CN117113539A - Vehicle body aluminum profile extrusion section design method based on topology optimization method - Google Patents
Vehicle body aluminum profile extrusion section design method based on topology optimization method Download PDFInfo
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Abstract
The application provides a design method of an extrusion section of an aluminum body of a new energy automobile facing complex working conditions, which comprises the following steps: step 1, establishing a new energy automobile body finite element analysis model; step 2, extracting and analyzing the boundary load of the connecting section of the member to be designed according to the unit node force result of the multi-working-condition finite element analysis; step 3, constructing a three-dimensional design domain finite element model for the structures including the threshold beams and the roof side beams; step 4, establishing a topology optimization model with weighted soft values of multiple working conditions as objective functions, and solving and calculating; step 5, performing geometric reconstruction of the cross sections of the threshold beam and the roof side rail to obtain a scheme of a cross section configuration; step 6, establishing a whole vehicle finite element model based on the reconstructed extrusion model, and developing a size optimization design; and 7, determining a scheme of the section thickness according to the manufacturing process requirement based on the result of the dimension analysis. The scheme provides a quick and efficient method for the lightweight section design of the aluminum profile.
Description
Technical Field
The application relates to the field related to a new energy automobile lightweight design method, in particular to a vehicle body aluminum profile extrusion section design method based on a topology optimization method, and especially relates to a new energy automobile aluminum alloy vehicle body extrusion section lightweight design facing complex working conditions.
Background
In order to improve the dynamic performance and cruising ability of an automobile, a lightweight technology is always an important research content. The aluminum alloy is a common metal material, has high specific strength and good toughness and plasticity, so that the aluminum alloy is widely applied to the field of automobiles. For the aluminum alloy structural part of the automobile body, reasonable section design has important significance. Through reasonable cross section design, the characteristic that the specific strength of the aluminum alloy material is high can be fully exerted, and a higher light weight level is realized. The rigidity and the deformation resistance of the vehicle body structure can be improved by improving the section moment of inertia through the section design, and the anti-collision performance of the vehicle is enhanced. The design of the cross section also optimizes the use of materials and reduces scrap and processing costs. Certain developments and improvements in aluminum alloy extrusion section design have been made in China, but some problems and disadvantages still exist, such as the dislocation between theoretical research and engineering application practice, the difficulty in using design software and the like. Therefore, there is a need for further enhancing research and development efforts to improve the level and quality of aluminum alloy extrusion cross-section design.
In the structure-light approach, topology optimization is a mathematical approach to find the optimal placement of materials within a given design space, which preserves the necessary material layout within the design space to meet given goals and constraints. Therefore, the topology optimization can reflect the load transmission path according to the arrangement of the materials, and a certain degree of weight saving can be achieved. The size optimization uses the size parameters of the parts as design variables, such as the thickness, the cross-sectional area and the like of the plate, and the combination of the optimal design parameters is found.
Disclosure of Invention
The application aims to combine a multi-target topological optimization theory and a size optimization method with specific engineering application, and provides a new energy automobile aluminum alloy body extrusion section design method facing complex working conditions, so that the high-efficiency load transmission path and the structure optimal design parameters of the section are obtained, flow guidance is provided for extrusion section design, and the weight reduction level of the automobile body is improved.
In order to achieve the above purpose, the specific technical scheme of the application is as follows:
step 1, establishing a finite element analysis model of a new energy automobile body, applying the loads of the whole automobile working conditions such as bending, torsion, collision and the like, and carrying out multi-working-condition finite element analysis;
step 2, extracting and analyzing the boundary load of the connecting section of the member to be designed according to the unit node force result of the multi-working-condition finite element analysis;
step 3, constructing a three-dimensional design domain finite element model for a typical extrusion part of a vehicle body, a sill beam, a roof side beam and other structures, applying the extracted boundary load as an equivalent load, and setting boundary conditions and manufacturability constraints;
step 4, establishing a topology optimization model with weighted soft values of multiple working conditions as objective functions, and solving and calculating;
step 5, based on the solving result, combining the design requirement and the manufacturing process requirement, carrying out geometric reconstruction of the cross section of the threshold beam and the roof side rail, and obtaining a conceptual scheme of the cross section configuration;
step 6, establishing a whole vehicle finite element model based on the reconstructed extrusion model, comprehensively considering working conditions such as bending, torsion, side collision, jacking and the like, taking performance as a target and quality as constraint, and developing a size optimization design;
and 7, based on the result of the size analysis, carrying out scheme determination of the section thickness according to the manufacturing process requirement, and carrying out performance verification and evaluation.
The application has the following benefits:
(1) The vehicle body extrusion section reconstruction lightweight design method based on topological optimization provided by the application has the advantage that the flow thought of the method can guide the lightweight design process in the whole vehicle development.
(2) The application provides a method for extracting a free body load from a global model and transmitting the free body load to a target design domain as a boundary condition for carrying out topology optimization analysis, solves the difficulty that the solution is difficult or the calculation efficiency is low in the topology optimization problem of a large-scale model and multiple design domains, and provides a quick and efficient method for the lightweight section design of the aluminum profile.
Drawings
Fig. 1 is a vehicle body structure according to the present application;
FIG. 2 is a graph of the conditions imposed on the design target in the present application;
FIG. 3 is a schematic view of the location of the connection surface of the design object of the present application;
FIG. 4 is a schematic drawing of the force extraction of the cross section of the threshold beam connecting surface;
FIG. 5 is a schematic representation of a design domain in the present application;
FIG. 6 illustrates the applied operating conditions of the threshold beam design domain;
FIG. 7 is a schematic illustration of the applied conditions of the roof side rail design domain;
FIG. 8 is a threshold beam optimization process;
FIG. 9 is a roof rail optimization process;
FIG. 10 is an optimized front cross section of a rocker beam and roof side rail;
FIG. 11 is an optimized cross section of a rocker beam and roof side rail;
Detailed Description
In order to make the technical scheme of the present application better understood by those skilled in the art, the present application will be further described in detail with reference to the accompanying drawings and examples.
The example provides a vehicle body aluminum profile extrusion section design method based on a topology optimization method, which specifically comprises the following steps:
step 1, establishing a new energy automobile body finite element analysis model, applying the whole automobile working condition loads including bending, torsion and collision, and carrying out multi-working condition finite element analysis;
FIG. 1 is a schematic view of the positions of a sill beam and a roof side rail on a vehicle body in an original scheme of the present application, wherein a bending condition and a torsion condition are applied to the vehicle body, respectively. As shown in fig. 2, the specific definition is as follows:
(1) Vehicle body bending conditions: the load is applied to a partial area of the upper surface of the threshold beam at the front end of the B-pillar, the load is 1500N, and the direction is the negative direction of the Z axis. The 23 degrees of freedom (Y, Z degrees of freedom of movement) of the front-wheel absorber mounting points are constrained, and the 123 degrees of freedom (X, Y, Z degrees of freedom of movement) of the rear-wheel absorber mounting points are constrained.
(2) Vehicle body torsion working condition: the load is applied to the left shock absorber mounting point and the right shock absorber mounting point of the front wheel, the load is 1674.8N, and the load direction is the positive Z-axis direction while the load direction is the negative Z-axis direction. The 3 degrees of freedom (Z-axis movement degree) of the center position of the front end face of the front anti-collision beam are restrained, and the 123 degrees of freedom (X, Y, Z-axis movement degree) of the mounting points of the rear wheel shock absorbers are restrained.
Step 2, extracting and analyzing the boundary load of the connecting section of the member to be designed according to the unit node force result of the multi-working-condition finite element analysis;
for the bending working condition of the vehicle body, the threshold beam and the roof side beam can be equivalent to simply supported beams, and the applied boundary conditions are relatively simple. In this example, therefore, the sectional forces of the unit related to the connecting section of the rocker beam and the roof side rail in the vehicle body torsion condition are emphasized, and fig. 3 is a schematic view of the positions of the respective main connecting surfaces. Fig. 4 is a schematic process of the cross-sectional force of the pillar region of the threshold Liang Diqu a, and the joint forces of the peripheral units of the connecting section are combined to obtain the cross-sectional force of the connecting surface, and the other connecting surfaces extract the cross-sectional force in the same manner. The cross-sectional forces at the interface are shown in the following table:
step 3, constructing a three-dimensional design domain finite element model on an extrusion part of the vehicle body, namely a structure comprising a threshold beam and a roof side beam, applying the extracted boundary load as an equivalent load, and setting boundary conditions and manufacturability constraints;
in order to reduce the difficulty of model processing and improve the calculation efficiency, the threshold beam and the roof side beam of the vehicle body are extracted independently in the embodiment, and the threshold beam and the roof side beam are symmetrical structures, so that a single side is adopted. The threshold beam and the roof side beam in the whole vehicle model are in a shell unit form, and a three-dimensional design domain of the threshold beam and the roof side beam is required to be constructed for the subsequent multi-objective topology optimization process. Removing ribs in the threshold beam and the roof side beam, retaining the outline characteristics, supplementing finite element grids of the sections at two ends, and generating a three-dimensional hexahedral grid according to the closed grid surface. The constructed design domain is shown in fig. 5, wherein the side length of a single grid is about 3mm, the threshold beams are 502427 hexahedral units, and the roof beams are 168347 units.
And then working conditions are respectively applied to the three-dimensional design areas of the threshold beam and the roof side rail. And applying bending equivalent working conditions, torsion equivalent working conditions and column collision equivalent working conditions to the threshold beam. And applying bending equivalent working conditions, torsion equivalent working conditions and top compression equivalent working conditions to the roof side rail.
As shown in fig. 6-7, the specific loads for each operating condition of the rocker and roof side rail are defined as follows:
(1) Threshold beam bending equivalent working condition: the load is applied to a partial area of the upper surface of the threshold beam at the front end of the B-pillar, the load is 1500N, and the direction is the negative direction of the Z axis. Six degrees of freedom of each node on the connecting surface of the restraining threshold beam and the front cabin, the connecting surface of the rear cabin, the connecting surface of the A column and the connecting surface of the C column;
(2) Threshold beam torsion equivalent working condition: applying loads in the X positive direction 85N and the Y positive direction 65N on the front cabin connecting surface; applying a load in the negative X direction 96N and the negative z direction 76N to the a-pillar connecting section; applying loads in the X negative direction 342N and the Z positive direction 210N at the connecting surface of the load transmission of the threshold beam and the B column; applying a load of 60.7N in the X positive direction and 106N in the Z positive direction on the C column connecting region; constraining six degrees of freedom of each node on the connection surface of the rear cabin;
(3) Threshold Liang Zhupeng equivalent condition: a load of 5000N in the Y positive direction is applied to a region, which is 200mm away from the outer side of the threshold beam and is close to the B column; six degrees of freedom of each node on the front and rear cabin connecting surfaces are respectively restrained;
(4) Bending equivalent working condition of roof beam: applying a load of 750N in the Z negative direction in the B column connecting area of the roof side rail; respectively restraining 2 and 3 degrees of freedom (Y, Z directions) of each node on the connecting surface of the A column and the C column and three degrees of freedom of movement of each node on the connecting surface of the D column;
(5) Torsion equivalent working condition of roof beam: applying loads in X negative directions 127N, Y negative directions 76N and Z negative directions 70N to the connecting area of the A column of the roof side beam; applying a load in the X direction 187N at the B-pillar connecting section; applying a load in the X positive direction 69N and a load in the Y negative direction 35N to the D connection region; constraining six degrees of freedom of each node on the C column connecting surface;
(6) The equivalent working condition of the top compression of the roof side rail: the pressure is applied to the top of the car body by a plane with an included angle of 5 degrees with the X axis and an included angle of-25 degrees with the Y axis, and the main stress area is an area with the front end of the roof side rail being about 250 mm. The top compression equivalent condition is to decompose the force into three orthogonal forces, assuming that the applied pressure is 5000N, the compression area is equivalently loaded by X direction 390N, Y direction 184N and Z negative direction 4980N; and respectively restraining three degrees of freedom of movement of each node on the connecting surfaces of the A column, the B column, the C column and the D column of the roof side rail.
Step 4, establishing a topology optimization model with weighted soft values of multiple working conditions as objective functions, and solving and calculating;
after loading the working conditions, topological optimization manufacturability constraints are respectively applied to the threshold beam and the roof side beam model, the volume fraction is 0.25, and extrusion constraints are applied along the forming direction. Then, respectively carrying out multi-objective topological optimization design on the model, wherein the multi-objective topological optimization method with flexibility weighting comprises the following steps:
find x＝{x 1 ,x 2 ,...,x i } T ,i＝1,2,...,n
s.t.KU e ＝F e
x min ≤x i ≤x max
wherein x is i Is the density of each unit; n is the total number of units; k is the total number of structural load working conditions; w (w) e The weight factor of the e working condition; c e (x) The compliance for the e-th condition; f (F) e And U e The load and displacement matrix corresponding to the e-th working condition are respectively adopted; k is the overall stiffness matrix; v i The volume of each unit; v (V) 0 To design a domain volume; f is the constrained volume fraction. In the design case, the total number of working conditions of the threshold beam and the roof side beam is 3. The volume fractions f were all 0.25. In the working conditions of the threshold beam, the weight of the torsion equivalent working condition and the bending equivalent working condition is 1, and the weight of the column collision equivalent working condition is 5. The weight values of the three working conditions of the roof side rail are all 1.
Step 5, carrying out geometric reconstruction of the cross section of the threshold beam and the roof side rail based on the solving result to obtain a scheme of a cross section configuration;
according to the design results of the threshold beam and the roof side beam after topology optimization solution, the section is subjected to conceptual design, which specifically comprises the following steps:
(1) The important characteristics in the force transmission path are reserved and converted into a shell unit;
(2) Ensuring that the newly built structure does not interfere with the part mounting holes and the connecting points in the original configuration;
(3) The unformed structure in the topology optimization result should also be preserved considering its irreplaceable role in the original model.
As shown in fig. 8, there is a comparison of the optimized front-to-rear version of the threshold beam. For a threshold beam, the topology optimization results show clear outline features and two middle transverse ribs. In the reconstructed section, considering the installation characteristics of the threshold beam and the battery pack, the middle vertical rib is required to be reserved, the upper transverse rib is reserved according to the topological path, the upper transverse rib is divided into two parts by the vertical rib, the transverse rib close to the inner side is kept parallel to the horizontal plane, and the transverse rib close to the outer side is required to be offset by an included angle of 15 degrees by the topological path; the lower transverse rib in the topological result interferes with the mounting point in the actual position, so that a certain distance is upwards offset in the reconstruction scheme; meanwhile, in order to maintain the stability of the structure, a transverse rib is additionally arranged below the mounting point, and the space divided by the vertical rib is close to the inner side.
Fig. 9 is a comparison of the top beam before and after optimization. For roof rails, the topology optimization results show clear profile features and material stacking near the outboard load bearing area. In the reconstructed section, consistent with the topological path, the through diagonal ribs are reserved. Meanwhile, in order to ensure structural rigidity, two short ribs are additionally arranged, and mounting points are avoided at the positions of the short ribs so as to prevent interference. According to the characteristics of the topological path, the inclined rib which is communicated with the inner side in the original scheme is changed into an inclined short rib.
Step 6, establishing a whole vehicle finite element model based on the reconstructed extrusion model, comprehensively considering bending, torsion, side collision and top pressure working conditions, taking performance as a target and quality as a constraint, and developing a size optimization design;
for the design of the threshold beam and the top side beam, the Shi Jiazhu collision working condition and the top pressurization working condition are used for simulating the situation when the vehicle body is subjected to side collision and overturns. In both accidents, irreversible shaping deformation of the threshold beam and the roof side rail occurs, which is a structural strength requirement. Therefore, stiffness cannot be a design constraint, it should be set as an objective function (characterizing stiffness in compliance), and mass as a constraint, at a target weight, through optimization of cross-sectional dimensions to achieve maximum stiffness under that condition.
The cross-sectional configuration of the original scheme is shown in fig. 10, and mass is used as constraint according to the optimization requirement. And applying the whole vehicle working conditions such as bending, torsion and the like and the local working conditions such as side column collision, top pressurization and the like, and carrying out size optimization analysis by taking flexibility as an objective function.
And 7, based on the result of the size analysis, determining a scheme of the section thickness according to the manufacturing process requirement, and performing performance verification and evaluation.
To match the manufacturing process, the sizing optimization result adjustment of step 6 is performed as follows:
(1) The excessive dimensional change of the adjacent structure is avoided as much as possible, so that the internal stress generated by the extrusion molding process is reduced;
(2) Considering the process characteristics of extrusion molding, in order not to generate manufacturing defects, the excessively thin dimension is avoided as much as possible;
(3) Rounded corners (not shown in the schematic configuration) are added at sharp corners and corners.
The optimized size configuration is shown in fig. 11, and the weight of the optimized threshold beam and the top beam are reduced by 22.6% and 4.3%, respectively.
For an optimized scheme, relevant performance verification should also be performed, and verification can only be adopted. The embodiment focuses on introducing the extrusion section lightweight reconstruction method, and specific performance test links are not repeated. The optimized configuration is verified to meet the design requirements and has been put into use.
The application takes typical extrusion structures such as a threshold beam, a roof beam and the like of a certain vehicle type as design objects, and completes the extrusion section design under complex working conditions based on a topology optimization and size optimization method. Firstly, establishing a finite element analysis model, applying the working condition loads of the whole vehicle such as bending, torsion and the like, and extracting and analyzing the boundary load of a member to be designed; then, establishing a finite element model of the three-dimensional design domain of the extrusion part, respectively applying the extracted equivalent boundary load and the local working condition of the analysis object, and carrying out finite element analysis; and finally, carrying out cross section reconstruction according to the analysis result, carrying out size optimization, and carrying out stiffness strength simulation verification on the optimization result. Compared with the initial design of the vehicle type, the weight of the threshold beam and the roof side rail is reduced by 22.6 percent and 4.3 percent respectively.
Claims (5)
1. A design method of an extrusion section of an aluminum body of a new energy automobile facing complex working conditions is characterized by comprising the following steps:
step 1, establishing a new energy automobile body finite element analysis model, applying the whole automobile working condition loads including bending, torsion and collision, and carrying out multi-working condition finite element analysis;
step 2, extracting and analyzing the boundary load of the connecting section of the member to be designed according to the unit node force result of the multi-working-condition finite element analysis;
step 3, constructing a three-dimensional design domain finite element model on an extrusion part of the vehicle body, namely a structure comprising a threshold beam and a roof side beam, applying the extracted boundary load as an equivalent load, and setting boundary conditions and manufacturability constraints;
step 4, establishing a topology optimization model with weighted soft values of multiple working conditions as objective functions, and solving and calculating;
step 5, carrying out geometric reconstruction of the cross section of the threshold beam and the roof side rail based on the solving result to obtain a scheme of a cross section configuration;
step 6, establishing a whole vehicle finite element model based on the reconstructed extrusion model, comprehensively considering bending, torsion, side collision and top pressure working conditions, taking performance as a target and quality as a constraint, and developing a size optimization design;
and 7, based on the result of the size analysis, determining a scheme of the section thickness according to the manufacturing process requirement, and performing performance verification and evaluation.
2. The method for designing the section of the extrusion of the aluminum body of the new energy automobile facing the complex working condition according to the claim 1 is characterized in that in the step 1,
the bending working condition of the vehicle body is that a load is applied to a partial area of the upper surface of a threshold beam at the front end of a B column, the load is 1500N, and the direction is the negative direction of a Z axis; a Y, Z axis movement degree of freedom of the front wheel damper mounting point is restrained, and a X, Y, Z axis movement degree of freedom of the rear wheel damper mounting point is restrained;
the torsion working condition of the vehicle body is that loads are applied to mounting points of left and right shock absorbers of the front wheels, wherein one side of the load is in a positive Z-axis direction, and the other side of the load is in a negative Z-axis direction; z-axis movement freedom of the center position of the front end face of the beam front anti-collision beam, and X, Y, Z-axis movement freedom of the mounting point of the beam rear wheel shock absorber.
3. The method for designing the section of the extrusion of the aluminum body of the new energy automobile facing the complex working condition according to claim 1, wherein in the step 3, ribs inside the threshold beam and the roof side rail are removed, the outline characteristics are reserved, the finite element grids of the sections at the two ends are supplemented, and a three-dimensional hexahedral grid is generated according to the closed grid surface.
4. The method for designing the section of the extrusion of the aluminum body of the new energy automobile facing the complex working condition according to the claim 1, wherein in the step 3,
the equivalent bending working condition of the threshold beam is that the direction of a partial area of the upper surface of the threshold beam, which is applied by a load at the front end of the B column, is a Z-axis negative direction, and six degrees of freedom of all nodes on the threshold beam, the front cabin connecting surface, the rear cabin connecting surface, the A column connecting surface and the C column connecting surface are restrained;
the equivalent torsion working condition of the threshold beam is that a load in the X positive direction and a load in the Y positive direction are applied to the front cabin connecting surface; applying a load in the X negative direction and the Z negative direction on the A column connecting area; applying a load in the X negative direction and a load in the Z positive direction at the connecting surface of the load transmission of the threshold beam and the B column; applying a load in the positive X direction and the positive Z direction to the C column connecting area; constraining six degrees of freedom of each node on the connection surface of the rear cabin;
the equivalent working condition of the threshold Liang Zhupeng is that a load of 5000N in the Y positive direction is applied to the outer side of the threshold beam close to the B column; six degrees of freedom of each node on the front and rear cabin connecting surfaces are respectively restrained;
the equivalent bending working condition of the roof side rail is that a load in the Z negative direction is applied to the connecting area of the B column of the roof side rail; respectively restraining Y, Z-direction freedom degrees of all the nodes on the connecting surfaces of the A column and the C column and three-direction movement freedom degrees of all the nodes on the connecting surface of the D column;
the torsion equivalent working condition of the roof side beam is that loads in the X negative direction, the Y negative direction and the Z negative direction are applied to the A column connecting area of the roof side beam; applying a load in the positive X direction to the B column connecting region; applying a load in the X positive direction and the Y negative direction to the D connection area; constraining six degrees of freedom of each node on the C column connecting surface;
the equivalent pressing condition of the top of the roof beam is that the pressure is applied to the top of the vehicle body by a plane with an included angle of 5 degrees with the X axis and an included angle of-25 degrees with the Y axis.
5. The method for designing the section of the extrusion of the aluminum body of the new energy automobile facing the complex working condition according to claim 1, wherein in the step 4, after the working condition loading is completed, topological optimization manufacturability constraints are respectively applied to the threshold beam and the roof side beam model, extrusion constraints are applied along the forming direction, and then the model is respectively subjected to multi-objective topological optimization design, and the multi-objective topological optimization method with flexibility weighting is as follows:
find x＝{x 1 ,x 2 ,...,x i } T ,i＝1,2,...,n
s.t.KU e ＝F e
x min ≤x i ≤x max
wherein x is i Is the density of each unit; n is the total number of units; k is the total number of structural load working conditions; w (w) e The weight factor of the e working condition; c e (x) The compliance for the e-th condition; f (F) e And U e The load and displacement matrix corresponding to the e-th working condition are respectively adopted; k is the overall stiffness matrix; v i The volume of each unit; v (V) 0 To design a domain volume; f is the constrained volume fraction. In the design case, the total number of working conditions of the threshold beam and the roof side beam is 3. The volume fractions f were all 0.25. In the working conditions of the threshold beam, the weight of the torsion equivalent working condition and the bending equivalent working condition is 1, the weight of the column collision equivalent working condition is 5, and the weight of the three working conditions of the roof side beam is 1.
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| CN115221602A (en) * | 2021-08-03 | 2022-10-21 | 广州汽车集团股份有限公司 | Vehicle body design method and device based on multi-working-condition topological optimization and storage medium |
| CN116522499A (en) * | 2023-05-04 | 2023-08-01 | 北京理工大学 | Vehicle body front end structure design method based on thin-wall lattice filling structure |
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| CN115221602A (en) * | 2021-08-03 | 2022-10-21 | 广州汽车集团股份有限公司 | Vehicle body design method and device based on multi-working-condition topological optimization and storage medium |
| CN116522499A (en) * | 2023-05-04 | 2023-08-01 | 北京理工大学 | Vehicle body front end structure design method based on thin-wall lattice filling structure |
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| 武敬伟;胡朝辉;丁晓明;张光亚;: "电动车车身正向概念轻量化设计", 机械设计与制造, no. 03, 8 March 2017 (2017-03-08), pages 246 - 249 * |
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