Lightweight design evaluation method for aluminum alloy thrust rod assembly based on CAE

Abstract

The application relates to a CAE-based lightweight design evaluation method for an aluminum alloy thrust rod assembly, which comprises the following steps: lightweight design, establishment of a half-assembly grid model, material attribute assignment, establishment of a statics model under a pre-pressing assembly state, evaluation of thrust rod fatigue performance and rigidity performance, establishment of a complete assembly grid model, material attribute assignment, establishment of a dynamics model under the pre-pressing assembly state, and evaluation of limit working condition performance. The evaluation method can more accurately analyze and evaluate the performance of the thrust rod assembly, saves time and shortens the development process.

Description

Technical Field

[0001] The present invention relates to an optimization design method based on CAE analysis, and in particular to a lightweight design evaluation method for an aluminum alloy thrust rod assembly based on CAE. Background Art

[0002] In recent years, with the intensification of environmental pollution, environmental protection has become increasingly stringent, and the National VI emission standards have been introduced accordingly. Therefore, automobile companies are in urgent need of improving automobile emission standards and reducing fuel consumption. Lightweighting of automobiles plays a key role in automobile emissions and improving the fuel economy of the entire vehicle.

[0003] The thrust rod assembly consists of a ball head, a rod body, a retaining ring, a rubber ball joint, and other components. Conventional thrust rod assemblies typically use steel for their metal components. To reduce weight, this steel has been replaced with aluminum alloy. To ensure that the aluminum alloy thrust rod assembly meets both lightweight requirements and actual performance requirements, a structural redesign is required. CAE technology can simulate and analyze the redesigned thrust rod assembly, evaluating whether the structure meets design requirements and providing guidance for its design and optimization.

[0004] The thrust rod is assembled from multiple components with complex contact relationships. The thrust rod assembly has a large working load and large deformation of the rubber ball joint. The mechanical properties of the materials of each component need to take into account the plastic properties of the material. Therefore, the CAE analysis of the thrust rod assembly is a highly nonlinear problem involving boundary nonlinearity, material nonlinearity, and geometric nonlinearity. During the simulation process, non-convergence of the calculation is very common, resulting in the inability to obtain the stress conditions of the thrust rod components under working loads. For example, the analysis method disclosed in the paper "Design Matching of Thrust Rods for Heavy Engineering Vehicles" (Ju Gang, Li Haibo, Xiu Yongzhi. Design Matching of Thrust Rods for Heavy Engineering Vehicles [J]. Special Purpose Vehicles, 2012, 000(002):74-77) simplifies the rubber ball joint and retaining ring, directly transferring the load to the ball head and rod body. Although this can overcome the non-convergence problem, such simplification does not consider the impact of the ball joint stiffness and deformation on the load transfer path, and cannot reflect the influence of the connection relationship of the various components of the thrust rod assembly on the stress distribution. This leads to inaccurate calculation results and the inability to identify common failure modes, thus defeating the purpose of simulation and failing to form a complete and accurate CAE-based design evaluation method for thrust rods. In addition, in order to improve the development efficiency of thrust rod assemblies, it is also necessary to shorten the CAE calculation and analysis time as much as possible.

[0005] Therefore, a more accurate and computationally efficient CAE-based lightweight design evaluation method for aluminum alloy thrust rod assemblies is needed. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a CAE-based lightweight design evaluation method for a thrust rod assembly in response to the current status of the existing technology. The method can more accurately analyze and evaluate the performance of the thrust rod assembly, save time, shorten the development process, and thus better assist in the lightweight structural design of the thrust rod assembly.

[0007] The technical solution adopted by the present invention to solve the above technical problems is:

[0008] A CAE-based lightweight design evaluation and optimization method for a thrust rod assembly includes the following steps:

[0009] S1. A thrust rod assembly is lightweight-designed according to a weight reduction target to obtain a structural geometric model of the thrust rod assembly. The various components of the thrust rod assembly include a rod body, a ball head, a retaining ring, and a ball joint assembly. The ball head is provided at both ends of the rod body, and a retaining ring mounting groove is provided in the ball head. In a pre-compression assembly state, the retaining ring is clamped in the retaining ring mounting groove so that the retaining ring abuts against the end face of the ball joint assembly, thereby mounting the ball joint assembly in the ball head. The ball joint assembly includes a ball pin, a ball joint rubber sleeved on the outside of the ball pin, and a ball joint upper end cover and a ball joint lower end cover respectively covering both ends of the ball joint rubber, wherein the ball pin, ball joint rubber, ball joint upper end cover, and ball joint lower end cover are integrated into one by vulcanization.

[0010] S2. Establish half of the assembly mesh model: Based on the structural geometric model, the plane perpendicular to the axis of the rod body and passing through the midpoint of the rod body is used as a dividing plane to divide the structural geometric model into two halves, and one half is used to establish half of the assembly mesh model; and the mesh model of the ball joint rubber is established in a free state under a non-prestressed assembly state.

[0011] Since the thrust rod is a centrally symmetrical structure, only half of the assembly mesh model is established in this step to simplify the calculation and improve analysis efficiency.

[0012] S3. Assigning material properties: Assign material properties to each component of the thrust rod assembly based on its material type. For metal components, assign Young's modulus, Poisson's ratio, density, and plastic stress-strain curve; for rubber, assign strain energy constitutive model parameters.

[0013] Preferably, determining the strain energy constitutive model type in the material properties of the ball-jointed rubber includes the following steps:

[0014] a. Prepare a rubber specimen using the same material as the ball-jointed rubber, and obtain stress-strain curve data by uniaxial tension, planar tension, and equibiaxial tension tests on the rubber specimen;

[0015] b. Importing the stress-strain curve data into the material property hyperelasticity module of the finite element analysis software Abaqus, fitting the Ogden, Mooney-Rivlin, and Yeoh strain energy models respectively to obtain the corresponding constitutive model parameters;

[0016] c. Use the corresponding constitutive model parameters to calculate the radial stiffness values ​​k1, k2, k3 corresponding to the Ogden, Mooney-Rivlin, and Yeoh strain energy models, and calculate the deviation rate with the measured stiffness value k of the rubber specimen. , select the strain energy model corresponding to the smallest deviation rate as the strain energy model of the ball joint rubber.

[0017] S4. Establishing a static model in a pre-pressed assembly state: using the half assembly mesh model, establish a static model in a pre-pressed assembly state, and calculate the initial stress distribution of the thrust rod assembly in the pre-pressed assembly state.

[0018] The preferred specific steps are:

[0019] a. Establishing and setting contact pairs: Using the mesh model of the half assembly, based on the contact relationships between the various components of the thrust rod assembly, static implicit contact pairs are used to establish the contact interaction relationship between the various components. An interference contact pair is established between the upper surface of the spherical joint upper end cover and the lower surface of the retaining ring to simulate the compression state of the spherical joint rubber in the preloaded assembly state. Interference is set according to the designed preload amount, and the interference amount and interference amplitude curve are set.

[0020] In order to improve the convergence of the model, automatic contact stabilization control is selected for each contact pair to solve the non-convergence problem caused by contact.

[0021] b. Assign unit type: For the convenience of calculation, the ball head and ball joint pin adopt implicit standard second-order tetrahedral modified unit type, the ball joint rubber adopts implicit standard first-order hexahedral hybrid unit type, and the ball joint upper and lower end covers, retaining ring and rod body adopt implicit standard first-order hexahedral unit type.

[0022] c. Create calculation analysis steps:

[0023] Analysis step 1: Simulate the pre-loaded assembly state based on the interference setting in step a and establish temporary constraint boundary conditions: constrain the three translational degrees of freedom of the upper and lower end surfaces of the ball joint; calculate the compressive rebound force of the ball joint rubber in the pre-loaded assembly state;

[0024] Analysis step 2: releasing temporary boundary conditions, defining axisymmetric constraints on the cross section of the rod body cut by the dividing plane, and calculating the initial stress distribution of the thrust rod assembly using the compression rebound force;

[0025] The simulation calculation of the present invention is divided into two analysis steps: Analysis Step 1 and Analysis Step 2. Because the thrust rod preloading process generates large compressive rebound forces and a large number of contact pairs, and the constraint position is far from the ball head, the ball head is prone to significant displacement within a very short analysis iteration, causing drastic changes in boundary conditions and plastic strain in the contact area, making convergence difficult when solving the equilibrium equation. By establishing temporary constraints on the upper and lower end surfaces of the ball head, significant displacement of the ball head during the preloading process is prevented, limiting drastic changes in boundary conditions and plastic strain at the contact point. This helps stabilize the solution of the equilibrium equation, improves convergence, and prevents non-convergence issues.

[0026] In the statics model analysis, the present invention adopts half of the assembly grid and axisymmetric constraints to evaluate the thrust fatigue performance and stiffness performance, thereby reducing the amount of calculation and improving the calculation efficiency.

[0027] S5. Evaluate the fatigue performance and stiffness performance of the thrust rod: If any one of the fatigue performance and stiffness performance does not meet the design requirements, it is unqualified and returns to step S1; if both the fatigue performance and stiffness performance meet the design requirements, it is qualified. The preferred specific steps are:

[0028] 5.1. Evaluate the Fatigue Performance of the Thrust Rod: Calculate the number of fatigue cycles using the static model in the pre-stressed assembly state in step S4 to evaluate the fatigue performance of the thrust rod assembly. Compare the calculated number of fatigue cycles with the design requirement. If the calculated number of fatigue cycles is greater than or equal to the design requirement, the thrust rod assembly is considered qualified. If the calculated number of fatigue cycles is less than the design requirement, the thrust rod assembly is considered unqualified, and the process returns to step S1.

[0029] Preferably, the specific steps of calculating the number of fatigue cycles are:

[0030] a. Use the reanalysis function to add a fatigue analysis step to the static model in step S4: set the loading point in the fatigue analysis step to the elastic center point of the ball pin, and set the fatigue condition required by the design;

[0031] Calculate the stresses of the ball head, retaining ring, upper end cover of the ball joint, lower end cover of the ball joint, ball pin, and rod body, and the logarithmic strain of the ball joint rubber;

[0032] b. Import the stress and logarithmic strain results into fatigue analysis software to calculate the number of fatigue cycles.

[0033] Using the reanalysis function in this step can help reduce analysis steps and save analysis time.

[0034] 5.2. Stiffness Performance Evaluation: Using the static model in the pre-stressed assembly state of step S4, calculate the radial stiffness, torsional stiffness, and yaw stiffness to evaluate the stiffness performance of the thrust rod assembly. Compare the calculated radial stiffness, torsional stiffness, and yaw stiffness with the corresponding design requirements, respectively. If the calculated radial stiffness, torsional stiffness, and yaw stiffness are within ±15% of the design requirements, the assembly passes. If the calculated radial stiffness, torsional stiffness, and yaw stiffness are outside the design requirements, the assembly fails, and the process returns to step S1.

[0035] Preferably, the specific steps of calculating the radial stiffness, torsional stiffness, and yaw stiffness are:

[0036] 1. Use the reanalysis function to add a stiffness analysis step to the statics model in S4. Set the loading point in the stiffness analysis step to the elastic center point of the ball pin, and set the corresponding loading ranges for the radial stiffness, torsional stiffness, and yaw stiffness required by the design. This will calculate the corresponding radial displacement, rotation angle, constraint reaction force, and constraint anti-torque.

[0037] 2. Read the calculated radial displacement, rotation angle, constraint reaction force, and constraint reaction torque and use the above data to make stiffness curves, thereby fitting the corresponding radial stiffness, torsional stiffness, and yaw stiffness.

[0038] S6. Establish a complete assembly grid model: Based on half of the assembly grid model established in step S2, the other half of the assembly grid model is established by rotating 180° with the center point of the split surface as the center of symmetry, thereby obtaining a complete assembly grid model.

[0039] S7. Assigning material properties: Assigning material properties to each component of the thrust rod assembly according to the material type;

[0040] S8. Establishing a dynamic model in a pre-pressed assembly state: Using the complete assembly mesh model, establish a dynamic model in a pre-pressed assembly state, and calculate the initial stress distribution of the thrust rod assembly in the pre-pressed assembly state. The specific steps are as follows:

[0041] a. Define the analysis time and the quality scaling factor.

[0042] Since the selection of the quality scaling factor affects the solution accuracy and calculation time, the present invention adopts a semi-automatic control scaling factor method. Through the grid quality inspection function, the average minimum stable time step of the grid is obtained, and this time step is used as the quality scaling factor adjustment target to achieve the purpose of taking into account both accuracy and calculation cost at the same time.

[0043] b. Based on the contact relationships between the various components of the thrust rod assembly, a dynamic explicit general contact pair method is used to establish the contact interaction relationship between the various components; wherein an interference contact pair is established between the upper surface of the spherical joint upper end cover and the lower bottom surface of the retaining ring to simulate the spherical joint rubber in a preloaded assembly state, and the interference is set according to the designed preload amount, and the interference amount and interference amplitude curve are set;

[0044] c. Assign the unit type. For the convenience of calculation, the ball head and ball joint pin adopt the explicit second-order tetrahedral modified unit type, and the ball joint rubber, upper and lower end covers, retaining ring and rod body adopt the explicit first-order hexahedral unit type.

[0045] d. Create calculation analysis step:

[0046] Analysis step 1: Simulate the preloaded assembly state based on the interference setting in step 2 and establish temporary constraint boundary conditions: constrain the three translational degrees of freedom of the upper and lower end surfaces of the ball joints at both ends; calculate the compressive rebound force of the ball joint rubber in the preloaded assembly state;

[0047] Analysis step 2: Release the temporary boundary conditions and define fixed constraints at the center points of the ball heads at both ends: constrain the 6 degrees of freedom of the center points of the ball heads at both ends, and use the compression rebound force to calculate the initial stress distribution of the thrust rod assembly.

[0048] The present invention controls the mass scaling factor by optimizing the average stable time step during dynamic model analysis, thereby improving computational efficiency while ensuring accuracy. By using the dynamic model, the problem of non-convergence caused by excessive rubber deformation of the thrust rod under extreme working conditions is solved.

[0049] S9. Evaluate the extreme working condition performance: Evaluate the extreme working condition performance of the thrust rod assembly after calculation using the dynamic model in the pre-stressed assembly state of step S8. The extreme working condition performance includes strength performance, rod body buckling performance, and circlip retaining ring locking performance. If any one of the strength performance, rod body buckling performance, and circlip retaining ring locking performance fails to meet the requirements, the system is deemed unqualified, and the process returns to step S1. If all of the strength performance, rod body buckling performance, and circlip retaining ring locking performance meet the requirements, the system is deemed qualified.

[0050] Preferably, the specific judgment method is:

[0051] Strength performance: Compare the calculated equivalent plastic strain with the corresponding design requirements. If the equivalent plastic strain is less than the design requirement, it is qualified. If the equivalent plastic strain is greater than the design requirement, it is unqualified and returns to step S1;

[0052] Rod buckling performance: Compare the calculated rod buckling limit critical load with the corresponding design requirement. If the rod buckling limit critical load is greater than the design requirement, the rod is qualified. If the rod buckling limit critical load is less than the design requirement, the rod is unqualified and the process returns to step S1.

[0053] Locking performance of the circlip retaining ring: Compare the calculated equivalent plastic strain at the contact point between the upper surface of the circlip retaining ring and the circlip mounting groove, and the warping displacement of the circlip retaining ring with the corresponding circlip retaining ring locking performance standard. If the comparison of the circlip retaining ring locking performance standard is met, it is qualified; otherwise, it is unqualified, and return to step S1.

[0054] Compared with the prior art, the advantages of the present invention are:

[0055] 1. The present invention establishes a CAE-based lightweight design evaluation method for aluminum alloy thrust rod assemblies, and defines evaluation indicators for the thrust rod assembly's stiffness performance, the fatigue performance of each assembly component, and the performance under extreme operating conditions. This method can help designers more accurately, comprehensively, and quickly determine whether the designed thrust rod assembly meets the design requirements, thereby accelerating the development efficiency of lightweight thrust rod assemblies.

[0056] 2. The stiffness performance of the thrust rod assembly, the fatigue performance of each component of the assembly, and the extreme operating performance are important indicators of the thrust rod performance. The present invention performs simulation analysis and calculation based on a thrust rod assembly model including each component without simplifying the model. It also takes into account the influence of the compressive rebound force of the ball joint rubber in the pre-stressed assembly state on the simulation analysis results. Combined with the corresponding analysis method, it avoids the problem of non-convergence of the calculation, can more accurately simulate the actual situation of the thrust rod assembly, and can more accurately obtain the stiffness performance of the thrust rod assembly, the fatigue performance of each component of the assembly, and the extreme operating performance.

[0057] 3. Poor locking performance of the retaining ring, which leads to its ejection, is also one of the main failure modes of the thrust rod assembly. However, there is no indicator in the prior art to evaluate this performance. The inventors of the present invention have identified the main failure mechanism and the corresponding retaining ring locking performance standard: the equivalent plastic strain at the contact point between the upper surface of the retaining ring and the retaining ring mounting groove is less than the material elongation, and the warping displacement h of the retaining ring is less than 2.5mm.

[0058] 4. The load for evaluating fatigue performance and stiffness performance is relatively small, and the ball joint rubber will not deform significantly. It is not easy to deform the rubber too much. The static model can be used to smoothly obtain the calculation results through the iteration of the equilibrium equation, and the analysis time is short and the accuracy is high. Therefore, for the evaluation of fatigue performance and stiffness, the static model is preferred for analysis. Due to the large load of the extreme working condition and the serious deformation of the rubber, it is difficult to obtain the calculation results through the iteration of the equilibrium equation. In addition, under the compressive limit working condition, the thrust rod involves complex contact relationships and rubber, which is a complex post-buckling analysis. The calculation method of the dynamic model adopts the central difference method, which does not require the solution of the equilibrium equation and has no convergence problem. It can solve the non-convergence problem caused by excessive rubber deformation, and can conveniently perform the post-buckling analysis of the thrust rod by applying displacement.

[0059] 5. In the static model analysis, the present invention uses half of the assembly grid to evaluate the thrust fatigue performance and stiffness performance, which reduces the amount of calculation and saves analysis time. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 A structural geometric model of a thrust rod assembly according to an embodiment of the present invention;

[0061] Figure 2 is a schematic diagram of a splitting surface according to an embodiment of the present invention;

[0062] Figure 3 This is a schematic structural diagram of a thrust rod assembly in a pre-compression assembly state according to an embodiment of the present invention;

[0063] Figure 4 A schematic diagram of an assembly grid model of half of an embodiment of the present invention;

[0064] Figure 5 is an interference amplitude curve diagram of an embodiment of the present invention;

[0065] Figure 6 A schematic diagram of a complete assembly grid model of an embodiment of the present invention;

[0066] Figure 7 The warping displacement cloud diagram and the equivalent plastic strain cloud diagram of the qualified and unqualified parts of the embodiment of the present invention;

[0067] Figure 8 is a flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0068] The specific implementation of the present invention is further described in detail below with reference to the accompanying drawings and examples.

[0069] The CAE-based lightweight design evaluation and optimization method for the thrust rod assembly includes the following steps:

[0070] S1. Perform lightweight design on the thrust rod assembly according to the weight reduction target to obtain the structural geometric model of the thrust rod assembly. The structural geometric model of the thrust rod assembly in this embodiment is as follows: Figure 1 shown.

[0071] The various components of the thrust rod assembly include a rod body 1, a ball head 12, a retaining ring 3, and a ball joint assembly 4; the ball head 12 is arranged at both ends of the rod body 1, and a retaining ring 13 is provided in the ball head 12; in the pre-stressed assembly state, the retaining ring 3 is clamped in the retaining ring 3 and the retaining ring 3 is pressed against the end face of the ball joint assembly 4, thereby installing the ball joint assembly 4 in the ball head 12; the ball joint assembly 4 includes a ball pin 41, a ball joint rubber 42 sleeved on the outside of the ball pin 41, and a ball joint upper end cover 43 and a ball joint lower end cover 44 respectively covering the two ends of the ball joint rubber 42, and the ball pin 41, the ball joint rubber 42, the ball joint upper end cover 43, and the ball joint lower end cover 44 are combined into one by vulcanization.

[0072] S2. Establish half of the assembly mesh model: Based on the structural geometric model, the plane perpendicular to the axial direction of the rod body 1 and passing through the midpoint of the rod body 1 is used as the dividing plane A to divide the structural geometric model into two halves, and one half is used to establish half of the assembly mesh model; and the mesh model of the ball joint rubber 42 is established in the free state under the non-prestressed assembly state; the half of the assembly mesh model of this embodiment is as follows Figure 4 shown.

[0073] S3. Assign material properties: Assign material properties to each component of the thrust rod assembly according to its material type:

[0074] The material properties of this embodiment include Young's modulus, Poisson's ratio, density, plastic stress-strain curve, and hyperelastic strain energy Ogden constitutive model parameters. The rod body 1 of this embodiment is made of 45# steel, and the material properties to be assigned are Young's modulus, Poisson's ratio, density, and plastic stress-strain curve. The ball head 12 is made of 45# steel, and the material properties to be assigned are Young's modulus, Poisson's ratio, density, and plastic stress-strain curve. The retaining ring 3 is made of 65Mn manganese steel, and the material properties to be assigned are Young's modulus, Poisson's ratio, density, and plastic stress-strain curve. Strain curve, the ball pin 41 is 40Cr chrome steel, and the material properties that need to be assigned are Young's modulus, Poisson's ratio, density, and plastic stress-strain curve. The ball hinge rubber 42 is natural rubber, and the hyperelastic strain energy Ogden constitutive model is selected for the ball hinge rubber 42. The ball hinge upper end cover 43 is 45 steel, and the material properties that need to be assigned are Young's modulus, Poisson's ratio, density, and plastic stress-strain curve. The ball hinge lower end cover 44 is 45 steel, and the material properties that need to be assigned are Young's modulus, Poisson's ratio, density, and plastic stress-strain curve.

[0075] The method for determining the constitutive model type of the ball joint rubber 42 includes the following steps:

[0076] a. Prepare a rubber specimen using the same material as the ball-jointed rubber 42, and obtain stress-strain curve data by uniaxial tension, planar tension, and equibiaxial tension tests on the rubber specimen;

[0077] b. Import the stress-strain curve data into the material property hyperelasticity module of the Abaqus module, and fit them using the Ogden, Mooney-Rivlin, and Yeoh strain energy models to obtain the corresponding constitutive model parameters;

[0078] c. Using the corresponding constitutive model parameters, calculate the radial stiffness values ​​k1, k2, k3 corresponding to the Ogden, Mooney-Rivlin, and Yeoh strain energy models, and calculate the deviation from the measured stiffness value k of the rubber specimen: In the results calculated in this embodiment, the deviation rate of the radial stiffness corresponding to Ogden is 4.2%, the deviation rate of the radial stiffness corresponding to Mooney-Rivlin is 10.6%, and the deviation rate of the radial stiffness corresponding to Yeoh is 8.4%. The deviation rate corresponding to the Ogden strain energy model is the smallest and closer to the actual stiffness value. Therefore, the Ogden constitutive model is selected to simulate the mechanical properties of the ball joint rubber 42.

[0079] S4. Establish a static model in the pre-stressed assembly state: Use half of the assembly mesh model to establish a static model in the pre-stressed assembly state and calculate the initial stress distribution of the thrust rod assembly in the pre-stressed assembly state. The specific steps are as follows:

[0080] a. Establishment and setting of contact pairs: Using half of the assembly mesh model, according to the contact relationship between the various components of the thrust rod assembly, the static implicit contact pairs are used to establish the contact interaction relationship between the various components; wherein an interference contact pair is established between the upper surface of the ball joint upper end cover 43 and the lower bottom surface of the retaining ring 3 to simulate the compression state of the ball joint rubber 42 in the pre-loaded assembly state, and the interference setting is performed according to the designed pre-load amount, and the interference amount and interference amplitude curve are set. The interference amount set in this embodiment is 3mm, and the interference amplitude curve is set as follows Figure 5 As shown;

[0081] In order to improve the convergence of the model, automatic contact stabilization control is selected for each contact pair to solve the non-convergence problem caused by contact.

[0082] b. Assigning unit type: In this embodiment, the ball head 12 and the ball joint pin 41 adopt the implicit standard second-order tetrahedral modified unit type, the ball joint rubber 42 adopts the implicit standard first-order hexahedral hybrid unit type, and the upper and lower end covers of the ball joint, the retaining ring 3 and the rod body 1 adopt the implicit standard first-order hexahedral unit type.

[0083] c. Create calculation analysis steps:

[0084] Analysis Step 1: Simulate the preloaded assembly state based on the interference setting in Step 1 and establish temporary constraint boundary conditions. The temporary constraint boundary conditions in this embodiment are: constraining the three translational degrees of freedom of the upper and lower end surfaces of the ball head 12; and calculating the compressive rebound force of the ball joint rubber 42 in the preloaded assembly state.

[0085] Analysis step 2: Release the temporary boundary conditions and define an axisymmetric constraint on the cross section of the rod body 1 cut by the dividing surface A. In this embodiment, the axisymmetric constraint is to constrain the six degrees of freedom of the dividing surface A of the rod body 1 and calculate the initial stress distribution of the thrust rod assembly using the compression rebound force.

[0086] S5. Evaluate the fatigue performance and stiffness performance of the thrust rod: If any one of the fatigue performance and stiffness performance does not meet the design requirements, it is unqualified and returns to step S1; if both the fatigue performance and stiffness performance meet the design requirements, it is qualified. The preferred specific steps are:

[0087] 5.1. Evaluation of the Fatigue Performance of the Thrust Rod: The number of fatigue cycles is calculated using the static model in the pre-stressed assembly state in step S4 to evaluate the fatigue performance of the thrust rod assembly. The calculated number of fatigue cycles is compared with the design requirement. The design requirement for this embodiment is 80,000 cycles. If the calculated number of fatigue cycles is equal to or greater than the design requirement, the thrust rod assembly passes the test. If the calculated number of fatigue cycles is less than the design requirement, the thrust rod assembly fails the test and the process returns to step S1.

[0088] The specific steps for calculating the number of fatigue cycles in this embodiment are:

[0089] a. Use the reanalysis function to add a fatigue analysis step to the static model in step S4: set the loading point in the fatigue analysis step to the elastic center point of the ball pin 41, and set the fatigue condition required by the design;

[0090] The calculated stress of the ball head 12, the retaining ring 3, the upper end cover 43 of the ball joint, the lower end cover 44 of the ball joint, the ball pin 41, the rod body 1, and the logarithmic strain of the ball joint rubber 42 are obtained.

[0091] b. Import the stress and logarithmic strain results into fatigue analysis software to calculate the number of fatigue cycles.

[0092] 5.2. Stiffness Performance Evaluation: The radial stiffness, torsional stiffness, and yaw stiffness are calculated using the static model in the pre-stressed assembly state of step S4 to evaluate the stiffness performance of the thrust rod assembly. The calculated radial stiffness, torsional stiffness, and yaw stiffness are compared with the corresponding design requirements. The design requirements for radial stiffness, torsional stiffness, and yaw stiffness of this embodiment are 40 kN / mm, 38 Nm / °, and 50 Nm / °, respectively. If the requirements are within ±15% of the design requirements, the assembly passes. If the requirements are outside the design requirements, the assembly fails, and the process returns to step S1.

[0093] The specific steps for calculating radial stiffness, torsional stiffness, and yaw stiffness in this embodiment are as follows:

[0094] a. Use the reanalysis function to add a stiffness analysis step to the statics model of S4. Set the loading point in the stiffness analysis step to the elastic center of the ball pin 41, and set the corresponding loading ranges for the radial stiffness, torsional stiffness, and yaw stiffness required by the design. This will calculate the corresponding radial displacement, rotation angle, constraint reaction force, and constraint countertorque.

[0095] b. Read the calculated radial displacement, rotation angle, constraint reaction force, and constraint reaction torque and use the above data to draw stiffness curves, thereby fitting the corresponding radial stiffness, torsional stiffness, and yaw stiffness;

[0096] S6. Establish a complete assembly grid model: Based on half of the assembly grid model established in step S2, the center point of the cut surface is used as the symmetry center, and the other half of the assembly grid model is established by rotating 180 degrees, thereby obtaining a complete assembly grid model. The dynamic model is established using the assembly grid model. The complete assembly grid model of this embodiment is as follows: Figure 6 shown.

[0097] S7, assigning material properties: assigning material properties to each component of the thrust rod assembly according to the material type. The setting of the material type and material properties of each component in this embodiment is the same as step S3;

[0098] S8. Establish a dynamic model in the pre-pressed assembly state: Use the complete assembly mesh model to establish a dynamic model in the pre-pressed assembly state and calculate the initial stress distribution of the thrust rod assembly in the pre-pressed assembly state. The specific steps are as follows:

[0099] a. Define the analysis time and the quality scaling factor.

[0100] Since the selection of the quality scaling factor affects the solution accuracy and calculation time, the present invention adopts a semi-automatic control scaling factor method. Through the grid quality inspection function, the average minimum stable time step of the grid is obtained, and this time step is used as the quality scaling factor adjustment target to achieve the purpose of taking into account both accuracy and calculation cost at the same time.

[0101] b. Based on the contact relationships between the various components of the thrust rod assembly, a dynamic explicit general contact pair method is used to establish the contact interaction relationship between the various components; an interference contact pair is established between the upper surface of the spherical joint upper end cover 43 and the lower bottom surface of the retaining ring 3 to simulate the spherical joint rubber 42 in a preloaded assembly state. The interference is set according to the designed preload amount, and the interference amount and interference amplitude curve are set. The interference amount and interference amplitude curve set in this embodiment are the same as those in step S4;

[0102] c. Assigning unit type: In this embodiment, the ball head 12 and the ball joint pin 41 use explicit second-order tetrahedral modified unit type, and the ball joint rubber 42, the upper and lower end covers of the ball joint, the retaining ring 3 and the rod body 1 use explicit first-order hexahedral unit type.

[0103] d. Create calculation analysis step:

[0104] Analysis Step 1: Simulate the preloaded assembly state based on the interference fit setting in Step 2 and establish temporary constraint boundary conditions. In this embodiment, the temporary constraint boundary conditions are: constraining the three translational degrees of freedom of the upper and lower end surfaces of the ball heads 12 at both ends; and calculating the compressive rebound force of the ball joint rubber 42 in the preloaded assembly state.

[0105] Analysis step 2: Release the temporary boundary conditions and define fixed constraints at the center points of the ball heads 12 at both ends. In this embodiment, the fixed constraints constrain the six degrees of freedom of the center points of the ball heads 12 at both ends. Use the compression rebound force to calculate the initial stress distribution of the thrust rod assembly.

[0106] S9. Evaluate the extreme working condition performance: Use the dynamic model calculation in the pre-stressed assembly state of step S8 to evaluate the extreme working condition performance of the thrust rod assembly. The extreme working condition performance includes strength performance, buckling performance of the rod body 1, and locking performance of the retaining spring 3. If any one of the strength performance, the buckling performance of the rod body 1, and the locking performance of the retaining spring 3 fails to meet the requirements, the assembly is deemed unqualified and the process returns to step S1. If all of the strength performance, the buckling performance of the rod body 1, and the locking performance of the retaining spring 3 meet the requirements, the assembly is deemed qualified.

[0107] The specific judgment method of this embodiment is:

[0108] Strength performance: Compare the calculated equivalent plastic strain with the corresponding design requirement. The design requirement for the equivalent plastic strain in this embodiment is 0.5%. If the equivalent plastic strain is less than the design requirement, the test is qualified. If the equivalent plastic strain is greater than the design requirement, the test is unqualified, and the process returns to step S1.

[0109] Buckling performance of rod 1: The calculated critical buckling load of rod 1 is compared with the corresponding design requirement. The design requirement for the critical buckling load of rod 1 in this embodiment is 250 kN. If the critical buckling load of rod 1 is greater than the design requirement, the rod is qualified. If the critical buckling load of rod 1 is less than the design requirement, the rod is unqualified and the process returns to step S1.

[0110] Locking performance of the retaining ring 3: Compare the calculated equivalent plastic strain at the contact point between the upper surface of the retaining ring 3 and the retaining groove 13, and the warping displacement of the retaining ring 3 with the corresponding locking performance standard of the retaining ring 3. The locking performance standard of the retaining ring 3 in this embodiment is that the equivalent plastic strain at the contact point between the upper surface of the retaining ring 3 and the retaining groove 13 is less than the material elongation, and the warping displacement of the retaining ring 3 is less than 2.5mm; if the locking performance standard of the retaining ring 3 is met, it is qualified; otherwise, it is unqualified, and returns to step S1.

[0111] The inventors of the present invention discovered that the main failure mechanism of the spring retaining ring 3 popping out is that the spring mounting groove 13 is subjected to force, and the area where the upper surface of the spring retaining ring 3 contacts the spring mounting groove 13 undergoes plastic deformation, and the height of the spring mounting groove 13 becomes higher, resulting in a change in the contact position between the spring retaining ring 3 and the ball joint assembly 4, and warping of the spring retaining ring 3, thereby increasing the risk of the spring popping out. Therefore, the present invention has determined the locking performance standard of the spring retaining ring 3 through empirical summary: Under extreme working conditions, this embodiment is loaded with ±250KN, and the equivalent plastic strain at the contact area between the upper surface of the spring retaining ring 3 and the spring mounting groove 13 is less than the material elongation, and the warping displacement h of the spring retaining ring 3 is less than 2.5mm. Figure 7 Shown are the warping displacement cloud diagram and equivalent plastic strain cloud diagram of qualified and unqualified parts respectively.

[0112] The lightweight design evaluation method of the aluminum alloy thrust rod assembly based on CAE is used to evaluate the lightweight designed aluminum alloy thrust rod assembly until all evaluation indicators meet the design requirements.

[0113] The technical means disclosed in the solutions of the present invention are not limited to those disclosed in the above-mentioned embodiments, but also include technical solutions composed of any combination of the above-mentioned technical features. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A CAE-based lightweight design evaluation and optimization method for thrust rod assemblies, characterized in that The following steps are involved: S1. A thrust rod assembly is lightweight designed according to a weight reduction target, and a structural geometric model of the thrust rod assembly is obtained; the various components of the thrust rod assembly include a rod body (1), a ball head (12), a retaining ring (3), and a ball joint assembly (4); the ball head (12) is arranged at both ends of the rod body (1), and a retaining ring (13) is provided in the ball head (12); in a pre-compression assembly state, the retaining ring (3) is clamped in the retaining ring (13), so that the retaining ring (3) ) is pressed against the end surface of the ball joint assembly (4), thereby installing the ball joint assembly (4) in the ball head (12); the ball joint assembly (4) comprises a ball pin (41), a ball joint rubber (42) sleeved on the outside of the ball pin (41), and a ball joint upper end cover (43) and a ball joint lower end cover (44) respectively covering the two ends of the ball joint rubber (42), and the ball pin (41), the ball joint rubber (42), the ball joint upper end cover (43), and the ball joint lower end cover (44) are combined into one by vulcanization; S2. Establishing a mesh model of half of the assembly: Based on the structural geometric model, the structural geometric model is divided into two halves using a plane perpendicular to the axial direction of the rod (1) and passing through the midpoint of the rod (1) as a dividing plane (A), and the mesh model of half of the assembly is established using one half; and the mesh model of the ball joint rubber (42) is established in a free state in a non-prestressed assembly state; S3. Assigning material properties: Assigning material properties to each component of the thrust rod assembly according to the material type; wherein the strain energy constitutive model type of the material properties of the ball joint rubber (42) is determined by the following steps: a rubber specimen prepared using the same material as the ball hinge rubber (42), the rubber specimen uniaxial tension, plane tension and equal biaxial tension test to obtain stress - strain curve data; b. The stress-strain curve data is imported into the material properties hyperelastic module of the finite element analysis software Abaqus, and the Ogden, Mooney-Rivlin, and Yeoh strain energy models are used for fitting to obtain the corresponding constitutive model parameters; c. Using the corresponding constitutive model parameters, calculate the radial stiffness values ​​k1, k2, k3 corresponding to the Ogden, Mooney-Rivlin, and Yeoh strain energy models, and calculate the deviation rate with the measured stiffness value k of the rubber specimen, deviation rate = |kn−k| / k, n=1,2,3, and select the strain energy model corresponding to the smallest deviation rate as the strain energy model of the ball joint rubber (42); S4. Establishing a static model in a pre-pressed assembly state: To establish a static model in a pre-pressed assembly state using the half-assembly mesh model, calculate the initial stress distribution of the thrust rod assembly in the pre-pressed assembly state; the specific steps are: a. Establishment and setting of contact pairs: According to the contact relationship between the various components of the thrust rod assembly, the contact interaction relationship between the various components is established using static implicit contact pairs; wherein the upper surface of the spherical hinge upper end cover (43) and the lower bottom surface of the retaining ring (3) are established with an interference contact pair, and the interference amount is set to 3 mm and the interference amplitude curve; b. Assign element type: The ball head (12) and the ball pin (41) use the implicit standard second-order tetrahedral modified element type, the ball joint rubber (42) uses the implicit standard first-order hexahedral hybrid element type, and the ball joint upper end cover (43), the ball joint lower end cover (44), the retaining ring (3) and the rod (1) use the implicit standard first-order hexahedral element type; c. Create a calculation analysis step: Analysis step 1: simulating a pre-loaded assembly state according to the interference setting of step a, constraining the three translational degrees of freedom of the upper and lower end surfaces of the ball head (12), and calculating the compression rebound force of the ball joint rubber (42); Analysis step 2: releasing the temporary boundary conditions, defining an axisymmetric constraint condition on the cross section of the rod (1) cut by the dividing plane (A), and calculating the initial stress distribution using the compression rebound force; S5. Evaluate the fatigue and stiffness performance of the thrust rod: Use the static model calculated in step S4 to evaluate the fatigue and stiffness performance. If any one of them fails, return to S1; if both are qualified, proceed to S6; S6. Establish a complete assembly mesh model: Based on half of the assembly mesh model established in step S2, the center point of the split surface (A) is used as the center of symmetry and rotated 180° to establish the other half of the assembly mesh model; S7. Assigning material properties: Assigning material properties according to the material type of each component of the thrust rod assembly; S8. Establishing a dynamic model in a pre-pressed assembly state: Establishing a dynamic model in a pre-pressed assembly state with a complete mesh model of the assembly, and calculating the initial stress distribution of the thrust rod assembly in the pre-pressed assembly state; the specific steps are: a. Define the analysis time and obtain the average minimum stable time step through mesh quality checks, which will be used as the target for adjusting the quality scaling factor. b. According to the contact relationship between the various components of the thrust rod assembly, a contact interaction relationship is established using a dynamic explicit general contact pair; wherein the upper surface of the ball joint upper end cover (43) and the lower bottom surface of the retaining ring (3) are established with an interference contact pair, and the interference amount is set to 3 mm and the interference amplitude curve; c. Assign element type: The ball head (12) and the ball pin (41) use explicit second-order tetrahedral modified element type, and the ball joint rubber (42), ball joint upper end cover (43), ball joint lower end cover (44), retaining ring (3) and rod (1) use explicit first-order hexahedral element type; d. Create a calculation analysis step: Analysis step 1: simulate the pre-pressed assembly state according to the interference setting in step b, constrain the three translational degrees of freedom of the upper and lower end surfaces of the ball heads (12) at both ends, and calculate the compression rebound force of the ball joint rubber (42); Analysis step 2: releasing the temporary boundary conditions, defining fixed constraints at the center points of the spherical heads (12) at both ends, and calculating the initial stress distribution using the compression rebound force; S9. Evaluate the extreme working condition performance: Use the dynamic model calculated in step S8 to evaluate the extreme working condition performance, including strength performance, buckling performance of the rod (1), and locking performance of the retaining ring (3); wherein the locking performance of the retaining ring (3) is determined by: a. Calculate the equivalent plastic strain and warping displacement at the contact point between the upper surface of the circlip retaining ring (3) and the circlip mounting groove (13); b. Compare the locking performance criteria: Equivalent plastic strain < material elongation and warpage displacement < 2.5 mm. If these criteria are met, the system passes. Otherwise, the system fails and returns to S1. If the strength performance, the flexure performance of the rod body (1), and the locking performance of the retaining ring (3) are all qualified, it is finally qualified.

2. The method according to claim 1, wherein: In step S5, the fatigue performance is evaluated by calculating the number of fatigue cycles, and the design requirement is ≥80,000 times.

3. The method according to claim 1, wherein: In step S5, the stiffness performance includes radial stiffness, torsional stiffness, and yaw stiffness, and the design requirements are 40 kN / mm, 38 N·m / °, and 50 N·m / °, respectively. The qualification standard is that the calculated value is within the range of ±15% of the design requirements.

4. The method according to claim 1, wherein: In step S9, the qualification standard of the strength performance is equivalent plastic strain <0.5%, and the qualification standard of the rod buckling performance is buckling limit critical load >250KN.

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