Simulation method and system for influence of interface pressure of prefabricated cable intermediate joint on ultrasonic non-linear parameters

Abstract

The invention discloses a method and a system for simulating influence of interface pressure of a prefabricated cable intermediate joint on ultrasonic non-linear parameters. The simulation method comprises the following steps: establishing a two-dimensional simulation solid mechanics geometric model; setting material parameters of the solid mechanical geometric model; setting boundary conditions of the solid mechanical geometric model; a solid mechanical geometric model and setting of material parameters and boundary conditions are utilized, and a steady-state mechanical analysis mode is adopted to conduct contact stress simulation under different stress conditions; importing the solid mechanical geometric model subjected to stress simulation into a sound field coupling model, coupling a solid mechanical physical field and an electrostatic physical field in a sound field, and performing ultrasonic signal simulation; and in combination with the actual state of the prefabricated cable intermediate joint, carrying out simulation calculation on the influence of different interface pressures on ultrasonic non-linear parameters. The accurate value of the interfacial pressure can be obtained by analyzing the nonlinear parameters of the echo signals.

Description

Technical Field

[0001] The invention belongs to the technical field of interface pressure of prefabricated cable intermediate joints, and in particular to a simulation method and system for the influence of interface pressure of prefabricated cable intermediate joints on ultrasonic nonlinear parameters. Background Art

[0002] Electric field distribution and interface pressure are the core elements of the insulation structure design of high-voltage cable accessories (such as cable intermediate joints). The interface pressure between the field strength control element and the cable insulator plays a decisive role in the insulation characteristics of the cable accessories (breakdown strength, partial discharge, etc.). The interface pressure is achieved through the interference fit between the cable accessories and the insulation layer of the cable body. If the interface pressure is too small, it cannot meet the electrical strength requirements of the cable accessories, and it is easy to produce air gaps and cavities, causing the cable accessories to break along the interface; if the interface pressure is too large, it will make the cable accessories difficult to install. Installation under interference fit will cause the cable accessories to crack and break, and after a period of operation, it is easy to cause stress relaxation. Summary of the invention

[0003] The technical problem to be solved by the present invention is to overcome the above-mentioned existing technical problems and provide a simulation method and system for the influence of the interface pressure of a prefabricated cable intermediate joint on ultrasonic nonlinear parameters. The method analyzes the accurate value of the interface pressure through the nonlinear parameters of the echo signal, and provides a reference basis for the safety quality inspection of the cable intermediate joint installation, the factory interface pressure test of the cable intermediate joint, and the operation and maintenance of the cable intermediate joint in operation.

[0004] To this end, the present invention adopts the following technical solution.

[0005] In a first aspect, the present invention provides a method for simulating the influence of interface pressure of a prefabricated cable intermediate joint on ultrasonic nonlinear parameters, which comprises: Based on the surface roughness measurement of the prefabricated cable intermediate joint and the cable body, a two-dimensional simulation solid mechanics geometric model is established according to the internal structure of the prefabricated cable intermediate joint; Set material parameters for solid mechanics geometry models; Set boundary conditions for solid mechanics geometry models; Using the solid mechanics geometric model and the setting of material parameters and boundary conditions, the steady-state mechanics analysis mode is used to simulate the contact stress under different stress conditions; The solid mechanics geometry model after stress simulation is imported into the acoustic field coupling model, and the solid mechanics physical field and the electrostatic physical field are coupled in the acoustic field to simulate the ultrasonic signal; The ultrasonic echo signal result under a certain pressure is obtained through ultrasonic signal simulation calculation, and the fundamental and harmonic amplitudes are obtained by fast Fourier transform of the echo signal. The ultrasonic nonlinear parameter value under the pressure is calculated to obtain the corresponding relationship between the ultrasonic nonlinear parameter and the pressure. Combined with the actual state of the prefabricated cable intermediate joint, the simulation calculation of the influence of different interface pressures on the ultrasonic nonlinear parameters is carried out.

[0006] Furthermore, the solid mechanics geometric model includes a silicone rubber geometric model, a semi-conductive silicone rubber geometric model and a cross-linked polyethylene geometric model connected in sequence. The contact surface between the semi-conductive silicone rubber geometric model and the cross-linked polyethylene geometric model is a rough contact interface. The model corresponding to the rough contact interface is a contact interface roughness geometric model. The contact interface roughness obeys the measurement results of the roughness of the surface of the prefabricated cable intermediate joint and the surface of the cable body. The material parameters of the solid mechanics geometric model include the Yeoh model parameters of silicone rubber, the Yeoh model parameters of the semi-conductive silicone rubber, and the density, Young's modulus and Poisson's ratio of cross-linked polyethylene.

[0007] Furthermore, the boundary conditions of the solid mechanics geometric model are set as follows: the lower interface of the semi-conductive silicone rubber geometric model is set as the upper rough contact interface, and the upper interface of the cross-linked polyethylene geometric model is set as the lower rough contact interface. A contact pair is formed by the upper and lower rough contact interfaces. A fixed constraint boundary condition is set on the lower surface of the cross-linked polyethylene geometric model, and a specified load is added to the upper surface of the silicone rubber geometric model to generate pressure on the contact interface.

[0008] Furthermore, when simulating ultrasonic signals, the solid mechanics geometric model after being subjected to force is used as the basic model for transient analysis of acoustic field simulation. An electrostatic material geometric model is added to the upper surface of the solid mechanics geometric model. An excitation potential is set at the lower boundary of the electrostatic material geometric model to simulate the excitation signal generated by the probe. The electrostatic physical field action domain is the electrostatic material geometric model.

[0009] Furthermore, the scope of the solid mechanics physical field is the entire solid mechanics geometric model and the electrostatic material geometric model. The lower boundary of the electrostatic material geometric model is set as a low reflection or zero reflection boundary, and both sides of the solid mechanics geometric model are set as low reflection or zero reflection boundaries.

[0010] Furthermore, when simulating ultrasonic signals, the mesh sizes of the electrostatic material, silicone rubber, semi-conductive silicone rubber and cross-linked polyethylene are set to be between 1 / 20 and 1 / 10 of the ultrasonic wave length.

[0011] Furthermore, the time step of the transient analysis of the acoustic field simulation is set to 1 / 20 of the second harmonic frequency of the measured echo signal.

[0012] Furthermore, a boundary probe is arranged on the lower surface of the electrostatic material geometric model, and the integral value of the detection signal on the lower surface of the electrostatic material geometric model is taken to calculate the echo signal diagram under a certain interface pressure.

[0013] Furthermore, the echo signal graph under a certain interface pressure is subjected to a fast Fourier transform, and the nonlinear parameters of the echo signal graph are analyzed. , and its calculation formula is: , Wherein, A2 is the second harmonic amplitude of the echo signal diagram after fast Fourier transform, and A1 is the first harmonic amplitude of the echo signal diagram after fast Fourier transform.

[0014] In a second aspect, the present invention provides a simulation system for the influence of the interface pressure of a prefabricated cable intermediate joint on ultrasonic nonlinear parameters, which comprises: Solid mechanics geometric model building unit: Based on the surface roughness measurement of the prefabricated cable intermediate joint and the cable body, a two-dimensional simulation solid mechanics geometric model is established according to the internal structure of the prefabricated cable intermediate joint; Material parameter setting unit: set the material parameters of the solid mechanics geometric model; Boundary condition setting unit: setting boundary conditions of solid mechanics geometric model; Contact stress simulation unit: using the solid mechanics geometric model and the setting of material parameters and boundary conditions, the steady-state mechanics analysis mode is used to simulate the contact stress under different stress conditions; Ultrasonic signal simulation unit: import the solid mechanics geometry model after stress simulation into the acoustic field coupling model, and use the solid mechanics physical field and electrostatic physical field coupling in the acoustic field to simulate the ultrasonic signal; Simulation calculation unit: The ultrasonic echo signal result under a certain pressure is obtained through ultrasonic signal simulation calculation, the fundamental and harmonic amplitudes are obtained by fast Fourier transform of the echo signal, and the ultrasonic nonlinear parameter value under the pressure is calculated to obtain the corresponding relationship between the ultrasonic nonlinear parameter and the pressure; combined with the actual state of the prefabricated cable intermediate joint, the simulation calculation of the influence of different interface pressures on the ultrasonic nonlinear parameters is carried out.

[0015] The beneficial effects of the present invention are as follows: The present invention can analyze the propagation law of ultrasound in the cable intermediate joint, and can detect the interface pressure values ​​of the cable intermediate joint under different interference amounts by means of simulation; the present invention makes up for the shortcomings of the existing cable intermediate joint that the interface pressure cannot be detected and the propagation law of ultrasound in the cable intermediate joint cannot be analyzed, and realizes the accurate detection of the interface pressure of the high-voltage cable intermediate joint, providing a reference basis for the safety quality inspection of the cable intermediate joint installation, the factory interface pressure test of the cable intermediate joint and the operation and maintenance of the cable intermediate joint in operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a flow chart of a simulation method for the influence of the interface pressure of a prefabricated cable intermediate joint on ultrasonic nonlinear parameters of the present invention; Figure 2 The rough morphology of the contact interface of the present invention, (a) is the rough morphology of the silicone rubber surface of the cable intermediate joint, (b) is the rough morphology of the cross-linked polyethylene surface; Figure 3 It is a solid mechanics geometric model diagram of the present invention; Figure 4 It is a geometric model diagram of the contact interface roughness of the present invention; Figure 5 It is a geometric model diagram of the sound field of the present invention; Figure 6 It is an interface pressure result diagram of a two-dimensional cross section of stress results calculated under solid mechanics simulation analysis conditions of the present invention; Figure 7 It is an ultrasonic primary echo signal diagram of the boundary probe detection interface in the sound field simulation analysis of the present invention; Figure 8 It is a structural diagram of a simulation system for the influence of interface pressure of a prefabricated cable intermediate joint on ultrasonic nonlinear parameters of the present invention. DETAILED DESCRIPTION

[0017] In order to facilitate the understanding of the present invention, the present invention is described in more detail below in conjunction with the accompanying drawings and specific embodiments. Preferred embodiments of the present invention are provided in the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0018] It should be noted that, unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0019] This embodiment provides a simulation method for the influence of the interface pressure of a prefabricated cable intermediate joint on ultrasonic nonlinear parameters. Figure 1 As shown, the steps are as follows: 1) Based on the surface roughness measurement of the prefabricated cable intermediate joint and the cable body, a two-dimensional simulation solid mechanics geometric model is established according to the internal structure of the prefabricated cable intermediate joint. The surface roughness of silicone rubber and cross-linked polyethylene was measured based on white light interferometry test. Figure 2 As shown. Figure 2, randomly select a curve in the x direction to measure its average surface roughness, the average surface roughness of prefabricated insulating silicone rubber and cross-linked polyethylene are 2.19μm and 2.453μm, respectively, and the peak values ​​of micro-convex bodies are 32.305μm and 136.42μm, respectively. A series of rough points that obey Gaussian probability distribution are generated by MATLAB and imported into the COMSO simulation software to form a two-dimensional interface line of rough distribution.

[0020] like Figure 3 The solid mechanics geometric model is composed of a silicone rubber geometric model 1, a semi-conductive silicone rubber geometric model 2 and a cross-linked polyethylene geometric model 3 which are connected in sequence. The silicone rubber geometric model 1 is a 8mm×25mm rectangle, the semi-conductive silicone rubber geometric model 2 is a 8mm×20mm rectangle, and the cross-linked polyethylene geometric model 3 is a 8mm×10mm rectangle.

[0021] The contact surface between the semi-conductive silicone rubber geometric model 2 and the cross-linked polyethylene geometric model 3 is a rough contact interface, and the corresponding model is the contact interface roughness geometric model, see Figure 4 .

[0022] 2) Set the material parameters of the solid mechanics geometry model Customize material parameters, add empty materials, and obtain Yeoh model parameters according to the stress-strain test fitting of the prefabricated cable intermediate joint material. Set the material parameters of silicone rubber geometry model 1 to the Yeoh geometry model silicone rubber parameters, the material parameters of semi-conductive silicone rubber geometry model geometry 2 to the Yeoh geometry model semi-conductive silicone rubber parameters, and the material parameters of cross-linked polyethylene geometry model 3 to the density, Young's modulus and Poisson's ratio of cross-linked polyethylene.

[0023] For specific parameters, please see Table 1.

[0024] Table 1

[0025] 3) Set the boundary conditions of the solid mechanics geometry model The lower interface of the semi-conductive silicone rubber geometric model is set as the upper rough contact interface, and the upper interface of the cross-linked polyethylene geometric model is set as the lower rough contact interface. A contact pair is formed by the upper and lower rough contact interfaces. A fixed constraint boundary condition is set on the lower surface of the cross-linked polyethylene geometric model, and a specified load is added to the upper surface of the silicone rubber geometric model to generate pressure on the contact interface.

[0026] 4) Set up the simulation grid In finite element simulation calculations, the solution area needs to be divided into a finite number of independent grids, each grid is non-repetitive, and the grids are connected through boundary nodes. The stress of each grid unit can be solved in series through displacement interpolation functions and functional principles. If the grid size is too large or too small, it will affect the simulation results and greatly affect the stability and accuracy of the numerical solution process. If the model grid size is too small, it will not affect the accuracy of the simulation results, but the solution time will be greatly increased, affecting the simulation efficiency; if the model grid size is too large, it will not be able to effectively simulate the characteristics of the simulation model, and it will not be able to effectively analyze the ultrasonic wavelength, which will cause the solution process to not converge or the solution results to be inaccurate. In the stress steady-state analysis mode, the grid is set to a standard grid.

[0027] 5) Using the solid mechanics geometric model and the above-mentioned setting conditions, the steady-state mechanics analysis mode is used to simulate the contact stress under different stress conditions.

[0028] 6) Add a 2D cross-section line to the data set of the simulation results. The position of the 2D cross-section line is the position of the rough contact interface (the length is 8mm and the height is set to 10mm). Add a 1D plot group to the simulation results. Select the 2D cross-section line as the data set of the 1D plot group. The calculated interface pressure result is as follows: Figure 6 shown.

[0029] 7) Simulation of ultrasonic field (solid mechanics and electrostatic coupling) The solid mechanics geometry model after force is used as the basic geometry model for transient analysis of acoustic field simulation (such as Figure 5 As shown), add and import the solid mechanics geometry model, import the solid mechanics geometry model into the acoustic field coupling model, use solid mechanics and electrostatic physics field coupling in the acoustic field, the solid mechanics physics field scope is the entire geometry model, the electrostatic physics field scope is the electrostatic material geometry model 4, the electrostatic material geometry model 4 is a 2mm×2mm rectangle, select PZT-5A from the software material library, set the excitation potential at the lower boundary of the electrostatic material to simulate the probe to generate an excitation signal, and the excitation signal is set to a sinusoidal signal modulated by the Hanning window A is the excitation signal amplitude, which is set to 300; f0 is the excitation signal frequency, which is set to 1.5MHz; both sides of the geometric model are set to low reflection or zero reflection boundaries to reduce interference with the echo signal. Figure 5 In the figure, the lower boundary condition of the electrostatic material geometry model 4 is set to a low reflection or zero reflection boundary.

[0030] 8) Divide the ultrasonic field simulation grid In the physical field simulation of the coupling of acoustic field and electrostatic field, in order to ensure the calculation accuracy and to minimize the amount of calculation of finite element simulation of ultrasonic propagation process, a highly adaptable free triangle network is used to divide the simulation model, and the grid size is set between 1 / 20 and 1 / 10 of the ultrasonic length, usually 1 / 16 of the wavelength. The maximum unit of the electrostatic material grid is set to 1.33×10 -4 m, the silicone rubber grid was set to 5.635 × 10 -5 m, the semi-conductive silicone rubber grid is set to 6.646 × 10 -5 m, the cross-linked polyethylene grid was set to 1.137 × 10 -4 m.

[0031] 9) Ultrasonic field simulation calculation The time step of ultrasonic transient analysis is set to 1 / 20 of the second harmonic frequency of the measured echo signal, that is, the time step is set to 2.5×10 -8 s, and the transient analysis time is set to the total time after the ultrasonic wave passes through the entire interface and is reflected as 1.01×10 -4 s.

[0032] 10) Set a boundary probe, the boundary probe position is the lower surface of the electrostatic material; add a probe drawing group to the data set of the simulation result, and the probe drawing group displays the ultrasonic echo signal, that is, the echo signal diagram under the interface pressure (such as Figure 7 as shown).

[0033] 11) Perform fast Fourier transform (FFT) on the echo signal measured under a certain interface pressure, and analyze the nonlinear parameters of the echo signal. The accurate value of the interface pressure is obtained through the analysis of the nonlinear parameters of the echo signal.

[0034] The calculation formula of nonlinear parameters is: , Among them, A2 is the second harmonic amplitude of the echo signal after FFT transformation, and A1 is the first harmonic amplitude.

[0035] Combined with the actual state of the prefabricated cable intermediate joint, simulation calculations of the influence of different interface pressures on ultrasonic nonlinear parameters were carried out.

[0036] This embodiment also provides a simulation system for the influence of the interface pressure of a prefabricated cable intermediate joint on ultrasonic nonlinear parameters. Figure 8 As shown, it includes: Solid mechanics geometric model building unit: Based on the surface roughness measurement of the prefabricated cable intermediate joint and the cable body, a two-dimensional simulation solid mechanics geometric model is established according to the internal structure of the prefabricated cable intermediate joint; Material parameter setting unit: set the material parameters of the solid mechanics geometric model; Boundary condition setting unit: setting boundary conditions of solid mechanics geometric model; Contact stress simulation unit: using the solid mechanics geometry model and the above settings, the steady-state mechanics analysis mode is used to simulate the contact stress under different stress conditions; Ultrasonic signal simulation unit: import the solid mechanics geometric model after force into the acoustic field coupling model, and use the solid mechanics physical field and electrostatic physical field coupling in the acoustic field to simulate the ultrasonic signal; Simulation calculation unit: The ultrasonic echo signal result under a certain pressure is obtained through ultrasonic signal simulation calculation, the fundamental and harmonic amplitudes are obtained by fast Fourier transform of the echo signal, and the ultrasonic nonlinear parameter value under the pressure is calculated to obtain the corresponding relationship between the ultrasonic nonlinear parameter and the pressure; combined with the actual state of the prefabricated cable intermediate joint, the simulation calculation of the influence of different interface pressures on the ultrasonic nonlinear parameters is carried out.

[0037] It should be noted that each unit in the above-mentioned simulation system of the influence of the interface pressure of the prefabricated cable intermediate joint on the ultrasonic nonlinear parameters can be fully or partially realized by software, hardware and their combination. The above-mentioned units can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above-mentioned modules. For the specific definition of the simulation system of the influence of the interface pressure of the prefabricated cable intermediate joint on the ultrasonic nonlinear parameters, please refer to the definition of the simulation method of the influence of the interface pressure of the prefabricated cable intermediate joint on the ultrasonic nonlinear parameters in the above text. The two have the same functions and effects, which will not be repeated here.

[0038] The above examples should be understood as being only used to illustrate the technical solutions of the present invention and not to limit the present invention. After reading the contents of the present invention, ordinary technicians in the field can still make various modifications or equivalent substitutions to the technical solutions of the present invention. These equivalent changes and modifications also fall within the scope defined by the claims of the present invention.

Claims

1. A simulation method for the influence of interface pressure of a prefabricated cable intermediate joint on ultrasonic nonlinear parameters, characterized in that: include: Based on the surface roughness measurement of the prefabricated cable intermediate joint and the cable body, a two-dimensional simulation solid mechanics geometric model is established according to the internal structure of the prefabricated cable intermediate joint; Set material parameters for solid mechanics geometry models; Set boundary conditions for solid mechanics geometry models; Using the solid mechanics geometric model and the setting of material parameters and boundary conditions, the steady-state mechanics analysis mode is used to simulate the contact stress under different stress conditions; The solid mechanics geometry model after stress simulation is imported into the acoustic field coupling model, and the solid mechanics physical field and the electrostatic physical field are coupled in the acoustic field to simulate the ultrasonic signal; The ultrasonic echo signal result under a certain pressure is obtained by ultrasonic signal simulation calculation, the echo signal is subjected to fast Fourier transform to obtain the fundamental wave and harmonic wave amplitudes, and the ultrasonic nonlinear parameter value under the pressure is calculated to obtain the corresponding relationship between the ultrasonic nonlinear parameter and the pressure; Combined with the actual state of the prefabricated cable intermediate joint, simulation calculations of the influence of different interface pressures on ultrasonic nonlinear parameters were carried out.

2. The simulation method according to claim 1, characterized in that: The solid mechanics geometric model includes a silicone rubber geometric model, a semi-conductive silicone rubber geometric model and a cross-linked polyethylene geometric model connected in sequence, the contact surface between the semi-conductive silicone rubber geometric model and the cross-linked polyethylene geometric model is a rough contact interface, the model corresponding to the rough contact interface is a contact interface roughness geometric model, and the contact interface roughness is subject to the measurement results of the roughness of the prefabricated cable intermediate joint surface and the cable body surface; The material parameters of the solid mechanics geometric model include Yeoh model parameters of silicone rubber, Yeoh model parameters of semi-conductive silicone rubber, density, Young's modulus and Poisson's ratio of cross-linked polyethylene.

3. The simulation method according to claim 2, characterized in that: The boundary conditions of the solid mechanics geometric model are set as follows: the lower interface of the semi-conductive silicone rubber geometric model is set as the upper rough contact interface, and the upper interface of the cross-linked polyethylene geometric model is set as the lower rough contact interface. The upper and lower rough contact interfaces form a contact pair. A fixed constraint boundary condition is set on the lower surface of the cross-linked polyethylene geometric model, and a specified load is added to the upper surface of the silicone rubber geometric model to generate pressure on the contact interface.

4. The simulation method according to claim 2, characterized in that: When simulating ultrasonic signals, the solid mechanics geometric model after being subjected to force is used as the basic model for transient analysis of acoustic field simulation. An electrostatic material geometric model is added to the upper surface of the solid mechanics geometric model. An excitation potential is set at the lower boundary of the electrostatic material geometric model to simulate the excitation signal generated by the probe. The electrostatic physical field domain is the electrostatic material geometric model.

5. The simulation method according to claim 4, characterized in that: The scope of the solid mechanics physical field is the entire solid mechanics geometric model and the electrostatic material geometric model. The lower boundary of the electrostatic material geometric model is set as a low reflection or zero reflection boundary, and both sides of the solid mechanics geometric model are set as low reflection or zero reflection boundaries.

6. The simulation method according to claim 4, characterized in that: When simulating ultrasonic signals, the mesh sizes of the electrostatic material, silicone rubber, semi-conductive silicone rubber and cross-linked polyethylene are set to between 1 / 20 and 1 / 10 of the ultrasonic wave length.

7. The simulation method according to claim 4, characterized in that: The time step of transient analysis of acoustic field simulation is set to 1 / 20 of the second harmonic frequency of the measured echo signal.

8. The simulation method according to claim 4, characterized in that: A boundary probe is set on the lower surface of the electrostatic material geometric model, the integral value of the detection signal on the lower surface of the electrostatic material geometric model is taken, and the echo signal diagram under a certain interface pressure is calculated.

9. The simulation method according to claim 8, characterized in that: Perform fast Fourier transform on the echo signal graph under a certain interface pressure and analyze the nonlinear parameters of the echo signal graph , and its calculation formula is: , Wherein, A2 is the second harmonic amplitude of the echo signal diagram after fast Fourier transform, and A1 is the first harmonic amplitude of the echo signal diagram after fast Fourier transform.

10. A simulation system for the influence of interface pressure of prefabricated cable intermediate joint on ultrasonic nonlinear parameters, characterized in that: include: Solid mechanics geometric model building unit: Based on the surface roughness measurement of the prefabricated cable intermediate joint and the cable body, a two-dimensional simulation solid mechanics geometric model is established according to the internal structure of the prefabricated cable intermediate joint; Material parameter setting unit: set the material parameters of the solid mechanics geometric model; Boundary condition setting unit: setting boundary conditions of solid mechanics geometric model; Contact stress simulation unit: using the solid mechanics geometric model and the setting of material parameters and boundary conditions, the steady-state mechanics analysis mode is used to simulate the contact stress under different stress conditions; Ultrasonic signal simulation unit: import the solid mechanics geometry model after stress simulation into the acoustic field coupling model, and use the solid mechanics physical field and electrostatic physical field coupling in the acoustic field to simulate the ultrasonic signal; Simulation calculation unit: The ultrasonic echo signal result under a certain pressure is obtained through ultrasonic signal simulation calculation, the fundamental and harmonic amplitudes are obtained by fast Fourier transform of the echo signal, and the ultrasonic nonlinear parameter value under the pressure is calculated to obtain the corresponding relationship between the ultrasonic nonlinear parameter and the pressure; combined with the actual state of the prefabricated cable intermediate joint, the simulation calculation of the influence of different interface pressures on the ultrasonic nonlinear parameters is carried out.

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