A Numerical Simulation-Based Optimization Method for Longitudinal Stretching Process Parameters of Skin

Abstract

This invention provides a numerical simulation-based method for optimizing longitudinal stretching process parameters of skin panels. By comprehensively modeling and performing finite element analysis on the skin, mold, and stretching equipment, targeted extraction and calculation of equipment and product data involved in the process can be achieved. Combined with repeated numerical simulations, iterative optimization of process parameters can be realized solely on the software platform. Based on this, the modeling and optimization process is further adjusted through a small number of actual equipment tests, ultimately outputting the optimal process parameters. This avoids the extensive and complex preliminary trial-and-error verification and empirical data collection processes found in existing technologies, ensuring not only the accuracy of process parameters and skin forming but also significantly improving efficiency.

Description

Technical Field

[0001] This invention belongs to the field of aircraft skin manufacturing and processing technology, specifically relating to a method for optimizing longitudinal stretching process parameters of skin based on numerical simulation. Background Technology

[0002] Currently, for the skin, a critical component in aircraft structures, the mainstream processing method is to obtain the required shape and size by performing metal stretching forming. Controlling and adjusting various process parameters such as clamping force, stretching stroke, and speed during the longitudinal stretching process is extremely complex. To ensure the precision of the stretching process and to ensure that the product quality and processing accuracy meet design requirements in actual production, extensive trial-and-error verification and experience-based optimization are often required in the early stages. With the emergence of various new skin component designs, repeated verification is unavoidable, leading to severely low efficiency. Furthermore, insufficient accumulation of relevant experience hinders the achievement of optimal parameter optimization results. Summary of the Invention

[0003] In view of this, and to address the technical problems existing in this field, the present invention provides a method for optimizing the longitudinal stretching process parameters of skin based on numerical simulation, specifically including the following steps:

[0004] Step 1: Based on the design shape and size of the skin component, establish a 3D model including the skin of a specific material, mold, clamp, and longitudinal tensioning equipment, and perform finite element simulation. Mesh the skin model and determine the various material property parameters of different parts of the skin model through simulation analysis.

[0005] Step 2: In the finite element simulation, the constraints during the stretching process are determined by setting the fixed part of the mold model to be movable part, and the loading actions of the clamp and longitudinal tensioning equipment model are designed.

[0006] Step 3: Execute the designed loading action based on the constraints, and perform initial numerical simulations on the deformation, stress, strain, and thickness of the skin model during the stretching process; identify product and process defects in the skin model, including wrinkling, cracking, slip lines, and springback, based on the initial simulation results, and adjust the constraints and process parameters related to the loading action; production cost factors are also considered in the parameter adjustment.

[0007] Step 4: Repeat the process of loading actions, numerical simulation, and parameter adjustment until the product and process defects of the skin model are eliminated and the design requirements are met, and output the corresponding combination of process parameters.

[0008] Step 5: Based on the process parameter combination obtained in Step 4, perform longitudinal tension verification of the skin on actual equipment, record the skin material variation parameters, product and process defects during the process, and compare the results with the numerical simulation process; based on the comparison results, revise the established three-dimensional model, constraints and loading actions again.

[0009] Step Six: Based on the process parameter combination obtained through dual verification by finite element simulation and actual equipment, further adjustments are made considering product quality, production efficiency, and cost to finally obtain the optimal process parameter combination.

[0010] Furthermore, in step one, when establishing the skin model, material property parameters, including elastic modulus, Poisson's ratio, and yield strength, are assigned to different mesh regions; and mesh refinement is performed on key skin regions, including contact surfaces and stress concentration areas.

[0011] Furthermore, the loading action designed in step two includes the loading trajectory and loading rate.

[0012] Furthermore, the production cost factors considered when adjusting process parameters should include at least material utilization and the total equipment load of the stretching process.

[0013] Furthermore, the combination of process parameters adjusted through numerical simulation results consists of process parameters such as mold closing pressure, mold closing distance, tie rod extension stroke, tie rod pitch angle, worktable lifting height, and extension action time.

[0014] The numerical simulation-based method for optimizing longitudinal stretching process parameters of skin provided by this invention enables the targeted extraction and calculation of equipment and product data involved in the process through comprehensive modeling and finite element analysis of the skin, mold, and stretching equipment. Combined with repeated numerical simulations, iterative optimization of process parameters can be achieved solely on the software platform. Based on this, the modeling and optimization process is further adjusted through a small number of actual equipment tests, ultimately outputting the optimal process parameters. This avoids the extensive and complex preliminary trial-and-error verification and empirical data collection processes found in existing technologies, ensuring not only the accuracy of process parameters and skin forming but also significantly improving efficiency. Attached Figure Description

[0015] Figure 1 A flowchart of the method provided by the present invention;

[0016] Figure 2 This is a schematic diagram of a longitudinal skin stretching device. Detailed Implementation

[0017] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] The method for optimizing longitudinal stretching process parameters of skin based on numerical simulation provided by this invention, such as... Figure 1 As shown, the specific steps include:

[0019] Step 1: Based on the design shape and size of the skin component, use software such as CATIA to create a skin model that includes specific materials, such as... Figure 2 The three-dimensional models of the mold, clamp, and longitudinal tensioning equipment are shown and imported into finite element analysis software for simulation. The skin model is meshed, and the various material property parameters of different parts of the skin model are determined through simulation analysis.

[0020] Step 2: In the finite element simulation, the constraints during the stretching process are determined by setting the mold model with some parts fixed and some parts movable. The loading actions of the clamp and longitudinal tensioning equipment model are designed. Through reasonable loading actions, the actual production process can be better simulated, providing a scientific basis for the subsequent optimization of process parameters.

[0021] Step 3: Execute the designed loading action based on the constraints, and perform initial numerical simulations on the deformation, stress, strain, and thickness of the skin model during the stretching process; identify product and process defects in the skin model, including wrinkling, cracking, slip lines, and springback, based on the initial simulation results, and adjust the constraints and process parameters related to the loading action; production cost factors are also considered in the parameter adjustment.

[0022] Step 4: Repeat the process of loading actions, numerical simulation, and parameter adjustment until the product and process defects of the skin model are eliminated and the design requirements are met, and output the corresponding combination of process parameters.

[0023] Step 5: Based on the process parameter combination obtained in Step 4, perform longitudinal tension verification of the skin on actual equipment. Record data during the process, such as tensile force, displacement, velocity, flow of skin material, and whether defects are generated. Compare the results with the numerical simulation process. If the two are close or consistent, it indicates that the process parameters obtained after the numerical simulation have reached a good level. If the two differ significantly, the simulation process and process parameter results need to be re-examined, and the established 3D model, constraints, and loading actions need to be revised again based on the comparison results.

[0024] Step Six: Based on the process parameter combination obtained through dual verification by finite element simulation and actual equipment, further adjustments are made considering product quality, production efficiency, and cost to finally obtain the optimal process parameter combination.

[0025] In a preferred embodiment of the present invention, step one involves assigning material property parameters, including elastic modulus, Poisson's ratio, and yield strength, to different mesh division regions when establishing the skin model; and performing mesh refinement processing on key skin regions, including contact surfaces and stress concentration areas.

[0026] In a preferred embodiment of the present invention, the loading action designed in step two includes a loading trajectory and a loading rate. The loading trajectory is designed for the shape of the mold to ensure that the skin fits the mold perfectly. The loading rate is adjusted according to the actual production situation to simulate the real stretching process.

[0027] In a preferred embodiment of the present invention, the production cost factors considered when adjusting process parameters include at least material utilization rate and total equipment load of the stretching process.

[0028] In a preferred embodiment of the present invention, the combination of process parameters adjusted by numerical simulation results specifically consists of process parameters such as mold closing pressure, mold closing distance, tie rod stretching stroke, tie rod pitch angle, worktable lifting height, and stretching action time.

[0029] In a specific embodiment of the present invention, preliminary process parameter optimization results can be obtained by performing the following numerical simulation process:

[0030] Initial parameter settings: For example, when producing a double-curvature skin for an aircraft, the initial settings for the stretching stroke are 60mm, the pitch angle is 30°, the table lifting height is 15mm, the upper mold pressure is 25MPa, and the mold closing distance is 3mm.

[0031] Numerical simulation: Using finite element analysis software, it was found that wrinkling occurred at the edge of the material, and the local thickness reduction rate exceeded 5%.

[0032] Parameter adjustment: Based on the simulation results, the stretching stroke was reduced to 55mm to decrease the stretching of the material; at the same time, the mold closing distance was increased to 3.5mm to avoid wrinkling. Keeping other parameters unchanged, the numerical simulation was performed again.

[0033] Multiple iterations: After several iterations, a better combination of parameters was found: stretching stroke of 50mm, pitch angle adjusted to 35°, table lifting height of 18mm, upper die pressure of 22MPa, and die closing distance of 3.2mm. Under these parameters, simulation results show that the material flow is more uniform, the thickness reduction rate is controlled within 4%, and there is no obvious wrinkling or cracking.

[0034] Convergence judgment: If the results of two consecutive iterations show little change without obvious wrinkling or cracking, and meet the preset convergence criteria (e.g., the change in thickness reduction rate is less than 1%), it is considered that the optimal combination of process parameters has been found.

[0035] It should be understood that the sequence number of each step in the embodiments of the present invention does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0036] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for optimizing longitudinal stretching process parameters of skin based on numerical simulation, characterized in that: Specifically, the following steps are included: Step 1: Based on the design shape and size of the skin component, establish a 3D model including the skin of a specific material, mold, clamp, and longitudinal tensioning equipment, and perform finite element simulation. Mesh the skin model and determine the various material property parameters of different parts of the skin model through simulation analysis. Step 2: In the finite element simulation, the constraints during the stretching process are determined by setting the mold model with some fixed parts and others moving, and the loading actions of the clamps and longitudinal tensioning equipment models are designed. Step 3: Execute the designed loading action based on the constraints, and perform initial numerical simulations on the deformation, stress, strain, and thickness data of the skin model during the stretching process; Based on the initial simulation results, product and process defects in the skin model, including wrinkling, cracking, slip lines, and springback, were identified, and the constraints and process parameters related to the loading action were adjusted. Production cost factors were also considered in the parameter adjustment. Step 4: Repeat the process of loading actions, numerical simulation, and parameter adjustment until the product and process defects of the skin model are eliminated and the design requirements are met, and output the corresponding combination of process parameters. Step 5: Based on the process parameter combination obtained in Step 4, perform longitudinal tension verification of the skin on actual equipment, record the skin material variation parameters, product and process defects during the process, and compare the results with the numerical simulation process; based on the comparison results, revise the established three-dimensional model, constraints and loading actions again. Step Six: Based on the process parameter combination obtained through dual verification by finite element simulation and actual equipment, further adjustments are made considering product quality, production efficiency, and cost to finally obtain the optimal process parameter combination.

2. The method as described in claim 1, characterized in that: Step one involves assigning material property parameters, including elastic modulus, Poisson's ratio, and yield strength, to different mesh regions when establishing the skin model; and performing mesh refinement for key skin regions, including contact surfaces and stress concentration areas.

3. The method as described in claim 1, characterized in that: The loading action designed in step two includes the loading trajectory and loading rate.

4. The method as described in claim 1, characterized in that: When adjusting process parameters, the production cost factors to be considered should include at least material utilization and the total equipment load of the stretching process.

5. The method as described in claim 1, characterized in that: The combination of process parameters adjusted based on numerical simulation results consists of mold closing pressure, mold closing distance, tie rod extension stroke, tie rod pitch angle, worktable lifting height, and extension action time parameters.

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