Method for evaluating damage tolerance and residual life of track element at non-wheel-rail contact position in turnout area

Abstract

The application discloses a method for evaluating damage tolerance and residual life of a track element at a non-wheel-rail contact position of a turnout area, obtains a sample material of a non-wheel-rail rolling contact area of a turnout track element, and obtains crack propagation data of the sample material through testing to fit Paris formula parameters. Then, finite element stress analysis of the turnout track element is carried out, the result file is imported into crack analysis software, and a crack is inserted at the non-wheel-rail rolling contact position of the track element to obtain a crack analysis model of the non-wheel-rail contact position part of the turnout track element. Finally, crack propagation simulation is carried out, the formula parameters are imported into the crack analysis software, and crack propagation simulation is carried out to obtain a calculated life. Indoor full-scale model verification is carried out, the calculated life is compared with an actual life, and it is confirmed whether the parameters and the model are accurate. If the parameters and the model are accurate, residual life of the turnout track element at the non-wheel-rail contact area is evaluated according to the model and the parameters. The application can save maintenance costs based on damage tolerance and residual life, and better guarantee the safety of railway operation.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of rail transit, and particularly relates to a method for evaluating damage tolerance and residual life of a rail piece at a non-wheel-rail contact position in a turnout area. BACKGROUND

[0002] A turnout is a lifeline of a railway line, is an important component of a railway track, is a connecting device for guiding a locomotive to turn into another lane, is an important device on a railway track, and is one of the weakest devices in a railway line. Ensuring the safety of the turnout is very important for the safety of the railway line.

[0003] The main function of a turnout rail is to guide the wheels to travel on the track and to transmit and bear various loads generated by the traveling vehicles. The service performance of the turnout rail piece plays an extremely important role in the safe operation of the railway vehicle. The turnout switch and the movable heart rail part change the position of the point rail or the heart rail by driving the point rail or the heart rail by a switch machine, so that the wheel load is transferred from the basic rail / wing rail to the point rail / heart rail, thereby making the locomotive turn the line. In these wheel load transition areas, there is usually a large wheel load impact. At the same time, due to the combination of multiple rail pieces, there are many parts in these turnout areas, and stress concentration is inevitable. Under the long-term action of wheel-rail load, such stress concentration may lead to the initiation of cracks.

[0004] Currently, scholars' researches are more focused on the crack damage and residual life of the wheel-rail contact position of the turnout. The damage forms in the wheel-rail contact area mainly include inclined cracks on the rail head, peeling and spalling, and wear. The wheel-rail contact area can be inspected by conventional methods, and there is no problem of rail breakage caused by wheel-rail contact. However, for the non-wheel-rail contact area of the turnout, due to the cooperation of multiple parts at the rail waist or rail bottom position (such as the contact of the rail waist with the bolt and the rigid contact of the rail bottom with the bed plate), the rigid contact of each part with the rail is inevitable. Under the long-term action of train load, cracks gradually initiate. The fatigue of the non-wheel-rail rolling area is relatively hidden, and it is difficult to be found by conventional inspection. After serving for a certain period of time, the cracks gradually expand to cause the rail to break, which threatens the safety of train operation.

[0005] Therefore, how to provide a method for evaluating the damage tolerance and residual life of a rail piece at a non-wheel-rail contact position in a turnout area is a problem that needs to be solved by those skilled in the art. Based on the evaluation of the damage tolerance limit value and the residual life of the rail piece, different types of defects can be analyzed and judged, and corresponding replacement or maintenance strategies can be developed. At the same time, it can provide a basis for the development of the detection cycle of the maintenance department, and ensure the safe service of the rail piece within the detection cycle. SUMMARY

[0006] In view of this, the present application provides a kind of switch area non-wheel rail contact position track piece damage tolerance and residual life evaluation method, combined with the actual damage situation statistical analysis of current railway switch track piece, the damage of switch non-wheel rail contact position is more likely to lead to the situation of track fracture, the existing life prediction object is mainly in the region of rail top surface, these regions are large stress, easy to simulate, relevant scholars have proposed a variety of wheel-rail contact area fatigue damage prediction model and propose corresponding damage limit value.The stress of switch area rail bottom region is usually small, the stress level is lower than the fatigue limit, and the crack propagation period is longer, the existing life prediction method is not suitable, leading to inaccurate life prediction of switch steel rail under different conditions, the present application can more accurately predict the residual life of switch by evaluating the life of switch non-contact position, and provide certain reference for the optimization of switch maintenance system, save maintenance cost and better guarantee the safety of railway operation.

[0007] In order to achieve the above purpose, the present application adopts the following technical scheme: a kind of switch area non-wheel rail contact position track piece damage tolerance and residual life evaluation method, comprising the following steps:

[0008] Step one: crack propagation data acquisition, first design switch steel rail sampling scheme, obtain the hardness of non-wheel rail contact area lower area by hardness test of switch steel rail section, sample in the area, obtain the sample material of switch main rail, process to obtain crack propagation sample, and obtain crack propagation data of sample material by crack propagation test, and obtain Paris formula parameters by data fitting curve;

[0009] Step two: switch steel rail piece finite element stress simulation, establish vehicle-switch dynamics coupling model, obtain switch and switch frog wheel load transition zone wheel-rail interaction load, establish fine switch steel rail component mechanical model, consider the interaction of combined steel rail piece, the action of connecting parts, fastener system, etc., focus on refining the area where the steel rail piece exists hard contact;Based on wheel-rail load and switch fine mechanical model, considering the variable cross-section characteristics of switch track piece and the impact load characteristics when train passes through switch, stress analysis of switch track piece is carried out, the analysis result file is imported into crack analysis software and crack is inserted in non-wheel rail contact position of switch steel rail piece, and crack analysis model of non-wheel rail contact position part of switch steel rail piece is obtained;

[0010] Step three: crack propagation simulation, based on step two, import formula parameters in step one into crack analysis software and carry out crack propagation simulation, based on the relationship between steel rail stress level and steel rail material crack propagation speed under wheel-rail load, obtain the residual life curve of switch main rail non-contact area;Obtain the calculated residual life under different defect and load conditions according to residual life curve;

[0011] Step four: indoor full-scale model test is carried out, precast defects are made on the rail bottom of the turnout rail, and fatigue loading test is carried out, the actual residual life of the rail under the current load and defect condition is obtained, the calculated residual life under the current load parameter and defect is obtained according to the residual life curve of step three, the calculated residual life is compared with the actual residual life, whether the parameters in step one and the model in step two are accurate is confirmed, if accurate, the model and the parameters can be used to evaluate the residual life of the non-wheel-rail contact area of the turnout rail.

[0012] Step five: the turnout is evaluated, the state of the turnout is checked, the defect condition of the non-wheel-rail contact area of the turnout rail at present is obtained, if there is a certain degree of processing defect or corrosion defect, when the size of the processing defect or the corrosion defect is greater than the damage tolerance limit value, the rail needs to be determined as scrap and needs to be replaced immediately. When the defect size is less than the damage tolerance limit value, the residual life of the current rail is obtained in combination with the residual life curve, and the rail needs to be checked again within the residual life cycle to ensure that the rail will not break.

[0013] The beneficial effects of the present application are: the present application evaluates the life based on the non-wheel-rail contact position of the turnout rail. At present, the high-speed turnout usually performs heat treatment on the rail top, and there is no strict standard for the material performance of the rail bottom. Based on the sampling of the rail bottom, the real fatigue parameters of the weak position are obtained, a refined and reliable life prediction model is established, the residual life prediction of different types of rail pieces of the turnout under different defect conditions can be realized, the residual life of the turnout can be more accurately estimated, the simulation model and formula parameters close to the actual situation can be obtained through the method, the residual life of the non-contact position of the turnout rail piece under different defect sizes and working conditions can be conveniently and quickly predicted through the simulation model and formula parameters, and the evaluation method can be popularized to the life prediction of other railway tracks or parts, thereby providing a reference for the optimization of railway repair schedule, saving labor cost and ensuring the safety of railway operation.

[0014] Preferably, in step two, the non-wheel-rail contact position that is analyzed is the basic rail and straight nose rail of the turnout wheel load transition area, and the heart rail and wing rail of the frog wheel load transition area.

[0015] The technical effects generated thereby are: there are many rail components in the turnout wheel load transition area, there is wheel load transition and wheel load impact, it is the place where the maximum stress of rail damage occurs, and it has the most obvious crack propagation trend.

[0016] Preferably, in step one, the rail sampling can be close to the rail bottom position, the hardness of this area is lower, and the fatigue performance is relatively weak compared to other areas. The stress intensity factor and crack depth corresponding to the scatter plot are obtained by conducting a crack propagation test on the sample material, the scatter plot is taken as logarithmic coordinates in the horizontal and vertical directions, and the scatter plot is fitted, and the slope and intercept of the obtained straight line are the parameters of the Paris formula.

[0017] The technical effect produced by this is that the weak area of the rail bottom is sampled to obtain the real fatigue parameters of the area, which facilitates further prediction of the residual life of the non-wheel-rail contact position of the basic rail of the turnout, and the data reliability is high.

[0018] Preferably, in steps three and four, under the same load condition, if the deviation between the calculated residual life and the actual residual life is small, it can be considered that the model and the parameters are reasonable, and then the residual life of the non-contact position of the turnout rail under different defect sizes and loads is calculated by the model and the parameters.

[0019] The technical effect produced by this is that the residual life of the basic rail of the turnout under different defect sizes and different load conditions can be calculated according to the model and the parameters, and the calculation result can be used as a reference for the actual situation.

[0020] Preferably, in step four, the damage tolerance is determined according to the change trend of the residual life curve of the turnout rail, when the crack size rapidly increases with the increase of the number of load actions, the corresponding crack size is defined as the damage tolerance limit value of the rail, and according to the comparison of the defect size of the rail and the damage tolerance limit value, the residual life of the non-wheel-rail rolling region of the turnout rail can be evaluated in combination with the residual life curve.

[0021] The technical effect produced by this is that the maintenance scheme of the turnout rail is determined based on the damage tolerance and the residual life, which saves the maintenance cost and better guarantees the safety of railway operation. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The flowchart of the method for evaluating the damage tolerance and the residual life of the non-wheel-rail contact position of the turnout rail;

[0023] Figure 2 The scatter plot of the crack propagation of the rail bottom material obtained by the specific embodiment of the present application;

[0024] Figure 3 The rail bottom finite element simulation stress nephogram of the turnout basic rail model under the condition of 235kN load;

[0025] Figure 4 The residual life curve of the 3mm initial defect of the non-contact position of the turnout basic rail under the condition of 235kN load obtained by the crack analysis software simulation. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the scope of protection of the present application.

[0027] For specific application embodiments, refer to the drawings of the present application Figures 1 to 4 Taking fatigue damage of a basic rail of a turnout switch as an example, based on the hardness test results of the turnout rail section, a reasonable sampling scheme is designed to obtain sample materials at the turnout rail bottom position, stress intensity factors and crack depth corresponding scatter plots are obtained by performing a crack propagation test on the sample materials, and reference is made to the scatter plots in the drawings of the present application. Figure 2 and the drawings of the present application Figure 3 The logarithmic coordinates of the horizontal and vertical axes of the scatter plot are taken and the scatter points are fitted, and the slope and intercept of the obtained straight line are the parameters of the Paris formula. Then, a vehicle-turnout dynamics coupling model is established to obtain the wheel-rail dynamic load in the transition zone of the switch and frog. Then, a fine simulation model of the basic rail of the turnout is established, the curved basic rail, the straight frog, the fastener, the rail under the rubber pad, the sliding bed plate, the elastic base plate and the contact relationship of each component are considered, and a 235kN wheel-rail load is applied to the top of the straight frog in the wheel load transition zone. The finite element result file is imported into the crack analysis software, and a 3mm initial defect is inserted at the non-contact position of the rail bottom. The initial defect position and size need to be consistent with the position and size of the full-scale rail test (this process is to obtain the real data), and then the Paris formula parameters obtained by the crack propagation test are imported to perform crack propagation simulation, and finally the residual life curve of the turnout basic rail under the 235kN load and the 3mm initial defect is obtained. According to the simulation model, it can be obtained that the number of cycles required for the crack to extend from 3mm to 20mm is about 420,000 times. A full-scale model of the switch rail is established in the laboratory, and the same load and initial defect in the model are applied and calculated. After 40 million times of fatigue load, the rail bottom crack extends to 20mm, and the model calculation result is close to the test data, so it can be considered that the model and parameters are reasonable, and then the model and parameters are used to calculate the non-contact position life of the turnout basic rail under different defect sizes and loads.

[0028] It should be noted that when the model is established, the related components such as the turnout basic rail, the frog, the sliding bed plate and the like are all established, but the verification of effectiveness is mainly the basic rail bottom part, so the mesh refinement needs to be performed on the basic rail bottom and the area where the basic rail bottom and the sliding bed plate have a hard contact.

[0029] The present application provides a method for evaluating the residual life of the non-contact area of the turnout rail piece. The method includes five steps of crack propagation data acquisition, finite element stress simulation, crack propagation simulation, indoor full-scale test and basic rail residual life judgment.

[0030] Firstly, the rail bottom is sampled, and the crack propagation specimen is processed after the block is taken from the rail, the crack propagation data of the switch basic rail bottom material is obtained through the test, and the Paris formula parameters are obtained through data fitting.

[0031] Secondly, a vehicle-switch dynamic coupling model is established to obtain the wheel load characteristics of the key section, a fine mechanical model of the switch rail piece is further established, the finite element stress analysis of the switch basic rail is carried out, the result file is imported into the crack analysis software, and the crack is inserted in the non-contact position of the software model of the switch, so that the crack propagation model of the basic rail bottom part is obtained.

[0032] Thirdly, according to step two, the formula parameters obtained by importing the test data into the crack analysis software are used for crack propagation simulation to obtain the calculation life of the rail under certain defect conditions.

[0033] Fourthly, indoor full-scale tests are carried out, the same load and defect as the calculation model are applied, the calculation residual life is compared with the test result, and whether the parameters and the model are accurate is confirmed, if accurate, the residual life of the non-contact area of the switch basic rail can be evaluated according to the model and the parameters.

[0034] Fifthly, the damage tolerance is defined at the position where the crack rapidly increases based on the residual life curve of the basic rail, and the residual life of the switch rail is evaluated in combination with the field rail state, so as to guide whether the rail piece needs to be replaced immediately or can be used continuously and the next flaw detection inspection is carried out in a certain period.

[0035] In addition, the rail section hardness test scheme is to obtain the area with the lowest hardness of the rail piece, the crack propagation test is carried out in this area, and the residual life of this area is used as the judgment standard to determine the maintenance or replacement scheme of the rail piece, which is more reliable for the entire switch.

[0036] Through the method, the simulation model and the formula parameters close to the actual situation can be obtained, the residual life of the non-contact position of the switch basic rail under different defect sizes and working conditions can be conveniently and quickly predicted through the simulation model and the formula parameters, the evaluation method can be popularized to the life prediction of other railway tracks or parts, a reference is provided for the optimization of the railway repair system, the resource and manpower cost is saved, and the safety of railway operation is better guaranteed.

[0037] The life of the non-contact position of the switch is evaluated, the residual life of the switch can be more accurately predicted, a certain reference is provided for the optimization of the switch maintenance system, the maintenance cost is saved, and the safety of railway operation is better guaranteed.

[0038] For the device and use method disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the related part is described in the method part.

[0039] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Numerous modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without the use of the inventive faculty. Therefore, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for assessing the damage tolerance and remaining life of rail components at non-wheel-rail contact locations in turnout areas, characterized in that, Includes the following steps: Step 1: Crack propagation data acquisition. Based on the hardness distribution test of the turnout rail section, a rail component sampling scheme is designed in the non-wheel-rail contact area with lower hardness. Sample materials of the turnout rail components are obtained, and crack propagation data of the sample materials are obtained through experimental testing. The Paris formula parameters are obtained by fitting the data curve. Step 2: Finite element stress simulation of turnout rail components. Considering the variable cross-section characteristics of turnout rail components and the impact load characteristics when trains pass through the turnout, stress analysis of turnout rail components is performed. The analysis results are imported into crack analysis software and cracks are inserted at the non-wheel-rail contact positions of turnout rail components to obtain crack analysis models of the non-wheel-rail contact positions of turnout rail components. Step 3: Crack propagation simulation. Based on Step 2, import the formula parameters from Step 1 into the crack analysis software and perform crack propagation simulation to obtain the remaining life curve of the non-wheel-rail contact area of ​​the turnout rail component. Based on the remaining life curve, obtain the calculated remaining life under different defect conditions. Step 4: Conduct indoor full-scale model tests. Prefabricate defects at the bottom of the turnout rail components and conduct fatigue loading tests to obtain the actual remaining life of the rail components under the current load and defect conditions. Based on the remaining life curve in Step 3, obtain the calculated remaining life under the current load parameters and defects. Compare the calculated remaining life with the actual remaining life to confirm whether the parameters in Step 1 and the model in Step 2 are accurate. If accurate, the remaining life of the non-wheel-rail contact area of ​​the turnout rail components can be evaluated based on the model and parameters.

2. The method for assessing damage tolerance and remaining life of rail components at non-wheel-rail contact positions in turnout areas according to claim 1, characterized in that, In step two, the non-wheel-rail contact range that needs to be evaluated mainly includes the main rail and straight tip rail in the turnout wheel-load transition zone, and the center rail and wing rail in the frog wheel-load transition zone.

3. The method for assessing damage tolerance and remaining life of rail components at non-wheel-rail contact positions in turnout areas according to claim 1, characterized in that, In step one, based on the hardness distribution of the turnout rail section, the region with the lowest hardness is analyzed and sampled in this region. A reasonable sampling range and sampling size are selected, and a crack propagation test is performed on the sample material to obtain a scatter plot corresponding to the stress intensity factor and crack depth. The horizontal and vertical axes of the scatter plot are taken as logarithmic coordinates and the scatter plot is fitted. The slope and intercept of the resulting straight line are the parameters of the Paris formula.

4. The method for assessing damage tolerance and remaining life of rail components at non-wheel-rail contact positions in turnout areas according to claim 1, characterized in that, In steps three and four, under the same load and defect conditions, if the calculated remaining life deviates little from the actual remaining life, the model and parameters can be considered reasonable. Then, the non-contact position life of the turnout rail under different defect sizes and loads can be calculated using the model and parameters.

5. The method for assessing damage tolerance and remaining life of rail components at non-wheel-rail contact positions in turnout areas according to claim 1, characterized in that, In step four, the damage tolerance is determined based on the changing trend of the remaining life curve of the turnout rail component. When the crack size increases rapidly with the increase of the number of load applications, the corresponding crack size is defined as the damage tolerance limit of the rail component. Based on the comparison between the rail component defect size and the damage tolerance limit, combined with the remaining life curve, the remaining life of the rail component in the non-wheel-rail rolling area of ​​the turnout can be evaluated.

6. A method for assessing damage tolerance and remaining life of rail components at non-wheel-rail contact positions in turnout areas according to any one of claims 1-5, characterized in that, It also includes step five, which involves evaluating the turnout, checking the condition of the turnout rail components, and obtaining the current defect status of the non-wheel-rail contact area of ​​the turnout rail components. If there are certain degrees of processing defects or corrosion defects, and the size of the processing defects or corrosion defects exceeds the damage tolerance limit, the rail component must be determined to be scrapped and must be replaced immediately. When the defect size is smaller than the damage tolerance limit, the remaining life of the rail is obtained by combining the remaining life curve. It needs to be inspected again within the remaining life cycle to ensure that the rail will not break.

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