 10 to achieve more accurate stress simulation. In order to improve the simulation accuracy of the one-dimensional beam element for the actual working condition of the connecting piece 10, in some embodiments of the present disclosure, the thickness of the layered structure in the middle region of the one-dimensional beam element is the same. It should be noted that the layering of the one-dimensional beam element model of the connecting piece 10 is essentially to form multiple connection units between the connecting piece 10 and the connected piece 20 to improve simulation accuracy. For the connecting piece 10 with uniform size, the region in contact with the connected piece 20 has a similar stress state. Therefore, the layered structure of the one-dimensional beam element in the middle region is set to have the same thickness to make the mechanical behavior of the middle region uniform and consistent. The middle region as the main load-bearing structure can balance the stress of the connecting piece 10 and improve the accuracy of the strength analysis of the peripheral structure of the connecting piece 10.

[0062] Further, in step S02, the generated and output unit and node information of the connecting piece 10 at least includes the number, size, position of the connecting piece 10, and the strength information corresponding to the material of the connecting piece 10 to provide more comprehensive and accurate data support for subsequent analysis. It should be noted that the number of the connecting piece 10 is used to uniquely identify each connecting piece 10 for easy management and reference in subsequent analysis. The size and position information limits the geometric characteristics and specific position of the connecting piece 10 in the structure. The material and strength information includes the elastic modulus, yield strength, and tensile strength of the connecting piece 10 material, which directly affects the mechanical response of the connecting piece 10 under stress. By outputting the above information, the traceability and partial parameter modification can be performed during the analysis process to perform comparative experimental analysis under different working conditions.

[0063] In step S01, when establishing the three-dimensional model, the position for installing the connecting piece 10 in the three-dimensional model is closed, that is, no hole digging operation is performed, so that the structure of the connected piece 20 in the three-dimensional model remains continuous, which can simplify the model and grid processing process and improve the efficiency of the analysis process. In steps S02 and S03, after the connecting piece 10 of the one-dimensional beam element model contacts the established three-dimensional model grid division structure, local grid processing is performed to directly adjust the layering and connection relationship between the connecting piece 10 of the one-dimensional beam element model and the connected piece 20 through the grid structure, thereby improving the efficiency of the modeling and analysis process.

[0064] Further, in step S03, the one-dimensional beam element model needs to output the number of layers after layering, the thickness information of each layer area, the position information of the connecting node on the three-dimensional model, and the connection area information of each layer area and the connected piece 20. The above output information can provide accurate input data for strength analysis, and can intuitively check the influencing factors according to the analysis results, so as to ensure the data integrity and reproducibility of the strength analysis process, and provide parameter basis for comparative experiment analysis.

[0065] In an embodiment of the present disclosure, a single shear connection structure is taken as an example for illustration. In this embodiment, four rows and two columns of connecting pieces 10 are arranged to fix the connected piece 20. Specifically, the connected piece 20 is 180 mm long, 56 mm wide, and 5 mm thick, and is offset and single-sidedly attached. The hole diameter of the connecting hole under actual working conditions is 5 mm, and the left end of the connecting structure is fixed and constrained, and the right end is subjected to a load of 10 KN.

[0066] The specific strength analysis steps of the connecting structure are as follows. Figure 6 Figure 7 The solid structure is as shown in Figure 10 Figure 11 The connected piece 20 is holed and only the connecting structure is arranged inside the holed area, as shown in Figure 8 Figure 9 Figure 12 The analysis steps are as follows:

[0067] Step 1: A three-dimensional solid model of the connected piece 20 is established by using a commercial software, and boundary conditions and other information are applied. The detail analysis model of the connected piece 20 is generated, which can include contact action, prestress, etc.

[0068] Step 2: Determine the connection position, mark eight array positions on the three-dimensional solid model, and number each position.

[0069] Step 3: According to the connected position, size and other information, a one-dimensional beam element is established to simulate the bolt. The element is divided into one unit, and in the subsequent layering connection, the beam element is automatically layered according to the number and size of the connected piece 20. The one-dimensional beam element information containing the connecting piece 10 is generated.

[0070] Step 4: According to the connection size of the connecting piece 10, the connection stiffness is calculated as the stiffness simulation information of the connecting element, and the automatic layering of the beam element is completed, and the grid connection division of each layer of the beam element and the connected piece 20 is completed.

[0071] Step 5: After the model processing is completed, stress analysis is performed, and the calculation results are shown in the following table.​​​​

[0072]

[0073] It can be seen that, by the nail connection structure strength analysis method of the embodiment of the present application, the analysis structure without the nail hole structure is generated, which has smaller load calculation error compared to the use condition of the solid nail, and has higher strength analysis accuracy.

[0074] As shown in the present application and claims, unless the context clearly indicates otherwise, the terms "comprise" and "include" only indicate the inclusion of the steps and elements explicitly identified, and these steps and elements do not constitute an exclusive list, and the method or device can also include other steps or elements. The element defined by the statement "comprises a" does not exclude the presence of another identical element in the process, method, product or device comprising the element.

[0075] The above description is merely preferred embodiments of the present application and a description of the applied technical principles, and is not intended to limit the present application. The present application can have various changes and modifications for those skilled in the art. The scope of the present application is not limited to the technical solutions formed by the specific combinations of the above technical features, and should also cover other technical solutions formed by any combination of the above technical features or equivalent features without departing from the above inventive concept. For example, the above features are replaced with the technical features disclosed in the present application (but not limited to) having similar functions to form a technical solution.

Claims

1. A method for strength analysis of nail connection structures, characterized in that, include: Establish a 3D model: Create a 3D solid element mesh structure for the structure to be analyzed, define the contact relationship between the connected parts and the boundary conditions for subsequent simulation calculations according to the analysis requirements, and output the results. Establish a one-dimensional beam element model of the connector: Based on the position, size and material information of the connector, establish a finite element model of the connector, and output the element and node information of the connector; Layered connection involves dividing the one-dimensional beam element model of the connector into layers along its length based on the number of connected components and the local connection thickness. For connected components with openings, subsequent geometric constraints are applied to the hole walls and the outer walls of the connector. For connected components without openings, the connection area is identified using the size information of the beam element. Displacement and stiffness constraints are applied to the newly generated segmented beam element nodes as required. Generate and analyze the model, output the connection model and node constraint information of the one-dimensional beam element and the connected parts according to the layering situation, import the generated layered connection model into general analysis software, and call the selected finite element solver to complete the simulation analysis of the nail connection structure.

2. The method for strength analysis of nail connection structures as described in claim 1, characterized in that, In the step of establishing the one-dimensional beam element model of the connector, the two ends of the one-dimensional beam element model of the connector extend beyond the surface of the connected component in the length direction; in the step of layered connection, the beam elements extending beyond the surface of the connected component are truncated.

3. The method for strength analysis of nail connection structures as described in claim 2, characterized in that, The two layered regions located at both ends of the connector are offset from the constraint center point of the connected component towards the middle region.

4. The method for strength analysis of nail connection structures as described in claim 2, characterized in that, The outermost part of the one-dimensional beam element model and the connected parts are subject to stiffness-displacement constraints and flexible constraints. Axial constraints are also set at the outermost surface nodes, and shear constraints are set between the connected parts and the connecting parts to simulate the axial constraints of bolt heads or nuts and the shear conditions of bolts in actual structures.

5. The method for strength analysis of nail connection structures as described in claim 4, characterized in that, The stiffness displacement constraint and the flexible constraint are connected by a spring element that simulates the shear stiffness of a bolt.

6. The method for strength analysis of nail connection structures as described in claim 5, characterized in that, In the radial direction of the connector, three nodes are arranged at the same position of the layered beam unit, namely flexible unit RBE3, spring unit and rigid unit RBE2. The outermost flexible unit constrains the axial direction and three rotational directions, and the spring unit is located in the middle position.

7. The method for strength analysis of nail connection structures as described in claim 3, characterized in that, The number of layers in the middle region of the one-dimensional beam unit is equal to the number of the connected parts, and the thickness of each layer is consistent with and aligned with the thickness of the corresponding connected part.

8. The method for strength analysis of nail connection structures as described in claim 1, characterized in that, In the step of establishing a one-dimensional beam element model of the connector, the generated and output element and node information of the connector includes at least the connector's number, size, position, and material to reflect the connector's geometric and stiffness information.

9. The method for strength analysis of nail connection structures as described in claim 1, characterized in that, In the establishment of the three-dimensional model, the three-dimensional model has three-dimensional element filling at the opening position of the connector. In the layered connection step, the one-dimensional beam element model of the connector directly passes through the three-dimensional element filling at the opening position.

10. The method for strength analysis of nail connection structures as described in claim 1, characterized in that, In the layered connection step, after the one-dimensional beam element model is layered, the number and thickness information of the beam element layers, node position information, and connection area information between each layered area and the connected component are output.

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