Friction welding method and system for launch vehicle body substructure

Abstract

The present invention provides a friction welding method and system for a secondary structure of a launch vehicle body, comprising the following steps: step S1: scanning the surface of the main structure of the body and the initial position of the secondary structure by a measuring system to obtain the installation position coordinates of the secondary structure; step S2: comparing the installation position coordinates of the secondary structure with its initial position coordinates to obtain the adjustment amount of the position and attitude of the secondary structure; step S3: adjusting the position and attitude of the secondary structure according to the adjustment amount of the position and attitude so that the secondary structure is located at the initial welding position; step S4: rotating the secondary structure at a set speed, and feeding along the rotation axis at a set axial feed speed to perform welding. The present invention converts the welding form of the secondary structure and the main structure from a fillet or lap weld to a plane butt weld, and optimizes the traditional fusion welding process to a friction welding process, effectively solving the problems of low fusion welding strength and large welding deformation.

Description

Technical Field

[0001] The invention relates to the field of friction welding, and in particular to a method and system for friction welding of a launch vehicle body substructure. Background Art

[0002] The rocket body structure is the base of the launch vehicle. It is used to maintain the shape of the rocket, store propellants, withstand various loads acting on the rocket during ground operations and flight, install all instruments, equipment and power devices connecting the various systems of the rocket, and connect all systems and components on the rocket into a whole. Among them, the propellant tank accounts for a large proportion of the total weight of the rocket and has complex load-bearing capacity. It is the most important main structure of the rocket body. Anti-sway, anti-vortex, cables, ducts, instruments, equipment, sensors and other propulsion system and flight control system parts or equipment will be installed on the tank, mainly through angle pieces, brackets, racks and other secondary structures installed on the main structure of the tank.

[0003] At present, the secondary structures of the tank, such as corner pieces, brackets, and racks, are generally connected to the main structure of the tank by manual TIG welding or resistance spot welding, and the connection form is corner joint or overlap. Both manual TIG welding and resistance spot welding are welding methods based on material melting. Melting occurs during the welding process, the welding peak temperature is high, the heat input is large, and metallurgical defects are prone to occur. There are problems such as large residual stress and deformation after welding, and the performance of the main structure parent material is significantly reduced. It is difficult to meet the welding needs of dissimilar aluminum alloys. The friction spot welding method can also be applied to the welding of launch vehicle secondary structures, and the connection form is overlap. The friction spot welding process is a solid-phase connection method with low welding temperature and high weld strength. Because the welding tool needs to pierce the secondary structure parent material and weld it to the main structure during the friction spot welding process, the maximum welding thickness is generally around 5mm. Some secondary structures with larger thickness and irregular shapes cannot be welded, and the welding application range is small.

[0004] The patent document with the publication number CN104718046A discloses a rotary tool for stir friction spot welding and a stir friction spot welding method using the rotary tool. In the rotary tool for stir friction spot welding the overlapping parts of aluminum materials, the probe arranged in a coaxially protruding manner at the top center of the cylindrical tool body is composed of a stepped structure including a coaxially protruding middle probe and a center probe, and the top surface of the tool body is constituted as a first shoulder surface, which is gradually concave toward the radial inside and connected to the base of the middle probe, and the top surface of the middle probe is constituted as a second shoulder surface, which is gradually concave toward the radial inside and connected to the base of the center probe. However, there is still a defect that some secondary structures with large thickness and irregular shape cannot be welded. Summary of the invention

[0005] In view of the defects in the prior art, the object of the present invention is to provide a method and system for friction welding of a launch vehicle body substructure.

[0006] According to a friction welding method for a launch vehicle body substructure provided by the present invention, the body main structure is fixed on an inner lining plate; the inner lining plate is located below the body main structure, and the inner lining plate is rigidly connected to the body main structure;

[0007] The secondary structure has rotational and axial freedom. The measuring system is installed above the main structure of the rocket body, and the measuring system and the secondary structure are installed on the same side of the main structure of the rocket body.

[0008] The specific steps include:

[0009] Step S1: Scan the surface of the main structure of the rocket body and the initial position of the secondary structure through the measurement system to obtain the position and posture information of the main structure of the rocket body, and compare it with the rocket body model to obtain the installation position coordinates of the secondary structure;

[0010] Step S2: Compare the installation position coordinates of the secondary structure with its initial position coordinates to obtain the adjustment amount of the position and posture of the secondary structure;

[0011] Step S3: adjusting the position and posture of the secondary structure according to the adjustment amount of the position and posture, and adjusting the rotation axis of the secondary structure to coincide with the normal line of the installation position coordinates, so that the axial distance between the end face of the secondary structure and the surface of the main structure of the rocket body is greater than or equal to 5 mm, and the secondary structure is located at the initial welding position;

[0012] Step S4: The secondary structure is rotated at a set rotation speed and fed along the rotation axis at a set axial feed speed for welding. The entire welding process is divided into four stages, and each stage adopts a different control method for welding.

[0013] Preferably, the stage from when the secondary structure is located at the initial welding position to when the secondary structure just contacts the surface of the main structure of the rocket body is the first stage, and the axial feed speed is recorded as V1. This stage adopts a constant speed control mode, and the axial feed speed of the secondary structure remains unchanged;

[0014] From the time when the secondary structure just contacts the surface of the main structure of the rocket body to the time when the pressure value reaches the preset pressure value is stage II, the axial feed speed is recorded as V2, and this stage adopts a constant speed control method, V2=(20%~40%)*V1, and the axial feed speed of the secondary structure remains unchanged; the pressure value is measured by the force measuring element on the inner liner plate;

[0015] The period from when the pressure value reaches the preset pressure value to when the secondary structure reaches the set axial movement amount is the third stage, in which a constant pressure control method is adopted to keep the pressure value measured by the force measuring element unchanged; the movement amount is obtained by collecting the position of the secondary structure in real time by the measuring system;

[0016] After the secondary structure reaches the set movement amount, the secondary structure adopts the emergency stop method. After the pressure maintains the set value for 2s to 3s, the axial pressure is released and the welding is completed. This is the fourth stage.

[0017] Preferably, during the welding process, the temperature measuring element on the inner lining plate monitors the bottom temperature of the main structure of the rocket body in real time. When the temperature exceeds the set value, the temperature measuring element controls the temperature by adjusting the flow of cooling gas or cooling liquid.

[0018] Preferably, after welding is completed, the measurement system scans the welding position of the secondary structure and compares it with the rocket body model to obtain the assembly accuracy of the secondary structure after welding.

[0019] Preferably, the size of the inner lining plate is larger than the contact area between the main structure of the arrow body and the secondary structure;

[0020] The inner liner plate is provided with a cooling groove inside, and the bottom of the main structure of the rocket body is cooled by cooling gas or cooling liquid;

[0021] The inner lining plate is provided with a temperature measuring element and a force measuring element to monitor the changes in temperature and pressure during the welding process.

[0022] Preferably, the friction end surface of the secondary structure is a curved surface structure with a convex middle and concave surroundings;

[0023] The middle raised area is 1mm to 2mm higher than the end surface, and a groove is arranged on the surface of the middle raised area. The groove is in the form of an involute or a concentric ring, and the depth of the groove is 0.5mm to 1mm.

[0024] Preferably, the measuring system obtains the position coordinates of the installation and movement of the secondary structure by measuring the surface of the main structure of the rocket body;

[0025] The measurement system calculates the installation position coordinates of the secondary structure on the main structure of the rocket body, the welding posture adjustment amount and the axial feed amount of the secondary structure based on the measured position coordinates of the main structure of the rocket body and the position coordinates of the secondary structure in combination with the rocket body model, and obtains the relative position information of the secondary structure and the main structure of the rocket body.

[0026] Preferably, the secondary structure is a regular body of revolution or an irregular shaped structure;

[0027] When the secondary structure is a regular body of revolution, the secondary structure is a solid bar or a hollow tube;

[0028] When the secondary structure is a hollow tube, cooling gas is introduced through the central cavity of the hollow tube during welding to cool the weld area;

[0029] The main structure of the arrow body and the secondary structure are made of the same material or different materials.

[0030] Preferably, the rotation axis of the secondary structure is perpendicular to the surface to be welded of the main structure of the rocket body, and passes through the center of mass of the contact area between the main structure of the rocket body and the secondary structure;

[0031] The axial feed direction of the secondary structure coincides with its rotation axis;

[0032] The initial contact position between the secondary structure and the main structure of the arrow body is set as the axial movement zero point, and the preset axial movement amount of the secondary structure is the depth of the end face groove plus 0.2mm to 0.5mm.

[0033] The present invention also provides a friction welding system for a launch vehicle body substructure, wherein the body main structure is fixed on an inner lining plate; the inner lining plate is located below the body main structure, and the inner lining plate is rigidly connected to the body main structure;

[0034] The secondary structure has rotational and axial freedom. The measuring system is installed above the main structure of the rocket body, and the measuring system and the secondary structure are installed on the same side of the main structure of the rocket body.

[0035] The modules include:

[0036] Module M1: Scan the surface of the main structure of the rocket body and the initial position of the secondary structure through the measurement system to obtain the position and attitude information of the main structure of the rocket body, and compare it with the rocket body model to obtain the installation position coordinates of the secondary structure;

[0037] Module M2: Compare the installation position coordinates of the secondary structure with its initial position coordinates to obtain the adjustment amount of the position and posture of the secondary structure;

[0038] Module M3: According to the adjustment amount of the position and attitude, the position and attitude of the secondary structure are adjusted, and the rotation axis of the secondary structure is adjusted to coincide with the normal of the installation position coordinates, so that the axial distance between the end face of the secondary structure and the surface of the main structure of the rocket body is greater than or equal to 5 mm, and the secondary structure is located in the initial welding position;

[0039] Module M4: The secondary structure is rotated at a set speed and fed along the axis of rotation at a set axial feed speed for welding. The entire welding process is divided into four stages, and different control methods are used for welding in each stage.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] 1. The present invention transforms the welding form of the secondary structure and the main structure from fillet or lap weld to flat butt weld, and optimizes the traditional fusion welding process to friction welding process, which effectively solves the problems of low fusion welding strength and large welding deformation; and there is no need to perform special treatment on the welding flash after welding, and there is no special requirement for the secondary structure form, and the process has a wider range of adaptability.

[0042] 2. Compared with the existing fusion welding process, the present invention adopts friction welding to weld the main structure and the secondary structure of the rocket body. The welding heat input is low and the weld strength is high. It replaces the manual fusion welding process and is easy to realize automated welding.

[0043] 3. Compared with the friction spot welding technology, the present invention has no special requirements on the material thickness and structural form of the secondary structure, the process is easy to implement and the process has a wider range of adaptability.

[0044] 4. The secondary structure of the present invention adopts an end face structure with a convex middle and concave surroundings, which can seal the metal flash extruded during the welding process inside the end face of the secondary structure. There is no need for additional processing of the flash after welding, eliminating the weld flash processing process and reducing manufacturing costs.

[0045] 5. The secondary structure end face designed with a groove structure adopted in the present invention reduces the initial contact area. In the initial welding stage, the secondary structure is moved in a constant low-speed control mode, which reduces the pressure value in the initial welding stage and ensures a stable welding process.

[0046] 6. The inner lining plate of the present invention can realize real-time control of the bottom temperature of the main structure of the rocket body during the welding process, prevent the loss of parent material strength and excessive welding deformation caused by excessive welding temperature, and improve the comprehensive strength of the weld joint and the dimensional accuracy of the workpiece after welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0048] Figure 1 Schematic diagram of the friction welding method between the main structure and the secondary structure of the rocket body;

[0049] Figure 2 It is a schematic diagram of the end surface structure with a convex middle and concave surrounding of the secondary structure;

[0050] Figure 3 It is a schematic diagram of the friction welding process of the substructure;

[0051] Figure 4 It is a schematic diagram of friction welding of special-shaped substructures;

[0052] Figure 5 The present invention is a flow chart of the steps of the friction welding method for the substructure of the launch vehicle body.

[0053] The figure shows:

[0054] Secondary structure 1, main structure of rocket body 2, inner lining plate 3, measuring system 4, metal flash 5, temperature measuring element 6, force measuring element 7, cooling liquid 8, friction end face 9. DETAILED DESCRIPTION

[0055] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0056] Embodiment 1:

[0057] like Figure 1-Figure 5 As shown, the main structure 2 of the rocket body is fixed on the inner lining plate 3; the inner lining plate 3 is located below the main structure 2 of the rocket body, and the inner lining plate 3 is rigidly connected to the main structure 2 of the rocket body; the secondary structure 1 has rotational and axial freedom of movement; the measurement system is installed above the main structure 2 of the rocket body, and the measurement system 4 and the secondary structure 1 are installed on the same side of the main structure 2 of the rocket body. The size of the inner lining plate 3 is larger than the contact area between the main structure 2 of the rocket body and the secondary structure 1; a cooling groove is arranged inside the inner lining plate 3, and the bottom of the main structure 2 of the rocket body is cooled by cooling gas or cooling liquid; a temperature measuring element and a force measuring element are arranged inside the inner lining plate 3 to monitor the changes in temperature and pressure during the welding process.

[0058] The friction end face of the secondary structure 1 is a curved surface structure with a convex middle and concave surroundings; the middle convex area is 1mm to 2mm higher than the end face, and a groove is arranged on the surface of the middle convex area. The groove is in the form of an involute or a concentric ring, and the depth of the groove is 0.5mm to 1mm.

[0059] This embodiment provides a method for friction welding a launch vehicle body substructure, comprising the following steps:

[0060] Step S1: Scan the surface of the rocket body main structure 2 and the initial position of the secondary structure 1 through the measurement system 4 to obtain the position and posture information of the rocket body main structure 2, and compare it with the rocket body model to obtain the installation position coordinates of the secondary structure 1;

[0061] Step S2: Compare the installation position coordinates of the secondary structure 1 with its initial position coordinates to obtain the adjustment amount of the position and posture of the secondary structure 1;

[0062] Step S3: According to the adjustment amount of the position and posture, the position and posture of the secondary structure 1 are adjusted, and the rotation axis of the secondary structure 1 is adjusted to coincide with the normal line of the installation position coordinate, so that the axial distance between the end face of the secondary structure 1 and the surface of the main structure 2 of the rocket body is greater than or equal to 5 mm, so that the secondary structure 1 is located at the initial welding position;

[0063] Step S4: rotating the secondary structure 1 at a set rotation speed and feeding along the rotation axis at a set axial feed speed for welding. The entire welding process is divided into four stages, and each stage adopts a different control method for welding.

[0064] From the time when the secondary structure 1 is located at the initial welding position to the time when the secondary structure 1 just contacts the surface of the main structure 2 of the rocket body is the first stage, and the axial feed speed is recorded as V1. This stage adopts a constant speed control mode, and the axial feed speed of the secondary structure 1 remains unchanged;

[0065] From the time when the secondary structure 1 just contacts the surface of the main structure 2 of the rocket body to the time when the pressure value reaches the preset pressure value is the second stage, the axial feed speed is recorded as V2, and the constant speed control method is adopted in this stage, V2=20%~40%*V1, and the axial feed speed of the secondary structure 1 remains unchanged; the pressure value is measured by the force measuring element on the inner lining plate 3;

[0066] From the time when the pressure value reaches the preset pressure value to the time when the secondary structure 1 reaches the set axial movement amount is the third stage, in which a constant pressure control method is adopted to keep the pressure value measured by the force measuring element unchanged; the movement amount is obtained by real-time acquisition of the position of the secondary structure 1 by the measuring system;

[0067] After the secondary structure 1 reaches the set movement amount, the secondary structure 1 adopts the emergency stop method. After the pressure maintains the set value for 2s to 3s, the axial pressure is released and the welding is completed. This is the fourth stage.

[0068] During the welding process, the temperature measuring element on the inner lining plate 3 monitors the bottom temperature of the main structure 2 of the rocket body in real time. When the temperature exceeds the set value, the temperature measuring element controls the temperature by adjusting the flow of cooling gas or cooling liquid. After welding, the measurement system 4 scans the welding position of the secondary structure 1 and compares it with the rocket body model to obtain the assembly accuracy of the secondary structure 1 after welding.

[0069] The measuring system 4 obtains the installation and movement position coordinates of the secondary structure 1 by measuring the surface of the main structure 2 of the rocket body; the measuring system 4 calculates the installation position coordinates of the secondary structure 1 on the main structure 2 of the rocket body, the welding posture adjustment amount and the axial feed amount of the secondary structure 1 based on the measured position coordinates of the main structure 2 of the rocket body and the position coordinates of the secondary structure 1, and combines the rocket body model to obtain the relative position information of the secondary structure 1 and the main structure 2 of the rocket body.

[0070] The secondary structure 1 is a regular body of revolution or an irregular shaped structure; when the secondary structure 1 is a regular body of revolution, the secondary structure 1 is a solid bar or a hollow tube; when the secondary structure 1 is a hollow tube, cooling gas is introduced through the central cavity of the hollow tube during welding to cool the weld area; the main structure 2 of the rocket body and the secondary structure 1 are the same material or different materials.

[0071] The rotation axis of the secondary structure 1 is perpendicular to the surface to be welded of the main structure 2 of the rocket body, and passes through the center of mass of the contact area between the main structure 2 of the rocket body and the secondary structure 1; the axial feed direction of the secondary structure 1 coincides with its rotation axis; the initial contact position of the secondary structure 1 and the main structure 2 of the rocket body is set as the axial movement zero point, and the preset axial movement amount of the secondary structure 1 is the end face groove depth plus 0.2mm~0.5mm.

[0072] The present invention also provides a launch vehicle body substructure friction welding system, which can be realized by executing the process steps of the launch vehicle body substructure friction welding method, that is, those skilled in the art can understand the launch vehicle body substructure friction welding method as a preferred implementation of the launch vehicle body substructure friction welding system.

[0073] Embodiment 2:

[0074] This embodiment provides a friction welding system for a launch vehicle body substructure, wherein a body main structure 2 is fixed on an inner lining plate 3; the inner lining plate 3 is located below the body main structure 2, and the inner lining plate 3 is rigidly connected to the body main structure 2;

[0075] The secondary structure 1 has rotational and axial freedom. The measuring system is installed above the main structure 2 of the rocket body, and the measuring system 4 and the secondary structure 1 are installed on the same side of the main structure 2 of the rocket body.

[0076] The modules include:

[0077] Module M1: Scan the surface of the rocket body main structure 2 and the initial position of the secondary structure 1 through the measurement system 4 to obtain the position and posture information of the rocket body main structure 2, and compare it with the rocket body model to obtain the installation position coordinates of the secondary structure 1;

[0078] Module M2: Compare the installation position coordinates of the secondary structure 1 with its initial position coordinates to obtain the adjustment amount of the position and posture of the secondary structure 1;

[0079] Module M3: According to the adjustment amount of the position and attitude, the position and attitude of the secondary structure 1 are adjusted, and the rotation axis of the secondary structure 1 is adjusted to coincide with the normal of the installation position coordinates, so that the axial distance between the end face of the secondary structure 1 and the surface of the main structure 2 of the rocket body is greater than or equal to 5 mm, so that the secondary structure 1 is located in the initial welding position;

[0080] Module M4: The secondary structure 1 is rotated at a set speed and fed along the rotation axis at a set axial feed speed for welding. The entire welding process is divided into four stages, and each stage adopts a different control method for welding.

[0081] Embodiment 3:

[0082] Those skilled in the art may understand this embodiment as a more specific description of Embodiment 1 and Embodiment 2.

[0083] The present embodiment provides a friction welding method for a launch vehicle rocket body substructure, comprising: a rocket body main structure, a substructure, an inner lining plate, and a measuring system, wherein the measuring system is installed above the rocket body main structure, and obtains coordinate information of the installation and movement of the substructure by measuring the surface of the rocket body main structure; the substructure and the measuring system are installed on the same side, and have rotational and axial freedom of movement; the inner lining plate is fixed below the rocket body main structure and is rigidly connected to the rocket body main structure.

[0084] The secondary structure friction end face is a curved surface structure with a convex middle and concave surroundings. The raised middle area is 1mm to 2mm higher than the end face. A groove is designed on the surface of the raised middle area. The groove is in the form of an involute or concentric ring, and the depth of the groove is 0.5mm to 1mm.

[0085] The size of the inner lining plate is larger than the contact area between the main structure and the secondary structure of the rocket body; a cooling groove is designed inside the inner lining plate to cool the bottom of the main structure of the rocket body by cooling gas or cooling liquid; a temperature measuring element and a force measuring element are installed inside the inner lining plate to monitor changes in temperature and pressure during the welding process.

[0086] The measuring system can simultaneously measure the relative positions of the main structure and the secondary structure of the rocket body, and can calculate the installation position of the secondary structure on the main structure of the rocket body, the welding posture adjustment amount and the axial feed amount of the secondary structure according to the rocket body drawing or model, and obtain the initial relative position information of the secondary structure and the main structure.

[0087] The welding process includes the following steps:

[0088] Step 1: The measurement system scans the surface of the main structure of the rocket body and the initial position of the secondary structure to obtain the position and posture information of the main structure of the rocket body, and compares it with the rocket body design drawing to obtain the installation position coordinates of the secondary structure; the installation position coordinates of the secondary structure are compared with the initial position coordinates to obtain the adjustment amount of the position and posture of the secondary structure; the rotation axis of the secondary structure is adjusted to coincide with the normal of the installation position coordinates, and the axial distance between the end face of the secondary structure and the surface of the main structure of the rocket body is not less than 5 mm, so as to obtain the initial welding position of the secondary structure.

[0089] Step 2: The secondary structure rotates according to the set value. From the initial welding position of the secondary structure to the surface of the main structure of the rocket body is the first stage, the speed is set to V1, and the constant speed control method is adopted in this stage; from the surface to the set pressure value is the second stage, the speed is recorded as V2, and the constant speed control method is adopted in this stage, V2=(20%~40%)*V1; from the secondary structure just reaching the set pressure value to reaching the set axial movement is the third stage, and the constant pressure control method is adopted in this stage: after the secondary structure reaches the set movement, the secondary structure adopts the emergency stop method, the pressure is maintained at the set value for 2s~3s, and the axial pressure is removed to complete the welding, which is the fourth stage. The pressure value is measured by the force measuring element on the inner liner plate, and the movement amount is obtained by real-time acquisition of the secondary structure position by the measurement system.

[0090] Step 3: During the welding process, the temperature measuring element on the inner lining plate monitors the temperature at the bottom of the main structure of the rocket body in real time. When the temperature exceeds the set value, the temperature measuring element controls the temperature by adjusting the flow of cooling gas or cooling liquid.

[0091] Step 4: After welding, the measurement system scans the secondary structure welding position and compares it with the rocket body drawing to obtain the assembly accuracy of the secondary structure after welding.

[0092] The secondary structure can be a regular body of revolution or an irregular shaped structure; the secondary structure and the main structure of the arrow body can be made of the same material or different materials.

[0093] During welding, the measurement system obtains the relative position information of the main structure and secondary structure of the rocket body, and adjusts to the initial welding position. The welding process is divided into four stages, and different control modes are used for welding in each stage.

[0094] In this embodiment, the welding form of the secondary structure and the main structure is transformed from a fillet or lap weld to a flat butt weld, and the traditional fusion welding process is optimized to a friction welding process, which effectively solves the problems of low fusion welding strength and large welding deformation; and there is no need to perform special treatment on the welding flash after welding, and there are no special requirements for the secondary structure form, and the process has a wider range of adaptability.

[0095] Embodiment 4:

[0096] Those skilled in the art may understand this embodiment as a more specific description of Embodiment 1 and Embodiment 2.

[0097] The present embodiment provides a friction welding method for a launch vehicle rocket body substructure, comprising a rocket body main structure, a substructure, an inner lining plate, and a measuring system, wherein the measuring system is installed above the rocket body main structure, and obtains coordinate information of the installation and movement of the substructure by measuring the surface of the rocket body main structure; the substructure and the measuring system are installed on the same side, and have rotational and axial freedom of movement; the inner lining plate is fixed below the rocket body main structure and is rigidly connected to the rocket body main structure.

[0098] Furthermore, the secondary structure friction end surface is a curved surface structure with a convex middle and concave surroundings, and the convex middle area is 1mm to 2mm higher than the end surface. The convex middle area is the area actually involved in the interface friction, and the concave surrounding areas are used to accommodate the metal flash 5 extruded during the welding process. The outermost end surface does not participate in the friction, and is used to prevent the metal flash from overflowing the secondary structure end surface area.

[0099] Among them, the surface of the middle raised area is designed with a groove, which is in the form of an involute or concentric ring, and the depth of the groove is 0.5mm to 1mm. The function of the groove is to reduce the initial contact area, reduce the pressure value in the initial welding stage, and ensure the stability of the welding process; at the same time, the involute or concentric ring form can play the role of gathering the metal flash and prevent the extruded metal flash from moving disorderly.

[0100] Furthermore, the size of the inner lining plate is larger than the contact area between the main structure of the rocket body and the secondary structure; a cooling groove is designed inside the inner lining plate to cool the bottom of the main structure of the rocket body by cooling gas or cooling liquid; a temperature measuring element is installed inside the inner lining plate to monitor the temperature changes at the bottom of the main structure of the rocket body during the welding process in real time, and adjust the flow of cooling gas or liquid to control the temperature; a force measuring element is installed inside the inner lining plate to monitor the pressure value changes during the welding process in real time, and realize the control mode transition in different welding stages.

[0101] Furthermore, the measurement system can simultaneously measure the relative positions of the main structure and the secondary structure of the rocket body, and can calculate the installation position coordinates of the secondary structure on the main structure of the rocket body, the welding posture adjustment amount and the axial feed amount of the secondary structure according to the rocket body drawing or model, and obtain the initial relative position information of the secondary structure and the main structure.

[0102] Furthermore, the welding process of the present invention comprises the following steps:

[0103] Step 1: The measurement system scans the surface of the main structure of the rocket body and the initial position of the secondary structure to obtain the position and posture information of the main structure of the rocket body, and compares it with the rocket body design drawing to obtain the installation position coordinates of the secondary structure; the installation position coordinates of the secondary structure are compared with the initial position coordinates to obtain the adjustment amount of the position and posture of the secondary structure; the rotation axis of the secondary structure is adjusted to coincide with the normal of the installation position coordinates, and the axial distance between the end face of the secondary structure and the surface of the main structure of the rocket body is not less than 5 mm, so as to obtain the initial welding position of the secondary structure.

[0104] Step 2: The secondary structure rotates according to the set value. From the initial welding position of the secondary structure to the surface of the main structure of the rocket body is the first stage, and the speed is set to V1. This stage adopts a constant speed control method; from just touching the surface to the set pressure value is the second stage, and the speed is recorded as V2. This stage adopts a constant speed control method, V2=(20%~40%)*V1; from the secondary structure just reaching the set pressure value to reaching the set axial movement is the third stage, and this stage adopts a constant pressure control method; after the secondary structure reaches the set movement, the secondary structure adopts an emergency stop method, and the pressure is maintained at the set value for 2s~3s, and the axial pressure is removed to complete the welding, which is the fourth stage. The pressure value is measured by the force measuring element on the inner liner plate, and the movement amount is obtained by real-time acquisition of the secondary structure position by the measurement system.

[0105] Among them, the first stage is the no-load movement stage; when the secondary structure contacts the surface of the main structure of the rocket body and the force measuring element on the inner lining plate detects an increase in pressure value, the welding process enters the second stage, i.e. the initial welding stage. In this stage, a constant low-speed control method is used to move the secondary structure axially to avoid a sudden increase in pressure caused by excessive movement speed, which causes the axial movement direction to shift; as the secondary structure moves axially, the pressure value continues to increase. When the force measuring element on the inner lining plate detects that the pressure value increases to the set value, the welding process enters the third stage, i.e. the formal welding stage. In this stage, a constant pressure control method is used to move the secondary structure axially; the measurement system monitors the axial movement of the secondary structure in real time. When the secondary structure reaches the set movement amount, the secondary structure stops suddenly and the welding process enters the fourth stage, i.e. the pressure holding stage. After the pressure is maintained at the set value for 2s to 3s, the axial pressure is released to complete the welding.

[0106] Step 3: During the welding process, the temperature measuring element on the inner lining plate monitors the temperature at the bottom of the main structure of the rocket body in real time. When the temperature exceeds the set value, the temperature measuring element controls the temperature by adjusting the flow of cooling gas or cooling liquid.

[0107] Step 4: After welding, the measurement system scans the secondary structure welding position and compares it with the rocket body drawing to obtain the assembly accuracy of the secondary structure after welding.

[0108] Furthermore, the secondary structure of the present invention may be a regular body of revolution or an irregular shaped structure; the secondary structure and the main structure of the arrow body may be made of the same material or different materials.

[0109] The principle on which this embodiment is based is: by means of friction and extrusion between the end face of the secondary structure and the surface of the main structure of the rocket body, a metallurgical welding interface is formed on the surface of the main structure, thereby achieving connection between the secondary structure and the main structure of the rocket body.

[0110] The present embodiment provides a friction welding method for the secondary structure of a launch vehicle body, which converts the welding form of the secondary structure and the main structure from a fillet or lap weld to a flat butt weld, and optimizes the traditional fusion welding process to a friction welding process, effectively solving the problems of low fusion welding strength and large welding deformation. There is no need for special treatment of the welding flash after welding, and there are no special requirements for the secondary structure form, so the process has a wider range of adaptability.

[0111] Embodiment 5:

[0112] Those skilled in the art may understand this embodiment as a more specific description of Embodiment 1 and Embodiment 2.

[0113] Reference Figure 1 As shown, this embodiment provides a friction welding method for a launch vehicle rocket body substructure, which is mainly composed of a rocket body main structure 2, a substructure 1, an inner lining plate 3, and a measuring system 4. Among them, the measuring system 4 is installed above the rocket body main structure 2, and obtains the coordinate information of the installation and movement of the substructure 1 by measuring the surface of the rocket body main structure 2; the substructure 1 and the measuring system 4 are installed on the same side, and have rotational and axial freedom of movement, and the material of the substructure 1 is aluminum alloy; the inner lining plate 3 is fixed below the rocket body main structure 2, and is rigidly connected to the rocket body main structure 2, and the material of the rocket body main structure 2 is aluminum alloy, and the material of the inner lining plate 3 is high-strength steel.

[0114] Reference Figure 2 As shown, the friction end face of the secondary structure 1 is a curved surface structure with a convex middle and concave surroundings. The convex middle area is higher than the end face by a dimension of H=1.5mm. A groove is designed on the surface of the convex middle area. The groove is in the form of an involute and has a depth of 0.5mm.

[0115] Reference Figure 3 As shown, a cooling groove is designed inside the inner lining plate 3 to cool the bottom of the main structure 2 of the arrow body through a cooling liquid 8; a temperature measuring element 6 and a force measuring element 7 are installed inside the inner lining plate 3 to monitor the changes in temperature and pressure during the welding process.

[0116] The welding process of this embodiment includes the following steps:

[0117] Step 1: The measurement system 4 scans the surface of the main structure 2 of the rocket body and the initial position of the secondary structure 1 to obtain the position and posture information of the main structure 2 of the rocket body, and compares it with the rocket body design drawing to obtain the installation position coordinates of the secondary structure 1 on the surface of the main structure 2 of the rocket body; compare the installation position coordinates of the secondary structure 1 with the initial position coordinates to obtain the adjustment amount of the position and posture of the secondary structure 1; adjust the rotation axis of the secondary structure 1 to coincide with the normal of the installation position coordinates, and adjust the axial distance between the end face of the secondary structure 1 and the surface of the main structure of the rocket body to 10 mm to obtain the initial welding position of the secondary structure 1.

[0118] Step 2: The secondary structure 1 rotates at a set speed of 5000r / min, and the secondary structure 1 moves axially from the initial welding position to the surface of the main structure 2 of the rocket body at a set speed of 50mm / min. When the secondary structure 1 contacts the surface of the main structure 2 of the rocket body, and the force measuring element 7 on the inner lining plate 3 detects that the pressure value begins to increase, the movement speed of the secondary structure 1 is reduced to 10mm / min, and continues to move axially at this constant speed; as the axial movement increases, the pressure value gradually increases. When the axial pressure value reaches the set value of 20kN, the movement of the secondary structure 1 adopts a constant pressure control method, and the axial pressure value is kept constant by adjusting the movement speed of the secondary structure 1. When the actual compression of the secondary structure reaches 1.5mm, the secondary structure 1 stops suddenly, and the axial pressure of 20kN is maintained for 2s to 3s, and then the axial pressure is removed, and the welding is completed.

[0119] Step 3: During the entire welding process, the temperature measuring element 6 on the inner lining plate 3 monitors the bottom temperature of the main structure 2 of the rocket body in real time. When the temperature exceeds the set value of 100°C, the temperature measuring element 6 controls the temperature by increasing the flow rate of the cooling liquid 8.

[0120] Step 4: After welding is completed, the measurement system 4 scans the welding position of the secondary structure 1 and compares it with the rocket body drawing to obtain the assembly accuracy of the secondary structure 1 after welding.

[0121] The friction welding method for the secondary structure of the launch vehicle body provided in this embodiment can be an irregular shaped structure. Figure 4 As shown, it is mainly composed of a main structure 2 of the rocket body, a secondary structure 1, an inner lining plate 3, and a measuring system 4. When the secondary structure 1 is an irregular L-shaped angle piece structure, the rotation axis of the secondary structure 1 is perpendicular to the surface of the main structure 2 of the rocket body, and passes through the center of mass of the contact interface between the main structure 2 of the rocket body and the secondary structure 1; the friction end surface 9 of the secondary structure 1 is a structure in which the middle is convex and the surroundings are concave; during welding, the secondary structure 1 moves along the rotation axis toward the surface of the main structure 2 of the rocket body to form a connection interface.

[0122] The present invention transforms the welding form between the secondary structure and the main structure from a fillet or lap weld to a flat butt weld, and optimizes the traditional fusion welding process to a friction welding process, thereby effectively solving the problems of low fusion welding strength and large welding deformation.

[0123] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A friction welding method for a launch vehicle body substructure, characterized in that: The main structure of the arrow body (2) is fixed on the inner lining plate (3); the inner lining plate (3) is located below the main structure of the arrow body (2), and the inner lining plate (3) is rigidly connected to the main structure of the arrow body (2); The secondary structure (1) has rotational and axial freedoms; the measuring system is installed above the main structure (2) of the rocket body, and the measuring system (4) and the secondary structure (1) are installed on the same side of the main structure (2) of the rocket body; The specific steps include: Step S1: Scanning the surface of the main structure (2) of the rocket body and the initial position of the secondary structure (1) by means of a measurement system (4) to obtain position and attitude information of the main structure (2) of the rocket body, and comparing it with the rocket body model to obtain the installation position coordinates of the secondary structure (1); Step S2: Compare the installation position coordinates of the secondary structure (1) with its initial position coordinates to obtain the adjustment amount of the position and posture of the secondary structure (1); Step S3: adjusting the position and posture of the secondary structure (1) according to the adjustment amount of the position and posture, and adjusting the rotation axis of the secondary structure (1) to coincide with the normal of the installation position coordinates, so that the axial distance between the end face of the secondary structure (1) and the surface of the main structure (2) of the rocket body is greater than or equal to 5 mm, so that the secondary structure (1) is located at the initial welding position; Step S4: rotating the secondary structure (1) at a set rotation speed and feeding along the rotation axis at a set axial feed speed for welding. The entire welding process is divided into four stages, and each stage adopts a different control method for welding. The period from when the secondary structure (1) is located at the initial welding position to when the secondary structure (1) just contacts the surface of the main structure (2) of the rocket body is the first stage, and the axial feed speed is recorded as V1. In this stage, a constant speed control method is adopted, and the axial feed speed of the secondary structure (1) remains unchanged; The second stage is from the time when the secondary structure (1) just contacts the surface of the main structure (2) of the rocket body to the time when the pressure value reaches the preset pressure value. The axial feed speed is recorded as V2. This stage adopts a constant speed control method, V2=(20%-40%)*V1, and the axial feed speed of the secondary structure (1) remains unchanged. The pressure value is measured by the force measuring element on the inner lining plate (3); The third stage is from the pressure value reaching the preset pressure value to the secondary structure (1) reaching the set axial movement amount. In this stage, a constant pressure control method is adopted to keep the pressure value measured by the force measuring element unchanged. The movement amount is obtained by real-time acquisition of the position of the secondary structure (1) by the measuring system. After the secondary structure (1) reaches the set movement amount, the secondary structure (1) adopts the emergency stop method. After the pressure maintains the set value for 2s to 3s, the axial pressure is released and the welding is completed. This is the fourth stage.

2. The friction welding method for a launch vehicle body substructure according to claim 1, characterized in that: During the welding process, the temperature measuring element on the inner lining plate (3) monitors the bottom temperature of the main structure (2) of the rocket body in real time. When the temperature exceeds a set value, the temperature measuring element controls the temperature by adjusting the flow rate of cooling gas or cooling liquid.

3. The friction welding method for a launch vehicle body substructure according to claim 2, characterized in that: After welding is completed, the measurement system (4) scans the welding position of the secondary structure (1) and compares it with the rocket body model to obtain the assembly accuracy of the secondary structure (1) after welding.

4. The friction welding method for a launch vehicle body substructure according to claim 1, characterized in that: The size of the inner lining plate (3) is larger than the contact area between the main structure (2) of the arrow body and the secondary structure (1); The inner lining plate (3) is provided with a cooling groove inside, and the bottom of the main structure (2) of the arrow body is cooled by cooling gas or cooling liquid; A temperature measuring element and a force measuring element are arranged inside the inner lining plate (3) to monitor changes in temperature and pressure during the welding process.

5. The friction welding method for a launch vehicle body substructure according to claim 1, characterized in that: The friction end surface of the secondary structure (1) is a curved surface structure with a convex middle and concave surroundings; The middle raised area is 1mm to 2mm higher than the end surface, and a groove is arranged on the surface of the middle raised area. The groove is in the form of an involute or a concentric ring, and the depth of the groove is 0.5mm to 1mm.

6. The friction welding method for a launch vehicle body substructure according to claim 1, characterized in that: The measuring system (4) obtains the position coordinates of the installation and movement of the secondary structure (1) by measuring the surface of the main structure (2) of the rocket body; The measurement system (4) calculates the installation position coordinates of the secondary structure (1) on the main structure (2) of the rocket body, the welding posture adjustment amount and the axial feed amount of the secondary structure (1) based on the measured position coordinates of the main structure (2) of the rocket body and the position coordinates of the secondary structure (1), in combination with the rocket body model, and obtains the relative position information of the secondary structure (1) and the main structure (2) of the rocket body.

7. The friction welding method for a launch vehicle body substructure according to claim 1, characterized in that: The secondary structure (1) is a regular body of revolution or an irregular shaped structure; When the secondary structure (1) is a regular body of revolution, the secondary structure (1) is a solid rod or a hollow tube; When the secondary structure (1) is a hollow tube, cooling gas is introduced through the central cavity of the hollow tube during welding to cool the weld area; The arrow body main structure (2) and the secondary structure (1) are made of the same material or different materials.

8. The friction welding method for a launch vehicle body substructure according to claim 5, characterized in that: The rotation axis of the secondary structure (1) is perpendicular to the surface to be welded of the main structure (2) of the rocket body, and passes through the center of mass of the contact area between the main structure (2) of the rocket body and the secondary structure (1); The axial feed direction of the secondary structure (1) coincides with its rotation axis; The initial contact position between the secondary structure (1) and the main structure (2) of the arrow body is set as the zero point of axial movement, and the preset axial movement amount of the secondary structure (1) is the depth of the groove plus 0.2 mm to 0.5 mm.

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