A Rotatable Telescopic Friction Stir Processing Tool and Processing Method

Abstract

The present invention relates to a rotatable telescopic friction stir processing head and a processing method. The rotatable telescopic friction stir processing head mainly includes: drive motor I, stirring head, stirring pin, hydraulic telescopic system, rotatable shoulder, transmission belt, drive motor II, landing gear to be processed. The rotational speeds of the stirring pin and the rotatable shoulder can be adjusted differently through different motors. The double-rotatable telescopic friction stir processing head of the present invention can perform stirring processing on the landing gear of an aircraft manufactured by laser additive manufacturing, while realizing adjustable surface and subsurface tissue structures of additive manufacturing, greatly improving the mechanical properties of the aircraft landing gear, reducing the surface roughness of the aircraft landing gear after additive manufacturing, improving the surface quality, and reducing the processing procedures for additive manufacturing of the aircraft landing gear.

Description

Technical Field

[0001] The present invention belongs to the field of surface treatment, and relates to a rotatable telescopic friction stir processing head and a processing method, specifically a rotatable telescopic friction stir processing head for an aircraft landing gear, which can refine columnar crystals while treating the surface of an additively manufactured aircraft landing gear to improve its surface quality. Background Art

[0002] Aircraft frequently experience "sprained ankle" accidents. The main reason is that the load borne by the aircraft landing gear during takeoff or landing exceeds its ultimate load-bearing capacity, directly resulting in the failure of key components of the aircraft landing gear. After statistics, it is mostly due to the mismatch between the strength and toughness of key components. When the aircraft is operating normally, the outer cylinder of the landing gear is displaced under the action of the piston to resist the energy brought by the impact. Stress concentration is inevitable at its interfaces and connections. Moreover, when the stress on the two wings of the landing gear is relatively small, in order to achieve the purpose of lightweight design, it needs to be optimized. The retractable landing gear requires the aircraft to lower it during takeoff and landing. While adding a retraction mechanism, on the one hand, the weight of the landing gear system significantly increases. On the other hand, during repeated fatigue use of the landing gear, cracks and fatigue fractures in the structure will inevitably occur.

[0003] Laser additive manufacturing technology has opened up a new process technology approach for the design and manufacturing of high-performance metal components, and can solve new challenges in materials, structures, processes, performance, applications, etc. during the development of fields such as aerospace. After years of development, metal components manufactured by laser deposition can reach or even exceed the mechanical properties of forgings, and their forming sizes are basically not limited, becoming an important emerging means for the rapid manufacturing of key aviation components.

[0004] However, in terms of microstructure, during the laser directed energy deposition (LDED) process, continuously growing columnar crystals are formed, resulting in low plasticity, damage tolerance, and fatigue performance of A100 high-strength steel components. In terms of metallurgical defects, metallurgical defects are generated in the interface regions within the deposition layer, between passes, and between layers, greatly reducing the mechanical properties of the formed parts. In addition, the structure of an aircraft landing gear is complex, and there are certain differences in the thickness and strength requirements of components at different positions. Therefore, there is an urgent need for a high-flexibility and high-efficiency strengthening technology to strengthen the components of aircraft landing gears fabricated by laser directed energy deposition. The friction stir processing (FSP) technology, as a severe plastic deformation technology, can change the shape of the stirring head as needed to control the depth and width of the processing area, with high flexibility. In terms of microstructure, the FSP process can disrupt the growth of coarse columnar crystals in the additive direction, refine the grains, and thereby improve the material properties. In terms of metallurgical defects, FSP can eliminate defects such as porosity and shrinkage in the product, improving the material density. Summary of the Invention

[0005] Technical Problems to be Solved

[0006] In order to avoid the deficiencies of the prior art, the present invention provides a rotatable telescopic friction stir processing head and a processing method. In view of the different thicknesses at different processing positions of the aircraft landing gear, the stirring pin extends different lengths to insert into the surface of the aircraft landing gear to regulate the columnar crystals formed by additive manufacturing. At the same time, the shoulder rotates at different speeds to synchronously perform surface treatment on the additive manufacturing components during the processing, improving the surface quality and mechanical properties of the aircraft landing gear.

[0007] Technical Solution

[0008] A rotatable telescopic friction stir processing head, characterized in that it includes a first driving motor Ⅰ1, a stirring head 2, a stirring pin 3, a hydraulic telescopic system 4, a rotatable shoulder 5, a transmission belt 6, and a second driving motor Ⅱ7. The first driving motor Ⅰ1 is connected to the stirring pin 3 inside the stirring head 2 through the hydraulic telescopic system 4. The hydraulic telescopic system 4 and the stirring pin 3 are located inside the rotatable shoulder 5, and the first driving motor Ⅰ1, the hydraulic telescopic system 4, the stirring head 2, the stirring pin 3, and the rotatable shoulder 5 are coaxial. The first driving motor Ⅰ1 drives the stirring head 2 to move downward through the hydraulic telescopic system 4. The rotatable shoulder 5 and the second driving motor Ⅱ7 are connected by the transmission belt 6. The stirring head 2 and the rotatable shoulder 5 rotate under the drive of the second driving motor Ⅱ7, and at the same time, the second driving motor Ⅱ7 applies a downward pressure to the stirring head 2.

[0009] The surface roughness of the lower surface of the rotatable shoulder 5 is Ra50 - 100.

[0010] A method for processing an aircraft landing gear using the rotatable telescopic friction stir processing head, characterized by the following steps:

[0011] Step 1: The rotatable shoulder 5 of the rotatable telescopic friction stir processing head is located directly above the surface of the aircraft landing gear to be processed, and the rotatable shoulder 5 is in contact with the surface of the aircraft landing gear to be processed;

[0012] Step 2: For different thicknesses at different processing positions of the aircraft landing gear, the stirring pin 3 extends by the required length and inserts into the surface and subsurface of the aircraft landing gear;

[0013] Start the first driving motor I1, so that the stirring pin 3 rotates at a high speed under the action of the first driving motor I1, stirs the columnar crystals after additive manufacturing, and realizes the grain refinement of the surface and subsurface;

[0014] At the same time, start the second driving motor II7, the transmission belt 6 drives the rotatable shoulder 5 to rotate, and at the same time provides the downward pressure F of the shoulder 5, realizes the material removal of the relatively rough surface after additive manufacturing, while the stirring pin 3 realizes grain refinement, reduces its surface roughness, and improves the surface quality.

[0015] The angular velocity ω of the rotatable shoulder 5 2 = kω 1 {1 / [(φ 2 / φ 1 ) 2 -1]}, where: φ 1 , φ 2 are the diameters of the stirring head and the shoulder respectively, ω 1 is the angular velocity of the stirring head, and k is a balance constant.

[0016] The downward pressure of the rotatable shoulder 5 determines the realization of grain refinement of the surface and subsurface, where: the F of aluminum alloy 0 is denoted as the reference downward pressure, the tensile strength of aluminum alloy is denoted as σ 0 , and the tensile strength of the target metal is denoted as σ.

[0017] The rotational speed of the stirring head is 200 - 300 r / min.

[0018] The downward pressure of the rotatable shoulder 5 on the processing surface is 20 - 50 N.

[0019] When the angular velocity is inversely proportional to its surface area, the optimal post-treatment shoulder surface is obtained at this time.

[0020] Beneficial effects

[0021] The present invention proposes a rotatable telescopic friction stir processing head and a processing method. The rotatable telescopic friction stir processing head mainly includes: a drive motor I, a stirring head, a stirring needle, a hydraulic telescopic system, a rotatable shaft shoulder, a transmission belt, a drive motor II, and a landing gear to be processed. Different motors are used to achieve differential adjustment of the rotation speed of the stirring needle and the rotatable shaft shoulder. The dual-rotatable telescopic friction stir processing head of the present invention can perform stirring processing on aircraft landing gear manufactured by laser additive manufacturing. While achieving adjustable surface and sub-surface organizational structures of additive manufacturing, it greatly improves the mechanical properties of the aircraft landing gear, reduces the surface roughness of the aircraft landing gear after additive manufacturing, improves the surface quality, and reduces the processing steps of additive manufacturing of aircraft landing gear.

[0022] Beneficial effects of the present invention:

[0023] 1. The metal surface treated by the stirring needle is post-processed by driving the shaft shoulder through the driving motor II. According to the different materials of the aircraft landing gear, different materials of the shaft shoulder are selected for post-processing. The downforce F of the aluminum alloy shaft shoulder is 0 As the benchmark, the tensile strength of aluminum alloy is recorded as σ 0 , the tensile strength of the target metal is denoted as σ, based on The optimal shoulder pressure F is obtained through specific calculation. The surface roughness can be greatly reduced and the surface quality can be improved.

[0024] 2 According to the different materials of aircraft landing gear, choose the mixing head of different materials and speed. At the same time, set the angular velocity inversely proportional to its surface area. In this case, the optimal post-processing shoulder surface is obtained. Assume that φ 1 ,φ 2 are the diameters of the stirring head and the shoulder, respectively, and the angular velocity of the shoulder 5 is ω 2 , the angular velocity of the stirring head is ω 1 , according to ω 2 =kω 1 {1 / [(φ 2 / φ 1 ) 2 -1]}k is the equilibrium constant to calculate the optimal angular velocity of the shoulder post-processing surface. Combined with the adjustable pressure F of the shoulder, the organizational structure of the material to be processed can be adjusted while ensuring the surface quality, and the comprehensive mechanical properties of the material can be regulated.

[0025] 3 Use a stirring needle with adjustable extension length to process the aircraft landing gear after additive manufacturing. The extension length of the stirring needle can be adjusted according to the thickness changes at different positions of the landing gear to process the landing gear, thereby improving the processing efficiency and the dimensional accuracy of the landing gear processing surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A cross-sectional view of the processing head of the present invention

[0027] Figure 2 For the lower surface of the spindle shoulder of the processing head of the present invention

[0028] Figure 3 For the connection relationship between the second drive motor II and the stirring head in the present invention

[0029] In the figure: 1 - the first drive motor I, 2 - the stirring head, 3 - the stirring pin, 4 - the hydraulic telescopic system, 5 - the rotatable shoulder, 6 - the transmission belt, 7 - the second drive motor II. Specific embodiments

[0030] The present invention will be further described below in conjunction with embodiments and the accompanying drawings:

[0031] This embodiment provides a double-rotating telescopic friction stir processing head for an aircraft landing gear, which is characterized by mainly including: a drive motor I 1, a stirring head 2, a stirring pin 3, a hydraulic telescopic system 4, a rotatable shoulder 5, a transmission belt 6, and a drive motor II 7. The hydraulic telescopic system 4 is connected to the stirring pin 3; the drive motor I 1, the stirring head 2, the stirring pin 3, and the rotatable shoulder 5 are coaxial with each other and are located directly above the surface of the landing gear to be processed; the rotatable shoulder 5 and the drive motor II 7 are connected by the transmission belt 6, and the stirring head 2 and the rotatable shoulder 5 rotate respectively under the drive of the drive motor I 1 and the drive motor II 7. It is characterized in that: the stirring pin 3 adjusts the protruding length through the hydraulic telescopic system 4, aiming at different thicknesses of different processing positions of the aircraft landing gear, the stirring pin 3 protrudes different lengths and inserts into the surface and subsurface of the aircraft landing gear. The stirring pin 3 rotates at a high speed under the action of the drive motor I 1 to stir the columnar crystals after additive manufacturing, realizing grain refinement of the surface and subsurface. At the same time, the shoulder 5 contacts the surface of the aircraft landing gear to be processed, is connected to the transmission belt 6, and rotates under the action of the drive motor II 7, realizing material removal of the relatively rough surface after additive manufacturing. While the stirring pin 3 realizes grain refinement, it reduces its surface roughness and improves the surface quality. It is characterized in that the angular velocity ω of the shoulder 5 2 can be calculated according to the angular velocity ω of the stirring head 1 ω 2 = kω 1 {1 / [(φ 2 / φ 1 ) 2 -1]}φ 1 where φ 2 are the diameters of the stirring head and the shoulder respectively, and k is a balance constant. When the angular velocity is inversely proportional to its surface area, the optimal post-treatment shoulder surface is obtained at this time. Among them, the downward pressure F of the shoulder 5 is changed under the action of the drive motor II 7, so as to better realize grain refinement of the surface and subsurface according to different surface materials, and can be calculated by where F for aluminum alloy is calculated0 Denoted as the reference downward pressure, the tensile strength of the aluminum alloy is denoted as σ 0 , and the tensile strength of the target metal is denoted as σ.

[0032] The depth of the columnar crystal refinement layer of the aircraft landing gear is determined by the depth at which the stirring pin 3 is inserted. The depth range is 3 - 6 mm, and the downward pressure is 40 - 80 N.

[0033] The friction stir processing parameters are that the rotation speed of the stirring head is 200 - 300 r / min, and the downward pressure of the shoulder 5 on the processing surface is 20 - 50 N.

[0034] The hydraulic telescopic system 4 is connected to the stirring pin 3, and the length L of the stirring pin deep inside is controlled by the telescopic movement of the hydraulic system.

[0035] The rotatable shoulder 5 is connected to the transmission belt 6 and the driving motor II 7, and rotates under the drive of the driving motor 7.

[0036] The roughness of the lower surface of the shoulder is Ra50 - 100.

[0037] Processing Example 1

[0038] In this embodiment, the material of the additively manufactured engine landing gear to be processed is A100 high-strength steel, and it is processed and strengthened using the stirring head designed by the present invention.

[0039] Before the friction stir processing, the stirring pin rotates driven by the driving motor I and inserts into the additively manufactured component. When the stirring pin is completely inserted into the additively manufactured component, the shoulder contacts the upper surface of the component. At the same time, the driving motor 2 starts to work, and the rotation directions of the stirring head and the shoulder are opposite.

[0040] During the stirring process, the stirring pin changes the length of the stirring pin extending out according to the thickness change of the aircraft landing gear under the control of the hydraulic control system. The depth range of the stirring pin inserted is 3 - 6 mm.

[0041] The technical parameters selected for the friction stir processing are: the depth limit range of the stirring pin inserted is 3 - 6 mm. The rotation speed of the stirring head is 250 r / min, the downward pressure of the shoulder on the processing surface is 40 N, the rotation speed of the shoulder is 150 r / min, and the parameter of the roughness of the lower surface of the shoulder is Ra 7.

[0042] After the entire stirring processing head is completely inserted into the component, it makes a feeding movement driven by the processing spindle to complete the post-treatment strengthening of the entire aircraft landing gear.

[0043] At the same time, the surface roughness and tensile properties of the components processed by the stirring head of the present invention are tested, and the obtained surface roughness and tensile strength results are shown in Table 1.

[0044] Processing Example 2

[0045] In this embodiment, the material of the additively manufactured engine landing gear to be processed is A100 high-strength steel, and it is processed and strengthened using a traditional stirring head.

[0046] Before friction stir processing, the stirring pin rotates driven by drive motor I and inserts into the additively manufactured component. The depth range of the stirring pin insertion is 4 mm.

[0047] The technical parameters selected for friction stir processing are as follows: the depth of the stirring pin insertion is 4 mm, the rotational speed of the stirring head is 250 r / min, and the downward pressure of the shoulder on the processing surface is 40 N.

[0048] After the entire friction stir processing head is fully inserted into the component, it makes a feeding motion driven by the processing spindle to complete the post-processing strengthening of the entire aircraft landing gear.

[0049] At the same time, the surface roughness and tensile properties of the components processed by the traditional stirring head are tested. The obtained surface roughness and tensile strength results are shown in Table 1.

[0050]

[0051] Table 1

[0052] In view of the deficiencies in the prior art, the present invention provides a double-rotating telescopic friction stir processing head for aircraft landing gears. Through the coordinated operation of the telescoping of the stirring pin and the rotation of the shoulder of the friction stir head, it effectively solves the problem of difficult control of columnar crystals in additively manufactured aircraft landing gears, effectively improves the surface quality of the components after friction stir processing, and realizes high-performance and high-efficiency processing of aircraft landing gears.

Claims

1. A method for processing an aircraft landing gear using a rotatable telescopic friction stir processing head. The rotatable telescopic friction stir processing head includes a first driving motor I (1), a stirring head (2), a stirring pin (3), a hydraulic telescopic system (4), a rotatable shoulder (5), a transmission belt (6), and a second driving motor II (7). The first driving motor I (1) is connected to the stirring pin (3) inside the stirring head (2) through the hydraulic telescopic system (4). The hydraulic telescopic system (4) and the stirring pin (3) are located inside the rotatable shoulder (5), and the first driving motor I (1), the hydraulic telescopic system (4), the stirring head (2), the stirring pin (3), and the rotatable shoulder (5) are coaxial. The first driving motor I (1) drives the stirring head (2) to move downward through the hydraulic telescopic system (4). The rotatable shoulder (5) and the second driving motor II (7) are connected by the transmission belt (6). The stirring head (2) and the rotatable shoulder (5) rotate under the drive of the second driving motor II (7), and at the same time, the second driving motor II (7) applies a downward pressure to the stirring head (2). It is characterized in that: The method steps are as follows: Step 1: The rotatable shoulder (5) of the rotatable telescopic friction stir processing head is located directly above the surface of the aircraft landing gear to be processed, and the rotatable shoulder (5) is in contact with the surface of the aircraft landing gear to be processed. Step 2: According to the different thicknesses of different processing positions of the aircraft landing gear, the stirring pin (3) extends to the required length and inserts into the surface and subsurface of the aircraft landing gear. Start the first driving motor I (1) to make the stirring pin (3) rotate at a high speed under the action of the first driving motor I (1), stir the columnar crystals after additive manufacturing, and realize the grain refinement of the surface and subsurface. Meanwhile, start the second driving motor II(7), and the transmission belt(6) drives the rotatable shoulder(5) to rotate. At the same time, provide the downward pressure F of the shoulder(5) to remove the material on the relatively rough surface after additive manufacturing. While the stirring pin(3) realizes grain refinement, reduce its surface roughness and improve the surface quality; the angular velocity of the rotatable shoulder(5) Where: are the diameters of the stirring head and the shoulder respectively, ω 1 is the angular velocity of the stirring head, and k is the equilibrium constant.

2. According to the method described in claim 1, It is characterized in that: The roughness of the lower surface of the rotatable shoulder (5) is Ra50 - 100.

3. According to the method described in claim 1, It is characterized in that: The downward pressure of the rotatable shoulder (5) determines the realization of grain refinement on the surface and subsurface, where: F of the aluminum alloy 0 is denoted as the reference downward pressure, and the tensile strength of the aluminum alloy is denoted as σ 0 , and the tensile strength of the target metal is denoted as σ.

4. According to the method described in claim 1, It is characterized in that: The rotation speed of the stirring head is 200 - 300 r / min.

5. According to the method described in claim 1, It is characterized in that: The downward pressure of the rotatable shoulder (5) on the processing surface is 20 - 50 N.

6. According to the method described in claim 1, It is characterized in that: When the angular velocity is inversely proportional to its surface area, the optimal post - processed shoulder surface is obtained at this time.

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