A method of improving the quality of the welding of a wing frame and a skin

Abstract

The present application relates to a kind of methods for improving wing skeleton and skin welding quality, belong to welding technical field, solve the multiple problems such as welding deformation, joint strength deficiency, weld is relatively wide, oxidation, blowhole, crack, unmelting, undercut, depression of existing laser welding technology when being applied in wing manufacturing.One kind of methods for improving wing skeleton and skin welding quality, comprising: S1, using 3D printing method to manufacture the parts of wing skeleton;S2, the parts of the wing skeleton to be welded are assembled on the fixture clamp of wing skeleton;S3: build a sealed cover in situ on the back of each butt joint;S4: positioning welding;S5: formal welding.The present application effectively solves the problems such as oxidation, blowhole, crack, unmelting, undercut, depression in the process of laser welding wing by optimizing joint form, fixture clamp, assembly process, gas protection measures, process parameters, while realizing small welding deformation, high welding strength, small weld width and high efficiency.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and in particular to a method for improving the welding quality of wing frames and skins. Background Technology

[0002] Laser welding, as a high-precision and high-efficiency welding method, plays an important role in wing manufacturing and brings many advantages, such as high energy density, precise heat input control, and a small heat-affected zone.

[0003] However, the application of existing laser welding technology in wing manufacturing still faces some challenges, especially in controlling welding quality. The main problems include: (a) due to unreasonable joint type, tooling fixtures, and assembly process design, the resulting wing is difficult to achieve small welding deformation, high strength, small weld width, and high efficiency; (b) the wing has a large number of welding joints, complex structure, and is made of thin-walled light metal. Most existing gas protection measures (especially back gas protection) are cumbersome and have unsatisfactory protection effects, making it difficult to ensure effective protection at each weld joint, which easily leads to oxidation and porosity; (c) due to the lack of use of process parameters with the best matching relationship with the workpiece (e.g., laser power, defocusing amount, welding speed, shielding gas flow rate), defects such as porosity, cracks, lack of fusion, undercut, and dents are very likely to occur during the welding process.

[0004] Therefore, there is an urgent need to provide a method that can effectively improve the welding quality of wing frames and skins, in order to solve the above-mentioned problems of existing laser welding methods in wing manufacturing, improve the welding quality and production efficiency of wings, and ensure the performance and safety of aircraft wings. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a method for improving the welding quality of wing frame and skin, in order to solve one or more of the following problems that easily occur after welding when existing laser welding technology is applied to wing manufacturing: welding deformation, insufficient joint strength, wide weld, weld oxidation, porosity, cracks, lack of fusion, undercut, and dents due to unreasonable design and setting of joint form, tooling fixtures, assembly process, gas protection measures, and process parameters.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] This invention provides a method for improving the welding quality of wing frame and skin, comprising the following steps:

[0008] S1. The wing skeleton parts are manufactured using 3D printing, including M longitudinal members distributed in parallel along a first direction and N transverse members distributed in parallel along a second direction. Each transverse member contains M-1 transverse ribs; M≥3, N≥3, and the first direction and the second direction are different.

[0009] Among them, the M longitudinal members include 2×N×(M-1) connecting ends along the second direction, which can be connected one by one with the two ends of the N×(M-1) transverse ribs to form 2×N×(M-1) butt joints, forming a grid structure with high welding strength; the inner sides of the two longitudinal members and two transverse members located on the outermost side of the wing frame include stepped grooves, the height of which is the same as the skin thickness.

[0010] S2. Assemble the parts of the wing frame to be welded onto the tooling fixture of the wing frame. Ensure that the mating joints are precisely aligned by using the clamping mechanism, side pressing mechanism and pushing mechanism on the tooling fixture.

[0011] S3. On the back of each butt joint, a sealing cover is built in situ using flexible sealing material, with gas inlet and outlet on the sealing cover to protect the weld from the back.

[0012] S4. Under the protection of the front and back sides of the weld seam by inert gas, perform tack welding on all butt joints.

[0013] S5. Under the protection of the front and back sides of the weld seam by inert gas, perform formal welding on all butt joints.

[0014] Furthermore, S2 specifically includes the following steps:

[0015] S21: Position the first longitudinal member with the tooling fixture, set two side pressing mechanisms between any two adjacent butt joints of the first longitudinal member, and set a clamping mechanism between the two side pressing mechanisms;

[0016] S22: Along one end of the first longitudinal member to the other end, N transverse ribs are sequentially assembled on the tooling fixture, and two side pressing mechanisms are set on each transverse rib.

[0017] S23: Assemble the second longitudinal member on the tooling fixture, and set a side pressure mechanism between any two adjacent butt joints of the second longitudinal member;

[0018] Alternately repeat S22 and S23 to assemble the remaining M-3 longitudinal members and N×(M-2) transverse ribs;

[0019] S24: Assemble the Mth longitudinal member on the tooling fixture, set two side pressing mechanisms between any two adjacent butt joints of the Mth longitudinal member, set a clamping mechanism between the two side pressing mechanisms, and set a pushing mechanism on the outside of the Mth longitudinal member and directly opposite each butt joint.

[0020] Furthermore, in S1, the wall thickness of the longitudinal members and transverse ribs is 2mm to 10mm.

[0021] Furthermore, the preferred process parameters for obtaining high-quality welds in S4 and S5 include:

[0022] Tack welding: Laser power of 750W~850W, defocusing amount of -1.5mm~-2.5mm, welding speed of 1.0m / min~2.0m / min; and / or,

[0023] Formal welding: Laser power is 1850W~1950W, defocusing amount is -4.5mm~-5.5mm, welding speed is 1.0m / min~2.0m / min.

[0024] Furthermore, it also includes the following steps:

[0025] S6. Assemble the wing frame and skin to be welded onto the tooling fixture for the wing frame and skin. Through the frame side pressing mechanism and skin clamping mechanism on the tooling fixture, ensure that the skin overlaps on the stepped groove to form a flush butt joint, thereby improving welding strength. Furthermore, each weld seam inside the wing frame is clamped on both sides by the skin clamping mechanism. Specifically, this includes the following steps:

[0026] S61: Ventilation holes are made in the longitudinal and transverse members inside the wing frame so that each of the grid structures is connected.

[0027] S62: Assemble the wing frame onto the tooling fixture, and set two frame side pressing mechanisms between the first longitudinal member and the Mth longitudinal member located between any two adjacent mating joints;

[0028] S63: The upper and lower skins are overlapped on the stepped groove. Two × (M+N-4) skin clamping mechanisms are provided on the outside of the upper and lower skins and along the contact portions of M-2 longitudinal members and N-2 transverse members in the wing frame with the upper and lower skins. Each skin clamping mechanism has a groove that is just the size of the contact surface between the corresponding longitudinal member or transverse member and the skin.

[0029] S7. By utilizing the wing frame with ventilation holes and the upper and lower skin to form a closed and connected air passage environment, inert gas enters from one end of the wing frame and exits from the other end of the wing frame, providing back protection for the weld seam.

[0030] S8. Under the protection of the front and back sides of the weld seam by inert gas, perform penetration welding on the inside of the wing frame and the skin.

[0031] S9. Under the protection of the front and back sides of the weld seam by inert gas, perform bottom-lock welding on the perimeter of the wing frame and the skin.

[0032] Furthermore, the wall thickness of the wing frame and skin is 2mm to 10mm.

[0033] Furthermore, the preferred process parameters for achieving high-quality through-welds in S8 include: laser power of 2000W to 2200W, defocusing amount of -4mm to -6mm, and welding speed of 0.02m / min to 0.03m / min.

[0034] Furthermore, it also includes, in S9, the root pass welding includes tack welding and the final pass welding; the preferred process parameters in S9 for obtaining high-quality welds include:

[0035] Tack welding: Laser power 750W~850W, defocusing amount -1.5mm~-2.5mm, welding speed 1.0m / min~2.0m / min; tack weld length 5mm~15mm, weld spacing 25mm~35mm; and / or,

[0036] Formal welding: Laser power is 950W~1050W, defocusing amount is -4mm~-6mm, welding speed is 1.0m / min~2.0m / min.

[0037] Furthermore, the front protective gas flow rate is 20 L / min to 40 L / min, and the back protective gas flow rate is 4 L / min to 6 L / min.

[0038] Furthermore, it also includes stopping the inert gas protection after cooling for 15 to 20 minutes after the formal welding is completed.

[0039] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0040] This invention provides a method for improving the welding quality of wing skeletons and skins, optimizing various aspects (including joint type, tooling fixtures, assembly procedures, gas protection measures, and process parameters). It effectively solves problems such as oxidation, porosity, cracks, lack of fusion, undercut, and dents that easily occur during laser welding of wings, while simultaneously achieving a balance of minimal welding deformation, high welding strength, narrow weld width, and high efficiency. Specifically, it includes:

[0041] (1) By optimizing the joint form, tooling fixtures, assembly process and gas protection measures, this invention effectively controls and reduces the problems of welding deformation, insufficient joint strength, wide weld, weld oxidation, porosity and cracks that are prone to occur in thin-walled wing parts during laser welding, and significantly improves the welding quality and welding efficiency of wing skeleton and skin.

[0042] a. Joint Type: The wing skeleton parts to be welded are manufactured using 3D printing, and then precision machined to ensure that the parts of the wing skeleton and the skeleton and skin can be precisely aligned to form a butt joint. For example, the longitudinal members include connecting ends along the second direction, which can be connected to the two ends of the transverse ribs to form a butt joint. The inner sides of the two longitudinal members and two transverse members on the outermost side of the wing skeleton include stepped grooves, and the skin overlaps on the stepped grooves to form a butt joint with a flush surface. Compared with the use of T-joints between wing skeleton parts and the direct lap joint between the wing skeleton and the skin, this invention uses 3D printing combined with precision machining and tooling fixtures to precisely process and align the butt joints, effectively improving the welding strength of the wing skeleton and skin, while the weld width is smaller and the welding efficiency is higher.

[0043] b. Tooling and assembly process: Through carefully designed tooling and fixtures and a reasonable arrangement of assembly processes, welding stress and deformation are effectively reduced, cracks caused by residual stress are avoided, and the dimensional accuracy of the welded wing frame and skin is ensured.

[0044] c. Gas protection measures: Inert gas is used for front and back protection at each weld joint; for example, when welding wing frame parts, a sealing cover is built in situ on the back of each joint using flexible sealing material; when welding wing frame and skin, the wing frame and upper and lower skin with ventilation holes form a closed and connected gas path environment; the above simple, easy-to-operate and reliable gas protection measures can effectively prevent air from contacting the molten pool, minimize oxidation, inclusions and porosity problems that may occur during the welding of light metal wings, thereby improving the internal quality of the weld.

[0045] (2) Based on the structural characteristics of the wing skeleton and skin to be welded, this invention optimizes the welding process parameters (including: laser power, defocusing amount, welding speed, shielding gas flow rate, tack welding position, length, spacing, and arc start-up and extinguishing distance) to effectively reduce defects such as porosity, cracks, lack of fusion, undercut, and dents in the laser welding process of the wing. At the same time, it avoids weld oxidation and inclusion problems, and significantly improves the welding quality of thin-walled wing parts.

[0046] (3) The present invention provides a sealing cover formed by bonding a sealing tape to the longitudinal members and / or transverse ribs near the back of each butt joint, and opening holes in the sealing cover to form an inlet and outlet for inert gas; the materials of this method are readily available, the operation is simple and the back gas protection effect is good, and the tape can be quickly removed after welding.

[0047] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0048] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0049] Figure 1 A schematic diagram (partial) of the wing frame provided for an embodiment of the present invention;

[0050] Figure 2 A partial schematic diagram of the wing frame on the tooling fixture provided in an embodiment of the present invention;

[0051] Figure 3 In the middle, (a) is Figure 2 The magnified three-dimensional diagram of part A, (b) is Figure 2 The magnified 3D schematic diagram of part B, (c) is Figure 2 The magnified 3D diagram of part C, (d) is Figure 2 The magnified three-dimensional diagram of part D, (e) is Figure 2 A magnified 3D diagram of section E;

[0052] Figure 4 A schematic diagram (partial) of the wing frame and skin provided in an embodiment of the present invention;

[0053] Figure 5 A partial schematic diagram of the wing frame and skin on a tooling fixture provided in an embodiment of the present invention;

[0054] Figure 6 The location diagram of welding deformation obtained from the chordal plane three-dimensional model of the wing skeleton before and after welding is provided for the embodiments of the present invention;

[0055] Figure 7 A partial photograph of the weld seam of the wing frame and skin bottom-lock weld provided in an embodiment of the present invention;

[0056] Figure 8A partial X-ray non-destructive test image of the weld seam of the wing frame and skin bottom weld provided in an embodiment of the present invention;

[0057] Figure label:

[0058] 100-Wing frame; 11-First main beam; 12-Second main beam; 13-Third main beam; 14-First transverse rib; 15-Second transverse rib; 16-Third transverse rib; 17-Fourth transverse rib; 18-Ventilation hole; 200-Tooling fixture for wing frame; 21-Positioning pin; 22a-Clamping mechanism; 22b-Side pressing mechanism; 22c-Pushing mechanism; 23a-First rotating mechanism; 23b-Second rotating mechanism; 24-Connecting end; 25-Butt joint; 26-Step groove; 300-Skin; 400-Tooling fixture for wing frame and skin; 41-Skin clamping mechanism; 42-Frame side pressing mechanism; 43a-First fixture rotating mechanism; 43b-Second fixture rotating mechanism. Detailed Implementation

[0059] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0060] This invention provides a method for improving the welding quality of wing frame and skin, comprising the following steps:

[0061] Step S1: Use 3D printing to manufacture the wing frame parts, including M longitudinal members distributed parallel to the first direction and N transverse members distributed parallel to the second direction. Each transverse member contains M-1 transverse ribs; M≥3, N≥3, and the first direction and the second direction are different.

[0062] Among them, the M longitudinal members include 2×N×(M-1) connecting ends along the second direction, which can be connected one by one with the two ends of the N×(M-1) transverse ribs to form 2×N×(M-1) butt joints, forming a grid structure with high welding strength; the inner sides of the two longitudinal members and two transverse members located on the outermost side of the wing frame include stepped grooves, the height of which is the same as the skin thickness.

[0063] Preferably, the angle between the first direction and the second direction is 85° to 95°; exemplarily, the angle between the first direction and the second direction is a right angle.

[0064] Preferably, the longitudinal members and transverse ribs are rod-shaped members; more preferably, the longitudinal members and transverse ribs are hollow rod-shaped members.

[0065] Optionally, the cross-sectional shape of the longitudinal members and transverse ribs can be, but is not limited to, one or a combination of I-shaped, Π-shaped, or similar shapes.

[0066] Preferably, the wall thickness of the longitudinal members and transverse ribs is 2mm to 10mm; more preferably, the wall thickness of the longitudinal members and transverse ribs is 2mm to 3mm.

[0067] Preferably, the materials of the longitudinal members and transverse ribs are one or a combination of titanium alloy, aluminum alloy, and steel.

[0068] Preferably, the above-mentioned 3D printing method further includes: after 3D printing, performing precision machining on all longitudinal components and transverse ribs (mainly the surfaces to be welded) to further improve the accuracy of alignment between longitudinal components and transverse ribs, and between the outermost longitudinal and transverse components of the wing frame and the surrounding skin. The precision machining method can be selected as needed, including but not limited to one or a combination of milling, grinding, scraping, lapping, ultra-precision machining, and polishing.

[0069] For example, see Figure 3 (d) The third main beam 13 includes a connecting end 24 along the second direction, which is connected to the left end face of the fourth transverse reinforcement 17 to form a butt joint 25.

[0070] It is worth noting that, compared with the T-joint between the longitudinal component and the transverse rib, the present invention obtains the longitudinal component by 3D printing and machining, and forms a butt joint by connecting the end of the longitudinal component to the two ends of the transverse rib one by one. This achieves at least the following beneficial effects: (1) Due to the symmetry of the butt joint formed at both ends of the transverse rib, a more uniform stress distribution can be provided in the welding area, reducing the risk of cracks and other welding defects caused by stress concentration; (2) The heat distribution is relatively uniform when the butt joint is welded, which helps to reduce the generation of welding defects such as porosity and lack of fusion; (3) The welding strength of the butt joint is higher and the weld width is smaller. No additional filling material or special edge design is required, which may be more economical in terms of material use and is conducive to achieving the requirements of both lightweight and high strength of the aircraft wing.

[0071] For example, see Figure 3 (e) The inner sides of the uppermost transverse member and the rightmost longitudinal member of the wing skeleton include stepped grooves 26, the height of which is the same as the thickness of the skin, so that the upper and lower skins overlap on the stepped grooves 26 to form a flush butt joint.

[0072] It is worth noting that, compared with the upper and lower skins being placed directly on the surface of the wing frame to form an overlapping joint, the present invention designs stepped grooves around the outermost edge of the wing frame so that the skins can overlap on the stepped grooves to form a butt joint with a flush surface. This achieves at least the following beneficial effects: (1) The contact area of ​​the welds around the wing frame and the skin is larger, which is conducive to improving the welding strength of the bottom lock weld around the edges. The weld width is also smaller, which is conducive to achieving both lightweight and high strength. (2) Due to the larger contact area around the wing frame and the skin, the heat distribution is relatively uniform during welding, which helps to reduce the generation of welding defects such as porosity and lack of fusion. (3) By utilizing the positioning function of the stepped grooves, the skin and the wing frame can be quickly positioned without additional positioning mechanisms. During the welding process, the relative position and structural stability of the skin and the wing frame can be maintained, reducing the risk of cracks and other welding defects caused by stress concentration.

[0073] Step S2: Assemble the parts of the wing frame to be welded onto the tooling fixture of the wing frame. Use the clamping mechanism, side-pressing mechanism, and pushing mechanism on the tooling fixture to ensure precise alignment of the mating joints. Specifically, this includes the following steps:

[0074] S21: Position the first longitudinal member with the tooling fixture, set two side pressing mechanisms between any two adjacent butt joints of the first longitudinal member, and set a clamping mechanism between the two side pressing mechanisms;

[0075] S22: Along one end of the first longitudinal member to the other end, N transverse ribs are sequentially assembled on the tooling fixture, and two side pressing mechanisms are set on each transverse rib.

[0076] S23: Assemble the second longitudinal member on the tooling fixture, and set a side pressure mechanism between any two adjacent butt joints of the second longitudinal member;

[0077] Alternately repeat S22 and S23 to assemble the remaining M-3 longitudinal members and N×(M-2) transverse ribs;

[0078] S24: Assemble the Mth longitudinal member on the tooling fixture, set two side pressing mechanisms between any two adjacent butt joints of the Mth longitudinal member, set a clamping mechanism between the two side pressing mechanisms, and set a pushing mechanism on the outside of the Mth longitudinal member and directly opposite each butt joint.

[0079] It should be noted that the tooling fixtures for the wing frame include: a base plate, a positioning mechanism set on the base plate, and a clamping mechanism; wherein, the clamping mechanism includes three types: a pressing mechanism, a side pressing mechanism, and a pushing mechanism.

[0080] Understandably, the shape of the substrate depends on the shape of the wing frame and can be designed as needed, as long as it can support and accommodate the parts to be welded onto the wing frame. For example, see... Figure 2 The substrate is a thin plate in the shape of a grid, with each grid containing a hollow structure.

[0081] It should be noted that the positioning mechanism on the substrate includes W positioning pins, where W ≥ 2; the W lugs of the first longitudinal member are engaged with the W positioning pins on the substrate to define the position of the first longitudinal member relative to the substrate along the first direction. This position will serve as the reference position for the installation of other members, thereby ensuring the relative position of each member during assembly.

[0082] Preferably, the positioning mechanism is located outside the area to be welded, avoiding the weld seam and ensuring the accessibility of the welding tools; in one possible design, see [reference needed]. Figure 2 The outer side of the first longitudinal member (i.e., the first main beam 11) includes two lugs spaced apart along the first direction. Each lug cooperates with a positioning pin 21 on the substrate. That is, the positioning pin 21 passes through the inner hole on the lug and accurately positions the first longitudinal member along the first direction at the position of the positioning pin on the substrate.

[0083] Preferably, each clamping mechanism includes a clamping bar, the two ends of which can be located on both sides of the same longitudinal member or transverse rib, and fixes and clamps the longitudinal member or transverse rib along the entire width direction onto the base plate to control the relative position of the parts to be welded in the wing frame and the thermal deformation during welding.

[0084] As an optional implementation, both ends of the clamping strip are fixed to the substrate by threaded connection; for example, see [link to example]. Figure 2 and Figure 3 (a) The clamping mechanism 22a includes a clamping bar with inner holes at both ends for screws or bolts to pass through and be screwed into the substrate.

[0085] Preferably, each side pressing mechanism includes a pressing plate, one end of which may be located on the surface of the longitudinal member or the transverse rib, and the other end is fixed to the base plate, for fixing and pressing the longitudinal member or the transverse rib along part or all of its width onto the base plate, so as to control the relative position of the parts to be welded in the wing frame and the thermal deformation during welding.

[0086] As an optional implementation, the clamping plate is fixed to the substrate by a threaded connection; for example, see [link to example]. Figure 2 and Figure 3 (b) The side pressing mechanism 22b includes a pressing plate with an inner hole in the portion that does not contact the longitudinal member or the transverse rib, so that a screw or bolt can pass through and be screwed into the substrate.

[0087] It is understood that the number of inner holes on the clamping plate can be designed as needed; for example, the clamping plate includes two inner holes to achieve effective fixation while ensuring that the clamping force is evenly distributed to avoid deformation due to local overtightness.

[0088] In one possible design, the clamping plate is also provided with a blind groove to accommodate the protrusions on the longitudinal members or transverse ribs, so as to adapt to the non-planar shape of the parts to be welded in the wing frame and facilitate the installation operation; the shape of the blind groove depends on the shape of the protrusions on the longitudinal members or transverse ribs.

[0089] Preferably, each pushing mechanism includes a pushing block and a mounting base. The pushing block includes a push rod and an end pressing part connected to each other. The mounting base is fixed to the base plate. The push rod is fixed in the mounting base by a rotatable connection. By rotating the push rod, the end pressing part is driven to abut against the side wall of the longitudinal member or transverse rib, so as to control the relative position of the parts to be welded in the wing frame and the thermal deformation during welding.

[0090] Preferably, the push rod and the mounting base are rotatably connected by threads; for example, see Figure 2 and Figure 3 (c) The pushing mechanism 22c engages with the thread in the inner hole of the mounting base through the thread on the outer surface of the push rod.

[0091] Preferably, in S21, the first longitudinal member is positioned with the positioning mechanism on the tooling fixture, and a side pressing mechanism is provided in the 1 / 5 to 2 / 5 and 3 / 5 to 4 / 5 sections of the first longitudinal member located between any two adjacent butt joints (based on any one of the two adjacent butt joints), and a clamping mechanism is provided in the 2 / 5 to 3 / 5 section; more preferably, a side pressing mechanism is provided at 1 / 4 and 3 / 4 of the first longitudinal member located between any two adjacent butt joints (based on any one of the two adjacent butt joints), and a clamping mechanism is provided at 1 / 2.

[0092] In one possible design, the W lugs of the first longitudinal member are engaged with W locating pins on the substrate to position the first longitudinal member relative to the substrate along a first direction; W ≥ 2.

[0093] Preferably, in S22, two side-pressing mechanisms are provided in the 1 / 3 to 2 / 3 section of each horizontal rib (based on either end of each horizontal rib); more preferably, one side-pressing mechanism is provided at 1 / 3 and 2 / 3 of each horizontal rib (based on either end of each horizontal rib).

[0094] Preferably, in S23, a side pressure mechanism is provided in the 1 / 5 to 4 / 5 section between any two adjacent butt joints of the second longitudinal member (based on any one of the two adjacent butt joints).

[0095] In one possible design, a side pressure mechanism is provided in the 2 / 5 to 3 / 5 section of the second longitudinal member located between any two adjacent butt joints (based on any one of the two adjacent butt joints).

[0096] In one possible design, a side pressure mechanism is provided in the 1 / 5 to 2 / 5 and 3 / 5 to 4 / 5 sections of the second longitudinal member located between any two adjacent butt joints (based on any one of the two adjacent butt joints).

[0097] Preferably, in S24, a side pressing mechanism is provided in the 1 / 5 to 2 / 5 and 3 / 5 to 4 / 5 sections of the Mth longitudinal member located between any two adjacent butt joints (based on any one of the two adjacent butt joints), and a clamping mechanism is provided in the 2 / 5 to 3 / 5 section.

[0098] More preferably, a side pressing mechanism is provided at 1 / 4 and 3 / 4 of the distance between any two adjacent butt joints (based on any one of the two adjacent butt joints) of the Mth longitudinal member, and a clamping mechanism is provided at 1 / 2.

[0099] It is worth noting that the present invention, through the carefully designed tooling fixtures for the wing skeleton and the adoption of a reasonable assembly sequence and the arrangement of clamping mechanisms (including pressing mechanisms, side pressing mechanisms, and pushing mechanisms) in appropriate positions, has achieved at least the following beneficial effects: (1) The tooling fixtures, in conjunction with the optimized assembly sequence and the setting of the clamping mechanisms, provide the necessary stability for welding the wing skeleton, preventing movement or vibration during the welding process, thereby ensuring the precise connection and consistency of the weld; (2) The tooling fixtures, in conjunction with the optimized assembly sequence and the setting of the clamping mechanisms, can provide appropriate clamping force and support for the wing parts, effectively control thermal deformation during the welding process, reduce stress concentration during the welding process, and avoid the generation of cracks and other welding defects; (3) The tooling fixtures, in conjunction with the optimized assembly sequence and the setting of the clamping mechanisms, ensure the precise alignment of the butt joints, ensure the uniformity and strength of the weld, improve production efficiency, and at the same time ensure the dimensional accuracy of the welded wing skeleton and skin.

[0100] Step S3: On the back of each butt joint, build a sealing cover in situ with flexible sealing material, and open an inert gas inlet and outlet on the sealing cover to protect the weld from the back.

[0101] In one possible design, a sealing cover is formed by bonding sealing tape to the longitudinal members and / or transverse ribs near the back of each butt joint, with openings in the sealing cover to form an inlet and outlet for inert gas; this method uses readily available materials, is simple to operate, provides good back gas protection, and the tape can be quickly removed after welding.

[0102] Furthermore, the gas inlet and outlet positions are designed based on the specific gravity of the selected inert gas compared to air; preferably, the inert gas is argon, with the gas inlet located at the lower part of the sealing cover and the gas outlet located at the upper part of the sealing cover; since argon is heavier than air, it is easier to obtain a higher concentration by filling argon from a lower position, resulting in better argon filling protection.

[0103] In one possible design, the existing drag shield protection method (nozzle + drag shield, inert gas is sprayed from the drag shield) is used to provide frontal protection for each weld.

[0104] Step S4: Under the protection of the front and back sides of the weld seam by inert gas, perform tack welding on all butt joints;

[0105] Specifically, the welding trajectory is first determined, ensuring that the laser spot is located in the middle of the weld; then, all butt joints of the wing frame are tack welded.

[0106] Preferably, the middle part of the butt joint is selected for tack welding; since the butt joints of the longitudinal components and transverse ribs of the wing frame are relatively short, selecting the middle part of the butt joint for tack welding can effectively ensure uniform heat input and reduce welding deformation and stress concentration.

[0107] The tack weld length can be selected according to the length and thickness of the welded joint; preferably, the tack weld length is 1 / 5 to 1 / 3 of the length of the welded joint; for example, the length of the welded joint is 30mm and the tack weld length is 10mm; if the tack weld length is too long, it may cause the welding area to overheat and melt excessively, while if the length is insufficient, it may cause the weld joint to be weak.

[0108] Optionally, the process parameters for tack welding are: laser power of 700W to 900W, defocusing amount of -1.0mm to -3.0mm, and welding speed of 0.5m / min to 2.5m / min; preferably, the process parameters for tack welding are: laser power of 750W to 850W, defocusing amount of -1.5mm to -2.5mm, and welding speed of 1.0m / min to 2.0m / min; for example, the laser power is 800W, the defocusing amount is -2mm, and the welding speed is 1.5m / min.

[0109] It is worth noting that in S4, the above-mentioned preferred laser power, defocusing amount and welding speed can not only effectively fix the wing parts to be welded, but also ensure appropriate heat input and molten pool size, so as to avoid excessive melting or incomplete penetration in the tack welding area, resulting in an unstable connection and affecting the welding quality during subsequent formal welding.

[0110] Step S5: Under the protection of the front and back sides of the weld seam by inert gas, perform formal welding on all butt joints.

[0111] Preferably, the wing frame is welded in the following order: from one end to the other along the first direction and from one side to the other along the second direction, in order to control welding deformation.

[0112] The above welding sequence allows the weld to shrink more freely, reducing the accumulation of welding stress and thus minimizing welding deformation caused by residual stress generated during laser welding, reducing defects such as cracks; at the same time, it facilitates welding operations and effectively ensures the straightness of welded joints located on the same straight line.

[0113] For example, see Figure 1 The eight welded joints are welded sequentially in the order of (①-⑧). That is, from top to bottom, along the second horizontal beam (including the second horizontal reinforcement 15 and the first horizontal reinforcement 14) from left to right, first weld the butt joint ① between the second horizontal reinforcement 15 and the third main beam 13, and the butt joint ② between the second horizontal reinforcement 15 and the second main beam 12; then weld the butt joint ③ between the first horizontal reinforcement 14 and the second main beam 12, and the butt joint ④ between the first horizontal reinforcement 14 and the first main beam 11; then, along the third horizontal beam (including the fourth horizontal reinforcement 17 and the third horizontal reinforcement 16) from left to right, first weld the butt joint ⑤ between the fourth horizontal reinforcement 17 and the third main beam 13, and the butt joint ⑥ between the fourth horizontal reinforcement 17 and the second main beam 12; then weld the butt joint ⑦ between the third horizontal reinforcement 16 and the second main beam 12, and the butt joint ⑧ between the third horizontal reinforcement 16 and the first main beam 11.

[0114] If ① and ④ are welded first, ② and ③ may not be able to be joined into a straight line due to different directions of thermal deformation.

[0115] Preferably, the welding sequence of steps S5 and S4 is the same. By following a consistent welding sequence for tack welding and final welding, it is helpful to better control the heat input and heat distribution during the welding process, thereby reducing welding deformation and improving welding quality.

[0116] Optionally, the formal welding process parameters are: laser power of 1700W to 2100W, defocusing amount of -3.5mm to -6.5mm, and welding speed of 0.5m / min to 2.5m / min; preferably, the formal welding process parameters are: laser power of 1850W to 1950W, defocusing amount of -4.5mm to -5.5mm, and welding speed of 1.0m / min to 2.0m / min; for example, the laser power is 1900W, the defocusing amount is -5mm, and the welding speed is 1.5m / min.

[0117] As an optional implementation, step S5 also includes the following welding sequence to reduce welding deformation and stress concentration, avoid defects such as cracks, and improve welding quality;

[0118] S51: Front weld of each butt joint of the welded wing frame;

[0119] S52: The tooling fixture is flipped by a rotating mechanism to weld the reverse side weld of each butt joint of the wing frame;

[0120] S53: Adjust the tooling fixtures using a rotating mechanism to weld the side welds of each butt joint.

[0121] In one possible design, for areas that are difficult to reach or observe during the welding process, i.e., processing dead corners, non-linear programming or flexible welding equipment, such as welding robots, can be used to adjust the welding torch angle according to the actual situation to ensure the accessibility of the welding torch.

[0122] Step S6: Assemble the wing frame and skin to be welded onto the tooling fixture. Using the frame side-pressing mechanism and skin clamping mechanism on the tooling fixture, ensure that the skin overlaps on the stepped groove to form a flush butt joint, thereby improving welding strength. Furthermore, each weld seam inside the wing frame is clamped on both sides by the skin clamping mechanism. Specifically, this includes the following steps:

[0123] S61: Ventilation holes are made in the longitudinal and transverse components inside the wing frame to make each grid structure connected.

[0124] S62: Assemble the wing skeleton onto the tooling fixture, and set two skeleton side pressure mechanisms between any two adjacent butt joints of the first longitudinal member and the Mth longitudinal member.

[0125] S63: The upper and lower skins are overlapped on the stepped groove. Two × (M+N-4) skin clamping mechanisms are set on the outside of the upper and lower skins and along the contact parts of M-2 longitudinal members and N-2 transverse members in the wing frame with the upper and lower skins. Each skin clamping mechanism has a groove that is just the size of the contact surface between the corresponding longitudinal member or transverse member and the skin.

[0126] Specifically, the main steps of S62 include: removing the welded wing skeleton from the tooling fixture 200 used for welding the wing skeleton in S5, and then assembling it onto another tooling fixture 400 used for welding the wing skeleton and skin; setting two skeleton side-pressure mechanisms between the first longitudinal member and the Mth longitudinal member at any two adjacent butt joints; see also Figure 5 The frame side pressing mechanism 42 is used to fix and press the wing frame onto the base plate.

[0127] It should be noted that the tooling fixtures for the wing frame and skin include: a base plate, a frame side pressing mechanism and a skin clamping mechanism disposed on the base plate;

[0128] Preferably, each frame side pressing mechanism includes a clamping plate, one end of which can be pressed on the surface of the outermost longitudinal or transverse member of the wing frame, and the other end is fixed to the base plate, thereby controlling the relative position of the wing frame and the tooling fixture.

[0129] Preferably, in step S62, a skeleton side pressure mechanism is provided in the 1 / 5 to 2 / 5 and 3 / 5 to 4 / 5 sections of the first longitudinal member and the Mth longitudinal member located between any two adjacent butt joints (based on any one of the two adjacent butt joints).

[0130] Preferably, each skin clamping mechanism includes a clamping strip with a groove on the clamping strip that is the size of the contact surface between the corresponding longitudinal or transverse member inside the wing frame and the skin and extends through the upper and lower surfaces of the clamping strip; more preferably, the clamping strip has a groove that is exactly the size of the contact surface between the corresponding longitudinal or transverse member and the skin and extends through the upper and lower surfaces of the clamping strip.

[0131] Understandably, a skin clamping mechanism is provided on the outer side of the contact portion between each longitudinal and transverse component inside the wing frame and the upper and lower skins. This fixes and clamps the wing frame, along with the upper and lower skins covering the wing frame surface, onto the base plate along the first and second directions. This arrangement allows control of the relative position of the wing frame and the upper and lower skins. At the same time, for this type of long through weld, the skin clamping mechanism clamps both sides of each weld inside the wing frame, effectively controlling the thermal deformation of the wing frame and skin. This improves the dimensional accuracy and quality of the weld, and avoids defects such as cracking and low joint strength caused by welding stress concentration.

[0132] As an optional implementation, the clamping strip is fixed to the substrate by a threaded connection; exemplary, the end of the clamping strip and / or along both sides of the groove are provided with a plurality of holes for screws or bolts to pass through and be screwed into the substrate and / or skin.

[0133] Preferably, the tooling fixture for welding the wing frame and the wing frame and skin also includes a rotating mechanism coaxially arranged on both sides of the base plate; the two rotating mechanisms are connected to the welding worktable, and by rotating the tooling fixture, welding can be easily performed at different angles of the wing frame and skin, improving the accessibility of the welding torch.

[0134] Preferably, two rotating mechanisms ( Figure 2 The first rotating mechanism 23a and the second rotating mechanism 23b in the middle, Figure 5The first clamping rotation mechanism 43a and the second clamping rotation mechanism 43b are coaxially arranged on both sides of the substrate and the rotation axis is perpendicular to the first direction; more preferably, the two rotation structures are coaxially arranged at the middle position on both sides of the substrate and the rotation axis is perpendicular to the first direction.

[0135] Step S7: By utilizing the wing frame with ventilation holes and the upper and lower skin to form a closed and connected air passage environment, inert gas enters from one end of the wing frame and exits from the other end of the wing frame, providing back protection for the weld seam.

[0136] It is worth noting that most of the materials used for the wings are lightweight metals, such as titanium alloys and aluminum alloys, which are prone to oxidation during welding. This invention achieves at least the following beneficial effects by using back gas protection in steps S3 and S7 in conjunction with front gas protection: (1) Preventing oxidation: Through the above gas protection (especially back gas protection), oxygen and nitrogen in the air can be effectively isolated, reducing the oxidation of lightweight metals at the wing weld joint in the high-temperature molten pool state and avoiding the formation of brittle oxides and nitrides; (2) Reducing porosity: Through the above gas protection (especially back gas protection), the flow of inert gas helps to remove the gas in the molten pool, reducing the formation of porosity; (3) Improving weld formation and welding efficiency: Through the above gas protection (especially back gas protection), the weld formation is improved, making the weld surface smoother and more uniform, which can reduce defects and rework in the welding process and improve welding efficiency and productivity.

[0137] Step S8: Under the protection of the front and back sides of the weld seam by inert gas, perform penetration welding on the interior of the wing frame and the skin.

[0138] Preferably, penetration welding is performed in the following welding sequence:

[0139] S81: Weld the second transverse member, the third transverse member, ... the N-1th transverse member in contact with the skin in sequence from one end to the other along the first direction; For each transverse member, weld in the same direction from one side to the other along the second direction.

[0140] S82: Along the second direction from both sides to the middle, weld the second longitudinal member, the M-1 longitudinal member, the third longitudinal member, the M-2 longitudinal member, ... up to the contact part between the 1 / 2*M longitudinal member or the 1 / 2*(M+1) longitudinal member and the skin. For each longitudinal member, weld symmetrically from both ends to the middle along the first direction.

[0141] The above welding sequence allows the weld to shrink more freely, reducing welding stress and deformation, improving the stability of the welded structure, and reducing defects such as cracking and decreased joint strength caused by residual stress generated during laser welding.

[0142] It should be noted that the preferred process parameters for achieving high-quality through-welds in S8 include: laser power of 2000W to 2200W, defocusing amount of -4mm to -6mm, and welding speed of 0.02m / min to 0.03m / min; for example, the laser power is 2100W, the defocusing amount is -5mm, and the welding speed is 0.025m / min.

[0143] Step S9: Under the protection of the front and back sides of the weld seam by inert gas, perform bottom-lock welding on the perimeter of the wing frame and the skin.

[0144] It should be noted that the bottom lock welding includes tack welding and the final welding;

[0145] The preferred process parameters for obtaining high-quality welds in step S9 include:

[0146] Tack welding: Laser power is 700W to 900W, defocusing amount is -1.0mm to -3.0mm, and welding speed is 0.5m / min to 2.5m / min; more preferably, laser power is 750W to 850W, defocusing amount is -1.5mm to -2.5mm, and welding speed is 1.0m / min to 2.0m / min; the length of the tack weld is 5mm to 15mm, and the weld spacing is 25mm to 35mm; if the tack weld length is too long, it may cause overheating and excessive melting in the welding area, while if the length is insufficient, it may cause the tack weld joint to be weak.

[0147] Formal welding: laser power of 900W to 1100W, defocusing amount of -3mm to -7mm, welding speed of 0.5m / min to 2.5m / min; more preferably, laser power of 950W to 1050W, defocusing amount of -4mm to -6mm, welding speed of 1.0m / min to 2.0m / min.

[0148] Preferably, in S4, S5, S8 and S9, the front protective gas flow rate is 20L / min to 40L / min, and the back protective gas flow rate is 4L / min to 6L / min; more preferably, the front protective gas flow rate is 20L / min to 30L / min; for example, the front protective cover gas flow rate is 25L / min, and the back protective gas flow rate is 5L / min.

[0149] Preferably, during the formal welding in S5 and S9 and the through welding in S8, the arc initiation and extinguishing distance is 3mm to 7mm; for example, the arc initiation and extinguishing distance is 5mm.

[0150] Preferably, in S5 and S9, after the formal welding is completed, the inert gas protection is stopped after cooling for 15 to 20 minutes; after welding is completed, the gas protection (mainly back gas protection) can protect the weld metal from the corrosion of harmful gases in the air during the cooling process, and maintain the purity and performance of the weld metal.

[0151] It is worth noting that in S4, S5, S8, and S9, using the aforementioned optimized process parameters (arc initiation and extinguishing distance, laser power, defocusing amount, welding speed, and shielding gas flow rate) can ensure the formation of a smooth and uniform weld surface between all weld joints, reduce welding defects, and improve the quality of the weld joints; specifically,

[0152] (1) Arc starting distance: Among S5, S8 and S9, the preferred arc starting distance can ensure that the starting part of the weld can be formed sequentially and maintain a stable welding process; if the arc starting distance is too short, it will cause the welding starting point to overheat, forming weld beads or burn-through; while if the arc starting distance is too long, it may cause insufficient penetration at the starting point, affecting the connection strength of the weld.

[0153] (2) Extinguishing distance: Among S5, S8 and S9, the preferred extinguishing distance mentioned above helps to maintain the continuity and uniformity of the welding process and ensure the quality of the weld end; if the extinguishing distance is too short, the weld end will overheat, forming crater cracks or other welding defects; while if the extinguishing distance is too long, the weld end will cool down too quickly, forming cold cracks or other micro defects.

[0154] (3) Laser power: Among S4, S5, S8 and S9, the above-mentioned preferred laser power can effectively ensure that there are no defects such as pores, cracks, lack of fusion, undercut, and depressions on the weld surface; specifically, a. if the laser power is too high, the temperature of the molten pool will be too high, the metal vapor will increase, and the gas will not escape from the molten pool in time, thus forming pores; b. if the laser power is too high, the temperature of the molten pool will be too high, the thermal stress of the material will increase, thus inducing the formation of cracks; c. if the laser power is insufficient, the temperature of the molten pool may not be high enough, and the material may not be fully melted, thus producing a lack of fusion; d. if the laser power is too high, the temperature of the molten pool will be too high, the melting range will expand, and it is easy to cause undercut; e. if the laser power is too high, the temperature of the center of the molten pool may be too high, and the metal in the center of the molten pool will solidify before the edge, forming a depression.

[0155] (4) Defocusing amount: Among S4, S5, S8 and S9, the above-mentioned preferred defocusing amount can effectively ensure that the weld surface is free from defects such as porosity, cracks, lack of fusion, undercut, and depressions; specifically, a. Excessive or insufficient defocusing amount leads to irregular shape of the molten pool, poor gas discharge, and increases the risk of porosity; b. Excessive or insufficient defocusing amount leads to uneven cooling of the molten pool, stress concentration in local areas, and increases the possibility of crack formation; c. Excessive defocusing amount leads to uneven laser energy distribution, with excessively high temperature at the center of the molten pool and insufficient temperature at the edge, which easily causes lack of fusion; d. Excessive or insufficient defocusing amount leads to inconsistent cooling rates at the edge of the molten pool, which easily causes undercut; e. Excessive or insufficient defocusing amount leads to uneven cooling of the molten pool, which easily forms depressions.

[0156] (5) Welding speed: Among S4, S5, S8 and S9, the above-mentioned preferred welding speed can effectively ensure that the weld surface is free from defects such as porosity, cracks, lack of fusion, undercut, and depressions; specifically, a. If the welding speed is too fast, the molten pool may cool too quickly, and the gas may not escape sufficiently, which can easily lead to porosity; b. If the welding speed is too slow, the molten pool may remain at a high temperature for a long time, which increases the thermal stress of the material and thus increases the risk of cracks; c. If the welding speed is too fast, the molten pool may cool too quickly, and the material may not melt sufficiently, which can easily lead to lack of fusion and undercut; d. If the welding speed is too fast, the metal in the center of the molten pool may not be fully filled, forming a depression.

[0157] (6) Protective gas flow rate: In S4, S5, S8 and S9, the above-mentioned preferred gas flow rate is used to protect the front and back of each weld, which can effectively prevent oxidation and inclusions in the weld area, ensure the stability and uniformity of the molten pool, and avoid defects such as porosity; too low a gas flow rate cannot provide sufficient protection, resulting in weld oxidation; while too high a gas flow rate will interfere with the stability of the molten pool and affect the formation of the weld.

[0158] Preferably, in steps S2 and S6, the assembly includes: trial assembly, repair and trial assembly to meet assembly tolerance requirements, and marking each component with matching marks; pickling to remove oxide scale and improve welding quality; formal assembly: after pickling, according to the matching marks on each component, assemble each component in sequence and clamp it with tooling fixtures to ensure that the assembly tolerance requirements are met.

[0159] Preferably, in steps S2 and S6, the assembly tolerance requirements include: the mating gap and step difference at each point of each joint shall not exceed 0.1 mm, and the mating gap and step difference with a cumulative length of not more than 30 mm within any local area of ​​100 mm shall not exceed 0.2 mm.

[0160] Preferably, before trial assembly, the area to be welded is pretreated until a metallic luster is exposed, and the surface roughness Ra of the surface to be welded is ≤3.2μm.

[0161] Specifically, the pretreatment mainly includes machining the area to be welded; specifically, machining is used to process the surface to be welded to ensure it is flat, smooth, burr-free, and retains its edges, with a surface roughness Ra≤3.2μm after machining; mechanical treatment is used to clean the area to be welded to remove surface oil, non-metallic impurities, etc., until a metallic luster is exposed; the area to be welded includes the surface to be welded and both sides of the weld; non-metallic impurities include oxides.

[0162] Optionally, the area to be welded includes 10mm to 30mm on each side of the weld; preferably, it includes 20mm on each side of the weld.

[0163] Optionally, the above machining methods include, but are not limited to, milling, grinding, scraping, lapping, ultra-precision machining, and polishing.

[0164] Optionally, the above mechanical processing method includes mechanical polishing. For example, the tools for mechanical polishing include, but are not limited to, wire brushes, sandpaper, and files.

[0165] It is understandable that pretreatment of the area to be welded (including the surface to be welded) can ensure the quality and reliability of the weld joint.

[0166] Preferably, in steps S4, S5 and S8, S9, chord plane measurement and shape correction are performed before and after welding, respectively.

[0167] It should be noted that the main steps of chord plane measurement include: selecting a suitable chord plane measuring device; using the chord plane measuring device to scan along the chord length direction of the wing skeleton, wing skeleton and skin assembly, and recording data points; inputting the collected data into computer-aided design (CAD) software for data analysis, and generating a chord plane 3D model of the wing skeleton, wing skeleton and skin assembly before and after welding.

[0168] Optionally, the chord plane measuring device includes at least one of a laser scanner and a laser tracker.

[0169] Furthermore, by comparing the chordal plane 3D models before and after welding, the location and amount of deformation points are obtained, and the wing frame, wing frame and skin assembly are corrected to further eliminate the minor deformations during the laser welding process.

[0170] Optionally, the calibration method includes one or a combination of mechanical calibration, thermal calibration, cold calibration, and CNC calibration. Among them, mechanical calibration includes, but is not limited to, manual calibration, pressure calibration, and tensile calibration; thermal calibration includes, but is not limited to, local heating and overall heating; cold calibration includes, but is not limited to, cooling shrinkage and cold stretching; and CNC calibration includes, but is not limited to, CNC calibration and robot calibration.

[0171] The technical solution of the present invention will be further described in detail below with reference to specific embodiments.

[0172] Example 1:

[0173] This embodiment provides a method for improving the welding quality of TA15 titanium alloy wing frame and skin, including the following steps:

[0174] Step S1: The wing frame parts are manufactured using the selective laser melting (SLM) method. See [link to relevant documentation]. Figures 1-5 The wing frame 100 includes a first main spar 11, a second main spar 12, and a third main spar 13 distributed parallel to a first direction, and a first crossbeam (not shown in the figure), a second crossbeam, a third crossbeam, and a fourth crossbeam (not shown in the figure) distributed parallel to a second direction; the second crossbeam includes a first cross rib 14 and a second cross rib 15 distributed in a straight line, and the third crossbeam includes a third cross rib 16 and a fourth cross rib 17 distributed in a straight line; the angle between the first direction and the second direction is 87°;

[0175] The first main beam 11 and the third main beam 13 each have four connecting ends on one side, and the second main beam 12 has four connecting ends on both sides. These can be connected one by one with the two ends of the eight transverse ribs (four of which are not shown in the figure) to form 16 butt joints, creating a high-welding-strength grid structure. The inner sides of the first main beam 11, the third main beam 13, the first transverse beam, and the fourth transverse beam include stepped grooves with a height of 2 mm.

[0176] The main beam and cross ribs are made of TA15 titanium alloy and are hollow structural members with a wall thickness of 3mm and an I-shaped cross section; the skin is made of TA15 titanium alloy with a wall thickness of 2mm.

[0177] Step S2: Assemble the parts of the wing frame to be welded onto the tooling fixture of the wing frame;

[0178] The tooling fixture 200 for the wing frame includes a base plate, a positioning mechanism, a clamping mechanism, a side pressing mechanism, a pushing mechanism, and two rotating mechanisms 23a and 23b symmetrically and coaxially distributed on both sides of the base plate.

[0179] The substrate is a thin plate in the shape of a grid, and each grid includes a quadrilateral or cross-shaped hollow structure;

[0180] The positioning mechanism includes two positioning pins 21 located on the substrate;

[0181] Each clamping mechanism 22a includes an elongated clamping bar with inner holes at both ends for screws to pass through and be screwed into the substrate;

[0182] Each side-pressing mechanism 22b includes a rectangular pressing plate, the portion of which does not contact the main beam or cross rib has two inner holes for screws to pass through and be screwed into the base plate;

[0183] Each pushing mechanism 22c includes a push block and a mounting base. The push block includes a push rod and an end pressing part that are connected to each other. The mounting base is fixed on the base plate. The outer surface of the push rod is threaded and engages with the thread of the inner hole of the mounting base. By rotating the push rod, the end pressing part is driven to abut against the side wall of the main beam.

[0184] Specifically, the assembly steps described above include:

[0185] S21: Position the two lugs on the right side of the first main beam 11 by engaging them with the two positioning pins on the base plate; Set a side pressing mechanism 22b at 1 / 4 and 3 / 4 of the first main beam 11 between any two adjacent joints, and set a clamping mechanism 22a at 1 / 2.

[0186] S22: Along the upper end to the lower end of the first main beam 11, four transverse ribs are sequentially assembled on the base plate, and a side pressure mechanism 22b is set at 1 / 3 and 2 / 3 of each transverse rib.

[0187] S23: Assemble the second main beam 12 on the base plate, and set two face-to-face side pressure mechanisms 22b at 2 / 5 of the distance between any two adjacent joints on the second main beam 12.

[0188] Repeat S22, and assemble the four transverse reinforcement bars between the second main beam 12 and the third main beam 13 in sequence;

[0189] S24: Assemble the third main beam 13 on the base plate, and set a side pressing mechanism 22b at 1 / 4 and 3 / 4 of the third main beam 13 between any two adjacent joints, and set a clamping mechanism 22a at 1 / 2; set a pushing mechanism 22c on the outside of the third main beam 13 and directly opposite each joint.

[0190] Step S3: Use 3M tape to bond a sealing cover to the main beam and / or cross rib near the back of each butt joint to form a sealing cover in situ. Make holes in the lower part of the sealing cover and introduce argon gas, and make holes in the upper part to form an argon gas outlet to protect the back of the weld.

[0191] Step S4: Under the protection of the front and back sides of the weld seam by argon gas, perform tack welding on all butt joints;

[0192] Before welding, a laser scanner is used to measure the chord plane of the wing frame; the collected data is then input into Geomagic Control X software to generate a three-dimensional model of the chord plane of the wing frame before welding.

[0193] Furthermore, using a laser welding device (device name: large-size three-dimensional multi-layer curved surface high-power high-precision laser welding equipment; manufacturer: Aerospace Sanjiang Laser), the welding trajectory is first determined, ensuring that the laser spot is located in the middle of the weld. The middle part of each butt joint is selected for tack welding, with a tack welding length of 10mm. The tack welding process parameters include: laser power of 800W, defocusing amount of -2mm, and welding speed of 1.5m / min.

[0194] Step S5: Under the protection of the front and back sides of the weld seam by argon gas, perform formal welding on all butt joints.

[0195] According to the welding sequence, that is, from top to bottom and from left to right (for example, for...). Figure 1 The eight butt joints shown are welded in sequence from ① to ⑧. First, the front welds of the 16 butt joints are welded in sequence. Then, the tooling fixture is flipped using rotating mechanisms 23a and 23b, and the back welds of the 16 butt joints are welded in sequence. Finally, the tooling fixture is adjusted using rotating mechanisms 23a and 23b, and the side welds of the 16 butt joints are welded in sequence.

[0196] The parameters for the formal welding include: laser power of 1900W, defocusing amount of -5mm, and welding speed of 1.5m / min.

[0197] After welding, a laser scanner is used to measure the chord plane of the welded wing frame. By comparing the 3D models of the chord plane of the wing frame before and after welding, the location and amount of deformation points are obtained. Cold straightening is performed by hot straightening and tapping with tools such as rubber mallets to correct the remaining minor deformations.

[0198] Step S6: Assemble the wing frame and skin to be welded onto the tooling fixture for the wing frame and skin.

[0199] The tooling fixture 400 for the wing frame 100 and skin 300 includes a base plate, a skin clamping mechanism, a frame side pressing mechanism, and two fixture rotation mechanisms 43a and 43b coaxially and symmetrically distributed on both sides of the base plate. The skin 300 includes an upper skin and a lower skin.

[0200] Each skin clamping mechanism 41 includes a long strip clamping plate with a groove on it that is just the size of the contact surface between the corresponding main beam or crossbeam and the skin.

[0201] Each frame side pressing mechanism 42 includes a rectangular pressing plate with two inner holes on the part of the pressing plate that does not contact the wing frame, so that screws can pass through and be screwed into the base plate.

[0202] Specifically, the assembly steps described above include:

[0203] S61: Ventilation holes 18 are made on the second main beam 12 and the first transverse rib 14, second transverse rib 15, third transverse rib 16 and fourth transverse rib 17 inside the wing frame so that the six grid structures can be connected.

[0204] S62: Assemble the wing frame obtained in step S5 onto the base plate, and set a frame side pressing mechanism 42 at 1 / 4 and 3 / 4 of the first main beam 11 and the third main beam 13 of the wing frame respectively between any two adjacent mating joints.

[0205] S63: The upper and lower skins are covered on the front and back of the wing frame. Six skin clamping mechanisms 41 are provided on the outer side of the contact parts between the second main beam 12, the second crossbeam and the third crossbeam inside the wing frame and the upper and lower skins. Figure 5 Only the three skin clamping mechanisms 41 on the front are shown.

[0206] Step S7: With the help of the wing frame with ventilation holes 18 and the upper and lower skin forming a closed and connected gas path environment, argon gas enters from the fourth crossbeam at the bottom of the wing frame and exits from the first crossbeam at the top of the wing frame, thus protecting the weld seam from the back.

[0207] Step S8: Under the protection of the front and back sides of the weld seam by argon gas, perform penetration welding on the interior of the wing frame and the skin.

[0208] Before welding, a laser scanner is used to measure the chord plane of the assembled wing skeleton and skin; the collected data is then input into Geomagic Control X software to generate a 3D chord plane model of the wing skeleton and skin assembly before welding.

[0209] like Figure 4 Following the sequence ①-⑤, perform through-welding on the contact parts of the third crossbeam, the second crossbeam, and the second main beam 12 with the upper skin; use the fixture rotation mechanisms 43a and 43b to flip the tooling fixture and perform through-welding on the contact parts of the third crossbeam, the second crossbeam, and the second main beam 12 with the lower skin in the sequence ①-⑤.

[0210] The process parameters for penetration welding include: laser power of 2100W, defocusing amount of -5mm, and welding speed of 0.025m / min.

[0211] Step S9: Under the protection of the front and back sides of the weld seam by argon gas, perform bottom-lock welding on the perimeter of the wing frame and the skin; bottom-lock welding includes tack welding and final welding.

[0212] The process parameters for tack welding are as follows: laser power is 800W, defocusing amount is -2mm, welding speed is 1.5m / min, tack welding length is 10mm, and weld spacing is 30mm.

[0213] The formal welding process parameters are as follows: laser power is 1000W, defocusing amount is -5mm, and welding speed is 1.5m / min.

[0214] In S4, S5, S8, and S9, the gas flow rate of the front protection shroud is 25 L / min; the flow rate of the back protection is 5 L / min. The front protection adopts the existing shroud + nozzle method, with argon gas being ejected from the shroud.

[0215] For formal welding in S5 and S9, and for penetration welding in S8, the arc initiation and extinguishing distance is 5mm.

[0216] In S5 and S9, after the formal welding is completed, the argon gas supply for back-side protection is stopped after 18 minutes of cooling. A laser scanner is used to measure the chord plane of the welded wing frame and skin assembly. The collected data is input into Geomagic Control X software to generate a 3D chord plane model of the welded assembly. The 3D chord plane models of the assembly before and after welding are compared to obtain the location and amount of deformation points. Cold straightening is performed using hot straightening and tapping with tools such as rubber mallets to correct any remaining minor deformations.

[0217] Implementation results:

[0218] 1. Chord plane measurement results show that the welding deformation of the welded wing skeleton, wing skeleton and skin assembly can be controlled below ±0.5%. Figure 6 As shown, the method provided by this invention can significantly reduce welding deformation, thereby reducing residual stress and cracking, and improving welding quality. Moreover, since the welding deformation is very small, little or no correction is needed to meet the standard requirements, thus achieving cost reduction and efficiency improvement.

[0219] 2. Visual inspection or inspection using a magnifying glass of 10x or less was performed on the weld seams. The results showed that the weld surfaces of the resulting wing frame and skin assembly were free of defects such as oxidation, inclusions, porosity, cracks, lack of fusion, undercut, and depressions. Figure 7 As shown;

[0220] 3. X-ray non-destructive testing showed that the weld quality of the welded wing frame, wing frame and skin assembly fully met the Class I weld requirements of QJ20465-2016 (Technical Requirements for Laser Welding of Titanium and Titanium Alloys). Figure 8 As shown;

[0221] 4. Room temperature tensile specimens were prepared from the weld seams, and the room temperature tensile mechanical properties of the joint were tested. The results showed that the room temperature tensile strength of the weld seams in the welded wing frame, wing frame and skin assembly could reach more than 95% of that of the base material; for example, Figure 1 The tensile strength of the four joints ①-④ is 900 MPa to 912 MPa, and the tensile strength of the base material is approximately 930 MPa.

[0222] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for improving the welding quality of wing frame and skin, characterized in that, Includes the following steps: S1. The wing skeleton parts are manufactured using 3D printing, including M longitudinal members distributed in parallel along a first direction and N transverse members distributed in parallel along a second direction. Each transverse member contains M-1 transverse ribs; M≥3, N≥3, and the first direction and the second direction are different. Among them, the M longitudinal members include 2×N×(M-1) connecting ends along the second direction, which can be connected one by one with the two ends of the N×(M-1) transverse ribs to form 2×N×(M-1) butt joints, forming a grid structure with high welding strength; the inner sides of the two longitudinal members and two transverse members located on the outermost side of the wing frame include stepped grooves, the height of which is the same as the skin thickness. S2. Assemble the parts of the wing frame to be welded onto the wing frame tooling fixture. Use the clamping mechanism, side-pressing mechanism, and pushing mechanism on the tooling fixture to ensure precise alignment of the mating joints. This includes the following steps: S21: Position the first longitudinal member with the tooling fixture, set two side pressing mechanisms between any two adjacent butt joints of the first longitudinal member, and set a clamping mechanism between the two side pressing mechanisms; S22: Along one end of the first longitudinal member to the other end, N transverse ribs are sequentially assembled on the tooling fixture, and two side pressing mechanisms are set on each transverse rib. S23: Assemble the second longitudinal member on the tooling fixture, and set a side pressure mechanism between any two adjacent butt joints of the second longitudinal member; Alternately repeat S22 and S23 to assemble the remaining M-3 longitudinal members and N×(M-2) transverse ribs; S24: Assemble the Mth longitudinal member on the tooling fixture, set two side pressing mechanisms between any two adjacent butt joints of the Mth longitudinal member, set a clamping mechanism between the two side pressing mechanisms, and set a pushing mechanism on the outside of the Mth longitudinal member and directly opposite each butt joint. S3. On the back of each butt joint, a sealing cover is built in situ using flexible sealing material, and an inert gas inlet and outlet are opened on the sealing cover to protect the weld from the back. S4. Under the protection of the front and back sides of the weld seam by inert gas, perform tack welding on all butt joints. S5. Under the protection of the front and back sides of the weld seam by inert gas, perform formal welding on all butt joints.

2. The method for improving the welding quality of wing frame and skin according to claim 1, characterized in that, In S1, the wall thickness of the longitudinal member and the transverse rib is 2mm~10mm.

3. The method for improving the welding quality of wing frame and skin according to claim 2, characterized in that, The preferred process parameters for obtaining high-quality welds in S4 and S5 include: The positioning weld: laser power is 750W~850W, defocusing amount is -1.5mm~-2.5mm, welding speed is 1.0m / min~2.0m / min; and / or, The formal welding process involves a laser power of 1850W~1950W, a defocusing amount of -4.5mm~-5.5mm, and a welding speed of 1.0m / min~2.0m / min.

4. The method for improving the welding quality of wing frame and skin according to claim 1, characterized in that, It also includes the following steps: S6. Assemble the wing frame and skin to be welded onto the tooling fixture for the wing frame and skin. Through the frame side pressing mechanism and skin clamping mechanism on the tooling fixture, ensure that the skin overlaps on the stepped groove to form a flush butt joint, thereby improving welding strength. Furthermore, each weld seam inside the wing frame is clamped on both sides by the skin clamping mechanism. Specifically, this includes the following steps: S61: Ventilation holes are made in the longitudinal and transverse members inside the wing frame so that each of the grid structures is connected. S62: Assemble the wing frame onto the tooling fixture, and set two frame side pressing mechanisms between the first longitudinal member and the Mth longitudinal member located between any two adjacent mating joints; S63: The upper and lower skins are overlapped on the stepped groove. Two × (M+N-4) skin clamping mechanisms are provided on the outside of the upper and lower skins and along the contact portions of M-2 longitudinal members and N-2 transverse members in the wing frame with the upper and lower skins. Each skin clamping mechanism has a groove that is just the size of the contact surface between the corresponding longitudinal member or transverse member and the skin. S7. By utilizing the wing frame with ventilation holes and the upper and lower skin to form a closed and connected air passage environment, inert gas enters from one end of the wing frame and exits from the other end of the wing frame, providing back protection for the weld seam. S8. Under the protection of the front and back sides of the weld seam by inert gas, perform penetration welding on the inside of the wing frame and the skin. S9. Under the protection of the front and back sides of the weld seam by inert gas, perform bottom-lock welding on the perimeter of the wing frame and the skin.

5. The method for improving the welding quality of wing frame and skin according to claim 4, characterized in that, The wing frame and skin have a wall thickness of 2mm to 10mm.

6. The method for improving the welding quality of wing frame and skin according to claim 5, characterized in that, The preferred process parameters for the penetration welding in S8 that can obtain high-quality welds include: laser power of 2000W~2200W, defocusing amount of -4mm~-6mm, and welding speed of 0.02m / min~0.03m / min.

7. The method for improving the welding quality of wing frame and skin according to claim 5, characterized in that, It also includes, in S9, the bottom-lock welding includes tack welding and final welding; the preferred process parameters in S9 for obtaining high-quality welds include: The tack welding: laser power is 750W~850W, defocusing amount is -1.5mm~-2.5mm, welding speed is 1.0m / min~2.0m / min; tack weld length is 5mm~15mm, weld spacing is 25mm~35mm; and / or, The formal welding process involves a laser power of 950W~1050W, a defocusing amount of -4mm~-6mm, and a welding speed of 1.0m / min~2.0m / min.

8. The method for improving the welding quality of wing frame and skin according to claim 1 or 4, characterized in that, The flow rate of the front protective gas is 20L / min to 40L / min, and the flow rate of the back protective gas is 4L / min to 6L / min.

9. The method for improving the welding quality of wing frame and skin according to claim 1 or 7, characterized in that, It also includes stopping the inert gas protection after cooling for 15 to 20 minutes after the formal welding is completed.

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