Method for determining optimal closing-in amount of self-locking nut

Abstract

The invention provides a method for determining the optimal closing-in amount of a self-locking nut. The method comprises the following steps: constructing a first finite element network model of the self-locking nut; applying a plurality of closing forces to the self-locking nut to obtain a plurality of corresponding closing amounts; screwing the bolt, the clamped piece and the self-locking nut after the closing force is applied to obtain a second finite element network model; a preset disturbance load in the radial direction of the self-locking nut is applied to the clamped piece; making a section of the second finite element network model along a second direction, and obtaining the holding force of the self-locking nut on the section; and the optimal closing amount is determined according to the holding force. According to the method, tightening simulation calculation is carried out on the target self-locking nuts through the method based on finite element simulation, the corresponding optimal closing-in amount when the anti-loosening performance is optimal can be rapidly obtained by comparing the magnitude of the holding force after the preset disturbance load, and the method is simple and easy to implement, high in calculation speed and high in accuracy. The self-locking nut can keep the optimal anti-loosening performance in the service process, and guidance is provided for engineering application.

Description

Technical Field

[0001] The present application relates to the field of mechanical manufacturing technology, and in particular to a method for determining an optimal closing amount of a self-locking nut. Background Art

[0002] Bolt connections have the advantages of simple structure, easy assembly and disassembly, and low price. They are widely used in various industrial products and mechanical structures. Self-locking nuts are special nuts that self-lock by friction and are mainly used for anti-loosening and anti-vibration in special occasions. The core principle of self-locking nuts is to generate additional self-locking torque between the inner and outer thread surfaces through the closing process, thereby improving its anti-loosening performance. Therefore, the size of the closing amount is a key factor that directly affects the anti-loosening performance.

[0003] In engineering applications, the determination of the amount of closing is mostly based on engineering experience, and there is a lack of accurate determination methods. At present, most scholars generally believe that the larger the closing amount, the better the anti-loosening performance. However, some engineering experience shows that when the closing amount increases to a certain extent, the anti-loosening performance of the self-locking nut will decrease, which contradicts the above conclusion and it is impossible to determine the closing amount when the anti-loosening performance is optimal.

[0004] Therefore, there is an urgent need for a method that can determine the optimal closing amount of a self-locking nut. Summary of the invention

[0005] In order to solve the above technical problems, the present application provides a method for determining the optimal closing amount of a self-locking nut, which can quickly obtain the closing amount with the best anti-loosening performance by comparing the size of the clamping force after a preset disturbance load. The method has the advantages of being simple and easy to operate and having a fast calculation speed.

[0006] The present application provides a method for determining the optimal closing amount of a self-locking nut, which is characterized in that it includes: constructing a first finite element network model of the self-locking nut; the first finite element network model includes geometric parameters of the self-locking nut; applying multiple closing forces to the self-locking nut to obtain multiple closing amounts corresponding to the closing forces; the closing force squeezes the self-locking nut along a first direction, and the first direction is perpendicular to the central axis of the self-locking nut; tightening the bolt and the clamped part with the self-locking nut after the closing force is applied to obtain a second finite element network model; applying a preset disturbance load along the radial direction of the self-locking nut to the clamped part; making a section of the second finite element network model after the preset disturbance load is applied along the second direction to obtain the clamping force of the self-locking nut on the section; the second direction is perpendicular to the first direction; and determining the optimal closing amount according to the clamping force.

[0007] In this way, the method for determining the optimal closing amount provided in the embodiment of the present application is based on the finite element simulation method, and tightening simulation calculations are performed on the target self-locking nuts respectively. By comparing the size of the clamping force after the preset disturbance load, the optimal closing amount corresponding to the optimal anti-loosening performance can be quickly obtained.

[0008] In some feasible implementations, obtaining the clamping force of the self-locking nut on the cross section includes: establishing a rectangular coordinate system on the cross section; wherein the central axis of the self-locking nut is the Y axis, and the direction perpendicular to the Y axis in the cross section is the X axis; obtaining the normal stress data of the self-locking nut in the normal direction of the cross section, and the coordinates of the normal stress data in the rectangular coordinate system; determining the clamping force of the self-locking nut according to the normal stress data and the coordinates. In this way, determining the clamping force by establishing a rectangular coordinate system can simplify the data processing process and effectively shorten the calculation time.

[0009] In some feasible implementations, the clamping force of the self-locking nut is determined based on the normal stress data and the coordinates, including: grouping the normal stress data according to the coordinates of the X-axis in the coordinates to obtain multiple groups of grouped data; performing a second discrete integration of each group of grouped data relative to the coordinates to obtain multiple clamping forces of the self-locking nut. In this way, discrete integration of stress data can reduce the complexity of data processing, simplify the calculation process, and shorten data processing time.

[0010] In some feasible implementations, determining the optimal closing amount according to the clamping force includes: obtaining the maximum clamping force among multiple clamping forces; determining the optimal closing amount based on the maximum clamping force; and the optimal closing amount is the closing amount corresponding to the maximum clamping force. In this way, the optimal closing amount can be quickly determined.

[0011] In some feasible implementations, the closing amount is the maximum deformation of the self-locking nut along the first direction under the action of the closing force.

[0012] In some feasible implementations, applying a closing force to a self-locking nut includes: using a rigid body pressure head to apply a closing force to the outer wall surface of the self-locking nut along a first direction; wherein the first direction is the moving direction of multiple rigid body pressure heads, the first direction is the direction from the outer wall surface of the self-locking nut to the central axis of the self-locking nut, and the closing force acts on two, three or four points on the outer wall surface, and the two, three or four points are symmetrically arranged about the central axis of the self-locking nut. In this way, the self-locking nut in real service can be simulated, and the fit between subsequent data and real data can be effectively guaranteed.

[0013] In some feasible implementations, a finite element network model of the bolt and the clamped part is established; the clamped part is assembled on the bolt; the bolt is screwed into the self-locking nut to obtain a second finite element network model. In this way, the bolt and the clamped part in real service can be simulated, effectively ensuring the accuracy of the subsequent determination of the optimal closing amount.

[0014] In some feasible implementations, the bolt and the clamped part are tightened with the self-locking nut after the closing force is applied to obtain the second finite element network model, which also includes: using the boltload function of the Abaqus software to load the preload force to reach the preset preload force; wherein the initial preload forces corresponding to the multiple closing amounts are the same. This is conducive to simulating the self-locking nuts in real service.

[0015] In some feasible implementations, the preset disturbance load is a displacement load, and a preset disturbance load is applied to the clamped part in the radial direction of the self-locking nut, including: applying a displacement load along the radial direction of the self-locking nut to the clamped part, so that the clamped part moves from an initial position to a preset position along the radial direction of the self-locking nut under the action of the displacement load, and then moves back to the initial position in the opposite direction.

[0016] In some feasible implementations, the contact conditions during the screwing process of the bolt and the clamped part into the self-locking nut and the application of the preset disturbance load are all Coulomb friction. This is conducive to simulating the force process of the self-locking nut under the same service conditions and effectively ensuring the accuracy of the subsequent determination of the optimal closing amount.

[0017] The method for determining the optimal closing amount of the self-locking nut provided in this application performs tightening simulation calculations on the target self-locking nuts respectively based on the finite element simulation method, and by comparing the size of the clamping force after the preset disturbance load, the optimal closing amount corresponding to the optimal anti-loosening performance can be quickly obtained. The method is simple and easy to implement, with fast calculation speed, which is conducive to maintaining the optimal anti-loosening performance of the self-locking nut during service and provides guidance for engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solution of the present application, the drawings required for use in the embodiments are briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0019] Figure 1 It is a schematic diagram of the closing method of a self-locking nut;

[0020] Figure 2 It is a schematic diagram of the process of the closing process;

[0021] Figure 3 It is a schematic diagram of the principle of a lateral vibration test method and the structure of the device;

[0022] Figure 4 It is a flow chart of a method for determining the optimal closing amount of a self-locking nut provided in an embodiment of the present application;

[0023] Figure 5It is a schematic diagram of a self-locking nut model and boundary conditions of the closing process provided in an embodiment of the present application;

[0024] Figure 6 This is a schematic diagram of boundary conditions in a tightening process provided by an embodiment of the present application;

[0025] Figure 7 It is a structural schematic diagram of a clamped component provided in an embodiment of the present application;

[0026] Figure 8 This is a schematic diagram of boundary conditions during an external disturbance process provided by an embodiment of the present application;

[0027] Fig. 9 It is a schematic diagram of a clamping force extraction position provided in an embodiment of the present application;

[0028] Fig.10 This is a schematic diagram of the relationship between the closing amount and the clamping force provided in an embodiment of the present application;

[0029] Fig.11 It is a flow chart of a method for determining an optimal seam closing amount in a specific implementation method provided in an embodiment of the present application;

[0030] Fig.12 It is a flowchart of a method for determining a clamping force in a specific implementation method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be described clearly below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments of the present application, other embodiments obtained by ordinary technicians in this field without making creative work all belong to the protection scope of the present application.

[0032] In the following, the terms "first", "second", etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0033] In addition, in the present application, directional terms such as "upper", "lower", "inner" and "outer" are defined relative to the orientation of the components schematically placed in the drawings. It should be understood that these directional terms are relative concepts. They are used for relative description and clarification, and they can change accordingly according to the changes in the orientation of the components placed in the drawings.

[0034] To facilitate the technical solution of the application, some concepts involved in the application are first explained below.

[0035] Self-locking nuts are threaded connection anti-loosening structures widely used in the aerospace field. The basic principle is to plastically deform the nut through radial multi-point extrusion, thereby producing an interference effect when mating with the bolt, which can generate additional friction torque (also known as self-locking torque) between the internal and external threads to increase its anti-loosening performance. According to the number of closing points, it can be divided into two-point closing, three-point closing, four-point closing, etc.

[0036] Figure 1 It is a schematic diagram of the closing method of a self-locking nut.

[0037] See also Figure 1 As shown. Among them, Figure 1 (a) shows a two-point closing method, where two pressure blocks form two force points on the outer surface of the self-locking nut along the closing directions a1 and a2 respectively; Figure 1 (b) shows a three-point closing method, where three pressure blocks form three force points on the outer surface of the self-locking nut along the closing directions b1, b2 and b3 respectively; Figure 1 The figure (c) shows a four-point closing method, in which four pressure blocks form four force points on the outer surface of the self-locking nut along the closing directions c1, c2, c3 and c4 respectively.

[0038] Figure 2 It is a flow chart of the closing process.

[0039] See also Figure 2 As shown in the figure, the closing process is introduced using a two-point closing method. Figure 2 (a) shows that the pressure head is in the initial position, with a certain distance from the outer surface of the self-locking nut. The two pressure heads are controlled to feed along the feeding directions A1 and A2 respectively toward the outer wall of the self-locking nut until the pressure head reaches the outer wall of the self-locking nut. Figure 2 As shown in (b), the pressure head is fed to the position where it contacts the outer wall of the self-locking nut. The two pressure heads are controlled to continue to press the outer wall of the self-locking nut along the feeding directions A1 and A2. The self-locking nut is continuously squeezed and a depression is formed on the outer wall. Figure 2 As shown in (c) in the figure. Until the extrusion amount of the self-locking nut reaches the maximum value, the extrusion amount of the self-locking nut at this time is called the maximum closing amount of the self-locking nut, see Figure 2 As shown in (d), the maximum closing amount is the distance d1 in the radial direction. After reaching the maximum closing amount, the pressure is maintained for a certain period of time to ensure that the self-locking nut has sufficient plastic deformation. After the pressure holding process is completed, the two pressure heads are controlled to retreat in the opposite directions of A2 and A1 respectively. Figure 2As shown in (e) in the figure. Until the pressure head retreats along the A2 direction and the A1 direction respectively to the state of being separated from the outer wall of the self-locking nut, the extrusion amount of the self-locking nut relative to the initial position is called the residual closing amount, see Figure 2 As shown in (f), the closing process of the self-locking nut is now completed.

[0040] Figure 3 It is a schematic diagram of the principle of a lateral vibration test method and a structural device.

[0041] A large number of studies at home and abroad have fully proved that lateral vibration load is usually the main load form that causes bolted joints to loosen. Therefore, in engineering, the anti-loosening performance of bolted joints is usually tested based on lateral vibration tests. The basic principle of lateral vibration test can be found in Figure 3 As shown in (a). This test is mainly carried out on typical bolt connection structures, including bolts, nuts, and two pressed parts. During the test, one pressed part is fixed (fixed part) and a periodic reciprocating load is applied to the other pressed part (movable part), so as to obtain the preload attenuation curve under different load conditions, and then the anti-loosening performance of the bolt connection can be evaluated. The principle of this test method was first seen in a paper published by German scholar Junker in 1969. This test method has been standardized, and the commonly used standards are my country's national standard GB / T 10431, German standard DIN-65151, and international standard ISO 16130. The basic principles of the tests specified in these standards are the same, but there are differences in the test process, load control method and result interpretation. Figure 3 (b) shows a schematic diagram of a test device designed in accordance with the requirements of ISO 16130. The bolts, nuts and clamped parts are mounted on the preload measuring device through a movable plate, a roller is provided between the movable plate and the preload measuring device, a lateral force measuring device is connected between the movable plate and the hydraulic servo actuator, a lateral displacement measuring device is connected to the movable plate, and the preload measuring device and the hydraulic servo actuator are mounted on a fixed plate.

[0042] In order to overcome the loose connection caused by the vibration load mentioned above, self-locking nuts usually rely on the amount of shrinkage to improve the anti-loosening effect. However, the relationship between the loose connection of the nut and the amount of shrinkage of the nut has not been clarified.

[0043] In order to determine the optimal closing amount of a self-locking nut, an embodiment of the present application provides a method for determining the optimal closing amount of a self-locking nut. The optimal closing amount corresponding to self-locking nuts of different specifications and materials can be determined by finite element simulation to provide guidance for engineering applications.

[0044] Figure 4 It is a flow chart of a method for determining the optimal closing amount of a self-locking nut provided in an embodiment of the present application.

[0045] See also Figure 4 The method for determining the optimal closing amount of a self-locking nut provided in an embodiment of the present application can be implemented by the following steps S1 to S6.

[0046] Step S1: constructing a first finite element network model of a self-locking nut.

[0047] The first finite element network model may include geometric parameters and material parameters of the self-locking nut, and the geometric parameters include the inner diameter size of the self-locking nut. The inner diameter size includes the major diameter, middle diameter and minor diameter in the internal thread of the self-locking nut. Among them, a self-locking nut with a UNJF thread having a major diameter of 4.826mm, a middle diameter of 4.384mm and a minor diameter of 4.3053mm can be used for simulation. The material parameters include: the material of the self-locking nut, such as steel, iron or other materials with a certain rigidity. In other words, when constructing the first finite element network model, the first finite element network model can be constructed according to the geometric parameters and material parameters of the self-locking nut required for the simulation.

[0048] In the process of establishing the finite element network model in step S1, the first finite element mesh model of the self-locking nut can be constructed by the Fukuoka method. It is understandable that the real self-locking nut usually has a hexagonal plate screw structure, but the main invention of the embodiment of the present application is to compare the anti-loosening performance of the self-locking nut under different closing amounts. Therefore, in order to facilitate the subsequent comparative analysis of the closing amount data, the self-locking nut is uniformly simplified into a cylinder.

[0049] Figure 5 : is a self-locking nut model and a schematic diagram of the boundary conditions of the closing process provided by the embodiment of the present application; wherein, Figure 5 (a) shows a cross-sectional view of the self-locking nut along the central axis direction; Figure 5 (b) is a schematic diagram of the boundary conditions during the closing process of the self-locking nut.

[0050] Combination Figure 4 and Figure 5 As shown, step S2: applying multiple closing forces to the self-locking nut to obtain multiple closing amounts corresponding to the closing forces.

[0051] This step can be understood as simulating the closing process of the self-locking nut. When closing the self-locking nut, a closing force needs to be applied to the self-locking nut. The rigid body pressure head can be controlled to move along the first direction to generate a lateral displacement, and a closing force along the first direction is applied to the outer wall surface of the self-locking nut during the lateral displacement, so that the outer wall surface of the self-locking nut is concave in the direction of the central axis of the self-locking nut. The specific closing process can be referred to above. Figure 2Related introduction in . The closing amount is the maximum deformation of the self-locking nut along the first direction under the action of the closing force. For example, when the closing force is the first closing force, the corresponding maximum deformation can be the first closing amount, and when the closing force is the second closing force, the corresponding maximum deformation can be the second closing amount. Among them, the first closing force can be different from the second closing force, and the first closing amount can be different from the second closing amount. In this way, by applying multiple closing forces to the self-locking nut, multiple closing amounts can be obtained, and the closing amounts and closing forces are set one by one.

[0052] Among them, the first direction is the direction extending along the outer wall of the self-locking nut towards the central axis of the self-locking nut, and the first direction is perpendicular to the central axis of the self-locking nut. It is worth noting that the first direction does not simply refer to one direction, but represents a type of direction. The first direction is the moving direction of multiple rigid body pressing heads, and the specific first direction is the direction from the outer wall surface of the self-locking nut to the central axis of the self-locking nut. That is, under the action of the closing force, multiple rigid body pressing heads all move along the first direction from the outer wall surface of the self-locking nut to the central axis direction of the self-locking nut, and the closing force acts on the outer wall surface of the self-locking nut at two, three or four points, and the two, three or four points are symmetrically arranged about the central axis of the self-locking nut.

[0053] When there are two points of action, the closing method of the self-locking nut can be a two-point closing method. When there are three points of action, the closing method of the self-locking nut can be a three-point closing method. When there are four points of action, the closing method of the self-locking nut can be a four-point closing method. Figure 5 Taking the example shown, the method provided in the embodiment of the present application is introduced with two points of action for a two-point closing method.

[0054] In step S2, considering that the pressure head has a larger rigidity than the self-locking nut, the pressure head body will basically not deform during the closing process, so the pressure head is defined as a rigid body. During the simulation process, the closing height of the closing force can be Figure 5 h shown in (b). The closing height can be the distance between the point where the pressure head acts on the outer wall of the self-locking nut and the lower end face of the self-locking nut, and h can be 4.1 mm. In this way, the self-locking nuts in actual service can be simulated, and the fit between subsequent data and actual data can be effectively guaranteed. Among them, the lower end face of the self-locking nut can be the end face when the self-locking nut is connected to the bolt and the bolt is screwed into the self-locking nut. In the process of simulating the self-locking nut, the contact condition can adopt Coulomb friction, and the friction coefficient is set to 0.1. The simulation adopts a static analysis step, and the simulation process imposes a fixed constraint on the lower end face of the self-locking nut, so as to match the authenticity of the self-locking nut when it is actually closed.

[0055] Continue to see Figure 5As shown in (b), when the two-point closing method is adopted, the first pressing head Y1 can be controlled to move along the first sub-direction B1 and the second pressing head Y2 can be controlled to move toward the central axis L of the self-locking nut along the second sub-direction B2, wherein the first direction includes the first sub-direction B1 and the second sub-direction B2. After the closing is completed, the two pressing heads are controlled to move in the opposite direction and separate from the self-locking nut, that is, the first pressing head Y1 retreats along the B2 direction (opposite to B1), and the second pressing head Y2 retreats along the B1 direction (opposite to B2), and the directions of the B1 direction and the B2 direction are opposite.

[0056] It should be emphasized that in the two-point closing method, the movement directions of the two pressure heads are opposite and symmetrical about the central axis of the self-locking nut, while in the three-point closing method, the movement directions of the three pressure heads are not opposite but only symmetrical; the four-point closing method can be regarded as two groups of two-point closing methods, which is similar to the movement method of the pressure heads in the two-point closing method. Therefore, whether the specific movement directions of the pressure heads are opposite needs to be determined according to the actual closing method. The simulation of the two-point closing method in the embodiment of the present application is only an example. The optimal closing amount determination method provided in the embodiment of the present application is not limited to the two-point closing method, but is also applicable to the three-point closing method, the four-point closing method, etc.

[0057] In a specific implementation, the number of self-locking nuts can be 5 groups. Each group has a self-locking nut, and the geometric parameters and material parameters of each group of self-locking nuts are the same, and a two-point closing method is adopted. The closing force of each group of self-locking nuts is different, and the closing amount obtained is also different. Of course, in the rest of the simulation process, the number of self-locking nuts can be 6 groups, 8 groups or 10 groups. The embodiment of the present application does not limit the number of self-locking nuts, but in order to ensure the accuracy of obtaining the optimal closing amount, the number of self-locking nuts should be greater than or equal to 5 groups.

[0058] Figure 6 Schematic diagram of boundary conditions of a tightening process provided by an embodiment of the present application. Figure 6 (a) shows a schematic diagram of the structure in which the bolt is screwed in; Figure 6 (b) shows a schematic diagram of the structure in which the clamp is screwed in.

[0059] Step S3: Tighten the bolt and the clamped part with the self-locking nut after applying the closing force to obtain a second finite element network model.

[0060] Step S3 can be understood as a process of simulating the tightening of the bolt and the clamped component, including the following steps S31 to S33.

[0061] Step S31: Establish a finite element network model of the bolt and the clamped component.

[0062] Step S32: Assemble the clamped component on the bolt.

[0063] Step S33: Screw the bolt into the self-locking nut to obtain a second finite element network model.

[0064] Combination Figure 4 and Figure 6 As shown, the finite element network model of the bolt and the clamped part can be constructed in the same direction as the first finite element network model. The geometric parameters and material parameters of the bolt and the clamped part can be the same as those of the self-locking nut, so as to ensure the uniformity of the data and the degree of coordination between the models. The bolt can be made of pure elastic material.

[0065] In step S31, the Fukuoka method is used to establish a finite element network model of the bolt and the clamped part. In step S32, the clamped part is assembled on the bolt to obtain a finite element network model of the bolt and the clamped part as a whole. Next, in the finite element network model of the bolt and the clamped part as a whole, the first finite element network model of each group of self-locking nuts that have completed the closing process is imported from the ODB (OpenOfficeBase, an open source desktop relational database program) file that completes the closing process, and the finite element network model of the bolt, the clamped part and the self-locking nut after tightening can be obtained. During the simulation process, the dynamic display analysis step can be used to apply a fixed constraint to the lower end face g1 of the self-locking nut to ensure stability during the bolt screwing process. At the same time, an angle constraint is applied to the bottom of the bolt to simulate the process of the bolt being screwed into the self-locking nut. The contact condition of the simulation process adopts Coulomb friction, and the friction coefficient is set to 0.1. Among them, the ODB file can be understood as a file with self-locking nut data exported after the first finite element network model is established.

[0066] The self-locking nut may include an internal thread, the bolt may include an external thread, and the internal thread is adapted to the external thread. The control bolt is screwed into the self-locking nut along the lower end surface of the self-locking nut through the angle constraint. During the process of screwing the bolt in, the external thread of the bolt is continuously screwed into the internal thread of the self-locking nut, and the screwing area of ​​the two is continuously increased until the bolt is completely screwed into the self-locking nut, and the screwing area of ​​the internal thread and the external thread reaches the maximum screwing area.

[0067] Specifically, the contact condition during the simulation process uses Coulomb friction, and the friction coefficient is set to 0.1. When applying angular constraints to the bolt, the side of the bolt head can be coupled with the central reference point first, so as to ensure that the force state of the bolt and the self-locking nut remains uniform during the bolt rotation process. The central reference point can be the center point of the lower end face of the self-locking nut. After the bolt and the self-locking nut complete the tightening process, an ODB file with the bolt and self-locking nut data can be exported.

[0068] It should be emphasized that Figure 6(a) shows the positional relationship between the bolt and the self-locking nut when the bolt is just screwed into the self-locking nut. In order to intuitively show the connection state of the bolt and the self-locking nut, the clamped part is not shown. Figure 6 (b) shows the connection state when the bolt and the clamped part are completely screwed into the self-locking nut.

[0069] Figure 7 It is a structural schematic diagram of a clamped component provided in an embodiment of the present application.

[0070] Combined with Figure 6 (b) and Figure 7 As shown, the inner diameter of the clamped part can be 5.6 mm, the outer diameter can be 16 mm, and the thickness can be 3 mm. The material of the clamped part can be set to the same pure elastic material as the bolt. In this way, the self-locking nut in real service can be simulated, and the fit between the subsequent data and the real data can be effectively guaranteed. In other specific implementations, the size of the clamped part can also be different from the above-mentioned size, and the specific size of the clamped part can be adaptively adjusted according to the size of the self-locking bolt and the service environment of the self-locking bolt.

[0071] Figure 7 The clamped part shown is screwed into Figure 6 The finite element network model shown in (a) can be obtained Figure 6 The second finite element network model shown in (b).

[0072] In step S31, the Fukuoka method is used to establish a size such as Figure 7 The finite element network model of the clamped part shown in the figure imports the network model of the bolt and the self-locking nut from the ODB file after the tightening is completed. In the load module, the stress field at the end of the screwing process is applied to the bolt and the self-locking nut to ensure that the state of the bolt and the self-locking nut after tightening remains unchanged. Among them, the stress field can be understood as the stress data set at the end of the tightening state of the bolt and the self-locking nut. After the clamped part is completely screwed in between the bolt and the self-locking nut, the bolt is located inside the clamped part, one surface of the clamped part is in contact with the lower end surface of the self-locking nut, and the self-locking nut is located on the upper part of the clamped part.

[0073] Specifically, the boltload function of the Abaqus software can be used to load the preload force during the tightening process to achieve the preset preload force. The contact conditions in the simulation process adopt general conditions, and the friction coefficient is set to 0.1. The simulation uses a static analysis step to apply fixed constraints to the side g2 of the bolt head and the side g3 of the clamped part, and the preset preload force is 1.5kN. It is conducive to simulating self-locking nuts under real service conditions. Among them, the initial preload corresponding to multiple closing amounts is the same. Thereby simulating the service conditions of self-locking nuts in the actual service process and ensuring the accuracy of the optimal closing amount.

[0074] Step S4: applying a preset disturbance load along the radial direction of the self-locking nut to the clamped part. Step S4 can be understood as simulating an external disturbance process.

[0075] In step S4, a new simulation file can be created to import the bolt, self-locking nut and clamped part models from the ODB file of the completed tightening process, and the stress field when the tightening is completed is applied to the three parts in the load module. The contact condition in the simulation process adopts Coulomb friction, and the friction coefficient is set to 0.1.

[0076] It can be understood that during the tightening process and disturbance process of the bolt, the clamped part, and the self-locking nut, the contact conditions are the same and are all Coulomb friction, and the friction coefficients are the same and are all 0.1, thereby simulating the force process of the self-locking nut under the same service conditions, and effectively ensuring the accuracy of the subsequent determination of the optimal closing amount.

[0077] Specifically, the preset disturbance load may be a displacement load, and step S4 may include: applying a displacement load along the radial direction of the self-locking nut to the clamped part, so that the clamped part moves from an initial position to a preset position along the radial direction of the self-locking nut under the action of the displacement load. After the clamped part moves to the preset position, the displacement load along the radial direction of the self-locking nut is canceled, so that the clamped part retreats from the preset position to the initial position in the opposite direction, so as to complete the entire process of applying the preset disturbance load.

[0078] For example, during the simulation of external disturbance, an external preset disturbance load can be applied based on the principle of lateral vibration experiment, and a displacement load in the radial direction can be applied to the clamped part, wherein the radial direction can specifically include the first sub-direction B1 or the second sub-direction B2 mentioned in the above implementation. After the clamped part moves to the preset position, the preset disturbance load is canceled, the clamped part no longer generates displacement in the radial direction of the self-locking nut, and the clamped part retreats from the preset position to the initial position in the opposite direction (the opposite direction corresponding to the first sub-direction B1 is the B2 direction, and the opposite direction corresponding to the second sub-direction B2 is the B1 direction), thereby completing the external disturbance process.

[0079] Figure 8 This is a schematic diagram of boundary conditions during an external disturbance process provided in an embodiment of the present application.

[0080] See also Figure 8As shown, a fixed constraint is applied to the side g2 of the bolt head, and a preset disturbance load is applied to the clamped part along the first sub-direction B1, so that the clamped part produces a lateral displacement along the first sub-direction B1, and the lateral displacement can be 0.3 mm, thereby simulating the external disturbance received by the self-locking nut during service. Among them, the specific value of the preset disturbance load can be adjusted according to the service environment of the self-locking nut. For example, if the self-locking nut serves in an environment with large vibration, the value of the preset disturbance load can be relatively large, and if the self-locking nut serves in an environment with small vibration, the value of the preset disturbance load can be relatively small. The value of the preset disturbance load is also related to the vibration period. For example, when the value of the preset disturbance load is relatively large, the vibration period can be relatively small, and when the value of the preset disturbance load is relatively small, the vibration period can be relatively large.

[0081] Specifically, the method of simulating external disturbance loads provided in step S4 of the present application only requires 0.5 cycles of vibration to simulate the external disturbance process of the clamped part, compared to a complete lateral vibration experiment, thereby effectively shortening the simulation time and increasing the rate of determining the optimal closing amount.

[0082] Step S5: making a cross section of the second finite element network model along a second direction to obtain the clamping force of the self-locking nut on the cross section; the second direction is perpendicular to the first direction.

[0083] Specifically, during the tightening process, the bolt causes the closing position of the self-locking nut to deform in the opposite direction, and the force generated by the self-locking nut to hold the bolt and prevent it from rotating and loosening is the holding force. The anti-loosening principle of the self-locking nut is to hold the bolt through interference fit to produce an anti-loosening effect, so the size of the holding force can reflect the size of the anti-loosening performance of the self-locking nut.

[0084] Fig. 9 It is a schematic diagram of the clamping force extraction position provided in an embodiment of the present application.

[0085] See also Fig. 9 As shown, the second finite element network model is sectioned along the second direction perpendicular to the closing direction (first direction) and passing through the central axis of the self-locking nut to obtain sections j1 and j2 of the self-locking nut. The clamping force can be extracted from the sections j1 and j2.

[0086] Specifically, step S5 can be implemented by the following steps S51 to S53.

[0087] Step S51: Establish a rectangular coordinate system on the cross section, wherein the central axis of the self-locking nut is the Y axis, and the direction perpendicular to the Y axis in the cross section is the X axis.

[0088] When establishing a rectangular coordinate system, a rectangular coordinate system can be made based on the cross section in the second direction, including the central axis of the self-locking nut as the Y axis, and the direction perpendicular to the Y axis in the cross section as the X axis. To facilitate the calculation of subsequent data, the origin O of the rectangular coordinate system can be the center of the lower end face of the self-locking nut. In this way, sections j1 and j2 are symmetrical about the Y axis. Of course, in other specific implementations, the origin O can also be any point on the central axis of the second finite element network model. Determining the clamping force by establishing a rectangular coordinate system can simplify the data processing process and effectively shorten the calculation time.

[0089] Step S52: Obtain the normal stress data of the self-locking nut in the normal direction of the cross section, and the coordinates of the normal stress data in the rectangular coordinate system.

[0090] In step S52, Abaqus software can be used to output the coordinates of the stress points of the self-locking nut on the cross section corresponding to the rectangular coordinate system, and then the stress data of the stress points of the self-locking nut in the normal direction of the cross section are extracted, and the stress data includes the stress magnitude and stress direction of the stress points.

[0091] Step S53: Determine the clamping force of the self-locking nut according to the normal stress data and the coordinates.

[0092] Specifically, step S53 can be implemented by the following steps S531 and S532.

[0093] Step S531: grouping the normal stress data according to the coordinates of the X-axis in the coordinate system to obtain multiple groups of grouped data.

[0094] In step S531, the stress data can be imported into the matlab software, and the findgroups command can be used to group the stress data according to the X coordinate to obtain multiple groups of grouped data, wherein the stress data with the same X coordinate can be grouped in the same group.

[0095] Step S532: Perform a second discrete integration of each set of grouped data relative to the coordinates to obtain a plurality of clamping forces of the self-locking nut.

[0096] In step S532, the trapz function can be used to simultaneously perform quadratic discrete integration of the X-axis and the Y-axis in the coordinates on each group of grouped data to obtain the corresponding clamping force of the self-locking nut with each closing amount after the external disturbance.

[0097] In step S52, discrete integration of stress data can reduce the complexity of data processing, simplify the calculation process, shorten the data processing time, and improve the efficiency of determining the optimal closing amount.

[0098] Step S6: Determine the optimal closing amount according to the clamping force.

[0099] Specifically, step S6 can be implemented by the following steps S61 and S62.

[0100] Step S61: Obtaining the maximum clamping force among multiple clamping forces. In step S5, multiple clamping forces can be obtained.

[0101] Step S62: Determine the optimal closing amount based on the maximum clamping force.

[0102] Specifically, the closing amount corresponding to the maximum clamping force is the optimal closing amount. It can be understood that the maximum clamping force indicates that the clamping force of the self-locking nut on the bolt is the largest, and the anti-loosening effect is the best at this time, and the corresponding closing amount is also the optimal closing amount. In this way, the optimal closing amount can be quickly determined.

[0103] Fig.10 It is a schematic diagram of the relationship between the closing amount and the clamping force provided in an embodiment of the present application.

[0104] See also Fig.10 As shown, the relationship between the closing amount and the clamping force is obtained by fitting. Among them, the horizontal axis is the closing amount, the unit is millimeter (mm), and the vertical axis is the clamping force, the unit is Newton (N). It can be seen that with the increase of the closing amount, the clamping force of the self-locking nut on the bolt shows a trend of first increasing and then decreasing. The closing amount with the largest clamping force is the optimal closing amount corresponding to the self-locking nut of this specification. At the optimal closing amount, the anti-loosening performance of the self-locking nut reaches the optimal state.

[0105] The method for determining the optimal closing amount of the self-locking nut provided in the embodiment of the present application first obtains self-locking nuts with different closing amounts by changing the feed amount of the pressure head during the closing amount, then performs tightening simulation on the self-locking nuts with different closing amounts to obtain the same initial preload, and finally applies an external preset disturbance load to the self-locking nut that completes the tightening process to simulate its service conditions, and compares the relative size of the clamping force after the external preset disturbance load. The closing amount corresponding to the maximum clamping force is the optimal closing amount of the self-locking nut of this specification. Through the method based on finite element simulation, tightening simulation calculations are performed on the target nuts themselves, and by comparing the size of the clamping force after the preset disturbance load, the optimal closing amount corresponding to the optimal anti-loosening performance can be quickly obtained. The method is simple and easy to implement, with fast calculation speed, which is conducive to the self-locking nut to maintain the optimal anti-loosening performance during service, and provides guidance for engineering applications.

[0106] Fig.11 It is a flow chart of a method for determining an optimal seam closing amount in a specific implementation manner provided in an embodiment of the present application.

[0107] See also Fig.11 The method for determining the optimal seam closing amount may include step S01 and step S05.

[0108] Step S01: Network model construction.

[0109] The network model is determined by inputting the geometric parameters and material parameters of the nut. This step may correspond to step S1 in the above implementation.

[0110] Step S02: Closing process.

[0111] Self-locking nuts with different closing amounts are obtained by different closing forces. This step may correspond to step S2 in the above implementation.

[0112] Step S03: Tightening process.

[0113] The bolt and the clamped part are respectively tightened with the nut, and the same initial pre-tightening force is maintained during tightening. This step may correspond to step S3 in the above implementation.

[0114] Step S04: External disturbance process.

[0115] Apply external disturbance, obtain the clamping force, and compare the relative magnitudes of the clamping force. This step may correspond to step S4 and step S5 in the above implementation.

[0116] Step S05: Optimal closing amount.

[0117] This step may correspond to step S6 in the above implementation.

[0118] Fig.12 It is a flowchart of a method for determining a clamping force in a specific implementation provided in an embodiment of the present application.

[0119] See also Fig.12 The method for determining the clamping force includes steps S001 to S004.

[0120] Step S001: Output section node coordinates.

[0121] Step S002: Output cross-section node stress data.

[0122] Step S001 and step S002 may correspond to step S52 in the above implementation.

[0123] Step S003: double discrete integration.

[0124] Step S004: Nut clamping force.

[0125] Step S003 and step S004 may correspond to step S53 in the above implementation.

[0126] It should be noted that those skilled in the art will easily think of other embodiments of the present application after considering the specification and practicing the application disclosed herein. The present application is intended to cover any variation, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary technical means in the art that are not disclosed in the present application.

[0127] It should be understood that the present application is not limited to the precise construction that has been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof, the true scope being indicated by the present application.

Claims

1. A method for determining the optimal closing amount of a self-locking nut, characterized in that: include: Constructing the first finite element network model of the self-locking nut; The first finite element network model includes geometric parameters of the self-locking nut; Applying a plurality of closing forces to the self-locking nut to obtain a plurality of closing amounts corresponding to the closing forces; The closing force acts on the self-locking nut along a first direction, and the first direction is perpendicular to the central axis of the self-locking nut; Tightening the bolt and the clamped part with the self-locking nut after the closing force is applied to obtain a second finite element network model; Applying a preset disturbance load along the radial direction of the self-locking nut to the clamped part; Making a cross section of the second finite element network model after the preset disturbance load is applied along a second direction, and obtaining the clamping force of the self-locking nut on the cross section; The second direction is perpendicular to the first direction; The optimum closing amount is determined based on the clamping force.

2. The method for determining the optimal closing amount of a self-locking nut according to claim 1, characterized in that: The obtaining of the clamping force of the self-locking nut on the cross section comprises: A rectangular coordinate system is established on the cross section, wherein the central axis of the self-locking nut is the Y axis, and the direction perpendicular to the Y axis in the cross section is the X axis; Obtaining normal stress data of the self-locking nut in the normal direction of the cross section, and coordinates of the normal stress data in the rectangular coordinate system; The clamping force of the self-locking nut is determined according to the normal stress data and the coordinates.

3. The method for determining the optimal closing amount of a self-locking nut according to claim 2, characterized in that: Determining the clamping force of the self-locking nut according to the normal stress data and the coordinates includes: Grouping the normal stress data according to the coordinates of the X-axis in the coordinates to obtain multiple groups of grouped data; Each set of the grouped data is subjected to a second discrete integration relative to the coordinates to obtain a plurality of clamping forces of the self-locking nut.

4. The method for determining the optimal closing amount of a self-locking nut according to claim 3, characterized in that: Determining the optimal closing amount according to the clamping force includes: Obtaining the maximum clamping force among the plurality of clamping forces; The optimal closing amount is determined based on the maximum clamping force; the optimal closing amount is the closing amount corresponding to the maximum clamping force.

5. The method for determining the optimal closing amount of a self-locking nut according to claim 4, characterized in that: The closing amount is the maximum deformation of the self-locking nut along the first direction under the action of the closing force.

6. The method for determining the optimal closing amount of a self-locking nut according to claim 5, characterized in that: The step of applying a closing force to the self-locking nut comprises: Using a rigid pressing head to apply a closing force to the outer wall surface of the self-locking nut along the first direction; Among them, the first direction is the moving direction of the multiple rigid pressure heads, the first direction is the direction from the outer wall surface of the self-locking nut to the central axis of the self-locking nut, the closing force acts on two, three or four points on the outer wall surface, and the two, three or four points of action are symmetrically arranged about the central axis of the self-locking nut.

7. The method for determining the optimal closing amount of a self-locking nut according to claim 6, characterized in that: The bolt and the clamped part are tightened with the self-locking nut after the closing force is applied to obtain a second finite element network model, including: Establish finite element network model of bolts and clamped parts; Assembling the clamped part on the bolt; The bolt is screwed into the self-locking nut to obtain a second finite element network model.

8. The method for determining the optimal closing amount of a self-locking nut according to claim 7, characterized in that: The bolt and the clamped part are tightened with the self-locking nut after the closing force is applied to obtain a second finite element network model, and further includes: The boltload function of the Abaqus software is used to perform preload loading to achieve a preset preload; wherein the initial preload corresponding to the plurality of closing amounts is the same.

9. The method for determining the optimal closing amount of a self-locking nut according to claim 8, characterized in that: The preset disturbance load is a displacement load; The step of applying a preset disturbance load to the clamped component along the radial direction of the self-locking nut comprises: A displacement load is applied to the clamped part along the radial direction of the self-locking nut, so that the clamped part moves from an initial position to a preset position along the radial direction of the self-locking nut under the action of the displacement load, and then moves back to the initial position along the reverse direction.

10. The method for determining the optimal closing amount of a self-locking nut according to any one of claims 1 to 9, characterized in that: The contact conditions during the screwing process of the bolt, the clamped part and the self-locking nut, and the process of applying the preset disturbance load are all Coulomb friction.

Images