Method for establishing rolling contact fatigue damage function of heavy haul railway steel rail

Abstract

The invention relates to the technical field of transportation, in particular to a method for establishing a heavy haul railway steel rail rolling contact fatigue damage function, which comprises the following steps of: 1, determining a rolling contact fatigue critical initiation position; 2, determining a fatigue initiation critical abrasion number; step 3, estimating a rolling contact fatigue initiation rate; and step 4, determining a damage function through the linear relation. According to the method, the damage function model can be well established.

Description

Technical Field

[0001] The invention relates to the technical field of transportation, and in particular to a method for establishing a rolling contact fatigue damage function of a heavy-load railway rail. Background Art

[0002] With the development of the national economy, heavy-duty freight railways have become an important mode of resource transportation in my country. Heavy-duty trains have a large axle weight, and the line travel frequency has increased, which greatly improves transportation efficiency. However, at the same time, it also deteriorates the service conditions of rails, making the rolling contact fatigue problem of rails in small radius curve sections prominent. Rolling contact fatigue deteriorates the service condition of wheels and rails, reduces driving safety, and significantly increases operation and maintenance costs.

[0003] The best way to treat rolling contact fatigue is to suppress its initiation. Therefore, in engineering, a rolling contact fatigue initiation prediction model is very necessary. The damage function model, as an engineering prediction tool for wheel-rail rolling contact fatigue, is widely accepted worldwide. Once the damage function of a certain material of rail is determined, combined with the prediction results of the train dynamics model that fully considers various influencing factors, it can be determined whether rolling contact fatigue occurs on rails in different sections and the severity of rolling contact fatigue damage. That is, the applicability of the material of the rail is obtained, which provides guidance for the selection of rails in different sections, preventive turning and other maintenance strategies. However, the establishment of the current damage function model is relatively complex and not accurate enough. Summary of the invention

[0004] The present invention provides a method for establishing a rolling contact fatigue damage function of a heavy-duty railway rail, which can better establish a damage function model.

[0005] A method for establishing a rolling contact fatigue damage function of a heavy-duty railway rail according to the present invention comprises the following steps:

[0006] Step 1: Determine the critical initiation position of rolling contact fatigue;

[0007] Step 2, determine the critical wear number for fatigue initiation;

[0008] Step 3: Estimation of rolling contact fatigue initiation rate;

[0009] Step 4: Determine the damage function through a linear relationship.

[0010] Preferably, in step 1, the method for determining the critical position of crack initiation is:

[0011] Along the running direction of the train, there is a phenomenon of rolling contact fatigue from non-existence to existence on the entry relaxation curve, and from existence to non-existence on the exit relaxation curve. The critical position where the crack just occurs corresponds to the first threshold value A of rolling contact fatigue. First, the critical position where the crack just occurs is determined, that is, the superelevation position where the relaxation curve segment changes from no crack to 2mm long on the crack surface as the superelevation increases, which is determined as the critical initiation position.

[0012] Preferably, in step 2, the wear number at the critical position of crack initiation is determined by train dynamics, that is, the abscissa of the threshold value A in the damage function is determined, as follows:

[0013] 1.1) Establish a train dynamics model;

[0014] A train dynamics model consisting of two locomotives and one freight car was established in the SIMPACK environment, and the other 104 freight cars were applied to the rear coupler of the freight car model in the form of equivalent loads; the guide wheelset of the front bogie of the locomotive was used for one axle, and by analogy, the last wheelset of the rear steering knuckle of the second locomotive in the inner coupling was 8 axles, and the same was true for the freight car; the locomotive sub-model included 1 car body, 2 frames and 4 wheelsets, with a total of 54 degrees of freedom, while the freight car sub-model included 1 car body, 4 side frames, 4 wheelsets, load saddles and bolsters, with a total of 68 degrees of freedom; the couplers between locomotives and locomotives, and between locomotives and freight cars were simulated by force elements; in the model, the car body and bogie were connected by secondary suspension, and the bogie and wheelsets were connected by primary suspension, and the first and second suspension elements of the spring and shock absorber were simulated by force elements; the dynamic simulation speed was the heavy-load train speed of 67km / h, and the time step was 0.02s, which corresponds to a moving distance of 0.37m;

[0015] In the track sub-model of the train dynamics model, the relevant superelevation and transition curve length parameters are set according to the actual situation of the line; the simulated train passing speed is taken as the train speed actually measured on site;

[0016] 1.2) Based on the wheel-rail rolling contact parameters of each axle at any time output by the train dynamics model, determine the wear number of each axle when passing through any position on the curved track.

[0017] Preferably, in step 3, the damage caused by each train is first determined, specifically: the number of trains passing when cracks initiate is calculated based on the number of days after cracks initiate on the new rail on the corresponding radius curve observed on site and the number of trains passing each day, and the reciprocal of the number of trains passing when cracks initiate is the damage caused by each train.

[0018] Preferably, in step 3, the rail rolling contact fatigue initiation rate, that is, the slope of the AB segment of the damage function is determined; specifically:

[0019] The damage caused by the locomotive and the freight car is calculated and linearly accumulated respectively, and it is assumed that the data points corresponding to the locomotive and the freight car are all on the AB segment; the vertical coordinate of the damage function is the damage amount D, and the horizontal coordinate is the wear number Tγ. The cross-sectional function of the AB segment is Tγ=mD+a, where the reciprocal of m is the slope of the AB segment, and a represents the horizontal coordinate of point A in the first segment of the damage function. Considering that the damage is laterally discrete in the contact spot, the total fatigue damage amount D caused by a train passing is:

[0020]

[0021] Among them, n L and n W represents the number of wheels of a train passing through the fatigue zone in the model. Only a single freight car is considered in the model, so the total damage of the freight cars in the whole train is 105 times that of the single freight car. L and b W It represents the transverse semi-axis length of the wheel-rail contact patch, and the subscripts L and W represent the locomotive and the freight car;

[0022] The total damage caused by each train derived from the number of days for fatigue crack initiation in the circular curve segment and the corresponding Tγ value obtained by simulation calculation are used to determine the corresponding m value under different radius curves through the above formula, and then the inverse k of m is taken as the corresponding slope, and then the average of all k obtained is taken, which is the slope of the AB segment of the damage function.

[0023] Preferably, in step 4, specifically:

[0024] 4.1) Determine the horizontal coordinate of point B:

[0025] First, calculate the average wear number of each wheel passing through the fatigue zone in the circular curve section; considering the significant differences between locomotives and freight cars, calculate the average wear number of each locomotive wheel passing through the fatigue zone Tγ Lm , and the average wear number Tγ of each truck wheel passing through the fatigue zone Wm ; The fatigue zone is the area with the largest wear number predicted by simulation; the average value Tγ Lm and the average value Tγ Wm The maximum number is taken as the horizontal coordinate of point B of the damage function;

[0026] 4.2) Determine the horizontal coordinate of point C;

[0027] Based on the damage function development report of RSSB, the slope of the wear BC segment is derived from the slope of the damage function AB segment, and then the coordinates of point C are obtained;

[0028] 4.3) According to the horizontal coordinate of the threshold value A in the damage function, the slope of segment AB, the horizontal coordinate of point B, and the horizontal coordinate of point C, the corresponding damage function model is obtained.

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

[0030] The present invention improves upon the original method of damage function development proposed by RSSB by taking into account the critical position of the onset of rolling contact fatigue (RCF) on the transition curve, thereby more accurately and efficiently determining the critical value of the onset of rolling contact fatigue (RCF).

[0031] The present invention is based on the actual observation of rolling contact fatigue of heavy-load rails, and takes the simulation of the operating conditions of actual operating trains as the core means. Therefore, it is more suitable for the service conditions of heavy-load rails and provides key support for more accurate prediction of heavy-load rail damage. The present invention can also be transplanted to other heavy-load lines to establish damage function models for rails of more materials under different operating conditions, and ultimately realize the selection of rails of different materials based on quantitative damage prediction, and personalized rail selection for any section. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a flow chart of a method for establishing a rolling contact fatigue damage function of a heavy-load railway rail in an embodiment;

[0033] Figure 2 Schematic diagram of a train dynamics model in the embodiment;

[0034] Figure 3 Schematic diagram of the comparison of RCF and wear rate of U75V quenched rail in the embodiment;

[0035] Figure 4 is the damage function model of the U75V quenched rail in the embodiment;

[0036] Figure 5 It is the damage function model of the U76CrRE (second generation rare earth) heat-treated rail in the embodiment. DETAILED DESCRIPTION

[0037] In order to further understand the content of the present invention, the present invention is described in detail in conjunction with the accompanying drawings and embodiments. It should be understood that the embodiments are only for explaining the present invention and are not intended to limit it.

[0038] Example

[0039] like Figure 1 As shown, this embodiment provides a method for establishing a rolling contact fatigue damage function of a heavy-duty railway rail, which includes the following steps:

[0040] Step 1: Determine the critical initiation position of rolling contact fatigue.

[0041] Determination of the critical position of crack initiation

[0042] Along the running direction of the train, there is a phenomenon of rolling contact fatigue from no to some on the entry relaxation curve, and from some to no on the exit relaxation curve. The critical position where the crack just occurs corresponds to the first threshold value A of rolling contact fatigue. First, the critical position where the crack just occurs is determined, that is, the position where the relaxation curve segment changes from no crack to a superelevation position of 2 mm long on the crack surface as the superelevation increases, which is determined as the critical initiation position.

[0043] Using the train dynamics model introduced above, the train passing behavior of curves with different radii is calculated respectively, and the wear number at the high / low fatigue decritical initiation position of concern on the relaxation curve is obtained, that is, the critical parameter A of the U75V quenched rail damage function is obtained.

[0044] The critical wear number A values ​​obtained from different curve transition curve segments are re-tabulated. Finally, the extracted wear numbers are averaged and rounded to 33N, which corresponds to point A in the damage function.

[0045] Step 2: Determine the critical wear number for fatigue initiation.

[0046] In step 2, the wear number at the critical position of crack initiation is determined by train dynamics, that is, the horizontal coordinate of the threshold value A in the damage function is determined as follows:

[0047] 1.1) Establish a train dynamics model;

[0048] A train dynamics model consisting of two locomotives and one freight car is established in the SIMPACK environment. The other 104 freight cars are applied to the rear coupler of the freight car model in the form of equivalent loads. Figure 2 As shown in the figure, the guide wheel pair of the front bogie of the locomotive is 1 axle, and the last wheel pair of the rear steering knuckle of the second locomotive in the inner coupling is 8 axles. The same is true for freight cars. Respectively represent the resistance of the engine and the truck, and 104 It represents the total resistance of the remaining 104 freight cars; the locomotive sub-model includes 1 car body, 2 frames and 4 wheelsets, with a total of 54 degrees of freedom, while the freight car sub-model includes 1 car body, 4 side frames, 4 wheelsets, load saddle and rocker, with a total of 68 degrees of freedom; the couplings between locomotives and locomotives, and between locomotives and freight cars are simulated by force elements; the secondary suspension is used to connect the car body and bogie, and the primary suspension is used to connect the bogie and wheelsets. The first and second suspension elements of springs and shock absorbers are simulated by force elements; the dynamic simulation speed is 67km / h for heavy-load trains (slightly higher for no-load trains), and the time step is 0.02s, corresponding to a moving distance of 0.37m.

[0049] In the track sub-model of the train dynamics model, the relevant superelevation and transition curve length parameters are set according to the actual situation of the line; the simulated train passing speed is taken as the train speed actually measured on site.

[0050] 1.2) Based on the wheel-rail rolling contact parameters (creep force / rate, contact point position, contact spot short semi-axis length, etc.) of each axle at any time output by the train dynamics model, determine the wear number of each axle passing through any position on the curved track. Develop the corresponding numerical program in MATLAB, introduce the obtained wear number into the damage function model, and realize the rolling contact fatigue damage prediction at any position of the curved rail.

[0051] It should be noted that rail rolling contact fatigue occurs basically continuously throughout the entire curve, indicating that its dominant factor is the quasi-steady-state or low-frequency dynamic interaction between the wheel and rail, which is unrelated to the medium- and high-frequency dynamic effects of the wheel and rail. Therefore, the multi-layer complex structure of the track is ignored during modeling and replaced by rigid rails of standard gauge, but the measured medium- and long-wave irregularities of the track are taken into account.

[0052] Step 3: Estimate the rail rolling contact fatigue initiation rate based on the threshold value A and the damage caused by each train.

[0053] In step 3, the damage caused by each train is first determined. Specifically, the number of trains passing through the track at the time of crack initiation is calculated based on the number of days after crack initiation on the new track on the corresponding radius curve from on-site observation (on-site tracking test) and the number of trains passing through the track every day. The reciprocal of the number of trains passing through the track at the time of crack initiation is the damage caused by each train.

[0054] In step 3, the rail rolling contact fatigue initiation rate, that is, the slope of the AB segment of the damage function, is determined; specifically:

[0055] The first section of the damage function is a straight line with a positive slope, and the intersection with the horizontal axis is the critical wear number A. Here, the damage caused by the locomotive and the freight car is calculated and linearly accumulated, and it is assumed that the data points corresponding to the locomotive and the freight car are on the AB section (that is, on the same straight line); the ordinate of the damage function is the damage amount D, the abscissa is the wear number Tγ, and the cross-sectional function of the AB section is Tγ=mD+a, where the reciprocal of m is the slope of the AB section, and a represents the abscissa of point A in the first section of the damage function. Considering that the damage is laterally discrete in the contact patch, the total fatigue damage amount D caused by a train passing is:

[0056]

[0057] Among them, n L and n W represents the number of wheels of a train passing through the fatigue zone in the model. Only a single freight car is considered in the model, so the total damage of the freight cars in the whole train is 105 times that of the single freight car. L and b W It represents the transverse semi-axis length of the wheel-rail contact patch. The subscripts L and W represent the locomotive and the freight car.

[0058] The total damage caused by each train derived from the number of days for fatigue crack initiation in the circular curve segment and the corresponding Tγ value obtained by simulation calculation are used to determine the corresponding m value under different radius curves through the above formula, and then the inverse k of m is taken as the corresponding slope, and then the average of all k obtained is taken, which is the slope of the AB segment of the damage function.

[0059] Step 4: Determine the damage function through a linear relationship.

[0060] In step 4, specifically:

[0061] 4.1) Determine the horizontal coordinate of point B:

[0062] First, calculate the average wear number of each wheel passing through the fatigue zone in the circular curve section; considering the significant differences between locomotives and freight cars, calculate the average wear number of each locomotive wheel passing through the fatigue zone Tγ Lm , and the average wear number Tγ of each truck wheel passing through the fatigue zone Wm ; The fatigue zone is the area with the largest wear number predicted by simulation; the average value Tγ Lm and the average value Tγ Wm The maximum number is taken as the horizontal coordinate of point B of the damage function.

[0063] In the final damage function, the coordinates of point A are (33, 0), and the slope of segment AB is 2.0×10 -6 , the coordinates of point B are (142, 2.2×10 -4 ), and finally the damage function AB segment equation is as follows:

[0064] D=Tγ*2×10 -6 -6.6×10 -5 .

[0065] 4.2) Determine the horizontal coordinate of point C.

[0066] Based on the damage function development report of RSSB, the slope of the wear BC segment is derived from the slope of the damage function AB segment, and then the coordinates of point C are obtained. Figure 3 It can be seen that when the wear number reaches 384.2, the wear and rolling contact fatigue of the U75V quenched rail are balanced, which is point C of the damage function.

[0067] 4.3) According to the horizontal coordinate of the threshold value A in the damage function, the slope of segment AB, the horizontal coordinate of point B, and the horizontal coordinate of point C, the corresponding damage function model is obtained.

[0068] Figure 4 The damage function model of the U75V quenched rail obtained above is shown.

[0069] Using the same method, the damage function of U76CrRE (second generation rare earth) heat treated rail can be obtained, such as Figure 5 The final damage functions are as follows: 1) U75V quenching: A(33,0), B(142,2.18E-4), C(384,0); 1) Rare earth second generation (U76CrRE): A(42,0), B(177,9.99E-5), C(455,0).

[0070] This embodiment takes into account the critical position where rolling contact fatigue (RCF) occurs on the transition curve, thereby more accurately and effectively determining the critical value for the onset of rolling contact fatigue (RCF), and the resulting damage function model is better.

[0071] The present invention and its embodiments are described schematically above, and the description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by it and designs a structural method and an embodiment similar to the technical solution without creativity without departing from the purpose of the invention, they shall all fall within the protection scope of the present invention.

Claims

1. A method for establishing a rolling contact fatigue damage function for heavy-duty railway rails, characterized in that: The following steps are involved: Step 1: Determine the critical initiation position of rolling contact fatigue; Step 2, determine the critical wear number for fatigue initiation; Step 3: Estimation of rolling contact fatigue initiation rate; Step 4: Determine the damage function through a linear relationship.

2. The method for establishing a rolling contact fatigue damage function of a heavy-duty railway rail according to claim 1, characterized in that: In step 1, the method for determining the critical position of crack initiation is: Along the running direction of the train, there is a phenomenon of rolling contact fatigue from non-existence to existence on the entry relaxation curve, and from existence to non-existence on the exit relaxation curve. The critical position where the crack just occurs corresponds to the first threshold value A of rolling contact fatigue. First, the critical position where the crack just occurs is determined, that is, the superelevation position where the relaxation curve segment changes from no crack to 2mm long on the crack surface as the superelevation increases, which is determined as the critical initiation position.

3. The method for establishing a rolling contact fatigue damage function of a heavy-duty railway rail according to claim 2, characterized in that: In step 2, the wear number at the critical position of crack initiation is determined by train dynamics, that is, the horizontal coordinate of the threshold value A in the damage function is determined as follows: 1.1) Establish a train dynamics model; A train dynamics model consisting of two locomotives and one freight car was established in the SIMPACK environment, and the other 104 freight cars were applied to the rear coupler of the freight car model in the form of equivalent loads; the guide wheelset of the front bogie of the locomotive was used for one axle, and by analogy, the last wheelset of the rear steering knuckle of the second locomotive in the inner coupling was 8 axles, and the same was true for the freight car; the locomotive sub-model included 1 car body, 2 frames and 4 wheelsets, with a total of 54 degrees of freedom, while the freight car sub-model included 1 car body, 4 side frames, 4 wheelsets, load saddles and bolsters, with a total of 68 degrees of freedom; the couplers between locomotives and locomotives, and between locomotives and freight cars were simulated by force elements; in the model, the car body and bogie were connected by secondary suspension, and the bogie and wheelsets were connected by primary suspension, and the first and second suspension elements of the spring and shock absorber were simulated by force elements; the dynamic simulation speed was the heavy-load train speed of 67km / h, and the time step was 0.02s, which corresponds to a moving distance of 0.37m; In the track sub-model of the train dynamics model, the relevant superelevation and transition curve length parameters are set according to the actual situation of the line; the simulated train passing speed is taken as the train speed actually measured on site; 1.2) Based on the wheel-rail rolling contact parameters of each axle at any time output by the train dynamics model, determine the wear number of each axle when passing through any position on the curved track.

4. The method for establishing a rolling contact fatigue damage function of a heavy-duty railway rail according to claim 3, characterized in that: In step 3, the damage caused by each train is first determined. Specifically, the number of trains passing through the track at the time of crack initiation is calculated based on the number of days after crack initiation on the new track on the corresponding radius curve observed on site and the number of trains passing through the track every day. The reciprocal of the number of trains passing through the track at the time of crack initiation is the damage caused by each train.

5. The method for establishing a rolling contact fatigue damage function of a heavy-duty railway rail according to claim 4, characterized in that: In step 3, the rail rolling contact fatigue initiation rate, that is, the slope of the AB segment of the damage function, is determined; specifically: The damage caused by the locomotive and the freight car is calculated and linearly accumulated respectively, and it is assumed that the data points corresponding to the locomotive and the freight car are all on the AB segment; the vertical coordinate of the damage function is the damage amount D, and the horizontal coordinate is the wear number Tγ. The cross-sectional function of the AB segment is Tγ=mD+a, where the reciprocal of m is the slope of the AB segment, and a represents the horizontal coordinate of point A in the first segment of the damage function. Considering that the damage is laterally discrete in the contact spot, the total fatigue damage amount D caused by a train passing is: Among them, n L and n W represents the number of wheels of a train passing through the fatigue zone in the model. Only a single freight car is considered in the model, so the total damage of the freight cars in the whole train is 105 times that of the single freight car. L and b W It represents the transverse semi-axis length of the wheel-rail contact patch, and the subscripts L and W represent the locomotive and the freight car; The total damage caused by each train derived from the number of days for fatigue crack initiation in the circular curve segment and the corresponding Tγ value obtained by simulation calculation are used to determine the corresponding m value under different radius curves through the above formula, and then the inverse k of m is taken as the corresponding slope, and then the average of all k obtained is taken, which is the slope of the AB segment of the damage function.

6. The method for establishing a rolling contact fatigue damage function of a heavy-duty railway rail according to claim 5, characterized in that: In step 4, specifically: 4.1) Determine the horizontal coordinate of point B: First, calculate the average wear number of each wheel passing through the fatigue zone in the circular curve section; considering the significant differences between locomotives and freight cars, calculate the average wear number of each locomotive wheel passing through the fatigue zone Tγ Lm , and the average wear number Tγ of each truck wheel passing through the fatigue zone Wm ; The fatigue zone is the area with the largest wear number predicted by simulation; the average value Tγ Lm and the average value Tγ Wm The maximum number is taken as the horizontal coordinate of point B of the damage function; 4.2) Determine the horizontal coordinate of point C; Based on the damage function development report of RSSB, the slope of the wear BC segment is derived from the slope of the damage function AB segment, and then the coordinates of point C are obtained; 4.3) According to the horizontal coordinate of the threshold value A in the damage function, the slope of segment AB, the horizontal coordinate of point B, and the horizontal coordinate of point C, the corresponding damage function model is obtained.

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