Aluminum alloy unequal thickness curved surface thin shell local difference temperature deep drawing forming method and device

Abstract

This invention provides a method and apparatus for localized differential temperature deep drawing of aluminum alloy curved thin shells with unequal thickness, relating to the field of metal manufacturing technology. The method includes: determining material flow requirements and designing an initial unequal thickness aluminum alloy blank based on target needs; heating the initial unequal thickness aluminum alloy blank to a basic forming temperature based on a preset local temperature control principle; placing the heated initial unequal thickness aluminum alloy blank on a die and setting a blank holder, pressing a punch onto the initial unequal thickness aluminum alloy blank; based on material flow requirements and local temperature control principles, heating the initial unequal thickness aluminum alloy blank using a heating device; cooling the thick area, thickness transition area, and thin area through a first cooling zone, a second cooling zone, and a third cooling zone, respectively; and controlling the punch to perform curved surface deep drawing to obtain the target aluminum alloy curved thin shell part with unequal thickness. This invention can solve the problem of deformation inconsistency caused by thickness differences in aluminum alloy curved thin shells with unequal thickness.

Description

Technical Field

[0001] This invention relates to the field of metal manufacturing technology, and more specifically, to a method and apparatus for localized differential temperature deep drawing of aluminum alloy unequal thickness curved thin shells. Background Technology

[0002] Aluminum alloys, with their low density, high specific strength, good corrosion resistance, and ease of achieving lightweight structures, are widely used in aerospace, transportation, and large thin-walled load-bearing structures. As lightweight structural design gradually shifts from overall thinning to on-demand material allocation, aluminum alloy curved thin-shell parts with unequal thickness often employ different wall thicknesses in different areas according to actual load-bearing requirements, thus forming structures with unequal thickness areas, thickness transition zones, and thin zones.

[0003] Compared to traditional uniform-thickness plates, unequal-thickness aluminum alloy slabs exhibit more pronounced deformation non-uniformity during forming. Due to the different initial thicknesses in different regions, their local cross-sectional area, stiffness, load-bearing capacity, and material flow state show significant differences. Under traditional isothermal deep-drawing conditions, all regions are at approximately the same temperature. Thicker regions, due to their larger initial thickness, typically possess higher local load-bearing capacity and greater deformation resistance, while thinner regions, with their smaller initial thickness, are more likely to preferentially enter the plastic deformation state. As the punch continues to move, plastic strain and local strain rates tend to concentrate in the thinner regions, leading to rapid thinning, local necking, or even premature cracking in the thinner regions, while the thicker regions may experience insufficient plastic flow participation.

[0004] In related technologies, existing deep drawing processes mainly improve material flow by adjusting mechanical parameters such as punch speed, blank holder force, die clearance, friction conditions, and the initial shape of the slab. These methods are effective for traditional sheet metal of uniform thickness, but for aluminum alloy slabs with significant initial thickness differences, relying solely on mechanical boundary condition adjustments is insufficient to actively alter the local flow resistance of the material in the thick and thin areas. This fails to effectively address the deformation inconsistency problem caused by thickness differences in unequal-thickness curved thin shells of aluminum alloys. Summary of the Invention

[0005] The problem solved by this invention is the deformation inconsistency caused by the thickness difference of aluminum alloy curved thin shells.

[0006] To address the aforementioned problems, this invention provides a method and apparatus for localized differential temperature deep drawing of aluminum alloy unequal thickness curved thin shells.

[0007] In a first aspect, the present invention provides a method for localized differential temperature deep drawing of aluminum alloy unequal thickness curved thin shells, comprising: Based on the target requirements, the material flow requirements are determined and the initial unequal thickness aluminum alloy slab is designed. The deep drawing zone of the initial unequal thickness aluminum alloy slab includes a thick zone, a thickness transition zone and a thin zone. Based on the preset local temperature control principle, the initial unequal thickness aluminum alloy slab is heated to the basic forming temperature; The heated initial unequal thickness aluminum alloy blank is placed on the die, and a blank holder is pressed circumferentially on the edge side of the initial unequal thickness aluminum alloy blank. The punch is pressed on the drawing zone. The die and / or the blank holder are equipped with a heating device. The punch includes a first cooling zone, a second cooling zone, and a third cooling zone corresponding to the thick zone, the thickness transition zone, and the thin zone, respectively. The first cooling zone, the second cooling zone, and the third cooling zone have at least one different cooling medium flow rate, temperature, pressure, or heat transfer coefficient. Based on the material flow requirements and the local temperature control principle, the initial unequal thickness aluminum alloy blank is heated by the heating equipment, and the thick area, the thickness transition area and the thin area are cooled by the first cooling area, the second cooling area and the third cooling area respectively. The punch is controlled to push the initial unequal thickness aluminum alloy blank to perform curved surface deep drawing, thereby obtaining the target aluminum alloy curved surface unequal thickness thin shell part.

[0008] Optionally, determining the material flow requirements based on the target demand includes: Based on the target requirements, obtain the target wall thickness distribution and the three-dimensional geometry of the target aluminum alloy curved surface thin-shell part with unequal thickness; Based on the target wall thickness distribution and the three-dimensional geometry, the target surface is discretized to obtain discrete regions, and the geometric wall thickness feature parameters of each discrete region are extracted. Based on the geometric wall thickness characteristic parameters, the inverse mapping method is used to establish the correspondence between the discrete region and the initial planar slab material region, and the material flow requirements are evaluated. Based on the geometric wall thickness characteristic parameters, the discrete regions, and the material flow requirements, a benchmark local differential temperature deep drawing finite element model is established for simulation and solution, and the simulation results of each discrete region are obtained. Based on the simulation results and preset thresholds, a distribution of potential risk locations is generated.

[0009] Optionally, the initial design of the unequal thickness aluminum alloy slab includes: Based on the target wall thickness distribution and material flow requirements, the initial unequal thickness aluminum alloy slab is designed, the thickness transition zone is a continuous and smooth transition structure, and the thickness ratio of the thick zone to the thin zone is greater than 1.

[0010] Optionally, the step of heating the initial unequal-thickness aluminum alloy slab using the heating device, and cooling the thick area, the thickness transition area, and the thin area through the first cooling area, the second cooling area, and the third cooling area respectively, includes: The actual temperatures of the thick region, the thickness transition region, and the thin region are obtained respectively using a temperature measuring device. Based on the aforementioned local temperature control principle, a temperature control method is adopted to control the heating equipment to heat the initial unequal thickness aluminum alloy slab according to the temperature deviation between the actual temperature and the target temperature, and to adjust the cooling medium flow rate of the first cooling zone, the second cooling zone, and the third cooling zone.

[0011] Optionally, the method for localized differential temperature deep drawing of aluminum alloy unequal thickness curved thin shells further includes: A pressure-bearing hot gas chamber is provided below the die. The pressure-bearing hot gas chamber is filled with hot gas medium through a hot gas medium passage. The hot gas medium is used to provide hot gas counter-pressure support to the initial unequal thickness aluminum alloy slab.

[0012] Optionally, the method for localized differential temperature deep drawing of aluminum alloy unequal thickness curved thin shells further includes: Based on the given thickness distribution of unequal-thickness slabs and the given target surface, determine multiple combinations of cooling medium flow rates for the first cooling region, the second cooling region, and the third cooling region. The forming process is carried out according to the cooling medium flow rate combination to obtain the forming result corresponding to each cooling medium flow rate combination; By comparing the various forming results, a reasonable combination of cooling medium flow rates corresponding to the given unequal thickness slab thickness distribution and the given target surface is determined.

[0013] Optionally, the method for localized differential temperature deep drawing of aluminum alloy unequal thickness curved thin shells further includes: Based on the given thickness distribution of unequal-thickness slabs and the given target surface, determine multiple sets of process parameter combinations including cooling medium flow rate, hot gas back pressure, hot gas temperature, punch speed, blank holder force, and endpoint holding time. The forming process is carried out according to the combination of process parameters to obtain the forming result corresponding to each combination of process parameters; By comparing the various forming results, a reasonable combination of process parameters corresponding to the given unequal thickness slab thickness distribution and the given target surface is determined.

[0014] Optionally, after obtaining the target aluminum alloy curved surface thin-shell part with unequal thickness, the method further includes: Obtain the actual curved surface and wall thickness distribution of the target aluminum alloy thin-shell part with unequal thickness, and determine the surface deviation based on the actual curved surface and the target curved surface in the target requirement; Based on the wall thickness distribution and the target wall thickness distribution in the target requirement, the wall thickness deviation is determined, wherein the surface deviation and the wall thickness deviation are used for the next round of temperature difference or process parameter correction.

[0015] Secondly, the present invention provides a local differential temperature deep drawing apparatus for aluminum alloy unequal thickness curved thin shells, comprising a die, a blank holder, and a punch. The die is used to place a heated initial unequal thickness aluminum alloy blank. The blank holder is pressed against the edge side circumferentially of the initial unequal thickness aluminum alloy blank. The punch presses on the deep drawing zone of the initial unequal thickness aluminum alloy blank. The die and / or the blank holder have a built-in heating device. The punch includes a first cooling zone, a second cooling zone, and a third cooling zone corresponding to the thick zone, the thickness transition zone, and the thin zone of the deep drawing zone, respectively. At least one of the cooling medium flow rate, temperature, pressure, or heat transfer coefficient of the first cooling zone, the second cooling zone, and the third cooling zone is different.

[0016] Optionally, the aluminum alloy unequal thickness curved thin shell local differential temperature deep drawing forming apparatus further includes a temperature measuring device 7, which is set at a representative position of the die 2, the blanking area of ​​the blanking part 3, the punch 4 or the initial unequal thickness aluminum alloy blank 1, and is used to obtain the actual temperature of the thick area, the thickness transition area and the thin area respectively. It also includes a pressurized hot gas chamber 5, which is located below the die 2. The pressurized hot gas chamber 5 is filled with hot gas medium 52 through the hot gas medium passage 51. The hot gas medium 52 is used to provide hot gas counter pressure support to the initial unequal thickness aluminum alloy slab 1. The first cooling zone 41 is provided with a first cooling water inlet 411 and a first cooling water outlet 412, the second cooling zone 42 is provided with a second cooling water inlet 421 and a second cooling water outlet 422, and the third cooling zone 43 is provided with a third cooling water inlet 431 and a third cooling water outlet 432. It also includes a controller equipped with local temperature control principles and temperature control methods.

[0017] The beneficial effects of the method and apparatus for local differential temperature deep drawing of aluminum alloy unequal thickness curved thin shells of the present invention are: Based on the target requirements, the material flow requirements are determined and an initial unequal-thickness aluminum alloy slab is designed. The deep drawing zone of the initial unequal-thickness aluminum alloy slab includes a thick zone, a thickness transition zone, and a thin zone. This allows for pre-matching of the load-bearing requirements and deformation characteristics of different regions of the curved thin shell, clarifying the spatial distribution of the thickness zones, and providing a precise basis for subsequent local temperature control. Simultaneously, the thickness transition zone avoids undesigned local stress concentrations caused by abrupt thickness changes. Based on the preset local temperature control principles, the initial unequal-thickness aluminum alloy slab is heated to the basic forming temperature, enabling the entire slab to first enter a uniform thermoplastic forming base state, laying the foundation for subsequent construction. A differentiated temperature field provides a consistent benchmark for material properties. A heated initial unequal-thickness aluminum alloy slab is placed on a die and a blank holder is provided. A punch is pressed onto the initial unequal-thickness aluminum alloy slab. The die and / or blank holder incorporate heating equipment. The punch includes a first cooling region, a second cooling region, and a third cooling region corresponding to the thick region, the thickness transition region, and the thin region. At least one of the cooling medium flow rate, temperature, pressure, or heat transfer coefficient differs among the first, second, and third cooling regions. This reduces the heat transfer on the initial unequal-thickness aluminum alloy slab by utilizing the heating equipment built into the die and blank holder. Unexpected heat dissipation from the surrounding molds maintains a stable thermal state around the slab. Furthermore, the three independent cooling zones within the punch, each with differentiated cooling parameters, overcome the limitations of traditional deep drawing processes that can only adjust mechanical boundary conditions. This provides a structural basis for actively controlling the material flow resistance in different areas of the slab. Based on material flow requirements and local temperature control principles, the initial unequal-thickness aluminum alloy slab is heated by a heating device. The thicker, transitional, and thinner areas are cooled by the first, second, and third cooling zones, respectively. The punch is then controlled to push the initial unequal-thickness aluminum alloy slab through curved surface deep drawing, resulting in the desired material. The standard aluminum alloy curved surface thin shell parts with unequal thickness can maintain a relatively high temperature in the thick area to reduce material flow resistance and improve the material compensation flow capacity in the thick area, allowing it to participate in the overall material migration. This avoids the thin area bearing excessive plastic deformation, while maintaining a relatively low temperature in the thin area to improve deformation resistance, suppress local strain concentration and excessive thinning. The thickness transition zone forms a smooth transition in temperature and material properties. In this way, the difference in material flow resistance caused by the temperature difference is used to compensate for the difference in geometric load-bearing capacity caused by the thickness difference. This effectively solves the problem of deformation incoordination of aluminum alloy curved surface thin shells with unequal thickness that cannot be improved by existing technologies relying solely on mechanical process parameters. Attached Figure Description

[0018] Figure 1 A schematic flowchart of the method for local differential temperature deep drawing of aluminum alloy unequal thickness curved thin shells provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the deep drawing process provided in an embodiment of the present invention; Figure 3This is one of the structural schematic diagrams of the deep drawing process and the pressurized hot gas cavity provided in the embodiments of the present invention; Figure 4 This is the second schematic diagram of the deep drawing process and the structure of the pressurized hot gas cavity provided in the embodiment of the present invention.

[0019] Explanation of reference numerals in the attached figures: 1. Initial unequal thickness aluminum alloy slab blank; 2. Die; 3. Blank holder; 4. Punch; 41. First cooling zone; 411. First cooling water inlet; 412. First cooling water outlet; 42. Second cooling zone; 421. Second cooling water inlet; 422. Second cooling water outlet; 43. Third cooling zone; 431. Third cooling water inlet; 432. Third cooling water outlet; 5. Pressurized hot air chamber; 51. Hot air medium passage; 52. Hot air medium; 6. Heating equipment; 7. Temperature measuring device. Detailed Implementation

[0020] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Although some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the accompanying drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0021] It should be understood that the various steps described in the method embodiments of the present invention may be performed in different orders and / or in parallel. Furthermore, the method embodiments may include additional steps and / or omit the steps shown. The scope of the present invention is not limited in this respect.

[0022] The term "comprising" and its variations as used herein are open-ended, meaning "including but not limited to"; the term "based on" means "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; and the term "optionally" means "optional embodiments". Definitions of other terms will be given in the following description. It should be noted that the concepts of "first," "second," etc., mentioned in this invention are used only to distinguish different devices, modules, or units, and are not intended to limit the order of functions performed by these devices, modules, or units or their interdependencies.

[0023] It should be noted that the terms "a" and "a plurality of" used in this invention are illustrative rather than restrictive. Those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0024] The names of the messages or information exchanged between the multiple devices in the embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of these messages or information.

[0025] like Figure 1 As shown in the embodiment of the present invention, a method for local differential temperature deep drawing of aluminum alloy unequal thickness curved thin shells includes: Based on the target requirements, the material flow requirements are determined and the initial unequal thickness aluminum alloy slab 1 is designed. The deep drawing zone of the initial unequal thickness aluminum alloy slab includes a thick zone, a thickness transition zone, and a thin zone.

[0026] Specifically, during implementation, the target requirements for the aluminum alloy curved surface unequal thickness thin-shell part to be formed are first obtained, covering the final wall thickness requirements and surface geometry requirements. Based on the actual load-bearing function of the target part and the deformation law during the forming process, the required material flow degree in different regions during deep drawing is analyzed. Regions prone to excessive thinning, local cracking, wrinkling, or insufficient deformation during forming are predicted, thereby dividing the spatial distribution of the thick, thickness transition, and thin regions corresponding to the part, and establishing a mapping relationship between each region of the target part and the corresponding region of the initial planar blank. Combining the above material flow requirements and region division results, the overall contour and thickness distribution of the initial unequal thickness aluminum alloy blank 1 are designed, so that the deep drawing region of the blank corresponds to three parts: a thick region, a thickness transition region, and a thin region. The thickness transition region is located between the thick and thin regions, achieving the connection between different thickness regions. The initial unequal thickness aluminum alloy blank 1 includes an edge side and a deep drawing region. The edge side is located at the four edges of the deep drawing region, which is used for deep drawing. The initial unequal-thickness aluminum alloy slab designed in this way can initially match the initial load-bearing capacity of different thickness regions with the deformation requirements in the subsequent forming process, providing a foundation for further compensation of deformation capacity differences caused by thickness variations through localized temperature control. This embodiment can plan the initial thickness distribution of the slab in advance according to the target wall thickness and curved surface forming requirements of the part, clarifying the spatial locations of thick areas, thickness transition areas, and thin areas, and constructing an initial thickness field adapted to the deformation requirements of the part. This provides a prerequisite for temperature field matching and control in subsequent localized differential temperature drawing, effectively reducing deformation inconsistencies caused by mismatch between the initial thickness design and forming requirements.

[0027] Based on the preset local temperature control principle, the initial unequal thickness aluminum alloy slab 1 is heated to the basic forming temperature.

[0028] Specifically, in implementation, the principle of local temperature control is first preset: Since different regions of the initial unequal thickness aluminum alloy slab 1 have different local load-bearing capacities during deep drawing, under similar conditions, the thicker region usually has a higher load-bearing capacity due to its larger cross-sectional area, while the thinner region is more likely to undergo plastic deformation preferentially. Therefore, it is not simply a matter of increasing the temperature of the entire slab, but rather actively changing the material flow resistance of different regions. For typical working conditions, the thicker region is kept at a relatively high temperature to reduce its local flow resistance through strong thermal softening, allowing it to participate more fully in plastic deformation, while the thinner region is kept at a relatively low temperature to increase its relative deformation resistance and reduce the tendency for plastic strain to concentrate too quickly in the thinner region. This forms a compensatory relationship between the geometric load-bearing difference caused by the thickness difference and the material flow resistance difference caused by the temperature difference. This principle does not require the thicker and thinner regions to have exactly the same strain in the end, but rather to achieve reasonable on-demand deformation based on the target curvature and the final wall thickness. Based on the above temperature control principles, the initial aluminum alloy slab of unequal thickness is heated as a whole to a basic forming temperature suitable for the current aluminum alloy material. Overall heating can be achieved using a heating furnace, resistance heating, induction heating, radiation heating, or other methods suitable for overall heating of the aluminum alloy slab. The purpose of this step is to bring the entire slab into a basic material state suitable for thermoplastic forming. At this stage, it is not required that the final temperature difference be immediately formed in different areas of the slab. Instead, after the basic heating is completed, subsequent mold-based regional heat exchange adjustment is used to further construct a localized non-uniform temperature field. The overall thermal control process follows the sequence of overall basic heating, mold-based regional heat exchange adjustment, and establishment of the target localized temperature difference. The representative temperature difference between the thick and thin areas is defined as... ,in For the temperature of the thick section, For the temperature of the thin area, under typical compensated operating conditions A temperature greater than 0 indicates that the temperature in the thicker region is higher than that in the thinner region, while the transition region forms a continuous intermediate temperature. This allows the material's mechanical properties to change gradually from the thicker to the thinner region, reducing local strain concentration caused by abrupt temperature changes. This embodiment clearly defines the core control logic of local temperature difference. By first heating the entire slab to the basic forming temperature to bring it into a thermoplastic state, and then using subsequent zoned heat exchange to construct the target temperature gradient, the basic forming performance of the slab is ensured. This also provides the prerequisite for precise temperature control to compensate for the difference in deformation capacity caused by thickness variations. At the same time, the gradual temperature transition avoids the problem of local strain concentration caused by abrupt temperature changes.

[0029] The heated initial unequal thickness aluminum alloy slab 1 is placed on the die 2, and a blank holder 3 is pressed circumferentially on the edge side of the initial unequal thickness aluminum alloy slab 1. The punch 4 is pressed on the drawing zone. The die 2 and / or the blank holder 3 are equipped with a heating device 6. The punch 4 includes a first cooling zone 41, a second cooling zone 42, and a third cooling zone 43 corresponding to the thick zone, the thickness transition zone, and the thin zone, respectively. The cooling medium flow rate, temperature, pressure, or heat transfer coefficient of the first cooling zone 41, the second cooling zone 42, and the third cooling zone 43 are different in at least one.

[0030] Specifically, such as Figure 2As shown, during implementation, the initial unequal thickness aluminum alloy slab 1, after basic heating, is placed on the die 2. A blank holder 3 is placed around the slab, and then the punch 4 is pressed onto the initial unequal thickness aluminum alloy slab 1. The die 2 adopts a common hollow structure, with a central hollow forming space allowing the slab to enter. The slab is constrained by the support area of ​​the die 2 and the blank holder 3. Both the die 2 and the blank holder 3 have built-in heating devices 6. The heating devices 6 preferably use embedded resistance heating rods, but heating tubes, heating plates, or other structures capable of actively heating localized areas of the mold can also be used. The heating devices 6 can be controlled in groups, allowing the die 2 and the blank holder 3 to use the same or different heating powers according to actual temperature requirements. Temperature sensors are placed at corresponding locations to monitor the temperature of the die 2 and the blank holder 3. The punch 4 adopts an integral structure, and its external working surface is a continuous curved surface to ensure that the slab can form a continuous target curved surface during the deep drawing process. The punch 4 is provided with three independent cooling areas: a first cooling area 41, a second cooling area 42, and a third cooling area 43. The three cooling areas correspond to the thick area, the thickness transition area, and the thin area of ​​the slab, respectively. The first cooling area 41 is provided with a first cooling water inlet 411 and a first cooling water outlet 412. The second cooling area 42 is provided with a second cooling water inlet 421 and a second cooling water outlet 422. The third cooling area 43 is provided with a third cooling water inlet 431 and a third cooling water outlet 432. Each cooling area has its own cooling flow channel and is independent of each other in the fluid circuit, so that the cooling water flow rate of each area can be controlled separately. That is, the cooling medium flow rate of the three cooling areas is different. In addition, the cooling medium flow rate, temperature, pressure, or heat transfer coefficient of the three cooling areas are different. The three cooling areas are all arranged inside the same integral punch 4, rather than being formed by splicing multiple independent punches, while meeting the requirements of continuous external curved surface and independent internal water cooling area. Based on the spatial location of the thick area, the thickness transition area, and the thin area, and the expected deformation degree of each area, three water-cooling zones are arranged. The first cooling zone 41 mainly acts on areas requiring higher temperatures or weaker cooling; the second cooling zone 42 mainly acts on the thickness and temperature transition area; and the third cooling zone 43 mainly acts on thin areas requiring stronger cooling or areas with high deformation risk. The water-cooling zones and the slab thickness areas do not need to strictly coincide geometrically. Due to the internal heat conduction of the punch 4 and the slab itself, adjacent water-cooling zones have a certain thermal influence range. The actual location of the water-cooling zones can be adjusted according to the slab thickness, target temperature field, curvature, and expected material flow state. This embodiment, through the partitioned independent cooling structure of the integral punch, achieves independent control of the cooling capacity of different areas while ensuring the continuity and integrity of the formed surface. Simultaneously, combined with the active heating structure of the die and the blank holder, the thermal state of the slab is maintained from the outside, jointly constructing a stable local thermal boundary, providing structural support for differential temperature control in the subsequent forming process.

[0031] Based on the material flow requirements and the local temperature control principle, the initial unequal thickness aluminum alloy blank 1 is heated by the heating device 6, and the thick area, the thickness transition area and the thin area are cooled by the first cooling area 41, the second cooling area 42 and the third cooling area 43 respectively. The punch 4 is controlled to push the initial unequal thickness aluminum alloy blank 1 to perform curved surface deep drawing, so as to obtain the target aluminum alloy curved surface unequal thickness thin shell part.

[0032] Specifically, such as Figure 2 As shown, during the implementation process, based on the predetermined material flow requirements and the preset local temperature control principle, the heating equipment 6 built into the die 2 and the blank holder 3 heats the corresponding areas of the initial unequal thickness aluminum alloy blank 1, maintaining the thermal state of the outer area of ​​the blank and compensating for the heat loss from the blank to the die. At the same time, the first cooling area 41, the second cooling area 42, and the third cooling area 43 inside the punch 4 provide differentiated cooling for the thick area, the thickness transition area, and the thin area of ​​the blank, respectively. This keeps the thick area at a relatively high temperature to reduce material flow resistance, keeps the thin area at a relatively low temperature to improve deformation resistance, and maintains the thickness transition area at an intermediate temperature, thereby forming a local temperature gradient inside the blank that matches the thickness distribution. Based on this, the punch 4 is controlled to move towards the die 2, pushing the initial unequal thickness aluminum alloy blank 1 to undergo curved surface deep drawing deformation. The blank gradually extends into the hollow area of ​​the die 2, and under the action of the continuous curved surface of the punch 4, it is gradually formed into the target curved surface shape, finally obtaining the target aluminum alloy curved surface unequal thickness thin shell part. During the forming process, the material flow of the slab is jointly regulated by the local temperature field, the mechanical movement of the punch, the constraint of the blank holder, and the friction state. The temperature difference compensates for the difference in deformation capacity caused by the thickness difference, enhancing the material flow compensation capacity of the thicker areas and suppressing excessive deformation in the thinner areas. This embodiment can compensate for the difference in geometric load-bearing capacity caused by the thickness difference of unequal-thickness slabs through localized temperature control, improving the problem of material flow incoordination between thick and thin areas. This allows different thickness areas to deform as needed, reducing the risk of excessive thinning and cracking in the thinner areas, while simultaneously enhancing the material flow compensation capacity of the thicker areas, ensuring the forming quality of the unequal-thickness curved thin shell.

[0033] Optionally, determining the material flow requirements based on the target demand includes: Based on the target requirements, obtain the target wall thickness distribution and the three-dimensional geometry of the target aluminum alloy curved surface thin-shell part with unequal thickness; Based on the target wall thickness distribution and the three-dimensional geometry, the target surface is discretized to obtain discrete regions, and the geometric wall thickness feature parameters of each discrete region are extracted. Based on the geometric wall thickness characteristic parameters, a reverse mapping method is used to establish the correspondence between the discrete region and the initial planar slab material region, and the material flow requirements are evaluated.

[0034] Specifically, in implementation, the target wall thickness distribution and three-dimensional geometry of the target aluminum alloy curved surface thin-shell part with unequal thickness are first extracted from the target requirements. The three-dimensional geometry encompasses complete geometric information such as the curvature distribution, forming depth, edge contour, and local transition structures of the part. Based on the target wall thickness distribution and three-dimensional geometry, the target surface is discretized into several discrete regions. For each discrete region, corresponding geometric wall thickness feature parameters are extracted, including the principal curvature, target wall thickness, and wall thickness gradient. The principal curvature characterizes the degree of surface curvature in that region, the target wall thickness is the final wall thickness value required for that region, and the wall thickness gradient reflects the rate of wall thickness change between adjacent regions. Based on the extracted geometric wall thickness feature parameters, a reverse mapping method is used to establish the spatial correspondence between the discrete regions on the target surface and the material regions of the initial planar slab. The reverse mapping method can be geometric inverse mapping, one-step inverse finite element method, or other applicable material inverse mapping methods. Through the mapping relationship, each region on the target surface is mapped to the corresponding position on the initial planar slab. Based on this, by combining the area change of the target region, the target wall thickness requirement, and the amount of material migration during the forming process, the material flow requirements of each corresponding region are quantitatively evaluated. This clarifies the amount of material that needs to flow in or out of each region during the deep drawing process, as well as the required degree of plastic deformation. Through this method, the geometric and wall thickness requirements of the target part can be accurately converted into the material flow requirements of each region of the initial slab, providing a precise quantitative basis for subsequent initial slab thickness design and local temperature control. This embodiment can establish a precise correspondence between the target surface and the initial slab through surface discretization and inverse mapping, quantitatively evaluating the material flow requirements of each region. This makes subsequent thickness design and temperature control more targeted, avoiding deviations caused by relying on experience-based judgments and improving the accuracy of unequal thickness slab forming design.

[0035] Based on the geometric wall thickness characteristic parameters, the discrete regions, and the material flow requirements, a benchmark local differential temperature deep drawing finite element model is established for simulation and solution, and the simulation results of each discrete region are obtained. Based on the simulation results and preset thresholds, a distribution of potential risk locations is generated.

[0036] Specifically, during implementation, based on the obtained geometric wall thickness characteristic parameters, the results of the discrete region division of the target surface, and the material flow requirements of each region, a benchmark local differential temperature deep drawing finite element model is established. The slab material performance parameters, die structure parameters, preset local temperature conditions, and deep drawing process parameters are imported into the finite element model for simulation and solution. After simulation, the simulation results corresponding to each discrete region are obtained, specifically including multi-dimensional forming response data such as the final wall thickness, maximum principal strain, minimum principal strain, local plastic strain, damage state, out-of-plane displacement, and final surface error of each region. Pre-set thresholds for each evaluation index are established, including allowable thinning threshold, material forming limit boundary, wrinkling judgment threshold, and allowable deformation deviation threshold. The simulated data for each region is compared with the corresponding preset thresholds: Over-thinning regions are identified based on the comparison between the actual thinning rate and the allowable thinning threshold; local cracking danger regions are identified based on the distance between the actual strain state and the forming limit boundary; wrinkling regions are identified based on in-plane compressive strain, out-of-plane fluctuations, and local curvature anomalies; and under-deformation regions are identified based on the final surface error, local plastic strain, and the deviation of the final wall thickness from the target wall thickness. By integrating the spatial locations of various risk regions, a complete distribution of forming risk locations on the target surface is generated, clarifying the risk type and risk level of different regions. This embodiment can predict various forming risks in the deep drawing process of unequal thickness slabs in advance through finite element simulation, obtaining the spatial distribution law of forming risks. This provides a design basis for subsequent initial slab thickness optimization and precise control of the local temperature field, effectively reducing the defect rate in the actual trial production process and reducing trial production costs and cycle time.

[0037] Optionally, the initial design of the unequal thickness aluminum alloy slab 1 includes: Based on the target wall thickness distribution and material flow requirements, the initial unequal thickness aluminum alloy slab 1 is designed, the thickness transition zone is a continuous and smooth transition structure, and the thickness ratio of the thick zone to the thin zone is greater than 1.

[0038] Specifically, during implementation, the thickness distribution of the initial unequal-thickness aluminum alloy slab is designed based on the target wall thickness distribution of the target part and the material flow requirements of each region during the forming process. The designed slab includes at least three parts: a thick region, a thickness transition region, and a thin region. The thick region corresponds to areas on the part with high load-bearing requirements and requiring more plastic deformation during forming. The thin region corresponds to areas on the part with thinner walls and prone to excessive deformation during forming. The thickness transition region is located between the thick and thin regions. A continuous and smooth thickness transition is preferred between the thick and thin regions, avoiding obvious steps, sharp corners, or sudden thinning structures. This reduces undesigned stress concentration caused by abrupt changes in thickness geometry and minimizes the risk of localized strain concentration and cracking during forming caused by sudden thickness changes. Let the initial thickness of the thick region be... The initial thickness of the thin region is The thickness ratio of the thick region to the thin region is defined as follows: Its calculation formula is The thickness is greater than This means the initial thickness of the thick area is greater than the initial thickness of the thin area. For thin-shell parts with complex structures, multiple thickness grades of slab structures can be used, or a continuous two-dimensional gradient thickness distribution can be adopted, not limited to a single thick or thin area, to adapt to more complex wall thickness distribution requirements. The initial unequal thickness aluminum alloy slab can be prepared by differential thickness rolling, machining, local thinning, or other processes that can obtain the predetermined initial thickness distribution. The appropriate preparation method can be selected according to the thickness difference of the slab, production batch, and precision requirements. This embodiment can reduce the risk of stress concentration caused by abrupt thickness changes through a continuous and smooth thickness transition design. At the same time, the degree of thickness difference between the thick and thin areas is clearly defined through the quantitative design of the thickness ratio. The thickness distribution form and preparation method can also be flexibly selected according to the complexity of the part to adapt to the forming requirements of unequal thickness curved thin shells with different levels of complexity.

[0039] Optionally, the step of heating the initial unequal-thickness aluminum alloy slab 1 through the heating device 6, and cooling the thick area, the thickness transition area, and the thin area through the first cooling area 41, the second cooling area 42, and the third cooling area 43 respectively, includes: The actual temperatures of the thick region, the thickness transition region, and the thin region are obtained by the temperature measuring device 7, respectively. Based on the local temperature control principle, a temperature control method is adopted to control the heating device 6 to heat the initial unequal thickness aluminum alloy slab 1 according to the temperature deviation between the actual temperature and the target temperature, and to adjust the cooling medium flow rate of the first cooling zone 41, the second cooling zone 42 and the third cooling zone 43.

[0040] Specifically, such as Figure 2As shown, during implementation, temperature measuring devices 7 are arranged at representative positions on the die 2, the pressing area of ​​the pressing part 3, the punch 4, or the initial unequal thickness aluminum alloy slab 1. The actual temperature data of the thick area, thickness transition area, and thin area of ​​the slab are acquired in real time through the temperature measuring devices 7. Temperature measurement can be performed using one of the following: thermocouple, infrared thermometer, or infrared thermal imager, or a combination of multiple measurement methods can be used to balance measurement accuracy and range. Based on a preset local temperature control principle, the target temperature corresponding to each area is pre-set. Using an appropriate temperature control method, the actual temperature of each area is compared with the corresponding target temperature, and the temperature deviation between the actual temperature and the target temperature is calculated. Based on the magnitude and trend of the temperature deviation, the heating power of the heating equipment 6 built into the die 2 and the blank holder 3 is controlled to adjust the heating intensity of the slab and compensate for the heat loss from the slab to the mold and the environment. Simultaneously, the cooling medium flow rates of the first cooling zone 41, the second cooling zone 42, and the third cooling zone 43 are adjusted. When the actual temperature of a certain zone is higher than the target temperature, the cooling water flow rate of the corresponding cooling zone is increased to enhance the cooling effect. When the actual temperature of a certain zone is lower than the target temperature, the cooling water flow rate of the corresponding cooling zone is decreased to weaken the cooling effect. When the temperature gradient between the thick and thin zones is too abrupt, the cooling flow rate of the intermediate second cooling zone 42 is adjusted to make the temperature distribution in the transition zone smoother. The temperature control method can be proportional-integral-derivative control, adaptive control, fuzzy control, or other methods suitable for multi-channel temperature control. The entire control process uses the actual thermal state of the slab as the final control target, rather than a fixed cooling water flow rate or heating power. This embodiment can form a closed-loop control through multi-region temperature feedback, and compensate for temperature drift caused by changes in slab thickness, contact pressure, punch stroke and heat exchange boundary in real time, so that the thick area, transition area and thin area can maintain the target temperature state throughout the forming process, and ensure the stability and accuracy of local differential temperature control.

[0041] For example, during the process of controlling the punch 4 to push the initial unequal thickness aluminum alloy blank 1 for curved surface drawing, the cooling medium flow rate of the first cooling zone 41, the second cooling zone 42 and the third cooling zone 43 can be dynamically adjusted according to the temperature deviation between the actual temperature and the target temperature of the thick zone, the thickness transition zone and the thin zone.

[0042] Optionally, the method for localized differential temperature deep drawing of aluminum alloy unequal thickness curved thin shells further includes: A pressure-bearing hot gas chamber 5 is provided below the die 2. The pressure-bearing hot gas chamber 5 is filled with hot gas medium 52 through the hot gas medium passage 51. The hot gas medium 52 is used to provide hot gas counter pressure support to the initial unequal thickness aluminum alloy slab 1.

[0043] Specifically, such as Figure 3 and Figure 4 As shown, Figure 3 This refers to the state where punch 4 has not been drawn. Figure 4 The drawing process is performed by the punch 4. A pressure-bearing hot gas chamber 5 is provided below the die 2. A hot gas medium passage 51 is connected to the pressure-bearing hot gas chamber 5. The hot gas medium 52 is filled into the pressure-bearing hot gas chamber 5 through the hot gas medium passage 51 and acts directly on the surface of the initial unequal thickness aluminum alloy slab 1 opposite to the punch 4. During the mechanical drawing process of the punch 4, the hot gas medium 52 applies a continuous distributed normal pressure to the slab in the opposite direction to the movement direction of the punch 4, i.e., hot gas counter-pressure support. This counter-pressure is not used to independently drive the slab forming, but serves as an auxiliary support condition during the punch drawing process. For the effective pressure area, the magnitude of its reaction force is related to the hot gas pressure and the actual pressure area. Since the curvature of the slab and the effective pressure area change continuously during the drawing process, the actual reaction force also changes dynamically with the punch stroke. The hot gas back pressure firstly provides continuous distributed support to the suspended areas of the slab. When thin or highly deformable areas tend to move too quickly into the die cavity, appropriate back pressure can reduce the rate of deformation development and suppress the rapid concentration of local strain and thinning. Secondly, the back pressure helps improve the fit between the slab and the working surface of the punch, making the fit more stable and the contact area and pressure more controllable. This allows the three cooling zones inside the punch to more stably transfer different cooling capacities to the slab, forming a synergistic effect of improved fit stability, more stable heat exchange, and enhanced local temperature control. Furthermore, the pressure medium uses a gas medium with a predetermined temperature. By controlling the gas temperature, unplanned heat dissipation from the high-temperature slab to the die cavity and surrounding environment can be reduced, while also assisting in adjusting the temperature gradient along the thickness direction of the slab. The back pressure support is the primary technical function of the hot gas medium, while temperature regulation is an additional function. This embodiment can suppress excessively rapid deformation and local thinning in the suspended area of ​​the slab by providing distributed counter-pressure support through the pressurized hot air cavity, while improving the bonding stability between the slab and the punch, enhancing the temperature control effect of local water cooling, and forming a synergistic effect with the partitioned cooling structure to further improve the forming quality of unequal thickness slabs.

[0044] For example, once the punch 4 moves downward to the final position corresponding to the target curved surface, its downward movement is immediately stopped, and it is held stably at this final position for a certain period of time, entering the endpoint holding stage. Endpoint holding primarily ensures stable contact between the formed part and the working surface of the punch 4, maintaining the target curved surface shape of the macroscopic geometric contour of the formed part throughout the holding process, preventing free deformation due to loss of load support. Simultaneously, since the aluminum alloy material of the formed part is still in a relatively high forming temperature range, under the constraint of essentially unchanged macroscopic geometry, the material can continuously redistribute internal stress through time-related viscoplastic adjustment, dislocation recovery, and other microstructural evolution processes, thus forming a progressive process of "final geometry retention → internal viscoplastic adjustment → gradual stress relaxation." This stress relaxation effect in the holding state effectively reduces the high peak stress level inside the formed part at the moment of deep drawing completion, reduces the accumulation and uneven distribution of internal residual stress, thereby reducing the elastic recovery of the formed part after subsequent unloading and demolding, suppressing local warping deformation, and reducing the final curved surface shape deviation. When using a pressurized hot gas medium die, it is preferable to maintain a certain gas back pressure during the final holding stage to ensure stable normal support for the slab during stress relaxation, preventing localized collapse or shape distortion due to stress relaxation. At this time, the formed part is simultaneously constrained by the frontal geometry of the punch 4, the outer periphery of the die 2 and the blank holder 3, and supported by the reverse pressure of the hot gas medium 52. Combined with the stress relaxation effect under high temperature conditions, this forms a stable final state of "punch geometric constraint + die / blade constraint + gas back pressure support + high temperature stress relaxation," ensuring the stress relaxation process proceeds fully under stable stress and geometric constraints. This embodiment can fully utilize the high-temperature viscoplasticity of aluminum alloys to promote internal stress relaxation through final holding, effectively reducing the residual stress level of the formed part and significantly reducing elastic recovery and local warping deformation after unloading. Combined with the back pressure support of the pressurized hot gas medium, it can further ensure the stress stability and shape stability of the slab during stress relaxation, improving the surface shape accuracy and dimensional consistency of unequal-thickness curved thin-shell parts.

[0045] Optionally, the method for localized differential temperature deep drawing of aluminum alloy unequal thickness curved thin shells further includes: Based on the given thickness distribution of unequal-thickness slabs and the given target surface, determine multiple combinations of cooling medium flow rates for the first cooling region 41, the second cooling region 42, and the third cooling region 43; The forming process is carried out according to the cooling medium flow rate combination to obtain the forming result corresponding to each cooling medium flow rate combination; By comparing the various forming results, a reasonable combination of cooling medium flow rates corresponding to the given unequal thickness slab thickness distribution and the given target surface is determined.

[0046] Specifically, in implementation, for a given unequal thickness slab thickness distribution and a given target surface, multiple different combinations of cooling medium flow rates are set, using the cooling medium flow rates of the first cooling region 41, the second cooling region 42, and the third cooling region 43 as variables. Each flow rate combination corresponds to a different regional cooling intensity combination, which can form different local temperature fields on the slab. For each combination of cooling medium flow rates, forming tests or simulation calculations are carried out according to the complete local differential temperature deep drawing process to obtain the forming results corresponding to each flow rate combination. The evaluation indicators of the forming results include the final wall thickness distribution of the formed part, the maximum thinning rate, cracking defects, wrinkling defects, maximum forming force, surface shape error, and unloading springback. The forming results corresponding to each flow rate combination are compared horizontally, and the performance of multiple dimensions such as wall thickness uniformity, defect suppression effect, forming load, and shape accuracy is comprehensively considered to select the combination with the best overall forming quality as the reasonable cooling medium flow rate combination corresponding to the given unequal thickness slab thickness distribution and the given target surface. Based on this, by further changing the thickness ratio of the unequal-thickness slabs and repeating the above flow rate combination optimization process, the corresponding process relationship between thickness ratio, three-zone water cooling flow rate, local temperature difference, and final forming quality can be established, forming a reference process parameter database. This provides parameter basis for the forming of unequal-thickness curved thin shells with different thickness differences in the same series. This embodiment can obtain the optimal cooling parameters adapted to specific slab thicknesses and target curved surfaces through comparative optimization of multiple sets of flow rate combinations. It can also further construct the process relationship between thickness ratio, cooling parameters, and forming quality, providing quantitative parameter guidance for the differential temperature deep drawing process of unequal-thickness curved thin shells, and improving the efficiency and accuracy of process design.

[0047] Optionally, the method for localized differential temperature deep drawing of aluminum alloy unequal thickness curved thin shells further includes: Based on the given thickness distribution of unequal-thickness slabs and the given target surface, determine multiple sets of process parameter combinations including cooling medium flow rate, hot gas back pressure, hot gas temperature, punch speed, blank holder force, and endpoint holding time. The forming process is carried out according to the combination of process parameters to obtain the forming result corresponding to each combination of process parameters; By comparing the various forming results, a reasonable combination of process parameters corresponding to the given unequal thickness slab thickness distribution and the given target surface is determined.

[0048] Specifically, in implementation, given the thickness distribution of unequal-thickness slabs and the given target curved surface, under the condition of using a pressurized hot gas medium die, the cooling medium flow rate, hot gas back pressure, hot gas temperature, punch speed, blank holder force, and end-point holding time are selected as optimization variables to design multiple different combinations of process parameters. Each combination of parameters corresponds to different temperature control, mechanical, and time process conditions. For each combination of process parameters, forming experiments or simulation calculations are carried out according to the complete local differential temperature deep drawing process. During the forming process, the cooling flow rate and hot gas back pressure in each region are simultaneously controlled. After the punch reaches the final stroke, it is held for the corresponding time according to the corresponding parameters. During the holding process, the die geometry constraint and hot gas back pressure are maintained. The viscoplastic behavior of aluminum alloy at high temperatures is used to promote internal stress relaxation. After the holding is completed, the pressure is gradually released and the die is demolded, finally obtaining the forming result corresponding to each combination of process parameters. The evaluation indicators of the forming results include the final wall thickness distribution, maximum thinning rate, cracking defects, wrinkling defects, maximum forming force, curved surface shape error, and unloading springback. By comparing the forming results corresponding to each combination of process parameters from multiple dimensions, and considering factors such as wall thickness control accuracy, defect suppression effect, forming efficiency, and shape stability, the combination with the best overall forming quality is selected as the reasonable combination of process parameters for the given working condition. Further modifying the slab thickness ratio through repeated optimization can establish a complete process relationship between thickness ratio, three-zone water cooling flow rate, local temperature difference, hot gas back pressure, and final forming quality. This embodiment can achieve synergistic optimization of multiple process parameters for the working condition supported by hot gas back pressure, obtaining the parameter combination with the best overall forming quality. Simultaneously, it can construct a complete database of process parameter relationships, fully leveraging the synergistic control effect of local temperature difference and hot gas back pressure to improve the forming accuracy and quality stability of unequal thickness curved thin shells.

[0049] Optionally, after obtaining the target aluminum alloy curved surface thin-shell part with unequal thickness, the method further includes: Obtain the actual curved surface and wall thickness distribution of the target aluminum alloy thin-shell part with unequal thickness, and determine the surface deviation based on the actual curved surface and the target curved surface in the target requirement; Based on the wall thickness distribution and the target wall thickness distribution in the target requirement, the wall thickness deviation is determined, wherein the surface deviation and the wall thickness deviation are used for the next round of temperature difference or process parameter correction.

[0050] Specifically, during implementation, after obtaining the target aluminum alloy curved surface unequal thickness shell part and completing demolding, a comprehensive inspection of the formed part's geometry, wall thickness distribution, and forming defects is conducted. For surface geometric accuracy, 3D optical scanning, laser scanning, or coordinate measurement methods are used to acquire the actual surface data of the formed part. This actual surface data is then registered and compared with the target 3D surface in the target requirements to calculate the overall contour deviation, local shape deviation, and unloading springback amount, thereby determining the surface deviation. For wall thickness distribution, ultrasonic thickness measurement, mechanical thickness measurement, cross-sectional measurement, or other applicable wall thickness detection methods are used to acquire the final wall thickness distribution data at various locations on the formed part. The actual wall thickness distribution is compared with the target wall thickness distribution in the target requirements to determine the wall thickness deviation at each location. Surface deviation and wall thickness deviation are used for the next round of temperature difference or process parameter correction. For any location, its local thinning rate can be calculated to quantify the degree of wall thickness change. The calculation formula is: ,in This represents the initial thickness of the slab at that location. This refers to the final thickness at this location after forming. During the inspection process, the focus is on evaluating whether the final wall thickness of the thick area meets the requirements, whether the wall thickness of the thickness transition zone is continuous and smooth, whether the minimum wall thickness of the thin area exceeds the critical value, and whether the maximum thinning rate of the part is within the allowable range. Simultaneously, crack locations and wrinkling areas are identified, surface shape errors and unloading springback are quantified, and the overall quality of the formed part is comprehensively evaluated. For different die structures, the final forming quality of a conventional hollow die and a pressurized hot gas medium die can be compared under the same local temperature conditions to evaluate the actual control effect of the back pressure. This embodiment can comprehensively quantify the wall thickness accuracy and surface accuracy of the formed part through multi-dimensional inspection and deviation calculation, clarify forming defects, provide data feedback for further optimization of process parameters, and verify the actual forming effect of different mold structures and process schemes.

[0051] like Figures 2 to 4 As shown in the figure, an embodiment of the present invention provides a local differential temperature deep drawing device for aluminum alloy unequal thickness curved thin shells, including a die 2, a blank holder 3, and a punch 4. The die 2 is used to place the heated initial unequal thickness aluminum alloy blank 1. The blank holder 3 is pressed against the edge side circumferentially of the initial unequal thickness aluminum alloy blank 1. The punch 4 is pressed on the deep drawing area of ​​the initial unequal thickness aluminum alloy blank 1. The die 2 and / or the blank holder 3 have a built-in heating device 6. The punch 4 includes a first cooling area 41, a second cooling area 42, and a third cooling area 43 corresponding to the thick area, the thickness transition area, and the thin area of ​​the deep drawing area, respectively. The cooling medium flow rate, temperature, pressure, or heat transfer coefficient of the first cooling area 41, the second cooling area 42, and the third cooling area 43 are different in at least one.

[0052] Optionally, the aluminum alloy unequal thickness curved thin shell local differential temperature deep drawing forming apparatus further includes a temperature measuring device 7, which is set at a representative position of the die 2, the blanking area of ​​the blanking part 3, the punch 4, or the initial unequal thickness aluminum alloy blank 1, and is used to obtain the actual temperature of the thick area, the thickness transition area and the thin area respectively.

[0053] Optionally, the aluminum alloy unequal thickness curved thin shell local differential temperature deep drawing forming device further includes a pressure-bearing hot gas chamber 5, which is disposed below the die 2. The pressure-bearing hot gas chamber 5 is filled with hot gas medium 52 through a hot gas medium passage 51. The hot gas medium 52 is used to provide hot gas counter-pressure support to the initial unequal thickness aluminum alloy slab 1.

[0054] Optionally, the first cooling zone 41 is provided with a first cooling water inlet 411 and a first cooling water outlet 412, the second cooling zone 42 is provided with a second cooling water inlet 421 and a second cooling water outlet 422, and the third cooling zone 43 is provided with a third cooling water inlet 431 and a third cooling water outlet 432.

[0055] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A method for localized differential temperature deep drawing of aluminum alloy unequal thickness curved thin shells, characterized in that, include: Based on the target requirements, the material flow requirements are determined and the initial unequal thickness aluminum alloy slab is designed (1). The deep drawing zone of the initial unequal thickness aluminum alloy slab includes a thick zone, a thickness transition zone and a thin zone. Based on the preset local temperature control principle, the initial unequal thickness aluminum alloy slab (1) is heated to the basic forming temperature; The heated initial unequal thickness aluminum alloy slab (1) is placed on the die (2), and a blank holder (3) is pressed circumferentially on the edge side of the initial unequal thickness aluminum alloy slab (1). The punch (4) is pressed on the drawing area. The die (2) and / or the blank holder (3) are equipped with a heating device (6). The punch (4) includes a first cooling area (41), a second cooling area (42), and a third cooling area (43) corresponding to the thick area, the thickness transition area, and the thin area, respectively. The cooling medium flow rate, temperature, pressure, or heat transfer coefficient of the first cooling area (41), the second cooling area (42), and the third cooling area (43) are different. Based on the material flow requirements and the local temperature control principle, the initial unequal thickness aluminum alloy blank (1) is heated by the heating device (6), and the thick area, the thickness transition area and the thin area are cooled by the first cooling area (41), the second cooling area (42) and the third cooling area (43) respectively. The punch (4) is controlled to push the initial unequal thickness aluminum alloy blank (1) to perform curved surface deep drawing to obtain the target aluminum alloy curved surface unequal thickness thin shell part.

2. The method for localized differential temperature deep drawing of aluminum alloy unequal thickness curved thin shells according to claim 1, characterized in that, The process of determining material flow requirements based on target needs includes: Based on the target requirements, obtain the target wall thickness distribution and the three-dimensional geometry of the target aluminum alloy curved surface thin-shell part with unequal thickness; Based on the target wall thickness distribution and the three-dimensional geometry, the target surface is discretized to obtain discrete regions, and the geometric wall thickness feature parameters of each discrete region are extracted. Based on the geometric wall thickness characteristic parameters, the inverse mapping method is used to establish the correspondence between the discrete region and the initial planar slab material region, and the material flow requirements are evaluated. Based on the geometric wall thickness characteristic parameters, the discrete regions, and the material flow requirements, a benchmark local differential temperature deep drawing finite element model is established for simulation and solution, and the simulation results of each discrete region are obtained. Based on the simulation results and preset thresholds, a distribution of potential risk locations is generated.

3. The method for localized differential temperature deep drawing of aluminum alloy unequal thickness curved thin shells according to claim 1, characterized in that, The initial design of the unequal thickness aluminum alloy slab (1) includes: Based on the target wall thickness distribution and material flow requirements, the initial unequal thickness aluminum alloy slab (1) is designed, the thickness transition zone is a continuous and smooth transition structure, and the thickness ratio of the thick zone to the thin zone is greater than 1.

4. The method for localized differential temperature deep drawing of aluminum alloy unequal thickness curved thin shells according to claim 1, characterized in that, The heating of the initial unequal thickness aluminum alloy slab (1) by the heating device (6), and the cooling of the thick area, the thickness transition area and the thin area by the first cooling area (41), the second cooling area (42) and the third cooling area (43) respectively, includes: The actual temperatures of the thick region, the thickness transition region, and the thin region are obtained by the temperature measuring device (7); Based on the local temperature control principle, a temperature control method is adopted to control the heating device (6) to heat the initial unequal thickness aluminum alloy slab (1) according to the temperature deviation between the actual temperature and the target temperature, and to adjust the cooling medium flow rate of the first cooling zone (41), the second cooling zone (42) and the third cooling zone (43).

5. The method for localized differential temperature deep drawing of aluminum alloy unequal thickness curved thin shells according to claim 1, characterized in that, Also includes: A pressure-bearing hot gas cavity (5) is provided below the die (2). The pressure-bearing hot gas cavity (5) is filled with hot gas medium (52) through a hot gas medium passage (51). The hot gas medium (52) is used to provide hot gas counter-pressure support to the initial unequal thickness aluminum alloy slab (1).

6. The method for localized differential temperature deep drawing of aluminum alloy unequal thickness curved thin shells according to claim 1, characterized in that, Also includes: Based on the given thickness distribution of unequal-thickness slabs and the given target surface, determine multiple combinations of cooling medium flow rates for the first cooling region (41), the second cooling region (42), and the third cooling region (43); The forming process is carried out according to the cooling medium flow rate combination to obtain the forming result corresponding to each cooling medium flow rate combination; By comparing the various forming results, a reasonable combination of cooling medium flow rates corresponding to the given unequal thickness slab thickness distribution and the given target surface is determined.

7. The method for localized differential temperature deep drawing of aluminum alloy unequal thickness curved thin shells according to claim 5, characterized in that, Also includes: Based on the given thickness distribution of unequal-thickness slabs and the given target surface, determine multiple sets of process parameter combinations including cooling medium flow rate, hot gas back pressure, hot gas temperature, punch speed, blank holder force, and endpoint holding time. The forming process is carried out according to the combination of process parameters to obtain the forming result corresponding to each combination of process parameters; By comparing the various forming results, a reasonable combination of process parameters corresponding to the given unequal thickness slab thickness distribution and the given target surface is determined.

8. The method for localized differential temperature deep drawing of aluminum alloy unequal thickness curved thin shells according to claim 1, characterized in that, After obtaining the target aluminum alloy curved surface thin-shell part with unequal thickness, the process further includes: Obtain the actual curved surface and wall thickness distribution of the target aluminum alloy thin-shell part with unequal thickness, and determine the surface deviation based on the actual curved surface and the target curved surface in the target requirement; Based on the wall thickness distribution and the target wall thickness distribution in the target requirement, the wall thickness deviation is determined, wherein the surface deviation and the wall thickness deviation are used for the next round of temperature difference or process parameter correction.

9. A localized differential temperature deep drawing apparatus for aluminum alloy unequal thickness curved thin shells, characterized in that, The device includes a die (2), a blank holder (3), and a punch (4). The die (2) is used to place the heated initial unequal thickness aluminum alloy blank (1). The blank holder (3) is pressed against the edge side circumferential of the initial unequal thickness aluminum alloy blank (1). The punch (4) is pressed on the drawing zone of the initial unequal thickness aluminum alloy blank (1). The die (2) and / or the blank holder (3) are equipped with a heating device (6). The punch (4) includes a first cooling zone (41), a second cooling zone (42), and a third cooling zone (43) corresponding to the thick zone, the thickness transition zone, and the thin zone of the drawing zone, respectively. The cooling medium flow rate, temperature, pressure, or heat transfer coefficient of the first cooling zone (41), the second cooling zone (42), and the third cooling zone (43) are different in at least one of the following: cooling medium flow rate, temperature, pressure, or heat transfer coefficient.

10. The aluminum alloy unequal thickness curved thin shell local differential temperature deep drawing apparatus according to claim 9, characterized in that, It also includes a temperature measuring device 7, which is set at a representative position of the die 2, the pressing area of ​​the pressing part 3, the punch 4 or the initial unequal thickness aluminum alloy blank 1, and is used to obtain the actual temperature of the thick area, the thickness transition area and the thin area respectively; It also includes a pressurized hot gas chamber 5, which is located below the die 2. The pressurized hot gas chamber 5 is filled with hot gas medium 52 through the hot gas medium passage 51. The hot gas medium 52 is used to provide hot gas counter pressure support to the initial unequal thickness aluminum alloy slab 1. The first cooling zone 41 is provided with a first cooling water inlet 411 and a first cooling water outlet 412, the second cooling zone 42 is provided with a second cooling water inlet 421 and a second cooling water outlet 422, and the third cooling zone 43 is provided with a third cooling water inlet 431 and a third cooling water outlet 432. It also includes a controller equipped with local temperature control principles and temperature control methods.

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