Fatigue life analysis method, device, equipment and medium for rear suspension lower support

Abstract

The application relates to a rear suspension lower support fatigue life analysis method and device, computer equipment, a storage medium and a computer program product. The method comprises the following steps: firstly, obtaining the relative torsion angle between a first main cross beam and a second main cross beam, the axial displacement of a spring shock absorber, three-directional acceleration of a suspension upper support and three-directional acceleration of a suspension lower support; then, pre-processing the obtained data; then, obtaining a first full-field time-domain stress and a first strain amplitude of the rear suspension lower support under a cab inertia load condition, a second full-field time-domain stress and a second strain amplitude of the rear suspension lower support under a vibration condition and a resonance response, and a third full-field time-domain stress and a third strain amplitude of the rear suspension lower support under a low-frequency torsion condition of a vehicle frame; and finally, analyzing the fatigue life of the rear suspension lower support according to the obtained stress and strain amplitude. The method provided by the application can accurately evaluate the actual fatigue life of the rear suspension lower support.

Description

Technical Field

[0001] This application relates to the field of reliable and durable technology, and in particular to a method, apparatus, computer equipment, storage medium, and computer program product for analyzing the fatigue life of a rear suspension underpin. Background Technology

[0002] For commercial vehicles, the primary function of the cab suspension is to transfer loads and dampen vibrations. The rear cab suspension bracket, in particular, is subjected not only to the inertial load of the cab on bumpy roads, but also, because it is fixed to the chassis, to bear additional loads from the torsional deformation of the chassis. Furthermore, the rear cab suspension bracket also supports vehicle components such as air filters or fuel filters, potentially leading to resonance due to the coupling of road excitation with the natural frequencies of these components. Under these complex load conditions, fatigue cracking of the lower rear cab suspension bracket frequently occurs in the product development process and during user operation of domestic OEMs.

[0003] Currently, CAE simulation technology is mainly used to analyze the fatigue cracking problem of the rear suspension lower bracket. For the load transmitted from the cab to the suspension bracket, empirical static loads are applied in the XYZ directions to evaluate the maximum static value or safety factor of the structure. For the load transmitted from the frame to the suspension bracket, under the condition of a complex finite element model of the whole vehicle, torsional displacement loads with fixed values ​​are applied to the front and rear axles to examine the structural safety factor. For the vibration problem caused by the components suspended on the suspension bracket, the industry mainly applies gravity field loads (commonly known as g-loads) or acceleration excitation based on power spectral density (PSD) to examine the structural stress response when resonance occurs. Since the responses generated by these different working conditions cannot be coupled or accumulated, it is impossible to accurately calculate and evaluate the actual fatigue life of the rear suspension lower bracket of the cab. Summary of the Invention

[0004] Therefore, it is necessary to provide a method, apparatus, computer equipment, computer-readable storage medium, and computer program product for analyzing the fatigue life of a rear suspension lower support, which can accurately evaluate the actual fatigue life of the rear suspension lower support, in order to address the above-mentioned technical problems.

[0005] In a first aspect, this application provides a method for fatigue life analysis of a rear-mounted lower support, the method comprising:

[0006] The relative torsional angle between the first and second main crossbeams and the axial displacement of the spring damper are obtained when the vehicle is driving on the test section. Based on the vehicle coordinate system, the three-way acceleration of the upper suspension bracket and the three-way acceleration of the lower suspension bracket are obtained when the vehicle is driving on the test section. The upper suspension bracket and the lower suspension bracket are connected by springs. The upper end of the upper suspension bracket is connected to the cab, and the lower end of the lower suspension bracket is connected to the vehicle frame. The first and second main crossbeams are the two main crossbeams of the vehicle frame directly below the cab. The second main crossbeam is close to the vehicle body.

[0007] Based on the actual vehicle speed, the preset vehicle speed, and the preset number of times the vehicle travels on the test section, the relative torsional angle, the axial displacement, the three-way acceleration of the upper suspension bracket, and the three-way acceleration of the lower suspension bracket are preprocessed respectively.

[0008] Based on the multibody dynamics model of the cab and suspension system, and the finite element model of the lower rear suspension bracket, the first full-field time-domain stress and the first strain amplitude of the lower rear suspension bracket under the cab inertial load condition are determined according to the first preset drive, the pre-processed axial displacement, the three-directional acceleration of the upper suspension bracket, and the three-directional acceleration of the lower suspension bracket.

[0009] Based on the finite element model and multibody dynamics model of the rear-suspension lower support, the second full-field time-domain stress and the second strain amplitude of the rear-suspension lower support under vibration conditions and resonance response are determined according to the second preset drive.

[0010] Based on the finite element model of the chassis, the third full-field time-domain stress and the third strain amplitude of the rear suspension under the low-frequency torsional condition of the chassis are determined according to the pre-processed relative torsion angle.

[0011] The fatigue life of the lower suspension bracket is analyzed based on the first full-field time-domain stress, the first strain amplitude, the second full-field time-domain stress, the second strain amplitude, the third full-field time-domain stress, and the third strain amplitude.

[0012] In one embodiment, the preprocessing of the relative torsional angle, the axial displacement, the three-directional acceleration of the upper suspension bracket, and the three-directional acceleration of the lower suspension bracket, based on the actual vehicle speed, the preset vehicle speed, and the preset number of times the vehicle travels on the test section, includes:

[0013] Based on the preset vehicle speed and the preset number of times, calculate the total pseudo-damage of the relative torsion angle, the axial displacement, the three-directional acceleration of the upper suspension bracket, and the three-directional acceleration of the lower suspension bracket each time the vehicle travels on the test section;

[0014] The median of all total pseudo-damages is determined as the target total pseudo-damage, and the relative torsional angle, axial displacement, three-directional acceleration of the upper suspension bracket, and three-directional acceleration of the lower suspension bracket corresponding to the target total pseudo-damage are determined as the target load spectrum signal.

[0015] Determine whether the difference between the actual vehicle speed corresponding to the target load spectrum signal and the preset vehicle speed is within the preset vehicle speed range. If the difference is not within the preset vehicle speed range, return to the steps of obtaining the relative torsional angle between the first main crossbeam and the second main crossbeam and the axial displacement of the spring damper when the vehicle is driving on the test section, and obtain the three-way acceleration of the upper suspension bracket and the three-way acceleration of the lower suspension bracket when the vehicle is driving on the test section based on the vehicle coordinate system, and continue to execute until the difference between the actual vehicle speed corresponding to the determined target load spectrum signal and the preset vehicle speed is within the preset vehicle speed range.

[0016] If the difference is within the preset vehicle speed range, then it is determined whether each parameter contained in the target load spectrum signal is within the corresponding first data range. If there are parameters that are not within the corresponding first data range, then the parameters that are not within the corresponding first data range are deleted.

[0017] If each parameter contained in the target load spectrum signal is within the corresponding first data range, then it is determined whether each parameter contained in the target load spectrum signal is within the corresponding second data range. If there is a parameter that is not within the corresponding second data range, then an alarm signal is issued. The alarm signal is used to indicate that the sensor measuring the corresponding parameter has malfunctioned or that the vehicle has malfunctioned. The upper limit of the second data range is less than the lower limit of the first data range.

[0018] In one embodiment, the multibody dynamics model based on the cab and suspension system, and the finite element model of the rear lower suspension bracket, determines the first full-field time-domain stress and the first strain amplitude of the rear lower suspension bracket under the cab inertial load condition based on the first preset drive, and the pre-processed axial displacement, the three-directional acceleration of the upper suspension bracket, and the three-directional acceleration of the lower suspension bracket, including:

[0019] Based on the preset start and end frequencies, the pre-processed axial displacement, the three-directional acceleration of the upper suspension bracket, and the three-directional acceleration of the lower suspension bracket are filtered to obtain the target signal;

[0020] White noise is determined based on the starting frequency and the preset boundary frequency, and pink noise is determined based on the boundary frequency and the termination frequency. The boundary frequency is greater than the starting frequency and less than the termination frequency. The white noise is a signal whose energy does not change with frequency, and the pink noise is a signal whose energy changes exponentially with frequency.

[0021] The white noise and the pink noise are input into the multibody dynamics model to obtain the frequency response function;

[0022] Based on the start frequency and the end frequency, and according to the first preset drive, it is determined whether the coherence of the frequency response function is greater than a preset coherence value;

[0023] If the coherence of the frequency response function is greater than the preset coherence value, then the target signal is input into the inverse function of the frequency response function to obtain the first driving signal;

[0024] Based on the multibody dynamics model and the finite element model, the first full-field time-domain stress and the first strain amplitude are determined according to the first driving signal and the preset weight value.

[0025] In one embodiment, after determining whether the coherence of the frequency response function is greater than a preset coherence value based on the start frequency and the end frequency, according to the target signal and the first preset drive, the method further includes:

[0026] If the coherence of the frequency response function is not greater than the preset coherence value, then the standard deviation of the white noise, the boundary frequency, and the curve exponent of the pink noise are adjusted. Based on the adjusted parameters, the step of inputting the white noise and the pink noise into the multibody dynamics model to obtain the frequency response function is returned and execution continues.

[0027] In one embodiment, determining the first full-field temporal stress and the first strain amplitude based on the multibody dynamics model and the finite element model, according to the first driving signal and a preset weight value, includes:

[0028] The first driving signal is input into the multibody dynamics model to obtain a response signal, which includes the three-directional acceleration of the upper suspension support, the three-directional acceleration of the lower suspension support, and the axial displacement.

[0029] According to the preset weight values, weights are assigned to each parameter contained in the target signal to obtain a weighted target signal, and weights are assigned to each parameter contained in the response signal to obtain a weighted response signal.

[0030] Determine whether the root mean square difference between the first root mean square value of the weighted target signal and the second root mean square value of the weighted response signal is less than a preset ratio of the first root mean square value.

[0031] If the root mean square difference is less than the preset ratio, and the relative damage of the weighted target acceleration in the three directions of the suspended lower support in the weighted target signal and the relative damage of the weighted response acceleration in the three directions of the suspended lower support in the weighted response signal are both within the preset damage range, then based on the multibody dynamics model and the finite element model, the first full-field time-domain stress and the first strain amplitude are determined according to the first driving signal.

[0032] In one embodiment, determining the first full-field temporal stress and the first strain amplitude based on the multibody dynamics model and the finite element model, according to the first driving signal, includes:

[0033] The first driving signal is used to drive the multibody dynamics model to obtain the time history load of the rear suspension under bracket;

[0034] By inputting a unit load at multiple preset points in the finite element model, the first unit stress corresponding to the unit load is obtained.

[0035] Based on the proportional relationship between the time history load and the unit load, the first full-field time-domain stress and the first strain amplitude corresponding to the time history load are determined according to the first unit stress.

[0036] In one embodiment, after determining whether the root mean square difference between the first root mean square value of the weighted target signal and the second root mean square value of the weighted response signal is less than a preset proportion of the first root mean square value, the method further includes:

[0037] If the root mean square difference is not less than the preset ratio value, the relative damage of the weighted target three-directional acceleration of the suspended support is not within the preset damage range, or the relative damage of the weighted response three-directional acceleration of the suspended support is not within the preset damage range, then the root mean square difference is input into the inverse function of the frequency response function to obtain the driving difference.

[0038] The first driving signal is adjusted according to the driving difference, and based on the adjusted first driving signal, the step of inputting the first driving signal into the multibody dynamics model to obtain the response signal is returned and execution continues.

[0039] In one embodiment, the determination of the second full-field time-domain stress and the second strain amplitude of the rear-suspension lower support under vibration conditions and resonance response, based on the finite element model and multibody dynamics model of the rear-suspension lower support and according to the second preset drive, includes:

[0040] The second preset drive is input into the multibody dynamics model to obtain the modal participation factor;

[0041] Based on the finite element model, modal calculations are performed to obtain the second unit stress;

[0042] The second full-field time-domain stress and the second strain amplitude are determined based on the second unit stress and the modal participation factor.

[0043] In one embodiment, determining the third full-field time-domain stress and third strain amplitude of the rear suspension lower bracket under low-frequency torsional conditions of the vehicle frame based on the preprocessed relative torsion angle, using the finite element model of the vehicle frame, includes:

[0044] A unit angular displacement is applied at the center of the second main crossbeam of the frame finite element model to obtain the third unit stress;

[0045] Based on the proportional relationship between the unit angular displacement and the pre-processed relative torsional angle, the third full-field time-domain stress and the third strain amplitude are determined according to the third unit stress.

[0046] In one embodiment, the step of analyzing the fatigue life of the lower suspension bracket based on the first full-field time-domain stress, the first strain amplitude, the second full-field time-domain stress, the second strain amplitude, the third full-field time-domain stress, and the third strain amplitude includes:

[0047] The critical plane is determined based on the first full-field time-domain stress, the second full-field time-domain stress, and the third full-field time-domain stress.

[0048] The first full-field time-domain stress, the second full-field time-domain stress, the third full-field time-domain stress, the first strain amplitude, the second strain amplitude, and the third strain amplitude are mapped to the critical plane;

[0049] Within the critical plane, based on rainflow projection, the target time-domain stress is obtained according to the first full-field time-domain stress, the second full-field time-domain stress, and the third full-field time-domain stress, and the target strain amplitude is obtained according to the first strain amplitude, the second strain amplitude, and the third strain amplitude;

[0050] Based on the target time-domain stress, the target strain amplitude, and the strain life curve of the rear suspension lower bracket, the single-cycle damage of the rear suspension lower bracket under different road conditions is determined when the vehicle travels once on the test road section. The strain life curve includes the strain life curve of the basic material and the strain life curve of the welding material.

[0051] Based on the single-cycle damage under different road conditions and the number of trips corresponding to each road condition, the total damage of the rear lower suspension bracket is calculated, and the fatigue life of the rear lower suspension bracket is determined based on the total damage and the length of the test section.

[0052] Secondly, this application also provides a fatigue life analysis device for a rear suspension lower bracket, the device comprising:

[0053] The acquisition module is used to acquire the relative torsional angle between the first and second main crossbeams and the axial displacement of the spring damper when the vehicle is driving on the test section. Based on the vehicle coordinate system, it acquires the three-way acceleration of the upper suspension bracket and the three-way acceleration of the lower suspension bracket when the vehicle is driving on the test section. The upper suspension bracket and the lower suspension bracket are connected by springs. The upper end of the upper suspension bracket is connected to the cab, and the lower end of the lower suspension bracket is connected to the vehicle frame. The first and second main crossbeams are two main crossbeams of the vehicle frame directly below the cab. The second main crossbeam is close to the vehicle body.

[0054] The preprocessing module is used to preprocess the relative torsion angle, the axial displacement, the three-way acceleration of the upper suspension bracket, and the three-way acceleration of the lower suspension bracket based on the actual vehicle speed, the preset vehicle speed, and the preset number of times the vehicle travels on the test section.

[0055] The first determining module is used to determine the first full-field time-domain stress and the first strain amplitude of the rear lower suspension under the inertial load condition of the cab based on the multibody dynamics model of the cab and the suspension system, and the finite element model of the rear lower suspension, according to the first preset drive, and the pre-processed axial displacement, the three-directional acceleration of the upper suspension and the three-directional acceleration of the lower suspension.

[0056] The second determining module is used to determine the second full-field time-domain stress and the second strain amplitude of the rear-suspended lower support under vibration conditions and resonance response, based on the finite element model and the multibody dynamics model of the rear-suspended lower support and according to the second preset drive.

[0057] The third determination module is used to determine the third full-field time-domain stress and the third strain amplitude of the rear suspension under the low-frequency torsional condition of the frame based on the finite element model of the frame and the preprocessed relative torsion angle.

[0058] The analysis module is used to analyze the fatigue life of the lower suspension bracket based on the first full-field time-domain stress, the first strain amplitude, the second full-field time-domain stress, the second strain amplitude, the third full-field time-domain stress, and the third strain amplitude.

[0059] Thirdly, this application also provides a computer device. The computer device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the steps of the methods in any of the above embodiments.

[0060] Fourthly, this application also provides a computer-readable storage medium. The computer-readable storage medium stores a computer program thereon, which, when executed by a processor, implements the steps of the methods in any of the above embodiments.

[0061] Fifthly, this application also provides a computer program product. The computer program product includes a computer program that, when executed by a processor, implements the steps of the methods in any of the above embodiments.

[0062] The aforementioned method, apparatus, computer equipment, storage medium, and computer program product for analyzing the fatigue life of the rear lower suspension bracket first obtain the relative torsional angle between the first and second main crossbeams and the axial displacement of the spring damper when the vehicle is traveling on the test section. Based on the vehicle coordinate system, the three-directional accelerations of the upper and lower suspension brackets are obtained when the vehicle is traveling on the test section. Then, based on the actual vehicle speed, a preset vehicle speed, and a preset number of times the vehicle has traveled on the test section, the relative torsional angle, axial displacement, and the three-directional accelerations of the upper and lower suspension brackets are preprocessed. Finally, based on the multibody dynamics model of the cab and suspension system, and the finite element model of the rear lower suspension bracket, and according to the first preset drive and the preprocessed axial displacement... The method utilizes the three-directional accelerations of the upper and lower suspension brackets to determine the first full-field time-domain stress and first strain amplitude of the lower rear suspension bracket under cab inertial load conditions. Based on the finite element model and multibody dynamics model of the lower rear suspension bracket, and according to the second preset drive, the second full-field time-domain stress and second strain amplitude of the lower rear suspension bracket under vibration and resonance response conditions are determined. Simultaneously, based on the finite element model of the chassis and according to the pre-processed relative torsion angle, the third full-field time-domain stress and third strain amplitude of the lower rear suspension bracket under low-frequency torsional conditions of the chassis are determined. Finally, based on the first, second, and third full-field time-domain stresses and strain amplitudes, the fatigue life of the lower rear suspension bracket is analyzed. The method provided in this application, by coupling the analysis of three full-field time-domain stresses and strain amplitudes, can accurately evaluate the actual fatigue life of the lower rear suspension bracket. Attached Figure Description

[0063] Figure 1 This is a flowchart illustrating a method for fatigue life analysis of the rear suspension under bracket in one embodiment;

[0064] Figure 2 This is a diagram showing the arrangement of sensor measurement points in one embodiment;

[0065] Figure 3 This is a schematic diagram of the inertial load decomposition point in one embodiment;

[0066] Figure 4 This is a flowchart illustrating a preprocessing method in one embodiment;

[0067] Figure 5 Here is a time-domain plot of the relative torsion angle in another embodiment;

[0068] Figure 6 This is a structural block diagram of a fatigue life analysis device for the rear suspension lower bracket in one embodiment;

[0069] Figure 7 This is an internal structural diagram of a computer device in one embodiment. Detailed Implementation

[0070] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0071] In one embodiment, such as Figure 1 As shown, a method for fatigue life analysis of a rear suspension lower bracket is provided. This embodiment illustrates the application of this method to a terminal. It is understood that this method can also be applied to a server, and to a system including both a terminal and a server, and implemented through interaction between the terminal and the server. In this embodiment, the method includes the following steps:

[0072] S102. Obtain the relative torsional angle between the first and second main crossbeams and the axial displacement of the spring damper when the vehicle is driving on the test section. Based on the vehicle coordinate system, obtain the three-directional acceleration of the upper suspension bracket and the three-directional acceleration of the lower suspension bracket when the vehicle is driving on the test section. The upper and lower suspension brackets are connected by springs. The upper end of the upper suspension bracket is connected to the cab, and the lower end of the lower suspension bracket is connected to the frame. The first and second main crossbeams are the two frame main crossbeams directly below the cab. The second main crossbeam is close to the vehicle body.

[0073] like Figure 2As shown, the three-directional acceleration of the upper suspension bracket is measured by four three-directional acceleration sensors arranged at measuring points 1, 2, 3, and 4 on the upper suspension bracket. The three-directional acceleration of the lower suspension bracket is measured by four three-directional acceleration sensors arranged at measuring points 5, 6, 7, and 8 on the lower suspension bracket. The XYZ channel direction of the acceleration sensors is consistent with the vehicle coordinate system used in the product design. The axial displacement of the spring damper is measured by four wire-type displacement sensors arranged at measuring points 9, 10, 11, and 12. The displacement sensors are defined as tensile as positive and compressive as negative. The torsion angle of the first main crossbeam is measured by a torsion angle testing device arranged at measuring point 13, and the torsion angle of the second main crossbeam is measured by a torsion angle testing device arranged at measuring point 14. The difference between the torsion angles measured by the two torsion angle testing devices is determined as the relative torsion angle between the first and second main crossbeams. In addition, it is necessary to obtain the vehicle's actual speed, latitude and longitude, and altitude based on conventional GPS measurements.

[0074] The test vehicle must be a target vehicle or reference vehicle in good condition after the break-in period, and the sampling rate must be 10 times the upper limit of the frequency range of interest (generally 0-50Hz), i.e., 500Hz.

[0075] S104. Based on the actual vehicle speed, the preset vehicle speed, and the preset number of times the vehicle travels on the test section, the relative torsional angle, axial displacement, acceleration in three directions of the upper suspension bracket, and acceleration in three directions of the lower suspension bracket are preprocessed respectively.

[0076] First, determine the relative torsional angle, axial displacement, three-directional acceleration of the upper suspension bracket, and three-directional acceleration of the lower suspension bracket for each test, and determine the target load spectrum signal based on the total pseudo-damage.

[0077] Then, check whether the deviation between the actual vehicle speed and the preset vehicle speed corresponding to the target load spectrum signal is within the preset range. If it is not within the preset range, repeat step S102.

[0078] Next, glitches in the target load spectrum signal are removed, that is, parameters in the target load spectrum signal that are much larger than the preset parameter range are deleted. For example, if the triaxial acceleration signal in the target load spectrum signal at a certain moment is 5 times higher than the normal triaxial acceleration signal, then the triaxial acceleration signal at that moment is deleted. After glitches are removed, the temperature drift of each corresponding sensor is corrected according to the target load spectrum signal, and the consistency of the same data measured by the sensors symmetrically on both sides of the vehicle is checked. At the same time, the sensors are checked according to the pointer direction of various sensors when the vehicle is under different operating conditions, such as braking, steering, and driving over potholes.

[0079] Finally, data on the vehicle's driving under different road conditions are extracted from the target load spectrum signal. For example, different road conditions can be cobblestone roads, potholes, and washboard roads. The signal files are then output according to the road segment names. The signal file type can be binary .asc or .rsp file format.

[0080] S106. Based on the multibody dynamics model of the cab and suspension system, and the finite element model of the lower rear suspension bracket, the first full-field time-domain stress and the first strain amplitude of the lower rear suspension bracket under the cab inertial load condition are determined according to the first preset drive, the pre-processed axial displacement, the three-directional acceleration of the upper suspension bracket, and the three-directional acceleration of the lower suspension bracket.

[0081] The construction process of the multibody dynamics model of the cab and suspension system is as follows: Using software such as MSC.Adams or Simcenter3D Motion, enter the multibody dynamics modeling environment. Import the coordinate table of key hard points for the cab and suspension system. Hard points are the coordinates of joints with connections or the coordinates of response points of interest. Based on the system's structural form, create component objects, mainly including the cab, occupant, frame, stabilizer bar, suspension brackets, hydraulic locks, linkages, and sensors. The cab requires inputting its measured mass, center of mass, and moment of inertia. Create elastic damping element units such as shock absorbers, springs, and bushing forces, inputting stiffness and damping curves, and defining the upper and lower free travel of the shock absorber, the stiffness of the compression buffer block, and the stiffness curve of the tension limit block. Create kinematic pairs, such as the cylindrical pair between the shock absorber piston and sleeve, and the rotary pair between the cab and the hydraulic lock. Flex the cab suspension brackets, especially the lower brackets (including the front shock absorber lower bracket, the rear hinged lower bracket of the front stabilizer bar, and the rear suspension lower bracket) and the front stabilizer bar. For the rear suspension lower bracket, besides ensuring the hard point position remains unchanged, it can be the structure of the reference prototype rather than the target structure, serving only as a load decomposition tool; therefore, no special requirements are placed on the finite element mesh details. In this step, the multibody dynamics modeling of the cab and suspension system is to solve the inertial load of the cab on the rear suspension lower bracket under vibration conditions. Therefore, the frame does not need flexible modeling and can be defined as a non-mass object. A virtual vibration table is established at the center coordinates of the rigid frame; it is essentially a virtual object, represented by a coordinate system. The virtual vibration table is fixed to the frame and connected to the ground, constraining all degrees of freedom. A static equilibrium condition under gravity alone is calculated to observe the displacement change of the spring damper. By adjusting the preload, the displacement of the spring damper is maintained at the designed equilibrium height to simulate the static equilibrium characteristics of the air spring damper. Linearity identification is performed, i.e., calculating the rigid body modes of the cab and suspension system to check for significant differences from measured or empirical values ​​and for any abnormal component motion postures, thereby further correcting the model. Establish a vibration condition and solve it jointly with the static equilibrium condition; that is, set a restart condition to avoid initial abnormal shocks to the model due to non-equilibrium states in subsequent iterations. Save the multibody dynamics model.

[0082] S108. Based on the finite element model and multibody dynamics model of the rear-suspension lower support, and according to the second preset drive, determine the second full-field time-domain stress and the second strain amplitude of the rear-suspension lower support under vibration conditions and resonance response.

[0083] like Figure 3As shown, at point 21 in the multibody dynamics model of the cab and suspension system, the 6-DOF drive of the rear suspension subsystem is output, which also includes linear displacement in 3 directions and angular displacement in 3 directions. Point 21 is located at the midpoint coordinate position between points 19 and 20. This 6-DOF drive is the second preset drive.

[0084] Create a new multibody dynamics rigid body model for the rear lower suspension bracket, remove all connections and connected objects, and make it flexible. Adjust the finite element model of the rear lower suspension bracket, rigidly connecting the left and right frame fixing points to a single point; this principal point is the drive position of the subsystem. Perform Craig-Bampton (CB) mode calculations, outputting modal displacements, stresses, nodal forces, and SPC support reactions. Obtain at least 10 vibration modes of the entire vehicle-mounted accessory system and 6 static displacement compensation modes, and assign modal damping ratios. Drive the rear lower suspension bracket dynamic model, calculate modal participation factors, output 16 modal coordinates, and save the participation factor data as an .asc binary file.

[0085] Matching modal stress results with participation factors. Establish a finite element-load matching set, input the result file of the above CB modal calculation and the modal participation factors, and match them by result keyword headers to obtain the full-field time-domain stress and strain amplitude of the rear-suspension support under vibration conditions and resonance response.

[0086] S110. Based on the finite element model of the chassis, the third full-field time-domain stress and the third strain amplitude of the rear suspension under the low-frequency torsion condition of the chassis are determined according to the pre-processed relative torsion angle.

[0087] Based on the finite element model of the chassis, at the center of the first main crossbeam of the chassis, i.e. Figure 2 At point 13, a fixed constraint of 6 degrees of freedom is applied, located at the center of the second main crossbeam of the frame, i.e. Figure 2 At point 14, apply a unit angular displacement along the X-axis in degrees. Establish a Nastran static calculation case, adjust the control card, and output the structural response of the rear suspension under static unit angular torsion, including displacement, stress, and nodal forces.

[0088] Matching the frame torsion results with the test angles. Establish a finite element-load matching set, input the relative torsion angle between the first and second main crossbeams when the vehicle is driving on the test section, as well as the structural response under static unit angle torsion conditions, and perform matching and scaling to obtain the full-field time-domain stress and strain amplitude of the rear suspension lower bracket under the low-frequency torsion conditions of the frame.

[0089] S112. Based on the first full-field time-domain stress, the first strain amplitude, the second full-field time-domain stress, the second strain amplitude, the third full-field time-domain stress, and the third strain amplitude, analyze the fatigue life of the lower suspension support.

[0090] Based on software such as Femfat or Simcenter3D Durability, the results of the first full-field time-domain stress, first strain amplitude, second full-field time-domain stress, second strain amplitude, third full-field time-domain stress, and third strain amplitude are mapped to obtain multiaxial stress-strain results at each time history sampling point. A critical plane solution condition with 18 equally divided angles in a plane is inserted, and the critical plane is found according to the tensor level and number. Based on the critical plane, rainflow projection and filtering are performed, and all stress amplitudes are projected and recalculated according to their respective angles. Fatigue life analysis is performed from two aspects: basic material fatigue life analysis and welding material fatigue life analysis.

[0091] The mean stress is corrected using the P-SWT (Smith-Watson-Topper) correction method. The survival rate of the material fatigue curve can be defined according to the company's reliability verification standards, typically 50% / 90% / 99%. Parameters are corrected based on material surface roughness, presence or absence of heat treatment processes, etc. Uncertain parameters can be set to a default value of 1. Elastic-plastic correction is performed using the Neuber notch stress condition formula combined with cyclic stress-strain curves. Rainflow counting is performed to obtain the number of cycles under different stress or strain amplitudes. Damage calculation and synthesis are performed using the advanced linear damage accumulation rule (Elementary Minor). The total damage of any unit = Σ single-cycle damage of each characteristic section * number of cycles. Post-processing is performed using fatigue analysis software, and the length of the test section can be used to convert it into structural fatigue life and reliable durability mileage.

[0092] In the above-mentioned fatigue life analysis method for the rear-mounted lower support, by coupling the stress and strain amplitude under three working conditions, the comprehensive fatigue life prediction accuracy of the rear-mounted lower support under complex conditions can be significantly improved. By combining the actual measured data with finite element analysis, the calculated fatigue life can be more consistent with the actual situation.

[0093] In some embodiments, such as Figure 4 As shown, Figure 4This is a flowchart illustrating a preprocessing method in one embodiment. Based on the actual vehicle speed, a preset vehicle speed, and a preset number of times the vehicle travels on the test section, preprocessing is performed on the relative torsional angle, axial displacement, three-way acceleration of the upper suspension bracket, and three-way acceleration of the lower suspension bracket. This includes: calculating the total pseudo-damage of the relative torsional angle, axial displacement, three-way acceleration of the upper suspension bracket, and three-way acceleration of the lower suspension bracket each time the vehicle travels on the test section, based on the preset vehicle speed and the preset number of times; determining the median of all total pseudo-damages as the target total pseudo-damage, and determining the relative torsional angle, axial displacement, three-way acceleration of the upper suspension bracket, and three-way acceleration of the lower suspension bracket corresponding to the target total pseudo-damage as the target load spectrum signal; determining whether the difference between the actual vehicle speed and the preset vehicle speed corresponding to the target load spectrum signal is within the preset vehicle speed range; if the difference is not within the preset vehicle speed range, then returning to obtain the relative torsional angle between the first and second main crossbeams and the spring damper during the vehicle's travel on the test section. The steps of axial displacement and obtaining the three-directional acceleration of the upper suspension bracket and the lower suspension bracket in the three-directional direction when the vehicle is traveling on the test section based on the vehicle coordinate system are continued until the difference between the actual vehicle speed corresponding to the determined target load spectrum signal and the preset vehicle speed is within the preset vehicle speed range. If the difference is within the preset vehicle speed range, it is determined whether each parameter contained in the target load spectrum signal is within the corresponding first data range. If there are parameters that are not within the corresponding first data range, they are deleted. If each parameter contained in the target load spectrum signal is within the corresponding first data range, it is determined whether each parameter contained in the target load spectrum signal is within the corresponding second data range. If there are parameters that are not within the corresponding second data range, an alarm signal is issued. The alarm signal is used to indicate that the sensor measuring the corresponding parameter has malfunctioned or that the vehicle has malfunctioned. The upper limit of the second data range is less than the lower limit of the first data range.

[0094] In this step, pseudo-damage refers to treating various load signals as generalized stress without considering the specific structure. Using the generalized stress as input, a specified standard SN curve is used, and the damage value is obtained by cyclic counting and damage accumulation in the same way as the calculation of real fatigue damage.

[0095] The method provided in this step, by preprocessing the parameters, can make the results of subsequent finite element analysis more accurate.

[0096] In some embodiments, based on the multibody dynamics model of the cab and suspension system, and the finite element model of the lower rear suspension bracket, the first full-field time-domain stress and the first strain amplitude of the lower rear suspension bracket under the cab inertial load condition are determined according to the first preset drive and the pre-processed axial displacement, the three-directional acceleration of the upper suspension bracket, and the three-directional acceleration of the lower suspension bracket. This includes: filtering the pre-processed axial displacement, the three-directional acceleration of the upper suspension bracket, and the three-directional acceleration of the lower suspension bracket according to preset start and end frequencies to obtain target signals; determining white noise according to the start frequency and preset boundary frequency, and determining pink noise according to the boundary frequency and end frequency. The boundary frequency is greater than the starting frequency and less than the ending frequency. White noise is a signal whose energy does not change with frequency, while pink noise is a signal whose energy changes exponentially with frequency. The white noise and pink noise are input into the multibody dynamics model to obtain the frequency response function. Based on the starting and ending frequencies, and according to the target signal and the first preset drive, it is determined whether the coherence of the frequency response function is greater than the preset coherence value. If the coherence of the frequency response function is greater than the preset coherence value, the target signal is input into the inverse function of the frequency response function to obtain the first drive signal. Based on the multibody dynamics model and the finite element model, and according to the first drive signal and the preset weight value, the first full-field time-domain stress and the first strain amplitude are determined.

[0097] In this step, using software such as Femfat Lab or Motion TWR, the start and end frequencies are defined, for example, a start frequency of 1Hz and an end frequency of 40Hz. The sampling rate and frame length are also set to ensure a frequency resolution < 0.5Hz. The target sensor channel is then configured, i.e., in the multibody dynamics model, in a manner such as... Figure 2 At measurement points 1 to 8, three acceleration channels are established at each location, totaling 24 acceleration channels. At measurement points 9 to 12, one channel is established at each location, totaling 4 displacement channels. Between the virtual vibration table established in the multibody dynamics model and the ground, a 6-DOF drive is established through the vehicle frame center point coordinate system. This 6-DOF drive consists of three linear displacement drives and three angular displacement drives, and is the first preset drive.

[0098] The pre-processed axial displacement, three-directional acceleration of the upper suspension bracket, and three-directional acceleration of the lower suspension bracket are input into the multibody dynamics model for channel-signal matching. Simultaneously, a 1-40Hz bandpass filter is used to filter the input data, removing data outside the 1-40Hz range to obtain the target signal. Boundary frequencies are set, defining white noise between the start and boundary frequencies and pink noise between the boundary and end frequencies. The curve exponent for pink noise and the standard deviation for white noise are also set. The multibody dynamics model is driven using white-pink noise to obtain the frequency response function (FRF). Then, the target signal and the first preset driving input are compared with a preset coherence function to verify the coherence between the FRF input and output. The coherence is ensured to be greater than 0.7 in the 1-4Hz range and greater than 0.85 in the 4-40Hz range. Otherwise, the standard deviation of white noise, boundary frequencies, and curve exponent for pink noise are readjusted until the coherence requirements are met. If the coherence requirements are met, the target signal is input into the inverse function of the frequency response function to obtain the first driving signal.

[0099] The method provided in this step determines the first driving signal only when the coherence requirement is met, thus ensuring the accuracy of the first driving signal.

[0100] In some embodiments, after determining whether the coherence of the frequency response function is greater than a preset coherence value based on the start frequency and the end frequency, according to the target signal and the first preset drive, the method further includes: if the coherence of the frequency response function is not greater than the preset coherence value, adjusting the standard deviation of the white noise, the boundary frequency and the curve exponent of the pink noise, and based on the adjusted parameters, returning to the step of inputting the white noise and pink noise into the multibody dynamics model to obtain the frequency response function and continuing to execute.

[0101] In this step, coherence refers to the degree of linear correlation between the input and output values ​​of the frequency response function.

[0102] The method provided in this step, by adjusting the corresponding parameters through coherence values, can ensure the accuracy of the frequency response function obtained from white-pink noise.

[0103] In some embodiments, based on the multibody dynamics model and the finite element model, determining the first full-field time-domain stress and the first strain amplitude according to the first driving signal and preset weight values ​​includes: inputting the first driving signal into the multibody dynamics model to obtain a response signal, the response signal including the three-directional acceleration of the upper suspension support, the three-directional acceleration of the lower suspension support, and the axial displacement of the response; assigning weights to each parameter contained in the target signal according to the preset weight values ​​to obtain a weighted target signal, and assigning weights to each parameter contained in the response signal. The weighted response signal is obtained by weighting the target signal; the root mean square difference between the first root mean square value of the weighted target signal and the second root mean square value of the weighted response signal is determined to be less than a preset proportion of the first root mean square value; if the root mean square difference is less than the preset proportion, and the relative damage of the weighted target acceleration in the three directions of the suspended lower support in the weighted target signal and the relative damage of the weighted response acceleration in the three directions of the suspended lower support in the weighted response signal are both within a preset damage range, then based on the multibody dynamics model and the finite element model, the first full-field time-domain stress and the first strain amplitude are determined according to the first driving signal.

[0104] In this step, for example, the weighting values ​​of the three-directional acceleration of the upper suspension support are 0.3-0.4, the weighting values ​​of the three-directional acceleration of the lower suspension support are 0.4-0.6, and the weighting value of the axial displacement is 0.2-0.3. When the root mean square difference between the weighted response signal and the weighted target signal is less than the preset root mean square value, and the relative damage of the weighted target acceleration of the lower suspension support in the weighted target signal and the relative damage of the weighted response acceleration of the lower suspension support in the weighted response signal are both between 0.85 and 1.15, then the first full-field time-domain stress and the first strain amplitude are determined according to the first driving signal.

[0105] The method provided in this step, by assigning weights to different parameters, can reduce errors in the system caused by nonlinearity and uncertainty.

[0106] In some embodiments, based on a multibody dynamics model and a finite element model, determining a first full-field time-domain stress and a first strain amplitude according to a first driving signal includes: using the first driving signal to drive the multibody dynamics model to obtain the time history load of the rear suspension under bracket; inputting a unit load at multiple preset points in the finite element model to obtain a first unit stress corresponding to the unit load; and determining the first full-field time-domain stress and the first strain amplitude corresponding to the time history load according to the first unit stress based on the proportional relationship between the time history load and the unit load.

[0107] In this step, such as Figure 3As shown, after driving the multibody dynamics model with the first drive signal, time history loads in 6 directions will be output at points 15, 16, 17, 18, 19 and 20, for a total of 36 channels. Points 15 and 16 are fixed points on the hydraulic lock, points 17 and 18 are fixed points on the rear shock absorber, and points 19 and 20 are fixed points on the rear suspension frame.

[0108] Based on finite element simulation software such as Hyperworks or ANSA, a detailed finite element model of the rear suspension underbody is established, including operations such as component classification and naming, geometric structure cleaning, finite element mesh generation, modeling and assembly of bolts and welds, assignment of materials and properties, element quality inspection, and verification of weight information. Figure 4 For each input point and channel in the model, a unit load case is established. No constraints are applied to the model. The inertial release calculation card in Nastran is used to establish the load step, outputting the element displacement, stress, and nodal force results. Finite element analysis is then performed, outputting the results in OP2 format.

[0109] Establish a finite element-load matching set, input the OP2 format result file obtained from the above finite element analysis and the time history load of the rear suspension lower bracket, and match them by the result keyword header to obtain the full-field time domain stress and strain amplitude of the rear suspension lower bracket under the inertial load condition of the cab.

[0110] The method provided in this step uses finite element analysis to obtain the full-field time-domain stress and strain amplitude of the rear suspension under cab inertial load conditions, which can improve the prediction accuracy of the first full-field time-domain stress and the first strain amplitude.

[0111] In some embodiments, after determining whether the root mean square difference between the first root mean square value of the weighted target signal and the second root mean square value of the weighted response signal is less than a preset proportion of the first root mean square value, the method further includes: if the root mean square difference is not less than the preset proportion, the relative damage of the weighted target acceleration in three directions under the suspension is not within a preset damage range, or the relative damage of the weighted response acceleration in three directions under the suspension is not within a preset damage range, then the root mean square difference is input into the inverse function of the frequency response function to obtain a driving difference; the first driving signal is adjusted according to the driving difference, and based on the adjusted first driving signal, the step of inputting the first driving signal into the multibody dynamics model to obtain a response signal is returned and execution continues.

[0112] In this step, when the root mean square difference is not less than a preset ratio, the relative damage of the weighted target acceleration in the three directions of the suspended support is not within a preset damage range, or the relative damage of the weighted response acceleration in the three directions of the suspended support is not within a preset damage range, the first driving signal is adjusted according to the driving difference.

[0113] The method provided in this step determines the driving signal through iteration, making the final determined driving signal more accurate.

[0114] In some embodiments, based on the finite element model and the multibody dynamics model of the rear-suspension underpinning support, and according to the second preset drive, the second full-field time-domain stress and the second strain amplitude of the rear-suspension under vibration conditions and resonance response are determined, including: inputting the second preset drive into the multibody dynamics model to obtain the modal participation factor; performing modal calculations based on the finite element model to obtain the second unit stress; and determining the second full-field time-domain stress and the second strain amplitude according to the second unit stress and the modal participation factor.

[0115] In this step, the modal participation factor is a parameter that describes the interaction between a mode and a certain vector excitation. The larger the value of the modal participation factor, the greater the contribution of the mode to the dynamic response.

[0116] The method provided in this step determines the second full-field time-domain stress and the second strain amplitude based on the modal participation factor, making the determined second full-field time-domain stress and the second strain amplitude more accurate.

[0117] In some embodiments, based on the finite element model of the frame, the third full-field time-domain stress and the third strain amplitude of the rear suspension under low-frequency torsional conditions of the frame are determined according to the pre-processed relative torsion angle. This includes: applying a unit angular displacement at the center position of the second main crossbeam of the finite element model of the frame to obtain the third unit stress; and determining the third full-field time-domain stress and the third strain amplitude based on the proportional relationship between the unit angular displacement and the pre-processed relative torsion angle, according to the third unit stress.

[0118] In this step, the finite element modeling of the vehicle frame includes: cutting the overall vehicle frame, retaining the longitudinal and transverse beam structures between the first and second main crossbeams, and deleting structures that do not provide torsional stiffness, including brackets for accessories mounted on one side of the vehicle frame, such as fuel tank brackets and after-processor brackets.

[0119] The method provided in this step determines the third full-field time-domain stress and the third strain amplitude based on the finite element model of the chassis, making the determined third full-field time-domain stress and the third strain amplitude more accurate.

[0120] In some embodiments, analyzing the fatigue life of the rear-suspension support based on the first full-field time-domain stress, the first strain amplitude, the second full-field time-domain stress, the second strain amplitude, the third full-field time-domain stress, and the third strain amplitude includes: determining a critical plane based on the first full-field time-domain stress, the second full-field time-domain stress, and the third full-field time-domain stress; mapping the first full-field time-domain stress, the second full-field time-domain stress, the third full-field time-domain stress, the first strain amplitude, the second strain amplitude, and the third strain amplitude to the critical plane; and within the critical plane, based on rainflow projection, analyzing the fatigue life of the rear-suspension support based on the first full-field time-domain stress, the second full-field time-domain stress, and the third full-field time-domain stress. The target time-domain stress is obtained by first strain amplitude, second strain amplitude, and third strain amplitude. Based on the target time-domain stress, target strain amplitude, and strain life curve of the rear lower suspension bracket, the single-cycle damage of the rear lower suspension bracket under different road conditions is determined when the vehicle travels once on the test section. The strain life curve includes the strain life curve of the basic material and the strain life curve of the welded material. Based on the single-cycle damage under different road conditions and the number of trips corresponding to each road condition, the total damage of the rear lower suspension bracket is calculated. Based on the total damage and the length of the test section, the fatigue life of the rear lower suspension bracket is determined.

[0121] In this step, the metal materials of the suspended support are grouped according to their grade, and the process proceeds to the basic material fatigue life analysis module, where a strain-based fatigue life analysis method is selected. Strain life curve parameters are set, including elastic modulus, tensile strength, stress intensity coefficient, stress intensity index, toughness coefficient, and toughness index. Cyclic stress-strain curve parameters are also set, including cyclic strength coefficient and cyclic strain hardening index. All of these parameters should be obtained through testing and fitting, or estimated using empirical formulas. If welding processes are present, such as seam welding, the process proceeds to the welding material fatigue life analysis module. Weld identification requires examining two sheet metal parts with different attribute cards, identifying them as T-type, Y-type, L-type, lap joint, or butt joint based on the welding angle and form. The nominal stress method is selected, and the welding material SN curve is defined according to the welding type or load form using standards such as BS7608. Alternatively, the notch stress method can be selected, assigning a virtual notch radius based on thickness, and defining the main SN curve using a sub-model method based on nodal forces and a weld joint notch stress database.

[0122] The method provided in this step performs fatigue life analysis from two aspects: fatigue life analysis of basic materials and fatigue life analysis of welding materials, making the analysis results of the rear suspension under bracket more comprehensive.

[0123] In one embodiment, another method for fatigue life analysis of the rear-mounted lower support is provided, including the following:

[0124] (1) Conduct a road load test to assess the reliability and durability of the entire vehicle. Measure the acceleration signals in three directions at the sprung and unsprung positions of the cab suspension system, measure the axial relative displacement signals of the spring dampers, and measure the relative torsional angle between the first and second main beams of the frame. The time-domain plot of the relative torsional angle is shown below. Figure 5 The aforementioned preprocessing operations, such as glitch removal, drift correction, and filtering, are performed on the signal within one period to obtain the target signal or input signal for subsequent load decomposition.

[0125] A multibody dynamics model was established, including the driver's cab, suspension brackets, elastic damping elements, virtual sensors, and virtual drive. Linearization identification was used to ensure that the system's sixth-order rigid body modes matched the measured values.

[0126] Using the sprung and unsprung acceleration signals and the axial relative displacement of the spring damper as target signals, and assigning different iteration weights, the system uses a hybrid rigid-flexible multibody dynamics model of the cab and suspension system as the transfer function. Iteratively, iteratively, the external driving signals are obtained to acquire the motion posture under real road conditions and the inertial loads transmitted from the cab to the suspension brackets. These loads include the hydraulic lock bushing load, the lower fixed-point bushing load of the rear suspension damper, and the support load at the virtual clamp (or frame) end, with a frequency range of 1-40Hz. Inertial release calculations are performed at each input point of the lower rear suspension bracket under a unit load to obtain the displacement and stress response. The finite element results are then matched with the time-domain inertial load to obtain the full-field stress and strain amplitudes.

[0127] (2) For the suspension support structure with attached vehicle accessories, the 6-DOF drive of the rear suspension support subsystem is output by solving the dynamic model of the cab and suspension. A detailed finite element model including the vehicle accessories is established. In the dynamic model, the flexible body file is obtained through CB modal calculation, and the modal damping ratio is input. The system drive containing 3 linear displacements and 3 angular displacements is input, and the multibody dynamic model is solved. The modal participation factor of the system is output to obtain the system response due to resonance. The finite element results (modal stress) are matched with the modal participation factor to obtain the full-field stress amplitude and strain amplitude.

[0128] (3) Establish a finite element model of the frame structure including the first main crossbeam and the second main crossbeam. Establish a fixed constraint at the center of the first main crossbeam, apply a unit torsional angle to the second main crossbeam, and output the displacement and stress of the rear suspension lower bracket. Match the finite element results with the time-domain frame torsional angle to obtain the full-field stress amplitude and strain amplitude.

[0129] (4) In the fatigue life analysis module, based on the full-field time-domain stress amplitude and strain amplitude under the above conditions, result mapping coupling and critical direction identification are performed to obtain the critical plane. Rainflow projection is then performed to obtain the corrected stress and strain amplitude based on the critical plane. Materials are classified according to their metal grades, and their respective strain-life curves and cyclic stress-strain curves are input. Average stress correction based on P-SWT is performed, and the Elementary-Minor damage accumulation criterion is used to calculate the cumulative damage. Finally, the fatigue life of the rear suspension bracket of the cab is evaluated.

[0130] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0131] Based on the same inventive concept, this application also provides a rear suspension lower support fatigue life analysis device for implementing the aforementioned rear suspension lower support fatigue life analysis method. The solution provided by this device is similar to the solution described in the above method. Therefore, the specific limitations of one or more rear suspension lower support fatigue life analysis device embodiments provided below can be found in the limitations of the rear suspension lower support fatigue life analysis method described above, and will not be repeated here.

[0132] In one embodiment, such as Figure 6 As shown, a fatigue life analysis device 600 for a rear suspension lower bracket is provided, comprising: an acquisition module 601, a preprocessing module 602, a first determination module 603, a second determination module 604, a third determination module 605, and an analysis module 606, wherein:

[0133] The acquisition module 601 is used to acquire the relative torsional angle between the first and second main crossbeams and the axial displacement of the spring damper when the vehicle is driving on the test section. Based on the vehicle coordinate system, it acquires the three-directional acceleration of the upper suspension bracket and the three-directional acceleration of the lower suspension bracket when the vehicle is driving on the test section. The upper suspension bracket and the lower suspension bracket are connected by springs. The upper end of the upper suspension bracket is connected to the cab, and the lower end of the lower suspension bracket is connected to the vehicle frame. The first and second main crossbeams are two main crossbeams of the vehicle frame directly below the cab, and the second main crossbeam is close to the vehicle body.

[0134] The preprocessing module 602 is used to preprocess the relative torsion angle, the axial displacement, the three-way acceleration of the upper suspension bracket, and the three-way acceleration of the lower suspension bracket based on the actual vehicle speed, the preset vehicle speed, and the preset number of times the vehicle travels on the test section.

[0135] The first determining module 603 is used to determine the first full-field time-domain stress and the first strain amplitude of the rear lower suspension under the inertial load condition of the cab based on the multibody dynamics model of the cab and the suspension system, and the finite element model of the rear lower suspension, according to the first preset drive, and the pre-processed axial displacement, the three-directional acceleration of the upper suspension and the three-directional acceleration of the lower suspension.

[0136] The second determining module 604 is used to determine the second full-field time-domain stress and the second strain amplitude of the rear-suspension lower support under vibration conditions and resonance response based on the finite element model and multibody dynamics model of the rear-suspension lower support and according to the second preset drive.

[0137] The third determining module 605 is used to determine the third full-field time-domain stress and the third strain amplitude of the rear suspension under the low-frequency torsion condition of the frame based on the finite element model of the frame and the pre-processed relative torsion angle.

[0138] Analysis module 606 is used to analyze the fatigue life of the lower suspension bracket based on the first full-field time-domain stress, the first strain amplitude, the second full-field time-domain stress, the second strain amplitude, the third full-field time-domain stress, and the third strain amplitude.

[0139] In some embodiments, the preprocessing module 602 is further configured to: calculate, based on the preset vehicle speed and the preset number of times, the total pseudo-damage of the relative torsion angle, the axial displacement, the three-directional acceleration of the upper suspension bracket, and the three-directional acceleration of the lower suspension bracket each time the vehicle travels on the test section; determine the median of all total pseudo-damages as the target total pseudo-damage, and determine the relative torsion angle, axial displacement, three-directional acceleration of the upper suspension bracket, and three-directional acceleration of the lower suspension bracket corresponding to the target total pseudo-damage as the target load spectrum signal; determine whether the difference between the actual vehicle speed corresponding to the target load spectrum signal and the preset vehicle speed is within the preset vehicle speed range; if the difference is not within the preset vehicle speed range, return to obtain the relative torsion angle between the first main crossbeam and the second main crossbeam, and the axial displacement of the spring damper when the vehicle travels on the test section, and obtain the vehicle's speed when traveling on the test section based on the vehicle coordinate system. The steps of calculating the three-way acceleration of the upper suspension bracket and the three-way acceleration of the lower suspension bracket are executed and continued until the difference between the actual vehicle speed corresponding to the determined target load spectrum signal and the preset vehicle speed is within the preset vehicle speed range. If the difference is within the preset vehicle speed range, it is determined whether each parameter contained in the target load spectrum signal is within the corresponding first data range. If there are parameters that are not within the corresponding first data range, the parameters that are not within the corresponding first data range are deleted. If each parameter contained in the target load spectrum signal is within the corresponding first data range, it is determined whether each parameter contained in the target load spectrum signal is within the corresponding second data range. If there are parameters that are not within the corresponding second data range, an alarm signal is issued. The alarm signal is used to indicate that the sensor measuring the corresponding parameter has malfunctioned or that the vehicle has malfunctioned. The upper limit of the second data range is less than the lower limit of the first data range.

[0140] In some embodiments, the first determining module 603 includes:

[0141] The filtering unit is used to filter the pre-processed axial displacement, the three-directional acceleration of the upper suspension bracket, and the three-directional acceleration of the lower suspension bracket according to the preset start frequency and end frequency, so as to obtain the target signal.

[0142] The first determining unit is configured to determine white noise based on the starting frequency and a preset boundary frequency, and to determine pink noise based on the boundary frequency and the termination frequency, wherein the boundary frequency is greater than the starting frequency and less than the termination frequency, the white noise is a signal whose energy does not change with frequency, and the pink noise is a signal whose energy changes exponentially with frequency.

[0143] The first input unit is used to input the white noise and the pink noise into the multibody dynamics model to obtain the frequency response function.

[0144] The judgment unit is used to determine, based on the start frequency and the end frequency, and according to the target signal and the first preset drive, whether the coherence of the frequency response function is greater than a preset coherence value.

[0145] The second input unit is used to input the target signal into the inverse function of the frequency response function to obtain the first driving signal if the coherence of the frequency response function is greater than the preset coherence value.

[0146] The second determining unit is used to determine the first full-field time-domain stress and the first strain amplitude based on the multibody dynamics model and the finite element model, according to the first driving signal and the preset weight value.

[0147] In some embodiments, the first determining module 603 is further configured to: if the coherence of the frequency response function is not greater than the preset coherence value, adjust the standard deviation of the white noise, the boundary frequency, and the curve exponent of the pink noise, and based on the adjusted parameters, return to the step of inputting the white noise and the pink noise into the multibody dynamics model to obtain the frequency response function and continue execution.

[0148] In some embodiments, the second determining unit includes:

[0149] The input subunit is used to input the first driving signal into the multibody dynamics model to obtain a response signal, which includes the three-directional acceleration of the upper suspension support, the three-directional acceleration of the lower suspension support, and the axial displacement of the response.

[0150] The weight allocation subunit is used to allocate weights to each parameter contained in the target signal according to the preset weight value to obtain a weighted target signal, and to allocate weights to each parameter contained in the response signal to obtain a weighted response signal.

[0151] The judgment subunit is used to determine whether the root mean square difference between the first root mean square value of the weighted target signal and the second root mean square value of the weighted response signal is less than a preset ratio value of the first root mean square value.

[0152] A sub-unit is defined for determining the first full-field time-domain stress and the first strain amplitude based on the first driving signal, if the root mean square difference is less than the preset ratio value, and the relative damage of the weighted target three-directional acceleration of the suspended lower support in the weighted target signal and the relative damage of the weighted response three-directional acceleration of the suspended lower support in the weighted response signal are both within the preset damage range.

[0153] In some embodiments, determining the sub-unit is further configured to: drive the multibody dynamics model using the first driving signal to obtain the time history load of the rear suspension under bracket; input the unit load at multiple preset points of the finite element model to obtain the first unit stress corresponding to the unit load; and determine the first full-field time-domain stress and the first strain amplitude corresponding to the time history load based on the proportional relationship between the time history load and the unit load, according to the first unit stress.

[0154] In some embodiments, the second determining unit is specifically configured to: if the root mean square difference is not less than the preset ratio value, the relative damage of the weighted target three-directional acceleration of the suspended stent is not within the preset damage range, or the relative damage of the weighted response three-directional acceleration of the suspended stent is not within the preset damage range, then input the root mean square difference into the inverse function of the frequency response function to obtain the driving difference; adjust the first driving signal according to the driving difference, and based on the adjusted first driving signal, return to the step of inputting the first driving signal into the multibody dynamics model to obtain the response signal and continue execution.

[0155] In some embodiments, the second determining module 604 is further configured to: input the second preset driving force into the multibody dynamics model to obtain the modal participation factor; perform modal calculations based on the finite element model to obtain the second unit stress; and determine the second full-field time-domain stress and the second strain amplitude according to the second unit stress and the modal participation factor.

[0156] In some embodiments, the third determining module 605 is further configured to: apply a unit angular displacement at the center position of the second main crossbeam of the frame finite element model to obtain a third unit stress; and determine the third full-field time-domain stress and the third strain amplitude based on the proportional relationship between the unit angular displacement and the pre-processed relative torsion angle, according to the third unit stress.

[0157] In some embodiments, the analysis module 606 is further configured to: determine a critical plane based on the first full-field time-domain stress, the second full-field time-domain stress, and the third full-field time-domain stress; map the first full-field time-domain stress, the second full-field time-domain stress, the third full-field time-domain stress, the first strain amplitude, the second strain amplitude, and the third strain amplitude to the critical plane; and within the critical plane, based on rainflow projection, obtain a target time-domain stress based on the first full-field time-domain stress, the second full-field time-domain stress, and the third full-field time-domain stress, and based on the first strain amplitude... The target strain amplitude is obtained by considering the first strain amplitude, the second strain amplitude, and the third strain amplitude. Based on the target time-domain stress, the target strain amplitude, and the strain life curve of the rear lower suspension bracket, the single-cycle damage of the rear lower suspension bracket under different road conditions is determined when the vehicle travels once on the test section. The strain life curve includes the strain life curve of the basic material and the strain life curve of the welding material. Based on the single-cycle damage under different road conditions and the number of trips corresponding to each road condition, the total damage of the rear lower suspension bracket is calculated, and the fatigue life of the rear lower suspension bracket is determined based on the total damage and the length of the test section.

[0158] Each module in the aforementioned fatigue life analysis device for the rear suspension support can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in the processor of a computer device in hardware form or independent of it, or stored in the memory of a computer device in software form, so that the processor can call and execute the corresponding operations of each module.

[0159] In one embodiment, a computer device is provided, which may be a terminal, and its internal structure diagram may be as follows: Figure 7As shown, the computer device includes a processor, memory, input / output interface, communication interface, display unit, and input device. The processor, memory, and input / output interface are connected via a system bus, and the communication interface, display unit, and input device are also connected to the system bus via the input / output interface. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage media. The input / output interface is used for exchanging information between the processor and external devices. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, mobile cellular networks, NFC (Near Field Communication), or other technologies. When the computer program is executed by the processor, it implements a method for fatigue life analysis of a rear-mounted lower support. The display unit is used to form a visually visible image and can be a display screen, projection device, or virtual reality imaging device. The display screen can be an LCD screen or an e-ink screen. The input device of the computer device can be a touch layer covering the display screen, or buttons, trackballs, or touchpads set on the casing of the computer device, or external keyboards, touchpads, or mice, etc.

[0160] Those skilled in the art will understand that Figure 7 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0161] In one embodiment, a computer device is provided, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to perform the following steps: acquiring the relative torsional angle between a first main crossbeam and a second main crossbeam, and the axial displacement of a spring damper, when a vehicle is traveling on a test road section; and acquiring, based on the vehicle coordinate system, the three-directional accelerations of the upper suspension bracket and the lower suspension bracket when the vehicle is traveling on the test road section, wherein the upper suspension bracket and the lower suspension bracket are connected by springs, the upper end of the upper suspension bracket is connected to the cab, and the lower end of the lower suspension bracket is connected to the vehicle frame; the first main crossbeam and the second main crossbeam are two main crossbeams of the vehicle frame directly below the cab, and the second main crossbeam is close to the vehicle body; and adjusting the relative torsional angle, the axial displacement, the three-directional accelerations of the upper suspension bracket and the lower suspension bracket based on the actual vehicle speed, a preset vehicle speed, and a preset number of times the vehicle has traveled on the test road section. The following steps are performed: Preprocessing is performed on each component. Based on the multibody dynamics model of the cab and suspension system, and the finite element model of the rear lower suspension bracket, the first full-field time-domain stress and first strain amplitude of the rear lower suspension bracket under cab inertial load conditions are determined according to the first preset drive, the preprocessed axial displacement, the three-directional acceleration of the upper suspension bracket, and the three-directional acceleration of the lower suspension bracket. Based on the finite element model and multibody dynamics model of the rear lower suspension bracket, and according to the second preset drive, the second full-field time-domain stress and second strain amplitude of the rear lower suspension bracket under vibration and resonance conditions are determined. Based on the finite element model of the chassis, and according to the preprocessed relative torsion angle, the third full-field time-domain stress and third strain amplitude of the rear lower suspension bracket under low-frequency torsion conditions of the chassis are determined. The fatigue life of the rear lower suspension bracket is analyzed based on the first full-field time-domain stress, the first strain amplitude, the second full-field time-domain stress, the second strain amplitude, the third full-field time-domain stress, and the third strain amplitude.

[0162] In one embodiment, when the processor executes the computer program, it performs preprocessing on the relative torsional angle, the axial displacement, the three-directional acceleration of the upper suspension bracket, and the three-directional acceleration of the lower suspension bracket based on the actual vehicle speed, the preset vehicle speed, and the preset number of times the vehicle travels on the test section. This includes: calculating the total pseudo-damage of the relative torsional angle, the axial displacement, the three-directional acceleration of the upper suspension bracket, and the three-directional acceleration of the lower suspension bracket each time the vehicle travels on the test section, based on the preset vehicle speed and the preset number of times; determining the median of all total pseudo-damages as the target total pseudo-damage, and determining the relative torsional angle, axial displacement, the three-directional acceleration of the upper suspension bracket, and the three-directional acceleration of the lower suspension bracket corresponding to the target total pseudo-damage as the target load spectrum signal; determining whether the difference between the actual vehicle speed corresponding to the target load spectrum signal and the preset vehicle speed is within the preset vehicle speed range; if the difference is not within the preset vehicle speed range, then returning to obtain the first main crossbeam and the second main crossbeam when the vehicle travels on the test section. The relative torsional angle between beams and the axial displacement of the spring damper are measured. Based on the vehicle coordinate system, the three-directional acceleration of the upper suspension bracket and the three-directional acceleration of the lower suspension bracket are obtained when the vehicle is traveling on the test section. This process continues until the difference between the actual vehicle speed corresponding to the determined target load spectrum signal and the preset vehicle speed is within the preset vehicle speed range. If the difference is within the preset vehicle speed range, it is determined whether each parameter contained in the target load spectrum signal is within the corresponding first data range. If there are parameters that are not within the corresponding first data range, they are deleted. If each parameter contained in the target load spectrum signal is within the corresponding first data range, it is determined whether each parameter contained in the target load spectrum signal is within the corresponding second data range. If there are parameters that are not within the corresponding second data range, an alarm signal is issued. The alarm signal is used to indicate that the sensor measuring the corresponding parameter has malfunctioned or that the vehicle has malfunctioned. The upper limit of the second data range is less than the lower limit of the first data range.

[0163] In one embodiment, when the processor executes a computer program, it implements a multibody dynamics model based on the cab and suspension system, and a finite element model of the rear lower suspension bracket. Based on a first preset drive and pre-processed axial displacement, three-directional acceleration of the upper suspension bracket, and three-directional acceleration of the lower suspension bracket, it determines the first full-field time-domain stress and first strain amplitude of the rear lower suspension bracket under the cab inertial load condition. This includes: filtering the pre-processed axial displacement, three-directional acceleration of the upper suspension bracket, and three-directional acceleration of the lower suspension bracket according to preset start and end frequencies to obtain target signals; determining white noise according to the start frequency and preset boundary frequency, and determining pink noise according to the boundary frequency and the end frequency, wherein the boundary frequency... The white noise is a signal whose energy does not change with frequency, and the pink noise is a signal whose energy changes exponentially with frequency. The white noise and pink noise are input into the multibody dynamics model to obtain a frequency response function. Based on the start frequency and the end frequency, and according to the first preset drive, it is determined whether the coherence of the frequency response function is greater than a preset coherence value. If the coherence of the frequency response function is greater than the preset coherence value, the target signal is input into the inverse function of the frequency response function to obtain a first drive signal. Based on the multibody dynamics model and the finite element model, and according to the first drive signal and a preset weight value, the first full-field time-domain stress and the first strain amplitude are determined.

[0164] In one embodiment, after the processor executes the computer program to determine whether the coherence of the frequency response function is greater than a preset coherence value based on the start frequency and the end frequency, according to the target signal and the first preset drive, the process further includes: if the coherence of the frequency response function is not greater than the preset coherence value, adjusting the standard deviation of the white noise, the boundary frequency, and the curve exponent of the pink noise, and based on the adjusted parameters, returning to the step of inputting the white noise and the pink noise into the multibody dynamics model to obtain the frequency response function and continuing execution.

[0165] In one embodiment, the processor, when executing a computer program, determines the first full-field time-domain stress and the first strain amplitude based on the multibody dynamics model and the finite element model, according to the first driving signal and preset weight values. This includes: inputting the first driving signal into the multibody dynamics model to obtain a response signal, the response signal including the three-directional acceleration of the upper suspension support, the three-directional acceleration of the lower suspension support, and the axial displacement; assigning weights to each parameter contained in the target signal according to the preset weight values ​​to obtain a weighted target signal, and assigning weights to each parameter contained in the response signal according to the preset weight values. Each parameter is assigned a weight to obtain a weighted response signal; the root mean square difference between the first root mean square value of the weighted target signal and the second root mean square value of the weighted response signal is determined to be less than a preset proportion of the first root mean square value; if the root mean square difference is less than the preset proportion, and the relative damage of the weighted target acceleration in the three directions of the suspended lower support in the weighted target signal and the relative damage of the weighted response acceleration in the three directions of the suspended lower support in the weighted response signal are both within a preset damage range, then based on the multibody dynamics model and the finite element model, and according to the first driving signal, the first full-field time-domain stress and the first strain amplitude are determined.

[0166] In one embodiment, the processor, when executing a computer program, determines the first full-field time-domain stress and the first strain amplitude based on the multibody dynamics model and the finite element model, according to the first driving signal, including: driving the multibody dynamics model using the first driving signal to obtain the time history load of the rear suspension underarm; inputting unit loads at multiple preset points in the finite element model to obtain the first unit stress corresponding to the unit load; and determining the first full-field time-domain stress and the first strain amplitude corresponding to the time history load based on the proportional relationship between the time history load and the unit load, according to the first unit stress.

[0167] In one embodiment, after the processor executes the computer program to determine whether the root mean square difference between the first root mean square value of the weighted target signal and the second root mean square value of the weighted response signal is less than a preset proportion of the first root mean square value, the process further includes: if the root mean square difference is not less than the preset proportion, the relative damage of the weighted target acceleration in three directions under the suspension is not within a preset damage range, or the relative damage of the weighted response acceleration in three directions under the suspension is not within a preset damage range, then the root mean square difference is input into the inverse function of the frequency response function to obtain a driving difference; the first driving signal is adjusted according to the driving difference, and based on the adjusted first driving signal, the process returns to the step of inputting the first driving signal into the multibody dynamics model to obtain a response signal and continues execution.

[0168] In one embodiment, when the processor executes a computer program, it implements a finite element model and a multibody dynamics model of the rear-suspension underpinning support. Based on a second preset drive, it determines the second full-field time-domain stress and the second strain amplitude of the rear-suspension under vibration conditions and resonance response. This includes: inputting the second preset drive into the multibody dynamics model to obtain a modal participation factor; performing modal calculations based on the finite element model to obtain a second unit stress; and determining the second full-field time-domain stress and the second strain amplitude based on the second unit stress and the modal participation factor.

[0169] In one embodiment, the processor, when executing a computer program, implements a finite element model of the vehicle frame to determine the third full-field time-domain stress and the third strain amplitude of the rear suspension lower bracket under low-frequency torsional conditions of the vehicle frame based on the pre-processed relative torsion angle. This includes: applying a unit angular displacement at the center position of the second main crossbeam of the vehicle frame finite element model to obtain a third unit stress; and determining the third full-field time-domain stress and the third strain amplitude based on the proportional relationship between the unit angular displacement and the pre-processed relative torsion angle, according to the third unit stress.

[0170] In one embodiment, the processor, when executing a computer program, analyzes the fatigue life of the suspended lower bracket based on the first full-field time-domain stress, the first strain amplitude, the second full-field time-domain stress, the second strain amplitude, the third full-field time-domain stress, and the third strain amplitude, including: determining a critical plane based on the first full-field time-domain stress, the second full-field time-domain stress, and the third full-field time-domain stress; mapping the first full-field time-domain stress, the second full-field time-domain stress, the third full-field time-domain stress, the first strain amplitude, the second strain amplitude, and the third strain amplitude to the critical plane; and within the critical plane, based on rainflow projection, analyzing the fatigue life of the suspended lower bracket based on the first full-field time-domain stress, the first strain amplitude, the second strain amplitude, and the third strain amplitude. The second and third full-field time-domain stresses are used to obtain the target time-domain stress, and the target strain amplitude is obtained based on the first, second, and third strain amplitudes. Based on the target time-domain stress, the target strain amplitude, and the strain life curve of the rear lower suspension bracket, the single-cycle damage of the rear lower suspension bracket under different road conditions is determined when the vehicle travels once on the test section. The strain life curve includes the strain life curve of the basic material and the strain life curve of the welding material. Based on the single-cycle damage under different road conditions and the number of trips corresponding to each road condition, the total damage of the rear lower suspension bracket is calculated, and the fatigue life of the rear lower suspension bracket is determined based on the total damage and the length of the test section.

[0171] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon that, when executed by a processor, implements the steps in the above method embodiments.

[0172] In one embodiment, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps in the above method embodiments.

[0173] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of the relevant data shall comply with the relevant laws, regulations and standards of the relevant countries and regions.

[0174] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0175] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0176] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method of analyzing fatigue life of a lower bracket of a rear suspension, characterized by, The method comprises: obtaining the relative torsion angle between the first main cross beam and the second main cross beam and the axial displacement of the spring shock absorber when the vehicle is running on the test section, and obtaining the three-directional acceleration of the upper suspension support and the three-directional acceleration of the lower suspension support of the vehicle when the vehicle is running on the test section based on the whole vehicle coordinate system, the upper suspension support and the lower suspension support being connected by a spring, the upper end of the upper suspension support being connected with the cab, the lower end of the lower suspension support being connected with the frame, the first main cross beam and the second main cross beam being two frame main cross beams directly below the cab, and the second main cross beam being close to the vehicle body; based on the actual vehicle speed, the preset vehicle speed and the preset number of times of running of the vehicle on the test section, the relative torsion angle, the axial displacement, the three-directional acceleration of the upper suspension support and the three-directional acceleration of the lower suspension support are pretreated respectively; based on the multi-body dynamics model of the cab and the suspension system and the finite element model of the rear lower suspension support, the first full-field time-domain stress and the first strain amplitude of the rear lower suspension support under the cab inertia load condition are determined according to the first preset driving and the pretreated axial displacement, the three-directional acceleration of the upper suspension support and the three-directional acceleration of the lower suspension support; based on the finite element model of the rear lower suspension support and the multi-body dynamics model of the rear lower suspension support, the second full-field time-domain stress and the second strain amplitude of the rear lower suspension support under the vibration condition and the resonance response are determined according to the second preset driving; based on the frame finite element model, the third full-field time-domain stress and the third strain amplitude of the rear lower suspension support under the frame low-frequency torsion condition are determined according to the pretreated relative torsion angle; the fatigue life of the rear lower suspension support is analyzed according to the first full-field time-domain stress, the first strain amplitude, the second full-field time-domain stress, the second strain amplitude, the third full-field time-domain stress and the third strain amplitude.

2. The method of claim 1, wherein, The pretreatment of the relative torsion angle, the axial displacement, the three-directional acceleration of the upper suspension support and the three-directional acceleration of the lower suspension support based on the actual vehicle speed, the preset vehicle speed and the preset number of times of running of the vehicle on the test section comprises: based on the preset vehicle speed and the preset number of times, the total pseudo-damage of the relative torsion angle, the axial displacement, the three-directional acceleration of the upper suspension support and the three-directional acceleration of the lower suspension support of the vehicle each time running on the test section is calculated; the median of all total pseudo-damages is determined as the target total pseudo-damage, and the relative torsion angle, the axial displacement, the three-directional acceleration of the upper suspension support and the three-directional acceleration of the lower suspension support corresponding to the target total pseudo-damage are determined as the target load spectrum signal; determining whether a difference between the actual vehicle speed corresponding to the target load spectrum signal and the preset vehicle speed is within a preset vehicle speed range, and if the difference is not within the preset vehicle speed range, returning to the steps of obtaining the relative torsion angle between the first main cross beam and the second main cross beam and the axial displacement of the spring damper when the vehicle is running on the test road section, and obtaining the three-direction accelerations of the upper suspension bracket and the lower suspension bracket of the vehicle based on the whole vehicle coordinate system, and continuing to execute until the difference between the actual vehicle speed corresponding to the target load spectrum signal and the preset vehicle speed is within the preset vehicle speed range; if the difference is within the preset vehicle speed range, determining whether each parameter included in the target load spectrum signal is within a corresponding first data range, and if there is a parameter not within the corresponding first data range, deleting the parameter not within the corresponding first data range; if each parameter included in the target load spectrum signal is within the corresponding first data range, determining whether each parameter included in the target load spectrum signal is within a corresponding second data range, and if there is a parameter not within the corresponding second data range, issuing an alarm signal, the alarm signal being used to indicate that a sensor for measuring the corresponding parameter has failed or the vehicle has failed, wherein the upper limit of the second data range is less than the lower limit of the first data range.

3. The method of claim 1, wherein, The multi-body dynamics model based on the cab and the suspension system and the finite element model of the lower rear suspension bracket determine the first full-field time-domain stress and the first strain amplitude of the lower rear suspension bracket under the cab inertia load condition according to the first preset driving and the preprocessed axial displacement, the three-direction accelerations of the upper suspension bracket and the lower suspension bracket, including: screening the preprocessed axial displacement, the three-direction accelerations of the upper suspension bracket and the lower suspension bracket according to a preset starting frequency and a preset ending frequency to obtain a target signal; determining white noise according to the starting frequency and a preset boundary frequency, and determining pink noise according to the boundary frequency and the ending frequency, the boundary frequency being greater than the starting frequency and less than the ending frequency, the white noise being a signal whose energy does not change with frequency, and the pink noise being a signal whose energy changes exponentially with frequency; inputting the white noise and the pink noise into the multi-body dynamics model to obtain a frequency response function; judging whether the coherence of the frequency response function is greater than a preset coherence value based on the starting frequency and the ending frequency and according to the first preset driving; if the coherence of the frequency response function is greater than the preset coherence value, inputting the target signal into an inverse function of the frequency response function to obtain a first driving signal; determining the first full-field time-domain stress and the first strain amplitude based on the multi-body dynamics model and the finite element model and according to the first driving signal and a preset weight value.

4. The method of claim 3, wherein, after judging whether the coherence of the frequency response function is greater than a preset coherence value based on the starting frequency and the ending frequency and according to the target signal and the first preset driving, the method further includes: If the coherence of the frequency response function is not greater than the preset coherence value, adjusting the standard deviation of white noise, the boundary frequency and the curve index of pink noise, and based on the adjusted parameters, returning to the step of inputting the white noise and the pink noise into the multi-body dynamics model to obtain the frequency response function and continuing to execute.

5. The method of claim 3, wherein, The first full-field time-domain stress and the first strain amplitude are determined based on the multi-body dynamics model and the finite element model according to the first driving signal and a preset weight value, including: The first driving signal is input into the multi-body dynamics model to obtain a response signal, and the response signal includes a response three-direction acceleration of a suspension upper support, a response three-direction acceleration of a suspension lower support and a response axial displacement; According to the preset weight value, a weight is respectively assigned to each parameter contained in the target signal to obtain a weighted target signal, and a weight is respectively assigned to each parameter contained in the response signal to obtain a weighted response signal; It is judged whether the root mean square difference value between the first root mean square value of the weighted target signal and the second root mean square value of the weighted response signal is less than a preset proportion value of the first root mean square value; If the root mean square difference value is less than the preset proportion value, and the relative damage of the suspension lower support weighted target three-direction acceleration in the weighted target signal and the relative damage of the suspension lower support weighted response three-direction acceleration in the weighted response signal are both within a preset damage range, the first full-field time-domain stress and the first strain amplitude are determined based on the multi-body dynamics model and the finite element model according to the first driving signal.

6. The method of claim 5, wherein, The first full-field time-domain stress and the first strain amplitude are determined based on the multi-body dynamics model and the finite element model according to the first driving signal, including: The multi-body dynamics model is driven by the first driving signal to obtain a time history load of the rear suspension lower support; A unit load is input at a plurality of preset points of the finite element model to obtain a first unit stress corresponding to the unit load; Based on the proportional relationship between the time history load and the unit load, the first full-field time-domain stress and the first strain amplitude corresponding to the time history load are determined according to the first unit stress.

7. The method of claim 5, wherein, After judging whether the root mean square difference value between the first root mean square value of the weighted target signal and the second root mean square value of the weighted response signal is less than a preset proportion value of the first root mean square value, it further includes: If the root mean square difference value is not less than the preset proportion value, the relative damage of the suspension lower support weighted target three-direction acceleration is not within the preset damage range, or the relative damage of the suspension lower support weighted response three-direction acceleration is not within the preset damage range, the root mean square difference value is input into an inverse function of the frequency response function to obtain a driving difference value; The first driving signal is adjusted according to the driving difference value, and based on the adjusted first driving signal, the step of inputting the first driving signal into the multi-body dynamics model to obtain a response signal is returned and continued to execute.

8. The method of claim 1, wherein, The finite element model based on the rear lower suspension support and the multi-body dynamics model of the rear lower suspension support determine a second full-field time-domain stress and a second strain amplitude of the rear lower suspension support under vibration working conditions and resonance response according to a second preset driving, and the method comprises the following steps: inputting the second preset driving into the multi-body dynamics model to obtain a modal participation factor; performing modal calculation based on the finite element model to obtain a second unit stress; determining the second full-field time-domain stress and the second strain amplitude according to the second unit stress and the modal participation factor.

9. The method of claim 1, wherein, The finite element model of the vehicle frame determines a third full-field time-domain stress and a third strain amplitude of the rear lower suspension support under a low-frequency torsion working condition of the vehicle frame according to the preprocessed relative torsion angle, and the method comprises the following steps: applying a unit angular displacement at the center position of the second main cross beam of the finite element model of the vehicle frame to obtain a third unit stress; determining the third full-field time-domain stress and the third strain amplitude according to the third unit stress based on the proportional relationship between the unit angular displacement and the preprocessed relative torsion angle.

10. The method of claim 1, wherein, The fatigue life of the rear lower suspension support is analyzed according to the first full-field time-domain stress, the first strain amplitude, the second full-field time-domain stress, the second strain amplitude, the third full-field time-domain stress and the third strain amplitude, and the method comprises the following steps: determining a critical plane according to the first full-field time-domain stress, the second full-field time-domain stress and the third full-field time-domain stress; mapping the first full-field time-domain stress, the second full-field time-domain stress, the third full-field time-domain stress, the first strain amplitude, the second strain amplitude and the third strain amplitude to the critical plane; obtaining a target time-domain stress according to the first full-field time-domain stress, the second full-field time-domain stress and the third full-field time-domain stress and a target strain amplitude according to the first strain amplitude, the second strain amplitude and the third strain amplitude in the critical plane based on rainflow projection; determining a single-cycle damage of the rear lower suspension support under different road conditions when the vehicle drives on the test road section once according to the target time-domain stress, the target strain amplitude and a strain life curve of the rear lower suspension support, wherein the strain life curve comprises a basic material strain life curve and a welded material strain life curve; calculating a total damage of the rear lower suspension support according to the single-cycle damage under different road conditions and the driving frequency corresponding to each road condition, and determining the fatigue life of the rear lower suspension support according to the total damage and the length of the test road section.

11. A device for analyzing fatigue life of a lower bracket of a rear suspension, characterized by, The device comprises: The acquisition module is configured to acquire a relative torsion angle between the first main cross beam and the second main cross beam when the vehicle is running on a test section, and an axial displacement of the spring damper, and acquire a three-directional acceleration of an upper suspension support and a three-directional acceleration of a lower suspension support of the vehicle when the vehicle is running on the test section based on a whole vehicle coordinate system, the upper suspension support and the lower suspension support being connected by a spring, an upper end of the upper suspension support being connected with a cab, a lower end of the lower suspension support being connected with a frame, the first main cross beam and the second main cross beam being two frame main cross beams directly below the cab, and the second main cross beam being close to a vehicle body; The preprocessing module is configured to preprocess the relative torsion angle, the axial displacement, the three-directional acceleration of the upper suspension support, and the three-directional acceleration of the lower suspension support based on an actual vehicle speed, a preset vehicle speed, and a preset number of times of running of the vehicle on the test section. The first determination module is configured to determine a first full-field time-domain stress and a first strain amplitude of the rear lower suspension support under a cab inertia load condition based on a multi-body dynamics model of the cab and the suspension system and a finite element model of the rear lower suspension support according to a first preset driving and the preprocessed axial displacement, three-directional acceleration of the upper suspension support, and three-directional acceleration of the lower suspension support. The second determination module is configured to determine a second full-field time-domain stress and a second strain amplitude of the rear lower suspension support under a vibration condition and a resonance response based on the finite element model of the rear lower suspension support and a multi-body dynamics model of the rear lower suspension support according to a second preset driving. The third determination module is configured to determine a third full-field time-domain stress and a third strain amplitude of the rear lower suspension support under a frame low-frequency torsion condition based on a frame finite element model and the preprocessed relative torsion angle. The analysis module is configured to analyze a fatigue life of the rear lower suspension support based on the first full-field time-domain stress, the first strain amplitude, the second full-field time-domain stress, the second strain amplitude, the third full-field time-domain stress, and the third strain amplitude.

12. A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that, The processor executes the computer program to implement the steps of the method of any one of claims 1 to 6.

13. A computer readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to implement the steps of the method of any one of claims 1 to 6.

14. A computer program product comprising a computer program, characterized in that, The computer program is executed by the processor to implement the steps of the method of any one of claims 1 to 6.

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