A method for predicting fatigue life of pantograph frame

Abstract

The present invention provides a method for predicting the fatigue life of a pantograph frame, which relates to the technical field of life prediction, and aims to solve the technical problems of inaccurate prediction of the service life of a pantograph frame and large errors in the prior art. The method for predicting the fatigue life of a pantograph frame comprises the following steps: establishing a structural stress model of the pantograph frame; obtaining a dangerous point stress time history according to the structural stress model; obtaining a dangerous point equivalent stress amplitude and the number of cycles of the dangerous point equivalent stress amplitude according to the dangerous point stress time history; obtaining a dangerous point equivalent stress probability density function of the pantograph frame according to the dangerous point equivalent stress amplitude and the number of cycles of the dangerous point equivalent stress amplitude; predicting the fatigue life of the pantograph frame according to the dangerous point equivalent stress probability density function and the material SN curve of the pantograph frame.

Description

Technical Field

[0001] The present invention relates to the technical field of life prediction, and in particular to a method for predicting fatigue life of a pantograph frame. Background Art

[0002] The pantograph is installed on rail vehicles such as electric locomotives or electric vehicles. The pantograph is an electrical device that obtains current from one or more contact wires or receiving rails. The pantograph generally consists of three parts: the pantograph head, the frame and the transmission device. The pantograph head is installed on the frame, and then the frame is fixed on the roof through insulators. The transmission device controls the pantograph raising and lowering process by connecting to the frame.

[0003] As an important component of a rail vehicle, the service life of a pantograph has a significant impact on the normal operation of the rail vehicle. In the prior art, a program spectrum combined with an SN curve is usually used to predict and analyze the service life of a pantograph frame.

[0004] However, the above method is inaccurate and has large errors. Based on this, not only can the service life of the pantograph frame not be accurately predicted, but also the normal operation of the rail vehicle will be affected. Summary of the invention

[0005] The object of the present invention is to provide a method for predicting the fatigue life of a pantograph frame, which is used to accurately predict the service life of the pantograph frame and improve the safety of rail vehicle operation.

[0006] In order to achieve the above object, the present invention provides a method for predicting the fatigue life of a pantograph frame. The method for predicting the fatigue life of a pantograph frame comprises the following steps:

[0007] Establish the structural stress model of the pantograph frame;

[0008] Obtain the stress time history of the dangerous point according to the structural stress model;

[0009] According to the stress-time history of the dangerous point, the equivalent stress amplitude of the dangerous point and the number of cycles of the equivalent stress amplitude of the dangerous point are obtained;

[0010] According to the equivalent stress amplitude at the dangerous point and the number of cycles of the equivalent stress amplitude at the dangerous point, the probability density function of the equivalent stress at the dangerous point of the pantograph frame is obtained;

[0011] The fatigue life of the pantograph frame is predicted based on the probability density function of equivalent stress at the dangerous point and the material SN curve of the pantograph frame.

[0012] Compared with the prior art, in the pantograph frame fatigue life prediction method provided by the present invention, a continuous spectrum is obtained using the above-mentioned dangerous point equivalent stress probability density function, that is, the above-mentioned steps can be used to obtain a continuous spectrum for predicting the fatigue life of the pantograph frame. Compared with the program block spectrum used in the prior art, the continuous spectrum can more accurately and comprehensively reflect information such as the dangerous point equivalent stress of the pantograph frame. At this time, the fatigue life of the pantograph frame predicted by the above-mentioned continuous spectrum and the material SN curve of the pantograph frame is more accurate than the prior art. Furthermore, the safe operation time of the rail vehicle using the pantograph can also be accurately predicted, so as to facilitate the timely maintenance and replacement of the pantograph, thereby improving the safety of rail vehicle operation.

[0013] In one implementation, the influencing factors of the structural stress model include the structural force and aerodynamic load on the pantograph frame, and the aerodynamic load is the resultant force of the positive wind load and the cross wind load. The structural stress model includes a positive wind model and a cross wind model.

[0014] When the above technical solution is adopted, there are many factors that affect the force change of the pantograph frame during actual application. For example, the structural force and aerodynamic load on the pantograph will affect the force of the pantograph frame. The present invention comprehensively considers the influence of structural force and aerodynamic load on the force of the pantograph, and analyzes the force change of the pantograph in multiple dimensions, which can more accurately simulate and analyze the force change of the pantograph frame during actual application, and then more accurately predict the fatigue life of the pantograph frame.

[0015] In one implementation, the structural stress model satisfies the following equation:

[0016]

[0017] [σ]=[D][B][y];

[0018] Where [M] represents the mass matrix; [C] represents the damping matrix; [K] represents the stiffness matrix; [y] represents the node displacement, represents the node speed, Column vector representing the node acceleration; [F r ] represents the pantograph frame under structural force and aerodynamic load F l The node load matrix under comprehensive action; [D] represents the elastic matrix; [B] represents the geometric matrix; [σ] represents the pantograph frame node stress matrix.

[0019] The positive wind model includes: the air flow is at an equal speed in the opposite direction to the pantograph running speed Around the pantograph, the inlet velocity is the mainstream velocity The outlet is standard atmospheric pressure.

[0020] The above crosswind model includes: crosswind with crosswind speed Around the pantograph, the crosswind direction is perpendicular to the pantograph running direction. The crosswind model satisfies the following equation:

[0021]

[0022] Among them, V ω (d) represents the crosswind speed at a height of d meters; V(10) represents the crosswind speed at a reference height of 10 meters; Represents the ground roughness coefficient related to the geographical environment.

[0023] According to the equation satisfied by the detached vortex simulation method, the three-dimensional airflow velocity component v of the pantograph is obtained i ; According to the three-dimensional airflow velocity component v of the pantograph i , and obtain the aerodynamic load F on the pantograph l ;.

[0024] According to the equation satisfied by the detached vortex simulation method, the three-dimensional airflow velocity component v of the pantograph is obtained i The steps include:

[0025] The detached eddy simulation method based on the Menter k-ωSST turbulence model is used to numerically simulate the flow field in the forward and crosswind directions to obtain the three-dimensional airflow velocity component v of the pantograph. i ; Wherein, the pantograph is set to be stationary and the ground is set to move.

[0026] The detached eddy simulation method based on the Menter k-ωSST turbulence model satisfies the following equation:

[0027]

[0028]

[0029] Where t represents time; ρ represents air density; k represents turbulent kinetic energy; x i represents the direction coordinate, i=1, 2, 3, respectively representing the three-dimensional direction of the pantograph; v i represents the airflow velocity component; P represents the turbulence generation term; β represents the first empirical constant; σ k represents the second empirical constant; σ ω2 represents the third empirical constant; σ ω represents the fourth empirical constant; γ represents the fifth empirical constant; ω represents the turbulence specific dissipation rate; F1 represents the distance from the vortex to the wall boundary, which takes a value of 0 to 1; μ1 represents the laminar viscosity coefficient; μ2 represents the eddy viscosity coefficient.

[0030] The aerodynamic load F on the pantograph is lSatisfies the following equation:

[0031] F l =0.5ρSV 2 ;

[0032]

[0033] Among them, ρ represents the air density; S represents the frontal area of ​​the pantograph frame; V represents the composite wind speed.

[0034] In one implementation, obtaining the stress time history of the dangerous point according to the structural stress model includes:

[0035] Obtain stress information of the pantograph frame according to the structural stress model;

[0036] The stress information is analyzed to obtain the stress time history of the dangerous point.

[0037] In one implementation, the method of obtaining the stress information of the pantograph frame according to the structural stress model is finite element analysis.

[0038] When the above technical solution is adopted, the finite element analysis method can integrate the structure and flow field into one, that is, the structural force and aerodynamic load on the pantograph can be integrated using large-scale general finite element analysis software to accurately calculate the stress on the pantograph frame, and then obtain the stress information of the pantograph frame.

[0039] In one implementation, obtaining the equivalent stress amplitude at the dangerous point and the number of cycles of the equivalent stress amplitude at the dangerous point according to the stress time history at the dangerous point includes:

[0040] According to the stress time history of the dangerous point, the stress amplitude of the dangerous point and the number of cycles of the stress amplitude of the dangerous point are obtained;

[0041] The GOODMAN equation is used to process the stress amplitude at the dangerous point and the number of cycles of the stress amplitude at the dangerous point to obtain the equivalent stress amplitude at the dangerous point and the number of cycles of the equivalent stress amplitude at the dangerous point.

[0042] In one implementation, the method of obtaining the stress amplitude of the dangerous point and the number of cycles of the stress amplitude of the dangerous point according to the stress time history of the dangerous point is a rain flow counting method.

[0043] When the above technical solution is adopted, on the one hand, the stress-strain hysteresis loop of the material plasticity of the pantograph frame can be associated with the amplitude and number of cycles of the stress it is subjected to by using the rain flow counting method, and the statistical counting results are more consistent with the fatigue mechanism characteristics of the pantograph material, providing a basis for accurately predicting the fatigue life of the pantograph frame. On the other hand, statistical counting using the rain flow counting method is simpler and more convenient, which improves the efficiency of predicting the fatigue life of the pantograph frame.

[0044] In one implementation, obtaining the probability density function of the dangerous point equivalent stress of the pantograph frame according to the dangerous point equivalent stress amplitude and the number of cycles of the dangerous point equivalent stress amplitude includes:

[0045] The Gaussian kernel density estimation method is used to process the critical point equivalent stress amplitude and the number of cycles of the critical point equivalent stress amplitude to obtain the critical point equivalent stress probability density function.

[0046] When the above technical solution is adopted, on the one hand, since the Gaussian kernel density estimation method has good smoothing characteristics, at this time, the probability density function of the equivalent stress at the dangerous point obtained by the Gaussian kernel density estimation method is more accurate. Based on this, the fatigue life of the pantograph frame is predicted more accurately by combining the probability density function of the equivalent stress at the dangerous point with the material SN curve of the pantograph frame. On the other hand, the above Gaussian kernel density estimation method is a non-parametric estimation method, which is more conducive to accurately obtaining the probability density function of the equivalent stress at the dangerous point compared to the parameter estimation method in the prior art, and thus is conducive to accurately predicting the fatigue life of the pantograph frame.

[0047] In one implementation, the probability density function of the hazardous point equivalent stress satisfies the following equation:

[0048]

[0049] Among them, σ f represents the random variable of equivalent stress at the dangerous point; σ i represents the samples of equivalent stress at the dangerous point obtained; n represents the number of equivalent stress samples at the dangerous point; h represents the given bandwidth.

[0050] The pantograph frame node stress matrix [σ] is processed to obtain σ f .

[0051] In one implementation, the fatigue life of the pantograph frame satisfies the following equation:

[0052]

[0053] Among them, σ r represents the fatigue limit of the pantograph frame material; σ max Indicates the maximum value of the equivalent stress amplitude at the dangerous point; P(σ f ) represents the stress probability density function of the pantograph frame; m and C represent the parameters in the power function expression of the material SN curve of the pantograph frame; T represents the fatigue life of the pantograph frame; σ f Represents the random variable of equivalent stress at the critical point.

[0054] The power function expression of the material SN curve of the pantograph frame satisfies the following equation:

[0055] S m ×N=C;

[0056] Among them, m and C are parameters related to material properties, specimen form, stress ratio and loading method.

[0057] When the above technical solution is adopted, the fatigue life of the pantograph frame can be accurately and quickly predicted using the equation satisfied by the fatigue life of the pantograph frame, thereby ensuring the normal operation of the rail vehicle using the pantograph and improving the safety of the rail vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0059] Figure 1 It is a flow chart of a method for predicting fatigue life of a pantograph frame in an embodiment of the invention;

[0060] Figure 2 It is a schematic diagram of the structure of the pantograph in an embodiment of the invention.

[0061] Reference numerals:

[0062] 1-upper arm, 2-lower arm, 3-pull rod, 4-bow head, 5-base. DETAILED DESCRIPTION

[0063] In order to clearly describe the technical solutions of the embodiments of the present invention, in the embodiments of the present invention, words such as "first" and "second" are used to distinguish the same items or similar items with basically the same functions and effects. For example, the first threshold and the second threshold are only used to distinguish different thresholds, and their order is not limited. Those skilled in the art can understand that words such as "first" and "second" do not limit the quantity and execution order, and words such as "first" and "second" do not necessarily limit them to be different.

[0064] It should be noted that, in the present invention, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0065] In the present invention, "at least one" means one or more, and "plurality" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, the combination of a and b, the combination of a and c, the combination of b and c, or the combination of a, b and c, where a, b, c can be single or multiple.

[0066] The pantograph is installed on rail vehicles such as electric locomotives or electric vehicles. The pantograph is an electrical device that obtains current from one or more contact wires or receiving rails. The pantograph generally consists of three parts: the pantograph head, the frame and the transmission device. The pantograph head is installed on the frame, and then the frame is fixed on the roof through insulators. The transmission device controls the pantograph raising and lowering process by connecting to the frame.

[0067] As an important component of a rail vehicle, the service life of a pantograph has a significant impact on the normal operation of the rail vehicle. In the prior art, a program spectrum combined with an SN curve is usually used to predict and analyze the service life of a pantograph frame.

[0068] However, the above method is inaccurate and has large errors. Based on this, not only can the service life of the pantograph frame not be accurately predicted, but also the normal operation of the rail vehicle will be affected.

[0069] In order to solve the above technical problems, an embodiment of the present invention provides a method for predicting fatigue life of a pantograph frame.

[0070] See also Figure 1 , the pantograph frame fatigue life prediction method includes the following steps:

[0071] Step 101: Establish a structural model of the pantograph frame;

[0072] Exemplarily, the structural model of the pantograph frame is established according to the actual pantograph frame. For example, a three-dimensional pantograph model is established in three-dimensional software according to the pantograph structure design to obtain the structural model of the pantograph frame.

[0073] Step 102: Establishing a structural stress model of the pantograph frame;

[0074] Exemplarily, the structural model of the pantograph frame is imported into the finite element software (ANSYS), and the pantograph material parameters are added, the grid is divided, constraints are added, and loads are applied in the finite element software. The above loads may include structural forces such as the pantograph-net contact force, gravity, lifting torque, hinge point force, positive wind flow field, and cross wind flow field. By applying a force (i.e., load) to the structural model of the pantograph frame, the actual stress condition of the pantograph frame during actual use is simulated, so as to provide a data basis for the later prediction of the fatigue life of the pantograph frame.

[0075] For details, see Figure 2 The above structural forces may include the gravity G1 of the upper arm 1, the gravity G2 of the lower arm 2, the gravity G3 of the pull rod 3, the gravity G4 of the bow head 4, the resultant force F acting on the bow head 4 by the contact network, and the inertial force F generated by the structure when the pantograph vibrates. dyn , lifting moment T, hinge point force F at hinge point A x2 、F y2 , hinge point force F at hinge point B x1 、F y1 , A and B are the hinge points between the pull rod 3 and the base 5, and the lower arm 2 and the base 5 respectively. The aerodynamic load F acting on the pantograph by the positive wind flow field and the cross wind flow field l The above V is the speed of the pantograph in the running direction. α is the angle between the upper arm 1 and the horizontal line, and δ is the angle between the lower arm 2 and the horizontal line.

[0076] Step 103: Obtain the stress time history of the dangerous point according to the structural stress model;

[0077] Step 104: obtaining the equivalent stress amplitude of the dangerous point and the number of cycles of the equivalent stress amplitude of the dangerous point according to the stress time history of the dangerous point;

[0078] Step 105: obtaining a probability density function of equivalent stress at a dangerous point of the pantograph frame according to the equivalent stress amplitude at the dangerous point and the number of cycles of the equivalent stress amplitude at the dangerous point;

[0079] Step 106: predict the fatigue life of the pantograph frame according to the probability density function of equivalent stress at the dangerous point and the SN curve of the material of the pantograph frame.

[0080] In the pantograph frame fatigue life prediction method provided by the embodiment of the present invention, a continuous spectrum is obtained using the above-mentioned danger point equivalent stress probability density function, that is, the above-mentioned steps can be used to obtain a continuous spectrum for predicting the fatigue life of the pantograph frame. Compared with the program block spectrum used in the prior art, the continuous spectrum can more accurately and comprehensively reflect information such as the danger point equivalent stress of the pantograph frame. At this time, the fatigue life of the pantograph frame predicted by the above-mentioned continuous spectrum and the material SN curve of the pantograph frame is more accurate than the prior art. Furthermore, the safe operation time of the rail vehicle using the pantograph can also be accurately predicted, so as to facilitate the timely maintenance and replacement of the pantograph, thereby improving the safety of the rail vehicle operation. In addition, since the fatigue life prediction of the pantograph frame is more accurate, it can provide a guiding basis for the early fatigue design and later safe operation of the pantograph frame.

[0081] As a possible implementation, the influencing factors of the structural stress model include the structural force and aerodynamic load on the pantograph frame, and the aerodynamic load is the resultant force of the positive wind load and the cross wind load. The structural stress model includes a positive wind model and a cross wind model.

[0082] In actual application, there are many factors that affect the force changes of the pantograph frame. For example, the pantograph structural force (such as pantograph-net contact force, gravity, lifting torque, hinge point force, etc.) and aerodynamic loads will affect the force of the pantograph frame. The present invention comprehensively considers the influence of the pantograph-net contact force, gravity, lifting torque, hinge point force and aerodynamic load on the force of the pantograph, and analyzes the force changes of the pantograph in multiple dimensions. It can more accurately simulate and analyze the force changes of the pantograph frame in actual application, and then more accurately predict the fatigue life of the pantograph frame.

[0083] In one implementation, the structural stress model satisfies the following equation:

[0084]

[0085] [σ]=[D][B][y];

[0086] Where [M] represents the mass matrix; [C] represents the damping matrix; [K] represents the stiffness matrix; [y] represents the node displacement, represents the node speed, Column vector representing the node acceleration; [F r ] represents the pantograph frame under structural force and aerodynamic load F l The node load matrix under comprehensive action; [D] represents the elastic matrix; [B] represents the geometric matrix; [σ] represents the pantograph frame node stress matrix.

[0087] Specifically, the structural forces on the pantograph frame include the above-mentioned G1, G2, G3, G4, F, T, F dyn , F x2 , F y2 , F x1 , F y1 For details, please refer to the previous description and will not be repeated here.

[0088] The positive wind model includes: the air flow is at an equal speed in the opposite direction to the pantograph running speed Around the pantograph, the inlet velocity is the mainstream velocity The outlet pressure is standard atmospheric pressure. Figure 2 , The numerical value of is consistent with the numerical value of the pantograph's operating speed V.

[0089] The above crosswind model includes: crosswind with crosswind speed Around the pantograph, the crosswind direction is perpendicular to the pantograph running direction. The crosswind model satisfies the following equation:

[0090]

[0091] Among them, V ω (d) represents the crosswind speed at a height of d meters; V(10) represents the crosswind speed at a reference height of 10 meters; Represents the ground roughness coefficient related to the geographical environment.

[0092] It should be understood that by constructing a headwind model and a crosswind model, the effects of the headwind load and the crosswind load on the pantograph during the actual movement of the pantograph can be analyzed.

[0093] According to the equation satisfied by the detached vortex simulation method, the three-dimensional airflow velocity component v of the pantograph is obtained. i ; According to the three-dimensional airflow velocity component v of the pantograph i Obtain the aerodynamic load F on the pantograph l .

[0094] According to the equation satisfied by the detached vortex simulation method, the three-dimensional airflow velocity component v of the pantograph is obtained i The steps include:

[0095] The relative motion method is used to simulate the pantograph's positive and negative flow fields, which are both steady-state compressible flow fields. Specifically, the Menter k-ωSST turbulence model-based detached eddy simulation method is used to perform numerical simulation calculations on the positive and negative flow fields to obtain the pantograph's three-dimensional airflow velocity component v i ; Wherein, the pantograph is set to be stationary and the ground is set to move.

[0096] The detached eddy simulation method based on the Menter k-ωSST turbulence model satisfies the following equation:

[0097]

[0098]

[0099] Where t represents time; ρ represents air density; k represents turbulent kinetic energy; x i represents the direction coordinate, i=1, 2, 3, respectively representing the three-dimensional direction of the pantograph; v i represents the airflow velocity component; P represents the turbulence generation term; β represents the first empirical constant; σ k represents the second empirical constant; σ ω2 represents the third empirical constant; σ ω represents the fourth empirical constant; β represents the fifth empirical constant; ω represents the turbulence specific dissipation rate; F1 represents the distance from the vortex to the wall boundary, which takes a value of 0 to 1; μ1 represents the laminar viscosity coefficient; μ2 represents the eddy viscosity coefficient.

[0100] The aerodynamic load F on the pantograph is l Satisfies the following equation:

[0101] F l =0.5ρSV 2 ;

[0102]

[0103] Among them, ρ represents the air density; S represents the flow area of ​​the pantograph frame (specifically, the impact on the pantograph frame rods); V represents the composite wind speed.

[0104] As a possible implementation, step 103: obtaining the stress time history of the dangerous point according to the structural stress model specifically includes:

[0105] Step 103.1: Obtain stress information of the pantograph frame according to the structural stress model;

[0106] In an example, the method of obtaining the stress information of the pantograph frame according to the structural stress model and obtaining the stress time history of the dangerous point according to the structural stress model may be finite element analysis.

[0107] The above-mentioned finite element analysis method can integrate the structure and flow field into one, that is, the structural force and aerodynamic load on the pantograph can be integrated using large-scale general finite element analysis software to accurately calculate the stress on the pantograph frame, and then obtain the stress information of the pantograph frame and the stress time history of the dangerous point.

[0108] For example, the stress information of each position in the pantograph frame can be obtained through the above structural stress model. The above stress information includes the magnitude of the stress value and the number of stress cycles at the same position in the pantograph frame at different times and in different scenarios.

[0109] Step 103.2: Analyze the stress information to obtain the stress time history of the critical point.

[0110] For example, the stress values ​​at various positions in the pantograph frame can be compared with a preset threshold value to obtain several positions with larger stress values, and then determine them as dangerous points in the pantograph frame. Alternatively, finite element software can be used to analyze the positions in the pantograph frame that are significantly deformed due to stress, and then determine them as dangerous points in the pantograph frame. Then, the stress time history of the dangerous point at the dangerous point is obtained to facilitate subsequent analysis.

[0111] In a possible implementation, step 104: obtaining the equivalent stress amplitude of the dangerous point and the number of cycles of the equivalent stress amplitude of the dangerous point according to the stress time history of the dangerous point specifically includes:

[0112] Step 104.1: Obtain the stress amplitude of the dangerous point and the number of cycles of the stress amplitude of the dangerous point according to the stress time history of the dangerous point;

[0113] In an example, the method of obtaining the stress amplitude of the dangerous point and the number of cycles of the stress amplitude of the dangerous point according to the stress time history of the dangerous point may be a rain flow counting method.

[0114] When the above technical solution is adopted, on the one hand, the stress-strain hysteresis loop of the material plasticity of the pantograph frame can be associated with the amplitude and number of cycles of the stress it is subjected to by using the rain flow counting method, and the statistical counting results are more consistent with the fatigue mechanism characteristics of the pantograph material, providing a basis for accurately predicting the fatigue life of the pantograph frame. On the other hand, statistical counting using the rain flow counting method is simpler and more convenient, which improves the efficiency of predicting the fatigue life of the pantograph frame.

[0115] Step 104.2: Use the GOODMAN equation to process the stress amplitude at the dangerous point and the number of cycles of the stress amplitude at the dangerous point to obtain the equivalent stress amplitude at the dangerous point and the number of cycles of the equivalent stress amplitude at the dangerous point.

[0116] As a possible implementation, step 105: obtaining the probability density function of the dangerous point equivalent stress of the pantograph frame according to the dangerous point equivalent stress amplitude and the number of cycles of the dangerous point equivalent stress amplitude specifically includes:

[0117] The Gaussian kernel density estimation method is used to process the critical point equivalent stress amplitude and the number of cycles of the critical point equivalent stress amplitude to obtain the critical point equivalent stress probability density function.

[0118] When the above technical solution is adopted, on the one hand, since the Gaussian kernel density estimation method has good smoothing characteristics, the probability density function of the equivalent stress at the dangerous point obtained by the Gaussian kernel density estimation method is more accurate. Based on this, the fatigue life of the pantograph frame is predicted more accurately by combining the probability density function of the equivalent stress at the dangerous point with the SN curve of the material of the pantograph frame.

[0119] On the other hand, the above-mentioned Gaussian kernel density estimation method is a non-parametric estimation method. Compared with the parameter estimation method in the prior art, it is more conducive to accurately obtaining the probability density function of the equivalent stress at the dangerous point, and thus is conducive to accurately predicting the fatigue life of the pantograph frame. Specifically, for the equivalent stress on the dangerous point of the pantograph frame, the model that the above-mentioned dangerous point equivalent stress data conforms to cannot be determined in advance. If the parameter estimation method in the prior art is adopted, that is, a model is first assumed and then the assumed model is tested and calculated to finally obtain the probability density function of the equivalent stress at the dangerous point. The parameter estimation method in the prior art is too cumbersome, time-consuming and labor-intensive, and prone to errors, which can easily lead to large errors in the fatigue life of the pantograph frame that is finally predicted. Therefore, the present invention adopts the Gaussian kernel density estimation method, a non-parametric estimation method, to obtain the probability density function of the equivalent stress at the dangerous point.

[0120] In one example, the above-mentioned probability density function of equivalent stress at the dangerous point satisfies the following equation:

[0121]

[0122] Among them, σ f represents the random variable of equivalent stress at the dangerous point; σ i represents each sample of equivalent stress at the dangerous point obtained; n represents the number of samples of equivalent stress at the dangerous point; h represents the given bandwidth;

[0123] The pantograph frame node stress matrix [σ] is processed to obtain σ f .

[0124] For example, the pantograph frame node stress matrix [σ] can be analyzed and processed using the rain flow counting method, the GOODMAN equation, and the Gaussian kernel density estimation method to obtain the dangerous point equivalent stress random variable σ f The specific processing method can be referred to the previous description, which will not be repeated here.

[0125] As a possible implementation, step 106: predicting the fatigue life of the pantograph frame according to the probability density function of the equivalent stress at the dangerous point and the SN curve of the material of the pantograph frame specifically includes:

[0126] The probability density function of the equivalent stress at the dangerous point P(σ f ) is combined with the material SN curve of the pantograph frame to predict the fatigue life of the pantograph frame.

[0127] The fatigue life of the above pantograph frame satisfies the following equation:

[0128]

[0129] Among them, σ r represents the fatigue limit of the pantograph frame material; σ max Indicates the maximum value of the equivalent stress amplitude at the dangerous point; P(σ f ) represents the stress probability density function of the pantograph frame; m and C represent the parameters in the power function expression of the material SN curve of the pantograph frame; T represents the fatigue life of the pantograph frame; σ f Represents the random variable of equivalent stress at the critical point.

[0130] The power function expression of the material SN curve of the pantograph frame satisfies the following equation:

[0131] S m ×N=C;

[0132] Among them, m and C are parameters related to material properties, specimen form, stress ratio and loading method.

[0133] The fatigue life of the pantograph frame can be accurately and quickly predicted by using the equation satisfied by the fatigue life of the pantograph frame, thereby ensuring the normal operation of the rail vehicle using the pantograph and improving the safety of the rail vehicle.

[0134] In addition, a pantograph frame fatigue life prediction device can also be made according to the above pantograph frame fatigue life prediction method. The pantograph frame fatigue life prediction device includes: a processor and a communication interface coupled to the processor. The processor is used to run a computer program or instruction, the pantograph frame fatigue life prediction method described in the above technical solution. As for the processor and the communication interface, they can be set and selected according to actual conditions, and no specific limitation is made here. Furthermore, a chip can also be made according to the above pantograph frame fatigue life prediction method. Instructions are stored in the chip, and when the instructions are executed, the pantograph frame fatigue life prediction method described in the above technical solution is executed.

[0135] Although the present invention is described herein in conjunction with various embodiments, in the process of implementing the claimed invention, those skilled in the art may understand and implement other variations of the disclosed embodiments by viewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "one" or "an" does not exclude multiple situations. A single processor or other unit may implement several functions listed in the claims. Certain measures are recorded in different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

[0136] Although the present invention has been described in conjunction with specific features and embodiments thereof, it is apparent that various modifications and combinations may be made thereto without departing from the spirit and scope of the present invention. Accordingly, this specification and the accompanying drawings are merely exemplary illustrations of the present invention as defined by the appended claims and are deemed to cover any and all modifications, variations, combinations or equivalents within the scope of the present invention. Obviously, those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, the present invention is intended to include such modifications and variations if they fall within the scope of the claims of the present invention and their equivalents.

Claims

1. A method for predicting fatigue life of a pantograph frame, characterized in that: Establish the structural stress model of the pantograph frame; Obtaining the stress time history of the dangerous point according to the structural stress model; Obtaining the equivalent stress amplitude of the dangerous point and the number of cycles of the equivalent stress amplitude of the dangerous point according to the stress time history of the dangerous point; Obtaining a probability density function of the dangerous point equivalent stress of the pantograph frame according to the dangerous point equivalent stress amplitude and the number of cycles of the dangerous point equivalent stress amplitude; Predicting the fatigue life of the pantograph frame according to the probability density function of equivalent stress at the dangerous point and the SN curve of the material of the pantograph frame; Obtaining the probability density function of the dangerous point equivalent stress of the pantograph frame according to the dangerous point equivalent stress amplitude and the number of cycles of the dangerous point equivalent stress amplitude includes: The Gaussian kernel density estimation method is used to process the equivalent stress amplitude of the dangerous point and the number of cycles of the equivalent stress amplitude of the dangerous point to obtain the probability density function of the equivalent stress of the dangerous point; The probability density function of equivalent stress at the dangerous point satisfies the following equation: ； in, represents the random variable of equivalent stress at the dangerous point; Indicates the samples of equivalent stress at dangerous points obtained; Indicates the sample size of equivalent stress at the dangerous point; Indicates a given bandwidth; The stress matrix of the pantograph frame node Process to obtain ; The fatigue life of the pantograph frame satisfies the following equation: ； in, Indicates the fatigue limit of the pantograph frame material; Indicates the maximum value of the equivalent stress amplitude at the dangerous point; represents a stress probability density function of the pantograph frame; , Representing the parameters in the power function expression of the material SN curve of the pantograph frame; Indicates the fatigue life of the pantograph frame; represents the random variable of equivalent stress at the dangerous point; The power function expression of the material SN curve of the pantograph frame satisfies the following equation: ； Among them, m and C are parameters related to material properties, specimen form, stress ratio and loading method.

2. The method for predicting fatigue life of a pantograph frame according to claim 1, characterized in that: The influencing factors of the structural stress model include structural forces and aerodynamic loads on the pantograph frame; The aerodynamic load is the combined force of the positive wind load and the cross wind load; The structural stress model includes a headwind model and a crosswind model.

3. The method for predicting fatigue life of a pantograph frame according to claim 2, characterized in that: The structural stress model satisfies the following equation: ； ； in, represents the mass matrix; represents the damping matrix; represents the stiffness matrix; represents the node displacement, represents the node speed, Column vector representing the node acceleration; Represents the pantograph frame under structural force and aerodynamic load Nodal load matrix under comprehensive action; represents the elasticity matrix; represents a geometric matrix; represents the pantograph frame node stress matrix; The positive wind model includes: The air flow is at an equal speed in the opposite direction to the pantograph operating speed. The flow around the pantograph is at the mainstream velocity. , the outlet is standard atmospheric pressure; The crosswind model includes: Crosswind speed The crosswind direction of the pantograph is perpendicular to the running direction of the pantograph; the crosswind model satisfies the following equation: ； in, express Crosswind speed at meter height; They represent the crosswind speed at a reference height of 10 meters respectively; Indicates the ground roughness coefficient related to the geographical environment; According to the equations satisfied by the detached vortex simulation method, the three-dimensional airflow velocity components of the pantograph are obtained. ; According to the three-dimensional airflow velocity component of the pantograph , obtain the aerodynamic load on the pantograph ; According to the equations satisfied by the detached vortex simulation method, the three-dimensional airflow velocity components of the pantograph are obtained. The steps include: Based on The detached eddy simulation method of the turbulence model is used to perform numerical simulation calculations on the positive wind flow field and the cross wind flow field to obtain the three-dimensional airflow velocity component of the pantograph. ; Wherein, the pantograph is assumed to be stationary and the ground is assumed to be moving; based on The detached eddy simulation method of the turbulence model satisfies the following equation: ； ； in, Indicates time; Indicates the air density; represents turbulent kinetic energy; represents the direction coordinate, , respectively represent the three-dimensional directions of the pantograph; represents the air flow velocity component; represents the turbulence generation term; represents the first empirical constant; represents the second empirical constant; represents the third empirical constant; represents the fourth empirical constant; represents the fifth empirical constant; represents the turbulence specific dissipation rate; Indicates the distance from the vortex to the wall boundary, with a value of 0~1; represents the laminar viscosity coefficient; represents the eddy viscosity coefficient; The aerodynamic load on the pantograph Satisfies the following equation: ； ； in, Indicates the air density; It represents the flow area of ​​the pantograph frame; Indicates the resultant wind speed.

4. The method for predicting fatigue life of a pantograph frame according to claim 1, characterized in that: The obtaining of the stress time history of the dangerous point according to the structural stress model comprises: Obtaining stress information of the pantograph frame according to the structural stress model; The stress information is analyzed to obtain the stress time history of the dangerous point.

5. The method for predicting fatigue life of a pantograph frame according to claim 4, characterized in that: The method of obtaining the stress information of the pantograph frame according to the structural stress model is finite element analysis.

6. The method for predicting fatigue life of a pantograph frame according to claim 1, characterized in that: The equivalent stress amplitude of the dangerous point and the number of cycles of the equivalent stress amplitude of the dangerous point are obtained according to the stress time history of the dangerous point, including: Obtaining the stress amplitude of the dangerous point and the number of cycles of the stress amplitude of the dangerous point according to the stress time history of the dangerous point; The stress amplitude at the dangerous point and the number of cycles of the stress amplitude at the dangerous point are processed by using the GOODMAN equation to obtain the equivalent stress amplitude at the dangerous point and the number of cycles of the equivalent stress amplitude at the dangerous point.

7. The method for predicting fatigue life of a pantograph frame according to claim 6, characterized in that: The method of obtaining the stress amplitude of the dangerous point and the number of cycles of the stress amplitude of the dangerous point according to the stress time history of the dangerous point is the rain flow counting method.

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