Method for suppressing boundary effect based on pre-stressed laser bending forming of sheet metal

Abstract

The application provides a boundary effect inhibition method and system based on metal sheet pre-stress laser bending forming, comprising the following steps: S1, splicing metal sheets 5 at both ends of a metal sheet to be formed 1, and applying a heat-conducting silica gel coating 4 at the splicing positions; S2, dividing a plurality of to-be-formed areas 8 with equal areas based on the width of the metal sheet to be formed 1; S3, pre-bending loading the to-be-formed area 8 and the spliced metal sheet 5 in the axial direction for an optional to-be-formed area 8; S4, reciprocating multi-pass scanning of the to-be-formed area 8 in the pre-bending loading by using a laser 6 to obtain a semi-formed part; S5, cooling the semi-formed part to room temperature and unloading the bending load; and repeating steps S2 to S4 to obtain a formed part. The application conducts accumulated heat to the metal sheet 5 through the high-heat-conducting silica gel, thereby reducing the scanning endpoint temperature, further effectively reducing the excessive deformation near the scanning endpoint, and inhibiting the "boundary effect".

Description

Technical Field

[0001] This invention belongs to the field of metal plastic forming technology, specifically, it relates to a method for suppressing boundary effects in prestressed laser bending forming of metal sheets. Background Technology

[0002] As a crucial component of advanced manufacturing technology, sheet metal forming technology is widely used in industries such as aerospace, shipbuilding, and automotive. For materials with poor room temperature plasticity, or wall panel structures with complex ribs, room temperature bending can lead to cracking, damage, and significant springback during unloading. In recent years, prestressed laser bending has emerged as a novel sheet metal bending technology. This technology involves applying prestress to the sheet metal to be formed, then scanning the bending deformation area with a laser beam to induce the conversion of elastic strain energy into plastic strain energy, thereby achieving plastic bending of the sheet. This technology effectively avoids overload damage and failure of the sheet metal, and through localized laser scanning heating, a large amount of the internal elastic strain after preloading is converted into plastic strain. Therefore, it exhibits low springback and high forming accuracy.

[0003] Patent document CN113894187A discloses a prestressed laser bending forming method for aluminum alloy high-stiffness wall panels. This method involves prestressing the aluminum alloy high-stiffness wall panel with bending load to induce slight plasticity in the forming area 8. Then, a laser beam is used to scan the stiffeners where elastic stress is concentrated, thereby achieving the bending forming of the aluminum alloy high-stiffness wall panel. This method avoids overload damage and destruction of the high-stiffness wall panel and improves the forming accuracy of the high-stiffness wall panel.

[0004] This method suffers from a "boundary effect" during laser scanning, meaning there is a significant temperature gradient along the laser scanning path, specifically manifested as follows:

[0005] 1. The temperature of the metal sheet to be formed 1 is low near the laser scanning starting point. This is because the laser spot gradually enters the sheet, resulting in less laser heat being absorbed near the starting point, hence the lower temperature.

[0006] 2. The temperature of the metal sheet to be formed 1 is relatively stable in the middle section of the laser scanning process;

[0007] 3. The temperature of the metal sheet 1 to be formed is too high near the end of the laser scan. This is because when the scan reaches the end of the sheet, the heat cannot continue to be conducted to the solid phase, resulting in heat accumulation at the end and an excessively high temperature. The temperature of the laser scan area is positively correlated with the degree of elastic strain to plastic strain conversion in the area. That is, the higher the temperature, the greater the degree of elastic strain to plastic strain conversion. This leads to insufficient deformation near the starting point of the laser scan, uniform strain distribution in the middle part, and excessive deformation near the end of the scan. This results in uneven axial deformation and large straightness error of the formed part along the laser scan direction. The straightness often fails to meet the requirements of high-precision components, and there is room for improvement. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for suppressing boundary effects based on prestressed laser bending forming of metal sheets.

[0009] A boundary effect suppression method based on prestressed laser bending forming of metal sheets, according to the present invention, includes:

[0010] Step S1: Splice metal plates 5 at both ends of the metal sheet 1 to be formed, and apply thermally conductive silicone coating 4 at the splice.

[0011] Step S2: Based on the width of the metal sheet 1 to be formed, divide it into multiple areas 8 of equal area to be formed;

[0012] Step S3: Select any area 8 to be formed, and pre-bend the area 8 to be formed and the spliced ​​metal plate 5 along the axial direction;

[0013] Step S4: Use laser 6 to perform reciprocating multi-pass scanning on the pre-bending loading area 8 to obtain a semi-formed part;

[0014] Step S5: Cool the semi-formed part to room temperature and unload the bending load; repeat steps S2 to S4 until all areas 8 to be formed are formed to obtain the formed part.

[0015] Preferably, the axial length of the metal plate 5 is more than 10 times the diameter of the laser spot used for laser scanning;

[0016] The specific heat capacity of the metal plate 5 is greater than or equal to the specific heat capacity of the metal plate material 1 to be formed;

[0017] The width and thickness of the metal plate 5 are the same as the width and thickness of the metal plate 1 to be formed.

[0018] In step S1:

[0019] The thickness of the thermally conductive silicone coating 4 is 0.5–3 mm; the thermal conductivity of the thermally conductive silicone coating 4 is 10–50 W / (m·K).

[0020] Preferably, in step S1:

[0021] The assembled metal sheet 1 and the metal sheet 5 are clamped together by the clamping fixture 7.

[0022] In step S2:

[0023] The area to be formed 8 overlaps with its adjacent areas to be formed 8 in a region 9.

[0024] The area of ​​the overlapping area 9 accounts for 20% to 40% of the area of ​​the area to be formed 8.

[0025] Preferably, in step S3:

[0026] Pre-bending loading is achieved by using a three-point bending method or a four-point bending method;

[0027] The three-point bending method employs one lower pressure head 2 and two upper pressure heads 3. The upper pressure heads 3 are fixed to the two sides of the area to be formed 8. The lower pressure head 2 applies an upward load to the middle of the area to be formed 8 to achieve three-point bending loading.

[0028] The four-point bending method employs two lower pressure heads 2 and two upper pressure heads 3. The upper pressure heads 3 are fixed in the middle of the area to be formed 8, and the two lower pressure heads 2 simultaneously apply the same upward load to both sides of the area to be formed 8 to achieve four-point bending. Furthermore, the distance between the two upper pressure heads 3 is more than twice the diameter of the laser spot.

[0029] The internal stress of the region to be formed 8 is between the yield strength and tensile strength of its material.

[0030] The surface of the metal sheet to be formed 1 is free of indentations, scratches and microcracks.

[0031] Preferably, in step S4:

[0032] The laser 6 is a continuous wave laser;

[0033] The laser beam from the continuous wave laser scans the region 8 to be formed along a preset path.

[0034] The scanning start point is set at the inner edge of the metal sheet 1 to be formed, and the scanning end point is set at the inner edge of the other end of the metal sheet 1 to be formed;

[0035] The temperature field of the region to be formed 8 is less than or equal to the melting point of the metal sheet 1 to be formed, which is 100°C.

[0036] The number of scans is a total of 4 passes.

[0037] A boundary effect suppression system based on prestressed laser bending forming of metal sheets, according to the present invention, comprises:

[0038] Module M1: Splice metal plates 5 at both ends of the metal sheet 1 to be formed, and apply thermally conductive silicone coating 4 at the splice.

[0039] Module M2: Based on the width of the metal sheet 1 to be formed, divide it into multiple forming areas 8 of equal area;

[0040] Module M3: Select any area 8 to be formed, and pre-bend the area 8 to be formed and the spliced ​​metal plate 5 along the axial direction;

[0041] Module M4: Use laser 6 to perform reciprocating multi-pass scanning on the pre-bending loading area 8 to obtain a semi-formed part;

[0042] Module M5: Cool the semi-formed part to room temperature and unload the bending load; repeat modules M2 to M4 until all areas 8 to be formed are formed to obtain the formed part.

[0043] Preferably, the axial length of the metal plate 5 is more than 10 times the diameter of the laser spot used for laser scanning;

[0044] The specific heat capacity of the metal plate 5 is greater than or equal to the specific heat capacity of the metal plate material 1 to be formed;

[0045] The width and thickness of the metal plate 5 are the same as the width and thickness of the metal plate 1 to be formed.

[0046] In step S1:

[0047] The thickness of the thermally conductive silicone coating 4 is 0.5–3 mm; the thermal conductivity of the thermally conductive silicone coating 4 is 10–50 W / (m·K).

[0048] Preferably, in module M1:

[0049] The assembled metal sheet 1 and the metal sheet 5 are clamped together by the clamping fixture 7.

[0050] In module M2:

[0051] The area to be formed 8 overlaps with its adjacent areas to be formed 8 in a region 9.

[0052] The area of ​​the overlapping area 9 accounts for 20% to 40% of the area of ​​the area to be formed 8.

[0053] Preferably, in module M3:

[0054] Pre-bending loading is achieved by using a three-point bending method or a four-point bending method;

[0055] The three-point bending method employs one lower pressure head 2 and two upper pressure heads 3. The upper pressure heads 3 are fixed to the two sides of the area to be formed 8. The lower pressure head 2 applies an upward load to the middle of the area to be formed 8 to achieve three-point bending loading.

[0056] The four-point bending method employs two lower pressure heads 2 and two upper pressure heads 3. The upper pressure heads 3 are fixed in the middle of the area to be formed 8, and the two lower pressure heads 2 simultaneously apply the same upward load to both sides of the area to be formed 8 to achieve four-point bending. Furthermore, the distance between the two upper pressure heads 3 is more than twice the diameter of the laser spot.

[0057] The internal stress of the region to be formed 8 is between the yield strength and tensile strength of its material.

[0058] The surface of the metal sheet to be formed 1 is free of indentations, scratches and microcracks.

[0059] Preferably, in module M4:

[0060] The laser 6 is a continuous wave laser;

[0061] The laser beam from the continuous wave laser scans the region 8 to be formed along a preset path.

[0062] The scanning start point is set at the inner edge of the metal sheet 1 to be formed, and the scanning end point is set at the inner edge of the other end of the metal sheet 1 to be formed;

[0063] The temperature field of the region to be formed 8 is less than or equal to the melting point of the metal sheet 1 to be formed, which is 100°C.

[0064] The number of scans is a total of 4 passes.

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] 1. This invention involves splicing a metal plate 5 at each end of a metal sheet 1 to be formed, and uniformly applying a thermally conductive silicone coating 4 of a specific thickness between the metal sheet 1 to be formed and the spliced ​​metal plates 5. The starting and ending points of the laser scanning are set at both ends of the metal sheet to be formed. The clamping fixture 7 ensures good contact between the metal sheet to be formed, the thermally conductive silicone, and the spliced ​​metal plates 5. During the laser scanning process, the accumulated heat at the end of the metal sheet 1 to be formed can be conducted to the metal plate 5 through the high thermal conductivity silicone, thereby reducing the scanning end temperature of the metal sheet 1 to be formed and effectively reducing excessive deformation near the scanning end point, thus suppressing the "boundary effect".

[0067] 2. This invention addresses the problem of insufficient deformation in the region near the starting point of laser scanning. By performing a reverse laser scan, the region near the starting point of the laser scan, which previously had insufficient deformation, becomes the region near the ending point of the reverse laser scan. During the reverse laser scan, a temperature field opposite to that of the previous scan is formed, thereby effectively increasing the deformation near the original starting point and improving the deformation uniformity of the laser scan path.

[0068] 3. By performing multiple reciprocating scans, this invention can more fully convert elastic strain in the laser scanning path into plastic strain, which helps to further reduce the plastic strain field gradient along the laser scanning path, suppress the "boundary effect", improve the uniformity of axial deformation in the laser scanning direction, and reduce straightness error. Attached Figure Description

[0069] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0070] Figure 1 A schematic diagram of laser prestressed bending forming of three-point bending provided by the present invention;

[0071] Figure 2 A schematic diagram of laser prestressed bending forming of four-point bending provided by the present invention;

[0072] Figure 3 This is a schematic diagram showing the division of the forming area 8 on the sheet material to be formed according to the present invention;

[0073] Figure 4 A schematic diagram of the laser scanning path with an odd number of passes provided by the present invention;

[0074] Figure 5 A schematic diagram of an even-numbered laser scanning path provided by the present invention;

[0075] Figure 6 This is a schematic diagram of laser prestressed bending forming without boundary effect suppression method provided by the present invention.

[0076] Detailed Implementation

[0077] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0078] A boundary effect suppression method based on prestressed laser bending forming of metal sheets, according to the present invention, includes:

[0079] Step S1: Splice metal plates 5 at both ends of the metal sheet 1 to be formed, and apply a layer of thermally conductive silicone coating 4 of a specific thickness evenly between the metal sheet 1 to be formed and the spliced ​​metal plates 5.

[0080] Step S2: Divide the sheet metal to be formed 1 into multiple equal forming areas 8;

[0081] Step S3: Select any region 8 to be formed, and pre-bend the region and the metal plate 5 spliced ​​on its outer side along the axial direction so that the internal stress of the region 8 to be formed is between its material yield strength and tensile strength.

[0082] Step S4: Use laser 6 to perform reciprocating multi-pass scanning on the pre-bent loaded forming area 8;

[0083] Step S5: After the reciprocating multi-pass scanning is completed, wait for all the metal sheets to cool completely to room temperature, unload the bending load, and complete the forming of the area to be formed 8 to obtain a semi-formed part.

[0084] Step S6: Repeat steps S3, S4, and S5 sequentially for all other areas 8 to be formed, and you can obtain the metal sheet bending forming part as the forming part.

[0085] Specifically, the metal plate 5 is a high heat storage metal plate, and the material is an alloy;

[0086] Specifically, in step S1:

[0087] The metal plates 5 spliced ​​at both ends of the metal sheet 1 to be formed have the following characteristics:

[0088] The axial length of the metal plate 5 is more than 10 times the diameter of the laser spot used for laser scanning;

[0089] The width and thickness of the metal plate 5 are the same as the width and thickness of the metal plate 1 to be formed.

[0090] The specific heat capacity of the metal plate 5 needs to be close to or higher than that of the metal plate 1 to be formed, or it can be made of the same material as the metal plate 1 to be formed.

[0091] Specifically, the thermally conductive silicone coating 4 applied to both axial ends of the metal sheet 1 to be formed in step S1 must have the following characteristics:

[0092] The thermally conductive silicone coating 4 has a high thermal conductivity of 10-50 W / (m·K), and the coating thickness between the metal sheet to be formed 1 and the spliced ​​metal sheet is 0.5-3 mm.

[0093] Specifically, after the two ends of the metal sheet 1 to be formed are spliced ​​with the metal sheet 5 in step S1, the three are clamped together by the clamping fixture 7 to ensure that they do not loosen or separate during the subsequent forming process.

[0094] Specifically, in step S2, there must be an overlap area 9 of 20% to 40% of the area of ​​any region 8 to be formed and its adjacent regions 8 to be formed.

[0095] Specifically, step S3 uses a three-point bending method or a four-point bending method to pre-bend the area 8 to be formed.

[0096] The three-point bending method employs one lower pressure head 2 and two upper pressure heads 3. The upper pressure heads 3 are fixed and located at the two edges of the area to be formed 8. The lower pressure head 2 applies an upward load to the middle of the area to be formed 8 to achieve three-point bending loading.

[0097] The four-point bending method involves using two lower pressure heads 2 and two upper pressure heads 3. The upper pressure heads 3 are fixed and located in the middle of the area to be formed 8. A distance of more than twice the diameter of the laser spot needs to be reserved between the two upper pressure heads 3 to allow the laser beam to pass through. The two lower pressure heads 2 simultaneously apply the same upward load to the two edges of the area to be formed 8 to achieve four-point bending.

[0098] The upper pressure head 3 and the lower pressure head 2 are rod-shaped.

[0099] Specifically, in step S3, the stress value after preloading needs to be calculated by finite element simulation to ensure that the internal stress of the area to be formed 8 after loading is between the yield strength and tensile strength of the material, and that no damage such as indentation, scratches and microcracks is generated on the surface of the metal sheet 1 to be formed.

[0100] Specifically, the specific process requirements for reciprocating multi-pass laser scanning in step S4 include:

[0101] Laser 6 must be a continuous wave laser. The laser scans the area 8 to be formed along a preset path. The scanning start point must be set at the inner edge of the metal sheet 1 to be formed, and the scanning end point must be set at the inner edge of the other end of the metal sheet 1 to be formed.

[0102] Each laser scan requires real-time monitoring of the temperature field of the area to be formed 8. The temperature field must be less than or equal to the melting point of the metal sheet 1 to be formed, 100°C, to ensure that the area to be formed 8 does not experience melting, oxidation, ablation, or other phenomena.

[0103] After each laser scanning process, the temperature of the metal sheet to be formed 1 and the spliced ​​metal sheet must be completely cooled to room temperature by air cooling, and then a reverse laser scan is performed along the previous scanning path.

[0104] The forward and reverse scanning needs to reach more than 2 cycles, which means a total of 4 laser scans in total.

[0105] The above method is illustrated with specific embodiments.

[0106] The titanium alloy sheet to be formed, designated as sheet 1, has dimensions of 1050mm × 600mm × 5mm, and the target forming shape is an arc with a radius of curvature of 300mm. A method for suppressing boundary effects in prestressed laser bending forming of metal sheets according to the present invention includes:

[0107] Step A1: As Figure 1 As shown, a titanium alloy plate of the same grade as the titanium alloy plate to be formed is spliced ​​to both ends of the titanium alloy plate to be formed, serving as metal plate 5. The dimensions of the titanium alloy plate are 1050mm×80mm×5mm. The diameter of the laser spot used later is 8mm. The two are spliced ​​together with a 1000mm edge. A layer of thermally conductive silicone coating 4 with a thickness of 2mm and a thermal conductivity of 15W / (m·K) is uniformly applied between the titanium alloy plate to be formed and the spliced ​​titanium alloy plate. After splicing, the three are clamped together by clamping fixture 7 to ensure that they do not loosen or separate during the subsequent forming process.

[0108] Step A2: As Figure 3 As shown, the titanium alloy sheet to be formed is divided into 5 forming areas 8 with the same area. Each forming area 8 has a width of 250mm, and the overlap area 9 between adjacent areas has a width of 50mm.

[0109] Step A3: As Figure 1 As shown, the forming region 8, located in the middle of the titanium alloy sheet to be formed, is selected. Pre-bending loading is applied to region 8 and the titanium alloy sheets spliced ​​on its outer side along the axial direction. A three-point bending method is used, with two upper pressure heads 3 fixed. The span of the upper pressure heads 3 is equal to the width of the forming region 8, and they are located at the two edges of the forming region 8, with a span of 250 mm. Finite element simulation calculations show that when the load applied upwards by the lower pressure head 2 is 87 kN, the maximum plastic strain generated in the bent titanium alloy sheet is approximately 5%, and the highest internal stress during the bending process is 892 MPa, which is between the yield strength and tensile strength of the titanium alloy material. No indentations, scratches, or microcracks are generated on the surface of the titanium alloy sheet to be formed.

[0110] Step A4: Use a continuous wave laser along... Figure 4The path shown is used to perform the first forward scan on the pre-bent and loaded forming area 8. The scanning start and end points are both located at the inner edge of the titanium alloy sheet to be formed, avoiding direct contact between the laser beam and the thermally conductive silicone coating 4, thus preventing melting or burning of the thermally conductive silicone coating 4. The main laser parameters used are: laser power 3850W, spot diameter 8mm, and scanning speed 8mm / s. After the first forward scan, all sheets are completely cooled to room temperature using air cooling. Subsequently, the laser parameters remain unchanged, and the scan continues along the path shown. Figure 5 The path shown is used for a second reverse scan. In this embodiment, a total of four laser scans are performed, namely forward-reverse-forward-reverse, and the sheet material needs to be cooled between each two laser scans. In this embodiment, the temperature field of the area to be formed 8 is monitored in real time by a non-contact infrared thermal imager. During the scanning process, the temperature in the middle section of the scanning path is stable at 811-826℃, and the highest temperature near the scanning endpoint reaches 858℃. No melting, oxidation, or ablation occurs in the area to be formed 8 during the entire laser scanning process.

[0111] The sheet material includes: titanium alloy sheet material to be formed, and titanium alloy plate;

[0112] Step A5: After four reciprocating scans, once all the sheet metal has completely cooled to room temperature, unload the bending load to complete the forming of the area 8 to be formed.

[0113] Step A6: Repeat steps S3, S4, and S5 sequentially for all remaining areas 8 to be formed, to obtain a titanium alloy sheet bending part with an outer surface curvature radius of 300mm. The straightness of this titanium alloy sheet bending part is measured to be 0.3mm / 600mm.

[0114] Comparative example;

[0115] The difference between the comparative example and the embodiment is that the boundary effect suppression method proposed in this patent was not used in the comparative example. The schematic diagram of the comparative example is as follows. Figure 6 As shown. The comparative example includes:

[0116] Step B1: As Figure 3 As shown, the titanium alloy sheet to be formed is divided into 5 forming areas 8 with the same area, where each forming area 8 is 250mm wide and the overlapping area 9 between adjacent areas is 50mm wide.

[0117] Step B2: As Figure 6 As shown, the forming area 8 located in the middle of the titanium alloy sheet to be formed is selected, and the forming area 8 is pre-bent loaded along the axial direction.

[0118] The bending method adopts a three-point bending method, in which two upper pressure heads 3 are fixed, the span of the upper pressure heads 3 is the same as the width of the area to be formed 8, and they are located at the two sides of the edge of the area to be formed 8, with the span set at 250mm; the displacement of the lower pressure head 2 is consistent with that of the embodiment, so that the area to be formed 8 reaches the same plastic strain as in the embodiment.

[0119] Step B3: Using a continuous wave laser, along as... Figure 6 The path shown scans the pre-bent and loaded region 8 to be formed. The starting and ending points of the scan are both located at the inner edge of the titanium alloy sheet to be formed. The actual laser parameters used are the same as in the embodiment. Throughout the experiment, the temperature field of the region 8 to be formed is monitored in real time using a non-contact infrared thermal imager. During the scanning process, the temperature in the middle section of the scanning path is stable at 808–824°C, and the highest temperature near the scanning endpoint reaches 927°C.

[0120] Step B4: After scanning is completed, wait for the titanium alloy sheet 1 to cool completely to room temperature, then unload the bending load to complete the forming of the area 8 to be formed.

[0121] Step B5: Repeat steps B2, B3, and B4 sequentially for all remaining areas 8 to be formed, to obtain a titanium alloy sheet bending part with an outer surface curvature radius of 300mm. The straightness of this titanium alloy sheet bending part is measured to be 1.6mm / 600mm.

[0122] Based on the test data of the comparative examples and comparative examples, it can be found that by adding the boundary effect suppression method proposed in this patent to the comparative examples, the temperature uniformity along the laser scanning direction is significantly improved during the laser scanning process, the straightness error of the formed part is significantly reduced, the forming accuracy is significantly improved, and the "boundary effect" of prestressed laser bending is effectively suppressed.

[0123] The present invention also provides a boundary effect suppression system based on prestressed laser bending of metal sheet. The boundary effect suppression system based on prestressed laser bending of metal sheet can be implemented by executing the process steps of the boundary effect suppression method based on prestressed laser bending of metal sheet. That is, those skilled in the art can understand the boundary effect suppression method based on prestressed laser bending of metal sheet as a preferred embodiment of the boundary effect suppression system based on prestressed laser bending of metal sheet.

[0124] A boundary effect suppression system based on prestressed laser bending forming of metal sheets, according to the present invention, comprises:

[0125] Module M1: Splice metal plates 5 at both ends of the metal sheet 1 to be formed, and apply thermally conductive silicone coating 4 at the splice.

[0126] Module M2: Based on the width of the metal sheet 1 to be formed, divide it into multiple forming areas 8 of equal area;

[0127] Module M3: Select any area 8 to be formed, and pre-bend the area 8 to be formed and the spliced ​​metal plate 5 along the axial direction;

[0128] Module M4: Use laser 6 to perform reciprocating multi-pass scanning on the pre-bending loading area 8 to obtain a semi-formed part;

[0129] Module M5: Cool the semi-formed part to room temperature and unload the bending load; repeat modules M2 to M4 until all areas 8 to be formed are formed to obtain the formed part.

[0130] Specifically, the axial length of the metal plate 5 is more than 10 times the diameter of the laser spot used for laser scanning;

[0131] The specific heat capacity of the metal plate 5 is greater than or equal to the specific heat capacity of the metal plate material 1 to be formed;

[0132] The width and thickness of the metal plate 5 are the same as the width and thickness of the metal plate 1 to be formed.

[0133] In step S1:

[0134] The thickness of the thermally conductive silicone coating 4 is 0.5–3 mm; the thermal conductivity of the thermally conductive silicone coating 4 is 10–50 W / (m·K).

[0135] Specifically, in module M1:

[0136] The assembled metal sheet 1 and the metal sheet 5 are clamped together by the clamping fixture 7.

[0137] In module M2:

[0138] The area to be formed 8 overlaps with its adjacent areas to be formed 8 in a region 9.

[0139] The area of ​​the overlapping area 9 accounts for 20% to 40% of the area of ​​the area to be formed 8.

[0140] Specifically, in module M3:

[0141] Pre-bending loading is achieved by using a three-point bending method or a four-point bending method;

[0142] The three-point bending method employs one lower pressure head 2 and two upper pressure heads 3. The upper pressure heads 3 are fixed to the two sides of the area to be formed 8. The lower pressure head 2 applies an upward load to the middle of the area to be formed 8 to achieve three-point bending loading.

[0143] The four-point bending method employs two lower pressure heads 2 and two upper pressure heads 3. The upper pressure heads 3 are fixed in the middle of the area to be formed 8, and the two lower pressure heads 2 simultaneously apply the same upward load to both sides of the area to be formed 8 to achieve four-point bending. Furthermore, the distance between the two upper pressure heads 3 is more than twice the diameter of the laser spot.

[0144] The internal stress of the region to be formed 8 is between the yield strength and tensile strength of its material.

[0145] The surface of the metal sheet 1 to be formed is free of indentations, scratches and microcracks.

[0146] Specifically, in module M4:

[0147] The laser 6 is a continuous wave laser;

[0148] The laser beam from the continuous wave laser scans the region 8 to be formed along a preset path.

[0149] The scanning start point is set at the inner edge of the metal sheet 1 to be formed, and the scanning end point is set at the inner edge of the other end of the metal sheet 1 to be formed;

[0150] The temperature field of the region to be formed 8 is less than or equal to the melting point of the metal sheet 1 to be formed, which is 100°C.

[0151] The number of scans is a total of 4 passes.

[0152] Those skilled in the art will understand that, besides implementing the system and its various devices, modules, and units provided by this invention in the form of purely computer-readable program code, the same functions can be achieved entirely through logical programming of the method steps, making the system and its various devices, modules, and units of this invention function in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers. Therefore, the system and its various devices, modules, and units provided by this invention can be considered as a hardware component, and the devices, modules, and units included therein for implementing various functions can also be considered as structures within the hardware component; alternatively, the devices, modules, and units for implementing various functions can be considered as both software modules implementing the method and structures within the hardware component.

[0153] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application 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. Therefore, they should not be construed as limitations on this application.

[0154] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for suppressing boundary effects in prestressed laser bending forming of metal sheets, characterized in that, include: Step S1: Splice metal plates (5) at both ends of the metal sheet to be formed (1) along the axial direction, and apply a thermally conductive silicone coating (4) at the splice. Step S2: Based on the width of the metal sheet to be formed (1), divide it into multiple areas (8) of equal area along the axial direction. Step S3: Select any area to be formed (8) and pre-bend the area to be formed (8) and the spliced ​​metal plate (5) along the axial direction; Step S4: Use a laser (6) to perform reciprocating multi-pass scanning on the area to be formed (8) under pre-bending loading to obtain a semi-formed part; Step S5: Cool the semi-formed part to room temperature and unload the bending load; repeat steps S2 to S4 until all areas to be formed (8) are formed to obtain the formed part.

2. The boundary effect suppression method based on prestressed laser bending forming of metal sheets according to claim 1, characterized in that, The axial length of the metal plate (5) is more than 10 times the diameter of the laser spot used for laser scanning; The specific heat capacity of the metal plate (5) is greater than or equal to the specific heat capacity of the metal plate material (1) to be formed; The width and thickness of the metal plate (5) are the same as the width and thickness of the metal plate material (1) to be formed; In step S1: The thickness of the thermally conductive silicone coating (4) is 0.5~3mm; the thermal conductivity of the thermally conductive silicone coating (4) is 10~50W / (m·K).

3. The boundary effect suppression method based on prestressed laser bending forming of metal sheets according to claim 1, characterized in that, In step S1: The spliced ​​metal sheet (1) to be formed is clamped to the metal sheet (5) by clamping fixture (7); In step S2: The area to be formed (8) overlaps with its adjacent areas to be formed (8) (9). The area of ​​the overlapping area (9) accounts for 20% to 40% of the area of ​​the area to be formed (8).

4. The boundary effect suppression method based on prestressed laser bending forming of metal sheets according to claim 1, characterized in that, In step S3: Pre-bending loading is achieved by using a three-point bending method or a four-point bending method; The three-point bending method uses one lower pressure head (2) and two upper pressure heads (3). The upper pressure head (3) is fixed to the two sides of the area to be formed (8). The lower pressure head (2) applies an upward load to the middle of the area to be formed (8) to achieve three-point bending loading. The four-point bending method employs two lower pressure heads (2) and two upper pressure heads (3). The upper pressure heads (3) are fixed in the middle of the area to be formed (8). The two lower pressure heads (2) simultaneously apply the same upward load to both sides of the area to be formed (8) to achieve four-point bending. Furthermore, the distance between the two upper pressure heads (3) is more than twice the diameter of the laser spot. The internal stress of the region to be formed (8) is between the yield strength and tensile strength of its material; The surface of the metal sheet to be formed (1) is free of indentations, scratches and microcracks.

5. The boundary effect suppression method based on prestressed laser bending forming of metal sheets according to claim 1, characterized in that, In step S4: The laser (6) is a continuous wave laser; The laser from the continuous wave laser scans the area to be formed (8) along a preset path; The scanning start point is set at the inner edge of the metal sheet (1) to be formed, and the scanning end point is set at the inner edge of the other end of the metal sheet (1) to be formed; The temperature field of the area to be formed (8) is less than or equal to the melting point of the metal sheet to be formed (1), which is 100°C. The number of scans is a total of 4 passes.

6. A boundary effect suppression system based on prestressed laser bending forming of metal sheets, characterized in that, include: Module M1: Splice metal plates (5) at both ends of the metal sheet to be formed (1) along the axial direction, and apply a thermally conductive silicone coating (4) at the splice. Module M2: Based on the width of the metal sheet to be formed (1), divide it into multiple areas (8) of equal area along the axial direction. Module M3: Select any area to be formed (8) and pre-bend the area to be formed (8) and the spliced ​​metal plate (5) along the axial direction; Module M4: Use a laser (6) to perform reciprocating multi-pass scanning on the area to be formed (8) under pre-bending loading to obtain a semi-formed part; Module M5: Cool the semi-formed part to room temperature and unload the bending load; repeat Modules M2 to M4 until all areas to be formed (8) are formed to obtain the formed part.

7. The boundary effect suppression system based on prestressed laser bending forming of metal sheets according to claim 6, characterized in that, The axial length of the metal plate (5) is more than 10 times the diameter of the laser spot used for laser scanning; The specific heat capacity of the metal plate (5) is greater than or equal to the specific heat capacity of the metal plate material (1) to be formed; The width and thickness of the metal plate (5) are the same as the width and thickness of the metal plate material (1) to be formed; In module M1: The thickness of the thermally conductive silicone coating (4) is 0.5~3mm; the thermal conductivity of the thermally conductive silicone coating (4) is 10~50W / (m·K).

8. The boundary effect suppression system based on prestressed laser bending forming of metal sheets according to claim 6, characterized in that, In module M1: The spliced ​​metal sheet (1) to be formed is clamped to the metal sheet (5) by clamping fixture (7); In module M2: The area to be formed (8) overlaps with its adjacent areas to be formed (8) (9). The area of ​​the overlapping area (9) accounts for 20% to 40% of the area of ​​the area to be formed (8).

9. The boundary effect suppression system based on prestressed laser bending forming of metal sheets according to claim 6, characterized in that, In module M3: Pre-bending loading is achieved by using a three-point bending method or a four-point bending method; The three-point bending method uses one lower pressure head (2) and two upper pressure heads (3). The upper pressure head (3) is fixed to the two sides of the area to be formed (8). The lower pressure head (2) applies an upward load to the middle of the area to be formed (8) to achieve three-point bending loading. The four-point bending method employs two lower pressure heads (2) and two upper pressure heads (3). The upper pressure heads (3) are fixed in the middle of the area to be formed (8). The two lower pressure heads (2) simultaneously apply the same upward load to both sides of the area to be formed (8) to achieve four-point bending. Furthermore, the distance between the two upper pressure heads (3) is more than twice the diameter of the laser spot. The internal stress of the region to be formed (8) is between the yield strength and tensile strength of its material; The surface of the metal sheet to be formed (1) is free of indentations, scratches and microcracks.

10. The boundary effect suppression system based on prestressed laser bending forming of metal sheets according to claim 6, characterized in that, In module M4: The laser (6) is a continuous wave laser; The laser from the continuous wave laser scans the area to be formed (8) along a preset path; The scanning start point is set at the inner edge of the metal sheet (1) to be formed, and the scanning end point is set at the inner edge of the other end of the metal sheet (1) to be formed; The temperature field of the area to be formed (8) is less than or equal to the melting point of the metal sheet to be formed (1), which is 100°C. The number of scans is a total of 4 passes.

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