Variable thickness plate finite element thickness gradient parameterized modeling method

Abstract

A parametric modeling method for thickness gradient in finite element models of variable thickness plates is disclosed. This method is applied to two plate types: variable thickness plates with constant strength and variable thickness plates with varying strengths. For variable thickness plates with constant strength, parametric representations of the thickness information at each node are established. For variable thickness plates with varying strengths, parametric representations of the thickness information at each node and the hardening characteristics of each element are also established. This method allows for rapid modeling and thickness information updates of the finite element model of a variable thickness plate based on a given thickness gradient design. It efficiently defines the thickness gradient of the variable thickness plate part in the finite element simulation model, providing a foundation for further parametric optimization of the thickness gradient.

Description

Technical Field

[0001] This invention belongs to the field of variable thickness rolling, specifically relating to a finite element thickness gradient parameterization modeling method for variable thickness plates. Background Technology

[0002] Variable rolled thickness (VRB) is a lightweighting technology that has emerged in recent years. During the steel sheet rolling process, computer-controlled roll gaps are used to obtain pre-defined variable cross-sectional thickness plates along the rolling direction. VRB plate thickness combinations offer significant flexibility and can be customized to suit the load-bearing characteristics of automotive structures. To fully leverage the advantages of VRB technology, the thickness gradient of the parts needs to be optimized to achieve the best structural performance and lightweighting level. Unlike conventional constant-thickness parts, variable-thickness plate parts exhibit thickness gradients in the thickness transition regions (e.g., ...). Figure 2 As shown in the figure, the material strength is affected by the rolling process and may also be related to the thickness, which makes it difficult to model the finite element model and to achieve parametric design optimization of the thickness gradient scheme.

[0003] Invention application CN 201710979164.7 discloses "a finite element modeling method for variable thickness composite laminates", the steps of which are as follows: specify the number N of sub-laminates in the model. L and the total number of layers N P Extract the model's outer surface S O and inner surface S I According to the thickness region, the outer surface S O Perform a first-level partitioning and assign it two-dimensional laminate properties; expand the layup sequence so that each first-level partition corresponds to N. L Create two secondary partitions; create equivalent materials and properties for each secondary partition; calculate the sublaminate thickness T for each secondary partition. X_Y ; External surface S O Grid the surface; copy the outer surface S O N on N The original node is used, and the copied node is projected onto the inner surface S. I The projected node set is formed; a node array is linearly inserted between the original nodes and the projected nodes; solid elements are generated by partitioning each second level in order from one bottom surface to another, and the corresponding cross-sectional properties are assigned.

[0004] The invention application with application number CN202011599522.X discloses "a finite element modeling method for thick composite material plate joints". The method includes: obtaining a solid structural model of the thick composite material plate joint; dividing the solid structural model into multiple cut layers along the ply thickness direction according to the estimated stress concentration and structural importance of the structure, wherein fine division is performed on the parts with high stress concentration and high structural importance; coarse division is performed on the parts with low stress concentration and low structural importance; cutting the solid structural model in the direction within the layer, and the cut models all have regular shapes; selecting rigid connections to simulate the connection relationship of each ply within the thick composite material plate joint; dividing the secondary cut solid structural model into mesh elements and assigning material properties. Summary of the Invention

[0005] To address the above problems, this invention provides a finite element method for thickness gradient parameterization modeling of variable thickness plates, the specific technical solution of which is as follows:

[0006] A method for parametric modeling of thickness gradient in a finite element model of a plate with variable thickness, characterized in that:

[0007] The parametric modeling method is applied to two plate types: variable thickness plates with constant strength and variable thickness plates with varying strengths.

[0008] A parameterized characterization of the thickness information of each node is established for a variable thickness plate with constant strength.

[0009] For plates with varying strength, parameterized characterization of the thickness information of each node and parameterized characterization of the hardening characteristics of each element are established.

[0010] A method for parametric modeling of thickness gradient in a finite element model of a variable thickness plate according to the present invention is characterized in that:

[0011] The thickness information of each node is obtained based on the mapping relationship between each node and the set thickness gradient curve.

[0012] A method for parametric modeling of thickness gradient in a finite element model of a variable thickness plate according to the present invention is characterized in that:

[0013] The hardening characteristics of each element are characterized by the pre-strain information of each element obtained based on the thickness information of each node.

[0014] A method for parametric modeling of thickness gradient in a finite element model of a variable thickness plate according to the present invention is characterized in that:

[0015] The thickness gradient curve is established based on the CAD data information of the variable thickness plate.

[0016] A method for parametric modeling of thickness gradient in a finite element model of a variable thickness plate according to the present invention is characterized in that:

[0017] Each node is mapped to a set reference ridge line, establishing a correspondence with each point on the thickness gradient curve.

[0018] A method for parametric modeling of thickness gradient in a finite element model of a variable thickness plate according to the present invention is characterized in that:

[0019] The reference ridge line is established according to the following steps:

[0020] S1: Based on the CAD data of the variable thickness plate, extract the geometric neutral layer and complete the basic CAE mesh model generation for finite element analysis;

[0021] S2: Establish the variable thickness coordinate system X2-Y2-Z2 based on the basic CAE mesh model;

[0022] S3: Extract feature points from the basic CAE surface to form a feature point set that can characterize the trend of a plate with variable thickness.

[0023] S4: Map the feature point set that can characterize the trend of the variable thickness plate onto the Y2-Z2 plane to form the mapped feature point set;

[0024] S5: Based on the mapped feature point set, interpolation is used to form a reference ridge.

[0025] A method for parametric modeling of thickness gradient in a finite element model of a variable thickness plate according to the present invention is characterized in that:

[0026] Each node is mapped to the reference ridge according to the following steps:

[0027] SS1: Based on the CAD data of the variable thickness plate, extract the geometric neutral layer and complete the basic CAE mesh model generation for finite element analysis;

[0028] SS2: Establish a variable thickness coordinate system X2-Y2-Z2 based on the basic CAE mesh model;

[0029] SS3: By first mapping the three-dimensional data of X2-Y2-Z2, which can represent the trend of the variable thickness plate, to the Y2-Z2 plane, and then mapping the two-dimensional data of Y2-Z2 to the reference ridge line, the mapping between each node and the reference ridge line is established.

[0030] A method for parametric modeling of thickness gradient in a finite element model of a variable thickness plate according to the present invention is characterized in that:

[0031] The variable thickness coordinate system X2-Y2-Z2 is established as follows:

[0032] set up

[0033] The origin of the coordinate system is any point on the interface between any region of uniform thickness and region of variable thickness.

[0034] On the horizontal plane, the direction perpendicular to the rolling direction is X2, and the direction parallel to the rolling direction is Y2.

[0035] A method for parametric modeling of thickness gradient in a finite element model of a variable thickness plate according to the present invention is characterized in that:

[0036] The pre-strain information for each element is obtained through the following steps:

[0037] S11: Obtain the thickness of each element based on the thickness of each node;

[0038] S12: Establish corresponding stress-strain curves based on the thickness of each unit, forming a cluster of curves in the stress-strain curve diagram;

[0039] S13: Set the stress-strain curve corresponding to the minimum stress with zero strain in this curve family as the reference hardening curve and set its pre-strain to zero; the remaining stress-strain curves are the target hardening curves.

[0040] S14: Perform a matching check between the reference hardening curve and each target hardening curve one by one, and complete the pre-strain calculation for each target hardening curve through the matching check.

[0041] A method for parametric modeling of thickness gradient in a finite element model of a variable thickness plate according to the present invention is characterized in that:

[0042] The matching test is performed by shifting the reference hardening curve to the left and checking the similarity between the shifted reference hardening curve and the corresponding target hardening curve.

[0043] When the similarity meets the set requirements, the matching is successful, and the corresponding translation amount is the pre-strain of the target hardening curve.

[0044] A method for parametric modeling of thickness gradient in a finite element model of a variable thickness plate according to the present invention is characterized in that:

[0045] The thickness of each element in step S11 is obtained by weighted average of their respective nodes.

[0046] A method for parametric modeling of thickness gradient in a finite element model of a variable thickness plate according to the present invention is characterized in that:

[0047] The establishment of corresponding stress-strain curves based on the thickness of each element in step S12 is as follows:

[0048] First, stress-strain curves for the uniform thickness region are obtained through tensile testing. Then, stress-strain curves for the corresponding thickness of the thickness transition region are obtained through interpolation.

[0049] A method for parametric modeling of thickness gradient in a finite element model of a variable thickness plate according to the present invention is characterized in that:

[0050] The similarity between the translated reference hardening curve and the corresponding target hardening curve is examined as follows:

[0051] The system moves to the left at a set step distance. After moving to the target area, the reference hardening curve is discretized after each step. The distance between each discretized point and the target hardening curve is calculated. The calculated result is then weighted and averaged and compared with the set interval. If the result does not fall into the set interval, the system continues to move and compare until the weighted average result falls into the set interval, which indicates a successful match.

[0052] A method for parametric modeling of thickness gradient in a finite element model of a variable thickness plate according to the present invention is characterized in that:

[0053] Each data processing step is executed in the form of a script.

[0054] This invention discloses a finite element method for parametric modeling of thickness gradient in variable thickness plates. First, it considers two scenarios: variable thickness plates with constant strength and variable thickness plates with varying strengths. Second, for variable thickness plates with varying strengths, based on the guiding principle that the strength differences in different thickness regions are caused by different rolling pressures and annealing processes, a pre-strain method is used to equivalently describe the influence of thickness on material hardening behavior. Third, in the parameterization of thickness information at each node, the following transformation structure is employed: using a reference ridge line representing the characteristic curve of the part as an intermediate connecting body, a correspondence is established between the thickness gradient curve completed based on CAD and each node. In the calculation of pre-strain for each element, a method based on the stress-strain curve and by shifting the set reference hardening curve to the left is adopted. The transformation structure and process employ a simple and easy-to-operate mechanism, enabling rapid modeling and thickness information updates of the variable thickness plate finite element model based on a given thickness gradient design. This allows for efficient definition of the thickness gradient of the variable thickness plate part in the finite element simulation model, providing a foundation for further parametric optimization of the thickness gradient. Attached Figure Description

[0055] Figure 1 This is a schematic diagram of the modeling process in the working principle of this invention;

[0056] Figure 2 This is a schematic diagram of a variable thickness plate part in the background art of this invention;

[0057] Figure 3This is a schematic diagram of the variable thickness coordinate system and reference ridge line in the working principle of this invention;

[0058] Figure 4 This is a schematic diagram showing the variable thickness gradient curve and its correspondence with the reference ridge line in the working principle of this invention.

[0059] Figure 5 This is a schematic diagram illustrating the process of obtaining pre-strain in the working principle of this invention;

[0060] Figure 6 This is a schematic diagram of the CAD and basic CAE mesh model of the variable thickness hot-stamped B-pillar part in an embodiment of the present invention;

[0061] Figure 7 , 8 This is a schematic diagram of the node coordinate transformation process in an embodiment of the present invention;

[0062] Figure 9 This is a schematic diagram of the thickness distribution of the stepped thickness in the finite element model of the variable thickness hot-stamped B-pillar in an embodiment of the present invention. Detailed Implementation

[0063] The following is a further detailed description of a finite element thickness gradient parameterized modeling method for a variable thickness plate according to the present invention, based on the accompanying drawings and specific embodiments.

[0064] A method for parametric modeling of thickness gradient in finite element model of variable thickness plate.

[0065] The parametric modeling method is applied to two plate types: variable thickness plates with constant strength and variable thickness plates with varying strengths.

[0066] A parameterized characterization of the thickness information of each node is established for a variable thickness plate with constant strength.

[0067] For plates with varying strength, parameterized characterization of the thickness information of each node and parameterized characterization of the hardening characteristics of each element are established.

[0068] in,

[0069] The thickness information of each node is obtained based on the mapping relationship between each node and the set thickness gradient curve.

[0070] in,

[0071] The hardening characteristics of each element are characterized by the pre-strain information of each element obtained based on the thickness information of each node.

[0072] in,

[0073] The thickness gradient curve is established based on the CAD data information of the variable thickness plate.

[0074] in,

[0075] Each node is mapped to a set reference ridge line, establishing a correspondence with each point on the thickness gradient curve.

[0076] in,

[0077] The reference ridge line is established according to the following steps:

[0078] S1: Based on the CAD data of the variable thickness plate, extract the geometric neutral layer and complete the basic CAE mesh model generation for finite element analysis;

[0079] S2: Establish the variable thickness coordinate system X2-Y2-Z2 based on the basic CAE mesh model;

[0080] S3: Extract feature points from the basic CAE surface to form a feature point set that can characterize the trend of a plate with variable thickness.

[0081] S4: Map the feature point set that can characterize the trend of the variable thickness plate onto the Y2-Z2 plane to form the mapped feature point set;

[0082] S5: Based on the mapped feature point set, interpolation is used to form a reference ridge.

[0083] in,

[0084] Each node is mapped to the reference ridge according to the following steps:

[0085] SS1: Based on the CAD data of the variable thickness plate, extract the geometric neutral layer and complete the basic CAE mesh model generation for finite element analysis;

[0086] SS2: Establish a variable thickness coordinate system X2-Y2-Z2 based on the basic CAE mesh model;

[0087] SS3: By first mapping the three-dimensional data of X2-Y2-Z2, which can represent the trend of the variable thickness plate, to the Y2-Z2 plane, and then mapping the two-dimensional data of Y2-Z2 to the reference ridge line, the mapping between each node and the reference ridge line is established.

[0088] in,

[0089] The variable thickness coordinate system X2-Y2-Z2 is established as follows:

[0090] set up

[0091] The origin of the coordinate system is any point on the interface between any region of uniform thickness and region of variable thickness.

[0092] On the horizontal plane, the direction perpendicular to the rolling direction is X2, and the direction parallel to the rolling direction is Y2.

[0093] in,

[0094] The pre-strain information for each element is obtained through the following steps:

[0095] S11: Obtain the thickness of each element based on the thickness of each node;

[0096] S12: Establish corresponding stress-strain curves based on the thickness of each unit, forming a cluster of curves in the stress-strain curve diagram;

[0097] S13: Set the stress-strain curve corresponding to the minimum stress with zero strain in this curve family as the reference hardening curve and set its pre-strain to zero; the remaining stress-strain curves are the target hardening curves.

[0098] S14: Perform a matching check between the reference hardening curve and each target hardening curve one by one, and complete the pre-strain calculation for each target hardening curve through the matching check.

[0099] in,

[0100] The matching test is performed by shifting the reference hardening curve to the left and checking the similarity between the shifted reference hardening curve and the corresponding target hardening curve.

[0101] When the similarity meets the set requirements, the matching is successful, and the corresponding translation amount is the pre-strain of the target hardening curve.

[0102] in,

[0103] The thickness of each element in step S11 is obtained by weighted average of their respective nodes.

[0104] in,

[0105] The establishment of corresponding stress-strain curves based on the thickness of each element in step S12 is as follows:

[0106] First, stress-strain curves for the uniform thickness region are obtained through tensile testing. Then, stress-strain curves for the corresponding thickness of the thickness transition region are obtained through interpolation.

[0107] in,

[0108] The similarity between the translated reference hardening curve and the corresponding target hardening curve is examined as follows:

[0109] The system moves to the left at a set step distance. After moving to the target area, the reference hardening curve is discretized after each step. The distance between each discretized point and the target hardening curve is calculated. The calculated result is then weighted and averaged and compared with the set interval. If the result does not fall into the set interval, the system continues to move and compare until the weighted average result falls into the set interval, which indicates a successful match.

[0110] in,

[0111] Each data processing step is executed in the form of a script.

[0112] Working process and principle

[0113] The following explanation can be combined with Figure 1 To understand this, the specific steps are as follows:

[0114] 1. Basic CAE mesh model preparation: Based on the CAD data of the variable thickness plate part, extract the geometric neutral layer, complete the basic CAE mesh model of the variable thickness part according to the specified mesh generation standard, and output keywords according to the solver requirements;

[0115] 2. Definition of a variable thickness coordinate system: such as Figure 3 As shown, based on the basic CAE mesh model of the variable thickness part, a variable thickness coordinate system X2-Y2-Z2 is defined. The origin of the variable thickness coordinate system is a point on the curved surface of the variable thickness part, which is the boundary between the uniform thickness region and the variable thickness region. The X2 direction of the variable thickness coordinate system is perpendicular to the variable thickness rolling direction, and the Y2 direction is parallel to the variable thickness rolling direction.

[0116] 3. Referencing the ridge line definition: Select a series of feature points p1, ... p2 on the CAE surface of the variable thickness part to reflect the overall trend of the part. n The projection is then onto the transformed coordinate system Y2-Z2 plane. Based on the projected feature points q1,...qn, a reference ridge line for the variable thickness part is established using interpolation, such as... Figure 3 As shown.

[0117] 4. Thickness Gradient Parameter Definition: Based on the design of the variable thickness part, a zero-variable thickness gradient curve is established from CAD data. Any point on this variable thickness gradient curve carries corresponding thickness location and thickness information. That is, the thickness gradient parameter is the reference position value (l1,…,ln) of the curve feature point and the corresponding thickness value (t1,…,tn); and it corresponds one-to-one with the projection points of the thickness boundary positions of the variable thickness part onto the reference ridge line. For example... Figure 4 As shown, the thickness of each node is obtained through the following steps: Project a point on the geometry of the part onto the Y2-Z2 plane of the variable thickness coordinate system, and then project projection point 1 onto the reference ridge to obtain projection point 2. The length of projection point 2 and the origin of the variable thickness coordinate system along the reference ridge is the variable thickness reference position. The corresponding thickness position and thickness value are obtained from the thickness gradient curve.

[0118] 5. Importing Node and Element Information: Using a custom script, import the keywords of the basic CAE mesh model of the variable thickness part from step 1 to obtain the element and node information of the variable thickness part.

[0119] 6. Node 3D coordinate transformation: Using a custom script, the node 3D coordinates imported in step 5 are transformed from the vehicle body coordinate system to the variable thickness coordinate system;

[0120] 7. Node Thickness Calculation: Using a custom script, following the steps in step 4, the nodes transformed in step 6 are projected onto the variable thickness coordinate system Y2-Z2 plane. Then, using the minimum distance method, the projected points are further projected onto the reference ridge line to obtain the variable thickness reference position of each node. The thickness value of each node is obtained based on the variable thickness reference position and the thickness gradient curve.

[0121] 8. Node thickness information update: Using a custom script, the node thickness information is updated in the keywords of the basic CAE mesh model according to the requirements of different analysis solvers.

[0122] 9. Definition of strength gradient information and update of element thickness information: If there is no difference in material strength in different thickness regions of a variable thickness part, then export the CAE mesh model keywords processed in step 8 according to the requirements of different analysis solvers; If there is a difference in material strength in different thickness regions of a variable thickness part, then calculate the thickness value of each element according to the element-node correspondence in step 5, and the element thickness value is the average value of the thickness of the corresponding node; and for different material thicknesses, first define a set of stress-strain curves for equal thickness regions through tensile tests, and form a stress-strain-thickness surface through interpolation.

[0123] 10. Unit Pre-strain Information Update: The strength difference in different thickness regions of a variable-thickness part can be considered as being caused by different rolling reductions and annealing processes. Therefore, applying pre-strain can be used to equivalently describe the influence of thickness on material hardening behavior. The operation procedure is as follows:

[0124] a) In a set of stress-strain curves, find the stress-strain curve with the minimum stress corresponding to zero strain. Use this stress-strain curve as reference hardening curve 1 (usually the stress-strain curve with the thickest thickness), and set this pre-strain to zero. Figure 5 As shown;

[0125] b) For each element, based on its element thickness value, obtain the stress-strain curve 2 corresponding to that thickness in the stress-strain-thickness surface;

[0126] c) Shift the hardening curve 1 to the left so that the shifted hardening curve 3 has the highest similarity to curve 2. Use the shifted value of hardening curve 1 as the pre-strain value of the unit. The highest similarity is determined by the set similarity test. Discretize the shifted curve and then calculate the weighted average of the distances between each point and curve 2. When the calculation result falls into the set interval, it is considered that the corresponding shifted hardening curve has reached the highest similarity to curve 2.

[0127] d) According to the requirements of different analysis solvers, update the element pre-strain values ​​to the mesh model keywords in step 8, export the final finite element model of the variable thickness plate, and define the hardening curve 1 as the material hardening curve of the variable thickness plate part.

[0128] Example

[0129] The following is a finite element modeling process for a variable thickness hot-stamped B-pillar part, using it as an example: (Refer to...) Figure 6 ,

[0130] 1. Import the CAD data of the variable thickness B-pillar part into the finite element preprocessing software to extract the neutral surface. Use 5mm shell elements to mesh the neutral surface and export the finite element mesh model as an LS-DYNA solver keyword file.

[0131] 2. Based on the variable thickness design scheme of the part, the following variable thickness coordinate system and reference ridge line are defined, where the X2 direction is perpendicular to the variable thickness rolling direction, the Y2 direction is parallel to the variable thickness rolling direction, and points p1 to p5 are feature points on the B-pillar basic mesh model, used to reflect the overall bending trend of the B-pillar part.

[0132] 3. Using a custom script file, import the keyword file from step 1 to obtain the coordinate information of the three points of the node, and refer to... Figure 7 .

[0133] 4. Based on the variable thickness coordinate system defined in step 2, perform node coordinate transformation and projection, and define the part thickness gradient information based on the thickness information in the CAD data, referring to... Figure 8 .

[0134] 5. Calculate node n i The projection point n on the reference ridge line i Then, by calculating the distance from that point along the reference ridge to the origin of the variable thickness coordinate system, the variable thickness reference position l is obtained. i Based on the thickness gradient curve, the thickness t corresponding to the node is obtained. i , refer to Figure 8 .

[0135] 6. Use the *ELEMENT_SHELL_THICKNESS keyword method to update the node thickness value to the keyword in step 1.

[0136] 7. Since the strength of hot-formed parts made of variable thickness plates is determined by the hot-forming process, and there is no significant difference in material strength between different regions after hot stamping, a strength gradient is not defined, and the pre-strain definition step is omitted.

[0137] Export the keywords processed in step 6 and import them into pre- and post-processing software to confirm the thickness gradient distribution of the variable thickness part, referring to... Figure 9 .

[0138] This invention discloses a finite element method for parametric modeling of thickness gradient in variable thickness plates. First, it considers two scenarios: variable thickness plates with constant strength and variable thickness plates with varying strengths. Second, for variable thickness plates with varying strengths, based on the guiding principle that the strength differences in different thickness regions are caused by different rolling pressures and annealing processes, a pre-strain method is used to equivalently describe the influence of thickness on material hardening behavior. Third, in the parameterization of thickness information at each node, the following transformation structure is employed: using a reference ridge line representing the characteristic curve of the part as an intermediate connecting body, a correspondence is established between the thickness gradient curve completed based on CAD and each node. In the calculation of pre-strain for each element, a method based on the stress-strain curve and by shifting the set reference hardening curve to the left is adopted. The transformation structure and process employ a simple and easy-to-operate mechanism, enabling rapid modeling and thickness information updates of the variable thickness plate finite element model based on a given thickness gradient design. This allows for efficient definition of the thickness gradient of the variable thickness plate part in the finite element simulation model, providing a foundation for further parametric optimization of the thickness gradient.

Claims

1. A method for parametric modeling of thickness gradient in a finite element model of a plate with variable thickness, characterized in that: The parametric modeling method is applied to two plate types: variable thickness plates with constant strength and variable thickness plates with varying strengths. A parametric characterization of the thickness information of each node is established for a variable thickness plate with constant strength. For plates with varying strength, parameterized characterizations of thickness information at each node and hardening characteristics of each element are established. The thickness information of each node is obtained based on the mapping relationship between each node and the set thickness gradient curve. The thickness gradient curve is established based on the CAD data information of the variable thickness plate. Each node is mapped to a set reference ridge line to establish a correspondence with a point on the thickness gradient curve. The reference ridge line is established according to the following steps: S1: Based on the CAD data of the variable thickness plate, extract the geometric neutral layer and complete the basic CAE mesh model generation for finite element analysis; S2: Establish the variable thickness coordinate system X2-Y2-Z2 based on the basic CAE mesh model; S3: Extract feature points from the basic CAE surface to form a feature point set that can characterize the trend of a plate with variable thickness. S4: Map the feature point set that can characterize the trend of the variable thickness plate onto the Y2-Z2 plane to form the mapped feature point set; S5: Based on the mapped feature point set, interpolation is used to form a reference ridge.

2. The method for parametric modeling of thickness gradient in a finite element model of a variable thickness plate according to claim 1, characterized in that: The hardening characteristics of each element are characterized by the pre-strain information of each element obtained based on the thickness information of each node.

3. The method for parametric modeling of thickness gradient in a finite element model of a variable thickness plate according to claim 1, characterized in that: Each node is mapped to the reference ridge according to the following steps: SS1: Based on the CAD data of the variable thickness plate, extract the geometric neutral layer and complete the basic CAE mesh model generation for finite element analysis; SS2: Establish a variable thickness coordinate system X2-Y2-Z2 based on the basic CAE mesh model; SS3: By first mapping the three-dimensional data of X2-Y2-Z2, which can represent the trend of the variable thickness plate, to the Y2-Z2 plane, and then mapping the two-dimensional data of Y2-Z2 to the reference ridge line, the mapping between each node and the reference ridge line is established.

4. A method for parametric modeling of thickness gradient in a finite element model of a variable thickness plate according to claim 1 or 3, characterized in that: The variable thickness coordinate system X2-Y2-Z2 is established as follows: set up The origin of the coordinate system is any point on the interface between any region of uniform thickness and region of variable thickness. On the horizontal plane, the direction perpendicular to the rolling direction is X2, and the direction parallel to the rolling direction is Y2.

5. The method for parametric modeling of thickness gradient in a finite element model of a variable thickness plate according to claim 2, characterized in that: The pre-strain information for each element is obtained through the following steps: S11: Obtain the thickness of each element based on the thickness of each node; S12: Establish corresponding stress-strain curves based on the thickness of each unit, forming a cluster of curves in the stress-strain curve diagram; S13: Set the stress-strain curve corresponding to the minimum stress with zero strain in this curve family as the reference hardening curve and set its pre-strain to zero; the remaining stress-strain curves are the target hardening curves. S14: Perform a matching check between the reference hardening curve and each target hardening curve one by one, and complete the pre-strain calculation for each target hardening curve through the matching check.

6. The method for parametric modeling of thickness gradient in a finite element model of a variable thickness plate according to claim 5, characterized in that: The matching test is performed by shifting the reference hardening curve to the left and checking the similarity between the shifted reference hardening curve and the corresponding target hardening curve. When the similarity meets the set requirements, the matching is successful, and the corresponding translation amount is the pre-strain of the target hardening curve.

7. The method for parametric modeling of thickness gradient in a finite element model of a variable thickness plate according to claim 5, characterized in that: The thickness of each element in step S11 is obtained by weighted average of their respective nodes.

8. The method for parametric modeling of thickness gradient in a finite element model of a variable thickness plate according to claim 5, characterized in that: The establishment of corresponding stress-strain curves based on the thickness of each element in step S12 is as follows: First, stress-strain curves for the uniform thickness region are obtained through tensile testing. Then, stress-strain curves for the corresponding thickness of the thickness transition region are obtained through interpolation.

9. The method for parametric modeling of thickness gradient in a finite element model of a variable thickness plate according to claim 6, characterized in that: The similarity between the translated reference hardening curve and the corresponding target hardening curve is examined as follows: The system moves to the left at a set step distance. After moving to the target area, the reference hardening curve is discretized after each step. The distance between each discretized point and the target hardening curve is calculated. The calculated result is then weighted and averaged and compared with the set interval. If the result does not fall into the set interval, the system continues to move and compare until the weighted average result falls into the set interval, which indicates a successful match.

10. The method for parametric modeling of thickness gradient in a finite element model of a variable thickness plate according to claim 1, characterized in that: Each data processing step is executed in the form of a script.

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