Friction stir repair process for shallow cracks of arc-shaped component

Abstract

The invention discloses a stirring friction repair process for shallow cracks of an arc-shaped component. The stirring friction repair process comprises the following steps: determining a defect position to be repaired on the arc-shaped component; preprocessing the defect position to be repaired; then defect repairing is conducted according to a set path, the plasticized metal material is made to conduct filling repairing on the defect position, and in the defect repairing process, the axis of the stirring head is perpendicular to the corresponding axis of the arc-shaped component all the time; and after defect repairing is finished, post-processing is conducted on the repaired area. With the adoption of the scheme, different types of arc-shaped component shallow crack repair can be adapted only by the same stirring friction tool, the requirement can be met only by configuring one set of stirring friction tool in the same workshop, and the tedious process of replacing the stirring friction tool is omitted.

Description

Technical Field

[0001] The present invention belongs to the technical field of friction stir material addition and defect repair, and specifically relates to a friction stir repair process for shallow cracks in arc-shaped components. Background Art

[0002] There are two main technical routes for repairing shallow cracks in curved components, such as aircraft tanks: one is conventional fusion welding repair, but when it is applied to the repair of high-strength aluminum alloy rocket tanks, the repair area has poor density, low bonding strength, serious degradation of mechanical properties, and poor repair quality; the other is solid-phase repair technology based on stirring friction. Stirring friction causes severe plastic deformation, which triggers dynamic recrystallization to form a fine and uniform microstructure, avoiding defects such as thermal cracks and pores caused by traditional fusion welding repair processes, and the performance of the repair area is excellent.

[0003] During the friction stir solid-phase repair process, since the repair area of ​​a curved component has a curved surface structure, a thick, large protrusion typically forms in the repaired area after defect repair. The smaller the radius of the curved component, the thicker and wider the protrusion per unit size, requiring post-processing of the repaired area. More importantly, due to the wide variety of aircraft tank types, the friction stir tool (stirring head) required to repair shallow cracks in corresponding curved components also requires adaptive adjustment. The same existing friction stir tool cannot adapt to different types of shallow crack repairs in curved components, requiring multiple friction stir tools to be deployed in the same workshop, which is very cumbersome. Summary of the Invention

[0004] The present invention aims to provide a friction stir repair process for shallow cracks in arc-shaped components, which can adapt to the repair of shallow cracks in arc-shaped components of different types (sizes) by only requiring a single set of friction stir tools.

[0005] The present invention adopts the following technical solutions.

[0006] A friction stir repair process for shallow cracks in arc-shaped components, comprising the following steps: S1, determining the location of the defect to be repaired on the arc-shaped component; S2, pre-processing the defect location to be repaired; S3, assembling a stirring head on the main shaft of the friction stir additive equipment, turning on the main unit of the friction stir additive equipment, and setting the process parameters. The stirring head adopts a split stirring head capable of regulating forming stress. The split stirring head has several layers of coaxially arranged cylinders that can move axially relative to the central rod, and the lower end of the cylinder can directly contact the surface of the arc-shaped component; a back support is installed on the back side of the defect position on the arc-shaped component; S4, starting the friction stir solid phase deposition additive repair equipment, and moving the stirring head to the starting point of the defect repair, starting the feeding mechanism, which is used to feed powder material to the defect location to be repaired, and then performing defect repair according to the set path, so that the plasticized metal material fills and repairs the defect location. During the defect repair process, the axis of the stirring head is always perpendicular to the axis corresponding to the arc-shaped component; S5, after the defect repair is completed, the repaired area is post-processed.

[0007] Preferably, during the defect repair process, the lower end of at least one cylinder is completely in contact with the surface of the arc-shaped component.

[0008] Furthermore, the split stirring head includes a central rod body, a stirring needle is provided at the middle of the lower end of the central rod body, and a plurality of layers of cylinders are sleeved on the central rod body and are coaxially arranged and can move axially relative to the central rod body. The wall thickness of each cylinder is 3 to 5 mm, and the outer wall of the outermost cylinder is sleeved with a cylindrical shell. Any two adjacent cylinders are in contact with the wall. A material cavity is provided on the central rod body, and the material cavity is communicated with the feeding pipe of the feeding mechanism; a disc spring is provided on the top of the cylinder, and each disc spring matches a cylinder. The central rod body and the cylindrical shell are The relative positions of the bodies are always fixed; an oil storage tank is provided on the outer wall of the cylinder, and a guide protrusion is also provided on the outer wall of the cylinder. The oil storage tank also serves as a guide groove, and the guide protrusions of two adjacent cylinders are gap-fitted in the guide groove; when the stirring head is in the initial state without defect repair, the lower ends of all cylinders, the lower end of the central rod body, and the cylindrical shell are located in the same horizontal plane; when the stirring head is in the process of implementing defect repair, the lower ends of some cylinders are higher than the lower end of the central rod body, and all cylinders, the central rod body and the cylindrical shell rotate synchronously.

[0009] Preferably, during the defect repair process, the rotation speed of the stirring head is 800-1200 r / min, and the travel speed of the stirring head is 500-800 mm / min.

[0010] Preferably, during the defect repair process, the moving direction of the stirring head is parallel to the axis corresponding to the arc-shaped component.

[0011] Beneficial effects: By adopting the solution of the present invention, only the same stir friction tool is needed to adapt to the repair of shallow cracks in different types of arc-shaped components. The same workshop can be equipped with only one set of stir friction tools to meet the requirements, eliminating the tedious process of replacing the stir friction tools; by adopting the solution of the present invention, the raised part formed in the repair area of ​​the arc-shaped component can be significantly reduced, and the raised part of the repair area of ​​the aircraft tank with a diameter of 2.25 meters can be reduced to within 3 mm (thickness) and 5 mm (width). BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Schematic diagram of the external structure of the split stirring head in Example 1 Figure 1; Figure 2 Schematic diagram of the external structure of the split stirring head in Example 1 Figure 2 ; Figure 3 Schematic cross-section of the split stirring head in Example 1; Figure 4 This is a schematic diagram of the disassembled state of the split stirring head in Example 1; Figure 5 This is a schematic diagram of the repair state of the test solution 1 applied in Example 1; Figure 6 This is a schematic diagram of the repair status of the second test solution applied in Example 1. DETAILED DESCRIPTION

[0013] The following is a clear and complete description of the technical solutions of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. Example 1

[0014] First, the split stirring head used in this embodiment is described. Figures 1 to 4As shown, the split stirring head includes a central rod body 5, a stirring needle 2 is provided at the middle of the lower end of the central rod body 5, and six layers of coaxially arranged cylinders 15 (including the first layer cylinder 6, the second layer cylinder 7, the third layer cylinder 8, the fourth layer cylinder 9, the fifth layer cylinder 10, and the sixth layer cylinder 11 arranged in sequence from the inside to the outside) are sleeved on the central rod body 5. The wall thickness of each cylinder 15 is 5 mm and the length is 15 cm. The outer wall of the outermost cylinder is sleeved with a cylindrical shell 12. Any two adjacent cylinders 15 are in contact with the wall (cooperation between adjacent cylinders 15). A material cavity is provided on the central rod body 5, and the discharge port 3 of the material cavity is located at the stirring needle. 2 side, the material cavity is connected to the feeding pipe of the feeding mechanism; wherein, an elastic element is connected to the top of the cylinder 15, and the relative position of the central rod body 5 and the cylindrical shell 12 is always fixed; when the stirring head is in the initial state without defect repair, the lower ends of all cylinders 15, the lower ends of the central rod body 5, and the cylindrical shell 12 are located at the same horizontal plane; when the stirring head is in the process of implementing defect repair, the lower ends of some cylinders 15 are higher than the lower end of the central rod body 5; the elastic element adopts six coaxially arranged disc springs 13, the wall thickness of the disc spring 13 is 3mm, the maximum compression amount of the disc spring 13 is 2.5mm, and each disc spring 13 matches one cylinder 15; an oil storage tank 14 is provided on the outer wall of the cylinder 15, The radius of the oil storage tank 14 is 1.5 mm, and the length of the oil storage tank 14 is 12 cm; a guide protrusion is also provided on the outer wall of the cylinder 15, and the length of the guide protrusion is 5 cm. The oil storage tank 14 is also used as a guide groove, and the guide protrusions of two adjacent cylinders 15 are gap-fitted in the guide groove. The oil storage tank 14 and one end of the guide protrusion are both located at the lower end of the cylinder 15. This specific structural arrangement and length of the oil storage tank 14 and the guide protrusion can not only smoothly realize the role of adaptively controlling the forming stress, but also prevent different cylinders 15 from rotating relative to each other, thereby facilitating stable defect repair.

[0015] This embodiment provides a friction stir repair process for shallow cracks in arc-shaped components, comprising the following steps: S1, determining the location of the defect to be repaired on the arc-shaped component; S2, pre-process the defect location to be repaired, mechanically dig the shallow crack defect into a regular shape, and dig into a columnar pit structure with a depth of 4mm and a width equal to the width of the shallow crack coverage area; S3, assembling a stirring head on the main shaft of the friction stir additive equipment, turning on the main unit of the friction stir additive equipment, and setting the process parameters. The stirring head adopts a split stirring head capable of regulating forming stress. The split stirring head has several layers of coaxially arranged cylinders that can move axially relative to the central rod, and the lower end of the cylinder can directly contact the surface of the arc-shaped component; a back support is installed on the back side of the defect position on the arc-shaped component; S4, start the friction stir solid phase deposition additive repair equipment, move the stirring head to the starting point of the defect repair, start the feeding mechanism, which is used to feed powder material to the defect position to be repaired, and then perform defect repair according to the set path, so that the plasticized metal material fills and repairs the defect position. During the defect repair process, the axis of the stirring head is always perpendicular to the axis corresponding to the arc-shaped component, and the moving direction of the stirring head is parallel to the axis corresponding to the arc-shaped component. All cylinders, the central rod body and the cylindrical shell rotate synchronously; S5, after the defect repair is completed, the repaired area is post-processed (machining).

[0016] In the first application test scheme, shallow cracks (length 8cm, maximum depth 3mm, maximum width 0.8mm, shallow crack coverage area width 12mm) on the surface of an aircraft tank specimen with a diameter of 2.25 meters were repaired. During the defect repair process, the rotation speed of the stirring head was controlled at 900r / min and the travel speed of the stirring head was 600mm / min. The state after the defect repair was as follows Figure 5 As shown in the figure, the maximum thickness of the single raised section in the repaired area is 2.7mm and the maximum width is 4.5mm. In the second application test scheme, a shallow crack (length 11cm, maximum depth 4mm, maximum width 1mm, and the width of the shallow crack covering the area is 12mm) on the surface of a 3-meter-diameter aircraft tank specimen was repaired. During the defect repair process, the rotation speed of the stirring head was controlled at 1000r / min and the travel speed of the stirring head was 800mm / min. The defect repair status is shown in the figure. Figure 6 As shown, the maximum cross-sectional thickness of a single raised portion formed in the defect repair area is 1.8 mm and the maximum width is 3.3 mm.

[0017] Comparative Example 1: A traditional stirring head with a stirring needle (stirring tool in document CN119077110A) was used to repair shallow cracks on the surface of an aircraft tank specimen with a diameter of 2.25 meters (length 9 cm, maximum depth 3 mm, maximum width 0.8 mm, and a width of an area covered by the shallow cracks of 10 mm) according to a set path. The stirring head was tilted backward by 3°, and the rotation speed and travel speed of the stirring head were the same as those in Application Scheme 1. The maximum cross-sectional thickness of a single raised portion formed in the defect-repaired area was 8.4 mm and the maximum width was 6.1 mm.

[0018] Comparative Example 2: A traditional stirring head with a stirring needle (stirring tool in document CN119077110A) was used to repair shallow cracks (length 10.5 cm, maximum depth 4.5 mm, maximum width 1 mm, and a width of 11 mm in the shallow crack coverage area) on the surface of an aircraft tank specimen with a diameter of 2.25 meters according to a set path. During the defect repair process, the axis of the stirring head was always perpendicular to the axis corresponding to the arc-shaped component. The rotation speed and travel speed of the stirring head were the same as those in Application Scheme 1. The maximum cross-sectional thickness of a single raised portion formed in the defect repaired area was 5.3 mm and the maximum width was 7.8 mm.

[0019] By adopting the solution of Example 1, only the same stir friction tool is needed to adapt to the repair of shallow cracks in different types of arc-shaped components. The same workshop can be equipped with only one set of stir friction tools to meet the requirements, eliminating the tedious process of replacing the stir friction tools. By adopting this solution, the raised portion formed in the repair area of ​​the arc-shaped component can be significantly reduced, and the raised portion of the repair area of ​​an aircraft tank with a diameter of 2.25 meters can be reduced to within 3 mm (thickness) and 5 mm (width).

[0020] In the embodiment, due to the use of a stirring head with a specific structure and a solution in which the axis of the stirring head is always perpendicular to the axis corresponding to the arc-shaped component, the size of the curved surface can be adaptively changed during the defect repair process. Each cylinder can move axially independently after being compressed. This multi-layer coaxial arrangement of cylinders with the lower end in direct contact with the surface of the arc-shaped component can repeatedly vertically roll the plasticized material. During use, no matter whether the curvature corresponding to the arc-shaped component becomes larger or smaller, at least one lower end of the cylinder is completely in contact with the surface of the arc-shaped component (for example, when the diameter corresponding to the arc-shaped component is larger, refer to Figure 6 As shown, at this time, the first layer of cylinder 6 and the second layer of cylinder 7 can completely rest on the surface of the arc-shaped component; when the diameter of the arc-shaped component is small, you can refer to Figure 5 As shown, at this time, the first layer of cylinder 6 can completely rest on the surface of the arc-shaped component), ensuring the plasticization and forming of the powder material, thereby implementing defect repair more stably, smoothly and evenly.

Claims

1. A stir friction repair process for shallow cracks in arc-shaped components, characterized in that the steps include: S1, determining the location of the defect to be repaired on the arc-shaped component; S2, pre-processing the defect location to be repaired; S3. Assemble the stirring head on the main shaft of the friction stir additive equipment, turn on the main unit of the friction stir additive equipment, and set the process parameters. The stirring head adopts a split stirring head that can adjust the forming stress. The split stirring head has several layers of coaxially arranged cylinders that can move axially relative to the central rod. The lower end of the cylinder can directly contact the surface of the arc-shaped component. Install a back support on the back side of the defect position on the arc-shaped component. S4, start the friction stir solid phase deposition additive repair equipment, move the stirring head to the defect repair starting point, start the feeding mechanism, which is used to feed powder material to the defect position to be repaired, and then perform defect repair according to the set path, so that the plasticized metal material fills and repairs the defect position. During the defect repair process, the axis of the stirring head is always perpendicular to the axis corresponding to the arc-shaped component; S5: After the defect repair is completed, the repaired area is post-processed.

2. The friction stir repair process for shallow cracks in arc-shaped components according to claim 1, characterized in that: During the defect repair process, at least one lower end of the cylinder is completely in contact with the surface of the arc-shaped component.

3. The friction stir repair process for shallow cracks in arc-shaped components according to claim 2, characterized in that: The split stirring head includes a central rod body, a stirring needle is provided at the middle of the lower end of the central rod body, and a plurality of layers of cylinders are coaxially arranged and can move axially relative to the central rod body. The wall thickness of each cylinder is 3 to 5 mm, and the outer wall of the outermost cylinder is provided with a cylindrical shell. Any two adjacent cylinders are in contact with the wall. A material cavity is provided on the central rod body, and the material cavity is communicated with the feeding pipe of the feeding mechanism; a disc spring is provided on the top of the cylinder, and each disc spring matches a cylinder. The central rod body and the cylindrical shell are in contact with each other. The position is always fixed; an oil storage tank is provided on the outer wall of the cylinder, and a guide protrusion is also provided on the outer wall of the cylinder. The oil storage tank also serves as a guide groove, and the guide protrusions of two adjacent cylinders are gap-fitted in the guide groove; when the stirring head is in the initial state without defect repair, the lower ends of all cylinders, the lower end of the center rod body, and the cylindrical shell are located in the same horizontal plane; when the stirring head is in the process of defect repair, the lower ends of some cylinders are higher than the lower end of the center rod body, and all cylinders, the center rod body and the cylindrical shell rotate synchronously.

4. The friction stir repair process for shallow cracks in arc-shaped components according to claim 3, characterized in that: During the defect repair process, The rotation speed of the stirring head is 800-1200 r / min, and the travel speed of the stirring head is 500-800 mm / min.

5. The friction stir repair process for shallow cracks in arc-shaped components according to claim 4, characterized in that: During the defect repair process, the moving direction of the stirring head is parallel to the axis corresponding to the arc-shaped component.

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