Lightweight structure with cross-shaped ribs and brazing manufacturing method

Abstract

A lightweight structure with cross-shaped ribs and a brazing manufacturing method are disclosed, belonging to the field of aircraft manufacturing technology. The brazing manufacturing method includes the following steps: pre-welding processing of the skin and ribs, forming T-joints at both ends of the ribs; setting interlocking grooves in the cross-intersection area of ​​the ribs, and setting multiple bosses at intervals on both sides of the grooves; pre-welding trimming of the ribs; pre-welding cleaning; fixing the cross-shaped ribs; adding brazing filler metal to the cross-shaped ribs; adding brazing filler metal to the skin; fixing the skin and cross-shaped ribs; heating the workpiece to be welded to the brazing temperature T at a certain heating rate, holding at that temperature for a period of time, and then cooling it to a low temperature with the furnace before opening the furnace door. The vacuum degree during brazing is required to be less than 8 × 10⁻⁶. ‑3 Pa; The workpiece is removed from the furnace after cooling through the furnace door. The brazing manufacturing method of the present invention significantly increases the brazing area and improves the brazing strength by using a T-joint to weld with the skin. By setting a boss, the problem of brazing filler metal falling off or being lost is solved.

Description

Technical Field

[0001] This invention relates to the field of aircraft manufacturing technology, specifically to a lightweight structure with cross-shaped ribs and a brazing manufacturing method. Background Technology

[0002] Some aircraft components are made of multiple ribs arranged in a cross shape and skin on both sides of the ribs. These ribs are welded together to form a frame structure and are also welded to the skin as a whole. This structure is used for long periods in harsh environments such as high temperature and vibration, and requires high rigidity, high temperature resistance, and good resistance to vibration fatigue.

[0003] Cross-ribbed lightweight structures offer advantages such as high specific strength and high specific stiffness. However, for large-sized aircraft engine rear fuselage sidewall structures exceeding 1500mm×800mm×150mm, the following technical challenges still exist:

[0004] (1) The panel and the cross-shaped ribs are in the form of T-shaped brazing joints. The strength of the brazing joints is positively correlated with the welding area. The welding area mainly depends on the wall thickness of the cross-shaped ribs. The wall thickness of the sandwich structure is usually designed to be about 1.5 or 2 mm. Due to the large size of the parts, the ribs are in near line contact with the upper and lower panels during the welding process, which is not conducive to applying pressure during brazing. At the same time, the brazing interface area is small, resulting in low joint strength. If the wall thickness of the ribs is increased, the overall weight of the component will increase significantly.

[0005] (2) When the height of the cross-shaped rib exceeds 100mm, the amount of brazing filler metal added will directly affect the strength of the brazed joint. When the brazing filler metal is added in a conventional way, the brazing filler metal melts under the action of gravity at the brazing temperature. On the one hand, there is a risk of brazing filler metal falling off; on the other hand, brazing filler metal will be lost at the top of the sandwich structure, which will lead to the risk of unwelded defects. Brazing filler metal will accumulate at the bottom, which will cause the root joint to be brittle.

[0006] Chinese invention patent application CN120793134A discloses a grid-reinforced panel for aircraft structures, its molding die, and a method thereof. Specifically, the grid-reinforced panel includes a grid frame with a skin panel on the frame. The skin panel includes an outer skin on the bottom surface of the grid frame and an inner skin on the grid frame. The grid frame includes connected transverse and longitudinal core materials. The inner skin is located between the transverse and longitudinal core materials. The connection between the transverse and longitudinal core materials is called a connection node, and each connection node has a molding block. The molding block is a preform composed of carbon fiber and resin blocks, and includes vertically distributed reinforcing members. The reinforcing members include a top plate and a limiting block at the bottom of the top plate, forming slots for the transverse and longitudinal core materials to be inserted. The corner areas of the inner skin have slits. In this design, although the strength is improved by requiring both an outer and inner skin, the presence of the inner skin increases the structural weight.

[0007] Chinese utility model patent CN214190067U discloses a co-cured longitudinally and transversely reinforced composite integral wall panel. The integral wall panel includes a co-cured component and an inner edge of an L-shaped ordinary frame. The co-cured component is formed by co-curing a skin, a T-shaped stringer, and an outer edge of the T-shaped ordinary frame. The T-shaped stringer and the outer edge of the T-shaped ordinary frame are interlaced on the skin surface. The inner edge of the L-shaped ordinary frame is fixed to the outer edge of the T-shaped ordinary frame. This solution improves the integrity of the skin and the longitudinally and transversely reinforced composite material and reduces the structural weight. However, it requires the use of composite materials and is not suitable for applications where metal materials such as titanium alloys are used as stiffeners. Summary of the Invention

[0008] This invention provides a lightweight structure with cross-shaped ribs and a brazing manufacturing method, aiming to at least partially solve the above-mentioned technical problems.

[0009] As a first aspect of the present invention, a brazing manufacturing method for a cross-shaped lightweight rib structure is provided. The cross-shaped lightweight rib structure includes a plurality of ribs arranged in a cross shape, and skins located on both sides of the ribs. The brazing manufacturing method includes the following steps:

[0010] S1. Pre-welding processing of skin and cross-shaped ribs: The skin and ribs are pre-welded according to the part drawings. The ribs are made of plates with a wall thickness of more than 3 times the thickness of the steel plate. The two ends of the ribs are formed into T-joints by mechanical processing. The wall thickness of the ribs is d, and the brazing interface width of the T-joint is D≥2d. Interlocking grooves are set in the cross-shaped intersection area of ​​the ribs. The depth of the grooves is not less than half the height of the ribs. The tolerance of the groove depth on one side is 0-0.1mm. Multiple bosses are set at intervals on both sides of the grooves to prevent the brazing filler metal from falling off under gravity at the brazing temperature.

[0011] S2. Pre-welding preparation of stiffeners: Insert and pre-assemble the stiffeners into a cross structure;

[0012] S3. Pre-welding cleaning: Use cleaning equipment to remove oil and metal shavings from the surface of the skin and stiffener panels;

[0013] S4. Cross-shaped rib fixing: Use titanium alloy or stainless steel foil strips to spot weld and fix the cross-shaped connection area of ​​the ribs using a welding machine;

[0014] S5. Adding brazing filler metal to the cross-shaped joint area: Add powdered or paste-like brazing filler metal to the cross-shaped joint area;

[0015] S6. Adding brazing filler metal to the skin: Add amorphous foil brazing filler metal to the area of ​​the skin to be soldered;

[0016] S7. Fixing the skin and cross-shaped ribs: Use titanium alloy or stainless steel foil strips to spot weld the ribs and skin together using a welding machine.

[0017] S8. Brazing Assembly and Furnace Loading: The assembled workpieces to be brazed are heated to the brazing temperature T at a certain heating rate, held at this temperature for a period of time, and then cooled to a low temperature with the furnace before the furnace door is opened. The vacuum degree during brazing must be less than 8 × 10⁻⁶. - 3 Pa;

[0018] S9. Brazing and unloading: The workpiece is unloaded after the furnace door is opened and the workpiece has cooled down.

[0019] The flange thickness h of the T-joint is in the range of d / 2≤h≤d, where d is the wall thickness of the reinforcing bar.

[0020] The spacing between the bosses is 4 to 6 times the thickness of the bosses.

[0021] The T-joint and the connection between the joint and the reinforcing bar are rounded.

[0022] The boss is formed on the rib by machining.

[0023] The skin is made of 2mm thick TA15 sheet metal, and the ribs are made of 6mm thick TA15 sheet metal.

[0024] After the brazing process, the workpiece is subjected to ultrasonic non-destructive testing, and the brazing weld rate of the workpiece is greater than 95%.

[0025] The wall thickness tolerance of the rib is -0.05 to +0.05 mm.

[0026] The skin has a size greater than 1000×1000mm.

[0027] As a second aspect of the invention, a lightweight cross-shaped rib structure for aircraft components is also provided, comprising a plurality of cross-shaped ribs and skins located on both sides of the ribs; the ribs have T-joints at both ends, wherein the wall thickness of the rib is d, and the brazing interface width of the T-joint is D≥2d; interlocking grooves are provided in the cross-shaped intersection area of ​​the ribs, the depth of the grooves is not less than half the height of the ribs, and the one-sided tolerance of the groove depth is 0-0.1mm; a plurality of bosses are provided at intervals on both sides of the grooves to prevent the brazing filler metal from falling off under gravity at the brazing temperature; and the structure is manufactured using the brazing manufacturing method described above.

[0028] Based on the above solution, it can be seen that the lightweight cross-shaped rib structure and brazing manufacturing method of the present invention have at least one of the following advantages over the prior art:

[0029] The brazing manufacturing method for the lightweight cross-ribbed structure of the present invention significantly increases the brazing area and improves the brazing strength by setting T-joints at both ends of the ribs and using the T-joints to weld to the skin. Furthermore, by setting protrusions at intervals on the cross-ribbed structure and filling the spaces between the protrusions with brazing filler metal, the problem of brazing filler metal detaching or leaking due to gravity after liquefying at high temperatures is effectively solved. This effectively avoids the risk of incomplete welding defects and prevents brazing filler metal accumulation at the bottom of the ribs, which can lead to brittle joints at the root. The brazing manufacturing method for the lightweight cross-ribbed structure of the present invention can achieve reliable connections of large-size, complex hollow structures, providing a technical foundation for the subsequent application of large-size, complex frame beam structures in the aerospace field. Attached Figure Description

[0030] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the embodiments will be briefly described below.

[0031] Figure 1 This is a schematic diagram of the lightweight structure of the cross-shaped ribs of the present invention;

[0032] Figure 2 A schematic diagram illustrating the connection relationship between the ribs and the skin;

[0033] Figure 3 for Figure 2 Enlarged view of a portion of point I in the middle;

[0034] Figure 4 A schematic diagram showing the grooves of the ribs;

[0035] Figure 5 This is a schematic diagram showing the cross intersection of the reinforcing bars.

[0036] In the diagram: 1. Rib; 2. Skin; 3. T-joint; 4. Boss; 5. Groove; 6. Relief groove. Detailed Implementation

[0037] To better understand the technical solutions of the embodiments of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0038] It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0039] like Figures 1 to 5 As shown, this invention discloses a brazing manufacturing method for a cross-rib lightweight structure. The cross-rib lightweight structure includes multiple cross-ribs 1 arranged in a cross shape, and skins 2 located on both sides of the ribs 1. This cross-rib lightweight structure is a component used in aircraft and other aircraft; for example, in this embodiment, the cross-rib lightweight structure is the rear sidewall of an aircraft engine. The cross-ribs in the cross-rib lightweight structure can be referred to as transverse ribs and longitudinal ribs, respectively. The transverse ribs are parallel to each other, and the longitudinal ribs are also parallel to each other, with an angle of 90° between the longitudinal and transverse ribs. Both the ribs 1 and the skins 2 are made of titanium alloy. The ribs 1 and the skins 2 are fixedly connected as a whole structure by brazing. The cross-ribs 1 combine to form a stable structural frame.

[0040] The brazing manufacturing method for this lightweight cross-shaped rib structure includes the following steps:

[0041] S1. Pre-welding machining of skin and cross-shaped ribs: Perform pre-welding machining on skin 2 and rib 1 according to the part drawings, such as... Figure 2 and Figure 3 As shown, the stiffener 1 is made of a plate with a wall thickness of more than 3 times the thickness of the steel plate, and T-joints 3 are formed at both ends of the stiffener through machining; the wall thickness of the stiffener 1 is d, and the brazing interface width D of the T-joint 3 is ≥ 2d; Figure 4 and Figure 5 As shown, interlocking grooves 5 are provided in the cross-shaped intersection area of ​​the reinforcing bars 1. The depth of the grooves 5 is not less than half the height of the reinforcing bars 1, and the tolerance of the groove depth on one side is 0-0.1mm. Multiple bosses 4 are provided at intervals on both sides of the grooves 5 to prevent the brazing filler metal from falling off under gravity at the brazing temperature. A clearance groove 6 is provided at the top of the grooves 5. The width of the clearance groove 6 is the same as the brazing interface width D of the T-joint 3, so it will not interfere with the T-joint 3 during insertion. See details... Figures 2 to 4When machining the T-joint 3, excess material in the sheet metal can be removed directly using a milling machine, leaving the remaining portions on both sides of the rib 1 to form the T-joint 3. The outermost plane of the T-joint 3 is the brazing interface for welding with the skin 2. The wall thickness tolerance of the rib 1 is -0.05mm to +0.05mm. The dimensions of the skin are greater than 1000×1000mm. This cross-rib lightweight structure is suitable for large-sized aircraft components.

[0042] S2. Pre-welding fitting of ribs: Insert and pre-assemble ribs 1 into a cross structure; during this process, tools such as sandpaper can be used to grind and fit the inside of the groove 5 to ensure that the horizontal and vertical ribs can be smoothly inserted.

[0043] S3. Pre-welding cleaning: Use cleaning equipment to remove oil and metal shavings from the surface of the skin 2 and the reinforcing strip 1 wall panel. The cleaning equipment can be an ultrasonic cleaner or similar equipment. After cleaning, it can prevent residual contaminants in the area to be welded from affecting the strength of the brazed joint.

[0044] S4. Fixing the cross-shaped ribs: Use titanium alloy or stainless steel foil strips to spot weld and fix the cross-shaped connection area of ​​rib 1 using a welding machine; the foil strips can be 0.05mm thick titanium alloy or stainless steel foil strips, and the welding machine can be a resistance spot welder, an argon arc welder, or a laser welder, etc. After welding, ensure that there is no misalignment or slippage between the cross-shaped ribs.

[0045] S5, Adding brazing filler metal to cross-shaped ribs: Add powdered or paste brazing filler metal to the cross-shaped connection area; when adding brazing filler metal, apply the powdered brazing filler metal to the area between the bosses 4, so that the area between these bosses 4 is completely filled with brazing filler metal.

[0046] S6. Adding brazing filler metal to the skin: Add amorphous foil brazing filler metal to the area to be welded on skin 2; the amorphous foil filler metal used is 0.03~0.05mm.

[0047] S7. Fixing the skin and cross-shaped ribs: Use 0.05mm titanium alloy or stainless steel foil strips to spot weld the ribs 1 and skin 2 together using a resistance spot welding machine to prevent misalignment and slippage between skin 2 and cross-shaped ribs 1.

[0048] S8. Brazing Assembly and Furnace Loading: The assembled workpieces to be brazed are heated to the brazing temperature T at a certain heating rate, held at this temperature for a period of time, and then cooled to a low temperature with the furnace after the holding period. The furnace door is then opened. During the brazing process, the vacuum level must be less than 8 × 10⁻⁶. -3Pa; The brazing temperature T is set above the melting point of the filler metal, a temperature that melts the filler metal but does not melt the base material of the reinforcing rib 1 and skin 2. For example, based on the melting point of a certain filler metal, setting T=950℃ ensures that the filler metal melts while the base material does not. Therefore, the brazing temperature can be set within a certain range according to the melting points of the filler metal and the base material during specific operation. The low temperature during furnace cooling is lower than the brazing temperature. For example, the low temperature mentioned here can refer to a temperature drop to 200℃~250℃. This temperature is much lower than the brazing temperature.

[0049] S9. Brazing and Removal from the Furnace: After the workpiece has cooled down in the furnace, it is removed from the brazing furnace. The workpiece is further cooled to near room temperature after the furnace door is opened, and then taken out of the brazing furnace.

[0050] The brazing manufacturing method of the cross-shaped rib lightweight structure of the present invention significantly increases the brazing area and improves the brazing strength by setting T-joints 3 at both ends of the ribs 1 and using the T-joints 3 to weld with the skin 2. In addition, by setting bosses 4 at intervals on the cross-shaped ribs 1 and filling the gaps between the bosses 4 with brazing filler metal, the problem of brazing filler metal falling off or flowing away due to gravity after turning into liquid at high temperature can be effectively solved. This effectively avoids the risk of incomplete welding defects and prevents brazing filler metal accumulation at the bottom of the ribs, which can lead to brittle root joints.

[0051] The brazing manufacturing method of the cross-shaped rib lightweight structure of the present invention can realize the reliable connection of large-size and complex hollow structures, and provide a technical foundation for the subsequent application of large-size and complex frame beam structures in the aerospace field.

[0052] Furthermore, the flange thickness h of the T-joint 3 is in the range of d / 2≤h≤d, where d is the wall thickness of the reinforcing bar.

[0053] The spacing between the bosses 4 is 4 to 6 times the thickness of the bosses 4. The bosses 4 are formed into the ribs 1 by machining.

[0054] The T-joint 3 and the reinforcing bar 1 are connected with a rounded corner.

[0055] The skin is made of 2mm thick TA15 sheet metal, and the ribs are made of 6mm thick TA15 sheet metal.

[0056] After the brazing process, the workpiece is subjected to ultrasonic non-destructive testing, and the brazing weld rate of the workpiece is greater than 95%.

[0057] Example 1

[0058] This embodiment specifically provides a brazing manufacturing method for a lightweight cross-ribbed structure, achieving high-quality brazing of large-size, complex hollow cavity titanium alloy aircraft components. The steps include:

[0059] S1. Pre-welding processing of skin and cross-shaped ribs: Skin 2 and rib 1 are pre-welded according to the part drawings. Skin 2 is made of 2mm thick TA15 titanium alloy sheet, and the part outline is machined for later use. Rib 1 is made of 6mm thick TA15 titanium alloy sheet. The wall thickness of rib 1 is d=1.5mm. The flange length of the T-joint 3 is 2mm, and the flange height is 1mm. The brazing interface width is the sum of the lengths of the two flanges and the wall thickness of rib 1, i.e., D=1.5mm+2mm+2mm=5.5mm. The wall thickness machining tolerance of rib 1 is designed to be -0.05~+0.05mm. Interlocking grooves 5 are provided in the cross-shaped area of ​​the reinforcing ribs 1. The depth of the grooves 5 is half the height of the reinforcing ribs 1, and the width is the wall thickness of the reinforcing ribs 1, with a tolerance of +0.15mm to +0.2mm. Multiple bosses 4 are provided at intervals on both sides of the grooves 5 to prevent the brazing filler metal from falling off under gravity at the brazing temperature. The thickness of the bosses 4 is 1mm, and the spacing between the bosses 4 is 5mm. After processing, the surface of the brazing grooves is polished with fine sandpaper.

[0060] S2. Pre-welding preparation of reinforcing bars: Insert reinforcing bars 1 and pre-assemble them into a cross structure.

[0061] S3. Pre-welding cleaning: Use cleaning equipment to remove oil and metal shavings from the surface of the skin and stiffener panels to prevent residual contaminants in the area to be welded from affecting the strength of the brazed joint.

[0062] S4. Cross-shaped rib fixing: Use titanium alloy or stainless steel foil strips to spot weld and fix the cross-shaped connection area of ​​the ribs using a welding machine;

[0063] S5. Adding brazing filler metal to the cross-shaped joint area: Add powdered or paste-like brazing filler metal to the cross-shaped joint area;

[0064] S6. Adding brazing filler metal to the skin: Add amorphous foil brazing filler metal to the area of ​​the skin to be soldered;

[0065] S7. Fixing the skin and cross-shaped ribs: Use 0.05mm titanium alloy foil strips to spot weld the ribs and skin together using a spot welding machine;

[0066] S8. Brazing Assembly and Furnace Loading: The assembled workpieces to be brazed are heated to the brazing temperature of 920℃ at a certain heating rate and held at this temperature for 60 minutes. After holding, the workpieces are cooled to 200℃ with the furnace before the furnace door is opened. The vacuum degree during brazing must be less than 8×10⁻⁶. -3 Pa;

[0067] S9. Brazing and unloading: The workpiece is unloaded after the furnace door is opened and the workpiece has cooled to room temperature.

[0068] The workpiece was subjected to ultrasonic non-destructive testing, and the brazing weld rate was 96%.

[0069] Example 2

[0070] This invention discloses a lightweight cross-shaped rib structure for aircraft components, comprising multiple ribs arranged in a cross shape and skins located on both sides of the ribs; each rib has a T-joint at both ends, wherein the wall thickness of the rib is d, and the brazing interface width of the T-joint is D≥2d; interlocking grooves are provided in the cross-shaped intersection area of ​​the ribs, the depth of the grooves is not less than half the height of the ribs, and the tolerance of the groove depth on one side is 0-0.1mm; multiple bosses are provided at intervals on both sides of the grooves to prevent the brazing filler metal from falling off under gravity at the brazing temperature; this lightweight cross-shaped rib structure is manufactured using the brazing manufacturing method of Embodiment 1.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A brazing manufacturing method for a cross-shaped lightweight rib structure, the cross-shaped lightweight rib structure comprising a plurality of cross-shaped ribs and skins located on both sides of the ribs, characterized in that, The brazing manufacturing method includes the following steps: S1. Pre-welding processing of skin and cross-shaped ribs: The skin and ribs are pre-welded according to the part drawings. The ribs are made of sheet metal with a wall thickness of at least 3 times the thickness of the rib, and the ends of the ribs are machined to form T-joints. The wall thickness of the rib is d, and the brazing interface width of the T-joint is D≥2d. Interlocking grooves are set in the cross-shaped intersection area of ​​the ribs. The depth of the groove is not less than half the height of the rib, and the width of the groove is the wall thickness of the rib, with a tolerance of +0.15~+0.2mm. Multiple bosses are set at intervals on both sides of the groove to prevent the brazing filler metal from falling off under gravity at the brazing temperature. A clearance groove is set at the top of the groove, and the width of the clearance groove is the same as the brazing interface width of the T-joint. S2. Pre-welding preparation of stiffeners: Insert and pre-assemble the stiffeners into a cross structure; S3. Pre-welding cleaning: Use cleaning equipment to remove oil and metal shavings from the surface of the skin and stiffener panels; S4. Cross-shaped rib fixing: Use titanium alloy or stainless steel foil strips to spot weld and fix the cross-shaped connection area of ​​the ribs using a welding machine; S5. Adding brazing filler metal to the cross-shaped joint area: Add powdered or paste-like brazing filler metal to the cross-shaped joint area; S6. Adding brazing filler metal to the skin: Add amorphous foil brazing filler metal to the area of ​​the skin to be soldered; S7. Fixing the skin and cross-shaped ribs: Use titanium alloy or stainless steel foil strips to spot weld the ribs and skin together using a welding machine. S8. Brazing Assembly and Furnace Loading: Heat the assembled workpieces to the brazing temperature T at a controlled heating rate, hold for 60 minutes, and then cool with the furnace to 200°C before opening the furnace door. The vacuum level during brazing must be less than 8 × 10⁻⁶. -3 Pa; S9. Brazing and unloading: The workpiece is unloaded after cooling through the furnace door; among which... The flange thickness h of the T-joint is in the range of d / 2≤h≤d, where d is the wall thickness of the reinforcing bar; the wall thickness tolerance of the reinforcing bar is -0.05mm to +0.05mm. The spacing between the bosses is 4 to 6 times the thickness of the bosses; The boss is formed onto the rib by machining. After the brazing process, the workpiece is subjected to ultrasonic non-destructive testing, and the brazing weld rate of the workpiece is greater than 95%.

2. The brazing manufacturing method of the lightweight cross-shaped rib structure according to claim 1, characterized in that, The T-joint and the connection between the joint and the reinforcing bar are rounded.

3. The brazing manufacturing method of the lightweight cross-ribbed structure according to claim 1, characterized in that, The skin is made of 2mm thick TA15 sheet metal, and the ribs are made of 6mm thick TA15 sheet metal.

4. The brazing manufacturing method of the lightweight cross-shaped rib structure according to claim 1, characterized in that, The skin dimensions are greater than 1000×1000mm.

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