A method for analyzing fatigue performance stability of a body cantilever structure

Abstract

The present application belongs to the field of automobile development CAE simulation technology, and relates to a kind of fatigue performance stability analysis method of vehicle body cantilever type structural member;Including vehicle body cantilever type structural member vibration fatigue analysis, vehicle body cantilever type structural member fatigue performance sensitivity analysis, vehicle body cantilever type structural member fatigue influencing factor discretization processing and influencing factor stability performance analysis steps.The present application vehicle body cantilever type structural member fatigue performance stability analysis method, fully considers the discretization condition of each factor influencing vibration fatigue result, according to scientific method, gives the improvement scheme suggestion with more stable performance;Through the method of the present application, the influence of related parameters of vehicle body cantilever type structural member on fatigue performance is analyzed, and according to the discretization property of influencing factors, the most stable value or interval of fatigue performance in the parameter range is identified by applying taguchi parameter design method, which shortens the development cycle, reduces the research and development cost, and improves the product design and development quality.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of CAE simulation technology in automobile development, and particularly relates to a vibration fatigue performance stability analysis method for a cantilever structure of a vehicle body. BACKGROUND

[0002] There are many installation structures on the vehicle body, including: battery, DCDC, electronic and electrical equipment, etc. Many structures need to be connected with the vehicle body, and inevitably become a suspended (cantilevered) structure after being connected. Such a structure form is prone to cause resonance phenomenon and fatigue damage of the structure due to resonance. If the problem is found at this stage of product development process, the improvement space is small, the difficulty is great, the cost is high, and the product development cycle is seriously delayed.

[0003] The fatigue due to resonance phenomenon in the traditional method is highly related to the structure mode, and the fatigue characteristics and input characteristics do not show a trend relationship. Moreover, due to the discreteness of load, material and structure size, the discreteness of the fatigue calculation result is large, and it is difficult to accurately evaluate the accurate vibration fatigue result, and the accuracy far cannot meet the complex engineering actual structure. Based on such calculation accuracy improvement suggestions, it is possible to have no meaning for the actual performance.

[0004] In recent years, with the shortening of the development cycle of passenger cars, it is necessary to intervene in each link in advance, and to use advanced technical means to ensure product quality. It is particularly important to evaluate the performance in the project platform vehicle stage. It is of great help to shorten the development cycle, improve the accuracy of risk identification, and improve the development efficiency to reasonably analyze and evaluate the vibration fatigue of the suspension structure at the initial stage of the vehicle body structure design and give a higher stability calculation result.

[0005] The prior art discloses a fatigue reliability analysis method considering random load and strength degradation, a safety margin equation of a product is established, a certain number of random loads are simulated, the minimum value of the safety margin and the corresponding load action times are calculated, a joint probability density function of the safety margin vector and the corresponding load action times vector is established by using a kernel function estimation, and finally a product fatigue reliability analysis model considering random load and strength degradation is established.

[0006] The prior art also discloses a subset simulation combined with a PCE turbine blade fatigue reliability analysis method, comprising the following steps: establishing a geometric simulation model of a turbine blade; analyzing the geometric simulation model of the turbine blade to determine an n-dimensional random vector x={x1, x2, …, xn}T that affects the fatigue life of the turbine blade, and the relationship between the n-dimensional random vector x={x1, x2, …, xn}T and the design life of the turbine blade; establishing a turbine blade fatigue reliability analysis model to obtain a function function y=g(x) of turbine blade failure; and estimating the fatigue reliability of the turbine blade.

[0007] The prior art also discloses a time-varying degradation quality characteristic compensation full-life-cycle quality robustness optimization method, which belongs to the field of electromagnetic relay quality optimization design. The key design parameters of the electromagnetic relay are analyzed and determined, linearity analysis is performed, the full-life-cycle of the electromagnetic relay is expanded into several sub-life-cycle intervals based on the KL expansion method, the quality robustness characteristic parameters of the sub-life-cycle intervals are modeled and uniformly expressed using the Kriging method, the full-life-cycle quality robustness model of the electromagnetic relay is established, the appropriate quality characteristic level is selected according to the quality robustness characteristic requirement level, the quality robustness characteristic offset degree of the electromagnetic relay under the action of the time-varying degradation parameter is calculated, the quality offset is compensated to the requirement of the full-life-cycle quality robustness, and the Monte Carlo method is used to generate a batch of samples, the output characteristics are calculated, and the optimization effect is verified.

[0008] However, the fatigue caused by resonance phenomenon in the traditional method is highly related to the structure mode, the fatigue characteristics and the input characteristics do not have a trend relationship, and due to the discreteness of load, material and structure size, the discreteness of the fatigue calculation result is large, it is difficult to accurately evaluate the accurate vibration fatigue result, and the accuracy cannot meet the complex engineering actual structure, and the improvement suggestion based on such calculation accuracy is meaningless to the actual performance. SUMMARY

[0009] The purpose of the present application is to solve the problem of the large discreteness of the fatigue calculation result of the traditional method, which is difficult to accurately evaluate the accurate vibration fatigue result, and the accuracy cannot meet the complex engineering actual structure.

[0010] The purpose of the present application is achieved by the following technical solutions:

[0011] A car body cantilever structure fatigue performance stability analysis method, comprising the following steps:

[0012] A, vibration fatigue analysis of the car body cantilever structure;

[0013] B, fatigue performance sensitivity analysis of the car body cantilever structure;

[0014] C. Discretization of fatigue influencing factors of the cantilever structure of the vehicle body and analysis of stability of the influencing factors;

[0015] D. According to the discretization properties of the influencing factors, the parameter range in which the fatigue performance is most stable is identified by using the Taguchi parameter design method.

[0016] Further, step A specifically refers to extracting the modal of the cantilever structure of the vehicle body and calculating the modal participation factor in the required frequency range based on the acceleration PSD load input at the connection point of the cantilever structure of the vehicle body and the vehicle body, and calculating the fatigue damage result of the cantilever structure of the vehicle body by using the Miner fatigue criterion based on the cut plane method and the dirik probability density function.

[0017] Further, the acceleration PSD curve at the connection point of the cantilever structure of the vehicle body and the vehicle body is taken as the load input, the constrained modal of the cantilever structure of the vehicle body is extracted, and the modal participation factor vector in the range of 0-100 Hz is calculated, and the vibration fatigue result of the structure is solved by using the cut plane method and the dirik probability density function.

[0018] Further, step B specifically refers to locking the parameters of the cantilever structure of the vehicle body that need to be optimized, specifying the design interval range, and performing parameter sensitivity analysis on the locked structure parameters with the minimum fatigue damage result as the target.

[0019] Further, step B specifically refers to locking the parameters of the cantilever structure of the vehicle body that need to be optimized, specifying the design interval range, and performing parameter sensitivity analysis on the locked structure parameters with the minimum fatigue damage result as the target.

[0020] Further, step C, the discretization of the fatigue influencing factors of the cantilever structure of the vehicle body specifically refers to selecting the discretization factors that affect the fatigue performance of the structure, and discretizing the factors: for factors with only a given deviation range, the discretization factors are processed as normal distribution; for factors with only different samples, three input samples are randomly selected, and the discretization factors are processed as webull distribution.

[0021] Further, the discretization factors include load input curve, material PSN curve and structure tolerance band.

[0022] Further, step C specifically includes the following steps:

[0023] C1. Discretization of the load input curve: given the factor of three measured load spectrum samples, process it as webull distribution;

[0024] C2, material curve discretization: replace the material S-N curve with the P-S-N curve;

[0025] C3, structure size discretization: to the thickness of the structure, according to the drawing tolerance, do normal distribution processing.

[0026] Further, step C, the stability performance analysis of the influence factor is specifically: based on the Taguchi orthogonal parameter design method, a parameter analysis process is built, the static system analysis function is applied in the parameter analysis step for the target of vibration fatigue, the design parameters selected in the fatigue performance sensitivity analysis step of the cantilever structure of the vehicle body are used as the control factor group, the discretization factors selected in the discretization processing step of the fatigue influence factor of the cantilever structure of the vehicle body are used as the noise factor group, the structure fatigue life and the structure mass are used as the system response, and the performance stability slope of the control factor group in the design interval is analyzed.

[0027] Further, step D is specifically: according to the relationship between the structure parameters and the fatigue performance and the overall mass obtained in steps A-C, corresponding parameter groups are selected according to the actual product development requirements, and the performance stability of each group of parameters is compared.

[0028] Compared with the prior art, the beneficial effects of the present application are:

[0029] The vehicle body cantilever structure fatigue performance stability analysis method fully considers the discretization of various factors affecting the vibration fatigue result, gives an improved scheme suggestion with more stable performance according to a scientific method, and through the method, the influence of the related parameters of the vehicle body cantilever structure on the fatigue performance is analyzed, and according to the discretization properties of the influence factors, the fatigue performance most stable value or interval in the parameter range is identified by applying the Taguchi parameter design method, which can effectively shorten the development cycle, reduce the research and development cost, and improve the product design and development quality. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor.

[0031] Figure 1 is the main implementation step flowchart of the present application;

[0032] Figure 2 is the vibration fatigue damage cloud chart of the cantilever structure of the vehicle body in the present application;

[0033] Figure 3It is the thickness of the car body cantilever structure member and the isight optimization implementation in the application;

[0034] Figure 4 It is the Taguchi static system design chart in the application.

[0035] Figure 5 It is the calculation result of the stability of the influence factor. DETAILED DESCRIPTION

[0036] The application will be further described below in conjunction with the embodiments:

[0037] The application will be further described below in conjunction with the embodiments:

[0038] It should be noted that: similar signs and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. Meanwhile, in the description of the application, the terms "first", "second" and the like are only used for distinguishing description, and cannot be understood as indicating or implying relative importance.

[0039] As shown in the figure, the fatigue performance stability analysis method of the car body cantilever structure member of the application comprises the following steps: Figure 1

[0040] 1. Vibration fatigue analysis of the car body cantilever structure member;

[0041] 2. Fatigue performance sensitivity analysis of the car body cantilever structure member;

[0042] 3. Discretization processing of the fatigue influence factor of the car body cantilever structure member, and analysis of the stability of the influence factor.

[0043] Through the method of the application, the influence of the related parameters of the car body cantilever structure member on the fatigue performance is analyzed, and according to the discretization property of the influence factors, the Taguchi parameter design method is applied to analyze and identify the most stable value or interval of the target performance (fatigue performance) in the parameter range.

[0044] Among them, the vibration fatigue analysis of the car body cantilever structure member comprises:

[0045] The acceleration time history curve of the connecting point of the car body cantilever structure is processed into a PSD curve;

[0046] ​Apply ABAQUS software platform, apply *frequency key extraction of car body cantilever structure constraint modal, constraint position is the car body cantilever structure connecting point, the frequency range is selected according to the frequency range of PSD curve, or can be selected according to experience (generally 1-100Hz);

[0047] Apply ABAQUS software platform, apply *STEADY STATE DYNAMICS keyword calculation frequency domain required frequency range (consistent with the modal extraction step) modal participation factor;

[0048] Apply FEMFAT software platform, integration of the above step PSD curve, modal participation factor calculation results file, based on the cut plane method and dilirk probability density function, application miner fatigue criterion to calculate the fatigue damage results of car body cantilever structure, such as Figure 2 As shown.

[0049] The fatigue performance sensitivity analysis of the car body cantilever structure includes:

[0050] Lock the car body cantilever structure parameters that need to be optimized, the largest fatigue damage result of the plate material in the structure, and specify the design interval range;

[0051] Apply isight software platform, with the minimum fatigue damage result of the locked structure parameters as the target, perform parameter sensitivity analysis, as shown in Figure 3 ;

[0052] The fatigue influencing factor discretization processing of the car body cantilever structure includes:

[0053] Select the discretization factors that affect the fatigue performance of the structure, such as load input curve, material PSN curve, structure tolerance band, etc. The factor discretization processing in this step is not limited to the above mentioned factors. In actual development process, other factors that affect fatigue results and have non-unique input (with a certain deviation range) can be proposed and discretized as factors. After selecting the factors, discretize the factors: for factors with only given deviation range, such as PSN curve and structure tolerance band, process the discrete factors with normal distribution; for factors with only given different samples, such as load input curve, randomly select three input samples, and process the discrete factors with webull distribution.

[0054] The stability performance analysis of the influencing factors includes:

[0055] Based on the Taguchi orthogonal parameter design method, a parameter analysis process is built. The parameter analysis process with vibration fatigue as the target applies the "static system analysis function", the design parameters selected in the "sensitivity analysis of the fatigue performance of the cantilever structure of the vehicle body" as the "control factor group", the discrete factors selected in the "discrete processing of the fatigue influence factors of the cantilever structure of the vehicle body" as the "noise factor group", and the structural fatigue life and the structural mass as the "system response", as shown in Figure 4 .

[0056] Based on the isight software platform, the "discrete processing of the fatigue influence factors of the cantilever structure of the vehicle body" parameters are set to the software platform, and according to the system framework designed in the previous step, the set parameters are referenced to the corresponding components of the process.

[0057] The performance stability slope of the control factor group (the selected structural material thickness) in the design interval is analyzed, that is, the signal-to-noise ratio and the variation coefficient, as shown in Figure 5 .

[0058] According to the above steps, the relationship between the structural parameters (structural material thickness or other) and the fatigue performance and the overall mass is obtained, the corresponding parameter group is selected according to the actual product development requirements, and the performance stability of each group of parameters is compared.

[0059] The method can overcome the fatigue caused by resonance in the traditional method, the fatigue characteristics are highly related to the structural modal, the fatigue characteristics and the input characteristics do not show a trend relationship, and due to the discreteness of the load, the material and the structural size, the discreteness of the fatigue calculation result is large, it is difficult to accurately evaluate the accurate vibration fatigue result, and the accuracy far cannot meet the complex engineering actual structure. Based on the improvement suggestion of the calculation accuracy, the actual performance is meaningless.

[0060] In order to achieve the above effects, the method fully considers the discretization of various factors affecting the vibration fatigue result, and gives an improved scheme suggestion with more stable performance according to a scientific method.

[0061] Note that the above is only a preferred embodiment of the present application and the technical principle applied. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and those skilled in the art can make various obvious changes, re-adjustments and substitutions without departing from the scope of the present application. Therefore, although the present application has been described in more detail through the above embodiments, the present application is not limited to the above embodiments, and can include more other equivalent embodiments without departing from the concept of the present application, and the scope of the present application is determined by the scope of the appended claims.

Claims

1. A method for analyzing the fatigue performance stability of a cantilevered structural component in a vehicle body, characterized in that, Includes the following steps: A. Vibration fatigue analysis of cantilevered structural components of the vehicle body; B. Sensitivity analysis of fatigue performance of cantilever structural components of vehicle body; C. Discretization of fatigue influencing factors and stability analysis of influencing factors for cantilever structural components of vehicle body; The discretization process for the fatigue influence factors of the cantilever structure of the vehicle body is as follows: Select discretization factors that affect the fatigue performance of the structure and discretize the factors: For factors that only give a deviation range, process the discrete factors as a normal distribution; For factors that only give different samples, randomly select three input samples and process the discrete factors as a Webull distribution; The discretization factors include the load input curve, the material PSN curve, and the structural tolerance zone; C1. Load input curve discretization: Given the factors of the load spectrum samples from three measurements, perform webull distribution processing on them; C2. Material curve discretization: Replace the material SN curve with the PSN curve; C3. Structural dimension discretization: The material thickness of the structure is processed according to the drawing tolerances, and a normal distribution is applied. D. Based on the discretization property of the influencing factors, the Taguchi parameter design method is applied to analyze and identify the most stable value or range of fatigue performance within the parameter range.

2. The fatigue performance stability analysis method for a cantilever structure component of a vehicle body according to claim 1, characterized in that, Step A specifically involves: based on the acceleration PSD load input at the connection point between the cantilever structure and the vehicle body, extracting the modes of the cantilever structure and calculating the modal participation factors within the required frequency range, and applying the Miner fatigue criterion based on the cutting plane method and the Dilirk probability density function to calculate the fatigue damage results of the cantilever structure.

3. The fatigue performance stability analysis method for a cantilever structure component of a vehicle body according to claim 2, characterized in that: Using the acceleration PSD curve of the connection point between the cantilever structure and the vehicle body as the load input, the constraint modes of the cantilever structure are extracted, and the modal participation factor vectors of each order in the 0-100Hz range are calculated. The vibration fatigue results of the structure are solved by applying the cutting plane method and the Dirik probability density function.

4. The fatigue performance stability analysis method for a cantilevered vehicle body structure according to claim 1, characterized in that, Step B specifically involves: locking the parameters of the cantilever structure of the vehicle body that need to be optimized, specifying the design range, and performing parameter sensitivity analysis on the locked structural parameters with the goal of minimizing fatigue damage.

5. The fatigue performance stability analysis method for a cantilever structure component of a vehicle body according to claim 4, characterized in that: Using the thickness of the cantilever structural component as the optimization parameter, vibration fatigue damage <1 as the constraint condition, and minimizing the structural mass as the optimization objective, the sensitivity of the structural component thickness to fatigue damage and structural mass is calculated.

6. The fatigue performance stability analysis method for a cantilevered vehicle body structure according to claim 1, characterized in that, Step C, the stability performance analysis of the influencing factors, specifically involves: based on the Taguchi orthogonal parameter design method, establishing a parameter analysis process; applying a static system analysis function in the parameter analysis step targeting vibration fatigue; using the design parameters selected in the fatigue performance sensitivity analysis step of the vehicle body cantilever structure as the control factor group; and using the discretization factor selected in the fatigue influencing factor discretization processing step of the vehicle body cantilever structure as the noise factor group. Taking structural fatigue life and structural quality as the system response, analyzing the performance stability slope of the control factor group within the specified design range.

7. The fatigue performance stability analysis method for a cantilevered vehicle body structure according to claim 1, characterized in that, Step D specifically involves: obtaining the relationship between structural parameters, fatigue performance, and overall quality from steps AC, selecting appropriate parameter groups based on actual product development needs, and comparing the performance stability of each parameter group.

Images