A bolt structure optimization design method

Abstract

The present invention relates to a bolt structure optimization design method, comprising: selecting a bolt connection structure comprising a connecting member and a connected member, and performing reliability analysis on the bolt connection structure to obtain a plurality of reliability analysis results; if there is a result item that does not meet a pre-designed target value in the reliability analysis result, determining that the bolt structure needs to be optimized, and screening and determining at least one key parameter in the bolt structure that affects the result item that does not meet the pre-designed target value; taking the result item that does not meet the pre-designed target value as a response and the key parameter as a factor, and performing a DOE experimental design on each response, comprising: setting a response target value, selecting factors associated with the response, and setting corresponding factor levels; and performing a DOE experiment in combination with all responses, all response target values, all selected factors, and all set factor levels to obtain an optimal solution for each factor when the response is the pre-designed target value.

Description

Technical Field

[0001] The invention relates to the field of automobile bolt connection structure design, and is a bolt structure optimization design method. Background Art

[0002] Bolts are essential components in the vehicle production process. These include both standard and non-standard bolts. Standard bolts are fully standardized in terms of structure, dimensions, and drawing method, ensuring industry versatility. Non-standard bolts require structural and dimensional design tailored to specific circumstances.

[0003] For vehicle bolts, standard parts can be selected from the bolt standard parts library; non-standard parts are mainly bolts that cannot use standard parts due to the actual connection structure and require structural design.

[0004] Automotive bolt structures can be divided into connecting parts and connected components. Currently, there is no design and optimization method specifically for automotive bolt structures. Connecting parts typically use standard bolts, while non-standard bolts vary widely, resulting in no systematic design approach. Connected components are typically sheet metal or metal parts, which are generally not considered when bolting.

[0005] The automobile bolt structure must ensure that the connection does not open during the use of the automobile, that is, a certain installation pre-tightening force must be maintained between the joint surfaces under the action of external loads to prevent the bolt connection from slipping, loosening, breaking, etc.

[0006] The installation preload of a bolt is primarily generated by applying an appropriate tightening torque. Therefore, for bolt structures, tightening torque is a crucial parameter for controlling bolt preload. The tightening torque must be properly designed. Excessive torque can damage the connection structure, while insufficient torque can compromise the reliability of the connection. Existing technologies lack specific design methods for bolt tightening torque.

[0007] In the prior art, there are methods for structural design of bolts, such as "A method for optimizing bolt preload and bolt structure design using finite element method", with patent application number CN201210278894.1. This method uses an improved model and method of two-dimensional FEA and is applicable to the modeling of various bolt structures. It takes into account the complex nonlinear factors such as contact, friction, and preload in threaded connections. The preload and external force are loaded in steps; based on the stress state of the thread, the maximum stress variation curve with external force and the maximum stress variation inside the thread with preload are defined; the optimal preload for the threaded connection is determined based on whether the contact surface is separated. Based on the maximum external force bearing capacity of the bolt structure and the required preload requirements, the optimized design and optimal parameter values ​​of the bolt structure are calculated.

[0008] First, this method uses a two-dimensional model for analysis, which is not conducive to reflecting the actual characteristics of the bolt connection structure compared to a three-dimensional model. Secondly, this method can focus on the stress changes of the threaded contact surface through finite element software. In addition to the threaded contact surface, bolt connections also need to pay attention to the contact surface between the bolt head and the connected parts, the contact surface between the connected parts, and the stress and strain of the bolt rod. In addition, this method can only obtain the optimal preload force of the bolt connection structure, and there is no specific description of the tightening torque required to achieve the optimal preload force. The installation preload force of the bolt is mainly applied through the tightening torque, and the optimal preload force is not convenient for guiding production practice. Most importantly, this method performs structural design on the bolt, and does not involve specific bolt structural parameters, let alone the connected parts. Summary of the Invention

[0009] The purpose of this invention is to provide a method for optimizing the design and torque of bolt structures using the DOE method combined with MDESIGN bolt analysis software. This method systematically addresses the parameter design and optimization issues of existing bolt structures by combining both the connecting and connected components. It also provides a reasonable bolt tightening torque, guiding production practices.

[0010] The purpose is to achieve this through the following technical solutions:

[0011] The present invention provides a bolt structure optimization design method, comprising:

[0012] Select a bolt connection structure including a connecting member and a connected member, perform reliability analysis on the bolt connection structure, and obtain several reliability analysis results;

[0013] If there are result items in the reliability analysis results that do not meet the pre-designed target values, it is determined that the bolt structure needs to be optimized, and at least one key parameter in the bolt structure that affects the result items that do not meet the pre-designed target values ​​is screened and determined;

[0014] The result items that do not meet the pre-designed target values ​​are taken as responses, and the key parameters are taken as factors. DOE experimental design is performed for each response, including: setting the response target value, selecting the factors associated with it, and setting the corresponding factor levels;

[0015] A DOE experiment is conducted by combining all responses, all response target values, all selected factors, and all set factor levels to obtain the optimal solution for each factor when the response is the pre-designed target value.

[0016] Based on the optimal solutions of each factor, the reliability analysis of the bolted connection structure is re-performed, and based on the new reliability analysis results, it is verified whether the optimal solutions of each factor meet the design requirements of the bolted connection structure, and the optimization is completed.

[0017] Preferably, the step of performing reliability analysis on the bolt connection structure includes:

[0018] Using the bolt analysis module in the MEDSIGN analysis software, input various parameters of the connecting and connected parts in the bolt connection structure, set boundary conditions, establish a bolt analysis model, and calculate the reliability analysis results;

[0019] Input parameters of the connecting parts in the bolt connection structure include: bolt parameters and nut parameters; input parameters of the connected parts in the bolt connection structure include: washer parameters and sheet metal parameters;

[0020] Bolt parameters include: bolt type, nominal diameter, thread pitch, boring diameter, bolt head bearing surface outer diameter, bolt head bearing surface inner diameter, thread length, screw diameter and screw length;

[0021] Nut parameters include: nut diameter, nut width across flats, nut load-bearing surface outer diameter, nut load-bearing surface inner diameter, nut thickness and diagonal length;

[0022] Gasket parameters include: gasket type, gasket inner diameter, gasket outer diameter, gasket thickness, average surface roughness;

[0023] Sheet metal parameters include: material type, thickness, load-bearing surface outer diameter and load-bearing surface inner diameter;

[0024] The boundary conditions set include: process, temperature, external load and tightening torque of the bolt structure.

[0025] Preferably, the result items in the reliability analysis result include at least: bolt clamping force, anti-yield safety factor, bolt head compressive safety factor, nut head compressive safety factor and anti-slip safety factor.

[0026] Preferably, when conducting a DOE test,

[0027] Generate a DOE test plan based on the selected factors associated with each result that does not meet the pre-designed target value and the set factor levels;

[0028] Using MEDSIGN software, the reliability analysis of the bolted connection structure was carried out according to the generated DOE test plan, and the analysis results of the DOE test design were obtained;

[0029] Based on the analysis results of the DOE experimental design, factor regression analysis and precision verification are performed to obtain the regression equation between the response and the factor;

[0030] Based on the regression equation of response and factor, the response is optimized in combination with the set response target value to obtain the optimal solution of each factor when the response is the pre-designed target value.

[0031] Preferably, the verification is specifically as follows: after obtaining the optimal solution of each factor, the bolt reliability analysis is performed again, and based on the new reliability analysis results, it is verified whether the optimal solution of each factor meets the bolt connection structure design requirements; if the result items of the new bolt reliability analysis all meet the pre-designed target values, the bolt structure design optimization is completed; if there are result items in the new reliability analysis results that do not meet the pre-designed target values, the optimization is performed again.

[0032] The present invention provides a feasible method for automotive bolt structure design and torque optimization, enabling accurate assessment of bolt structure design parameters and design of various parameters for both the connecting and connected parts. It also optimizes the tightening torque of the bolt structure, guiding industrial production. The proposed method can systematically design automotive bolt structures and is applicable to bolted connection structures in components across industries such as automotive, aviation, machinery, and bridges, as well as to optimizing bolt structures within similar products. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a flow chart of the technical solution involved in the present invention;

[0034] Figure 2 A diagram showing the structure of an automobile bolt involved in an embodiment of the present invention;

[0035] Figure 3 The Pareto diagram of the effect between the bolt clamping force E and the factors involved in the embodiment of the present invention;

[0036] Figure 4 The main effect diagram, interaction diagram, and residual diagram of the bolt clamping force E involved in the embodiment of the present invention;

[0037] Figure 5 A Pareto diagram showing the effect between the anti-slip safety factor F and the factors involved in the embodiment of the present invention;

[0038] Figure 6 These are the main effect diagram, interaction diagram, and residual diagram of the anti-slip safety factor F involved in an embodiment of the present invention. DETAILED DESCRIPTION

[0039] In order to clearly illustrate the technical solution of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] The present invention is not limited to the specific details and can also be implemented by other similar methods that are different from the methods described herein. Therefore, the protection scope of the present invention is not limited to the following embodiments.

[0041] A method for automobile bolt structure design and torque optimization is proposed. The method mainly uses the DOE method combined with MDESIGN bolt analysis software to systematically design and optimize the automobile bolt structure.

[0042] The method mainly includes the following steps:

[0043] 11. Bolt reliability analysis.

[0044] 111. Preliminary bolt selection. Preliminary selection of fasteners (bolts and nuts) is based on the vehicle's bolt structure. Whether to use standard or non-standard parts can be determined by referring to the VDI design manual to determine the bolt type and the target value for the bolt clamping force.

[0045] 112. Perform a bolt reliability analysis on a bolted connection structure using the bolt analysis module in the MEDSIGN analysis software. The bolt reliability analysis process includes: inputting various parameters of the connecting and connected parts in the bolted connection structure, setting boundary conditions, establishing a bolt analysis model, and calculating the analysis results.

[0046] The boundary conditions include: the process of the bolt structure, temperature, external load, tightening torque, etc. Usually, after determining the position of the automobile bolt structure, the main focus is on the tightening torque of the connection part.

[0047] The present invention can optimize the tightening torque.

[0048] Based on the analysis results, consider whether to perform an optimized design for the connecting parts or the connected parts.

[0049] 12. Identification of key parameters.

[0050] 121. Determine the response to be verified and the design target value of the response.

[0051] After performing a bolt reliability analysis, several reliability analysis results can be output. These include bolt clamping force, yield safety factor, fatigue safety factor, compressive safety factor, anti-slip safety factor, and bolt utilization. If any results do not meet the pre-designed target values, optimization design is required for the structural parameters or boundary conditions of the connecting or connected parts; the boundary condition is primarily the tightening torque.

[0052] The above analysis results can be used as a single result or multiple results as the response to be optimized and verified. The design target value of the response is mainly determined based on the VDI design manual and engineer experience.

[0053] 122. Key parameters can be identified by combining the specific results of bolt reliability analysis with the actual situation for bolt connection structures that do not meet the design target values.

[0054] The key parameters are related parameters of the connecting parts and the connected parts (gaskets, sheet metal clamped by bolts).

[0055] Connecting parts usually refer to bolts and nuts, and connected parts usually refer to gaskets, components or sheet metal parts connected or clamped by bolts; their key parameters include but are not limited to: bolt parameters, nut parameters, washer parameters, sheet metal parameters, etc.

[0056] The bolt parameters include: bolt type, nominal diameter, pitch, boring diameter, bolt head bearing surface outer diameter / inner diameter, thread length, screw diameter, screw length, etc.

[0057] The nut parameters are: nut diameter, nut width across flats, nut bearing surface outer diameter / inner diameter, nut thickness, diagonal length, etc.

[0058] The gasket parameters include: gasket type, gasket inner diameter / outer diameter, gasket thickness, average surface roughness, etc.

[0059] The sheet metal parameters include: material type, thickness, outer diameter and inner diameter of the bearing surface, etc.

[0060] The present invention can design the above bolt structural parameters as a single parameter or multiple parameters.

[0061] The structural parameters or boundary conditions that need to be optimized are determined as factors, and the factors and factor levels can be set according to the VDI design manual, engineering experience of vehicle development and actual conditions.

[0062] 13. DOE experimental design.

[0063] 131. Conduct DOE experimental design based on the identified key parameters.

[0064] Determine the response and the target value of the response, mainly including the number of responses, the size of the target value and the range of values; determine the factors and the levels of the factors, mainly including the number of factors, the selection of levels and the range of values.

[0065] 132. Perform DOE data analysis.

[0066] Based on the selected factors and levels, a DOE test plan is generated. Using MEDSIGN software, the bolted connection structure is analyzed according to the generated DOE test plan to obtain the analysis results of the DOE test design.

[0067] 133. Perform regression analysis and precision check to obtain the regression equation.

[0068] Perform factor regression analysis on the data to obtain the factor regression analysis results; based on the factor regression results, judge the significance relationship between the fitting model and each coefficient. If there are factor items with a P value greater than 0.05, eliminate one factor item at a time and re-perform the factor regression analysis until there are no factor items with a P value greater than 0.05, and obtain the standardized effect Pareto chart and residual chart of the response.

[0069] If the P values ​​are all less than 0.05, the effect is significant; otherwise, the effect is not significant.

[0070] If the curvature value is greater than 0.05, the model curvature is not significant; otherwise, the model curvature is significant and RSM response surface analysis is required.

[0071] If the values ​​of R-Sq / R-Sq(adjusted) / R-Sq(predicted) are close and all the values ​​are greater than 99%, it means that the model fits well; otherwise, the model fits poorly, the credibility of the results is reduced, and refitting is required.

[0072] According to the fitting results, the regression equation between the response and the factors is obtained.

[0073] 14. Optimize design.

[0074] Perform response optimization on key parameters, set target optimization for the response, and clearly define the target value and upper and lower limits of the response optimization.

[0075] If only one response is optimized, the weight of that response is set to 1; if two or more responses are optimized, the weights are assigned based on the actual vehicle development situation.

[0076] Obtain the results of parameter optimization and determine the bolt structure design and torque design scheme.

[0077] 15. Verify the target value.

[0078] Substitute the parameter optimization results obtained from the optimization design in 14 into the bolt reliability analysis model, calculate the analysis results, and verify the accuracy of the bolt structure design and torque optimization scheme.

[0079] If the plan cannot be implemented, or the analysis results do not meet the target value requirements, the fourth step of optimization design will be carried out again.

[0080] The following is a specific example of the structural design and torque optimization of the bolts connecting the front pillar and the body of the car. This embodiment shows a method for the structural design and torque optimization of automobile bolts. The main analysis software used is: MDESIGN and Minitab. The analysis process is as follows: Figure 1 As shown, specifically including:

[0081] 21. Bolt reliability analysis.

[0082] 211. Preliminary bolt selection. This embodiment is mainly for the front pillar and the body mounting point bolts, the bolts at this position are prone to thread stripping problems, please refer to Figure 2 .

[0083] The bolts selected are three M10 hexagonal bolts with nuts. The connection features a small number of connected parts, a short clamping length, and low contact surface flatness. The bolt tightening torque is typically designed empirically; in this example, the initial tightening torque is 81.5 N·m.

[0084] 212. Bolt reliability analysis of bolt connection structure is carried out through the bolt analysis module in MEDSIGN analysis software.

[0085] The process of performing bolt reliability analysis on a bolt connection structure includes: inputting various parameters of the connecting parts and the connected parts in the bolt connection structure, setting boundary conditions, establishing a bolt analysis model, and calculating the analysis results.

[0086] In this embodiment, the parameters of the input connecting parts (bolts and nuts) are as shown in Table 1 below:

[0087] parameter unit Numerical Nominal diameter mm 10 Pitch mm 1.25 Boring diameter mm 11 Bolt head bearing surface outer diameter mm 16 Inner diameter of bolt head bearing surface mm 10.7 Thread length mm 19 Screw diameter mm 10.6 Screw length mm 5 Nut width across flats mm 21 Inner diameter of nut bearing surface mm 14 Nut bearing surface outer diameter mm 20.5 Nut thickness mm 11

[0088] Table 1

[0089] The input parameters of the connected parts are shown in Table 2 below:

[0090] Material name Density (g / cm^3) Elastic modulus (MPa) Poisson's ratio A380 2.7 70000 0.33 QT450 7.2 170000 0.3 Standard 7.85 210000 0.3

[0091] Table 2

[0092] The boundary conditions set include: process, temperature, external load, tightening torque, etc. of the bolt structure.

[0093] The analysis results were obtained through the bolt analysis module in the MDESIGN analysis software, as shown in Table 3 below:

[0094] Calculated Items result Target value Remark Tightening torque / N·m 81.5 Bolt clamping force / KN 49.3 ≤44.5KN Wangda Safety factor against yield 1.06 ≥1 Bolt head compressive safety factor 0.87 ≥1 Not meeting goals Nut head compressive safety factor 2.71 ≥1 Anti-slip safety factor 4.02 ≥1

[0095] Table 3

[0096] From the calculation results in Table 3, it can be seen that the bolt head compressive safety factor does not meet the requirements. Therefore, the bolt head compressive safety factor needs to be taken as the main response.

[0097] 22. Identification of key parameters.

[0098] 221. Determine the response to be verified and the design target value of the response.

[0099] In this embodiment, according to the analysis results in Table 3, the bolt head compressive safety factor does not meet the requirements, so the key parameters to be identified are the bolt clamping force and the bolt head compressive safety factor.

[0100] The value of the bolt head compressive safety factor F should be greater than or equal to 1 to ensure that there is no crushing. According to the VDI design manual, the bolt head compressive safety factor F should be greater than or equal to 1.

[0101] In order to ensure that the bolt clamping does not loosen, the bolt clamping force E should be greater than the minimum clamping force required for the bolt clamping; in order to ensure that there is no crushing, the bolt clamping force E should be less than the allowable installation preload of the bolt.

[0102] According to preliminary analysis, the minimum required bolt clamping force in this embodiment is 6.67 kN. Based on the VDI design manual, the target bolt clamping force is 44.5 kN. Therefore, the optimized bolt clamping force E should be greater than the minimum clamping force of 6.67 kN while remaining as close to the target value of 44.5 kN as possible.

[0103] 222. Key parameters can be identified by analyzing the specific results of bolt reliability analysis and combining them with the actual situation for bolted joints that do not meet design targets. Based on engineering experience, two common issues with bolts at the front pillar and body mounting points are loosening of the bolt clamp or crushing of the bolt head contact surface. The bolt head bearing surface outer diameter, bolt head bearing surface inner diameter, and tightening torque are identified as factors associated with the response, i.e., key parameters, and serve as inputs.

[0104] 23. DOE experimental design.

[0105] 231. Conduct DOE experimental design based on the identified key parameters. Determine factors and levels, including the number of factors and the values ​​of the levels; determine the response and the target of the response.

[0106] The responses and target values ​​of this embodiment are shown in Table 4 below:

[0107] response name Target value E Bolt clamping force (N) ≤44453.0 F Bolt head compressive safety factor (mm) ≥1

[0108] Table 4

[0109] The factors and levels of this example are shown in Table 4:

[0110]

[0111] Table 5

[0112] 232. DOE data analysis.

[0113] Generate a DOE experimental plan based on the selected factors and levels. This example uses a full factorial experiment with 3 factors and 2 levels, inserting 2 center points.

[0114] Specifically, a DOE test plan was generated using MINITAB software, requiring 10 bolt reliability analyses. The test plan and analysis results are shown in Table 6 below, where E is the bolt clamping force and F is the bolt head compressive safety factor.

[0115]

[0116] Table 6

[0117] 233. Regression analysis and precision verification are performed simultaneously to obtain the regression equation of response and factor.

[0118] Since the response of this embodiment is mainly concerned with the bolt head compressive safety factor F, a factor regression analysis is performed on the response F and factors A, B, and C to obtain the factor regression analysis results, namely: Figure 3 Pareto diagram of the effect of the bolt head compressive safety factor F.

[0119] Through the results of factor regression analysis, the significant relationship between the fitting model and each coefficient was obtained. For factor items with P values ​​greater than 0.05, one factor item was eliminated at a time, and the factor regression analysis was performed again until there were no factor items with P values ​​greater than 0.05.

[0120] After deleting the factors with P values ​​greater than 0.05, the standardized effect Pareto chart of the bolt head compressive safety factor F is obtained. Figure 4 ; At the same time, residual analysis is performed to obtain the residual graph, see Figure 5 .

[0121] According to the obtained standardized effect Pareto chart and residual inset results, it can be seen that: all P values ​​are less than 0.05, the effect is significant; the curvature value is 0.023, which is less than 0.05, the center point is significant, the model is a nonlinear model, and RSM response surface regression analysis is required.

[0122] Perform RSM response surface regression analysis on response F and obtain the main effect diagram, see Figure 6 .

[0123] The regression equation of the response F is as follows:

[0124] F=-2.367+0.3715A-0.3094B+0.02796C+0.005354A*A+0.001284A*B-0.003902A*C+0.002105B*C

[0125] 24. Optimize design.

[0126] The response F is optimized, and the target of F is set to Wangmu, the target value is 1.5, the lower limit is 1, the upper limit is 1.9, the weight is set to 1, and the importance is 1.

[0127] The value ranges of variables A, B, and C are set according to step 231.

[0128] The optimal solution is: A=17.97mm, B=10.7mm, C=75Nm.

[0129] Therefore, the optimized solution is: the outer diameter of the bolt head bearing surface is 18.6mm, the inner diameter is 10.7mm; the tightening torque is 75NM.

[0130] 25. Verify the target value.

[0131] Substitute the parameter optimization results into the bolt reliability analysis model and calculate the analysis results shown in Table 7 below.

[0132] Calculated Items result Target value Remark Tightening torque / N·m 75 Bolt clamping force / KN 43.2 ≤44.5KN Wangda Safety factor against yield 1.21 ≥1 Bolt head compressive safety factor 1.66 ≥1 Nut head compressive safety factor 3.1 ≥1 Anti-slip safety factor 3.41 ≥1 Shear safety factor 18.7 ≥1.5

[0133] Table 7

[0134] The compressive safety factor of the bolt head is 1.66, and all other results meet the targets. The bolt structure design and torque optimization scheme are feasible.

[0135] In an embodiment of the present invention, the bolt structure design and tightening torque optimization method can accurately evaluate the eligibility of bolt structure design parameters. For automobile bolt structures that do not meet design requirements, the relevant parameters of the connecting parts and the connected parts can be optimized; at the same time, the tightening torque can be optimized for the bolt structure to guide industrial production.

[0136] The method of the present invention is applicable to the situation where parts in the automotive, aviation, machinery, bridge and other industries have bolt connection structures, or to the optimization problem of bolt structures in similar products.

Claims

1. A bolt structure optimization design method, characterized in that: include: Select a bolt connection structure including a connecting member and a connected member, perform reliability analysis on the bolt connection structure, and obtain several reliability analysis results; If there are result items in the reliability analysis results that do not meet the pre-designed target values, it is determined that the bolt structure needs to be optimized, and at least one key parameter in the bolt structure that affects the result items that do not meet the pre-designed target values ​​is screened and determined; The result items that do not meet the pre-designed target values ​​are taken as responses, and the key parameters are taken as factors. DOE experimental design is performed for each response, including: setting the response target value, selecting the factors associated with it, and setting the corresponding factor levels; Combine all responses, all response target values, all selected factors, and all set factor levels to conduct DOE experiments, and obtain the optimal solution of each factor when the response is the pre-designed target value for verification; When conducting a DOE experiment, Generate a DOE test plan based on the selected factors associated with each result that does not meet the pre-designed target value and the set factor levels; Using MDESIGN software, the reliability analysis of the bolted connection structure is carried out according to the generated DOE test plan, and the analysis results of the DOE test design are obtained; Based on the analysis results of the DOE experimental design, factor regression analysis and precision verification are performed to obtain the regression equation between the response and the factor; Based on the regression equation of response and factor, the response is optimized in combination with the set response target value to obtain the optimal solution of each factor when the response is the pre-designed target value.

2. The bolt structure optimization design method according to claim 1, characterized in that: The steps for reliability analysis of bolted connection structures include: Using the bolt analysis module in the MDESIGN analysis software, input various parameters of the connecting and connected parts in the bolt connection structure, set boundary conditions, establish a bolt analysis model, and calculate the reliability analysis results; Input parameters of the connecting parts in the bolt connection structure include: bolt parameters and nut parameters; input parameters of the connected parts in the bolt connection structure include: washer parameters and sheet metal parameters; Bolt parameters include: bolt type, nominal diameter, thread pitch, boring diameter, bolt head bearing surface outer diameter, bolt head bearing surface inner diameter, thread length, screw diameter and screw length; Nut parameters include: nut diameter, nut width across flats, nut load-bearing surface outer diameter, nut load-bearing surface inner diameter, nut thickness and diagonal length; Gasket parameters include: gasket type, gasket inner diameter, gasket outer diameter, gasket thickness, average surface roughness; Sheet metal parameters include: material type, thickness, load-bearing surface outer diameter and load-bearing surface inner diameter; The boundary conditions set include: process, temperature, external load and tightening torque of the bolt structure.

3. The bolt structure optimization design method according to claim 1, characterized in that: The result items in the reliability analysis results include at least: bolt clamping force, anti-yield safety factor, bolt head compressive safety factor, nut head compressive safety factor and anti-slip safety factor.

4. The bolt structure optimization design method according to claim 1, characterized in that: The verification is specifically as follows: after obtaining the optimal solution of each factor, the bolt reliability analysis is performed again, and based on the new reliability analysis results, it is verified whether the optimal solution of each factor meets the bolt connection structure design requirements. If the result items of the new bolt reliability analysis all meet the pre-designed target values, the bolt structure design optimization is completed. If there are result items in the new reliability analysis results that do not meet the pre-designed target values, the optimization is performed again.

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