Method for analyzing dynamic characteristics of riveted structure

Abstract

The application designs a riveting structure dynamics characteristic analysis method, and belongs to the field of dynamics characteristic analysis; the rivet's own tensile stiffness and shear stiffness are calculated; the rivet riveting pressure forming pressure is obtained based on the disc part die forging calculation formula; the riveting structure local detail finite element model is established, the stiffness attribute and damping attribute caused by the rivet riveting pressure forming under the quasi-static and dynamic load of the riveting structure under the action of the pressure P are obtained through the display dynamics, the riveting structure dynamics simulation analysis detail finite element model containing the contact element is established; finally, the riveting structure dynamics characteristic analysis result is obtained; the method has a wide application space in the riveting structure dynamics characteristic analysis of aviation, aerospace, machinery and the like, can reduce the test cycle and test cost, and greatly shorten the research and development time and reduce the research and development cost, and has a wide practical application prospect.

Description

Technical Field

[0001] This invention belongs to the field of dynamic characteristic analysis, and in particular relates to a method for analyzing the dynamic characteristics of riveted structures. Background Technology

[0002] Rivets are widely used in aviation, aerospace, and machinery. Existing methods for analyzing the dynamic characteristics of riveted structures (which consist of rivets and connected structures) only consider the stiffness of the rivet itself. They do not consider the influence of factors such as rivet clamping force and clamping speed during the rivet assembly process on the dynamic characteristics of the riveted structure, including the contact stiffness and contact damping between the rivet and the rivet hole, as well as the contact stiffness and contact damping between the contact surfaces of the connected structures.

[0003] During the riveting process, factors such as rivet clamping force and clamping speed significantly affect the contact stiffness and contact damping between the rivet and the rivet hole, as well as the contact stiffness and contact damping between the connected structural surfaces. If these influencing factors are ignored and only the stiffness of the rivet itself is considered in relation to the dynamic characteristics of the riveting structure, the analysis of the dynamic characteristics of the riveting structure will be inaccurate and unreliable. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention presents a method for analyzing the dynamic characteristics of riveted structures.

[0005] A method for analyzing the dynamic characteristics of riveted structures, specifically including the following steps:

[0006] Step 1: Calculate the tensile stiffness K of the rivet itself. t and shear stiffness K s ;

[0007]

[0008]

[0009] in, L = t1 + t2; D is the rivet diameter in mm; E is the rivet material elasticity model in MPa; G is the rivet material shear model in MPa; t1 and t2 are the thicknesses of the connected parts in mm.

[0010] Step 2: Obtain the riveting clamping force P of the rivet based on the calculation formula for die forging of disc-shaped parts;

[0011]

[0012] Where, σ b A represents the yield strength of the rivet material, expressed in MPa. bThe projected area of ​​the rivet head is in mm. 2 A d The area of ​​the rivet shank is in mm. 2 b is the width of the rivet head in mm; h is the height of the rivet head in mm; D is the diameter of the rivet in mm.

[0013] Step 3: Establish a finite element model of the local details of the riveting structure;

[0014] By displaying dynamics, the contact stiffness Kc_r between the rivet and the rivet hole, the contact damping Dc_r between the rivet and the rivet hole, the contact stiffness kc_s between the contact surfaces of the connected structures, and the contact damping Dc_s between the contact surfaces of the connected structures caused by quasi-static and dynamic loads under the action of clamping force P are obtained. The specific implementation steps are as follows:

[0015] First, the finite element method is defined: the riveting structure, namely the rivet and its connected parts, is simulated by solid elements, and the connection between the rivet and the connected parts is achieved by surface-to-surface contact elements.

[0016] Material definition: The material model for the riveted structure uses an elasto-plastic material constitutive model;

[0017] Attribute definition: The solid attribute is selected for riveting structure attributes;

[0018] Load application: The rivet is pressed against the rivet by the rigid wall at both ends. The rigid wall moves at two speeds, quasi-static and dynamic. The maximum pressing load of the rigid wall is P.

[0019] Constraint application: Fixed constraints are applied around the connected parts; the detailed finite element model of the riveting structure is built; the dynamic analysis of the detailed finite element model of the riveting structure is performed using display dynamics software to obtain the stiffness and damping properties of the contact elements of the riveting structure under the action of clamping force P.

[0020] Step 4: Based on the local detail finite element model of the riveting structure obtained in Step 3, establish a detailed finite element model of the riveting structure dynamics simulation analysis containing contact elements, and finally obtain the analysis results of the dynamic characteristics of the riveting structure.

[0021] In summary, by combining the contact stiffness Kc_r between the rivet and the rivet hole, the contact damping Dc_r between the rivet and the rivet hole, the contact stiffness kc_s between the contact surfaces of the connected structures, the contact damping Dc_s between the contact surfaces of the connected structures, and the rivet type reduction factor K1, a detailed finite element model for dynamic simulation analysis of the riveted structure containing contact elements is established; finally, the dynamic characteristic analysis results of the riveted structure are obtained.

[0022] The established finite element model for dynamic simulation analysis of the riveted structure containing contact elements includes rivet elements, connection elements, and contact elements. The rivet element includes the tensile stiffness Kt and shear stiffness Ks of the rivet itself. The contact element includes the contact stiffness Kc_r between the rivet and the rivet hole, the contact damping Dc_r between the rivet and the rivet hole, the contact stiffness Kc_s between the contact surfaces of the connected structures, and the contact damping Dc_s between the contact surfaces of the connected structures.

[0023] Beneficial technical effects of the present invention:

[0024] The present invention comprehensively considers the stiffness of the rivet itself, as well as the influence of factors such as the clamping force and clamping speed of the rivet under quasi-static and dynamic loads during the rivet assembly process on the contact stiffness and contact damping between the rivet and the rivet hole, and the contact stiffness and contact damping between the contact surfaces of the connected structures, thus ensuring the accuracy and reliability of the dynamic characteristic analysis of the riveted structure. This invention has wide applications in the dynamic characteristic analysis of riveted structures in aerospace, aviation, and machinery, reducing experimental cycles and costs, thereby significantly shortening development time and reducing development costs, and has broad practical application prospects. Attached Figure Description

[0025] Figure 1 A flowchart of a method for analyzing the dynamic characteristics of a riveted structure according to an embodiment of the present invention. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments;

[0027] This invention provides a method for analyzing the dynamic characteristics of riveted structures, making it applicable to the dynamic characteristic analysis of different riveted structures.

[0028] This invention calculates the tensile stiffness Kt and shear stiffness Ks of the rivet itself; it obtains the rivet pressing force P based on the forging calculation formula for disc-type parts; it establishes a local detailed finite element model of the riveting structure, and obtains the contact stiffness Kc_r between the rivet and the rivet hole, the contact damping Dc_r between the rivet and the rivet hole, the contact stiffness kc_s between the contact surfaces of the connected structures, and the contact damping Dc_s between the contact surfaces of the connected structures under quasi-static and dynamic loads caused by the rivet pressing force P through explicit dynamics; it integrates the contact stiffness Kc_r between the rivet and the rivet hole, the contact damping Dc_r between the rivet and the rivet hole, the contact stiffness kc_s between the contact surfaces of the connected structures, the contact damping Dc_s between the contact surfaces of the connected structures, and the rivet form reduction coefficient K1 to establish a detailed finite element model of the riveting structure dynamics simulation analysis containing contact elements; finally, it obtains the analysis results of the dynamic characteristics of the riveting structure.

[0029] A method for analyzing the dynamic characteristics of riveted structures, as shown in the attached figure. Figure 1 As shown, the specific steps include:

[0030] Step 1: Calculate the tensile stiffness K of the rivet itself. t and shear stiffness K s ;

[0031]

[0032]

[0033] in, L = t1 + t2; D is the rivet diameter in mm; E is the rivet material elasticity model in MPa; G is the rivet material shear model in MPa; t1 and t2 are the thicknesses of the connected parts in mm.

[0034] Step 2: Obtain the riveting clamping force P of the rivet based on the calculation formula for die forging of disc-shaped parts;

[0035]

[0036] Where, σ b A represents the yield strength of the rivet material, expressed in MPa. b The projected area of ​​the rivet head is in mm. 2 A d The area of ​​the rivet shank is in mm. 2 b is the width of the rivet head in mm; h is the height of the rivet head in mm; D is the diameter of the rivet in mm.

[0037] Step 3: Establish a finite element model of the local details of the riveting structure;

[0038] By displaying dynamics, the contact stiffness Kc_r between the rivet and the rivet hole, the contact damping Dc_r between the rivet and the rivet hole, the contact stiffness kc_s between the contact surfaces of the connected structures, and the contact damping Dc_s between the contact surfaces of the connected structures caused by quasi-static and dynamic loads under the action of clamping force P are obtained. The specific implementation steps are as follows:

[0039] First, the finite element method is defined: the riveting structure, namely the rivet and its connected parts, is simulated by solid elements, and the connection between the rivet and the connected parts is achieved by surface-to-surface contact elements.

[0040] Material definition: The material model for the riveted structure uses an elastoplastic constitutive model, taking the Johnson-Cook constitutive model as an example. The calculation is performed using the Johnson-Cook constitutive model:

[0041] σ=(A+Bε n )(1+Clnε * (1-T) *m (2)

[0042] Where ε: equivalent strain; ε * : Dimensionless plastic strain rate; T * : Normalized temperature; A: Yield strength of the material at the reference strain rate and reference temperature; B and n: Strain hardening coefficients; C: Strain rate sensitivity coefficient; m: Temperature softening coefficient;

[0043] Attribute definition: The solid attribute is selected for riveting structure attributes;

[0044] Load application: The rivet is pressed against the rivet by the rigid wall at both ends. The rigid wall moves at two speeds, quasi-static and dynamic. The maximum pressing load of the rigid wall is P.

[0045] Constraint application: Fixed constraints are applied around the connected parts; the detailed finite element model of the riveting structure is built; the dynamic analysis of the detailed finite element model of the riveting structure is performed using display dynamics software to obtain the stiffness and damping properties of the contact elements of the riveting structure under the action of clamping force P.

[0046] Step 4: Based on the local detail finite element model of the riveting structure obtained in Step 3, establish a detailed finite element model of the riveting structure dynamics simulation analysis containing contact elements, and finally obtain the analysis results of the dynamic characteristics of the riveting structure.

[0047] In summary, by combining the contact stiffness Kc_r between the rivet and the rivet hole, the contact damping Dc_r between the rivet and the rivet hole, the contact stiffness kc_s between the contact surfaces of the connected structures, the contact damping Dc_s between the contact surfaces of the connected structures, and the rivet type reduction factor K1, a detailed finite element model for dynamic simulation analysis of the riveted structure containing contact elements is established; finally, the dynamic characteristic analysis results of the riveted structure are obtained.

[0048] The reduction factor K1 for the rivet type is shown in the table below:

[0049] Semi-circular rivet head, barrel rivet, upset rivet 0.4 Semi-circular rivet head, semi-circular rivet, upset rivet 0.6 Countersunk rivets, barrel rivets, upset rivets 0.2 Countersunk rivet head, semi-circular rivet, upset rivet 0.3

[0050] The established finite element model for dynamic simulation analysis of the riveted structure containing contact elements includes rivet elements, connection elements, and contact elements. The rivet element includes the tensile stiffness Kt and shear stiffness Ks of the rivet itself. The contact element includes the contact stiffness Kc_r between the rivet and the rivet hole, the contact damping Dc_r between the rivet and the rivet hole, the contact stiffness Kc_s between the contact surfaces of the connected structures, and the contact damping Dc_s between the contact surfaces of the connected structures.

Claims

1. A method for analyzing the dynamic characteristics of a riveted structure, characterized in that, Specifically, the following steps are included: Step 1: Calculate the tensile stiffness and shear stiffness of the rivet itself; Step 2: Obtain the riveting clamping force of the rivet based on the calculation formula for die forging of disc-shaped parts; Step 3: Establish a finite element model of the local details of the riveting structure; Step 4: Based on the local detail finite element model of the riveting structure obtained in Step 3, establish a detailed finite element model of the riveting structure dynamics simulation analysis containing contact elements, and finally obtain the analysis results of the dynamic characteristics of the riveting structure. Step 3: Based on the finite element model of the local details of the riveting structure, the contact stiffness Kc_r between the rivet and the rivet hole, the contact damping Dc_r between the rivet and the rivet hole, the contact stiffness kc_s between the contact surfaces of the connected structures, and the contact damping Dc_s between the contact surfaces of the connected structures are obtained by displaying dynamics under quasi-static and dynamic loads of the riveting structure under clamping force P. Step 4: By combining the contact stiffness Kc_r between the rivet and the rivet hole, the contact damping Dc_r between the rivet and the rivet hole, the contact stiffness kc_s between the contact surfaces of the connected structures, the contact damping Dc_s between the contact surfaces of the connected structures, and the rivet type reduction factor K1, a detailed finite element model of the riveting structure dynamics simulation analysis with contact elements is established; finally, the analysis results of the dynamic characteristics of the riveting structure are obtained. The detailed finite element model for dynamic simulation analysis of the riveted structure with contact elements established in step 4 includes rivet elements, connection elements, and contact elements. The rivet element includes the tensile stiffness Kt and shear stiffness Ks of the rivet itself. The contact element includes the contact stiffness Kc_r between the rivet and the rivet hole, the contact damping Dc_r between the rivet and the rivet hole, the contact stiffness Kc_s between the contact surfaces of the connected structures, and the contact damping Dc_s between the contact surfaces of the connected structures.

2. The method for analyzing the dynamic characteristics of a riveted structure according to claim 1, characterized in that, Step 1: Tensile stiffness of the rivet itself and shear stiffness Specifically: （1）； （2）； in, , , D represents the rivet diameter in mm; E represents the rivet material elasticity model in MPa; G represents the rivet material shear model in MPa. , These represent the thickness of the connected components, in mm.

3. The method for analyzing the dynamic characteristics of a riveted structure according to claim 1, characterized in that, The specific clamping force P for riveting the rivet in step 2 is as follows: P= （3）； in, This represents the yield strength of the rivet material, expressed in MPa. The projected area of ​​the rivet head is given in units of 1. ; The area of ​​the rivet rod is expressed in units of... ; This refers to the width of the rivet head, in mm. D is the rivet head height in mm; D is the rivet diameter in mm.

4. The method for analyzing the dynamic characteristics of a riveted structure according to claim 1, characterized in that, Step 3, establishing the finite element model of the local details of the riveting structure, specifically involves: First, the finite element method is defined: the riveting structure, namely the rivet and its connected parts, is simulated by solid elements, and the connection between the rivet and the connected parts is achieved by surface-to-surface contact elements. Material definition: The material model for the riveted structure uses an elasto-plastic material constitutive model; Attribute definition: The solid attribute is selected for riveting structure attributes; Load application: The rivet is pressed against the rivet by the rigid wall at both ends. The rigid wall moves at two speeds, quasi-static and dynamic. The maximum pressing load of the rigid wall is P. Constraint application: Fixed constraints are applied around the connected parts; a detailed finite element model of the riveting structure is built; dynamic analysis of the detailed finite element model of the riveting structure is performed using display dynamics software to obtain the stiffness and damping properties of the contact elements of the riveting structure under the action of clamping force P.

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