A forming process for high yield strength metal twisted honeycomb panels

Abstract

The application relates to the technical field of metal plate processing and manufacturing, and discloses a forming process of a high-yield-strength metal twisted honeycomb plate, which comprises the following steps: processing a solid wood mold according to a three-dimensional skin model; respectively placing 316 stainless steel face plates and O-state aluminum back plates on the solid wood mold to independently form curved surfaces; coating polyurethane double-component glue on the inner side surfaces of the twisted 316 stainless steel face plates and the twisted O-state aluminum back plates; placing an aluminum honeycomb core between the two layers of face plates, and then placing the aluminum honeycomb core into a composite mold for pressure preservation and curing to obtain a blank; carving and cutting the blank; and installing supporting aluminum angles at the preset overhanging surface parts of the cut twisted honeycomb plate. The process of independently forming the face plates and the back plates and then compositely curing the face plates and the back plates is adopted, so that the aluminum honeycomb core is prevented from being crushed due to direct pressing, and the curved surface forming precision of the product is improved; the supporting aluminum angles are used to prevent the unsupported edges from being deformed during logistics transportation, and the high-rigidity decoration demand of the building hyperbolic plate is met.

Description

Technical Field

[0001] This invention relates to the field of metal sheet processing and manufacturing technology, specifically to a forming process for a high yield strength metal twisted honeycomb panel. Background Technology

[0002] With the development of parametric design of building forms, a large number of double-sided twisted shapes are gradually appearing in building curtain walls. Designers' demand for hyperbolic metal decorative panels is constantly expanding. Metal honeycomb panels, due to their light weight and high structural strength, are widely used in lightweight building structural design.

[0003] Existing polyhedral curved metal honeycomb panels exhibit significant structural defects during manufacturing and application. In the curved surface forming stage, traditional processes typically involve pre-pressing the surface metal sheet, honeycomb core, and bottom metal sheet into a sandwich composite panel before integral curved forging. Due to the differences in yield point and springback stress between the face and back metals under bending stress, the overall pressing process easily leads to uneven stress on the internal aluminum honeycomb core and localized crushing deformation, resulting in a decrease in the overall stiffness of the finished product. Furthermore, simply increasing the thickness of the stainless steel surface layer to meet the high yield strength requirements of building facades increases residual forming stress within the metal, causing curvature springback deformation after demolding. Consequently, the final surface shape of the finished product fails to meet the dimensional accuracy requirements preset in the digital model.

[0004] Furthermore, conventional curved honeycomb panels lack effective structural support at their cantilevered edges after processing. Larger polyhedral twisted honeycomb panels are susceptible to physical deformation at their unsupported cantilevered edges during logistics transportation and on-site hoisting and handling, due to overload or external mechanical impacts. This results in the final panel dimensions arriving on-site failing to meet the splicing accuracy requirements of the original design drawings. Existing twisted metal honeycomb panels also lack standardized pre-embedded mechanical connection nodes at the decorative edges, relying solely on temporary external connectors for forced fixation. This leads to cumbersome on-site installation procedures and poor safety when multiple metal panels are spliced ​​together under load. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a molding process for high-yield-strength metal twisted honeycomb panels. This process aims to solve the problems of existing technologies, such as the tendency for the internal aluminum honeycomb core to crush and deform during integral pressing of the metal twisted honeycomb panel, low precision in curved surface forming, susceptibility to physical deformation of the overhanging edges during transportation, and difficulties in on-site installation due to the lack of standardized mechanical connection nodes. To address the above problems, the present invention provides the following technical solution: a forming process for a high yield strength metal twisted honeycomb panel, comprising the following steps: The wooden mold substrate is processed according to the three-dimensional surface model to obtain a solid wooden mold; A 316 stainless steel panel is placed on a solid wooden mold and curved to obtain a twisted 316 stainless steel panel. The O-state aluminum backplate is placed on a solid wooden mold and curved to obtain a twisted O-state aluminum backplate. Apply polyurethane two-component adhesive to the inner surface of the twisted 316 stainless steel panel and the inner surface of the twisted O-state aluminum back panel to obtain the coated twisted 316 stainless steel panel and the coated twisted O-state aluminum back panel. The aluminum honeycomb core is placed between the glued twisted 316 stainless steel panel and the glued twisted O-state aluminum back plate, and then placed in a composite mold for pressure curing to obtain a twisted honeycomb panel blank. The twisted honeycomb panel blank is carved and cut to obtain the cut twisted honeycomb panel; By installing supporting aluminum angles at the pre-set cantilevered portion of the cut twisted honeycomb panel, a high yield strength metal twisted honeycomb panel is obtained.

[0006] By adopting the above technical solution, and using solid wooden molds to forge and shape the 316 stainless steel panel and the O-state aluminum back plate separately, followed by composite curing, a high forming precision, low internal stress, and excellent overall structural rigidity are achieved. The specific mechanism includes: Step one involves fabricating a solid wooden mold using a parametrically constructed 3D skin model, enabling the mold to accurately map the spatial contours of the twisted surface. Under moderate pressure, the solid wooden mold provides uniform support and reaction force, absorbing some of the forging impact energy and preventing indentations on the metal panel surface.

[0007] Step two involves selecting a 316 stainless steel panel as the surface layer and an O-state aluminum backing plate as the back layer, and then independently molding each layer onto a solid wooden mold. The 316 stainless steel panel provides high surface yield strength and corrosion resistance; the O-state aluminum backing plate has a lower yield point and high plasticity, allowing it to conform to the mold shape and reduce backing plate springback. Separate molding of both layers avoids the crushing and deformation of the internal honeycomb core that would result from directly pressing together a sandwich structure.

[0008] Step 3: Using a two-component polyurethane adhesive, the twisted 316 stainless steel panel, aluminum honeycomb core, and twisted O-state aluminum backsheet are assembled and placed in a composite mold for pressure curing. The pressure-holding process induces a cross-linking reaction in the polyurethane two-component adhesive at a specific temperature, forming an adhesive layer with a certain degree of toughness. During the curing process, the adhesive layer absorbs and releases the residual molding stress of the 316 stainless steel panel, integrating the surface layer, honeycomb core, and back layer into a high-rigidity load-bearing whole.

[0009] Step four involves carving and cutting the cured twisted honeycomb panel blank, removing irregular excess material from the edges, and installing supporting angle aluminum at the pre-set cantilevered surfaces. The supporting angle aluminum creates a local rigid frame at the unsupported cantilevered edges, blocking the transmission of edge peeling stress and preventing deformation of the cantilevered surfaces during use.

[0010] Preferably, the composite surface of the 316 stainless steel panel is pre-polished before being placed on the solid wooden mold.

[0011] By employing the above technical solution, grinding can remove the oxide layer and impurities from the 316 stainless steel panel composite surface, increasing the micro-roughness of the metal surface. The roughened surface improves the mechanical bonding force of the polyurethane two-component adhesive, enhancing the peel strength between the surface layer and the aluminum honeycomb core.

[0012] Preferably, the thickness of the 316 stainless steel panel is 0.8-1.5mm; the forging pressure for forming the curved surface of the 316 stainless steel panel is 10-30MPa.

[0013] By adopting the above technical solution, 0.8-1.5mm thick 316 stainless steel panels achieve both the rigidity to resist external impacts and the flexibility to adapt to torsional deformation. Combined with a forging pressure of 10-30MPa, the 316 stainless steel panels undergo sufficient plastic deformation to reach a stable state, preventing outward springback deformation recovery force after forming.

[0014] Preferably, the thickness of the O-state aluminum backing plate is 0.8-2.0 mm; the forging pressure for forming the O-state aluminum backing plate is 10-30 MPa.

[0015] By adopting the above technical solution, the residual stress network inside the material can be eliminated by forging a 0.8-2.0mm thick O-state aluminum backing plate under a forging pressure of 10-30MPa. Because the O-state aluminum backing plate is relatively soft, appropriate pressure causes the aluminum molecular lattice to slide and recombine along the surface of the wooden mold, achieving stress-free bonding.

[0016] Preferably, when applying the two-component polyurethane adhesive, the coating amount of the two-component polyurethane adhesive is 150-300 g / m2.

[0017] By adopting the above technical solution, a coating amount of 150-300 g / m² can ensure that the adhesive forms a complete adhesive semi-circle on the end face of the aluminum honeycomb core. A coating amount below the lower limit will result in insufficient adhesive and detachment, while a coating amount above the upper limit will increase the overall weight of the board and cause adhesive overflow, affecting the edge cutting accuracy.

[0018] Preferably, the pressure-holding curing temperature is 20-60℃, and the pressure-holding curing time is 2-10h.

[0019] By employing the above technical solution, a constant temperature environment of 20-60℃ provides the activation energy required for the crosslinking reaction of isocyanate groups and hydroxyl groups in the polyurethane two-component adhesive. Maintaining constant temperature and pressure for 2-10 hours allows the reaction macromolecular chains to fully extend and penetrate the metal interface, forming a three-dimensional network structure and completely curing the honeycomb composite structure.

[0020] Preferably, the specific implementation method for carving and cutting the twisted honeycomb panel blank is as follows: place the twisted honeycomb panel blank on a 5-axis engraving machine, and use a tungsten carbide cutter to carve and cut the twisted honeycomb panel blank along the three-dimensional forming line.

[0021] By adopting the above technical solutions, the 5-axis engraving machine can adapt to changes in the spatial curvature of the twisted honeycomb panel blank. The tungsten carbide blade possesses high hardness and wear resistance, enabling smooth cutting along the three-dimensional forming line, avoiding serrated tears and residual cutting stress at curved surface edges caused by flat cutting tools.

[0022] Preferably, the specific implementation method for processing the wood mold substrate according to the three-dimensional skin model is as follows: by using parametric design technology, a three-dimensional skin model is established at a 1:1 scale and a wood mold processing drawing is exported, and the wood mold substrate is processed according to the wood mold processing drawing.

[0023] By adopting the above technical solutions, parametric design technology ensures lossless conversion of data from 3D digital models to physical wooden molds. The 1:1 scale directly eliminates dimensional errors caused by scaling compensation, ensuring that the curvature of the final machined metal honeycomb panel matches the design model.

[0024] Preferably, after obtaining the cut and twisted honeycomb panel, the method further includes: bonding a stainless steel twisted edge banding plate to the side of the cut and twisted honeycomb panel, and installing connecting angle aluminum at a preset position on the cut and twisted honeycomb panel.

[0025] By adopting the above technical solution, the stainless steel twisted edge panel seals the exposed sides of the aluminum honeycomb core, preventing environmental moisture from penetrating the honeycomb interior and causing electrochemical corrosion. Connecting angle aluminum provides standard mechanical installation nodes at preset positions, distributing the load of the twisted honeycomb panel itself to the main building structure's keel.

[0026] Preferably, when applying the two-component polyurethane adhesive, the two-component polyurethane adhesive is evenly applied to the inner surface of the twisted 316 stainless steel panel and the inner surface of the twisted O-state aluminum back panel.

[0027] By employing the above technical solution, uniform coating avoids localized shrinkage differences in the adhesive layer during curing. Consistent localized shrinkage maintains the flatness of the metal panel surface, preventing wavy textures on the composite panel and thus ensuring consistent optical reflection of the building skin.

[0028] This invention provides a molding process for a high-yield-strength metal torsion honeycomb panel. It has the following beneficial effects: 1. In this invention, a solid wooden mold is used to forge and press the 316 stainless steel panel and the O-state aluminum backing plate separately. After forming, they are then combined with the aluminum honeycomb core in a composite mold. This step-by-step forming method can create multi-faceted curved surfaces, meeting the decorative requirements of architectural designs for hyperbolic metal honeycomb panels. The independent forging of the face and back layers avoids the direct pressing of sandwich panels, which could cause the internal aluminum honeycomb core to collapse, ensuring that the high-yield-strength metal torsion honeycomb panel maintains its original structural strength while possessing complex curved surfaces.

[0029] 2. This invention uses a 316 stainless steel panel as the decorative surface layer and an O-state aluminum backing plate as the backing layer, with an aluminum honeycomb core sandwiched in between. These three components are bonded and cured together using a two-component polyurethane adhesive. The sandwich hollow structure, combined with the high yield strength of the 316 stainless steel panel, allows the processed metal twisted honeycomb panel to possess both lightweight and high rigidity. By installing connecting angle aluminum at pre-set positions on the cut twisted honeycomb panel, standardized mechanical connection nodes are established, making the composite panel easy to install on building frames and ensuring reliable load-bearing capacity.

[0030] 3. This invention installs supporting aluminum angles at the pre-set cantilevered areas of the cut twisted honeycomb panel. These supporting aluminum angles establish a localized rigid load-bearing framework in the unsupported edge areas of the twisted honeycomb panel, preventing the transmission of overload stress into the metal panel. The supporting structure ensures that the cantilevered areas of the high-yield-strength metal twisted honeycomb panel do not undergo physical deformation after demolding and during logistics transportation, guaranteeing that the final dimensions of the finished panel fully meet the processing accuracy requirements set by the three-dimensional skin model. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the stainless steel twisted aluminum honeycomb panel of the present invention.

[0032] Figure 2 This is a diagram illustrating the wood mold processing in an embodiment of the present invention.

[0033] Figure 3 This is a processing diagram of a stainless steel twisted decorative panel in an embodiment of the present invention.

[0034] Figure 4 This is a processing diagram of the aluminum backplate in an embodiment of the present invention.

[0035] Figure 5 This is a processing diagram of the stainless steel twisted aluminum honeycomb panel edge banding in an embodiment of the present invention.

[0036] Figure 6 This is a diagram illustrating the forming process of a stainless steel twisted aluminum honeycomb panel in an embodiment of the present invention.

[0037] Figure 7 This is a loss tangent diagram of the test specimen of the heterogeneous metal composite structure of the present invention at different temperatures.

[0038] Figure 8 This is a load-displacement diagram of the twisted honeycomb panel blank of the present invention during the roller peeling test.

[0039] Figure 9 This is a load-displacement diagram of the test specimen of the present invention during a localized compression test.

[0040] Figure 10 This is a graph showing the change in echo amplitude as a function of scanning position during ultrasonic nondestructive testing of the twisted honeycomb panel blank of the present invention.

[0041] Figure 11 This is a graph showing the deformation deviation of the high yield strength metal twisted honeycomb panel of the present invention as a function of the measurement point position during three-dimensional shape and position accuracy testing. Detailed Implementation

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] Examples 1-3: Example 1: Reference Appendix Figure 1-6 This embodiment provides a molding process for a high yield strength metal twisted honeycomb panel, including the following steps: Using parametric design technology, a three-dimensional surface model is created at a 1:1 scale and a wood mold processing drawing is exported. The wood mold substrate is then processed according to the wood mold processing drawing to obtain a solid wood mold. A 1.0mm thick 316 stainless steel panel with a polished composite surface is placed on a solid wooden mold. The 316 stainless steel panel is then curved using a forming device with a forging pressure of 20MPa to obtain a twisted 316 stainless steel panel. A 1.2mm thick O-state aluminum backing plate is placed on a solid wooden mold, and a forming device is used to form the O-state aluminum backing plate into a curved surface under a forging pressure of 20MPa to obtain a twisted O-state aluminum backing plate. A uniform coating of 200 g / m² was applied to the inner surface of the obtained twisted 316 stainless steel panel and the inner surface of the obtained twisted O-state aluminum backplate. 2 A two-component polyurethane adhesive was used to obtain a twisted 316 stainless steel panel and a twisted O-state aluminum back panel. The aluminum honeycomb core is placed between the obtained coated twisted 316 stainless steel panel and the obtained coated twisted O-state aluminum back plate. The aluminum honeycomb core, the coated twisted 316 stainless steel panel and the coated twisted O-state aluminum back plate are placed in a composite mold and cured under pressure at 40°C for 4 hours to obtain a twisted honeycomb panel blank. The obtained twisted honeycomb panel blank is placed on a 5-axis engraving machine, and a tungsten carbide cutter is used to engrave and cut the twisted honeycomb panel blank along the three-dimensional forming line to obtain the cut twisted honeycomb panel. Stainless steel twisted edge banding is bonded to the side of the obtained cut twisted honeycomb panel. Connecting angle aluminum is installed at the preset position of the cut twisted honeycomb panel, and supporting angle aluminum is installed at the cantilever surface of the cut twisted honeycomb panel to obtain a high yield strength metal twisted honeycomb panel.

[0044] Example 2: Reference Appendix Figure 1-6 This embodiment provides a molding process for a high yield strength metal twisted honeycomb panel, including the following steps: Using parametric design technology, a three-dimensional surface model is created at a 1:1 scale and a wood mold processing drawing is exported. The wood mold substrate is then processed according to the wood mold processing drawing to obtain a solid wood mold. A 1.5mm thick 316 stainless steel panel with a polished composite surface is placed on a solid wooden mold. The 316 stainless steel panel is then curved using a forming device with a forging pressure of 30MPa to obtain a twisted 316 stainless steel panel. A 2.0mm thick O-state aluminum backing plate is placed on a solid wooden mold, and a forming device is used to form the O-state aluminum backing plate into a curved surface under a forging pressure of 30MPa to obtain a twisted O-state aluminum backing plate. A uniform coating of 300 g / m² was applied to the inner surface of the obtained twisted 316 stainless steel panel and the inner surface of the obtained twisted O-state aluminum backing plate. 2 A two-component polyurethane adhesive was used to obtain a twisted 316 stainless steel panel and a twisted O-state aluminum back panel. The aluminum honeycomb core is placed between the obtained coated twisted 316 stainless steel panel and the obtained coated twisted O-state aluminum back plate. The aluminum honeycomb core, the coated twisted 316 stainless steel panel and the coated twisted O-state aluminum back plate are placed in a composite mold and cured under pressure at 60°C for 2 hours to obtain a twisted honeycomb panel blank. The obtained twisted honeycomb panel blank is placed on a 5-axis engraving machine, and a tungsten carbide cutter is used to engrave and cut the twisted honeycomb panel blank along the three-dimensional forming line to obtain the cut twisted honeycomb panel. Stainless steel twisted edge banding is bonded to the side of the obtained cut twisted honeycomb panel. Connecting angle aluminum is installed at the preset position of the cut twisted honeycomb panel, and supporting angle aluminum is installed at the cantilever surface of the cut twisted honeycomb panel to obtain a high yield strength metal twisted honeycomb panel.

[0045] Example 3: Reference Appendix Figure 1-6 This embodiment provides a molding process for a high yield strength metal twisted honeycomb panel, including the following steps: Using parametric design technology, a three-dimensional surface model is created at a 1:1 scale and a wood mold processing drawing is exported. The wood mold substrate is then processed according to the wood mold processing drawing to obtain a solid wood mold. A 0.8mm thick 316 stainless steel panel with a polished composite surface is placed on a solid wooden mold. The 316 stainless steel panel is then curved using a forming device with a forging pressure of 10MPa to obtain a twisted 316 stainless steel panel. A 0.8mm thick O-state aluminum backing plate is placed on a solid wooden mold, and a forming device is used to form the O-state aluminum backing plate into a curved surface under a forging pressure of 10MPa to obtain a twisted O-state aluminum backing plate. A uniform coating of 150 g / m² was applied to the inner surface of the obtained twisted 316 stainless steel panel and the inner surface of the obtained twisted O-state aluminum backing plate. 2 A two-component polyurethane adhesive was used to obtain a twisted 316 stainless steel panel and a twisted O-state aluminum back panel. The aluminum honeycomb core is placed between the obtained coated twisted 316 stainless steel panel and the obtained coated twisted O-state aluminum back plate. The aluminum honeycomb core, the coated twisted 316 stainless steel panel and the coated twisted O-state aluminum back plate are placed in a composite mold and cured under pressure at 20°C for 10 hours to obtain a twisted honeycomb panel blank. The obtained twisted honeycomb panel blank is placed on a 5-axis engraving machine, and a tungsten carbide cutter is used to engrave and cut the twisted honeycomb panel blank along the three-dimensional forming line to obtain the cut twisted honeycomb panel. Stainless steel twisted edge banding is bonded to the side of the obtained cut twisted honeycomb panel. Connecting angle aluminum is installed at the preset position of the cut twisted honeycomb panel, and supporting angle aluminum is installed at the cantilever surface of the cut twisted honeycomb panel to obtain a high yield strength metal twisted honeycomb panel.

[0046] Comparative Examples 1-3: Comparative Example 1: Compared with Example 1, the difference is that instead of separately forging and molding the 316 stainless steel panel and the O-state aluminum back plate, the 316 stainless steel panel, aluminum honeycomb core, and O-state aluminum back plate in a flat state are first bonded together by applying a two-component polyurethane adhesive and then pressure-curing to obtain a flat honeycomb panel blank. Then, the obtained flat honeycomb panel blank is directly forged and molded into a curved surface using molding equipment to obtain a twisted honeycomb panel blank. All other aspects are the same.

[0047] Comparative Example 2: Compared with Example 1, the difference is that the "1.0mm thick composite surface polished 316 stainless steel panel" was replaced with a regular "1.0mm thick aluminum alloy panel", and all other aspects were the same.

[0048] Comparative Example 3: Compared with Example 1, the difference is that instead of using a 5-axis engraving machine to carve and cut the twisted honeycomb panel blank along the three-dimensional forming line with a tungsten carbide cutter, conventional mechanical cutting equipment is used to cut the twisted honeycomb panel blank in a straight line to obtain the cut twisted honeycomb panel; at the same time, no supporting angle aluminum is installed at the cantilever surface of the cut twisted honeycomb panel, and everything else is the same.

[0049] Test Examples 1-5: Test Example 1: Test steps: (1) Rectangular strips with a length of 50 mm and a width of 10 mm were cut from the central area of ​​the twisted honeycomb board blanks prepared in Example 1, Example 2, Example 3 and Comparative Example 1, respectively, as test strips.

[0050] (2) Fix the test strip in the double cantilever fixture of the dynamic thermomechanical analyzer.

[0051] (3) Set the test frequency of the dynamic thermomechanical analyzer to 1 Hz, the heating rate to 3 ℃ / min, and the scanning temperature range to -40 ℃ to 120 ℃.

[0052] (4) Start the dynamic thermomechanical analyzer to continuously scan the test sample by increasing the temperature, and record the data of the loss tangent of the test sample changing with temperature within the scanning temperature range.

[0053] (5) Organize the loss tangent data during the scanning process and output the spectrum.

[0054] Table 1. Loss tangent test data of test specimens from different embodiments and comparative examples at a specific temperature.

[0055] Note: Each test sample was tested 3 times. The data in the table is the average of the 3 test results.

[0056] Test conclusion: Based on the data in Table 1 and Figure 1 As can be seen from the content, the loss tangent curves of the test samples obtained in Examples 1, 2, and 3 exhibit a single-peak structure in the range of -20℃ to 110℃, with the peak value of the loss tangent appearing around 70℃. The peak value of the loss tangent of the test sample obtained in Comparative Example 1 shifts towards the low-temperature region, with the peak value of the loss tangent appearing around 50℃, and the peak shape of the loss tangent curve in Comparative Example 1 broadens.

[0057] In the composite structure of 316 stainless steel panel and O-state aluminum backplate, the difference in thermal expansion coefficients between the 316 stainless steel panel and the O-state aluminum backplate leads to interlayer thermal stress due to temperature changes. The 316 stainless steel panel and O-state aluminum backplate are first separately forged and curved, then coated with a two-component polyurethane adhesive. This polyurethane adhesive forms a continuous adhesive network at the contact interfaces between the 316 stainless steel panel and the aluminum honeycomb core, and between the O-state aluminum backplate and the aluminum honeycomb core. This continuous adhesive network provides a damping medium for absorbing and dissipating interlayer thermal stress.

[0058] Comparative Example 1 employs a process of first compounding and pressure curing, followed by integral forging and curved surface forming. During the integral forging and curved surface forming stage, different shear deformations occur between the 316 stainless steel panel, the O-state aluminum backplate, and the aluminum honeycomb core. These different shear deformations disrupt the molecular chain network formed by the cross-linking and curing of the polyurethane two-component adhesive, resulting in localized debonding and internal stress concentration zones at the interfaces of the panel, backplate, and honeycomb core. These localized debonding and internal stress concentration zones reduce the thermomechanical stability of the adhesive interface. Under heated conditions, the damaged molecular chain segments slip at lower temperatures, causing the loss tangent peak of Comparative Example 1 to shift towards lower temperatures and broaden its peak shape.

[0059] Examples 1 to 3 include different panel thicknesses, forging pressures, adhesive application amounts, and curing temperature parameters. The loss tangent curves of Examples 1 to 3 are similar in shape, indicating that the molding step of separately forging and molding the 316 stainless steel panel and the O-state aluminum backplate before bonding avoids damage to the adhesive interface caused by mechanical forming and ensures the stability of the polyurethane two-component adhesive layer under different ambient temperatures.

[0060] Test Example 2: Test steps: (1) Rectangular strips with a length of 250 mm and a width of 25 mm were cut from the central area of ​​the twisted honeycomb board blanks prepared in Example 1, Example 2, Example 3 and Comparative Example 1 as test strips.

[0061] (2) The 316 stainless steel panel of the test strip is pre-peeled from the end of the aluminum honeycomb core.

[0062] (3) Install the pre-peeled test strip in the roller peeling fixture of the universal testing machine and fix the end of the panel to the roller.

[0063] (4) Set the tensile speed of the universal testing machine to 25 mm / min.

[0064] (5) Start the universal testing machine to stretch upwards and record the data of the load of the test specimen changing with displacement during the stretching process.

[0065] (6) Organize displacement and load data and output the graph.

[0066] Table 2. Test data of roller peel load at a specific displacement for test specimens of different embodiments and comparative examples.

[0067] Note: Each test sample was tested 3 times. The data in the table is the average of the 3 test results.

[0068] Test conclusion: Based on the data in Table 2 and Figure 2 As can be seen from the content, with the increase of tensile displacement, the load of the test specimens obtained in Examples 1, 2 and 3 increases and enters the stable peeling stage. The load in the stable peeling stage is maintained between 160N and 250N with small fluctuations. The load of the test specimen obtained in Comparative Example 1 is between 40N and 90N in the stable peeling stage, and the load curve of Comparative Example 1 shows sawtooth fluctuations.

[0069] First, the 316 stainless steel panel and the O-state aluminum backplate are individually forged and curved to achieve the designed curvature. During the polyurethane two-component adhesive lamination stage, the aluminum honeycomb core adapts to the pre-formed 316 stainless steel panel and O-state aluminum backplate in the lamination mold. The polyurethane two-component adhesive forms an adhesive layer at the interface between the 316 stainless steel panel and the aluminum honeycomb core, and at the interface between the O-state aluminum backplate and the aluminum honeycomb core, providing peel resistance after cross-linking and curing. In the roller peel test, the adhesive layer hinders peel crack propagation, maintaining the load between 160N and 250N.

[0070] Comparative Example 1 employs a process where a flat 316 stainless steel panel, an O-state aluminum backplate, and an aluminum honeycomb core are first composited and pressure-cured, followed by integral forging and curved surface forming. During the integral forging and curved surface forming process, the flat honeycomb panel blank undergoes bending deformation. Due to the different neutral layer positions of the 316 stainless steel panel, aluminum honeycomb core, and O-state aluminum backplate, the bending deformation generates interlaminar shear forces at the interfaces. These interlaminar shear forces cause the adhesive joints formed by the cured polyurethane two-component adhesive to break, and tear the pores within the aluminum honeycomb core. In the roller peel test, the peel cracks penetrate upon encountering the fracture joints and torn pores, resulting in a decrease in peel resistance, causing a reduction in the load value of Comparative Example 1 and a sawtooth-shaped fluctuation in the load curve.

[0071] Examples 1 to 3 include different panel thicknesses, forging pressures, adhesive application amounts, and curing temperature parameters. Examples 1 to 3 exhibited stable loads ranging from 160N to 250N in roller peel tests, indicating that the molding process of separately forging and curing the 316 stainless steel panel and the O-state aluminum backing plate before applying a two-component polyurethane adhesive provides a continuous adhesive layer, ensuring the interfacial peel performance of the twisted honeycomb panel in its curved state.

[0072] Test Example 3: Test steps: (1) Square samples with a size of 300mm×300mm were cut from the central protrusion area of ​​the twisted honeycomb panel samples prepared in Example 1, Example 2, Example 3 and Comparative Example 2 as test samples.

[0073] (2) Fix the test sample on the bottom support platform of the universal testing machine.

[0074] (3) Install a hemispherical steel indenter with a diameter of 50 mm on the movable crossbeam of the universal testing machine.

[0075] (4) Control the hemispherical steel indenter to align with the center of the outer metal panel of the test sample, and set the downward pressing speed of the hemispherical steel indenter to 2 mm / min.

[0076] (5) Start the universal testing machine and control the hemispherical steel indenter to press down the test specimen. Record the data of the load of the test specimen changing with displacement during the pressing process. Continue testing until obvious plastic deformation appears on the surface of the test specimen and the load slowly increases.

[0077] (6) Organize displacement and load data and output the graph.

[0078] Table 3. Load-displacement data of test specimens from different embodiments and comparative examples in local compression tests.

[0079] Note: Each test sample was tested 3 times. The data in the table is the average of the 3 test results.

[0080] Test conclusion: Based on the data in Table 3 and Figure 3 As can be seen from the content, with the increase of the downward displacement of the hemispherical steel indenter, the load of the test specimens obtained in Examples 1, 2, and 3 increases, and a yield inflection point appears when the load reaches the range of 2.4 kN to 5.1 kN, followed by the plastic deformation stage. The test specimen obtained in Comparative Example 2 shows a yield inflection point and undergoes plastic deformation when the load reaches about 0.9 kN.

[0081] The yield stress of 316 stainless steel panels is higher than that of aluminum alloy panels. Forging and curving 316 stainless steel panels allows for a degree of work hardening during cold plastic deformation, which improves their resistance to plastic deformation. The formed 316 stainless steel panel, polyurethane two-component adhesive, aluminum honeycomb core, and O-state aluminum backing plate transfer loads under pressure. When a localized load is applied to the surface of the test specimen, the outer 316 stainless steel panel bears tensile and compressive stresses.

[0082] Comparative Example 2 replaced the 316 stainless steel panel with an aluminum alloy panel. The aluminum alloy panel has a low yield stress, and when subjected to the local load of the hemispherical steel indenter, it reaches the yield limit and undergoes plastic deformation, causing the load curve of Comparative Example 2 to deflect in the low load region.

[0083] Examples 1, 2, and 3 include different thicknesses of the 316 stainless steel panel, the thickness of the O-state aluminum backplate, and forging pressure parameters. The yield load values ​​of Examples 1, 2, and 3 are higher than the yield load value of Comparative Example 2, indicating that the composite structure of the 316 stainless steel panel, aluminum honeycomb core, and O-state aluminum backplate, and the forging and curved forming process of the 316 stainless steel panel during the forming process, provide resistance to plastic deformation caused by local pressure.

[0084] Test Example 4: Test steps: (1) Select curved areas of the same size from the twisted honeycomb plate blanks prepared in Example 1, Example 2, Example 3 and Comparative Example 1 as scanning areas.

[0085] (2) Place the probe of the ultrasonic non-destructive testing equipment on the surface of the 316 stainless steel panel outside the scanning area, and apply ultrasonic coupling agent between the probe and the 316 stainless steel panel.

[0086] (3) Set the scanning frequency of the ultrasonic non-destructive testing equipment to 5MHz, set the scanning path to a straight line passing through the center of the scanning area, and set the scanning length to 200mm.

[0087] (4) Start the ultrasonic non-destructive testing equipment and control the probe to move along the scanning path, and record the data of the effective bottom surface echo amplitude received by the probe as the scanning position changes.

[0088] (5) Organize the scanning position and ultrasonic echo amplitude data and output the spectrum.

[0089] Table 4. Test data of effective bottom surface echo amplitude of tortuous honeycomb panel blanks at specific scanning positions in different embodiments and comparative examples.

[0090] Note: Each test sample was tested 3 times. The data in the table is the average of the 3 test results.

[0091] Test conclusion: Based on the data in Table 4 and Figure 4 As can be seen from the content, with the increase of the scanning position, the ultrasonic echo amplitude of the twisted honeycomb panel blanks obtained in Examples 1, 2, and 3 fluctuates within the range of 70% to 85%. When the scanning position of the twisted honeycomb panel blank obtained in Comparative Example 1 is within the range of 60mm to 160mm, the ultrasonic echo amplitude drops to the range of 10% to 25% and fluctuates.

[0092] First, the 316 stainless steel panel and the O-state aluminum backplate are individually forged and curved to achieve the designed curvature. During the polyurethane two-component adhesive lamination stage, the aluminum honeycomb core is bonded to the curved 316 stainless steel panel and O-state aluminum backplate in a composite mold. The cross-linked and cured polyurethane two-component adhesive forms a continuous interface between the 316 stainless steel panel and the aluminum honeycomb core. This continuous interface transmits ultrasonic signals, resulting in minimal fluctuations in the ultrasonic echo amplitude along the scanning path.

[0093] Comparative Example 1 employs a process where a flat 316 stainless steel panel, an O-state aluminum backplate, and an aluminum honeycomb core are first composited and pressure-cured, followed by integral forging and curved surface forming. During the integral forging and curved surface forming stage, the flat honeycomb panel blank undergoes bending deformation. The interlayer shear force generated by the bending deformation breaks the cured polyurethane two-component adhesive layer and causes crushing deformation inside the aluminum honeycomb core. The fractured adhesive layer and the crushed aluminum honeycomb core form an air gap beneath the 316 stainless steel panel. The air gap weakens the effective coupling of ultrasonic waves between the panel, adhesive layer, and aluminum honeycomb core, and causes ultrasonic signal scattering or attenuation, resulting in attenuation of the effective bottom surface echo amplitude in the central region of Comparative Example 1.

[0094] Examples 1, 2, and 3 involve different thicknesses of the 316 stainless steel panel, the O-state aluminum backplate, and forging pressure parameters. The effective bottom echo amplitude of Examples 1, 2, and 3 is higher than that of the central region of Comparative Example 1, indicating that the molding step of separately forging the 316 stainless steel panel and the O-state aluminum backplate and then applying a two-component polyurethane adhesive helps reduce the risk of crushing deformation of the aluminum honeycomb core and delamination at the interface.

[0095] Test Example 5: Test steps: (1) The edge region of the cantilever surface with a length of 500 mm was selected as the test area from the high yield strength metal twisted honeycomb panels prepared in Example 1, Example 2, Example 3 and Comparative Example 3.

[0096] (2) Fix the high yield strength metal twisted honeycomb panel on the worktable of the coordinate measuring machine.

[0097] (3) Import the three-dimensional theoretical model of the high yield strength metal torsion honeycomb panel into the control software of the coordinate measuring machine.

[0098] (4) Set the coordinate measuring machine to plan a measurement path with a length of 500mm along the test area.

[0099] (5) Start the coordinate measuring machine, control the probe to perform equidistant point measurements along the measurement path, and record the actual three-dimensional coordinate data of each measurement point.

[0100] (6) Compare the actual three-dimensional coordinate data with the three-dimensional coordinate data of the three-dimensional theoretical model, calculate and organize the deformation deviation data of each measurement point and output the graph.

[0101] Table 5. Deformation deviation test data of high yield strength metal torsion honeycomb panels in different embodiments and comparative examples at specific measurement points.

[0102] Note: Each test sample was tested 3 times. The data in the table is the average of the 3 test results.

[0103] Test conclusion: Based on the data in Table 5 and Figure 5 As can be seen from the data, with the increase of the measurement point position, the deformation deviation of the high yield strength metal twisted honeycomb panels obtained in Examples 1, 2, and 3 fluctuates within the range of 0.1 mm to 0.8 mm. In Comparative Example 3, the deformation deviation of the high yield strength metal twisted honeycomb panel increases to the range of 3.5 mm to 4.8 mm when the measurement point position is in the range of 300 mm to 500 mm.

[0104] A 5-axis CNC engraving machine is used to perform three-dimensional cutting along the curves of the twisted honeycomb panel blank. The five-axis linkage matches the spatial curvature of the twisted honeycomb panel blank, allowing the cutting direction to better adapt to the curved surface contour and reducing the three-dimensional residual stress generated during the cutting process. Supporting aluminum angles are installed at the edge of the cantilever surface. The supporting aluminum angles provide support and form a geometric constraint frame, limiting the release of residual stress and elastic rebound of the cantilever surface during placement.

[0105] Comparative Example 3 did not use a 5-axis CNC engraving machine for 3D line cutting, and no angle aluminum was installed at the edge of the cantilever surface. Conventional cutting methods generate cutting stress at the edge of curved surfaces. The cantilever surface lacks the constraint of angle aluminum, and under the action of cutting stress and structural self-weight, it produces elastic rebound, resulting in increased deformation deviation at the edge of the cantilever surface in Comparative Example 3.

[0106] Examples 1, 2, and 3 include different thicknesses of 316 stainless steel panels, O-state aluminum backplates, and forging pressure parameters. The deformation deviation values ​​of Examples 1, 2, and 3 are lower than those of Comparative Example 3, indicating that the three-dimensional line cutting step of the 5-axis engraving machine and the step of installing the supporting angle aluminum at the edge of the cantilever surface work together to help ensure the three-dimensional positional accuracy of the high yield strength metal twisted honeycomb panel.

Claims

1. A molding process for a high yield strength metal twisted honeycomb panel, characterized in that, Includes the following steps: The wooden mold substrate is processed according to the three-dimensional surface model to obtain a solid wooden mold; A 316 stainless steel panel is placed on the solid wooden mold and curved to obtain a twisted 316 stainless steel panel. The O-state aluminum back plate is placed on the solid wooden mold and curved to obtain a twisted O-state aluminum back plate. Apply a two-component polyurethane adhesive to the inner surface of the twisted 316 stainless steel panel and the inner surface of the twisted O-state aluminum back panel to obtain an adhesive-coated twisted 316 stainless steel panel and an adhesive-coated twisted O-state aluminum back panel. The aluminum honeycomb core is placed between the glued twisted 316 stainless steel panel and the glued twisted O-state aluminum back plate, and then placed in a composite mold for pressure curing to obtain a twisted honeycomb panel blank. The twisted honeycomb panel blank is carved and cut to obtain a cut twisted honeycomb panel; A supporting aluminum angle is installed at the pre-set cantilevered portion of the cut twisted honeycomb panel to obtain a high yield strength metal twisted honeycomb panel.

2. The forming process of the high yield strength metal twisted honeycomb panel according to claim 1, characterized in that, Before placing the 316 stainless steel panel on the solid wooden mold, the composite surface of the 316 stainless steel panel is pre-polished.

3. The forming process of the high yield strength metal twisted honeycomb panel according to claim 1, characterized in that, The thickness of the 316 stainless steel panel is 0.8-1.5mm; The forging pressure for forming the curved surface of the 316 stainless steel panel is 10-30 MPa.

4. The forming process of the high yield strength metal twisted honeycomb panel according to claim 1, characterized in that, The thickness of the O-state aluminum back plate is 0.8-2.0 mm; The forging pressure for forming the O-state aluminum back plate into a curved surface is 10-30 MPa.

5. The forming process of the high yield strength metal twisted honeycomb panel according to claim 1, characterized in that, When applying the two-component polyurethane adhesive, the coating amount of the two-component polyurethane adhesive is 150-300 g / m². 2 .

6. The forming process of the high yield strength metal twisted honeycomb panel according to claim 1, characterized in that, The pressure holding and curing temperature is 20-60℃, and the pressure holding and curing time is 2-10h.

7. The forming process of the high yield strength metal twisted honeycomb panel according to claim 1, characterized in that, The specific implementation method for carving and cutting the twisted honeycomb panel blank is as follows: The twisted honeycomb panel blank is placed on a 5-axis engraving machine, and a tungsten carbide cutter is used to engrave and cut the twisted honeycomb panel blank along the three-dimensional forming line.

8. The forming process of the high yield strength metal twisted honeycomb panel according to claim 1, characterized in that, The specific implementation method of processing the wood mold substrate according to the three-dimensional surface model is as follows: Using parametric design technology, a three-dimensional skin model is established at a 1:1 scale, and a wood mold processing drawing is exported. The wood mold substrate is then processed according to the wood mold processing drawing.

9. The forming process of a high yield strength metal twisted honeycomb panel according to claim 1, characterized in that, After obtaining the cut and twisted honeycomb panel, the process further includes: Stainless steel twisted edge banding is bonded to the side of the cut twisted honeycomb panel, and connecting angle aluminum is installed at a predetermined position on the cut twisted honeycomb panel.

10. The forming process of a high yield strength metal twisted honeycomb panel according to claim 1, characterized in that, When applying the polyurethane two-component adhesive, the polyurethane two-component adhesive is evenly applied to the inner surface of the twisted 316 stainless steel panel and the inner surface of the twisted O-state aluminum back plate.

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