Method and system for judging circumferential crack initiation condition of wheel tread of railway wagon

Abstract

The invention provides a method and a system for judging a circumferential crack initiation condition of a wheel tread of a railway wagon. The method comprises the following steps of: establishing a railway wagon dynamic model; based on the action relation between the circumferential cracks and the shear stress borne by the wheels, the bogie working condition with the suspension failure is set in the railway wagon dynamic model; on the basis of the railway wagon dynamics model, statistics is conducted on the dynamics simulation result of each wheel of each bogie working condition, the bogie working condition when transverse force and transverse creep force borne by the wheels are maximum is obtained, and the bogie load working condition when circumferential cracks are generated is judged; based on the preliminarily judged bogie load working condition when the circumferential crack is generated, the maximum Hertz contact stress borne by the wheel is calculated through the Hertz contact theory; based on a dynamic simulation result, the maximum Hertz contact stress borne by the wheel and the shear yield limit of a wheel material, a wheel stability diagram is drawn by combining a stability theory; and judging the mechanism of circumferential crack initiation by analyzing a wheel stability diagram.

Description

Technical Field

[0001] This invention relates to the field of fatigue crack technology for railway wheel treads, and in particular to a method and system for determining the initiation of circumferential cracks in railway freight car treads. Background Technology

[0002] During rolling contact, fatigue damage caused by cyclic mechanical stress is called rolling contact fatigue (RCF). When the stress value on the surface and subsurface regions of the wheel tread exceeds the material's stability limit, plastic strain will continuously accumulate; this process is called the ratchet effect. Under the action of the ratchet effect, the surface and subsurface of the wheel tread undergo very severe plastic deformation, eventually leading to the initiation of rolling contact fatigue cracks. Currently, it is known that Type 1 cracks are initiated by the interaction between the wheel and the lower track of a curve, Type 2 cracks are generated by the interaction between the wheel and the upper track of a curve, Type 3 cracks are caused by excessive longitudinal creep force, and Type 4 circumferential cracks are caused by excessive transverse creep force. Among these, the load conditions for the initiation of circumferential cracks have been studied less.

[0003] Current research on circumferential cracks in railway freight car treads faces significant challenges. Firstly, limited research on Type IV circumferential cracks makes it difficult to define the load conditions for crack initiation. Secondly, a method is lacking that can combine tread mechanical properties to determine crack initiation. To address these shortcomings, a method for evaluating the initiation of circumferential cracks in railway freight car treads is proposed.

[0004] Existing research on wheel-rail rolling contact fatigue cracks, such as the Chinese invention patent publication CN113528967B which discloses a heavy-duty locomotive wheel steel and wheel production method resistant to surface contact fatigue, improves the hardness and toughness of the wheel steel by optimizing the chemical composition and heat treatment process, thereby enhancing its resistance to surface contact fatigue and extending the service life of the wheel under high-load operating conditions. However, it does not study the mechanism of fatigue crack initiation in wheels, nor does it clarify the load conditions for fatigue crack initiation. Summary of the Invention

[0005] The embodiments of the present invention provide a method and system for determining the initiation of circumferential cracks in the tread of railway freight car wheels, which is used to solve the technical problems existing in the prior art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution.

[0007] Methods for determining the initiation of circumferential cracks in the tread of railway freight car wheels include:

[0008] S1 establishes a railway freight car dynamics model for the freight car to which the faulty wheel belongs, and sets track conditions in the railway freight car dynamics model;

[0009] Based on the interaction between circumferential cracks and shear stress on wheels, S2 sets up a bogie working condition with suspension failure in the dynamic model of railway freight cars for dynamic simulation.

[0010] S3 is based on the railway freight car dynamics model that has been executed in step S2. It statistically analyzes the dynamic simulation results of each wheel for each bogie working condition, obtains the bogie working condition when the lateral force and lateral creep force on the wheel are the maximum, and determines the bogie load working condition when circumferential cracks are initiated.

[0011] S4, based on the preliminary judgment of the bogie load conditions when the circumferential cracks initiate, calculates the maximum Hertzian contact stress on the wheel using Hertzian contact theory.

[0012] S5 uses dynamic simulation results, the maximum Hertzian contact stress on the wheel and the shear yield limit of the wheel material to draw a wheel stability diagram based on stability theory.

[0013] S6 determines the mechanism of circumferential crack initiation by analyzing the wheel stability diagram;

[0014] The judgment result of step S6 is used for fault analysis of railway freight car wheels.

[0015] Preferably, step S1 includes:

[0016] S11 used SIMPACK software to build a dynamic model of a C70 truck with a 23t axle load, and the wheel tread was selected as LM tread.

[0017] In the railway freight car dynamics model, S12 is set with a CN60 track and a total length of 500m for the track's horizontal curve model, including a circular curve with a radius of 800m and a length of 100m, a transition curve of 120m and straight sections at both ends of the curve. The track superelevation is set to 150mm, and the train speed is 80km / h.

[0018] S13 Through-type

[0019]

[0020] Establish a lateral track irregularity excitation; where S(Ω) is the track irregularity power spectral density cm² / (rad / m); Ω is the spatial frequency of the track irregularity rad / m; A a , is the roughness coefficient cm2·rad / m; Ωc is the cutoff frequency rad / m; k is the safety factor, taken as 0.25.

[0021] Preferably, step S3 includes:

[0022] Dynamic simulation analysis of the C70 truck crossing a small radius curve with R=800m was conducted under normal operating conditions, primary suspension failure conditions, and secondary suspension failure conditions, with and without lateral irregularity excitation.

[0023] Preferably, step S4 includes:

[0024] The formula for calculating the maximum Hertzian contact stress

[0025]

[0026] The maximum Hertzian contact stress on the wheel is calculated; where σ max Where is the maximum Hertzian contact stress, F is the vertical force between the wheel and rail, and a and b are the major and minor semi-axes of the contact ellipse, respectively, satisfying the following equations:

[0027]

[0028] In the formula, α and β are coefficients related to the geometry and material properties of the contact body; R is the equivalent radius of curvature, calculated using the following formula: Where R1 and R2 are the radii of curvature of the wheel and rail, respectively; E * It is the equivalent elastic modulus.

[0029] Preferably, step S6 includes:

[0030] Through

[0031]

[0032] The friction coefficient of the wheel is calculated; where F ξ and F η F represents the longitudinal and transverse creep forces, respectively. n Normal force;

[0033] Through

[0034]

[0035] The fatigue index of the wheel surface was calculated; FI surf It is a function of the traction coefficient, Hertzian contact geometry, shear yield stress, and vertical load. a and b are the major and minor semi-axises of the Hertzian contact patch, respectively, and F... z It is a vertical load.

[0036] Secondly, the present invention provides a system for determining the initiation of circumferential cracks in the tread of railway freight car wheels, comprising:

[0037] The modeling and analysis module is used for:

[0038] Establish a dynamic model of the freight car to which the faulty wheel belongs, and set track conditions in the dynamic model of the freight car;

[0039] Based on the relationship between circumferential cracks and shear stress on wheels, a bogie case with suspension failure is set in the dynamic model of railway freight cars for dynamic simulation.

[0040] Based on the railway freight car dynamics model that has undergone the above process, the dynamic simulation results of each wheel under each bogie working condition are statistically analyzed to obtain the bogie working condition when the lateral force and lateral creep force on the wheel are at their maximum, and to determine the bogie load working condition when circumferential cracks initiate.

[0041] Based on the preliminary judgment of the bogie load conditions at the initiation of circumferential cracks, the maximum Hertzian contact stress on the wheel was calculated using Hertzian contact theory.

[0042] Based on the dynamic simulation results, the maximum Hertzian contact stress on the wheel and the shear yield limit of the wheel material, a wheel stability diagram was drawn in conjunction with stability theory.

[0043] The discrimination module is used to determine the mechanism of circumferential crack initiation by analyzing the wheel stability diagram;

[0044] The output module is used to output the discrimination results of the discrimination module.

[0045] As can be seen from the technical solutions provided by the embodiments of the present invention above, the present invention provides a method and system for determining the initiation of circumferential cracks in the tread of railway freight cars. The method includes: establishing a railway freight car dynamic model and setting track conditions in the railway freight car dynamic model; based on the interaction between the circumferential crack and the shear stress on the wheel, setting a bogie working condition with suspension failure in the railway freight car dynamic model; based on the above-mentioned railway freight car dynamic model, statistically analyzing the dynamic simulation results of each wheel for each bogie working condition, obtaining the bogie working condition when the lateral force and lateral creep force on the wheel are maximum, and determining the bogie load condition when circumferential cracks initiate; based on the preliminarily determined bogie load condition when circumferential cracks initiate, calculating the maximum Hertzian contact stress on the wheel using Hertzian contact theory; based on the dynamic simulation results, the maximum Hertzian contact stress on the wheel, and the shear yield limit of the wheel material, drawing a wheel stability diagram in conjunction with stability theory; and determining the mechanism of circumferential crack initiation by analyzing the wheel stability diagram. The method provided by this invention establishes a method for evaluating the initiation of circumferential cracks in the tread of railway freight car wheels. First, a dynamic model of the freight car is established, and dynamic simulations are performed under different failure conditions in a small radius curve. The load conditions for the initiation of circumferential cracks in the tread of railway freight car wheels are analyzed. Then, using stability theory combined with dynamic results, stability analysis is performed on wheel steel materials with different hardnesses from the perspective of wheel material, providing a theoretical basis for improving the wheel's resistance to circumferential cracks.

[0046] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and will become apparent from the description or may be learned by practice of the invention. Attached Figure Description

[0047] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 A flowchart illustrating the processing of a method for determining the initiation of circumferential cracks in the tread of railway freight car wheels provided by the present invention;

[0049] Figure 2 This invention provides a dynamic model of a C70 freight car based on the initiation of circumferential cracks in the wheel tread of a railway freight car.

[0050] Figure 3 This invention provides a C70 freight car bogie model illustrating the initiation of circumferential cracks in the wheel tread of a railway freight car.

[0051] Figure 4This invention provides a track lateral irregularity excitation method for the initiation of circumferential cracks in the tread of railway freight car wheels.

[0052] Figure 5 A stability diagram of the initiation of circumferential cracks in the tread of a railway freight car, provided by the present invention;

[0053] Figure 6 This invention provides a stability diagram of a CL60 freight car wheel under different working conditions, illustrating the initiation of circumferential cracks in the tread of a railway freight car wheel.

[0054] Figure 7 This invention provides a stability diagram of a CL65 freight car wheel under different working conditions, illustrating the initiation of circumferential cracks in the tread of a railway freight car wheel.

[0055] Figure 8 This invention provides a stability diagram of a CL70 freight car wheel under different working conditions, illustrating the initiation of circumferential cracks in the tread of a railway freight car wheel.

[0056] Figure 9 A logic block diagram of a system for determining the initiation of circumferential cracks in the tread of railway freight car wheels, provided by the present invention;

[0057] Figure 10 This is a process diagram of a preferred embodiment of a method for determining the initiation of circumferential cracks in the tread of railway freight car wheels provided by the present invention. Detailed Implementation

[0058] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0059] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when we say an element is “connected” or “coupled” to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, “connected” or “coupled” as used herein can include wireless connections or couplings. The term “and / or” as used herein includes any and all combinations of one or more of the associated listed items.

[0060] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0061] To facilitate understanding of the embodiments of the present invention, the following will provide further explanation and description with reference to the accompanying drawings and several specific embodiments. These embodiments do not constitute a limitation on the embodiments of the present invention.

[0062] See Figure 1 This invention provides a method for determining the initiation of circumferential cracks in the tread of railway freight car wheels, comprising the following steps:

[0063] S1 establishes a railway freight car dynamics model for the freight car to which the faulty wheel belongs, and sets track conditions in the railway freight car dynamics model;

[0064] Based on the interaction between circumferential cracks and shear stress on wheels, S2 sets up a bogie working condition with suspension failure in the dynamic model of railway freight cars for dynamic simulation.

[0065] S3 is based on the railway freight car dynamics model that has been executed in step S2. It statistically analyzes the dynamic simulation results of each wheel for each bogie working condition, obtains the bogie working condition when the lateral force and lateral creep force on the wheel are the maximum, and determines the bogie load working condition when circumferential cracks are initiated.

[0066] S4, based on the preliminary judgment of the bogie load conditions when the circumferential cracks initiate, calculates the maximum Hertzian contact stress on the wheel using Hertzian contact theory.

[0067] S5 uses dynamic simulation results, the maximum Hertzian contact stress on the wheel and the shear yield limit of the wheel material to draw a wheel stability diagram based on stability theory.

[0068] S6 determines the mechanism of circumferential crack initiation by analyzing the wheel stability diagram.

[0069] The results of this analysis are used for fault analysis of railway freight car wheels and bogie structures.

[0070] This paper provides a method for evaluating the initiation of circumferential cracks in the tread of railway freight car wheels. By conducting dynamic simulation of railway vehicles, the paper explores the working conditions of excessive lateral forces and lateral creep forces. Using stability theory, stability analysis is performed on wheel steels of different hardness materials under each working condition. Combining the results of dynamic simulation and stability analysis, the load conditions for the generation of circumferential cracks are identified, and a theoretical basis is provided for improving the wheel's resistance to circumferential cracks.

[0071] The following example, using a specific vehicle model, illustrates the specific execution process of each step.

[0072] like Figure 10 As shown, this embodiment relates to a method for evaluating the initiation of circumferential cracks in the tread of railway freight car wheels, comprising the following steps:

[0073] Step 1: Use SIMPACK software to establish a dynamic model of railway freight cars;

[0074] Step 2: Set track conditions, such as track excitation and track curves;

[0075] Step 3: Since circumferential cracks are generated under large shear stress, and research shows that bogie structural failure leads to increased lateral force, dynamic simulations were performed under failure conditions of primary and secondary suspension parameters. Step 4: Each wheel was numbered 1-8, and the dynamic simulation results of each wheel under each working condition were statistically analyzed, such as wheelset lateral displacement, lateral force, lateral creep force, longitudinal creep force, and vertical force. Based on the dynamic simulation results, the working condition with the largest lateral force and lateral creep force was identified, and the load condition for the initiation of circumferential cracks was preliminarily determined.

[0076] Step 5: Calculate the maximum Hertzian contact stress using Hertzian contact theory;

[0077] Step 6: Using the dynamic simulation results, the calculated maximum Hertzian contact stress, and the shear yield limit of the wheel material, we input them into the stability theory to draw a stability diagram and perform stability analysis on the wheel.

[0078] This invention specifically relates to a method for evaluating the initiation of circumferential cracks in the tread of railway freight car wheels. Taking a C70 type open wagon with an axle load of 23t as an example, a multibody dynamics simulation model is established using SIMPACK software, such as... Figure 2 As shown. The C70 open wagon is equipped with a K6 type cross-braced bogie, as... Figure 3As shown, its main components consist of wheelsets, side frames, bolsters, springs, wedges, and crossbars. During modeling, the wheelsets, side frames, and bolsters are treated as rigid bodies; springs and crossbars are converted into equivalent force elements; and nonlinear elements such as the bogie guide frame positioning clearance, the central suspension wedge friction pair, and the two-stage stiffness springs are appropriately simplified. The C70 truck dynamics model established in this study has a wheel rolling circle radius of 420mm, a wheelset inner distance of 1353mm, and a wheel rolling circle lateral span of 1493mm. Its vehicle parameters are shown in Table 1. The specific dynamic parameters include those for the car body, frame, wheelsets, primary suspension, and secondary suspension, as shown in Table 2. It should be understood that these parameters have been converted into data form during the implementation of this method for establishing the multibody dynamics simulation model.

[0079] Table 1 C70 Truck Vehicle Parameters

[0080]

[0081] Table 2. Dynamic parameters of C70 truck

[0082]

[0083]

[0084] The total length of the planar curve model in this application is 500m, including a circular curve with a radius of 800m and a length of 100m, a transition curve of 120m and straight sections at both ends of the curve. The superelevation is set at 150mm, and the train speed is 80km / h. Orientation irregularities are lateral offsets between the two tracks, causing a lateral deviation of the track. The main causes of directional irregularities include auxiliary track construction, overall line operation, accumulation of residual deformation on the track side, and unequal wear on both sides of the track. The consequence is lateral swaying of the vehicle during operation, thereby increasing the lateral force between the wheel and rail. This study utilizes the track irregularity power spectral density obtained by the Federal Railroad Administration from a large amount of measured track irregularity data, and fits a power spectrum representing track directional irregularities using curve fitting methods:

[0085]

[0086] In the formula, s(Ω) is the power spectral density of the track irregularity (cm² / (rad / m)); Ω is the spatial frequency of the track irregularity (rad / m); A a Ωc is the roughness coefficient (cm²·rad / m); k is the cutoff frequency (rad / m); and k is the safety factor, typically taken as 0.25. The transverse irregularity excitation of the track is established using the American five-level spectrum, such as... Figure 4 As shown.

[0087] This study analyzes the impact of bogie structural failure on the increase of lateral force in the wheels, leading to circumferential cracks in the wheel tread. Each wheel is numbered as shown in Table 3. This application simulates and analyzes the effect of lateral force on circumferential cracks in the wheel tread under normal operating conditions, primary suspension failure, and secondary suspension failure, with and without excitation. Dynamic simulation software is used to obtain the wheelset lateral displacement, wheel-rail lateral force, wheel-rail vertical force, wheel-rail lateral creep force, and wheel-rail longitudinal creep force, and then the results are analyzed.

[0088] Table 3 Wheel Numbers

[0089]

[0090] The development of rolling contact fatigue depends on the pressure and creep force on the contact patch. If the stress exceeds the so-called stability limit, fatigue cracks will form on the surface due to the accumulation of plastic strain. Stability diagrams are typically used to compare contact conditions and the stability limit. Figure 5 For stability. Figure 5 The midline BC is the stability limit, WP is the operating point, and FI is the horizontal distance from the operating point WP to the stability limit BC. surf This is the surface fatigue index. In the stability diagram, the operating point WP is the maximum contact pressure p. o Divide by the material shear yield stress k and use a function of the friction coefficient η;

[0091] Before drawing the stability diagram, the maximum Hertzian contact stress of a C70 truck with a 23t axle load needs to be calculated using Hertzian contact theory.

[0092] Formula for calculating maximum Hertzian contact stress between wheel and rail:

[0093]

[0094] In the formula, σ max It is the maximum Hertzian contact stress, F is the vertical force between the wheel and the rail, and a and b are the major and minor axes of the contact ellipse, respectively.

[0095]

[0096] In the formula, α and β are coefficients related to the geometry and material properties of the contact body; R is the equivalent radius of curvature, calculated using the following formula: Where R1 and R2 are the radii of curvature of the wheel and rail, respectively; E * It is the equivalent elastic modulus.

[0097] The coefficient of friction is defined as the ratio of tangential force to normal force.

[0098]

[0099] In the formula, F ξ and F η F represents the longitudinal and transverse creep forces, respectively. n It is the normal force.

[0100] Surface fatigue index:

[0101]

[0102] In the formula, FI surf It is a function of the traction coefficient, Hertzian contact geometry, shear yield stress, and vertical load. a and b are the major and minor semi-axises of the Hertzian contact patch, respectively, and F... z It is a vertical load.

[0103] When the mechanical response (normal and tangential forces) of the wheel-rail contact patch is within the elastic region, the wheel will not experience contact fatigue and is in a safe state. Within the elastically stable region, the material will exhibit high-cycle fatigue. Within the plastically stable region, the material will exhibit low-cycle fatigue. Within the ratchet effect region, increasing the tangential load causes the increase in plastic strain to accumulate until the material loses its toughness and fails. Therefore, three different hardness truck wheel steel materials—CL60, CL65, and CL70—were selected, and stability analysis was conducted based on the results of dynamic simulations. Figure 6 , Figure 7 , Figure 8 The stability diagrams of CL60, CL65, and CL70 steels under four working conditions are presented to further verify the load conditions for circumferential crack initiation in wheel treads and to provide methods for improving the ability of wheels to resist circumferential crack initiation.

[0104] Secondly, the present invention provides a system for determining the initiation of circumferential cracks in the tread of railway freight car wheels, such as... Figure 9 As shown, it includes:

[0105] Modeling and analysis module 901 is used for:

[0106] Establish a dynamic model of the freight car to which the faulty wheel belongs, and set track conditions in the dynamic model of the freight car;

[0107] Based on the relationship between circumferential cracks and shear stress on wheels, a bogie case with suspension failure is set in the dynamic model of railway freight cars for dynamic simulation.

[0108] Based on the railway freight car dynamics model that has undergone the above process, the dynamic simulation results of each wheel under each bogie working condition are statistically analyzed to obtain the bogie working condition when the lateral force and lateral creep force on the wheel are at their maximum, and to determine the bogie load working condition when circumferential cracks initiate.

[0109] Based on the preliminary judgment of the bogie load conditions at the initiation of circumferential cracks, the maximum Hertzian contact stress on the wheel was calculated using Hertzian contact theory.

[0110] Based on the dynamic simulation results, the maximum Hertzian contact stress on the wheel and the shear yield limit of the wheel material, a wheel stability diagram was drawn in conjunction with stability theory.

[0111] The discrimination module 902 is used to determine the mechanism of circumferential crack initiation by analyzing the wheel stability diagram;

[0112] Output module 903 is used to output the discrimination result of discrimination module 902.

[0113] In summary, this invention provides a method and system for determining the initiation of circumferential cracks in the tread of railway freight cars. The method includes: establishing a railway freight car dynamics model and setting track conditions within the model; based on the interaction between the circumferential crack and the shear stress on the wheel, setting a bogie condition with suspension failure in the model; based on the aforementioned railway freight car dynamics model, statistically analyzing the dynamic simulation results of each wheel for each bogie condition to obtain the bogie condition with the maximum lateral force and lateral creep force on the wheel, and determining the bogie load condition at the initiation of circumferential cracks; based on the preliminarily determined bogie load condition at the initiation of circumferential cracks, calculating the maximum Hertzian contact stress on the wheel using Hertzian contact theory; based on the dynamic simulation results, the maximum Hertzian contact stress on the wheel, and the shear yield limit of the wheel material, drawing a wheel stability diagram using stability theory; and analyzing the wheel stability diagram to determine the mechanism of circumferential crack initiation. The method provided by this invention establishes a method for evaluating the initiation of circumferential cracks in the tread of railway freight car wheels. First, a dynamic model of the freight car is established, and dynamic simulations are performed under different failure conditions in a small radius curve. The load conditions for the initiation of circumferential cracks in the tread of railway freight car wheels are analyzed. Then, using stability theory combined with dynamic results, stability analysis is performed on wheel steel materials with different hardnesses from the perspective of wheel material, providing a theoretical basis for improving the wheel's resistance to circumferential cracks.

[0114] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of one embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing the present invention.

[0115] As can be seen from the above description of the embodiments, those skilled in the art can clearly understand that the present invention can be implemented by means of software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments of the present invention.

[0116] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for apparatus or system embodiments, since they are basically similar to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. The apparatus and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0117] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for determining the initiation of circumferential cracks in the tread of railway freight car wheels, characterized in that, include: S1 establishes a railway freight car dynamics model for the freight car to which the faulty wheel belongs, and sets track conditions in the railway freight car dynamics model; Based on the relationship between circumferential cracks and shear stress on wheels, S2 sets up a bogie working condition with suspension failure in the dynamic model of railway freight cars for dynamic simulation. S3 is based on the railway freight car dynamics model that has been executed in step S2. It statistically analyzes the dynamic simulation results of each wheel for each bogie working condition, obtains the bogie working condition when the lateral force and lateral creep force on the wheel are the maximum, and determines the bogie load working condition when circumferential cracks are initiated. S4, based on the preliminary judgment of the bogie load conditions when the circumferential cracks initiate, calculates the maximum Hertzian contact stress on the wheel using Hertzian contact theory. S5 uses dynamic simulation results, the maximum Hertzian contact stress on the wheel and the shear yield limit of the wheel material to draw a wheel stability diagram based on stability theory. S6 determines the mechanism of circumferential crack initiation by analyzing the wheel stability diagram; The judgment result of step S6 is used for fault analysis of railway freight car wheels.

2. The discrimination method according to claim 1, characterized in that, Step S1 includes: S11 used SIMPACK software to build a dynamic model of a C70 truck with a 23t axle load, and the wheel tread was selected as LM tread. In the railway freight car dynamics model, S12 is set with a CN60 track and a total length of 500m for the track's horizontal curve model, including a circular curve with a radius of 800m and a length of 100m, a transition curve of 120m and straight sections at both ends of the curve. The track superelevation is set to 150mm, and the train speed is 80km / h. S13 Through-type Establish a lateral track irregularity excitation; where S(Ω) is the track irregularity power spectral density cm² / (rad / m); Ω is the spatial frequency of the track irregularity rad / m; A a , is the roughness coefficient cm2·rad / m; Ωc is the cutoff frequency rad / m; k is the safety factor, taken as 0.

25.

3. The discrimination method according to claim 2, characterized in that, Step S3 includes: Dynamic simulation analysis of the C70 truck crossing a small radius curve with R=800m was conducted under normal operating conditions, primary suspension failure conditions, and secondary suspension failure conditions, with and without lateral irregularity excitation.

4. The discrimination method according to claim 3, characterized in that, Step S4 includes: The formula for calculating the maximum Hertzian contact stress The maximum Hertzian contact stress on the wheel is calculated; where σ max Where is the maximum Hertzian contact stress, F is the vertical force between the wheel and rail, and a and b are the major and minor semi-axes of the contact ellipse, respectively, satisfying the following equations: In the formula, α and β are coefficients related to the geometry and material properties of the contact body; R is the equivalent radius of curvature, calculated using the following formula: Where R1 and R2 are the radii of curvature of the wheel and rail, respectively; E * It is the equivalent elastic modulus.

5. The discrimination method according to claim 4, characterized in that, Step S6 includes: Through The friction coefficient of the wheel is calculated; where F ξ and F η F represents the longitudinal and transverse creep forces, respectively. n Normal force; Through The fatigue index of the wheel surface was calculated; FI surf It is a function of the traction coefficient, Hertzian contact geometry, shear yield stress, and vertical load. a and b are the major and minor semi-axises of the Hertzian contact patch, respectively, and F... z It is a vertical load.

6. A system for determining the initiation of circumferential cracks in the tread of railway freight car wheels, characterized in that, include: The modeling and analysis module is used for: Establish a dynamic model of the freight car to which the faulty wheel belongs, and set track conditions in the dynamic model of the freight car; Based on the interaction between circumferential cracks and shear stress on the wheel, a bogie case with suspension failure is set in the dynamic model of railway freight cars for dynamic simulation. Based on the railway freight car dynamics model that has undergone the above process, the dynamic simulation results of each wheel under each bogie working condition are statistically analyzed to obtain the bogie working condition when the lateral force and lateral creep force on the wheel are at their maximum, and to determine the bogie load working condition when circumferential cracks initiate. Based on the preliminary judgment of the bogie load conditions at the initiation of circumferential cracks, the maximum Hertzian contact stress on the wheel was calculated using Hertzian contact theory. Based on the dynamic simulation results, the maximum Hertzian contact stress on the wheel and the shear yield limit of the wheel material, a wheel stability diagram was drawn in conjunction with stability theory. The discrimination module is used to determine the mechanism of circumferential crack initiation by analyzing the wheel stability diagram; The output module is used to output the discrimination result of the discrimination module.

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