Fastener multi-load state simulation finite element modeling method with unidirectional compression inhibition

Abstract

The invention provides a fastener multi-load state simulation finite element modeling method with one-way compression inhibition. Comprising the following steps: 1) designing a multi-unit collaborative modeling structure; 2) designing an asymmetric load transfer mechanism; and 3) designing a calculation efficiency optimization strategy. The technical problems that in traditional entity unit modeling, computing resource consumption is large, force transmission path simulation is inaccurate, and fastener connection modeling is difficult are solved.

Description

Technical Field

[0001] This invention belongs to the field of structural mechanics simulation technology, and specifically relates to a finite element modeling method for simulating multi-load states of fasteners with unidirectional compression suppression. Background Technology

[0002] (1) Deficiencies of traditional fastener modeling methods Current finite element modeling methods for fasteners mainly rely on the following techniques: Solid element modeling: simulates the geometry of bolts / rivets through fine meshes, but it is computationally expensive (solid element modeling requires at least 10 times the mesh density of the actual structure, resulting in low computational efficiency).

[0003] Simplified rigid connection: RBE2 / RBE3 elements are used to simulate fastener connections, but the transmission paths of tensile, shear and compressive loads cannot be distinguished (this method may overestimate the structural stiffness under compression conditions, resulting in distorted results).

[0004] (2) Lack of asymmetric load transfer In existing technologies, fastener models generally cannot achieve the asymmetric mechanical properties of transmitting only tensile / shear loads while suppressing compressive loads. For example: Standard CBAR / CBUSH elements: Although they can simulate axial tensile stiffness, they cannot actively suppress the transmission of compressive loads (e.g., the stiffness function of the ANSYS RSTAB170 element remains non-zero under compressive conditions, which cannot meet the asymmetric requirements).

[0005] (3) The contradiction between computational efficiency and accuracy High-precision solid element modeling requires significant computational resources, while simplified models (such as rigid elements) sacrifice the realism of mechanical behavior. For example: The computation time for solid element modeling is 3-5 times that of CBAR / CBUSH hybrid modeling, but the accuracy is only improved by 5%-8%; the iterative convergence time of traditional contact algorithms increases by 40%-60% under nonlinear conditions, which limits the simulation efficiency of large-scale assemblies. Summary of the Invention

[0006] The purpose of this invention is to provide a finite element modeling method for simulating multiple load states of fasteners with unidirectional compression suppression. This invention solves the technical problems of high computational resource consumption, inaccurate force transmission path simulation, and difficulty in modeling fastener connections in traditional solid element modeling.

[0007] Technical solution. A finite element modeling method for simulating multi-load states of fasteners with unidirectional compression suppression, comprising the following steps: 1) Multi-unit collaborative modeling structure design; 2) Design of asymmetric load transfer mechanism; 3) Design of computational efficiency optimization strategies.

[0008] In the aforementioned finite element modeling method for simulating multi-load states of fasteners with unidirectional compression suppression, the design of step 1) includes: Solid unit: Used to simulate the body structure of the hexagonal head of the fastener, and to set the contact algorithm with the contact surface of the connected parts; CBAR element: simulates the axial tensile stiffness of fasteners, allowing only tensile loads to be transmitted; CBUSH element: Combining Huth's formula, K2 and K3 are defined to simulate the shear load transfer between the fastener and the connected parts; In the aforementioned finite element modeling method for simulating multi-load states of fasteners with unidirectional compression suppression, step 1) further includes the following design: Rigid element: connects the connected part to the CBAR element and the CBUSH element.

[0009] In the aforementioned finite element modeling method for simulating multi-load states of fasteners with unidirectional compression suppression, step 2) includes the following design: Tensile and shear coupling design: The axial stiffness of the CBAR element and the shear constraint of the CBUSH element are used to achieve the coordinated transfer of tensile and shear loads.

[0010] In the aforementioned finite element modeling method for simulating multi-load states of fasteners with unidirectional compression suppression, step 2) further includes the following design: Compression suppression: By using the nonlinear stiffness function of the CBUSH element, the stiffness is set to zero under compression conditions to prevent the transmission of compressive force.

[0011] In the aforementioned finite element modeling method for simulating multi-load states of fasteners with uniaxial compression suppression, the nonlinear stiffness function of the CBUSH element is designed based on the Huth formula.

[0012] In the aforementioned finite element modeling method for simulating multi-load states of fasteners with unidirectional compression suppression, the optimization in step 3) includes mesh simplification: based on hybrid modeling of solid elements and CBAR / CBUSH elements.

[0013] In the aforementioned finite element modeling method for simulating multi-load states of fasteners with unidirectional compression suppression, the optimization of step 3) also includes parallel computing support: parallel processing of the solution of the CBUSH element and the iterative process of the contact algorithm.

[0014] Beneficial Effects: This invention provides an efficient structural simulation method based on multiple types of finite element elements, effectively solving the technical problems of high computational resource consumption, inaccurate force transmission path simulation, and difficulty in modeling fastener connections in traditional solid element modeling. This invention innovatively adopts a collaborative combination architecture of solid elements, rigid elements, and CBAR / CBUSH elements to establish a dynamic balance between geometric accuracy and computational efficiency, achieving a technological breakthrough by reducing computational resource consumption by more than 50% compared to traditional methods. Specifically targeting the need for active suppression of compressive loads, this invention designs a force transmission path optimization algorithm coupled with multiple types of elements. Through the collaborative force transmission mechanism of rigid elements and beam / rod elements, the load transmission path is precisely controlled. Simultaneously, an innovative refined modeling technique for fastener connections is developed, employing a collaborative simulation strategy of CBUSH elements and contact algorithms to achieve high-fidelity simulation of fastener connection stiffness, damping, and nonlinear behavior, significantly improving the accuracy of predicting the mechanical response of complex assembly structures in finite element analysis.

[0015] From the perspective of precise control of asymmetric load transfer, this invention achieves fasteners that only transfer tensile and shear loads and completely suppress compressive loads through the customized stiffness function and contact algorithm of the CBUSH unit, which meets the requirements of actual working conditions.

[0016] In terms of the efficiency of multi-element collaborative modeling, this invention combines solid elements with CBAR / CBUSH elements, taking into account both geometric accuracy and computational efficiency, saving more than 50% of computational resources compared with traditional solid modeling methods.

[0017] In summary, this invention achieves the following significant technical effects through its innovative multi-type unit collaborative modeling method: 1) Optimization of computational resources: The intelligent combination architecture of solid elements and CBAR / CBUSH elements is adopted, which reduces the consumption of computational resources by more than 50% compared with the traditional solid modeling scheme, while maintaining the high fidelity of the geometric model. 2) Precise control of force transmission path: Based on the collaborative force transmission mechanism of rigid elements and beam / rod elements, a dynamic equilibrium multi-element coupling algorithm is constructed to effectively solve the problem of active suppression of compressive loads and significantly improve the load transmission prediction accuracy of complex structures. 3) High-precision simulation of fastener connections: By using a collaborative simulation strategy of CBUSH elements and contact algorithms, the accuracy bottleneck of traditional fastener modeling is broken through, and high-fidelity characterization of connection stiffness, damping characteristics and nonlinear behavior is achieved. 4) Multi-objective performance balance: Under the premise of ensuring the accuracy of mechanical response prediction, a dynamic optimization system for geometric accuracy and computational efficiency is established to provide a technical solution that combines accuracy and economy for the efficient simulation of large assembly structures. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a finite element modeling method for simulating multi-load states of fasteners with unidirectional compression suppression. Figure 2 This is a partial schematic diagram of a finite element modeling method for simulating multi-load states of fasteners with unidirectional compression suppression. Figure 3 This is a schematic diagram of the efficient finite element modeling principle for simulating multi-load states of fasteners with unidirectional compression suppression. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.

[0022] In the description of this invention, it should be noted that the directions or positional relationships indicated by terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing and simplifying the invention, and should not be construed as limiting the invention. Furthermore, the use of ordinal numbers (e.g., "first and second," etc.) is for distinguishing objects and is not limited to this order, and should not be construed as indicating or implying relative importance.

[0023] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly, encompassing both direct connection and indirect connection via an intermediate medium. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0024] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0025] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0026] Example 1. A finite element modeling method for simulating multi-load states of fasteners with unidirectional compression suppression, see [link to example]. Figures 1-3 This method can transmit shear loads and only tensile loads, not compressive loads. It uses a combination of solid elements, rigid elements, CBAR elements, and CBUSH elements, combined with contact algorithms and Huth formulas, to establish this finite element connection. This modeling method has high computational efficiency; specifically, it includes the following steps: 1) Multi-unit collaborative modeling structure Solid unit: Used to simulate the body structure of the hexagonal head of the fastener, and to set the contact algorithm with the contact surface of the connected parts; CBAR element: simulates the axial tensile stiffness of fasteners, allowing only tensile loads to be transmitted; CBUSH element: Combining Huth's formula, K2 and K3 are defined to simulate the shear load transfer between the fastener and the connected parts; Rigid element: connects the connected component to the CBAR element and the CBUSH element; 2) Asymmetric load transfer mechanism Tensile and shear coupling: The axial stiffness of the CBAR element and the shear constraint of the CBUSH element are used to achieve the coordinated transfer of tensile and shear loads. Compression suppression: By using the nonlinear stiffness function of the CBUSH element (based on the Huth formula), the stiffness is set to zero under compression conditions to prevent the transmission of compressive force; 3) Computational efficiency optimization strategies Mesh simplification: By using hybrid modeling of solid elements and CBAR / CBUSH elements, the area of ​​fine mesh is reduced, thus reducing computational cost; Parallel computing support: The solution of CBUSH elements and the iterative process of the contact algorithm can be parallelized, adapting to large-scale assembly analysis.

[0027] Example 2. A finite element modeling method for simulating multi-load states of fasteners with unidirectional compression suppression, see [link to example]. Figures 1-3 The principle behind this method is as follows: In the finite element model, the bolt structure is decomposed into two parts: the bolt head and the screw. The screw is constructed using superimposed CBAR and CBUSH elements, while the bolt head is constructed using solid elements. The connection logic is as follows: (1) The solid element is connected to the connected part 1 through contact, and frictionless contact is set; (2) At the same time, the solid element and the CBAR element are connected through a common node; (3) The other end of the CBAR element is connected to the connected part 2 through a rigid element; (4) Thus, if the connected part 1 and the connected part 2 move away from each other, the screw simulated by the CBAR element is subjected to tension; if the connected part 1 and the connected part 2 move towards each other, the two connected parts are compressed, and the contact between the bolt head and the connected part 1 is ineffective, thereby achieving only transmission. (5) The connected part 1 is connected to the CBUSH unit through a rigid unit; (6) The other end of the CBUSH unit is connected to the connected part 2 through a rigid unit; (7) K1 of the CBUSH unit is set to 0 (the screw simulated by the CBUSH unit does not provide axial stiffness), and K2 and K3 are calculated by the Huth formula; (8) With the frictionless contact between the bolt head and the connected part 1, the CBUSH unit transmits all the shear load, ensuring the accuracy of the shear force in the shear load extraction.

[0028] Example 3. A finite element modeling method for simulating multi-load states of fasteners with unidirectional compression suppression, see [link to example]. Figures 1-3 The following example illustrates the implementation of finite element modeling for the engine mount of the AG50 light sport aircraft: The engine mount is a critical load-bearing component of the aircraft's power system, requiring high-precision and high-efficiency prediction of its mechanical response in the AG50 aircraft's full-aircraft finite element model. This solution utilizes a finite element modeling method based on unidirectional compression suppression and multi-load state simulation of fasteners, and performs customized modeling for the AG50 engine mount subsystem. Key optimization measures include: Load transfer path: Through the coordinated constraint conditions of the rigid element (RBE2) and the CBAR element, the engine vibration load is ensured to be transferred to the fuselage through a preset path, avoiding unexpected local stress concentration; Unit number control: The total number of units in the engine bracket subsystem is controlled at around 35,000 (traditional solid modeling requires more than 70,000), which improves the computational efficiency of the whole machine model by 60%.

[0029] This solution achieves the following breakthroughs in the modeling of the AG50 engine bracket: Improved computational efficiency: By combining solid elements, rigid elements, CBAR elements, and CBUSH elements, the computational resource consumption of the support subsystem is reduced by 60%, and the solution time of the whole model is shortened to 1 / 3 of that of the traditional method; High-precision characterization of nonlinear behavior: The combination of CBUSH unit and contact algorithm realizes the prediction of nonlinear response under engine vibration load for the first time in AG50, providing key data for the optimization of vibration reduction system.

[0030] The above detailed embodiments are a description of the present invention. It should not be considered that the specific embodiments of the present invention are limited to these descriptions. For those skilled in the art, several simple deductions and substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the protection scope of the present invention.

Claims

1. A finite element modeling method for simulating multi-load states of fasteners with unidirectional compression suppression, characterized in that, Includes the following steps: 1) Multi-unit collaborative modeling structure design; 2) Design of asymmetric load transfer mechanism; 3) Design of computational efficiency optimization strategies.

2. The finite element modeling method for simulating multi-load states of fasteners with unidirectional compression suppression according to claim 1, characterized in that, Step 1) of the design includes: Solid unit: Used to simulate the body structure of the hexagonal head of the fastener, and to set the contact algorithm with the contact surface of the connected parts; CBAR element: simulates the axial tensile stiffness of fasteners, allowing only tensile loads to be transmitted; CBUSH element: Combining the Huth formula, K2 and K3 are defined to simulate the shear load transfer between the fastener and the connected parts.

3. The finite element modeling method for simulating multi-load states of fasteners with unidirectional compression suppression according to claim 2, characterized in that, Step 1) of the design also includes: Rigid element: connects the connected part to the CBAR element and the CBUSH element.

4. The finite element modeling method for simulating multi-load states of fasteners with unidirectional compression suppression according to claim 1, characterized in that, Step 2) of the design includes: Tensile and shear coupling design: The axial stiffness of the CBAR element and the shear constraint of the CBUSH element are used to achieve the coordinated transfer of tensile and shear loads.

5. The finite element modeling method for simulating multi-load states of fasteners with unidirectional compression suppression according to claim 4, characterized in that, Step 2) of the design also includes: Compression suppression: By using the nonlinear stiffness function of the CBUSH element, the stiffness is set to zero under compression conditions to prevent the transmission of compressive force.

6. The finite element modeling method for simulating multi-load states of fasteners with unidirectional compression suppression according to claim 5, characterized in that, The nonlinear stiffness function of the CBUSH element is designed based on the Huth formula.

7. The finite element modeling method for simulating multi-load states of fasteners with unidirectional compression suppression according to claim 1, characterized in that, Step 3) optimization includes mesh simplification: based on hybrid modeling of solid elements and CBAR / CBUSH elements.

8. The finite element modeling method for simulating multi-load states of fasteners with unidirectional compression suppression according to claim 7, characterized in that, The optimization in step 3) also includes parallel computing support: parallel processing of the solution of the CBUSH cell and the iterative process of the contact algorithm.

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