Rail bottom stress estimating method and lateral pressure estimating method

Abstract

To provide a method to estimate rail bottom stress in curved rail sections, taking into account rail bottom stress not only in vertical but also horizontal components.SOLUTION: An estimating method includes: a step S2 of, by numerical analysis modeling rails and rail fastening devices, estimating the relationship between the lateral pressure acting on the rails and the stress difference obtained based on the rail bottom stress generated on the inside and outside of the rail gauge, as lateral pressure-stress difference relationship; a step S5 of estimating the rail bottom stress based on the lateral pressure generated on the curved section from the lateral pressure acting on the curved section and the lateral pressure-stress difference relationship; and a step S20 of estimating the overall rail bottom stress by adding the separately estimated vertical components of the rail bottom stress to the rail bottom stress based on the lateral pressure.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for estimating stress at the bottom of a rail in a curved section of a rail, and a method for estimating lateral pressure. [Background technology]

[0002] Fatigue failure from the rail bottom occurs when stress at the rail bottom increases due to unevenness on the rail head surface and floating sleepers when a train passes. To date, methods have been developed to estimate stress at the rail bottom using the amount of unevenness on the rail head surface and the amount of floating sleepers obtained from track inspection data, etc., in order to identify areas at risk of rail breakage on operating lines (see Patent Document 1).

[0003] The method disclosed in Patent Document 1 estimates the vertical component of rail bottom stress mainly due to the wheel load of a train, etc. In short, the vertical component of rail bottom stress generated in the rail when a train passes can be estimated by inputting information such as the wheel load, the amount of unevenness on the rail top surface, and the amount of floating sleeper. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7477489 Summary of the Invention [Problem to be solved by the invention]

[0005] However, while Patent Document 1 describes that rail bottom stress differs between the inner and outer gauge due to lateral pressure in curved track sections, it does not disclose a specific method for estimating the horizontal component of rail bottom stress due to lateral pressure.Since the contribution of lateral pressure becomes significant in curved rail sections, it is desirable to consider not only the vertical component of rail bottom stress but also the horizontal component of rail bottom stress.

[0006] Therefore, an object of the present invention is to provide a method for estimating rail bottom stress in curved rail sections, taking into account not only vertical but also horizontal components of rail bottom stress, and a method for estimating the related lateral pressure. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the method of estimating rail bottom stress of the present invention is a method of estimating rail bottom stress in a curved section of a rail, comprising the steps of: estimating, by numerical analysis using a model of the rail and its fastening devices, a relationship between the lateral pressure acting on the rail and a stress difference determined based on the rail bottom stress occurring on the inner and outer gauge sides of the rail, as a lateral pressure-stress difference relationship; estimating the rail bottom stress due to the lateral pressure occurring on the curved section from the lateral pressure acting on the curved section and the lateral pressure-stress difference relationship; and estimating the total rail bottom stress by adding a separately estimated vertical component of the rail bottom stress to the rail bottom stress due to the lateral pressure.

[0008] Here, the lateral pressure-stress difference relationship is determined by calculating the difference between the rail bottom stress on the outer gauge and the average of the rail bottom stresses on the inner and outer gauges as the stress difference. The lateral pressure-stress difference relationship is also determined as a linear relationship between the lateral pressure and the stress difference. Furthermore, the lateral pressure acting on the curved section can be a value estimated by a wheel load lateral pressure estimation formula based on the curve radius and cant of the curved section and vehicle conditions. The vertical component of the rail bottom stress can be estimated based on the amount of unevenness on the rail head surface and the amount of loose sleepers.

[0009] On the other hand, a method for estimating lateral force is a method for estimating lateral force acting on a curved section of a rail, comprising the steps of: estimating, by numerical analysis using a model of the rail and its fastening devices, a relationship between the lateral force acting on the rail and a stress difference obtained based on rail bottom stresses occurring on the inner and outer gauge of the rail at the curved section, as a lateral pressure-stress difference relationship; calculating the rail bottom stresses on the inner and outer gauge from peak values ​​measured by strain gauges installed on the inner and outer gauge of the rail bottom at the curved section when a vehicle passes through the curved section; and estimating the lateral force occurring on the curved section from the stress difference calculated based on the strain gauge measurements and the lateral pressure-stress difference relationship, wherein the stress difference is the difference between the rail bottom stress on the outer gauge and an average value of the rail bottom stresses on the inner and outer gauge. [Effects of the Invention]

[0010] In the method for estimating rail bottom stress of the present invention configured as described above, the relationship between the lateral pressure acting on the rail and the stress difference obtained based on the rail bottom stresses occurring on the inner and outer gauge sides of the rail is estimated in advance through numerical analysis as the lateral pressure-stress difference relationship.

[0011] Then, by using the relationship between lateral pressure and stress difference obtained through the analysis, the rail bottom stress generated by the lateral pressure acting on the curved section is estimated, and by adding the separately estimated vertical component of the rail bottom stress, the overall rail bottom stress is estimated.

[0012] Therefore, it is possible to estimate the rail bottom stress in curved rail sections, taking into account not only the vertical component but also the horizontal component of the rail bottom stress. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a flowchart illustrating a processing flow of a method for estimating stress at the rail bottom according to an embodiment of the present invention. [Figure 2]FIG. 1 is an explanatory diagram showing an outline of an FEM analysis model of a rail. [Figure 3] FIG. 2 is an explanatory diagram showing details of an FEM analysis model of a rail. [Figure 4] FIG. 1 is an explanatory diagram showing an outline of a curved section of a rail that was measured on-site. [Figure 5] FIG. 10 is an explanatory diagram showing the relationship between wheel load and stress obtained from the measurement results. [Figure 6] FIG. 10 is an explanatory diagram showing the relationship between lateral pressure and stress difference obtained from the measurement results. [Figure 7] FIG. 10 is an explanatory diagram comparing the relationship between lateral pressure and stress difference obtained from the measurement results with the relationship between lateral pressure and stress difference obtained from the FEM analysis results. [Figure 8] FIG. 10 is an explanatory diagram showing track conditions for curved sections. [Figure 9] FIG. 10 is an explanatory diagram showing the relationship between lateral pressure and stress difference obtained from the results of FEM analysis. [Figure 10] FIG. 10 is an explanatory diagram of an analytical model for wheel load fluctuation simulation with floating sleepers installed. [Figure 11] FIG. 10 is an explanatory diagram showing the relationship between the amount of lift and the amount of unevenness obtained by a wheel load fluctuation simulation and the stress at the rail bottom. [Figure 12] 10 is a flowchart illustrating a process flow of a lateral force estimation method according to the first embodiment. [Figure 13] 1A and 1B are diagrams for explaining the positions at which strain gauges are attached, in which (a) is an explanatory diagram showing a schematic plan view of a curved portion of a rail, and (b) is an explanatory diagram showing a perspective view of the rail. [Figure 14] FIG. 1 is an explanatory diagram illustrating the waveform of stress at the bottom of a rail when a train passes. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a flowchart illustrating the process flow of a method for estimating stress at the rail bottom according to the present embodiment.

[0015] As mentioned above, it is known that fatigue failure from the rail bottom occurs when the stress at the rail bottom increases due to the influence of unevenness on the rail head surface and floating sleepers when a train passes. Therefore, as described in Patent Document 1 and as will be described later, the vertical component of the stress at the rail bottom that occurs in the rail when a train passes is estimated by inputting information such as the wheel load, unevenness on the rail head surface, and floating sleepers (see step S10).

[0016] On the other hand, it is known that in curved sections of track, the horizontal component of the rail bottom stress increases due to the lateral pressure acting on the rail from the vehicle wheels when a train passes. In particular, it is highly important to accurately understand the rail bottom stress on the outer gauge, which is greater than the rail bottom stress on the inner gauge.

[0017] For example, when evaluating the integrity of rails at any rail position (kilometers) on a railway line in operation, it is necessary to evaluate the integrity of rails in curved sections by taking into account not only the vertical component of stress at the bottom of the rail, but also the horizontal component of stress at the bottom of the rail.

[0018] Therefore, in the method for estimating the rail bottom stress in a curved section of a rail according to this embodiment, first, the rail bottom stress based on the lateral pressure acting on the curved section of the rail is estimated. The lateral pressure acting on the curved section of the rail can be estimated from the linear conditions of the track and the vehicle conditions of the train running on the track (see step S1).

[0019] There are several known methods for estimating the lateral force acting on curved rail sections, so any of these methods can be used. For example, the "Railway Technical Research Institute: Design Standards and Commentary for Railway Structures, 2012" describes a wheel load and lateral force estimation formula that can estimate the lateral force acting on curved sections by setting linear conditions such as curve radius and cant, as well as vehicle conditions. The method described here also takes track irregularity into account. It is also possible to estimate the lateral force acting on curved rail sections by simulating vehicle operation using numerical analysis.

[0020] Meanwhile, the relationship between lateral pressure and stress difference, which will be described later, is estimated by numerical analysis (FEM analysis) in which the rail and rail fastening devices are modeled (see step S2). Fig. 2 is an explanatory diagram showing an overview of the FEM analysis model of the rail. Fig. 3 is an explanatory diagram showing the details of the FEM analysis model of the rail.

[0021] FEM analysis is performed by modeling the rail R that forms the inner rail and the rail R that forms the outer rail in the curved section, as shown in Figure 2. Each rail R is fixed to and supported by a sleeper via a fastening device, so support conditions for the rail R of the sleeper, such as vertical and horizontal springs, are set. In addition, the longitudinal direction of the rail R is constrained by boundary conditions.

[0022] Each rail R is divided into meshes as shown in Figure 3. For the rail fastening device, a tip spring T1 connected to the top surface of the rail bottom, and vertical and horizontal springs T2 connecting the rail bottom and the top surface of the sleeper are set.

[0023] In FEM analysis, simulations are repeated by varying the lateral pressure acting horizontally on the head of the rail R while the wheel load of the vehicle, which acts as a vertical load, is applied to the top surface of the rail R. In each simulation, attention is focused on the stress generated on the inside R1 and outside R2 of the rail bottom. In other words, the rail bottom stress generated on the inside R1 and outside R2 in the gauge direction between the inner and outer rails is found for any lateral pressure.

[0024] Here, the behavior of the rail R, which is related to the stress at the rail bottom when lateral pressure is applied, is more complex than in straight sections where only vertical wheel load is applied. In curved sections, different lateral pressures act on the rail R of the inner and outer rails, and when lateral pressure is applied, horizontal bending and torsional bending occur simultaneously. Furthermore, the characteristics of the fastening devices that support the rail R will differ depending on the fastening spacing and type of fastening springs (T1, T2). In order to obtain the relationship between lateral pressure and stress taking these behaviors into account, an FEM analysis is performed.

[0025] Then, the relationship between the lateral pressure acting on the rail and the stress difference calculated based on the rail bottom stress generated on the inner (R1) and outer (R2) sides of the rail gauge is derived as the lateral pressure-stress difference relationship.

[0026] Here, the relationship between lateral pressure and stress at the bottom of a rail will be explained based on the results of actual measurements taken at a curved section. Figure 4 is an explanatory diagram showing an outline of a curved section of a rail where on-site measurements were taken.

[0027] The on-site measurements were carried out on single-track sections of commercial lines running in both up and down directions, measuring the stress at the bottom of the rail in uneven areas where unevenness and loose sleepers had occurred on the rail head surface, as well as in healthy sections. The curved section where the on-site measurements were carried out was a ballast track with a rail type of 50 kgN, a curve radius R of 300 m, and a cant C of 105 mm.

[0028] The uneven section had significant irregularities on the rail head surface, and there was also a 4mm loose sleeper. On the other hand, the sound section had almost no irregularities. Strain gauges were therefore installed in the sound section and the uneven section to measure the wheel load and lateral pressure when a train passed, as well as the stress at the bottom of the rail.

[0029] The results of measurements taken when each axle of 16 trains that traveled through this curved section were passed are summarized in Figure 5. Figure 5 is an explanatory diagram showing the relationship between wheel load and stress obtained from the measurement results. In detail, the peak value of wheel load was extracted, and the stress was calculated as the average value of the inner and outer radius R1 and R2 of the rail bottom (see Figure 3).

[0030] Looking at the measurement results in Figure 5, the measured values ​​are plotted in three groups: healthy section, uneven section (downbound), and uneven section (upbound), and it can be seen that the relationships between each group are quite different. On the other hand, when the relationship between the peak value of lateral force and the stress difference (described below) is reorganized as in Figure 6, it can be seen that a certain relationship is observed regardless of the conditions of the healthy section or the upbound and downbound trains in the uneven section.

[0031] The stress difference, plotted on the vertical axis of Fig. 6, is the difference in stress obtained by subtracting the average value of the rail bottom stress from the stress at the rail bottom on the outer gauge (R2). In other words, the stress difference, which is the difference between the rail bottom stress at the outer gauge (R2) and the average value of the rail bottom stresses at the inner gauge (R1) and outer gauge (R2), is plotted on the vertical axis of Fig. 6. The relationship between lateral pressure and stress difference obtained in this way shows that the same linear relationship is observed between lateral pressure and stress difference, regardless of the conditions of up and down trains on healthy sections and uneven sections.

[0032] In curved sections, the rail bottom stress value on the outer side R2 is larger, so if the effect of lateral pressure is considered a risk, the rail bottom stress on the outer side of the gauge (R2), where the risk is higher, will be used.

[0033] The stress difference is then calculated by subtracting the average of the rail bottom stresses on the inner gauge (R1) and outer gauge (R2) from the rail bottom stress on the outer gauge (R2). This makes it possible to calculate a stress difference in which the vertical component due to the wheel load is canceled out. This type of stress difference makes it possible to highlight the influence of lateral pressure in the left-right direction (inside and outside the gauge).

[0034] Therefore, the average value of the rail bottom stress on the inside gauge (R1) and the rail bottom stress on the outside gauge (R2) is calculated from the stresses at the rail bottom for each lateral force obtained by simulation using FEM analysis (see step S3).

[0035] The difference between the stress at the bottom of the rail on the outer gauge and the average value of the stress at the bottom of the rail is then calculated as the stress difference (see step S4). The relationship between the lateral pressure and the stress difference obtained by this calculation is summarized as the result of FEM analysis. Figure 7 is an explanatory diagram comparing the relationship between the lateral pressure and the stress difference obtained from the measurement results and the relationship between the lateral pressure and the stress difference obtained from the FEM analysis results.

[0036] The results in Figure 7 show that the FEM analysis is able to accurately reproduce the values ​​of on-site measurements. Furthermore, it is clear that the relationship between the lateral pressure and stress difference in the curved section can be derived simply by performing FEM analysis, without having to perform on-site measurements.

[0037] Fig. 8 is an explanatory diagram showing track conditions for a curved section of a certain track. An example of applying the rail bottom stress estimation method of this embodiment shown in the flowchart of Fig. 1 to the rail bottom stress occurring in the curved section under these track conditions will be described below.

[0038] The lateral force acting on the curved section estimated in step S1 can be estimated by inputting track linear conditions, such as a curve radius of 300m and a cant of 80mm, as well as vehicle conditions, such as a train speed of 70km / h and a wheel load of 60kN, into the wheel load lateral force estimation formula described in "Railway Technical Research Institute: Design Standards and Commentary for Railway Structures, etc., Track Structures, 2012." The lateral force calculated from the conditions of this curved section was estimated to be 19.0kN.

[0039] The FEM analysis in step S2 is performed as described above using parameters such as rail type 50 kgN, PC No. 6 sleepers, track pad spring constant 110 MN / m, slack 20 mm, and fastening spacing and fastening spring of the fastening device. This FEM analysis makes it possible to determine the stress on the inside and outside of the gauge at the bottom of the rail in response to various lateral forces given as variables.

[0040] In step S3, the average value of the rail bottom stress on the inside of the gauge (inside R1 in Figure 3) and the rail bottom stress on the outside of the gauge (outside R2 in Figure 3) obtained by FEM analysis is calculated.

[0041] In the next step S4, the stress difference is calculated by subtracting the average value of the rail bottom stress calculated in step S3 from the stress at the rail bottom on the outer side of the gauge (outside R2 in Fig. 3). Fig. 9 is a graph showing the relationship between the lateral pressure and the stress difference obtained from the results of this FEM analysis.

[0042] In step S5, the lateral pressure of 19 kN acting on the curved section estimated in step S1 is input into the graph of the lateral pressure vs. stress difference relationship (Fig. 9). The stress difference calculated from this is 38.8 MPa. In other words, the horizontal component of the stress at the bottom of the rail due to the lateral pressure is 38.8 MPa.

[0043] Meanwhile, in parallel with or before or after the process of estimating the horizontal component of rail bottom stress due to lateral pressure, the vertical component of rail bottom stress is estimated using a stress estimation method with parameters of a wheel load of 60 kN, the amount of unevenness on the rail top surface, and the amount of floating sleeper (step S10).

[0044] In recent years, advances in track inspection technology have made it possible to obtain information on the amount of unevenness and the amount of loose sleepers at each rail position. Regarding the amount of unevenness on the rail head surface, there are methods for estimating it from the axle box acceleration obtained from track inspection ("Study on the condition evaluation and management method of rail corrugation using axle box acceleration measured by a track inspection vehicle" (Tanaka et al., Journal of Structural Engineering, Japan Society of Civil Engineers, Vol. 63A, March 2017)), and continuous measurement methods ("Development of a continuous rail unevenness measurement device using the eccentric arrow method and its application to measuring rail corrugation" (Tanaka et al., Journal of the Japan Society of Mechanical Engineers, Vol. 85, No. 880, 2019, p. 19-00235)). In addition, technology for estimating the amount of floating sleepers is disclosed in JP 2020-16094 A and in "Method for detecting floating sleepers based on track displacement data" (Kusuda et al., Journal of the Japan Society of Civil Engineers, Vol. 59, No. 66, pp. 33-35, 2012).

[0045] Next, the method of estimating the vertical component of rail bottom stress generated in the rail when a train passes, which is disclosed in Patent Document 1, will be outlined with reference to Fig. 10. Fig. 10 is an explanatory diagram of an analytical model for wheel load fluctuation simulation with floating sleepers installed.

[0046] The wheel load variation simulation with floating sleepers is a numerical analysis using an analytical model of wheel running with floating sleepers, as shown in Fig. 10. In this analytical model, the amount of unevenness on the rail head surface is also set.

[0047] Fig. 11 is an explanatory diagram showing the relationship between the amount of lift d and the amount of unevenness z obtained from the wheel load fluctuation simulation and the rail bottom stress S. As shown in Fig. 11, the vertical component of rail bottom stress S generated on the rail when a train passes can be estimated if there is information on the amount of unevenness z on the rail head surface and the amount of lift d of the floating sleeper in addition to information on the wheel load acting on the rail. S=16.4z+6.63d+31.5 Here, 31.5 MPa represents the vertical component due to the wheel load.

[0048] Finally, in step S20, the vertical component of the stress at the rail bottom calculated in step S10 is added to the horizontal component of the stress at the rail bottom calculated in step S5. For example, if there is no uplift d or unevenness z, the vertical component of the stress at the rail bottom is calculated as 31.5 MPa from the above formula, so the total stress at the rail bottom is 70.3 MPa, which is 31.5 MPa (vertical component due to wheel load) + 38.8 MPa (horizontal component due to lateral pressure). In this example, the horizontal component due to lateral pressure in the curved section accounts for more than half of the total stress at the rail bottom, so it is clear that the contribution of lateral pressure is significant when estimating the stress at the rail bottom in the curved section, and its influence cannot be ignored.

[0049] The rail bottom stress estimated in this way can be used to evaluate the rail soundness. For example, the rail soundness for approximately one kilometer of a curved section can be evaluated based on the current rail fatigue strength and the estimated rail stress. Details of the rail soundness evaluation index are described in Patent Document 1, but it can be calculated using the following formula. Rail soundness = 1 - (stress at rail base) / (rail fatigue strength)

[0050] Rail soundness is calculated quantitatively as a number below 1. For example, if the calculated rail soundness value is below a threshold set by the railway operator, the area can be judged as a point requiring attention or other rail action. For rail locations (distance in kilometers) judged to be areas requiring action, the site is inspected and action such as rail replacement or installation of fish plates is taken.

[0051] Next, the operation of the rail bottom stress estimation method of this embodiment will be described. In the method for estimating rail bottom stress according to this embodiment configured as described above, the relationship between the lateral pressure acting on the rail and the stress difference obtained based on the rail bottom stresses occurring on the inner and outer gauge sides of the rail is estimated in advance by numerical analysis as a lateral pressure-stress difference relationship (see Figs. 7 and 9).

[0052] The rail bottom stress based on the lateral pressure is then estimated using the relationship between the lateral pressure and the stress difference, and the total rail bottom stress is then estimated by adding the separately estimated vertical component of the rail bottom stress.

[0053] This makes it possible to estimate rail bottom stress in curved rail sections, taking into account not only the vertical component of rail bottom stress but also the horizontal component of rail bottom stress, which is likely to have a significant impact. [Example]

[0054] A method for estimating lateral force, which has been developed based on the findings of the method for estimating rail bottom stress in the above-described embodiment, will now be described with reference to Figures 12 to 14. Note that the same or equivalent parts as those described in the above-described embodiment will be described using the same terms or symbols.

[0055] In the method for estimating lateral pressure in Example 1, the lateral pressure acting on a curved section of a rail is estimated from the measurement value of a strain gauge. A conventional method for estimating the lateral pressure acting on a curved section by attaching strain gauges to a rail is a well-known lateral pressure measurement method using the shear strain method. This shear strain method measures the lateral pressure of a train acting on the rail in a curved section by attaching a total of eight strain gauges to the top surface of the rail bottom, both inside and outside the gauge, to eliminate the influence of longitudinal bending of the rail. This required the time-consuming task of attaching strain gauges in eight locations.

[0056] In contrast, in the method for estimating lateral force according to the first embodiment, only two strain gauges need to be attached to the rail, which significantly reduces the amount of work required. Fig. 12 is a flowchart illustrating the processing flow of the method for estimating lateral force according to the first embodiment.

[0057] In step S31, strain gauges are installed on rails located in curved sections of the track. Figure 13 is a diagram explaining the positions at which strain gauges are attached, with Figure 13(a) being an explanatory diagram showing a schematic plan view of the curved section of the rail. Strain gauges are attached to the inside and outside gauge of the outer rail, which is the outer rail where lateral pressure is greater in the curved section. Figure 13(b) is an explanatory diagram showing the positions at which strain gauges are attached in a perspective view of rail R. As shown in this figure, strain gauges are attached to both side surfaces of the bottom of rail R.

[0058] Two strain gauges installed in the curved section measure strain when a train passes, and the strain value is converted into stress (step S32). Figure 14 is an explanatory diagram showing an example of the waveform of stress at the bottom of the rail measured when a train passes.

[0059] Since strain is measured on both the inside and outside of the rail bottom, waveforms of "rail bottom stress - inside" and "rail bottom stress - outside" are generated (see R1 and R2 in Figure 3). Furthermore, it is also possible to generate a waveform of the average value of "rail bottom stress - outside" and "rail bottom stress - inside" (rail bottom stress - average).

[0060] Therefore, the peak values ​​of these waveforms are extracted and the average values ​​of the rail bottom stress on the inner and outer gauges are calculated (steps S32 and S33). Next, in step S34, the difference between the peak value of the rail bottom stress on the outer gauge and the average value of the rail bottom stress is calculated as the stress difference.

[0061] On the other hand, in step S35, as explained in the above embodiment, a simulation is performed by FEM analysis using parameters such as rail type, fastening interval, fastening spring, etc., to obtain the relationship between lateral pressure and stress difference as shown in FIG. 7 or FIG. 9.

[0062] Then, in step S36, the stress difference obtained from the strain gauge measurement value obtained in step S34 is input into the lateral pressure-stress difference relationship of FIG. 7 or FIG. 9, thereby estimating the value of the lateral pressure.

[0063] With the lateral force estimation method of Example 1 configured as described above, the lateral force acting on the rail due to the passage of a train can be estimated simply by attaching two strain gauges to the bottom of the rail in the curved section. This significantly reduces the amount of work required for installation compared to the conventional method of installing strain gauges in eight locations. The other configurations and effects are substantially the same as those of the above embodiment, and therefore the description thereof will be omitted.

[0064] The embodiments of the present invention have been described above in detail with reference to the drawings, but the specific configuration is not limited to these embodiments or examples, and design changes that do not deviate from the gist of the present invention are included in the present invention.

[0065] For example, in the above embodiment, the rail bottom stress estimated by the rail bottom stress estimation method is used to evaluate the rail soundness, but the present invention is not limited to this.

[0066] In the above-described embodiment and Example 1, the relationship between the lateral pressure and the stress difference is described as being linear. However, the present invention is not limited to this. Even if the relationship between the lateral pressure and the stress difference is nonlinear, the method for estimating the rail bottom stress or the method for estimating the lateral pressure of the present invention can be applied. [Explanation of symbols]

[0067] R: Rail R1: Inside (inside gauge) R2: Outside (gauge outside)

Claims

1. A method for estimating rail bottom stress in a curved section of a rail, comprising the steps of: a step of estimating, through a numerical analysis in which a rail and a fastening device of the rail are modeled, a relationship between a lateral pressure acting on the rail and a stress difference obtained based on rail bottom stresses occurring on the inner and outer gauge sides of the rail, as a lateral pressure-stress difference relationship; estimating a rail bottom stress due to the lateral pressure acting on the curved section from the lateral pressure acting on the curved section and the lateral pressure-stress difference relationship; and estimating the total stress at the bottom of the rail by adding a separately estimated vertical component of the stress at the bottom of the rail to the stress at the bottom of the rail due to the lateral pressure.

2. 2. The method for estimating rail bottom stress according to claim 1, wherein the lateral pressure-stress difference relationship is determined by determining a difference between the rail bottom stress on the outer gauge and an average value of the rail bottom stresses on the inner and outer gauge as a stress difference.

3. 3. The method for estimating stress at the rail bottom according to claim 1, wherein the lateral pressure-stress difference relationship is a linear relationship between the lateral pressure and the stress difference.

4. 3. The method for estimating rail bottom stress according to claim 1, wherein the lateral force acting on the curved section is a value estimated by a wheel load lateral force estimation formula based on the curve radius and cant of the curved section and vehicle conditions.

5. 3. The method for estimating rail-bottom stress according to claim 1, wherein the vertical component of rail-bottom stress is estimated based on the amount of unevenness on the rail head surface and the amount of floating sleeper.

6. A method for estimating lateral pressure acting on a curved portion of a rail, comprising: a step of estimating, by a numerical analysis in which a rail and a fastening device of the rail are modeled, a relationship between a lateral pressure acting on the rail and a stress difference obtained based on rail bottom stresses occurring on the inner and outer gauge sides of the rail in the curved section, as a lateral pressure-stress difference relationship; calculating the stresses at the bottom of the rail on the inner and outer gauges from peak values ​​measured by strain gauges installed on the inner and outer gauges of the rail bottom of the curved section when a vehicle passes through the curved section; and estimating the lateral pressure generated in the curved portion from the stress difference calculated based on the measurement value of the strain gauge and the lateral pressure / stress difference relationship, a stress difference between the stress at the bottom of the rail on the outer gauge and an average value of the stresses at the bottom of the rail on the inner gauge and the outer gauge,

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