A method for constructing an accelerated life test load spectrum of integral chasers

Abstract

The application discloses a kind of whole sling's accelerated life test load spectrum construction methods, this method is according to the fatigue load and current data of whole sling simulation, respectively constructs vibration fatigue load spectrum and pulse alternating current load spectrum, after completing the vibration fatigue load spectrum and pulse alternating current load spectrum, superimposed loading is carried out in combination, and according to Miner damage principle and electroplastic effect mechanism, deduce the test loading spectrum of whole sling, constructs fatigue-alternating impact superposition test loading spectrum;The construction method is based on real working condition, effectively combines the action mechanism of current and mechanical stress, not only can more accurately reflect the working state of sling, and more in line with the actual failure mode of sling, the fatigue-alternating impact superposition loading spectrum constructed, can reflect the stress superposition effect of sling under complex environment, by more comprehensively simulating the multi-working condition environment of sling, further improve the reliability of test result.

Description

Technical Field

[0001] This invention relates to the field of electrified railway technology, specifically to a method for constructing the load spectrum of an integral dropper in accelerated life testing. Background Technology

[0002] The high-speed overhead contact system has shifted from the large-scale design and construction phase to the operation and maintenance phase, and some high-speed overhead contact systems have begun to enter the middle and late stages of service. How to formulate a scientific and reasonable strategy for the precise measurement and maintenance of the overhead contact system is a problem that my country's power supply maintenance departments must face.

[0003] Accurately assessing the reliable lifespan of in-service overhead contact line components and predicting their remaining lifespan is crucial for determining the timing of batch replacement of similar components. From a cost perspective, large-scale online monitoring of the technical condition of a massive number of overhead contact line components is not yet feasible. Therefore, according to relevant regulations, in-service components should be disassembled and inspected, and their performance should be evaluated through special tests to determine whether they are nearing the end of their service life. Extensive engineering practice has proven that, taking the overall dropper as an example, accelerated life testing in reliability engineering can quickly and accurately evaluate its reliability. Therefore, accelerated life testing of the overall dropper of high-speed overhead contact lines provides a practical technical path for evaluating the performance and lifespan of the overall dropper. However, accelerated life testing needs to maintain the original failure mechanisms and modes of the overall dropper, so a working load spectrum consistent with actual operating conditions must be constructed. How to construct the working load spectrum of the overall dropper is the key to accelerated life testing of components.

[0004] While existing accelerated life testing methods for integral droppers can effectively assess their role in evaluating performance and lifespan, they suffer from the following drawbacks:

[0005] (1) Many existing load spectrum construction methods only consider a single stress level or idealized stress distribution, while ignoring the stress changes of the overall suspension cable at different working stages and positions, which makes the accuracy and reliability of the load spectrum insufficient.

[0006] (2) Some existing methods rely on limited test data or historical data, making it difficult to obtain comprehensive and accurate failure modes and their distribution of droppers, resulting in the constructed load spectrum being unable to truly simulate the actual working conditions of droppers.

[0007] (3) Current traditional construction methods are often based on general load conditions and cannot fully consider the specific effects of different environments and working conditions. For example, in practical applications, droppers are subject to complex vibration and alternating loads, and existing methods cannot accurately reflect these factors in the load spectrum.

[0008] (4) The load spectrum of the suspension wire usually involves random stress changes, such as wind load and temperature changes. However, the existing construction methods usually use steady loads and lack consideration of these random factors, resulting in a large deviation between the test results and the actual situation.

[0009] (5) Existing methods often fail to accurately predict the fatigue life of droppers, leading to questions about the reliability of test results. Especially when the life distribution is wide, existing life models are unable to reflect the actual life curve of droppers. Summary of the Invention

[0010] To overcome the shortcomings of existing technologies, this invention proposes a method for constructing the accelerated life test load spectrum of an integral dropper, mainly including a method for constructing the working load spectrum under vibration fatigue and pulsed alternating current, and a method for constructing the test load spectrum. This method realistically simulates the fatigue life of the dropper under various load environments and can be used in high-speed railway and subway systems to evaluate and test the fatigue life of integral droppers, helping railway operators determine the optimal dropper maintenance and replacement cycle, thereby improving the safety and reliability of the railway system.

[0011] The objective of this invention can be achieved through the following technical solutions:

[0012] A method for constructing the accelerated life test load spectrum of an integral dropper, the method includes constructing a vibration fatigue load spectrum and a pulsed AC current load spectrum, and after completing the vibration fatigue load spectrum and the pulsed AC current load spectrum, combining the two for superposition loading to simulate the actual operating conditions of the integral dropper and constructing a fatigue-AC impact superimposed test load spectrum.

[0013] The method for constructing the vibration fatigue load spectrum specifically includes the following steps:

[0014] S11: Based on the dynamic simulation of the bow and catenary dynamics, the dynamic characteristics of the dropper are studied. The penalty function method is used to describe the dynamic contact force of the bow and catenary, realize the coupling of the bow and catenary models, and construct the dynamic model of the bow and catenary.

[0015] S12: Extract the coordinates of the connection nodes between the dropper and the catenary and the contact wire to obtain the tension-relaxation condition of the dropper and the vibration frequency of the dropper.

[0016] S13: Using the four-point rainflow counting method and extrapolating with the Epanechnikov kernel function, a mean-amplitude histogram of fatigue load cycles is obtained to characterize the load cycle frequency of the fatigue load spectrum of the dropper.

[0017] S14: Applying Miner's linear cumulative damage theory and the fatigue life model of the suspension wire, calculate the fatigue damage of mechanical parts and obtain the peak load corresponding to fatigue load cycles under different levels.

[0018] S15: Calculate the damage distribution under different peak load levels, and based on Miner's cumulative damage rule, calculate the cumulative fatigue damage of the working fatigue load spectrum of the dropper, the cumulative fatigue damage value of the train passing the dropper once under single-panel working condition, and the cumulative fatigue damage value of the train passing the dropper once under double-panel working condition.

[0019] The method for constructing the pulsed alternating current load spectrum specifically includes the following steps:

[0020] S21: Establish a chain circuit model for a multi-conductor parallel traction power supply system;

[0021] S22: Based on the simulation model of the chain circuit of the traction power supply system taking into account the elastic sling, the effective value distribution curve of the current flowing through the sling is obtained through simulation calculation;

[0022] S23: Extract the two-dimensional working spectrum of the current based on the electroplastic effect threshold to form the working load spectrum of the overall dropper working current;

[0023] S24: Considering the influence of current density on electroplasticity, the current working spectrum exceeding the peak current threshold is taken as the test current loading spectrum.

[0024] Furthermore, the Newmark method is used to simulate and solve the dynamic model of the pantograph-catenary system.

[0025] Furthermore, in order to accelerate the fatigue test of the dropper, typical parameters were selected within the peak load distribution range of the extrapolated load spectrum of the dropper. Among the peak loads of the different levels of fatigue load cycles, 700N was selected as the tensile force parameter for the fatigue test of the dropper. This value is less than the maximum vertical working load of the entire dropper (1.3kN), which belongs to the low-frequency large load under the full working condition of the dropper. This can accelerate the fatigue test of the dropper while ensuring that the fatigue failure mechanism of the dropper remains unchanged.

[0026] Furthermore, in the process of constructing the vibration fatigue load spectrum, according to the barrel principle, the maximum compression amplitude within the vibration cycle of the dropper is taken as the test compression amplitude parameter, and the vibration frequency of the dropper is used as the loading frequency for cyclic loading. The dropper fatigue test cycle is cyclically loaded until the dropper fails, thus obtaining the number of loading cycles before the dropper fails and breaks.

[0027] Furthermore, in constructing the fatigue-AC impact superimposed test loading spectrum, the test loading time for a single pantograph pass is determined based on the loading frequency of the dropper's mechanical load. The fatigue damage of the string was equivalent to 2060 bow frame cycles by loading 14352 test cycles.

[0028] Furthermore, during the construction of the fatigue-AC impact superimposed test loading spectrum, the turn-off interval of the current generator is set. And every interval Apply an AC pulse current, and simultaneously apply the current for a duration at the start of the compression condition in the first test cycle. An AC pulse of 0.11 seconds is used. This process is repeated to form the loading spectrum for the combined fatigue and electrical load test of the suspension cable.

[0029] Compared with the prior art, the present invention has the following technical effects:

[0030] (1) Based on real working conditions, this invention constructs fatigue working load spectrum and pulse current load spectrum by simulating the actual fatigue load and current data of the dropper, making the load spectrum closer to the working conditions of the dropper in actual use. Compared with traditional methods, the proposed construction method based on real working conditions can more accurately reflect the working state of the dropper.

[0031] (2) This invention fully considers the plastic effect of current on the dropper material and derives the experimental loading spectrum based on the Miner damage accumulation principle and the electroplastic effect mechanism. The proposed method for constructing the vibration fatigue load spectrum and pulsed AC current load spectrum effectively combines the action mechanism of current and mechanical stress, which is more consistent with the actual failure mode of the dropper.

[0032] (3) Based on the basic load spectrum, this invention further constructs a fatigue-AC impact superposition test load spectrum, which enables the test load spectrum to reflect the stress superposition effect of the dropper under complex environment. This superposition method overcomes the problem of ignoring random factors in traditional methods, helps to more comprehensively simulate the multi-condition environment of the dropper, and improves the reliability of the test results. Attached Figure Description

[0033] Figure 1 This is the overall flowchart of the present invention;

[0034] Figure 2 Diagram showing the tension-relaxation state of the dropper and the vibration frequency of the dropper;

[0035] Figure 3 A histogram showing the mean-amplitude of fatigue load cycles;

[0036] Figure 4 This is a schematic diagram of the fatigue test process for the suspension wire;

[0037] Figure 5 A simulation model of the chain circuit for the traction power supply system;

[0038] Figure 6 This is a graph showing the effective value distribution of the current flowing through the dropper.

[0039] Figure 7 The working load spectrum of the overall dropper working current;

[0040] Figure 8 The current loading spectrum for the overall dropper test;

[0041] Figure 9 The loading spectrum is for the fatigue and electrical load superposition test of the suspension wire. Detailed Implementation

[0042] 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.

[0043] like Figure 1 As shown, a method for constructing the accelerated life test load spectrum of an integral dropper is provided. The method includes constructing a vibration fatigue load spectrum and a pulsed AC current load spectrum. After completing the vibration fatigue load spectrum and the pulsed AC current load spectrum, the two are superimposed to simulate the actual operating conditions of the integral dropper and construct the fatigue-AC impact superimposed test load spectrum.

[0044] The method for constructing the vibration fatigue load spectrum specifically includes the following steps:

[0045] S11: Based on the dynamic simulation of the bow and catenary dynamics, the dynamic characteristics of the dropper are studied. The penalty function method is used to describe the dynamic contact force of the bow and catenary, realize the coupling of the bow and catenary model, construct the dynamic model of the bow and catenary, and use the Newmark method to simulate and solve the dynamic model of the bow and catenary.

[0046] S12: Extract the coordinates of the connection nodes between the dropper and the catenary and the contact wire to obtain the tension-slack condition of the dropper and the vibration frequency of the dropper, such as... Figure 2 As shown;

[0047] S13: Using the four-point rainflow counting method and extrapolating with the Epanechnikov kernel function, such as... Figure 3 As shown, a mean-amplitude histogram of fatigue load cycles is obtained to characterize the load cycle frequency of the fatigue load spectrum of the dropper.

[0048] S14: Applying Miner's linear cumulative damage theory and the fatigue life model of the suspension wire, calculate the fatigue damage of mechanical parts and obtain the peak load corresponding to fatigue load cycles under different levels.

[0049] S15: Calculate the damage distribution under different peak load levels, and based on Miner's cumulative damage rule, calculate the cumulative fatigue damage of the working fatigue load spectrum of the dropper, the cumulative fatigue damage value of the train passing the dropper once under single-panel working condition, and the cumulative fatigue damage value of the train passing the dropper once under double-panel working condition.

[0050] To accelerate the fatigue testing of the dropper, typical parameters were selected within the peak load distribution range of the dropper extrapolated load spectrum. Among the peak loads of the different levels of fatigue load cycles, 700N was selected as the tensile force parameter for the dropper fatigue test. This value is less than the maximum vertical working load of the entire dropper (1.3kN), which belongs to the low-frequency large load under the full working conditions of the dropper. This can accelerate the fatigue testing of the dropper while ensuring that the fatigue failure mechanism of the dropper remains unchanged.

[0051] In constructing the vibration fatigue load spectrum, based on the barrel principle, the maximum compression amplitude within the suspension string's vibration cycle is taken as the test compression amplitude parameter, and the suspension string's vibration frequency is used as the loading frequency for cyclic loading. The suspension string fatigue test cycle is cyclically loaded until the suspension string fails, thus obtaining the number of loading cycles before suspension string failure and fracture. The suspension string fatigue test process is as follows: Figure 4 As shown.

[0052] The method for constructing the pulsed alternating current load spectrum specifically includes the following steps:

[0053] S21: As Figure 5 As shown, a chain circuit model is established for a traction power supply system with multiple parallel conductors.

[0054] S22: Based on the simulation model of the chain circuit of the traction power supply system considering the elastic sling, the effective value distribution curve of the current flowing through the suspension cable is obtained through simulation calculation, such as... Figure 6 As shown;

[0055] S23: Extract the two-dimensional working spectrum of the current based on the electroplastic effect threshold to form the working load spectrum of the overall dropper working current, such as Figure 7 As shown;

[0056] S24: Considering the effect of current density on electroplasticity, the current operating spectrum exceeding the peak current threshold is taken as the experimental current loading spectrum, such as... Figure 8 As shown.

[0057] In constructing the fatigue-AC impact superimposed test loading spectrum, based on the equivalent peak load cycle number corresponding to the dropper working load spectrum, every 14352 test cycles can be equivalent to 2060 pantograph-times of dropper fatigue damage. To achieve the superposition of dropper fatigue load and electrical load under 2060 pantograph passes, the test loading time corresponding to a single pantograph pass is determined based on the dropper mechanical load loading frequency. At the start of the compression condition in the first test cycle, the duration of synchronous loading... A 0.11-second AC pulse was applied, and then the current generator was set to turn off at a specific interval. Each interval Apply another AC pulse current. Repeat this process to form the loading spectrum for the combined fatigue and electrical load test of the suspension wire, as shown below. Figure 9 As shown.

[0058] In summary, based on the fatigue load and current data of the integral dropper simulation, the fatigue working load spectrum and pulsed AC current load spectrum of the integral dropper were constructed respectively. Based on the Miner damage principle and the electroplastic effect mechanism, the experimental loading spectrum of the integral dropper was derived, and the experimental loading spectrum of fatigue-AC impact superposition was further constructed.

[0059] To verify the rationality of the overall dropper fatigue working load spectrum and pulse current load spectrum constructed in this invention, and to ensure the accuracy of the superimposed loading spectrum in simulating the actual working conditions and life prediction of the dropper, this invention has conducted the following... Figures 2-9 Experimental design and verification of the system shown. The actual working state of the dropper under complex conditions was simulated by superimposing the fatigue load spectrum and the pulsed AC current load spectrum in the simulation model. The parameters of this superimposed loading spectrum were adjusted based on experimental data to ensure that the overall dropper stress change under multiple loads conformed to the actual situation.

[0060] The construction method proposed in this invention can be applied to applications requiring precise simulation and evaluation of dropper life, particularly in rail transit and power transmission. In high-speed rail and subway systems, it can be used to assess and test the fatigue life of the entire dropper. By using this test loading spectrum, the fatigue life of the dropper under various load environments can be simulated more realistically, helping railway operators determine the optimal dropper maintenance and replacement cycle, thereby improving the safety and reliability of the railway system. It is also used for fatigue life testing of conductors, insulators, and other equipment in high-voltage transmission lines. The loading spectrum constructed using this invention, which combines pulsed current and mechanical stress, can more realistically simulate the operating conditions of these devices under current surges and mechanical loads, supporting accurate life assessment of power system equipment.

Claims

1. A method for constructing the load spectrum of an accelerated life test for an integral dropper, characterized in that, After constructing the vibration fatigue load spectrum and the pulsed AC current load spectrum, these two spectra are simultaneously applied to simulate the actual operating conditions of the integral dropper, thus constructing the fatigue-AC impact superimposed test loading spectrum. During the construction of the fatigue-AC impact superimposed test loading spectrum, the off-time of the current generator is set. And every interval Apply an AC pulse current, and simultaneously apply the current for a duration at the start of the compression condition in the first test cycle. An AC pulse of 0.11 seconds; The method for constructing the vibration fatigue load spectrum specifically includes the following steps: S11: Based on the dynamic simulation of the pantograph-catenary dynamics, the dynamic characteristics of the dropper are studied. The penalty function method is used to describe the dynamic contact force of the pantograph-catenary and to couple the models to construct a dynamic pantograph-catenary model. S12: Extract the coordinates of the connection nodes between the dropper and the catenary and the contact wire to obtain the tension-relaxation condition of the dropper and the vibration frequency of the dropper. S13: Using the four-point rainflow counting method and Epanechnikov kernel function extrapolation, a mean-amplitude histogram of fatigue load cycles is obtained; S14: Applying Miner's linear cumulative damage theory and the fatigue life model of the suspension wire, calculate the fatigue damage of mechanical parts and obtain the peak load of different levels of fatigue load cycles. S15: Calculate the damage distribution under different peak load levels. Based on Miner's cumulative damage rule, calculate the cumulative fatigue damage of the working fatigue load spectrum of the dropper, the cumulative fatigue damage value of the train passing the dropper once under single pantograph condition, and the cumulative fatigue damage value of the train passing the dropper once under double pantograph condition. The method for constructing the pulsed alternating current load spectrum specifically includes the following steps: S21: Establish a chain circuit model for a multi-conductor parallel traction power supply system; S22: Considering the influence of the elastic sling, the effective value distribution curve of the current flowing through the sling is obtained through simulation calculation; S23: Extract the two-dimensional working spectrum of the current based on the electroplastic effect threshold to form the working current load spectrum of the overall suspension cable; S24: Considering the influence of current density on electroplasticity, the current working spectrum exceeding the peak current threshold is selected as the test current loading spectrum.

2. The method for constructing the accelerated life test load spectrum of the integral dropper according to claim 1, characterized in that, The Newmark method was used to simulate and solve the dynamic model of the pantograph-catenary system.

3. The method for constructing the accelerated life test load spectrum of the integral dropper according to claim 2, characterized in that, Among the peak loads of the different levels of fatigue load cycles, 700N was selected as the tensile force parameter for the fatigue test of the dropper. This value is less than the maximum vertical working load of the entire dropper (1.3kN), and the test is accelerated under the premise that the fatigue failure mechanism of the dropper remains unchanged.

4. The method for constructing the accelerated life test load spectrum of the integral dropper according to claim 3, characterized in that, In the process of constructing the vibration fatigue load spectrum, according to the barrel principle, the maximum compression amplitude within the vibration cycle of the suspension string is taken as the test compression amplitude parameter, and the vibration frequency of the suspension string is used as the loading frequency for cyclic loading.

5. The method for constructing the accelerated life test load spectrum of the integral dropper according to claim 4, characterized in that, In constructing the fatigue-AC impact superimposed test loading spectrum, the test loading time for a single pantograph pass is determined based on the loading frequency of the dropper's mechanical load. The fatigue damage of the string was equivalent to 2060 bow frame cycles by loading 14352 test cycles.

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