A reverse design method for variable thickness thin-walled energy-absorbing structures

Abstract

This invention belongs to the technical field of automotive energy-absorbing structures, specifically relating to a reverse design method for variable-thickness thin-walled energy-absorbing structures. This method allows for the design of thickness variations based on the energy absorption characteristics of the thin-walled energy-absorbing structure itself. For a given impact load condition, the thickness of the automotive thin-walled energy-absorbing structure is used as the design variable, and the total energy absorption value of the thin-walled energy-absorbing structure is used as the design objective. Under the constraint of limiting the total mass of the thin-walled energy-absorbing structure, the aim is to improve crashworthiness. This method starts with reverse design, with the core idea of ​​increasing thickness where needed (where energy absorption is high) and decreasing thickness where it is not needed (where energy absorption is low), aiming for a rational material distribution within the structure. Through this method, engineers can quickly design variable-thickness energy-absorbing structures. This method simplifies the energy-absorbing structure design process, controls costs, and has good operability and convenience.

Description

Technical Field

[0001] This invention belongs to the field of automotive energy-absorbing structure technology, specifically relating to a reverse design method for a variable-thickness thin-walled energy-absorbing structure. Background Technology

[0002] The basic structure of a car body consists of thin-walled energy-absorbing components. When a collision occurs, the plastic deformation of these thin-walled energy-absorbing structures dissipates most of the collision energy, while simultaneously transferring the collision load to other parts of the vehicle body to minimize injury to the occupants. The energy absorption characteristics of these thin-walled structures directly determine the acceleration and impact response of the vehicle during a collision, which in turn directly affects occupant safety. With the increasing severity of automotive lightweighting issues, how to rationally design the car body structure and effectively arrange high-performance, energy-absorbing thin-walled structures to meet automotive crashworthiness requirements has become a hot research topic for many scientists.

[0003] Traditional car body structures are primarily composed of thin-walled metal sheets of uniform thickness. However, a uniformly thick energy-absorbing structure may not necessarily utilize all the material to absorb energy through plastic deformation most efficiently. During actual deformation, the load-bearing capacity of a thin-walled energy-absorbing structure is non-uniform across its various parts. If a uniform design approach is still adopted, the load-bearing capacity and material utilization rate of each part of the structure are not fully exploited, nor is the impact of material distribution on the crashworthiness of the thin-walled structure considered. Therefore, there is an urgent need to develop novel energy-absorbing structures with different thickness combinations to maximize crashworthiness and material utilization. Variable-thickness thin-walled energy-absorbing structures for car bodies are of significant engineering importance for balancing lightweight design and crashworthiness, and have broad application value in the field of car body energy absorption.

[0004] However, current researchers typically predetermine the thickness segmentation or variation trend of the structure based on experience when designing variable thickness structures before performing the variable thickness optimization design. But this is only a variable thickness design under specific circumstances and may not be optimal. To efficiently and conveniently design variable thickness thin-walled energy-absorbing structures, this patent provides a novel reverse design method for variable thickness thin-walled energy-absorbing structures. This method designs the thickness of the units based on the unit energy information of the energy-absorbing structure, allocating more thickness to units with higher energy absorption and less thickness to units with lower energy absorption, thereby improving the energy absorption characteristics of the thin-walled energy-absorbing structure. Summary of the Invention

[0005] The purpose of this invention is to provide a reverse design method for a variable thickness thin-walled energy-absorbing structure, which can efficiently and quickly design a variable thickness energy-absorbing structure based on the unit energy information of the energy-absorbing structure.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A reverse design method for a variable-thickness thin-walled energy-absorbing structure, comprising the following steps:

[0008] Step 1: Determine the design range (t) for thickness variation based on the design requirements of the thin-walled energy-absorbing structure to be designed. min ,t max The thin-walled energy-absorbing structure to be designed is meshed, and boundary constraints and load conditions are applied to obtain the finite element analysis model.

[0009] Step 2: Based on the thickness design range and mesh division, determine the number of design variables n(x1, x2, x3...x...). n ), and determine the unit number and number contained in each design variable;

[0010] Step 3: Perform finite element analysis, extract the energy information of the design variables from the result file, and round the energy information of the design variables using Bezier curves to obtain the rounded energy information E of each design variable. i (i = 1, 2, 3, ..., n).

[0011] Step 4: Perform reverse design based on the rounded design variable energy information and thickness variation range. Adjust the thickness of the design variables according to the rounded design variable energy information. Assign a large thickness to design variables with large energy information and a small thickness to design variables with small energy information. The energy information is a series of values ​​greater than 0, with varying values. Assign the thickness according to the value of the energy information. A large thickness is assigned to areas with large energy information values, and a small thickness is assigned to areas with small energy information values.

[0012] Step 5: Perform finite element analysis on the reverse-designed variable-thickness thin-walled energy-absorbing structure, extract the total energy absorption and total mass of the entire structure, and determine whether the structure meets the design requirements based on the total energy absorption and total mass of the entire structure. If it does not meet the requirements, repeat steps 1-5 above until the structure meets the design requirements.

[0013] Further, step 2 specifically refers to determining the number of design variables based on the thickness design range and grid division, and determining the unit number and quantity contained in each design variable. The variable thickness design of the thin-walled energy-absorbing structure has two cases: variable thickness along the axial direction and variable thickness along the circumferential direction of the cross section. When the design requires variable thickness along the axial direction, each row of units or several rows of units is considered as one design variable; when the design requires variable thickness along the circumferential direction of the cross section, each column of units or several columns of units is considered as one design variable. The number of design variables, as well as the unit number and quantity contained in each design variable, can be determined based on the thickness design range and grid division.

[0014] Further, step 3 specifically refers to extracting the energy absorption of one or more rows or columns of elements corresponding to each design variable from the finite element analysis result file. Depending on the design requirements or mesh generation, the size and number of elements contained in each design variable may not be exactly the same. Therefore, the extracted energy absorption of the elements contained in the design variable must be divided by the total mass of the elements contained in the design variable to obtain preliminary energy information of the design variable. Then, Bezier curves are used to round off the preliminary energy information of the design variable to obtain the rounded energy information E for each design variable. i (i = 1, 2, 3, ..., n).

[0015] Furthermore, step 4 specifically refers to determining the variable thickness range (t) according to the design requirements. min ,t max The energy information E of each design variable after rounding. i Determine the thickness of each design variable, with the design variable E having the highest energy information. max Corresponding to the maximum thickness t max The design variable E with the least energy information min Corresponding to the minimum thickness t min The intermediate design variables are obtained based on the corresponding relationship, which is as follows: in Then, the finite element model is readjusted based on the thickness changes of the design variables.

[0016] Furthermore, step 5 specifically refers to extracting the total energy absorption and total mass of the energy-absorbing structure after the corresponding variable thickness design, and then comparing the total energy absorption and total mass of the structure before and after the design to see if the total energy absorption and total mass meet the design requirements.

[0017] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0018] This invention provides a reverse design method for variable-thickness thin-walled energy-absorbing structures. By extracting energy information from the design variables, different thicknesses are assigned to the design variables. The thickness is increased in areas with high energy absorption and decreased in areas with low energy absorption, thereby obtaining an optimal variable-thickness energy-absorbing structure. This method achieves variable-thickness design according to specific design requirements, thus enabling the design of optimal variable-thickness energy-absorbing structures under different working conditions, making it suitable for various operating conditions. Attached Figure Description

[0019] Figure 1 This is a flowchart of the present invention;

[0020] Figure 2(a) is a three-dimensional schematic diagram of an embodiment of the present invention;

[0021] Figure 2(b) is a top view and a side view of an embodiment of the present invention;

[0022] Figure 3(a) shows the axial variable thickness design of the present invention, including the energy information of the design variables and the energy information after Bezier rounding.

[0023] Figure 3(b) shows the circumferential variable thickness design of the present invention, including the energy information of the design variables and the energy information after Bezier rounding.

[0024] Figure 4(a) is a comparison of the total energy absorption and total mass of the energy-absorbing structure after the axial variable thickness design in the embodiment of the present invention and the energy-absorbing structure before the design.

[0025] Figure 4(b) is a comparison of the total energy absorption and total mass of the energy-absorbing structure after the circumferential variable thickness design in the embodiment of the present invention and the energy-absorbing structure before the design. Detailed Implementation

[0026] The method proposed in this invention will now be described using the design of the cap-shaped thin-walled energy-absorbing structure shown in Figures 2(a) and 2(b) as an example. In this embodiment, the total energy absorption of the cap-shaped thin-walled energy-absorbing structure is the design target, which should be as large as possible; the total mass is the constraint target, which requires that the total mass of the designed structure cannot be greater than the total mass before the design.

[0027] Step 1: For the cap-shaped thin-walled energy-absorbing structures shown in Figures 2(a) and 2(b), a variable thickness design is performed along both the axial and circumferential directions (constraining the thickness to remain constant in one direction while changing in the other). The thickness variation range for the axial variable thickness design is (1.0, 2.0), and the thickness variation range for the circumferential variable thickness design is (1.3, 2.0). Considering the symmetry of the forces acting on the cap-shaped thin-walled energy-absorbing structure, the number of design variables for the axial variable thickness design is selected symmetrically around the axial axis of symmetry, with 60 design variables for the upper cap structure and 60 design variables for the lower cap structure; the number of design variables for the circumferential variable thickness design is selected symmetrically around the circumferential axis of symmetry, with 22 design variables for the upper cap structure and 22 design variables for the lower cap structure.

[0028] Step 2: Mesh the structure according to the thickness variation range and the number of design variables. For axial variable thickness design, each row of elements is a design variable; for circumferential variable thickness design, each column of elements is a design variable. After meshing, apply boundary constraints and load conditions to obtain the finite element analysis model. The material used for the simulation of the cap-shaped thin-walled energy-absorbing structure is DP590 steel with an initial thickness of 1.5mm.

[0029] Step 3: Perform finite element analysis using LS-dyna software. After the analysis, extract the energy absorption of a row or column of elements corresponding to each design variable using LS-PrePost software. Divide the extracted energy absorption of the elements containing the design variable by the total mass of the elements containing the design variable to obtain preliminary energy information of the design variable. Then, use Bezier curves to round the preliminary energy information of the design variable to obtain the rounded energy information E of each design variable. i (i = 1, 2, 3...n). The initial energy information of the design variables for axial and circumferential variable thickness designs, and the energy information after rounding the Bezier curves, are as follows: Figures 3(a)-3(b) As shown.

[0030] Step 4: Determine the thickness of each design variable based on the rounded design variable energy information and the thickness variation range, with the design variable E having the largest energy information. max Corresponding to the maximum thickness t max The design variable E with the least energy information min Corresponding to the minimum thickness t min The intermediate design variables are obtained based on the corresponding relationship, which is as follows: in Then, the finite element model is readjusted based on the thickness changes of the design variables.

[0031] Step 5: Perform finite element analysis on the reverse-designed variable-thickness thin-walled energy-absorbing structure using LS-dyna software, and extract the total energy absorption and total mass of the structure using LS-PrePost software. Then compare the total energy absorption and total mass of the structure before and after the design. Figures 4(a)-4(b) As shown, it can be seen that regardless of whether it is an axially variable thickness design or a circumferentially variable thickness design, the designed structure significantly improves the total energy absorption without increasing the total mass of the structure.

[0032] The above description is merely a preferred embodiment of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention by those skilled in the art within the scope of the technology disclosed in the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.

Claims

1. A reverse design method for a variable thickness thin-walled energy-absorbing structure, characterized in that, Includes the following steps: Step 1: Determine the design range (t) for thickness variation based on the design requirements of the thin-walled energy-absorbing structure to be designed. min ,t max The thin-walled energy-absorbing structure to be designed is meshed, and boundary constraints and load conditions are applied to obtain the finite element analysis model. Step 2: Based on the design range of the thickness variation and the mesh division, determine the number of design variables n(x1, x2, x3...x...). n ), and determine the unit number and number contained in each design variable; Step 3: Perform finite element analysis, extract the energy information of the design variables from the result file, and round the energy information of the design variables using Bezier curves to obtain the rounded energy information E of each design variable. i , i = 1, 2, 3 ... n; Step 4: Perform reverse design based on the rounded design variable energy information and the design range of thickness variation, and based on the rounded design variable energy information E i Adjust the thickness of design variables, assigning a larger thickness to design variables with relatively large energy information and a smaller thickness to design variables with relatively small energy information; Step 4 specifically refers to determining the variable thickness range (t) according to design requirements. min ,t max The energy information E of each design variable after rounding. i Determine the thickness of each design variable, with the design variable E having the highest energy information. max Corresponding to the maximum thickness t max The design variable E with the least energy information min Corresponding to the minimum thickness t min The intermediate design variables are obtained based on the corresponding relationship, which is as follows: in Then, based on the thickness variations of the design variables, the finite element model is readjusted; Step 5: Perform finite element analysis on the reverse-designed variable-thickness thin-walled energy-absorbing structure, extract the total energy absorption and total mass of the entire structure, and determine whether the structure meets the design requirements based on the total energy absorption and total mass of the entire structure. If it does not meet the requirements, repeat steps 1-5 above until the structure meets the design requirements.

2. The reverse design method for a variable thickness thin-walled energy-absorbing structure according to claim 1, characterized in that: Step 2 specifically refers to determining the number of design variables based on the design range of the thickness variation and the grid division, and determining the unit number and quantity of each design variable. The variable thickness design of the thin-walled energy-absorbing structure has two cases: variable thickness along the axial direction and variable thickness along the circumferential direction of the cross section. When the design requires variable thickness along the axial direction, each row of units or several rows of units is considered as one design variable; when the design requires variable thickness along the circumferential direction of the cross section, each column of units or several columns of units is considered as one design variable. The number of design variables, as well as the unit number and quantity of each design variable, can be determined based on the design range of the thickness variation and the grid division.

3. The reverse design method for a variable thickness thin-walled energy-absorbing structure according to claim 1 or 2, characterized in that: Step 3 specifically refers to extracting the energy absorption of one or more rows or columns of elements corresponding to each design variable from the finite element analysis result file. Depending on the design requirements or mesh generation, the size and number of elements contained in each design variable may not be exactly the same. Therefore, the extracted energy absorption of the elements contained in the design variable must be divided by the total mass of the elements contained in the design variable to obtain preliminary energy information of the design variable. Then, a Bezier curve is used to round off the preliminary energy information of the design variable to obtain the rounded energy information E for each design variable. i , i = 1, 2, 3...n.

4. A reverse design method for a variable thickness thin-walled energy-absorbing structure according to any one of claims 1 to 3, characterized in that: Step 5 specifically refers to extracting the total energy absorption and total mass of the energy-absorbing structure after the corresponding variable thickness design, and then comparing the total energy absorption and total mass of the structure before and after the design to determine whether the total energy absorption and total mass meet the design requirements.

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