A longitudinal beam section optimization method based on section coefficient and longitudinal beam

Abstract

The present invention discloses a method for optimizing the cross-section of a longitudinal beam based on the section modulus and a longitudinal beam, which includes designing an initial version of the longitudinal beam cross-section, determining the centroid coordinates of the initial version of the longitudinal beam cross-section based on the area moment of each closed cross-section, and establishing a new coordinate system with the centroid as the reference; determining the flexural section modulus of the initial version of the longitudinal beam cross-section based on the new coordinate system; determining the cross-section lightweight coefficient k of the initial version of the longitudinal beam cross-section based on the flexural section modulus; determining the section modulus limit conditions according to the section modulus of a competing vehicle and product definition; and optimizing the longitudinal beam cross-section based on the objective function k to determine the optimal inner panel thickness t1, outer panel thickness t2, cross-section height H, and cross-section width W. The present invention introduces the concept of the cross-section lightweight coefficient, obtains the optimal shape and material thickness combination, and achieves the purpose of cross-section optimization.

Description

Background Art

[0002] The material thickness and size design of the longitudinal beam section have a great influence on the torsional and bending stiffness of the longitudinal beam as a whole, but increasing the cross section will lead to an increase in weight. How to achieve a lightweight design of the longitudinal beam section while meeting the bending and torsional stiffness of the entire vehicle is a problem often faced in longitudinal beam design.

[0003] Traditional design methods such as Figure 2 As shown, it usually needs to go through the section design stage, solution data design stage, and vehicle performance analysis stage. According to the performance analysis results, the section size and material thickness are repeatedly optimized until the performance and lightweight requirements are met.

[0004] Since traditional methods require whole vehicle performance simulation and repeated adjustments are time-consuming, there is no way to fully consider the balance between lightweight design and performance during the cross-section design stage. Summary of the invention

[0005] In view of the technical problems existing in the prior art, the present invention provides a longitudinal beam cross-section optimization method based on section coefficient. By introducing the concept of cross-section lightweight coefficient, the optimal shape and material thickness combination is obtained to achieve the purpose of cross-section optimization.

[0006] The present invention discloses a longitudinal beam section optimization method based on section coefficient, comprising designing a preliminary longitudinal beam section, the preliminary longitudinal beam section being composed of a combination of a plurality of closed sections, determining the centroid coordinates of the preliminary longitudinal beam section based on the area moments of the respective closed sections, and establishing a new coordinate system based on the centroid; determining the bending section coefficient of the preliminary longitudinal beam section based on the new coordinate system; determining the section lightweight coefficient k of the preliminary longitudinal beam section based on the bending section coefficient, the section lightweight coefficient k being a function of the section shape being k=f(t 1 ,t 2 ,H,W), where t1 is the inner sheet thickness, t2 is the outer sheet thickness, H is the section height, and W is the section width); determine the section coefficient restriction conditions based on the competing vehicle section coefficient and product definition; select the inner sheet thickness t 1 , outer sheet thickness t 2 , section height H, section width W are substituted into the objective function k = f(t 1 ,t 2 ,H,W), when the lightweight factor k=f(t 1 ,t 2 ,H,W) is maximum and the section coefficient restriction condition is met at the same time, the optimal inner sheet thickness t is obtained. 1 , outer sheet thickness t 2 , section height H, section width W; based on the optimal inner sheet thickness t 1 , outer sheet thickness t 2 , section height H, and section width W optimize the longitudinal beam cross-section.

[0007] In a preferred embodiment of the present invention, the method for determining the centroid coordinates of the preliminary longitudinal beam section comprises:

[0008] Area moment of the first version of the longitudinal beam section about the Y axis

[0009] Area moment of the first version of the longitudinal beam section about the X axis

[0010] Among them, A 1 , A 2 , A 3 ...are the areas of the closed cross sections, x 1 、x 2 、x 3 ...is the X-axis coordinate of the centroid of each section, y 1 ,y 2 ,y 3 ...is the Y-axis coordinate of the centroid of each section

[0011]

[0012]

[0013] In a preferred embodiment of the present invention, a new coordinate system is established based on the centroid.

[0014] Based on the new coordinate system, the maximum absolute value of the X-axis coordinates of all points on the cross section is x max =max{|xx c |};

[0015] Based on the new coordinate system, the maximum absolute value of the Y coordinates of all points on the cross section is y max =max{|yy c |}.

[0016] In a preferred embodiment of the present invention, the method for obtaining the bending section coefficient comprises:

[0017] I x =∫ A y 2 dI y =∫ A x 2 dA

[0018] I x is the moment of inertia about the X axis, I y is the moment of inertia about the Y axis, dA is the micro area;

[0019]

[0020]

[0021] σ maxX is the maximum normal bending stress about the X axis, σ maxY is the maximum bending normal stress about the Y axis; M x M is the bending moment of the cross section about the X axis, y W is the bending moment of the cross section about the Y axis; x is the bending section coefficient about the X axis, W y is the bending section coefficient about the Y axis.

[0022] In a preferred embodiment of the present invention, the higher the cross-sectional lightweight coefficient k is, the better the bending resistance under this shape is. The cross-sectional lightweight coefficient k is not related to the actual size but only to the cross-sectional shape.

[0023] In a preferred embodiment of the present invention, Among them, a and b are pre-calibrated weight coefficients, reflecting the importance of the cross section for the bending resistance of the X-axis and Y-axis. In this example, a and b are both 1.

[0024] In a preferred embodiment of the present invention, the section coefficient restriction condition includes the expected value of the section coefficient of the current vehicle model. Standard deviation x ,σ y

[0025] I x =∫ A y 2 dI y =∫ A x 2 dA

[0026] I x is the moment of inertia about the X axis, I y is the moment of inertia about the Y axis, dA is the micro area;

[0027]

[0028] W x is the bending section coefficient about the X axis, W y is the bending section coefficient about the Y axis

[0029]

[0030]

[0031] Where N is the number of competing products, and the constraints are

[0032] In a preferred embodiment of the present invention, the inner sheet thickness t is determined based on the layout constraints. 1 , outer sheet thickness t 2 The value ranges of the four parameters of section height H and section width W are used to form multiple sets of preset solutions based on the permutations and combinations within the value ranges. Each set of preset solutions is substituted into k = f(t 1 ,t 2 ,H,W) obtain the lightweight coefficient k=f(t 1 ,t 2 ,H,W).

[0033] In a preferred embodiment of the present invention, first determine whether each set of preset solutions satisfies the constraint condition: Under the premise of satisfying the constraints, select the maximum lightweight coefficient k = f (t 1 ,t 2 ,H,W) corresponding to a set of preset solutions is the optimal solution.

[0034] The beneficial effect of the present invention is: the present invention proposes a set of optimization methods for lightweight design of cross-section size and material thickness in the cross-section design stage (i.e., lightweight design optimization is performed in the early stage of design). The method of the present invention sets a target value of the bending section coefficient as a constraint based on reference to competing products. The influence of the cross-section size on the performance and weight of the longitudinal beam can be fully evaluated in the cross-section design stage. At the same time, the cross-section size and material thickness are set as variables, and the variable range is confirmed according to the tire envelope and the feasibility of the suspension arrangement. Finally, the variable value with the highest cross-section lightweight coefficient and meeting the cross-section coefficient target is selected from the sample, so that the longitudinal beam can be lightweight designed under the premise of meeting the bending and torsional stiffness performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a flow chart of a longitudinal beam section optimization method based on section coefficient of the present invention;

[0036] Figure 2 Flow chart of the conventional design method of the longitudinal beam section in the prior art;

[0037] Figure 3 It is a schematic diagram of a new coordinate system of a longitudinal beam cross section optimization method based on a section coefficient of the present invention;

[0038] Figure 4 It is a schematic diagram of a cross section of a competitor product of a longitudinal beam cross section optimization method based on a cross section coefficient of the present invention;

[0039] Figure 5 It is a table of all preset solutions and optimal solutions of a longitudinal beam section optimization method based on section coefficient of the present invention. DETAILED DESCRIPTION

[0040] The technical solution of the present invention (including the preferred technical solution) is further described in detail below by means of the accompanying drawings and by listing some optional embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] The present invention discloses a longitudinal beam section optimization method based on section coefficient, comprising designing a preliminary longitudinal beam section, the preliminary longitudinal beam section being composed of a combination of a plurality of closed sections, determining the centroid coordinates of the preliminary longitudinal beam section based on the area moments of the respective closed sections, and establishing a new coordinate system based on the centroid; determining the bending section coefficient of the preliminary longitudinal beam section based on the new coordinate system; determining the section lightweight coefficient k of the preliminary longitudinal beam section based on the bending section coefficient, the section lightweight coefficient k being a function of the section shape being k=f(t 1 ,t 2 ,H,W), where t1 is the inner sheet thickness, t2 is the outer sheet thickness, H is the section height, and W is the section width); determine the section coefficient restriction conditions based on the competing vehicle section coefficient and product definition; select the inner sheet thickness t 1 , outer sheet thickness t 2 , section height H, section width W are substituted into the objective function k = f(t 1 ,t 2 ,H,W), when the lightweight factor k=f(t 1 ,t 2 ,H,W) is maximum and the section coefficient restriction condition is met at the same time, the optimal inner sheet thickness t is obtained. 1 , outer sheet thickness t 2 , section height H, section width W; based on the optimal inner sheet thickness t 1 , outer sheet thickness t 2 , section height H, and section width W optimize the longitudinal beam cross-section.

[0042] In a preferred embodiment of the present invention, the method for determining the centroid coordinates of the preliminary longitudinal beam section comprises:

[0043] Area moment of the first version of the longitudinal beam section about the Y axis

[0044] Area moment of the first version of the longitudinal beam section about the X axis

[0045] Among them, A 1 , A 2 , A 3 ...are the areas of the closed cross sections, x 1 、x2 、x 3 ...is the X-axis coordinate of the centroid of each section, y 1 ,y 2 ,y 3 ...is the Y-axis coordinate of the centroid of each section

[0046]

[0047]

[0048] In a preferred embodiment of the present invention, a new coordinate system is established based on the centroid.

[0049] Based on the new coordinate system, the maximum absolute value of the X-axis coordinates of all points on the cross section is x max =max{|xx c |};

[0050] Based on the new coordinate system, the maximum absolute value of the Y coordinates of all points on the cross section is y max =max{|yy c |}.

[0051] In a preferred embodiment of the present invention, the method for obtaining the bending section coefficient comprises:

[0052] I x =∫ A y 2 dI y =∫ A x 2 dA

[0053] I x is the moment of inertia about the X axis, I y is the moment of inertia about the Y axis, dA is the micro area;

[0054]

[0055]

[0056] σ maxX is the maximum normal bending stress about the X axis, σ maxY is the maximum bending normal stress about the Y axis; M x M is the bending moment of the cross section about the X axis, y W is the bending moment of the cross section about the Y axis; x is the bending section coefficient about the X axis, W y is the bending section coefficient about the Y axis.

[0057] In a preferred embodiment of the present invention, the higher the cross-sectional lightweight coefficient k is, the better the bending resistance under this shape is. The cross-sectional lightweight coefficient k is not related to the actual size but only to the cross-sectional shape.

[0058] In a preferred embodiment of the present invention, Among them, a and b are pre-calibrated weight coefficients, reflecting the importance of the cross section for the bending resistance of the X-axis and Y-axis. In this example, a and b are both 1.

[0059] In a preferred embodiment of the present invention, the section coefficient restriction condition includes the expected value of the section coefficient of the current vehicle model. Standard deviation x ,σ y

[0060] I x =∫ A y 2 dI y =∫ A x 2 dA

[0061] I x is the moment of inertia about the X axis, I y is the moment of inertia about the Y axis, dA is the micro area;

[0062]

[0063] W x is the bending section coefficient about the X axis, W y is the bending section coefficient about the Y axis

[0064]

[0065]

[0066] Where N is the number of competing products, and the constraints are

[0067] In a preferred embodiment of the present invention, the inner sheet thickness t is determined based on the layout constraints. 1 , outer sheet thickness t 2 The value ranges of the four parameters of section height H and section width W are used to form multiple sets of preset solutions based on the permutations and combinations within the value ranges. Each set of preset solutions is substituted into k = f(t 1 ,t 2 ,H,W) obtain the lightweight coefficient k=f(t 1 ,t 2 ,H,W).

[0068] In a preferred embodiment of the present invention, first determine whether each set of preset solutions satisfies the constraint condition: Under the premise of satisfying the constraints, select the maximum lightweight coefficient k = f (t 1 ,t 2 ,H,W) corresponding to a set of preset solutions is the optimal solution

[0069] In a preferred embodiment of the present invention, the inner sheet material thickness t 1 , outer sheet thickness t 2 The selection is mainly based on the recommended nominal thickness in the enterprise standards of major OEMs, see the table below.

[0070] Unit is mm

[0071]

[0072] The section height H and section width W are mainly limited by the layout conditions. In order to save calculation time, three values ​​(maximum, minimum and middle value) are generally selected.

[0073] In an implementation case: the cross section of a competitor is measured as follows: Figure 4 As shown, the section height H before optimization is 126mm. According to the layout restrictions, the section height can be selected within the range of 120-126mm. The width is 80mm. Due to the restrictions of tire envelope and battery layout, adjustment is not allowed for the time being. Material thickness t before optimization 1 =1.6mm t 2 =1.4mm, you can choose from the recommended material list: HC420 / 7801.4, 1.5, 1.6, 1.8 (mm).

[0074] Based on the above input, we can get k = f(1.6, 1.4, 123) = 2.3697 before optimization.

[0075] Determine restrictions based on competing products:

[0076]

[0077] Variable settings H = 120, 123, 126, t 1 / t 2 =1.4, 1.5, 1.6, 1.8;

[0078] Substitute k = f(t 1 ,t 2 ,H) get Figure 5 Table, get k max =f(1.5,1.4,126)=2.4258;

[0079] Get the optimal solution t 1 =1.5mm t 2=1.4mm H=126mm.

[0080] It is easy for those skilled in the art to understand that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, combinations, replacements, improvements, etc. made within the spirit and principles of the present invention are included in the protection scope of the present invention.

Claims

1. A longitudinal beam section optimization method based on section coefficient, comprising designing a preliminary longitudinal beam section, the preliminary longitudinal beam section being composed of a combination of multiple closed sections, Features: Determine the centroid coordinates of the initial longitudinal beam section based on the area moment of each closed section, and establish a new coordinate system based on the centroid; Determine the bending section coefficient of the preliminary longitudinal beam section based on the new coordinate system; determine the section lightweight coefficient k of the preliminary longitudinal beam section based on the bending section coefficient, and the function of the section lightweight coefficient k for the section shape is k=f(t 1 ,t 2 ,H,W), where t1 is the inner sheet thickness, t2 is the outer sheet thickness, H is the section height, and W is the section width; determine the section coefficient restriction conditions based on the competing vehicle section coefficient and product definition; select the inner sheet thickness t 1 , outer sheet thickness t 2 , section height H, section width W are substituted into the objective function k = f(t 1 ,t 2 ,H,W), when the lightweight factor k=f(t 1 ,t 2 ,H,W) is maximum and the section coefficient restriction condition is met at the same time, the optimal inner sheet thickness t is obtained. 1 , outer sheet thickness t 2 , section height H, section width W; based on the optimal inner sheet thickness t 1 , outer sheet thickness t 2 , section height H, section width W optimize the longitudinal beam section; Based on the new coordinate system, the maximum absolute value of the X-axis coordinates of all points on the cross section is x max =max{|xx c |}; Based on the new coordinate system, the maximum absolute value of the Y coordinates of all points on the cross section is y max =max{|yy c |}; The methods for obtaining the bending section coefficient include: I x =∫ A y 2 dA I y =∫ A x 2 dA I x is the moment of inertia about the X axis, I y is the moment of inertia about the Y axis, dA is the micro area; σ maxX is the maximum normal bending stress about the X axis, σ maxY is the maximum bending normal stress about the Y axis; M x M is the bending moment of the cross section about the X axis, y W is the bending moment of the cross section about the Y axis; x is the bending section coefficient about the X axis, W y is the bending section coefficient with respect to the Y axis. The larger the bending section coefficient is, the stronger the ability of the section to resist bending deformation is.

2. The longitudinal beam cross-section optimization method based on section coefficient according to claim 1, Features: The higher the cross-sectional lightweight coefficient k, the better the bending resistance of this shape under the same weight conditions. The cross-sectional lightweight coefficient k is not related to the actual size, but only to the cross-sectional shape ratio.

3. The longitudinal beam section optimization method based on section coefficient according to claim 1, Features: Among them, a and b are pre-calibrated weight coefficients, reflecting the importance of the cross section for the bending resistance of the X-axis and Y-axis.

4. The longitudinal beam section optimization method based on section coefficient according to claim 1, Features: Section coefficient constraints include the expected value of the current model's section coefficient Standard deviation x ,σ y I x =∫ A y 2 dA I y =∫ A x 2 dA I x is the moment of inertia about the X axis, I y is the moment of inertia about the Y axis, dA is the micro area; W x is the bending section coefficient about the X axis, W y is the bending section coefficient about the Y axis Where N is the number of competing products, and the constraints are 5. The longitudinal beam cross-section optimization method based on section coefficient according to claim 1, Features: Determine the inner sheet thickness t based on layout constraints 1 , outer sheet thickness t 2 The value ranges of the four parameters of section height H and section width W are used to form multiple sets of preset solutions based on the permutations and combinations within the value ranges. Each set of preset solutions is substituted into k = f(t 1 ,t 2 ,H,W) obtain the lightweight coefficient k=f(t 1 ,t 2 ,H,W).

6. The longitudinal beam section optimization method based on section coefficient according to claim 5, Features: First, determine whether each set of preset solutions meets the constraints. Under the premise of satisfying the constraints, select the maximum lightweight coefficient k = f (t 1 ,t 2 ,H,W) is the optimal solution.

7. A longitudinal beam, Features: The inner sheet thickness of the cross section is t 1 , outer sheet thickness t 2 , section height H, and section width W are determined according to the longitudinal beam section optimization method based on section coefficient as described in any one of claims 1-6.

Images