Numerical simulation method and application of creep aging forming based on initial defects of compressive stress distribution

Abstract

The present invention discloses a numerical simulation method and application of creep aging forming based on initial defects of compressive stress distribution. The method includes establishing a perfect finite element model of creep aging forming without initial defects; extracting finite element simulation results and establishing initial defects based on compressive stress distribution; using the initial defects based on compressive stress distribution to establish a finite element model with initial defects introduced; based on the finite element model with initial defects introduced, after determining material parameters and boundary conditions, perform finite element analysis to obtain wrinkling simulation results. The solution provided by the present invention can improve the accuracy of wrinkling prediction during creep aging forming of sheet metal.

Description

Technical Field

[0001] The invention relates to the technical field of creep aging forming, and in particular to a creep aging forming numerical simulation method and application of initial defects based on compressive stress distribution. Background Art

[0002] With the demand for lightweight, enhanced and high-precision production of products in aerospace, defense, automotive and other manufacturing fields, wrinkling of thin-walled components is becoming more and more common in various forming processes. Wrinkling will affect the forming accuracy, appearance, and subsequent assembly processes. Therefore, the prediction of wrinkling instability defects has gradually become a focus in the field of plastic forming.

[0003] From a mechanical point of view, wrinkling refers to the phenomenon of buckling and post-buckling of plates or shells under local compression overload in a plane. In order to accurately predict wrinkling, scholars have conducted a lot of research, among which analytical methods and numerical simulation methods are the two main analytical methods. The analytical method derives the analytical relationship between the buckling response of the plate and the forming parameters based on the energy method or bifurcation theory, but it is difficult to apply to the actual forming process under complex boundary conditions with strong nonlinearity. The improvement of computing power has made numerical simulation methods the main tool for solving wrinkling instability problems. With the advancement of finite element method (FEM) and the improvement of computer computing power, numerical simulation methods have been widely used in industry and have become a standard tool for design and analysis in the field of plastic forming.

[0004] At present, the numerical simulation methods used to deal with the stability problem of thin shells mainly include eigenvalue buckling analysis method, Riks arc length algorithm, and buckling analysis method with initial defects. Among them, the eigenvalue buckling analysis method is based on linear elastic theory and simplifies the wrinkling problem into solving the eigenvalue problem of the structure, that is, finding the eigenvalue and eigenvector of the structural stability equation. However, since all inelastic effects are ignored in the eigenvalue buckling analysis and all contacts are determined by the basic conditions, its application in nonlinear problems is limited, such as large displacement, large deformation and contact nonlinearity. The Riks arc length method tracks the instability point of the structural force-displacement curve by controlling the arc length on the loading path. However, for some wrinkling instability problems in the plastic forming process, such as the wrinkling problem of non-uniform stretching of plates and the wrinkling problem of flanges, the wrinkling instability of the component does not show an obvious instability point on the force-displacement curve, making the predicted structure of the Riks arc length method unreliable. The finite element analysis method with initial defects is widely used in wrinkling prediction. The purpose of applying initial defects is to establish a deformation mode of the later mesh so as to induce the mesh to achieve correct post-buckling deformation. However, the prediction results are affected by the initial defects imposed. At present, the sources of initial defects mainly include eigenvalue buckling mode, random geometric initial defects, and experimental wrinkling mode. Among them, eigenvalue buckling mode and random geometric initial defects fail to reflect the complex boundary conditions in the actual process of sheet metal forming, and sometimes the real wrinkling mode cannot be obtained. Experimental wrinkling mode can obtain more and better simulation results, but it is "post-hoc", that is, it cannot be known before the actual test.

[0005] In summary, the existing numerical simulation methods for predicting wrinkling during sheet creep aging forming are not accurate enough. Summary of the invention

[0006] In order to solve the technical problem that the existing numerical simulation method for predicting wrinkling during creep aging forming of sheet metal is not accurate enough, an embodiment of the present invention provides a numerical simulation method and application of creep aging forming of initial defects based on compressive stress distribution.

[0007] The technical solution of the embodiment of the present invention is achieved as follows:

[0008] An embodiment of the present invention provides a numerical simulation method for creep aging forming based on initial defects of compressive stress distribution, the method comprising: establishing a perfect finite element model of creep aging forming without initial defects; extracting finite element simulation results and establishing initial defects based on compressive stress distribution; using the initial defects based on compressive stress distribution to establish a finite element model introducing initial defects; based on the finite element model introducing initial defects, after determining material parameters and boundary conditions, perform finite element analysis to obtain wrinkling simulation results.

[0009] In one embodiment, the establishment of a perfect finite element model of creep aging forming without initial defects includes: using preset software to adopt a static implicit algorithm to perform finite element modeling; after determining material parameters and boundary conditions, performing finite element analysis to obtain compressive stress distribution simulation results; based on the compressive stress distribution simulation results, establishing a perfect finite element model of creep aging forming without initial defects.

[0010] In one embodiment, the finite element modeling is performed using a static implicit algorithm using preset software, including: during the modeling process, the mold in the finite element model adopts a smooth surface after springback compensation; the component adopts a forming slab, and the forming slab is an isosceles trapezoidal plate; the lower surface of the component contacts the upper surface of the mold, the contact algorithm is a penalty function method, and the friction coefficient is 0.3; in the finite element model, the forming slab is discretized using No. 75 shell units, 5 integration points are set along the thickness direction, and the unit size is 10mm by 10mm.

[0011] In one embodiment, determining the material parameters includes: determining that the material is 2219T35 aluminum alloy with a density of 0.0027 g / mm 3 , Young's modulus is 67552, Poisson's ratio is 0.3, yield strength is 275.7MPa, and tensile strength is 344.2MPa.

[0012] In one embodiment, determining the boundary conditions includes: determining that all nodes on the central axis of the component limit displacement in y directions; the edge nodes at the small end of the component limit displacement in x directions; and the uniformly distributed compressive stress on the top surface of the unit increases from 0 MPa to 1 MPa in 1 unit time.

[0013] In one embodiment, the finite element analysis includes: simulating a self-weight contact stage, a vacuum preloading stage and an in-tank loading stage; in the self-weight contact stage, the simulated component is in contact with the component under the action of gravity; in the vacuum preloading stage, the component is simulated in the preloading stage of vacuuming outside the tank, and the unit surface pressure rises to 0.1 MPa within 0.1 unit time; in the in-tank loading stage, the component is simulated to be subjected to gas pressurization in the autoclave, and the unit surface pressure rises from 0.1 MPa to 1 MPa within 0.9 time units.

[0014] In one embodiment, the extraction of finite element simulation results and the establishment of initial defects based on compressive stress distribution include: extracting the node numbers and corresponding compressive stress values ​​of the plastic compressive stress zone where the principal stress is less than the yield strength, and normalizing the compressive stress values ​​between the yield strength and the maximum principal stress value to obtain a normalized value.

[0015] In one embodiment, the initial defects based on the compressive stress distribution are used to establish a finite element model with initial defects, including: based on the node number of the plastic compressive stress zone and the normalized value, applying a Z-direction displacement with an amplitude of the normalized value multiplied by the thickness multiplied by 2% to the node corresponding to the node number of the plastic compressive stress zone, so as to perform displacement disturbance on the perfect finite element model of creep aging forming without initial defects, and obtain a finite element model with initial defects.

[0016] An embodiment of the present invention also provides an application of any of the above-mentioned methods for numerical simulation of initial defects of creep aging forming based on compressive stress distribution in the fields of aerospace, national defense and automobile.

[0017] The embodiment of the present invention provides a method and application for numerical simulation of creep aging forming based on initial defects of compressive stress distribution, establishes a perfect finite element model of creep aging forming without initial defects; extracts finite element simulation results, establishes initial defects based on compressive stress distribution; uses the initial defects based on compressive stress distribution to establish a finite element model with initial defects introduced; based on the finite element model with initial defects introduced, determines material parameters and boundary conditions, performs finite element analysis, and obtains wrinkling simulation results. The solution provided by the present invention obtains the introduced initial defect mode by analyzing the stress-strain distribution in the component forming process, and after experimental verification, can accurately predict wrinkling in the creep aging forming process of the component. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a flow chart of a numerical simulation method of creep aging forming based on initial defects of compressive stress distribution according to an embodiment of the present invention;

[0019] Figure 2 It is a schematic diagram of a perfect finite element model of creep aging forming without initial defects in an embodiment of the present invention;

[0020] Figure 3 Schematic diagram of stress-plastic deformation curve of the material of the embodiment of the present invention;

[0021] Figure 4 It is a schematic diagram of initial defects based on compressive stress distribution according to an embodiment of the present invention;

[0022] Figure 5 A schematic diagram of a finite element model for introducing an initial defect in an embodiment of the present invention;

[0023] Figure 6 It is a schematic diagram of the overall process of an embodiment of the present invention;

[0024] Figure 7 This is a schematic diagram of an initial blank according to an embodiment of the present invention;

[0025] Figure 8This is a schematic diagram of the performance of the aluminum alloy material 2219 according to the embodiment of the present invention;

[0026] Fig. 9 This is a schematic diagram of the experimental forming results of an embodiment of the present invention;

[0027] Fig.10 Schematic diagram of the simulation results of the initial defect model of an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0029] The embodiment of the present invention provides a numerical simulation method for creep aging forming of initial defects based on compressive stress distribution, such as Figure 1 As shown, the method includes:

[0030] Step 101: Establishing a perfect finite element model of creep aging forming without initial defects;

[0031] Step 102: extract finite element simulation results and establish initial defects based on compressive stress distribution;

[0032] Step 103: using the initial defect based on the compressive stress distribution, establishing a finite element model with the initial defect introduced;

[0033] Step 104: Based on the finite element model with the initial defects introduced, after determining the material parameters and boundary conditions, a finite element analysis is performed to obtain a wrinkling simulation result.

[0034] The numerical simulation method of creep aging forming based on initial defects of compressive stress distribution proposed in this embodiment obtains the introduced initial defect mode by analyzing the stress-strain distribution during the component forming process. After experimental verification, it can accurately predict the wrinkling during the creep aging forming process of the component.

[0035] Specifically, in one embodiment, the establishment of a perfect finite element model of creep aging forming without initial defects includes: using preset software to adopt a static implicit algorithm to perform finite element modeling; after determining material parameters and boundary conditions, performing finite element analysis to obtain compressive stress distribution simulation results; based on the compressive stress distribution simulation results, establishing a perfect finite element model of creep aging forming without initial defects.

[0036] Here, the large commercial finite element software MSC.MARC can be used for finite element modeling. Considering the complex boundary conditions in the forming process, a static implicit algorithm is used for the stability and convergence of the numerical results. Figure 2As shown in the figure, the mold is a smooth surface after springback compensation and is regarded as a rigid body in the finite element model. The formed plate blank is a component, which is an isosceles trapezoidal plate with a long side of 1400mm, a short side of 600mm, a height of 1400mm, and a thickness of 5mm. It is discretized using shell elements No. 75 in the finite element model, and 5 integration points are set along the thickness direction. The unit size is 10mm by 10mm, and the convergence has been verified. The lower surface of the component will come into contact with the upper surface of the mold. The contact algorithm is the penalty function method, and the friction coefficient is 0.3.

[0037] Here, as shown in Table 1, the material parameters can be determined as follows: The material is determined to be 2219T35 aluminum alloy with a density of 0.0027g / mm 3 , Young's modulus is 67552, Poisson's ratio is 0.3, yield strength is 275.7MPa, and tensile strength is 344.2MPa. In addition, the stress-plastic deformation curve of the material is as follows Figure 3 shown.

[0038] Table 1

[0039]

[0040] Correspondingly, the boundary conditions can be set as follows: the mold serves as a support for the component and is fixedly constrained in all three directions; due to the symmetry of the component, all nodes on the central axis of the component limit displacement in the y direction; the edge nodes at the small end of the component limit displacement in the x direction; the air pressure applied to the component by the autoclave is regarded as a uniformly distributed compressive stress on the top surface of the unit, which increases from 0 MPa to 1 MPa in 1 unit time.

[0041] After determining the material parameters and boundary conditions, a finite element analysis is carried out, which includes three stages. The first working condition is the deadweight contact stage, which simulates the contact between components under the action of gravity. The second working condition is the vacuum preloading stage, which simulates the preloading stage of components being vacuumed outside the tank. The unit surface pressure rises to 0.1 MPa in 0.1 unit time. The third working condition is the in-tank loading stage, which simulates the components being subjected to gas pressurization in the autoclave, and the unit surface pressure rises from 0.1 MPa to 1 MPa in 0.9 time units.

[0042] The above is the process of establishing a perfect finite element model of creep aging forming without initial defects. However, this embodiment introduces initial defects based on compressive stress distribution, and establishes a finite element model with initial defects based on the initial defects of compressive stress distribution; based on the finite element model with initial defects, numerical simulation is performed to obtain wrinkling simulation results.

[0043] Here, the process of extracting the finite element simulation results using python and establishing the initial defect based on the compressive stress distribution is as follows: After analyzing the finite element model established in the first step, the compressive stress distribution simulation results of the perfect defect are obtained, such as Figure 4 As shown. The finite element simulation results are extracted using the python py_post module, and the node numbers of the plastic compressive stress zone where the principal stress is less than the yield strength σ0 are extracted and recorded as Cnodes. The corresponding compressive stress value is recorded as Cstress, and the Cstress value is normalized between the yield strength sigma0 and the maximum principal stress value, recorded as Cstress'. For example, when the compressive stress value is -275.7 (yield strength), it is normalized to 0; when the compressive stress value is -315.2 (maximum compressive stress), it is normalized to 1; when the compressive stress value is -300.0MPa, it is normalized to 0.385.

[0044] After establishing the initial defect based on the compressive stress distribution, Python can be used to apply the initial displacement defect and establish a finite element model with the introduction of the initial defect, referred to as the initial defect model. The specific process is as follows:

[0045] The node number Cnodes of the plastic compressive stress zone and the normalized compressive stress CSTRESS' are obtained. The original mesh model is perturbed by displacement using Python, that is, a Z-direction displacement with an amplitude of CSTRESS' multiplied by the thickness multiplied by 2% is applied to each node in Cnodes to obtain the initial defect model, as shown in Figure 5 As shown in the figure, the cloud diagram is the initial Z-axis displacement defect. The remaining model parameters are consistent with the perfect model, and finite element simulation is performed.

[0046] The embodiment of the present invention provides a numerical simulation method for creep aging forming based on initial defects of compressive stress distribution, establishes a perfect finite element model of creep aging forming without initial defects; extracts finite element simulation results, establishes initial defects based on compressive stress distribution; uses the initial defects based on compressive stress distribution to establish a finite element model with initial defects introduced; based on the finite element model with initial defects introduced, determines material parameters and boundary conditions, performs finite element analysis, and obtains wrinkling simulation results. The solution provided by the present invention obtains the introduced initial defect mode by analyzing the stress-strain distribution in the component forming process, and can accurately predict wrinkling in the creep aging forming process of the component after experimental verification.

[0047] The present application scheme will be described below with a specific experimental case.

[0048] like Figure 6 As shown, this embodiment first constructs a perfect model without initial defects, and then uses a python node perturbation script to establish an initial defect model based on compressive stress distribution.

[0049] Here, the construction process of the perfect model without initial defects is: geometric modeling, determining material parameters, determining boundary conditions, performing finite element analysis, and obtaining compressive stress distribution simulation results. The establishment process of the initial defect model based on compressive stress distribution is: geometric modeling, using Python node perturbation scripts to obtain initial defects based on compressive stress distribution, determining material parameters, determining boundary conditions, performing finite element analysis, and obtaining wrinkling simulation results.

[0050] Specifically, the case adopted in this embodiment is: creep aging forming of 3350mm melon petals of Al2219 aluminum alloy.

[0051] Material 2219 aluminum alloy, component blank size 1400x600x1400mm (isosceles trapezoid), thickness 5mm, such as Figure 7 As shown, the air pressure load is 1MPa and the loading rate is 0.1bar / min. The material properties are shown in Table 2 and the plastic properties are shown in Figure 8 .

[0052] Table 2

[0053]

[0054] The experimental process of this embodiment is as follows: wrap the component with breathable felt, place it on the mold, attach a vacuum bag, evacuate it and move it into the autoclave, and finally load it to 1MPa. The experimental results are as follows Fig. 9 As shown in the figure, a wrinkle defect occurs in the middle of the large end of the component.

[0055] Finite element modeling of this embodiment: the component is discretized using a 4-node shell element, and the mold is regarded as a rigid body. The boundary conditions are: a surface load perpendicular to the unit surface is applied to the upper surface of the component, and the load is uniformly loaded to 1MPa over time; the y-direction displacement constraint is applied to the symmetry line of the component, and the x-direction displacement constraint is applied to the edge node of the small end of the component; the contact between the component and the mold adopts the Coulomb friction model, and the friction coefficient is 0.15. This model has no initial defects and is recorded as a perfect model.

[0056] Initial defects: The simulation results of the perfect model did not cause wrinkling and instability. Extract the nodes and compressive stress in the compressive stress area, use the python script to perform an initial disturbance displacement of the model nodes with an amplitude of (compressive stress value x 0.033%) (so that the maximum deflection amplitude is 2% of the thickness), use the python pymentat module to apply it to the corresponding nodes in the perfect simulation model, and submit the finite element simulation calculation.

[0057] Simulation results: The finite element simulation results with initial displacement defects are shown in Figure 2. Fig.10 As shown, wrinkling defects were produced which were consistent with the test.

[0058] This embodiment proposes a numerical simulation method for introducing initial defects based on compressive stress distribution. The introduced initial defect mode is obtained by analyzing the stress-strain distribution during the component forming process. After experimental verification, it can accurately predict wrinkling during the creep aging forming process of the component.

[0059] This embodiment also provides an application of any of the above-mentioned methods for numerical simulation of initial defects of creep aging forming based on compressive stress distribution in the fields of aerospace, national defense and automobile.

[0060] In order to implement the method of the embodiment of the present invention, the embodiment of the present invention further provides a numerical simulation device for creep aging forming based on initial defects of compressive stress distribution, and the numerical simulation device for creep aging forming based on initial defects of compressive stress distribution includes:

[0061] The first building module is used to build a perfect finite element model of creep aging forming without initial defects;

[0062] Extraction module, used to extract finite element simulation results and establish initial defects based on compressive stress distribution;

[0063] A second establishment module is used to establish a finite element model introducing initial defects by using the initial defects based on the compressive stress distribution;

[0064] The analysis module is used to perform finite element analysis based on the finite element model with the initial defects introduced, after determining the material parameters and boundary conditions, to obtain the wrinkling simulation results.

[0065] In practical applications, the above modules can all be implemented by a processor in a numerical simulation device for creep aging forming of initial defects based on compressive stress distribution.

[0066] It should be noted that: when the above-mentioned device provided in the above-mentioned embodiment is executed, only the division of the above-mentioned program modules is used as an example. In actual application, the above-mentioned processing can be assigned to different program modules as needed, that is, the internal structure of the terminal is divided into different program modules to complete all or part of the above-mentioned processing. In addition, the above-mentioned device provided in the above-mentioned embodiment and the above-mentioned method embodiment belong to the same concept, and the specific implementation process is detailed in the method embodiment, which will not be repeated here.

[0067] In order to implement the method of the embodiment of the present invention, the embodiment of the present invention also provides a computer program product, which includes computer instructions, and the computer instructions are stored in a computer-readable storage medium. The processor of the computer device reads the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions, so that the computer device performs the steps of the above method.

[0068] Based on the hardware implementation of the above program module, and in order to implement the method of the embodiment of the present invention, the embodiment of the present invention also provides an electronic device (computer device). Specifically, in one embodiment, the computer device may be a terminal. The computer device includes a processor, a network interface, a display screen, an input device and a memory connected through a system bus. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes an internal memory and a non-volatile storage medium. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The network interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, the method of any one of the above embodiments is implemented. The display screen of the computer device may be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device may be a touch layer covered on the display screen, or a key, trackball or touchpad provided on the housing of the computer device, or an external keyboard, touchpad or mouse, etc.

[0069] The device provided by the embodiment of the present invention includes a processor, a memory, and a program stored in the memory and executable on the processor. When the processor executes the program, the method of any one of the above embodiments is implemented.

[0070] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0071] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0072] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0073] Computer readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. Information can be computer readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer readable media does not include temporary computer readable media (transitory media), such as modulated data signals and carrier waves.

[0074] It can be understood that the memory of the embodiment of the present invention can be a volatile memory or a non-volatile memory, and can also include both volatile and non-volatile memories. Among them, the non-volatile memory can be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), a magnetic random access memory (FRAM), a flash memory, a magnetic surface memory, an optical disc, or a compact disc read-only memory (CD-ROM); the magnetic surface memory can be a disk memory or a tape memory. The volatile memory can be a random access memory (RAM), which is used as an external cache. By way of example and not limitation, many forms of RAM are available, such as static random access memory (SRAM), synchronous static random access memory (SSRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDRSDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link dynamic random access memory (SLDRAM, SyncLink Dynamic Random Access Memory), and direct RAMbus random access memory (DRRAM, Direct Rambus Random Access Memory).The memories described in the embodiments of the present invention are intended to include, but are not limited to, these and any other suitable types of memories.

[0075] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0076] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. A numerical simulation method for creep aging forming of initial defects based on compressive stress distribution, characterized in that: The method comprises: A perfect finite element model of creep aging forming without initial defects is established; the finite element simulation result of the perfect finite element model of creep aging forming without initial defects is that wrinkling instability does not occur; Extract the finite element simulation results and establish the initial defect based on the compressive stress distribution; Using the initial defect based on the compressive stress distribution, a finite element model with the initial defect introduced is established; the simulation result of the finite element model with the initial defect introduced is wrinkling instability; Based on the finite element model with the initial defects introduced, after determining the material parameters and boundary conditions, a finite element analysis is performed to obtain a wrinkling simulation result; Wherein, the establishment of a perfect finite element model of creep aging forming without initial defects comprises: Finite element modeling using static implicit algorithms using preset software; After determining the material parameters and boundary conditions, a finite element analysis is performed to obtain a compressive stress distribution simulation result; based on the compressive stress distribution simulation result, a perfect finite element model of creep aging forming without initial defects is established; The extracting of finite element simulation results and establishing initial defects based on compressive stress distribution include: Extract the node numbers and corresponding compressive stress values ​​of the plastic compressive stress zone where the principal stress is less than the yield strength, and normalize the compressive stress value between the yield strength and the maximum principal stress value to obtain a normalized value; Wherein, the use of the initial defect based on the compressive stress distribution to establish a finite element model introducing the initial defect includes: Based on the node number of the plastic compressive stress zone and the normalized value, a Z-direction displacement with an amplitude of the normalized value multiplied by the thickness multiplied by 2% is applied to the node corresponding to the node number of the plastic compressive stress zone, so as to perform displacement disturbance on the perfect finite element model of creep aging forming without initial defects, and obtain a finite element model with initial defects introduced.

2. The method for numerical simulation of creep aging forming based on initial defects of compressive stress distribution according to claim 1, characterized in that: The finite element modeling is performed using a static implicit algorithm using preset software, including: In the modeling process, the mold in the finite element model adopts a smooth surface after springback compensation; the component adopts a forming plate blank, and the forming plate blank is an isosceles trapezoidal plate; the lower surface of the component contacts the upper surface of the mold, the contact algorithm is a penalty function method, and the friction coefficient is 0.3; The formed slab is discretized using No. 75 shell elements in the finite element model, 5 integration points are set along the thickness direction, and the element size is 10 mm by 10 mm.

3. The method for numerical simulation of creep aging forming based on initial defects of compressive stress distribution according to claim 1, characterized in that: Determine material parameters, including: The material is determined to be 2219T35 aluminum alloy with a density of 0.0027g / mm 3 , Young's modulus is 67552, Poisson's ratio is 0.3, yield strength is 275.7MPa, and tensile strength is 344.2MPa.

4. The method for numerical simulation of creep aging forming based on initial defects of compressive stress distribution according to claim 1, characterized in that: Determine boundary conditions, including: It is determined that all nodes on the central axis of the component limit displacement in the y direction; the edge nodes at the small end of the component limit displacement in the x direction; the uniformly distributed compressive stress on the top surface of the unit increases from 0MPa to 1MPa in 1 unit time.

5. The method for numerical simulation of creep aging forming based on initial defects of compressive stress distribution according to claim 4, characterized in that: The finite element analysis comprises: Simulate the deadweight contact stage, vacuum preload stage and tank loading stage; In the self-weight contact stage, the simulated components come into contact with each other under the action of gravity; in the vacuum preloading stage, the simulated components are in the preloading stage of vacuuming outside the tank, and the unit surface pressure rises to 0.1MPa in 0.1 unit time; in the in-tank loading stage, the simulated components are subjected to gas pressurization in the autoclave, and the unit surface pressure rises from 0.1MPa to 1MPa in 0.9 time units.

6. Application of the creep aging forming numerical simulation method based on initial defects of compressive stress distribution according to any one of claims 1 to 5 in the fields of aerospace, national defense and automobile.

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