Apparatus, method, and program for determining necessity of rail reprofiling

Abstract

To provide an apparatus, a method, and a program capable of easily determining the necessity of rail reprofiling.SOLUTION: A rail reprofiling necessity determination device (5) determines whether a rail requires reprofiling on the basis of the measurement results of the residual shear stress of the rail. The rail reprofiling necessity device (5) includes a reprofiling necessity determination unit (5b) for determining the necessity of reprofiling of the rail on the basis of the residual shear stress value of the rail measured by the X-ray stress measurement device (4). The reprofiling necessity determination unit (5b) determines that the rail requires reprofiling when the residual shear stress value exceeds a determined reference value.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an apparatus, method, and program for determining whether a rail needs to be refaced, based on the results of measuring the residual shear stress of the rail. [Background technology]

[0002] Cracks that form on the top surface of a rail are measured using non-destructive testing such as ultrasonic testing to measure their size, and measures such as rail reinforcement or rail replacement are determined based on the severity of the problem. On railways, rail grinding is performed to remove layers affected by rolling contact on the top surface of the rail and tiny cracks that cannot be detected by ultrasonic testing, which is effective in reducing the occurrence of cracks in the rail. However, the frequency and amount of grinding required are standardized, and if it were possible to estimate the efficient and effective frequency for each railway line, it would lead to cost reductions.

[0003] A conventional method for determining the timing for removing a fatigue layer (hereinafter referred to as Prior Art 1) measures at least one of the crystallite size or non-uniform strain of a rail, and determines the timing for removing a fatigue layer of the rail based on at least one of the crystallite size or non-uniform strain of the rail (see, for example, Patent Document 1). Prior Art 1 predicts the occurrence of rolling fatigue cracks by measuring the crystallite size or non-uniform strain on the rail surface, and determines the time interval for performing rail redressing.

[0004] In a fracture mechanics analysis of fatigue damage in railway rails (hereinafter referred to as Prior Art 2), a criterion for crack initiation due to damage is proposed based on the shear fatigue strength of the rail (see, for example, Non-Patent Document 1). In an X-ray triaxial stress measurement of railway rails (hereinafter referred to as Prior Art 3), the results of measuring the shear stress of actually used rails are reported (see, for example, Non-Patent Document 2). In an X-ray measurement of triaxial residual stress in rail steel using a twin-roller rolling contact tester (hereinafter referred to as Prior Art 4), it is reported that in a twin-roller rolling contact fatigue test simulating rolling-sliding contact between a wheel and a rail, the direction of slippage experienced by the rail tends to correspond to the sign of the shear stress. In a triaxial residual stress measurement and metallographic changes in rail steel used in a twin-roller rolling contact tester (hereinafter referred to as Prior Art 5), it is reported that in a twin-roller rolling contact fatigue test, the sign of residual shear stress tends to correspond to the direction of slippage experienced by the rail. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-018114

[0006] [Non-Patent Document 1] Kenji Hirakawa, "Fracture Mechanics Analysis of Fatigue Damage in Railway Rails (2) Rolling Contact Fatigue Crack Initiation Limit Diagram", Railway Vehicles and Technology, Vol. 137, No. 10, 2007, pp. 40-50

[0007] [Non-patent document 2] Noriaki Inui and two others, "X-ray triaxial stress measurement of railway rails," 2014, Japan Institute of Metals and Iron and Steel Institute of Japan Hokuriku Branch Joint Lecture Meeting, December 5, 2015, p. 507

[0008] [Non-patent document 3] Yoshikazu Kanematsu and 1 other collaborators, "X-ray Measurement of Triaxial Residual Stress in Rail Steel Using a Two-Roller Rolling Contact Tester," Japan Society of Civil Engineers, 29th Joint Symposium on Railway Technology and Policy (J-RAIL2022), December 9, 2022

[0009] [Non-patent document 4] Yoshikazu Kanematsu, "Triaxial Residual Stress Measurement and Changes in Metallographic Structure of Rail Steel Tested on a Two-Roller Rolling Contact Tester," Japan Society of Civil Engineers, 30th Joint Symposium on Railway Technology and Policy (J-RAIL2023), December 13, 2023 Summary of the Invention [Problem to be solved by the invention]

[0010] One of the phenomena that can occur in rails due to repeated wheel contact is the formation of cracks due to rolling contact fatigue. To prevent shelling, a type of damage caused by rolling contact fatigue, rail reconditioning is performed by grinding away the rail surface with a rotating grinding wheel. Shelling occurs and grows due to the stress and repeated sliding contact caused by the wheels rolling on the rail. Compared to the expansion of internal cracks, the cracks that appear on the surface are small and therefore difficult to detect visually. Shelling can occur in two forms: horizontal cracks, which develop horizontally to a depth of about 5 mm from the surface, and transverse cracks, which develop vertically from the horizontal crack. Horizontal cracks can lead to spalling if they penetrate back to the surface, but spalling itself does not cause rail fracture, so it is not as important as transverse cracks. Transverse cracks, on the other hand, can cause rail fracture, so rail reconditioning is necessary while they are still small.

[0011] In Prior Art 1, in order to predict the occurrence of rolling contact fatigue cracks, it was necessary to cut test specimens from rails and measure crystallite size or non-uniform strain, which posed a problem in that the cutting of test specimens was time-consuming in order to determine the timing of rail grinding. Prior Art 2 and 3 proposed criteria for rail crack occurrence and reported the results of measuring rail shear stress, but did not go so far as to determine the rail condition at which rail grinding was necessary. Prior Art 4 and 5 reported the relationship between shear stress and changes in the metal structure of rail steel subjected to rolling contact fatigue, but did not go so far as to determine the state of microcracks in rails.

[0012] An object of the present invention is to provide an apparatus, method, and program for determining whether rail refinishing is necessary, which can easily determine whether rail refinishing is necessary. [Means for solving the problem]

[0013] The present invention solves the above problems by the means described below. Although the description will be given with reference numerals corresponding to the embodiments of the present invention, the present invention is not limited to these embodiments. The invention of claim 1 is a rail grinding necessity determination device (5) that determines whether or not grinding of a rail (2) is necessary based on the measurement results of the residual shear stress of the rail, as shown in Figures 1 and 2, and is characterized in that it is equipped with a grinding necessity determination unit (5b) that determines whether or not grinding of the rail is necessary based on the residual shear stress value of the rail measured by an X-ray stress measurement device (4).

[0014] The invention of claim 2 is the device for determining whether rail reconditioning is necessary, as described in claim 1, characterized in that the reconditioning necessity determination unit determines that reconditioning of the rail is necessary when the residual shear stress value exceeds a determination reference value.

[0015] The invention of claim 3 is a method for determining whether a rail (2) needs to be re-ground, as shown in Figures 1 and 3, for determining whether the rail needs to be re-ground based on the measurement results of the residual shear stress of the rail, and is a method (#100) for determining whether the rail needs to be re-ground, characterized in that it includes a re-grounding determination step (#110) for determining whether the rail needs to be re-ground based on the residual shear stress value of the rail measured by an X-ray stress measurement device (4).

[0016] The invention of claim 4 is a rail grinding necessity determination program for determining whether or not a rail (2) needs grinding based on the measurement results of the residual shear stress of the rail, as shown in Figures 1 and 4, characterized in that it causes a computer to execute grinding necessity determination procedures (S120, S130) for determining whether or not the rail needs grinding based on the residual shear stress value of the rail measured by an X-ray stress measurement device (4). [Effects of the Invention]

[0017] According to the present invention, it is possible to easily determine whether or not rail regrind is required. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram of an X-ray stress measuring device in a rail grinding necessity determination system according to an embodiment of the present invention. [Figure 2] FIG. 1 is a configuration diagram of a rail grinding necessity determination device according to an embodiment of the present invention. [Figure 3] FIG. 1 is a process diagram of a method for determining whether rail refining is necessary according to an embodiment of the present invention. [Figure 4] 1 is a flowchart for explaining the operation of a rail refining necessity determination device according to an embodiment of the present invention. [Figure 5] FIG. 1 is a schematic diagram showing a coordinate system during X-ray stress measurement. [Figure 6] 1 is a graph showing the relationship between the number of repetitions and the shear stress value. [Figure 7] 1 is a metallographic photograph showing, as an example, a crack formed in a rail-side test piece. [Figure 8] 1 is a graph showing the relationship between the number of cracks and the shear stress value. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 is a passageway (track) on which vehicles run. The track 1 allows rail vehicles such as electric trains, diesel railcars, locomotives, passenger cars, and freight cars to run. The track 1 includes a pair of rails 2 on the left and right.

[0020] The rail 2 shown in Figure 1 is a component that supports and guides the wheels of a vehicle, allowing the vehicle to travel. The rail 2 comprises a rail head 2a, a rail bottom (flange portion) 2b, and a rail web (web portion) 2c. The rail head 2a is the portion that comes into contact with the wheels of the vehicle. The rail head 2a comprises a head top surface (head upper surface) 2d that directly supports the wheels, head side surfaces 2e that form the left and right side portions of the rail head 2a and are continuous with the head top surface 2d, and gauge corner surfaces 2f where the flange surfaces of the vehicle wheels come into contact with the head side surfaces 2e when passing through a sharp curve. The rail bottom 2b is the portion that is attached to a bearing that supports the rail 2. The rail bottom 2b is fastened and attached to a bearing such as a sleeper or a track slab (slab slab) by a rail fastening device. The rail web portion 2c is the portion that connects the rail head 2a and rail bottom 2b. The rail web portion 2c transmits the load acting on the rail head 2a to the rail bottom 2b. The rail 2 shown in FIG. 1 is, for example, an ordinary rail made of high-carbon steel with a carbon content of 0.63 to 0.75% and a pearlite structure with a hardness of 235HB or more, and used mainly in straight sections; a heat-treated rail in which the head of an ordinary rail is heat-treated to improve wear resistance, and used mainly in sharp curves or joints; or a special rail used for turnouts.

[0021] The grinding necessity determination system 3 shown in Figures 1 and 2 determines whether rail grinding is necessary based on the measurement results of the residual shear stress of the rail 2. Here, rail grinding refers to the process of grinding the top surface 2d of the rail 2 using a grinder to remove and smooth out irregularities on the top surface 2d. Rail grinding is performed to restore the cross-sectional shape of the rail 2 for purposes such as reducing train noise during operation. Residual shear stress is shear stress that exists inside a material in the absence of external forces or thermal gradients. It occurs within the material as a result of non-uniform plastic deformation caused by sudden changes such as rolling, cutting, forging, heating, cooling, heat treatment, or welding. As shown in Figures 1 and 2, the grinding necessity determination system 3 includes an X-ray stress measurement device 4 and a grinding necessity determination device 5. The grinding necessity determination system 3 determines whether rail grinding is necessary using the grinding necessity determination device 5 based on the measurement results of the shear stress of the rail 2 measured by the X-ray stress measurement device 4.

[0022] The X-ray stress measurement device 4 shown in Figures 1 and 2 is an apparatus that measures the shear stress on the surface of a rail 2 using diffracted X-rays L2. The X-ray stress measurement device 4 nondestructively measures the residual shear stress on the top surface 2d of the rail 2. The X-ray stress measurement device 4 detects changes in the lattice spacing of crystals in the rail 2 caused by stress applied to the rail 2 as changes in the diffraction angle of the X-ray diffraction peak, and measures the residual shear stress of the rail 2 based on the strain calculated from the changes in lattice spacing. As shown in Figure 1, the X-ray stress measurement device 4 is equipped with an X-ray generation unit 4a, an X-ray irradiation unit 4b, an imaging unit 4c, a reading unit 4d, a measurement unit 4e, and a transmission unit 4f. The X-ray stress measurement device 4 is a small, lightweight, portable measurement device that operates using a rechargeable secondary battery.

[0023] The X-ray generating unit 4a shown in Figure 1 is a means for generating X-rays L1. The X-ray generating unit 4a generates X-rays L1 by colliding an electron beam with a target. The X-ray irradiating unit 4b is a means for irradiating the rail 2 with X-rays L1. The X-ray irradiating unit 4b focuses the X-rays L1 generated by the X-ray generating unit 4a into a parallel beam and irradiates the surface of the rail 2 with the parallel beam so that the beam is incident on the surface of the rail 2 at a predetermined incident angle ψ0.

[0024] The imaging unit 4c is a means for receiving the diffracted X-rays L2 generated from the rail 2 and capturing a diffraction image. The imaging unit 4c accumulates the energy of the diffracted X-rays L2 and captures an image of the diffraction ring. The imaging unit 4c is, for example, an imaging plate (IP) that captures an entire image of the diffraction ring by utilizing a photo-stimulated luminescence phenomenon in which X-ray energy is temporarily accumulated and then fluorescence is generated by excitation with light.

[0025] The reading unit 4d is a means for reading the diffraction ring image captured by the imaging unit 4c. The reading unit 4d detects the intensity of diffracted X-rays L2 at the irradiation position of the laser beam L3 based on the intensity of light emitted from the imaging unit 4c when the imaging unit 4c is irradiated with the laser beam L3. The reading unit 4d is, for example, an IP reader that scans and irradiates the imaging unit 4c with the laser beam L3, amplifies the fluorescence generated from the X-ray energy accumulation portion in the imaging unit 4c, measures the intensity of the X-rays L1, and reads out the diffraction ring image.

[0026] The measuring unit 4e is a means for measuring the residual shear stress value of the rail 2 based on the diffraction ring image captured by the imaging unit 4c. The measuring unit 4e analyzes the image information of the diffraction ring output by the reading unit 4d based on an image analysis program, and measures the residual shear stress of the rail 2. The measuring unit 4e calculates the residual shear stress value of the rail 2, for example, using Bragg's diffraction condition equation and the cos α method based on the theory of elasticity. The transmitting unit 4f is a means for transmitting the measurement results of the measuring unit 4e. The transmitting unit 4f transmits the residual shear stress value measured by the measuring unit 4e to the grinding necessity determining device 5 as residual shear stress value data (residual shear stress value signal).

[0027] The grinding necessity determination device 5 shown in Figures 1 and 2 is a device that determines whether grinding of the rail 2 is necessary based on the measurement results of the residual shear stress of the rail 2. The grinding necessity determination device 5 determines whether or not a predetermined number of cracks have occurred on the top surface 2d of the rail 2 and it is time to grind the rail 2, based on the residual shear stress value of the rail 2 measured by the X-ray stress measurement device 4. As shown in Figure 2, the grinding necessity determination device 5 includes a receiving unit 5a, a grinding necessity determination unit 5b, a determination reference value setting unit 5c, a data storage unit 5d, a grinding necessity determination program storage unit 5e, a display unit 5f, and a control unit 5g. The grinding necessity determination device 5 is configured, for example, by a personal computer, and executes predetermined processing in accordance with the grinding necessity determination program.

[0028] 2 is a means for receiving the residual shear stress value data transmitted by the X-ray stress measurement device 4. The receiving unit 5a outputs the residual shear stress value data transmitted by the transmitting unit 4f of the X-ray stress measurement device 4 to the control unit 5g.

[0029] The grinding necessity determination unit 5b is a means for determining whether grinding of the rail 2 is necessary based on the residual shear stress value of the rail 2 measured by the X-ray stress measurement device 4. The grinding necessity determination unit 5b determines whether the residual shear stress value of the rail 2 exceeds a judgment reference value (threshold value). Here, the judgment reference value is a reference value used to determine whether grinding of the rail 2 is necessary. The judgment reference value is, for example, the residual shear stress value of the rail 2 when the number of cracks occurring on the top surface 2d of the rail 2 reaches a predetermined number. When the residual shear stress value of the rail 2 exceeds the judgment reference value, the grinding necessity determination unit 5b determines that grinding of the rail 2 is necessary. On the other hand, when the residual shear stress value of the rail 2 is equal to or less than the judgment reference value, the grinding necessity determination unit 5b determines that grinding of the rail 2 is not necessary. The grinding necessity determination unit 5b outputs the determination result of whether grinding of the rail 2 is necessary to the control unit 5g as determination result data (determination result signal).

[0030] The judgment reference value setting unit 5c is a means for setting a judgment reference value. The judgment reference value setting unit 5c sets a judgment reference value for each type or material of the rail 2, such as a normal rail, a heat-treated rail, or a special rail. The judgment reference value setting unit 5c is an input device or auxiliary input device for inputting the judgment reference value. The judgment reference value setting unit 5c outputs the set judgment reference value to the control unit 5g as judgment reference value data.

[0031] The data storage unit 5d is a means for storing various data related to the grinding necessity determination device 5. The data storage unit 5d stores rail residual shear stress value data measured by the X-ray stress measurement device 4 and judgment result data on the necessity of rail grinding determined by the grinding necessity determination unit 5b for each measurement point of the rail 2. The data storage unit 5d stores judgment reference value data set by the judgment reference value setting unit 5c for each type or material of the rail 2. The data storage unit 5d is, for example, a storage device that stores various data.

[0032] The grinding necessity determination program storage unit 5e is a means for storing a grinding necessity determination program for determining whether grinding of the rail 2 is necessary based on the measurement results of the residual shear stress of the rail 2. The grinding necessity determination program storage unit 5e is a storage device or the like that stores a grinding necessity determination program read from an information recording medium or a grinding necessity determination program downloaded via an electric communication line.

[0033] The display unit 5f is a means for displaying various information related to the grinding necessity determination device 5. The display unit 5f is a display device that displays, for example, the residual shear stress value of the rail 2 measured by the X-ray stress measurement device 4, the determination result of the grinding necessity determination device 5 as to whether grinding of the rail 2 is necessary, and the like on a screen.

[0034] The control unit 5g is a central processing unit (CPU) that controls various operations related to the grinding necessity determination device 5. The control unit 5g reads out a grinding necessity determination program from the grinding necessity determination program storage unit 5e, and executes grinding necessity determination processing in accordance with this grinding necessity determination program. The control unit 5g, for example, instructs the data memory unit 5d to store the residual shear stress value data input from the receiving unit 5a, reads out the residual shear stress value data and judgment standard value data from the data memory unit 5d and outputs them to the grinding necessity determination unit 5b, instructs the grinding necessity determination unit 5b to determine whether grinding of the rail 2 is necessary, instructs the data memory unit 5d to store the judgment result data output by the grinding necessity determination unit 5b, instructs the data memory unit 5d to store the judgment standard value data output by the judgment standard value setting unit 5c, reads out the residual shear stress value data, judgment result data and judgment standard value data from the data memory unit 5d and outputs them to the display unit 5f, and instructs the display unit 5f to display the residual shear stress value data, judgment result data and judgment standard value data. The control unit 5g is connected to the receiving unit 5a, the grinding necessity determination unit 5b, the determination reference value setting unit 5c, the data storage unit 5d, the grinding necessity determination program storage unit 5e, and the display unit 5f so that they can communicate with each other.

[0035] Next, a method for determining whether rail refining is necessary according to an embodiment of the present invention will be described. The grinding necessity determination method #100 shown in Fig. 3 is a method for determining whether grinding of a rail 2 is necessary based on the residual shear stress value of the rail 2 measured by the X-ray stress measurement device 4. The grinding necessity determination method #100 includes a residual shear stress measurement step #110 and a grinding necessity determination step #120.

[0036] The residual shear stress measurement process #110 is a process for measuring the residual shear stress of the rail 2. In the residual shear stress measurement process #110, as shown in FIG. 1, the X-ray stress measurement device 4 measures the residual shear stress of the top surface 2d of the rail 2. X-rays L1 are irradiated onto the illumination surface, which is the contact point between the rail 2 and the wheel, to obtain diffracted X-rays L2, and the data of the diffracted X-rays L2 is analyzed to calculate the residual shear stress value. As a result, the residual shear stress value of the top surface 2d of the rail 2 is measured by the X-ray stress measurement device 4, and the residual shear stress value data is transmitted from the transmitter 4f of the X-ray stress measurement device 4 to the receiver 5a of the grinding necessity determination device 5.

[0037] The grinding necessity determination process #120 is a process for determining whether grinding of the rail 2 is necessary based on the residual shear stress value measured by the X-ray stress measurement device 4. In the grinding necessity determination process #120, the grinding necessity determination unit 5b of the grinding necessity determination device 5 determines whether grinding of the rail 2 is necessary, for example, depending on whether the residual shear stress value of the rail 2 exceeds a determination reference value.

[0038] Next, the operation of the rail refining necessity determining device according to the embodiment of the present invention will be described. The following description will focus on the operation of the control unit 5g shown in FIG. 4, the control unit 5g reads the grinding necessity determination program from the grinding necessity determination program storage unit 5e. When the control unit 5g reads the grinding necessity determination program, the control unit 5g starts a series of grinding necessity determination processes.

[0039] In S110, the control unit 5g commands the grinding necessity determination unit 5b to determine whether or not the residual shear stress value exceeds the judgment reference value. The grinding necessity determination unit 5b determines whether or not grinding of the rail 2 is necessary based on the residual shear stress value of the rail 2 measured by the X-ray stress measurement device 4. As a result, if the grinding necessity determination unit 5b determines that the residual shear stress value of the rail 2 exceeds the judgment reference value, the process proceeds to S120, and if the grinding necessity determination unit 5b determines that the residual shear stress value of the rail 2 is equal to or less than the judgment reference value, the process proceeds to S130.

[0040] In S120, the grinding necessity determination unit 5b determines that grinding is necessary for the rail 2. When the grinding necessity determination unit 5b determines that the residual shear stress value of the rail 2 exceeds the determination reference value, the grinding necessity determination unit 5b determines that the number of cracks occurring in the rail 2 has reached the maintenance target value that requires rail grinding.

[0041] In S130, the grinding necessity determination unit 5b determines that grinding is not necessary for the rail 2. When the grinding necessity determination unit 5b determines that the residual shear stress value of the rail 2 is equal to or less than the determination reference value, the grinding necessity determination unit 5b determines that the number of cracks occurring in the rail 2 has not reached the maintenance target value that requires rail grinding.

[0042] In S140, the control unit 5g commands the display unit 5f to display the determination result of whether or not grinding of the rail 2 is necessary. As a result, the determination result of whether or not grinding of the rail 2 is necessary is displayed on the screen of the display unit 5f.

[0043] The device, method, and program for determining whether rail refining is necessary according to the embodiment of the present invention have the following effects. (1) In this embodiment, the necessity of grinding the rail 2 is determined based on the residual shear stress value of the rail 2 measured by the X-ray stress measurement device 4. Therefore, the necessity of grinding the rail 2 can be easily evaluated from the relationship between the residual shear stress value of the rail 2 and the number of microcracks.

[0044] (2) In this embodiment, when the shear stress value exceeds the judgment reference value, it is determined that grinding of the rail 2 is necessary. Therefore, by using an index based on a threshold value such as the number of minute cracks, the condition of the rail 2 can be determined at the railway site, and the need for rail grinding can be easily evaluated and diagnosed. [Example]

[0045] Next, an embodiment of the present invention will be described. In order to confirm that it is possible to judge whether rail redressing is necessary or not from the residual shear stress value of the rail, the relationship between the residual shear stress value and cracks was clarified by a two-roller rolling contact fatigue test.

[0046] (Two-cylinder rolling contact fatigue test) The two-roller rolling contact fatigue test was carried out using a two-roller rolling contact fatigue testing machine at the Railway Technical Research Institute, a public interest incorporated foundation. The two-roller rolling contact fatigue test was carried out by applying an arbitrary load to two ring-shaped test pieces, bringing them into contact and rotating them at different speeds set by the gear ratio, creating a rolling-sliding contact state.

[0047] (Test piece) The rail-side test specimens (rail test specimens) were taken from standard rails (carbon content: 0.63-0.75%, tensile strength: 800 MPa or more, metal structure: pearlite) specified in JIS E 1101. The wheel-side test specimens (wheel test specimens) were taken from the rim of SSW-QS wheels (carbon content: 0.60-0.75%, tensile strength: 790-980 MPa, metal structure: pearlite) specified in JIS E 5402. The rail-side test specimens and wheel-side test specimens had a gradient at their contact surfaces, and the difference in diameter between the test specimens created a slight slippage. The slip ratio was 0.4%.

[0048] (Test conditions) The test conditions were dry, with the gear set slip ratio at 0.00% and the rotation speeds at 100, 500, 1,000, 3,000, 5,000, 10,000, 30,000, 100,000, and 300,000 revolutions. The contact pressure was set at 860 MPa, typical for conventional lines, with a combination of a 50N rail and a corrected arc surface. The rotation speed was 50 rpm up to 500 revolutions, 500 rpm up to 5,000 revolutions, and 1,000 rpm thereafter.

[0049] (X-ray stress measurement conditions) X-ray stress measurements were performed at the largest diameter part of the rolling contact surface of the rail-side test piece. Measurements were also taken at two locations on the rail-side test piece, at 0 degrees and 120 degrees. Figure 5 is a schematic diagram showing the coordinate system used during X-ray stress measurements. Table 1 shows the X-ray stress measurement conditions.

[0050] [Table 1]

[0051] In this example, an X-ray residual stress measurement method using a two-dimensional detector was used, and the triaxial stress was measured by applying the triaxial stress measurement method (Third Method (Toshihiko Sasaki et al., "Study on Improvement of Area Detector Type X-ray Triaxial Stress Measurement Method", Transactions of the Japan Society of Mechanical Engineers, Series A, 75(750), 2009, pp. 219-227, Proc. R. Soc. Lond. A, 1998, 454, pp. 1523-1534)) to the diffraction information obtained by the two-dimensional detector.

[0052] (X-ray stress measurement results) Figure 6 shows the relationship between the number of repetitions and the residual shear stress value τ when the slip ratio is 0.4%. zy The vertical axis in Fig. 6 shows the residual shear stress value τ zy The horizontal axis represents the number of rotations (rpm). Figure 7 is a metallographic photograph showing an example of cracks formed in a rail-side test piece after 300,000 rotations at a slip ratio of 0.4%. The plot for 0 in Figure 6 is the measurement result before the start of the test, and represents the residual stress value due to test piece processing. As shown in Figure 7, cracks were observed in the rail-side test piece after 300,000 rotations, and the residual shear stress value τ zy It is thought that when the stress exceeds 100 MPa, cracks that require rail grinding become apparent.

[0053] Figure 8 shows the relationship between the number of cracks and the residual shear stress value τ when the slip ratio is 0.4%. zy The vertical axis in FIG. 8 represents the number of cracks, and the horizontal axis represents the residual shear stress value τ zy (MPa). As shown in Figure 8, the residual shear stress value τ zy The number of cracks increases at 100 MPa, and the residual shear stress value τ zyIt is thought that when the residual shear stress value τ exceeds 100 MPa, the number of cracks that require rail grinding becomes apparent. zy Measure the residual shear stress value τ zy It is thought that it is time to grind the rail when the stress exceeds 100 MPa.

[0054] The present invention is not limited to the above-described embodiment, and various modifications and alterations are possible as described below, and these are also within the scope of the present invention. (1) In this embodiment, the case where the shear stress of the surface of the rail 2 is measured by the X-ray stress measurement device 4 has been described as an example. However, the present invention can also be applied to a case where the X-ray stress measurement device 4 is measured while the X-ray stress measurement device 4 is traveling. For example, the present invention can be applied to a case where the X-ray stress measurement device 4 or the grinding necessity determination system 3 is mounted on a vehicle such as a track inspection vehicle, a road-rail vehicle, or a truck and measurements are performed while the vehicle is traveling on the track 1 by mechanical power, or to a case where the X-ray stress measurement device 4 or the grinding necessity determination system 3 is mounted on a measurement vehicle such as a bogie and measurements are performed while the vehicle is traveling on the track 1 by the human power of an operator. Furthermore, in this embodiment, the case where analysis is performed on-site by the on-board X-ray stress measurement device 4 and the grinding necessity determination device 5 has been described as an example. However, the present invention can also be applied to a case where on-site measurement is performed by the on-board X-ray stress measurement device 4 and then a determination is made by the ground-based grinding necessity determination device 5. Furthermore, in this embodiment, an example has been described in which X-rays L1 are irradiated from a direction perpendicular to the top surface 2d of the rail 3, but the present invention can also be applied to a case in which X-rays L1 are irradiated from an oblique direction to the top surface 2d.

[0055] (2) In this embodiment, the case where the image of the diffraction ring captured by the imaging unit 4c is read by the reading unit 4d has been described as an example. However, this invention can also be applied to a case where the entire image of the diffraction ring is captured and read by an X-ray CCD (Charge Coupled Device), which converts X-ray energy into an electrical signal and outputs it. Furthermore, in this embodiment, the case where the residual shear stress on the top surface 2d of the rail 2 is measured nondestructively to determine whether the top surface 2d needs to be redressed has been described as an example. However, the determination location is not limited to the top surface 2d. For example, this invention can also be applied to a case where the residual shear stress on the rail bottom portion 2b, rail web portion 2c, head side surface 2e, or gauge corner surface 2f is measured nondestructively to determine whether these surfaces need to be redressed. [Explanation of symbols]

[0056] 1 track 2 Rails 2a Rail head 2d parietal plane 3. Grinding necessity determination system 4. X-ray stress measurement device 5 Device to determine whether or not cutting is necessary 5b Cutting necessity judgment part L1X-ray L2 diffracted X-rays L3 laser light

Claims

1. A rail grinding necessity determination device that determines whether or not a rail needs grinding based on a measurement result of the residual shear stress of the rail, a grinding necessity determination unit that determines whether grinding of the rail is necessary based on the residual shear stress value of the rail measured by the X-ray stress measurement device; A rail grinding necessity determination device characterized by the above.

2. The rail grinding necessity determination device according to claim 1, the grinding necessity determination unit determines that grinding of the rail is necessary when the residual shear stress value exceeds a determination reference value; A rail grinding necessity determination device characterized by the above.

3. A method for determining whether or not a rail needs to be reground, based on a measurement result of residual shear stress in the rail, comprising: a grinding necessity determination step for determining whether grinding of the rail is necessary based on the residual shear stress value of the rail measured by the X-ray stress measurement device; A method for determining whether rail grinding is necessary, characterized by the above.

4. A rail grinding necessity determination program for determining whether or not a rail needs grinding based on measurement results of the residual shear stress of the rail, comprising: causing a computer to execute a grinding necessity determination procedure for determining whether grinding of the rail is necessary based on the residual shear stress value of the rail measured by the X-ray stress measurement device; A program that determines whether rail grinding is necessary.

Images