Fastening system connection property solving method, computer storage medium and program product

Abstract

The application relates to a fastening system connection characteristic solution method, a computer storage medium and a program product, relates to the field of threaded connection performance prediction and nonlinear evolution, and comprises the following steps: according to a threaded structure, a fastening terminal and a threaded interface friction coefficient, the friction heat of a screwing distance is calculated; hardness-temperature test data of a metal material of the threaded structure are obtained through experiments; a material softening model of the threaded structure is obtained according to the friction heat Q i and the hardness-temperature test data; a material stress state is obtained according to the material softening model; a refined finite element model of the threaded structure is constructed in finite element analysis software, the refined finite element model comprises material properties, and the material softening model is added in the material property module; and a stress field is solved by means of the finite element analysis software according to the friction heat Q i , material hardness H, material stress state and the refined finite element model. The problems of poor reality in threaded connection stress state analysis, poor simulation model precision, high test cost and difficulty in application are solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of thread connection performance prediction and its nonlinear evolution in the aircraft manufacturing industry, and particularly relates to a fine calculation method for connection characteristics of a number-real combined fastening system. BACKGROUND

[0002] Thread connection has the advantages of simple structure, convenient disassembly and maintenance, and low cost, and is widely used 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 should be within a reasonable range and the distribution state should be as uniform as possible. However, in the actual fastening process of thread connection, it is inevitably affected by factors such as material, geometric error, surface quality and fastening process, and the stress level and distribution of thread connection are difficult to achieve the expected target.

[0003] The thread connection fastening process parameters involve the tightening speed. When the nut is rotated relative to the bolt at this speed, friction heat will be generated between the thread pair, which directly affects the stress level and distribution state of the thread connection, and the material softening caused by the temperature rise will further cause the stress distribution. Therefore, the stress analysis of thread connection is a thermal-mechanical coupling problem, and the stress of thread connection under the coupling action of temperature and preload must be studied in depth.

[0004] At present, the research on thread connection stress is mostly based on experiments and finite elements, and thread connection stress measuring devices and methods such as 202311298536.1 and 202310238074.8 have been developed, as well as finite element models such as ignoring the screw model of thread, three-dimensional axisymmetric model, tetrahedral mesh division model, thread and screw modeling separately and then binding model. However, the existing thread connection stress measurement methods are based on experimental environment and specific assumptions, and are not suitable for assembly or maintenance sites. And the existing finite element models do not consider the real thread geometric characteristics, that is, the influence of the non-symmetry of the structure caused by the thread lead angle is ignored. 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 thread connection performance prediction and its nonlinear evolution. SUMMARY

[0005] The technical problem solved by the present application is to overcome the shortcomings of the prior art and provide a fine calculation method for connection characteristics of a number-real combined fastening system, which solves the problems of insufficient reality in thread connection stress state analysis, poor simulation model precision, high test cost and difficulty in application.

[0006] The technical scheme provided by the present application is as follows:

[0007] A fine calculation method for connection characteristics of a number-real combined fastening system, 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. Obtain the hardness-temperature test data of the metal material of the thread structure through experiment, and obtain the material softening model of the thread structure according to the friction heat Q i and the hardness-temperature test data;

[0010] Obtain the stress state of the material according to the material softening model;

[0011] S30. Construct a refined finite element model of the thread structure in the finite element analysis software, the refined finite element model comprising material properties, adding the material softening model in the material property module; add parameters of the material properties and set initial boundary conditions;

[0012] S40. Solve the stress field by means of the finite element analysis software according to the friction heat Q i , the material hardness H, the stress state of the material and the refined finite element model.

[0013] The S10 comprises: calculating the screwing distance according to the thread structure and the fastening terminal; calculating the friction force in 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 is:

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

[0016] characterized in that the S20 comprises: measuring the hardness of the metal material at different temperatures to obtain the hardness-temperature test data of the metal material of the thread structure; obtaining the thermal coefficient C of the hardness according to the curve fitted from the hardness-temperature test data of the metal material; and obtaining the temperature load T caused by the friction heat according to the thermal coefficient C of the hardness and the friction heat Q i ; and obtaining the material softening model of the thread structure according to the thermal coefficient C of the hardness and the temperature load T caused by the friction heat.

[0017] characterized in that the material softening model is H=H0e -CT , wherein H is the material hardness, H0 is the normal temperature hardness of the material, C is the thermal coefficient of the hardness, and T is the temperature load caused by the friction heat, which is obtained according to the friction heat Q i .

[0018] A computer readable storage medium having stored thereon computer programs / instructions which, when executed by a processor, implement the steps of any of the above described methods.

[0019] A computer program product comprising computer programs / instructions which, when executed by a processor, implement the steps of any of the above described methods.

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

[0021] Compared with the prior art, the present application considers the coupling effect of force and thermal load and the real thread geometry, solves the problems of poor accuracy of simulation model and under-realistic stress state analysis of threaded connection, has higher numerical solution accuracy and efficiency, is strong in operability and simple to operate, reduces the high cost brought by purchase of test equipment, and can realize engineering application. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A flowchart of the threaded connection characteristic numerical-physical joint analysis.

[0023] Figure 2 A friction force and relative rotation distance diagram when the relative rotation angle of the nut to the bolt is θi. DETAILED DESCRIPTION

[0024] To make the purpose, technical solutions and advantages of the present application clearer, the following will combine the drawings to further describe the disclosed embodiments of the present application in detail.

[0025] The embodiments of the present application disclose a numerical-physical joint fastening system connection characteristic fine calculation method, which is a method considering the coupling effect of temperature and pre-tightening force, visualizing the analysis results and convenient for engineering application, and includes friction heat calculation, data-driven material softening model correction, fine finite element model and softening model loading, and threaded connection stress calculation caused by thermal force coupling.

[0026] The following will combine Figure 1 The flowchart of the threaded connection characteristic numerical-physical joint analysis shown in FIG. 1 is used to describe the technical solutions in the embodiments of the present application in more detail. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application. Based on the embodiments in the present application, other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0027] A numerical-physical joint fastening system connection characteristic fine calculation method, as shown in Figure 1 The steps for implementing the method include:

[0028] S10. Calculate the engagement path based on the thread structure and fastening end; calculate the frictional force during thread engagement based on the thread interface friction coefficient; calculate the frictional heat of the engagement path based on the engagement path and frictional force.

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

[0030] Given the gradient loading of the preload, the frictional force increases linearly. Figure 2 The figure shows the rotation angle θ between the nut thread and the bolt thread. i The frictional force and the relative rotational distance at that time. Therefore, the frictional force F... fi and relative spin path S i These are quantities related to the thread engagement process, all of which are related to the angle of rotation of the nut relative to the bolt, and the frictional heat Q. i It is the work done by friction over the relative rotational distance, that is...

[0031]

[0032] Where, k c It refers to the threaded connection stiffness, where P is the pitch and μ is the threaded connection stiffness. t α is the friction coefficient of the thread pair, α is the tooth profile half angle, and θ is the thread friction coefficient. i β is the relative rotation angle between the nut and the bolt, and β is the thread helix angle.

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

[0034] The softening model for meshing thread materials was corrected using experimental data. Specifically, the hardness of the metal material was measured at different temperatures, and the parameter C in the softening model was improved based on the fitted curve. The material softening model is expressed as follows:

[0035] H = H0e -CT

[0036] Where H is the material hardness, H0 is the material's hardness at room temperature, C is the thermal coefficient of hardness, and T is the temperature load caused by frictional heat, T is determined by the frictional heat Q. i Obtained through calculation.

[0037] The relationship between the material stress state and the material hardness H is obtained by solving the problem of continuum mechanics. The material stress state is obtained based on the relationship between the material stress state and the material hardness H.

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

[0039] S301 Based on the thread geometry mathematical equation of the threaded connection structure, a refined finite element model is constructed, and the grid nodes are checked.

[0040] S302 The parameters of the material properties of the refined finite element model are added, the initial boundary value conditions (the end faces of the clamping parts are fixed support constraints), the friction heat application mode (the friction heat adopts imprint loading), the pre-tightening force control mode (directly load the pre-tightening force) and the contact state (the normal contact behavior adopts penalty function contact) are set.

[0041] S40. According to the friction heat Q i , material hardness H, material stress state and refined finite element model, the stress field is solved by means of finite element analysis software.

[0042] In the above method, the influence of friction heat Q i on the material stress state is considered, so the above process is a force-heat coupled analysis, and the stress field under the action of temperature and pre-tightening force is obtained by force-heat coupled analysis.

[0043] The contents not described in detail in the specification of the present application are the known technology of those skilled in the art.

[0044] The present application is described in detail above in combination with specific embodiments and exemplary examples, but these descriptions cannot be understood as limitations of the present application. Those skilled in the art understand that various equivalent replacements, modifications or improvements can be made to the technical solutions and embodiments of the present application without departing from the spirit and scope of the present application, and these all fall within the scope of the present application. The protection scope of the present application is subject to the appended claims.

Claims

1. A method of calculating the connection properties of a fastening system, characterized in that Comprise: S10. According to the thread structure, the fastening terminal and the thread interface friction coefficient, the friction heat of the screwing distance is calculated; S20. The hardness-temperature test data of the metal material of the threaded structure is obtained by experiment, according to the friction heat Q i A material softening model of the threaded structure is obtained according to the hardness-temperature test data. According to the material softening model, the stress state of the material is obtained; S30. According to the thread structure, a refined finite element model is constructed in the finite element analysis software, the refined finite element model includes material properties, the material softening model is added in the material property module; The parameters of the material properties are added, and the initial boundary value condition is set. S40. According to the frictional heat Q i , material hardness H, material stress state and refined finite element model, the stress field is solved by means of finite element analysis software; Said S20 comprises: The hardness of the metal material at different temperatures is measured to obtain hardness-temperature test data of the metal material of the thread structure; a thermal coefficient C of hardness is obtained according to a curve fitted based on the hardness-temperature test data of the metal material; a temperature load T caused by friction heat Q is calculated i ; a material softening model of the thread structure is obtained according to the thermal coefficient C of hardness and the temperature load T caused by friction heat; the material softening model is H=H0e -CT -αQT, where H0 is the hardness of the metal material at room temperature, and α is a constant. where H is the hardness of the material, H0is the hardness of the material at room temperature, C is the thermal coefficient of hardness, T is the temperature load caused by friction heat Q i is calculated.

2. The method of claim 1, wherein: Said S10 comprises: According to the thread structure and the fastening terminal, the screwing distance is calculated; According to the thread interface friction coefficient, the friction force in the thread screwing process is calculated; According to the screwing distance and the friction force, the friction heat of the screwing distance is calculated.

3. The method of claim 1 or 2, wherein: The friction heat Q i is: where k c is the thread connection stiffness, P is the pitch, μ t is the thread pair friction coefficient, a is the half angle of the tooth profile, θ i is the relative rotation angle of the nut and the bolt, and β is the thread angle of rise.

4. A computer readable storage medium having stored thereon computer programs or instructions, characterized in that, The computer programs or instructions are executed by the processor to realize the steps of the method of any one of claims 1-3.

5. A computer program product comprising computer programs or instructions, characterized in that, The computer programs or instructions are executed by the processor to realize the steps of the method of any one of claims 1-3.

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