Vehicle fatigue analysis method based on VPG and modal stress recovery, analysis terminal and storage medium

Abstract

The invention provides a whole vehicle fatigue analysis method based on VPG and modal stress recovery, an analysis terminal and a storage medium, and belongs to the technical field of whole vehicle fatigue analysis. Configuring a vehicle body finite element model, and performing modal analysis to obtain a modal neutral file and a modal result file; coupling the modal neutral file with the vehicle dynamics model to generate a rigid-flexible coupling model; carrying out vehicle dynamics analysis by taking the actual test field virtual road surface as input, and outputting a modal coordinate file; stress recovery and fatigue life prediction are carried out based on a fatigue analysis algorithm, the equivalent fatigue stress of the whole vehicle body is obtained, and fatigue analysis of the vehicle body is completed in combination with an S-N curve. According to the method, the vibration relation between the external load frequency and the inherent frequency of the structure can be effectively considered, the more accurate fatigue life is further obtained, and the method has good application value in engineering.

Description

Technical Field

[0001] The present invention belongs to the technical field of vehicle fatigue analysis, and in particular relates to a vehicle fatigue analysis method based on VPG and modal stress recovery, an analysis terminal and a storage medium. Background Art

[0002] During the driving process of the car, due to reasons such as uneven road surface and tire dynamic imbalance, the parts are subjected to alternating dynamic loads for a long time. This alternating load is generally lower than the strength limit, but under its repeated action, it often leads to crack initiation and expansion, or even fracture (fatigue failure). Therefore, in the process of automobile research and development and manufacturing, fatigue life prediction becomes one of the main goals.

[0003] The traditional fatigue test method is to use a prototype vehicle to conduct road tests on a test track or road, which has a long cycle and high cost. The automotive industry generally uses quasi-static fatigue analysis methods to predict fatigue life. Although the quasi-static method has the advantages of simple process and high calculation efficiency, it cannot examine the dynamic characteristics of the structure.

[0004] The modes in the existing technology are the inherent characteristics of the structure itself. Which modes of the structure have a greater impact on its fatigue life, and which order of the structure has a greater impact on the fatigue of the structure, these issues are the key points that need to be considered in the fatigue analysis of the whole vehicle. To solve the above problems, fatigue life analysis must be performed based on the modes to analyze the impact of each mode on fatigue life. At this time, the quasi-static fatigue analysis method commonly used in the industry cannot consider the impact of the mode on fatigue damage. When the natural frequency of the structure is close to the external load frequency, the fatigue life cannot be accurately predicted. Summary of the invention

[0005] The present invention provides a whole vehicle fatigue analysis method based on VPG and modal stress recovery. The method can ensure the accuracy of fatigue life analysis and prediction when the natural frequency of the structure is close to the external load frequency, and can improve the reliability of fatigue analysis.

[0006] Methods include:

[0007] S101: Establish vehicle dynamics model;

[0008] S102: configuring a vehicle body finite element model, performing modal analysis to obtain a modal neutral file and a modal result file;

[0009] S103: coupling the modal neutral file with the vehicle dynamics model to generate a rigid-flexible coupling model;

[0010] S104: Perform vehicle dynamics analysis using the actual test field virtual road surface as input and output a modal coordinate file;

[0011] S105: Perform stress recovery and fatigue life prediction based on fatigue analysis algorithm to obtain equivalent fatigue stress of the vehicle body, and then complete fatigue analysis of the vehicle body in combination with SN curve.

[0012] S106: The fatigue equivalent stress is obtained through fatigue analysis and compared with the failure position of the actual vehicle in the test field. Overall, the fatigue analysis results of modal stress recovery are consistent with the reliability test results at the failure position. This analysis method has good application value in engineering.

[0013] It should be further explained that in step S103, the rigid-flexible coupling model includes: front and rear suspensions, a powertrain, tires, a steering system, a stabilizer bar, a rear leaf spring, a flexible body-mounted vehicle body, and a load system.

[0014] It should be further explained that the tires in the vehicle multi-body dynamics model in the method use the FTire tire model.

[0015] It should be further explained that in step S104, the elastic displacement is represented by a linear combination of the modal vector and the modal coordinates, the deformation motion is described by calculating the elastic displacement of the object at each moment, and the modal coordinates of the flexible body are obtained by multi-body dynamics simulation.

[0016] It should be further explained that step S105 also includes: the response of any point in the vehicle body is expressed as the product of each order modal value and the modal coordinate, that is, the linear superposition of the response generated at the position of each order mode, expressed as the following form:

[0017]

[0018] Where: q r (ω) is the r-order modal coordinate; is the r-order mode shape vector of point l.

[0019] It should be further explained that for N measuring points, the modal vibration vectors of each order form a column vector, which becomes the r-order modal vibration shape, and the formula is:

[0020]

[0021] The modal vibration shape and modal coordinates composed of each order modal vector are expressed as:

[0022]

[0023] It should be further explained that the modal stress σ is obtained based on the modal stress recovery algorithm in the method.

[0024] σ=QE σ (5)

[0025] Where Eσ is the modal stress matrix. The values ​​of each element in the modal stress matrix are related to the elastic modulus and Poisson's ratio of the material, and depend on the material properties assigned by the finite element model.

[0026] It should be further explained that the amplitude of the load and stress cycle in the method changes with time. When the material is subjected to cyclic stress, it is defined that each cycle will cause damage to the material. The value of the damage is 1 / N, and the damage is cumulative. The damage caused by n equal-amplitude loads is equal to its cycle ratio C = n / N, and the damage caused by variable-amplitude loads is equal to the sum of their cycle ratios, that is,

[0027]

[0028] Where l is the stress level of the variable amplitude load; n i is the fatigue life under the i-th load level.

[0029] According to another embodiment of the present application, an analysis terminal is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps of a vehicle fatigue analysis method based on VPG and modal stress recovery are implemented.

[0030] According to another embodiment of the present application, a storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps of the vehicle fatigue analysis method based on VPG and modal stress recovery are implemented.

[0031] It can be seen from the above technical solutions that the present invention has the following advantages:

[0032] The vehicle fatigue analysis method based on VPG and modal stress recovery provided by the present invention can perform vehicle fatigue analysis at the vehicle design stage through virtual prototyping technology and finite element analysis, avoiding the long period of time required for manufacturing physical prototypes and conducting actual vehicle tests in traditional methods, thereby speeding up the vehicle development process and reducing vehicle R&D costs.

[0033] This method combines multi-body dynamics simulation and finite element analysis, and can more accurately simulate the dynamic response and stress distribution of vehicles under complex road conditions. By coupling the modal neutral file with the vehicle dynamics model, a rigid-flexible coupling model that is closer to the actual working conditions is generated, thereby improving the accuracy of fatigue life prediction. Moreover, in the modal analysis, the vehicle body is treated as a flexible body, taking into account its deformation and vibration characteristics under dynamic loads. It also makes the fatigue analysis more comprehensive, can reveal potential fatigue failure areas, and provide strong support for structural optimization design.

[0034] The vehicle fatigue analysis method based on VPG and modal stress recovery provided by the present invention can discover potential fatigue problems through simulation in the early stage of vehicle design, which helps users to conduct troubleshooting and optimize design in a timely manner and improve product reliability and durability.

[0035] The method uses the virtual road surface of the actual test site as input for simulation analysis, making the fatigue analysis closer to the actual use scenario. The fatigue performance of the whole vehicle under different road conditions can be evaluated, providing a basis for the adaptive design and improvement of the whole vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solution of the present invention, the accompanying drawings required for use in the description will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0037] Figure 1 This is a flow chart of the vehicle fatigue analysis method based on VPG and modal stress recovery;

[0038] Figure 2 The flowchart of the embodiment of the vehicle fatigue analysis method based on VPG and modal stress recovery;

[0039] Figure 3 This is a schematic diagram of the rigid-flexible coupling model of the whole vehicle;

[0040] Figure 4 Schematic diagram of the modal coordinate history of the vehicle body. DETAILED DESCRIPTION

[0041] The specific implementation of the vehicle fatigue analysis method based on VPG and modal stress recovery provided by the present application is described in detail below. For the purpose of explanation rather than limitation, specific details such as specific system structures and technologies are proposed to facilitate a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application can also be implemented in other embodiments without these specific details.

[0042] It should be understood that when used in the present specification, the term "includes" indicates the presence of the described features, integral bodies, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integral bodies, steps, operations, elements, components and / or their collections. The terms "include", "comprise", "have" and their variations all mean "including but not limited to", unless otherwise specifically emphasized.

[0043] It should be understood that the "one or more" mentioned in this application refers to one, two or more than two, and the "multiple" mentioned in this application refers to two or more. In the description of this application, unless otherwise specified, " / " means or, for example, A / B can mean A or B. The "and / or" in this article is just a way to describe the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone.

[0044] In order to clearly describe the technical solution of the present application, the words "first", "second" and the like are used to distinguish the same or similar items with substantially the same functions and effects. Those skilled in the art can understand that the words "first", "second" and the like do not limit the quantity and execution order, and the words "first", "second" and the like do not necessarily limit the difference.

[0045] The phrases such as "one embodiment" or "some embodiments" described in the present application mean that the specific features, structures or characteristics described in the embodiment are included in one or more embodiments of the present application. Therefore, the phrases such as "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments" etc. that appear in different places in the present application do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways.

[0046] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] See also Figure 1 FIG. 1 is a flow chart of a vehicle fatigue analysis method based on VPG and modal stress recovery in a specific embodiment, the method comprising:

[0048] S101: Establish vehicle dynamics model.

[0049] In some embodiments of the present application, a whole vehicle dynamics model may be established using virtual prototyping technology.

[0050] Alternatively, multi-body dynamics software such as ADAMS and Simulink can be used to build a vehicle dynamics model. Specifically, the corresponding rigid body components can be created in the virtual prototype technology according to the vehicle's wheelbase, track width, mass distribution, center of mass position, and geometric shape, and the connection relationship between them can be set. According to the analysis needs, the accuracy of the model can also be verified. Here, the reliability of the model is ensured by comparing the simulation results with known experimental data or theoretical calculation values.

[0051] S102: configuring a vehicle body finite element model, and performing modal analysis to obtain a modal neutral file and a modal result file.

[0052] In some embodiments, a vehicle body finite element model is established by finite element software, and modal analysis is performed to obtain a modal neutral file (i.e., a flexible body file for establishing a rigid-flexible coupling model) and a modal result file.

[0053] As an example, finite element analysis software such as Hypermesh, SolidWorks Simulation, ANSYS, etc. can be used to perform geometric modeling and meshing on the car body.

[0054] This embodiment can define the physical properties of the material, such as elastic modulus, density, Poisson's ratio, etc., as well as fixed constraints, loads, etc., while modeling.

[0055] When performing modal analysis, this embodiment can solve the natural frequency and vibration mode of the vehicle body and generate a modal neutral file and a modal result file.

[0056] The modal neutral file in this embodiment includes the modal information of the vehicle body and necessary data of the flexible body, which is used for the subsequent establishment of the rigid-flexible coupling model.

[0057] S103: The modal neutral file is coupled with the vehicle dynamics model to generate a rigid-flexible coupling model.

[0058] In some embodiments, the modal neutral file is coupled with the vehicle dynamics model to generate a rigid-flexible coupling model of the vehicle.

[0059] Optionally, the rigid-flexible coupling model includes front and rear suspensions, a powertrain, tires, a steering system, a stabilizer bar, a rear leaf spring, a flexible body-mounted vehicle body, a load system, and an accessory system.

[0060] In order to ensure the accuracy requirements of the entire vehicle, nonlinear bushings and elastic damping elements are considered in the chassis elements, and a three-link leaf spring model is established for the rear suspension.

[0061] The tire of this embodiment is a component that transmits virtual road excitation, and a high-precision tire is required to present the load. Therefore, the tire uses the FTire tire model in the whole vehicle multi-body dynamics model.

[0062] S104: Perform vehicle dynamics analysis using the actual test site virtual road surface as input, and output a modal coordinate file.

[0063] In some embodiments, the actual test field virtual road surface is used as input for vehicle dynamics analysis, and a modal coordinate file is output. The modeling idea of ​​a flexible body is to give the flexible body a modal set, use a linear combination of modal vectors and modal coordinates to represent the elastic displacement, and describe its deformation motion by calculating the elastic displacement of the object at each moment, so the modal coordinates of the flexible body can be obtained through multi-body dynamics simulation.

[0064] In some specific embodiments, a virtual road surface file can be generated using road simulation software or a self-written program according to the road conditions of the actual test site. The virtual road surface file is loaded into the rigid-flexible coupling model of the whole vehicle as input to perform dynamic simulation analysis. During the simulation process, the dynamic response of the vehicle under different working conditions is recorded and analyzed, and key data such as the modal coordinate file is output.

[0065] S105: Perform stress recovery and fatigue life prediction based on fatigue analysis algorithm to obtain equivalent fatigue stress of the vehicle body, and then complete fatigue analysis of the vehicle body in combination with SN curve.

[0066] In an embodiment of the present invention, based on step S105, a possible embodiment is given below to illustrate its specific implementation scheme in a non-limiting manner.

[0067] In this embodiment, stress recovery and fatigue life prediction are performed by fatigue analysis software to obtain the equivalent fatigue stress of the vehicle body.

[0068] It can be understood that the response of any point in the vehicle body can be expressed as the product of each modal vibration shape and modal coordinates, that is, the linear superposition of the responses generated by each mode at this position.

[0069] That is: response = modal vibration shape × modal coordinates.

[0070] In this embodiment, the modal coordinates are weighted coefficients, which are the contribution of each mode to the response. Therefore, the response of any point in the system can be expressed as the product of each modal value and the modal coordinates, that is, the linear superposition of the responses generated by each mode at this position, which can be expressed as follows:

[0071]

[0072] Where: q r (ω) is the r-order modal coordinate; is the r-order mode shape vector of point l.

[0073] For N measuring points, the modal vibration vectors of each order can be combined into a column vector, which becomes the r-order modal vibration shape. The formula is:

[0074]

[0075] Then the modal vibration shape and modal coordinates composed of each order modal vector can be expressed as:

[0076]

[0077] The modal stress σ can be obtained by the modal stress recovery algorithm

[0078] σ=QE σ (5)

[0079] Where E σ is the modal stress matrix. The values ​​of each element in the matrix are related to the elastic modulus and Poisson's ratio of the material, and depend on the material properties assigned by the finite element model.

[0080] This embodiment can be benchmarked with the actual failure position of the vehicle body in the test field. The fatigue analysis method involved in this application is used to perform body fatigue analysis on a certain Van vehicle, and the equivalent fatigue stress is obtained, which is benchmarked with the failure position of the fatigue test of the actual vehicle in the test field to verify the feasibility of this fatigue analysis method.

[0081] Further, as a refinement and expansion of the specific implementation of the above embodiment, in order to fully illustrate the specific implementation process of this embodiment, as shown below Figure 2 and Figure 3 As shown, a specific implementation method of the vehicle fatigue analysis method based on VPG and modal stress recovery is provided in this application. The method specifically includes:

[0082] S201: Establish a vehicle dynamics model.

[0083] In this implementation, the multi-body dynamics software Adams Car can be used to establish the vehicle dynamics model.

[0084] S202: Analyze the vehicle body mode.

[0085] In some embodiments, the body solid model is meshed according to the three-dimensional solid digital model of the prototype vehicle, and then the body is subjected to modal analysis using OptiStruct to obtain an Adams modal neutral file and a modal result file.

[0086] S203: Establish a rigid-flexible coupling model of the entire vehicle.

[0087] like Figure 3As shown in the figure, it is a rigid-flexible coupling model of the whole vehicle. According to actual needs, the load-bearing body is modeled as a flexible body (that is, the modal neutral file obtained by modal analysis). The flexible body model of the body obtained by modal analysis is imported into the Adams Car environment, replacing the original corresponding rigid body parts. The remaining subsystems are treated as rigid bodies to establish a rigid-flexible coupling vehicle dynamics model.

[0088] S204: Output the modal coordinate file.

[0089] like Figure 4 As shown, the modal coordinate history of each order of the vehicle body is shown. This embodiment uses the whole vehicle simulation command in Adams Car to call the existing test field virtual road surface file that is consistent with the physical test, build a virtual test field (VPG) to simulate the whole vehicle virtual road test, and output the modal coordinate file that can be recognized by the subsequent fatigue analysis software through the output port of Adams.

[0090] S205: Perform fatigue life analysis.

[0091] In some specific embodiments, under normal driving conditions, fatigue failure of automobile components is mostly high-cycle fatigue damage. In the fatigue analysis software, modal stress recovery is performed based on the finite element modal analysis results and the modal coordinate history, and the fatigue analysis of the car body is completed in combination with the SN curve.

[0092] In actual engineering, the amplitude of load and stress cycles varies with time. When a material is subjected to cyclic stress, it is considered that each cycle will cause damage to the material. The damage value is 1 / N, and the damage can be accumulated. The damage caused by n equal-amplitude loads is equal to its cycle ratio C = n / N, and the damage caused by variable-amplitude loads is equal to the sum of their cycle ratios, that is,

[0093]

[0094] In formula (6), l is the stress level of variable amplitude load; n i is the fatigue life under the i-th level load. When the damage accumulation reaches the critical damage value, failure occurs.

[0095] S206: Execute simulation and test, and perform benchmarking.

[0096] Specifically, the simulation and test are benchmarked, and the benchmarking results can show that the fatigue analysis results of modal stress recovery and the reliability test results have good consistency in the failure position, providing a theoretical basis for the optimization and design of the vehicle body.

[0097] It can be seen that the analysis method based on modal stress recovery involved in this application can effectively consider the vibration relationship between the external load frequency and the natural frequency of the structure itself, thereby obtaining a more accurate fatigue life. This method has great application value in engineering.

[0098] The present application also provides an analysis terminal, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the steps of a vehicle fatigue analysis method based on VPG and modal stress recovery are implemented.

[0099] The shooting method provided in the embodiment of the present application can be applied to the analysis terminal. For example, the analysis terminal can be a mobile terminal (MT), a mobile station (MS), a mobile unit (MU), a wireless unit, a remote unit, a user agent, a mobile client, etc. For example, the analysis terminal can be a mobile phone, a smart screen device, a tablet computer, a wearable device, a digital camera, a vehicle-mounted device, an augmented reality (AR) device, a virtual reality (VR) device, a laptop computer, an ultra-mobile personal computer (UMPC), a netbook, a personal digital assistant (PDA), a laptop computer, etc., and the embodiment of the present application does not limit this.

[0100] The analysis terminal may include a processor, a memory, a universal serial bus interface, a wireless communication module, an audio module, a mouse and keyboard, a display screen, and a user identification module card interface.

[0101] It is understandable that the structure illustrated in the embodiment of the present application does not constitute a specific limitation on the analysis terminal. The processor may include one or more processing units, for example: the processor may include a central processing unit (CPU), an application processor (AP), a modem processor, a graphics processing unit (GPU), an image signal processor (ISP), a controller, a memory, a video codec, a digital signal processor (DSP), a baseband processor, and / or a neural-network processing unit (NPU), etc. Among them, different processing units may be independent devices or integrated in one or more processors.

[0102] The analysis terminal can realize the display function through a GPU, a display screen, and an application processor. The display screen is used to display images, videos, etc. The display screen includes a display panel.

[0103] The vehicle fatigue analysis method based on VPG and modal stress recovery provided by the present invention is a combination of the units and algorithm steps of each example described in the embodiments disclosed herein, and can be implemented by electronic hardware, computer software or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in terms of function in the above description. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0104] In the storage medium involved in this application, a program product capable of implementing the above method of this specification is stored. In some possible implementations, various aspects of the present disclosure can also be implemented in the form of a program product, which includes a program code. When the program product is run on a terminal device, the program code is used to enable the terminal device to execute the steps according to various exemplary implementations of the present disclosure described in the above "Exemplary Method" section of this specification.

[0105] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A vehicle fatigue analysis method based on VPG and modal stress recovery, characterized in that: Methods include: S101: Establish vehicle dynamics model; S102: configuring a vehicle body finite element model, performing modal analysis to obtain a modal neutral file and a modal result file; S103: coupling the modal neutral file with the vehicle dynamics model to generate a rigid-flexible coupling model; S104: Perform vehicle dynamics analysis using the actual test field virtual road surface as input and output a modal coordinate file; S105: Perform stress recovery and fatigue life prediction based on fatigue analysis algorithm to obtain equivalent fatigue stress of the vehicle body, and then complete fatigue analysis of the vehicle body in combination with SN curve.

2. The vehicle fatigue analysis method based on VPG and modal stress recovery according to claim 1 is characterized in that: In step S103, the rigid-flexible coupling model includes: front and rear suspensions, a powertrain, tires, a steering system, a stabilizer bar, a rear leaf spring, a flexible body-mounted vehicle body, and a load system.

3. The vehicle fatigue analysis method based on VPG and modal stress recovery according to claim 2 is characterized in that: The tire in the vehicle multibody dynamics model in the method uses the FTire tire model.

4. The vehicle fatigue analysis method based on VPG and modal stress recovery according to claim 1 is characterized in that: In step S104, elastic displacement is represented by a linear combination of modal vectors and modal coordinates, the deformation motion is described by calculating the elastic displacement of the object at each moment, and the modal coordinates of the flexible body are obtained by multi-body dynamics simulation.

5. The vehicle fatigue analysis method based on VPG and modal stress recovery according to claim 1 is characterized in that: Step S105 also includes: the response of any point in the vehicle body is expressed as the product of each order modal value and the modal coordinate, that is, the linear superposition of the response generated at the position of each order mode, expressed as follows: Where: qr(ω) is the r-order modal coordinate; is the r-order mode shape vector of point l.

6. The vehicle fatigue analysis method based on VPG and modal stress recovery according to claim 5 is characterized in that: For N measuring points, the modal vibration vectors of each order form a column vector, which becomes the r-order modal vibration shape. The formula is: The modal vibration shape and modal coordinates composed of each order modal vector are expressed as:

7. The vehicle fatigue analysis method based on VPG and modal stress recovery according to claim 6 is characterized in that: In this method, the modal stress σ is obtained based on the modal stress recovery algorithm. σ=QE σ (5) Where E σ is the modal stress matrix. The values ​​of each element in the modal stress matrix are related to the material elastic modulus and Poisson's ratio, and depend on the material properties assigned by the finite element model.

8. The vehicle fatigue analysis method based on VPG and modal stress recovery according to claim 1 or 2, characterized in that: The method is based on the change of the amplitude of the load and stress cycle over time. When the material is subjected to cyclic stress, it is defined that each cycle will cause damage to the material. The value of the damage is 1 / N, and the damage is cumulative. The damage caused by n times of equal amplitude load is equal to its cycle ratio C = n / N, and the damage caused by variable amplitude load is equal to the sum of its cycle ratios, that is, Where l is the stress level of the variable amplitude load; n i is the fatigue life under the i-th load level.

9. An analysis terminal, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps of the vehicle fatigue analysis method based on VPG and modal stress recovery as described in any one of claims 1 to 8 are implemented.

10. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the vehicle fatigue analysis method based on VPG and modal stress recovery as claimed in any one of claims 1 to 8 are implemented.

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