A vibration test method, system, and medium for a vehicle pedestrian protection beam test bench.

Abstract

The present invention relates to a vibration test method, system and medium for a vehicle pedestrian protection beam stand, comprising the following steps: S1, installing a three-dimensional acceleration sensor at two installation points on the left and right of the pedestrian protection beam, arranging a strain gauge sensor at the middle position of the pedestrian protection beam, collecting and processing load information of each road surface; S2, constructing a finite element model; S3, fitting a fatigue acceleration load spectrum A i ; S4, fitting acceleration load spectrum A in S3 i S5. Perform fatigue calculation on the pedestrian protection beam when it vibrates in three directions at the same time, and obtain the damage value D1 of the pedestrian protection beam; S6. Calculate the total fatigue damage spectrum All for the test duration M FDS , convert it into the test bench PSD spectrum with a test duration of N; S7, confirm the final test bench PSD spectrum and test time. The acceleration load spectrum of fatigue acceleration is fitted by collecting the acceleration spectra of the two installation points, and the model is benchmarked with the physical object to ensure the accuracy of the simulation iteration input.

Description

Technical Field

[0001] The invention relates to the field of vibration testing, and in particular to a vibration testing method and system for a vehicle pedestrian protection beam stand and a medium. Background Art

[0002] Vibration fatigue is a common failure mode in automotive structures. Vibration fatigue risks are usually discovered during vehicle road tests, and it is difficult to assess vibration fatigue risks during the part design verification phase. How to convert vehicle-level vibration durability into component-level vibration durability is a difficult problem faced by all OEMs. Since vibration fatigue is strongly correlated with the modes of parts, the modes of parts are generally considered during part design. The low-order modes of designed parts need to avoid strong road excitation frequencies to avoid resonance. During road tests, acceleration sensors are placed on the parts to obtain the excitation of the road on the parts, and Fourier transforms are performed to obtain a power spectral density curve. The frequency corresponding to the peak in the curve is the frequency that the part mode needs to avoid. However, this method can only be used as one of the initial judgment bases.

[0003] Furthermore, the power spectrum density curve obtained above can be used as simulation input to obtain the vibration fatigue analysis results of the parts, and then the input of the vibration bench test can be formulated according to the fatigue damage equivalence principle to verify the vibration bench test. There is no unified standard for this process, and how to obtain accurate power spectrum density, how to perform damage equivalence, and how to ensure the consistency between the vibration finite element model and the actual object are all difficult problems faced by engineers. More importantly, the vibration bench load input usually obtained may make the test time too long and force the experiment to be interrupted.

[0004] The invention application with publication number CN 112461548 A proposes a bench durability test method for a light truck fender bracket assembly, and the test method includes the following steps: collecting the acceleration load spectrum of the whole vehicle road test at the installation point of the fender bracket assembly and performing data processing; calculating the frequency response stress of the fender bracket assembly, converting the time domain acceleration signal into a frequency domain signal, performing fatigue analysis on the fender, and obtaining a compensation coefficient; performing fatigue acceleration based on damage equivalence; and finally multiplying the accelerated bench test time by the compensation coefficient to obtain the final bench test time.

[0005] The public document shows that the fender has two mounting points, but only one set of acceleration data is collected without explanation; if the distance between the two mounting points is close, only one set of acceleration data can be measured, but if the distance between the two mounting points is large, the acceleration of the two mounting points will be quite different. How to make a choice? The invention ignores this issue, or the two mounting points of the fender are very close in the invention and do not involve this issue. Secondly, the invention does not compare the simulation load model with the real object, nor does it describe the comparison method, which will increase the randomness and uncontrollability during fatigue acceleration in the later stage, increase iteration time, or make iteration difficult. Summary of the invention

[0006] The present invention provides a vibration test method, system and medium for a vehicle pedestrian protection beam stand, which solves the above-mentioned technical problems by collecting acceleration spectra of two installation points to fit the acceleration load spectrum of fatigue acceleration, and benchmarking the model with the physical object to ensure the accuracy of simulation iterative input.

[0007] The present invention solves the above technical problems in the following way: A vibration test method for a vehicle pedestrian protection beam stand comprises the following steps:

[0008] S1. The pedestrian protection beam is mounted on the front bracket of the vehicle, and three-dimensional (specifically, front-to-rear, left-to-right, and up-to-down) acceleration sensors are installed at the left and right installation points of the pedestrian protection beam. A strain gauge sensor is arranged in the middle of the pedestrian protection beam to collect load information of various road surfaces (including washboard roads, long slope roads, stone roads, cobblestone roads, twisted roads, noisy roads, etc.), and the time domain load information collected by the three-dimensional acceleration sensor is preprocessed, including resampling, deburring, drift removal, etc. After processing, the time domain load spectrum a of the left installation point of the pedestrian protection beam is obtained. Lx 、a Ly 、a Lz , time domain load spectrum of the right installation point a Rx , a Ry 、a Rz ; The strain spectrum is derived from the strain load information collected by the strain gauge sensor;

[0009] S2. Construct a finite element model based on the geometric model of the physical structure of the pedestrian protection beam;

[0010] S3. Through the acceleration spectrum, the acceleration load spectrum A of the three-dimensional fatigue is fitted according to the fatigue contribution of the pedestrian protection beam. i , i = x, y, z (i represents direction, x, y, z represent front-back direction, left-right direction, up-down direction respectively);

[0011] S4. Load A in the finite element model x , Ay , A z (A x , A y , A z is the acceleration load spectrum A i , i = x, y, z), obtain the virtual strain spectrum, introduce the correction coefficient, make the curve phase and trend of the virtual strain spectrum consistent with the measured strain spectrum, so as to correct the fitted acceleration load spectrum A in S3 i ;

[0012] S5. Perform frequency response analysis of pedestrian protection beam under unit acceleration, combined with the modified acceleration load spectrum A i The auto-power spectrum and cross-power spectrum are obtained by transformation, and the vibration fatigue calculation of the pedestrian protection beam is performed to obtain the damage value D1 of the pedestrian protection beam under three-way simultaneous vibration;

[0013] S6. The fatigue damage spectrum FDS obtained by collecting the time domain load spectrum of various road surfaces is used to calculate the total fatigue damage spectrum All of the vehicle with a road test duration of M hours. FDS According to the damage equivalence principle, the total fatigue damage spectrum All FDS Converted into the rig PSD spectrum of the rig vibration test with a test duration of N hours;

[0014] S7. Use the bench PSD spectrum obtained in S6 as the input load to perform vibration fatigue analysis on the pedestrian protection beam, and obtain the damage value D2 of the pedestrian protection beam bench vibration test. Compare the values ​​of D1 and D2, and adjust the bench vibration test duration so that the absolute value of the difference between D1 and D2 is within the preset range, and confirm the final bench vibration test duration.

[0015] Preferably, S3 includes the following steps in sequence:

[0016] S31. In the finite element model, fix the installation point of the pedestrian protection beam, calculate the stress obtained by applying unit acceleration load in three directions, and import the stress results into the fatigue software;

[0017] S32: In the fatigue software, the stress results calculated by S31 are used as the input of fatigue calculation, and the three-dimensional time domain load spectrum a collected from the left installation point of the pedestrian protection beam is loaded at the left and right installation points in turn. Lx 、a Ly 、a Lz , and obtain the maximum damage value L max ;

[0018] S33: In the fatigue software, the stress results calculated by S31 are used as the input of fatigue calculation, and the three-dimensional time domain load spectrum a collected from the right installation point of the pedestrian protection beam is loaded on the left and right installation points in turn. Rx , a Ry 、aRz , and obtain the maximum damage value R max ;

[0019] S34: Order L max , R max Substitute into the formula and calculate the compensation coefficients λ1 and λ2;

[0020] S35: The fitted acceleration load spectrum A i =λ1a Li +λ2a Ri , i = x, y, z

[0021] Preferably, the S4 comprises the following steps in sequence:

[0022] S41: In the fatigue software, the analysis results in S31 are imported, and a three-dimensional virtual strain gauge is set at the middle reference point of the pedestrian protection beam in the result model. This position is the same as the strain gauge sensor attached during the road test;

[0023] S42: Load A at the left and right mounting points in sequence x , A y , A z , and obtain the virtual strain spectrum of the reference point respectively;

[0024] S43: Compare the obtained virtual strain spectrum with the measured strain spectrum, introduce correction coefficients μ1 and μ2, multiply them by λ1 and λ2 respectively, and adjust A i The value of is used to ensure that the phase and trend of the virtual strain spectrum are consistent with the measured strain spectrum.

[0025] Preferably, the S5 comprises the following steps in sequence:

[0026] S51: In the finite element model, the frequency response analysis of the pedestrian protection beam under unit acceleration is performed to obtain the frequency response stress;

[0027] S52: A x , A y , A z Perform Fourier transform respectively to obtain the power spectrum density curve PSD in three directions;

[0028] S53: converting the three-directional power spectrum density curve PSD to obtain an auto-power spectrum and a cross-power spectrum;

[0029] S54: The obtained mutual power spectrum and autopower spectrum are used as input loads, the above-mentioned frequency response stress is used as the result of input stress, the SN curve of the material is input, and vibration fatigue calculation is performed to obtain the damage value D1 of the pedestrian protection beam vibrating in three directions simultaneously. The SN curve here is measured through experiments.

[0030] Preferably, the S6 comprises the following steps in sequence:

[0031] S61: Calculate the impact response spectrum SRS and the limit response spectrum ERS of each road surface according to the collected time domain load spectra of different road surfaces, and obtain the fatigue damage spectrum FDS of each road surface;

[0032] S62: Perform damage superposition based on the number of cycles of each road surface and the corresponding fatigue damage spectrum, and calculate the total fatigue damage spectrum All of the vehicle road test duration M hours FDS ;

[0033] S63: According to the total fatigue damage spectrum All FDS , the output bench vibration test time is N hours, damage and All FDS Consistent bench PSD spectrum.

[0034] Preferably, the S7 comprises the following steps in sequence:

[0035] S71: Use the PSD spectrum as input load and the frequency response stress obtained in S51 as stress input to perform vibration fatigue analysis. The test duration is N hours, and the damage value of the pedestrian protection beam vibration test is D2.

[0036] S72: compare the values ​​of D1 and D2, and adjust the loading time of the PSD spectrum in S71 so that the absolute value of the difference between D1 and D2 is less than 10%;

[0037] S73: The test duration adjusted by S72 is the final test duration of the bench vibration test.

[0038] Preferably, the sampling frequency of the time domain load spectrum in S1 is 1024 Hz, and the analysis frequency range in S51 is 0 to 200 Hz.

[0039] Preferably, the numerical ranges of the correction coefficients μ1 and μ2 in S43 are both 0.8 to 1.2.

[0040] The vehicle pedestrian protection beam bench vibration test system provided by the present invention based on the above test method includes a time domain load spectrum and strain spectrum acquisition module, a finite element model construction module, an acceleration load spectrum acquisition module, an acceleration load spectrum correction module, a fatigue vibration analysis and calculation module, a vehicle road test conversion bench vibration test module, and a bench vibration test correction module;

[0041] The finite element model building module is used to build a finite element model based on a geometric model of the physical structure of the pedestrian protection beam;

[0042] The acceleration load spectrum acquisition module is used to fit the acceleration load spectrum according to the fatigue contribution of the pedestrian protection beam through the time domain load spectrum;

[0043] The acceleration load spectrum correction module is used to correct the acceleration load spectrum by introducing a correction coefficient to make the curve phase and trend of the virtual strain spectrum consistent with the measured strain spectrum;

[0044] The fatigue vibration analysis and calculation module is used to perform frequency response analysis on the pedestrian protection beam under unit acceleration, and to calculate the vibration fatigue of the pedestrian protection beam by combining the modified acceleration load spectrum with the auto-power spectrum and the cross-power spectrum obtained by transformation, and to obtain the damage value D1 of the pedestrian protection beam under three-way simultaneous vibration;

[0045] The vehicle road test conversion bench vibration test module is used to calculate the total fatigue damage spectrum All of the vehicle road test duration M hours FDS Converted into the rig PSD spectrum of the rig vibration test with a test duration of N hours;

[0046] The bench vibration test correction module is used to perform vibration fatigue analysis through the bench PSD spectrum, obtain the damage value D2 of the pedestrian protection beam bench vibration test, compare the values ​​of D1 and D2, and adjust the bench vibration test duration so that the absolute value of the difference between D1 and D2 is within the preset range, and confirm the final bench vibration test duration.

[0047] The present invention also provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the steps of the above-mentioned automobile pedestrian protection beam platform vibration test method are implemented.

[0048] The beneficial effects of the present invention are: the original input load is confirmed by the contribution of the loads at the left and right installation points to the damage of the pedestrian protection beam; at the same time, by arranging virtual strain gauges, the finite element model is benchmarked with the physical object to further confirm the consistency of the simulation input load and model with the actual load and model, ensuring the accuracy of subsequent accelerated tests and simulation iteration inputs. Based on the benchmarked loads and models, the pedestrian protection beam is subjected to a durability analysis of simultaneous vibration in three directions to obtain the total damage. During the fatigue acceleration process, this total damage is used as an indicator to determine whether the accelerated test meets the standard. Another indicator is the total fatigue damage rate during the accelerated test. The total damage is controlled to remain unchanged from these two aspects, making the results more reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0050] Figure 1 It is a flow chart of the vibration calculation method of the automobile pedestrian protection beam stand of the present invention;

[0051] Figure 2 A flow chart of processing collected load information according to an embodiment of the present invention;

[0052] Figure 3 A schematic diagram of a finite element model constructed for an embodiment of the present invention;

[0053] Figure 4 This is a flow chart of calculating the maximum damage value through the time domain load spectrum according to an embodiment of the present invention;

[0054] Figure 5 A schematic diagram of setting a three-dimensional virtual strain gauge in a finite element model according to an embodiment of the present invention;

[0055] Figure 6 It is a comparison diagram of the virtual strain curve and the measured strain spectrum of the embodiment of the present invention;

[0056] Figure 7 The flowchart of converting the three-directional power spectrum density curve PSD to obtain the auto-power spectrum and the cross-power spectrum in the embodiment of the present invention;

[0057] Figure 8 A flow chart of converting a time domain load spectrum into a shock response spectrum SRS, an extreme response spectrum ERS and a fatigue damage spectrum FDS according to an embodiment of the present invention;

[0058] Fig. 9 A flow chart of outputting a bench PSD spectrum according to an embodiment of the present invention;

[0059] Fig.10 A flow chart for confirming the final bench PSD spectrum and test time for an embodiment of the present invention;

[0060] Fig.11 It is a schematic diagram of a vibration test system for a vehicle pedestrian protection beam stand in an embodiment of the invention. DETAILED DESCRIPTION

[0061] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0062] The present invention provides a vibration test method for a vehicle pedestrian protection beam stand, comprising the following steps:

[0063] S1. The pedestrian protection beam is mounted on the front bracket of the vehicle, and three-dimensional (specifically, front-to-back, left-to-right, and up-to-down) acceleration sensors are installed at the left and right installation points of the pedestrian protection beam. A strain gauge sensor is arranged in the middle of the pedestrian protection beam to collect load information of various road surfaces (including washboard roads, long slope roads, stone roads, cobblestone roads, twisted roads, noisy roads, etc.), and the time domain load information collected by the three-dimensional acceleration sensor is signal preprocessed. The sampling frequency of the time domain load spectrum is 1024 Hz, including resampling, deburring, drift removal and other processes, such as Figure 1 As shown; after processing, the time domain load spectrum a of the installation point on the left side of the pedestrian protection beam is obtained Lx 、a Ly 、a Lz , time domain load spectrum a of the right installation point Rx , a Ry 、a Rz ; The strain spectrum is derived from the strain load information collected by the strain gauge sensor;

[0064] S2. Construct a finite element model based on the geometric model of the physical structure of the pedestrian protection beam; Figure 2 As shown in the figure, the model assigns material properties to the longitudinal arm, crossbeam, and weld respectively, and the thickness of the fillet weld is the sum of the thickness of the two plates divided by The thickness of the lap weld is twice the thickness of the thin plate, and the average unit size is 5mm.

[0065] S3. Through the acceleration spectrum, the fatigue acceleration load spectrum A is fitted according to the fatigue contribution of the pedestrian protection beam. i , i = x, y, z (i represents direction, x, y, z represent front and back direction, left and right direction, up and down direction respectively), specifically including the following steps:

[0066] S31. In the finite element model, fix the installation point of the pedestrian protection beam, calculate the stress obtained by applying unit acceleration load in three directions, and import the stress results into the fatigue software;

[0067] S32. In fatigue software, if Figure 3 As shown in the figure, the stress result calculated by S31 is used as the input of fatigue calculation, and the three-dimensional time domain load spectrum a collected from the left installation point of the pedestrian protection beam is loaded at the left and right installation points in turn. Lx 、a Ly 、a Lz , and obtain the maximum damage value L max =0.31;

[0068] S33. In fatigue software, if Figure 3 As shown in the figure, the stress result calculated by S31 is used as the input of fatigue calculation, and the three-dimensional time domain load spectrum a collected from the right installation point of the pedestrian protection beam is loaded on the left and right installation points in turn.Rx , a Ry 、a Rz , and obtain the maximum damage value R max =0.10;

[0069] S34, Order L max , R max Substituting into the formula, we can calculate the compensation coefficients λ1=0.76, λ2=0.24;

[0070] S35: Get the fitted acceleration load spectrum A i =0.76a Li +0.24a Ri , i=x, y, z.

[0071] S4. Load A in the finite element model x , A y , A z (A x , A y , A z is the acceleration load spectrum A i , i = x, y, z), obtain the virtual strain spectrum, introduce the correction coefficient, make the curve phase and trend of the virtual strain spectrum consistent with the measured strain spectrum, so as to correct the fitted acceleration load spectrum A in S3 i , specifically including the following steps:

[0072] S41: In the fatigue software, import the analysis results in S31, such as Figure 4 As shown, a three-dimensional virtual strain gauge is set at the middle reference point of the pedestrian protection beam in the result model, and this position is the same as the strain gauge sensor attached during the road test;

[0073] S42: Load A at the left and right mounting points in sequence x , A y , A z , and obtain the virtual strain spectrum of the reference point respectively;

[0074] S43: Compare the obtained virtual strain spectrum with the measured strain spectrum, introduce correction coefficients μ1 and μ2, multiply them by λ1 and λ2 respectively, and adjust A i The value of Figure 5 As shown, to ensure the consistency of the phase and trend of the two curves, the value range of μ1 and μ2 is 0.8~1.2.

[0075] S5. Perform frequency response analysis of pedestrian protection beam under unit acceleration, combined with the modified acceleration load spectrum A iThe auto-power spectrum and the cross-power spectrum are obtained by transformation, and the vibration fatigue calculation of the pedestrian protection beam is performed to obtain the damage value D1 of the pedestrian protection beam vibrating in three directions simultaneously, which specifically includes the following steps:

[0076] S51: In the finite element model, the frequency response analysis of the pedestrian protection beam under unit acceleration is performed, and the analysis frequency range is 0 to 200 Hz to obtain the frequency response stress;

[0077] S52: A x , A y , A z Perform Fourier transform respectively to obtain the power spectrum density curve PSD in three directions;

[0078] S53: Figure 6 As shown, the three-directional power spectrum density curve PSD is converted into the auto-power spectrum and the cross-power spectrum;

[0079] S54: The obtained mutual power spectrum and autopower spectrum are used as input loads, the above-mentioned frequency response stress is used as the result of input stress, the SN curve of the material is input, and vibration fatigue calculation is performed to obtain the damage value D1=1.21 of the pedestrian protection beam. The SN curve here is measured through experiments.

[0080] S6. Calculate the total fatigue damage spectrum of the vehicle for a road test duration of 310 hours. FDS According to the damage equivalence principle, the total fatigue damage spectrum All FDS The conversion into the bench PSD spectrum of the bench vibration test with a test duration of 50 hours specifically includes the following steps:

[0081] S61: Figure 7 As shown, according to the collected time domain load spectra of different road surfaces, the impact response is calculated to obtain the impact response spectrum SRS of each road surface, and the fatigue damage spectrum FDS of each road surface is obtained at the same time through Fourier transform and calculation of the limit response limit response spectrum ERS;

[0082] S62: Based on the number of cycles of each road surface and the corresponding fatigue damage spectrum, damage superposition is performed to calculate the total fatigue damage spectrum All of the vehicle road test duration of 310h FDS ;

[0083] S63: Figure 8 As shown, according to the total fatigue damage spectrum All FDS The output bench vibration test time is 50h, damage and All FDS Consistent bench PSD spectrum.

[0084] S7. Confirm the final bench vibration test time, which specifically includes the following steps:

[0085] S71: Fig. 9 As shown, the bench PSD spectrum is used as the input load, and the frequency response stress obtained by S51 is used as the stress input to perform vibration fatigue analysis. The test duration is N hours, and the damage value of the pedestrian protection beam bench vibration test is obtained as D2 = 0.93;

[0086] S72: compare the values ​​of D1 and D2, and adjust the test time of the PSD spectrum in S71 so that the absolute value of the difference between D1 and D2 is less than 10%;

[0087] S73: Finally confirm that the duration of the bench vibration test is 62 hours.

[0088] The present invention provides a vehicle pedestrian protection beam stand vibration test system based on the above test method, such as Fig.11 As shown, it includes a time domain load spectrum and strain spectrum acquisition module, a finite element model construction module, an acceleration load spectrum acquisition module, an acceleration load spectrum correction module, a fatigue vibration analysis calculation module, a vehicle road test conversion bench vibration test module, and a bench vibration test correction module;

[0089] The finite element model building module is used to build a finite element model based on a geometric model of the physical structure of the pedestrian protection beam;

[0090] The acceleration load spectrum acquisition module is used to fit the acceleration load spectrum according to the fatigue contribution of the pedestrian protection beam through the time domain load spectrum;

[0091] The acceleration load spectrum correction module is used to correct the acceleration load spectrum by introducing a correction coefficient to make the curve phase and trend of the virtual strain spectrum consistent with the measured strain spectrum;

[0092] The fatigue vibration analysis and calculation module is used to perform frequency response analysis on the pedestrian protection beam under unit acceleration, and to calculate the vibration fatigue of the pedestrian protection beam by combining the modified acceleration load spectrum with the auto-power spectrum and the cross-power spectrum obtained by transformation, and to obtain the damage value D1 of the pedestrian protection beam under three-way simultaneous vibration;

[0093] The vehicle road test conversion bench vibration test module is used to calculate the total fatigue damage spectrum All of the vehicle road test duration M hours FDS Converted into the rig PSD spectrum of the rig vibration test with a test duration of N hours;

[0094] The bench vibration test correction module is used to perform vibration fatigue analysis through the bench PSD spectrum to obtain the damage value D2 of the pedestrian protection beam bench vibration test, and to adjust the bench vibration test duration so that the absolute value of the difference between D1 and D2 is within the preset range, thereby confirming the final bench vibration test duration.

[0095] The present invention also provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the steps of the above-mentioned automobile pedestrian protection beam platform vibration test method are implemented.

[0096] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any ordinary technician in the industry can smoothly implement the present invention as shown in the drawings and described above. However, any equivalent changes, modifications and evolutions made by technicians familiar with the profession without departing from the scope of the technical solution of the present invention using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the technical solution of the present invention.

Claims

1. A vibration test method for a vehicle pedestrian protection beam stand, characterized in that: The following steps are involved: S1. A pedestrian protection beam is mounted on the vehicle, a three-axis acceleration sensor is installed at the left and right installation points of the pedestrian protection beam, a strain gauge sensor is arranged at the middle position of the pedestrian protection beam, load information of various road surfaces is collected, and signal preprocessing is performed on the time domain load information collected by the three-axis acceleration sensor to obtain the time domain load spectrum of the installation points on the left and right sides of the pedestrian protection beam; and a strain spectrum is derived from the strain load information collected by the strain gauge sensor; S2. Construct a finite element model based on the geometric model of the physical structure of the pedestrian protection beam; S3. Through the time domain load spectrum, the acceleration load spectrum A of the three-dimensional fatigue is fitted according to the fatigue contribution of the pedestrian protection beam. i ; S4. Load the acceleration load spectrum A in the finite element model i , a virtual strain spectrum is obtained, and a correction coefficient is introduced to make the curve phase and trend of the virtual strain spectrum consistent with the measured strain spectrum, thereby correcting the fitted acceleration load spectrum A in S3 i ; S5. Perform frequency response analysis of pedestrian protection beam under unit acceleration, combined with the modified acceleration load spectrum A i The obtained auto-power spectrum and cross-power spectrum are used to perform vibration fatigue calculation on the pedestrian protection beam, and the damage value D1 of the pedestrian protection beam under three-way simultaneous vibration is obtained; S6. The fatigue damage spectrum FDS obtained by collecting the time domain load spectrum of various road surfaces is used to calculate the total fatigue damage spectrum All of the vehicle with a road test duration of M hours. FDS According to the damage equivalence principle, the total fatigue damage spectrum All FDS Converted into the rig PSD spectrum of the rig vibration test with a test duration of N hours; S7. Use the bench PSD spectrum obtained in S6 as the input load to perform vibration fatigue analysis on the pedestrian protection beam, and obtain the damage value D2 of the pedestrian protection beam bench vibration test. By adjusting the bench vibration test duration, the absolute value of the difference between D1 and D2 is within the preset range, and the final bench vibration test duration is confirmed.

2. A vibration test method for a vehicle pedestrian protection beam stand according to claim 1, characterized in that: The S3 comprises the following steps in sequence: S31. In the finite element model, fix the installation point of the pedestrian protection beam, calculate the stress obtained by applying unit acceleration load in three directions, and import the stress results into the fatigue software; S32. In the fatigue software, the stress result calculated in S31 is used as the input of fatigue calculation. The three-dimensional time domain load spectrum collected from the left installation point of the pedestrian protection beam is loaded at the left and right installation points in turn to obtain the maximum damage value L max ; S33. In the fatigue software, the stress result calculated in S31 is used as the input of fatigue calculation. The three-dimensional time domain load spectrum collected from the installation point on the right side of the pedestrian protection beam is loaded on the left and right installation points in turn to obtain the maximum damage value R max ; S34, according to L max , R max , calculate and obtain the compensation coefficients λ1 and λ2; S35, bring λ1 and λ2 into the acceleration load spectrum A i , i=x, y, z.

3. A vibration test method for a vehicle pedestrian protection beam stand according to claim 2, characterized in that: The S4 comprises the following steps in sequence: S41. In the fatigue software, the analysis results in S31 are imported, and a three-dimensional virtual strain gauge is set at the middle reference point of the pedestrian protection beam in the result model. This position is the same as the strain gauge sensor attached during the road test; S42, load A at the left and right installation points in sequence x , A y , A z , respectively obtain the virtual strain spectrum of the reference point; S43, compare the obtained virtual strain spectrum with the measured strain spectrum, introduce correction coefficients μ1 and μ2, multiply them by λ1 and λ2 respectively, and adjust A i The value of is used to ensure that the phase and trend of the curve of the virtual strain spectrum are consistent with that of the measured strain spectrum.

4. A vehicle pedestrian protection beam rig vibration test method according to claim 1, characterized in that: The S5 comprises the following steps in sequence: S51. In the finite element model, the frequency response analysis of the pedestrian protection beam under unit acceleration is performed to obtain the frequency response stress; S52, A x , A y , A z Perform Fourier transform respectively to obtain the power spectrum density curve PSD in three directions; S53, converting the three-directional power spectrum density curve PSD to obtain an auto-power spectrum and a cross-power spectrum; S54, using the obtained mutual power spectrum and autopower spectrum as input loads, using the above-mentioned frequency response stress as the result of input stress, inputting the SN curve of the material, performing vibration fatigue calculation, and obtaining the damage value D1 of the pedestrian protection beam when vibrates in three directions simultaneously.

5. A vehicle pedestrian protection beam rig vibration test method according to claim 4, characterized in that: The S6 comprises the following steps in sequence: S61, according to the collected time domain load spectra of different road surfaces, the impact response spectrum SRS and the limit response spectrum ERS of each road surface are calculated, and the fatigue damage spectrum FDS of each road surface is obtained; S62, based on the number of cycles of each road surface and the corresponding fatigue damage spectrum, damage superposition is performed to calculate the total fatigue damage spectrum All of the vehicle with a road test duration of M hours. FDS ; S63, according to the total fatigue damage spectrum All FDS , the output bench vibration test time is N hours, damage and All FDS Consistent bench PSD spectrum.

6. A vibration test method for a vehicle pedestrian protection beam stand according to claim 5, characterized in that: The S7 comprises the following steps in sequence: S71, using the PSD spectrum as input load and the frequency response stress obtained in S51 as stress input, conduct vibration fatigue analysis, the test duration is N hours, and the damage value of the pedestrian protection beam vibration test is D2; S72, comparing the values ​​of D1 and D2, and adjusting the test time of the PSD spectrum in S71 so that the absolute value of the difference between D1 and D2 is less than 10%; S73. The test duration adjusted by S72 is the final test duration of the bench vibration test.

7. A vibration test method for a vehicle pedestrian protection beam stand according to claim 4, characterized in that: The sampling frequency of the time domain load spectrum in S1 is 1024 Hz, and the analysis frequency range in S51 is 0 to 200 Hz.

8. A vehicle pedestrian protection beam rig vibration test method according to claim 3, characterized in that: The correction coefficients μ1 and μ2 in S43 are both in the range of 0.8 to 1.

2.

9. A vehicle pedestrian protection beam stand vibration test system according to the test method of claim 1, characterized in that: It includes a time domain load spectrum and strain spectrum acquisition module, a finite element model construction module, an acceleration load spectrum acquisition module, an acceleration load spectrum correction module, a fatigue vibration analysis calculation module, a vehicle road test conversion bench vibration test module, and a bench vibration test correction module; The time domain load spectrum and strain spectrum acquisition module is used to perform signal preprocessing on the collected load information to obtain the time domain load spectrum and strain spectrum of the installation points on the left and right sides of the pedestrian protection beam; The finite element model building module is used to build a finite element model based on a geometric model of the physical structure of the pedestrian protection beam; The acceleration load spectrum acquisition module is used to fit the acceleration load spectrum according to the fatigue contribution of the pedestrian protection beam through the time domain load spectrum; The acceleration load spectrum correction module is used to correct the acceleration load spectrum by introducing a correction coefficient to make the curve phase and trend of the virtual strain spectrum consistent with the measured strain spectrum; The fatigue vibration analysis and calculation module is used to perform frequency response analysis on the pedestrian protection beam under unit acceleration, and to obtain the auto-power spectrum and cross-power spectrum obtained by transformation in combination with the modified acceleration load spectrum, and to perform vibration fatigue calculation on the pedestrian protection beam to obtain the damage value D1 of the pedestrian protection beam under three-way simultaneous vibration; The vehicle road test conversion bench vibration test module is used to calculate the total fatigue damage spectrum All of the vehicle road test duration M hours FDS Converted into the rig PSD spectrum of the rig vibration test with a test duration of N hours; The bench vibration test correction module is used to perform vibration fatigue analysis through the bench PSD spectrum to obtain the damage value D2 of the pedestrian protection beam bench vibration test, and to adjust the bench vibration test duration so that the absolute value of the difference between D1 and D2 is within the preset range, thereby confirming the final bench vibration test duration.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the vehicle pedestrian protection beam rig vibration test method as claimed in any one of claims 1 to 8 are implemented.

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