Method for analyzing crimping strength of steel wire rope for electric connector based on nonlinear finite element

Abstract

The invention relates to the technical field of aviation electric connectors, and discloses a method for analyzing the crimping strength of a steel wire rope for an electric connector based on a nonlinear finite element. Firstly, a steel wire rope structure geometric model is established and grid division is carried out; then defining elastic-plastic constitutive related parameters and contact parameters of the material; stretching numerical simulation of the steel wire rope is carried out based on a power explicit method; the elastic-plastic parameters of the material are calibrated in combination with a tensile numerical simulation result; then, geometric models of the punch and the sleeve shell are established and assembled; and establishing a stamping-stretching power explicit analysis calculation step and carrying out numerical simulation. By considering the actual winding geometric model of the steel wire rope, the interaction between the steel wire ropes in the stretching process can be effectively simulated; by carrying out material elastic-plastic parameter calibration, the accuracy of a numerical simulation result can be improved; the defect that the crimping strength of the steel wire rope is difficult to directly measure through a test method is overcome, and the nonlinear deformation characteristic of the structure in an extremely severe working environment can be predicted.

Description

Technical Field

[0001] This invention relates to the field of aviation electrical connector technology, and discloses a method for analyzing the crimping strength of steel wire ropes for electrical connectors based on nonlinear finite element method. Background Technology

[0002] As a flexible helical steel structure, steel wire rope has received widespread attention in the field of mechanical connection design, and its structural reliability is crucial for the safe operation of the connected components. In the field of aerospace connectors, steel wire rope is often used in pull-out mechanisms due to its excellent flexibility and strength. Currently, with the increasing demands for withstanding harsh environments and operating conditions, pull-out connectors based on steel wire rope are prone to wire breakage or detachment at the stamping points. To meet the usability and maintainability requirements of steel wire rope suspensions, it is urgent to establish a reliable method for analyzing the crimping strength of steel wire rope after stamping.

[0003] Theoretical analysis of wire rope strength is very difficult. Since the 1950s, domestic researchers have mainly established wire rope analysis models through semi-continuous and discrete methods. However, with the development and improvement of computer technology and computing power, the finite element method has gradually become one of the most powerful tools for solving wire rope strength problems.

[0004] In currently available research, numerical simulations of steel wire ropes using the finite element method mainly focus on the tensile strength of the rope itself and the analysis of its twisting and forming, lacking strength analysis of steel wire rope structures in actual complex component applications. For aerospace pull-out connectors, the connection strength between the steel wire rope and the suspension is crucial, namely, whether the stamped casing can guarantee that the steel wire rope will not detach under ultimate load. Since the connection strength of the casing is often greater than the tensile strength of the steel wire rope, and stress concentration is easily generated at the restrained end when the steel wire rope is restrained in the experiment, it is difficult to directly obtain the crimping strength of the casing to the steel wire rope through experimental methods. Therefore, numerical simulation based on the nonlinear finite element method has become one of the effective analysis methods.

[0005] For the stamping-tensioning process analysis of wire rope and sheath structures, large material deformation and nonlinearity are involved. Therefore, accurately defining the elastic-plastic constitutive parameters of the material becomes a key issue to ensure the accuracy and reliability of numerical simulation. Currently, conventional aerospace connector structure design generally adopts an elastic simplification design concept, which cannot accurately predict the nonlinear deformation characteristics of structures under extreme operating environments. Summary of the Invention

[0006] The purpose of this invention is to provide a nonlinear finite element method for analyzing the crimping strength of steel wire ropes for electrical connectors, which can accurately calibrate the elastoplastic constitutive parameters of steel wire rope materials and predict the nonlinear deformation characteristics of structures under extreme and harsh operating environments.

[0007] To achieve the above-mentioned technical effects, the technical solution adopted by the present invention is as follows: A method for analyzing the crimping strength of steel wire ropes for electrical connectors based on nonlinear finite element method includes the following steps: Step S1: Based on the actual structural characteristics of the wire rope, establish a geometric model of the wire rope winding state and perform mesh generation to obtain the wire rope structure mesh model. Step S2: Determine the fracture strain and contact friction coefficient of the wire rope structure mesh model according to the material grade of the wire rope; Step S3: Establish the dynamic explicit calculation and analysis step of the axial tension of the wire rope, set the loads and boundary constraints at both ends of the wire rope, and then perform structural tension numerical simulation to obtain the structural tension numerical simulation results. Step S4: Based on the fracture strain of the wire rope material and the given minimum breaking tensile force of the wire rope, calibrate the yield stress of the wire rope material to complete the calibration of the constitutive parameters of the wire rope material. Step S5: Establish the geometric model of the pressure head and the casing and perform mesh generation, then assemble it with the wire rope structure mesh model to obtain the mesh model of the press assembly. Step S6: Establish the wire rope stamping analysis step and tensile analysis step using the dynamic explicit method. Define the loads and boundary conditions of the indenter, sleeve and wire rope in the stamping analysis step and tensile analysis step respectively. Then, perform a full numerical simulation of the stamping-tensile process on the mesh model of the press-fit assembly to obtain the full numerical simulation results of the stamping-tensile process of the mesh model of the press-fit assembly. Step S7: Based on the numerical simulation results of the entire stamping-tensioning process of the crimped assembly mesh model, evaluate the crimping strength of the wire rope. If the wire rope does not detach from the casing under the maximum design tensile force, it is determined that the crimping strength of the wire rope meets the requirements.

[0008] Further, in step S1, in the geometric model of the wire rope winding state, each wire rope has a preset spacing, which is 1% of the diameter of each wire rope.

[0009] Furthermore, in step S1, when meshing the geometric model of the wire rope winding state, the formula for calculating the minimum mesh size of the contact area between two adjacent wire ropes is: ; In the formula: This is the minimum grid size for the contact area between two adjacent wire ropes; It is half the width of the contact surface between two adjacent wire ropes; This represents the contact force between two adjacent strands of wire rope. This is the line contact length between two adjacent steel wire ropes; and These are the coefficients of friction of two adjacent steel wire ropes; and These are the elastic moduli of two adjacent steel wire ropes, respectively. and These are the individual rope radii of two adjacent steel wire ropes.

[0010] Furthermore, in step S2, a linearly reinforced ideal elastoplastic model is used to describe the yield and plastic deformation characteristics of the wire rope material.

[0011] Furthermore, in step S4, based on the fracture strain of the wire rope material and the given minimum breaking tensile force of the wire rope, and combined with the axial tensile numerical simulation results, the elastic-plastic parameters of the wire rope are calibrated. By iteratively modifying the value of the ultimate stress of the wire rope, the maximum strain of the wire rope reaches the fracture strain when the tensile force applied to the wire rope reaches the given minimum breaking tensile force.

[0012] Furthermore, in step S6, a dynamic explicit method is used to perform a full-process numerical simulation of the stamping and stretching of the mesh model of the press-fit assembly; in the stamping analysis step, displacement constraints are applied to the two press heads, so that they can only translate vertically, and a linearly increasing stamping force is applied to each press head; in the stretching analysis step, a specified tensile force is applied to one end of the wire rope, and a rigid fixing constraint is applied to the end face of the sleeve on one side of the stretching direction. Based on the tensile deformation state of the wire rope obtained from the numerical simulation, it is determined whether the press-fit strength of the sleeve to the wire rope meets the requirements.

[0013] Furthermore, the material properties of the steel wire rope include density, elastic modulus, Poisson's ratio, and yield stress.

[0014] Furthermore, the structural tensile numerical simulation results include tensile force, tensile displacement, tensile stress, and strain.

[0015] Furthermore, the numerical simulation results of the entire stamping-stretching process include indenter displacement, tensile force, tensile displacement, stress, and strain.

[0016] Compared with the prior art, the beneficial effects of this invention are: This invention first establishes a geometric model of the wire rope structure and performs mesh generation; then, it defines the relevant parameters of the material's elastoplastic constitutive model and contact parameters; subsequently, it conducts a tensile numerical simulation of the wire rope based on a dynamic explicit method; the material's elastoplastic parameters are calibrated based on the tensile numerical simulation results; next, it establishes geometric models of the punch and casing and completes the structural assembly; it establishes a punch-tension dynamic explicit analysis calculation step and conducts numerical simulation to realize the interaction between the wire rope and the casing during the entire punch-tension process and the simulation solution of the structural elastoplastic deformation. This invention, by considering the actual winding geometric model of the wire rope, can effectively simulate the interaction between each wire rope during the tensioning process; by calibrating the material's elastoplastic parameters, it can improve the accuracy of the numerical simulation results; it overcomes the deficiency of directly measuring the wire rope crimping strength through experimental methods and can predict the nonlinear deformation characteristics of structures under extreme and harsh operating environments. Attached Figure Description

[0017] Figure 1 This is a flowchart of the nonlinear finite element method for analyzing the crimping strength of steel wire ropes for electrical connectors in this embodiment; Figure 2 This is a schematic diagram of the wire rope structure mesh model and cross-sectional features in this embodiment; Figure 3 This is a schematic diagram of the linear stress-strain strengthening curve of the steel wire rope material in this embodiment; Figure 4 This is a schematic diagram of the tensile force and displacement response results applied in the numerical simulation of this embodiment; Figure 5 This is a schematic diagram showing the change of equivalent stress in the wire rope during the axial tension process in this embodiment; Figure 6 This is a schematic diagram showing the change of equivalent plastic strain of the wire rope during axial tension in this embodiment; Figure 7 This is a schematic diagram of the mesh model of the crimping assembly consisting of wire rope, casing, and crimp head in this embodiment; Figure 8 This is a schematic diagram of the loads applied during the stamping analysis step and the tensile analysis step in this embodiment; Figure 9 This is a schematic diagram of the tensile force load and longitudinal tensile displacement in this embodiment; Figure 10 This is a schematic diagram showing the change of equivalent stress in the structure during the stretching process in this embodiment. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings. However, this should not be construed as limiting the scope of the above-described subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0019] See Figure 1 This invention provides a method for analyzing the crimping strength of steel wire ropes for electrical connectors based on nonlinear finite element method, comprising the following steps: Step S1: Based on the actual structural characteristics of the wire rope, establish a geometric model of the wire rope winding state and perform mesh generation to obtain the wire rope structure mesh model. Step S2: Determine the fracture strain and contact friction coefficient of the wire rope structure mesh model according to the material grade of the wire rope; Step S3: Establish the dynamic explicit calculation and analysis step of the axial tension of the wire rope, set the loads and boundary constraints at both ends of the wire rope, and then perform structural tension numerical simulation to obtain the structural tension numerical simulation results. Step S4: Based on the fracture strain of the wire rope material and the given minimum breaking tensile force of the wire rope, calibrate the yield stress of the wire rope material to complete the calibration of the constitutive parameters of the wire rope material. Step S5: Establish the geometric model of the pressure head and the casing and perform mesh generation, then assemble it with the wire rope structure mesh model to obtain the mesh model of the press assembly. Step S6: Establish the wire rope stamping analysis step and tensile analysis step using the dynamic explicit method. Define the loads and boundary conditions of the indenter, sleeve and wire rope in the stamping analysis step and tensile analysis step respectively. Then, perform a full numerical simulation of the stamping-tensile process on the mesh model of the press-fit assembly to obtain the full numerical simulation results of the stamping-tensile process of the mesh model of the press-fit assembly. Step S7: Based on the numerical simulation results of the entire stamping-tensioning process of the crimped assembly mesh model, evaluate the crimping strength of the wire rope. If the wire rope does not detach from the casing under the maximum design tensile force, it is determined that the crimping strength of the wire rope meets the requirements.

[0020] This invention first establishes a geometric model of the wire rope structure and performs mesh generation; then, it defines the relevant parameters of the material's elastoplastic constitutive model and contact parameters; subsequently, it conducts a tensile numerical simulation of the wire rope based on a dynamic explicit method; the material's elastoplastic parameters are calibrated based on the tensile numerical simulation results; next, it establishes geometric models of the punch and casing and completes the structural assembly; it establishes a punch-tension dynamic explicit analysis calculation step and conducts numerical simulation to realize the interaction between the wire rope and the casing during the entire punch-tension process and the simulation solution of the structural elastoplastic deformation. This invention, by considering the actual winding geometric model of the wire rope, can effectively simulate the interaction between each wire rope during the tensioning process; by calibrating the material's elastoplastic parameters, it can improve the accuracy of the numerical simulation results; it overcomes the deficiency of directly measuring the wire rope crimping strength through experimental methods and can predict the nonlinear deformation characteristics of structures under extreme and harsh operating environments.

[0021] Example This embodiment further illustrates the present invention in detail, specifically including the following steps: Step S1: Based on the actual structural characteristics of wire ropes specified in GB / T9944-2015 standard, a geometric model of the wire rope winding state is established. The nominal diameter of the wire rope is 2mm, the lay length is 7 times the rope diameter, and the rope length is 20mm. To effectively simulate the mutual contact between the wires in the wire rope, the circular cross-sections of the wires are separated during geometric modeling. A preset spacing is set between each wire rope, which is 1% of the rope diameter per strand, to ensure that there is no interference between the wires. This allows for independent meshing of each wire rope. Then, based on the geometric model, the wire rope is meshed to construct a wire rope structural mesh model. The wire rope structural mesh model uses eight-node reduced integral solid elements. The feature length of the cross-section element is 0.05mm, and the feature length of the longitudinal element is 0.2mm. Figure 2 As shown.

[0022] It should be noted that, when meshing the geometric model of the wire rope winding state, in order to accurately capture the stress change gradient, the minimum mesh size calculation formula for the contact area between two adjacent wire ropes is as follows: ; In the formula: This is the minimum grid size for the contact area between two adjacent wire ropes; It is half the width of the contact surface between two adjacent wire ropes; This represents the contact force between two adjacent strands of wire rope. This is the line contact length between two adjacent steel wire ropes; and These are the coefficients of friction of two adjacent steel wire ropes; and These are the elastic moduli of two adjacent steel wire ropes, respectively. and These are the single-strand radii of two adjacent wire ropes. Step S2: Describe the yield and plastic deformation characteristics of the wire rope material using a linearly strengthened ideal elastic-plastic model, and determine the initial yield stress of the wire rope material. The value is 205 MPa, when the element stress exceeds... At this point, the wire rope material yields and begins to produce plastic strain; the fracture strain of the wire rope material... When the value is 0.4, the yield stress increases linearly to the ultimate stress as the plastic strain increases to 0.4. After the plastic strain exceeds 0.4, the yield stress will remain at the ultimate stress. And it no longer changes; the stress-strain relationship of the wire rope material is as follows: Figure 3As shown, the contact between the steel wires inside the steel wire rope is defined, and the contact friction coefficient is taken as 0.15.

[0023] Step S3: Establish the dynamic explicit calculation and analysis step of the axial tension of the wire rope, set the loads and boundary constraints at both ends of the wire rope, complete the structural tension numerical simulation, and obtain the structural tension numerical simulation results, including tensile force, tensile displacement, stress, and strain.

[0024] Step S4: Based on the fracture strain of the wire rope material (0.4t) and the given minimum breaking tensile force of the wire rope (0.3t), the yield stress of the wire rope material is calibrated. During the calibration process, a tensile load is applied to the wire rope in a linearly increasing manner with time. The ultimate yield stress of the wire rope material reaches a maximum of 0.3t in 0.05s and remains constant. After repeated iterative calculations, the ultimate yield stress of the wire rope material is determined. When the value is 3250 MPa, the minimum breaking tensile force requirement is met. The change in wire rope length during the tensile process, obtained from numerical simulation, is shown below. Figure 4 As shown, during the wire rope stretching process, the end tensile force reaches 0.1. 0.5 And 1.0 At that time, the equivalent stress and equivalent plastic strain distribution characteristics of the wire rope are as follows: Figure 5 and Figure 6 As shown.

[0025] Step S5: Establish and mesh the geometric model of the pressure head and casing, then assemble it with the wire rope structure mesh model. Assemble a pressure head and a casing at each end of the wire rope to obtain the mesh model of the press-fit assembly. Due to the geometric symmetry of the press-fit assembly, to improve the efficiency of numerical calculation, this embodiment uses half of the complete press-fit assembly mesh model for subsequent numerical simulation. For example... Figure 7 As shown, the mesh model of the press-fit assembly consists of a wire rope, a casing, and a press head. The casing has a thickness of 1.25 mm, a length of 9 mm, a half-width of 4.35 mm, and an inner diameter of 2.2 mm. The press head has a length of 9 mm and a width of 1.9 mm. Both the casing and the press head use eight-node reduced integral solid elements with an element feature length of 0.25 mm. The material parameters of the casing are the same as those of the wire rope, and a linearly reinforced ideal elastoplastic model is used. The press head is defined as an analytical rigid body, and the friction coefficient between different components is taken as 0.15.

[0026] Step S6: Establish the wire rope stamping analysis step and tensile analysis step using the dynamic explicit method, and define the loads and boundary conditions for the indenter, casing, and wire rope in the stamping and tensile analysis steps, respectively. In the stamping analysis step, displacement constraints are applied only to the two indenters, allowing them to translate only vertically. The maximum stamping force applied by each indenter is... The maximum tensile force is 1.25t. In the tensile analysis step, a tensile force is applied to one end of the wire rope. The load is 0.175t, and a rigid fixing constraint is applied to the end face of the casing on one side along the tensile direction. The time-history loads applied in the two analysis steps are as follows: Figure 8 As shown, based on symmetry, symmetric displacement boundary conditions were applied to the symmetry plane of the shell to complete the numerical simulation of the entire process of stamping-tensioning of the structure. The numerical simulation results of the entire process of stamping-tensioning of the press-fit assembly mesh model were obtained, including indenter displacement, tensile force, tensile displacement, stress, and strain.

[0027] Step S7: Based on the numerical simulation results of the entire pressing-tensioning process of the crimped assembly mesh model, evaluate the crimping strength of the wire rope. According to the design requirements of the wire rope, the wire rope should meet the requirement of being able to withstand the maximum design tensile force. If the wire rope does not detach from the casing under a force of 0.175t, then the crimping strength of the wire rope is deemed to meet the requirements. Figure 9 The variation of longitudinal tensile displacement with tensile force is given. Figure 10 The stress and strain response characteristics of the wire rope and the casing during the stretching process after stamping are given. Under the combined action of extrusion deformation and the constraint of the casing, the inner and outer twists of the wire rope on the left side of the casing undergo relative movement, which causes the outer twist to diffuse and eventually block at the left end of the casing, so that the leftmost end of the wire rope no longer displaces. The calculation results show that the casing after stamping can effectively hold the wire rope and prevent it from being completely pulled out.

[0028] This invention uses numerical simulation to analyze the ultimate tensile strength characteristics of crimped steel wire ropes, enabling effective assessment of the structural safety of steel wire ropes even without relevant testing conditions. This invention considers the complex nonlinear contact between the strands inside the wire rope and between the wire rope and the casing. By using a dynamic explicit integration method, it visually represents the crimping-tensioning process of the wire rope, which can more realistically simulate the mechanical behavior under actual working conditions. This provides a more accurate numerical basis for evaluating the crimping strength of the wire rope. Moreover, it can effectively shorten the calculation cycle and improve design efficiency while ensuring calculation accuracy.

[0029] This invention uses a linearly reinforced ideal elastoplastic model to describe the material constitutive relationship of steel wire ropes, and adopts a constitutive parameter calibration method based on the minimum breaking tensile force of steel wire ropes and the material fracture strain. This method can ensure the accuracy of numerical simulation results according to the specified mechanical indicators even in the absence of measured material constitutive curves.

[0030] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for analyzing the crimping strength of steel wire ropes for electrical connectors based on nonlinear finite element method, characterized in that, Includes the following steps: Step S1: Based on the actual structural characteristics of the wire rope, establish a geometric model of the wire rope winding state and perform mesh generation to obtain the wire rope structure mesh model. Step S2: Determine the fracture strain and contact friction coefficient of the wire rope structure mesh model according to the material grade of the wire rope; Step S3: Establish the dynamic explicit calculation and analysis step of the axial tension of the wire rope, set the loads and boundary constraints at both ends of the wire rope, and then perform structural tension numerical simulation to obtain the structural tension numerical simulation results. Step S4: Based on the fracture strain of the wire rope material and the given minimum breaking tensile force of the wire rope, calibrate the yield stress of the wire rope material to complete the calibration of the constitutive parameters of the wire rope material. Step S5: Establish the geometric model of the pressure head and the casing and perform mesh generation, then assemble it with the wire rope structure mesh model to obtain the mesh model of the press-fit assembly. Step S6: Establish the wire rope stamping analysis step and tensile analysis step using the dynamic explicit method. Define the loads and boundary conditions of the indenter, sleeve and wire rope in the stamping analysis step and tensile analysis step respectively. Then perform numerical simulation of the entire stamping-tensile process on the mesh model of the press-fit assembly to obtain the numerical simulation results of the entire stamping-tensile process of the mesh model of the press-fit assembly. Step S7: Based on the numerical simulation results of the entire stamping-tensioning process of the crimped assembly mesh model, evaluate the crimping strength of the wire rope. If the wire rope does not detach from the casing under the maximum design tensile force, it is determined that the crimping strength of the wire rope meets the requirements.

2. The numerical analysis method for the crimping strength of steel wire rope for electrical connectors according to claim 1, characterized in that, In step S1, in the geometric model of the wire rope winding state, each wire rope has a preset spacing, which is 1% of the diameter of each wire rope.

3. The numerical analysis method for the crimping strength of steel wire rope for electrical connectors according to claim 2, characterized in that, In step S1, when meshing the geometric model of the wire rope winding state, the formula for calculating the minimum mesh size of the contact area between two adjacent wire ropes is: ； In the formula: This is the minimum grid size for the contact area between two adjacent wire ropes; It is half the width of the contact surface between two adjacent wire ropes; This represents the contact force between two adjacent strands of wire rope. This is the line contact length between two adjacent steel wire ropes; and These are the coefficients of friction of two adjacent steel wire ropes; and These are the elastic moduli of two adjacent steel wire ropes, respectively. and These are the individual rope radii of two adjacent steel wire ropes.

4. The numerical analysis method for the crimping strength of steel wire rope for electrical connectors according to claim 3, characterized in that, In step S2, a linearly reinforced ideal elastoplastic model is used to describe the yield and plastic deformation characteristics of the wire rope material.

5. The numerical analysis method for the crimping strength of steel wire rope for electrical connectors according to claim 4, characterized in that, In step S4, based on the fracture strain of the wire rope material and the given minimum breaking tensile force of the wire rope, and combined with the axial tensile numerical simulation results, the elastic-plastic parameters of the wire rope are calibrated. By iteratively modifying the value of the ultimate stress of the wire rope, the maximum strain of the wire rope reaches the fracture strain when the tensile force applied to the wire rope reaches the given minimum breaking tensile force.

6. The numerical analysis method for the crimping strength of steel wire rope for electrical connectors according to claim 5, characterized in that, In step S6, a dynamic explicit method is used to perform a full-process numerical simulation of the stamping and stretching of the mesh model of the crimped assembly. In the stamping analysis step, displacement constraints are applied to the two pressure heads, allowing them to only translate vertically, and a linearly increasing stamping force is applied to each pressure head. In the stretching analysis step, a specified tensile force is applied to one end of the wire rope, and a rigid fixing constraint is applied to the end face of the sleeve on one side along the stretching direction. Based on the tensile deformation state of the wire rope obtained from the numerical simulation, it is determined whether the crimping strength of the sleeve to the wire rope meets the requirements.

7. The numerical analysis method for the crimping strength of steel wire rope for electrical connectors according to claim 1, characterized in that, The material properties of the steel wire rope include density, elastic modulus, Poisson's ratio, and yield stress.

8. The numerical analysis method for the crimping strength of steel wire rope for electrical connectors according to claim 1, characterized in that, The numerical simulation results of the structural tension include tensile force, tensile displacement, tensile stress, and strain.

9. The numerical analysis method for the crimping strength of steel wire rope for electrical connectors according to claim 1, characterized in that, The numerical simulation results of the entire stamping-stretching process include indenter displacement, tensile force, tensile displacement, stress, and strain.

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