A design method for double-disc rolling rail specimen considering bending stress

Abstract

The present invention relates to the technical field of wheel-rail double-disc rolling simulation, and specifically discloses a double-disc rolling rail specimen design method that takes into account the effect of bending stress. The present invention realizes the effect of bending stress on the extension of rail rolling contact fatigue cracks on the double-disc rolling specimen, and combines finite element analysis methods and rolling contact fatigue and wear testing machines, SEM scanning electron microscopes and other equipment to analyze the cross-sectional crack morphology and maximum bending stress value σ of the double-disc rolling rail specimen. simRmax The cross-sectional shapes of the specimens are optimized 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 field service, and the total height H of the simulated beam cross section of the specimen is continuously modified until it meets σ simRmax =σ Rmax , and then combined with the rolling contact fatigue and wear testing machine to verify the rationality of the test structure again, to ensure that the rolling contact fatigue crack damage of the full-size rail under bending stress can be reproduced in the laboratory.

Description

Technical Field

[0001] The invention relates to the technical field of wheel-rail double-disc rolling simulation technology, and in particular to a double-disc rolling rail sample design method considering bending stress action. Background Art

[0002] With the rapid development of rail transit in my country, wheel and rail damage and wear are becoming increasingly prominent. When subjected to cyclical loads from wheels, fatigue cracks initiate on the rail surface and propagate internally, eventually leading to partial material spalling or even fracture, seriously endangering train safety. To better replicate the actual damage process of rails in the field, many researchers have used a double-disc rolling contact fatigue testing machine to conduct double-disc rolling simulation tests to study rolling contact fatigue of rails.

[0003] Since the wheel and rail are in an open environment during the actual process, once a crack initiates on the rail surface, as the contact load between the wheel and rail continues to increase, the crack propagates inward along the plastic flow line of the material under the action of the alternating contact load. If a third body medium exists between the wheel and rail interface, an oil wedge effect will occur, causing the crack propagation rate to increase sharply. When the crack propagates to a certain depth, the bending stress on the rail plays a dominant role in crack propagation. However, in previous double-disc rolling simulation tests, most researchers only considered the effects of contact stress, third body medium, and tangential load on the growth of rolling contact fatigue cracks in the rail, and did not consider the effect of bending stress on the growth of rolling contact fatigue cracks in the rail. Some researchers have used numerical simulation to study the effect of bending stress on the growth of rolling contact fatigue cracks in the rail, but this method lacks experimental verification, and the results cannot better reveal the mechanism of rolling contact fatigue crack propagation in the actual process. Other researchers, such as He Chenggang and Zeng Qingfei, have considered the effect of bending stress on wheel-rail rolling contact fatigue cracks. However, their methods employ mechanical processing to pre-fabricate cracks at the bottom of their specimens and study the fatigue crack propagation behavior at the pre-fabricated crack tip. However, under actual working conditions, rolling contact fatigue cracks in rails subjected to bending stress develop from initiation to propagation on the rail surface. Using pre-fabricated cracks to study the effect of bending stress on rolling contact fatigue cracks in rails fails to simulate the actual propagation behavior of rolling contact fatigue cracks in rails subjected to bending stress.

[0004] In summary, current research on rail rolling contact fatigue cracking in twin-disc rolling simulation tests still has many deficiencies. Therefore, introducing the effect of bending stress in twin-disc rolling simulation tests has important engineering significance for further studying the rolling contact fatigue damage behavior of rails. Summary of the Invention

[0005] In order to solve the problem in the prior art that rails are subjected to bending stress in railway sites but its influence on rolling contact fatigue cracks is difficult to simulate in the laboratory, the present invention provides a double-disc rolling rail specimen design method taking into account the effect of bending stress, which can better simulate the rolling contact fatigue damage behavior of rails under actual working conditions and solve the problems mentioned in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for designing a double-disc rolling rail specimen taking into account the effect of bending stress, comprising the following steps:

[0007] S1. Based on the profile 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.

[0008] S2. Conduct rolling tests on the double-disc rolling rail specimens in S1 using a rolling contact fatigue and wear testing machine. Based on the cross-sectional crack morphologies of the double-disc rolling rail specimens with different structures, determine the simulated beam cross-sectional shape of the double-disc rolling rail specimens designed to take bending stress into account.

[0009] S3. Obtain the bending moment value of any rail section in the full-size wheel-rail model using 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. Based on 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 using Hypermesh and ABAQUS software. The bending moment value of any section of the double-disc rolling rail specimen of the structure is calculated, and the maximum bending stress value σ of the double-disc rolling rail specimen of the corresponding structure is obtained by substituting it into the mechanical formula. simRmax ;

[0011] S5. Taking the total height H of the simulated beam section of the double-disc rolling rail specimen as a variable, gradually increase the total height H of the simulated beam section of the double-disc rolling rail specimen, and repeatedly optimize and analyze using finite element software until the maximum bending stress value of the double-disc 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.

[0012] Preferably, in step S1, the following steps are specifically included:

[0013] S11. Based on the sleeper spacing and sleeper width of adjacent sleepers in the full-size wheel-rail model, a ratio of sleeper width to sleeper spacing is obtained, thereby determining the distance L between the arc grooves and the width S of the arc grooves of the double-disc rolling rail specimen;

[0014] S12. Determine the height H1 of the arc groove of the double-disc rolling rail specimen in proportion to the height of the full-size rail. Above the arc groove is a simulated beam. The total height H of the simulated beam section is determined by the height h of different parts according to different cross-sectional shapes. i composition;

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

[0016] Preferably, in step S2, the criterion for determining the cross-sectional shape design of the simulated beam of the double-disc rolling rail specimen considering 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. The cross-sectional crack morphology characteristics of the full-size rail in service are that during the crack propagation process, the angle between the tangent direction of the crack and the wheel-rail rolling direction gradually increases along the interior of the material until it approaches 90°.

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

[0018]

[0019] Among them, M x is the bending moment value of any rail section; k is the correction coefficient, whose value is related to factors such as train speed, wheel load eccentricity, and lateral action; 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.

[0020] Preferably, in step S4, the following steps are specifically included:

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

[0022] 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;

[0023] 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 ;

[0024] 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 , the bending stress value σ of any section of the rail specimen in the formula simR and bending moment value M simR Relationship satisfaction:

[0025]

[0026] 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.

[0027] Preferably, in step S5, 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 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.

[0028] Preferably, in step S5, after completing the design of the double-disc rolling rail specimen considering the effect 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 cracks extending along the material depth direction appear in the cross-section of the double-disc rolling rail specimen after rolling, gradually increase the total height H of the simulated beam section, and repeat the design of the double-disc rolling rail specimen considering the effect of bending stress until its cross-section crack morphology is similar to the cross-section crack morphology of the full-size rail after service.

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

[0030] 1) The method of the present invention can realize the extension of rolling contact fatigue crack of rail under bending stress on double-disc rolling specimen, and combines finite element analysis method and rolling contact fatigue and wear testing machine, SEM scanning electron microscope and other equipment to analyze the cross-sectional crack morphology and maximum bending stress value σ of double-disc rolling rail specimen. simRmax The cross-sectional shapes of the specimens are optimized 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 field service, and the total height H of the simulated beam cross section of the specimen is continuously modified until it meets σ simRmax =σ Rmax , and then combined with the rolling contact fatigue and wear testing machine to verify the rationality of the test structure again, to ensure that the rolling contact fatigue crack damage of the full-size rail under bending stress can be reproduced in the laboratory.

[0031] 2) By comparing the rolling contact fatigue damage of rails subjected to bending stress using the present method with that of conventional double-disc rolling tests without bending stress, the present method more closely simulates the rolling contact fatigue damage of rails in service, thereby further revealing the mechanism of rolling contact fatigue damage. This present method fills a gap in the field of double-disc wheel-rail rolling simulation tests, enriches the research methodologies for rolling contact fatigue cracks in rails, and lays the foundation for further research on the mechanism of rolling contact fatigue crack propagation in full-scale rails in the field. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0034] Figure 3 The local cross-sectional views of the double-disc rolling rail specimens of three simulated beam sections;

[0035] Figure 4 OM images of cross-sectional fatigue crack morphologies of three types of double-disc rolling rail specimens simulating beam cross-sections;

[0036] Figure 5 This is a schematic diagram of the full-scale 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 This is a schematic diagram of the finite element calculation model of a double-disc rolling rail specimen considering bending effect in the present invention;

[0039] Figure 8 This is a schematic diagram of the path for extracting the bending moment value of a double-disc rolling rail specimen considering the bending effect of the present invention;

[0040] Figure 9 The dynamic bending stress curve of any rail section of the full-scale wheel-rail finite element model;

[0041] Figure 10 This is a diagram showing the relationship between the total height H of the simulated beam section and the bending stress of the double-disc rolling rail specimen considering the bending effect of the present invention;

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

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

[0044] Figure 13 OM diagram of fatigue crack morphology of double-disc rolling U75V rail specimen with a total beam section height of H = 3 mm and considering bending effect;

[0045] Figure 14 OM diagram of fatigue crack morphology of double-disc rolling U75V rail specimen with a total beam section height of H = 3.5 mm and considering bending effect;

[0046] Figure 15 OM diagram of fatigue crack morphology of double-disc rolling U75V rail specimen with a total beam section height of H = 4 mm and considering bending effect;

[0047] Figure 16 Schematic diagram of the detailed dimensions of the double-disc rolling U75V rail specimen considering bending stress. DETAILED DESCRIPTION

[0048] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0049] The present invention provides a technical solution: a design method for a double-disc rolling rail specimen taking into account the effect of bending stress, such as Figure 1 As shown, the following steps are included:

[0050] 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 effect, double-disc rolling rail specimens with different structures that consider the bending stress effect are designed.

[0051] like Figure 2 and Figure 3 As shown in the figure, the double-disc rolling rail specimen considering the bending stress of the present invention is in the shape of a disk, with 5 arc grooves set on both sides. The width of the arc groove is S, the distance between the arc grooves is L, the height of the arc groove is H1, and the simulated beam is located above the arc groove. 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.

[0052] The specific steps include:

[0053] S11. Based on the sleeper spacing and sleeper width of adjacent sleepers in the full-size wheel-rail model, a ratio of sleeper width to sleeper spacing is obtained, thereby determining the distance L between the arc grooves and the width S of the arc grooves of the double-disc rolling rail specimen;

[0054] S12. Determine the height H1 of the arc groove of the double-disc rolling rail specimen in proportion to the height of the full-size rail. Above the arc groove is a simulated beam. The total height H of the simulated beam section is determined by the height h of different parts according to different cross-sectional shapes. i composition;

[0055] S13. Determine the cross-sectional shape of the double-disc rolling rail specimen based on the cross-sectional shape of the full-size rail and the actual wheel-rail contact state, including three cross-sectional shapes: I-section, inverted T-section, and rectangular section.

[0056] S2. Use a rolling contact fatigue and wear testing machine to conduct a rolling test on the double-disc rolling rail specimen in S1. Based on the cross-sectional crack morphology of the double-disc rolling rail specimens with different structures, determine the simulated beam cross-sectional shape of the double-disc rolling rail specimen designed to take bending stress into consideration.

[0057] The design criteria for the cross-sectional shape of the simulated beam of the double-disc rolling rail specimen, which considers bending stress, is based on whether the cross-sectional crack morphology of the rail specimen after the rolling test is similar to the cross-sectional crack morphology of the full-scale rail in service. The cross-sectional crack morphology of the full-scale rail in service is characterized by a crack propagation angle between the tangent direction and the wheel-rail rolling direction that gradually increases along the material until it approaches 90°.

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

[0059] The correction formula is as follows:

[0060]

[0061] Among them, M x is the bending moment value of any rail section; k is the correction coefficient, whose value is related to factors such as train speed, wheel load eccentricity, and lateral action; 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.

[0062] S4. Based on 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 using Hypermesh and ABAQUS software. The bending moment value of any section of the double-disc rolling rail specimen of the structure is calculated, and the maximum bending stress value σ of the double-disc rolling rail specimen of the corresponding structure is obtained by substituting it into the mechanical formula. simRmax .

[0063] The specific steps include:

[0064] S41. Create 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 , the bending stress value σ of any section of the rail specimen in the formula 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-disc rolling rail specimen as a variable, gradually increase the total height H of the simulated beam section of the double-disc rolling rail specimen, and repeatedly optimize and analyze using finite element software until the maximum bending stress value of the double-disc 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 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.

[0072] Furthermore, after completing the design of the double-disc rolling rail specimen considering the effect 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 cracks extending along the depth direction of the material appear in the cross-section of the double-disc rolling rail specimen after rolling, gradually increase the total height H of the simulated beam section and repeat the design of the double-disc rolling rail specimen considering the effect of bending stress until its cross-section crack morphology is similar to the cross-section crack morphology of the full-size rail after service.

[0073] Implementation Verification

[0074] Step 1: Select U75V rail material and C-grade wheel material as the rail and wheel materials for the double-disc rolling wheel-rail specimen. The diameter of the wheel-rail specimen is 60 mm, the thickness is 10 mm, and the contact width is 6 mm. Figure 11 As shown;

[0075] Step 2: Based on the contour 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, such as Figure 2 、 Figure 3 The specific steps are as follows:

[0076] 1) Based on the sleeper spacing and sleeper width of adjacent sleepers in the full-scale wheel-rail model, the ratio of sleeper width to sleeper spacing is calculated, thereby determining the spacing L between adjacent arcuate grooves and the groove width S of the arcuate grooves on the double-disc rolling rail specimen. In this example, the sleeper spacing used is 600 mm and the sleeper width is 200 mm. The sleeper structure of this model is consistent with the actual sleeper installation structure on site.

[0077] 2) The height H1 of the arc groove of the double-disc rolling rail specimen is determined by proportionally taking a value according to the height of the full-size rail. In this embodiment, the arc groove height H1 is selected to be 5 mm.

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

[0079] Step 3: Use a rolling contact fatigue and wear tester to conduct rolling tests on the double-disc rolling rail specimens with different simulated beam cross sections in step 2, use electric spark wire cutting to sample the double-disc rolling rail specimens after the test, perform metallographic processing on the cut cross-section specimens, and use an ultra-depth of field optical microscope to observe the fatigue cracks on the cross-section, such as Figure 4 shown.

[0080] Observe the cross-sectional crack morphology of double-disc rolling rail specimens with different simulated beam cross sections, and only consider whether the cross-sectional cracks extend along the material depth direction, and whether they are consistent with the cross-sectional crack morphology of the full-size rail after service (such as Figure 12 The cross-sectional 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 rail section 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 of the full-scale wheel-rail model Rmax ,like Figure 9 As shown in the curve of Cpress1222MPa;

[0082] The pre-processing process of the model is as follows:

[0083] 1) Establish a full-size wheel-rail 3D model, where the total length of the rail is 27.2m, the wheelbase is 1.83m, and the fixed distance is 9m. Figure 5 shown.

[0084] 2) Perform pre-processing of the full-scale wheel-rail 3D model for finite element simulation, including meshing, assigning material properties, and exporting the inp file.

[0085] 3) Set the static analysis step and field output, and establish the coupling constraints between the inner hole surface of the wheel and their 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 in the contact area between the bottom of the rail and the top of the sleeper. The transverse stiffness and damping values, as well as the longitudinal stiffness and damping values, are determined according to the type of fastener. In this embodiment, the DTVI2 fastener used on site is used as an example. Its vertical and transverse stiffness values ​​are 40.73 MN / m and 8.79 MN / m, respectively, and its vertical and transverse damping values ​​are 9898.70 Ns / m and 1927.96 Ns / m, respectively.

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

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

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

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

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

[0093] M=k·M

[0094] real x

[0095] Where M x is the bending moment value of any rail section, k is the correction coefficient, and its value is related to the train speed, wheel load eccentricity, lateral effect, etc.

[0096] 10) Bending stress value σ of any section of full-size rail real and bending moment value M real Relationship satisfaction:

[0097]

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

[0099] Step 5: Based on the double-disc rolling rail specimen structure with an inverted T-shaped simulated beam section determined in step 3, a finite element calculation model of the specimen is established using Hypermesh and ABAQUS software. The bending moment value of any section of the double-disc rolling rail specimen is calculated and substituted into the mechanical formula to obtain the maximum bending stress value σ of the double-disc rolling rail specimen. simRmax ,like Figure 10 As shown;

[0100] The specific process of model pre-processing and post-processing is as follows:

[0101] 1) Construct the finite element model of the wheel-rail double disc rolling specimen, such as Figure 7As shown in the figure, the mesh size of the rail specimen in the contact area is 0.2 mm, the 2D 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 consistent with those of the full-scale wheel-rail model.

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

[0103] 3) Post-process the model and define the slice curve extraction path, such as Figure 8 Select the Z-Plane plane, set the total number of slices to 100, output the slice result file, and obtain the bending moment value of any rail specimen section of the double-disc rolling rail specimen.

[0104] 4) Bending stress value σ of any section of rail specimen simR and bending moment value M simR Relationship satisfaction:

[0105]

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

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

[0108] like Figure 3 As shown, by adjusting the height h of different parts of the cross-sectional shape i In order to change the total height H of the simulated beam section, the simulated beam section shape initially selected in this embodiment is an inverted T-shape, and the cross-sectional shape and size are composed of two parts: the upper web height h1 and the lower flange height h2. By adjusting the upper web height h1 and the lower flange height h2 until σ simRmax =σ Rmax , simulates the relationship between the total height H of the beam section and the bending stress, such as Figure 10 shown.

[0109] Step 7: After completing the design of the double-disc rolling rail specimen considering the bending stress, further verify it using a rolling contact fatigue and wear tester to ensure the rationality of the designed structure. If no cracks extending along the material depth direction appear in the cross-section of the double-disc rolling rail specimen after rolling, gradually increase the total height H of the simulated beam section, and repeat S4 and S5 to design 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. The cross-section crack morphologies of the double-disc rolling rail specimens with different total heights H of the simulated beam section (H=3mm, H=3.5mm, H=4mm) in this embodiment are as follows: Figure 13 、 Figure 14 、 Figure 15 The final double-disc rolling U75V rail specimen considering bending stress is shown in Figure 16 shown.

[0110] By comparison, it can be seen that the method of the present invention considers 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-disc rolling test without bending stress, and can more closely simulate the rolling contact fatigue damage of the rails in service on the field, and thus can better reveal the mechanism of rolling contact fatigue damage of the rails.

[0111] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the 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", "an", "the" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0113] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0114] The word "if," as used herein, may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to the determination" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)," depending on the context.

[0115] The references to "first" and "second" in the embodiments merely distinguish similar objects and do not represent a specific ordering of the objects. It is understood that the specific order or precedence of "first" and "second" can be interchanged where appropriate. It should be understood that the objects distinguished by "first" and "second" can be interchanged where appropriate, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein.

[0116] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection 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 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. The specific steps include: S11. Based on the sleeper spacing and sleeper width of adjacent sleepers in the full-size wheel-rail model, a ratio of sleeper width to sleeper spacing is obtained, thereby determining the distance L between the arc grooves and the width S of the arc grooves of the double-disc rolling rail specimen; S12. Determine the height H1 of the arc groove of the double-disc rolling rail specimen in proportion to the height of the full-size rail. Above the arc groove is a simulated beam. The total height H of the simulated beam section is determined by the height h of different parts according to different cross-sectional shapes. i composition; S13. Determine the cross-sectional shape of the double-disc rolling rail specimen based on the cross-sectional shape of the full-size rail and the actual wheel-rail contact state, including three cross-sectional shapes: I-section, inverted T-section, and rectangular section; S2. Conduct rolling tests on the double-disc rolling rail specimens in S1 using a rolling contact fatigue and wear testing machine. Based on the cross-sectional crack morphologies of the double-disc rolling rail specimens with different structures, determine the simulated beam cross-sectional shape of the double-disc rolling rail specimens designed to take bending stress into account. S3. Obtain the bending moment value of any rail section in the full-size wheel-rail model using 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. Based on 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 using Hypermesh and ABAQUS software. The bending moment value of any section of the double-disc rolling rail specimen of the structure is calculated, and the maximum bending stress value σ of the double-disc rolling rail specimen of the corresponding structure is obtained by substituting it into the mechanical formula. simRmax ; S5. Taking the total height H of the simulated beam section of the double-disc rolling rail specimen as a variable, gradually increase the total height H of the simulated beam section of the double-disc rolling rail specimen, and repeatedly optimize and analyze using finite element software until the maximum bending stress value of the double-disc 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 method for designing a double-disc rolling rail specimen considering bending stress according to claim 1, characterized in that: In step S2, the criterion for determining the cross-sectional shape design of the simulated beam of the double-disc rolling rail specimen considering the effect of 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 angle formed between the tangential direction of the crack and the wheel-rail rolling direction gradually increases along the interior of the material until it approaches 90°.

3. The method for designing a double-disc rolling rail specimen considering bending stress according to claim 1, 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.

4. The method for designing a double-disc rolling rail specimen considering bending stress according to claim 1, characterized in that: In step S4, the following steps are specifically included: S41. Create 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 , the bending stress value σ of any section of the rail specimen in the formula 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.

5. 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.

6. 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 no cracks extending along the material depth direction appear in the cross-section of the double-disc rolling rail specimen after rolling, 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.

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