Skin longitudinal drawing process parameter optimization method based on numerical simulation

Abstract

According to the numerical simulation-based skin longitudinal stretching process parameter optimization method provided by the invention, comprehensive modeling and finite element analysis are carried out on a skin, a mold and longitudinal stretching equipment, so that equipment and product data involved in the process can be extracted and calculated in a targeted manner. And in cooperation with repeatedly executed numerical simulation, iterative optimization of process parameters can be realized only on a software platform. On the basis, the modeling and optimizing process is adjusted again through a small number of actual equipment tests, the optimal technological parameters are finally output, a large number of complicated early-stage trial and error verification and empirical data collection processes in the prior art are avoided, the technological parameters and the skin forming precision are guaranteed, and efficiency is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of aircraft skin manufacturing and processing, and in particular relates to a method for optimizing skin longitudinal drawing process parameters based on numerical simulation. Background Art

[0002] At present, the mainstream processing method for the skin, a key component in the aircraft structure, is to obtain the required shape and size by performing the stretch forming process of metal materials. The control and adjustment of various process parameters such as clamping force, stretching stroke and speed during the longitudinal stretching of the skin is very complicated. In order to ensure the control accuracy of the stretching process and make the product quality and processing accuracy meet the design requirements during actual production, it is often necessary to conduct a lot of trial and error verification in the early stage and combine experience to obtain better parameters. With the emergence of various new skin component designs, it is inevitable to repeatedly perform the above verification work, which makes the efficiency seriously low. At the same time, the insufficient accumulation of relevant experience is not conducive to obtaining better parameter optimization results. Summary of the invention

[0003] In view of this, in order to solve the technical problems existing in the art, the present invention provides a method for optimizing skin longitudinal drawing process parameters based on numerical simulation, which specifically includes the following steps:

[0004] Step 1: According to the designed shape and size of the skin parts, a three-dimensional model including the skin of specific materials, molds, clamps and longitudinal pulling equipment is established and finite element simulation is performed, the skin model is meshed, and various material property parameters of different parts of the skin model are determined through simulation analysis;

[0005] Step 2: In the finite element simulation, the constraint conditions in the stretching process are determined by setting the mold model to be partially fixed and partially movable, and the loading action of the clamp and longitudinal stretching equipment model is designed;

[0006] Step 3: Execute the designed loading action based on the constraint conditions, and perform initial numerical simulation on the deformation, stress, strain, thickness and other data of the skin model during the stretching process; identify the product and process defects of the skin model including wrinkles, ruptures, slip lines and springback according to the initial simulation results, and adjust the process parameters related to the constraint conditions and loading action; and consider the production cost factor in the parameter adjustment;

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

[0008] Step 5: Based on the process parameter combination obtained in step 4, the skin longitudinal pulling verification is carried out on the actual equipment, the skin material change parameters, product and process defects in the process are recorded, and the results are compared with the numerical simulation process; according to the comparison results, the established three-dimensional model, constraint conditions and loading actions are revised again;

[0009] Step 6: For the process parameter combination obtained after dual verification through finite element simulation and actual equipment verification, make adjustments again by comprehensively considering product quality, production efficiency and cost, and finally obtain the best process parameter combination.

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

[0011] Furthermore, the loading action designed in step 2 includes a loading trajectory and a loading rate.

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

[0013] Furthermore, the process parameter combination adjusted by the numerical simulation results specifically consists of process parameters such as mold clamping pressure, mold clamping distance, tie rod stretching stroke, tie rod pitch angle, workbench lifting height, and stretching action time.

[0014] The method for optimizing the process parameters of longitudinal skin stretching based on numerical simulation provided by the present invention enables the equipment and product data involved in the process to be extracted and calculated in a targeted manner by comprehensively modeling and finite element analysis of the skin, mold and longitudinal stretching equipment. With the help of repeated numerical simulation, iterative optimization of process parameters can be achieved only on the software platform. On this basis, the modeling and optimization process is adjusted again through a small amount of actual equipment tests, and the optimal process parameters are finally output, thereby avoiding a large number of complicated preliminary trial and error verification and empirical data collection processes in the prior art, which not only ensures the accuracy of process parameters and skin forming, but also significantly improves efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0016] Figure 2 Schematic diagram of the longitudinal skin stretching equipment. DETAILED DESCRIPTION

[0017] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] The method for optimizing the process parameters of the longitudinal drawing of the skin based on numerical simulation provided by the present invention is as follows: Figure 1 As shown, the specific steps include:

[0019] Step 1: Based on the design shape and size of the skin parts, use CATIA and other software to create a skin with specific materials, such as Figure 2 The three-dimensional models of the mold, clamp and longitudinal drawing equipment shown in the figure are imported into the finite element analysis software for simulation, the skin model is meshed, and 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 constraint conditions in the stretching process are determined by setting the mold model to be partially fixed and partially movable, and the loading action of the clamp and longitudinal drawing equipment model is designed. Through reasonable loading actions, the actual production process can be better simulated to provide a scientific basis for the optimization of subsequent process parameters;

[0021] Step 3: Execute the designed loading action based on the constraint conditions, and perform initial numerical simulation on the deformation, stress, strain, thickness and other data of the skin model during the stretching process; identify the product and process defects of the skin model including wrinkles, ruptures, slip lines and springback according to the initial simulation results, and adjust the process parameters related to the constraint conditions and loading action; and consider the production cost factor in the parameter adjustment;

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

[0023] Step 5: Based on the process parameter combination obtained in step 4, the skin longitudinal pulling verification is carried out on the actual equipment, and the data in the process such as tensile force, displacement, speed, flow of skin material, whether defects are generated, etc. are recorded, and the results are compared with the numerical simulation process. If the two are close or consistent, it means that the process parameters obtained after the completion of the numerical simulation have reached a good level; if the two are very different, it is necessary to review the simulation process and process parameter results, and the established three-dimensional model, constraint conditions and loading actions need to be revised again according to the comparison results;

[0024] Step 6: For the process parameter combination obtained after dual verification through finite element simulation and actual equipment verification, make adjustments again by comprehensively considering product quality, production efficiency and cost, and finally obtain the best process parameter combination.

[0025] In a preferred embodiment of the present invention, step one allocates material property parameters including elastic modulus, Poisson's ratio, yield strength, etc. to different mesh division areas when establishing the skin model; and performs mesh refinement processing on key skin areas 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 according to the mold shape to ensure that the skin fits the mold perfectly, and the loading rate is adjusted according to actual production conditions to simulate the real stretching process.

[0027] In a preferred embodiment of the present invention, the production cost factors considered when adjusting the 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 process parameter combination adjusted by numerical simulation results specifically consists of process parameters such as mold clamping pressure, mold clamping distance, tie rod stretching stroke, tie rod pitch angle, workbench lifting height, and stretching action time.

[0029] In a specific example of the present invention, a preliminary process parameter optimization result can be obtained by executing the following numerical simulation process:

[0030] Initial parameter setting: For example, when producing a hyperbolic skin for an aircraft, through longitudinal pulling equipment processing, the initial setting of the stretching stroke is 60mm, the pitch angle is 30°, the workbench lifting height is 15mm, the upper mold pressure is 25MPa, and the mold spacing is 3mm.

[0031] Numerical simulation: Finite element analysis software was used for simulation, and it was found that wrinkles appeared in the edge area of ​​the material, and the local thickness reduction rate exceeded 5%.

[0032] Parameter adjustment: According to the simulation results, the stretching stroke was reduced to 55mm to reduce the stretching degree of the material; at the same time, the mold spacing 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: the stretching stroke was 50mm, the pitch angle was adjusted to 35°, the worktable lifting height was 18mm, the upper die pressure was 22MPa, and the die spacing was 3.2mm. Under this set of parameters, the simulation results showed that the material flow was more uniform, the thickness reduction rate was controlled within 4%, and there was no obvious wrinkling or cracking.

[0034] Convergence judgment: In the absence of obvious wrinkling or cracking, if the results of two consecutive iterations change little and meet the preset convergence criteria (for example, the change in thickness reduction rate is less than 1%), it is considered that the optimal process parameter combination has been found.

[0035] It should be understood that the size of the serial numbers of the steps in the embodiment of the present invention does not mean 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 embodiment of the present invention.

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

Claims

1. A method for optimizing skin longitudinal drawing process parameters based on numerical simulation, characterized in that: The specific steps include: Step 1: According to the designed shape and size of the skin parts, a three-dimensional model including the skin of specific materials, molds, clamps and longitudinal pulling equipment is established and finite element simulation is performed, the skin model is meshed, and various material property parameters of different parts of the skin model are determined through simulation analysis; Step 2: In the finite element simulation, the constraint conditions in the stretching process are determined by setting the mold model to be partially fixed and partially movable, and the loading action of the clamp and longitudinal stretching equipment model is designed; Step 3: Execute the designed loading action based on the constraint conditions, and perform initial numerical simulation on the deformation, stress, strain, thickness and other data of the skin model during the stretching process; Identify product and process defects of the skin model including wrinkles, cracks, slip lines and springback based on the initial simulation results, and adjust the process parameters related to the constraints and loading actions; also consider production cost factors in parameter adjustment; Step 4: Repeat the process of action loading-numerical simulation-parameter adjustment until the product and process defects of the skin model are eliminated and the design requirements are met, and output the corresponding process parameter combination; Step 5: Based on the process parameter combination obtained in step 4, the skin longitudinal pulling verification is carried out on the actual equipment, the skin material change parameters, product and process defects in the process are recorded, and the results are compared with the numerical simulation process; according to the comparison results, the established three-dimensional model, constraint conditions and loading actions are revised again; Step 6: For the process parameter combination obtained after dual verification through finite element simulation and actual equipment verification, make adjustments again by comprehensively considering product quality, production efficiency and cost, and finally obtain the best process parameter combination.

2. The method according to claim 1, characterized in that: Step 1: When establishing the skin model, material property parameters including elastic modulus, Poisson's ratio, and yield strength are specifically allocated to different mesh division areas; mesh refinement is performed on key skin areas including contact surfaces and stress concentration areas.

3. The method according to claim 1, characterized in that: The loading action designed in step 2 includes loading trajectory and loading rate.

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

5. The method according to claim 1, characterized in that: The process parameter combination adjusted by numerical simulation results specifically consists of mold clamping pressure, mold clamping distance, tie rod stretching stroke, tie rod pitch angle, workbench lifting height, and stretching action time parameters.

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