Fatigue analysis and calculation method for automobile shock absorber

Abstract

The invention discloses a fatigue analysis and calculation method for an automobile shock absorber. The fatigue analysis and calculation method comprises the steps that 1, a whole automobile experiment is conducted to obtain a load spectrum at the center of a wheel, and meanwhile an acceleration spectrum at the center of the wheel is measured; 2, measuring each hard point position of the automobile suspension, and building a whole automobile multi-body dynamic model; 3, the load spectrum at the wheel center is input into Adams software for simulation calculation, and a shock absorber load spectrum and a wheel center acceleration spectrum are extracted; 4, verifying the experiment and simulation wheel center acceleration spectrum, and converting into corresponding frequency spectrum density for secondary verification so as to ensure the simulation result precision; step 5, carrying out Hypermesh secondary development on the model; and step 6, entering a fatigue calculation plate in the Hypermesh software, and performing fatigue simulation calculation in combination with an S-N curve fitted by the software. According to the method, the fatigue simulation calculation of the automobile shock absorber can be carried out according to different requirements, the action condition of the road load of the shock absorber is truly simulated, the fatigue simulation calculation precision of the automobile shock absorber is improved, and the research and development period is shortened.

Description

Technical Field

[0001] The invention relates to the field of automobile shock absorber fatigue analysis, and in particular to an automobile shock absorber fatigue analysis method. Background Art

[0002] Shock absorbers are important components in the vehicle suspension system. They can mitigate the impact of the road and absorb vibrations during driving. Their performance is directly related to the driving safety and comfort of the car. Therefore, fatigue research can help identify and prevent cracks that may cause shock absorber failure, thereby avoiding oil and air leakage, ensuring the long-term stable operation of the shock absorber, and protecting the comfort and safety of passengers.

[0003] At present, there are two main methods for fatigue analysis of automobile shock absorbers. The first method is to rely solely on experiments. Although the fatigue data measured is relatively accurate, it has disadvantages such as long cycle and high cost. The second method is to combine experiments with simulations. The general process in China is to use road scanners to collect road surfaces, establish high-precision road models, simulate the established vehicle models with virtual road surfaces to obtain load spectra, and then perform fatigue calculations through simulation software, and finally compare with experiments. This method consumes a lot of time, manpower and material resources. Not only is the R&D cycle long and costly, but the accuracy may not be up to standard.

[0004] At present, the key to automobile shock absorber fatigue analysis calculation lies in how to obtain accurate load spectrum, establish accurate vehicle and shock absorber simulation models, shorten the simulation time, and select appropriate fatigue stress correction methods. Summary of the invention

[0005] In view of the above technical problems, the present invention proposes a fatigue analysis and calculation method for automobile shock absorbers. The method uses a six-component wheel center force sensor to measure the load spectrum of the actual wheel center, then extracts the load spectrum on the shock absorber in Adams software, and establishes a finite element model of the shock absorber in Hypermesh to perform strength simulation and perform secondary development to simplify the simulation process, and then performs fatigue analysis and calculation of the shock absorber.

[0006] The technical solution of the present invention is as follows:

[0007] A fatigue analysis calculation method for an automobile shock absorber comprises the following steps:

[0008] Step 1: Use the wheel center six-component force instrument to conduct a whole vehicle test to obtain the load spectrum at the center of the wheel and measure the acceleration spectrum at the center of the wheel;

[0009] Step 2: Measure the positions of the hard points of the vehicle suspension and build a multi-body dynamics model of the vehicle in Adams software;

[0010] Step 3: Input the load spectrum at the wheel center into the Adams software for simulation calculation, and extract the shock absorber load spectrum and wheel center acceleration spectrum;

[0011] Step 4: Verify the experimental and simulated wheel center acceleration spectra, and convert them into corresponding frequency spectrum density for secondary verification to see whether the trends of the two are consistent. If the trends are inconsistent, compare the hard point positions of the actual vehicle suspension and adjust the hard points in the Adams software until the trends are basically consistent to ensure the accuracy of the simulation results.

[0012] Step 5: Import the shock absorber assembly model into the Hypermesh software, simplify the structure, perform the Hypermesh secondary development simplification process, establish the corresponding connection settings, set the corresponding materials and properties and divide the mesh, set the boundaries, and perform strength simulation under the inertia release condition;

[0013] Step 6: Enter the fatigue calculation section in the Hypermesh software, import the strength simulation results and select the corresponding stress correction method. At the same time, load the load spectrum extracted in step 3 and align the output channels, and perform fatigue simulation calculations in combination with the SN curve fitted by the software.

[0014] Furthermore, in the fatigue analysis calculation method for automobile shock absorber of the present invention, the step 5 is specifically as follows:

[0015] 5.1. Secondary development: (1) Material creation and attribute assignment: Use the *createentity mats cardimage=MAT1 includeid=0name=$matname command to create a material card and assign density, Poisson's ratio and elastic modulus through the *setvalue mats name=$matname STATUS=11=$E, *setvalue mats name=$matname STATUS=1 3=$nu, *setvalue mats name=$matname STATUS=14=$rho variables, and use the if{! [hm_entityinfo exist mats$matname-byname]} command to check whether there is a duplicate material; use the if{[string equal$proptype**]} command to determine the selected attribute, and based on the attribute, the PSHELL attribute displays "thickness", the PBARL attribute displays "radius", and the PSOLID attribute displays "NO DATA". Finally, use the *setvalueprops id=$propid materialid={mats$matid} command to assign materials and attributes. (2) Mesh division and inspection module: Use the if{[string equal$element_type"**"]} command to determine the selected mesh type, and then use the for loop to mesh each face. After the division is completed, use the proc**{}{hm_callpanel**} command to call the mesh inspection interface to adjust the mesh quality. (3) Washer module: *createmarkpanel comps 1"pleaseselect comps" command to select the required components to add washers, first use foreach traversal to obtain the node numbers contained in each hole, and then use foreach traversal to obtain the first node number of each hole node, define these node numbers in a variable, and finally use the *createstringarray 2"layer_number=1uniform_layers=1hole_density=6""0 1.0" and *add_multi_washer_elements 230121200 commands for each node in the foreach loop to create washers to improve the mesh quality around the holes.(4) Boundary condition module: Use the *collectorcreate loadcols"**"""12 command to batch create Loda Collectors, use the *currentcollector loadcols"***", *createmark nodes 1****, *loadcreateonentity_curve nodes commands to batch create unit forces and unit moments, and finally use the *loadstepscreate"***"1, *setvalue loadsteps id=1STATUS=14147={Loadcols*} commands to batch create Load Step and assign unit forces and unit moments to them, and then use the *feoutputwithdata"D: / ProgramFiles / Altair / 2021 / hwdesktop / tem plates / feoutput / optistruct / optistruct""*: / * / *" command to perform strength simulation.

[0016] 5.2. Model simplification: Simplify the valve system model in the shock absorber assembly into solid parts;

[0017] 5.3. Meshing: In the meshing stage, the sleeve, bracket and other parts are divided in the form of shell elements, and the piston, piston rod and other parts are divided in the form of solid elements;

[0018] 5.4. Define material properties: Assign the mechanical properties of each component of the shock absorber to isotropic linear elastic materials. The material density, elastic modulus and Poisson's ratio are based on the measured material.

[0019] 5.5. Connection settings: rbe2 is used to simulate the bolt connection between brackets, seam is used to simulate the welding between components, spot is used to simulate the welding points between the outer bracket and the inner bracket, the contact settings are divided into TIE and CONTACT, and the control card selects inertia release and automatic constraint;

[0020] 5.6. Define the load: Set the unit force and unit moment loading in the x, y, and z directions. The loading point is on the simulated bolt to obtain a complete finite element model of the automobile shock absorber.

[0021] Furthermore, in the fatigue analysis calculation method for automobile shock absorbers of the present invention, step 4 is to verify the experimental and simulated wheel center acceleration spectra, and convert them into corresponding frequency spectrum densities for secondary verification to observe whether the trends of the two are consistent. If the trends are inconsistent, the hard point positions of the actual vehicle suspension are compared, and the hard points are adjusted in the Adams software until the trends are basically consistent to ensure the accuracy of the simulation results.

[0022] Furthermore, in the fatigue analysis calculation method for automobile shock absorber of the present invention, the step 6 is specifically as follows:

[0023] 6.1. Import the calculation results in step 5 into the Hypermesh fatigue calculation module;

[0024] 6.2. Select a suitable stress correction algorithm and fit the SN curve according to the material properties;

[0025] 6.3. Import the load spectrum, align the channels of the load spectrum, and perform fatigue simulation analysis.

[0026] The beneficial effects of the present invention are as follows:

[0027] The method of the present invention is based on the load spectrum measured by the six-component force sensor of the wheel center, and a simulation model of the whole vehicle is constructed in Adams; to ensure the accuracy and motion reliability of the geometric model, the experimental and simulated wheel center acceleration spectra are verified, and converted into corresponding frequency spectrum density for secondary verification, and the trends of the two are observed to be consistent, so as to ensure the accuracy of the simulation results; the collected load spectrum is input into the Adams software for the simulation of the whole vehicle, and the load spectrum on the shock absorber is extracted; the shock absorber simulation model is established in the Hypermesh software, and the Hypermesh secondary development simplified process is performed, which includes selecting appropriate mesh types, defining material properties, connection settings, defining loads and meshing, and then performing unit force strength simulation under the condition of relational release, ensuring the accuracy and reliability of the finite element model and simplifying the simulation process; finally, the simulation results are imported into the fatigue calculation module, the Goodman nominal stress correction is selected, the load spectrum is imported and the channel is aligned, and the fatigue simulation is performed in combination with the SN curve fitted by the software. The method can realize the fatigue simulation analysis of automobile shock absorbers under different parameters according to different needs.

[0028] Compared with the prior art, the present invention establishes a geometric model by mapping the actual size of the actual vehicle structure, verifies the accuracy of the whole vehicle simulation results with experimental and simulated wheel center acceleration, and performs pre-report processing on the collected load spectrum signal in the Ncode software to verify the feasibility and reliability of the load spectrum signal. The valve system components inside the shock absorber are simplified, rbe2 is used to simulate bolt connections, seam is used for welding, spot is used for welds, and contact settings are divided into TIE and CONTACT, which have higher calculation efficiency, accuracy and reliability. The use of Hypermsh secondary development code simplifies the simulation process and greatly shortens the simulation time. At the same time, the present invention can also perform simulation evaluation for the early stage of shock absorber design, reduce sample manufacturing costs, shorten the development cycle, and improve ergonomics. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1A flow chart of the automobile shock absorber fatigue analysis method provided by the present invention;

[0030] Figure 2 The six-component force load spectrum of the left front wheel of the automobile provided by the present invention;

[0031] Figure 3 The Ncode software signal pre-report processing result provided by the present invention;

[0032] Figure 4 The whole vehicle simulation model in Adams provided by the present invention;

[0033] Figure 5 The experimental and simulated wheel center acceleration spectra provided by the present invention are compared and verified;

[0034] Figure 6 A finite element model of an automobile shock absorber in a specific embodiment provided by the present invention;

[0035] Figure 7 Various modified stress method curves provided by the present invention;

[0036] Figure 8 A fatigue life cloud diagram of fatigue simulation of an automobile shock absorber in an embodiment provided by the present invention;

[0037] Fig. 9 This is a physical picture of the structural destruction of the automobile shock absorber fatigue experiment provided by the present invention. DETAILED DESCRIPTION

[0038] In order to describe the purpose of the invention, the advantages of the invention, and the technical solution of the present invention more clearly, the present invention is described in detail below in conjunction with the accompanying drawings and implementation methods. However, it should be understood that the implementation methods described below are only used to explain the present invention and are not limited to the present invention. The present invention is described in detail below, and through these detailed descriptions, those skilled in the art can fully understand the present invention.

[0039] See also Figure 1-9 The fatigue analysis calculation method for automobile shock absorber of the present invention comprises the following specific steps:

[0040] Step 1: Use a wheel center six-component force instrument to conduct a whole vehicle test to obtain the load spectrum at the center of the wheel and measure the acceleration spectrum at the center of the wheel;

[0041] Step 2: Measure the positions of the hard points of the vehicle suspension and build a multi-body dynamics model of the vehicle in Adams software;

[0042] Step 3: Input the load spectrum at the wheel center into the Adams software for simulation calculation, and extract the shock absorber load spectrum and wheel center acceleration spectrum;

[0043] Step 4: Verify the experimental and simulated wheel center acceleration spectra, and convert them into corresponding frequency spectrum density for secondary verification to see whether the trends of the two are consistent. If the trends are inconsistent, compare the hard point positions of the actual vehicle suspension and adjust the hard points in the Adams software until the trends are basically consistent to ensure the accuracy of the simulation results.

[0044] Step 5, import the shock absorber assembly model into Hypermesh software, simplify the structure, perform secondary development of Hypermsh software to simplify the simulation process, establish corresponding connection settings, set corresponding materials and properties and divide the grid, set boundaries, and perform strength simulation under inertia release conditions; Step 5 specifically includes: simplifying the valve system model in the shock absorber assembly into solid parts; in the grid division stage, the sleeve, bracket and other parts are divided in the form of shell units, and the piston, piston rod and other parts are divided in the form of solid units; the mechanical properties of each component of the shock absorber are given isotropic linear elastic materials, and the material density, elastic modulus and Poisson's ratio are all based on the measured material as the standard; connection settings: rbe2 is used to simulate the bolt connection between the brackets, seam is used to simulate the welding between the components, spot is used to simulate the welding point between the outer bracket and the inner bracket, the contact settings are divided into TIE and CONTACT, and the control card selects inertia release and automatic constraint; define the load: set the unit force and unit moment loading in the three directions of x, y, and z, and the loading point is on the simulated bolt to obtain a complete automobile shock absorber finite element model;

[0045] Step 6. Enter the fatigue calculation section in the Hypermesh software, import the strength simulation results and select the corresponding stress correction method. At the same time, load the extracted load spectrum and output the corresponding channel, and perform fatigue simulation calculation in combination with the SN curve fitted by the software.

[0046] Example:

[0047] The load spectrum collection experiment was carried out on the Belgian road. The sensor placement positions are shown in Table 1. The collected load spectrum is shown in Figure 2 As shown, the collected load spectrum is input into Ncode software for pre-report analysis, such as Figure 3 As shown in the figure, the amplitude, power spectrum density and rain flow count data are analyzed to improve the reliability and feasibility of the signal data. The hard point position is extracted according to the suspension model, and the whole vehicle model is established in the Adams software, such as Figure 4 The load spectrum obtained from the experiment is input into the Adams software for vehicle simulation. The load spectrum on the shock absorber is extracted from the simulation results. At the same time, the acceleration of the wheel center is extracted and compared with the experimental wheel center acceleration. At the same time, it is converted into the corresponding frequency spectrum density for secondary verification, as shown in Figure 5As shown, the trends of the acceleration frequency spectral density obtained by the experiment and the simulation are basically consistent, which can verify the accuracy of the simulation results (when implementing the present invention, if the trends are inconsistent, the hard point positions of the actual vehicle suspension are compared, and the hard points are adjusted in the Adams software until the trends are basically consistent).

[0048] Table 1 Sensor settings

[0049]

[0050] The finite element model is established based on the geometric model. The geometric model of the automobile shock absorber device is relatively complex. In order to improve the calculation efficiency of the model and reduce the workload of building the finite element model, the geometric cleaning tool in Hypermesh is used to remove the geometric features in the model that have little impact on the analysis results, such as positioning holes, chamfers, etc., and simplify the structures of the geometric model that are difficult to mesh, reducing the difficulty of modeling, such as the ruler used for model positioning.

[0051] Secondary development of Hypermesh software: (1) Material creation and attribute assignment: Use *createentitymats cardimage=MAT1 includeid=0name=$matname command to create material card and assign density, Poisson's ratio and elastic modulus through *setvalue mats name=$matname STATUS=1 1=$E, *setvalue mats name=$matnameSTATUS=13=$nu, *setvalue mats name=$matname STATUS=14=$rho variables, and query whether there is a duplicate material through if{! [hm_entityinfo exist mats$matname-byname]} command; if{[string equal$proptype**]} command determines the selected attribute, and according to the attribute, PSHELL attribute displays "thickness", PBARL attribute displays "radius", PSOLID attribute displays "NO DATA", and finally assigns materials and attributes through *setvalue props id=$propid materialid={mats$matid} command. (2) Mesh division and inspection module: Use the if{[string equal$element_type"**"]} command to determine the selected mesh type, and then use the for loop to mesh each face. After the division is completed, use the proc**{}{hm_callpanel**} command to call the mesh inspection interface to adjust the mesh quality. (3) Washer module: *createmarkpanel comps1"please select comps" command to select the required components to add washers, first use the foreach traversal to obtain the node numbers contained in each hole, and then use a foreach traversal to obtain the first node number of each hole node, define these node numbers in a variable, and finally use the *createstringarray 2"layer_number=1uniform_layers=1hole_density=6""01.0" and *add_multi_washer_elements 230121200 commands for each node in the foreach loop to create washers to improve the mesh quality around the holes.(4) Boundary condition module: Use the *collectorcreate loadcols"**"""12 command to batch create LodaCollectors, use the *currentcollector loadcols"***", *createmark nodes 1****, *loadcreateonentity_curve nodes commands to batch create unit forces and unit moments, and finally use the *loadstepscreate"***"1, *setvalue loadsteps id=1STATUS=14147={Loadcols*} command to batch create Load Step and assign unit forces and unit moments to it, and then use the *feoutputwithdata"D: / ProgramFiles / Altair / 2021 / hwdesktop / tem plates / feoutput / optistruct / optistruct""*: / * / *" command to perform strength simulation.

[0052] The model meshing was carried out in the Optistruct environment. For the parts with simple geometric structures of the main body of the shock absorber model, the midsurface method in Geom was used to extract the midsurface and perform meshing. The mesh type was quadrilateral mesh, and the mesh sizes of the outer cylinder, inner cylinder, upper bracket, lower bracket and stabilizer bracket were 2mm, 1.5mm, 2.5mm, 2.3mm and 3.2mm respectively. For the spring disk, outer bracket and inner bracket with complex structures in the shock absorber model, the offset method was used to extract the midsurface, that is, first extract the surface of the part and then offset it by half the thickness. Shell elements were used for meshing, and the mesh type was quadrilateral. The mesh sizes of the spring disk, outer bracket and inner bracket were 3mm, 2.3mm and 2.3mm respectively. The unit mass was controlled according to the unit conditions shown in Table 2, and the remaining solid parts were divided by hexahedral meshes.

[0053] Table 2 Unit mesh quality control conditions

[0054] category Quadrilateral element Triangular unit Hexahedral element Wedge unit Tetrahedral element Aspect Ratio ≤5.0 ≤5.0 ≤5.0 ≤5.0 ≤5.0 Warpage ≤16° ≤18° ≤18° Skewness ≤60° ≤60° ≤60° ≤60° ≤60° inner angle 40°～135° 20°～120° 40°～135° 20°～120° 20°～120°

[0055] The welding connection between each component is defined by seam, and the welding point between the outer bracket and the inner bracket is defined by spot. There are two types of contact settings: TIE and CONTACT. TIE connection is used to fix two components, such as between the outer bracket and the outer cylinder; CONTACT is used between components with relative motion, such as between the piston and the inner cylinder. At the same time, PCONT attributes need to be created to prevent unit penetration. Use reb2 to simulate the bolt connection of the bracket. Apply unit force and unit moment in the three directions of x, y and z at the simulated bolt. Set the inertia release control card, set AUTOSPC to Yes, and set INREL to -2 for strength simulation.

[0056] This embodiment establishes a complete finite element model of the automobile shock absorber. The final finite element model is as follows: Figure 6 Open FatigueProcess in Hypermesh software to establish a new fatigue analysis process, import the strength simulation results in the previous step, and according to the material properties and the formula conclusion of the modified stress method, as shown in Figure 7 As shown. Select the Goodman method for calculation, input the yield limit and tensile limit of the material into the software for fitting to obtain the SN curve of the material, and set the component properties and materials to be calculated in the software. Import the shock absorber load spectrum extracted by simulation and correspond it to the force and torque channels set in the strength simulation one by one, and perform fatigue simulation analysis of the shock absorber. The results are shown in Figure 8 shown.

[0057] After the fatigue simulation analysis of the shock absorber, the fatigue simulation results were compared with the experimental results (such as Fig. 9 The comparison shows that the smaller life of the fatigue simulation results is basically consistent with the damaged part of the experimental shock absorber, which verifies the accuracy of the simulation method. For shock absorbers that do not meet the fatigue requirements during the simulation process, the model morphology parameters, material performance parameters, etc. can be directly modified in the design stage, and then the simulation test can be carried out. Compared with the traditional design process, that is, making shock absorber samples for evaluation and then modifying them, this method can significantly shorten the design cycle.

[0058] The fatigue analysis calculation method for automobile shock absorbers provided by the present invention can utilize the load spectrum obtained from the whole vehicle experiment to input the simulation software to extract the load spectrum on the shock absorber, and build a finite element model of the shock absorber for simulation calculation, thereby achieving the purpose of evaluating the fatigue life of the shock absorber.

[0059] The above general description of the invention involved in this application and the description of its specific implementation methods should not be understood as limiting the technical solutions of the invention. Based on the disclosure of this application, those skilled in the art can add, reduce or combine the disclosed technical features in the above general description and / or specific implementation methods (including examples) without violating the constituent elements of the invention involved, to form other technical solutions within the scope of protection of this application.

Claims

1. A fatigue analysis calculation method for automobile shock absorber, characterized in that: The steps include: Step 1: Use the wheel center six-component force instrument to conduct a whole vehicle test to obtain the load spectrum at the center of the wheel and measure the acceleration spectrum at the center of the wheel; Step 2: Measure the positions of the hard points of the vehicle suspension and build a multi-body dynamics model of the vehicle in Adams software; Step 3: Input the load spectrum at the wheel center into the Adams software for simulation calculation, and extract the shock absorber load spectrum and wheel center acceleration spectrum; Step 4: Verify the experimental and simulated wheel center acceleration spectra, and convert them into corresponding frequency spectrum density for secondary verification to see whether the trends of the two are consistent. If the trends are inconsistent, compare the hard point positions of the actual vehicle suspension and adjust the hard points in the Adams software until the trends are basically consistent to ensure the accuracy of the simulation results. Step 5: Import the shock absorber assembly model into the Hypermesh software, simplify the structure, perform the Hypermesh secondary development simplification process, establish the corresponding connection settings, set the corresponding materials and properties and divide the mesh, set the boundaries, and perform strength simulation under the inertia release condition; Step 6: Enter the fatigue calculation section in the Hypermesh software, import the strength simulation results and select the corresponding stress correction method. At the same time, load the load spectrum extracted in step 3 and align the output channels, and perform fatigue simulation calculations in combination with the SN curve fitted by the software.

2. The fatigue analysis calculation method for automobile shock absorber according to claim 1, characterized in that: The step 5 is specifically as follows: 5.

1. Secondary development: (1) Material creation and attribute assignment: Use the *createentity mats cardimage=MAT1includeid=0name=$matname command to create a material card and assign density, Poisson's ratio and elastic modulus through *setvalue mats name=$matnameSTATUS=11=$E, *setvalue mats name=$matname STATUS=1 3=$nu, *setvalue matsname=$matname STATUS=14=$rho, and assign density, Poisson's ratio and elastic modulus through if{! [hm_entityinfo exist mats$matname-byname]} command is used to check whether there is a duplicate material name; if{[stringequal$proptype**]} command is used to determine the selected property, and based on the property, the PSHELL property displays "thickness", the PBARL property displays "radius", and the PSOLID property displays "NO DATA". Finally, the material and property are assigned through the *setvalue propsid=$propid materialid={mats$matid} command; (2) Mesh division and inspection module, through the if{[string equal$element_type"**"]} command to determine the selected mesh type, and then through the for loop to mesh each face, after the division is completed, the proc**{}{hm_callpanel**} command is used to call the mesh inspection interface to adjust the mesh quality; (3) Washer module: *createmarkpanel comps 1"pleaseselect comps" command to select the required components to add washers, first use foreach traversal to obtain the node numbers contained in each hole, then use foreach traversal again to obtain the first node number of each hole node, define these node numbers in a variable, and finally use the *createstringarray 2"layer_number=1uniform_layers=1hole_density=6""0 1.0" and *add_multi_washer_elements 230121200 commands for each node through a foreach loop to create washers to improve the mesh quality around the holes.(4) Boundary condition module: Use the *collectorcreate loadcols"**"""12 command to batch create Loda Collectors, use the *currentcollector loadcols"***", *createmark nodes 1****, *loadcreateonentity_curve nodes 111100001000000 commands to batch create unit forces and unit moments, and finally use the *loadstepscreate"***"1, *setvalue loadsteps id=1STATUS=14147={Loadcols*} commands to batch create Load Step and assign unit forces and unit moments to them, and then use the *feoutputwithdata"D: / ProgramFiles / Altair / 2021 / hwdesktop / tem plates / feoutput / optistruct / optistruct""***"10211 command to perform strength simulation. 5.

2. Model simplification: Simplify the valve system model in the shock absorber assembly into solid parts; 5.

3. Meshing: In the meshing stage, the sleeve, bracket and other parts are divided in the form of shell elements, and the piston, piston rod and other parts are divided in the form of solid elements; 5.

4. Define material properties: Assign the mechanical properties of each component of the shock absorber to isotropic linear elastic materials. The material density, elastic modulus and Poisson's ratio are based on the measured material. 5.

5. Connection settings: rbe2 is used to simulate the bolt connection between brackets, seam is used to simulate the welding between components, spot is used to simulate the welding points between the outer bracket and the inner bracket, the contact settings are divided into TIE and CONTACT, and the control card selects inertia release and automatic constraint; 5.

6. Define the load: Set the unit force and unit moment loading in the x, y, and z directions. The loading point is on the simulated bolt to obtain a complete finite element model of the automobile shock absorber.

3. The fatigue analysis calculation method for automobile shock absorber according to claim 1 is characterized in that: The step 4 is to verify the experimental and simulated wheel center acceleration spectra, and convert them into corresponding frequency spectrum density for secondary verification to observe whether the trends of the two are consistent. If the trends are inconsistent, compare the hard point positions of the actual vehicle suspension, and adjust the hard points in the Adams software until the trends are basically consistent to ensure the accuracy of the simulation results.

4. The fatigue analysis calculation method for automobile shock absorber according to claim 1, characterized in that: The step 6 is specifically as follows: 6.

1. Import the calculation results in step 5 into the Hypermesh fatigue calculation module; 6.

2. Select a suitable stress correction algorithm and fit the SN curve according to the material properties; 6.

3. Import the load spectrum, align the channels of the load spectrum, and perform fatigue simulation analysis.

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