CN116793650A - Method, device, equipment and medium for analyzing fatigue life of rear suspension lower bracket - Google Patents
Method, device, equipment and medium for analyzing fatigue life of rear suspension lower bracket Download PDFInfo
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Abstract
The application relates to a method, a device, a computer device, a storage medium and a computer program product for analyzing fatigue life of a rear suspension lower bracket. The method comprises the following steps: firstly, acquiring a relative torsion angle between a first main beam and a second main beam, axial displacement of a spring damper, three-direction acceleration of a suspension upper bracket and three-direction acceleration of a suspension lower bracket, then preprocessing acquired data, respectively acquiring first full-field time-domain stress and first strain amplitude of the rear suspension lower bracket under a cab inertial load working condition, second full-field time-domain stress and second strain amplitude of the rear suspension lower bracket under a vibration working condition and a resonance response, and third full-field time-domain stress and third strain amplitude of the rear suspension lower bracket under a frame low-frequency torsion working condition, and analyzing the fatigue life of the rear suspension lower bracket according to the acquired stress and the strain amplitude. The method provided by the application can accurately evaluate the actual fatigue life of the rear suspension lower bracket.
Description
Technical Field
The application relates to the technical field of reliability and durability, in particular to a method, a device, computer equipment, a storage medium and a computer program product for analyzing the fatigue life of a rear suspension lower bracket.
Background
For commercial vehicles, the primary function of cab suspension is to transfer loads and dampen vibrations. The rear suspension bracket of the cab is not only subjected to the inertial load of the cab on a bumpy road surface, but also bears the additional load caused by torsional deformation of the frame due to the fact that the lower part of the rear suspension bracket is fixed with the frame, and in addition, the rear suspension bracket of the cab is also used for mounting a whole vehicle component, such as an air filter or a fuel filter, and the like, so that resonance phenomenon coupled with the natural frequency of the whole vehicle component due to road surface excitation can be generated. Under the complex load condition, the fatigue cracking problem of the suspended lower bracket after the cab often occurs in the product development process and the use process of the product delivery user of the domestic main engine factory.
At present, the fatigue cracking problem of a rear suspension lower bracket is mainly analyzed by using a CAE simulation technology, wherein an empirical static load is applied to a load transmitted to the suspension bracket by a cab in the XYZ direction, so that the maximum static value or safety coefficient of a structure is evaluated, a torsion displacement load with a fixed value is applied to a front shaft and a rear shaft under the condition of a complex finite element model of the whole vehicle for the load transmitted to the suspension bracket by a frame, the safety coefficient of the structure is inspected, the vibration problem caused by a part suspended on the suspension bracket is mainly applied by a gravity field load (commonly called g load) in industry, or acceleration excitation based on Power Spectrum Density (PSD) is applied, the structural stress response of the structure when resonance is generated is inspected, and the actual fatigue life of the rear suspension lower bracket of the cab cannot be accurately calculated and evaluated because the responses generated by the working conditions cannot be coupled or accumulated.
Disclosure of Invention
In view of the foregoing, it is desirable to provide a rear suspension subframe fatigue life analysis method, apparatus, computer device, computer-readable storage medium, and computer program product that can accurately evaluate the actual fatigue life of a rear suspension subframe.
In a first aspect, the present application provides a method for analyzing fatigue life of a rear suspension subframe, the method comprising:
acquiring a relative torsion angle between a first main beam and a second main beam and axial displacement of a spring damper when a vehicle runs on a test road section, and acquiring three-direction acceleration of a suspension upper bracket and three-direction acceleration of a suspension lower bracket when the vehicle runs on the test road section based on a whole vehicle coordinate system, wherein the suspension upper bracket and the suspension lower bracket are connected through springs, the upper end of the suspension upper bracket is connected with a cab, the lower end of the suspension lower bracket is connected with a frame, the first main beam and the second main beam are two frame main beams under the cab, and the second main beam is close to a vehicle body;
based on an actual vehicle speed, a preset vehicle speed and preset times of running of the vehicle on the test road section, respectively preprocessing the relative torsion angle, the axial displacement, the three-direction acceleration of the suspension upper bracket and the three-direction acceleration of the suspension lower bracket;
Determining a first full-field time-domain stress and a first variable amplitude of the rear suspension lower bracket under the inertial load working condition of the cab according to a first preset driving, the preprocessed axial displacement, the three-direction acceleration of the suspension upper bracket and the three-direction acceleration of the suspension lower bracket based on a multi-body dynamics model of the cab and the suspension system and a finite element model of the rear suspension lower bracket;
determining a second full-field time-domain stress and a second strain amplitude of the rear suspension lower bracket under a vibration working condition and a resonance response according to a second preset drive based on the finite element model of the rear suspension lower bracket and the multi-body dynamics model of the rear suspension lower bracket;
based on a frame finite element model, determining a third full-field time-domain stress and a third strain amplitude of the rear suspension lower bracket under a frame low-frequency torsion working condition according to the preprocessed relative torsion angle;
and analyzing the fatigue life of the suspended lower bracket according to the first full-field time-domain stress, the first amplitude of stress, the second full-field time-domain stress, the second amplitude of strain, the third full-field time-domain stress and the third amplitude of strain.
In one embodiment, the preprocessing is performed on the relative torsion angle, the axial displacement, the three-direction acceleration of the suspension upper bracket and the three-direction acceleration of the suspension lower bracket based on the actual vehicle speed, the preset vehicle speed and the preset number of times that the vehicle runs on the test road section, respectively, and the preprocessing includes:
Calculating total pseudo damage of the relative torsion angle, the axial displacement, the three-direction acceleration of the suspended upper support and the three-direction acceleration of the suspended lower support when the vehicle runs on the test road section each time based on the preset vehicle speed and the preset times;
determining the median of all total pseudo injuries as a target total pseudo injury, and determining the relative torsion angle, axial displacement, three-direction acceleration of a suspended upper bracket and three-direction acceleration of a suspended lower bracket corresponding to the target total pseudo injury as a target load spectrum signal;
judging whether the difference value between the actual vehicle speed corresponding to the target load spectrum signal and the preset vehicle speed is within a preset vehicle speed range, if the difference value is not within the preset vehicle speed range, returning to obtain the relative torsion angle between the first main beam and the second main beam and the axial displacement of the spring damper when the vehicle runs on a test road section, and obtaining the three-direction acceleration of the suspension upper bracket and the three-direction acceleration of the suspension lower bracket when the vehicle runs on the test road section based on a whole vehicle coordinate system, and continuing to execute until the difference value 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 value is in the preset vehicle speed range, judging whether each parameter contained in the target load spectrum signal is in a corresponding first data range, and if the parameter which is not in the corresponding first data range exists, deleting the parameter which is not in the corresponding first data range;
and if the parameters contained in the target load spectrum signal are in the corresponding first data range, judging whether the parameters contained in the target load spectrum signal are in the corresponding second data range, and if the parameters which are not in the corresponding second data range exist, sending out an alarm signal, wherein the alarm signal is used for indicating that a sensor for measuring the corresponding parameters fails or the vehicle fails, and the upper limit of the second data range is smaller than the lower limit of the first data range.
In one embodiment, the determining the first full-field time-domain stress and the first stress amplitude of the rear suspension subframe under the inertial load condition of the cab according to the first preset driving, the preprocessed axial displacement, the three-direction acceleration of the suspension subframe and the three-direction acceleration of the suspension subframe based on the multi-body dynamics model of the cab and the suspension system and the finite element model of the rear suspension subframe includes:
Screening the preprocessed axial displacement, the three-direction acceleration of the suspended upper bracket and the three-direction acceleration of the suspended lower bracket according to a preset starting frequency and a preset ending frequency to obtain a target signal;
white noise is determined according to the initial frequency and a preset boundary frequency, pink noise is determined according to the boundary frequency and the termination frequency, the boundary frequency is larger than the initial frequency and smaller than the termination frequency, the white noise is a signal with energy unchanged with frequency, and the pink noise is a signal with energy changed 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 larger than a preset coherence value or not according to the first preset drive based on the initial frequency and the termination frequency;
if the coherence of the frequency response function is larger than the preset coherence value, inputting the target signal into an inverse function of the frequency response function to obtain a first driving signal;
and determining the first full-field time-domain stress and the first amplitude of the stress according to the first driving signal and a preset weight value based on the multi-body dynamics model and the finite element model.
In one embodiment, after determining whether the coherence of the frequency response function is greater than a preset coherence value according to the target signal and the first preset driving based on the start frequency and the end frequency, the method further includes:
and 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 returning to the step of inputting the white noise and the pink noise into the multi-body dynamics model based on the adjusted parameters to obtain the frequency response function and continuously executing the step.
In one embodiment, the determining the first full-field time-domain stress and the first amplitude of the stress according to the first driving signal and a preset weight value based on the multi-body dynamics model and the finite element model includes:
inputting the first driving signal into the multi-body dynamics model to obtain a response signal, wherein the response signal comprises three-direction acceleration of the suspension upper bracket, three-direction acceleration of the suspension lower bracket and response axial displacement;
respectively distributing weights to each parameter contained in the target signal according to the preset weight value to obtain a weighted target signal, and respectively distributing weights to each parameter contained in the response signal to obtain a weighted response signal;
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 smaller than the preset proportional value of the first root mean square value;
and if the root mean square difference is smaller than the preset proportional value, and the relative damage of the suspended subframe weighted target three-direction acceleration in the weighted target signal and the relative damage of the suspended subframe weighted response three-direction acceleration in the weighted response signal are both in a preset damage range, determining the first full-field time-domain stress and the first variable amplitude according to the first driving signal based on the multi-body dynamics model and the finite element model.
In one embodiment, the determining the first full-field time-domain stress and the first amplitude of the stress from the first driving signal based on the multi-body dynamics model and the finite element model includes:
driving the multi-body dynamics model by using the first driving signal to obtain a time history load of the rear suspension lower bracket;
inputting unit loads at a plurality of preset points of the finite element model to obtain first unit stress corresponding to the unit loads;
and determining a first full-field time-domain stress and a first amplitude corresponding to the time history load according to the first unit stress based on the proportional relation between the time history load and the unit load.
In one embodiment, the 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 smaller than the preset proportional value of the first root mean square value further includes:
if the root mean square difference is not smaller than the preset proportional value, the relative damage of the suspended lower bracket weighted target three-direction acceleration is not in the preset damage range, or the relative damage of the suspended lower bracket weighted response three-direction acceleration is not in the preset damage range, inputting the root mean square difference into an inverse function of the frequency response function to obtain a driving difference;
and adjusting the first driving signal according to the driving difference value, returning the first driving signal to be input into the multi-body dynamics model based on the adjusted first driving signal, obtaining a response signal, and continuing to execute the step.
In one embodiment, the determining, based on the finite element model of the rear suspension subframe and the multi-body dynamics model of the rear suspension subframe according to a second preset driving, a second full-field time-domain stress and a second strain amplitude of the rear suspension subframe under a vibration condition and a resonance response includes:
Inputting the second preset drive 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;
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.
In one embodiment, the determining, based on the frame finite element model and according to the preprocessed relative torsion angle, a third full-field time-domain stress and a third strain amplitude of the rear suspension subframe under a low-frequency torsion condition of the frame includes:
applying unit angular displacement at the center position of a second main beam of the frame finite element model to obtain a third unit stress;
and determining the third full-field time-domain stress and the third strain amplitude according to the third unit stress based on the proportional relation between the unit angular displacement and the preprocessed relative torsion angle.
In one embodiment, the analyzing the fatigue life of the post-suspension subframe based on the first full-field time-domain stress, the first amplitude of stress, the second full-field time-domain stress, the second amplitude of strain, the third full-field time-domain stress, and the third amplitude of strain comprises:
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;
in the critical plane, based on rain flow projection, obtaining 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 obtaining target strain amplitude according to the first strain amplitude, the second strain amplitude and the third strain amplitude;
determining single-cycle damage of the rear suspension subframe under different road conditions when a vehicle runs once in the test road section according to the target time domain stress, the target strain amplitude and a strain life curve of the rear suspension subframe, wherein the strain life curve comprises a basic material strain life curve and a welding material strain life curve;
and calculating the total damage of the rear suspension lower bracket according to the single-cycle damage under different road conditions and the running times corresponding to each road condition, and determining the fatigue life of the rear suspension lower bracket according to the total damage and the length of the test road section.
In a second aspect, the present application also provides a rear suspension subframe fatigue life analysis device, the device comprising:
the acquisition module is used for acquiring the relative torsion angle between the first main beam and the second main beam and the axial displacement of the spring damper when the vehicle runs on the test road section, acquiring the three-direction acceleration of the suspension upper bracket and the three-direction acceleration of the suspension lower bracket when the vehicle runs on the test road section based on a whole vehicle coordinate system, wherein the suspension upper bracket and the suspension lower bracket are connected through springs, the upper end of the suspension upper bracket is connected with a cab, the lower end of the suspension lower bracket is connected with a vehicle frame, the first main beam and the second main beam are two vehicle frame main beams under the cab, and the second main beam is close to a vehicle body;
the preprocessing module is used for respectively preprocessing the relative torsion angle, the axial displacement, the three-direction acceleration of the suspension upper bracket and the three-direction acceleration of the suspension lower bracket based on the actual speed, the preset speed and the preset times of the running of the vehicle on the test road section;
the first determining module is used for determining a first full-field time domain stress and a first variable amplitude of the rear suspension lower bracket under the inertial load working condition of the cab according to a first preset driving, the preprocessed axial displacement, the three-direction acceleration of the suspension upper bracket and the three-direction acceleration of the suspension lower bracket based on the multi-body dynamics model of the cab and the suspension system and the finite element model of the rear suspension lower bracket;
The second determining module is used for determining a second full-field time-domain stress and a second strain amplitude of the rear suspension lower bracket under the vibration working condition and the resonance response according to a second preset drive based on the finite element model of the rear suspension lower bracket and the multi-body dynamics model of the rear suspension lower bracket;
the third determining module is used for determining a third full-field time-domain stress and a third strain amplitude of the rear suspension lower bracket under the low-frequency torsion working condition of the frame according to the preprocessed relative torsion angle based on the frame finite element model;
the analysis module is used for analyzing the fatigue life of the suspended lower bracket according to the first full-field time-domain stress, the first amplitude of stress, the second full-field time-domain stress, the second amplitude of strain, the third full-field time-domain stress and the third amplitude of strain.
In a third aspect, the present application also provides a computer device. The computer device comprises a memory storing a computer program and a processor implementing the steps of the method of any of the embodiments described above when the processor executes the computer program.
In a fourth aspect, the present application also provides a computer-readable storage medium. The computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the steps of the method of any of the embodiments described above.
In a fifth aspect, the present application also provides a computer program product. The computer program product comprising a computer program which, when executed by a processor, implements the steps of the method of any of the embodiments described above.
The method, the device, the computer equipment, the storage medium and the computer program product for analyzing the fatigue life of the rear suspension lower bracket, firstly obtain the relative torsion angle between the first main beam and the second main beam and the axial displacement of the spring shock absorber when the vehicle runs on a test road section, obtain the three-directional acceleration of the suspension upper bracket and the three-directional acceleration of the suspension lower bracket when the vehicle runs on the test road section based on a whole vehicle coordinate system, respectively preprocess the relative torsion angle, the axial displacement, the three-directional acceleration of the suspension upper bracket and the three-directional acceleration of the suspension lower bracket based on the actual vehicle speed, the preset vehicle speed and the preset times of the vehicle running on the test road section, then based on a multi-body dynamics model of a cab and a suspension system and a finite element model of the rear suspension lower bracket, determining a first full-field time-domain stress and a first strain amplitude of the rear suspension lower bracket under a cab inertia load working condition according to a first preset drive and the preprocessed axial displacement, the three-direction acceleration of the suspension upper bracket and the three-direction acceleration of the suspension lower bracket, determining a second full-field time-domain stress and a second strain amplitude of the rear suspension lower bracket under a vibration working condition and a resonance response according to a second preset drive based on a finite element model of the rear suspension lower bracket and a multi-body dynamics model of the rear suspension lower bracket, simultaneously determining a third full-field time-domain stress and a third strain amplitude of the rear suspension lower bracket under a frame low-frequency torsion working condition according to the preprocessed relative torsion angle based on the frame finite element model, finally, 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, the fatigue life of the post-suspension subframe was analyzed. According to the method provided by the application, the three full-field time-domain stresses and the variable amplitude are subjected to coupling analysis, so that the actual fatigue life of the rear suspension lower bracket can be accurately evaluated.
Drawings
FIG. 1 is a flow chart of a method for analyzing fatigue life of a rear suspension subframe according to an embodiment;
FIG. 2 is a diagram of a sensor station arrangement in one embodiment;
FIG. 3 is a schematic diagram of an inertial load decomposition point in one embodiment;
FIG. 4 is a flow diagram of a pretreatment method in one embodiment;
FIG. 5 is a time domain plot of relative torsion angles in another embodiment;
FIG. 6 is a block diagram of a rear suspension subframe fatigue life analysis device according to an embodiment;
fig. 7 is an internal structural diagram of a computer device in one embodiment.
Detailed Description
The present application will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present application more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.
In one embodiment, as shown in fig. 1, a method for analyzing fatigue life of a rear suspension subframe is provided, and the embodiment is applied to a terminal for illustration by using the method, it is understood that the method can also be applied to a server, and can also be applied to a system including the terminal and the server, and is implemented through interaction between the terminal and the server. In this embodiment, the method includes the steps of:
S102, acquiring relative torsion angles between a first main beam and a second main beam of a vehicle when the test road section runs and axial displacement of a spring shock absorber, and acquiring three-direction acceleration of a suspension upper bracket and three-direction acceleration of a suspension lower bracket of the vehicle when the test road section runs based on a whole vehicle coordinate system, wherein the suspension upper bracket and the suspension lower bracket are connected through springs, the upper end of the suspension upper bracket is connected with a cab, the lower end of the suspension lower bracket is connected with a frame, the first main beam and the second main beam are two frame main beams under the cab, and the second main beam is close to a vehicle body.
As shown in fig. 2, the three-directional acceleration of the suspended upper bracket is measured by four three-directional acceleration sensors arranged at the measuring points 1, 2, 3 and 4 of the suspended upper bracket, the three-directional acceleration of the suspended lower bracket is measured by four three-directional acceleration sensors arranged at the measuring points 5, 6, 7 and 8 of the suspended lower bracket, the XYZ channel directions of the acceleration sensors are consistent with the whole vehicle coordinate system used for product design, the axial displacement of the spring damper is measured by four stay wire displacement sensors arranged at the measuring points 9, 10, 11 and 12, wherein the displacement sensors are specified to stretch in a positive direction and compress in a negative direction, the torsion angle of the first main beam is measured by a torsion angle testing device arranged at the measuring point 13, the torsion angle of the second main beam is measured by a torsion angle testing device arranged at the measuring point 14, and the difference of the torsion angles measured by the two torsion angle testing devices is determined as the relative torsion angle between the first main beam and the second main beam. In addition, the actual speed, longitude and latitude and altitude of the vehicle need to be obtained according to conventional GPS measurement.
The test sample vehicle needs to be a target vehicle or a reference vehicle with good running-in state, and the sampling rate needs to be 10 times of the upper limit of the concerned frequency range (generally 0-50 Hz), namely 500Hz.
S104, based on the actual speed, the preset speed and the preset times of running of the vehicle on the test road section, respectively preprocessing the relative torsion angle, the axial displacement, the three-direction acceleration of the suspension upper bracket and the three-direction acceleration of the suspension lower bracket.
Firstly, determining total pseudo damage of relative torsion angle, axial displacement, three-direction acceleration of the suspended upper bracket and three-direction acceleration of the suspended lower bracket during each test, and determining a target load spectrum signal according to the total pseudo damage.
Then, it is checked whether the deviation between the actual vehicle speed corresponding to the target load spectrum signal and the preset vehicle speed is within the preset range, and if not, the step S102 is re-executed.
Then, removing burrs in the target load spectrum signal, namely deleting parameters far larger than a preset parameter range in the target load spectrum signal, for example, deleting the three-direction acceleration signal at a certain moment in the target load spectrum signal, which is higher than the normal three-direction acceleration signal by 5 times, and deleting the three-direction acceleration signal at the moment. After deburring, each corresponding sensor temperature drift is corrected according to the target load spectrum signal, the consistency check is carried out on the vehicle according to the consistency of the same data measured by the symmetrical sensors on both sides of the vehicle, and meanwhile, the sensors are checked according to the pointer direction conditions of various sensors when the vehicle is in different working conditions, for example, the different working conditions can be braking, steering and pit passing.
Finally, data of the vehicle when driving on different road conditions are extracted from the target load spectrum signal, for example, the different road conditions can be pebble road, repair lost pit and washboard road, and signal files are output according to road section names, and the types of the signal files can be binary asc or rsp file formats.
S106, determining a first full-field time domain stress and a first variable amplitude of the rear suspension lower bracket under the inertial load working condition of the cab according to the first preset driving, the preprocessed axial displacement, the three-direction acceleration of the suspension upper bracket and the three-direction acceleration of the suspension lower bracket based on the multi-body dynamics model of the cab and the suspension system and the finite element model of the rear suspension lower bracket.
The process of constructing the multi-body dynamics model of the cab and suspension system is as follows: and entering a multi-body dynamics modeling environment by using software such as MSC.Adams or Simcenter3D Motion. And (3) importing a key hard point coordinate table of the cab and the suspension system, wherein the hard points are joint coordinates with a connection relation or coordinates of a concerned response point. According to the structural form of the system, component objects are established, mainly including a cab, passengers, a frame, a stabilizer bar, a suspension bracket, a hydraulic lock, a connecting rod, a sensor and the like, wherein the cab is required to input actually measured mass, mass center and rotational inertia. And (3) establishing elastic vibration damping element units such as a vibration damper, a spring, bushing force and the like, inputting a stiffness curve and a damping curve, and defining an upper free stroke, a lower free stroke, a compression buffer block stiffness and a tension limiting block stiffness curve of the vibration damper. Kinematic pairs are established, for example cylindrical pairs between the damper piston and the sleeve, and revolute pairs between the cab and the hydraulic lock. The cab suspension brackets, particularly the lower brackets (including the front shock absorber lower bracket, the front stabilizer bar rear articulation lower bracket, the rear suspension lower bracket) and the front stabilizer bar are flexible. The rear suspension lower bracket can be a structure of a reference sample car instead of a target structure except for ensuring the position of a hard point to be unchanged, and is only used for load decomposition, so that the detail of the finite element grid is not particularly required. In the step, the multi-body dynamics modeling of the cab and the suspension system is to solve the inertial load of the cab on the rear suspension lower bracket under the vibration working condition, so that the frame does not need to be modeled flexibly and can be defined as a non-mass object. At the center coordinates of the rigid frame, a virtual vibrating gantry is created, which is essentially a virtual object, replaced with a coordinate system. The virtual vibration bench and the frame are fixed, and the virtual vibration bench is connected with the ground to restrict all degrees of freedom. And calculating a static balance working condition under the influence of gravity only, checking the displacement change of the spring damper, and maintaining the displacement of the spring damper at a designed balance height by adjusting the preload, so as to simulate the static balance characteristic of the air spring damper. And carrying out linearization identification, namely calculating rigid body modes of the cab and the suspension system, checking whether the rigid body modes have larger differences from actual measurement or experience values, and checking whether abnormal part motion postures exist, so as to further correct the model. And establishing a vibration working condition and carrying out joint solution with a static balance working condition, namely setting a restarting working condition so as to avoid initial abnormal impact of the model caused by an unbalanced state in subsequent iterative calculation. And (5) saving the multi-body dynamics model.
S108, determining a second full-field time-domain stress and a second strain amplitude of the rear suspension lower bracket under the vibration working condition and the resonance response according to a second preset drive based on the finite element model of the rear suspension lower bracket and the multi-body dynamics model of the rear suspension lower bracket.
As shown in fig. 3, at the position of a point 21 in the multi-body dynamics model of the cab and the suspension system, the output rear suspension subsystem 6 degrees of freedom drive also includes linear displacement in 3 directions and angular displacement in three directions, wherein the point 21 is located at the midpoint coordinate position of the point 19 and the point 20, and the 6 degrees of freedom drive is the second preset drive.
And (3) newly creating a multi-body dynamics rigid body model of the rear suspension lower bracket, removing all connected and connected objects, performing flexibility, adjusting the rear suspension lower bracket finite element model, rigidly connecting the left and right frame fixing points to form a point, and taking a main point as a subsystem driving position. And calculating a Craig-Bampton (CB) mode, and outputting mode displacement, stress, node force and spc branch counter force. And obtaining a vibration mode of a whole vehicle mounting accessory system with at least 10 orders and a static displacement compensation mode with 6 orders, and endowing a mode damping ratio. And (3) driving a rear suspension lower bracket dynamics model, performing modal participation factor calculation, outputting a 16-order modal coordinate, and storing participation factor data into an asc binary file.
And matching the modal stress result with the participation factor. And establishing a finite element-load matching set, inputting a result file of CB modal calculation and a modal participation factor, and matching through a result keyword head to obtain full-field time domain stress and strain amplitude of the rear suspension subframe under the vibration working condition and resonance response.
S110, determining a third full-field time-domain stress and a third strain amplitude of the rear suspension lower bracket under the low-frequency torsion working condition of the frame based on the frame finite element model according to the preprocessed relative torsion angle.
Based on the frame finite element model, a 6 degree of freedom fixed constraint is imposed at the frame first main beam center location, as at point 13 in fig. 2, and a unit angular displacement along the X-axis, in degrees, is imposed at the frame second main beam center location, as at point 14 in fig. 2. And establishing a Nastran static calculation working condition, adjusting a control card, and outputting the structural response of the static unit angle torsion working condition of the rear suspension lower bracket, wherein the structural response comprises displacement, stress and node force.
And matching the frame torsion result with the test angle. And establishing a finite element-load matching set, inputting the relative torsion angle between the first main beam and the second main beam and the static unit angle torsion working condition structural response of the vehicle when the vehicle runs on a test road section, and carrying out matching and scaling to obtain the full-field time domain stress and strain amplitude of the rear suspension lower bracket under the frame low-frequency torsion working condition.
S112, analyzing the fatigue life of the suspension lower bracket according to the first full-field time-domain stress, the first amplitude of stress, the second full-field time-domain stress, the second amplitude of strain, the third full-field time-domain stress and the third amplitude of strain.
Based on software such as Femfat or Simcenter3D Durability, the result mapping is carried out on the first full-field time-domain stress, the first variable amplitude, the second full-field time-domain stress, the second variable amplitude, the third full-field time-domain stress and the third variable amplitude, a multi-axis stress strain result under each time history sampling point is obtained, a critical plane solving condition of 18 equal-division angles in one plane is inserted, and a critical plane is found according to tensor levels and quantity. And according to the critical plane, performing rain flow projection and filtering, and performing projection and recalculation on all stress amplitude according to the angle. And performing fatigue life analysis from both the base material fatigue life analysis and the welding material fatigue life analysis.
The average stress is corrected, and a correction method based on P-SWT (Smith-Watson-Topper) is selected, so that the survival rate of a material fatigue curve can be defined according to the reliability verification standard of enterprises, and is generally 50%/90%/99%. The parameters are corrected according to the surface roughness of the material, the presence or absence of a heat treatment step, etc., and the parameters that are unclear may be set to 1 by default. And (3) carrying out elastoplastic correction by utilizing a Neuber notch stress condition formula and combining a cyclic stress strain curve. And (3) performing rain flow counting to obtain the cycle number under different stress or strain amplitudes, and performing damage calculation and synthesis by using a progressive linear damage accumulation rule (element Minor). Total injury=Σ single cycle injury per characteristic segment for any element. And the post-treatment is carried out through fatigue analysis software, and the length of the combined test road section can be converted into structural fatigue life and reliable durability mileage.
According to the fatigue life analysis method for the rear suspension lower bracket, the stress and the strain amplitude under three working conditions are subjected to coupling analysis, so that the comprehensive fatigue life prediction accuracy of the rear suspension lower bracket under a complex condition can be remarkably improved, and the calculated fatigue life can be more in line with the actual situation by combining the actual measured data with the finite element analysis.
In some embodiments, as shown in fig. 4, fig. 4 is a schematic flow chart of a preprocessing method in one embodiment, and based on an actual vehicle speed, a preset vehicle speed and a preset number of times the vehicle travels on a test road section, preprocessing a relative torsion angle, an axial displacement, a three-direction acceleration of an upper suspension bracket and a three-direction acceleration of a lower suspension bracket respectively, including: calculating total pseudo damage of relative torsion angle, axial displacement, three-direction acceleration of the suspension upper bracket and three-direction acceleration of the suspension lower bracket when the vehicle runs on a test road section each time based on a preset vehicle speed and preset times; the median of all the total pseudo injuries is determined as the target total pseudo injury, and the relative torsion angle, the axial displacement, the three-direction acceleration of the suspended upper bracket and the three-direction acceleration of the suspended lower bracket corresponding to the target total pseudo injury are determined as target load spectrum signals; judging whether the difference value between the actual vehicle speed corresponding to the target load spectrum signal and the preset vehicle speed is within a preset vehicle speed range, if the difference value is not within the preset vehicle speed range, returning to obtain the relative torsion angle between the first main beam and the second main beam and the axial displacement of the spring damper when the vehicle runs on the test road section, and obtaining the three-direction acceleration of the suspension upper bracket and the three-direction acceleration of the suspension lower bracket of the suspension upper bracket when the vehicle runs on the test road section based on the whole vehicle coordinate system, and continuing to execute until the difference value 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 value is in the preset vehicle speed range, judging whether each parameter contained in the target load spectrum signal is in the corresponding first data range, and if the parameters which are not in the corresponding first data range exist, deleting the parameters which are not in the corresponding first data range; if each parameter contained in the target load spectrum signal is in the corresponding first data range, judging whether each parameter contained in the target load spectrum signal is in the corresponding second data range, and if the parameters which are not in the corresponding second data range exist, sending out an alarm signal, wherein the alarm signal is used for indicating that a sensor for measuring the corresponding parameter fails or a vehicle fails, and the upper limit of the second data range is smaller than the lower limit of the first data range.
In this step, the pseudo damage refers to a damage value obtained by directly considering various load signals as generalized stress without considering a specific structure, using the generalized stress as input, using a specified standard S-N curve, and performing cycle counting and damage accumulation in the same manner as the actual fatigue damage.
According to the method provided by the step, after the parameters are preprocessed, the result of the follow-up finite element analysis can be more accurate.
In some embodiments, determining a first full field time domain stress and a first strain amplitude of the rear suspension subframe under cab inertial load conditions based on the multi-body dynamics model of the cab and suspension system, and the finite element model of the rear suspension subframe from the first preset drive, and the preprocessed axial displacement, suspension upper subframe tri-directional acceleration, suspension lower subframe tri-directional acceleration, comprises: screening the preprocessed axial displacement, the three-direction acceleration of the suspended upper bracket and the three-direction acceleration of the suspended lower bracket according to a preset starting frequency and a preset ending frequency to obtain a target signal; white noise is determined according to the initial frequency and a preset boundary frequency, pink noise is determined according to the boundary frequency and the end frequency, the boundary frequency is larger than the initial frequency and smaller than the end frequency, the white noise is a signal with energy unchanged with frequency, and the pink noise is a signal with energy exponentially changed with frequency; inputting white noise and pink noise into a multi-body dynamics model to obtain a frequency response function; judging whether the coherence of the frequency response function is larger than a preset coherence value or not according to the target signal and the first preset drive based on the starting frequency and the ending frequency; if the coherence of the frequency response function is larger than a preset coherence value, inputting the target signal into an inverse function of the frequency response function to obtain a first driving signal; based on the multi-body dynamics model and the finite element model, determining a first full-field time-domain stress and a first amplitude according to the first driving signal and a preset weight value.
In this step, based on software such as Femfat Lab or Motion TWR, a start frequency and a stop frequency are defined, for example, the start frequency is 1Hz, the stop frequency is 40Hz, and a sampling rate and a frame length are set to ensure that the frequency resolution is less than 0.5Hz. The target sensor channels are set, namely in the multi-body dynamics model, acceleration channels in three directions are established at the positions from the measuring point 1 to the measuring point 8 in fig. 2, 24 acceleration channels are formed in total at each position, one channel is established at the positions from the measuring point 9 to the measuring point 12, and 4 displacement channels are formed in total at each position. And a 6-degree-of-freedom drive, namely a linear displacement drive in three directions and an angular displacement drive in three directions, is established between the virtual vibration rack established in the multi-body dynamics model and the ground through a frame center point coordinate system, and the 6-degree-of-freedom drive is a first preset drive.
Inputting the preprocessed axial displacement, the three-direction acceleration of the suspension upper bracket and the three-direction acceleration of the suspension lower bracket into a multi-body dynamics model, performing channel-signal matching, and simultaneously screening input data through a band-pass filter of 1-40Hz, and removing data which is not in the range of 1-40Hz, so as to obtain a target signal. Setting boundary frequency, defining white noise between the starting frequency and the boundary frequency, pink noise between the boundary frequency and the ending frequency, setting curve index of the pink noise and standard deviation of the white noise. The Frequency Response Function (FRF) is obtained using white-pink noise to drive the multi-body dynamics model. And then, carrying out coherence verification between the input and output of the frequency response function by inputting a preset coherence function to the target signal and the first preset drive, ensuring that the coherence in the range of 1-4Hz is greater than the coherence in the range of 0.7,4-40Hz and greater than 0.85, otherwise, readjusting the standard deviation of white noise, the boundary frequency and the curve index of pink noise until the coherence meets the requirements. And under the condition that the coherence meets the requirement, inputting the target signal into an inverse function of the frequency response function to obtain a first driving signal.
The method provided by the step can determine the first driving signal under the condition that the coherence meets the requirement, so that the accuracy of the first driving signal can be ensured.
In some embodiments, after determining whether the coherence of the frequency response function is greater than a preset coherence value according to the target signal and the first preset drive based on the start frequency and the end frequency, further comprising: if the coherence of the frequency response function is not greater than the preset coherence value, the standard deviation, the boundary frequency and the curve index of the pink noise of the white noise are adjusted, and based on the adjusted parameters, the steps of inputting the white noise and the pink noise into the multi-body dynamics model to obtain the frequency response function are returned, and the steps are continuously executed.
In this step, coherence refers to the degree of linear correlation between the input value and the output value of the frequency response function.
According to the method provided by the step, the corresponding parameters are adjusted through the coherence value, so that the accuracy of a frequency response function obtained through white-pink noise can be ensured.
In some embodiments, determining the first full-field time-domain stress and the first amplitude of the stress from the first drive signal and a preset weight value based on the multi-volumetric dynamics model and the finite element model comprises: inputting the first driving signal into the multi-body dynamics model to obtain a response signal, wherein the response signal comprises three-direction acceleration of the suspension upper bracket, three-direction acceleration of the suspension lower bracket and response axial displacement; respectively distributing weights to each parameter contained in the target signal according to the preset weight value to obtain a weighted target signal, and respectively distributing weights to each parameter contained in the response signal to obtain a weighted response signal; 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 smaller than the preset proportional value of the first root mean square value; and if the root mean square difference is smaller than the preset proportional value, and the relative damage of the suspended subframe weighted target three-direction acceleration in the weighted target signal and the relative damage of the suspended subframe weighted response three-direction acceleration in the weighted response signal are both in a preset damage range, determining the first full-field time-domain stress and the first variable amplitude according to the first driving signal based on the multi-body dynamics model and the finite element model.
In this step, for example, the weight value of the three-directional acceleration of the suspension upper bracket is 0.3-0.4, the weight value of the three-directional acceleration of the suspension lower bracket is 0.4-0.6, the weight value of the axial displacement is 0.2-0.3, and when the root mean square difference between the weighted response signal and the weighted target signal is smaller than the preset root mean square value, and the relative damage of the three-directional acceleration of the suspension lower bracket weighted target in the weighted target signal and the relative damage of the three-directional acceleration of the suspension lower bracket weighted response in the weighted response signal are both between 0.85-1.15, the first full-field time-domain stress and the first amplitude are determined according to the first driving signal.
The method provided by the step can reduce errors in the system due to nonlinearity and uncertainty factors by distributing weights to different parameters.
In some embodiments, determining the first full-field time-domain stress and the first amplitude of the stress from the first drive signal based on the multi-volumetric dynamics model and the finite element model comprises: driving the multi-body dynamics model by using a first driving signal to obtain a time history load of the rear suspension lower bracket; inputting unit loads at a plurality of preset point positions of the finite element model to obtain first unit stress corresponding to the unit loads; and determining a first full-field time domain stress and a first amplitude corresponding to the time history load according to the first unit stress based on the proportional relation between the time history load and the unit load.
In this step, as shown in fig. 3, after the multi-body dynamics model is driven by the first driving signal, 6-direction time history loads are output at points 15, 16, 17, 18, 19 and 20, respectively, for a total of 36 channels, wherein 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.
Based on Hyperworks or ANSA and other finite element simulation software, a detailed rear suspension lower bracket finite element model is established, and the detailed rear suspension lower bracket finite element model comprises operations of part classification naming, geometry cleaning, finite element meshing, modeling and assembling of bolts and welding, endowing materials and attributes, unit quality inspection, checking of weight information and the like. In each of the input points and channels in fig. 4, a unit load condition is established, no constraint is imposed on the model, the inertial release calculation card in Nastran is adopted, load steps are established, and the displacement, stress and node force results of the units are output. And (5) performing finite element analysis and calculation, and outputting a result file in the OP2 format.
And establishing a finite element-load matching set, inputting the result file of the OP2 format obtained by finite element analysis and the time course load of the rear suspension lower bracket, and matching through a result keyword head to obtain the full-field time domain stress and strain amplitude of the rear suspension lower bracket under the working condition of the inertial load of the cab.
According to the method provided by the step, the full-field time domain stress and the strain amplitude of the rear suspension lower bracket under the working condition of the inertial load of the cab are obtained through finite element analysis, and the prediction accuracy of the first full-field time domain stress and the first strain amplitude can be improved.
In some embodiments, 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 the preset ratio value of the first root mean square value further comprises: if the root mean square difference is not smaller than the preset proportional value, the relative damage of the suspended lower bracket weighted target three-direction acceleration is not in the preset damage range, or the relative damage of the suspended lower bracket weighted response three-direction acceleration is not in the preset damage range, inputting the root mean square difference into an inverse function of the frequency response function to obtain a driving difference; and adjusting the first driving signal according to the driving difference value, returning the first driving signal to be input into the multi-body dynamics model based on the adjusted first driving signal, obtaining a response signal, and continuing to execute the step.
In the step, when the root mean square difference is not smaller than a preset proportional value, the relative damage of the three-direction acceleration of the weighted target of the suspended lower bracket is not in a preset damage range, or the relative damage of the weighted response of the suspended lower bracket is not in the preset damage range, the first driving signal is adjusted according to the driving difference.
According to the method provided by the step, the driving signal is determined in an iterative mode, so that the finally determined driving signal is more accurate.
In some embodiments, determining a second full field time domain stress and a second strain amplitude of the rear suspension subframe at the vibration regime and the resonance response based on the finite element model of the rear suspension subframe and the multi-body dynamics model of the rear suspension subframe according to a second preset drive comprises: inputting a second preset drive 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; and determining a second full-field time-domain stress and a second strain amplitude according to the second unit stress and the modal participation factor.
In this step, the modal participation factor is a parameter describing the interaction relation between the modal and a certain vector excitation, and the larger the value of the modal participation factor is, the larger the contribution of the modal to the dynamic response is represented.
According to the method provided by the step, the second full-field time-domain stress and the second strain amplitude are determined according to the modal participation factors, so that the determined second full-field time-domain stress and the determined second strain amplitude are more accurate.
In some embodiments, determining a third full-field time-domain stress and a third strain amplitude of the rear suspension subframe under a low-frequency torsional condition of the frame based on the frame finite element model according to the preprocessed relative torsion angles comprises: applying unit angular displacement at the center position of a second main beam of the frame finite element model to obtain a third unit stress; and determining a third full-field time-domain stress and a third strain amplitude according to the third unit stress based on the proportional relation between the unit angular displacement and the preprocessed relative torsion angle.
In this step, the contents of the frame finite element modeling include: cutting the whole frame, reserving the longitudinal beam and the beam structure between the first main beam and the second main beam, deleting the structure which does not provide torsional rigidity, and including the support of accessories mounted on one side of the frame end, such as an oil tank support, a post processor support and the like.
According to the method provided by the step, the third full-field time-domain stress and the third strain amplitude are determined based on the frame finite element model, so that the determined third full-field time-domain stress and third strain amplitude are more accurate.
In some embodiments, analyzing the fatigue life of the post-suspension subframe based on the first full-field time-domain stress, the first amplitude of stress, the second full-field time-domain stress, the second amplitude of strain, the third full-field time-domain stress, and the third amplitude of strain, comprises: 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 a critical plane; in a critical plane, based on the rain flow projection, 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 obtaining a target strain amplitude according to the first strain amplitude, the second strain amplitude and the third strain amplitude; determining single-cycle damage of the rear suspension lower bracket under different road conditions when the vehicle runs once in a test road section according to the target time domain stress, the target strain amplitude and the strain life curve of the rear suspension lower bracket, wherein the strain life curve comprises a basic material strain life curve and a welding material strain life curve; and calculating the total damage of the rear suspension lower bracket according to the single-cycle damage under different road conditions and the running times corresponding to each road condition, and determining the fatigue life of the rear suspension lower bracket according to the total damage and the length of the tested road section.
In the step, grouping is carried out according to the marks of the metal materials of the suspension lower support, the metal materials enter a basic material fatigue life analysis module, and a fatigue life analysis method based on strain is selected. Setting strain life curve parameters including elastic modulus, tensile strength, stress intensity coefficient, stress intensity index, toughness intensity coefficient and toughness intensity index. Setting a cyclic stress-strain curve parameter comprising a cyclic strength coefficient and a cyclic strain hardening index. All the above parameters should be fitted after testing or estimated by empirical formulas. If a welding process, such as seam welding, is present, a weld material fatigue life analysis module is entered. The identification of the welding seam is completed by two sheet metal parts with cards of different attributes, and the welding seam is identified as T-shaped, Y-shaped, L-shaped, lap joint, butt joint and other types according to the welding angle and the form. And selecting a nominal stress method, and defining an SN curve of the welding material according to the welding type or the load form through standards such as BS 7608. Or selecting a notch stress method, endowing the virtual notch with the radius through thickness, and defining a main SN curve through a node force-based submodel method and a welding joint notch stress database.
According to the method provided by the step, fatigue life analysis is performed from two aspects of basic material fatigue life analysis and welding material fatigue life analysis, so that the analysis result of the rear suspension lower bracket is more comprehensive.
In one embodiment, another method for analyzing fatigue life of a rear suspension subframe is provided, comprising the following:
(1) And (3) testing the road load of the reliability and durability of the whole vehicle, measuring three-way acceleration signals at the sprung position and the unsprung position of a cab suspension system, measuring the axial relative displacement signal of a spring damper, and measuring the relative torsion angle between a first main beam and a second main beam of the frame, wherein the time domain diagram of the relative torsion angle is shown in figure 5. And performing preprocessing operations such as deburring, drift correction, filtering and the like on the signals in one period to obtain target signals or input signals for subsequent load decomposition.
And establishing a multi-body dynamics model comprising a cab, a suspension bracket, an elastic damping element, a virtual sensor and a virtual drive. And through linearization identification, the 6-order rigid body mode of the system is ensured to be consistent with the measured value.
The method comprises the steps of taking sprung acceleration signals and axial relative displacement of a spring damper as target signals, distributing different iteration weights, taking a rigid-flexible hybrid multi-body dynamics model of a cab and a suspension system as a transfer function, and reversely and iteratively solving driving signals outside the system to obtain a motion gesture under the condition of a real road surface and inertial load transmitted by the cab by a suspension bracket, wherein the inertial load comprises a hydraulic lock bushing load, a fixed point bushing load under a rear suspension damper and a supporting load of a virtual clamp (or a frame) end, and the frequency range is 1-40Hz. And (3) carrying out inertial release calculation under unit load on each force input point of the rear suspension lower bracket to obtain displacement and stress response, and carrying out matching of a finite element result and a time domain inertial load to obtain full-field stress amplitude and strain amplitude.
(2) And for a suspension lower bracket structure for mounting the whole vehicle accessory, outputting the subsystem 6 degree-of-freedom drive of the rear suspension bracket by solving a cab and a suspension dynamics model. And establishing a detailed finite element model containing the whole vehicle accessory, obtaining a flexible body file in a dynamics model through CB mode calculation, and inputting a mode damping ratio. And (3) inputting a system drive comprising 3 linear displacements and 3 angular displacements, solving a multi-body dynamics model, and outputting a modal participation factor of the system to obtain a response of the system due to resonance. And matching the finite element result (modal stress) with a modal participation factor to obtain a full-field stress amplitude and a strain amplitude.
(3) A finite element model is created that includes a frame structure between a first main beam and a second main beam. And (3) establishing fixed constraint at the center of the first main beam, applying a unit torsion angle to the second main beam, and outputting the displacement and the stress of the rear suspension lower bracket. And matching the finite element result with the torsion angle of the time domain frame to obtain a full-field stress amplitude and a strain amplitude.
(4) And in the fatigue life analysis module, according to the full-field time domain stress amplitude and the strain amplitude of the various conditions, carrying out result mapping coupling and dangerous direction identification to obtain a critical plane, and carrying out rain flow projection to obtain corrected stress and strain amplitude based on the critical plane. Classifying according to the marks of the metal materials, and inputting respective strain-life curves and cyclic stress-strain curves. And carrying out average stress correction based on the P-SWT, carrying out accumulated calculation of damage by adopting an element-Minor damage accumulation criterion, and finally evaluating the fatigue life of the suspension bracket behind the cab.
It should be understood that, although the steps in the flowcharts related to the embodiments described above are sequentially shown as indicated by arrows, these steps are not necessarily sequentially performed in the order indicated by the arrows. The steps are not strictly limited to the order of execution unless explicitly recited herein, and the steps may be executed in other orders. Moreover, at least some of the steps in the flowcharts described in the above embodiments may include a plurality of steps or a plurality of stages, which are not necessarily performed at the same time, but may be performed at different times, and the order of the steps or stages is not necessarily performed sequentially, but may be performed alternately or alternately with at least some of the other steps or stages.
Based on the same inventive concept, the embodiment of the application also provides a rear suspension lower bracket fatigue life analysis device for realizing the above-mentioned rear suspension lower bracket fatigue life analysis method. The implementation of the solution provided by the device is similar to that described in the above method, so the specific limitations in the embodiments of one or more rear suspension subframe fatigue life analysis devices provided below can be referred to above for the limitations of the rear suspension subframe fatigue life analysis method, and are not repeated here.
In one embodiment, as shown in fig. 6, there is provided a rear suspension subframe fatigue life analysis device 600, 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:
the acquisition module 601 is used for acquiring relative torsion angles between a first main beam and a second main beam and axial displacement of a spring shock absorber when a vehicle runs on a test road section, acquiring three-direction acceleration of a suspension upper bracket and three-direction acceleration of a suspension lower bracket when the vehicle runs on the test road section based on a whole vehicle coordinate system, wherein the suspension upper bracket is connected with the suspension lower bracket through a spring, the upper end of the suspension upper bracket is connected with a cab, the lower end of the suspension lower bracket is connected with a vehicle frame, the first main beam and the second main beam are two vehicle frame main beams under the cab, and the second main beam is close to a vehicle body.
The preprocessing module 602 is configured to respectively preprocess the relative torsion angle, the axial displacement, the three-direction acceleration of the suspended upper bracket, and the three-direction acceleration of the suspended lower bracket based on an actual vehicle speed, a preset vehicle speed, and a preset number of times the vehicle travels on the test road section.
The first determining module 603 is configured to determine, based on the multi-body dynamics model of the cab and the suspension system and the finite element model of the rear suspension lower bracket, a first full-field time-domain stress and a first amplitude of the rear suspension lower bracket under the inertial load condition of the cab according to the first preset driving and the preprocessed axial displacement, the three-direction acceleration of the suspension upper bracket, and the three-direction acceleration of the suspension lower bracket.
A second determining module 604, configured to determine a second full-field time-domain stress and a second strain amplitude of the rear suspension subframe under the vibration condition and the resonance response according to a second preset driving based on the finite element model of the rear suspension subframe and the multi-body dynamics model of the rear suspension subframe.
The third determining module 605 is configured to determine, based on the frame finite element model, a third full-field time-domain stress and a third strain amplitude of the rear suspension subframe under the frame low-frequency torsion condition according to the preprocessed relative torsion angle.
The analysis module 606 is configured to analyze the fatigue life of the post-suspension subframe according to the first full-field time-domain stress, the first amplitude of stress, the second full-field time-domain stress, the second amplitude of strain, the third full-field time-domain stress, and the third amplitude of strain.
In some embodiments, the preprocessing module 602 is further configured to: calculating total pseudo damage of the relative torsion angle, the axial displacement, the three-direction acceleration of the suspended upper support and the three-direction acceleration of the suspended lower support when the vehicle runs on the test road section each time based on the preset vehicle speed and the preset times; determining the median of all total pseudo injuries as a target total pseudo injury, and determining the relative torsion angle, axial displacement, three-direction acceleration of a suspended upper bracket and three-direction acceleration of a suspended lower bracket corresponding to the target total pseudo injury as a target load spectrum signal; judging whether the difference value between the actual vehicle speed corresponding to the target load spectrum signal and the preset vehicle speed is within a preset vehicle speed range, if the difference value is not within the preset vehicle speed range, returning to obtain the relative torsion angle between the first main beam and the second main beam and the axial displacement of the spring damper when the vehicle runs on a test road section, and obtaining the three-direction acceleration of the suspension upper bracket and the three-direction acceleration of the suspension lower bracket when the vehicle runs on the test road section based on a whole vehicle coordinate system, and continuing to execute until the difference value 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 value is in the preset vehicle speed range, judging whether each parameter contained in the target load spectrum signal is in a corresponding first data range, and if the parameter which is not in the corresponding first data range exists, deleting the parameter which is not in the corresponding first data range; and if the parameters contained in the target load spectrum signal are in the corresponding first data range, judging whether the parameters contained in the target load spectrum signal are in the corresponding second data range, and if the parameters which are not in the corresponding second data range exist, sending out an alarm signal, wherein the alarm signal is used for indicating that a sensor for measuring the corresponding parameters fails or the vehicle fails, and the upper limit of the second data range is smaller than the lower limit of the first data range.
In some embodiments, the first determining module 603 includes:
and the screening unit is used for screening the preprocessed axial displacement, the three-direction acceleration of the suspended upper bracket and the three-direction acceleration of the suspended lower bracket according to the preset starting frequency and the preset ending frequency to obtain a target signal.
The first determining unit is configured to determine white noise according to the initial frequency and a preset boundary frequency, and determine pink noise according to the boundary frequency and the termination frequency, where the boundary frequency is greater than the initial 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.
And the first input unit is used for inputting the white noise and the pink noise into the multi-body dynamics model to obtain a frequency response function.
And the judging unit is used for judging whether the coherence of the frequency response function is larger than a preset coherence value or not according to the target signal and the first preset drive based on the initial frequency and the termination frequency.
And the second input unit is used for inputting the target signal into the inverse function of the frequency response function if the coherence of the frequency response function is larger than the preset coherence value, so as to obtain a first driving signal.
And the second determining unit is used for determining the first full-field time-domain stress and the first amplitude according to the first driving signal and a preset weight value based on the multi-body dynamics model and the finite element model.
In some embodiments, the first determining module 603 is further configured to: and 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 returning to the step of inputting the white noise and the pink noise into the multi-body dynamics model based on the adjusted parameters to obtain the frequency response function and continuously executing the step.
In some embodiments, the second determining unit comprises:
and the input subunit is used for inputting the first driving signal into the multi-body dynamics model to obtain a response signal, and the response signal comprises three-direction acceleration of the suspension upper bracket, three-direction acceleration of the suspension lower bracket and response axial displacement.
And the weight distribution subunit is used for respectively distributing weights to each parameter contained in the target signal according to the preset weight value to obtain a weighted target signal, and respectively distributing weights to each parameter contained in the response signal to obtain a weighted response signal.
And the judging subunit is used for 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 smaller than the preset proportion value of the first root mean square value.
And the determining subunit is configured to determine, based on the multi-body dynamics model and the finite element model, the first full-field time-domain stress and the first variable amplitude according to the first driving signal if the root mean square difference is smaller than the preset proportional value and the relative damage of the suspended subframe weighted target three-direction acceleration in the weighted target signal and the relative damage of the suspended subframe weighted response three-direction acceleration in the weighted response signal are both within a preset damage range.
In some embodiments, the determining subunit is further configured to: driving the multi-body dynamics model by using the first driving signal to obtain a time history load of the rear suspension lower bracket; inputting unit loads at a plurality of preset points of the finite element model to obtain first unit stress corresponding to the unit loads; and determining a first full-field time-domain stress and a first amplitude corresponding to the time history load according to the first unit stress based on the proportional relation between the time history load and the unit load.
In some embodiments, the second determining unit is specifically configured to: if the root mean square difference is not smaller than the preset proportional value, the relative damage of the suspended lower bracket weighted target three-direction acceleration is not in the preset damage range, or the relative damage of the suspended lower bracket weighted response three-direction acceleration is not in the preset damage range, inputting the root mean square difference into an inverse function of the frequency response function to obtain a driving difference; and adjusting the first driving signal according to the driving difference value, returning the first driving signal to be input into the multi-body dynamics model based on the adjusted first driving signal, obtaining a response signal, and continuing to execute the step.
In some embodiments, the second determining module 604 is further configured to: inputting the second preset drive 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; 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.
In some embodiments, the third determining module 605 is further configured to: applying unit angular displacement at the center position of a second main beam of the frame finite element model to obtain a third unit stress; and determining the third full-field time-domain stress and the third strain amplitude according to the third unit stress based on the proportional relation between the unit angular displacement and the preprocessed relative torsion angle.
In some embodiments, the analysis module 606 is further configured to: 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; in the critical plane, based on rain flow projection, obtaining 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 obtaining target strain amplitude according to the first strain amplitude, the second strain amplitude and the third strain amplitude; determining single-cycle damage of the rear suspension subframe under different road conditions when a vehicle runs once in the test road section according to the target time domain stress, the target strain amplitude and a strain life curve of the rear suspension subframe, wherein the strain life curve comprises a basic material strain life curve and a welding material strain life curve; and calculating the total damage of the rear suspension lower bracket according to the single-cycle damage under different road conditions and the running times corresponding to each road condition, and determining the fatigue life of the rear suspension lower bracket according to the total damage and the length of the test road section.
The above-described respective modules in the rear suspension subframe fatigue life analysis device may be implemented in whole or in part by software, hardware, and combinations thereof. The above modules may be embedded in hardware or may be independent of a processor in the computer device, or may be stored in software in a memory in the computer device, so that the processor may call and execute operations corresponding to the above modules.
In one embodiment, a computer device is provided, which may be a terminal, and the internal structure of which may be as shown in fig. 7. The computer device includes a processor, a memory, an input/output interface, a communication interface, a display unit, and an input means. The processor, the memory and the input/output interface are connected through a system bus, and the communication interface, the display unit and the input device are connected to the system bus through the input/output interface. Wherein the processor of the computer device is configured to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. 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 of the computer device is used to exchange information between the processor and the external device. The communication interface of the computer device is used for carrying out wired or wireless communication with an external terminal, and the wireless mode can be realized through WIFI, a mobile cellular network, NFC (near field communication) or other technologies. The computer program, when executed by a processor, implements a method for analyzing fatigue life of a rear suspension subframe. The display unit of the computer device is used for forming a visual picture, and can be a display screen, a projection device or a virtual reality imaging device. The display screen can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer equipment can be a touch layer covered on the display screen, can also be a key, a track ball or a touch pad arranged on the shell of the computer equipment, and can also be an external keyboard, a touch pad or a mouse and the like.
It will be appreciated by those skilled in the art that the structure shown in FIG. 7 is merely a block diagram of some of the structures associated with the present inventive arrangements and is not limiting of the computer device to which the present inventive arrangements may be applied, and that a particular computer device may include more or fewer components than shown, or may combine some of the components, or have a different arrangement of components.
In one embodiment, a computer device is provided comprising a memory and a processor, the memory having stored therein a computer program, the processor when executing the computer program performing the steps of: acquiring a relative torsion angle between a first main beam and a second main beam and axial displacement of a spring damper when a vehicle runs on a test road section, and acquiring three-direction acceleration of a suspension upper bracket and three-direction acceleration of a suspension lower bracket when the vehicle runs on the test road section based on a whole vehicle coordinate system, wherein the suspension upper bracket and the suspension lower bracket are connected through springs, the upper end of the suspension upper bracket is connected with a cab, the lower end of the suspension lower bracket is connected with a frame, the first main beam and the second main beam are two frame main beams under the cab, and the second main beam is close to a vehicle body; based on an actual vehicle speed, a preset vehicle speed and preset times of running of the vehicle on the test road section, respectively preprocessing the relative torsion angle, the axial displacement, the three-direction acceleration of the suspension upper bracket and the three-direction acceleration of the suspension lower bracket; determining a first full-field time-domain stress and a first variable amplitude of the rear suspension lower bracket under the inertial load working condition of the cab according to a first preset driving, the preprocessed axial displacement, the three-direction acceleration of the suspension upper bracket and the three-direction acceleration of the suspension lower bracket based on a multi-body dynamics model of the cab and the suspension system and a finite element model of the rear suspension lower bracket; determining a second full-field time-domain stress and a second strain amplitude of the rear suspension lower bracket under a vibration working condition and a resonance response according to a second preset drive based on the finite element model of the rear suspension lower bracket and the multi-body dynamics model of the rear suspension lower bracket; based on a frame finite element model, determining a third full-field time-domain stress and a third strain amplitude of the rear suspension lower bracket under a frame low-frequency torsion working condition according to the preprocessed relative torsion angle; and analyzing the fatigue life of the suspended lower bracket according to the first full-field time-domain stress, the first amplitude of stress, the second full-field time-domain stress, the second amplitude of strain, the third full-field time-domain stress and the third amplitude of strain.
In one embodiment, the preprocessing of the relative torsion angle, the axial displacement, the suspended upper bracket three-direction acceleration and the suspended lower bracket three-direction acceleration based on the actual vehicle speed, the preset vehicle speed and the preset number of times the vehicle travels on the test road section, which are implemented when the processor executes the computer program, includes: calculating total pseudo damage of the relative torsion angle, the axial displacement, the three-direction acceleration of the suspended upper support and the three-direction acceleration of the suspended lower support when the vehicle runs on the test road section each time based on the preset vehicle speed and the preset times; determining the median of all total pseudo injuries as a target total pseudo injury, and determining the relative torsion angle, axial displacement, three-direction acceleration of a suspended upper bracket and three-direction acceleration of a suspended lower bracket corresponding to the target total pseudo injury as a target load spectrum signal; judging whether the difference value between the actual vehicle speed corresponding to the target load spectrum signal and the preset vehicle speed is within a preset vehicle speed range, if the difference value is not within the preset vehicle speed range, returning to obtain the relative torsion angle between the first main beam and the second main beam and the axial displacement of the spring damper when the vehicle runs on a test road section, and obtaining the three-direction acceleration of the suspension upper bracket and the three-direction acceleration of the suspension lower bracket when the vehicle runs on the test road section based on a whole vehicle coordinate system, and continuing to execute until the difference value 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 value is in the preset vehicle speed range, judging whether each parameter contained in the target load spectrum signal is in a corresponding first data range, and if the parameter which is not in the corresponding first data range exists, deleting the parameter which is not in the corresponding first data range; and if the parameters contained in the target load spectrum signal are in the corresponding first data range, judging whether the parameters contained in the target load spectrum signal are in the corresponding second data range, and if the parameters which are not in the corresponding second data range exist, sending out an alarm signal, wherein the alarm signal is used for indicating that a sensor for measuring the corresponding parameters fails or the vehicle fails, and the upper limit of the second data range is smaller than the lower limit of the first data range.
In one embodiment, a multi-body dynamics model based on a cab and suspension system and a finite element model of a rear suspension subframe implemented when a processor executes a computer program, determines a first full field time domain stress and a first strain amplitude of the rear suspension subframe under a cab inertial load condition according to a first preset drive and a preprocessed axial displacement, a suspension subframe three-way acceleration, and a suspension subframe three-way acceleration, comprising: screening the preprocessed axial displacement, the three-direction acceleration of the suspended upper bracket and the three-direction acceleration of the suspended lower bracket according to a preset starting frequency and a preset ending frequency to obtain a target signal; white noise is determined according to the initial frequency and a preset boundary frequency, pink noise is determined according to the boundary frequency and the termination frequency, the boundary frequency is larger than the initial frequency and smaller than the termination frequency, the white noise is a signal with energy unchanged with frequency, and the pink noise is a signal with energy changed 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 larger than a preset coherence value or not according to the first preset drive based on the initial frequency and the termination frequency; if the coherence of the frequency response function is larger than the preset coherence value, inputting the target signal into an inverse function of the frequency response function to obtain a first driving signal; and determining the first full-field time-domain stress and the first amplitude of the stress according to the first driving signal and a preset weight value based on the multi-body dynamics model and the finite element model.
In one embodiment, after determining whether the coherence of the frequency response function is greater than a preset coherence value according to the target signal and the first preset drive based on the start frequency and the end frequency implemented when the processor executes the computer program, the method further includes: and 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 returning to the step of inputting the white noise and the pink noise into the multi-body dynamics model based on the adjusted parameters to obtain the frequency response function and continuously executing the step.
In one embodiment, determining the first full-field time-domain stress and the first amplitude of stress based on the multi-body dynamics model and the finite element model, as implemented when the processor executes the computer program, from the first driving signal and a preset weight value comprises: inputting the first driving signal into the multi-body dynamics model to obtain a response signal, wherein the response signal comprises three-direction acceleration of the suspension upper bracket, three-direction acceleration of the suspension lower bracket and response axial displacement; respectively distributing weights to each parameter contained in the target signal according to the preset weight value to obtain a weighted target signal, and respectively distributing weights to each parameter contained in the response signal to obtain a weighted response signal; 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 smaller than the preset proportional value of the first root mean square value; and if the root mean square difference is smaller than the preset proportional value, and the relative damage of the suspended subframe weighted target three-direction acceleration in the weighted target signal and the relative damage of the suspended subframe weighted response three-direction acceleration in the weighted response signal are both in a preset damage range, determining the first full-field time-domain stress and the first variable amplitude according to the first driving signal based on the multi-body dynamics model and the finite element model.
In one embodiment, determining the first full-field time-domain stress and the first amplitude of the stress from the first driving signal based on the multi-volumetric dynamics model and the finite element model implemented when the processor executes the computer program comprises: driving the multi-body dynamics model by using the first driving signal to obtain a time history load of the rear suspension lower bracket; inputting unit loads at a plurality of preset points of the finite element model to obtain first unit stress corresponding to the unit loads; and determining a first full-field time-domain stress and a first amplitude corresponding to the time history load according to the first unit stress based on the proportional relation between the time history load and the unit load.
In one embodiment, the determining, implemented when the processor executes the computer program, 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 the preset proportional value of the first root mean square value further comprises: if the root mean square difference is not smaller than the preset proportional value, the relative damage of the suspended lower bracket weighted target three-direction acceleration is not in the preset damage range, or the relative damage of the suspended lower bracket weighted response three-direction acceleration is not in the preset damage range, inputting the root mean square difference into an inverse function of the frequency response function to obtain a driving difference; and adjusting the first driving signal according to the driving difference value, returning the first driving signal to be input into the multi-body dynamics model based on the adjusted first driving signal, obtaining a response signal, and continuing to execute the step.
In one embodiment, the determining, by the processor executing the computer program, a second full-field time-domain stress and a second strain amplitude of the rear suspension subframe under the vibration condition and the resonance response according to a second preset drive based on the finite element model of the rear suspension subframe and the multi-body dynamics model of the rear suspension subframe, includes: inputting the second preset drive 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; 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.
In one embodiment, the determining, based on the frame finite element model implemented when the processor executes the computer program, the third full-field time-domain stress and the third strain amplitude of the rear suspension subframe under the frame low-frequency torsion condition according to the preprocessed relative torsion angle includes: applying unit angular displacement at the center position of a second main beam of the frame finite element model to obtain a third unit stress; and determining the third full-field time-domain stress and the third strain amplitude according to the third unit stress based on the proportional relation between the unit angular displacement and the preprocessed relative torsion angle.
In one embodiment, analyzing the fatigue life of the post-suspension subframe according to the first full-field time-domain stress, the first amplitude of stress, the second full-field time-domain stress, the second amplitude of strain, the third full-field time-domain stress, and the third amplitude of strain, as implemented by the processor when executing the computer program, comprises: 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; in the critical plane, based on rain flow projection, obtaining 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 obtaining target strain amplitude according to the first strain amplitude, the second strain amplitude and the third strain amplitude; determining single-cycle damage of the rear suspension subframe under different road conditions when a vehicle runs once in the test road section according to the target time domain stress, the target strain amplitude and a strain life curve of the rear suspension subframe, wherein the strain life curve comprises a basic material strain life curve and a welding material strain life curve; and calculating the total damage of the rear suspension lower bracket according to the single-cycle damage under different road conditions and the running times corresponding to each road condition, and determining the fatigue life of the rear suspension lower bracket according to the total damage and the length of the test road section.
In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored which, when executed by a processor, carries out the steps of the method embodiments described above.
In an embodiment, a computer program product is provided, comprising a computer program which, when executed by a processor, implements the steps of the method embodiments described above.
It should be noted that, the user information (including but not limited to user equipment information, user personal information, etc.) and the data (including but not limited to data for analysis, stored data, presented data, etc.) related to the present application are information and data authorized by the user or sufficiently authorized by each party, and the collection, use and processing of the related data need to comply with the related laws and regulations and standards of the related country and region.
Those skilled in the art will appreciate that implementing all or part of the above described methods may be accomplished by way of a computer program stored on a non-transitory computer readable storage medium, which when executed, may comprise the steps of the embodiments of the methods described above. Any reference to memory, database, or other medium used in embodiments provided herein may include at least one of non-volatile and volatile memory. The nonvolatile Memory may include Read-Only Memory (ROM), magnetic tape, floppy disk, flash Memory, optical Memory, high density embedded nonvolatile Memory, resistive random access Memory (ReRAM), magnetic random access Memory (Magnetoresistive Random Access Memory, MRAM), ferroelectric Memory (Ferroelectric Random Access Memory, FRAM), phase change Memory (Phase Change Memory, PCM), graphene Memory, and the like. Volatile memory can include random access memory (Random Access Memory, RAM) or external cache memory, and the like. By way of illustration, and not limitation, RAM can be in the form of a variety of forms, such as static random access memory (Static Random Access Memory, SRAM) or dynamic random access memory (Dynamic Random Access Memory, DRAM), and the like. The databases referred to in the embodiments provided herein may include at least one of a relational database and a non-relational database. The non-relational database may include, but is not limited to, a blockchain-based distributed database, and the like. The processor referred to in the embodiments provided in the present application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic unit, a data processing logic unit based on quantum computing, or the like, but is not limited thereto.
The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The foregoing examples illustrate only a few embodiments of the application and are described in detail herein without thereby limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of the application should be assessed as that of the appended claims.
Claims (14)
1. A method for analyzing fatigue life of a rear suspension subframe, the method comprising:
acquiring a relative torsion angle between a first main beam and a second main beam and axial displacement of a spring damper when a vehicle runs on a test road section, and acquiring three-direction acceleration of a suspension upper bracket and three-direction acceleration of a suspension lower bracket when the vehicle runs on the test road section based on a whole vehicle coordinate system, wherein the suspension upper bracket and the suspension lower bracket are connected through springs, the upper end of the suspension upper bracket is connected with a cab, the lower end of the suspension lower bracket is connected with a frame, the first main beam and the second main beam are two frame main beams under the cab, and the second main beam is close to a vehicle body;
Based on an actual vehicle speed, a preset vehicle speed and preset times of running of the vehicle on the test road section, respectively preprocessing the relative torsion angle, the axial displacement, the three-direction acceleration of the suspension upper bracket and the three-direction acceleration of the suspension lower bracket;
determining a first full-field time-domain stress and a first variable amplitude of the rear suspension lower bracket under the inertial load working condition of the cab according to a first preset driving, the preprocessed axial displacement, the three-direction acceleration of the suspension upper bracket and the three-direction acceleration of the suspension lower bracket based on a multi-body dynamics model of the cab and the suspension system and a finite element model of the rear suspension lower bracket;
determining a second full-field time-domain stress and a second strain amplitude of the rear suspension lower bracket under a vibration working condition and a resonance response according to a second preset drive based on the finite element model of the rear suspension lower bracket and the multi-body dynamics model of the rear suspension lower bracket;
based on a frame finite element model, determining a third full-field time-domain stress and a third strain amplitude of the rear suspension lower bracket under a frame low-frequency torsion working condition according to the preprocessed relative torsion angle;
and analyzing the fatigue life of the suspended lower bracket according to the first full-field time-domain stress, the first amplitude of stress, the second full-field time-domain stress, the second amplitude of strain, the third full-field time-domain stress and the third amplitude of strain.
2. The method according to claim 1, wherein the preprocessing of the relative torsion angle, the axial displacement, the suspended upper bracket three-directional acceleration, and the suspended lower bracket three-directional acceleration, respectively, based on an actual vehicle speed, a preset vehicle speed, and a preset number of times the vehicle travels on the test road section, includes:
calculating total pseudo damage of the relative torsion angle, the axial displacement, the three-direction acceleration of the suspended upper support and the three-direction acceleration of the suspended lower support when the vehicle runs on the test road section each time based on the preset vehicle speed and the preset times;
determining the median of all total pseudo injuries as a target total pseudo injury, and determining the relative torsion angle, axial displacement, three-direction acceleration of a suspended upper bracket and three-direction acceleration of a suspended lower bracket corresponding to the target total pseudo injury as a target load spectrum signal;
judging whether the difference value between the actual vehicle speed corresponding to the target load spectrum signal and the preset vehicle speed is within a preset vehicle speed range, if the difference value is not within the preset vehicle speed range, returning to obtain the relative torsion angle between the first main beam and the second main beam and the axial displacement of the spring damper when the vehicle runs on a test road section, and obtaining the three-direction acceleration of the suspension upper bracket and the three-direction acceleration of the suspension lower bracket when the vehicle runs on the test road section based on a whole vehicle coordinate system, and continuing to execute until the difference value 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 value is in the preset vehicle speed range, judging whether each parameter contained in the target load spectrum signal is in a corresponding first data range, and if the parameter which is not in the corresponding first data range exists, deleting the parameter which is not in the corresponding first data range;
and if the parameters contained in the target load spectrum signal are in the corresponding first data range, judging whether the parameters contained in the target load spectrum signal are in the corresponding second data range, and if the parameters which are not in the corresponding second data range exist, sending out an alarm signal, wherein the alarm signal is used for indicating that a sensor for measuring the corresponding parameters fails or the vehicle fails, and the upper limit of the second data range is smaller than the lower limit of the first data range.
3. The method of claim 1, wherein determining the first full field time domain stress and the first strain amplitude of the rear suspension subframe under the cab inertial load conditions based on the cab and suspension system based multi-body dynamics model and the rear suspension subframe finite element model based on the first preset drive and the preprocessed axial displacement, the suspension subframe tri-directional acceleration, and the suspension subframe tri-directional acceleration comprises:
Screening the preprocessed axial displacement, the three-direction acceleration of the suspended upper bracket and the three-direction acceleration of the suspended lower bracket according to a preset starting frequency and a preset ending frequency to obtain a target signal;
white noise is determined according to the initial frequency and a preset boundary frequency, pink noise is determined according to the boundary frequency and the termination frequency, the boundary frequency is larger than the initial frequency and smaller than the termination frequency, the white noise is a signal with energy unchanged with frequency, and the pink noise is a signal with energy changed 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 larger than a preset coherence value or not according to the first preset drive based on the initial frequency and the termination frequency;
if the coherence of the frequency response function is larger than the preset coherence value, inputting the target signal into an inverse function of the frequency response function to obtain a first driving signal;
and determining the first full-field time-domain stress and the first amplitude of the stress according to the first driving signal and a preset weight value based on the multi-body dynamics model and the finite element model.
4. The method of claim 3, wherein 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, further comprising:
and 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 returning to the step of inputting the white noise and the pink noise into the multi-body dynamics model based on the adjusted parameters to obtain the frequency response function and continuously executing the step.
5. The method of claim 3, wherein said determining said first full-field time-domain stress and said first amplitude of stress based on said multi-volumetric dynamics model and said finite element model from said first drive signal and a preset weight value comprises:
inputting the first driving signal into the multi-body dynamics model to obtain a response signal, wherein the response signal comprises three-direction acceleration of the suspension upper bracket, three-direction acceleration of the suspension lower bracket and response axial displacement;
Respectively distributing weights to each parameter contained in the target signal according to the preset weight value to obtain a weighted target signal, and respectively distributing weights to each parameter contained in the response signal to obtain a weighted response signal;
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 smaller than the preset proportional value of the first root mean square value;
and if the root mean square difference is smaller than the preset proportional value, and the relative damage of the suspended subframe weighted target three-direction acceleration in the weighted target signal and the relative damage of the suspended subframe weighted response three-direction acceleration in the weighted response signal are both in a preset damage range, determining the first full-field time-domain stress and the first variable amplitude according to the first driving signal based on the multi-body dynamics model and the finite element model.
6. The method of claim 5, wherein said determining said first full-field time-domain stress and said first amplitude of stress from said first drive signal based on said multi-volumetric dynamics model and said finite element model comprises:
Driving the multi-body dynamics model by using the first driving signal to obtain a time history load of the rear suspension lower bracket;
inputting unit loads at a plurality of preset points of the finite element model to obtain first unit stress corresponding to the unit loads;
and determining a first full-field time-domain stress and a first amplitude corresponding to the time history load according to the first unit stress based on the proportional relation between the time history load and the unit load.
7. The method of claim 5, wherein 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 the predetermined ratio of the first root mean square value further comprises:
if the root mean square difference is not smaller than the preset proportional value, the relative damage of the suspended lower bracket weighted target three-direction acceleration is not in the preset damage range, or the relative damage of the suspended lower bracket weighted response three-direction acceleration is not in the preset damage range, inputting the root mean square difference into an inverse function of the frequency response function to obtain a driving difference;
and adjusting the first driving signal according to the driving difference value, returning the first driving signal to be input into the multi-body dynamics model based on the adjusted first driving signal, obtaining a response signal, and continuing to execute the step.
8. The method of claim 1, wherein determining a second full field time domain stress and a second strain amplitude of the rear suspension subframe at the vibration regime and the resonance response based on the finite element model of the rear suspension subframe and the multi-body dynamics model of the rear suspension subframe according to a second preset drive comprises:
inputting the second preset drive 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;
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.
9. The method of claim 1, wherein determining a third full field time domain stress and a third strain amplitude of the rear suspension subframe under low frequency torsional conditions of the frame based on the frame finite element model from the preprocessed relative torsion angles comprises:
applying unit angular displacement at the center position of a second main beam of the frame finite element model to obtain a third unit stress;
and determining the third full-field time-domain stress and the third strain amplitude according to the third unit stress based on the proportional relation between the unit angular displacement and the preprocessed relative torsion angle.
10. The method of claim 1, wherein analyzing the fatigue life of the post-suspension subframe based on the first full-field time-domain stress, the first amplitude of stress, the second full-field time-domain stress, the second amplitude of strain, the third full-field time-domain stress, and the third amplitude of strain, comprises:
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;
in the critical plane, based on rain flow projection, obtaining 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 obtaining target strain amplitude according to the first strain amplitude, the second strain amplitude and the third strain amplitude;
determining single-cycle damage of the rear suspension subframe under different road conditions when a vehicle runs once in the test road section according to the target time domain stress, the target strain amplitude and a strain life curve of the rear suspension subframe, wherein the strain life curve comprises a basic material strain life curve and a welding material strain life curve;
And calculating the total damage of the rear suspension lower bracket according to the single-cycle damage under different road conditions and the running times corresponding to each road condition, and determining the fatigue life of the rear suspension lower bracket according to the total damage and the length of the test road section.
11. A rear suspension subframe fatigue life analysis device, the device comprising:
the acquisition module is used for acquiring the relative torsion angle between the first main beam and the second main beam and the axial displacement of the spring damper when the vehicle runs on the test road section, acquiring the three-direction acceleration of the suspension upper bracket and the three-direction acceleration of the suspension lower bracket when the vehicle runs on the test road section based on a whole vehicle coordinate system, wherein the suspension upper bracket and the suspension lower bracket are connected through springs, the upper end of the suspension upper bracket is connected with a cab, the lower end of the suspension lower bracket is connected with a vehicle frame, the first main beam and the second main beam are two vehicle frame main beams under the cab, and the second main beam is close to a vehicle body;
the preprocessing module is used for respectively preprocessing the relative torsion angle, the axial displacement, the three-direction acceleration of the suspension upper bracket and the three-direction acceleration of the suspension lower bracket based on the actual speed, the preset speed and the preset times of the running of the vehicle on the test road section;
The first determining module is used for determining a first full-field time domain stress and a first variable amplitude of the rear suspension lower bracket under the inertial load working condition of the cab according to a first preset driving, the preprocessed axial displacement, the three-direction acceleration of the suspension upper bracket and the three-direction acceleration of the suspension lower bracket based on the multi-body dynamics model of the cab and the suspension system and the finite element model of the rear suspension lower bracket;
the second determining module is used for determining a second full-field time-domain stress and a second strain amplitude of the rear suspension lower bracket under the vibration working condition and the resonance response according to a second preset drive based on the finite element model of the rear suspension lower bracket and the multi-body dynamics model of the rear suspension lower bracket;
the third determining module is used for determining a third full-field time-domain stress and a third strain amplitude of the rear suspension lower bracket under the low-frequency torsion working condition of the frame according to the preprocessed relative torsion angle based on the frame finite element model;
the analysis module is used for analyzing the fatigue life of the suspended lower bracket according to the first full-field time-domain stress, the first amplitude of stress, the second full-field time-domain stress, the second amplitude of strain, the third full-field time-domain stress and the third amplitude of strain.
12. A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that the processor implements the steps of the method of any of claims 1 to 6 when the computer program is executed.
13. A computer readable storage medium, on which a computer program is stored, characterized in that the computer program, when being executed by a processor, implements the steps of the method of any of claims 1 to 6.
14. A computer program product comprising a computer program, characterized in that the computer program, when being executed by a processor, implements the steps of the method of any of claims 1 to 6.
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| CN202310308374.9A CN116793650A (en) | 2023-03-27 | 2023-03-27 | Method, device, equipment and medium for analyzing fatigue life of rear suspension lower bracket |
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| CN202310308374.9A CN116793650A (en) | 2023-03-27 | 2023-03-27 | Method, device, equipment and medium for analyzing fatigue life of rear suspension lower bracket |
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