Fixture and method for friction stir welding of skin and reinforcing rib

Abstract

The invention provides a skin and reinforcing rib friction stir welding clamp which comprises a pedestal, a clamping device, a clamping device and a clamping device. The plurality of I-shaped beams are arranged on the pedestal; wherein the reinforcing ribs are arranged on the I-shaped beam, and the skin is arranged on the reinforcing ribs; the clamping top frames are located above the corresponding skins, the two ends of each clamping top frame are arranged on the pedestal, and the middles of the clamping top frames are used for pressing the skins and reinforcing ribs; meanwhile, the invention further provides a skin and reinforcing rib friction stir welding method. The problem that a to-be-welded part is difficult to clamp when a plurality of welding seams are welded on the same plane through a traditional clamp is solved, and the possibility of welding deformation is reduced.

Description

Technical Field

[0001] The present application belongs to the technical field of aviation vehicle skin manufacturing, and in particular relates to a fixture and method for friction stir welding of skin and reinforcement ribs. Background Art

[0002] Reinforced skin is a typical structural form on aircraft and has been used in parts such as wings and fuselage. The ribs greatly enhance the rigidity of the skin. The ribs also bear part of the aerodynamic force acting on the skin and transmit it to other components of the fuselage.

[0003] Riveting is the most commonly used method of connecting skin and reinforcement ribs. It has been proven over time that riveted joints have high connection strength and are easy to replace. However, a large number of rivets are used and the structure increases weight significantly, causing the aircraft to carry a large load and easily causing stress concentration or cracks in the fuselage, posing a safety hazard.

[0004] As a new type of solid-phase joining technology, friction stir welding uses the relative movement between the welding contact end faces to generate heat on the friction surface under the action of constant or increasing pressure and torque, so that the temperature of the weld area rises, but the temperature is generally lower than the melting point of the material, and the deformation resistance of the material is reduced. Under the action of the forging pressure of the stirring head, plastic flow occurs in the weld. Welding is achieved through molecular diffusion and recrystallization at the interface. It is a solid-state welding method with good weld formation and is not prone to defects such as pores and cracks produced in traditional fusion welding. It is particularly suitable for the connection of non-ferrous metals such as aluminum alloys, and is widely used in the welding of low-temperature containers of spacecraft, welding of large light alloy structures, skin welding, and high-speed train welding.

[0005] In the relative technology, the locking clamping is realized during the friction stir welding or flat plate welding to ensure that the two plates do not crack in the middle and the two plates do not warp during the flat plate welding process, so as to obtain a welding joint with good performance. However, when there are multiple welds on the same flat plate, it will be impossible to clamp and thus fail to weld. Summary of the invention

[0006] Purpose of the invention: To provide a friction stir welding fixture and method for overlapping skin and reinforcing ribs, so as to solve the problems of difficult clamping and welding deformation when welding skin and reinforcing ribs.

[0007] In a first aspect, the present application provides a fixture for friction stir welding of a skin and a reinforcement, the fixture comprising:

[0008] A pedestal, which is arranged on a machine tool;

[0009] A plurality of I-beams are arranged on the pedestal; wherein the reinforcing ribs are arranged on the I-beams, and the skin is arranged on the reinforcing ribs;

[0010] A plurality of clamping top frames are provided, wherein the clamping top frames are located above the corresponding skins, the two ends of the clamping top frames are arranged on the pedestal, and the middle part of the clamping top frames is used for pressing the skins and the reinforcing ribs.

[0011] Preferably, the pedestal comprises:

[0012] Base plate;

[0013] A plurality of first rectangular grooves are evenly arranged in the middle area of ​​the bottom plate, and the first rectangular grooves are used to install the I-beam;

[0014] Two second rectangular grooves are arranged on both sides of the bottom plate, and the second rectangular grooves are used to fix the two ends of the clamping top frame;

[0015] A rectangular slot is arranged at a first end and a second end of the base plate, the first end is symmetrical to the second end, and the first end and the second end are close to the second rectangular slot; wherein the rectangular slot matches the T-shaped slot of the machine tool, and the base is fixed to the upper surface of the machine tool workbench by a first T-shaped bolt.

[0016] Preferably, the clamping top frame includes a first top frame and a second top frame, and the first top frame and the second top frame are the same; wherein the first top frame is a π-shaped structure.

[0017] Preferably, the first top frame comprises:

[0018] A cross bar, wherein a front end surface of the cross bar is provided with a protrusion, and a first threaded hole is provided on the protrusion;

[0019] A vertical rod, one end of which is vertically connected to one end of the horizontal rod, and a connecting plate is horizontally arranged at the other end of the vertical rod, and bolt holes are arranged on the connecting plate; wherein the horizontal rod and the vertical rod are coplanar.

[0020] Preferably, the pedestal further comprises:

[0021] A T-shaped groove, arranged below the second rectangular groove, wherein the connecting plate can be accommodated in the second rectangular groove;

[0022] a second T-bolt, the head of the second T-bolt being capable of being received in the T-groove;

[0023] The second T-bolt passes through the bolt hole and cooperates with the nut to fix the first top frame and the second top frame at appropriate positions on the pedestal.

[0024] Preferably, the vertical rod is provided with a protrusion, the protrusion is provided with a second threaded hole, and the clamp further comprises:

[0025] A latch pin is disposed in the second threaded hole; wherein the latch pin has threads;

[0026] A locking washer is connected to the latch; the locking washer is used to lock the first top frame and the second top frame to prevent shaking.

[0027] Preferably, the first rectangular groove is horizontally arranged in the middle area of ​​the bottom plate, and the second rectangular groove is vertically arranged on both sides of the bottom plate.

[0028] Preferably, the clamp further comprises:

[0029] A layer strip, arranged on the skin;

[0030] A clamping bolt is arranged in the first threaded hole, and the lower end surface of the clamping bolt presses against the pressure strip.

[0031] Preferably, the reinforcing rib is Z-shaped, and the reinforcing rib is inverted on the I-beam.

[0032] In a second aspect, the present application also provides a method for friction stir welding of a skin and a reinforcement, the method comprising:

[0033] The reinforcing ribs are inverted on the upper top surface of the I-beam, the skin is laid on the reinforcing ribs, and the pressure strips are laid on the skin;

[0034] Compressing the stiffener and the skin with a clamping top frame;

[0035] The friction stir welding tool obtains a work instruction; wherein the friction stir welding tool comprises a stirring head and a stirring needle, and the work instruction comprises a preset welding speed, a preset rotation speed and a preset tilt angle;

[0036] The stirring needle is inserted into the surface of the skin in the middle area based on a preset inclination angle, and the stirring head carries the stirring needle to start welding the skin in the middle area and the reinforcing ribs based on the preset welding speed and the preset rotation speed;

[0037] After the welding of the skin and reinforcement ribs in the middle area is completed, start welding the skin and reinforcement ribs in the two side areas.

[0038] Beneficial technical effects of this application:

[0039] The present application uses the upper clamping top frame and the lower I-beam to play a major role in positioning the skin and reinforcement to be welded, thereby solving the problem of difficulty in clamping the welded parts when traditional clamps are faced with welding multiple welds on the same plane, and reducing the possibility of welding deformation. At the same time, since the distance between the clamping top frames is adjustable, it also has high versatility when facing different weld widths. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is the overall structural assembly provided by the embodiment of the present application;

[0041] Figure 2 It is an exploded view of the overall structure assembly provided by the embodiment of the present application;

[0042] Figure 3 yes Figure 2 Side view of the exploded diagram;

[0043] Figure 4 is a schematic diagram of a clamping top frame provided in an embodiment of the present application;

[0044] Figure 5 It is a front view of the pedestal provided in the embodiment of the present application;

[0045] Figure 6 is a top view of a pedestal provided in an embodiment of the present application;

[0046] Figure 7 is a schematic diagram of an I-beam provided in an embodiment of the present application;

[0047] Figure 8 is a schematic diagram of a limiting shell provided in an embodiment of the present application;

[0048] Fig. 9 is a schematic diagram of a locking sheet 2 provided in an embodiment of the present application;

[0049] Fig.10 is a schematic diagram of a locking sheet 1 provided in an embodiment of the present application;

[0050] Fig.11 is a welding process flow chart provided in an embodiment of the present application;

[0051] Fig.12 This is a schematic diagram of the multi-pass welding sequence provided in the embodiment of the present application. Figure 1 ;

[0052] Fig.13 This is a schematic diagram of the multi-pass welding sequence provided in the embodiment of the present application. Figure 2 ;

[0053] Fig.14 This is a schematic diagram of the multi-pass welding sequence provided in the embodiment of the present application. Figure 3 . DETAILED DESCRIPTION

[0054] See also Figures 1 to 14The present application provides a friction stir welding fixture, including two protruding rectangular slots on both sides of a base 1, the rectangular slots match the T-grooves of a machine tool, and the base 1 is fixed to the upper surface of the machine tool workbench by T-bolts. The second rectangular grooves are provided on both sides of the upper surface of the base 1, and the two side bases of a clamping top frame 14 in a group of two are arranged in the second rectangular grooves on the upper surface of the base 1.

[0055] Among them, a T-shaped groove is provided below the second rectangular groove, and a through hole is provided at the base of the clamping top frame 14. After the T-shaped bolt 8 passes through, the nut is tightened to fix it at a suitable position on the upper surface of the pedestal 1. Each weld requires two clamping top frames 14 as a group to complete the clamping work. The two clamping top frames 14 are connected by a first locking gasket 9, a second locking gasket 10 and a latch 11. The first locking gasket 9 and the second locking gasket 10 are both provided with threaded holes. After the first locking gasket 9 is inserted into the suitable position of the second locking gasket 10, the latch 11 is inserted to connect the first locking gasket 9 and the second locking gasket 10. The bolt 5 passes through the through hole of the limit shell 4 to match the limit shell 4 at both ends of the upper surface of the I-beam 2, and the movement of the limit shell 4 on the I-beam 2 is adjusted by the bolt 5.

[0056] Among them, five first rectangular grooves are provided on the upper surface of the pedestal 1 for installing the I-beam 2. After the I-beam 2 is placed in the first rectangular groove, the I-beam 2 is fixed to the pedestal 1 with bolts 3, and the reinforcing ribs 6 are buckled on the upper surface of the I-beam 2. The skin 7 is laid on the reinforcing ribs 6. After adjusting the positions of the skin 7 and the reinforcing ribs 6, the spacing of the clamping top frame 14 in the same group is adjusted according to the required width of the weld, and the clamping bolt 12 is screwed into the first threaded hole on the side of the clamping top frame 14. The pressure strip 13 is laid on the skin 7, and the lower end face of the clamping bolt 12 is against the pressure strip 13. The skin 7 and the reinforcing rib 6 are pressed against the I-beam 2 by screwing in the clamping bolt 12.

[0057] In other embodiments of the present application, the present application also discloses the following:

[0058] Process parameters

[0059] The friction stir welding process parameters of the skin and the reinforcement mainly include welding speed, rotation speed, press-in amount, and welding inclination. Each specification of weldment should be subjected to process tests according to the requirements of the technical documents, and the welding process parameters should be determined. The typical process parameters of friction stir welding of aluminum alloy and titanium alloy for skin and reinforcement are shown in Table 1 Stirring needle size parameters and Table 2 Welding process parameters.

[0060] Table 1

[0061]

[0062] Table 2

[0063]

[0064] Process

[0065] The typical process flow of friction stir welding of skin and reinforcement is as follows: Fig.11 As shown, it generally includes process verification, pre-welding preparation, assembly, welding, inspection, post-weld processing and acceptance.

[0066] Process Validation

[0067] Before each trial production or batch production welding, prepare a test piece or simulation piece with the same material grade, heat treatment status and thickness as the welded parts. The recommended size of the test piece is 400mm×100mm×δ, δ is the welding thickness, and the thickness should represent the maximum and minimum dimensions of the product; the surface roughness Ra value of the test piece or simulation piece to be welded should be less than 6.3μm. According to the appearance quality, internal quality and mechanical properties of the welded joint, the welding process parameters can be appropriately adjusted, but the adjustment range should not exceed 10%.

[0068] Preparation before welding

[0069] Before welding, the oil stains on the surface of the parts should be removed, and then the oxide film on the surface of the parts to be welded should be cleaned by mechanical methods such as a stainless steel brush (the diameter of the steel wire should not exceed 0.1mm) and a scraper or chemical cleaning methods.

[0070] The welded parts with cleaned surfaces can be directly welded within 3h (2A12) and 12h (TA2). The welded parts that have been welded for more than 6h (2A12) and 24h (TA2) should be mechanically cleaned again. Before welding, the welded area of ​​the welded parts and the surface of the fixtures in contact with the materials must be wiped with white silk cloth or fine-grained white cloth dipped in industrial alcohol or industrial acetone. There must be no oil stains, paint, rust spots, fusible metals and other pollutants that affect the welding quality and welding process.

[0071] assembly

[0072] During the installation of the parts to be welded, the center of the stirring needle should be checked and the centering deviation should be adjusted. The centering deviation is required to be ≤0.3mm over the entire length.

[0073] The weld lap gap requirement before welding should be ≤0.05mm. For parts that cannot meet the assembly accuracy, mechanical grinding is allowed within the part size tolerance range to meet the pre-welding assembly requirements.

[0074] To ensure the assembly positioning of parts, stir friction welding can be used for positioning welding. The positioning welding points or positioning welding sections should be symmetrical and uniform, without cracks and can be covered by the weld.

[0075] Welding

[0076] If welding lead-in plates and welding lead-out plates are used, their material grade, thickness and state should be the same as those of the parts, and their pre-welding preparation should be carried out as above, and they should be processed and removed after welding.

[0077] Before TA2 welding, ventilate the argon nozzle for 3 to 5 seconds and place it 10mm to 20mm from the welded area. The output pressure should be no less than 0.3MPa. The argon nozzle moves with the stirring head and stays for 3 to 5 seconds after welding is completed before turning off the gas. (Note: The purity of argon gas must be above 99.999%)

[0078] The friction stir welding process of the skin and the reinforcement should be continuous. If interruption occurs, the welding should be restarted at the interruption point and the area should be treated as a defect.

[0079] The welding sequence of multi-pass welding of the whole plate should be "Z" type welding sequence. Pre-suppression of deformation before welding, please refer to Fig.12 , Fig.13 and Fig.14 .

[0080] The rib welded components of the friction stir welding of the skin and the rib often produce buckling and instability deformation due to the eccentric arrangement of the weld. A reasonable design should try to arrange the weld on or close to the neutral axis of the structural section, and strive to make the deformation on both sides of the neutral axis equal in size and opposite in direction to offset each other.

[0081] Large and complex welded structures can be divided into several simple components as long as conditions permit, welded separately, and then assembled into a whole. The divided components should be easy to control welding deformation, and the welding amount should be small during assembly, which is also convenient for controlling total deformation. The weld being welded should be as close to the neutral axis of the structural section as possible. For structures with asymmetrical welds, the side with fewer welds should be welded first during assembly welding. Structures with symmetrical welds should be welded symmetrically with an even number of welding passes.

[0082] Suppressing deformation during welding

[0083] During welding, heat dissipation can be used to suppress deformation. By adding pneumatic loads, liquid cooling, etc., the heat at the welding site can be quickly dissipated, reducing the heat-affected area of ​​the weld and its vicinity, and at the same time greatly reducing the degree of heat in the heat-affected area, thereby achieving the purpose of reducing welding deformation. During welding, a follow-up impact device can also be applied to suppress deformation.

[0084] Post-weld deformation treatment

[0085] After welding, deformation correction can be carried out by manual correction, mechanical correction, flame heating correction, post-weld heat treatment, etc.

Claims

1. A fixture for friction stir welding of skin and reinforcement, characterized in that: The fixture comprises: A pedestal, which is arranged on a machine tool; A plurality of I-beams are arranged on the pedestal; wherein the reinforcing ribs are arranged on the I-beams, and the skin is arranged on the reinforcing ribs; A plurality of clamping top frames are provided, wherein the clamping top frames are located above the corresponding skins, the two ends of the clamping top frames are arranged on the pedestal, and the middle part of the clamping top frames is used for pressing the skins and the reinforcing ribs.

2. The clamp according to claim 1, characterized in that: The pedestal includes: Base plate; A plurality of first rectangular grooves are evenly arranged in the middle area of ​​the bottom plate, and the first rectangular grooves are used to install the I-beam; Two second rectangular grooves are arranged on both sides of the bottom plate, and the second rectangular grooves are used to fix the two ends of the clamping top frame; A rectangular slot is arranged at a first end and a second end of the base plate, the first end is symmetrical to the second end, and the first end and the second end are close to the second rectangular slot; wherein the rectangular slot matches the T-shaped slot of the machine tool, and the base is fixed to the upper surface of the machine tool workbench by a first T-shaped bolt.

3. The clamp according to claim 2, characterized in that: The clamping top frame includes a first top frame and a second top frame, wherein the first top frame is the same as the second top frame; wherein the first top frame is a π-shaped structure.

4. The clamp according to claim 3, characterized in that: The first top frame comprises: A cross bar, wherein a front end surface of the cross bar is provided with a protrusion, and a first threaded hole is provided on the protrusion; A vertical rod, one end of which is vertically connected to one end of the horizontal rod, and a connecting plate is horizontally arranged at the other end of the vertical rod, and bolt holes are arranged on the connecting plate; wherein the horizontal rod and the vertical rod are coplanar.

5. The clamp according to claim 4, characterized in that: The pedestal further comprises: A T-shaped groove, arranged below the second rectangular groove, wherein the connecting plate can be accommodated in the second rectangular groove; a second T-bolt, the head of the second T-bolt being capable of being received in the T-groove; The second T-bolt passes through the bolt hole and cooperates with the nut to fix the first top frame and the second top frame at appropriate positions on the pedestal.

6. The clamp according to claim 5, characterized in that: The vertical rod is provided with a protrusion, and the protrusion is provided with a second threaded hole, and the clamp further includes: A latch pin is disposed in the second threaded hole; wherein the latch pin has threads; A locking washer is connected to the latch; the locking washer is used to lock the first top frame and the second top frame to prevent shaking.

7. The clamp according to claim 6, characterized in that The first rectangular groove is horizontally arranged in the middle area of ​​the bottom plate, and the second rectangular groove is vertically arranged on both sides of the bottom plate.

8. The clamp according to claim 7, characterized in that: The fixture also includes: A layer strip, arranged on the skin; A clamping bolt is arranged in the first threaded hole, and the lower end surface of the clamping bolt presses against the pressure strip.

9. The clamp according to claim 1, characterized in that: The reinforcing rib is Z-shaped and is inverted on the I-beam.

10. A method for friction stir welding of a skin and a reinforcement, characterized in that: The method comprises: The reinforcing ribs are inverted on the upper top surface of the I-beam, the skin is laid on the reinforcing ribs, and the pressure strips are laid on the skin; Compressing the stiffener and the skin with a clamping top frame; The friction stir welding tool obtains a work instruction; wherein the friction stir welding tool comprises a stirring head and a stirring needle, and the work instruction comprises a preset welding speed, a preset rotation speed and a preset tilt angle; The stirring needle is inserted into the surface of the skin in the middle area based on a preset inclination angle, and the stirring head carries the stirring needle to start welding the skin in the middle area and the reinforcing ribs based on the preset welding speed and the preset rotation speed; After the welding of the skin and reinforcement ribs in the middle area is completed, start welding the skin and reinforcement ribs in the two side areas.

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