Insulation silicone rubber thermal aging state detection method, device and equipment based on cable accessory

Abstract

The invention relates to a cable accessory-based insulation silicone rubber thermal aging state detection method, apparatus and device. The method comprises the steps of obtaining a correlation model and a to-be-detected sample; transmitting ultrasonic waves to the to-be-detected sample for aging test to obtain a primary echo time domain signal; processing the primary echo time domain signal to obtain a spectrogram, and extracting a fundamental wave amplitude and a second harmonic amplitude from the spectrogram; calculating a relative nonlinear coefficient according to the fundamental wave amplitude and the second harmonic amplitude; and inputting the relative nonlinear coefficient into the correlation model for analysis to obtain the thermal aging degree. The method comprises the following steps: transmitting and receiving ultrasonic waves to and from a sample to be detected to obtain a primary echo time-domain signal, processing the primary echo time-domain signal to obtain a relative nonlinear coefficient, and inputting the relative nonlinear coefficient into a correlation model to analyze and evaluate the thermal aging degree of the identified thermal aging state of the sample to be detected. The microstructure change of the to-be-detected sample caused by thermal aging can be accurately captured, and the thermal aging state can be accurately evaluated.

Description

Technical Field

[0001] The present application relates to the technical field of aging detection, and in particular to a method, device and equipment for detecting the thermal aging state of insulating silicone rubber based on cable accessories. Background Art

[0002] With the high-quality development of the economy and society and the in-depth advancement of urbanization, power cables are gradually replacing overhead lines and becoming the main power supply method for urban power grids due to their low operation and maintenance costs and low operation failure rate. Cable accessories, as an important part of power cables, play a role of connection and transition in power transmission, and their reliability is the key to the safe operation of power systems. Silicone rubber is widely used as the main insulating material for cable accessories due to its excellent mechanical, thermal and electrical properties. During the actual operation of the cable, the temperature at the conductor of the intermediate cable accessories is much higher than the temperature at the conductor of the cable body, and long-term high temperature environment will accelerate the aging of silicone rubber, resulting in a decline in its various performances, and ultimately causing cable line operation failures.

[0003] At present, the evaluation methods for aging damage of silicone rubber insulation include sample analysis method and non-destructive testing method. Sample analysis method includes tensile test method, dielectric property test method, Fourier infrared spectroscopy test method, etc. The sample analysis method requires extracting some materials from the sample for analysis, which is a destructive test and will cause irreversible damage to the test sample. Non-destructive testing methods include ultrasonic testing technology, X-ray testing technology, etc. Among them, compared with other non-destructive testing methods that can be applied to non-metallic materials, ultrasonic testing technology is harmless to the human body and does not pollute the surface of the test sample. It is used in defect detection of electrical insulation materials to a certain extent.

[0004] Traditional ultrasonic nondestructive testing technology is mainly based on the principle of linear reflection and scattering when sound waves propagate in materials. Although traditional ultrasonic nondestructive testing technology can detect some defects, it can usually only detect linear defects in materials, such as cracks, delamination, etc. In addition, traditional ultrasonic nondestructive testing technology has high requirements on the surface state of the material. If there is roughness or oxide layer on the surface of the material, it may affect the propagation and reflection of ultrasonic waves, thereby affecting the accuracy of the test results. For specimens with complex shapes or irregular shapes, traditional ultrasonic nondestructive testing technology may encounter difficulties during detection, such as because the propagation path of the ultrasonic wave may be affected by the shape of the specimen, resulting in the inability to accurately obtain defect information. Summary of the invention

[0005] The present application provides a method, device and equipment for detecting the thermal aging state of insulating silicone rubber based on cable accessories, which is used to solve the technical problem that the traditional ultrasonic non-destructive testing technology is used to test the insulation aging damage of materials, and the ultrasonic wave will be affected by the surface of the material, resulting in inaccurate test results.

[0006] In order to achieve the above objectives, this application provides the following technical solutions:

[0007] On the one hand, a method for detecting thermal aging state of insulating silicone rubber based on cable accessories is provided, comprising the following steps:

[0008] S1. Obtaining the correlation model between the relative nonlinear coefficient and the degree of thermal aging and the sample to be tested;

[0009] S2. The sample to be tested is subjected to an aging test by transmitting an ultrasonic wave to obtain a time domain signal of an echo consisting of a reflected ultrasonic wave signal;

[0010] S3. Processing the time domain signal of the primary echo to obtain a spectrum diagram including a fundamental frequency band and a second harmonic frequency band, and extracting the fundamental amplitude and the second harmonic amplitude from the spectrum diagram;

[0011] S4. Calculate the relative nonlinear coefficient based on the fundamental amplitude and the second harmonic amplitude;

[0012] S5. Input the relative nonlinear coefficient into the correlation model for analysis to obtain the degree of thermal aging corresponding to the sample to be tested.

[0013] Preferably, calculating according to the fundamental wave amplitude and the second harmonic amplitude to obtain the relative nonlinear coefficient includes: calculating the fundamental wave amplitude to obtain first data; and calculating the second harmonic amplitude and the first data to obtain the relative nonlinear coefficient.

[0014] Preferably, emitting ultrasonic waves to the sample to be tested for aging test, and obtaining a time-domain echo signal composed of reflected ultrasonic signals includes: using nonlinear ultrasonic testing equipment to emit ultrasonic waves to the sample to be tested for aging test, and obtaining a time-domain echo signal composed of reflected ultrasonic signals.

[0015] Preferably, the insulating silicone rubber thermal aging state detection method based on cable accessories includes: the nonlinear ultrasonic detection equipment uses a pulse reflection method and transmits ultrasonic waves to the sample to be detected through a probe, and the probe and the sample to be detected are coated with an ultrasonic flaw detection coupling agent.

[0016] Preferably, processing the first echo time domain signal to obtain a spectrum diagram including a fundamental frequency band and a second harmonic frequency band comprises: processing the first echo time domain signal using a fast Fourier transform to obtain a spectrum diagram including a fundamental frequency band and a second harmonic frequency band.

[0017] Preferably, obtaining a correlation model between the relative nonlinear coefficient and the degree of thermal aging includes:

[0018] Processing each of the sample pieces using steps S2 to S4 to obtain a relative nonlinear coefficient of the sample corresponding to each of the sample pieces;

[0019] Normalizing the relative nonlinear coefficients of all the samples to obtain corresponding fitting data;

[0020] An error bar scatter plot is constructed according to all the fitting data and the corresponding heat aging degree, and linear fitting is performed on all the fitting data on the error bar scatter plot to obtain a fitting curve and use the fitting curve as the correlation model.

[0021] In yet another aspect, there is provided an insulating silicone rubber thermal aging state detection device based on cable accessories, comprising a model and sample acquisition module, a test module, a signal processing module, a calculation module and an analysis module;

[0022] The model and sample acquisition module is used to obtain the correlation model between the relative nonlinear coefficient and the thermal aging degree and the sample to be tested;

[0023] The testing module is used to transmit ultrasonic waves to the sample to be tested to perform an aging test, and obtain a primary echo time domain signal composed of a reflected ultrasonic signal;

[0024] The signal processing module is used to process the primary echo time domain signal to obtain a frequency spectrum including a fundamental frequency band and a second harmonic frequency band, and extract the fundamental amplitude and the second harmonic amplitude from the frequency spectrum;

[0025] The calculation module is used to calculate the relative nonlinear coefficient according to the fundamental wave amplitude and the second harmonic amplitude;

[0026] The analysis module is used to input the relative nonlinear coefficient into the correlation model for analysis to obtain the thermal aging degree corresponding to the sample to be tested.

[0027] Preferably, the calculation module is further used to calculate the fundamental wave amplitude to obtain first data; and calculate the second harmonic amplitude and the first data to obtain a relative nonlinear coefficient.

[0028] Preferably, the test module is also used to use nonlinear ultrasonic detection equipment to emit ultrasonic waves to the sample to be tested for aging test, and obtain a single echo time domain signal composed of reflected ultrasonic signals; wherein the nonlinear ultrasonic detection equipment uses a pulse reflection method and emits ultrasonic waves to the sample to be tested through a probe, and both the probe and the sample to be tested are coated with ultrasonic flaw detection coupling agent.

[0029] In another aspect, a terminal device is provided, comprising a processor and a memory;

[0030] The memory is used to store program codes and transmit the program codes to the processor;

[0031] The processor is used to execute the above-mentioned method for detecting the thermal aging state of insulating silicone rubber based on cable accessories according to the instructions in the program code.

[0032] The insulating silicone rubber thermal aging state detection method, device and equipment based on cable accessories, the insulating silicone rubber thermal aging state detection method based on cable accessories comprises obtaining a correlation model between a relative nonlinear coefficient and a thermal aging degree and a sample to be detected; transmitting ultrasonic waves to the sample to be detected for aging test, and obtaining a first echo time domain signal composed of a reflected ultrasonic wave signal; processing the first echo time domain signal to obtain a spectrum diagram including a fundamental frequency band and a second harmonic frequency band, and extracting the fundamental amplitude and the second harmonic amplitude from the spectrum diagram; calculating according to the fundamental amplitude and the second harmonic amplitude to obtain a relative nonlinear coefficient; inputting the relative nonlinear coefficient into the correlation model for analysis, and obtaining a thermal aging degree corresponding to the sample to be detected.

[0033] It can be seen from the above technical scheme that the present application has the following advantages: the insulating silicone rubber thermal aging state detection method based on cable accessories obtains an echo time domain signal by emitting and receiving ultrasonic waves to the sample to be detected, and then processes the echo time domain signal to obtain the relative nonlinear coefficient of the ultrasonic wave, and inputs the relative nonlinear coefficient into the correlation model to analyze and evaluate the degree of thermal aging of the sample to be detected to identify the thermal aging state, so that the microstructural changes caused by thermal aging of the sample to be detected can be sensitively and accurately captured, thereby achieving accurate evaluation of the thermal aging state; it solves the technical problem of inaccurate detection results caused by the influence of the surface of the material on the insulation aging damage test of the material by the traditional ultrasonic nondestructive testing technology.

[0034] The insulating silicone rubber thermal aging state detection device based on cable accessories realizes thermal aging detection of the sample to be detected by using nonlinear ultrasonic detection technology through a model and sample acquisition module, a test module, a signal processing module, a calculation module and an analysis module. The nonlinear effect generated by the interaction between the sound waves of the nonlinear ultrasonic detection technology and the microstructure of the sample to be detected during the propagation process can detect nonlinear defects that are closely related to the microstructure and performance changes of the material. The relative nonlinear coefficient is used to effectively characterize the microstructural changes of the sample to be detected, thereby evaluating the thermal aging damage of the sample to be detected. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0036] Figure 1 This is a flowchart of the steps of the method for detecting the thermal aging state of insulating silicone rubber based on cable accessories according to an embodiment of the present application;

[0037] Figure 2 It is a schematic diagram of a fitting curve in the method for detecting thermal aging state of insulating silicone rubber based on cable accessories described in an embodiment of the present application;

[0038] Figure 3 This is a schematic diagram of the framework of the insulating silicone rubber thermal aging state detection device based on cable accessories described in an embodiment of the present application. DETAILED DESCRIPTION

[0039] In order to make the purpose, features, and advantages of the invention of this application more obvious and easy to understand, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the embodiments described below are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0040] In the description of the embodiments of the present application, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0041] In the embodiments of the present application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0042] This patent application term:

[0043] Commonly used coupling agents for ultrasonic flaw detection include the following:

[0044] Water: It is easy to obtain and cheap, and is suitable for situations where the requirements are not strict or for temporary emergencies. However, it has high fluidity, poor wetting properties, is easy to evaporate, and is prone to errors. It has requirements for the workpiece being tested, and some workpieces need to be rust-proofed after testing.

[0045] Engine oil: The most widely used coupling agent, usually No. 20 to No. 40 engine oil. Engine oil has strong viscosity, high wettability, and strong fluidity. It is harmless to the inspector's body and non-corrosive to the workpiece. However, it is sensitive to acoustic contact pressure, and temperature changes will affect its viscosity, which requires high operating skills of the operator.

[0046] Lubricating oil: including compressor lubricating oil, steam engine lubricating oil, industrial vaseline, butter, grease, etc. It is suitable for workpieces with rough surfaces and for overhead or vertical probes. The disadvantage is that it has poor fluidity, is easy to mix with impurities, and wears the workpiece and probe surface.

[0047] Glycerin: It has good sound transmission effect and is insensitive to acoustic contact pressure. It is suitable for workpieces with high surface finish. However, it is expensive and has strong water absorption. It is easy to change the concentration due to the absorption of moisture in the air, which affects the performance consistency. The workpiece to be tested needs to be cleaned in time to prevent rust.

[0048] Water glass (sodium silicate): It has good sound transmission effect and is relatively cheap. However, it has strong water absorption and its concentration changes easily due to the absorption of moisture in the air. It is necessary to test and adjust the concentration regularly to maintain the best coupling effect.

[0049] In addition, there are some high-performance coupling agent products, such as Ultragel II, Sonotrace, Echogel, UT-XPowder and Soundsafe, which are suitable for different detection needs and environmental conditions.

[0050] Fast Fourier Transform (FFT) is an algorithm for efficiently calculating Discrete Fourier Transform (DFT) and its inverse transform. DFT is a mathematical operation that converts a complex sequence (usually discrete samples of a real signal) into another complex sequence, while FFT is a fast implementation of DFT. It uses the symmetry, periodicity and redundancy of DFT to reduce the computational complexity from O(N) to ^2） Reduced to O(NlogN).

[0051] Nonlinear ultrasonic testing equipment is an instrument that uses the nonlinear effect generated by the interaction between ultrasonic waves and material micro-defects to detect and evaluate material properties. It emits high-energy single-frequency ultrasonic waves, which interact with tiny defects (such as microcracks, pores, etc.) in the test piece to produce nonlinear effects, thereby realizing the detection of micro-defects and the evaluation of material properties. For example, the electromagnetic ultrasonic nonlinear tester is a special testing instrument used in the fields of material science, electronics and communication technology.

[0052] The embodiment of the present application provides a method, device and equipment for detecting the thermal aging state of insulating silicone rubber based on cable accessories, which solves the technical problem that the traditional ultrasonic nondestructive testing technology performs insulation aging damage tests on materials, and the ultrasonic wave is affected by the surface of the material, resulting in inaccurate detection results. The method, device and equipment for detecting the thermal aging state of insulating silicone rubber based on cable accessories obtains data through nonlinear ultrasonic detection technology, and utilizes the nonlinear effect generated by the interaction between the sound wave and the microstructure of the sample to be detected (such as silicone rubber insulating material) during the propagation process. By transmitting and receiving ultrasonic signals and processing them, the relative nonlinear coefficient of the ultrasonic wave is obtained, and the correlation model is constructed based on the fitting curve between the relative nonlinear coefficient and the degree of thermal aging. The thermal aging state of the sample to be detected can be detected and evaluated based on the relative nonlinear coefficient on the correlation model. The method, device and equipment for detecting the thermal aging state of insulating silicone rubber based on cable accessories are less restricted by the shape and surface state of the sample to be detected.

[0053] Embodiment 1:

[0054] Figure 1 This is a flowchart of the steps of the method for detecting the thermal aging state of insulating silicone rubber based on cable accessories described in an embodiment of the present application.

[0055] like Figure 1 As shown, the embodiment of the present application provides a method for detecting the thermal aging state of insulating silicone rubber based on cable accessories, comprising the following steps:

[0056] S1. Obtain a correlation model between the relative nonlinear coefficient and the degree of thermal aging and the sample to be tested.

[0057] It should be noted that step S1 is to obtain a correlation model for evaluating the thermal aging state of the sample to be tested (such as silicone rubber insulation material); and to obtain the sample to be tested. In this embodiment, the correlation model obtained in step S1 and the sample to be tested provide a basis for subsequent steps. Among them, the sample to be tested can be the silicone rubber insulation material of the cable.

[0058] S2. Transmit ultrasonic waves to the sample to be tested for aging test, and obtain a time domain signal of an echo consisting of a reflected ultrasonic signal.

[0059] It should be noted that step S2 is to perform nonlinear ultrasonic testing on the sample to be tested, and obtain a time domain signal of a primary echo consisting of a detection reflected ultrasonic signal. In this embodiment, the thermal aging state detection method of insulating silicone rubber based on cable accessories uses a nonlinear ultrasonic testing device to transmit ultrasonic waves to the sample to be tested for aging testing, and obtains a time domain signal of a primary echo consisting of a reflected ultrasonic signal. Among them, the nonlinear ultrasonic testing device uses a pulse reflection method and transmits ultrasonic waves to the sample to be tested through a probe, and both the probe and the sample to be tested are coated with an ultrasonic flaw detection coupling agent.

[0060] In the embodiment of the present application, the nonlinear ultrasonic detection equipment mainly utilizes the high-order harmonic signals generated when ultrasonic waves interact with microscopic damage in the material to evaluate the degree of damage inside the material.

[0061] It should be noted that the pulse reflection method is a measurement method. The ultrasonic testing coupling agent is evenly applied between the probe and the sample to be tested to reduce the energy attenuation of the sound wave and the nonlinear effect introduced by the air gap at the coupling point. The nonlinear ultrasonic detection equipment uses the pulse reflection method to transmit ultrasonic waves to the sample to be tested, and the nonlinear ultrasonic detection equipment receives the reflected ultrasonic signal to obtain a single echo time domain signal. In this embodiment, in order to reduce the detection error, the nonlinear ultrasonic detection equipment uses the pulse reflection method to transmit ultrasonic waves close to the center of the sample to be tested.

[0062] S3. Process the time domain signal of the primary echo to obtain a spectrum diagram including a fundamental frequency band and a second harmonic frequency band, and extract the fundamental amplitude and the second harmonic amplitude from the spectrum diagram.

[0063] It should be noted that in step S3, the first echo time domain signal obtained in step S2 is processed to obtain a corresponding spectrum diagram, and the fundamental wave amplitude and the second harmonic amplitude are extracted from the spectrum diagram. In this embodiment, the insulating silicone rubber thermal aging state detection method based on cable accessories processes the first echo time domain signal using fast Fourier transform to obtain a spectrum diagram containing a fundamental wave frequency band and a second harmonic frequency band.

[0064] S4. Calculate the relative nonlinear coefficient based on the fundamental wave amplitude and the second harmonic amplitude.

[0065] It should be noted that step S4 is to calculate the relative nonlinear coefficient β' of the sample to be tested based on the fundamental amplitude A1 and the second harmonic amplitude A2 obtained in step S3. In this embodiment, the thermal aging state detection method of insulating silicone rubber based on cable accessories characterizes the thermal aging state of the sample to be tested by the relative nonlinear coefficient. Compared with the traditional nondestructive testing technology for the thermal aging state of insulating silicone rubber for cable accessories, the thermal aging state detection method of insulating silicone rubber based on cable accessories is less restricted by the shape, appearance and surface state of the sample to be tested, and can be widely used in thermal aging state detection of different types of samples to be tested (such as insulating silicone rubber for cable accessories).

[0066] S5. Input the relative nonlinear coefficient into the correlation model for analysis to obtain the degree of thermal aging corresponding to the sample to be tested.

[0067] It should be noted that, in step S5, the relative nonlinear coefficient obtained in step S4 is input into the correlation model to evaluate the thermal aging state of the sample to be tested. The thermal aging degree is used to evaluate the thermal aging state of the sample to be tested. In this embodiment, for the same sample to be tested (such as silicone rubber insulation material), the larger the relative nonlinear coefficient β' is, the deeper the thermal aging degree of the sample to be tested (such as silicone rubber insulation material) is.

[0068] In an embodiment of the present application, before the relative nonlinear coefficient is input into the correlation model, the insulating silicone rubber thermal aging state detection method based on cable accessories includes: normalizing the relative nonlinear coefficient to obtain coefficient fitting data.

[0069] It should be noted that the relative nonlinear coefficient can be obtained by performing nonlinear ultrasonic testing on the sample to be tested using the insulation silicone rubber thermal aging state detection method based on cable accessories. The thermal aging state of the sample to be tested can be evaluated by substituting the coefficient fitting data of the normalized relative nonlinear coefficient into the corresponding fitting curve.

[0070] In the embodiment of the present application, the insulating silicone rubber thermal aging state detection method based on cable accessories transmits and receives ultrasonic waves to the sample to be detected by a nonlinear ultrasonic detection device to obtain a time-domain echo signal, and the relative nonlinear coefficient of the ultrasonic wave is obtained by processing the time-domain echo signal, and the relative nonlinear coefficient is input into the correlation model to analyze and evaluate the degree of thermal aging of the thermal aging state of the sample to be detected. The insulating silicone rubber thermal aging state detection method based on cable accessories can sensitively and accurately capture the microstructural changes caused by thermal aging of the sample to be detected, thereby achieving an accurate evaluation of the thermal aging state.

[0071] The present application provides a method for detecting the thermal aging state of insulating silicone rubber based on cable accessories, comprising obtaining a correlation model between a relative nonlinear coefficient and a degree of thermal aging and a sample to be detected; transmitting ultrasonic waves to the sample to be detected for aging test, and obtaining a first echo time domain signal composed of a reflected ultrasonic wave signal; processing the first echo time domain signal to obtain a spectrum diagram including a fundamental frequency band and a second harmonic frequency band, and extracting the fundamental amplitude and the second harmonic amplitude from the spectrum diagram; calculating according to the fundamental amplitude and the second harmonic amplitude to obtain a relative nonlinear coefficient; inputting the relative nonlinear coefficient into the correlation model for analysis to obtain the degree of thermal aging corresponding to the sample to be detected. The thermal aging state detection method of insulating silicone rubber based on cable accessories obtains a time-domain echo signal by transmitting and receiving ultrasonic waves to the sample to be detected, and then processes the time-domain echo signal to obtain a relative nonlinear coefficient of the ultrasonic wave. The relative nonlinear coefficient is input into a correlation model to analyze and evaluate the degree of thermal aging of the sample to be detected to identify the thermal aging state. The method can sensitively and accurately capture the microstructural changes of the sample to be detected caused by thermal aging, thereby achieving an accurate evaluation of the thermal aging state. The method solves the technical problem of inaccurate detection results caused by the influence of the material surface on the insulation aging damage test of the material by the traditional ultrasonic nondestructive testing technology.

[0072] In one embodiment of the present application, obtaining the relative nonlinear coefficient according to the fundamental wave amplitude and the second harmonic amplitude includes: calculating the fundamental wave amplitude to obtain first data; and calculating the second harmonic amplitude and the first data to obtain the relative nonlinear coefficient.

[0073] It should be noted that the thermal aging state detection method of insulating silicone rubber based on cable accessories can calculate the relative nonlinear coefficient using the coefficient calculation formula according to the fundamental wave amplitude and the second harmonic amplitude. The coefficient calculation formula is:

[0074]

[0075] In the formula, A1 2 is the first data.

[0076] In an embodiment of the present application, the step of obtaining a coefficient calculation formula of the insulating silicone rubber thermal aging state detection method based on cable accessories includes:

[0077] A. When large-amplitude ultrasonic waves are used for detection, the nonlinear stress-strain constitutive relationship of the solid medium is used for description. The nonlinear stress-strain constitutive relationship is: , where is stress, E is the elastic modulus of the material (a physical quantity describing the stiffness of the material), ε is the strain (the relative change in length of the material after being subjected to force), and β is the second-order nonlinear coefficient of the degree of nonlinear effect;

[0078] B. A one-dimensional longitudinal wave propagates along the x direction in a solid medium, and its operating equation is:

[0079]

[0080] Where ρ is the material density, u is the displacement of the particle in the x direction, t is the propagation time, and x is the propagation distance of the sound wave.

[0081] C. According to the nonlinear stress-strain constitutive relationship and the operating equation, the wave equation of the longitudinal wave is obtained:

[0082]

[0083] D. Using the perturbation method, a series of single-frequency sinusoidal ultrasonic longitudinal waves with amplitude A1, angular frequency ω, and wave number k enter the solid medium, and the expression of the second-order nonlinear coefficient is obtained. The expression of the second-order nonlinear coefficient is:

[0084]

[0085] Where A1 and A2 are the amplitude of the fundamental wave and the amplitude of the second harmonic respectively.

[0086] E. From the expression of the second-order nonlinear coefficient, it can be seen that, without changing the wave number k and the sound wave propagation distance x, β is only related to the fundamental wave amplitude and the second harmonic amplitude. Therefore, according to the expression of the second-order nonlinear coefficient, the coefficient calculation formula for calculating the relative nonlinear coefficient β' is obtained.

[0087] It should be noted that by measuring the amplitude of the fundamental wave and the second harmonic amplitude, the degree of nonlinear effect of the material sample to be tested can be characterized, reflecting the microstructural changes inside the material, thereby evaluating the thermal aging damage of the material.

[0088] Figure 2 It is a schematic diagram of a fitting curve in the method for detecting the thermal aging state of insulating silicone rubber based on cable accessories described in an embodiment of the present application.

[0089] In one embodiment of the present application, obtaining a correlation model between the relative nonlinear coefficient and the degree of thermal aging includes:

[0090] Obtain specimens with different degrees of thermal aging;

[0091] Each sample is processed by steps S2 to S4 to obtain a relative nonlinear coefficient of each sample;

[0092] The relative nonlinear coefficients of all samples were normalized to obtain the corresponding fitting data;

[0093] An error bar scatter plot is constructed based on all the fitting data and the corresponding thermal aging degree. A linear fit is performed on all the fitting data on the error bar scatter plot to obtain a fitting curve, and the fitting curve is used as the correlation model.

[0094] It should be noted that if the sample to be tested is a silicone rubber insulation material for cable accessories, a section of the insulating silicone rubber sample can be cut from the cable accessories to be tested as an insulating silicone rubber sample to ensure its representativeness. Perform necessary pretreatment on the insulating silicone rubber sample, such as cleaning and drying. Perform heat aging on all insulating silicone rubber samples. For example, 200°C is selected as the accelerated heat aging test temperature, and the insulating silicone rubber sample is heat aged at a heat aging time of 0 to obtain a specimen. The insulating silicone rubber sample is heat aged at a heat aging time of 72 to obtain another specimen. It can be inferred that the insulating silicone rubber samples are heat aged at heat aging times of 168, 336, 504, 672, 840, 1008h, etc., and specimens with corresponding heat aging degrees are obtained. Thus, specimens with different heat aging degrees can be obtained. Then, all the samples are processed according to step S2 to step S4 to calculate the relative nonlinear coefficients of the samples with different heat aging times, and the relative nonlinear coefficients of all the samples are normalized to obtain the corresponding fitting data. According to all the fitting data and the corresponding heat aging degrees, the error bar scatter plots of different heat aging degrees and the corresponding fitting data are drawn, as shown in FIG. Figure 2 By performing linear fitting on all the fitting data in the error bar scatter plot, a fitting curve between the fitting data and the degree of thermal aging can be obtained.

[0095] Embodiment 2:

[0096] Figure 3 This is a schematic diagram of the framework of the insulating silicone rubber thermal aging state detection device based on cable accessories described in an embodiment of the present application.

[0097] like Figure 3 As shown, the embodiment of the present application provides an insulating silicone rubber thermal aging state detection device based on cable accessories, including a model and sample acquisition module 10, a test module 20, a signal processing module 30, a calculation module 40 and an analysis module 50;

[0098] A model and sample acquisition module 10 is used to obtain a correlation model between the relative nonlinear coefficient and the degree of thermal aging and a sample to be tested;

[0099] The test module 20 is used to transmit ultrasonic waves to the sample to be tested to perform an aging test and obtain a primary echo time domain signal composed of a reflected ultrasonic signal;

[0100] The signal processing module 30 is used to process the time domain signal of the primary echo to obtain a spectrum diagram including a fundamental frequency band and a second harmonic frequency band, and extract the fundamental amplitude and the second harmonic amplitude from the spectrum diagram;

[0101] A calculation module 40, used for calculating the relative nonlinear coefficient according to the fundamental wave amplitude and the second harmonic amplitude;

[0102] The analysis module 50 is used to input the relative nonlinear coefficient into the correlation model for analysis to obtain the thermal aging degree corresponding to the sample to be tested.

[0103] It should be noted that the contents of the modules in the device of Example 2 have been described in the contents of the steps in the method of Example 1, and the contents of the modules of the device for detecting thermal aging of insulating silicone rubber based on cable accessories will not be repeated in this embodiment. In this embodiment, the device for detecting thermal aging of insulating silicone rubber based on cable accessories uses a model and sample acquisition module, a test module, a signal processing module, a calculation module and an analysis module to implement thermal aging detection of the sample to be detected using nonlinear ultrasonic detection technology. The nonlinear effect generated by the interaction between the sound waves of the nonlinear ultrasonic detection technology and the microstructure of the sample to be detected during the propagation process can detect nonlinear defects that are closely related to the microstructure and performance changes of the material. The relative nonlinear coefficient is used to effectively characterize the microstructural changes of the sample to be detected, thereby evaluating the thermal aging damage of the sample to be detected.

[0104] In the embodiment of the present application, the calculation module 40 is further used to calculate the fundamental wave amplitude to obtain the first data; and to calculate the second harmonic amplitude and the first data to obtain the relative nonlinear coefficient.

[0105] In an embodiment of the present application, the test module 20 is also used to use a nonlinear ultrasonic detection device to transmit ultrasonic waves to the sample to be detected for aging testing, and obtain a single echo time domain signal composed of a reflected ultrasonic signal; wherein the nonlinear ultrasonic detection device uses a pulse reflection method and transmits ultrasonic waves to the sample to be detected through a probe, and both the probe and the sample to be detected are coated with an ultrasonic flaw detection coupling agent.

[0106] Embodiment three:

[0107] An embodiment of the present application provides a terminal device, including a processor and a memory;

[0108] A memory, used for storing program codes and transmitting the program codes to a processor;

[0109] The processor is used to execute the above-mentioned method for detecting the thermal aging state of insulating silicone rubber based on cable accessories according to the instructions in the program code.

[0110] It should be noted that the processor is used to execute the steps in the above-mentioned embodiment of a method for detecting thermal aging state of insulating silicone rubber based on cable accessories according to the instructions in the program code. Alternatively, the processor implements the functions of each module / unit in the above-mentioned system / device embodiments when executing the computer program.

[0111] Exemplarily, the computer program may be divided into one or more modules / units, one or more modules / units are stored in a memory and executed by a processor to complete the present application. One or more modules / units may be a series of computer program instruction segments capable of completing a specific function, and the instruction segments are used to describe the execution process of the computer program in a terminal device.

[0112] The terminal device may be a computing device such as a desktop computer, a notebook, a PDA, or a cloud server. The terminal device may include, but is not limited to, a processor and a memory. Those skilled in the art will appreciate that this does not constitute a limitation on the terminal device, and may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the terminal device may also include input and output devices, network access devices, buses, etc.

[0113] The processor may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0114] The memory can be an internal storage unit of the terminal device, such as a hard disk or memory of the terminal device. The memory can also be an external storage device of the terminal device, such as a plug-in hard disk equipped on the terminal device, a SmartMedia Card (SMC), a Secure Digital (SD) card, a Flash Card, etc. Furthermore, the memory can also include both the internal storage unit of the terminal device and the external storage device. The memory is used to store computer programs and other programs and data required by the terminal device. The memory can also be used to temporarily store data that has been output or is to be output.

[0115] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0116] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0117] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0118] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0119] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc. Various media that can store program codes.

[0120] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for detecting thermal aging status of insulating silicone rubber based on cable accessories, characterized in that: The following steps are involved: S1. Obtaining the correlation model between the relative nonlinear coefficient and the degree of thermal aging and the sample to be tested; S2. The sample to be tested is subjected to an aging test by transmitting an ultrasonic wave to obtain a time domain signal of an echo consisting of a reflected ultrasonic wave signal; S3. Processing the time domain signal of the primary echo to obtain a spectrum diagram including a fundamental frequency band and a second harmonic frequency band, and extracting the fundamental amplitude and the second harmonic amplitude from the spectrum diagram; S4. Calculate the relative nonlinear coefficient based on the fundamental amplitude and the second harmonic amplitude; S5. Input the relative nonlinear coefficient into the correlation model for analysis to obtain the degree of thermal aging corresponding to the sample to be tested.

2. The method for detecting thermal aging state of insulating silicone rubber based on cable accessories according to claim 1 is characterized in that: Calculating according to the fundamental wave amplitude and the second harmonic amplitude to obtain the relative nonlinear coefficient includes: calculating the fundamental wave amplitude to obtain first data; calculating the second harmonic amplitude and the first data to obtain the relative nonlinear coefficient.

3. The method for detecting thermal aging state of insulating silicone rubber based on cable accessories according to claim 1 is characterized in that: The method of transmitting ultrasonic waves to the sample to be tested for aging test and obtaining a time domain echo signal composed of reflected ultrasonic waves includes: transmitting ultrasonic waves to the sample to be tested for aging test using nonlinear ultrasonic testing equipment and obtaining a time domain echo signal composed of reflected ultrasonic waves.

4. The method for detecting thermal aging state of insulating silicone rubber based on cable accessories according to claim 3 is characterized in that: include: The nonlinear ultrasonic testing device adopts a pulse reflection method and transmits ultrasonic waves to the sample to be tested through a probe, and ultrasonic flaw detection coupling agent is applied to both the probe and the sample to be tested.

5. The method for detecting thermal aging state of insulating silicone rubber based on cable accessories according to claim 1 is characterized in that: Processing the first echo time domain signal to obtain a frequency spectrum diagram including a fundamental frequency band and a second harmonic frequency band includes: processing the first echo time domain signal using a fast Fourier transform to obtain a frequency spectrum diagram including a fundamental frequency band and a second harmonic frequency band.

6. The method for detecting thermal aging state of insulating silicone rubber based on cable accessories according to any one of claims 1 to 5, characterized in that: The correlation model between the relative nonlinear coefficient and the degree of thermal aging includes: Obtain specimens with different degrees of thermal aging; Processing each of the sample pieces using steps S2 to S4 to obtain a relative nonlinear coefficient of the sample corresponding to each of the sample pieces; Normalizing the relative nonlinear coefficients of all the samples to obtain corresponding fitting data; An error bar scatter plot is constructed according to all the fitting data and the corresponding heat aging degree, and linear fitting is performed on all the fitting data on the error bar scatter plot to obtain a fitting curve and use the fitting curve as the correlation model.

7. A device for detecting thermal aging status of insulating silicone rubber based on cable accessories, characterized in that: include: Model and sample acquisition module, test module, signal processing module, calculation module and analysis module; The model and sample acquisition module is used to obtain the correlation model between the relative nonlinear coefficient and the thermal aging degree and the sample to be tested; The testing module is used to transmit ultrasonic waves to the sample to be tested to perform an aging test, and obtain a primary echo time domain signal composed of a reflected ultrasonic signal; The signal processing module is used to process the primary echo time domain signal to obtain a frequency spectrum including a fundamental frequency band and a second harmonic frequency band, and extract the fundamental amplitude and the second harmonic amplitude from the frequency spectrum; The calculation module is used to calculate the relative nonlinear coefficient according to the fundamental wave amplitude and the second harmonic amplitude; The analysis module is used to input the relative nonlinear coefficient into the correlation model for analysis to obtain the thermal aging degree corresponding to the sample to be tested.

8. The insulating silicone rubber thermal aging state detection device based on cable accessories according to claim 7 is characterized in that: The calculation module is also used to calculate the fundamental wave amplitude to obtain first data; and calculate the second harmonic amplitude and the first data to obtain a relative nonlinear coefficient.

9. The insulating silicone rubber thermal aging state detection device based on cable accessories according to claim 7 is characterized in that: The test module is also used to use nonlinear ultrasonic detection equipment to transmit ultrasonic waves to the sample to be tested for aging test, and obtain a primary echo time domain signal composed of reflected ultrasonic signals; wherein the nonlinear ultrasonic detection equipment uses a pulse reflection method and transmits ultrasonic waves to the sample to be tested through a probe, and both the probe and the sample to be tested are coated with ultrasonic flaw detection coupling agent.

10. A terminal device, characterized in that: including a processor and a memory; The memory is used to store program codes and transmit the program codes to the processor; The processor is used to execute the method for detecting the thermal aging state of insulating silicone rubber based on cable accessories as described in any one of claims 1 to 6 according to the instructions in the program code.

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