A method of welding a wing frame and skin

Abstract

The application relates to a wing skeleton and skin welding method, and belongs to the technical field of welding, which solves the problems that the existing laser welding method is difficult to control welding deformation and difficult to guarantee welding quality when applied to wing manufacturing. A wing skeleton and skin welding method comprises the following steps: S1, designing a tool clamp for welding a wing skeleton; S2, adopting a 3D printing method to manufacture all longitudinal members and cross ribs of the wing skeleton; S3, assembling all longitudinal members and cross ribs on the tool clamp; and S4, performing front protection and back protection on the welding seam, and performing welding under the protection of inert gas to obtain the wing skeleton. Through optimization of joint form, tool clamp, assembly process, welding sequence, gas protection measures and process parameters, the welding deformation can be controlled below 0.5%, the defects easily occurring in the process of laser welding of the wing are reduced, and the welding joint can simultaneously meet the requirements of light weight, high strength and high welding efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of welding, in particular to a welding method for a wing framework and a skin. BACKGROUND

[0002] Laser welding has the advantages of high energy density, small heat-affected zone, flexible spatial position conversion, and fast welding speed, and shows great potential and advantages in the manufacturing of thin-walled wings in the aerospace field.

[0003] However, the application of laser welding in wing manufacturing faces a series of challenges, especially in controlling welding deformation and ensuring welding quality; the following are the main difficulties and reasons for laser welding wings: (1) difficult to control welding deformation: a. The high energy input in the laser welding process can cause the temperature in the welding area and its vicinity to rise rapidly, resulting in thermal expansion and uneven thermal stress, causing deformation; b. The components of the wing are usually made of light metal materials such as titanium alloy and are all thin-walled parts, due to the high thermal expansion coefficient of light metal materials and the small rigidity of thin-walled parts, which can cause the welding deformation to be intensified; c. The structure of the wing is relatively complex, and there are more welding joint positions, which are more likely to cause the accumulation of welding stress and lead to structural deformation; (2) difficult to guarantee welding quality: a. In the multi-joint welding of the wing, it is a challenge to achieve a simple and easy-to-operate method that effectively protects each weld from back gas protection, and poor back gas protection can cause defects such as oxidation and inclusion of the weld; b. Due to the structure and material characteristics of the wing, it is highly sensitive to welding parameters, and small changes in parameters can lead to welding defects such as pores, cracks, incomplete fusion, undercut, and depression; c. In the multi-joint welding of the wing, it is difficult to simultaneously meet the requirements of lightweight, high strength, and high welding efficiency due to unreasonable joint design or limitations of manufacturing and assembly processes.

[0004] Based on the above analysis, it is urgent to provide a welding method for a wing framework and a skin to effectively control and reduce welding deformation and significantly improve welding quality, which is of great significance to improve the overall performance and reliability of the aircraft. SUMMARY

[0005] In view of the above analysis, the present application aims to provide a welding method for a wing framework and a skin to solve the problems of difficult to control welding deformation and difficult to guarantee welding quality in the existing laser welding method applied to wing manufacturing.

[0006] The purpose of the present application is achieved by the following technical solutions:

[0007] The present application provides a welding method for a wing framework and a skin, comprising the following steps:

[0008] S1, designing a tooling fixture for welding the wing framework;

[0009] The wing framework is a thin-walled grid structure mainly formed by M longitudinal members parallel along a first direction and N transverse members parallel along a second direction through M*N nodes, each transverse member containing M-1 transverse ribs; M≥3, N≥3; the first direction is different from the second direction.

[0010] The tooling fixture of the wing framework comprises a base plate, a positioning mechanism and a clamping mechanism arranged on the base plate.

[0011] S2, all longitudinal members and transverse ribs of the wing framework are manufactured by a 3D printing method; wherein, when a model of 3D printing is established, the M longitudinal members are designed to include 2×N×(M-1) connecting end heads along the second direction to accurately butt joint with two end faces of each transverse rib to form 2×N×(M-1) butt joints; the inner side edges of the longitudinal members and the transverse members located at the outermost side of the wing framework are designed to include stepped grooves with the same thickness as the skin; and air holes are reserved on the longitudinal members and the transverse ribs located inside the wing framework to make each grid structure communicate.

[0012] S3, all longitudinal members and transverse ribs are assembled on the tooling fixture, and the positioning mechanism and the clamping mechanism are reasonably designed to control welding deformation and meet the assembly tolerance requirements.

[0013] S4, front protection and back protection are performed on the welds, and the 2×N×(M-1) butt joints of the wing framework are sequentially welded from one end to the other end along the first direction and from one side to the other side along the second direction under the protection of inert gas to obtain the wing framework.

[0014] Further, S3 specifically comprises the following steps,

[0015] S31, the first longitudinal member is matched with the positioning mechanism and positioned, and the clamping mechanism is arranged on the 1 / 5-4 / 5 section of the first longitudinal member between any two adjacent butt joints.

[0016] S32, the N transverse ribs are sequentially assembled on the base plate from one end to the other end of the first longitudinal member, and the clamping mechanism is arranged on the 1 / 3-2 / 3 section of each transverse rib.

[0017] S33, the second longitudinal member is assembled on the base plate, and the clamping mechanism is arranged on the 1 / 5-4 / 5 section of the second longitudinal member between any two adjacent butt joints.

[0018] S32 and S33 are alternately repeated to assemble the third longitudinal member to the M-1 longitudinal member and the remaining transverse ribs.

[0019] S34: Assembling the Mth longitudinal member on the base plate; setting the clamping mechanism at 1 / 5-4 / 5 section between any two adjacent butt joints of the Mth longitudinal member, and setting the clamping mechanism on the outside of the Mth longitudinal member and opposite to each butt joint.

[0020] Further, in S1, the included angle between the first direction and the second direction is 85-95°.

[0021] Further, in S1, the cross-sectional shape of the longitudinal member and the cross rib is one of I-shaped, Π-shaped or a combination thereof; and / or, the wall thickness of the longitudinal member and the cross rib is 2-10 mm.

[0022] Further, the method further comprises the following steps:

[0023] S5: Assembling the wing skeleton and the skin to be welded obtained in S4 on the tooling fixture for welding the wing skeleton and the skin; controlling the welding deformation and meeting the assembly tolerance requirement through the rationally designed skeleton side pressing mechanism and skin pressing mechanism on the tooling fixture; specifically comprising the following steps:

[0024] S51: Assembling the wing skeleton on the tooling fixture, and setting two skeleton side pressing mechanisms between any two adjacent butt joints of the first longitudinal member and the Mth longitudinal member;

[0025] S52: Lapping the upper skin and the lower skin on the step groove in S2, and ensuring the skin to be fixed and pressed on the tooling fixture and the skin four around to form the surface flush butt joint with the wing skeleton through setting 2×(M+N-4) skin pressing mechanisms on the outside of the upper skin and the lower skin and along the M-2 longitudinal members and N-2 cross members in the wing skeleton and the contact part of the upper skin and the lower skin; a groove with a size capable of accommodating the contact surface of the corresponding longitudinal member or cross member and the skin is formed on each skin pressing mechanism;

[0026] S6: Carrying out the front protection and the back protection on the weld seam, and carrying out the welding under the protection of the inert gas to obtain the combination of the wing skeleton and the upper and lower skins; specifically comprising the following steps:

[0027] S61: Welding the contact part of the second cross member, the third cross member, the N-1 cross member and the skin in sequence from one end to the other end along the first direction; for each cross member, welding in the same direction from one side to the other side along the second direction;

[0028] S62: Welding the contact part of the second longitudinal member, the M-1 longitudinal member, the third longitudinal member, the M-2 longitudinal member, …, the 1 / 2*M longitudinal member or the 1 / 2*(M+1) longitudinal member and the skin in sequence from both sides to the middle along the second direction; for each longitudinal member, welding symmetrically from both ends to the middle along the first direction;

[0029] S63: bottom welding of the contact part of the two longitudinal members and the two transverse members outside the wing skeleton with the skin.

[0030] Further, in S4, the main steps of back protection include: in the back of each butt joint, a sealing cover is built in situ with flexible sealing material, and holes are opened on the sealing cover to form the inlet and outlet of inert gas; and / or,

[0031] In S6, the main steps of back protection include: the wing skeleton with the upper and lower skins form a closed and connected gas path environment by using the vent hole reserved in step S2, and the inert gas enters from one end of the wing skeleton and is discharged from the other end.

[0032] Further, in S3 and S5, the assembly tolerance requirements include: the butt joint gap and step difference at each point of each joint is not more than 0.1mm, and the butt joint gap and step difference within a local arbitrary 100mm cumulative length is not more than 0.2mm.

[0033] Further, in steps S4 and S6, chord plane measurement is performed before and after welding, respectively, and the shape is corrected by comparing the chord plane measurement results.

[0034] Further, in steps S3 and S5, the assembly includes trial assembly, repair of trial assembly; pickling, removing the oxide skin; formal assembly.

[0035] Further, it also includes: before trial assembly, the welding area is pretreated until the metal luster is exposed, and the surface roughness Ra of the welding surface is ≤3.2μm.

[0036] Compared with the prior art, the present application can at least achieve one of the following beneficial effects:

[0037] The present application provides a welding method for wing skeleton and skin, which is optimized from multiple aspects (such as: tooling fixture and assembly process, welding sequence, chord plane measurement and shape correction), effectively controls and significantly reduces the deformation problem of wing skeleton and skin during laser welding process, and the welding deformation can be controlled below ±0.5%; specifically,

[0038] (1) The present application optimizes the fixture and assembly process, including positioning scheme, clamping scheme (clamping mechanism type, clamping point position and number, assembly sequence), effectively controls the movement and misplacement during welding, and significantly reduces the welding deformation;a. Positioning scheme: when assembling the parts of the wing skeleton, first cooperate with the first longitudinal member through the positioning mechanism on the fixture clamp to determine the position of the first longitudinal member relative to the base plate along the first direction and use it as the reference position when installing other members to ensure the relative position of each member during assembly;b. Clamping scheme: by selecting appropriate clamping mechanism type (including pressing mechanism, side pressing mechanism, pushing mechanism, skeleton side pressing mechanism, skin pressing mechanism), and setting appropriate number of clamping mechanisms at appropriate positions, using appropriate assembly sequence to rigidly fix each part, ensuring uniform distribution of clamping force, avoiding unnecessary constraints in the welding area, and at the same time providing suitable support points for the parts to be welded by the base plate, effectively controlling the movement and misplacement during welding, and significantly reducing the welding deformation.

[0039] (2) The present application optimizes the welding sequence to reduce welding stress and welding deformation; for example, when welding the parts of the wing skeleton, the preferred welding sequence (i.e., welding in sequence from one end to the other end along the first direction, and from one side to the other side along the second direction) is adopted to perform tack welding first, and then formal welding; when welding the wing skeleton and the skin, the preferred welding sequence (including welding two longitudinal members from both sides to the middle along the second direction, and symmetrically welding each longitudinal member from both ends to the middle along the first direction) is adopted to perform penetration welding first, and then the preferred welding sequence (including welding the outermost longitudinal member first, and then welding the outermost transverse member) is adopted to perform four-around lock bottom welding; the above welding sequence can make the weld shrink freely, reduce the accumulation of welding stress, and minimize the welding deformation caused by the residual stress generated during laser welding.

[0040] (3) The present application further eliminates the slight deformation caused by welding through chord plane measurement and shape correction, and ensures the geometric dimension accuracy of the wing skeleton and the skin after welding; specifically, the chord plane measurement is performed on the wing skeleton, the combination of the wing skeleton and the upper and lower skins before and after welding respectively, the deformation point position and deformation amount are obtained by comparison, and the wing skeleton and the combination of the wing skeleton and the upper and lower skins are corrected.

[0041] The present application provides a welding method for wing skeleton and skin, which optimizes from multiple aspects (such as joint form, fixture and assembly process, gas protection measures, process parameters), effectively reduces the defects (including oxidation, inclusion, porosity, crack, incomplete fusion, undercut, indentation) prone to occur during laser welding of wing, and the welded joint can meet the requirements of lightweight, high strength and high welding efficiency at the same time, thereby improving the welding quality; specifically including:

[0042] (1) The present application can simultaneously meet the requirements of high strength, light weight and high welding efficiency for the welded joint by optimizing the joint form, tooling fixture and assembly process, and effectively reduces the crack defects.

[0043] a. Joint form: the to-be-welded parts of the wing skeleton are processed by 3D printing, and the parts of the wing skeleton are precisely aligned to form the form of the butt joint by cooperating with the machining finishing, that is, the longitudinal member includes a connecting end head in the second direction, which can be butt-jointed with two end faces of the cross rib to form a butt joint, the inner side edges of the longitudinal member and the transverse member located at the outermost side of the wing skeleton include a stepped groove, and the skin is lapped on the stepped groove to form a butt joint with flush surface. Compared with the T-shaped joint between the parts of the wing skeleton and the lap joint between the four sides of the wing skeleton and the skin, the present application precisely processes and aligns to form the butt joint by 3D printing, machining finishing and tooling fixture, effectively improves the welding strength of the wing skeleton and the skin, and simultaneously has smaller welding seam width and facilitates welding operation, so that the welded joint can have the advantages of high strength, light weight, high welding efficiency and the like.

[0044] b. Tooling fixture and assembly process: the welding stress and deformation are effectively reduced by the carefully designed tooling fixture and the reasonably arranged assembly process, the crack defects caused by residual stress are avoided, and the size precision of the wing skeleton and the skin obtained by welding is ensured.

[0045] (2) The present application effectively reduces the defects of oxidation, inclusion and porosity by optimizing the gas protection measures.

[0046] Specifically, inert gas is used for front protection and back protection at each welding seam, for example, when welding the parts of the wing skeleton, a sealing cover is built in situ on the back of each butt joint by using flexible sealing material; when welding the wing skeleton and the skin, the wing skeleton with air holes and the upper and lower skins form a closed and connected gas path environment; the above simple and reliable gas protection measures can effectively prevent air from contacting the molten pool, and can effectively reduce the problems of oxidation, inclusion and porosity of the light metal material wing during welding, thereby improving the internal quality of the welding seam.

[0047] (3) The present application effectively reduces the problems of oxidation, inclusion, porosity, crack, incomplete fusion, undercut and depression by optimizing the process parameters of welding, that is, selecting appropriate process parameters according to the structure characteristics of the to-be-welded wing skeleton and skin, including laser power, defocusing amount, welding speed, arc striking and extinguishing distance, and protective gas flow, thereby significantly improving the welding quality of the thin-walled wing parts.

[0048] The technical solutions in the present application can be combined with each other to realize more preferred combination solutions. Other features and advantages of the present application will be described in the following description, and some advantages will become apparent from the description, or will be understood by those skilled in the art through implementation of the present application. The objects and other advantages of the present application can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0049] The accompanying drawings are included to provide a further understanding of the present application, and are incorporated herein and constitute a part of the detailed description. The drawings illustrate embodiments of the present application and, together with the description, serve to explain the principles of the present application. In the drawings:

[0050] Figure 1 Schematic view of a wing frame (part) provided by an embodiment of the present application;

[0051] Figure 2 Schematic view of a wing frame on a tooling fixture (part) provided by an embodiment of the present application;

[0052] Figure 3 In (a), a schematic view of a wing frame provided by an embodiment of the present application is shown; Figure 2 In (a), a schematic view of a wing frame provided by an embodiment of the present application is shown; Figure 2 In (a), a schematic view of a wing frame provided by an embodiment of the present application is shown; Figure 2 In (a), a schematic view of a wing frame provided by an embodiment of the present application is shown; Figure 2 In (a), a schematic view of a wing frame provided by an embodiment of the present application is shown; Figure 2 In (a), a schematic view of a wing frame provided by an embodiment of the present application is shown;

[0053] Figure 4 Schematic view of a wing frame and a skin (part) provided by an embodiment of the present application;

[0054] Figure 5 Schematic view of a wing frame and a skin on a tooling fixture (part) provided by an embodiment of the present application;

[0055] Figure 6 Schematic view of a wing frame and a skin on a tooling fixture (part) provided by an embodiment of the present application;

[0056] Figure 7 Photo of a weld seam of a wing frame and a skin provided by an embodiment of the present application (part);

[0057] Figure 8 Photo of a weld seam of a wing frame and a skin provided by an embodiment of the present application (part);

[0058] REFERENCE NUMERALS:

[0059] 100 - wing frame; 11 - first main beam; 12 - second main beam; 13 - third main beam; 14 - first cross rib; 15 - second cross rib; 16 - third cross rib; 17 - fourth cross rib; 18 - vent hole; 200 - tooling fixture of wing frame; 21 - positioning pin; 22a - pressing mechanism; 22b - side pressing mechanism; 22c - pushing mechanism; 23a - first rotating mechanism; 23b - second rotating mechanism; 24 - connecting end; 25 - butt joint; 26 - stepped groove; 300 - skin; 400 - tooling fixture of wing frame and skin; 41 - skin pressing mechanism; 42 - frame side pressing mechanism; 43a - first fixture rotating mechanism; 43b - second fixture rotating mechanism. DETAILED DESCRIPTION

[0060] The preferred embodiments of the present application will be described in detail below with reference to the drawings, which form a part of this application. The drawings illustrate embodiments of the application and, together with the description, serve to explain the principles of the application. It should be noted that the drawings are not to scale. In the drawings, like reference numerals refer to like elements throughout.

[0061] The present application provides a welding method of wing frame and skin, comprising the following steps:

[0062] Step S1, designing a tooling fixture for welding the wing frame;

[0063] The wing frame is a thin-walled grid structure mainly formed by M longitudinal members parallel along a first direction and N transverse members parallel along a second direction through MxN nodes, each transverse member containing M-1 cross ribs; M≥3, N≥3; the first direction is different from the second direction.

[0064] The tooling fixture of the wing frame comprises a base plate, a positioning mechanism and a clamping mechanism arranged on the base plate.

[0065] Preferably, the angle between the first direction and the second direction is 85°-95°; illustratively, the angle between the first direction and the second direction is a right angle.

[0066] Preferably, the longitudinal members and the cross ribs are rod-shaped members; more preferably, the longitudinal members and the cross ribs are hollow rod-shaped members.

[0067] Optionally, the cross-sectional shape of the longitudinal members and the cross ribs can be one or a combination of I-shaped, Π-shaped, but not limited to.

[0068] Preferably, the wall thickness of the longitudinal members and the cross ribs is 2mm-10mm; more preferably, the wall thickness of the longitudinal members and the cross ribs is 2mm-3mm.

[0069] Preferably, the material of the longitudinal members and the cross ribs is one or a combination of titanium alloy, aluminum alloy, steel.

[0070] It can be understood that the shape of the substrate depends on the shape of the wing skeleton, and can be designed as required, as long as it can support and support the to-be-welded parts of the wing skeleton. Exemplarily, referring to Figure 2 , the shape of the substrate is a mesh-shaped thin plate, and each mesh inside includes a hollow structure.

[0071] It should be noted that the positioning mechanism on the substrate includes W positioning pins, W≥2; the W lugs contained in the first longitudinal member are matched with the W positioning pins to limit the position of the first longitudinal member relative to the substrate in the first direction, which will serve as the reference position when other members are installed, thereby ensuring the relative position of each member during assembly.

[0072] Preferably, the positioning mechanism is arranged outside the to-be-welded area to avoid the weld position and ensure the accessibility of the welding tool; in one possible design, referring to Figure 2 , the outer side of the first longitudinal member (i.e., the first main beam 11) includes two lugs arranged at intervals in the first direction, and each lug is matched with the positioning pin 21 on the substrate, i.e., the positioning pin 21 passes through the inner hole on the lug to accurately position the first longitudinal member on the substrate at the position where the positioning pin is located.

[0073] It should be noted that the clamping mechanism on the substrate includes one or a combination of three types of pressing mechanisms, side pressing mechanisms, and pushing mechanisms, and the number and position of each type of clamping mechanism can be designed as required.

[0074] Preferably, the clamping mechanism includes a combination of three types of pressing mechanisms, side pressing mechanisms, and pushing mechanisms.

[0075] Preferably, each pressing mechanism includes a pressing strip, and the two ends of the pressing strip can be located on both sides of the same longitudinal member or cross rib and fix and press the longitudinal member or cross rib in the overall width direction on the substrate to control the relative position of the to-be-welded parts in the wing skeleton and the thermal deformation during welding.

[0076] As an optional embodiment, the two ends of the pressing strip are fixed on the substrate by threaded connection; exemplarily, referring to Figure 2 and Figure 3 (a), the pressing mechanism 22a includes a pressing strip, and the two ends of the pressing strip have inner holes for the screws or bolts to pass through and screw into the substrate.

[0077] Preferably, each side pressing mechanism includes a pressing sheet, and one end of the pressing sheet can be located on the surface of the longitudinal member or cross rib, and the other end is fixed on the substrate, for fixing and pressing the longitudinal member or cross rib in part or all of the width direction on the substrate to control the relative position of the to-be-welded parts in the wing skeleton and the thermal deformation during welding.

[0078] As an alternative, the pressing piece is fixed to the base plate by screwing; see, for example, Figure 2 and Figure 3 (b), the part of the pressing piece of the side pressing mechanism 22b that does not contact the longitudinal member or the cross rib is provided with an inner hole for the screw or bolt to pass through and screw into the base plate.

[0079] It can be understood that the number of inner holes on the pressing piece can be designed as needed; for example, the pressing piece includes two inner holes to achieve effective fixation while ensuring uniform distribution of clamping force and avoiding deformation caused by local over-tightening.

[0080] In a possible design, the pressing piece is also provided with a blind groove for accommodating a protrusion on the longitudinal member or the cross rib to adapt to the non-planar shape of the to-be-welded part in the wing skeleton and facilitate installation operation; the shape of the blind groove is determined by the shape of the protrusion on the longitudinal member or the cross rib.

[0081] Preferably, each pushing mechanism includes a pushing block and a mounting seat, the pushing block includes a top rod and an end pressing portion connected to each other, the mounting seat is fixed to the base plate, the top rod is fixed in the mounting seat by rotary connection, and the end pressing portion is driven to abut against the side wall of the longitudinal member or the cross rib by rotating the top rod; to control the relative position of the to-be-welded part in the wing skeleton and the thermal deformation during welding.

[0082] Preferably, the top rod and the mounting seat are connected by rotary connection through threads; see, for example, Figure 2 and Figure 3 (c), the pushing mechanism 22c is connected to the mounting seat through threads provided on the outer surface of the top rod and the threads in the inner hole of the mounting seat.

[0083] Preferably, the tooling fixture for welding the wing skeleton further includes rotary mechanisms coaxially arranged on both sides of the base plate; the two rotary mechanisms are connected to the welding workbench, the tooling fixture is adjusted through the rotary mechanisms, the different angles of the wing skeleton are conveniently welded, and the accessibility of the welding gun is improved.

[0084] Preferably, the two rotary mechanisms Figure 2 (the first rotary mechanism 23a and the second rotary mechanism 23b) are coaxially arranged on both sides of the base plate with the rotary axes perpendicular to the first direction; more preferably, the two rotary mechanisms are coaxially arranged at the middle positions on both sides of the base plate with the rotary axes perpendicular to the first direction.

[0085] Step S2, manufacturing all longitudinal members and cross ribs of the wing skeleton by 3D printing method; wherein, when establishing the model of 3D printing, the M longitudinal members are designed to include 2×N×(M-1) connecting end heads along the second direction to accurately butt joint with two end faces of each cross rib to form 2×N×(M-1) butt joints; the inner side edges of the longitudinal members and cross ribs located at the outermost side of the wing skeleton are designed to include stepped grooves with the same thickness as the skin; and air holes are reserved on the longitudinal members and cross ribs located inside the wing skeleton to make each grid structure communicate;

[0086] Preferably, the above-mentioned 3D printing method further comprises: after 3D printing, performing machining finishing on all longitudinal members and cross ribs (mainly the welding surface) to further improve the accuracy when the butt joints of the longitudinal members and cross ribs, the longitudinal members and cross ribs located at the outermost side of the wing skeleton and the skin around the four sides are aligned. The machining finishing mode can be selected as needed, including but not limited to one or a combination of milling, grinding, scraping, grinding, superfinishing and polishing.

[0087] Exemplarily, referring to Figure 3 (d), the third main beam 13 includes a connecting end head 24 along the second direction to accurately butt joint with the left end face of the fourth cross rib 17 to form a butt joint 25.

[0088] It is worth noting that, compared with the T-shaped joint between the longitudinal members and the cross ribs, the longitudinal members obtained by 3D printing and cooperating with machining finishing are connected with the two ends of the cross rib one by one to form a butt joint through the connecting end head, which at least achieves the following beneficial effects: (1) due to the symmetry of the butt joint formed by the two ends of the cross rib, 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 pores and incomplete fusion; (3) the welding strength of the butt joint is higher, and the weld width is smaller, without the need for additional filler material or special edge design, which may be more economical in material use, and is conducive to realizing the requirement of the wing to balance light weight and high strength.

[0089] Exemplarily, referring to Figure 3 (e), the inner side edges of the cross rib located at the uppermost end of the wing skeleton and the longitudinal member located at the rightmost side include a stepped groove 26 with the same height as the skin thickness, so that the upper and lower skins are lapped on the stepped groove 26 to form a butt joint with flush surface.

[0090] It is worth noting that, compared with the lap joint formed by directly placing the upper and lower skins on the surface of the wing skeleton, the present application forms a flush butt joint by designing a step groove on the outermost side of the wing skeleton for the skin to lap on the step groove. At least the following beneficial effects are achieved: (1) The contact area of the weld seam between the wing skeleton and the skin is larger, which is conducive to improving the welding strength of the all-around lock-bottom welding, and the weld seam width is smaller, which is conducive to achieving the balance of light weight and high strength; (2) Due to the larger contact area of the weld seam between the wing skeleton and the skin, the heat distribution is relatively uniform during welding, which helps to reduce the generation of welding defects such as pores and incomplete fusion; (3) By using the positioning function of the step groove, no additional positioning mechanism is needed to quickly position the skin and the wing skeleton, and the relative position and structural stability of the skin and the wing skeleton can be maintained during welding, reducing the risk of cracks and other welding defects caused by stress concentration.

[0091] Exemplarily, referring to Figure 1 , all the longitudinal members and cross ribs inside the wing skeleton (such as the second main beam 12 and the third cross rib 16) are reserved with air holes to make each grid structure communicate.

[0092] Step S3, assemble all the longitudinal members and cross ribs on the fixture clamp, control the welding deformation and meet the assembly tolerance requirements through the reasonably designed positioning mechanism and clamping mechanism; specifically including the following steps:

[0093] S31: cooperate and position the first longitudinal member with the positioning mechanism, and set the clamping mechanism on the 1 / 5-4 / 5 section of the first longitudinal member between any two adjacent butt joints;

[0094] In one possible design, W lugs contained in the first longitudinal member are cooperated and positioned with W positioning pins on the base plate to define the relative position of the first longitudinal member relative to the base plate along the first direction; W≥2.

[0095] Preferably, one side pressing mechanism is respectively arranged on the 1 / 5-2 / 5 and 3 / 5-4 / 5 sections of the first longitudinal member between any two adjacent butt joints (based on any one joint of the two adjacent butt joints), and one pressing mechanism is arranged on the 2 / 5-3 / 5 section;

[0096] More preferably, one side pressing mechanism is respectively arranged on the 1 / 4 and 3 / 4 of the first longitudinal member between any two adjacent butt joints (based on any one joint of the two adjacent butt joints), and one pressing mechanism is arranged on the 1 / 2.

[0097] S32: sequentially assemble N cross ribs on the base plate along one end to the other end of the first longitudinal member, and set the clamping mechanism on the 1 / 3-2 / 3 section of each cross rib;

[0098] Preferably, two side-pressing mechanisms are arranged at 1 / 3~2 / 3 section of each horizontal rib (based on any one of the two ends of each horizontal rib);

[0099] S33: assembling the second longitudinal member on the base plate, and arranging the clamping mechanism at 1 / 5~4 / 5 section of the second longitudinal member between any two adjacent butt joints;

[0100] Specifically, the second longitudinal member is placed on the base plate and abuts against the end of the N horizontal ribs in step S32, and the clamping mechanism is arranged at 1 / 5~4 / 5 section of the second longitudinal member between any two adjacent butt joints (based on any one of the two adjacent butt joints).

[0101] Preferably, the side-pressing mechanism is arranged at 1 / 5~4 / 5 section of the second longitudinal member between any two adjacent butt joints (based on any one of the two adjacent butt joints).

[0102] In one possible design, one side-pressing mechanism is arranged at 2 / 5~3 / 5 section of the second longitudinal member between any two adjacent butt joints (based on any one of the two adjacent butt joints).

[0103] In one possible design, one side-pressing mechanism is arranged at 1 / 5~2 / 5 and 3 / 5~4 / 5 section of the second longitudinal member between any two adjacent butt joints (based on any one of the two adjacent butt joints).

[0104] S32 and S33 are alternately repeated to assemble the third longitudinal member to the M-1 longitudinal member and the remaining horizontal ribs.

[0105] Specifically, the third longitudinal member is assembled according to S33, the N horizontal ribs between the third longitudinal member and the fourth longitudinal member are assembled according to S32, and so on; the M-1 longitudinal member is assembled according to S33, and the N horizontal ribs between the M-1 longitudinal member and the M longitudinal member are assembled according to S32.

[0106] S34: assembling the M longitudinal member on the base plate; arranging the clamping mechanism at 1 / 5~4 / 5 section of the M longitudinal member between any two adjacent butt joints, and arranging the clamping mechanism on the outside of the M longitudinal member and opposite to each butt joint;

[0107] Preferably, one side-pressing mechanism is arranged at 1 / 5~2 / 5 and 3 / 5~4 / 5 of the section between the Mth longitudinal member and any two adjacent butt joints (based on any one of the two adjacent butt joints), one pressing mechanism is arranged at 2 / 5~3 / 5 of the section, and one pushing mechanism is arranged outside the Mth longitudinal member and opposite to each butt joint.

[0108] More preferably, one side-pressing mechanism is arranged at 1 / 4 and 3 / 4 of the section between the Mth longitudinal member and any two adjacent butt joints (based on any one of the two adjacent butt joints), and one pressing mechanism is arranged at 1 / 2 of the section.

[0109] Referring to Figure 2 A pushing mechanism 22c is arranged outside the Mth longitudinal member and opposite to each butt joint.

[0110] In step S4, the front and back of the weld are protected, and the 2×N×(M-1) butt joints of the wing skeleton are welded in turn from one end to the other end in the first direction and from one side to the other side in the second direction under the protection of inert gas to obtain the wing skeleton.

[0111] In step S41, the front and back of the weld are protected by inert gas.

[0112] Specifically, the tooling fixture assembled with the wing skeleton parts to be welded is placed on the laser welding platform and fixed, and the front and back of the weld are protected by inert gas. In a possible design, the tooling fixture is assembled and fixed with the laser welding platform through the rotating mechanisms on both sides of the tooling fixture. The front protection can be achieved by the existing shielding protection method (nozzle + shielding, inert gas is sprayed from the shielding).

[0113] Preferably, in step S4, the main steps of the back protection include: building a sealing cover (sealed at the weld) in situ on the back of each butt joint by using flexible sealing material, and opening holes on the sealing cover to form the inlet and outlet of inert gas.

[0114] In a possible design, a sealing tape is used to bond a sealing cover on the longitudinal members and / or the stringers near the back of each weld, holes are opened on the sealing cover to form the inlet and outlet of inert gas. This way has the advantages of easy availability of materials, simple operation and good back gas protection effect, and the tape can be quickly removed after welding.

[0115] Further, the positions of the gas inlet and outlet are designed according to the specific gravity of the selected inert gas and air. Preferably, the inert gas is argon, the gas inlet is located at the lower part of the sealing cover, and the gas outlet is located at the upper part of the sealing cover. Argon is heavier than air, and it is easier to obtain a higher concentration by filling argon from a lower position, and the argon protection effect is better.

[0116] Step S42: welding the 2xNx(M-1) butt joints of the wing skeleton in turn from one side to the other side along the second direction from one end to the other end of the first direction under the protection of inert gas; comprising the following steps:

[0117] S421: positioning welding;

[0118] Specifically, the welding track is first found, that is, the laser spot is ensured to be located at the middle position of the weld; then positioning welding is performed on all the welding joints of the wing skeleton.

[0119] Preferably, the middle part of the welding joint is selected for positioning welding; since the length of the welding joint of the longitudinal member and the cross rib of the wing skeleton is relatively short, positioning welding is performed on the middle part of the joint, which can effectively ensure uniform heat input and reduce welding deformation and stress concentration.

[0120] The length of the positioning welding can be determined according to the length of the welding joint; preferably, the length of the positioning welding is 1 / 5-1 / 3 of the length of the welding joint; for example, the length of the welding joint is 30mm, and the length of the positioning welding is 10mm.

[0121] Optionally, the process parameters of the positioning welding are as follows: the laser power is 700W-900W, the defocusing amount is -1.0mm--3.0mm, and the welding speed is 0.5m / min-2.5m / min; preferably, the process parameters of the positioning welding are as follows: the laser power is 750W-850W, the defocusing amount is -1.5mm--2.5mm, and the welding speed is 1.0m / min-2.0m / min; for example, the laser power is 800W, the defocusing amount is -2mm, and the welding speed is 1.5m / min.

[0122] Step S422: formal welding;

[0123] Preferably, the 2xNx(M-1) butt joints of the wing skeleton are welded in turn from one side to the other side along the second direction from one end to the other end of the first direction according to the welding sequence.

[0124] The above welding sequence can make the weld shrink freely, reduce the accumulation of welding stress, and thus minimize the welding deformation caused by the residual stress generated in the laser welding process; at the same time, it is convenient for welding operation and can effectively ensure the straightness of the welding joints located on the same straight line.

[0125] For example, see Figure 1, eight welding joints are welded in sequence according to (①-⑧); that is, from top to bottom, along the second cross beam (including the second cross rib 15 and the first cross rib 14) from left to right, first weld the butt joint ① of the second cross rib 15 and the third main beam 13, and the butt joint ② of the second cross rib 15 and the second main beam 12; then weld the butt joint ③ of the first cross rib 14 and the second main beam 12, and the butt joint ④ of the first cross rib 14 and the first main beam 11; then, along the third cross beam (including the fourth cross rib 17 and the third cross rib 16) from left to right, first weld the butt joint ⑤ of the fourth cross rib 17 and the third main beam 13, and the butt joint ⑥ of the fourth cross rib 17 and the second main beam 12; then weld the butt joint ⑦ of the third cross rib 16 and the second main beam 12, and the butt joint ⑧ of the third cross rib 16 and the first main beam 11.

[0126] If ① and ④ are welded first, ② and ③ may not be able to butt joint into a straight line due to different directions of thermal deformation.

[0127] Preferably, the welding sequence of steps S422 and S421 is the same. By following a consistent welding sequence for tack welding and formal welding, it is helpful to better control the heat input and heat distribution during welding, thereby reducing welding deformation.

[0128] Optionally, the process parameters of formal welding are: laser power is 1700W-2100W, defocusing amount is -3.5mm--6.5mm, and welding speed is 0.5m / min-2.5m / min; preferably, the process parameters of formal welding are: laser power is 1850W-1950W, defocusing amount is -4.5mm--5.5mm, and welding speed is 1.0m / min-2.0m / min; exemplarily, laser power is 1900W, defocusing amount is -5mm, and welding speed is 1.5m / min.

[0129] As an optional embodiment, step S422 further includes the following welding sequence to reduce welding deformation:

[0130] S4221: weld the front weld of each joint of the wing skeleton;

[0131] S4222: turn over the tooling fixture by the rotating mechanism, and weld the back weld of each joint of the wing skeleton;

[0132] S4223: adjust the tooling fixture by the rotating mechanism, and weld the side weld of each joint.

[0133] In a possible design, for the area that is difficult to reach or difficult to observe during welding, i.e. the dead angle position, nonlinear programming or flexible welding equipment such as welding robot can be used to adjust the angle of the welding torch according to the actual situation to ensure the reachability of the welding torch.

[0134] Step S5, the wing skeleton and the skin to be welded obtained in step S4 are assembled on a tooling fixture for welding the wing skeleton and the skin; the reasonable skeleton side pressing mechanism and the skin pressing mechanism designed on the tooling fixture are used to control the welding deformation and meet the assembly tolerance requirements;

[0135] The tooling fixture for welding the wing skeleton and the skin comprises a base plate, a skeleton side pressing mechanism and a skin pressing mechanism arranged on the base plate.

[0136] Preferably, each skeleton side pressing mechanism comprises a pressing piece, one end of the pressing piece is capable of being pressed on the surface of the outermost longitudinal member or transverse member of the wing skeleton, and the other end is fixed on the base plate; so as to control the relative position of the wing skeleton and the tooling fixture and the thermal deformation.

[0137] Step S5 specifically comprises the following steps:

[0138] S51: assembling the wing skeleton on the tooling fixture, and arranging two skeleton side pressing mechanisms between the first longitudinal member and the Mth longitudinal member located between any two adjacent butt joints.

[0139] Specifically, the welded wing skeleton in S4 is disassembled from the tooling fixture 200 for welding the wing skeleton, and then is assembled on another tooling fixture 400 for welding the wing skeleton and the skin, and two skeleton side pressing mechanisms are arranged between the first longitudinal member and the Mth longitudinal member located between any two adjacent butt joints; see Figure 5 The skeleton side pressing mechanism 42 is used to fix and press the wing skeleton on the base plate.

[0140] Preferably, one skeleton side pressing mechanism is arranged in each of the 1 / 5-2 / 5 and 3 / 5-4 / 5 sections between 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).

[0141] S52: overlapping the upper skin and the lower skin on the step groove in S2, and arranging 2×(M+N-4) skin pressing mechanisms on the outside of the upper skin and the lower skin and along the M-2 longitudinal members and N-2 transverse members in the wing skeleton and the contact part of the upper skin and the lower skin, so as to ensure that the skin is fixed and pressed on the tooling fixture, and the skin forms a surface flush butt joint with the wing skeleton around; a groove capable of accommodating the size of the contact surface of the corresponding longitudinal member or transverse member and the skin is formed on each skin pressing mechanism.

[0142] Preferably, each skin pressing mechanism comprises a pressing strip, and a groove capable of accommodating the size of the contact surface of the corresponding longitudinal member or transverse member and the upper skin or lower skin and penetrating through the upper and lower surfaces of the pressing strip is formed on the pressing strip.

[0143] It can be understood that the skin pressing mechanism is used to fix and press the wing frame together with the upper skin and / or lower skin covering the surface of the wing frame on the base plate along the first direction and / or the second direction; the skin pressing mechanism can control the relative position of the wing frame and the upper and lower skins, and meanwhile, for the penetration welding of such long welds, the skin pressing mechanism is arranged along the welds of the wing frame and the upper and lower skins, which can effectively control the thermal deformation of the wing frame and the skin during welding.

[0144] As an optional embodiment, the pressing strips are fixed to the base plate through threaded connection; for example, the end of the pressing strip and / or the two sides of the groove are provided with a plurality of holes for the screw or bolt to pass through and screw into the base plate and / or the skin.

[0145] Preferably, the tooling fixture for welding the wing frame and the skin further comprises rotating mechanisms coaxially arranged on both sides of the base plate; the two rotating mechanisms are connected with the welding workbench, and the different angles of the wing frame and the skin are conveniently welded by rotating the tooling fixture, thereby improving the accessibility of the welding torch.

[0146] Preferably, the two rotating mechanisms Figure 5 The first fixture rotating mechanism 43a and the second fixture rotating mechanism 43b) are coaxially arranged on both sides of the base plate and the rotation axes are perpendicular to the first direction; more preferably, the two rotating structures are coaxially arranged at the middle positions of both sides of the base plate and the rotation axes are perpendicular to the first direction.

[0147] Step S6, front protection and back protection are performed on the welds, and welding is performed under the protection of inert gas to obtain the combination of the wing frame and the upper and lower skins;

[0148] S61: along the first direction from one end to the other end, the contact portions of the second transverse member, the third transverse member, …, the N-1th transverse member and the skin are sequentially welded; for each transverse member, welding is performed in the same direction along the second direction from one side to the other side;

[0149] S62: along the second direction from both sides to the middle, the contact portions of the second longitudinal member, the M-1th longitudinal member, the third longitudinal member, the M-2th longitudinal member, …, to the 1 / 2*Mth longitudinal member or the 1 / 2*(M+1)th longitudinal member and the skin are sequentially welded; for each longitudinal member, welding is performed symmetrically along the first direction from both ends to the middle;

[0150] S63: bottom locking is performed on the contact portions of the two longitudinal members and the two transverse members outside the wing frame and the skin.

[0151] Preferably, in S63, the first longitudinal member and the Mth longitudinal member are welded first, and then the first transverse member and the Nth transverse member are welded. In this way, the longitudinal member with greater rigidity is welded first, and then the transverse member with smaller rigidity is welded, so as to ensure the stability and precision of the overall structure.

[0152] The welding sequence of S61 to S63 can make the welding seam shrink freely, reduce welding stress and deformation, improve the stability of the welded structure, and reduce defects such as cracking and joint strength reduction caused by residual stress generated during laser welding.

[0153] Preferably, in S6, the main steps of back protection include: using the wing skeleton and the upper and lower skins reserved with the air holes in S2 to form a closed and connected air path environment, and inert gas enters from one end of the wing skeleton and is discharged from the other end.

[0154] In S6, the front protection adopts the method of the existing technology of the drag cover + nozzle.

[0155] It should be noted that in S61 and S62, the preferred process parameters of the penetration welding that can obtain high-quality welding seams include: laser power of 2000W-2200W, defocusing amount of -4mm-6mm, and welding speed of 0.02m / min-0.03m / min; and exemplarily, the laser power is 2100W, the defocusing amount is -5mm, and the welding speed is 0.025m / min.

[0156] In S63, the lock bottom welding includes positioning welding and formal welding; and the preferred process parameters of the penetration welding that can obtain high-quality welding seams include:

[0157] Positioning welding: laser power of 700W-900W, defocusing amount of -1.0mm-3.0mm, and welding speed of 0.5m / min-2.5m / min; more preferably, laser power of 750W-850W, defocusing amount of -1.5mm-2.5mm, and welding speed of 1.0m / min-2.0m / min; the length of the positioning welding is 5mm-15mm, and the welding seam spacing is 25mm-35mm; too long positioning welding length may cause overheating and excessive melting in the welding area, and insufficient length may cause the positioning welding point to be not firmly connected.

[0158] Formal welding: laser power of 900W-1100W, defocusing amount of -3mm-7mm, and welding speed of 0.5m / min-2.5m / min; more preferably, laser power of 950W-1050W, defocusing amount of -4mm-6mm, and welding speed of 1.0m / min-2.0m / min.

[0159] Preferably, in S4 and S6, 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; more preferably, the front protective gas flow rate is 20 L / min to 30 L / min; illustratively, the front protective gas flow rate is 25 L / min, and the back protective gas flow rate is 5 L / min.

[0160] Preferably, in S4 and S6, the arc striking distance and the arc extinguishing distance are 3 mm to 7 mm when welding; illustratively, the arc striking distance and the arc extinguishing distance are 5 mm.

[0161] Preferably, in S4 and S6, after welding is completed, the inert gas protection is stopped after 15 min to 20 min of cooling; after welding is completed, the gas protection (mainly back gas protection) can protect the weld metal from the erosion of harmful gases in the air during the cooling process, and maintain the purity and performance of the weld metal.

[0162] It is worth noting that, in S4 and S6, the above-mentioned preferred arc striking distance and arc extinguishing distance and welding parameters (including laser power, welding speed, defocusing amount, and protective gas flow rate) can ensure that smooth and uniform weld surfaces are formed between all welded joints, reduce welding defects, and improve the quality of the welded joints; specifically,

[0163] (1) Arc striking distance: In S4 and S6, the above-mentioned preferred arc striking distance can ensure that the weld starting portion can be sequentially formed and maintain a stable welding process; if the arc striking distance is too short, the weld starting point will be overheated, forming a weld bead or burn-through; and if the arc striking distance is too long, the weld starting point will have insufficient penetration, affecting the connection strength of the weld.

[0164] (2) Arc extinguishing distance: In S4 and S6, the above-mentioned preferred arc extinguishing distance helps to maintain the continuity and uniformity of the welding process, and ensures the quality of the weld end; if the arc extinguishing distance is too short, the weld end will be overheated, forming an arc pit crack or other welding defects; and if the arc extinguishing distance is too long, the weld end will cool too quickly, forming a cold crack or other microscopic defects.

[0165] (3) Laser power: In S4 and S6, the above-mentioned preferred laser power can effectively ensure that the weld surface is free of defects such as pores, cracks, incomplete fusion, undercut, and depression; specifically, a. Too high laser power leads to too high molten pool temperature, increased metal vapor, and gas that fails to escape the molten pool in time, thereby forming pores; b. Too high laser power leads to too high molten pool temperature, increased thermal stress of the material, and thus the formation of cracks; c. Insufficient laser power can lead to insufficient molten pool temperature, making it impossible to achieve full melting of the material, thereby resulting in incomplete fusion; d. Too high laser power leads to too high molten pool temperature and an expanded melting range, easily causing undercut; e. Too high laser power can lead to too high molten pool center temperature, with the metal at the center solidifying before the edges, forming a depression.

[0166] (4) Defocusing amount: In S4 and S6, the above-mentioned preferred defocusing amount can effectively ensure that the weld surface is free of defects such as pores, cracks, incomplete fusion, undercut, and depression; specifically, a. Too large or too small defocusing amount leads to irregular molten pool shape, poor gas exhaust, and increased risk of pore formation; b. Too large or too small defocusing amount leads to uneven molten pool cooling, stress concentration in local areas, and increased likelihood of crack formation; c. Too large defocusing amount leads to uneven laser energy distribution, too high molten pool center temperature and insufficient edge temperature, easily causing incomplete fusion; d. Too large or too small defocusing amount leads to inconsistent cooling speed at the edges of the molten pool, easily causing undercut; e. Too large or too small defocusing amount leads to uneven molten pool cooling, easily forming a depression.

[0167] (5) Welding speed: In S4 and S6, the above-mentioned preferred welding speed can effectively ensure that the weld surface is free of defects such as pores, cracks, incomplete fusion, undercut, and depression; specifically, a. Too fast welding speed can lead to too fast molten pool cooling, insufficient gas escape, and easily formed pores; b. Too slow welding speed can lead to the molten pool being in a high-temperature state for a long time, increasing the thermal stress of the material and thus increasing the risk of cracks; c. Too fast welding speed can lead to too fast molten pool cooling, insufficient melting of the material, and easily incomplete fusion and undercut; d. Too fast welding speed can lead to insufficient filling of the metal at the center of the molten pool, forming a depression.

[0168] (6) Gas flow rate: In S4 and S6, the above-mentioned preferred gas flow rate for front and back protection of each weld can effectively prevent oxidation and inclusion in the weld area, ensure molten pool stability and uniformity, and avoid defects such as pores; too low gas flow rate cannot provide sufficient protection, leading to weld oxidation; and too high gas flow rate can interfere with the stability of the molten pool, affecting the formation of the weld.

[0169] Preferably, in steps S3 and S5, the assembling comprises: trial assembling, repairing the trial assembling, meeting the assembling tolerance requirements, marking the matching marks on each component; pickling, removing the oxide skin, and improving the welding quality; formal assembling: after pickling, assembling each component according to the matching marks on each component, and clamping with a fixture to ensure that the assembling tolerance requirements are met.

[0170] Preferably, in steps S3 and S5, the assembling tolerance requirements comprise: the butt joint gap and step at each point of each joint is not greater than 0.1 mm, and the butt joint gap and step within a local arbitrary 100 mm cumulative length is not greater than 0.2 mm.

[0171] Preferably, before the trial assembling, the welding area is pretreated until the metal luster is exposed, and the surface roughness Ra of the welding surface is less than or equal to 3.2 μm.

[0172] Specifically, the pretreatment mainly comprises: processing the welding area by machining finishing; specifically, machining the welding surface by a machining method to ensure that the welding surface is flat, smooth, burr-free, and maintains the edges and corners, and the surface roughness Ra of the processed welding surface is less than or equal to 3.2 μm; cleaning the welding area by a mechanical treatment method to remove surface oil stains, non-metallic impurities, and the like until the metal luster is exposed; wherein, the welding area comprises the welding surface and both sides of the weld; and the non-metallic impurities comprise oxides.

[0173] Optionally, the welding area comprises 10 mm to 30 mm on both sides of the weld; preferably, 20 mm on both sides of the weld.

[0174] Optionally, the machining method comprises but is not limited to milling, grinding, scraping, grinding, superfinishing, and polishing.

[0175] Optionally, the mechanical treatment method comprises mechanical polishing, and the tool for mechanical polishing comprises but is not limited to a steel wire brush, sandpaper, and a file.

[0176] It can be understood that, by pretreating the welding area (including the welding surface), the quality and reliability of the welded joint can be ensured.

[0177] Preferably, in steps S4 and S6, chord plane measurement is performed before and after welding, respectively, to correct the shape.

[0178] It should be noted that, the main steps of the chord plane measurement comprise: selecting a suitable chord plane measurement device; scanning along the chord length direction of the wing skeleton, the wing skeleton and skin combination using the chord plane measurement device, and recording the data points; inputting the collected data into computer aided design (CAD) software, performing data analysis, and generating the chord plane three-dimensional model of the wing skeleton, the wing skeleton and skin combination before and after welding.

[0179] Optionally, the chord plane measuring device comprises at least one of a laser scanner and a laser tracker.

[0180] Further, the chord plane three-dimensional model before and after welding is compared to obtain the deformation point position and deformation amount, and the wing skeleton, the wing skeleton and the skin combination are corrected to further eliminate the slight deformation in the laser welding process.

[0181] Optionally, the correction method comprises one or a combination of mechanical correction, thermal correction, cold correction and numerical control correction. The mechanical correction includes but is not limited to manual correction, pressure correction and stretching correction; the thermal correction includes but is not limited to local heating and overall heating; the cold correction includes but is not limited to cooling shrinkage and cold stretching; and the numerical control correction includes but is not limited to numerical control correction and robot correction.

[0182] The technical solutions of the present application are further described in detail in combination with specific embodiments.

[0183] Embodiment 1:

[0184] The embodiment provides a welding method for a TA15 titanium alloy wing skeleton and skin, comprising the following steps:

[0185] S1: designing a tool fixture for welding the wing skeleton;

[0186] Referring to Figures 1-5 , the wing skeleton 100 comprises a first main beam 11, a second main beam 12 and a third main beam 13 distributed in parallel along a first direction, and a first cross beam (not shown in the figure), a second cross beam, a third cross beam and a fourth cross beam (not shown in the figure) distributed in parallel along a second direction; wherein the second cross beam comprises a first cross rib 14 and a second cross rib 15 distributed in a straight line, and the third cross beam comprises a third cross rib 16 and a fourth cross rib 17 distributed in a straight line; the included angle between the first direction and the second direction is 87°.

[0187] The main beams and the cross ribs are made of TA15 titanium alloy and are hollow structural rods with a wall thickness of 3 mm and a cross-sectional shape of an I-shaped section; the skin is made of TA15 titanium alloy with a wall thickness of 2 mm.

[0188] The tool fixture 200 for welding the wing skeleton comprises a base plate, a positioning mechanism, a pressing mechanism, a side pressing mechanism, a pushing mechanism, and two rotating mechanisms 23a and 23b symmetrically and coaxially distributed in the middle of both sides of the base plate.

[0189] The base plate is in the shape of a grid-shaped thin plate, and each grid inside comprises a quadrilateral or cross-shaped hollow structure;

[0190] The positioning mechanism comprises two positioning pins 21 on the base plate;

[0191] Each pressing mechanism 22a includes a long strip with two holes at both ends for screws to pass through and screw into the base plate;

[0192] Each side pressing mechanism 22b includes a long strip with two holes at the part not in contact with the main beam or cross rib for screws to pass through and screw into the base plate;

[0193] Each pushing mechanism 22c includes a pushing block and a mounting seat, the pushing block includes a top rod and an end pressing part connected to each other, the mounting seat is fixed on the base plate, the outer surface of the top rod is provided with threads matched with the threads in the hole of the mounting seat, and the end pressing part is driven to abut against the side wall of the main beam by rotating the top rod.

[0194] Step S2, using selective laser melting (SLM) method to manufacture all the main beams and cross ribs of the wing skeleton 100 in S1;

[0195] In the process of establishing the 3D printing model, the first main beam 11 and the third main beam 13 each contain four connecting end heads on one side, the second main beam 12 contains four connecting end heads on both sides respectively, and can be matched with the two end faces of eight cross ribs (four cross ribs are not shown in the figure) to form sixteen matching joints; the inner side edges of the first main beam 11, the third main beam 13, the first cross beam and the fourth cross beam include stepped grooves with a height of 2 mm; the second main beam 12 and the first cross rib 14, the second cross rib 15, the third cross rib 16 and the fourth cross rib 17 are provided with air holes 18 in advance to make the six grid structures communicate.

[0196] Step S3, assembling all the main beams and cross ribs of the wing skeleton obtained by printing in S2 on the tool fixture 200;

[0197] S31: match and position the two lugs on the right side of the first main beam 11 with the two positioning pins 21 on the base plate; set one side pressing mechanism 22b at 1 / 4 and 3 / 4 of the first main beam 11 between any two adjacent matching joints, and set one pressing mechanism 22a at 1 / 2;

[0198] S32: sequentially assemble four cross ribs on the base plate from the upper end to the lower end of the first main beam 11, and set one side pressing mechanism 22b at 1 / 3 and 2 / 3 of each cross rib;

[0199] S33: assemble the second main beam 12 on the base plate, and set two side pressing mechanisms 22b distributed face to face at 2 / 5 of the second main beam 12 between any two adjacent matching joints;

[0200] Repeat S32 to sequentially assemble four cross ribs between the second main beam 12 and the third main beam 13;

[0201] S34: Assembling the third main beam 13 on the base plate, setting a side pressing mechanism 22b at 1 / 4 and 3 / 4 of the third main beam 13 between any two adjacent butt joints, and setting a pressing mechanism 22a at 1 / 2; setting a pushing mechanism 22c on the outside of the third main beam 13 and opposite to each butt joint.

[0202] Further, after assembly, a laser scanner is used to measure the chord plane of the wing skeleton; the collected data is input into the Geomagic Control X software to generate a three-dimensional model of the chord plane of the wing skeleton before welding.

[0203] Step S4: A sealing cover is formed in situ on the main beam and / or the cross rib near the back of each butt joint by using 3M adhesive tape, and a hole is made in the lower part of the sealing cover and argon is introduced, and a hole is made in the upper part of the sealing cover to form an argon outlet, thereby protecting the back of the weld joint; the front protection is performed by using the existing technology of the drag cover + nozzle method;

[0204] Under the protection of argon on the front and back of the weld joint, in the order from top to bottom and from left to right, a laser welding device (name: large-size three-dimensional multi-layer curved surface high-power high-precision laser welding equipment, manufacturer: Aerospace Sanjiang Laser) is used to sequentially perform positioning welding on the 16 butt joints, and then perform formal welding.

[0205] The positioning welding includes: first finding the welding track, i.e. ensuring that the laser spot is located at the middle position of the weld joint; selecting the middle part of each butt joint for positioning welding, and the length of the positioning welding is 10 mm; the process parameters of the positioning welding include: the laser power is 800 W, the defocusing amount is -2 mm, and the welding speed is 1.5 m / min.

[0206] The parameters of the formal welding include: the laser power is 1900 W, the defocusing amount is -5 mm, and the welding speed is 1.5 m / min; the arcing and extinguishing distance is 5 mm.

[0207] After the formal welding is completed, the argon for back protection is stopped after cooling for 20 min; a laser scanner is used to measure the chord plane of the welded wing skeleton; the collected data is input into the Geomagic Control X software to generate a three-dimensional model of the chord plane of the welded wing skeleton; the three-dimensional models of the chord plane of the wing skeleton before and after welding are compared to obtain the deformation point position and deformation amount, and cold correction is performed by using tools such as heat correction and rubber wood hammer to correct the residual small deformation.

[0208] Step S5: Assembling the wing skeleton obtained in S4 and the skin to be welded on a tooling fixture for welding the wing skeleton and the skin; specifically including the following steps:

[0209] S51: Assemble the wing skeleton on the base plate, and set one skeleton side pressing mechanism 42 at 1 / 4 and 3 / 4 of the first main beam 11 and the third main beam 13 between any two adjacent butt joints;

[0210] S52: Lap the upper and lower skins on the stepped groove of the wing skeleton, and set 6 skin pressing mechanisms 41 at the contact parts of the second main beam 12, the second cross beam and the third cross beam with the upper and lower skins; ensure that the skins are fixed and pressed on the tooling fixture, and that the skins form surface flush butt joints with the wing skeleton around.

[0211] Step S6, before welding, use a laser scanner to measure the chord plane of the assembled wing skeleton and skin; input the collected data into the Geomagic Control X software to generate a chord plane three-dimensional model of the wing skeleton and skin assembly before welding;

[0212] Use argon to protect the front and back of the weld, wherein the wing skeleton and the upper and lower skins form a relatively closed and connected gas path environment by using the reserved air hole 18, argon enters from the fourth cross beam at the lower part of the wing skeleton and is discharged from the first cross beam at the upper part of the wing skeleton to protect the back of the weld; the front is protected by the existing technology in the form of a drag cover + nozzle;

[0213] Under the protection of argon, weld in the following order to obtain the assembly of the wing skeleton and the upper and lower skins;

[0214] S61 and S62: as Figure 4 , sequentially penetrate weld the third cross beam, the second cross beam, the second main beam 12 and the skin contact part in the order of ①-⑤;

[0215] S63: as Figure 4 , sequentially weld the third main beam 13, the first main beam 11, and then weld the first cross beam at the upper part and the fourth cross beam at the lower part (not shown in the figure).

[0216] In S61 and S62, the laser power is 2100W, the defocusing amount is -5mm, and the welding speed is 0.025m / min;

[0217] In S63, the positioning weld: the laser power is 800W, the defocusing amount is -2mm, the welding speed is 1.5m / min, the positioning weld length is 10mm, and the weld spacing is 30mm; the formal weld: the laser power is 1000W, the defocusing amount is -5mm, the welding speed is 1.5m / min, and the arc striking and extinguishing distance is 5mm.

[0218] In S4 and S6, the flow rate of the drag cover gas for front protection is 25L / min; the back protection flow rate is 5L / min.

[0219] In S6, after the formal welding is completed, the argon gas for back protection is stopped after 20 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 model of the chord plane of the welded assembly. The 3D models of the chord plane of the assembly before and after welding are compared to obtain the location and amount of deformation. Cold straightening is performed by hot straightening and tapping with tools such as rubber mallets to correct the remaining minor deformations.

[0220] Implementation results:

[0221] 1. Chord plane measurements 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.

[0222] 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.

[0223] 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;

[0224] 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.

[0225] 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 of welding a wing frame and skin, characterized by, The method comprises the following steps: S1, designing a fixture for welding a wing framework; The wing framework is a thin-walled grid structure mainly formed by M longitudinal members parallel along a first direction and N transverse members parallel along a second direction through M×N nodes, each transverse member comprising M-1 cross ribs; M≥3, N≥3; the first direction is different from the second direction; The fixture for the wing framework comprises a base plate, a positioning mechanism and a clamping mechanism arranged on the base plate; S2, manufacturing all longitudinal members and cross ribs of the wing framework by a 3D printing method; when a 3D printing model is established, the M longitudinal members are designed to comprise 2×N×(M-1) connecting end heads along the second direction to accurately butt joint with two end faces of each cross rib to form 2×N×(M-1) butt joints; the inner side edges of the longitudinal members and the transverse members located at the outermost side of the wing framework are designed to comprise step grooves with the same thickness as the skin; and air holes are reserved on the longitudinal members and the cross ribs located inside the wing framework to make each grid structure communicate; S3, assembling all longitudinal members and cross ribs on the fixture, and controlling welding deformation and meeting assembly tolerance requirements by the rationally designed positioning mechanism and clamping mechanism; S4, performing front protection and back protection on the welds, and welding the 2×N×(M-1) butt joints of the wing framework from one end to the other end along the first direction and from one side to the other side along the second direction under the protection of inert gas to obtain the wing framework.

2. The method of welding a wing frame and skin of claim 1, wherein, S3 specifically comprises the following steps, S31, matching and positioning the first longitudinal member with the positioning mechanism, and arranging the clamping mechanism on the 1 / 5-4 / 5 section of the first longitudinal member between any two adjacent butt joints; S32, sequentially assembling N cross ribs on the base plate from one end to the other end of the first longitudinal member, and arranging the clamping mechanism on the 1 / 3-2 / 3 section of each cross rib; S33, assembling the second longitudinal member on the base plate, and arranging the clamping mechanism on the 1 / 5-4 / 5 section of the second longitudinal member between any two adjacent butt joints; alternately repeating S32 and S33 to assemble the third longitudinal member to the M-1 longitudinal member and the remaining cross ribs; S34, assembling the Mth longitudinal member on the base plate, and arranging the clamping mechanism on the 1 / 5-4 / 5 section of the Mth longitudinal member between any two adjacent butt joints and on the outer side of the Mth longitudinal member opposite to each butt joint.

3. The method of welding a wing frame and skin of claim 1, wherein, In S1, the included angle between the first direction and the second direction is 85°-95°.

4. The method of welding a wing skeleton and skin of claim 1, wherein, In S1, the cross-sectional shape of the longitudinal member and the cross rib is one of an I-shaped section or a Π-shaped section or a combination thereof; and / or, the wall thickness of the longitudinal member and the cross rib is 2mm-10mm.

5. The method of welding a wing skeleton and skin of claim 1, wherein, The method further comprises the following steps: S5, assembling the wing framework obtained in S4 and the skin to be welded on a fixture for welding the wing framework and the skin; controlling welding deformation and meeting assembly tolerance requirements by the rationally designed skeleton side pressing mechanism and skin pressing mechanism on the fixture; comprising the following steps: S51: Assemble the wing skeleton on the fixture clamp, and set two skeleton side pressing mechanisms between the first longitudinal member and the Mth longitudinal member at any two adjacent butt joints; S52: Lap the upper and lower skins on the step groove in S2, and ensure the skin to be fixed and pressed on the fixture clamp, and the skin around the wing skeleton to form a surface flush butt joint by setting 2x(M+N-4) skin pressing mechanisms on the outside of the upper and lower skins and along the M-2 longitudinal members and N-2 transverse members in the wing skeleton and the upper and lower skin contact parts; a groove with a size corresponding to the longitudinal member or transverse member and the skin contact surface is formed on each skin pressing mechanism; S6, front and back protection is performed on the weld seam, and welding is performed under the protection of inert gas to obtain the combination of the wing skeleton and the upper and lower skins; including the following steps: S61: Weld the contact parts of the second transverse member, the third transverse member, …, the N-1th transverse member and the skin in sequence from one end to the other end along the first direction; for each transverse member, welding is performed in the same direction from one side to the other side along the second direction; S62: Weld the contact parts of the second longitudinal member, the M-1th longitudinal member, the third longitudinal member, the M-2th longitudinal member, …, to the 1 / 2*Mth longitudinal member or the 1 / 2*(M+1)th longitudinal member and the skin in sequence from both sides to the middle along the second direction; for each longitudinal member, welding is performed symmetrically from both ends to the middle along the first direction; S63: Bottom locking is performed on the contact parts of the two longitudinal members and the two transverse members outside the wing skeleton and the skin.

6. The method of welding a wing frame and skin of claim 1 or 5, wherein, In S4, the main steps of the back protection include: building a sealing cover in situ on the back of each butt joint with flexible sealing material, and opening holes on the sealing cover to form the inlet and outlet of the inert gas; and / or, In S6, the main steps of the back protection include: using the closed and connected gas path environment formed by the wing skeleton and the upper and lower skins with the reserved vent holes in S2, the inert gas enters from one end of the wing skeleton and exits from the other end.

7. The method of welding a wing skeleton and skin according to claim 1 or 5, characterized in that, In S3 and S5, the assembly tolerance requirements include: the butt joint gap and step difference at each point of each joint is not greater than 0.1mm, and the butt joint gap and step difference of the local cumulative length not greater than 30mm within any 100mm is not greater than 0.2mm.

8. The method of welding a wing skeleton and skin according to claim 1 or 5, characterized in that, In steps S4 and S6, chord plane measurement is performed before and after the welding, respectively, and the shape is corrected by comparing the chord plane measurement results.

9. The method of welding a wing skeleton and skin according to claim 1 or 5, characterized in that, In steps S3 and S5, the assembly includes trial assembly, repair of trial assembly; pickling, and removal of oxide scale; formal assembly.

10. The method of welding a wing frame and skin of claim 9, wherein, Further comprising: Before the trial assembly, the welding area is pretreated until the metal luster is exposed, and the surface roughness Ra of the welding surface is ≤3.2μm.

Images