Double-disc rolling steel rail sample design method considering bending stress effect

Abstract

The invention relates to the technical field of wheel-rail double-disc rolling simulation, and particularly discloses a double-disc rolling steel rail sample design method considering the action of bending stress, which realizes the expansion of the bending stress on the rolling contact fatigue crack of a steel rail on a double-disc rolling sample. A finite element analysis method, a rolling contact fatigue and wear testing machine, an SEM scanning electron microscope and other equipment are combined to analyze the profile crack morphology and the maximum bending stress value sigma simRmax of the double-disc rolling steel rail sample, and different section shapes of the sample are optimized according to analysis results. And continuously correcting the total height H of the simulated beam section of the sample until sigma simRmax is equal to sigma Rmax, and verifying the reasonability of the test structure again by combining a rolling contact fatigue and wear testing machine, and the rolling contact fatigue crack damage of the full-size steel rail under the action of the bending stress can be reproduced in a laboratory.

Description

Technical Field

[0001] The present invention relates to the technical field of wheel-rail double-disk rolling simulation, and particularly relates to a design method for a double-disk rolling steel rail specimen considering the action of bending stress. Background Art

[0002] With the rapid development of rail transit in China, the problems of wheel-rail damage and wear have become increasingly prominent. Under the action of cyclic alternating loads from the wheels, fatigue cracks initiate on the surface of the steel rail and continuously expand into the material interior, eventually leading to the spalling of some materials or even causing fractures, seriously endangering the operation safety of trains. Therefore, in order to better reproduce the actual damage process of on-site steel rails, many scholars have conducted double-disk rolling simulation tests using a double-disk rolling contact fatigue testing machine to study the rolling contact fatigue of steel rails.

[0003] Since in the actual process, the wheel-rail is in an open environment, when a crack initiates on the surface of the steel rail, with the continuous increase of the contact load between the wheel and the rail, the crack expands along the plastic flow line of the material under the action of the alternating contact load. If there is a third-body medium between the wheel-rail interface, an oil wedge effect will occur, resulting in a sharp increase in the crack propagation rate. When the crack expands to a certain depth, the bending stress acting on the steel rail plays a dominant role in the crack propagation. However, in previous double-disk rolling simulation test studies, most scholars only considered the effects of contact stress, third-body medium, tangential load, etc. on the propagation of rolling contact fatigue cracks in steel rails, and did not consider the influence of bending stress on the propagation of rolling contact fatigue cracks in steel rails. Some scholars used numerical simulation calculations to study the influence of bending stress on the propagation of rolling contact fatigue cracks in steel rails, but this method lacks experimental verification, and the results cannot better reveal the mechanism of rolling contact fatigue crack propagation in the actual wheel-rail process. There are also some scholars such as He Chenggang and Zeng Qingfei who considered the influence of bending stress on wheel-rail rolling contact fatigue cracks, but the drawback is that they all used mechanical processing methods to prefabricate cracks at the bottom of the specimen to study the propagation behavior of fatigue cracks at the tip of the prefabricated cracks. However, in actual working conditions, the rolling contact fatigue crack of the steel rail under the action of bending stress is a process from initiation to propagation on the surface of the steel rail. Using the method of prefabricated cracks to study the influence of bending stress on the rolling contact fatigue crack of the steel rail cannot simulate the propagation behavior of the rolling contact fatigue crack of the steel rail after being affected by bending stress in the actual process.

[0004] In summary, there are still many deficiencies in the current research on rolling contact fatigue cracks of steel rails in double-disk rolling simulation tests. Therefore, introducing the action of bending stress in double-disk rolling simulation tests has important engineering significance for further studying the rolling contact fatigue damage behavior of steel rails. Summary of the Invention

[0005] To solve the problem that in the prior art, the rail in the railway field is subjected to bending stress, but it is difficult to simulate its influence on rolling contact fatigue cracks in the laboratory, the present invention provides a design method for a double-disk rolling rail specimen considering the action of bending stress, which can better simulate the rolling contact fatigue damage behavior of the rail under actual working conditions and solve the problems mentioned in the above background art.

[0006] To achieve the above object, the present invention provides the following technical solutions: A design method for a double-disk rolling rail specimen considering the action of bending stress, comprising the following steps:

[0007] S1. Based on the profile shape of the full-size rail and the structure of the existing double-disk rolling specimen without considering the action of bending stress, design double-disk rolling rail specimens with different structures considering the action of bending stress;

[0008] S2. Use a rolling contact fatigue and wear testing machine to conduct rolling tests on the double-disk rolling rail specimens in S1, and based on the cross-sectional crack morphologies of the double-disk rolling rail specimens with different structures, determine the simulated beam cross-sectional shape of the designed double-disk rolling rail specimens considering the action of bending stress;

[0009] S3. Obtain the bending moment value of any cross-section of the rail in the full-size wheel-rail model through ABAQUS software, and substitute it into the correction formula to obtain the maximum dynamic bending stress value σ of the full-size rail Rmax ;

[0010] S4. According to the structure of the designed double-disk rolling rail specimen determined in S2, use Hypermesh and ABAQUS software to establish a finite element calculation model of the double-disk rolling rail specimen with this structure, calculate the bending moment value of any cross-section of the double-disk rolling rail specimen with this structure, and substitute it into the mechanical formula to obtain the maximum bending stress value σ of the double-disk rolling rail specimen with the corresponding structure simRmax ;

[0011] S5. Taking the total height H of the simulated beam cross-section of the double-disk rolling rail specimen as a variable, gradually increase the total height H of the simulated beam cross-section of the double-disk rolling rail specimen, and use finite element software to repeatedly optimize and analyze until the maximum bending stress values of the double-disk rolling rail specimens are equivalent, that is, σ simRmax = σ Rmax , and finally determine all the geometric dimensions of the double-disk rolling rail specimen considering the action of bending stress, and complete the design of the double-disk rolling rail specimen considering the action of bending stress.

[0012] Preferably, in step S1, it specifically includes the following steps:

[0013] S11. According to the sleeper spacing and sleeper width between adjacent sleepers in the full-size wheel-rail model, obtain the ratio of the sleeper width to the sleeper spacing, so as to determine the distance L between the arc grooves of the double-disk rolling rail specimen and the width S of the arc grooves;

[0014] S12. Determine the height H of the arc-shaped groove of the double-disk rolling rail specimen by taking values proportionally according to the height of the full-size rail. 1 Above the arc-shaped groove is a simulated beam. The total height H of the cross-section of the simulated beam consists of the heights h of different parts according to different cross-sectional shapes. i ;

[0015] S13. Determine the cross-sectional shape of the double-disk rolling rail specimen according to the cross-sectional shape of the full-size rail and the actual wheel-rail contact state, including three cross-sectional shapes: I-shaped cross-section, inverted T-shaped cross-section, and rectangular cross-section.

[0016] Preferably, in step S2, the determination criterion for the design of the cross-sectional shape of the simulated beam of the double-disk rolling rail specimen considering the bending stress effect is whether the profile crack morphology of the rail specimen after the rolling test is similar to the profile crack morphology characteristics of the on-site full-size rail after service. The profile crack morphology characteristics of the on-site full-size rail after service are that the expansion angle formed by the tangent direction of the crack and the wheel-rail rolling direction gradually increases along the material interior during the crack propagation until it approaches 90°.

[0017] Preferably, in step S3, the correction formula is as follows:

[0018]

[0019] where M x is the bending moment value of any rail cross-section; k is the correction coefficient, and its value is related to factors such as the train speed, wheel load eccentricity, and lateral action; σ R is the bending stress value of any cross-section of the rail; I R is the polar moment of inertia of the rail cross-section, and Z R is the distance between the wheel-rail contact point and the neutral axis on the cross-section of the full-size rail.

[0020] Preferably, in step S4, it specifically includes the following steps:

[0021] S41. Build a three-dimensional geometric model of the double-disk rolling rail specimen;

[0022] S42. Conduct mesh generation in Hypermesh software, refine the mesh in the contact area according to the contact area, input the material parameters, and export the finite element model.inp file of the specimen;

[0023] S43. Import the.inp file of the finite element model of the specimen into ABAQUS for calculation to obtain the bending moment value M of any cross-section of the double-disk rolling rail specimen simR ;

[0024] S44. Take the obtained bending moment value M of any cross-section of the specimen simR, substitute it into the mechanical formula to calculate the maximum bending stress value σ of the double-disk rolling rail specimen simRmax , where the bending stress value σ of any cross-section of the rail specimen simR and the bending moment value M simR are related as follows:

[0025]

[0026] In the formula, M simR is the bending moment value of any cross-section of the rail specimen, I simR is the polar moment of inertia of the cross-section of the rail specimen, and Z is the distance between the wheel-rail specimen contact point and the neutral axis on the cross-section of the rail specimen.

[0027] Preferably, in step S5, by adjusting the height h of different parts of the cross-sectional shape i the total height H of the simulated beam cross-section is changed; if the cross-section is an I-shaped structure, its cross-sectional shape dimensions consist of the height h of the simulated rail head 1 , the height h of the simulated rail web 2 , and the height h of the simulated rail base 3 ; if the cross-section is an inverted T-shaped structure, its cross-sectional shape dimensions consist of the height h of the upper flange 1 and the height h of the lower flange 2 .

[0028] Preferably, in step S5, after completing the design of the double-disk rolling rail specimen considering the action of bending stress, it is necessary to use the rolling contact fatigue and wear testing machine again to further verify the rationality of the designed structure; if no crack that extends along the material depth direction appears in the cross-section of the double-disk rolling rail specimen after rolling, gradually increase the total height H of the simulated beam cross-section, and repeat the design of the double-disk rolling rail specimen considering the action of bending stress until the crack morphology of its cross-section is similar to the crack morphology of the full-size rail cross-section after service.

[0029] The beneficial effects of the present invention are:

[0030] 1) The method of the present invention can realize the propagation of bending stress on the double-disk rolling specimen to the rolling contact fatigue crack of the rail. By combining the finite element analysis method and equipment such as the rolling contact fatigue and wear testing machine and the SEM scanning electron microscope, analyze the cross-section crack morphology and the maximum bending stress value σ simRmax of the double-disk rolling rail specimen, optimize the different cross-sectional shapes of the specimen according to the analysis results until the crack morphology of the specimen cross-section is close to the crack morphology of the rail cross-section after on-site service, and continuously correct the total height H of the simulated beam cross-section of the specimen until σ simRmax = σ Rmax, combined with a rolling contact fatigue and wear testing machine, the rationality of the test structure is verified again to ensure that the rolling contact fatigue crack damage of full-size rails under bending stress can be reproduced in the laboratory.

[0031] 2) By comparing the rolling contact fatigue damage of rails considering bending stress in the method of the present invention with the rolling fatigue damage of rails in the traditional double-disk rolling test without bending stress, it can more closely simulate the rolling contact fatigue damage of in-service rails on-site, and thus can better reveal the mechanism of rolling contact fatigue damage of rails. The present invention fills the gap in the wheel-rail double-disk rolling simulation test, enriches the research methods of rolling contact fatigue cracks of rails, and lays a foundation for further research on the mechanism of rolling contact fatigue crack propagation of full-size rails on-site. Brief Description of the Drawings

[0032] Figure 1 Schematic flow chart of the design method of the double-disk rolling rail specimen considering bending stress in the embodiment of the present invention;

[0033] Figure 2 Schematic diagram of the structure of the double-disk rolling rail specimen considering bending stress;

[0034] Figure 3 Partial cross-sectional view of the double-disk rolling rail specimens with three simulated beam cross-sections;

[0035] Figure 4 OM diagram of the profile fatigue crack morphology of the double-disk rolling rail specimens with three simulated beam cross-sections;

[0036] Figure 5 Schematic diagram of the full-size wheel-rail finite element calculation model;

[0037] Figure 6 Schematic diagram of the path for extracting the bending moment value of the full-size rail;

[0038] Figure 7 Schematic diagram of the finite element calculation model of the double-disk rolling rail specimen considering bending in the present invention;

[0039] Figure 8 Schematic diagram of the path for extracting the bending moment value of the double-disk rolling rail specimen considering bending in the present invention;

[0040] Figure 9 Dynamic bending stress curve diagram of any rail cross-section of the full-size wheel-rail finite element model;

[0041] Figure 10 Relationship diagram between the total height H of the simulated beam cross-section of the double-disk rolling rail specimen considering bending in the present invention and the bending stress;

[0042] Figure 11It is the dimension diagram of the wheel-rail double-disc rolling specimen;

[0043] Figure 12 It is the OM diagram of the fatigue crack morphology of the full-size rail profile after service;

[0044] Figure 13 It is the OM diagram of the fatigue crack morphology of the double-disc rolling U75V rail specimen profile considering bending effect with the total height H of the simulated beam section being 3 mm;

[0045] Figure 14 It is the OM diagram of the fatigue crack morphology of the double-disc rolling U75V rail specimen profile considering bending effect with the total height H of the simulated beam section being 3.5 mm;

[0046] Figure 15 It is the OM diagram of the fatigue crack morphology of the double-disc rolling U75V rail specimen profile considering bending effect with the total height H of the simulated beam section being 4 mm;

[0047] Figure 16 It is the detailed dimension schematic diagram of the double-disc rolling U75V rail specimen considering bending stress. Specific implementation mode

[0048] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0049] The present invention provides a technical solution: a design method for a double-disc rolling rail specimen considering bending stress, as Figure 1 shown, including the following steps:

[0050] S1. Based on the contour shape of the full-size rail and the structure of the existing double-disc rolling specimen without considering bending stress, design double-disc rolling rail specimens with different structures considering bending stress.

[0051] As Figure 2 and Figure 3 shown, the double-disc rolling rail specimen considering bending stress in the present invention is disc-shaped, with 5 arc-shaped grooves provided on both sides. The width of the arc-shaped groove is S, the distance between the arc-shaped grooves is L, and the height of the arc-shaped groove is H 1 , and above the arc-shaped groove is a simulated beam. The total height H of the simulated beam section is composed of the heights h i of different parts according to different cross-sectional shapes.

[0052] Specifically, it includes the following steps:

[0053] S11. Obtain the ratio of the sleeper width to the sleeper spacing according to the sleeper spacing and the sleeper width between adjacent sleepers in the full-scale wheel-rail model, so as to determine the distance L between the arc grooves of the double-disk rolling rail specimen and the width S of the arc grooves.

[0054] S12. Determine the height H of the arc grooves of the double-disk rolling rail specimen by taking values proportionally according to the height of the full-scale rail. 1 ; Above the arc grooves is a simulated beam, and the total height H of the cross-section of the simulated beam consists of the heights h of different parts according to different cross-section shapes. i ;

[0055] S13. Determine the cross-section shape of the double-disk rolling rail specimen according to the cross-section shape of the full-scale rail and the actual contact state of the wheel-rail, including three cross-section shapes: I-shaped cross-section, inverted T-shaped cross-section, and rectangular cross-section.

[0056] S2. Conduct a rolling test on the double-disk rolling rail specimen in S1 using a rolling contact fatigue and wear testing machine, and determine the cross-section shape of the simulated beam of the double-disk rolling rail specimen designed considering the bending stress based on the profile crack morphology of the double-disk rolling rail specimens with different structures.

[0057] The determination criterion for the cross-section shape design of the simulated beam of the double-disk rolling rail specimen considering the bending stress is whether the profile crack morphology of the rail specimen after the rolling test is similar to the profile crack morphology characteristics of the full-scale rail in service on-site. The profile crack morphology characteristics of the full-scale rail in service on-site are that the expansion angle formed by the tangent direction of the crack and the wheel-rail rolling direction gradually increases along the material interior during the crack propagation process until it approaches 90°.

[0058] S3. Obtain the bending moment value of any cross-section of the rail in the full-scale wheel-rail model through the ABAQUS software, and substitute it into the correction formula to obtain the maximum dynamic bending stress value σ of the full-scale rail. Rmax .

[0059] The correction formula is as follows:

[0060]

[0061] Among them, M x is the bending moment value of any rail cross-section; k is a correction coefficient, and its value is related to factors such as the train speed, wheel load eccentricity, and lateral action; σ R is the bending stress value of any rail cross-section; I R is the polar moment of inertia of the rail cross-section, and Z R is the distance between the wheel-rail contact point and the neutral axis on the cross-section of the full-scale rail.

[0062] S4. According to the double-disc rolling rail specimen structure designed in S2, a finite element calculation model of the double-disc rolling rail specimen of the structure is established by using Hypermesh and ABAQUS software, and the bending moment value of any section of the double-disc rolling rail specimen of the structure is calculated. Substituting it into the mechanical formula, the maximum bending stress value σ of the double-disc rolling rail specimen of the corresponding structure is obtained. simRmax .

[0063] The specific steps include:

[0064] S41, building a three-dimensional geometric model of the double-disc rolling rail specimen;

[0065] S42. Perform meshing in Hypermesh software, refine the contact area mesh according to the contact area, input material parameters, and export the finite element model .inp file of the specimen;

[0066] S43. Import the finite element model .inp file of the sample into ABAQUS for calculation to obtain the bending moment value M of any section of the double-disc rolling rail sample. simR ;

[0067] S44, the obtained bending moment value M of any section of the sample simR , substitute into the mechanical formula to calculate the maximum bending stress value σ of the double-disc rolling rail sample simRmax , where the bending stress value σ of any section of the rail specimen is simR and bending moment value M simR Relationship satisfaction:

[0068]

[0069] Where M simR is the bending moment value of any section of the rail specimen, I simR is the polar moment of inertia of the rail specimen cross section, and Z is the distance between the wheel-rail specimen contact point and the neutral axis on the rail specimen cross section.

[0070] S5. Taking the total height H of the simulated beam section of the double-disk rolling rail specimen as a variable, gradually increase the total height H of the simulated beam section of the double-disk rolling rail specimen, and use finite element software to repeatedly optimize and analyze until the maximum bending stress value of the double-disk rolling rail specimen is equivalent, that is, σ simRmax =σ Rmax Finally, all the geometric dimensions of the double-disc rolling rail specimen considering the bending stress are determined, and the design of the double-disc rolling rail specimen considering the bending stress is completed.

[0071] By adjusting the height h of different parts of the cross-sectional shape i To achieve the change of the total height H of the simulated beam section; if the section is an I-shaped structure, its cross-sectional shape and size are determined by the simulated rail head height h 1, simulated web height h 2 , simulated rail base height h 3 It consists of three parts; if the cross-section is an inverted T-shaped structure, its cross-sectional shape and size are composed of the upper flange height h 1 and the lower flange height h 2 which consists of two parts.

[0072] Furthermore, after completing the design of the double-disk rolling rail specimen considering the bending stress, it is necessary to use the rolling contact fatigue and wear testing machine again to further verify the rationality of the designed structure; if no crack that extends along the material depth direction appears in the cross-section of the double-disk rolling rail specimen after rolling, gradually increase the total height H of the simulated beam cross-section, and repeat the design of the double-disk rolling rail specimen considering the bending stress until the crack morphology of its cross-section is similar to that of the full-scale rail cross-section after service.

[0073] Implementation verification

[0074] Step 1: Select U75V rail material and C-class wheel material as the rail and wheel materials of the double-disk rolling wheel-rail specimen. The diameters of the wheel-rail specimens are all 60 mm, the specimen thicknesses are all 10 mm, and the contact widths are all 6 mm, as Figure 11 shown;

[0075] Step 2: Based on the contour shape of the full-scale rail and the existing double-disk rolling specimen structure without considering the bending stress, design double-disk rolling rail specimens with different structures considering the bending stress, as Figure 2 , Figure 3 shown. The specific steps are as follows:

[0076] 1) According to the sleeper spacing and sleeper width between adjacent sleepers in the full-scale wheel-rail model, obtain the ratio of the sleeper width to the sleeper spacing, so as to determine the spacing L between adjacent arc grooves and the groove width S of the arc grooves on the double-disk rolling rail specimen. In this embodiment, the selected sleeper spacing is 600 mm and the sleeper width is 200 mm. The sleeper structure of this model is consistent with the actual laying structure of the on-site sleepers.

[0077] 2) According to the height of the full-scale rail, take values in proportion to determine the height H 1 of the arc grooves of the double-disk rolling rail specimen. In this embodiment, the selected height H 1 of the arc grooves is 5 mm.

[0078] 3) According to the cross-sectional shape of the full-scale rail and the actual contact state of the wheel-rail, determine the cross-sectional shape and cross-sectional dimensions of the double-disk rolling rail specimen, including three cross-sectional shapes: I-shaped cross-section, inverted T-shaped cross-section, and rectangular cross-section, as Figure 3 shown.

[0079] Step 3: Use a rolling contact fatigue and wear testing machine to conduct rolling tests on the double-disk rolling rail specimens with different simulated beam cross-sections in Step 2. Use wire electrical discharge machining to sample the tested double-disk rolling rail specimens, conduct metallographic treatment on the cut cross-section samples, and use a super-depth-of-field optical microscope to observe the cross-section fatigue cracks, as Figure 4 shown.

[0080] Observe the cross-section crack morphologies of the double-disk rolling rail specimens with different simulated beam cross-sections. Only based on whether their cross-section cracks extend along the material depth direction, and it must be similar to the cross-section crack morphology of the full-scale rail after service (as Figure 12 shown) as the standard for completing the preliminary design of the specimen. The cross-section shape of the simulated beam initially selected in this embodiment is an inverted T shape.

[0081] Step 4: Obtain the bending moment value of any cross-section of the rail in the full-scale wheel-rail model through ABAQUS software, and substitute it into the correction formula to obtain the maximum bending stress value σ Rmax of the full-scale wheel-rail model, as shown by the curve of Cpress1222MPa in Figure 9 ;

[0082] The preprocessing process of the model is specifically as follows:

[0083] 1) Establish a three-dimensional model of the full-scale wheel-rail, where the total length of the rail is 27.2 m, the wheelbase is 1.83 m, and the fixed distance is 9 m, as Figure 5 shown.

[0084] 2) Conduct preprocessing for finite element simulation on the three-dimensional model of the full-scale wheel-rail, including operations such as mesh generation and material property assignment, and export the inp file.

[0085] 3) Set the static analysis step and field output, and establish the coupling constraint between the inner hole surface of the wheel and its respective reference points.

[0086] 4) Establish the MPC constraint between the front and rear wheels and the contact interaction between the wheel tread and the rail surface, where the type of MPC constraint is LINK connection.

[0087] 5) Establish a node set at the contact area between the bottom of the rail and the sleeper, and use a python script to establish a point-to-point spring at the contact area between the bottom of the rail and the top of the sleeper. The lateral stiffness and damping values, as well as the longitudinal stiffness and damping values, are determined according to different types of fasteners. In this embodiment, taking the on-site DTVI2 fasteners as an example, their vertical and lateral stiffness values are 40.73 MN / m and 8.79 MN / m respectively, and their vertical and lateral damping values are 9898.70 Ns / m and 1927.96 Ns / m respectively.

[0088] 6) Establish the force constraints and displacement constraints of the full-scale wheel-rail model. The magnitude of the vertical load depends on the axle load of the train. In this embodiment, the selected axle load of the train is 21t.

[0089] For the constructed full-scale wheel-rail finite element model, as Figure 5 shown, the specific post-processing process of the model is as follows:

[0090] 7) Define the straight-line extraction path of the bending moment of any cross-section of the rail, as Figure 6 shown. Along the longitudinal positive direction of the rail center line, starting from one end of the rail, a path point is set every 100 mm.

[0091] 8) In the View Cut module, select the Z-Plane plane, and the slicing direction is along the pre-set straight-line path for slicing. The total number of slices is 100, and the sliced result file is output to obtain the bending moment value of any rail cross-section.

[0092] 9) Since in the actual operation process, the wheel-rail relationship is affected by various factors, the bending moment value of the rail obtained by simulation calculation needs to be corrected, and its relationship satisfies the formula:

[0093] M = k·M

[0094] real x

[0095] In the formula, M x is the bending moment value of any rail cross-section, k is the correction coefficient, and its value is related to the train speed, wheel load eccentric load, lateral action, etc.

[0096] 10) The bending stress value σ real of any cross-section of the full-scale rail and the bending moment value M real satisfy the relationship:

[0097]

[0098] In the formula, M real is the actual bending moment value of any cross-section of the full-scale rail, I R is the polar moment of inertia of the rail cross-section, Z R is the distance between the rail top contact point and the neutral axis of the rail. The calculated dynamic bending stress curve is as Figure 9 shown.

[0099] Step 5: According to the double-disk rolling rail specimen structure of the inverted T-shaped simulated beam cross-section determined in Step 3, use Hypermesh and ABAQUS software to establish the finite element calculation model of the specimen, calculate the bending moment value of any cross-section of the double-disk rolling rail specimen, and substitute it into the mechanical formula to obtain the maximum bending stress value σ simRmax of the double-disk rolling rail specimen, as Figure 10 shown;

[0100] The specific processes of pre - processing and post - processing of the model are as follows:

[0101] 1) Construct a finite - element model of a wheel - rail double - disk rolling specimen. As Figure 7 shown, the mesh size of the contact area of the rail specimen is 0.2 mm, the 2D surface mesh size of the non - contact area is 0.5 mm, and the mesh size of the wheel specimen is 0.5 mm. The material properties of the rail and wheel specimens are the same as those of the full - scale wheel - rail model.

[0102] 2) Set the analysis step, force constraints, displacement constraints, field output, and the interaction of wheel - rail contact, and submit the calculation task.

[0103] 3) Conduct post - processing on the model, define the extraction path of the slice curve, as Figure 8 shown. Select the Z - Plane plane, the total number of slices is 100, output the slice result file, and obtain the bending moment value of any cross - section of the double - disk rolling rail specimen.

[0104] 4) The relationship between the bending stress value σ simR of any cross - section of the rail specimen and the bending moment value M simR satisfies:

[0105]

[0106] In the formula, M simR is the actual bending moment value of any cross - section of the rail specimen, I R is the polar moment of inertia of the rail cross - section, and Z is the distance between the rail - top contact point and the neutral axis of the rail.

[0107] Step 6: Take the total height H of the simulated beam cross - section of the double - disk rolling rail specimen as a variable, gradually increase the total height H of the simulated beam cross - section of the double - disk rolling rail specimen, and use finite - element software to repeatedly optimize and analyze until the maximum bending stress values of the double - disk rolling rail specimens obtained in S1 and S2 are equivalent (σ simRmax = σ Rmax ). Finally, determine all the geometric dimensions of the double - disk rolling rail specimen considering the action of bending stress, and complete the design of the double - disk rolling rail specimen considering the action of bending stress.

[0108] As Figure 3 shown, by adjusting the height h i of different parts of the cross - section shape, the total height H of the simulated beam cross - section can be changed. In this embodiment, the initially selected shape of the simulated beam cross - section is an inverted T - shape. The cross - section shape size consists of the height h 1 of the upper flange and the height h 2 of the lower flange. By adjusting the height h 1 of the upper flange and the height h 2 of the lower flange, until σsimRmax = σ Rmax , simulating the relationship between the total height H of the simulated beam cross-section and the bending stress, as Figure 10 shown.

[0109] Step 7: After completing the design of the double-disk rolling rail specimen considering the action of bending stress, use a rolling contact fatigue and wear testing machine to further verify it to ensure the rationality of the designed structure. If no crack that extends along the material depth direction appears in the cross-section of the double-disk rolling rail specimen after rolling, gradually increase the total height H of the simulated beam cross-section, and repeat S4 and S5 to design the double-disk rolling rail specimen considering the action of bending stress until the crack morphology of its cross-section is similar to that of the full-size rail cross-section after service. In this embodiment, the crack morphologies of the cross-sections of the double-disk rolling rail specimens with different total heights H of the simulated beam cross-section (H = 3 mm, H = 3.5 mm, H = 4 mm) are respectively as Figure 13 , Figure 14 , Figure 15 shown. The finally obtained double-disk rolling U75V rail specimen considering the action of bending stress is as Figure 16 shown.

[0110] It can be known by comparison that the method of the present invention considering the rolling contact fatigue damage of the rail under the action of bending stress and the rolling fatigue damage of the rail in the traditional double-disk rolling test without the action of bending stress can be closer to simulating the rolling contact fatigue damage of the in-service rail on-site, and thus can better reveal the mechanism of the rolling contact fatigue damage of the rail.

[0111] It should be noted that in this article, the terms "including", "comprising" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of another identical element in the process, method, article or device including the said element.

[0112] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "the" and "said" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms unless the context clearly dictates otherwise.

[0113] It should be understood that the term "and / or" used herein is merely a description of the relationship between associated objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. Additionally, the character " / " in this text generally represents an "or" relationship between the associated objects before and after it.

[0114] Depending on the context, the word "if" as used herein can be interpreted as "when" or "while" or "in response to determining" or "in response to detecting". Similarly, depending on the context, the phrase "if determined" or "if detecting (stated condition or event)" can be interpreted as "when determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)".

[0115] The "first / second" mentioned in the embodiments is merely to distinguish similar objects and does not represent a specific order for the objects. It can be understood that the "first / second" can be interchanged in the specific order or sequence when permitted. It should be understood that the objects distinguished by the "first / second" can be interchanged under appropriate circumstances so that the embodiments described herein can be implemented in an order other than those illustrated or described herein.

[0116] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A design method for a double-disc rolling rail specimen considering bending stress, characterized in that: The steps include: S1. Based on the profile shape of the full-size rail and the existing double-disc rolling rail specimen structure that does not consider the bending stress, design double-disc rolling rail specimens with different structures that consider the bending stress. S2. Perform rolling test on the double-disc rolling rail specimen in S1 using a rolling contact fatigue and wear testing machine, and determine the simulated beam cross-sectional shape of the double-disc rolling rail specimen designed to take bending stress into consideration based on the cross-sectional crack morphology of the double-disc rolling rail specimens with different structures; S3. Obtain the bending moment value of any section of the rail in the full-size wheel-rail model through ABAQUS software, and substitute it into the correction formula to obtain the maximum dynamic bending stress value σ of the full-size rail. Rmax ; S4. According to the double-disc rolling rail specimen structure designed in S2, a finite element calculation model of the double-disc rolling rail specimen of the structure is established by using Hypermesh and ABAQUS software, and the bending moment value of any section of the double-disc rolling rail specimen of the structure is calculated. Substituting it into the mechanical formula, the maximum bending stress value σ of the double-disc rolling rail specimen of the corresponding structure is obtained. simRmax ; S5. Taking the total height H of the simulated beam section of the double-disk rolling rail specimen as a variable, gradually increase the total height H of the simulated beam section of the double-disk rolling rail specimen, and use finite element software to repeatedly optimize and analyze until the maximum bending stress value of the double-disk rolling rail specimen is equivalent, that is, σ simRmax =σ Rmax Finally, all the geometric dimensions of the double-disc rolling rail specimen considering the bending stress are determined, and the design of the double-disc rolling rail specimen considering the bending stress is completed.

2. The double-disc rolling rail specimen design method considering bending stress according to claim 1 is characterized in that: In step S1, the following steps are specifically included: S11, according to the sleeper spacing and sleeper width of adjacent sleepers in the full-size wheel-rail model, the ratio of the sleeper width to the sleeper spacing is obtained, so as to determine the distance L between the arc grooves and the width S of the arc grooves of the double-disc rolling rail sample; S12. Determine the height H1 of the arc groove of the double-disc rolling rail specimen according to the proportion of the height of the full-size rail; the simulated beam is located above the arc groove, and the total height H of the simulated beam section is composed of the heights h of different parts according to different cross-sectional shapes. i composition; S13. According to the cross-sectional shape of the full-size rail and the actual contact state between the wheel and the rail, the cross-sectional shape of the double-disc rolling rail specimen is determined, including three cross-sectional shapes: I-shaped cross-section, inverted T-shaped cross-section, and rectangular cross-section.

3. The double-disc rolling rail specimen design method considering bending stress according to claim 1 is characterized in that: In step S2, the determination standard for the design of the cross-sectional shape of the simulated beam of the double-disc rolling rail specimen considering the bending stress is whether the cross-sectional crack morphology of the rail specimen after the rolling test is similar to the cross-sectional crack morphology characteristics of the full-size rail in service on site; the cross-sectional crack morphology characteristics of the full-size rail in service on site are that during the crack propagation process, the expansion angle between the tangent direction of the crack and the wheel-rail rolling direction gradually increases along the inside of the material until it is close to 90°.

4. The double-disc rolling rail specimen design method considering bending stress according to claim 1 is characterized in that: In step S3, the correction formula is as follows: Among them, M x is the bending moment value of any rail section; k is the correction coefficient; σ R is the bending stress value of any section of the rail; I R is the polar moment of inertia of the rail section, Z R It is the distance between the wheel-rail contact point and the neutral axis on the full-size rail cross section.

5. The double-disc rolling rail specimen design method considering bending stress according to claim 1 is characterized in that: In step S4, the following steps are specifically included: S41, building a three-dimensional geometric model of the double-disc rolling rail specimen; S42. Perform meshing in Hypermesh software, refine the contact area mesh according to the contact area, input material parameters, and export the finite element model .inp file of the specimen; S43. Import the finite element model .inp file of the sample into ABAQUS for calculation to obtain the bending moment value M of any section of the double-disc rolling rail sample. simR ; S44, the obtained bending moment value M of any section of the sample simR , substitute into the mechanical formula to calculate the maximum bending stress value σ of the double-disc rolling rail sample simRmax , where the bending stress value σ of any section of the rail specimen is simR and bending moment value M simR Relationship satisfaction: Where M simR is the bending moment value of any section of the rail specimen, I simR is the polar moment of inertia of the rail specimen cross section, and Z is the distance between the wheel-rail specimen contact point and the neutral axis on the rail specimen cross section.

6. The method for designing a double-disc rolling rail specimen considering bending stress according to claim 1, characterized in that: In step S5, the height h of different parts of the cross-sectional shape is adjusted. i To achieve the change of the total height H of the simulated beam section; if the section is an I-shaped structure, its cross-sectional shape and size are composed of three parts: the simulated rail head height h1, the simulated rail waist height h2, and the simulated rail bottom height h3; if the section is an inverted T-shaped structure, its cross-sectional shape and size are composed of two parts: the upper web height h1 and the lower flange height h2.

7. The method for designing a double-disc rolling rail specimen considering bending stress according to claim 1, characterized in that: In step S5, after completing the design of the double-disc rolling rail specimen considering the bending stress, it is necessary to use the rolling contact fatigue and wear testing machine again to further verify the rationality of the designed structure; if the cross-section of the double-disc rolling rail specimen after rolling does not show cracks extending along the material depth direction, gradually increase the total height H of the simulated beam section, and repeat the design of the double-disc rolling rail specimen considering the bending stress until its cross-section crack morphology is similar to the cross-section crack morphology of the full-size rail after service.

Images