Method for constructing accelerated life test load spectrum of integral dropper

Abstract

The invention discloses a method for constructing an accelerated life test load spectrum of an integral dropper, which comprises the following steps of: respectively constructing a vibration fatigue load spectrum and a pulse alternating current load spectrum according to simulated fatigue load and current data of the integral dropper, and constructing an accelerated life test load spectrum of the integral dropper after the vibration fatigue load spectrum and the pulse alternating current load spectrum are completed. Performing superposition loading by combining the two, deducing a test loading spectrum of the integral dropper according to a Miner damage principle and an electroplastic effect mechanism, and constructing a fatigue-alternating current impact superposition test loading spectrum; according to the construction method, the action mechanisms of current and mechanical stress are effectively combined on the basis of real working conditions, the working state of the dropper can be reflected more accurately, the actual failure mode of the dropper is better met, the constructed fatigue-alternating current impact superimposed loading spectrum can reflect the stress superimposed effect of the dropper in a complex environment, and the application range of the dropper is widened. By more comprehensively simulating the multi-working-condition environment of the dropper, the reliability of the test result is further improved.

Description

Technical Field

[0001] The invention relates to the technical field of electrified railways, and in particular to a method for constructing a load spectrum of an accelerated life test of an integral suspension string. Background Art

[0002] High-speed contact networks have fully shifted from the large-scale design and construction stage to the operation and maintenance stage, and some high-speed contact networks have begun to enter the middle and late stages of service. How to formulate a scientific and reasonable contact network precision measurement and maintenance strategy is a problem that my country's power supply maintenance departments must face.

[0003] Accurately assessing the reliable life of in-service contact network components and accurately predicting their remaining life are of great significance for selecting the timing of batch replacement of the same type of components. Considering the cost, the time is not yet ripe for large-scale online monitoring of the technical status of massive contact network components. Therefore, according to the provisions of TG / GD-2014 "Rules for Operation and Maintenance of High-speed Railway Contact Network", in-service components should be disassembled and inspected, and the performance of components should be evaluated through special tests to determine whether they are nearing the end of their life. A large number of engineering practices have proved that taking the integral hanging string of components as an example, the accelerated life test of reliability engineering can quickly and accurately evaluate its reliability. Therefore, the accelerated life test of the integral hanging string of high-speed contact network provides a practical technical path for the performance and life evaluation of the integral hanging string. However, the accelerated life test needs to maintain the original failure mechanism and mode of the integral hanging string, so it is necessary to construct a working load spectrum that matches the actual operating conditions. How to construct the working load spectrum of the integral hanging string is the key to the accelerated life test of components.

[0004] Although the existing accelerated life test method for integral suspension strings can well evaluate the performance and life of the integral suspension strings, it has the following defects:

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

[0006] (2) Some existing methods rely on limited test data or historical data, which makes it difficult to obtain comprehensive and accurate failure modes and distributions of the suspension strings. As a result, the constructed load spectrum cannot truly simulate the actual working conditions of the suspension strings.

[0007] (3) Traditional construction methods are often based on general load conditions and fail to fully consider the specific impacts of different environments and working conditions. For example, in actual applications, suspension strings are subject to complex vibrations and alternating loads, and existing methods have difficulty accurately reflecting these factors into the load spectrum.

[0008] (4) The load spectrum of the suspension string usually involves random stress changes, such as wind load, temperature change, etc. However, the existing construction methods usually adopt 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 suspension strings, which leads to doubts about the reliability of test results. In particular, when the life distribution is wide, the existing life model fails to reflect the actual life curve of the suspension string. Summary of the invention

[0010] In order to overcome the defects of the prior art, the present invention proposes a method for constructing a load spectrum for an accelerated life test of an integral suspension string, which mainly includes a method for constructing a working load spectrum under the action of vibration fatigue and pulsed alternating current and a method for constructing a test load spectrum. This method can be used to evaluate and test the fatigue life of the integral suspension string in high-speed railway and subway systems by realistically simulating the fatigue life of the suspension string under various load environments, helping railway operators determine the optimal maintenance and replacement cycle of the suspension string, thereby improving the safety and reliability of the railway system.

[0011] The purpose of the present invention can be achieved by the following technical solutions:

[0012] A method for constructing an accelerated life test load spectrum of an integral suspension string, the method comprising constructing a vibration fatigue load spectrum and a pulse alternating current load spectrum, and after completing the vibration fatigue load spectrum and the pulse alternating current load spectrum, combining the two for superimposed loading to simulate the actual operating conditions of the integral suspension string, and constructing a fatigue-AC impact superimposed test load spectrum;

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

[0014] S11: Based on the pantograph dynamics simulation, the dynamic characteristics of the suspension string are studied, the dynamic contact force of the pantograph and the catenary is described by the penalty function method, the coupling of the pantograph and the catenary model is realized, and the dynamic model of the pantograph and the catenary is constructed;

[0015] S12: Extract the coordinates of the nodes connecting the suspension string and the load-bearing cable with the contact line to obtain the stretching-relaxation condition of the suspension string and the vibration frequency of the suspension string;

[0016] S13: Using the four-point rain flow counting method and the Epanechnikov kernel function extrapolation, the mean-amplitude histogram of fatigue load cycles is obtained to characterize the load cycle frequency of the fatigue load spectrum of the suspension string;

[0017] S14: Apply Miner's linear cumulative damage theory and the fatigue life model of the suspension string to calculate the fatigue damage of mechanical parts and obtain the peak load corresponding to the fatigue load cycle at different levels;

[0018] S15: Calculate the damage distribution under different peak load levels, and based on Miner's cumulative damage law, calculate the cumulative fatigue damage of the suspension string working fatigue load spectrum, the cumulative fatigue damage value of the train passing the suspension string once under the single-bow working condition, and the cumulative fatigue damage value of the train passing the suspension string once under the double-bow working condition;

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

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

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

[0022] S23: extracting the two-dimensional working spectrum of the current according to the threshold value of the electroplastic effect to form the working load spectrum of the working current of the overall suspension string;

[0023] S24: Considering the influence of current density on the electroplastic effect, 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 bow-catenary dynamic model.

[0025] Furthermore, in order to accelerate the fatigue test of the suspension string, typical parameters are selected within the peak load distribution range of the extrapolated load spectrum of the suspension string. Among the peak loads of the fatigue load cycles of different levels, 700N is selected as the tensile force parameter of the fatigue test of the suspension string. This value is less than the maximum vertical working load of the entire suspension string of 1.3kN, which is a low-frequency large load under the full working condition of the suspension string. It can achieve the acceleration of the fatigue test of the suspension string while ensuring that the fatigue failure mechanism of the suspension string 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 period 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. The suspension string fatigue test cycle is cyclically loaded until the suspension string fails, and the number of loading times before the suspension string fails and breaks can be obtained.

[0027] Furthermore, in the construction of the fatigue-AC impact superposition test loading spectrum, the test loading time T of a single pantograph passing is determined according to the mechanical load loading frequency of the suspension string. d And by loading 14352 test cycles, the fatigue damage of the suspension string equivalent to 2060 bow stances was obtained.

[0028] Furthermore, in the process of constructing the fatigue-AC impact superposition test loading spectrum, the off interval time T of the current generator is set g , and every interval T g Load an AC pulse current once, and at the beginning of the compression condition of the first test cycle, synchronize the loading duration T e It is an AC pulse of 0.11 seconds. By analogy, the loading spectrum of the suspension string fatigue and electrical load superposition test is formed.

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

[0030] (1) Based on real working conditions, the present invention constructs fatigue working load spectrum and pulse current load spectrum by simulating the actual fatigue load and current data of the suspension string, respectively, so that the load spectrum is closer to the working conditions of the suspension string in actual use. Compared with the traditional method, the proposed construction method based on real working conditions can more accurately reflect the working state of the suspension string.

[0031] (2) The present invention fully considers the influence of current on the plasticity of the suspension string material, and derives the test loading spectrum based on the Miner damage accumulation principle and the electroplastic effect mechanism. The proposed vibration fatigue load spectrum and pulse AC current load spectrum construction method effectively combines the action mechanism of current and mechanical stress, which is more in line with the actual failure mode of the suspension string.

[0032] (3) Based on the basic load spectrum, the present invention further constructs a fatigue-AC impact superposition test load spectrum, so that the test load spectrum can reflect the stress superposition effect of the suspension string in a complex environment. This superposition method overcomes the problem of traditional methods ignoring random factors, helps to more comprehensively simulate the multi-condition environment of the suspension string, and improves the reliability of the test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is the overall flow chart of the present invention;

[0034] Figure 2 The diagram is the stretching-relaxation condition of the suspension string and the vibration frequency of the suspension string;

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

[0036] Figure 4 This is a schematic diagram of the hanging string fatigue test process;

[0037] Figure 5 It is a simulation model of chain circuit for traction power supply system;

[0038] Figure 6 It is the effective value distribution curve of the current flowing through the suspension string;

[0039] Figure 7 is the working load spectrum of the overall suspension string working current;

[0040] Figure 8 This is the current loading spectrum of the overall hanging string test;

[0041] Fig. 9 This is the loading spectrum of the suspension string fatigue and electrical load superposition test. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the invention, all other embodiments obtained by ordinary technicians in this field without creative work, any modifications, equivalent substitutions, improvements, etc., should be included in the protection scope of the present invention.

[0043] like Figure 1 As shown, a method for constructing a load spectrum of an accelerated life test of an integral suspension string, the method comprising constructing a vibration fatigue load spectrum and a pulsed alternating current load spectrum, after completing the vibration fatigue load spectrum and the pulsed alternating current load spectrum, combining the two for superimposed loading, simulating the actual operating conditions of the integral suspension string, and constructing a fatigue-AC impact superimposed test loading spectrum;

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

[0045] S11: Based on the pantograph dynamics simulation, the dynamic characteristics of the suspension string are studied, the dynamic contact force of the pantograph is described by the penalty function method, the pantograph model coupling is realized, the pantograph dynamic model is constructed, and the Newmark method is used to simulate and solve the pantograph dynamic model;

[0046] S12: Extract the coordinates of the nodes connecting the suspension string and the load-bearing cable with the contact line to obtain the tension-relaxation of the suspension string and the vibration frequency of the suspension string, such as Figure 2 As shown;

[0047] S13: Use the four-point rain flow counting method and use the Epanechnikov kernel function extrapolation, such as Figure 3 As shown, the mean-amplitude bar graph of the fatigue load cycle is obtained to characterize the load cycle frequency of the fatigue load spectrum of the suspension string;

[0048] S14: Apply Miner's linear cumulative damage theory and the fatigue life model of the suspension string to calculate the fatigue damage of mechanical parts and obtain the peak load corresponding to the fatigue load cycle at different levels;

[0049] S15: Calculate the damage distribution under different peak load levels, and based on Miner's cumulative damage law, calculate the cumulative fatigue damage of the suspension string working fatigue load spectrum, the cumulative fatigue damage value of the train passing the suspension string once under the single-bow working condition, and the cumulative fatigue damage value of the train passing the suspension string once under the double-bow working condition;

[0050] In order to accelerate the fatigue test of the hanging string, typical parameters are selected within the peak load distribution range of the extrapolated load spectrum of the hanging string. Among the peak loads of the fatigue load cycles of different levels, 700N is selected as the tensile force parameter of the hanging string fatigue test. This value is smaller than the maximum vertical working load of the entire hanging string of 1.3kN, which belongs to the low-frequency large load under the full working condition of the hanging string. It can achieve the acceleration of the fatigue test of the hanging string under the premise of ensuring that the fatigue failure mechanism of the hanging string remains unchanged.

[0051] In the process of constructing the vibration fatigue load spectrum, according to the barrel principle, the maximum compression amplitude within the vibration period 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. The suspension string fatigue test cycle is cyclically loaded until the suspension string fails, and the number of loading times before the suspension string fails and breaks can be obtained. The suspension string fatigue test process is as follows Figure 4 shown.

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

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

[0054] S22: Based on the chain circuit simulation model of the traction power supply system taking into account the elastic suspension cable, 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 threshold of the electroplastic effect to form the working load spectrum of the overall suspension string working current, such as Figure 7 As shown;

[0056] S24: Considering the influence of current density on the electroplastic effect, the current working spectrum exceeding the peak current threshold is taken as the test current loading spectrum, such as Figure 8 shown.

[0057] In the construction of the fatigue-AC impact superposition test loading spectrum, according to the equivalent peak load cycle number corresponding to the working load spectrum of the suspension string, each loading of 14352 test cycles can be equivalent to 2060 pantograph passes of the suspension string fatigue damage. In order to achieve the superposition of the suspension string fatigue load and the electrical load under 2060 pantograph passes, the test loading time T corresponding to a single pantograph pass is determined according to the mechanical load loading frequency of the suspension string.d At the beginning of the first test cycle compression condition, the synchronous loading duration T e The AC pulse is 0.11 seconds, and then the current generator is turned off for an interval of T g =T d -T e , each interval time T g Then load the AC pulse current again. By analogy, the loading spectrum of the suspension string fatigue and electrical load superposition test is formed, such as Fig. 9 shown.

[0058] In summary, according to the fatigue load and current data of the overall suspension string simulation, the fatigue working load spectrum and pulse AC current load spectrum of the overall suspension string were constructed respectively. According to the Miner damage principle and the electroplastic effect mechanism, the experimental loading spectrum of the overall suspension string was derived, and the fatigue-AC impact superposition experimental loading spectrum was further constructed.

[0059] In order to verify the rationality of the fatigue working load spectrum and pulse current load spectrum of the whole suspension string constructed by the present invention and ensure the accuracy of the superimposed loading spectrum in simulating the actual working condition and life prediction of the suspension string, the present invention has carried out the following Figure 2 to Figure 9 Experimental design and verification of the system shown. The fatigue working load spectrum and the pulse AC current load spectrum are superimposed in the simulation model to simulate the actual working state of the suspension string under complex working conditions. The parameters of the superimposed loading spectrum are adjusted according to the experimental data to ensure that the overall stress change of the suspension string under multiple loads conforms to the actual situation.

[0060] The construction method proposed in the present invention can be applied to situations where accurate simulation and evaluation of the life of the suspension strings are required, especially in the fields of rail transit, power transmission, etc. In high-speed railway and subway systems, it can be used to evaluate and test the fatigue life of the overall suspension strings. By using this test loading spectrum, the fatigue life of the suspension strings under various load environments can be more realistically simulated, helping railway operators to determine the optimal maintenance and replacement cycle of the suspension strings, thereby improving the safety and reliability of the railway system. It is also used for fatigue life testing of equipment such as conductors and insulators in high-voltage transmission lines. The loading spectrum of pulse current and mechanical stress superposition constructed using the inventive method can more realistically simulate the use of these devices under current shock and mechanical load, and support accurate life assessment of power system equipment.

Claims

1. A method for constructing a load spectrum for an accelerated life test of an integral suspension string, characterized in that: After the vibration fatigue load spectrum and the pulse AC current load spectrum are constructed, the vibration fatigue load spectrum and the pulse AC current load spectrum are loaded simultaneously to simulate the actual operating conditions of the overall suspension string and construct a fatigue-AC impact superposition test loading spectrum; The method for constructing the vibration fatigue load spectrum specifically comprises the following steps: S11: Based on the pantograph dynamics simulation, the dynamic characteristics of the suspension string are studied, the penalty function method is used to describe the dynamic contact force of the pantograph and the pantograph is coupled, and the dynamic model of the pantograph and the pantograph is constructed; S12: Extract the coordinates of the nodes connecting the suspension string and the load-bearing cable with the contact line to obtain the stretching-relaxation condition of the suspension string and the vibration frequency of the suspension string; S13: Using the four-point rainflow counting method and Epanechnikov kernel function extrapolation, the mean-amplitude histogram of fatigue load cycles is obtained; S14: Apply Miner's linear cumulative damage theory and the fatigue life model of the suspension string to calculate the fatigue damage of mechanical parts and obtain the peak loads of different levels of fatigue load cycles; S15: Calculate the damage distribution under different peak load levels. Based on Miner's cumulative damage law, calculate the cumulative fatigue damage of the suspension string working fatigue load spectrum, the cumulative fatigue damage value of the train passing the suspension string once under the single-bow working condition, and the cumulative fatigue damage value of the train passing the suspension string once under the double-bow working condition. The method for constructing the pulse alternating current load spectrum specifically comprises the following steps: S21: Establish a chain circuit model of 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: extracting a two-dimensional working spectrum of the current according to the threshold value of the electroplastic effect to form a working current load spectrum of the overall suspension string; S24: Considering the influence of current density on the electroplastic effect, the current working spectrum exceeding the peak current threshold is selected as the test current loading spectrum.

2. The method for constructing a load spectrum for an accelerated life test of an integral suspension string according to claim 1, characterized in that: The Newmark method is used to simulate and solve the bow-catenary dynamic model.

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

4. The method for constructing a load spectrum for an accelerated life test of an integral suspension string 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 period of the suspension string is taken as the test compression amplitude parameter, and the vibration frequency of the suspension string is taken as the loading frequency for cyclic loading.

5. The method for constructing a load spectrum for an accelerated life test of an integral suspension string according to claim 4, characterized in that: In the construction of the fatigue-AC impact superposition test loading spectrum, the test loading time T of a single pantograph passing is determined according to the mechanical load loading frequency of the suspension string. d And by loading 14352 test cycles, the fatigue damage of the suspension string equivalent to 2060 bow stances was obtained.

6. The method for constructing a load spectrum for an accelerated life test of an integral suspension string according to claim 5, characterized in that: In the process of constructing the fatigue-AC impact superposition test loading spectrum, the off interval time T of the current generator is set g , and every interval T g Load an AC pulse current once, and at the beginning of the compression condition of the first test cycle, synchronize the loading duration T e It is an AC pulse of 0.11 seconds.

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