Method for controlling formability and creep age forming property of aluminum alloy sheet

Abstract

The application discloses a kind of aluminum alloy sheet creep age shape nature synergic regulation and control method, it is in warm box simultaneously, then through local pulse electromagnetic field auxiliary localized regulation and control aluminum alloy sheet's creep age behavior of difficult forming weak performance area, improve the mechanical properties and size accuracy of aluminum alloy sheet.One aspect, the thermal effect and non-thermal effect of pulse electromagnetic field can promote the phase transition and recrystallization of the difficult forming area of aluminum alloy sheet, thereby refining grains, improve the mechanical properties of aluminum alloy sheet;On the other hand, temperature control and vacuum loading are used to apply stress to the aluminum alloy sheet, and under the combined action of eddy current, pulse magnetic field and alternating Lorentz force generated by electromagnetic field, the release of residual stress in the difficult forming area of aluminum alloy sheet is accelerated, so that the originally difficult forming area realizes forming quickly, improves the forming efficiency and forming accuracy of aluminum alloy sheet, and achieves the goal of overall component shape nature synergic manufacturing.

Description

Technical Field

[0001] This invention relates to the field of creep aging forming technology for aluminum alloy components, and particularly to a method for controlling the synergistic effect of creep aging forming properties on thin aluminum alloy sheets. Background Technology

[0002] Aluminum alloy sheets are widely used in aerospace products, and their performance directly impacts product usability. To achieve excellent form and properties simultaneously, creep aging forming technology, employing a form-property co-manufacturing approach, has been developed both domestically and internationally. This technology primarily involves packaging components and molds in vacuum bags and using vacuum pressure loading to achieve bonding between the components and molds. Form-property co-manufacturing is then achieved through temperature and pressure control. However, due to the complex stress state of large aluminum alloy sheets during creep aging forming, insufficient deformation in localized areas results in poor mechanical properties, making it difficult to simultaneously achieve both forming accuracy and mechanical property control across different regions of the aluminum alloy sheet. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for controlling the creep aging and shape properties of aluminum alloy thin plates in a coordinated manner. This method solves the problem that it is difficult to balance the forming accuracy and mechanical properties of aluminum alloy components, and significantly improves the mechanical properties, forming accuracy and forming efficiency of large aluminum alloy thin plates.

[0004] The technical solution adopted by this invention to solve the above-mentioned technical problems is as follows: a method for controlling the synergistic effect of creep aging on aluminum alloy thin plates, comprising the following specific steps:

[0005] (1) A creep aging constitutive model of aluminum alloy thin plate under normal conditions was established by using MATLAB software and numerical optimization algorithm;

[0006] (2) Embed the creep aging constitutive model under normal conditions into the finite element analysis software, establish the conventional creep aging finite element simulation model of aluminum alloy thin plate, and determine the difficult-to-form weak performance region of aluminum alloy thin plate and the arrangement region of electromagnetic induction coil.

[0007] (3) Based on the determined arrangement area of ​​the electromagnetic induction coil, a creep aging constitutive model of aluminum alloy thin plate under pulsed electromagnetic field assisted conditions is established by MATLAB software and numerical optimization algorithm.

[0008] (4) Embed the creep aging constitutive model under pulsed electromagnetic field assisted conditions into the finite element analysis software, establish the creep aging finite element simulation model of aluminum alloy thin plate after local pulsed electromagnetic field assisted conditions, and determine the optimal pulsed electromagnetic field parameters.

[0009] (5) Place the aluminum alloy sheet on the mold and fix an insulating film in the difficult-to-form and weak performance area of ​​the aluminum alloy sheet.

[0010] (6) Wrap a breathable felt around the coil and place the coil wrapped with the breathable felt on an insulating film. Then cover the aluminum alloy sheet with a vacuum bag and seal the vacuum bag with the mold to keep the aluminum alloy sheet in a closed environment.

[0011] (7) Place the entire mold containing the aluminum alloy sheet into the temperature chamber, evacuate the vacuum bag, and perform creep aging forming. At the same time, perform pulse electromagnetic field treatment on the aluminum alloy sheet. Specifically, turn on the pulse power supply device and pass a pulse current through the coil above the aluminum alloy sheet. The pulse electromagnetic field parameters are the optimal pulse electromagnetic field parameters determined in step (3). Then, a pulse magnetic field is generated around the coil, which generates an induced pulse current, a pulse magnetic field, and an alternating Lorentz force on the aluminum alloy sheet below the coil, so that the aluminum alloy sheet is rapidly heated to the target temperature.

[0012] (8) After creep is complete, turn off the pulse power supply and remove the aluminum alloy sheet from the temperature chamber.

[0013] Furthermore, the creep-aging constitutive model in steps (1) and (3) is a system of nonlinear differential equations, specifically:

[0014] (01) (02)

[0015] Wherein: (01) is the constitutive model of creep aging under normal conditions; (02) is the constitutive model of creep aging assisted by pulsed electromagnetic field; ε eq σ is the equivalent yield strain of the aluminum alloy sheet. eq f is the equivalent yield stress of the aluminum alloy sheet. v σ represents the volume fraction of the precipitated phase in the aluminum alloy sheet, ρ represents the dislocation density of the aluminum alloy sheet material; y σ is the yield strength of the aluminum alloy sheet material. i σ represents the strength of the aluminum matrix. dis σ is the dislocation strength of the aluminum alloy sheet material. ss σ is the solid solution strength of aluminum alloy sheet material. ppt Let be the precipitation intensity of the aluminum alloy sheet, l be the length of the precipitated phase in the aluminum alloy sheet, d be the thickness of the precipitated phase in the aluminum alloy sheet, q be the ratio of the length to the thickness of the precipitated phase, t be the creep aging time of the aluminum alloy sheet, i be the induced current density of the pulsed electromagnetic field, and T be the induced magnetic field strength of the pulsed electromagnetic field.

[0016] Furthermore, the finite element analysis software used in steps (2) and (4) is Abaqus finite element analysis software.

[0017] Further, in step (4), the specific process for determining the optimal pulse electromagnetic field parameters is as follows: First, use ANSYS simulation software to simulate the electromagnetic field module of the aluminum alloy sheet. Then, use ANSYS simulation software to output the simulation results of the pulse electromagnetic field parameters as an .inp file and import them into the Abaqus finite element analysis software as boundary conditions for the creep aging forming of the aluminum alloy sheet. Next, calculate the creep aging forming deformation. After the simulation is completed, compare the deviation between the surface of the aluminum alloy sheet after creep and the required surface. If the deviation is less than the target range, the pulse electromagnetic field parameters obtained above are taken as the optimal pulse electromagnetic field parameters. If the deviation is greater than the target range, the pulse electromagnetic field parameters are changed according to the deviation results, and the above simulation steps are repeated until the deviation between the simulated surface of the aluminum alloy sheet and the required surface is within the target range, and the corresponding pulse electromagnetic field parameters are taken as the optimal pulse electromagnetic field parameters.

[0018] Furthermore, the pulsed electromagnetic field parameters are Lorentz force, pulsed eddy current, and magnetic field strength.

[0019] Furthermore, in step (7), the vacuum atmospheric pressure inside the vacuum bag is 0.06 to 0.1 MPa.

[0020] Furthermore, in step (6), the diameter of the metal wire in the coil is 1 to 5 mm, and the number of coil turns is 5 to 20.

[0021] Furthermore, in step (7), the temperature of the temperature chamber is controlled to be 120-180°C, and the parameters of the pulse current introduced are: current of 50-500A, pulse period of 0.02-0.1s, pulse duration of 0.001-0.03s, and magnetic field strength of 0.05-0.3T.

[0022] Compared with existing technologies, the advantages of this invention are: while employing vacuum creep aging of aluminum alloy sheets in a temperature chamber, the creep aging behavior of the difficult-to-form, weak-performance regions of the aluminum alloy sheets is further controlled by localized pulsed electromagnetic fields, significantly improving the mechanical properties and dimensional accuracy of the aluminum alloy sheets. On the one hand, the thermal and non-thermal effects of the pulsed electromagnetic field can promote phase transformation and recrystallization in the difficult-to-form regions of the aluminum alloy sheets, thereby refining the grains and improving the mechanical properties of the aluminum alloy sheets. On the other hand, while applying compressive stress to the aluminum alloy sheets using temperature control in the temperature chamber and vacuum loading, the release of residual stress inside the difficult-to-form regions of the aluminum alloy sheets is accelerated under the combined action of eddy currents, pulsed magnetic fields, and alternating Lorentz forces generated by the electromagnetic field, enabling the originally difficult-to-form regions to be formed quickly, improving the forming efficiency and forming accuracy of the aluminum alloy sheets, and achieving the goal of synergistic manufacturing of the overall component's shape and properties. In addition, the pulsed electromagnetic field can promote dislocation movement in the aluminum alloy sheets, accelerate the precipitation of precipitates, and improve the strength of the aluminum alloy sheets. Attached Figure Description

[0023] Figure 1 This is a structural diagram of the creep aging forming apparatus of the present invention;

[0024] Figure 2 for Figure 1 A magnified view of a portion of point A in the middle;

[0025] Figure 3 This is a flowchart of the local pulsed electromagnetic field-assisted creep aging simulation of the present invention;

[0026] Figure 4a The diagram shows the forming deviation of aluminum alloy sheet after conventional creep aging forming.

[0027] Figure 4b The figure shows the forming deviation results of aluminum alloy sheet after creep aging forming assisted by local pulsed electromagnetic field. Detailed Implementation

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

[0029] As shown in the figure, a method for synergistic control of creep aging and shape properties in aluminum alloy thin sheets includes the following specific steps:

[0030] (1) A creep aging constitutive model of aluminum alloy thin sheet under normal conditions was established by using MATLAB software and numerical optimization algorithm; the normal conditions here refer to the existing creep aging forming method mentioned in the background technology, that is, without the addition of pulse electromagnetic field auxiliary conditions.

[0031] (2) Embed the creep aging constitutive model under normal conditions into the Abaqus finite element analysis software to establish a conventional creep aging finite element simulation model of aluminum alloy thin plate, and determine the difficult-to-form weak performance region of aluminum alloy thin plate and the arrangement region of electromagnetic induction coil.

[0032] (3) Based on the determined arrangement area of ​​the electromagnetic induction coil, a creep aging constitutive model of aluminum alloy thin plate under pulsed electromagnetic field assisted conditions is established by MATLAB software and numerical optimization algorithm.

[0033] The creep-aging constitutive model is a set of nonlinear differential equations, specifically:

[0034] (01) (02)

[0035] Wherein: (01) is the constitutive model of creep aging under normal conditions; (02) is the constitutive model of creep aging assisted by pulsed electromagnetic field; ε eq σ is the equivalent yield strain of the aluminum alloy sheet. eqf is the equivalent yield stress of the aluminum alloy sheet. v σ represents the volume fraction of the precipitated phase in the aluminum alloy sheet, ρ represents the dislocation density of the aluminum alloy sheet material; y σ is the yield strength of the aluminum alloy sheet material. i σ represents the strength of the aluminum matrix. dis σ is the dislocation strength of the aluminum alloy sheet material. ss σ is the solid solution strength of aluminum alloy sheet material. ppt Let be the precipitation intensity of the aluminum alloy sheet, l be the length of the precipitated phase in the aluminum alloy sheet, d be the thickness of the precipitated phase in the aluminum alloy sheet, q be the ratio of the length to the thickness of the precipitated phase, t be the creep aging time of the aluminum alloy sheet, i be the induced current density of the pulsed electromagnetic field, and T be the induced magnetic field strength of the pulsed electromagnetic field.

[0036] (4) Embed the creep aging constitutive model under pulsed electromagnetic field assistance into the Abaqus finite element analysis software to establish a creep aging finite element simulation model of aluminum alloy thin plate after local pulsed electromagnetic field assistance. Then determine the optimal pulsed electromagnetic field parameters, which are Lorentz force, pulsed eddy current, and magnetic field strength. The specific method for determining the optimal pulsed electromagnetic field parameters is as follows:

[0037] First, the electromagnetic field module of the aluminum alloy sheet is simulated using ANSYS simulation software. The simulation results of the pulse electromagnetic field parameters are output as an .inp file by ANSYS simulation software and imported into Abaqus finite element analysis software as boundary conditions for the creep aging forming of the aluminum alloy sheet. Then, the creep aging forming deformation is calculated. After the simulation is completed, the deviation between the surface of the aluminum alloy sheet after creep and the required surface is compared and analyzed. If the deviation is less than the target range, the pulse electromagnetic field parameters obtained above are taken as the optimal pulse electromagnetic field parameters. If the deviation is greater than the target range, the pulse electromagnetic field parameters are changed according to the deviation results, and the above simulation steps are repeated until the deviation between the simulated surface of the aluminum alloy sheet and the required surface is within the target range, and the corresponding pulse electromagnetic field parameters are taken as the optimal pulse electromagnetic field parameters.

[0038] (5) Place the aluminum alloy sheet 1 on the mold 2, and lay an insulating film 3 in the difficult-to-form weak performance area of ​​the aluminum alloy sheet 1. The insulating film 3 completely covers the difficult-to-form weak performance area of ​​the aluminum alloy sheet 1, and is pasted to the aluminum alloy sheet 1 with sealant, and is kept flat and without overlap above the difficult-to-form area.

[0039] (6) Wrap the coil 4 with a breathable felt 5 and place the coil 4 wrapped with the breathable felt 5 on the insulating film 3. The diameter of the metal wire in the coil 4 is 1-5 mm and the number of coil turns is 5-20. Then cover the aluminum alloy sheet 1 with a vacuum bag 6 and fix the vacuum bag 6 to the mold 2 with sealant so that the aluminum alloy sheet 1 is in a closed environment. Wrapping the coil 4 with the breathable felt 5 can prevent the coil 4 from contacting the vacuum bag 6 and causing the vacuum bag to break.

[0040] (7) Place the entire mold 2 containing the aluminum alloy sheet 1 into the temperature chamber 7, control the temperature of the temperature chamber 7 to be 120-180℃, evacuate the vacuum bag 6 through the vacuum tube 8 and vacuum pump 9, control the vacuum atmospheric pressure in the vacuum bag 6 to be 0.06-0.1MPa, and carry out creep aging forming. At the same time, the aluminum alloy sheet 1 is subjected to pulse electromagnetic field treatment. Specifically, first turn on the pulse power supply device and pass a pulse current to the coil 4 above the aluminum alloy sheet 1. The pulse current parameters are obtained by converting the optimal pulse electromagnetic field parameters determined in step (4) through the existing formula, and then a pulse magnetic field is generated around the coil, which generates an induced pulse current, a pulse magnetic field and an alternating Lorentz force on the aluminum alloy sheet 1 below the coil 4, so that the aluminum alloy sheet 1 is rapidly heated to the target temperature. Here, a data logger can be used to monitor the surface temperature of the aluminum alloy sheet 1.

[0041] (8) After creep is complete, turn off the pulse power supply and remove the aluminum alloy sheet 1 from the temperature chamber 7.

[0042] The following is a specific verification of the synergistic effect of the shape and properties of aluminum alloy thin sheets after creep aging forming using the method of the present invention.

[0043] Taking a 2198 aluminum-lithium alloy trapezoidal sheet as an example, the dimensions of the trapezoidal sheet are: top base × bottom base × height: 116mm × 585mm × 995mm, with a thickness of 8mm. Finite element simulation was used to determine the difficult-to-form weak performance region and the optimal pulse electromagnetic field parameters of the trapezoidal sheet. The optimal pulse current parameters were then calculated from the pulse electromagnetic field parameters: pulse period of 0.05s, pulse duration of 0.005s, and current of 106A. This corresponds to setting the frequency of the pulse power supply device to 20Hz and the duty cycle to 10%. The trapezoidal sheet to be creeped was then placed on the mold surface. An insulating film was laid on the difficult-to-form weak performance region of the aluminum alloy sheet. A coil was wrapped with breathable felt and placed on the insulating film. The wires leading from both ends of the coil were wrapped with insulating tape and then with breathable felt. Finally, a vacuum bag was used to cover the aluminum alloy sheet, and the vacuum bag was fixed to the mold with sealant. The aluminum alloy sheet is placed in a closed environment, and the entire mold containing the trapezoidal sheet is placed in a temperature chamber. The wires leading from both ends of the coil extend to the outside of the vacuum bag and are connected to the pulse power supply device through the wire outlet on the temperature chamber. Then, the vacuum bag is evacuated, and the vacuum atmospheric pressure inside the vacuum bag is controlled to 0.1 MPa. At the same time, the temperature of the temperature chamber is increased to 160°C, and the pulse power supply device is turned on to perform local pulse electromagnetic field-assisted creep aging forming on the trapezoidal sheet. After the pulse current is passed through the coil, a pulse magnetic field is generated around the coil, which in turn generates an induced pulse current, a pulse magnetic field, and an alternating Lorentz force on the trapezoidal sheet below the coil. The Joule heating effect of the pulse current causes the temperature of the trapezoidal sheet to rise rapidly to 183°C. The trapezoidal sheet undergoes creep deformation at a temperature of 183°C and a vacuum atmospheric pressure of 0.1 MPa. The temperature of the trapezoidal sheet is monitored and recorded by a data logger.

[0044] Aluminum-lithium alloy trapezoidal sheets of the same specifications were subjected to creep aging forming under conventional conditions, and compared with the trapezoidal sheets formed by local pulsed electromagnetic field-assisted creep aging. The maximum forming deviation in the difficult-to-form, weak-performance areas of the trapezoidal sheet formed by conventional creep aging forming process was -8.33 mm. Figure 4a As shown; however, the maximum deviation of the difficult-to-form, weak-performance region of the trapezoidal thin plate after creep aging forming assisted by local pulsed electromagnetic field is -3.17 mm, as... Figure 4b As shown, the local pulsed electromagnetic field-assisted creep aging forming process can greatly improve the forming accuracy of aluminum alloy sheets.

[0045] The scope of protection of this invention includes, but is not limited to, the above embodiments. The scope of protection is defined by the claims. Any substitutions, modifications, or improvements to this technology that are easily conceived by those skilled in the art fall within the scope of protection of this invention.

Claims

1. A method for controlling the synergistic effect of creep aging and deformation properties in aluminum alloy thin sheets, characterized in that... The specific steps include the following: (1) A creep aging constitutive model of aluminum alloy thin plate under normal conditions was established by using MATLAB software and numerical optimization algorithm; (2) Embed the creep aging constitutive model under normal conditions into the finite element analysis software, establish the conventional creep aging finite element simulation model of aluminum alloy thin plate, and determine the difficult-to-form weak performance region of aluminum alloy thin plate and the arrangement region of electromagnetic induction coil. (3) Based on the determined arrangement area of ​​the electromagnetic induction coil, a creep aging constitutive model of aluminum alloy thin plate under pulsed electromagnetic field assisted conditions is established by MATLAB software and numerical optimization algorithm. (4) Embed the creep aging constitutive model under pulsed electromagnetic field assisted conditions into the finite element analysis software, establish the creep aging finite element simulation model of aluminum alloy thin plate after local pulsed electromagnetic field assisted conditions, and then determine the optimal pulsed electromagnetic field parameters. (5) Place the aluminum alloy sheet on the mold and fix an insulating film in the difficult-to-form and weak performance area of ​​the aluminum alloy sheet. (6) Wrap a breathable felt around the coil and place the coil wrapped with the breathable felt on an insulating film. Then cover the aluminum alloy sheet with a vacuum bag and seal the vacuum bag with the mold to keep the aluminum alloy sheet in a closed environment. (7) Place the entire mold containing the aluminum alloy sheet into the temperature chamber, evacuate the vacuum bag, and perform creep aging forming. At the same time, perform pulse electromagnetic field treatment on the aluminum alloy sheet. Specifically, turn on the pulse power supply device and pass a pulse current through the coil above the aluminum alloy sheet. The pulse electromagnetic field parameters are the optimal pulse electromagnetic field parameters determined in step (3). Then, a pulse magnetic field is generated around the coil, which generates an induced pulse current, a pulse magnetic field, and an alternating Lorentz force on the aluminum alloy sheet below the coil, so that the aluminum alloy sheet is rapidly heated to the target temperature. (8) After creep is complete, turn off the pulse power supply and remove the aluminum alloy sheet from the temperature chamber.

2. The method for controlling the synergistic effects of creep aging on aluminum alloy thin plates as described in claim 1, characterized in that: The creep-aging constitutive model in steps (1) and (3) is a set of nonlinear differential equations, specifically: Wherein: (01) is the constitutive model of creep aging under normal conditions; (02) is the constitutive model of creep aging assisted by pulsed electromagnetic field; ε eq σ is the equivalent yield strain of the aluminum alloy sheet. eq f is the equivalent yield stress of the aluminum alloy sheet. v σ represents the volume fraction of the precipitated phase in the aluminum alloy sheet, ρ represents the dislocation density of the aluminum alloy sheet material; y σ represents the yield strength of the aluminum alloy sheet material. i For the strength of the aluminum matrix, σ dis σ is the dislocation strength of the aluminum alloy sheet material. ss σ is the solid solution strength of aluminum alloy sheet material. ppt Let be the precipitation intensity of the aluminum alloy sheet, l be the length of the precipitated phase in the aluminum alloy sheet, d be the thickness of the precipitated phase in the aluminum alloy sheet, q be the ratio of the length to the thickness of the precipitated phase, t be the creep aging time of the aluminum alloy sheet, i be the induced current density of the pulsed electromagnetic field, and T be the induced magnetic field strength of the pulsed electromagnetic field.

3. The method for controlling the synergistic effects of creep aging on aluminum alloy thin plates as described in claim 1, characterized in that: The finite element analysis software used in steps (2) and (4) is Abaqus finite element analysis software.

4. The method for controlling the synergistic effects of creep aging on aluminum alloy thin plates as described in claim 1, characterized in that: In step (4), the specific process for determining the optimal pulse electromagnetic field parameters is as follows: First, use ANSYS simulation software to simulate the electromagnetic field module of the aluminum alloy sheet. Then, use ANSYS simulation software to output the simulation results of the pulse electromagnetic field parameters as an .inp file and import them into the Abaqus finite element analysis software as boundary conditions for the creep aging forming of the aluminum alloy sheet. Next, calculate the creep aging forming deformation. After the simulation is completed, compare the deviation between the surface of the aluminum alloy sheet after creep and the required surface. If the deviation is less than the target range, the pulse electromagnetic field parameters obtained above are taken as the optimal pulse electromagnetic field parameters. If the deviation is greater than the target range, change the pulse electromagnetic field parameters according to the deviation results and repeat the above simulation steps until the deviation between the simulated surface of the aluminum alloy sheet and the required surface is within the target range, and take the corresponding pulse electromagnetic field parameters as the optimal pulse electromagnetic field parameters.

5. The method for controlling the synergistic effects of creep aging on aluminum alloy thin plates as described in claim 1, characterized in that: The pulsed electromagnetic field parameters are Lorentz force, pulsed eddy current, and magnetic field strength.

6. The method for controlling the synergistic effects of creep aging on aluminum alloy thin plates as described in claim 1, characterized in that: In step (7), the vacuum atmospheric pressure inside the vacuum bag is 0.06 to 0.1 MPa.

7. The method for controlling the synergistic effects of creep aging on aluminum alloy thin plates as described in claim 1, characterized in that: In step (6), the diameter of the metal wire in the coil is 1 to 5 mm, and the number of coil turns is 5 to 20.

8. The method for controlling the synergistic effects of creep aging on aluminum alloy thin plates as described in claim 1, characterized in that: In step (7), the temperature of the chamber is controlled to be 120-180°C, and the pulse current parameters are: current of 50-500A, pulse period of 0.02-0.1s, pulse duration of 0.001-0.03s, and magnetic field strength of 0.05-0.3T.

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