Fatigue damage prediction method for ballastless track of high-speed railway with speed of 400km / h

Abstract

The invention provides a fatigue damage prediction method for a ballastless track of a high-speed railway with the speed of 400km / h. Finite element software is adopted to establish a ballastless track model and a train model; enabling the train model to simulate and run on the ballastless track model for one time according to a given speed, and carrying out primary simulation loading; obtaining performance degradation curves of the concrete and the steel bars according to the primary simulation result; calculating fatigue physical parameters of the concrete and the steel bars according to the fatigue loading times, substituting the fatigue physical parameters into the ballastless track model considering the temperature effect, updating a plastic constitutive model of the concrete and the steel bars, and performing failure judgment according to a simulation result; if not, adjusting the number of fatigue loading times to repeat simulation until the designed age limit is reached or the fatigue fails; and drawing a fatigue damage ratio development time history curve to realize fatigue damage prediction. According to the method, the train fatigue load and the temperature effect are coupled, the concrete fatigue damage ratio development time history curve is constructed through few times of simulation, and the prediction precision and efficiency are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-speed railway, and particularly relates to a fatigue damage prediction method for a ballastless track of a high-speed railway with a speed of 400km / h. BACKGROUND

[0002] With the continuous improvement of the design and operation speed of railways, ballastless tracks are widely used in the construction of high-speed railways. As the force transmission structure between trains and the ground, the running of high-speed trains will exert repeated load on the track, causing fatigue deterioration of the track structure. The fatigue deterioration state of the track structure will directly affect the stability and safety of high-speed train operation. Accurate prediction of the service state of the ballastless track structure can ensure the safety of train operation and guide the maintenance of the track structure, which is of great significance to the operation and maintenance of the railway after construction.

[0003] At present, most of the existing researches obtain the fatigue deterioration law of the track structure through experiments, which is high in cost and long in cycle and is not convenient for actual operation and popularization. Most of the existing numerical simulation researches on track structure fatigue convert the train dynamic load into static load through the equivalent static force method for research, and there are few researches considering both train dynamic load and temperature effect, which lack accuracy. Most of the existing researches consider the case of train speed of 300km / h, and few researches consider the fatigue damage of ballastless track concrete structure under the condition of train speed of 400km / h, so they lack applicability. The high-speed railway with a speed of 400km / h is one of the future directions of high-speed railway development. Therefore, it is necessary to provide a method for predicting the fatigue damage of the ballastless track of the high-speed railway with a speed of 400km / h under the long-term service state. SUMMARY

[0004] In order to overcome the defects of the prior art, the application provides a fatigue damage prediction method for a ballastless track of a high-speed railway with a speed of 400km / h, to ensure the stability and safety of train operation.

[0005] To achieve the above-mentioned purpose, the application realizes the following technical scheme.

[0006] The application provides a fatigue damage prediction method for a ballastless track of a high-speed railway with a speed of 400km / h, comprising the following steps:

[0007] S1, the running speed of a high-speed train with a speed of 400km / h is given, the train cycle of the high-speed train with a speed of 400km / h is estimated according to the existing high-speed train marshalling condition and train cycle, and the fatigue loading frequency N0 of the ballastless track per year is obtained according to the train cycle;

[0008] S2, the parameters of the ballastless track and the parameters of the train are collected, and a finite element software is used to establish a ballastless track model and a train model under static state;

[0009] S3, let the train model simulate running on the ballastless track model at a given running speed once, perform initial simulation loading, and obtain upper and lower limits of fatigue tension and compression stresses of the concrete structure and upper and lower limits of fatigue stresses of the steel bar;

[0010] S4, substitute the parameters obtained in S3 into the concrete performance degradation curve model and the steel bar performance degradation curve model to obtain the concrete performance degradation curve and the steel bar performance degradation curve;

[0011] S5, in the static state of the ballastless track model, apply temperature load to the ballastless track, obtain the deformation of the ballastless track through numerical simulation, apply the obtained deformation as an initial condition to another ballastless track model in the static state, obtain the stress and strain distribution of the concrete structure and the steel bar through numerical simulation, and obtain the ballastless track model considering the temperature effect;

[0012] S6, obtain the fatigue loading number N = tN0 according to N0 and the train running time t, substitute the fatigue loading number N into the performance degradation curve obtained in S4 to obtain the physical parameters of the concrete and the steel bar after fatigue loading N times; the concrete and the steel bar are simulated by using a plastic constitutive model, the obtained physical parameters are input into the ballastless track model considering the temperature effect in S5, the parameters in the plastic constitutive model are updated, and the stress and strain distribution of the concrete structure and the steel bar are obtained through numerical simulation;

[0013] S7, judge fatigue failure according to the simulation results obtained in S6, if the ballastless track fails, stop the simulation; if it does not fail, increase the train running time t, and repeat step S6 until the ballastless track reaches the design service life or the fatigue failure state;

[0014] S8, define the ratio of the crack area in a cross section of the concrete structure to the cross section area as the fatigue damage ratio; obtain the crack area of the ballastless track concrete structure at different N according to all the simulation results obtained in S7, then fit the fatigue damage ratio development time curve according to the fatigue damage ratio at different N, and predict the fatigue damage of the ballastless track concrete structure according to the obtained curve.

[0015] Further, in S2, the ballastless track parameters include the geometric parameters, the initial elastic modulus, the Poisson's ratio, the linear expansion coefficient, the cylinder compressive strength, the axial tensile strength, the density of the concrete structure, and the initial tensile yield strength of the steel bar; the train parameters include the primary suspension parameters, the secondary suspension parameters, and the mass and moment of inertia of the car body, the frame and the wheelset.

[0016] Further, in S4, the concrete performance degradation curve model includes a stiffness degradation curve model and a strength degradation curve model of the concrete, and the strength degradation curve model includes an anti-compressive strength degradation curve model and an anti-tensile strength degradation curve model.

[0017] The expression of the concrete stiffness degradation curve model is as formula (4.1):

[0018] (4.1)

[0019] In the formula, E N is the elastic modulus of the concrete after fatigue loading N times; N is the fatigue loading times; E0 is the initial elastic modulus of the concrete; N f is the fatigue life of the concrete, N f is obtained through the S-N f curve of the concrete, and the values of the concrete in the tensile state and the compressive state are not the same;

[0020] The expression of the concrete compressive strength degradation curve model is as formula (4.4):

[0021] (4.4)

[0022] In the formula, is the fatigue residual compressive strength of the concrete after fatigue loading N times; is the maximum compressive stress generated by the concrete in the initial simulation loading, which is directly obtained from the initial simulation result; v is a constant related to the fatigue stress level;

[0023] The expression of the concrete tensile strength degradation curve model is as formula (4.5):

[0024] (4.5)

[0025] In the formula, is the fatigue residual tensile strength of the concrete after fatigue loading N times; is the correction coefficient of the fatigue residual tensile strength of the concrete; is the initial tensile strength of the steel bar; a and b are the concrete fatigue tensile test constants, which can be taken as a=-0.0913 and b=1.

[0026] Further, in S4, the expression of the steel strength degradation curve model is as formula (4.6):

[0027] (4.6)

[0028] In the formula, is the equivalent fatigue residual tensile strength of the steel bar after fatigue loading N times; N is the fatigue loading times; is the fatigue life of the steel bar, obtained from the S- curve of the steel bar; is the initial tensile yield strength of the steel bar; The stress upper limit for the initial simulation load.

[0029] Further, in S5, the temperature load is determined according to the environment temperature of the ballastless track.

[0030] Further, in S6, the train operation time t is selected in a time span of 1-10 years, preferably 2-5 years.

[0031] Further, in S6, the physical parameters include the elastic modulus, the fatigue residual compressive strength, the fatigue residual tensile strength of the concrete and the equivalent fatigue residual tensile strength of the steel bar after fatigue loading N times.

[0032] Further, in S6, the expression of the plastic constitutive model of the concrete under compression is as shown in formula (6.1)-(6.5):

[0033] (6.1)

[0034] (6.2)

[0035] (6.3)

[0036] (6.4)

[0037] (6.5)

[0038] In the formula: is a correction coefficient; represents a shape parameter of the descending section of the uniaxial compression strain curve; , are the fatigue residual compressive strength and the corresponding peak compressive strain of the concrete after fatigue loading N times, respectively, can be obtained according to in the Concrete Structure Design Standard (GB / T50010-2010); is the residual compressive strain of the concrete after fatigue loading N times;

[0039] wherein, the expression of is as shown in formula (6.6):

[0040] (6.6)

[0041] In the formula: is the compressive strain of the concrete after fatigue loading N times; , are the upper and lower limits of the stress of the concrete compression zone during fatigue loading N times, respectively; is the elastic modulus of the compression concrete after unloading after fatigue loading N times;

[0042] wherein, is obtained by formula (6.7):

[0043] (6.7)

[0044] wherein, is the compressive strain of concrete under fatigue loading N times; is the peak compressive strain of concrete corresponding to the standard value of uniaxial compressive strength, is the initial elastic modulus of concrete.

[0045] Further, in S6, the expression of the plastic constitutive model of concrete under tension is as formula (6.9)-(6.12):

[0046] (6.9)

[0047] (6.10)

[0048] (6.11)

[0049] (6.12)

[0050] wherein, is the correction coefficient; represents the shape parameter of the descending segment in the uniaxial tensile strain curve; , are the fatigue residual tensile strength and the corresponding peak tensile strain of concrete after fatigue loading N times respectively, can be obtained according to according to the Standard for Design of Concrete Structures (GB / T50010-2010); is the residual tensile strain of concrete after fatigue loading N times;

[0051] wherein, the expression of is as formula (6.13):

[0052] (6.13)

[0053] wherein, is the tensile strain of concrete after fatigue loading N times; , are the upper and lower limits of the stress of concrete under tension during fatigue loading N times respectively; is the elastic modulus of the unloading of tensile concrete after fatigue loading N times;

[0054] wherein, is obtained by formula (6.14):

[0055] (6.14)

[0056] In the formula: is the tensile strain of concrete after fatigue loading N times; is the peak tensile strain of concrete corresponding to the standard value of uniaxial tensile strength; is the initial elastic modulus of concrete.

[0057] Further, in S7, the expression of the concrete compressive fatigue failure criterion is as formula (7.1):

[0058] (7.1)

[0059] In the formula: is the residual compressive strain of concrete; is the initial compressive strength of concrete; is the initial elastic modulus of concrete;

[0060] The expression of the steel fatigue failure criterion is as formula (7.2):

[0061] (7.2)

[0062] In the formula: is the maximum stress suffered by the steel after fatigue loading N times, which is directly obtained from the simulation result; is the equivalent fatigue residual tensile strength of the steel after fatigue loading N times.

[0063] Compared with the prior art, the beneficial technical effects of the present application are:

[0064] 1) The present application couples the temperature effect of the environment with the train dynamic load, and simultaneously considers the effects of the environmental temperature and the vehicle dynamic load on the track structure, which is more accurate than the research method of equivalent static load method which equivalent train dynamic load to static load, and the fatigue damage prediction is more accurate;

[0065] 2) The present application establishes a vehicle-track model based on finite element software, and obtains the service state of the track structure at different fatigue deterioration periods through numerical simulation, which is lower in resource consumption and stronger in repeatability compared with traditional experimental methods; and the present application obtains the performance degradation curves of concrete and steel through initial simulation, then obtains the fatigue physical parameters of concrete and steel according to the fatigue loading times, and performs numerical simulation according to the obtained parameters, which greatly shortens the simulation time, so that the present application constructs the fatigue damage ratio development time curve of the ballastless track with fewer simulation times and shorter simulation time, and realizes the prediction of fatigue load; the fatigue loading times can be flexibly selected according to the prediction accuracy, and the efficiency of simulation and prediction is improved. BRIEF DESCRIPTION OF DRAWINGS

[0066] Figure 1 This is a flowchart of the method of the present invention.

[0067] Figure 2 This is a schematic diagram of the ballastless track model in the implementation method.

[0068] Figure 3 This is a stress cloud diagram of the ballastless track slab during the initial simulation loading in the implementation method.

[0069] Figure 4 This is a stress cloud diagram of the ballastless track slab after 20 years of simulated train operation in the implementation method.

[0070] Figure 5 This is a crack cloud map of a cross section of the ballastless track after two years of simulated train operation, as shown in the implementation method.

[0071] Figure 6 This is a time-varying curve of fatigue damage ratio of a certain cross section of the ballastless track slab in the implementation method. Detailed Implementation

[0072] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0073] The specific description of Example 1 is as follows:

[0074] like Figure 1 As shown in the figure, an embodiment of the present invention provides a method for predicting fatigue damage of ballastless track on high-speed railways with speeds of 400 km / h and above, comprising the following steps:

[0075] S1. Given the operating speed of a high-speed train with a speed of 400 km / h+, estimate the operating cycle of the high-speed train with a speed of 400 km / h+ based on the existing high-speed train formation and operating cycle, and obtain the number of fatigue loading times N0 per year for the ballastless track based on the operating cycle.

[0076] The annual fatigue loading number N0 of ballastless track is also the annual cycle loading number of the train load. Current high-speed trains typically operate at speeds below 350 km / h.

[0077] S2. Collect ballastless track parameters and train parameters. Based on the obtained parameters, use finite element software to establish a static ballastless track model and a train model.

[0078] The parameters of the ballastless track concrete structure include the geometric parameters of the concrete components, initial elastic modulus, Poisson's ratio, coefficient of linear expansion, compressive strength of the cylinder, axial tensile strength, density, and initial tensile yield strength of the steel reinforcement; the train parameters include the primary suspension parameters, secondary suspension parameters, and the mass and moment of inertia of the car body, frame, and wheelsets.

[0079] Specifically, the embodiment adopts CRTS II track slab, and a ballastless track model is constructed by using a finite element software ABAQUS, wherein a C3D8R unit is used for modeling the concrete structure part, and a T3D2 unit is used for modeling the steel bar. The track slab and the mortar layer, the mortar layer and the base plate, and the base plate and the roadbed are all bound by contact, and the steel bar and the concrete are embedded by an "embed" module. The ballastless track model in a static state established in the embodiment is as shown in Figure 2 The establishment of the train model is a conventional technical means in the field, and will not be described here.

[0080] S3, let the train model simulate running on the ballastless track model once at a given running speed, perform initial dynamic simulation loading, and obtain the upper and lower limits of the fatigue tension and compression stresses of the concrete structure and the upper and lower limits of the fatigue stress of the steel bar in the initial simulation loading process;

[0081] The simulation running once is 1 time of fatigue loading. The stress nephogram of the track slab at a certain moment obtained by performing the initial dynamic simulation loading on the ballastless track is as shown in Figure 3 . It can be known from Figure 3 that the maximum stress of the track slab at this time appears at the rail supporting platform below 1 / 3 of the distance from the slab end, and is 6.4 MPa.

[0082] S4, the parameters obtained in S3 are substituted into the concrete performance degradation curve model and the steel bar performance degradation curve model to obtain the concrete performance degradation curve and the steel bar performance degradation curve;

[0083] The concrete performance degradation curve includes the stiffness degradation curve and the strength degradation curve of the concrete, and the strength degradation curve includes the compression strength degradation curve and the tension strength degradation curve.

[0084] The expression of the concrete stiffness degradation curve model is as shown in formula (4.1):

[0085] (4.1)

[0086] In the formula, E N is the elastic modulus of the concrete after N times of fatigue loading; E0 is the initial elastic modulus of the concrete; N is the number of fatigue loadings; N f is the fatigue life of the concrete, and the values of the concrete in the tension state and the compression state are not the same.

[0087] The fatigue life N f of the concrete can be obtained by the S-N f curve of the concrete, and the S-N f curves of the concrete in the tension state and the compression state are as follows:

[0088] The S-Nf The expression of the curve is as shown in equation (4.2):

[0089] (4.2)

[0090] In the equation: , ; , are the upper limit and the lower limit of the fatigue tensile stress of the concrete structure in the initial simulation loading process, respectively; is the axial tensile strength of the concrete; , are material-related coefficients, = 1.0, = 0.0685.

[0091] The expression of the S-N curve of the concrete in the compression state is as shown in equation (4.3): f

[0092] (4.3)

[0093] In the equation: , ; , are the upper limit and the lower limit of the fatigue compressive stress of the concrete structure in the initial simulation, respectively; is the compressive strength of the concrete cylinder; , are material-related coefficients, = 1.0, = 0.064-0.085.

[0094] The expression of the compressive strength degradation curve model of the concrete is as shown in equation (4.4):

[0095] (4.4)

[0096] In the equation: is the fatigue residual compressive strength of the concrete after N times of fatigue loading; is the maximum compressive stress generated by the concrete in the initial simulation loading, which can be directly obtained from the initial simulation result; and v is a constant related to the fatigue stress level.

[0097] The expression of the tensile strength degradation curve model of the concrete is as shown in equation (4.5):

[0098] (4.5)

[0099] In the equation: is the fatigue residual tensile strength of the concrete after N times of fatigue loading; ​is the fatigue residual tensile strength correction coefficient of concrete; f is the initial tensile strength of steel bar; a and b are fatigue tensile test constants of concrete, which can be taken as a =-0.0913 and b =1. is the initial tensile strength of steel bar; a and b are fatigue tensile test constants of concrete, which can be taken as a =-0.0913 and b =1.

[0100] The expression of the steel bar strength degradation curve model is as formula (4.6):

[0101] (4.6)

[0102] In the formula, is the equivalent fatigue residual tensile strength of the steel bar after N times of fatigue loading; N is the loading times of the fatigue load; is the fatigue life of the steel bar, which can be obtained from the S- curve of the steel bar; is the initial tensile yield strength of the steel bar; is the stress upper limit in the initial simulation loading;

[0103] In the formula, the expression of the S- curve of the steel bar is as formula (4.7):

[0104] (4.7)

[0105] In the formula, is the fatigue life of the steel bar; is the fatigue stress amplitude of the steel bar, which is the difference between the stress upper limit and the stress lower limit of the steel bar in the initial simulation loading; C and m are fatigue performance constants and material property constants.

[0106] The existing research shows that the stress level of the steel bar in the track slab is relatively low during the whole service process, and does not reach the yield limit, so it can be considered that the elastic modulus does not deteriorate throughout the process, and the stress still conforms to the linear elastic assumption, and the steel bar strength degradation curve can be obtained by the above formula.

[0107] S5, in the ballastless track model in the static state, temperature load is applied to the ballastless track, and the deformation of the ballastless track is obtained by numerical simulation through the finite element software; the obtained deformation is applied as an initial condition to another ballastless track model in the static state, and the stress and strain distribution of the concrete structure and the steel bar is obtained by numerical simulation, so as to obtain the ballastless track model considering temperature action;

[0108] The temperature action is applied to the ballastless track model in the static state, and in this embodiment, the average temperature is 30℃ and the positive temperature gradient of 50℃ per meter is used to simulate the environmental temperature. The positive temperature gradient means that the temperature decreases linearly from the surface of the ballastless track downward. The deformation data of the ballastless track concrete structure under the temperature action is obtained by numerical simulation, and the deformation data is assigned as an initial condition to the ballastless track concrete structure and dynamic simulation is performed to obtain the stress and strain distribution.

[0109] S6, obtaining the fatigue loading number N = tN0according to N0and the train operation time t, and substituting the fatigue loading number N into the performance degradation curve of the concrete and the steel bar obtained in S4 to obtain the physical parameters of the concrete and the steel bar after N times of fatigue loading; the concrete and the steel bar are simulated by using a plastic constitutive model, the obtained physical parameters are input into the ballastless track model considering the temperature effect in S5 to update the parameters in the plastic constitutive model, and an equivalent ballastless track model after N times of fatigue loading is obtained, and the stress and strain distribution of the concrete structure and the steel bar is obtained through numerical simulation;

[0110] Substituting the fatigue loading number N into the performance degradation curve of the concrete and the steel bar, the elastic modulus, the fatigue residual compressive strength, the fatigue residual tensile strength of the concrete and the equivalent residual fatigue strength of the steel bar after N times of loading are obtained. The above physical parameters are input into the ballastless track model considering the temperature effect to replace the initial elastic modulus, the cylinder compressive strength, the axial tensile strength of the concrete and the initial tensile yield strength of the steel bar in the plastic constitutive model of the concrete and the steel bar, so as to obtain the structural deterioration model after N times of fatigue loading.

[0111] The expression of the plastic constitutive model of the concrete under compression is as formula (6.1)-(6.5):

[0112] (6.1)

[0113] (6.2)

[0114] (6.3)

[0115] (6.4)

[0116] (6.5)

[0117] In the formula: is a correction coefficient; represents a shape parameter of the descending segment in the uniaxial compression strain curve; , respectively, the fatigue residual compressive strength and the corresponding peak compressive strain of the concrete after N times of fatigue loading are obtained ; is the residual compressive strain of the concrete after N times of fatigue loading;

[0118] wherein, the expression of is as formula (6.6):

[0119] ​ (6.6)

[0120] wherein: is the compressive strain of concrete after fatigue loading N times; , are the upper and lower limits of compressive stress of concrete during fatigue loading N times, respectively; is the elastic modulus of the compressive concrete after fatigue loading N times;

[0121] wherein, is obtained according to formula (6.7):

[0122] (6.7)

[0123] wherein: is the compressive strain of concrete after fatigue loading N times; is the peak compressive strain of concrete corresponding to the standard value of uniaxial compressive strength, is the initial elastic modulus of concrete.

[0124] The expressions of the plastic constitutive model of concrete under tension are as shown in formula (6.9)~(6.12):

[0125] (6.9)

[0126] (6.10)

[0127] (6.11)

[0128] (6.12)

[0129] wherein: is the correction coefficient; represents the shape parameter of the descending segment of the uniaxial tensile strain curve; , are the fatigue residual tensile strength and the corresponding peak tensile strain of concrete after fatigue loading N times, respectively, wherein is obtained and then is obtained according to the Standard for Design of Concrete Structures (GB / T50010-2010); ; is the residual tensile strain of concrete after fatigue loading N times;

[0130] wherein, the expression of is as shown in formula (6.13):

[0131] (6.13)

[0132] wherein: is the tensile strain of concrete after fatigue loading N times; , are the upper and lower limits of stress in the tensile zone of concrete during fatigue loading N times, respectively; is the elastic modulus of the tensile concrete after unloading after fatigue loading N times;

[0133] wherein, is obtained according to formula (6.14):

[0134] (6.14)

[0135] wherein, is the tensile strain of concrete after fatigue loading N times; is the peak tensile strain of concrete corresponding to the standard value of uniaxial tensile strength; is the initial elastic modulus of concrete.

[0136] S7, fatigue failure is judged according to the simulation results obtained in S6, if the ballastless track is fatigue failure, the simulation is stopped; if it is not failure, the train running time t is increased, and step S6 is repeated until the ballastless track reaches the design service life or the fatigue failure state;

[0137] According to the concrete fatigue failure criterion and the steel fatigue failure criterion, the fatigue failure of concrete and steel after fatigue loading N times is judged respectively, if failure occurs, the simulation is stopped; if it is not failure, the fatigue loading times N is increased (the train running time t is increased), and the parameters in the plastic constitutive model are further updated, and the simulation is carried out again according to step S7 to judge whether fatigue failure occurs; so on and so forth, until the concrete structure of the ballastless track reaches the design service life or the fatigue failure state.

[0138] The expression of the concrete compressive fatigue failure criterion is as formula (7.1):

[0139] (7.1)

[0140] wherein, is the residual compressive strain of concrete; is the initial compressive strength of concrete; is the initial elastic modulus of concrete.

[0141] The expression of the steel fatigue failure criterion is as formula (7.2):

[0142] (7.2)

[0143] wherein, is the maximum stress of steel after fatigue loading N times, which is directly obtained from the simulation results; The equivalent fatigue residual tensile strength of the steel bar after N times of fatigue loading.

[0144] According to the train operation cycle collected in step S1, the number of train operations in a year is calculated. The time span is selected according to the research accuracy requirement. It is suggested that the time span is at least 2 years in the rapid development period of the crack in the first ten years, and the time span is 5 years or 10 years in the stable development period after ten years. The number of cyclic loadings in each adjustment is determined according to the time span, and steps S6, S7 and S8 are repeated. Before each adjustment of the number of cyclic loadings, it is judged whether fatigue failure occurs in the current concrete and steel bar. If one of them occurs, the calculation is stopped.

[0145] It is assumed that the number of fatigue load cycles N0 of the ballastless track per year is 300,000 times in the embodiment, that is, the number of fatigue load cycles N0 of the ballastless track per year is 300,000 times, and that the simulation time step is 5 years, that is, the train operation time t is 5 years. The increment of the number of fatigue load cycles N is 30*5 million times. The number of fatigue loadings N is started from 0 and increased by 1.5 million times each time, that is, N1=1.5 million times, N2=1.5*2 million times, and so on. The number of fatigue loadings N in each simulation is substituted into the performance degradation curves of the concrete and the steel bar to obtain the physical parameters of the material after performance degradation, and the obtained physical parameters are updated to the ballastless track model considering the temperature effect. With the increase of the number of simulations, the train operation time t (unit: year) gradually increases. The train operation time t can also be selected according to an arithmetic sequence. The time span is generally 1 year to 10 years. For example, the time span is 2 years, t=2, 4, 6. For example, the time span is 5 years, t=5, 10, 15. The larger the time span, the fewer the simulation times, but the lower the prediction accuracy. The smaller the time span, the higher the prediction accuracy, but the more the simulation times. In the embodiment, t=1, 2, 3, 4, 6, 10, 20, 30, 40, 50, 60. There are 10 simulations.

[0146] Figure 4 It is the stress nephogram of the ballastless track slab after 20 years in the embodiment. In the embodiment, when the train operation time t is 60 years, that is, the number of fatigue load cycles N0 is 45 million times, the concrete reaches the fatigue failure state, and the subsequent simulation is stopped.

[0147] It should be noted that although the concrete structure has a tension phenomenon, and a concrete tension constitutive model is used to describe this phenomenon in the numerical simulation process, the concrete has weak tension capacity, and engineering design often makes the concrete mainly bear pressure rather than tension stress, so as to avoid the first tension failure, make the compression failure appear before the tension failure, and thus maximize the advantages of the concrete. Therefore, the compression failure is mainly considered when judging the fatigue failure.

[0148] S8, define the ratio of the crack area of the non-ballasted track in a certain cross section to the cross section area as the fatigue damage ratio; according to all the simulation results obtained in S7, the crack area of the concrete structure under different fatigue loading times N is obtained, and the fatigue damage ratio development time-varying curve is fitted according to the fatigue damage ratio under different fatigue loading times N, and the fatigue damage of the non-ballasted track concrete structure is predicted according to the obtained curve.

[0149] With the increase of the fatigue loading times N, the strain of the concrete structure gradually increases, and in the finite element software ABAQUS, there is a parameter that can measure the relationship between the strain of the concrete and the development of the non-ballasted track crack, which is the stiffness degradation rate, when the stiffness degradation rate reaches 1, it indicates that the part of the concrete is cracked due to fatigue damage. For example, as shown in Figure 5 , Figure 5 is the crack cloud map of a certain cross section of the non-ballasted track after simulating the train operation for 2 years in the embodiment, at this time, the stiffness degradation rate of the non-ballazed track at a certain place reaches 0.72, which is close to 1, indicating that the place is about to crack. Then, by investigating the area of the region where the stiffness degradation rate of a certain cross section of the non-ballazed track reaches 1 in the simulation results, the total crack area is obtained by dividing the cross section area of the non-ballazed track, and the fatigue damage ratio is obtained. According to the damage conditions of the non-ballazed track obtained by the simulation experiment, the cross section with the largest crack of the track plate is taken as the criterion, the crack area to cross section area ratio is used to describe the damage degree, and the track plate damage ratio-time curve is drawn to guide the practice. Figure 6 is the fatigue damage ratio-time varying curve of a certain cross section of the non-ballazed track plate, as shown in the figure, the crack of the track plate develops rapidly at the initial stage of service, and the crack degree of the track plate tends to be stable after 10 years of service.

[0150] In the process of simulation for a certain specific working condition, the temperature load needs to be obtained according to the actual environmental temperature load suffered by the non-ballazed track under the working condition, and the temperature load varies with different regions. The actual size of the temperature load can be determined according to the relevant specifications in the art.

[0151] After predicting the fatigue damage of the non-ballazed track concrete structure, the engineering design can be guided, and the non-ballazed track structure design can be adjusted to meet the operation requirements of the 400km / h+ high-speed train, so as to ensure the stability and safety of the high-speed train in the long-term service state. When adjusting the non-ballazed track structure design, the parameters such as the strength, thickness of the concrete, the strength, diameter and spacing of the steel bars are considered. By using the method of the present application, the fatigue damage ratio development time-varying curve of the concrete structure under a certain design working condition can be obtained with fewer simulation times, and even if the non-ballazed track structure design is adjusted, the simulation and prediction can be completed in a short time, which takes into account the prediction efficiency and prediction accuracy.

[0152] The above examples are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit and essence of the present application shall be covered within the protection scope of the present application.

Claims

1. A fatigue damage prediction method for a high-speed railway ballastless track with a speed of 400 km+, characterized in that: The method comprises the following steps: S1, a running speed of a 400km / h+ high-speed train is given, a train cycle of the 400km / h+ high-speed train is estimated according to a marshalling condition and a train cycle of an existing high-speed train, and a fatigue loading number N0 of the ballastless track per year is obtained according to the train cycle; S2, parameters of the ballastless track and parameters of the train are collected, and a ballastless track model and a train model in a static state are established by using a finite element software; S3, the train model is simulated to run on the ballastless track model once according to the given running speed, initial simulation loading is performed, and upper and lower limits of fatigue tensile and compressive stresses of the concrete structure and upper and lower limits of fatigue stresses of the steel bar are obtained; S4, the parameters obtained in S3 are substituted into a concrete performance degradation curve model and a steel bar performance degradation curve model to obtain the concrete performance degradation curve and the steel bar performance degradation curve; S5, a temperature load is applied to the ballastless track in the ballastless track model in the static state, and deformation of the ballastless track is obtained through numerical simulation; the obtained deformation is applied to another ballastless track model in the static state as an initial condition, stress and strain distribution of the concrete structure and the steel bar is obtained through numerical simulation, and a ballastless track model considering the temperature effect is obtained; S6, a fatigue loading number N=tN0 is obtained according to N0 and a train running time t, the fatigue loading number N is substituted into the performance degradation curve obtained in S4 to obtain physical parameters of the concrete and the steel bar after fatigue loading N times; the concrete and the steel bar are simulated by using a plastic constitutive model, the obtained physical parameters are input into the ballastless track model considering the temperature effect in S5, parameters in the plastic constitutive model are updated, and stress and strain distribution of the concrete structure and the steel bar is obtained through numerical simulation; S7, fatigue failure is judged according to the simulation result obtained in S6, if the ballastless track fails, the simulation is stopped, and if the ballastless track does not fail, the train running time t is increased, and step S6 is repeated until the ballastless track reaches a design service life or a fatigue failure state; S8, a ratio of a crack area to a cross-sectional area of the ballastless track in a certain cross section is defined as a fatigue damage ratio, the simulation result obtained in S7 is used to obtain crack areas of the concrete structure of the ballastless track at different N, and then a fatigue damage ratio development time curve is fitted according to the fatigue damage ratios at different N, and fatigue damage of the concrete structure of the ballastless track is predicted according to the obtained curve.

2. The fatigue damage prediction method for a 400 km / h+ high-speed railway ballastless track according to claim 1, characterized in that: In S2, the parameters of the ballastless track include geometric parameters, an initial elastic modulus, a Poisson's ratio, a linear expansion coefficient, a cylinder compressive strength, an axial tensile strength, a density of the concrete structure, and an initial tensile yield strength of the steel bar; and the parameters of the train include one-system suspension parameters, two-system suspension parameters, and masses and moments of inertia of a car body, a frame and a wheel set.

3. The fatigue damage prediction method for a 400 km / h+ high-speed railway ballastless track according to claim 1, characterized in that: In S4, the concrete performance degradation curve model includes a concrete stiffness degradation curve model and a strength degradation curve model, and the strength degradation curve model includes a compressive strength degradation curve model and a tensile strength degradation curve model; an expression of the concrete stiffness degradation curve model is as formula (4.1): （4.1） wherein: E N is the modulus of elasticity of the concrete after N cycles of fatigue loading; N is the number of fatigue loading cycles; E0is the initial modulus of elasticity of the concrete; N f is the fatigue life of the concrete, N f is obtained from the S-N f curve of the concrete; an expression of the concrete compressive strength degradation curve model is as formula (4.4): （4.4） In the formula: is the fatigue residual compressive strength of the concrete after N times of fatigue loading; is the initial compressive strength of the concrete; is the maximum compressive stress generated by the concrete during the initial simulation loading; v is a constant related to the fatigue stress level; The expression of the concrete tensile strength degradation curve model is as shown in formula (4.5): （4.5） In the formula: is the fatigue residual tensile strength of the concrete after N times of fatigue loading; is the correction coefficient of the fatigue residual tensile strength of the concrete; is the initial tensile strength of the steel bar; a and b are the fatigue tensile test constants of the concrete.

4. The fatigue damage prediction method for a 400 km / h+ high-speed railway ballastless track according to claim 1, characterized in that: In S4, the expression of the steel strength degradation curve model is as shown in formula (4.6): （4.6） In the formula, is the equivalent fatigue residual tensile strength of the steel bar after N fatigue loadings. N is the number of loading times of fatigue load; is the fatigue life of steel bar, which is obtained from the S- curve of steel bar; is the initial tensile yield strength of steel bar; is the stress upper limit when loading for the first time.

5. The fatigue damage prediction method for a 400 km / h+ high-speed railway ballastless track according to claim 1, characterized in that: In S6, the train operation time t is selected according to a time span of 1-10 years.

6. The fatigue damage prediction method for a 400 km / h+ high-speed railway ballastless track according to claim 1, characterized in that: In S6, the physical parameters include the elastic modulus, the fatigue residual compressive strength, the fatigue residual tensile strength of the concrete and the equivalent fatigue residual tensile strength of the steel after fatigue loading N times.

7. The fatigue damage prediction method for a 400 km / h+ high-speed railway ballastless track according to claim 1, characterized in that: In S6, the expression of the plastic constitutive model of the concrete under compression is as shown in formula (6.1)-(6.5): （6.1） （6.2） （6.3） （6.4） （6.5） In the formula: is a correction factor; represents a shape parameter of the descending section of the uniaxial compressive strain curve; , respectively represent the fatigue residual compressive strength and the corresponding peak compressive strain of the concrete after fatigue loading N times; is the residual compressive strain of the concrete after fatigue loading N times; wherein The expression of (6.6) is as formula (6.6): （6.6） wherein: is the compressive strain of the concrete after N cycles of fatigue loading; , are the upper and lower limits of the compressive stress in the concrete during N cycles of fatigue loading, respectively; is the elastic modulus of the concrete under compression after N cycles of fatigue loading; wherein According to equation (6.7) we obtain: （6.7） wherein: is the compressive strain of the concrete when fatigue loaded N times; is the peak compressive strain of the concrete corresponding to the standard value of uniaxial compressive strength, is the initial elastic modulus of the concrete.

8. The fatigue damage prediction method for a 400 km / h+ high-speed railway ballastless track according to claim 1, characterized in that: In S6, the expression of the plastic constitutive model of the concrete under tension is as shown in formula (6.9)-(6.12): （6.9） （6.10） （6.11） （6.12） In the formula: is a correction factor; represents a shape parameter of the descending section of the uniaxial tensile strain curve; , respectively represent the fatigue residual tensile strength and the corresponding peak tensile strain of the concrete after fatigue loading N times; is the residual tensile strain of the concrete after fatigue loading N times; wherein The expression of (6.13) is as formula (6.13): （6.13） wherein: is the tensile strain of the concrete after N cycles of fatigue loading; , are the upper and lower stress limits of the tensile region of the concrete during N cycles of fatigue loading, respectively; is the elastic modulus of the tensile concrete after N cycles of fatigue loading. wherein According to equation (6.14) we obtain: （6.14） In the formula: is the tensile strain of the concrete after N cycles of fatigue loading; is the peak tensile strain of the concrete corresponding to the standard value of uniaxial tensile strength; is the initial elastic modulus of the concrete.

9. The fatigue damage prediction method for a 400 km / h+ high-speed railway ballastless track according to claim 1, characterized in that: In S7, the expression of the concrete compression fatigue failure criterion is as shown in formula (7.1): （7.1）； wherein: is the residual compressive strain of the concrete; is the initial compressive strength of the concrete; is the initial elastic modulus of the concrete; The expression of the steel fatigue failure criterion is as shown in formula (7.2): （7.2）； In the formula: is the maximum stress of the steel bar after N times of fatigue loading, which is directly obtained from the simulation results; is the equivalent fatigue residual tensile strength of the steel bar after N times of fatigue loading.

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