Equal-strength bridge shell structures with dual variable properties and arbitrary curved cross sections and their design methods

Abstract

The application discloses a kind of double variable attribute arbitrary curved edge cross section equal strength axle housing structure and its design method, and the shape of bridge housing cross section is arbitrary curved edge cross section;The size and shape of the bridge housing cross section are controlled by a set of control equations, and there are 8 constraint parameters in the equation, and the shape parameter and the size parameter each account for 4. Along the length direction of bridge housing, the shape of the bridge housing cross section is specifically designed as arbitrary curved edge shape in the middle cross section, and the outer circle inner ellipse ring is designed in the two ends and hub bearing matching section. The shape of the cross section changes along the axle, which specifically shows that the outer circle inner ellipse ring transitions to arbitrary curved edge shape. Compared with the existing design method, the cross section shape of the present application is arbitrary, flexible in design, and various bridge housing cross sections that do not exist at present can be designed. Compared with the existing circular bridge housing, it has higher bending resistance. Compared with the existing rectangular bridge housing, there is no stress concentration phenomenon on the cross section.

Description

Technical Field

[0001] This invention belongs to the field of automotive axle lightweighting, and particularly relates to an equal-strength axle shell structure with dual variable properties and arbitrary curved cross-section and its design method. Background Technology

[0002] The driven axle housing mainly supports the sprung mass of the vehicle and bears the transmission of vertical force, longitudinal force, lateral force and braking torque between the frame or monocoque body and the wheels.

[0003] This type of driven bridge structure, which withstands complex external forces, can be regarded as a general beam structure. However, by designing it as an equal-strength beam structure, its weight can be greatly reduced, achieving lightweighting. This is because, under the condition of achieving the same mechanical performance, equal-strength beams have significant advantages such as light weight, small space occupation, and high structural utilization.

[0004] Currently, the design of equal-strength beam structures mainly focuses on their geometric dimensions, with very little research on their cross-sectional shape. Furthermore, most research and design work targets circular and rectangular tubular beams. For example, the axle shells of driven axles are mostly rectangular in large trucks, primarily because rectangular sections have a higher bending section modulus in the vertical direction. However, rectangular axle shells not only bear vertical forces but also the rearward braking force transmitted from the brake drums during operation. This causes stress concentration at the rectangular corners of the axle shell cross-section, leading to a deterioration in the overall mechanical properties of the structure. Therefore, it is necessary to design new cross-sectional shapes that possess both a high bending section modulus and avoid stress concentration at the cross-section.

[0005] Besides the shape of the bridge shell cross-section, the current use of uniform cross-section bridge shells limits optimization to a few sections, resulting in a limited number of optimization surfaces. Furthermore, for the optimization of the dimensions of the same cross-section, the limitations of finite element software restrict most optimization parameters to the bridge shell thickness. Specifically, this involves fixing the dimensions of the inner cross-section and optimizing the outer cross-section, or vice versa. Simultaneous optimization of both inner and outer cross-section dimensions is not possible, leading to limited optimization parameters, localized optimization, and solutions that are not globally optimal. Therefore, a better optimal design method is needed, combining advanced design theories and technological conditions to achieve the optimal design of the bridge shell dimensions. Summary of the Invention

[0006] In view of the above-mentioned technical problems, this invention proposes a bridge shell structure with dual variable properties and arbitrary curved cross-section, and its design method, which achieves better bending resistance and a lighter structural design method, and can avoid stress concentration.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0008] A bridge shell structure with dual variable properties and arbitrary curved cross section, characterized in that: the cross-sectional shape of the bridge shell is an arbitrary curved cross section; the size and shape of the cross-section of the bridge shell are controlled by a unified set of control equations, which have a total of 8 constraint parameters, with 4 shape parameters and 4 size parameters.

[0009] In the above technical solution, the governing equation for the bridge shell cross-section is:

[0010]

[0011] The parameters are as follows: outer contour width 2A, height 2B, inner contour width 2a, height 2b. These four parameters control the size of the cross-section. N1, N2, n1, and n2 are shape harmony parameters, which control the shape of the cross-section.

[0012] In the above technical solutions, the thickness of each cross section varies along the circumferential and axial directions.

[0013] In the above technical solution, along the length of the axle shell, the cross-sectional shape of the axle shell is specifically designed as an arbitrary curved shape in the middle section, and the sections at both ends that mate with the wheel hub bearings are designed as an outer circle with an inner elliptical ring; the change in cross-sectional shape along the axle shaft is specifically manifested as an outer circle with an inner elliptical ring transitioning to an arbitrary curved shape.

[0014] A design method for a bridge shell structure with dual variable properties and arbitrary curved cross-section, characterized by comprising:

[0015] Step S1: Take half of the bridge shell along the length as the design object, and design the entire bridge shell structure symmetrically from left to right;

[0016] Step S2: Optimize the design of key sections contained in half of the bridge shell to determine the design variables of the bridge shell cross-section; where,

[0017] The equation for the cross-section of the bridge shell is:

[0018]

[0019] The parameters are as follows: outer contour width 2A, height 2B, inner contour width 2a, height 2b. These four parameters control the size of the cross-section. N1, N2, n1, and n2 are shape harmony parameters, which control the shape of the cross-section.

[0020] Step S3: Perform a stress analysis on the half of the bridge shell and calculate the moment at each section;

[0021] Step S4: Determine the cross-section design variables based on the moment and dimensional parameter constraints of the cross-section, and then substitute them into the arbitrary curved section optimization model. Use Matlab programming to iteratively calculate the optimal dimensions and shape parameters of each cross-section. The arbitrary curved section optimization model for the bridge shell cross-section is as follows:

[0022] Objective function: The objective is to minimize the cross-sectional area, min S.

[0023] Design variables: The undetermined parameters a, b, A, B, n1, n2, N1, and N2 of the control equation for arbitrary curved sections are used as design variables;

[0024] The constraints include variable constraints and maximum stress value constraints, among which,

[0025] Variable constraints:

[0026]

[0027] h is the cross-sectional thickness;

[0028] Maximum stress constraint:

[0029]

[0030] Step S5: Import the optimal solution set into Inventor 3D modeling software using Excel to build the entire bridge shell model;

[0031] Step S6: Import the model into Hypermesh for finite element analysis, compare the stress results with the theoretical values, obtain the stress concentration factor in the stress concentration region, import the factor into the arbitrary curved section optimization model to obtain the optimal solution again, and finally design the equal strength bridge shell structure with dual variable property arbitrary curved section.

[0032] In the above technical solution, the cross-sectional design variables in step S2 are determined according to the following steps:

[0033] Set up the first variable assignment group to construct the cross-sectional model and perform stress solution. When the stress solution result meets the strength requirements, the first variable group is used as the design variable to be optimized.

[0034] When the cross-sectional model constructed using the first variable assignment group does not meet the strength requirements, the second variable assignment group is set to reconstruct the cross-sectional model and perform stress solution. When the stress solution result of the reconstructed cross-sectional model meets the strength requirements, the second variable group is used as the design variable to be optimized.

[0035] When the cross-sectional model constructed using the second variable assignment group does not meet the strength requirements, the third variable assignment group is set to reconstruct the cross-sectional model and perform stress solution. When the stress solution result of the reconstructed cross-sectional model meets the strength requirements, if the equal thickness or constant thickness scheme is used for optimization design, the third variable group is used as the design variable to be optimized. If the variable thickness scheme is used for optimization design, the fourth variable group is used as the design variable to be optimized.

[0036] If the stress solution results of the reconstructed cross-section model do not meet the strength requirements, return to set the constraints and start from scratch to determine the cross-section variables to be optimized.

[0037] Each assignment group in step S2 includes the assignment of the outer contour width 2A, height 2B, inner contour width 2a, height 2b, and shape harmony parameters N1, N2, n1, n2; each variable group includes at least variables and constants.

[0038] In the above technical solution, the four variable assignment groups in step S2 are performed according to the following optimization schemes:

[0039] S21: When the first set of variables is used as the design variables to be optimized, the shape harmony parameter and the section thickness are taken to the minimum value. Only the appearance dimension variables A and B of the section need to be optimized, that is, the appearance dimension variables A and B are determined as the specific design variables to be optimized.

[0040] S22: When the second set of variables is used as the design variables to be optimized, the cross-sectional thickness is taken as the minimum value, the external dimensions are taken as the maximum value, and the cross-section is designed as a barrel cross-section with equal thickness. That is, two sets of shape harmony parameters N1, N2, n1, n2 are determined as specific design variables to be optimized.

[0041] S23: When the third set of variables is used as the design variables to be optimized, the cross-sectional appearance dimensions are taken to their maximum values, that is, the two sets of shape harmony parameters N1, N2, n1, n2 and thickness h of the cross-section are determined as the specific design variables to be optimized.

[0042] S24: When the optimization problem cannot be optimized using the above three schemes, the fourth variable assignment group is adopted, and the cross-sectional appearance dimensions are taken as the maximum value. That is, the two sets of shape harmony parameters N, N2, n1, n2 and inner contour dimensions a, b of the cross-section are determined as the specific design variables to be optimized.

[0043] In the above technical solution, in step S2, when the maximum stress of each section is less than the theoretical allowable stress, the stress solution result is considered to meet the strength requirements.

[0044] In the above technical solution, the mechanical model and optimization mathematical model used for each set of optimization schemes in step S2 are the same, only the design variables and cross-sectional control equations are different, and the optimization algorithm adopts the differential evolution algorithm or the immune clonal selection algorithm.

[0045] This invention takes a driven axle with a rated load of 5 tons as an example. The material used is Q460C with a yield strength of 460 MPa. Considering the stress concentration problem, the maximum theoretical stress of its axle shell cross-section under extreme working conditions is set at 300 MPa. The extreme working condition is when the axle shell is subjected to impact load and braking force simultaneously, at which point the torque, vertical, and lateral bending moments on the driven axle shell are at their maximum. Calculations show that the maximum stress of most sections is between 250-300 MPa. Stress concentration at the axle shell corners is unavoidable. Due to size constraints, the optimized dimensions and thickness at the axle shell corners are also limited. Therefore, the final maximum stress value at the axle shell corner section is greater than the theoretical value, while the maximum stress value of other sections (over 90%) is approximately equal to the theoretical value, indicating that most sections have the same maximum stress value and exhibit equal strength characteristics.

[0046] Therefore, the bridge shell cross-section of this invention possesses dual variable properties: variable shape and variable size, enabling synergistic optimization of shape and size. The cross-sectional shape of the bridge shell is an arbitrary curved section, which can be optimized to produce circular, elliptical, rectangular, square, and numerous transitional sections, many of which offer superior performance. The size and shape of the bridge shell cross-section are controlled by a unified set of equations with eight parameters, four for shape and four for size, representing a novel method of coupling shape and size optimization. Unlike traditional cross-section optimization through a cross-section database, this method features continuous shape optimization rather than discrete shape optimization using several cross-section forms, thus exhibiting variable shape properties. The bridge shell cross-section also exhibits variable thickness along both the circumferential and axial directions, thus possessing variable size properties. The overall structure of the bridge shell is designed as a single unit based on the theory of equal strength, thus possessing equal strength properties. By employing a dual variable property arbitrary curved section design for the bridge shell, the goal of lightweighting the bridge shell is achieved.

[0047] Furthermore, the cross-sectional shape of the bridge shell is specifically designed as follows: the middle cross-section is designed as an arbitrary curved shape, and the sections at both ends that mate with the wheel hub bearings are designed as an outer circle with an inner elliptical ring. The change in cross-sectional shape along the bridge axis is specifically manifested as the transition from an outer circle with an inner elliptical ring to an arbitrary curved shape. The arbitrary curved cross-section includes most types of cross-sectional shapes, so the arbitrary curved cross-section model is used uniformly in the design, and then the optimal design method is determined to optimize the model.

[0048] Furthermore, the optimal design method is to establish an optimization model for arbitrary curved cross sections, using the eight parameters of the control equation of the arbitrary curved cross section as design variables, and the cross-sectional area as the objective function. The constraints can be divided into linear constraints and nonlinear constraints. The linear constraints specifically include shape and size constraints and minimum thickness constraints. The nonlinear constraints stipulate that the maximum stress of the cross section is less than the allowable stress, and the fourth strength theory is used for verification.

[0049] Furthermore, based on the different constraints imposed on the structure, four different variable optimization schemes were designed to optimize the structural cross-section, so as to improve optimization efficiency while ensuring the best results.

[0050] Furthermore, due to the different stresses and dimensional constraints on the cross section, the resulting cross section shape and size are also different, thus exhibiting the characteristics of a variable cross section.

[0051] Furthermore, since the optimal solution obtained from the optimization model of arbitrary curved cross sections is subject to the allowable stress as the greatest constraint, the maximum stress of the cross section is exactly equal to the allowable stress, thus exhibiting the characteristic of equal strength.

[0052] Therefore, the present invention provides a bridge shell structure with dual variable properties and arbitrary curved cross sections, which is formed by lofting modeling of arbitrary curved cross sections of different shapes and sizes. The dimensional parameters of each cross section are obtained through optimal design method, and the whole structure has the characteristics of variable cross section, variable properties and equal strength.

[0053] The present invention has the following beneficial effects: the bridge shell designed by the present invention is lighter than that of traditional bridge shells, and the cross-sectional shape of the bridge shell is arbitrary, allowing for flexible design and the creation of various bridge shell cross-sections not currently available; compared with existing circular bridge shells, the present invention has higher bending resistance while possessing the characteristics of circular bridge shells, such as smooth cross-sectional transitions and low stress concentration coefficients; compared with existing rectangular bridge shells, the present invention does not exhibit stress concentration on the cross-section. Although rectangular bridge shells have a high bending resistance coefficient, stress concentration occurs at the rectangular corners, greatly reducing their bending resistance performance, while the arbitrary curved cross-section has a uniform curvature transition and does not produce cross-sectional stress concentration. Attached Figure Description

[0054] Figure 1 This is a schematic diagram of the inner and outer cross-sectional contour curves of the present invention, based on the equation of arbitrary curved cross-sections and taking different shape harmonic parameters.

[0055] Figure 2 The cross-sectional shape of the present invention is a specific shape and parameter adjustment; a) is an ellipse; b) is a rectangle; c) is a angular thick-side wave shape; d) is a barrel shape with equal thickness.

[0056] Figure 3 This is a quarter model of the driven bridge shell of the present invention. Ten sections are taken for optimization. Since the driven bridge shell is a left-right symmetrical structure along the length direction and the force is also left-right symmetrical, only half needs to be designed. The sections to be optimized are marked from left to right.

[0057] Figure 4 This is the design space and load model of the bridge shell to be optimized in this invention.

[0058] Figure 5This invention describes the process for determining cross-sectional design variables for arbitrary curved cross-sections.

[0059] Figure 6 The design route of this invention is a bridge shell with dual variable properties and arbitrary curved cross-section of equal strength. It includes taking half of the bridge shell, selecting the key section, taking the first section, stress analysis, calculating the moment Mz, My, T, determining the cross-section design variables based on variable constraints, cross-section optimization model, programming to solve for the optimal parameters, storing the solution set X, iterating 10 times, outputting the solution set X, three-dimensional model, finite element analysis and stress cloud diagram.

[0060] Figure 7 This is a force and moment diagram of the left half of the axle housing of the present invention, including the vertical bending moment generated by 2.5 times the rated load, i.e., the impact load, the lateral bending moment generated by the braking force, and the braking torque.

[0061] Figure 8 This is a graph showing the change of the horizontal axis dimension of the arbitrary curved contour inside and outside the present invention with the position of the cross section, including the curve of the change of the horizontal axis dimension of the inner cross section and the curve of the change of the horizontal axis dimension of the outer cross section.

[0062] Figure 9 This is a graph showing the change of the longitudinal axis dimension of the arbitrary curved contour inside and outside the present invention with the position of the cross section, including the curve of the change of the longitudinal axis dimension of the inner cross section and the curve of the change of the longitudinal axis dimension of the outer cross section.

[0063] Figure 10 This is a graph showing the variation of four shape harmony parameters of the arbitrary curved contour of the inner and outer sections with the cross-sectional position, including the variation curves of two shape harmony parameters of the arbitrary curved contour of the inner section and the variation curves of two shape harmony parameters of the arbitrary curved contour of the outer section.

[0064] Figure 11 The three-dimensional model of the bridge shell was established for this invention.

[0065] Figure 12 for Figure 3 Optimization results of 10 key sections of the middle axle shell in the half-model of the middle axle shell.

[0066] Figure 13 This is the stress cloud diagram of the bridge shell of the present invention. Detailed Implementation

[0067] The following detailed description of the present invention, with reference to the accompanying drawings and embodiments, provides an example of a bridge shell structure with dual variable properties and arbitrary curved cross-sections of equal strength.

[0068] like Figure 1 The figure shows the arbitrary curved cross-sectional profile shape used in this invention. Different profile shapes can be obtained by taking different shape harmonic parameter values. For example, taking a specific shape harmonic parameter value can obtain a profile like... Figure 2The outline shapes shown are (ellipse, rectangle, thick corner and thin side, and copper mold of equal thickness).

[0069] The present invention proposes arbitrary curved cross-sections for, for example Figure 3 The bridge shell shown is designed with 10 key sections optimized. The design space and constraints of the bridge shell are as follows: Figure 4 As shown, to improve optimization speed and ensure optimal results while reducing the design space of variables, this invention designs as follows: Figure 5 The flowchart illustrates the method for determining cross-sectional design variables. Figure 5 In the table, the values ​​of three sets of variable assignments are shown in Table 1, and the values ​​of four different sets of optimization variables are shown in Table 2. Specifically, the four parameters—outer contour width 2A, height 2B, inner contour width 2a, and height 2b—control the size of the cross-section; N1, N2, n1, and n2 are shape harmony parameters that control the shape of the cross-section; and h is the cross-section thickness, with a minimum thickness h. min .

[0070] Table 1 Three groups of variable assignment groups

[0071]

[0072]

[0073] Table 2. Variable sets for determining optimization under different constraints.

[0074]

[0075] like Figure 6 The diagram shows a flowchart of a design method for a bridge shell structure with an arbitrary curved cross-section and dual variable properties according to the present invention, including the following steps:

[0076] Step 1: Since the driven bridge housing is symmetrical, half of the housing is taken as the design object.

[0077] Step 2: Optimize the design of key cross-sections of the bridge shell.

[0078] Step 3: Perform a stress analysis on the bridge shell and calculate the moment at each section.

[0079] Step 4: Determine the cross-section design variables based on the moment and size parameter constraints of the cross-section, and then substitute them into the arbitrary curved cross-section optimization model. Use Matlab programming to iteratively calculate the optimal size and shape parameters of each cross-section.

[0080] Step 5: Import the optimal solution set into Inventor 3D modeling software using Excel to build the entire bridge shell model.

[0081] Step 6: Import the model into Hypermesh for finite element analysis, compare the stress results with the theoretical values, obtain the stress concentration factor in the stress concentration region, import the factor into the arbitrary curved section optimization model to obtain the optimal solution again, and finally design the equal strength bridge shell structure with dual variable property arbitrary curved section.

[0082] Because the bridge shell has some turning areas and load-constrained areas along the axial direction, stress concentration is inevitable in these areas. Due to constraints such as size, their strength cannot be consistent with other areas. Therefore, it is impossible to achieve equal strength in the structural design of these areas, and heat treatment processes are needed to improve their strength.

[0083] Design theory of the present invention

[0084] 1) Mathematical model of arbitrary curved cross section

[0085] Inspired by the equation of an ellipse, the following governing equations for arbitrary curved cross sections were designed.

[0086]

[0087] Among them, the outer contour width 2A, height 2B, inner contour width 2a, and height 2b are four parameters that control the size of the cross-section; N1, N2, n1, and n2 are shape harmony parameters that control the shape of the cross-section.

[0088] Based on the above governing equations, the cross-section is designed with A = 5, B = 7, a = 3, and b = 5. All four shape harmony parameters are taken with the same value, ranging from 0.5 to 10, with a step size of 0.5. The inner and outer cross-sectional profile curves are drawn as follows: Figure 1 As shown.

[0089] As shown in Figure 1, the contour curve includes all transitional sections between the rectangle and the rhombus. When the shape harmony parameter is greater than 0.5 and less than 1, a clear arc transition appears at the midpoint of the inner and outer section edges. When the shape harmony parameter is greater than 1, the midpoint of the inner and outer section edges has a small curvature, which is approximately a straight line segment, and the length of this line segment increases with the increase of the shape harmony parameter.

[0090] When all shape harmony parameters are set to 1, the cross-section is elliptical; when a large value is taken (e.g., 100), the cross-section is rectangular; when N1 = N2 = 3 and n1 = n2 = 0.9 in the shape harmony parameters, a cross-section with thick corners and thin sides is designed; when N1 = n1 = 3 and N2 = n2 = 0.9 in the shape harmony parameters, a cylindrical cross-section with uniform thickness is designed, etc. Figure 2 As shown.

[0091] Such as Figure 2 There are many other cross-sectional shapes shown, and the optimal or functional cross-section can be designed according to actual needs.

[0092] 2) Optimization model for arbitrary curved cross sections

[0093] Objective function:

[0094] Minimize the cross-sectional area

[0095] min S

[0096] Design variables

[0097] The undetermined parameters of the control equation for arbitrary curved cross sections are taken as design variables, namely a, b, A, B, n1, n2, N1, and N2.

[0098] Constraints

[0099] Variable constraints:

[0100]

[0101] h is the cross-sectional thickness.

[0102] The maximum stress value is constrained.

[0103]

[0104] Based on the relationship between constraints and optimal solutions, the following optimization schemes are designed. Different optimization schemes are selected according to different constraints, thereby increasing the probability of obtaining the optimal solution and reducing the optimization time.

[0105] Optimization Scheme 1: When the optimization problem has weak constraints on appearance dimensions, the shape harmony parameter and cross-sectional thickness are minimized, and only the appearance dimension variables A and B of the cross-section need to be optimized.

[0106] Weak constraint judgment: When the cross section is a low-order cross section (low-order means that the four shape harmonic parameters are at their minimum values), and the external dimensions are at their maximum values ​​and the thickness is at its minimum values, the mechanical analysis of the cross section meets the strength requirements, and the external dimensions meet the weak constraint condition.

[0107] Optimization Scheme 2: When the optimization problem is a strong constraint on the appearance dimensions, the cross-section thickness is taken as the minimum value, the appearance dimension is taken as the maximum value, the cross-section is designed as a barrel cross-section with equal thickness, and only the two sets of shape harmony parameters of the cross-section need to be optimized.

[0108] Strong constraint judgment: When the cross section is a high-order cross section (high-order means that the four shape harmonic parameters are at their maximum values), and the appearance dimension is at its maximum value and the thickness is at its minimum value, the mechanical analysis of the cross section meets the strength requirements, and the appearance dimension is a strong constraint condition.

[0109] Optimization Scheme 3: When the optimization problem exceeds the strong constraint of appearance size and there is a solution within the constraint conditions, if the cross section is required to be designed as a cross section with equal thickness, then the appearance size of the cross section is taken as the maximum value, and the two sets of shape harmony parameters and thickness of the cross section need to be optimized.

[0110] Determining if there is a solution within the constraints: When the cross section is a high-order cross section, and the external dimensions and thickness are at their maximum values, the mechanical analysis of the cross section satisfies the strength requirements, thus satisfying the condition that there is a solution within the constraints.

[0111] Optimization Scheme 4: When the above three schemes cannot be used to optimize the problem, Scheme 4 is adopted. The external dimensions are taken as the maximum value, and the shape harmony parameters and inner contour dimensions of the cross section need to be optimized.

[0112] The flowchart for determining the cross-sectional design variables based on the optimized scheme is as follows: Figure 5 .

[0113] Each optimization scheme uses the same mechanical model and optimization mathematical model, only the design variables and cross-sectional control equations are different. The optimization algorithm uses either differential evolution algorithm or immune clonal selection algorithm.

[0114] 3) Specific operations for optimizing arbitrary curved cross-sections

[0115] This invention takes a driven axle with a rated load of 5 tons as an example. The material used is Q460C with a yield strength of 460 MPa. Considering the stress concentration problem, the maximum theoretical stress of its axle shell cross-section under extreme working conditions is set at 300 MPa. The extreme working condition is when the axle shell is subjected to an impact load while a braking force is applied. Under this condition, the torque, vertical and lateral bending moments experienced by the driven axle shell are at their maximum. Figure 4 As shown.

[0116] like Figure 7 The torque acting on the left half of the bridge shell is shown. Using the torque and the theoretical maximum stress of 300 MPa, combined with dimensional constraints, the optimal dimensional parameters for each section are obtained. An optimization algorithm is then used to obtain the optimal dimensional and shape parameters, and subsequently, the optimal inner ellipse dimensions are calculated, as shown below. Figure 8-10 As shown. Next, the desired curve data is imported into 3D modeling software to create a 3D model of the bridge shell, as follows. Figure 11 As shown. The designed bridge housing has a variable thickness along the axial direction, such as... Figure 8-10 As shown, it also exhibits varying thickness along the circumferential direction, such as... Figure 12 As shown in the figure. Then, finite element analysis was performed on the axle housing. After meshing, a vertical load of 6.25 tons was applied to both ends to simulate the impact load on the vehicle. Simultaneously, a lateral load of 5 tons was applied to simulate the braking load during an impact. A torque of 20,580,000 N*mm was applied at the junction of the axle housing and the drum brake base plate to simulate the braking torque. The stress contour plot obtained from the finite element analysis is shown in the figure. Figure 13 As shown, the maximum stress in most sections is between 250-300 MPa, which meets the constraint that the theoretical maximum stress is 300 MPa. Stress concentration at the bridge shell corner is unavoidable. Due to size constraints, the optimized size and thickness at the bridge shell corner are also limited. Therefore, the maximum stress value of the section at the bridge shell corner is greater than the theoretical value but less than the material yield strength. The maximum stress value of other sections (more than 90%) is approximately equal to the theoretical value. That is, most sections have the same maximum stress value and have the characteristics of equal strength.

[0117] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A dual variable property arbitrary curved sided cross section constant strength bridge housing structure characterized by: The cross section shape of the axle housing is arbitrary curved side section; the size and shape of the cross section of the axle housing are controlled by a unified set of control equations, and the equations have 8 constraint parameters, with 4 shape parameters and 4 size parameters; Along the length direction of the axle housing, the cross section shape is specifically that the middle cross section is designed as arbitrary curved side section, and the two ends are designed as outer circle and inner ellipse ring matched with the hub bearing; the cross section shape changes along the axle shaft, and specifically, the outer circle and inner ellipse ring is changed into arbitrary curved side section; The control equation of the cross section of the axle housing is: ； Wherein, each parameter is as follows: outer contour width 2 A , height 2 B , inner contour width 2a , height 2b The four parameters control the size of the cross section; N 1 ,N 2 ,n 1 ,n 2 are shape harmonic parameters, and the four parameters control the shape of the cross section.

2. The dual variable property arbitrary curved sided cross section constant strength axle housing structure of claim 1 wherein: The thickness of each cross section is different in the circumferential direction and the axial direction.

3. A method of designing a dual variable property constant strength bridge housing structure of arbitrary curved cross section, characterized by It comprises: Step S1: taking the half axle housing in the length direction as the design object, the whole axle housing structure is designed symmetrically; Step S2: the key cross sections contained in the half axle housing are taken for optimization design, and the design variables of the cross section of the axle housing are determined; wherein, The cross section equation of the axle housing is: ； Wherein, each parameter is as follows: outer contour width 2 A , height 2 B , inner contour width 2a , height 2b The four parameters control the size of the cross section; N 1 ,N 2 ,n 1 ,n 2 are shape harmonic parameters, and the four parameters control the shape of the cross section; Step S3: the force moment of each cross section is calculated through stress analysis of the half axle housing; Step S4: based on the force moment of the cross section and the size parameter constraint, the design variables of the cross section are determined, and then the optimal size and shape parameters of each cross section are calculated through Matlab programming cycle by substituting into the arbitrary curved side section optimization model; the arbitrary curved side section optimization model of the cross section of the axle housing is: Objective function: Minimize cross-sectional area ; Design variables: arbitrary curved side section control equation undetermined parameters a, b, A, B, n 1 、n 2 、N 1 、N 2 as design variables; The constraint conditions include variable constraint and maximum stress value constraint, wherein, Variable constraint: h for the cross-sectional thickness; Maximum stress value constraint: ； Step S5: the optimal solution set is imported into the inventor three-dimensional modeling software through excel, and the whole axle housing model is established; Step S6: the model is imported into hypermesh for finite element analysis, the stress results are compared with the theoretical values, the stress concentration coefficient of the stress concentration area is obtained, the coefficient is imported into the arbitrary curved side section optimization model to obtain the optimal solution again, and finally the equal strength axle housing structure with double variable properties and arbitrary curved side section is designed.

4. The method of designing a dual-attribute arbitrary curved sided cross-section constant strength axle housing structure of claim 3, wherein The cross section design variables in step S2 are determined as follows: When the stress solving result of the cross section model constructed by the first variable assignment group meets the strength requirement, the first variable group is used as the design variable to be optimized; When the cross section model constructed by the second variable assignment group does not meet the strength requirement, the second variable assignment group is set to reconstruct the cross section model and perform stress solving; when the stress solving result of the reconstructed cross section model meets the strength requirement, the second variable group is used as the design variable to be optimized; When the cross section model constructed by the second variable assignment group does not meet the strength requirement, the second variable assignment group is set to reconstruct the cross section model and perform stress solving; when the stress solving result of the reconstructed cross section model meets the strength requirement, the second variable group is used as the design variable to be optimized; When the stress solving result of the above reconstructed cross section model does not meet the strength requirement, the constraint condition is set again, and the cross section design variable to be optimized is determined from the beginning; Each assignment group of step S2 includes an outer contour width 2 A , a height 2 B , an inner contour width 2a, a height 2b, a shape harmony parameter N 1 ,N 2 , n 1 ,n 2. Each variable group includes at least a variable and a constant.

5. The dual attribute arbitrary curved sided cross-section isogrid bridge housing structure design method according to claim 3 or 4, characterized in that The four variable assignment groups in step S2 are respectively optimized according to the following optimization scheme: S21: when the first variable group is used as the design variable to be optimized, the shape harmony parameter and the cross-section thickness take the minimum value, and only the appearance size variable of the cross-section needs to be optimized, i.e., the appearance size variable of the cross-section is determined as the specific design variable to be optimized; A and B S22: when the second variable group is used as the design variable to be optimized, the shape harmony parameter and the cross-section thickness take the minimum value, and only the appearance size variable of the cross-section needs to be optimized, i.e., the appearance size variable of the cross-section is determined as the specific design variable to be optimized; A and B S23: when the third variable group is used as the design variable to be optimized, the shape S22: When the second variable group is used as the design variable to be optimized, the cross section thickness takes the minimum value, the appearance size takes the maximum value, the cross section is designed as an equal-thickness barrel cross section, i.e. two groups of shape harmonic parameters are determined N 1 ,N 2 ,n 1 ,n 2 as the specific design variable to be optimized; S23: When the third variable group is taken as the design variables to be optimized, the cross-sectional appearance size takes the maximum value, i.e. the two groups of shape harmonic parameters of the cross section are determined N 1 ,N 2 ,n 1 ,n 2 and thickness h as the specific design variables to be optimized; S24: When the optimization problem cannot be optimized using the above three schemes, then the fourth variable assignment group is adopted, the cross-sectional appearance size is taken as the maximum value, that is, the two groups of shape harmonic parameters of the cross section are determined N 、 N 2 ,n 1 ,n 2and inner contour size a, b as a specific design variable to be optimized.

6. The method of designing a dual attribute arbitrary curved sided cross section constant strength axle housing structure as claimed in claim 3 wherein When the maximum stress of each section is less than the allowable stress in step S2, it is considered that the stress solution result meets the strength requirement.

7. The method of designing a dual attribute arbitrary curved sided cross section constant strength axle housing structure as claimed in claim 3 wherein The mechanical model adopted by each set of optimization scheme in step S2 is the same as the optimization mathematical model, only the design variable and the section control equation are different, and the optimization algorithm adopts the differential evolution algorithm or the immune clone selection algorithm.

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