A forming method for suppressing delamination cracking of high-strength aluminum alloy grid wall panels

Abstract

The application provides a forming method for inhibiting delamination cracking of a high-strength aluminum alloy grid wallboard, the wallboard is provided with a plurality of ribs, a grid structure is formed through the ribs, and a skin area is formed between the grid structures; the thickness of the ribs is 7.5 mm, and the thickness of the skin area is 2.8 mm; the wallboard is provided with a flange area, a first boss area and a second boss area; the first boss area is provided with two longitudinally arranged first square bosses; and the second boss area is provided with two transversely arranged second square bosses; the forming method comprises the following steps: S1, optimizing the structure of the two first square bosses of the wallboard; S2, optimizing the structure of the two second square bosses of the wallboard; S3, optimizing the structure of the circular boss of the wallboard; and S4, roll bending forming; and the application can prevent cracking in local areas of the wallboard.

Description

Technical Field

[0001] This invention belongs to the field of spacecraft manufacturing technology, and in particular relates to a forming method for suppressing delamination cracking of high-strength aluminum alloy mesh panels. Background Technology

[0002] The new generation of launch vehicle propellant tanks uses 2195 aluminum-lithium alloy. Based on load-bearing and accessory installation requirements, it is processed using 2195-T8 temper material. The wall panel ribs are 7.5mm thick, and the skin area is 2.8mm thick. The structure is diverse with complex mesh relationships, including flange bosses and square bosses without ribs to restrict corners (these are parts that need to be machined). The product features an internal mesh structure.

[0003] Because 2195 aluminum-lithium alloy has a high yield strength ratio, large springback, and low elongation, it exhibits a significant tendency to crack due to structural differences in the product. This makes the forming process more technically challenging. During the forming process, the stress distribution inside the material is uneven, and the stress in local areas may exceed the material's yield strength or tensile strength, making it more prone to crack initiation and propagation.

[0004] Therefore, based on the material properties, part structure characteristics, and unexpected situations during the forming process, this invention adopts a method of "multiple structural optimization design + multiple small reduction rolling bending method + crease critical definition + online rolling bending measurement + transition zone gradient reinforcement" to rationally design the forming process path and parameters, and produce qualified products that meet assembly requirements.

[0005] In engineering applications, 2195 aluminum-lithium alloy built-in triangular mesh panels are usually formed by roll bending in the T34 state, and then artificially aged to finally improve their performance indicators to the heat-treated strengthened state.

[0006] The main problems encountered during the direct bending forming of heat-treated T8 state 2195 aluminum-lithium alloy panels are large and difficult to control springback. Aluminum-lithium alloy itself has high yield strength and high elastic modulus, resulting in significant springback after roll bending, especially for panels in the T8 state, which are often accompanied by large openings, large boss structures, and large flange structures. Springback deformation may cause the final shape to fail to meet assembly requirements. During roll bending, the skin is under tension and the ribs are under compression. Due to the discontinuity of stiffness in abrupt transition areas, the ribs are prone to lateral instability, manifesting as skin bending in abrupt transition areas and delamination cracking of the ribs, leading to the scrapping of parts.

[0007] There is currently no precedent in China for the direct bending forming of heat-treated T8 state 2195 aluminum-lithium alloy mesh panels. T8 state 2195 aluminum-lithium alloy has a high yield strength ratio, a small process window, and greater springback compared to 2219 alloy, making it prone to delamination and cracking. To address the issue of abrupt cracking and delamination in areas of structural abrupt change during cold roll bending of this material, the following measures were taken: weakening of local boss stiffness; elimination of variable thickness structures in individual meshes and variable thickness design of transition ribs; reinforcement design with discrete inner lining plates in hollow areas; overall structural optimization; prevention of localized cracking; and rational design of roll bending and shaping process parameters to produce parts with high dimensional accuracy.

[0008] This T8-state 2195 aluminum-lithium alloy features a unique internal mesh panel structure with large bosses and flanges. It was formed using a normal roll bending method. Due to uneven stress distribution within the material, delamination and cracking occurred in the triangular ribs at the transition area between the flange area and the mesh structure; and instability and cracking occurred at the root fillet of the transition area between the uniform-thickness square boss area and the mesh. Summary of the Invention

[0009] In view of this, the present invention aims to provide a forming method for suppressing delamination cracking of high-strength aluminum alloy mesh panels, thereby preventing cracking in localized areas.

[0010] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0011] A forming method for suppressing delamination cracking of high-strength aluminum alloy mesh wall panels, wherein the wall panel is provided with a number of ribs, which form a mesh structure, and the area between the meshes is a skin area, the thickness of the ribs is 7.5 mm, and the thickness of the skin area is 2.8 mm;

[0012] The wall panel is provided with a flange area, a first boss area and a second boss area. The first boss area is a boss area that can be reduced in size; the second boss area is a boss area that cannot be moved or reduced in size.

[0013] The first protrusion area has two longitudinally arranged square protrusions, and the second protrusion area has two transversely arranged square protrusions; the thickness of both the first and second square protrusions is 7.5mm.

[0014] Before the wall panel is formed, the flange area is a circular boss with a diameter of 390mm;

[0015] After the wall panel is formed, a flange through hole is drilled at the center of the circular boss. The diameter of the flange through hole is 300mm.

[0016] A forming method for suppressing delamination cracking in high-strength aluminum alloy mesh panels includes the following steps;

[0017] S1. Optimize the structure of the two No. 1 square protrusions on the wall panel;

[0018] S2. Optimize the structure of the two No. 2 square bosses on the wall panel;

[0019] S3. Optimize the structure of the circular bosses on the wall panel;

[0020] S4. Roll forming.

[0021] Furthermore, in step S1, the area of ​​the first square boss located on the upper part of the wall panel is reduced, and this boss is designated as the first square boss A; the overall thickness is reduced to 5mm, and the 6mm wide rectangular rib on the outer ring of the optimized first square boss is left unprocessed, while the thinned area of ​​the rib is expanded. Deburring, rounding the corners to R10, and blunting the sharp edges to a minimum of 0.5mm.

[0022] Furthermore, if there is a residual thick area of ​​unprocessed material at the junction of the optimized square boss and the rib, it needs to be thinned to 5mm.

[0023] Furthermore, in step S1, the area of ​​the first square boss located at the bottom of the wall panel is also reduced, and it is designated as the first square boss B.

[0024] The first square boss B extends outward to the first side shaded area on the other side of the rib. The first side shaded area is thinned to 5mm and smoothly transitions with the thin area of ​​the triangular mesh. The thinned part smoothly transitions with the bottom corner R3 of the adjacent axial rib and the bottom corner R3 of the adjacent upper and lower parts.

[0025] The shaded area in section one is thinned to 5mm, while the outer 6mm wide rectangular rib is left unprocessed. The thinned boss and the bottom corner of the surrounding ribs are R8, and the corners are smoothly transitioned to a rounded corner of R10. The burrs are removed, and the sharp edges are blunted to a minimum of 0.5.

[0026] Furthermore, in step S2, the two square bosses of number two are connected to form a square boss and extended to the longitudinal ribs on both sides. The shaded area in number two is thinned to 5mm and smoothly transitions with the thin area of ​​the triangular mesh. The thinned part smoothly transitions with the bottom corner R3 of the adjacent axial rib and with the bottom corner R3 of the adjacent upper and lower parts.

[0027] The entire shaded area of ​​No. 2 is thinned to 5mm. The rectangular rib with a width of 6mm is left unprocessed in the shaded area of ​​No. 2 on the outer ring. The bottom corner of the thinned boss and the surrounding ribs is R8. The thinned boss and the ribs are connected and extended outwards by 20-25mm to form a slope. The corners are smoothly transitioned with a radius of R10. The burrs are removed and the sharp edges are blunted to a minimum of 0.5.

[0028] Furthermore, the slope is designed with a transition of 7.5mm-5mm.

[0029] Furthermore, in step S3, the circular shaded area within the 290mm diameter range of the optimized circular boss is thinned to 2.8mm, and the bottom angle between the thinned boss and the original boss is R8; the circular side shaded area with the bottom angle of the outer ring with a diameter of 390mm is processed to R8, allowing for processing 5-6mm inward on one side; deburring and blunting the sharp edges to a depth of not less than 0.5mm.

[0030] Furthermore, in step S4, a three-axis plate rolling machine is used for roll bending. Of the three rollers, the two lower rollers are driving rollers, and the upper roller is a driven roller. The different radii of curvature of the part can be controlled by changing the relative positions between the rollers. The two lower rollers are on the same horizontal line, the vertical distance between the straight line containing the center point of the lower roller and the straight line containing the center point of the upper roller is 'a', and the distance between the center points of the two lower rollers is 'b'.

[0031] Furthermore, the specific solution adopted for the roll bending is as follows:

[0032] S41. Judgment of creases from multiple passes of small reduction rolling bending;

[0033] S42. Sheet material measurement mechanism during roll bending process;

[0034] S43, Gradient strengthening in the transition zone; During the early roll forming process of T8 state 2195 aluminum-lithium alloy mesh wall panel, due to the presence of local bosses, flanges and abrupt changes in thickness, the strain gradient increases sharply, which can easily induce cross-sectional delamination.

[0035] Furthermore, the specific method for gradient enhancement in the transition region is as follows:

[0036] S431. Lay a conformal pad on the lower surface of the abrupt change zone;

[0037] S432, The front end of the pad is designed with a wedge-shaped transition to ensure smooth migration of the rigid plate;

[0038] S433, Correction;

[0039] S434, Packaging and Delivery.

[0040] Compared with existing technologies, the forming method for suppressing delamination cracking of high-strength aluminum alloy mesh panels described in this invention has the following advantages:

[0041] (1) The forming method for suppressing delamination cracking of high-strength aluminum alloy mesh wall panel described in this invention improves the forming feasibility: T8 state 2195 aluminum-lithium alloy mesh wall panel is transformed by a series of structural optimizations, changing the original structure boss to skin abrupt change at 90°, and the rib slope change, etc., so as to systematically suppress delamination cracking from the structural design.

[0042] (2) The forming method for suppressing delamination cracking of high-strength aluminum alloy mesh wall panels described in this invention significantly improves the defect suppression rate: T8 state 2195 aluminum-lithium alloy mesh wall panels are formed by exploring the experience of folding criticality-crack precursor as the criterion. Before the folding criticality appears, the arc reaches R3500mm-R3600mm. The combination strategy of "padding thickness less than thickness difference by 0.2-0.4mm + wedge transition" is introduced to effectively eliminate crack defects.

[0043] (3) The forming method for suppressing delamination cracking of high-strength aluminum alloy mesh wall panel described in this invention improves forming accuracy: T8 state 2195 aluminum-lithium alloy mesh wall panel optimizes and solidifies process parameters through "small step progressive" three-axis rolling bending strategy and forms crease critical-crack precursor empirical criterion, and introduces "transition zone gradient strengthening" strategy, which effectively improves forming accuracy, and the final product meets the curvature of R2496.

[0044] (4) The forming method for suppressing delamination cracking of high-strength aluminum alloy mesh wall panels described in this invention has a universal process window: the method with "structural optimization - small step progressive triaxial rolling bending + gradient strengthening of the transition zone before the crease" as the core has been successfully applied to the same material state and the same series of built-in triangular mesh wall panels, realizing one-click reuse of process parameters and significantly reducing the trial production cost of new products.

[0045] (5) The forming method for suppressing delamination cracking of high-strength aluminum alloy mesh wall panels described in this invention forms a detection database and greatly improves production efficiency: a horizontal measurement and vertical correspondence mechanism for the rolling bending process of thin-walled T8 state 2195 aluminum-lithium alloy mesh wall panels is established, forming an effective and reliable correspondence relationship, which is conducive to detection during the forming process and improves product production efficiency. Attached Figure Description

[0046] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0047] Figure 1 This is a schematic diagram of the wall panel before optimization as described in an embodiment of the present invention;

[0048] Figure 2 This is a schematic diagram of the first square boss A before optimization, as described in an embodiment of the present invention.

[0049] Figure 3 This is a schematic diagram of the first square boss B before optimization, as described in an embodiment of the present invention.

[0050] Figure 4 This is a schematic diagram of the second square boss before optimization, as described in an embodiment of the present invention.

[0051] Figure 5This is a schematic diagram of the circular boss before optimization as described in an embodiment of the present invention;

[0052] Figure 6 This is a schematic diagram of the optimized square boss A as described in an embodiment of the present invention;

[0053] Figure 7 This is a schematic diagram of the optimized square boss B according to an embodiment of the present invention;

[0054] Figure 8 This is a schematic diagram of the optimized second square boss as described in an embodiment of the present invention;

[0055] Figure 9 This is a schematic diagram of the optimized circular boss according to an embodiment of the present invention;

[0056] Figure 10 This is a schematic diagram of the optimized wall panel according to an embodiment of the present invention;

[0057] Figure 11 This is a schematic diagram of step S4, the three-axis rolling process, as described in an embodiment of the present invention.

[0058] Figure 12 This is a schematic diagram of the horizontal measurement position area according to an embodiment of the present invention;

[0059] Figure 13 This is a schematic diagram illustrating the horizontal measurement principle described in an embodiment of the present invention;

[0060] Figure 14 This is a schematic diagram of the pad wedge according to an embodiment of the present invention;

[0061] Figure 15 This is a schematic diagram of a 6mm wide square boss rib as described in an embodiment of the present invention.

[0062] Explanation of reference numerals in the attached figures

[0063] 1. Square boss A (No. 1); 2. Square boss B (No. 1); 21. Shaded area on the side (No. 1); 22. Shaded area in the middle (No. 1); 3. Square boss (No. 2); 31. Shaded area in the middle (No. 2); 32. Shaded area on the side (No. 2); 4. Circular boss; 51. Rib; 52. Flange through hole; 54. Front roller; 55. Rear roller; 561. Horizontal actual state; 562. Horizontal ground; 661. Aluminum alloy plate; 662. PE sheet; 71. Flange area; 72. Boss area (No. 1); 73. Boss area (No. 2). Detailed Implementation

[0064] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0065] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0066] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0067] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0068] The wall panel is provided with several ribs 51, which form a grid structure. The area between the grids is the skin area. The thickness of the ribs 51 is 7.5 mm, and the thickness of the skin area is 2.8 mm.

[0069] like Figure 1 As shown, the process structure before optimization is as follows: the wall panel is provided with a flange area 71, a first boss area 72 and a second boss area 73; the first boss area 72 is designed to be a boss area that can be reduced in size; the second boss area 73 is designed to be a boss area that cannot be moved or reduced in size; optimizing the wall panel structure under the premise of meeting the design requirements is an important problem to be solved by this application.

[0070] Before optimization, area 72 of protrusion 1 had two longitudinally arranged square protrusions of protrusion 1. The square protrusion 1 located on the upper part of the wall panel was designated as square protrusion 1 A1, as shown below. Figure 2 As shown; the first square boss located at the bottom of the wall panel is designated as square boss B2, as follows. Figure 3 As shown;

[0071] Before optimization, the second protrusion area 73 had two horizontally arranged second square protrusions, the structure of which was as follows: Figure 4 As shown;

[0072] Before optimization, the thickness of both the No. 1 and No. 2 square bosses was 7.5mm.

[0073] The circular boss before optimization is as follows Figure 5 As shown, before the wall panel is formed, the flange area is a circular boss 4 with a diameter of 390mm.

[0074] After the wall panel is formed, a flange through hole is drilled at the center of the circular boss 4. The diameter of the flange through hole is 300mm. Forming refers to bending forming. The flange area is formed by drilling the flange hole after bending forming. The area from the flange through hole to the outer ring of the circular boss is still the boss area.

[0075] Optimized process structure: During the forming process, it was found that all bosses of equal height experienced varying degrees of delamination and cracking. Therefore, the boss design should be thinned during structural processing. For abrupt transition areas, ribs also exhibit severe delamination and cracking; therefore, a gradual buffer structure design is particularly important. Furthermore, special attention needs to be paid to avoiding two thicknesses within individual mesh structures, which could exacerbate delamination and cracking. Therefore, an optimization scheme was investigated:

[0076] A forming method for suppressing delamination cracking in high-strength aluminum alloy mesh panels includes the following steps;

[0077] S1. Optimize the structure of the two No. 1 square protrusions on the wall panel;

[0078] S2. Optimize the structure of the two No. 2 square bosses on the wall panel;

[0079] S3. Optimize the structure of the circular bosses on the wall panel;

[0080] S4. Roll forming.

[0081] Preferably, in step S1, the area of ​​the first square protrusion A1 located on the upper part of the wall panel is reduced, such as... Figure 6 As shown, the overall thickness is reduced to 5mm. The 6mm wide rectangular rib on the outer ring of the optimized square boss is left unprocessed, and the thinned area of ​​the rib is expanded. Deburr, fillet R10, and blunt the sharp edges to a minimum of 0.5.

[0082] Furthermore, if there is a residual thick area of ​​unprocessed material at the junction of the optimized square boss and the rib, it needs to be thinned to 5mm.

[0083] Furthermore, such as Figure 7As shown, in step S1, the area of ​​the first square protrusion B2 located at the lower part of the wall panel is also reduced.

[0084] The first square boss B2 extends outward to the first side shaded area on the other side of the rib. The first side shaded area is thinned to 2.8mm and smoothly transitions with the thin area of ​​the triangular mesh. The thinned part smoothly transitions with the bottom corner R3 of the adjacent axial rib and with the bottom corner R3 of the adjacent upper and lower parts.

[0085] The shaded area in section one is thinned to 5mm, while the outer 6mm wide rectangular rib is left unprocessed. The thinned boss and the bottom corner of the surrounding ribs are R8, and the corners are smoothly transitioned to a rounded corner of R10. The burrs are removed, and the sharp edges are blunted to a minimum of 0.5.

[0086] Preferred, such as Figure 8 As shown, in step S2, the two square bosses 3 are connected to form a square boss and extend to the longitudinal ribs on both sides. The shaded area 31 in the second part is thinned to 5mm and smoothly transitions with the thin area of ​​the triangular mesh. The thinned part smoothly transitions with the bottom corner R3 of the adjacent axial rib and with the bottom corner R3 of the adjacent upper and lower parts.

[0087] The shaded area 31 in section 2 is thinned to 5mm, while the 6mm wide rectangular rib in the outer shaded area of ​​section 2 is left unprocessed. For further illustration, an enlarged diagram of the 6mm wide rectangular rib structure is shown below. Figure 15 As shown; the thinned boss and the bottom corner of the surrounding ribs are R8, and the thinned boss and the ribs are connected and extended outwards by 20-25mm to form a slope. The corners are smoothly transitioned with a rounded corner of R10, deburred, and the sharp edges are blunted to a depth of not less than 0.5. Preferably, the slope is a transition design of 7.5mm-5mm.

[0088] Preferably, in step S3, the diameter of the central region of the optimized circular boss 4 is 290mm; the shaded area at the center of the circular boss within the specified range is thinned to 2.8mm, such as... Figure 9 As shown, the bottom angle of the thinned boss is R8; the circular side shadow area with the bottom angle of the outer ring with a diameter of 390mm is machined to R8, and machining 5-6mm inward on one side is allowed; deburr and blunt the sharp edge by not less than 0.5.

[0089] The mesh is machined using a milling machine. For the boss structure, the boss is thinned. In the structural areas with abrupt transitions, a gradual buffer structure design is adopted. Within a single local mesh structure, two thicknesses are avoided to prevent cracking. Based on the above principles, the sheet metal is machined while meeting the assembly requirements.

[0090] like Figure 10The diagram shows the optimized flat panel structure, with a maximum thickness of 5mm in the boss area. During the roll bending process, the structural abrupt change zone of the mesh panel is a stress concentration sensitive area. Initially, a four-axis roll bending forming method was adopted. During the production process, due to the clamping of the upper and lower rollers, the root of the rib is called the curvature abrupt change point, and the curvature change in the forming area is strong. A high strain gradient is easily formed in the transition area between the boss and the skin, inducing shear cracking, which is particularly obvious in the forming process of T8 state 2195 aluminum-lithium alloy.

[0091] Preferably, given this, during the roll bending process, the lower roller is avoided from participating, and a three-axis roll bending forming method is adopted, such as... Figure 11 As shown, due to the long forming force transmission path and uniform stress-strain distribution, local strain abrupt changes can be effectively avoided to a large extent, thereby reducing the probability of root crack initiation in the transition region. Of the three rollers, the two lower rollers are driving rollers, and the upper roller is a driven roller. Different radii of curvature of the part can be controlled by changing the relative positions between the rollers. The two lower rollers are on the same horizontal line, the vertical distance between the straight line containing the center point of the lower roller and the straight line containing the center point of the upper roller is 'a', and the distance between the center points of the two lower rollers is 'b'.

[0092] The preferred roll bending solution is as follows:

[0093] S41. Judgment of creases from multiple passes of small reduction rolling bending;

[0094] During the initial roll forming process of T8 state 2195 aluminum-lithium alloy mesh wall panel, it exhibits a significant "low strain rate - high springback" characteristic. After showing obvious springback in the initial rolling stage, the curvature hardly increases, and the wall panel seems to "hold" the upper roller. When the amount of pressure exceeds a certain critical point, a strain localization zone is generated inside, the curvature jumps instantaneously, and the overall forming changes from "slow" to "sudden bending".

[0095] Based on this phenomenon, after multiple verification experiments, a "small step progression" strategy was finally adopted: that is, the upper roller presses down slightly at a fixed step distance, while the curvature is measured in real time with an arc measuring instrument and the outer surface of the product is monitored step by step. According to practical experience, once obvious creases appear on the outer surface, it is usually a precursor to cracks. Based on the crease phenomenon, the location of the creases and the forming critical point at that location are identified; as shown in Table 1 below: T8 state aluminum-lithium alloy mesh wall panel roll bending forming process parameter table.

[0096] Table 1:

[0097]

[0098] Analysis confirmed that the creases on the outer surface were all located in transitional zones of abrupt structural changes, such as the transition area from the boss to the mesh, and the transition area from the mesh to the flat plate. Statistically, when creases appeared in the transition area from the boss / large flange area to the mesh, the curvature at that crease was typically <R2496, while the curvature in other areas generally reached R3000-R3200. When creases appeared in the transition area from the mesh to the flat plate, the curvature at that crease was typically <R2496, while the curvature in other areas generally reached R2600-R2700.

[0099] S42. Sheet material measurement mechanism during roll bending process;

[0100] During roll forming of weakly rigid thin-walled aluminum-lithium alloy mesh panels, the measurement data during the forming process is not the actual measurement data under the upright state due to the influence of self-weight deflection. Therefore, a set of measurement data parameters was formed based on a "horizontal-standing" dual-state measurement and conversion mechanism. Because the bending arc is 120° and the circumferential length of the 5m diameter sheet is relatively long, the surface appears relatively straight during horizontal forming. Generally, the fixed horizontal measurement position is within 100-150mm behind the rear roller 55, with the rear roller 55 slightly raised and overlapping. Figure 12 As shown in Table 2 below, the corresponding measurement data correspondence is as follows: Measurement data within the 400mm area at the end of the T8 state aluminum-lithium alloy mesh wall panel.

[0101] Table 2:

[0102]

[0103] When measured with the opening facing upwards and placed horizontally, after forming to R2496mm, the distance between the end and the ground is approximately 600-700mm. For example... Figure 13 As shown.

[0104] S43. Gradient strengthening in the transition zone: During the early roll forming of T8 state 2195 aluminum-lithium alloy mesh panels, the strain gradient increases sharply due to the presence of local bosses, flanges, and abrupt changes in thickness, which easily induces cross-sectional delamination. Preliminary verification shows that this type of defect exhibits a three-stage evolution characteristic of "crease-microcrack-propagation": when the overall curvature is still on the order of R3000mm, creases appear first in the abrupt change zone, with a strain concentration factor exceeding 2.5; subsequently, cracks propagate rapidly along the interface of the transition zone ribs.

[0105] Based on the above mechanism, this pass introduces a "transition zone gradient enhancement" strategy in the target curvature R3500mm-R3600mm stage:

[0106] S431. A conformal (2A14T8 state or 2219C10SY state) aluminum alloy plate 661 and PE plate 662 composite pad (thickness-stiffness coupling pad, less than 0.2-0.4mm thickness difference, parameters are stable and controllable) is laid on the lower surface of the transition zone. The length ratio of the aluminum alloy plate to the PE plate 662 is 1:2. One end of the aluminum alloy pad is close to the position of the boss with strong stiffness, and the PE plate 662 is far away from the boss position, which can suppress local wrinkles without excessive hardening.

[0107] S432, the front end of the pad is designed with a wedge-shaped transition to ensure smooth migration of the rigid board; such as Figure 14 As shown,

[0108] The results show that the crease incidence rate in the abrupt change zone decreased from 100% to 5%, the effective surface delamination and cracking were controlled, and the forming accuracy was controllable.

[0109] S433, Shaping; Due to the limitations of the three-axis rolling bending method, the straight sections at the ends of the parts inevitably exist during the forming process, and manual shaping is required.

[0110] S434, Packaging and Delivery.

[0111] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A forming method for suppressing delamination cracking in high-strength aluminum alloy mesh panels, characterized in that: The wall panel has several ribs that form a grid structure. The area between the grids is the skin area. The thickness of the ribs is 7.5 mm, and the thickness of the skin area is 2.8 mm. The wall panel is provided with a flange area, a first boss area and a second boss area. The first boss area is a boss area that can be reduced in size; the second boss area is a boss area that cannot be moved or reduced in size. The first protrusion area has two longitudinally arranged square protrusions, and the second protrusion area has two transversely arranged square protrusions; the thickness of both the first and second square protrusions is 7.5mm. Before the wall panel is formed, the flange area is a circular boss with a diameter of 390mm; After the wall panel is formed, a flange through hole is drilled at the center of the circular boss. The diameter of the flange through hole is 300mm. A forming method for suppressing delamination cracking in high-strength aluminum alloy mesh panels includes the following steps; S1. Optimize the structure of the two No. 1 square protrusions on the wall panel; S2. Optimize the structure of the two No. 2 square bosses on the wall panel; S3. Optimize the structure of the circular bosses on the wall panel; S4. Roll forming; In step S1, the area of ​​the first square boss set on the upper part of the wall panel is reduced, and this boss is designated as the first square boss A; the overall thickness is reduced to 5mm, the outer 6mm wide rectangular rib of the optimized first square boss is left unprocessed, and the thinning area of ​​the rib is expanded; deburring, rounding the corners to R10, deburring, and blunting the sharp edges to a depth of not less than 0.

5.

2. The forming method for suppressing delamination cracking of high-strength aluminum alloy mesh panels according to claim 1, characterized in that: If the area where the optimized square boss meets the rib has a residual thick area from the initial unprocessed stage, it needs to be thinned to 5mm.

3. The forming method of claim 1, wherein: In step S1, the area of ​​the first square protrusion located at the bottom of the wall panel is also reduced, and it is designated as the first square protrusion B. The first square boss B extends outward to the first side shaded area on the other side of the rib. The first side shaded area is thinned to 2.8mm and smoothly transitions with the thin area of ​​the triangular mesh. The thinned part smoothly transitions with the bottom corner R3 of the adjacent axial rib and with the bottom corner R3 of the adjacent upper and lower parts. The shaded area in section one is thinned to 5mm, while the outer 6mm wide rectangular rib is left unprocessed. The thinned boss and the bottom corner of the surrounding ribs are R8, and the corners are smoothly transitioned to a rounded corner of R10. The burrs are removed, and the sharp edges are blunted to a minimum of 0.5mm.

4. The method of claim 1 wherein: the high strength aluminum alloy panel is formed by a process comprising: providing a high strength aluminum alloy panel having a first surface and a second surface; and applying a first coating to the first surface of the high strength aluminum alloy panel; and applying a second coating to the second surface of the high strength aluminum alloy panel. In step S2, the two square bosses No. 2 are connected to form a square boss and extended to the longitudinal ribs on both sides. The shaded area in No. 2 is thinned to 5mm and smoothly transitions with the thin area of ​​the triangular mesh. The thinned part smoothly transitions with the bottom corner R3 of the adjacent axial rib and with the bottom corner R3 of the adjacent upper and lower parts. The entire shaded area of ​​No. 2 is thinned to 5mm. The rectangular rib with a width of 6mm is left unprocessed in the shaded area of ​​No. 2 on the outer ring. The bottom corner of the thinned boss and the surrounding ribs is R8. The thinned boss and the ribs are connected and extended outwards by 20-25mm to form a slope. The corners are smoothly transitioned with a radius of R10. The burrs are removed and the sharp edges are blunted to a minimum of 0.

5.

5. The method of claim 4, wherein the method further comprises: applying a coating to the high strength aluminum alloy grid panel. The slope has a transition design of 7.5mm-5mm.

6. The forming method for suppressing delamination cracking of high-strength aluminum alloy mesh panels according to claim 1, characterized in that: In step S3, the circular shaded area within the 290mm diameter range of the optimized circular boss is thinned to 2.8mm, and the bottom angle between the thinned boss and the original boss is R8; the circular side shaded area with the bottom angle of the outer ring with a diameter of 390mm is processed to R8, and 5-6mm of processing is allowed on one side; deburring and blunting the sharp edge by not less than 0.

5.

7. The forming method for suppressing delamination cracking of high-strength aluminum alloy mesh panels according to claim 1, characterized in that: In step S4, a three-axis plate rolling machine is used for roll bending. Of the three rollers, the two lower rollers are driving rollers and the upper roller is driven roller. The different radii of curvature of the parts can be controlled by changing the relative positions between the rollers. The two lower rollers are on the same horizontal line. The vertical distance between the straight line where the center point of the lower roller is located and the straight line where the center point of the upper roller is located is a, and the distance between the center points of the two lower rollers is b.

8. The forming method for suppressing delamination cracking of high-strength aluminum alloy mesh panels according to claim 7, characterized in that: The specific solution adopted for the roll bending method is as follows: S41. Judgment of creases from multiple passes of small reduction rolling bending; S42. Sheet material measurement mechanism during roll bending process; S43, Gradient enhancement in the transition zone.

9. The method of claim 8, wherein the method further comprises: applying a coating to the high strength aluminum alloy grid panel. The specific method for gradient enhancement in the transition region is as follows: S431. Lay a conformal pad on the lower surface of the abrupt change zone; S432, The front end of the pad is designed with a wedge-shaped transition to ensure smooth migration of the rigid plate; S433, Correction; S434, Packaging and Delivery.

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