Method for determining the parameters of wheel-rail rolling contact fatigue damage function

Abstract

This invention discloses a method for determining the parameters of wheel-rail rolling contact fatigue damage function that considers the microscopic contact solution within the contact patch, is applicable to different railway systems, and has good predictive performance. The method includes the following steps: solving for transient wheel-rail contact state parameters; calculating the macroscopic rolling contact solution and the microscopic contact solution within the contact patch; and solving for the transient wear number Tγ and the total transient damage value D within the contact patch at any given time. t and peak transient damage value h m Solve for the local wear coefficient τγ within the contact patch. L ; with h m As τγ L d L , thus obtaining τγ L with h m The corresponding relationship; by changing the working conditions, Tγ and τγ covering the entire domain of the macroscopic damage function model under different traction coefficients are obtained. L The relationship between them; for τγ at the critical point L The reduction is calculated based on the wear reduction until the total local damage value d within the corresponding contact patch is reached. t Total transient damage value D within the contact patch t Equal to each other, we obtain the reduced τγ L With d L The relationship is as follows: the parameters of the local damage function model are obtained by fitting and / or the parameters of the macroscopic damage function model of another railway system are derived by reverse calculation.

Description

Technical Field

[0001] This invention relates to the technical field of wheel-rail rolling contact fatigue damage, and more specifically, to a method for determining the functional parameters of wheel-rail rolling contact fatigue damage. Background Technology

[0002] Rolling contact fatigue is a common form of wheel-rail damage. In modern railways, it often originates from excessive creep rate / force between the wheel and rail when passing through curves. It is a direct result of the accumulation of plastic strain in the surface material under the cyclic action of rolling contact loads until the ductility is exhausted. In the early stage, it manifests as surface cracks, and in the later stage, it often develops into spalling and flaking. In rare cases, it can lead to the fracture of the wheel rim and rail, threatening traffic safety.

[0003] Heavy-haul railways are characterized by high axle load and high transport capacity. In small-radius curves where wheel-rail interaction is intense, rail rolling contact fatigue is common and is one of the main causes of rail replacement. Rail rolling contact fatigue in curves is often referred to as oblique cracks or fish-scale cracks. It is generally continuous and approximately stable along the longitudinal direction, with crack intervals as low as 1 mm. The crack direction is at a certain angle to the longitudinal direction, which is a typical continuous rolling contact fatigue.

[0004] The crack initiation stage is defined as the period from initial crack initiation to a visible crack diameter of 2 mm. Research on the initiation and development mechanism and mitigation measures of wheel-rail rolling contact fatigue has always been a hot topic in the industry. For continuous rolling contact fatigue, the academic community has established several widely accepted predictive models for wheel-rail rolling contact fatigue initiation, such as the BS11 rail damage function model proposed by the Rail Safety Society (RSSB) and the U75V quenched rail damage function model derived from hardness estimation. The damage function model is a piecewise linear relationship curve between the wear number and the damage value.

[0005] However, due to the significant differences between railway systems worldwide, the damage function model is not well-suited for various railway systems. The main reasons for this poor usability are: firstly, the model's development process is relatively simplistic, limiting the number and types of stations selected and failing to consider the broader characteristics of railway systems; secondly, regarding the size of crack initiation, the damage function model's calculations of wear and energy are based on macroscopic rolling contact solutions (referred to as the macroscopic damage function model in this patent), neglecting microscopic contact solutions within the crack patch, thus failing to accurately reflect the local load conditions of the rail.

[0006] Despite the aforementioned application issues, the relationship between fatigue and wear supported by the damage function model has been widely proven to be correct. Therefore, when applying the damage function model to predictive analysis within target track systems, many scholars employ two main improvement strategies: one is to adjust the parameters of the damage function model based on the wheel-rail material hardness and shear strength, including adjusting the wear values ​​at key points and the extreme values ​​of the damage function; the other is to conduct on-site measurements and multibody dynamics simulation calibration to obtain damage function parameters suitable for the target track system. The former is simpler, but the predictive effect of the resulting new damage function is generally poor; the latter yields a better predictive effect, but requires more time and economic costs.

[0007] In summary, the widespread application of damage function models still lacks a general method for quickly determining the parameters of damage function models applicable to different railway systems. This method needs to improve upon the inaccuracies of the original damage function model while also overcoming the shortcomings of the two damage function parameter adjustment strategies mentioned above. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a method for determining the parameters of wheel-rail rolling contact fatigue damage function that considers the microscopic contact solution within the spot, is applicable to different railway systems, and has good prediction effect.

[0009] To achieve the above objectives, this invention provides a method for determining the parameters of wheel-rail rolling contact fatigue damage function, the technical solution of which is as follows:

[0010] The method for determining the parameters of wheel-rail rolling contact fatigue damage function includes the following steps:

[0011] Step 100: Establish a dynamic model of the vehicle system of a certain railway system and solve for the transient wheel-rail contact state parameters;

[0012] Step 200: Based on the transient wheel-rail contact state parameters, establish a three-dimensional wheel-rail transient rolling contact finite element model, and calculate the macroscopic rolling contact solution and the microscopic contact solution within the contact patch; the macroscopic rolling contact solution includes the rigid creep rate and rigid creep force at the wheel-rail contact interface; the microscopic contact solution within the contact patch includes the local creep rate and local tangential contact stress within the wheel-rail contact patch;

[0013] Step 300: Using a macroscopic damage function model based on macroscopic rolling contact solution, the transient wear number Tγ and the total transient damage value D within the contact patch at any given time are calculated based on the rigid creep rate. t and peak transient damage value h m ;

[0014] Step 400: Solve for the local wear number τγ within the contact patch based on the local creep rate and tangential contact stress. L ;

[0015] Step 500, using the peak transient damage value h m τγ, the maximum local wear number within the contact patch L Local damage value d L The local wear number τγ was obtained. L Peak value of transient damage h m The correspondence;

[0016] Step 600: By varying the operating conditions, obtain the transient wear number Tγ and the local wear number τγ covering the entire macroscopic damage function model under different traction coefficients. L The relationship between them;

[0017] Step 700, calculate the local wear number τγ at the critical point Lc. L The reduction is calculated based on the wear reduction until the total local damage value d within the corresponding contact patch is reached. t Total transient damage value D within the contact patch t Equal to each other, we obtain the reduced local wear number τγ. L With local damage value d L Relationship;

[0018] Step 800: Fit the parameters of the local damage function model of a railway system based on the microscopic contact solution within the patch and / or inversely deduce the parameters of the macroscopic damage function model of another railway system.

[0019] It is evident that the method for determining the wheel-rail rolling contact fatigue damage function parameters of the present invention has the following advantages:

[0020] First, this invention addresses rolling contact fatigue by employing a microscopic contact solution within the contact patch. Utilizing a macroscopic damage function model based on the macroscopic rolling contact solution, local wear reduction, and changes in operating conditions, parameters for a local damage function model based on the microscopic contact solution within the contact patch are fitted. This allows for the establishment of a rail rolling contact fatigue initiation model based on the microscopic rolling contact solution within the contact patch. This model can quickly and easily predict the fatigue initiation at local locations at a scale closer to the essence of fatigue initiation, providing better and more comprehensive prediction results. It has significant guiding significance for the prevention and control of this type of fatigue failure, and is particularly suitable for predicting the initiation of rolling contact fatigue in heavy-duty rails.

[0021] Secondly, when the properties of wheel-rail materials (wear resistance and fatigue resistance) do not change significantly, the relationship between the local wear number within the wheel-rail contact patch and the rolling contact fatigue initiation life is the same across different railway systems. However, the parameters of the macroscopic damage function model differ across different railway systems. This is the main reason why existing damage function models are not well-suited for different railway systems. This invention provides a general method for quickly determining the parameters of damage function models applicable to different railway systems. Specifically, by using the damage function model parameter determination method of this invention, the parameters of a local damage function model for a specific railway system are used as a calibration basis to quickly back-calculate the macroscopic damage function model parameters for another railway system where the wheel-rail material properties do not change significantly.

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0023] The accompanying drawings, which form part of this invention, are used to aid in understanding the invention. The content provided in the drawings and their related descriptions can be used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0024] Figure 1 This is a photograph of rolling contact fatigue cracks on the rail surface of a circular curve section with a radius of 800m on a heavy-haul railway.

[0025] Figure 2 This is a schematic diagram of a three-dimensional wheel-rail transient rolling contact finite element model.

[0026] Figure 3 The curves showing the creep force and angle of the inner and outer rails as a function of rolling distance in the vehicle system dynamics model and the three-dimensional wheel-rail transient rolling contact finite element model.

[0027] Figure 4 This is a projection of the local tangential contact stress of the outer rail onto the xOy plane in a three-dimensional wheel-rail transient rolling contact finite element model, as a function of rolling distance and lateral position.

[0028] Figure 5 This is a projection of the local tangential contact stress of the inner rail onto the xOy plane in a three-dimensional wheel-rail transient rolling contact finite element model, as a function of rolling distance and lateral position.

[0029] Figure 6 This is a schematic diagram of the damage function model for U75V quenched steel rails.

[0030] Figure 7The curves showing the change of transient wear number Tγ with rolling distance in the vehicle system dynamics model and the three-dimensional wheel-rail transient rolling contact finite element model.

[0031] Figure 8 τγ is the local wear number of the inner and outer rails in the contact patch of the three-dimensional wheel-rail transient rolling contact finite element model. L A three-dimensional distribution map showing the lateral position and rolling distance.

[0032] Figure 9 τγ is the local wear number of the inner rail within the contact patch in the three-dimensional wheel-rail transient rolling contact finite element model. L A three-dimensional distribution map showing the lateral position and rolling distance.

[0033] Figure 10 The local wear number τγ in the three-dimensional wheel-rail transient rolling contact finite element model L Peak value of transient damage h m The correspondence diagram.

[0034] Figure 11 The transient wear number Tγ and local wear number τγ on the outer rail side in the finite element model of transient rolling contact between wheel and rail under typical working conditions. L The curve showing the change of peak value with rolling distance.

[0035] Figure 12 The transient wear number Tγ and local wear number τγ on the inner rail side in the finite element model of transient rolling contact between wheel and rail under typical working conditions. L The curve showing the change of peak value with rolling distance.

[0036] Figure 13 Transient wear number Tγ and local wear number τγ on the outer rail side in the finite element model of transient rolling contact between wheel and rail under different traction coefficients μ. L The curve showing the change of peak value with rolling distance.

[0037] Figure 14 The transient wear number Tγ and local wear number τγ of the inner and outer rail sides under different traction coefficients μ. L Correlation plot between peaks.

[0038] Figure 15 The transient wear number Tγ and local wear number τγ at all times under different traction conditions. L A graph showing the relationship between peak values.

[0039] Figure 16 The local wear number τγ before and after reduction L With local damage value d L The curve showing the change.

[0040] Figure 17The graph shows the variation of local damage values ​​within the contact patch on the outer rail side as predicted by the local damage function model, along with the transient wear number Tγ.

[0041] Figure 18 The results show the predicted values ​​of rolling contact fatigue damage on the inner and outer rail surfaces under typical working conditions, as a function of rolling distance (longitudinal) and lateral position.

[0042] Figure 19 This is a distribution diagram of rolling contact fatigue damage values ​​of the inner and outer rails predicted by the damage function model and the local damage function model of a U75V quenched steel rail in a cross section under typical working conditions. Detailed Implementation

[0043] The present invention will now be clearly and completely described in conjunction with the accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. Before describing the present invention in conjunction with the accompanying drawings, it should be particularly noted that:

[0044] The technical solutions and features provided in the various parts of this invention, including the following description, can be combined with each other without conflict.

[0045] Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0046] Regarding the terminology and units used in this invention: The terms "comprising," "having," and any variations thereof in the specification, claims, and related parts of this invention are intended to cover non-exclusive inclusion.

[0047] The specific implementation of the method for determining the wheel-rail rolling contact fatigue damage function parameters of the present invention includes the following steps:

[0048] Step 100: Establish a vehicle system dynamics model for a railway system and solve for the transient wheel-rail contact state parameters; preferably, establish the vehicle system dynamics model in SIMPACK.

[0049] Step 200: Based on the transient wheel-rail contact state parameters, establish a three-dimensional wheel-rail transient rolling contact finite element model, and calculate the macroscopic rolling contact solution and the microscopic contact solution within the contact patch; the macroscopic rolling contact solution includes the rigid creep rate and rigid creep force at the wheel-rail contact interface; the microscopic contact solution within the contact patch includes the local creep rate and local tangential contact stress within the wheel-rail contact patch; preferably, the three-dimensional wheel-rail transient rolling contact finite element model is established in ANSYS / Ls-dyna.

[0050] Step 300: Using a macroscopic damage function model based on macroscopic rolling contact solution, the transient wear number Tγ and the total transient damage value D within the contact patch at any given time are calculated based on the rigid creep rate. t and peak transient damage value h m ;

[0051] Step 400: Solve for the local wear number τγ within the contact patch based on the local creep rate and tangential contact stress. L ;

[0052] Step 500, using the peak transient damage value h m τγ, the maximum local wear number within the contact patch L Local damage value d L The local wear number τγ was obtained. L Peak value of transient damage h m The correspondence;

[0053] Step 600: By varying the operating conditions, obtain the transient wear number Tγ and the local wear number τγ covering the entire macroscopic damage function model under different traction coefficients. L The relationship between them;

[0054] Step 700, calculate the local wear number τγ at the critical point. L The reduction is calculated based on the wear reduction until the total local damage value d within the corresponding contact patch is reached. t Total transient damage value D within the contact patch t Equal to each other, we obtain the reduced local wear number τγ. L With local damage value d L Relationship;

[0055] Step 800: Fit the parameters of the local damage function model of a railway system based on the microscopic contact solution within the patch and / or inversely deduce the parameters of the macroscopic damage function model of another railway system.

[0056] In the above steps, the rigid creep rate, local creep rate, transient wear coefficient Tγ, and peak transient damage value h are... m The calculation expressions are as follows:

[0057]

[0058]

[0059]

[0060]

[0061] Tγ=T x γ x +T y γy (Equation 5)

[0062]

[0063] τγ I =τ x γ Lx +τ y γ Ly (Equation 7)

[0064] In the formula, γ x For longitudinal rigidity creep; γ y For transverse rigid creep; γ Lx The longitudinal local creep rate; γ Ly ω is the lateral local creep rate; r is the wheel speed; v0 is the actual rolling circle radius of the selected tread output point set; v0 is the longitudinal velocity of the wheel axle; v y Δv is the lateral translational velocity of the wheel relative to the track. x Let Δv be the longitudinal relative sliding velocity between the wheel and rail at any point within the contact patch; y T represents the lateral relative sliding velocity between the wheel and rail at any point within the contact patch; x For longitudinal rigid creep force; T y τ is the lateral rigid creep force; b is the lateral semi-axis length of the contact patch; π is pi; x τ is the longitudinal component of the local tangential contact stress. y This represents the transverse component of the local tangential contact stress.

[0065] The following specific application examples illustrate the beneficial effects of the present invention.

[0066] Severe rolling contact fatigue occurred on a circular curve section with a radius of less than 1000m on a domestic 25t axle load coal transport railway. Figure 1 This is a photograph of fatigue cracks on the rail surface of a circular curve section with a radius of 800m on a heavy-haul railway. Figure 1 As shown, continuous oblique cracks exist at the gauge angle of the outer (high) rail and on the top surface of the inner (low) rail, accompanied by scattered small-piece spalling on the inner rail. The fatigue zone at the gauge angle of the outer rail is approximately 11.50 mm wide, with its center approximately 18.50 mm from the centerline of the rail top, a crack spacing of approximately 2 mm, and an angle of approximately -50° with the direction of travel. The fatigue zone of the inner rail is roughly at the center of the rail top (i.e., the centerline of the rail top and the fatigue zone approximately coincide), approximately 28.50 mm wide, with a crack spacing of approximately 1.5 mm, and an angle of approximately 75° with the direction of travel. Based on relevant literature, this can be determined to be a typical surface-initiated rolling contact fatigue, dominated by the tangential contact load between the wheel and rail, and can be predicted using a damage function model.

[0067] Step 100

[0068] against Figure 1 For the 800m radius circular curve segment, a vehicle system dynamics model considering a single C80 freight car was established in SIMPACK, with key parameters shown in Table 1. The vehicle system dynamics model adopted new wheel-rail profiles, LM and CN60N respectively. The car body, side frames, wheelsets, etc., were simplified to rigid bodies with 6 degrees of freedom, and the total number of degrees of freedom of the model was 68. Suspension elements were simulated using spring and damping force elements. The primary suspension (axle box) connects the wheelset to the bogie side frame, and the secondary suspension (load saddle and bolster) connects the side frame to the car body. The track sub-model includes straight, transition curve, and circular curve segments, with lengths of 150m, 380m, and 300m respectively, for a total length of 830m. The wheel-rail method and tangential contact were calculated using the widely accepted Hertz contact spring and FASTSIM respectively, with friction characterized by the Coulomb friction model, and the friction coefficient f was taken as a typical value of 0.5 under dry conditions. Further considering actual operation, it was assumed that the vehicle passed through the curve at a constant speed, and the calculation time step was taken as 0.02s. The rigid rail assumption is adopted, taking into account factors such as gauge, superelevation, rail profile, and rail base slope, but neglecting the subrail structure.

[0069] Table 1

[0070]

[0071] Therefore, the transient wheel-rail contact parameters of the front bogie guide wheelset when the vehicle passes through the circular curve section at a constant speed of 80km / h are obtained as follows: lateral displacement is 8.2mm, roll angle is 0.0784°, and yaw angle is 0.0882°.

[0072] Step 200

[0073] Using the wheel-rail transient rolling contact modeling method, and taking the circular curve segment through which the guide wheel of the C80 freight car front bogie passes as the object, a model was established in ANSYS / Ls-dyna. Figure 2 The three-dimensional wheel-rail transient rolling contact finite element model shown simulates the wheel-rail transient rolling contact behavior when the wheelset passes through a circular curve segment with a radius of 800m.

[0074] The finite element model considers the actual geometry of the wheelsets and rails, as well as the discrete support structure of the ballasted track. The track length is 14.4m, containing 25 sets of fasteners (0.6m span). The vehicle only considers the vertical suspension characteristics, ignoring the primary suspension structure (only its mass) which has almost no impact on transient rolling contact behavior. The wheelset structure, wheel-rail profile, suspension parameters, speed, superelevation, and railbed slope are all consistent with the vehicle system dynamics model (see Tables 1 and 2) to ensure comparability.

[0075] Table 2

[0076]

[0077] The wheel-rail system is discretized using hexahedral solid elements, taking into account its realistic three-dimensional geometry. A non-uniform mesh is used, with the finest mesh (1.0 mm element size) at the contact surface to ensure accurate contact calculations. The primary suspension is represented by spring-damped elements, connecting the sprung mass simulated by mass elements to the axis nodes, coupling the lateral and longitudinal degrees of freedom of the nodes at both ends of the primary suspension to ensure that the sprung mass translates together with the wheelset. For the discretized "fastener-sleeper-ballast" support structure under the rail, vertical spring-damped elements are used to represent the fasteners and ballast, neglecting the elasticity and mass in the other two directions. The sleepers are discretized using sparse hexahedral solid elements, taking into account their approximate geometric and mass characteristics. The total number of elements and nodes in the model is approximately 1.57 million and 1.73 million, respectively.

[0078] A surface-to-surface contact algorithm based on the penalty function method and the Coulomb friction model is used to calculate the normal / tangential contact between the wheel and rail. The time integration employs a combination of implicit and explicit strategies. Specifically, in the calculation, the wheelset... Figure 2 The wheelset begins rolling forward from initial position A. The initial attitude of the wheelset is set according to the transient wheel-rail contact state parameters described above. First, the equilibrium deformation field of the system under gravity is obtained using implicit integration, initializing the subsequent explicit integration calculations. The dynamic relaxation region AB is 0.52m long, attenuating the disturbance caused by imperfect stress initialization. In the solution region BC, the wheelset approximately reaches quasi-steady-state rolling. The explicit time integration exhibits conditional stability characteristics, and the time step is taken as 5.67 × 10⁻⁶. -8 This facilitates capturing transient changes in wheel-rail contact behavior. An overall coordinate system Oxyz is established with its origin at the center of the track corresponding to point A, where x, y, and z are along the longitudinal, lateral, and vertical directions, respectively.

[0079] The corresponding rigid creep rate and rigid creep force (hereinafter referred to as creep rate and creep force) are calculated using Equation 1-2. Figure 3 This section presents the curves showing the variation of creep force and its angle between the inner and outer rails with rolling distance in the vehicle system dynamics model and the three-dimensional wheel-rail transient rolling contact finite element model. (Example:) Figure 3 As shown, considering dynamic fluctuations, the prediction results of the two models are still roughly consistent. Specifically, the creep force on the outer rail side predicted by the finite element model fluctuates around the steady-state value of 29.30 kN predicted by the dynamic model, with an angle of around 36.97° with the running direction. The creep force on the inner rail side has a smaller amplitude, fluctuating around 24.54 kN, but it is slightly larger than the result predicted by the dynamic model, with an angle of around 187.33° with the running direction.

[0080] Using only a three-dimensional wheel-rail transient rolling contact finite element model, at time t = 0.0256s (the wheelset is located at x = 647.25mm in the refined solution region), the corresponding local creep rate and local tangential contact stress are calculated using Equation 3-4. Figure 4-5These are projections of the local tangential contact stress of the outer and inner rails in the xOy plane as a function of rolling distance and lateral position in a three-dimensional wheel-rail transient rolling contact finite element model. Figure 4-5 As shown, the contact spot on the outer rail side is close to the gauge angle side (rail top center y = 741 mm), while the contact spot on the inner rail side is approximately at the rail top center (y = -760 mm). The maximum local tangential contact stress on the outer rail side is located at the rear edge of the contact spot and is biased towards the gauge angle side, at approximately 379 MPa, and the effect of spin is clearly visible. The maximum local tangential contact stress on the inner rail side is also located at the rear edge of the contact spot, but its direction is basically along the longitudinal direction, meaning that spin can be ignored.

[0081] Step 300

[0082] The macroscopic damage function model used in this step, based on the macroscopic rolling contact solution, is the U75V quenched rail damage function model. Figure 6 This is a schematic diagram of the damage function model for U75V quenched steel rails. It is a three-segment linear curve of transient wear number Tγ and transient damage value, with three critical points La, Lb, and Lc. Among them, the critical point Lc is the dividing point between fatigue initiation and severe wear state. Fatigue occurs before the critical point Lc, and severe wear replaces fatigue after the critical point Lc. Table 3 shows the transient wear number Tγ and transient damage value at the three critical points La, Lb, and Lc.

[0083] Using Equation 5 and the U75V quenched rail damage function model, the transient wear number Tγ and the total transient damage value D within the contact patch at any given time are solved based on the rigid creep rate. t . Figure 7 This shows the curves of the transient wear number Tγ as a function of rolling distance in the vehicle system dynamics model and the three-dimensional wheel-rail transient rolling contact finite element model. Figure 7 As shown, the values ​​predicted by the finite element model fluctuate significantly with the contact patch position (proportional to time), but their average value roughly matches the prediction results of the multibody dynamics model. The difference between the two models lies in the fact that the finite element model's prediction results include fluctuations caused by vibrations of the system structure and continuum under imperfect initial conditions, while the dynamics model's predictions, due to neglecting interface excitation, correspond to a quasi-steady-state curve that does not include the aforementioned vibration effects. Therefore, to recreate the actual wheel-rail contact behavior, the data used in subsequent steps are all obtained from the three-dimensional wheel-rail transient rolling contact finite element model.

[0084] Then, the total transient damage value D within the contact patch is calculated using Equation 6. t Discretize the transient damage value h along the transverse direction of the contact patch according to the semi-elliptical distribution. m .

[0085] Step 400

[0086] Using only a three-dimensional wheel-rail transient rolling contact finite element model, Equation 7 is used to solve for the local wear coefficient τγ within the contact patch based on the local creep rate. L . Figure 8-9 These are the local wear numbers τγ of the inner and outer rails and the inner rail, respectively, in the three-dimensional wheel-rail transient rolling contact finite element model. L A three-dimensional distribution map showing the relationship between lateral position and rolling distance. Combined with... Figure 4-5 As can be seen from 8-9, at the same time, the local wear number τγ L Consistent with the distribution of local tangential contact stress, the local wear number τγ within the contact patch on the outer rail side... L The peak value is located at the trailing edge of the contact patch and is biased towards the gauge angle. The local wear number τγ corresponds to the positions of the three critical points La, Lb, and Lc. L The values ​​are 0.69 MPa, 2.21 MPa, and 3.80 MPa, respectively.

[0087] Step 500

[0088] Peak transient damage value h m τγ, the maximum local wear number within the contact patch L Local damage value d L The local wear number τγ was obtained. L Peak value of transient damage h m (The peak value in the figure is abbreviated as h) m The correspondence diagram is as follows: Figure 10 As shown in the figure, each point represents a time point. For ease of understanding, the parameters of the local damage function model finally proposed in this invention (details below) are also shown. Figure 9 From. Figure 10 It can be seen that although the results at each time point have a certain degree of dispersion, the peak value of the transient damage h is relatively consistent. m With local wear number τγ L The high correlation between peak values ​​confirms the feasibility of the parameter determination method of the present invention.

[0089] Step 600

[0090] The operating conditions set in the above steps are typical operating conditions (traction coefficient μ = 0). Figure 11-12 These represent the transient wear number Tγ and the local wear number τγ on the outer and inner rail sides of the wheel-rail transient rolling contact finite element model under typical working conditions. L The curve showing the change of peak value with rolling distance. (Example) Figure 11-12 As shown, regardless of whether it is the outer rail side or the inner rail side, the transient wear number Tγ and the local wear number τγ L The peak values ​​are all basically the same, and the trends of change are roughly the same. Compared with the outer rail side, the transient wear number Tγ and the local wear number τγ of the inner rail side are different. L The peak values ​​are all lower.

[0091] In particular, the present invention applies a corresponding traction torque to the wheelset to simulate working conditions with different adhesion utilization rates, ensuring that the obtained transient wear number Tγ covers the entire domain of the U75V quenched rail damage function model, and thus obtains the local damage function model parameters based on the micro-contact solution within the spot.

[0092] Figure 13 Transient wear number Tγ and local wear number τγ on the outer rail side in the finite element model of transient rolling contact between wheel and rail under different traction coefficients μ. L The curve showing the change of peak value with rolling distance. Figure 14 The transient wear number Tγ and local wear number τγ of the inner and outer rail sides under different traction coefficients μ. L The correlation plot between peaks, with the correlation coefficient R calculated using the Pearson linear correlation test. Combined with... Figure 13-14 It can be seen that the transient wear number Tγ and the local wear number τγ on the inner and outer rail sides are... L The peak value remains relevant under different traction coefficients.

[0093] Figure 15 The transient wear number Tγ and local wear number τγ at all times under different traction conditions. L The graph shows the relationship between peak values. The boundary points of segments I, II, and III correspond to the two critical wear numbers in the U75V quenched rail damage function model, namely 23N and 100N. The black solid line represents the curve obtained using a fourth-order polynomial nonlinear fitting. Figure 15 As shown, the transient wear number Tγ and the local wear number τγ L The peak values ​​are strongly correlated. When wheelsets with applied traction and wheelsets without traction pass through a circular curve section, the longitudinal creep force generated on the outer rail side is in the same direction, while that on the inner rail side is in the opposite direction. Therefore, the transient wear number Tγ on the outer rail side increases with the increase of the traction coefficient μ, while the transient wear number Tγ on the inner rail side first decreases and then increases. That is, the average transient Tγ value on the outer rail side covers a wider range.

[0094] Steps 700-800

[0095] The total local damage value d within the contact patch at the critical point Lc, obtained from the above calculations, is obtained. t Since the value is not zero, in order to fully consider the influence of wear in the LbLc segment, the local damage function model based on the microscopic contact solution within the pitted area proposed in this invention can suppress rolling contact fatigue under the premise of wheelset lateral displacement, and introduces a wear reduction factor, that is, the local wear number τγ corresponding to the critical point Lc. L The reduction is calculated based on the wear reduction until the total local damage value d within the corresponding contact patch is reached. t Total transient damage value D within the contact patch t Equal. After reduction calculation, the local wear number τγ corresponding to the critical point Lc is...L The pressure was reduced from 3.80 MPa to 3.04 MPa, and the local wear number τγ corresponding to the three critical points was finally obtained. L / N and local damage values ​​are shown in Table 3.

[0096] Table 3

[0097]

[0098] Analogous to the traditional U75V quenched rail damage function model, the local damage function model proposed in this invention is also constructed linearly in three segments, that is, the coordinates (local wear number τγ) corresponding to the three critical points. L Connect / N, local damage value (the critical point constructor is not shown in the figure). Figure 16 The local wear number τγ before and after reduction L With local damage value d L The curve of change. For example... Figure 16 As shown, the reduced change curve (the function after reduction before wear in the figure) is the local damage function model based on the microscopic contact solution within the freckles proposed in this invention.

[0099] Effect Verification: Prediction of Fatigue Initiation in Contact Spots

[0100] Typical transient wear numbers Tγ at different stages in the U75V quenched rail damage function model were selected, and the local damage distribution within the contact patch on the outer rail side was predicted using the local damage function model obtained above. Figure 17 The graph shows the variation of local damage values ​​within the contact patch on the outer rail side as a function of transient wear number Tγ, as predicted by the local damage function model. The local damage values ​​greater than, equal to, and less than 0 correspond to rolling contact fatigue (the corresponding local damage values ​​are called rolling contact fatigue damage values), slight wear, and severe wear regions, respectively. The area proportions of these regions within the contact patch are shown in Table 4. These detailed distribution results within the patch cannot be obtained by traditional damage function models (such as the BS11 rail damage function model and the U75V quenched rail damage function model).

[0101] Table 4

[0102] Transient wear number Tγ 64N 100N 189N 253N 302N 371N Slight wear area 89.22％ 80.64％ 63.51％ 53.64％ 45.45％ 37.45％ Rolling contact fatigue zone 10.78％ 19.36％ 35.14％ 38.25％ 40.00％ 38.00％ Severe wear area 0％ 0％ 1.35％ 8.11％ 14.55％ 24.55％

[0103] like Figure 17 As shown in Table 4, the area of ​​the rolling contact fatigue zone increases with the increase of the transient wear number Tγ. When the transient wear number Tγ is close to or greater than Lc = 253 N, a severe wear zone begins to appear inside the rolling contact fatigue zone, which can inhibit the occurrence of rolling contact fatigue. It is worth noting that due to the continuity and non-uniformity of the damage value distribution within the contact patch, when the transient wear number Tγ is greater than 253 N, a rolling contact fatigue zone still exists within the contact patch. However, changes in the position of the severe wear zone caused by different lateral displacements can inhibit the initiation of rolling contact fatigue.

[0104] Figure 18 This shows the predicted rolling contact fatigue damage values ​​(abbreviated as damage values ​​in the figure) of the inner and outer rail surfaces under typical working conditions, varying with rolling distance (longitudinal) and lateral position. Figure 18 As shown, the rolling contact fatigue damage values ​​exhibit a non-uniform distribution along the longitudinal direction, reflecting the dynamic changes in the wheel-rail contact state, i.e., uneven energy dissipation on the rail surface. This is not entirely consistent with the distribution of rolling contact fatigue cracks in the field. Figure 1 The phenomenon matches perfectly, highlighting the advantages of the local damage function model of this invention.

[0105] Figure 19 This is a distribution diagram of the rolling contact fatigue damage values ​​(abbreviated as damage values) of the inner and outer rails, predicted by the damage function model and the local damage function model of a U75V quenched steel rail within a certain cross-section under typical working conditions. Figure 19 As shown, the maximum damage values ​​predicted by the two models are basically consistent, which to some extent proves the rationality of the local damage function model of this invention. However, the U75V quenched rail damage function model predicts that damage also exists at the edge of the contact patch where the contact stress is very low, which is obviously inconsistent with the laws of physics. This point is corrected in the local damage function model. As can be seen from the figure, the rolling contact fatigue zone predicted by the local damage function model is narrower.

[0106] Application: Determination of parameters for macroscopic damage function models of arbitrary railway systems

[0107] In summary, the local damage function model obtained in this invention can accurately calculate the microscopic tangential contact load within the contact patch, and can predict the fatigue initiation situation at local locations at a scale closer to the essence of fatigue initiation. Local wear number τγ L This reflects the essence of the damage function prediction results and is more related to the mechanism leading to fatigue initiation and lifespan.

[0108] Extensive wear test results demonstrate that, besides being related to the energy input to the contact interface, the wear resistance of the material itself is the determining factor in the solid contact friction wear rate. This invention posits that the parameters of the local damage function model are only related to the wheel-rail material properties, representing a microscopic expression of the macroscopic damage function model. Therefore, based on the characteristics and calculation logic of the aforementioned local damage function model of this invention, it can be reasonably inferred that determining the damage function of another railway system (system B) with no significant change in wheel-rail material properties based on the damage function parameters of a known railway system (system A) is both reasonable and practical. The specific implementation method is as follows:

[0109] (1) Obtain the key parameters of the local damage function model of system A calibrated according to the macroscopic damage function model according to steps 100-700.

[0110] (2) Conduct the same simulation in system B, and deduce the parameters of the macroscopic damage function model applicable to system B based on the local damage function model obtained in step (1).

[0111] The foregoing has described the relevant content of the present invention. Those skilled in the art will be able to implement the present invention based on these descriptions. All other embodiments obtained by those skilled in the art based on the above description of the present invention without inventive effort should fall within the scope of protection of the present invention.

Claims

1. A method for determining the parameters of wheel-rail rolling contact fatigue damage function, characterized in that: Includes the following steps: Step 100: Establish a dynamic model of the vehicle system of a certain railway system and solve for the transient wheel-rail contact state parameters; Step 200: Based on the transient wheel-rail contact state parameters, establish a three-dimensional wheel-rail transient rolling contact finite element model, and calculate the macroscopic rolling contact solution and the microscopic contact solution within the contact patch; the macroscopic rolling contact solution includes the rigid creep rate and rigid creep force at the wheel-rail contact interface; the microscopic contact solution within the contact patch includes the local creep rate and local tangential contact stress within the wheel-rail contact patch; Step 300: Using a macroscopic damage function model based on macroscopic rolling contact solution, the transient wear number Tγ and the total transient damage value D within the contact patch at any given time are calculated based on the rigid creep rate. t and peak transient damage value h m ; Step 400: Solve for the local wear number τγ within the contact patch based on the local creep rate and tangential contact stress. L ; Step 500, using the peak transient damage value h m τγ, the maximum local wear number within the contact patch L Local damage value d L The local wear number τγ was obtained. L Peak value of transient damage h m The correspondence; Step 600: By varying the operating conditions, obtain the transient wear number Tγ and the local wear number τγ covering the entire macroscopic damage function model under different traction coefficients. L The relationship between them; Step 700, calculate the local wear number τγ at the critical point Lc. L The reduction is calculated based on the wear reduction until the total local damage value d within the corresponding contact patch is reached. t Total transient damage value D within the contact patch t Equal to each other, we obtain the reduced local wear number τγ. L With local damage value d L Relationship; Step 800: Fit the parameters of the local damage function model of a railway system based on the microscopic contact solution within the patch and / or inversely deduce the parameters of the macroscopic damage function model of another railway system.

2. The method for determining the parameters of wheel-rail rolling contact fatigue damage function as described in claim 1, characterized in that: In step 100, a vehicle system dynamics model is established in the multibody dynamics software SIMPACK.

3. The method for determining the parameters of wheel-rail rolling contact fatigue damage function as described in claim 1, characterized in that: In step 200, a three-dimensional wheel-rail transient rolling contact finite element model is established in the finite element solver ANSYS / Ls-dyna.

4. The method for determining the parameters of wheel-rail rolling contact fatigue damage function as described in claim 3, characterized in that: In step 200, the expression for calculating the rigid creep rate is: The expression for calculating local creep rate is: In the formula, γ x For longitudinal rigidity creep; γ y For transverse rigid creep; γ Lx The longitudinal local creep rate; γ Ly ω is the lateral local creep rate; r is the wheel speed; v0 is the actual rolling circle radius of the selected tread output point set; v0 is the longitudinal velocity of the wheel axle; v y Δv is the lateral velocity of the wheel relative to the rail. x Let Δv be the longitudinal relative sliding velocity between the wheel and rail at any point within the contact patch; y The lateral relative sliding velocity between the wheel and rail at any point within the contact patch.

5. The method for determining the parameters of wheel-rail rolling contact fatigue damage function as described in claim 4, characterized in that: In step 300, the expression for calculating the transient wear number Tγ is: Peak transient damage value h m The calculation expression is: In the formula, T x For longitudinal rigid creep force; T y π represents the lateral rigid creep force; b represents the lateral semi-axis length of the contact patch; and π represents pi.

6. The method for determining the parameters of wheel-rail rolling contact fatigue damage function as described in claim 4, characterized in that: In step 400, the local wear number τγ L The calculation expression is: Tg L =t x c Lx +t y c Ly ; In the formula, τ x τ is the longitudinal component of the local tangential contact stress. y This represents the transverse component of the local tangential contact stress.

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