A method for evaluating the rigidity of an automotive outer panel after forming

Abstract

The present invention relates to a method for rigid evaluation of an automotive outer panel after forming. The rigid evaluation method includes the following steps: S1. Establish a digital model of the outer panel and a styling CAS surface, and simulate the stamping forming simulation process of the outer panel; S2. Simulate the drawing process; S3. Export the drawn part after stress release with thickness and strain information from the finite element simulation software; S4. Simulate the process of placing the drawn part on the ground; and export the drawn part in a balanced state containing thickness and strain result information; S5. Simulate the process of an object pressing on the drawn part; analyze the deformation information of the force-bearing area of the drawn part in a balanced state, and export the analysis result; S6. Evaluate and compare the rigidity of the drawn part of the outer panel based on the analysis result in S5 and the material parameters of the outer panel. The present invention can theoretically quantitatively evaluate the rigidity of the drawn part of the automotive outer panel in the early stage of styling design, product design and process design.

Description

Technical Field

[0001] The present invention relates to the technical field of automobile outer panel body manufacturing processes, and particularly relates to a method for evaluating the rigidity of an automobile outer panel after forming. Background Art

[0002] The existing anti-denting performance test standards and CAE finite element simulation evaluation methods for automobile outer panels only target the assembly of automobile outer panels. Automobile body panels are large thin plate stamping parts with relatively gentle curved surfaces. During forming, due to the inadequacy and non-uniformity of their plastic deformation, certain parts often have poor rigidity. Cover panels with poor rigidity will produce hollow sounds when vibrating and are prone to vibration during high-speed driving, resulting in early damage to the cover panels. Therefore, it is very necessary to ensure that they have a certain stiffness.

[0003] Regarding the rigidity evaluation of the drawn parts of automobile outer panels, the traditional method is to tap the parts to distinguish the similarities and differences in the sounds of different parts, or to press them by hand to see if there is any relaxation or fluttering phenomenon. The evaluation results are relatively subjective and difficult to quantify; some automobile manufacturers use the object pressing method, such as Figure 1 As shown, the specific method is: take the center point of the part, place an object of a certain weight at the center of the part; place a specified heavy object on the object and use the self-weight of the specified heavy object to press the part; after pressing, measure the area size after deformation and compare the stiffness and strength of the part. Although it can be quantified, it can only be evaluated after the part is manufactured. If the part has poor rigidity and then product or process adjustments are made, it will lead to an increase in the development cycle and cost. There is currently a lack of a method for theoretically quantifying the rigidity of the drawn parts of automobile outer panels in the styling stage, in the early stage of product design or process design. Summary of the Invention

[0004] To solve the problems existing in the above-mentioned prior art, the present invention provides a method for evaluating the rigidity of an automobile outer panel after forming, which can theoretically quantify the rigidity of the drawn parts of the automobile outer panel in the early stage of styling design, product design, and process design. This theoretical evaluation method can consider the influence of the thickness and strain of the outer panel caused by the drawing process, as well as the deformation state of the drawn part when placed on the ground, making the evaluation results closer to the actual situation.

[0005] To achieve the above object, the specific technical solution of the present invention is as follows: A method for evaluating the rigidity of an automobile outer panel after forming, the rigidity evaluation method includes the following steps:

[0006] S1. Establish a digital model of the outer panel and a styling CAS surface, and simulate the stamping forming simulation process of the outer panel;

[0007] S2. Simulate the drawing process;

[0008] Construct the drawing process surface of the outer panel and conduct a simulation analysis on the drawability of the outer panel; use finite element simulation software to perform springback analysis on the drawn part of the outer panel to obtain the drawn part after stress release;

[0009] S3. Export the drawn part after stress release with thickness and strain information from the finite element simulation software;

[0010] S4. Simulate the process of placing the drawn part on the ground;

[0011] After placing the drawn part after stress release on the ground, apply a load to the drawn part after stress release at a predetermined acceleration until the drawn part after stress release reaches equilibrium, and export the drawn part in the equilibrium state containing thickness and strain result information;

[0012] S5. Simulate the process of an object pressing on the drawn part;

[0013] Apply a load to the drawn part in the equilibrium state, then analyze the deformation information of the stressed area of the drawn part in the equilibrium state, and export the analysis results;

[0014] S6. Evaluate and compare the rigidity of the drawn part of the outer panel based on the analysis results in S5 and the material parameters of the outer panel.

[0015] Furthermore, in step S5, first, constrain the drawn part in the equilibrium state according to the object pressing method, then apply a load to the centroid position of the drawn part in the equilibrium state, and then use the solver to analyze and solve the deformation amount, stress value, and plastic strain of the stressed area of the drawn part in the equilibrium state, and export the analysis results.

[0016] Furthermore, in step S6, the evaluation and comparison mean: compare the maximum stress received by the stressed area of the drawn part in the equilibrium state with the yield strength of the outer panel material, and evaluate the magnitude of the deformation amount and the size of the deformation range of the stressed area of the drawn part in the equilibrium state.

[0017] Furthermore, in step S4, first, establish a finite element tool body for the ground and set the property of the ground as a rigid body; secondly, set the contact relationship between the drawn part after stress release and the ground; then apply a load to the drawn part after stress release at a preset acceleration; finally, submit the preset acceleration to the solver for simulation calculation of the process of the drawn part placed on the ground, form the drawn part in the equilibrium state, and conduct an object pressing force analysis on it.

[0018] Further, the process of analyzing the force applied to the drawn part in the equilibrium state: Import the drawn part in the equilibrium state containing thickness and strain result information and the finite element tool body on the ground into the finite element simulation software, set the contact relationship between the ground and the drawn part in the equilibrium state, apply a predetermined load F at the centroid position of the drawn part in the equilibrium state, and submit the load F to the solver to calculate the deformation amount, deformation range, and stress magnitude of the force-bearing area of the drawn part in the equilibrium state.

[0019] Further, in step S2, the simulation process of the draw formability of the outer panel: Import the draw process surface of the outer panel established in step S1 into the finite element simulation software, perform mesh division on the draw process surface of the outer panel, establish a tool body. The tool body consists of a die, a flattening ring, and a punch from top to bottom. The blank is set between the die and the flattening ring, and the size of the blank is set according to the size of the draw process surface of the outer panel, and the blank is meshed; Set the material properties, material performance parameters, stamping process parameters, and simulation analysis parameters of the blank, and submit them to the solver to simulate the drawing process of the blank and obtain the drawn part of the outer panel.

[0020] Further, in step S2, use the finite element simulation software to perform a free springback simulation analysis on the drawn part of the outer panel, submit the free springback setting file of the drawn part of the outer panel to the solver, and through the solver, perform an internal stress release calculation on the drawn part of the outer panel with internal stress information. After the stress release, the drawn part of the outer panel deforms to form the drawn part after stress release.

[0021] Further, the stamping process parameters include the movement stroke of the tool body, the magnitude of the blank holder force, and the friction coefficient; the simulation analysis parameters include the mesh refinement level, the minimum mesh size, and the result output.

[0022] Further, in step S2, establish the CAS surface or product digital model of the outer panel, combine the stamping process experience of the outer panel, determine the stamping direction, blank holding surface, and process supplement connection part of the outer panel, and place the CAS surface or product digital model on the blank holding surface through the process supplement connection part to construct the draw process surface of the outer panel.

[0023] Further, in step S1, simulate the stamping formability simulation of the outer panel through 3D modeling software or professional stamping forming simulation software.

[0024] The beneficial effects of the present invention:

[0025] The theoretical quantitative evaluation method for the rigidity of the drawn part of the automotive outer panel provided by the present invention can theoretically quantitatively evaluate the rigidity of the drawn part of the automotive outer panel in the early stage of styling design, product design, and process design, and reduce the increase in development cycle and development cost caused by the changes in styling, product, process, and die due to insufficient rigidity of the outer panel.

[0026] The evaluation method of the present invention simultaneously considers the stress release after the blank drawing of the automotive outer panel and factors affecting the rigidity of the drawn part, such as the thickness change and plastic strain of the drawn part of the outer panel after drawing, which is consistent with the actual manufacturing process of the outer panel, making the evaluation result closer to the actual situation. Moreover, this evaluation method simulates the process of dynamically placing the drawn part on the ground, which is consistent with the actual part placement method for evaluation, improving the accuracy of the evaluation result.

[0027] The present invention is not only applicable to automotive outer panels, but also applicable to the rigidity evaluation of parts after stamping forming in the fields of aviation, aerospace, shipbuilding, household appliances, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the rigidity evaluation of the drawn part of the automotive outer panel by using the object pressing method in the prior art;

[0029] Figure 2 It is a technical flow chart of the rigidity evaluation method for the formed automotive outer panel of the present invention;

[0030] Figure 3 It is a drawing showing the change of the drawn part during the theoretical quantification process of evaluating the rigidity with the drawn part of the outer panel of the engine hood as an example in the present invention;

[0031] Figure 4 It is a schematic diagram of the CAS surface or product digital model of the outer panel of the engine hood in the present invention;

[0032] Figure 5 It is a schematic diagram of the drawing process surface of the outer panel of the engine hood in the present invention;

[0033] Figure 6 It is a schematic diagram of the finite element model of the blank drawing in the present invention;

[0034] Figure 7 It is a schematic diagram of the drawn part of the outer panel of the engine hood after the blank is formed in the present invention;

[0035] Figure 8 It is a comparison diagram of stress values before (Figure a) and after (Figure b) stress release in the present invention;

[0036] Figure 9 It is a comparison diagram of the part surface before and after stress release and a numerical cloud diagram of the part surface change in the present invention;

[0037] Figure 10 It is a schematic diagram of the drawn part with stamping thickness information in the present invention;

[0038] Figure 11 It is a schematic diagram of the drawn part with stamping strain information in the present invention;

[0039] Figure 12Schematic diagram of the finite element model of the drawing part of the present invention placed on the ground;

[0040] Figure 13 Schematic diagram of the drawing part of the present invention placed on the ground and reaching the equilibrium state;

[0041] Figure 14 Front and rear stress comparison diagram of the drawing part of the present invention before and after being placed on the ground;

[0042] Figure 15 Schematic diagram of the finite element model for the object pressure analysis of the drawing part of the present invention;

[0043] Figure 16 Profile comparison diagram of the drawing part of the present invention before and after being pressured;

[0044] Figure 17 Schematic diagram of the deformation range of the drawing part of the present invention;

[0045] Figure 18 Schematic diagram of the Z - direction deformation amount of the drawing part of the present invention;

[0046] Figure 19 Stress nephogram of the drawing part of the present invention.

[0047] Wherein: 1 - CAS surface or product digital model, 2 - blank - holding surface, 3 - process - supplementary connection part, 4 - female die, 5 - flattening ring, 6 - male die, 7 - blank, 8 - outer panel drawing part of the engine hood, 9 - drawing part after stress release, 10 - ground, 11 - drawing part reaching the equilibrium state, 12 - drawing part subjected to force and deformation. Detailed implementation manners

[0048] In order to enable those skilled in the art to better understand the technical solutions of the present application, the following will further describe the present invention in detail with reference to the accompanying drawings and embodiments.

[0049] The orientation terms such as up, down, left, right, front and back in this application document are established based on the positional relationship shown in the drawings. If the drawings are different, the corresponding positional relationship may also change accordingly. Therefore, it should not be understood as a limitation of the protection scope.

[0050] In the present invention, the terms "installation", "connection", "engagement", "connection", "fixation", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, an integral connection, a mechanical connection, an electrical connection or a connection that can communicate with each other, a direct connection, an indirect connection through an intermediate medium, a connection inside two components, or an interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0051] This embodiment describes a method for evaluating the rigidity of an automotive outer panel after forming, which is used to theoretically quantify and evaluate the rigidity of the drawing part of the automotive outer panel in the early stages of styling design, product design, and process design.

[0052] In order to more realistically reflect the actual stress and deformation during the process of applying pressure to the object from the product digital model to the drawing part of the outer panel, as Figure 2 and Figure 3 shown, the evaluation method includes the following steps:

[0053] 1. Establish the digital model of the outer panel and the styling CAS surface, and simulate the stamping forming simulation process of the outer panel;

[0054] 2. Simulate the drawing process;

[0055] First, construct the drawing process surface of the outer panel through the stamping forming simulation of the outer panel, and then conduct the drawing formability simulation analysis of the outer panel; use the finite element simulation software to conduct the springback analysis on the drawing part of the outer panel, that is, the internal stress release analysis, to obtain the drawn part after stress release with thickness and strain information, so as to more realistically evaluate the rigidity of the drawn part in the subsequent steps;

[0056] 3. Export the drawn part after stress release with thickness and strain information obtained in step 2 from the finite element simulation software for subsequent simulation processes;

[0057] 4. Simulate the process of placing the drawn part on the ground;

[0058] After placing the drawn part after stress release in the previous step on the ground, apply a load to the drawn part after stress release at a predetermined acceleration so that the drawn part after stress release reaches equilibrium under the ground support, forming a drawn part in the equilibrium state, and export the drawn part in the equilibrium state containing thickness and strain result information for subsequent object pressure stress analysis.

[0059] 5. Simulate the process of an object pressing on the drawn part;

[0060] First, constrain the drawn part in the equilibrium state according to the object pressure method, then apply a load to the centroid position of the drawn part in the equilibrium state, and then use the solver to analyze and solve the deformation amount, stress value, plastic strain, etc. of the force-bearing area of the drawn part in the equilibrium state, and export the analysis results;

[0061] In this embodiment, the solver uses the dynamic display algorithm for analysis and solution, and its equilibrium equation:

[0062]

[0063] M D = diagM

[0064] Solution method:

[0065]

[0066]

[0067]

[0068] Wherein, F: external force, P: internal force, t: time, x: current coordinate, u: displacement, K: stiffness matrix, M: mass matrix, M D represents a diagonal matrix, that is, the diagonal matrix of the mass matrix M, velocity, acceleration, k: this time step, k - 1: the previous time step, n: this time step, n - 1: the previous time step, Δt: the time increment between the previous time step and this time step.

[0069] 6. Evaluate and compare the rigidity of the drawn part based on the analysis results derived in step 5 and the material parameters of the outer panel.

[0070] Specifically, the evaluation and comparison means: comparing the maximum stress received by the stressed area of the drawn part in the equilibrium state with the yield strength of the outer panel material, and evaluating the magnitude of the deformation and the size of the deformation range of the stressed area of the drawn part in the equilibrium state.

[0071] For parts of the same type, when subjected to the same load, the greater the deformation and the larger the deformation range, the worse the rigidity; conversely, the better the rigidity. When the maximum stress value of the drawn part in the equilibrium state is less than the yield strength of the outer panel material, the part does not undergo plastic deformation and has good rigidity; conversely, it undergoes plastic deformation and has poor rigidity.

[0072] This embodiment takes the outer panel of the engine hood as an example to illustrate this evaluation method, and conducts a rigid theoretical quantification evaluation on the blank drawn part before the forming of the outer panel of the engine hood. The implementation steps are as follows:

[0073] 1) Establish the stamping process surface of the drawn part

[0074] In this embodiment, a three-dimensional modeling software or a professional stamping forming simulation software is used to simulate the blank stamping forming simulation to complete the establishment of the stamping process surface of the outer panel of the engine hood.

[0075] Specifically, first establish the CAS surface or product digital model 1 of the outer panel of the engine hood (see Figure 4 ), and in combination with the stamping process experience of the outer panel of the engine hood, determine the stamping direction, blank holding surface 2 and process supplementary connection part 3 of the outer panel of the engine hood, such as Figure 5As shown, the CAS surface or the product digital mock-up 1 is placed on the blank holding surface 2 through the process supplement connection part 3, and then the drawing process surface of the outer panel of the engine hood is constructed using 3D modeling software or professional stamping forming simulation software.

[0076] 2) Simulation analysis of the drawing process

[0077] Import the drawing process surface of the outer panel of the engine hood established in step 1) into the finite element simulation software and perform mesh division on it. Establish tool bodies, such as Figure 6 As shown, the tool bodies from top to bottom are the female die 4, the flattening ring 5, and the male die 6 in sequence. The blank 7 is set between the female die 4 and the flattening ring 5. The size of the blank 7 is set according to the size of the drawing process surface of the outer panel of the engine hood, and mesh division is performed on the blank 7.

[0078] In the finite element simulation software, set the material properties and material performance parameters of the blank 7. For example, the blank 7 uses a galvanized steel sheet with the material grade of HC180BD+Z, and the blank thickness is 0.65 mm; set the stamping process parameters, such as the movement stroke of the tool body, the magnitude of the blank holding force, the friction coefficient, etc.; set the simulation analysis parameters, such as the mesh refinement level, the minimum mesh size, the result output, etc.

[0079] Submit the parameter information of the blank 7 and the set stamping and simulation parameters to the solver respectively to simulate the drawing process of the blank 7. The blank 7 is formed into the drawn part of the outer panel of the engine hood 8 according to the drawing process surface of the outer panel of the engine hood (see Figure 7 ).

[0080] 3) Stress release of the drawn part

[0081] There are internal stresses in the drawn parts produced in actual production. When the drawn parts are taken out of the mold, the internal stresses will be automatically released. In order to more realistically reflect the true state of the drawn parts, use the finite element simulation software to perform springback analysis on the drawn parts, that is, internal stress release analysis, to obtain a more accurate shape of the drawn parts, so as to more realistically evaluate the rigidity of the drawn parts in the follow-up.

[0082] For the drawn part of the outer panel of the engine hood 8 after the blank 7 is drawn and formed in the simulation analysis of the drawing process in step 2), set the free springback (stress release) simulation analysis step, and submit the free springback setting file of the drawn part of the outer panel of the engine hood 8 to the solver. The solver performs internal stress release calculation on the drawn part of the outer panel of the engine hood 8 with internal stress information.

[0083] In this embodiment, the solver uses the static implicit algorithm to perform internal stress release calculation, and its equilibrium equation is:

[0084] R(u,x,t)=F(x,t)-P(u,x)=0

[0085] Solution method:

[0086] Δu k =- t+Δt K k -1t+Δt R k

[0087] t+Δt u k+1 = t+Δt u k +Δu k

[0088] Where R: residual force, F: external force, P: internal force, x: current coordinate, u: displacement, K: stiffness matrix.

[0089] After stress release, the drawing part 8 of the outer panel of the engine hood reaches force balance, deforms, and forms the drawing part 9 after stress release. The shape of the drawing part 9 after stress release is the precise shape of the drawing part. The states of the internal stress of the drawing part 8 of the outer panel of the engine hood before and after stress release are as Figure 8 shown, where Figure a shows the internal stress state of the drawing part 8 of the outer panel of the engine hood before stress release, and Figure b shows the stress state of the drawing part 9 after stress release. The comparison of the shape changes of the drawing part before and after stress release is shown in Figure 9 shown, where it can be seen from Figure 9 a) that after stress release, the shape of the drawing part 8 of the outer panel of the engine hood has changed significantly. Figure 9 b) is the numerical comparison nephogram of the shape deformation of the drawing part 8 of the outer panel of the engine hood.

[0090] 4) Export the drawing part 9 after stress release with thickness and strain information

[0091] Since the blank 7 undergoes the drawing process and the stress release process, the thickness of the blank changes, and corresponding plastic strain is also generated. These result information will directly affect the rigidity of the drawing part. As Figure 10 and Figure 11 shown, export the result file of the drawing part 9 after stress release with the thickness and strain information after stamping from the finite element simulation software for the subsequent process simulation of placing the drawing part on the ground.

[0092] 5) Process simulation of placing the drawing part on the ground 10

[0093] Import the drawing part 9 after stress release with thickness and strain information exported in the previous step into the finite element simulation software; as Figure 12 ​As shown, first, establish a finite element tool for the ground 10 and set the property of the ground 10 as a rigid body. Secondly, set the contact relationship between the drawn part 9 after stress release and the ground 10. Then, apply a load to the drawn part 9 after stress release with an acceleration (such as gravitational acceleration g) in a preset finite element file. Finally, submit the preset finite element setting file A (including relevant information such as the drawn part with a preset acceleration load, the ground, etc.) to the solver for simulation calculation of the placement process of the drawn part on the ground 10, so that the drawn part 9 after stress release reaches equilibrium under the support of the ground 10, forming Figure 13 the drawn part 11 shown in the figure that reaches the equilibrium state.

[0094] In this step, the calculation process used by the solver is the same as that in step 3, and the dynamic display algorithm is also used for analysis and solution. Its equilibrium equation:

[0095]

[0096] Solution method:

[0097]

[0098]

[0099]

[0100] where F: external force, P: internal force, x: current coordinate, u: displacement, K: stiffness matrix, M: mass matrix, velocity, acceleration.

[0101] For the stress comparison before and after the drawn part 9 after stress release is placed on the ground 10, see Figure 14 as shown. Finally, export the result file of the drawn part 11 that reaches the equilibrium state containing thickness and strain result information for subsequent object pressing force analysis.

[0102] 6) Object pressing force analysis of the drawn part

[0103] Import the drawn part 11 that reaches the equilibrium state containing thickness and strain result information into the finite element simulation software, and also import the finite element tool for the ground 10 in step 5), as Figure 15 shown. Set the contact relationship between the ground 10 and the drawn part 11 that reaches the equilibrium state, and apply a certain load F at the centroid position of the drawn part 11 that reaches the equilibrium state. The magnitude of the load F is determined according to the stiffness evaluation requirements, and submit the preset finite element setting file B (including relevant information such as the drawn part with the applied load F, the ground, etc.) to the solver for calculation, and calculate the deformation amount, deformation range, and stress magnitude of the force-bearing area of the drawn part 11 that reaches the equilibrium state.

[0104] 7) Evaluation of Stiffness Quantification Index

[0105] After the calculation, the rigidity of the drawn part 11 is evaluated through the analysis results such as the deformation amount, deformation range, and stress magnitude of the stressed area of the drawn part 11 that has reached the equilibrium state. For parts of the same type, when subjected to the same load, the greater the deformation amount and the larger the deformation range, the worse the rigidity; conversely, the better the rigidity.

[0106] Figure 16 For the comparison of the surface (i.e., shape deformation amount) of the drawn part 11 before and after being pressured to reach the equilibrium state, the drawn part 12 with stress-induced deformation is formed after the drawn part 11 that has reached the equilibrium state is pressured. It can be clearly seen from the figure that the drawn part undergoes obvious deformation in the stressed area. Figure 17 Schematic diagram of the deformation range of the drawn part 12 with stress-induced deformation. The deformation range in the middle of the drawn part 12 with stress-induced deformation is the part within the circle in the figure, and the diameter is

[0107] Figure 18 Contour map of the Z-direction deformation amount of the drawn part 12 with stress-induced deformation. It can be seen from the figure that the value of the middle depression is the largest, and the depression amount is 6.147 mm. Figure 19 Contour map of the stress on the drawn part 12 with stress-induced deformation. It can be seen from the figure that the stress in the middle of the drawn part 12 with stress-induced deformation is relatively large, and the maximum stress is 132.789 MPa. The yield strength of the blank 7 material HC180BD+Z > 180 MPa, and the maximum stress on the drawn part 12 with stress-induced deformation is 132.789 MPa, which does not exceed the material yield strength, that is, no plastic deformation occurs. If the stress on the drawn part 12 with stress-induced deformation exceeds the material yield strength, irreversible plastic deformation will occur, and the rigidity of the part will be poor.

[0108] Although the principle of the present invention has been described in detail above in combination with the preferred embodiments of the present invention, those skilled in the art should understand that the above embodiments are only explanations of the illustrative implementation manners of the present invention and do not limit the scope of the present invention. The details in the embodiments do not constitute a limitation on the scope of the present invention. Without departing from the spirit and scope of the present invention, any obvious changes such as equivalent transformations and simple substitutions based on the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A method for evaluating the rigidity of an automobile exterior covering part after forming, characterized in that The rigid evaluation method includes the following steps: S1. Establish the digital model of the outer panel and the styling CAS surface, and simulate the stamping forming simulation process of the outer panel; S2. Simulate the drawing process; Construct the drawing process surface of the outer panel, and conduct the formability simulation analysis of the outer panel drawing; use the finite element simulation software to conduct the springback analysis of the drawn part of the outer panel to obtain the drawn part after stress release; S4. Export the drawn part after stress release with thickness and strain information from the finite element simulation software; S5. Simulate the process of placing the drawn part on the ground; After placing the drawn part after stress release on the ground, apply a load to the drawn part after stress release at a predetermined acceleration until the drawn part after stress release reaches equilibrium, and export the drawn part in the equilibrium state containing thickness and strain result information; S7. Simulate the process of an object pressing on the drawn part; Apply a load to the drawn part in the equilibrium state, and then analyze the deformation information of the stressed area of the drawn part in the equilibrium state, and export the analysis results; S6. Evaluate and compare the rigidity of the drawn part of the outer panel based on the analysis results in S5 and the material parameters of the outer panel.

2. The method for evaluating the rigidity of an outer automotive covering after forming according to claim 1, characterized in that, In step S5, first, constrain the drawn part in the equilibrium state according to the object pressing method, then apply a load to the centroid position of the drawn part in the equilibrium state, and then use the solver to analyze and solve the deformation amount, stress value, and plastic strain of the stressed area of the drawn part in the equilibrium state, and export the analysis results.

3. The rigid evaluation method for the formed outer automotive panel according to claim 2, characterized in that In step S6, the evaluation and comparison mean: compare the maximum stress received by the stressed area of the drawn part in the equilibrium state with the yield strength of the outer panel material, and evaluate the magnitude of the deformation amount and the size of the deformation range of the stressed area of the drawn part in the equilibrium state.

4. The rigid evaluation method for the formed outer automotive panel according to claim 1, wherein, In step S4, first, establish the finite element tool body of the ground (10), and set the attribute of the ground (10) as a rigid body; second, set the contact relationship between the drawn part (9) after stress release and the ground (10); then apply a load to the drawn part (9) after stress release at a preset acceleration; finally, submit the preset acceleration to the solver for the simulation calculation of the process of the drawn part placed on the ground (10) to form the drawn part (11) in the equilibrium state, and conduct the force analysis of the object pressing on it.

5. The rigid evaluation method for the formed outer automotive panel according to claim 4, characterized in that The process of conducting the force analysis of the object pressing on the drawn part (11) in the equilibrium state: Import the drawn part (11) in the equilibrium state containing thickness and strain result information and the finite element tool body of the ground (10) into the finite element simulation software together, set the contact relationship between the ground (10) and the drawn part (11) in the equilibrium state, and apply a predetermined load F to the centroid position of the drawn part (11) in the equilibrium state, and submit the load F to the solver to calculate the deformation amount, deformation range, and stress magnitude of the stressed area of the drawn part (11) in the equilibrium state.

6. The rigid evaluation method for the formed outer automotive panel according to claim 1, wherein In step S2, the simulation process of the drawing formability of the outer panel: Import the drawing process surface of the outer panel established in step S1 into the finite element simulation software, and perform mesh division on the drawing process surface of the outer panel to establish a tool body. The tool body includes a die (4), a flattening ring (5), and a punch (6) from top to bottom. The blank (7) is arranged between the die (4) and the flattening ring (5). The size of the blank (7) is set according to the size of the drawing process surface of the outer panel, and the blank (7) is meshed; Set the material properties, material performance parameters, stamping process parameters, and simulation analysis parameters of the blank (7), and submit them to the solver to simulate the drawing process of the blank (7) to obtain the drawn part of the outer panel.

7. The method for evaluating the rigidity of an outer automotive covering part after forming according to claim 6, characterized in that In step S2, use the finite element simulation software to perform a free springback simulation analysis on the drawn part of the outer panel. Submit the free springback setting file of the drawn part of the outer panel to the solver, and the solver performs an internal stress release calculation on the drawn part of the outer panel with internal stress information. After the stress release, the drawn part of the outer panel deforms to form the drawn part after stress release.

8. The method for evaluating the rigidity of the formed outer automotive cover according to claim 6, characterized in that, The stamping process parameters include the movement stroke of the tool body, the size of the blank holding force, and the friction coefficient; The simulation analysis parameters include the mesh refinement level, the minimum mesh size, and the result output.

9. The method for evaluating the rigidity of an outer automotive panel after forming according to claim 1, wherein In step S2, establish the CAS surface or product digital model (1) of the outer panel. Combine the stamping process experience of the outer panel to determine the stamping direction, blank holder surface (2), and process supplementary connection part (3) of the outer panel. The CAS surface or product digital model (1) is placed on the blank holder surface (2) through the process supplementary connection part (3) to construct the drawing process surface of the outer panel.

10. The rigid evaluation method for the formed outer covering part of an automobile according to claim 1, characterized in that In step S1, simulate the stamping forming simulation of the outer panel through 3D modeling software or professional stamping forming simulation software.

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