Bolt torque setting method and device

Abstract

The invention discloses a bolt torque setting method and device, and relates to the field of mechanical design, and the method comprises the steps: determining the nominal torque of a bolt according to the nominal diameter, strength grade and thread form of the bolt; a preset assembly preload is applied to the bolt, and the telescopic length of the bolt is obtained; determining the axial force, the thread friction force and the supporting surface friction force of the bolt according to the telescopic length of the bolt, and carrying out weighted calculation on each force to obtain the tightening torque of the bolt; and according to the nominal torque and the tightening torque of the bolt, the design torque of the bolt is obtained through weighted calculation. The design torque of the bolt is determined through the nominal torque and the tightening torque of the bolt, the theoretical value (the nominal torque) and the actual experience data (the tightening torque) are combined, the accuracy of the set bolt torque is improved, and then the design requirement is met.

Description

Technical Field

[0001] This application relates to the field of mechanical design, and specifically relates to a method and device for setting bolt torque. Background Art

[0002] During the vehicle loading stage of a mule car (i.e., a prototype or test vehicle), accurate setting of bolt torque is a key link to ensure the structural integrity and safety of the vehicle. This stage involves the assembly of a large number of complex components, including engines, chassis, body structures, and various electrical and mechanical systems. Among them, bolt connections are the main fastening method, and the precise control of their torque directly affects the overall performance and durability of the vehicle.

[0003] In related technologies, usually after referring to mechanical manuals, standards, or industry experience, theoretical calculations are carried out according to the actual working conditions to determine the bolt torque during the vehicle loading stage of the mule car.

[0004] However, the above method does not combine theoretical values and actual experience data, and the accuracy of the obtained bolt torque is too low to meet the design requirements. Summary of the Invention

[0005] This application provides a method and device for setting bolt torque, which can solve the problem of low accuracy in setting bolt torque during the vehicle loading stage of the mule car in the prior art.

[0006] In a first aspect, an embodiment of this application provides a method for setting bolt torque, and the method includes:

[0007] Determine the nominal torque of the bolt according to the nominal diameter, strength grade, and thread profile of the bolt;

[0008] Apply a preset assembly preloading force to the bolt to obtain the elongation length of the bolt;

[0009] Determine the axial force, thread friction force, and support surface friction force of the bolt according to the elongation length of the bolt, and perform weighted calculation on each force to obtain the tightening torque of the bolt;

[0010] According to the nominal torque and tightening torque of the bolt, obtain the design torque of the bolt through weighted calculation.

[0011] Combined with the first aspect, in an implementation manner, the determining the nominal torque of the bolt according to the nominal diameter, strength grade, and thread profile of the bolt includes:

[0012] Determine the minimum friction coefficient of the bolt according to the nominal diameter, strength grade, and thread profile of the bolt;

[0013] Obtain the corresponding maximum assembly torque according to the minimum friction coefficient of the bolt;

[0014] Determine the nominal torque of the bolt according to the maximum assembly torque and the preset tolerance bandwidth of the assembly torque.

[0015] In combination with the first aspect, in one embodiment, the axial force generated after applying the maximum assembly torque to the bolt is equal to the result of multiplying the yield strength of the bolt by the first percentage value.

[0016] In combination with the first aspect, in one embodiment, determine the preset assembly preloading force according to the assembly point position of the bolt and the thickness of the connected part.

[0017] In combination with the first aspect, in one embodiment, determine the axial force of the bolt according to the elongation length of the bolt, including:

[0018] Determine the axial force of the bolt according to the elongation length of the bolt and the elastic coefficient of the bolt.

[0019] In combination with the first aspect, in one embodiment, determine the thread friction force of the bolt according to the elongation length of the bolt, including:

[0020] Determine the thread friction force of the bolt according to the axial force of the bolt, the nominal diameter of the bolt, the preset friction coefficient of the thread contact surface, and the preset correction coefficient.

[0021] In combination with the first aspect, in one embodiment, the preset friction coefficient of the thread contact surface is set according to different thread profiles of the bolt.

[0022] In combination with the first aspect, in one embodiment, determine the support surface friction force of the bolt according to the elongation length of the bolt, including:

[0023] Determine the support surface friction force of the bolt according to the axial force of the bolt, the nominal diameter of the bolt, the preset support surface friction coefficient, and the preset correction coefficient.

[0024] In combination with the first aspect, in one embodiment, if the bolt has a flange end face, before determining the support surface friction force, the preset support surface friction coefficient needs to be replaced with the result of multiplying it by the second percentage value.

[0025] In a second aspect, an embodiment of the present application provides a bolt torque setting device based on the method described in any one of the above, and the device includes:

[0026] An objective calculation module, configured to determine the nominal torque of the bolt according to the nominal diameter, strength grade, and thread profile of the bolt;

[0027] A subjective calculation module, configured to determine the axial force, thread friction force, and support surface friction force of the bolt according to the elongation length of the bolt, perform weighted calculation on each force, and obtain the tightening torque of the bolt;

[0028] A measuring module, configured to apply a preset assembly preloading force to the bolt and obtain the telescopic length of the bolt.

[0029] A correction module, configured to obtain the design torque of the bolt through weighted calculation according to the nominal torque and the tightening torque of the bolt.

[0030] The beneficial effects brought by the technical solution provided in the embodiment of the present application include:

[0031] In the present application, the design torque of the bolt is determined through weighted calculation according to the nominal torque and the tightening torque of the bolt, combining the theoretical value (nominal torque) and the actual empirical data (tightening torque), improving the accuracy of setting the bolt torque, and thus meeting the design requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic flow chart of the bolt torque setting method in the embodiment of the present application;

[0033] Figure 2 It is a schematic structural diagram of the bolt torque setting device in the embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] In order to enable those skilled in the art to better understand the solution of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Apparently, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0035] To make the purpose, technical solution and advantages of the present application clearer, the embodiments of the present application will be further described in detail below with reference to the accompanying drawings.

[0036] In a first aspect, please refer to Figure 1 , Figure 1 It is a schematic flow chart of the bolt torque setting method in the embodiment of the present application. The bolt torque setting method provided in this embodiment includes the following steps:

[0037] Step S1: Determine the nominal torque of the bolt according to the nominal diameter, strength grade and thread profile of the bolt.

[0038] Step S2: Apply a preset assembly preloading force to the above bolt and obtain the telescopic length of the bolt.

[0039] Step S3: Determine the axial force, thread friction, and support surface friction of the bolt based on the above-mentioned telescopic length of the bolt, and perform weighted calculation on each force to obtain the tightening torque of the bolt.

[0040] Step S4: Obtain the design torque of the bolt through weighted calculation based on the nominal torque and tightening torque of the above-mentioned bolt.

[0041] This method determines the design torque of the bolt through the nominal torque and tightening torque of the bolt, combines the theoretical value (nominal torque) and actual empirical data (tightening torque), improves the accuracy of setting the bolt torque in the vehicle mule car loading stage, and thus meets the design requirements.

[0042] The vehicle mule car loading stage refers to the manufacturing and assembly stage of the first-round prototype vehicle. The main purpose of this stage is to verify the design feasibility, production achievability, and overall vehicle performance of the vehicle. Problems in vehicle design and assembly can be discovered through the vehicle mule car loading stage, providing a basis for the optimization and improvement of subsequent vehicle production.

[0043] In some embodiments, in the above step S1, to determine the nominal torque of the bolt according to the nominal diameter, strength grade, and thread profile of the bolt, the following steps are included:

[0044] S11: Determine the minimum friction coefficient of the bolt according to the nominal diameter, strength grade, and thread profile of the bolt.

[0045] S12: Obtain the corresponding maximum assembly torque according to the minimum friction coefficient of the above-mentioned bolt.

[0046] S13: Determine the nominal torque of the bolt according to the above-mentioned maximum assembly torque and the preset assembly torque tolerance bandwidth.

[0047] It should be noted that before the vehicle mule car loading stage begins, it is necessary to confirm the positions of the fasteners on the vehicle body, and confirm the number and dimensions of the fastening points required for the fasteners. According to the dimensions of the fastening points, select bolts of suitable sizes and obtain the corresponding nominal diameter, strength grade, and thread profile of the bolts.

[0048] In some embodiments, in the above step S11, when determining the minimum friction coefficient of the bolt, it is assumed that the friction coefficients of the threads of the bolt and each connecting part of the bolt are the same on all contact surfaces.

[0049] It should be noted that the purpose of assuming that the friction coefficients of all contact surfaces are the same is to simplify the calculation process of the thread friction and support surface friction of the bolt. When designing, there is no need to consider the differences in friction coefficients between different contact surfaces, thereby reducing the complexity and uncertainty in calculation. Through this simplification, the calculation results can be obtained quickly, thereby improving the setting efficiency of the bolt torque.

[0050] In some embodiments, in step S11 above, when determining the minimum friction coefficient of the bolt, in the bolt supplier database, select the minimum friction coefficient under the manufacturable level robust characteristics corresponding to the bolt.

[0051] It should be noted that since bolts with a smaller friction coefficient require less torque during the tightening process, unnecessary performance loss during bolt installation can be reduced, and production efficiency can be improved. In addition, a smaller friction coefficient can also reduce the probability of thread wear, extend the service life of the bolt, and thus reduce the frequency of replacing and repairing the bolt.

[0052] In some embodiments, in step S12 above, according to the minimum friction coefficient of the bolt, obtain the corresponding maximum assembly torque, including the following steps:

[0053] According to the minimum friction coefficient of the bolt, obtain the maximum assembly torque corresponding to the minimum friction coefficient of the bolt from the national standard database.

[0054] It should be noted that by selecting the maximum assembly torque corresponding to the minimum friction coefficient of the bolt, it can ensure that the bolt reaches the required pre-tightening force during the assembly process, thereby improving the reliability and stability of the bolt connection.

[0055] In some embodiments, in step S13 above, according to the above maximum assembly torque and the preset assembly torque tolerance bandwidth, determine the nominal torque of the bolt. The specific formula is as follows:

[0056] M 公 = M * 0.9 ± M * 0.1 Formula (1)

[0057] In Formula (1), M 公 is the nominal torque of the bolt, M is the maximum assembly torque, and the preset assembly torque tolerance bandwidth is ±10%. The assembly torque tolerance bandwidth refers to the tolerance bandwidth that allows the assembly torque to vary within a certain range during the assembly process. Setting the assembly torque tolerance bandwidth is to ensure that during the assembly process of the bolt, even if there are slight differences in size and shape, the tightness and stability between components can be ensured by adjusting the assembly torque. In this embodiment, the fluctuation range of M 公 is specified by the assembly torque tolerance bandwidth to be between 90% - 110% of the maximum assembly torque.

[0058] In some embodiments, the axial force generated after applying the above maximum assembly torque to the bolt is equal to the result of multiplying the yield strength of the bolt by the first percentage value.

[0059] It should be noted that the yield strength of the bolt is the maximum stress value at which the bolt material begins to undergo plastic deformation when subjected to an external force. Controlling the axial force generated after applying the maximum assembly torque to the bolt within a certain percentage of the yield strength of the bolt can ensure that the bolt does not undergo plastic deformation or fracture due to excessive stress under normal working conditions, thereby improving safety performance. Preferably, in this embodiment, the first percentage value is set to 90%.

[0060] In some embodiments, in the above step S2, the preset assembly preloading force is determined according to the assembly position of the bolt and the thickness of the connected part.

[0061] It should be noted that the assembly position of the bolt determines the stress direction and size of the bolt, and the thickness of the connected part will affect the pre-tightening effect of the bolt. A thicker connected part may require a greater pre-tightening force to ensure the tightness of the connection, while a thinner connected part may require a smaller pre-tightening force to avoid deformation or damage of the connected part due to excessive pressing. Therefore, it is necessary to determine the preset assembly preloading force according to the assembly position of the bolt and the thickness of the connected part, so as to ensure the tight connection between the bolt and the connected part without damaging the structure of the connected part.

[0062] In some embodiments, in the above step S3, determining the axial force of the bolt according to the telescopic length of the bolt includes the following steps:

[0063] Determine the axial force of the bolt according to the telescopic length of the bolt and the elastic coefficient of the bolt.

[0064] Specifically, the calculation formula for the axial force of the bolt is as follows:

[0065] f = K × ΔL Formula (2)

[0066] In Formula (2), f is the axial force of the bolt, K is the elastic coefficient of the bolt, and ΔL is the telescopic length of the bolt. It should be noted that the telescopic length of the bolt is specifically the length by which the bolt elongates or compresses under the action of the preset assembly preloading force.

[0067] In some embodiments, in the above step S3, determining the thread friction force of the bolt according to the telescopic length of the bolt includes the following steps:

[0068] Determine the thread friction force of the bolt according to the axial force of the bolt, the nominal diameter of the bolt, the preset friction coefficient of the thread contact surface, and the preset correction coefficient.

[0069] Specifically, the calculation formula for the thread friction force of the bolt is as follows:

[0070] f 纹 = f × d × μ 纹 × ω 纹Formula (3)

[0071] In Formula (3), f 纹 is the frictional force of the thread of the bolt, f is the axial force of the bolt, d is the nominal diameter of the bolt, and μ 纹 is the preset friction coefficient of the thread contact surface, and ω 纹 is the preset correction coefficient when calculating the frictional force of the thread of the bolt.

[0072] Preferably, since bolts with different thread profiles have differences in structure, thread angle, pitch, etc., these differences will cause the friction characteristics of the bolts to be different when they are stressed. Therefore, the friction coefficient of the thread contact surface is set according to different thread profiles. When the thread profile is coarse thread, the friction coefficient of the thread contact surface is set to 0.12, and when the thread profile is fine thread, the friction coefficient of the thread contact surface is set to 0.16. The correction coefficient is set to 0.58 according to empirical values.

[0073] In some embodiments, in the above step S3, to determine the frictional force of the support surface of the bolt according to the telescopic length of the bolt, the following steps are included:

[0074] Determine the frictional force of the support surface of the bolt according to the axial force of the bolt, the nominal diameter of the bolt, the preset friction coefficient of the support surface, and the preset correction coefficient.

[0075] Specifically, the calculation formula for the frictional force of the support surface of the bolt is as follows:

[0076] f 面 = f × d × μ 面 × ω 面 Formula (4)

[0077] In Formula (4), f 面 is the frictional force of the support surface of the bolt, f is the axial force of the bolt, d is the nominal diameter of the bolt, and μ 面 is the preset friction coefficient of the support surface, and ω 面 is the preset correction coefficient when calculating the frictional force of the support surface of the bolt.

[0078] Preferably, the friction coefficient of the support surface is set to 0.5, and the correction coefficient is set to 0.5 according to empirical values.

[0079] In some embodiments, if the bolt has a flange end face, before determining the frictional force of the support surface, the above preset friction coefficient of the support surface needs to be replaced with the result of multiplying it by a second percentage value.

[0080] The flange end face will affect the friction characteristics of the support surface. By introducing a second percentage value for adjustment, the actual friction condition can be more accurately reflected, thereby improving the accuracy of calculating the frictional force of the support surface.

[0081] In practical applications, the appropriate second percentage value can be determined through experiments according to the specific flange end face. In this embodiment, preferably, the second percentage value is set to 110%.

[0082] In some embodiments, in the above step S3, the axial force of the bolt, the thread friction force, and the support surface friction force are weighted and calculated to obtain the tightening torque of the bolt. The specific formula is as follows:

[0083] M 估 =αf + βf 纹 +γf 面 Formula (5)

[0084] In formula (5), M 估 is the tightening torque of the bolt, f is the axial force of the bolt, α is the weight coefficient of the axial force of the bolt, f 纹 is the thread friction force, β is the weight coefficient of the thread friction force, f 面 is the support surface friction force, and γ is the weight coefficient of the support surface friction force. The sum of α, β, and γ is 1.

[0085] Preferably, α is set to 0.1, β is set to 0.4, and γ is set to 0.5.

[0086] In some embodiments, in the above step S4, according to the nominal torque and tightening torque of the above bolt, through weighted calculation, the design torque of the bolt is obtained. The specific formula is as follows:

[0087]

[0088] M = M 综 ×0.9 ± M 综 ×0.1 Formula (7)

[0089] In formula (6), M 综 is the comprehensive weighted torque of the bolt, M 公 is the nominal torque of the bolt, ρ is the weight coefficient of the nominal torque of the bolt, M 估 is the tightening torque of the bolt, is the weight coefficient of the tightening torque of the bolt.

[0090] In formula (7), M is the design torque of the bolt.

[0091] Preferably, when setting ρ and in accordance with the multi-index evaluation system, Table 1 can be referred to. Specifically, the multi-index evaluation system is a system that describes and evaluates different attributes of a certain thing or phenomenon by using multiple related or independent indexes. In this embodiment, by setting subjective weights and objective weights for ρ and and according to ρ and Calculate ρ and of the comprehensive weight, and use ρ and of the comprehensive weight to determine the importance of the nominal torque and the tightening torque in the bolt torque setting.

[0092] Table 1

[0093]

[0094]

[0095] In Table 1, the objective weight of ρ is 0.7, and the subjective weight of ρ is 0.6. The objective weight of is 0.3, and the subjective weight of is 0.4. According to the calculation, the final comprehensive weight of ρ is 0.78, and the comprehensive weight of

[0096]

[0097] In Formulas (8) and (9), ρ 综 is the comprehensive weight of ρ, is of the comprehensive weight, ρ 客 is the objective weight of ρ, ρ 主 is the subjective weight of ρ, is of the objective weight, is of the subjective weight.

[0098] Second, please refer to Figure 2 Figure 2 which is the structural schematic diagram of the bolt torque setting device according to the embodiment of the present application. The bolt torque setting method device provided in this embodiment includes the following modules:

[0099] Objective calculation module, which is used to determine the nominal torque of the bolt according to the nominal diameter, strength grade and thread profile of the bolt.

[0100] Subjective calculation module, which is used to determine the axial force, thread friction force and support surface friction force of the bolt according to the elongation length of the bolt, and perform weighted calculation on each force to obtain the tightening torque of the bolt.

[0101] Measurement module, which is used to apply a preset assembly preloading force to the bolt and obtain the elongation length of the bolt.

[0102] Correction module, which is used to obtain the design torque of the bolt through weighted calculation according to the nominal torque and the tightening torque of the bolt. ​

[0103] This device applies a preset assembly preloading force to the bolt through a measurement module to obtain the expansion and contraction length of the bolt, determines the nominal torque of the bolt through an objective calculation module, obtains the tightening torque of the bolt through a subjective calculation module, and determines the design torque of the bolt through a correction module according to the nominal torque and the tightening torque of the bolt. By combining the theoretical value (nominal torque) and the actual empirical data (tightening torque), the accuracy of setting the bolt torque in the vehicle mule car loading stage is improved, thereby meeting the design requirements in the vehicle mule car loading stage.

[0104] It should be noted that the serial numbers of the embodiments of the present application above are only for description and do not represent the superiority or inferiority of the embodiments.

[0105] The terms "including" and "having" and any variations thereof in the specification, claims and drawings of the present application are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products or devices. The descriptions such as "first", "second" and "third" are used to distinguish different objects, etc., and do not represent the order of precedence, nor do they limit that "first", "second" and "third" are different types.

[0106] In the description of the embodiments of the present application, "exemplary", "for example" or "for instance" etc. are used to indicate examples, illustrations or explanations. Any embodiment or design solution described as "exemplary", "for example" or "for instance" in the embodiments of the present application should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Rather, the use of words such as "exemplary", "for example" or "for instance" is intended to present relevant concepts in a specific manner.

[0107] In the description of the embodiments of the present application, unless otherwise specified, " / " means "or". For example, A / B may mean A or B; "and / or" in the text is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of the present application, "a plurality of" means two or more than two.

[0108] In some processes described in the embodiments of the present application, multiple operations or steps appear in a specific order. However, it should be understood that these operations or steps may not be executed in the order in which they appear in the embodiments of the present application or may be executed in parallel. The serial numbers of the operations are only used to distinguish different operations, and the serial numbers themselves do not represent any execution order. In addition, these processes may include more or fewer operations, and these operations or steps may be executed in order or in parallel, and these operations or steps may be combined.

[0109] Through the description of the above embodiments, those skilled in the art can clearly understand that the above-described embodiment methods can be implemented by means of software plus a necessary general hardware platform. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation. Based on such an understanding, the technical solution of the present application, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. The computer software product is stored in a storage medium as described above (such as ROM / RAM, magnetic disk, optical disk) and includes several instructions for causing a terminal device to execute the methods described in the various embodiments of the present application.

[0110] The above are only the preferred embodiments of the present application, and do not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present application, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present application.

Claims

1. A method for setting bolt torque, characterized in that, The method includes: Determine the nominal torque of the bolt according to the nominal diameter, strength grade and thread profile of the bolt; Apply a preset assembly preloading force to the bolt to obtain the elongation length of the bolt; Determine the axial force, thread friction force and support surface friction force of the bolt according to the elongation length of the bolt, and perform weighted calculation on each force to obtain the tightening torque of the bolt; Obtain the design torque of the bolt through weighted calculation according to the nominal torque and tightening torque of the bolt.

2. The bolt torque setting method according to claim 1, wherein The step of determining the nominal torque of the bolt according to the nominal diameter, strength grade and thread profile of the bolt includes: Determine the minimum friction coefficient of the bolt according to the nominal diameter, strength grade and thread profile of the bolt; Obtain the corresponding maximum assembly torque according to the minimum friction coefficient of the bolt; Determine the nominal torque of the bolt according to the maximum assembly torque and the preset assembly torque tolerance bandwidth.

3. The bolt torque setting method according to claim 2, wherein, The axial force generated after applying the maximum assembly torque to the bolt is equal to the result of multiplying the yield strength of the bolt by the first percentage value.

4. The bolt torque setting method according to claim 1, characterized in that, Determine the preset assembly preloading force according to the assembly point position of the bolt and the thickness of the connected parts.

5. The bolt torque setting method according to claim 1, characterized in that, The step of determining the axial force of the bolt according to the elongation length of the bolt includes: Determine the axial force of the bolt according to the elongation length of the bolt and the elastic coefficient of the bolt.

6. The bolt torque setting method according to claim 5, wherein, The step of determining the thread friction force of the bolt according to the elongation length of the bolt includes: Determine the thread friction force of the bolt according to the axial force of the bolt, the nominal diameter of the bolt, the preset thread contact surface friction coefficient and the preset correction coefficient.

7. The bolt torque setting method according to claim 6, wherein The preset thread contact surface friction coefficient is set according to different thread profiles of the bolt.

8. The bolt torque setting method according to claim 5, characterized in that, The step of determining the support surface friction force of the bolt according to the elongation length of the bolt includes: Determine the support surface friction force of the bolt according to the axial force of the bolt, the nominal diameter of the bolt, the preset support surface friction coefficient and the preset correction coefficient.

9. The bolt torque setting method according to claim 8, characterized in that, If the bolt has a flange end face, before determining the support surface friction force, the preset support surface friction coefficient needs to be replaced with the result of multiplying it by the second percentage value.

10. A bolt torque setting device based on the method according to any one of claims 1-9, characterized in that, The device includes: An objective calculation module for determining the nominal torque of the bolt according to the nominal diameter, strength grade and thread profile of the bolt; A subjective calculation module for determining the axial force, thread friction force and support surface friction force of the bolt according to the elongation length of the bolt, and performing weighted calculation on each force to obtain the tightening torque of the bolt; A measurement module for applying a preset assembly preloading force to the bolt to obtain the elongation length of the bolt; A correction module for obtaining the design torque of the bolt through weighted calculation according to the nominal torque and tightening torque of the bolt.

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