A bogie structure design method based on modal stress

Abstract

The application discloses a bogie structure design method based on modal stress, comprising the following steps: obtaining the distribution section and length of a line track bed and a damping fastener; installing a vibration accelerometer, collecting data of the vibration accelerometer; analyzing the axle box vibration acceleration of a bogie to be tested; establishing a finite element model; obtaining the modal frequency, modal vibration mode and modal stress of the bogie; checking the modal frequency of each order of the bogie until the modal frequency of each order of the bogie does not satisfy a judgment formula; checking the modal vibration mode and the modal stress of each order of the bogie; and until there is no obvious modal stress concentration phenomenon in each order of the bogie. The application eliminates local modal stress concentration through bogie structure improvement, so that the overall modal stress level is low; the service life of the bogie is prolonged, the failure probability of the bogie is reduced, the bogie has better line adaptability, and the operation and maintenance cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of railway vehicle bogie technology, and more specifically, to a bogie structure design method based on modal stress. Background Technology

[0002] Abnormal local failures may occur in the bogie frame of subway vehicles during line operation. These failures are impossible to occur under normal standard loads.

[0003] When a vehicle is running on the track, the wheel-rail contact force exhibits two peak values: P1 force (greater than 500Hz) and P2 force (typically between 30-100Hz), which are used as indicators of the strength of the vertical dynamic action between the wheel and rail. P2 force is the response force generated by the unsprung weight due to the elastic vibration of the track caused by P1 force. Its duration is longer than that of P1 force, and it can propagate directly to the under-rail components, causing greater damage to track deformation and the under-rail foundation, thus leading to abnormal track vibration.

[0004] Abnormal vibrations in the track can induce local modal resonance in the vehicle's bogie frame, leading to local modal stress concentration and subsequent failure. Therefore, a bogie frame structural design method based on modal stress is needed to reduce the stress when the bogie frame experiences local modal resonance, thereby reducing or preventing structural failure.

[0005] Currently, the understanding of structural modes in the field of railway vehicle bogie technology, both domestically and internationally, is mostly limited to the level of displacement modes, with very little understanding of structural modal stress. Structural design also remains at the level of static load design, and the concept of dynamic load design based on modal stress has not been widely adopted; while modal stress refers to the stress distribution of a structure under dynamic loads at a specific vibration mode.

[0006] Existing bogie frame structural designs are all based on static loads, without considering the stress of the frame under certain mode vibrations under the dynamic loads of the track. This can lead to the failure of the frame structure in actual track operation due to local modal stress concentration.

[0007] There are currently no effective solutions to the problems in the relevant technologies. Summary of the Invention

[0008] In view of the problems in the related technologies, the present invention proposes a bogie structure design method based on modal stress to overcome the above-mentioned technical problems existing in the existing related technologies.

[0009] Therefore, the specific technical solution adopted by the present invention is as follows:

[0010] A bogie structure design method based on modal stress, comprising the following steps:

[0011] S1. Obtain the distribution sections and lengths of the track bed and the distribution sections and lengths of the vibration damping fasteners;

[0012] S2. Install a vibration accelerometer for vibration acceleration testing on the axle box of the bogie to be tested, operate it normally according to the rail vehicle's operating route diagram, and collect data from the vibration accelerometer.

[0013] S3. Analyze the axle box vibration acceleration of the bogie to be tested based on the distribution sections of the track bed and the distribution sections of the vibration damping fasteners.

[0014] S4. Establish a finite element model of the bogie frame used on the operating line, simulate large mass equipment with mass points and establish a connection relationship with the frame;

[0015] S5. Perform modal calculations on the frame to obtain the modal frequencies, mode shapes, and modal stresses of the frame;

[0016] S6. Check the modal frequencies of each order of the structure. If the modal frequencies meet the judgment formula, it means that the structure is at risk of resonance with the line P2 force, and the modal frequencies can be changed by changing the structure of the structure.

[0017] S7. Repeat steps S4-S6 until the modal frequencies of each order of the architecture do not meet the judgment formula.

[0018] S8. Check the mode shapes and modal stresses of the structure at each order;

[0019] S9. Repeat steps S4-S8 until there is no obvious modal stress concentration in each mode of the framework.

[0020] Furthermore, the time-domain signal of the axle box vibration acceleration of the bogie under test is a continuous-time non-periodic signal, and the acquired values ​​are discrete sampled values ​​of the continuous signal.

[0021] Furthermore, the analysis of the axle box vibration acceleration of the bogie under test based on the distribution sections of the track bed and the distribution sections of the vibration damping fasteners also includes performing Fourier transform on the discrete sampled values ​​of the acquired continuous signal to obtain the time-frequency value of the vibration acceleration.

[0022] Furthermore, the formula for calculating the Fourier transform of the discrete sampled values ​​of the acquired continuous signal is as follows:

[0023]

[0024] Where x(n) represents the discrete sampled value of the time-domain continuous signal of the axle box vibration acceleration;

[0025] N represents the number of discrete sampling points, and n = 0, 1, ..., N-1;

[0026] k represents the number of vibration cycles in the sampling time domain;

[0027] W N This represents the k-th harmonic component.

[0028] Furthermore, the k-th harmonic component W N The calculation formula is:

[0029]

[0030] Where e represents the base of the natural logarithm function, and e = 2.71828182…;

[0031] j represents the imaginary unit, which is equal to the square root of -1.

[0032] Furthermore, the finite element model of the steering frame used on the operating line is established using Hypemesh software.

[0033] Furthermore, the modal calculation of the framework also includes solving for the natural frequencies and natural mode shapes of the multi-degree-of-freedom system.

[0034] Furthermore, changing the modal frequency by altering the frame structure includes changing the weight or center of gravity of the large-mass equipment, changing the width of the connection between the frame's side beams, changing the box-shaped cross-section dimensions of the frame's side beams, changing the box-shaped cross-section dimensions of the frame's cross beams, and changing the weight of the end structure of the side beams.

[0035] Furthermore, the process of examining the modal vibration modes and modal stresses of the framework also includes optimizing the framework structure to eliminate modal stress concentration if the stress level in the modal stress concentration region exceeds 40 MPa.

[0036] Furthermore, the optimization of the framework structure to eliminate modal stress concentration includes:

[0037] Structural adjustments were made to the internal stiffening plates of the crossbeams in the area of ​​the large-mass equipment hoisting seat in the frame.

[0038] The original integral casting type of large-mass equipment lifting base was cancelled, and a large-mass equipment lifting base made of forgings and welded plates was adopted.

[0039] Increase the width of the crossbeam connections in the frame, increase the weld burrs in the load-bearing parts, and increase the plate thickness.

[0040] The beneficial effects of this invention are as follows:

[0041] 1. The bogie structure design method based on modal stress of the present invention is a supplement to the existing bogie frame structure design that only considers static load. It can evaluate the frame structure in multiple dimensions and shorten the cycle of bogie structure optimization design.

[0042] 2. The bogie structure designed and optimized by the present invention based on the modal stress-based bogie structure design method avoids modal resonance between the structure and the P2 force of the line. The structure improvement eliminates local modal stress concentration, resulting in a low overall modal stress level. This can extend the service life of the structure, reduce the failure probability of the structure, make the structure more adaptable to the line, and reduce operation and maintenance costs. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a time-domain plot of vibration acceleration test data of the bogie under test in a bogie structure design method based on modal stress according to an embodiment of the present invention;

[0045] Figure 2 This is a time-frequency diagram of P2 force in a bogie structure design method based on modal stress according to an embodiment of the present invention;

[0046] Figure 3 This is a local modal stress cloud diagram of a large-mass equipment in a bogie structure design method based on modal stress according to an embodiment of the present invention;

[0047] Figure 4 This is an optimized local modal stress cloud map of a large-mass equipment in a bogie structure design method based on modal stress according to an embodiment of the present invention;

[0048] Figure 5 This is a flowchart of a bogie structure design method based on modal stress according to an embodiment of the present invention. Detailed Implementation

[0049] To further illustrate the various embodiments, the present invention provides accompanying drawings, which are part of the disclosure of the present invention. These drawings are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these drawings, those skilled in the art should be able to understand other possible implementation methods and the advantages of the present invention. The components in the drawings are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0050] According to an embodiment of the present invention, a bogie structure design method based on modal stress is provided.

[0051] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments, such as... Figure 5 As shown, the bogie structure design method based on modal stress according to an embodiment of the present invention includes the following steps:

[0052] S1. Obtain the distribution sections and lengths of the track bed and the distribution sections and lengths of the vibration damping fasteners;

[0053] S2. Install a vibration accelerometer for vibration acceleration testing on the axle box of the bogie to be tested (new wheels or after turning). Operate the bogie normally according to the rail vehicle's operating route diagram and collect data from the vibration accelerometer; Figure 1 As shown;

[0054] Specifically, the time-domain signal of the axle box vibration acceleration of the bogie under test is a continuous-time non-periodic signal, and the collected values ​​are discrete sampled values ​​of the continuous signal.

[0055] S3. Analyze the axle box vibration acceleration of the bogie to be tested based on the distribution sections of the track bed and the distribution sections of the vibration damping fasteners.

[0056] Specifically, the analysis of the axle box vibration acceleration of the bogie under test based on the distribution sections of the track bed and the distribution sections of the vibration damping fasteners also includes performing Fourier transform on the discrete sampled values ​​of the acquired continuous signal to obtain the time-frequency value of the vibration acceleration.

[0057] Specifically, the formula for calculating the Fourier transform of the discrete sampled values ​​of the acquired continuous signal is as follows:

[0058]

[0059] Where x(n) represents the discrete sampled value of the time-domain continuous signal of the axle box vibration acceleration;

[0060] N represents the number of discrete sampling points, and n = 0, 1, ..., N-1;

[0061] k represents the number of vibration cycles in the sampling time domain;

[0062] W N The k-th harmonic component is represented;

[0063] Specifically, the kth harmonic component W N The calculation formula is:

[0064]

[0065] Where e represents the base of the natural logarithm function, and e = 2.71828182…;

[0066] j represents the imaginary unit, which is equal to the square root of -1.

[0067] Specifically, such as Figure 2 As shown, the frequency Mi of P2 force was identified on the ordinary track bed + ZX2 vibration damping fastener (80-90s section);

[0068] S4. Establish a finite element model of the bogie frame used on the operating line, simulate large mass equipment with mass points and establish a connection relationship with the frame;

[0069] Specifically, the finite element model of the bogie frame used on the operating line is established using Hypemesh software;

[0070] Specifically, the finite element model of the bogie frame used on the line is established by using the Hypemesh software, that is, a solution domain representing a structure or continuum is discretized into several subdomains (elements), and they are connected into a composite body through the nodes on their boundaries;

[0071] Specifically, the unknown field variables to be solved in the solution domain are represented piecewise by the approximate function assumed within each unit; and the approximate function within each unit is expressed by the values ​​of the unknown field function (or its derivative) at each node of the unit and its corresponding interpolation function; since the field function has the same value at the nodes connecting adjacent units, they are used as the basic unknowns for numerical solution; thus, the problem of solving the original field function with infinite degrees of freedom is transformed into solving the field function with finite degrees of freedom at the node values.

[0072] By using variational principles or weighted residual methods equivalent to the original mathematical model, a system of algebraic equations or ordinary differential equations is established to solve the basic unknowns (nodal values ​​of field functions), i.e., the finite element solution equations, and expressed in normalized matrix form. Then, the equations are solved using the corresponding numerical methods to obtain the solution to the original problem.

[0073] S5. Perform modal calculations on the frame to obtain the modal frequencies, mode shapes, and modal stresses of the frame;

[0074] Specifically, the modal frequency is set between 1 and 100 Hz.

[0075] Specifically, the modal calculation of the framework also includes solving for the natural frequencies and natural mode shapes of the multi-degree-of-freedom system.

[0076] Specifically, a mode is the vibrational pattern of a multi-degree-of-freedom system when it vibrates at a certain inherent frequency; a mode shape is a certain proportional relationship between the displacements of various points in the system at this time; regardless of the damping condition, the response of a mechanical structure to external forces can be expressed as a superposition of various mode shapes composed of parameters such as the natural frequency, mode shape, and damping ratio; the differential equation of motion for a multi-degree-of-freedom system is:

[0077]

[0078] Where [M] represents the mass matrix;

[0079] [C] represents the damping matrix;

[0080] [K] represents the stiffness matrix;

[0081] {χ} and {χ} represent the acceleration, velocity, and displacement of a multi-degree-of-freedom system, respectively;

[0082] {F} represents the load vector.

[0083] Specifically, when solving for the natural frequencies and mode shapes of a multi-degree-of-freedom system, since the effect of structural damping on the modal frequencies and mode shapes is negligible, the free vibration equations of the multi-degree-of-freedom system can be simplified to:

[0084]

[0085]

[0086] Where {φ} represents the magnitude of the displacement vector;

[0087] Indicates angular frequency;

[0088] t represents time.

[0089] Therefore, based on the two formulas above, we can obtain... This holds true at any time t, and then removing the terms containing t yields...

[0090] The necessary and sufficient condition for a system of linear algebraic equations to have non-zero solutions:

[0091] By solving, a set of discrete roots can be obtained. Substitute into the formula From this, the corresponding vector φ can be obtained. i (i = 1, 2, ..., n), and φ i These are the structure's natural frequencies and corresponding mode shapes;

[0092] S6. Check the modal frequencies of each order of the structure. If the modal frequencies meet the judgment formula, it means that the structure is at risk of resonance with the line P2 force, and the modal frequencies can be changed by changing the structure of the structure.

[0093] The calculation formula for the judgment formula is as follows:

[0094]

[0095] Where Mj represents the modal frequency;

[0096] Mi represents the frequency of the P2 force;

[0097] Specifically, changing the modal frequency by altering the frame structure includes changing the weight or center of gravity of the large-mass equipment, changing the width of the connection between the frame's side beams, changing the box-shaped cross-section dimensions of the frame's side beams, changing the box-shaped cross-section dimensions of the frame's cross beams, and changing the weight of the end structure of the side beams.

[0098] S7. Repeat steps S4-S6 until the modal frequencies of each order of the architecture do not meet the judgment formula.

[0099] S8. Examine the mode shapes and modal stresses of the structure; pay special attention to the local modes of large-mass equipment (motors);

[0100] Specifically, such as Figure 3 As shown, the process of checking the mode shapes and modal stresses of the frame also includes optimizing the frame structure to eliminate modal stress concentration if the stress level in the modal stress concentration area exceeds 40 MPa.

[0101] Specifically, optimizing the framework structure to eliminate modal stress concentration includes:

[0102] Structural adjustments were made to the internal stiffening plates of the crossbeams in the area of ​​the large-mass equipment hoisting seat in the frame; this allows for smoother load transfer within the frame.

[0103] The original integral casting type of large-mass equipment hanger was replaced with a large-mass equipment hanger made of forgings and welded plates; this allows the rigidity of the large-mass equipment (motor) hanger to be better matched with the overall rigidity of the frame.

[0104] Increase the width of the crossbeam connections in the frame, increase the weld burrs in the load-bearing parts, and increase the plate thickness;

[0105] S9. Repeat steps S4-S8 until there is no obvious modal stress concentration in any mode of the framework. The optimized framework is as follows: Figure 4 As shown, there is no obvious modal stress concentration phenomenon, and the modal stress at the same location has decreased from 55.3MPa to 27.8MPa (less than 40MPa), a reduction of nearly half, and the optimization effect is significant.

[0106] Specifically, due to the differences in the distribution and length of the track bed and vibration damping fasteners on the urban rail vehicle operating lines, the bogie frame often experiences abnormal vibrations during vehicle operation, which can trigger local modal resonance. When designing the bogie frame structure, it is necessary to conduct modal frequency and modal stress analysis of the bogie frame structure for large-mass equipment, identify whether the structure will resonate with the P2 force frequency of the line, and identify whether there are high-risk areas of local modal stress concentration in the structure.

[0107] Specifically, the method in this invention can also be extended to other mechanical structures of rail vehicles, such as the car body, undercarriage suspension equipment, bogie equipment supports, etc.

[0108] In summary, by utilizing the above-mentioned technical solutions of this invention, the bogie structure design method based on modal stress is a supplement to the existing bogie frame structure design that only considers static loads. It can evaluate the frame structure in multiple dimensions and shorten the bogie structure optimization design cycle. The frame designed and optimized by the bogie structure design method based on modal stress avoids modal resonance between the frame structure and the track P2 force. The frame structure improvement eliminates local modal stress concentration, resulting in a low overall modal stress level. This can extend the service life of the frame, reduce the failure probability of the frame, give the frame better track adaptability, and reduce operation and maintenance costs.

[0109] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A bogie structure design method based on modal stress, characterized in that, The method includes the following steps: S1. Obtain the distribution sections and lengths of the track bed and the distribution sections and lengths of the vibration damping fasteners; S2. Install a vibration accelerometer for vibration acceleration testing on the axle box of the bogie to be tested, operate it normally according to the rail vehicle's operating route diagram, and collect data from the vibration accelerometer. S3. Analyze the axle box vibration acceleration of the bogie to be tested based on the distribution sections of the track bed and the distribution sections of the vibration damping fasteners. S4. Establish a finite element model of the bogie frame used on the operating line, simulate large mass equipment with mass points and establish a connection relationship with the frame; S5. Perform modal calculations on the frame to obtain the modal frequencies, mode shapes, and modal stresses of the frame; the modal calculations on the frame also include solving for the natural frequencies and mode shapes of the multi-degree-of-freedom system; S6. Check the modal frequencies of each order of the structure. If the modal frequencies satisfy the judgment formula, it indicates that the structure has a risk of resonance with the line P2 force, and the modal frequencies can be changed by changing the structure of the structure. The calculation formula of the judgment formula is as follows: Where Mj represents the modal frequency; Mi represents the frequency of the P2 force; S7. Repeat steps S4-S6 until the modal frequencies of each order of the architecture do not meet the judgment formula. S8. Check the mode shapes and modal stresses of the structure at each order; S9. Repeat steps S4-S8 until there is no obvious modal stress concentration in each mode of the framework.

2. The bogie structure design method based on modal stress according to claim 1, characterized in that, The time-domain signal of the axle box vibration acceleration of the bogie under test is a continuous-time non-periodic signal, and the collected values ​​are discrete sampled values ​​of the continuous signal.

3. The bogie structure design method based on modal stress according to claim 2, characterized in that, The analysis of the axle box vibration acceleration of the bogie under test based on the distribution sections of the track bed and the distribution sections of the vibration damping fasteners also includes performing Fourier transform on the discrete sampled values ​​of the acquired continuous signal to obtain the time-frequency value of the vibration acceleration.

4. The bogie structure design method based on modal stress according to claim 3, characterized in that, The formula for calculating the Fourier transform of the discrete sampled values ​​of the acquired continuous signal is as follows: in, Represents the discrete sampled values ​​of the time-domain continuous signal of axle box vibration acceleration; N represents the number of discrete sampling points, and n = 0, 1, ..., N-1; k represents the number of vibration cycles in the sampling time domain; This represents the k-th harmonic component.

5. The bogie structure design method based on modal stress according to claim 4, characterized in that, The kth harmonic component The calculation formula is: Where e represents the base of the natural logarithm function, and e = 2.71828182…; j represents the imaginary unit, which is equal to the square root of -1.

6. The bogie structure design method based on modal stress according to claim 1, characterized in that, The finite element model of the bogie frame used on the operating line was established using Hypemesh software.

7. The bogie structure design method based on modal stress according to claim 1, characterized in that, The method of changing modal frequencies by altering the frame structure includes changing the weight or center of gravity of the large-mass equipment, changing the width of the connection between the frame's side beams, changing the box-section dimensions of the frame's side beams, changing the box-section dimensions of the frame's cross beams, and changing the weight of the end structure of the side beams.

8. The bogie structure design method based on modal stress according to claim 1, characterized in that, The process of examining the modal vibration modes and modal stresses of the framework also includes optimizing the framework structure to eliminate modal stress concentration if the stress level in the modal stress concentration area exceeds 40 MPa.

9. The bogie structure design method based on modal stress according to claim 8, characterized in that, The optimization of the framework structure to eliminate modal stress concentration includes: Structural adjustments were made to the internal stiffening plates of the crossbeams in the area of ​​the large-mass equipment hoisting seat in the frame. The original integral casting type of large-mass equipment lifting base was cancelled, and a large-mass equipment lifting base made of forgings and welded plates was adopted. Increase the width of the crossbeam connections in the frame, increase the weld burrs in the load-bearing parts, and increase the plate thickness.

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