Construction of load spectrum and test method for accelerated degradation test of transverse electrical connection of catenary

Abstract

This invention discloses a method for constructing and testing the accelerated degradation test load spectrum of the lateral electrical connection of the overhead contact system. By analyzing the vibration characteristics of the electrical connection and considering the vibration simulation and measured amplitude power spectral density characteristics, the method constructs the amplitude power spectral density of the electrical connection. In the reliability design and operation and maintenance of the high-speed railway traction power supply system, this method realistically simulates the service state of the electrical connection under the pantograph-catenary coupling vibration environment, helping operating units to scientifically predict the remaining life of the electrical connection, optimize maintenance cycles and replacement strategies, thereby improving the operational safety and power supply reliability of the overhead contact system. Furthermore, through the degradation test based on the power spectral density amplitude, the method efficiently obtains the performance degradation law of the electrical connection under random vibration loads, providing data support and theoretical basis for the structural design improvement, material selection, and process optimization of the electrical connection.

Description

Technical Field

[0001] This invention relates to the field of railway electrification technology, specifically to the construction and testing method of the load spectrum for accelerated degradation test of the lateral electrical connection of the overhead contact system. Background Technology

[0002] my country's high-speed rail has achieved leapfrog development, building the world's fastest and largest high-speed rail network. Having achieved optimal development during the construction phase, the focus is now shifting to a new stage of "optimal growth," emphasizing both safe operation and maintenance and quality improvement. The industry is at a critical juncture, transitioning from "scale expansion" to "quality enhancement." The simultaneous improvement in speed levels, transport density, and life-cycle cost constraints makes the reliability and life-cycle management of high-speed rail infrastructure the core issues for ensuring operational safety.

[0003] As a core component of the high-speed railway traction power supply system, the service condition of the overhead contact system directly determines the current collection quality of the pantograph-catenary system, thus affecting the safety and efficiency of train operation. The electrical connection undertakes the important functions of parallel power supply, potential equalization, and connection of electrical sections; its reliability has a critical impact on the stability of the overhead contact system. However, the electrical connection is constantly subjected to complex vibrations caused by the high-speed passage of the pantograph, and its fatigue performance and dynamic response are closely related. Accelerated degradation testing needs to maintain the original failure mechanisms and modes of the electrical connection; therefore, it is essential to construct a working load spectrum that conforms to actual operating conditions. How to construct the working load spectrum of the electrical connection is the key to accelerated degradation testing.

[0004] While existing accelerated degradation testing methods for electrical connections play an important role in assessing the lifespan and performance of electrical connections, they still have some shortcomings and limitations: (1) Existing accelerated degradation tests are mainly based on random vibration loading using a single power spectral density function, and are constructed based on simulation and a small amount of measured data. This fails to fully reproduce the complex load environment that electrical connections are subjected to in the field, such as pantograph-catenary impact, wind vibration, temperature cycling, current thermal effects and their interactions.

[0005] (2) Existing accelerated tests mainly shorten the test time by increasing the amplitude of the power spectral density. This does not take into account the influence of frequency distribution changes, multiaxial stress state or load sequence on fatigue damage.

[0006] (3) Existing accelerated degradation tests of electrical connections mainly focus on mechanical vibration fatigue, without systematically introducing the key environmental factors faced by electrical connections in actual service, such as acid rain / salt spray corrosion, humidity changes, and the coupling effect of current carrying (current surge, Joule heating) and vibration.

[0007] (4) Existing accelerated degradation tests for electrical connections have certain defects and limitations in terms of technical simulation, cost control, data reliability, and practical application. These shortcomings not only affect the accuracy and reliability of the test results, but also limit their application in electrical connection life assessment and fault prediction. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies, this invention proposes a method for constructing and testing accelerated degradation test load spectra for lateral electrical connections in overhead contact lines. This method can be applied to situations requiring accurate simulation and evaluation of the lifespan of overhead contact line electrical connections, particularly in the reliability design and operation and maintenance of high-speed railway traction power supply systems. By using a dedicated vibration load spectrum constructed based on the fusion of simulation and measured data, the service status of electrical connections under pantograph-catenary coupling vibration environments can be simulated more realistically. This helps operating units scientifically predict the remaining lifespan of electrical connections, optimize maintenance cycles and replacement strategies, thereby improving the operational safety and power supply reliability of the overhead contact line system. Simultaneously, through degradation tests based on power spectral density amplitude acceleration, the performance degradation patterns of electrical connections under random vibration loads can be efficiently obtained, providing data support and theoretical basis for structural design improvements, material selection, and process optimization of electrical connections.

[0009] The objective of this invention can be achieved through the following technical solutions: The load spectrum construction and test method for accelerated degradation test of transverse electrical connection of contact wire are proposed. By analyzing the vibration characteristics of electrical connection, considering the vibration simulation and measured amplitude power spectral density characteristics of electrical connection, the amplitude power spectral density of electrical connection is constructed, and this power spectral density is used for accelerated life test of electrical connection. The electrical connection vibration characteristic analysis specifically includes steps S1, S2, S3, and S4: S1: The finite element model of the contact network is constructed using the absolute node coordinate method, and the vibration amplitude data of the contact wire electrical connection clamp located near the dropper is extracted by simulation. S2: Based on the finite discrete Fourier transform, the power spectral density function of the vibration signal is derived, and a calculation method for solving the frequency domain power spectral density from time-domain vibration data is established. S3: Using the calculation method described in step S2, process the vibration amplitude data obtained from the simulation in step S1 and the measured vibration signal data from externally acquired TB / T 2074 to obtain the simulated power spectral density curve and the measured power spectral density curve respectively. S4: By comprehensively analyzing the simulated power spectral density curve and the measured power spectral density curve, the frequency domain characteristics of the electrical connection vibration are determined, several significant spectral peaks constituting the main frequency components of the electrical connection vibration and their corresponding frequency and spectral density values ​​are identified and extracted, and the total power of the electrical connection vibration signal is calculated. The construction of the electrical connection amplitude power spectral density includes steps S5, S6, and S7: S5: Based on the analysis results of S4, and taking into account the amplitude power spectral density characteristics of electrical connection vibration simulation and actual measurement, a general power spectral density curve for accelerated life testing of electrical connections is constructed; the general power spectral density curve includes a main spectral peak and at least one secondary spectral peak, and the corresponding spectral density value and total power are set. S6: Set the amplification factor and acceleration factor, and amplify the power spectral density curve constructed in step S5 according to the amplification factor to increase the total power of the power spectral density, thereby shortening the test time and obtaining the accelerated power spectral density and its curve. S7: Convert the accelerated power spectral density into the corresponding amplitude time history signal to obtain the vibration loading input conditions for the accelerated life test of electrical connection.

[0010] Furthermore, the accelerated life testing system for electrical connections reveals the fatigue failure mechanism and performance degradation law of electrical connections under pantograph-catenary coupling, specifically including the following steps: S21: Prepare electrical connection test samples and group them; S22: Based on the amplitude time history signal obtained in step S7, different acceleration levels are set, and vibration loading tests are performed on the grouped electrical connection test samples respectively. S23: Monitor the changes in the state of the electrically connected specimen during the test and record the failure time when the specimen fails. S24: Based on the failure time data under different acceleration levels and combined with the set acceleration factor, establish a vibration failure model and solve for the model parameters.

[0011] Furthermore, the finite element model of the contact network constructed using the absolute node coordinate method is an elastic chain suspension contact network model, and its equipment geometry and material parameters are set according to the actual contact network line; the equipment includes contact wire, catenary, elastic suspension cable, rigid dropper and electrical connection; the material parameters include structural height, span, pull-out value, anchor section length, elastic suspension cable length, and dropper spacing within the span.

[0012] Furthermore, the power spectral density function of the vibration signal is derived based on the finite discrete Fourier transform, specifically including: considering the one-sided power spectrum definition as shown in equation (A1), we obtain equation (A2): (A1) In the formula, Representative signal The power spectral density function in angular frequency form is used to describe the signal at angular frequencies. Energy distribution at that location; Represents the two-sided power spectral density function; Representative signal The autocorrelation function reflects the time delay of the signal. The degree of relevance.

[0013] (A2) In the formula, Representative signal In frequency The power spectral density function at; This represents the sampling time length of the signal.

[0014] Let the discrete frequency values ​​at discrete frequency points be... for The power spectral density estimate is derived as shown in equation (A3): (A3) In the formula, represent In frequency Power spectral density at that point Represents the number of signal sampling points. Represents the signal sampling time interval. This represents the vibration displacement of the electrical connection.

[0015] According to the finite discrete Fourier transform The formula for calculating the power spectral density estimate is derived, as shown in equation (A4): (A4) In the formula, Represents the sampling frequency, satisfying .

[0016] According to equation (A4), the power spectral density function is solved for the measured signal and the finite element simulation waveform of TB / T 2074.

[0017] Furthermore, analysis of the simulated and measured power spectral density curves reveals that the vibration energy is concentrated in the 0-1.5Hz frequency band, which exhibits several significant spectral peaks, constituting the main frequency components of the electrical connection vibration. The area under the power spectral density curve (also known as the total signal power or variance) represents the total energy of the signal across the entire frequency range. It reflects the overall level of signal vibration intensity and is a core indicator for measuring signal energy. Therefore, the total power of the electrical connection vibration signal is calculated using the integration method shown in Equation (A5), thereby obtaining the power spectral characteristics of the electrical connection. (A5).

[0018] Furthermore, the plurality of significant spectral peaks includes one primary spectral peak and at least two secondary spectral peaks; the primary spectral peak has a frequency range of 1.0-1.5 Hz and a spectral density of 400-450 mm² / Hz; the secondary spectral peaks have a frequency range of 0-1.0 Hz and a spectral density of 250-380 mm² / Hz; and the total power is 150-200 mm². Preferred power spectral densities are as follows: with a primary frequency of 1.2 Hz, the spectral density is set to 420 mm² / Hz; including two secondary spectral peaks at 0.07 Hz and 0.4 Hz, the spectral densities are limited to 360 mm² / Hz and 280 mm² / Hz respectively, and the total power is set to 180 mm².

[0019] Furthermore, the pantograph requires 15 seconds to complete one vibration cycle. If the amplitude time history is used as the test load, the test time would be too long. Therefore, the amplitude must be accelerated. According to GJB150.16A, the test time can be shortened by increasing the power spectral density of the amplitude. The acceleration factor AF is given by equation (A5): (A5) In the formula, Power spectral density representing accelerated testing; Power spectral density representing a standard test; Represents the original power spectral density The duration of the test at the point of failure; Represents the power spectral density under load The duration of the test at the point of failure; The fatigue damage index represents the sensitivity of vibration load amplitude to the fatigue life of a structure. Its value depends on the component materials, structural form, and failure mode.

[0020] Let the magnification factor be K, that is: (A6) The acceleration factor AF and the amplification factor K satisfy equation (A7): (A7).

[0021] Furthermore, in step S7, the spectral density of the increased total power is converted into an amplitude time history signal for loading using the minimum phase method. Specifically, a Hilbert filter is defined as shown in equation (A8), and an analytic signal as shown in equation (A10) is constructed through the Hilbert transform as shown in equation (A9). The instantaneous phase is calculated as shown in equation (A11) to obtain the time domain signal corresponding to the accelerated power spectral density, as shown in equation (A12). (A8) (A9) (A10) (A11) (A12) By selecting different amplification factors, the amplitude time history corresponding to the accelerated power spectral density is obtained, which is used as the vibration loading input condition for the subsequent accelerated life test of the electrical connection. Specifically, it is used in the displacement control mode of the dropper and electrical connection vibration fatigue testing machine to simulate the vibration waveform generated when the locomotive pantograph passes by.

[0022] Furthermore, in step S21, the electrical connection test sample uses a TJR95 electrical connection, and the installation structure adopts a C-type; the grouping specifically includes: the first group uses actual working conditions, the second group uses 1.5 times the power spectral density acceleration conditions, and the third group uses 2 times the power spectral density acceleration conditions. In steps S22 and S23, a vibration fatigue testing machine for suspension wires and electrical connections in displacement control mode is used to load the test specimens and monitor their state changes. When the specimens show signs of broken strands or strand disintegration, the test is immediately terminated and the failure time is accurately recorded. In step S24, the electrical connection resistance is selected as a degradation parameter to establish a vibration failure model. Combined with the set acceleration factor and the results of accelerated tests, the fatigue strength index of the material is solved by inversion.

[0023] Compared with the prior art, the present invention has the following technical effects: (1) In view of the problem that traditional sinusoidal vibration test is difficult to truly characterize the random vibration characteristics of electrical connection in the field, this invention summarizes the power spectral density of random vibration of electrical connection through simulation and actual measurement, and the constructed accelerated degradation test load spectrum is more consistent with the vibration situation of electrical connection in the field.

[0024] (2) The invention systematically compares and integrates the “pantograph-catenary coupling dynamics simulation results” with the “measured vibration data in the industry standard (TB / T 2074)”, and uses them together as the basis for constructing the load spectrum. The load spectrum constructed based on simulation and measurement not only contains the mechanism insights of the theoretical model, but also conforms to the actual service environment of the electrical connection.

[0025] (3) Through systematic analysis of the vibration response of the electrical connection at different locations, it was found that its vibration energy is not concentrated at a single frequency, but rather exhibits a cluster characteristic of "1.2 Hz as the main frequency, and 0.07 Hz and 0.4 Hz as stable secondary frequencies". The power spectral density constructed based on this is more able to reflect its true dynamic characteristics under multi-mode coupling excitation.

[0026] (4) The acceleration method used in the invention is not simply to increase the vibration frequency or change the waveform, but to accelerate by increasing the overall power spectral density amplitude (i.e. vibration magnitude) while keeping the power spectral density spectrum of the actual vibration energy distribution completely unchanged. This can better maintain the damage mechanism similar to that under actual working conditions. Attached Figure Description

[0027] Figure 1 This is the overall flowchart of the present invention; Figure 2 Vibration time history waveforms from multiple data sources; among them, a) Measured vibration time history waveform according to TB / T 2074; b) Vibration time history waveform of electrical connection located near the first dropper; c) The vibration time history waveform of the electrical connection located near the second suspension wire; d) The vibration time history waveform of the electrical connection located near the third suspension wire in finite element simulation; Figure 3 Power spectral density curves from multiple data sources; among them, a) Power spectral density curve based on measured data from TB / T 2074; b) Power spectral density curve of finite element simulation data where the electrical connection is located near the first dropper; c) Power spectral density curve of finite element simulation data where the electrical connection is located near the second dropper; d) Power spectral density curve of finite element simulation data where the electrical connection is located near the third dropper; Figure 4 The amplitude power spectral density curve of the constructed electrical connection; Figure 5 The graphs show the power spectral density curves after acceleration at different amplification factors; where, a) Power spectral density curve when the magnification factor is 1; b) Power spectral density curve at an amplification factor of 1.5; c) Rate spectral density curve when the magnification factor is 2; Figure 6 The following are amplitude-time histories of the power spectral density after acceleration at different amplification factors; where, a) The time-domain signal with an amplification factor of 1; b) Time-domain signal with an amplification factor of 1.5; c) Time-domain signal with an amplification factor of 2. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the invention, any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art to all other embodiments obtained without creative effort should be included within the protection scope of the present invention.

[0029] like Figure 1 As shown, the load spectrum construction and test method of the accelerated degradation test of the transverse electrical connection of the contact network are described. By analyzing the vibration characteristics of the electrical connection, considering the vibration simulation and measured amplitude power spectral density characteristics of the electrical connection, the amplitude power spectral density of the electrical connection is constructed, and this power spectral density is used for the accelerated life test of the electrical connection. The electrical connection vibration characteristic analysis specifically includes steps S1, S2, S3, and S4: S1: A finite element model of the overhead contact system was constructed using the absolute nodal coordinate method. Vibration amplitude data of the contact wire clamps located near the droppers were extracted through simulation. The constructed finite element model is an elastic catenary suspension model, with its equipment geometry and material parameters set according to the actual overhead contact line. System structural parameters include structural height, span, pull-out value, anchor length, elastic suspender length, and dropper spacing within the span, as shown in Table 1. The equipment includes the contact wire, catenary, elastic suspenders, rigid droppers, and electrical connections, as shown in Table 2.

[0030] Table 1 Structural parameters of high-speed railway catenary system

[0031] Table 2 Parameters of High-speed Railway Overhead Contact System Suspension Components

[0032] S2: Based on the finite discrete Fourier transform, the power spectral density function of the vibration signal is derived, and a calculation method for solving the frequency domain power spectral density from time-domain vibration data is established; specifically including: Considering the one-sided power spectrum definition shown in equation (A1), we obtain equation (A2): (A1) In the formula, Representative signal The power spectral density function in angular frequency form is used to describe the signal at angular frequencies. Energy distribution at that location; Represents the two-sided power spectral density function; Representative signal The autocorrelation function reflects the time delay of the signal. The degree of relevance.

[0033] (A2) In the formula, Representative signal In frequency The power spectral density function at; This represents the sampling time length of the signal.

[0034] Let the discrete frequency values ​​at discrete frequency points be... for The power spectral density estimate is derived as shown in equation (A3): (A3) In the formula, represent In frequency Power spectral density at that point Represents the number of signal sampling points. Represents the signal sampling time interval. This represents the vibration displacement of the electrical connection.

[0035] According to the finite discrete Fourier transform The formula for calculating the power spectral density estimate is derived, as shown in equation (A4): (A4) In the formula, Represents the sampling frequency, satisfying .

[0036] Through finite element simulation, vibration amplitude data of the contact wire clamps located near the first to sixth droppers in the established contact network model were extracted. For the random vibration load of the electrical connections, the power spectral density in the frequency domain was used to characterize the vibration load characteristics. According to equation (A4), the power spectral density function was solved for the measured signal from TB / T 2074 and the finite element simulation waveform, resulting in the following... Figure 2 The vibration time history waveform shown is Figure 3 The power spectral density curve is shown. Wherein, Figure 2 (a) is the measured vibration time history waveform according to TB / T 2074. Figure 2 (b) ~ Figure 2 (d) are the finite element simulation vibration time history waveforms when the electrical connection is located near the first, second, and third suspension wires, respectively; Figure 3 (a) is the power spectral density curve based on measured data from TB / T 2074. Figure 3 (b) ~ Figure 3 (d) are the power spectral density curves of finite element simulation data when the electrical connection is located near the first, second, and third suspension wires, respectively.

[0037] S3: Using the calculation method described in step S2, process the vibration amplitude data obtained from the simulation in step S1 and the measured vibration signal data from externally acquired TB / T 2074 to obtain the simulated power spectral density curve and the measured power spectral density curve respectively. S4: By comprehensively analyzing the simulated power spectral density curve and the measured power spectral density curve, the frequency domain characteristics of the electrical connection vibration are determined, several significant spectral peaks constituting the main frequency components of the electrical connection vibration and their corresponding frequency and spectral density values ​​are identified and extracted, and the total power of the electrical connection vibration signal is calculated. Analysis of the simulated and measured power spectral density curves reveals that the vibration energy is concentrated in the 0-1.5Hz frequency band, which exhibits several significant spectral peaks. The total power of the electrical connection vibration signal is calculated using the integration method shown in Equation (A5), thus obtaining the power spectral characteristics of the electrical connection, as shown in Table 3. (A5) The construction of the electrical connection amplitude power spectral density includes steps S5, S6, and S7: Table 3. Characteristic parameters of power spectral density of electrical connections from different data sources

[0038] S5: Based on the analysis results of S4, and taking into account the amplitude power spectral density characteristics of electrical connection vibration simulation and actual measurement, a general power spectral density curve for accelerated life testing of electrical connections is constructed; the general power spectral density curve includes a main spectral peak and at least one secondary spectral peak, and the corresponding spectral density value and total power are set. The plurality of significant spectral peaks include one primary spectral peak and at least two secondary spectral peaks; the primary spectral peak has a frequency range of 1.0-1.5 Hz and a spectral density of 400-450 mm² / Hz; the secondary spectral peaks have a frequency range of 0-1.0 Hz and a spectral density of 250-380 mm² / Hz; the total power is 150-200 mm². A preferred power spectral density is as follows: with 1.2 Hz as the primary frequency, its spectral density is set to 420 mm² / Hz; including two secondary spectral peaks at 0.07 Hz and 0.4 Hz, their spectral densities are limited to 360 mm² / Hz and 280 mm² / Hz respectively; the total power is set to 180 mm², and the constructed power spectral density curve is shown below. Figure 4 As shown.

[0039] S6: The pantograph takes 15 seconds to complete one vibration cycle. If the amplitude time history is used as the test load, the test time will be too long. Therefore, the amplitude must be accelerated. Set the amplification factor and acceleration factor, and amplify the power spectral density curve constructed in step S5 according to the amplification factor to increase the total power of the power spectral density, thereby shortening the test time and obtaining the accelerated power spectral density and its curve. According to GJB150.16A, the acceleration factor AF is used to shorten the test time by increasing the power spectral density of the amplitude, as shown in equation (A5): (A5) In the formula, Power spectral density representing accelerated testing; Power spectral density representing a standard test; Represents the original power spectral density The duration of the test at the point of failure; Represents the power spectral density under load The duration of the test at the point of failure; The fatigue damage index represents the sensitivity of vibration load amplitude to the fatigue life of a structure. Its value depends on the component materials, structural form, and failure mode.

[0040] Let the magnification factor be K, that is: (A6) The acceleration factor AF and the amplification factor K satisfy equation (A7): (A7) By selecting an amplification factor of 1, the power spectral density curve after acceleration can be obtained, as shown below. Figure 5 As shown in (a); by selecting an amplification factor of 1.5, the accelerated power spectral density curve can be obtained, as shown in (a). Figure 5 As shown in (b); by selecting an amplification factor of 2, the accelerated power spectral density curve can be obtained, as shown in [example]. Figure 5 As shown in (c).

[0041] S7: The spectral density of the increased total power is converted into an amplitude time history signal using the minimum phase method for loading. Specifically, the Hilbert filter is defined as shown in Equation (A8), and the Hilbert transform is performed as shown in Equation (A9). The analytical signal is constructed as shown in Equation (A10), and the instantaneous phase is calculated as shown in Equation (A11) to obtain the time domain signal corresponding to the accelerated power spectral density, as shown in Equation (A12). (A8) (A9) (A10) (A11) (A12) By selecting amplification factors of 1, 1.5, and 2, the time-domain signals corresponding to the accelerated power spectral density are obtained, as shown below. Figure 6 (a) Figure 6 (b) and Figure 6 (c) serves as the vibration loading input condition for subsequent accelerated life testing of electrical connections. Specifically, it is used in the displacement control mode of the dropper and electrical connection vibration fatigue testing machine to simulate the vibration waveform generated when the locomotive pantograph passes by.

[0042] To verify the rationality of the vibration load spectrum for electrical connections constructed in this invention and to ensure the accuracy of accelerated degradation testing in simulating actual working conditions and life prediction of electrical connections, a systematic experimental design and verification were conducted. The vibration load spectrum based on power spectral density was applied using a comprehensive fatigue performance testing machine specifically designed for electrical connections to simulate the actual working state of the electrical connection under high-speed pantograph-catenary coupling vibration. The parameters of this vibration load spectrum were adjusted based on the fusion analysis results of finite element simulation and measured data to ensure that the dynamic response and stress changes of the electrical connection under random vibration conform to actual conditions, thus providing a reliable basis for the effectiveness of the accelerated degradation test. The specific accelerated degradation test scheme for electrical connections is as follows: I. Experimental Objective This experiment, conducted in a controlled laboratory environment, rapidly reproduces and intensifies the dominant vibration loads experienced by electrical connections in actual service, systematically revealing the fatigue failure mechanism and performance degradation patterns of electrical connections under pantograph-catenary coupling in a short period. Through accelerated degradation testing, the electrical connection resistance is selected as the degradation parameter to establish a vibration failure model, thereby predicting its remaining life. Ultimately, this provides quantitative evidence and scientific support for the reliability assessment, structural optimization, maintenance strategy formulation, and improvement of relevant testing standards for electrical connections.

[0043] II. Test Equipment (1) Vibration fatigue testing machine for droppers and electrical connections: This testing machine adopts a displacement control mode to simulate the vibration waveform generated when the pantograph of a locomotive passes by. It has the following functions: a. to realize vibration test of electrical connections under different structural heights; b. to set control parameters with different frequencies and displacement amplitudes; c. to automatically record the number of test cycles.

[0044] (2) Electrical connection installation equipment: hydraulic type electrical connection clamp crimping device.

[0045] (3) Ultra-low DC resistance tester.

[0046] III. Test Samples and Grouping (1) Test sample: 10 TJR95 electrical connectors were selected, and the electrical connector installation structure adopted type C.

[0047] (2) Experimental groups: The first group is the experimental group under actual working conditions, the second group adopts the accelerated test method under 1.5 times the power spectral density, and the third group adopts the accelerated test method under 2 times the power spectral density.

[0048] The first group is numbered I-1 and I-2; the second group is numbered II-1, II-2, II-3, and II-4; and the third group is numbered III-1, III-2, III-3, and III-4. The power spectral density curve for operating condition group I with an input amplification factor of 1 is shown in the figure below. Figure 5 As shown in (a); the power spectral density curve of the input amplification factor of 1.5 for operating condition group II is shown in the figure. Figure 5 (b) shows the power spectral density curve for operating condition group III with an input amplification factor of 2. The specific input waveform is as follows: Figure 5 As shown in (c).

[0049] IV. Test Procedure Test procedure for conditions I-V: (1) Sample preparation: Prepare 10 brand new TJR95 electrical connection test specimens, and inspect and number them one by one; (2) Start the vibration test platform, divide the electrical connection specimens into two groups, and load them according to the set vibration load conditions; (3) For the electrical connection test specimens of installation condition I, life tests were carried out under the set load conditions, and their status changes were monitored. When the specimens showed failure modes such as broken strands or loose strands, the test of the specimens was terminated immediately, and the failure time was accurately recorded; (4) Complete the tests of the remaining samples in working condition group I in sequence to ensure that the data of each group is complete and valid; (5) Repeat steps (2) to (4) to conduct life tests on the test specimens of working condition II and III; (6) Statistically calculate the failure time of each sample under different working conditions, calculate its arithmetic mean, and combine the set acceleration factor and the results of accelerated test to solve the fatigue strength index m of the material.

Claims

1. A load spectrum construction and test method for accelerated degradation test of transverse electrical connection of catenary, characterized in that, By analyzing the vibration characteristics of electrical connections, and considering the simulated and measured amplitude power spectral density characteristics of electrical connection vibration, an amplitude power spectral density of electrical connection is constructed for accelerated life testing of electrical connections. The electrical connection vibration characteristic analysis specifically includes steps S1, S2, S3, and S4: S1: Construct a finite element model of the overhead contact system and extract vibration amplitude data of the contact system electrical connection clamps located near the droppers through simulation; S2: Derive the power spectral density function of the vibration signal and establish a calculation method for solving the frequency domain power spectral density from time-domain vibration data; S3: Using the calculation method in S2, the vibration amplitude data obtained from the simulation and the measured vibration signal data from externally acquired TB / T 2074 are processed to obtain the simulated power spectral density curve and the measured power spectral density curve, respectively. S4: Based on the simulated power spectral density curve and the measured power spectral density curve, analyze the frequency domain characteristics of the electrical connection vibration, identify and extract several significant spectral peaks that constitute the main frequency components of the electrical connection vibration and their corresponding frequency and spectral density values, and calculate the total power of the electrical connection vibration signal. The construction of the electrical connection amplitude power spectral density includes steps S5, S6, and S7: S5: Based on the simulated power spectral density characteristics and the measured power spectral density characteristics, a general power spectral density curve for accelerated life testing of electrical connections is constructed; the general power spectral density curve includes a main spectral peak and at least one secondary spectral peak, and the corresponding spectral density value and total power are set. S6: Set the amplification factor and acceleration factor, and amplify the power spectral density curve constructed in S5 according to the amplification factor to increase the total power of the power spectral density, thereby shortening the test time and obtaining the accelerated power spectral density and its curve. S7: Convert the accelerated power spectral density into the corresponding amplitude time history signal to obtain the vibration loading input conditions for the accelerated life test of electrical connection.

2. The method of claim 1, wherein the method further comprises: determining a load spectrum for the accelerated degradation test based on the load spectrum of the contact wire system. The accelerated life testing system for electrical connections reveals the fatigue failure mechanism and performance degradation law of electrical connections under pantograph-catenary coupling, specifically including the following steps: S21: Prepare electrical connection test samples and group them; S22: Based on the amplitude time history signal obtained in step S7, different acceleration levels are set, and vibration loading tests are performed on the grouped electrical connection test samples respectively. S23: Monitor the changes in the state of the electrically connected specimen during the test and record the failure time when the specimen fails. S24: Based on the failure time data under different acceleration levels and combined with the set acceleration factor, establish a vibration failure model and solve for the model parameters.

3. The method of claim 2, wherein the method further comprises: determining the load spectrum based on the load spectrum of the test vehicle and the load spectrum of the reference vehicle. The finite element model of the contact network constructed using the absolute node coordinate method is an elastic chain suspension contact network model. Its equipment geometry and material parameters are set according to the actual contact network line. The equipment includes contact wire, catenary, elastic suspenders, rigid droppers and electrical connections. The material parameters include structural height, span, pull-out value, anchor length, elastic suspender length, and dropper spacing within the span.

4. The method of claim 3, wherein the method further comprises: determining the load spectrum of the accelerated degradation test based on the load spectrum of the actual operation of the overhead contact system. The power spectral density function of the vibration signal is derived based on the finite discrete Fourier transform, specifically including: considering the one-sided power spectrum, according to the definition of the one-sided power spectral density and the finite discrete Fourier transform, the calculation formula of the power spectral density estimate is derived, as shown in equation (1): ； （1） wherein represents at a frequency power spectral density, represents the number of signal samples, represents the signal sampling time interval, represents the electrical connection vibration displacement, represents the sampling frequency.

5. The method for constructing and testing the accelerated degradation test load spectrum of the lateral electrical connection of the contact network according to claim 4, characterized in that, Analysis of the simulated and measured power spectral density curves shows that the vibration energy is concentrated in the 0-1.5Hz frequency band, which exhibits several significant spectral peaks, constituting the main frequency components of the electrical connection vibration. The total power of the electrical connection vibration signal is calculated using the integration method shown in equation (2), thereby obtaining the power spectral characteristics of the electrical connection: （2）。 6. The method for constructing and testing the load spectrum of the accelerated degradation test for the transverse electrical connection of the contact network according to claim 5, characterized in that, The significant spectral peaks include one primary spectral peak and at least two secondary spectral peaks; the primary spectral peak has a frequency range of 1.0-1.5 Hz and a spectral density of 400-450 mm² / Hz; the secondary spectral peaks have a frequency range of 0-1.0 Hz and a spectral density of 250-380 mm² / Hz; and the total power is 150-200 mm².

7. The method for constructing and testing the load spectrum of the accelerated degradation test for the transverse electrical connection of the contact wire according to claim 6, characterized in that, In step S6, according to GJB150.16A, the test time is shortened by increasing the power spectral density of the amplitude. The amplification factor K is set to a value greater than 1, and the acceleration factor AF is as shown in equation (3): ； （3） The acceleration factor AF and the amplification factor K satisfy equation (4): （4）。 8. The method for constructing and testing the accelerated degradation test load spectrum of the lateral electrical connection of the contact wire according to claim 7, characterized in that, In step S7, the spectral density of the increased total power is converted into an amplitude time history signal using the minimum phase method for loading. Specifically, a Hilbert filter is defined, an analytical signal is constructed through Hilbert transform, and the instantaneous phase is calculated to obtain the time domain signal corresponding to the accelerated power spectral density. Different amplification coefficients are selected to obtain the amplitude time history corresponding to the accelerated power spectral density, which serves as the vibration loading input condition for the subsequent accelerated life test of the electrical connection. Specifically, it is used in the displacement control mode of the dropper and electrical connection vibration fatigue testing machine to simulate the vibration waveform generated when the locomotive pantograph passes by.

9. The method for constructing and testing the accelerated degradation test load spectrum of the lateral electrical connection of the contact network according to claim 8, characterized in that, In step S21, the electrical connection test sample uses TJR95 electrical connection and the installation structure adopts type C; the grouping specifically includes: the first group uses actual working conditions, the second group uses 1.5 times power spectral density acceleration conditions, and the third group uses 2 times power spectral density acceleration conditions. In steps S22 and S23, a vibration fatigue testing machine for suspension wires and electrical connections in displacement control mode is used to load the test specimens and monitor their state changes. When the specimens show signs of broken strands or strand disintegration, the test is immediately terminated and the failure time is accurately recorded. In step S24, the electrical connection resistance is selected as a degradation parameter to establish a vibration failure model. Combined with the set acceleration factor and the results of accelerated tests, the fatigue strength index of the material is solved by inversion.

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