A method for spinning forming a non-circular aircraft engine lip

Abstract

The present invention discloses a non-circular aircraft engine lip spinning forming method, which belongs to the field of spinning forming technology. The non-circular aircraft engine lip spinning forming method includes the following steps: pre-treatment of the blank, stabilization treatment of the blank; design and manufacture of spinning tooling, design of supporting core mold according to the shape of the part; spinning trajectory design and program compilation; simulation verification; hot spinning forming. The present invention can break the limitations of the traditional spinning process, and use the calculation method of discrete increments to discretize the surface trajectory into a curve trajectory, and discretize the curve trajectory into a point set. Through a CNC spinning machine tool, the asymmetric spinning forming of the lip part is realized. The present invention only needs one set of spinning molds to complete the forming, which greatly reduces the mold cost and improves the forming accuracy compared to stamping forming. At the same time, it can realize integrated forming without the need for petal separation and assembly.

Description

Technical Field

[0001] The invention relates to the technical field of spin forming, and more specifically to a spin forming method for a non-circular aircraft engine lip. Background Art

[0002] The lip of an aircraft engine is the skin component of the engine. It is located at the front end of the air intake casing and is generally made of high-strength aluminum alloy or stainless steel. It has a perfect circle or non-perfect circle shape and is a key aerodynamic component of the engine. In the past, the lip was formed by drop hammer forming, hydraulic forming, superplastic forming, and spinning forming. Forming methods other than spinning can only achieve petal forming, and a correction process is required after forming, and finally welded as a whole. Drop hammer forming is a relatively backward forming process. The drop hammer guide accuracy is poor, the noise is high, the processing parameters are unstable, and the processing range is narrow. It has gradually been eliminated. Hydraulic forming requires multiple sets of molds, and requires punches and concave molds. Some lips with complex shapes even require 2-3 sets of molds, with low processing efficiency and high tooling costs. The temperature range required by the superplastic forming process is relatively narrow, which is easy to cause changes in the material structure and cannot guarantee the performance of the component. In the past, the traditional spinning method could only form parts with a central symmetric axis. For non-perfect circular lips with special aerodynamic requirements, this method could not form parts. Therefore, there is an urgent need for a spinning method that can achieve the overall spinning forming of special-shaped lips. Therefore, we propose a spinning forming method for non-circular aircraft engine lip. Summary of the invention

[0003] The object of the present invention is to provide a non-circular aircraft engine lip spinning forming method to solve the problems raised in the above background technology:

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A non-circular aircraft engine lip spinning forming method comprises the following steps:

[0006] Blank pretreatment: Stabilization treatment of the blank;

[0007] Design and manufacture spinning tooling: design the supporting core mold according to the shape of the parts;

[0008] Spinning trajectory design and program compilation: The trajectory control method adopts the trajectory control method based on angle increment. Through the discrete decomposition method, the surface is discretized into a finite number of coordinate points. After the coordinate points are calculated, the CNC machine tool is programmed. The trajectory analysis and calculation: The non-circular engine intake lip is a semi-ring part, which is divided into an inner semi-ring and an outer semi-ring. There is no order in the forming of the inner semi-ring and the outer semi-ring;

[0009] The lip side is assumed to be composed of three surfaces, and the spatial surface equations are as follows: , , , parts along The total height of the direction is ;

[0010] First, the z direction is discretized into discrete quantities, then each discrete increment is , there is the following relationship = ; Take any discrete value and get the outer ring space curve under a z plane. Then the space curve consists of six space curves, three of which are symmetrical along the axis, namely , ;

[0011] The angle increment method is used to program the CNC spinning machine. Assuming that there is a coordinate origin O (0, 0), the curve of a certain section is discretized into three parts. , then for each angle increment , and get the distance from the corresponding point on the curve to the center origin, that is ,in , get the distance calculation method corresponding to a plane angle increment under the length increment in the z direction, and so on, set the number of increments according to the size of the part;

[0012] Simulation verification, according to step 3 calculated The value and the corresponding angular increment and the discrete increment in the z direction form a one-to-one correspondence. The CNC spinning machine moves according to these three parameters. The spindle of the machine tool rotates according to the angular increment, and the spinning wheel rotates according to ( , ) coordinates to move, and countless coordinate points are combined to obtain the discrete forming trajectory of the asymmetric surface; after the trajectory is obtained, it is imported into the CNC spinning machine tool, and simulation is performed on the CNC spinning machine tool to confirm the correctness;

[0013] Hot spinning forming: after confirming the correctness, fix the formed blank on the supporting core mold through the tail top, preheat the blank, use a thermal imager to monitor the temperature, and form it after reaching the temperature;

[0014] Unloading, cool the formed lip on the mold in a conformal manner, and after cooling to room temperature, use a lifting tool to remove the lip.

[0015] Preferably, in step one, the blank is a plate material, and the plate material is an aluminum alloy or a stainless steel material.

[0016] Preferably, during the stabilization treatment, the aluminum alloy material is kept at 170°C-250°C for 10 hours, and the stainless steel material is kept at 880°C-950°C for 8 hours.

[0017] Preferably, the supporting core mold is mold steel, which is used after being hardened by heat treatment and quenching by casting or welding process, and the supporting core mold is finely processed on a multi-axis CNC milling machine;

[0018] The supporting core mold is designed with a lip inner surface contour and reserved assembly space. The supporting core mold is connected to the spindle of the spinning machine through screws or chucks and rotates synchronously with the spindle during the processing.

[0019] Preferably, the preheating is performed by spray gun preheating or by resistance furnace preheating.

[0020] Preferably, during preheating, the preheating temperature of the aluminum alloy material is 200°C-350°C, and the preheating temperature of the stainless steel material is 350°C-550°C.

[0021] Preferably, during molding, the outer half ring is molded first, and after the outer half ring is molded and fixed by a locking tool, the inner half ring is molded.

[0022] Preferably, cooling is performed by forced cooling with a coolant or by air cooling.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention can break the limitations of the traditional spinning process, propose a trajectory control method based on angle increments, use the calculation method of discrete increments to discretize the surface trajectory into a curve trajectory, and discretize the curve trajectory into a point set. Through a CNC spinning machine, the asymmetric integral spinning forming of the lip part is realized. The present invention only needs one set of spinning dies to complete the forming, which greatly reduces the mold cost and improves the forming accuracy compared to stamping forming. At the same time, it realizes integrated forming without the need for petal separation and assembly.

[0025] (2) The present invention provides a forming method for various large-diameter asymmetric aircraft engine lip parts, which is particularly suitable for non-circular combined lips. Through a discretized calculation method, complex trajectories are simplified into coordinate points, and flat materials are used for spin forming. Compared with traditional processing technology, the tooling cost is reduced, and the processed parts have the advantages of consistency and no welds. It is mainly suitable for aircraft engine lips made of aluminum alloy and stainless steel. At the same time, it provides a new forming idea for various asymmetric parts, and is also applicable to other high-temperature formed parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the basic structure of the engine lip of the present invention;

[0027] Figure 2 This is a schematic diagram of the processing of the outer half ring of the lip of the present invention;

[0028] Figure 3 This is a schematic diagram of the processing of the inner half ring of the lip of the present invention;

[0029] Figure 4 It is a schematic diagram of the cross section of the lip of the present invention;

[0030] Figure 5 It is a schematic diagram of the outer ring space curve under a certain cross section of the present invention;

[0031] Figure 6 It is a schematic diagram of the lower angle increment of a certain cross section of the present invention and the distance length from the corresponding point to the center of the circle.

[0032] Explanation of the numbers in the figure: 1. Outer half ring; 2. Inner half ring; 3. Support core mold; 4. Spinning wheel; 5. Blank; 6. Tail top; 7. Locking tooling. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0034] Example:

[0035] See also Figure 1-6 A non-circular aircraft engine lip spinning forming method comprises the following steps:

[0036] Step 1: Pretreatment of the blank, stabilization treatment of the blank; the blank is a sheet material, and the sheet material is an aluminum alloy or stainless steel material; during the stabilization treatment, the aluminum alloy material is kept at 170℃-250℃ for 10 hours, and the stainless steel material is kept at 880℃-950℃ for 8 hours. Stabilization treatment can improve the organizational state of the material before spinning, reduce the risk of cracking during deformation, and improve the stability of the processing process.

[0037] Step 2: Design and manufacture spinning tooling, and design the supporting core mold according to the shape of the part; a spinning wheel is used during spinning, and the spinning wheel is a universal force-applying tool. It is only necessary to design the supporting core mold according to the shape of the part; the supporting core mold is die steel, which is cast or welded and then hardened by heat treatment and quenching. Since the supporting core mold is not a perfect circle, it needs to be finely processed on a multi-axis CNC milling machine;

[0038] The support core mold is designed with a lip inner surface profile and reserved assembly space. The support core mold is connected to the spindle of the spinning machine through screws or chucks, and rotates synchronously with the spindle during processing. In order to make the flat material rotate synchronously with the spindle, it is necessary to use the tail to apply pressure to push the flat plate against the support core mold, and rely on friction to transmit the torque of synchronous rotation.

[0039] Step 3: Spinning trajectory design and program compilation: The trajectory control method adopts the trajectory control method based on angle increment. Through the discrete decomposition method, the surface is discretized into a finite number of coordinate points. After the coordinate points are calculated, the CNC machine tool is programmed to make the CNC machine tool run according to the predetermined trajectory;

[0040] Trajectory analysis and calculation: Figure 1 As shown, the non-circular engine intake lip is a semi-ring part, which is divided into an inner semi-ring and an outer semi-ring. There is no order in the molding of the inner semi-ring and the outer semi-ring. The lip structure generally has no central rotation axis, but there is a central symmetry line. The structures on both sides are symmetrical with the central symmetry line as the center. One side is analyzed as follows, and the other side can be analyzed symmetrically in the same way.

[0041] Specifically, the lip side is assumed to be composed of three surfaces. If the number of surfaces is greater, the same analysis is performed. The spatial surface equations (assuming that the wall thickness has been considered and the spatial equation is a collection of the motion trajectories of the spinning wheel) are as follows: , , , parts along The total height of the direction is ;

[0042] First, the z direction is discretized. According to the product precision requirements, the more discretizations there are, the more curves are generated, the more coordinate points are generated, and the higher the processing precision is, but the molding time will increase. discrete quantities, then each discrete increment is , there is the following relationship = ; Take any discrete value and get the outer ring space curve under a certain z plane as Figure 5 As shown, the space curve consists of six space curves, three of which are symmetrical along the axis, namely , ,like Figure 5 As shown in;

[0043] The angle increment method is used to program the CNC spinning machine. Assuming that there is a coordinate origin O (0, 0), the curve of a certain section is discretized into three parts. , then for each angle increment , and get the distance from the corresponding point on the curve to the center origin, that is ,in , get the distance calculation method corresponding to the angle increment of a plane under the length increment in the z direction, and so on, set the number of increments according to the size of the part; set the increment (n in the z direction and the angle increment) according to the size of the part ), the more discrete the number, The more the number of generated, the higher the dimensional accuracy of the molded part, and vice versa. After the outer half ring is calculated, the inner half ring is analyzed and calculated using the same method.

[0044] Step 4: Simulation verification, based on the calculation in step 3 The value and the corresponding angular increment and the discrete increment in the z direction form a one-to-one correspondence. The CNC spinning machine moves according to these three parameters. The spindle of the machine tool rotates according to the angular increment, and the spinning wheel rotates according to ( , ) coordinates to move, and countless coordinate points are combined to obtain the discrete forming trajectory of the asymmetric surface; after the trajectory is obtained, it is imported into the CNC spinning machine tool, and simulation is performed on the CNC spinning machine tool to confirm the correctness;

[0045] Step 5: Hot spinning forming. After confirming the correctness, fix the formed blank on the supporting core mold through the tail top and preheat the blank. The purpose of preheating the blank is to improve the forming accuracy of the material and improve the material die-sticking effect. The preheating is carried out by spray gun preheating or by resistance furnace preheating, and the temperature is monitored by thermal imager in real time. After reaching the temperature, the forming is carried out. When preheating, the preheating temperature of aluminum alloy material is 200℃-350℃, and the preheating temperature of stainless steel material is 350℃-550℃. When forming, the outer half ring is formed first, and after the outer half ring is formed, it is fixed by locking tooling, and then the inner half ring is formed; Figure 2 As shown in , when forming the outer half ring, the spinning wheel moves from the side close to the tail top to the edge end of the outer half ring of the supporting core mold, as shown in Figure 3 As shown in , when forming the inner half ring, the spinning wheel moves from the side close to the tail top to the edge end of the inner half ring of the supporting core mold. In this embodiment, the forming trajectory is designed according to one-pass forming. If a multi-pass forming trajectory is used, the first pass is designed according to the maximum fitting circle, and the last film pasting pass adopts the method of revising the parametric surface equation or the trajectory design method in step three, and then adds a discrete angle variable for calculation.

[0046] Specifically, due to the asymmetry of the formed parts, the processing process is different from the traditional multi-pass ordinary spinning. The spinning forming of asymmetric parts is achieved through point-by-point trajectory control. Therefore, the trajectory is more complex, and the feed axis and the machine tool spindle need to realize the linkage function during the processing. In order to improve the part mold accuracy and reduce the deformation resistance of the material, it is necessary to preheat the sheet according to the material. The preheating is carried out by spray gun preheating or by resistance furnace preheating. After preheating, the temperature is measured by thermocouple.

[0047] Step 6: Unloading, cool the formed lip on the mold in a conformal manner, use coolant forced cooling or air cooling during cooling, and after cooling to room temperature, use lifting tools to remove the lip.

[0048] There are two trajectory control methods for forming asymmetric spun parts, one is based on constant force control, and the other is based on trajectory control. Trajectory control has high accuracy, but the calculation method is complicated.

[0049] The present invention proposes a trajectory control method based on angle increments. Through the method of discrete decomposition, the surface is discretized into a finite number of coordinate points. After the coordinate points are calculated, the CNC machine tool is operated according to a predetermined trajectory, thereby realizing the integral spinning forming of the asymmetric engine lip parts. The method proposed in this application is not only suitable for the asymmetric spinning forming of lip parts, but also for the spinning of other special-shaped parts. This method broadens the shape range of the spun parts and can realize the integral spinning forming of the non-circular air intake nacelle (lip) of the aircraft engine.

[0050] The present invention provides a forming method for various large-diameter asymmetric aircraft engine lip parts, and is particularly suitable for non-circular combined lips. Through a discretized calculation method, complex trajectories are simplified into coordinate points, and flat materials are used for spin forming. Compared with traditional processing technology, the tooling cost is reduced, and the processed parts have the advantages of consistency and no welds. It is mainly suitable for aircraft engine lips made of aluminum alloy and stainless steel. At the same time, it provides a new forming idea for various asymmetric parts, and is also applicable to other high-temperature formed parts.

[0051] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A non-circular aircraft engine lip spinning forming method, characterized in that: The steps include: Blank pretreatment: Stabilization treatment of the blank; Design and manufacture spinning tooling: design the supporting core mold according to the shape of the parts; Spinning trajectory design and program compilation: The trajectory control method adopts the trajectory control method based on angle increment. Through the discrete decomposition method, the surface is discretized into a finite number of coordinate points. After the coordinate points are calculated, the CNC machine tool is programmed; trajectory analysis and calculation: The non-circular engine intake lip is a semi-ring part, which is divided into an inner semi-ring and an outer semi-ring. There is no order when the inner semi-ring and the outer semi-ring are formed; one side of the lip is assumed to be composed of three surfaces, and the spatial surface equations are as follows: , , , parts along The total height of the direction is ; Discretize the z direction into discrete quantities, then each discrete increment is , there is the following relationship = ; Taking any discrete value, we get the outer ring space curve under a z plane. Then the space curve consists of six space curves, three of which are symmetrical along the axis, namely , ; The angle increment method is used to program the CNC spinning machine. Assuming that there is a coordinate origin O (0, 0), the curve of a certain section is discretized into three parts. , then for each angle increment , and get the distance from the corresponding point on the curve to the center origin, that is ,in , get the distance calculation method corresponding to a plane angle increment under the length increment in the z direction, and so on, set the number of increments according to the size of the part; Step 4: Simulation verification, based on the calculation in step 3 The value and the corresponding angular increment and the discrete increment in the z direction form a one-to-one correspondence. The CNC spinning machine moves according to these three parameters. The spindle of the machine tool rotates according to the angular increment, and the spinning wheel rotates according to ( , ) coordinates to move, and countless coordinate points are combined to obtain the discrete forming trajectory of the asymmetric surface; after the trajectory is obtained, it is imported into the CNC spinning machine tool, and simulation is performed on the CNC spinning machine tool to confirm the correctness; Step 5: Hot spinning forming: after confirming the correctness, fix the formed blank on the supporting core mold through the tail top, preheat the blank, use a thermal imager to monitor the temperature, and spin forming after reaching the temperature; Step 6: Unloading, cool the formed lip on the supporting core mold to maintain its shape, and after cooling to room temperature, use a lifting tool to remove the lip.

2. A non-circular aircraft engine lip spinning forming method according to claim 1, characterized in that: The blank is a plate material, and the plate material is an aluminum alloy or a stainless steel material.

3. A non-circular aircraft engine lip spinning forming method according to claim 2, characterized in that: During the stabilization treatment, the aluminum alloy material is kept at 170°C-250°C for 10 hours, and the stainless steel material is kept at 880°C-950°C for 8 hours.

4. The non-circular aircraft engine lip spinning forming method according to claim 1, characterized in that: The supporting core mold is made of die steel and is used after being hardened by heat treatment and quenching by casting or welding process, and the supporting core mold is finely processed on a multi-axis CNC milling machine; The supporting core mold is designed with a lip inner surface profile and reserved for assembly space. The supporting core mold is connected to the spindle of the spinning machine tool through screws or a chuck and rotates synchronously with the spindle during the processing.

5. The non-circular aircraft engine lip spinning forming method according to claim 2, characterized in that: Preheating is done by spray gun or resistance furnace.

6. A non-circular aircraft engine lip spinning forming method according to claim 5, characterized in that: During preheating, the preheating temperature of aluminum alloy materials is 200℃-350℃, and the preheating temperature of stainless steel materials is 350℃-550℃.

7. The non-circular aircraft engine lip spinning forming method according to claim 5, characterized in that: During molding, the outer half ring is molded first, and after the outer half ring is molded and fixed by a locking tool, the inner half ring is molded.

8. The non-circular aircraft engine lip spinning forming method according to claim 1, characterized in that: During cooling, coolant forced cooling or air cooling is adopted.

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