Fastening system connection characteristic resolving method, computer storage medium and program product

Abstract

The invention discloses a fastening system connection characteristic resolving method, a computer storage medium and a program product, and relates to the field of threaded connection performance prediction and nonlinear evolution thereof, and the method comprises the following steps: calculating friction heat of a screwing path according to a thread structure, a fastening terminal and a thread interface friction coefficient; testing to obtain hardness-temperature test data of the metal material of the thread structure, and obtaining a material softening model of the thread structure according to the friction heat Qi and the hardness-temperature test data; obtaining a material stress state according to the material softening model; a refined finite element model is constructed in finite element analysis software according to the thread structure, the refined finite element model comprises material attributes, and a material softening model is added in a material attribute module; and solving a stress field by virtue of finite element analysis software according to the friction heat Qi, the material hardness H, the material stress state and the refined finite element model. The problems that threaded connection stress state analysis is not real enough, simulation model precision is not good enough, test cost is high, and application is difficult are solved.

Description

Technical Field

[0001] The present invention belongs to the field of threaded connection performance prediction and nonlinear evolution in aircraft manufacturing industry, and in particular to a numerical-real combined method for fine calculation of connection characteristics of a fastening system. Background Art

[0002] Threaded connection has the advantages of simple structure, convenient assembly and disassembly, and low maintenance cost. It is a widely used mechanical connection form in aircraft, spacecraft, rockets and other aircraft products. In order to ensure the assembly quality and service performance of the product, the stress level of the assembly structure must be within a reasonable range and its distribution state should be as uniform as possible. However, in the actual tightening process of threaded connection, it is inevitable that it is affected by the combined effects of factors such as materials, geometric errors, surface quality and tightening process, and the stress level and distribution of threaded connection are difficult to achieve the expected goals.

[0003] The tightening process parameters of threaded connection involve the tightening speed. When the nut is screwed relative to the bolt at this speed, friction heat will be generated between the thread pairs. The temperature rise caused by it not only directly affects the stress level and distribution state of the threaded connection, but also the softening of the material will inevitably further cause the stress distribution. Therefore, the stress analysis of threaded connection is a thermal-mechanical coupling problem, and the threaded connection stress under the coupling of temperature and preload must be studied in depth.

[0004] At present, the research on threaded connection stress is mostly based on experiments and finite elements. Threaded connection stress measurement devices and methods such as 202311298536.1 and 202310238074.8 have been developed, as well as screw models that ignore threads, three-dimensional axisymmetric models, tetrahedral meshing models, and finite element models such as separate modeling of threads and screws and then binding models. However, the existing threaded connection stress measurement methods are based on test environments and specific assumptions and are not suitable for assembly or maintenance sites. The existing finite element models do not consider the real thread geometry, that is, they ignore the influence of structural asymmetry caused by the thread lead angle. Considering the visibility and operability of the finite element simulation method, how to propose an accurate finite element simulation analysis method has always been a key problem in the field of threaded connection performance prediction and its nonlinear evolution. Summary of the invention

[0005] The technical problem solved by the present application is: to overcome the deficiencies of the prior art and provide a method for fine-tuning the connection characteristics of a fastening system by combining numerical and real elements, so as to solve the problems of insufficient authenticity in the analysis of the stress state of threaded connections, poor accuracy of simulation models, high test costs and difficulty in application.

[0006] The technical solutions provided by this application are as follows:

[0007] A numerical-realistic method for calculating the connection characteristics of a fastening system in a refined manner, comprising:

[0008] S10. Calculate the friction heat of the screwing distance according to the thread structure, the fastening terminal and the thread interface friction coefficient;

[0009] S20. Experimental hardness-temperature test data of metal materials with threaded structure is obtained according to the friction heat Q i The material softening model of the thread structure is obtained based on the hardness-temperature test data;

[0010] According to the material softening model, the material stress state is obtained;

[0011] S30. Constructing a refined finite element model in the finite element analysis software according to the thread structure, the refined finite element model includes material properties, adding a material softening model in the material property module; adding parameters of the material properties, and setting initial and boundary value conditions;

[0012] S40. Based on friction heat Q i , material hardness H, material stress state and refined finite element model, and solve the stress field with the help of finite element analysis software.

[0013] The S10 includes: calculating the screwing distance according to the thread structure and the fastening terminal; calculating the friction force during the screwing process according to the thread interface friction coefficient; and calculating the friction heat of the screwing distance according to the screwing distance and the friction force.

[0014] The friction heat Q i for:

[0015] Among them, k c is the thread connection stiffness, P is the thread pitch, μ t is the friction coefficient of the thread pair, α is the tooth profile half angle, θ i is the relative rotation angle between the nut and the bolt, and β is the thread lead angle.

[0016] The S20 includes: measuring the hardness of the metal material at different temperatures to obtain the hardness-temperature test data of the metal material of the threaded structure; obtaining the thermal coefficient C of the hardness according to the curve fitted by the hardness-temperature test data of the metal material; obtaining the thermal coefficient C of the hardness according to the friction heat Q i The temperature load T caused by friction heat is obtained by calculation; the material softening model of the threaded structure is obtained according to the thermal coefficient C of hardness and the temperature load T caused by friction heat.

[0017] Characterized in that: the material softening model is H = H0e -CT , where H is the material hardness, H0 is the material's room temperature hardness, C is the thermal coefficient of hardness, and T is the temperature load caused by friction heat. T is calculated based on the friction heat Q i Obtained by calculation.

[0018] A computer-readable storage medium stores a computer program / instruction, which implements the steps of any of the above methods when executed by a processor.

[0019] A computer program product comprises a computer program / instruction, which implements the steps of any of the above methods when executed by a processor.

[0020] In summary, this application at least includes the following beneficial technical effects:

[0021] Compared with the prior art, the present invention takes into account the coupling effect of mechanical and thermal loads and the actual geometric characteristics of the thread, solves the problems of insufficient authenticity in the analysis of the stress state of threaded connections and poor accuracy of the simulation model, has higher numerical solution accuracy and efficiency, strong operability and simple operation, reduces the high cost of purchasing test equipment, and can be applied in engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Flow chart of the numerical-real joint analysis of threaded connection characteristics;

[0023] Figure 2 This is the friction force and relative engagement distance diagram when the nut rotates relative to the bolt at an angle of θi. DETAILED DESCRIPTION

[0024] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments disclosed in the present invention will be further described in detail below with reference to the accompanying drawings.

[0025] The embodiment of the present application discloses a method for fine-tuning the connection characteristics of a fastening system by combining numerical and real elements. The method considers the coupling effects of temperature and preload force, and the analysis results are visualized and convenient for engineering application. The method includes friction heat calculation, data-driven material softening model correction, refined finite element model and softening model loading, and solution of threaded connection stress caused by thermal-mechanical coupling.

[0026] Combine the following Figure 1 The flowchart of the numerical-real joint analysis of the threaded connection characteristics shown in the figure describes the technical solution in the embodiment of the present invention in more detail. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0027] A numerical-realistic method for calculating the connection characteristics of fastening systems in detail, such as Figure 1 As shown, the steps of implementing the method include:

[0028] S10. Calculate the screwing distance according to the thread structure and the fastening terminal; calculate the friction force during the screwing process according to the thread interface friction coefficient; calculate the friction heat of the screwing distance according to the screwing distance and the friction force.

[0029] When the nut is screwed into the bolt, the friction between the thread pairs will do work, and the mechanical energy will inevitably be converted into thermal energy. The temperature rise caused by this energy will not only affect the stress of the threaded connection, but also soften the material and cause stress redistribution.

[0030] Given the gradient loading of the preload, the friction force increases linearly. Figure 2 The nut thread is rotated relative to the bolt thread by an angle of θ. i The friction force and relative rotation distance at that time. It can be seen from this that the friction force F fi and relative rotation distance S i It is the quantity of the thread screwing process, which is related to the angle of rotation of the nut relative to the bolt. The friction heat Q i is the work done by friction in the relative rotational distance, that is,

[0031]

[0032] Among them, k c is the thread connection stiffness, P is the thread pitch, μ t is the friction coefficient of the thread pair, α is the tooth profile half angle, θ i is the relative rotation angle between the nut and the bolt, and β is the thread lead angle.

[0033] S20. Optimize the softening model of meshing thread material based on hardness-temperature test data.

[0034] The material softening model of meshing thread is modified by test data, that is, the hardness of metal materials at different temperatures is measured, and the parameter C in the softening model is improved based on the fitting curve. The material softening model is expressed as

[0035] H=H0e -CT

[0036] Among them, H is the material hardness, H0 is the material's room temperature hardness, C is the thermal coefficient of hardness, T is the temperature load caused by friction heat, and T is calculated based on the friction heat Q i Obtained by calculation.

[0037] The relationship between the stress state of the material and the material hardness H is obtained according to the solution of continuum mechanics, and the stress state of the material is obtained according to the relationship between the stress state of the material and the material hardness H.

[0038] S30. Based on the threaded connection structure of aerospace equipment, a refined finite element model is established. The refined finite element model includes material properties, and a material softening model is added to the material property module.

[0039] S301 constructs a refined finite element model based on the mathematical equations of the thread geometry characteristics of the threaded connection structure and checks the mesh nodes.

[0040] S302 adds material property parameters to the refined finite element model, sets the initial boundary conditions (the end faces of the clamps are all fixed support constraints), friction heat application method (friction heat is applied by imprint loading), preload control method (direct loading of preload) and contact state (normal contact behavior adopts penalty function contact).

[0041] S40. Based on friction heat Q i , material hardness H, material stress state and refined finite element model, and solve the stress field with the help of finite element analysis software.

[0042] In the above method, the friction heat Q is taken into account i The influence of the stress state of the material, so the above process is a mechanical-thermal coupling analysis, through which the stress field under the simultaneous action of temperature and preload is obtained.

[0043] The contents not described in detail in this application specification belong to the common knowledge of those skilled in the art.

[0044] The present application is described in detail above in conjunction with specific implementation methods and exemplary examples, but these descriptions cannot be understood as limiting the present application. Those skilled in the art understand that, without departing from the spirit and scope of the present application, a variety of equivalent replacements, modifications or improvements can be made to the technical solution of the present application and its implementation methods, all of which fall within the scope of the present application. The scope of protection of the present application shall be subject to the attached claims.

Claims

1. A method for calculating the connection characteristics of a fastening system, characterized in that: include: S10. Calculate the friction heat of the screwing path according to the thread structure, fastening terminal and thread interface friction coefficient; S20. Experimental hardness-temperature test data of metal materials with threaded structure were obtained. The material softening model of the thread structure is obtained based on the hardness-temperature test data; According to the material softening model, the material stress state is obtained; S30. Construct a refined finite element model in the finite element analysis software according to the thread structure, wherein the refined finite element model includes material properties, and a material softening model is added to the material property module; parameters of the material properties are added, and initial and boundary value conditions are set; S40. Based on friction heat , material hardness H, material stress state and refined finite element model, and solve the stress field with the help of finite element analysis software.

2. The method for calculating the connection characteristics of a fastening system according to claim 1, characterized in that: The S10 includes: The screwing distance is calculated according to the thread structure and the fastening terminal; the friction force during the screwing process is calculated according to the thread interface friction coefficient; the friction heat of the screwing distance is calculated according to the screwing distance and the friction force.

3. The method for calculating the connection characteristics of a fastening system according to claim 1 or 2, characterized in that: The friction heat for: in, k c is the threaded connection stiffness, P is the thread pitch, μ t is the friction coefficient of the thread pair, α It is the tooth type half angle. θ i is the relative rotation angle between the nut and the bolt, β is the thread lead angle.

4. The method for calculating the connection characteristics of a fastening system according to claim 1, characterized in that: The S20 includes: The hardness of metal materials at different temperatures is measured to obtain the hardness-temperature test data of metal materials with threaded structures; the thermal coefficient C of hardness is obtained based on the curve fitted by the hardness-temperature test data of metal materials; Calculate the temperature load caused by friction heat T ; The material softening model of the threaded structure is obtained based on the thermal coefficient C of hardness and the temperature load T caused by friction heat.

5. The method for calculating the connection characteristics of a fastening system according to claim 1 or 4, characterized in that: The material softening model is , in, H is the material hardness, H 0 is the hardness of the material at room temperature, C is the thermal coefficient of hardness, T is the temperature load caused by frictional heat, T According to friction heat Obtained by calculation.

6. A computer-readable storage medium having a computer program / instruction stored thereon, characterized in that: When the computer program / instructions are executed by a processor, the steps of any method described in claims 1-5 are implemented.

7. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instructions are executed by a processor, the steps of any method described in claims 1-5 are implemented.

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