A method for controlling springback defects during room temperature forming of TC1 high-curvature titanium alloy semi-tubes

Abstract

This invention discloses a method for controlling springback defects during room temperature forming of TC1 high-curvature titanium alloy semi-tubes. The method includes: constructing a theoretically drawn semi-tube body; unfolding the theoretically drawn semi-tube body to form an unfolded blank; constructing a theoretically stamped semi-tube body; manufacturing a drawing die, punch, and blank holder based on the theoretically drawn semi-tube body; manufacturing a shaping die based on the theoretically stamped semi-tube body; manufacturing a laser cutting fixture for the semi-tube based on the theoretically stamped semi-tube body; blanking; pre-forming by deep drawing on the drawing die; stress-relieving annealing; stamping and shaping on the shaping die; laser cutting the final semi-tube body in the laser cutting fixture; trimming the shape of the final semi-tube body; cutting positioning lugs at both ends to obtain a titanium alloy semi-tube part that meets the shape tolerance requirements. This invention solves the problems of difficult quality control, long manufacturing cycle, and high cost in hot forming of thin titanium TC1 bent semi-tubes, while cold forming technology is lacking, and has universal applicability.

Description

Technical Field

[0001] This invention relates to a sheet metal parts forming technology in the field of aircraft manufacturing, specifically a room temperature forming springback control method for thin-walled titanium alloy and large-curvature bent semi-tube parts, which is particularly suitable for cold drawing deep forming of thin-walled parts made of TC1 material. Background Technology

[0002] To address the frequent cracking failures in the high-temperature, high-pressure bleed air ducts of aircraft environmental control systems, the duct material was optimized from stainless steel to titanium alloy to improve the overall strength of the aircraft environmental control ducts and reduce their weight. The environmental control ducts are welded from a series of straight pipes, tapered pipes, and bent half-pipes. To achieve the desired application functionality and avoid assembly obstacles, the duct structures vary considerably.

[0003] Titanium alloys exhibit high deformation resistance during cold forming, but also have a small forming limit and severe springback and warping. Traditional sheet metal cold forming processes are unsuitable for manufacturing titanium alloy pipes with high yield strength ratios. For regularly shaped titanium alloy straight and tapered pipes, the utility model patent "A Bending Die for Forming Straight Round Pipes" proposes a progressive gate forming method, which uses multiple bending iterations and approximation of the arc radius to produce qualified parts. However, for titanium alloy bent half-pipes with varying curvatures, current processes utilize titanium alloy hot forming, which relies on temperature, pressure, and time to process the parts. Titanium alloy hot forming is costly, has a long production cycle, consumes a lot of energy, and is difficult to control manually. Existing titanium alloy half-pipe hot forming technologies suffer from uncontrollable material flow and severe wrinkling, increasing the difficulty of welding and repair. Its forming accuracy also restricts the quality and progress of environmentally controlled pipeline assembly. Researching room temperature forming processes for complex-shaped titanium alloy parts is of great significance for reducing the manufacturing cost of titanium alloy structural components.

[0004] In aircraft environmental control piping, titanium alloy bent half-tubes are mostly in the TC1-M state. Considering both piping strength and weight, the titanium tube thickness ranges from 0.8mm to 1.2mm, and the half-tube diameter ranges from 50mm to 130mm. There are numerous half-tube specifications, with structures exhibiting uniform curvature, gradual changes, and irregularities. However, the overall forming quality and assembly precision standards remain consistent, requiring strict conformity and a smooth surface finish. Each half-tube has two longitudinal welds and two circumferential welds, with stringent requirements for roundness, fit, and seam accuracy. Previously, the welding and assembly of stainless steel half-tubes inevitably involved extensive finishing work due to springback and residual stress. The springback of titanium alloy at room temperature is at least three times that of stainless steel. Attempting to manually eliminate springback defects in high-strength titanium alloy parts and induce shrinkage deformation is virtually impossible. Finding a mechanical forming method and finishing technique that allows the titanium alloy material to easily yield and fit into the forming mold is a pressing technical challenge. Summary of the Invention

[0005] To address the challenges of poor quality control, long manufacturing cycles, and high costs associated with hot forming of thin titanium TC1 bent semi-tubes, coupled with a lack of cold forming technology, this invention aims to provide a method for controlling springback defects during room temperature forming of TC1 large-curvature titanium alloy semi-tubes.

[0006] A method for controlling springback defects during room temperature forming of TC1 high-curvature titanium alloy semi-tubes, comprising the following steps:

[0007] Step 1: Construct a semi-theoretical deep-drawn body, wherein the deep-drawn body comprises:

[0008] A transition surface, which is offset from the theoretical shape of the digital model of the semi-tube product by a specific value to the center. get, The formula for determining the value of is: , in the formula The range of values ​​is The radius of the half-pipe is denoted as . The value of is related to the bending angle of the half-pipe. Related, when hour, ,when hour, ,when hour, ,when hour, .

[0009] One end wrapping surface is formed by rotating the end curves at both ends of the transition surface 90° around the center line;

[0010] A flange face, located below the transition surface and the end wrapping surface, is connected to the end wrapping surface and the transition surface via a connecting surface to form a semi-manual theoretical deep-drawn body. The height of the connecting surface is... The value is determined according to the formula. Calculation, where The radius of the transition fillet is determined by the formula. Perform calculations. The thickness of half-tube material, The height is extended by the normal. According to the formula Calculation, where For the semi-physical theoretical external surface end face arc length, The arc length of the curve at the end of the transition surface. Transition fillet radius. The value of is related to the bending angle of the half-pipe. Related, when hour, ,when hour, ,when hour, .

[0011] The outer edge of the flange face is formed by offsetting the bottom outline of the connecting surface outward by a certain amount. , The offset corresponding to the outer edge of the concave curvature of the transition surface is , The offset corresponding to the boundary line of the end-wrap surface ball head is , .

[0012] Step 2: Unfold the semi-manual theoretical deep-drawn part to form an unfolded blank, and use finite element analysis to determine the maximum material thickness reduction rate of the unfolded blank. Predict the maximum thinning rate. At that time, offset and Take the minimum value; otherwise, take the maximum value.

[0013] Step 3: Construct a semi-manufacturing theoretical stamping body, including:

[0014] A stamping correction surface, which is consistent with the theoretical outer shape of the digital model of the semi-tube product;

[0015] A stamping blanking surface is located below the stamping correction surface and is connected to the stamping correction surface via a stamping transition surface to form a semi-theoretical stamped body. The height of the stamping transition surface is... The value is determined according to the formula. Calculation, where The radius of the transition angle is given by the formula. Configure settings. For process compensation height, According to the formula calculate.

[0016] The outer edge of the stamping blanking surface is formed by offsetting the bottom contour line of the stamping transition surface outward by a certain amount. The offset of the bottom contour line of the stamping transition surface corresponding to the convex contour line of the stamping correction surface is... , The offset corresponding to the concave contour line of the stamping correction surface is , .

[0017] Multiple positioning lugs are set at the middle of both ends of the stamping correction surface; multiple positioning holes are set on the positioning lugs.

[0018] Step 4: Based on the semi-theoretical deep drawing body, manufacture the die, punch, and blank holder for the deep drawing die. The working surface of the punch consists of the punch wrapping surface and the punch bending surface. The punch wrapping surface corresponds to the transition surface of the semi-theoretical deep drawing body, and the punch bending surface corresponds to the end wrapping surface of the semi-theoretical deep drawing body. Draw the outline of the unfolded blank on the blank holder; the gap between the punch wrapping surface and the corresponding part of the die cavity... According to the formula Design of the gap between the curved surface of the punch and the corresponding part of the die cavity. According to the formula design.

[0019] Step 5: Manufacture a straightening die based on the semi-manufactured theoretical stamped body. The straightening die includes a straightening male die and a straightening female die. Mark the outer contour lines and positioning holes of the semi-manufactured theoretical stamped body, as well as the concave and convex contour lines of the semi-manufactured theoretical outer surface, on the straightening female die. The design tolerance of the straightening female die is... The shape of the positive mold matches the shape of the negative mold.

[0020] Step 6: A laser cutting fixture for manufacturing a semi-tube based on the semi-tube theoretical stamping body. The laser cutting fixture includes: a base with a cutting groove that is consistent with the edge of the stamping correction surface of the semi-tube theoretical stamping body; and a bracket fixed on the base, the bracket having the same shape as the stamping correction surface of the semi-tube theoretical stamping body, and process holes on both sides that are consistent with the positioning holes on the positioning lugs.

[0021] Step 7: Cut the blank according to the unfolded shape;

[0022] Step 8: Pre-draw the material on a drawing die;

[0023] 8-1: Install the drawing die, apply lubricating oil to the contact area between the blank and the blank holder and the contact area between the blank and the die, and place the blank on the working surface of the blank holder according to the outline of the blank on the blank holder. The punch, die, and blank holder are controlled by guide posts to control the drawing direction.

[0024] 8-2: Forming begins. The guide post connected to the punch enters the guide post guide hole of the die through the guide post through hole of the blank holder. The die and blank holder clamp and unfold the blank and begin to draw according to the working surface of the punch. Under the combined action of blank holder force and drawing force, the material around the unfolded blank gradually flows into the die cavity, and finally forms the actual drawn body of the half tube.

[0025] Step 9: Stress-relieving annealing;

[0026] Step 10: Perform stamping and shaping on the shaping die.

[0027] 10-1: Cut the actual deep-drawn half-tube according to the outline of the semi-tube theoretical stamping body, remove the end ball head compensation surface, retain the positioning lug, and obtain the actual stamping body before stamping correction;

[0028] 10-2: Install the male and female dies of the straightening die, lubricate the actual stamped body of the half-tube and the working surface of the straightening die, and place the actual stamped body before stamping and straightening according to the theoretical stamped body outline on the female die;

[0029] 10-3: Start stamping and shaping. The shaping male die presses the actual stamped half-tube into the shaping female die to obtain the stamped and shaped half-tube semi-finished product. According to the positioning hole positions on the shaping female die, make two end positioning holes on the half-tube semi-finished product.

[0030] Step 11: Perform laser cutting of the final semi-tube shape in a laser cutting fixture;

[0031] 11-1: Install the laser cutting fixture, place the stamped and shaped semi-finished tube on the positioning bracket of the laser cutting fixture, and align the positioning holes of the semi-finished tube with the process holes of the positioning bracket. Fix the semi-finished tube on the laser cutting fixture with positioning pins.

[0032] 11-2: Cut the semi-finished tube according to the designed laser cutting program, retaining the positioning lugs at both ends. The cutting tolerance is... The final semi-tube shape with two positioning ear pieces is obtained.

[0033] Step 12: Trim the final shape of the semi-tube, cut the positioning lugs at both ends, and obtain a titanium alloy semi-tube part that meets the shape tolerance requirements.

[0034] The beneficial effects of this invention are as follows: 1) This method provides a springback compensation profile design method for TC1 titanium alloy bent half-tubes. By designing different offsets for half-tubes of different specifications, a waist-shaped theoretical deep-drawn body with a ball head is obtained, solving the problem of uncontrollable springback of titanium alloy half-tubes and having significant practical value. 2) Utilizing the good ductility and poor shrinkage of TC1 titanium alloy, a deep-drawing die structure with controllable gap for bent half-tubes is designed, improving the processability of the waist-shaped theoretical deep-drawn body of titanium alloy, making it possible to form complex structures of TC1 titanium alloy at room temperature. The installation and operation of the new die are the same as traditional dies, making it easy to promote and implement. 3) This method organically combines stress-relieving annealing and stamping correction, solving the problems of large springback, poor precision, and inability to release stress in TC1 titanium alloy room temperature forming. It breaks free from the long-standing monopoly of hot forming processes, long processing cycles, and lack of technology in bent half-tubes, and has high promotional value. 4) This method describes in detail the process design of TC1 titanium alloy bent half-tubes and the key points of die design. The design concept is complete and can guide the forming design of thin-walled TC1 titanium alloy bent half-tubes, with strong versatility.

[0035] The present application will be further described in detail below with reference to the accompanying drawings of the embodiments. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the titanium alloy ring control pipeline assembly structure.

[0037] Figure 2 This is a schematic diagram of a semi-tube transition surface structure.

[0038] Figure 3 This is a schematic diagram of a semi-management deep-drawing forming structure.

[0039] Figure 4 This is a schematic diagram of the unfolded blank structure of a semi-management deep-drawn body.

[0040] Figure 5 This is a schematic diagram of a semi-management-theoretical stamping structure.

[0041] Figure 6 A comparison of the semi-manual theoretical deep-drawn bodies and their theoretical stamped body structures.

[0042] Figure 7 This is a schematic diagram of a semi-tube deep drawing die structure.

[0043] Figure 8 This is a schematic diagram of a semi-tube straightening die structure.

[0044] Figure 9 This is a schematic diagram of a half-tube laser cutting fixture.

[0045] Figure 10 This is a schematic diagram of the assembly of a semi-finished tube with a laser cutting fixture.

[0046] Figure 11 This is a schematic diagram of the structure of a semi-tube and its final formed body.

[0047] Numbering in the diagram: 1. Half-pipe, 2. Straight pipe, 3. Transition surface, 4. End curve, 5. Center line, 6. Concave curvature outer edge line, 7. Convex curvature outer edge line, 8. End wrapping surface, 9. Connecting surface, 10. Flange face, 11. Theoretical deep-drawn body, 12. Bottom outline line, 13. Ball head boundary line, 14. Unrolled blank, 15. Theoretical stamped body, 16. Concave profile line, 17. Convex profile line, 18. Stamping transition surface, 19. Stamping blank holder surface, 20. Positioning lug, 21. Positioning hole, 22. Stamping correction surface 23 Die, 24 Punch, 25 Blanket Ring, 26 Through Hole, 27 Guide Hole, 28 Die Cavity, 29 Die Flange, 30 Punch Wrapping Surface, 31 Punch Bending Surface, 32 Drawing Die, 33 Correcting Female Die, 34 Correcting Male Die, 35 Theoretical Stamped Body Outline, 36 Laser Cutting Fixture, 37 Positioning Pin, 38 Cutting Groove, 39 Bracket, 40 Base, 41 Process Hole, 42 Longitudinal Support, 43 Transverse Support, 44 Semi-finished Pipe, 45 Final Formed Body Detailed Implementation

[0048] Referring to the accompanying drawings, the aircraft environmental control piping design provided in the embodiment is as follows: Figure 1 As shown, the aircraft environmental control piping system consists of a series of components including straight pipes 2, tapered pipes, and bent half-pipes 1. The bent half-pipe 1 is welded to form a bent transition pipe, achieving a bypass connection for the environmental control piping. Half-pipe 1 is a typical curved half-pipe component made of thin titanium TC1. The diameter of half-pipe 1 ranges from 50mm to 130mm, and the material thickness of half-pipe 1 is denoted as... , The bending angle of half-pipe 1 is denoted as , The biggest problem with existing titanium alloy hot forming technology is the long manufacturing cycle, high production cost, and complex hot forming protection measures, which cannot meet the assembly schedule of a large number of environmental control pipelines and the ever-increasing annual aircraft production.

[0049] like Figure 2-11 As shown, a method for controlling springback defects during room temperature forming of TC1 large-curvature titanium alloy semi-tubes includes the following steps:

[0050] Step 1: Construct a theoretical deep-drawn half-tube 11

[0051] In the CATIA environment, the theoretical deep-drawn forming body 11 is designed based on the digital model of the semi-tube 1 product. The theoretical deep-drawn forming body 11 includes a transition surface 3, an end wrapping surface 8, a connecting surface 9, and a flange surface 10.

[0052] Step 1-1: Extract the theoretical outer shape of the digital model of half-tube 1. The radius of half-tube 1 is denoted as... The arc length of the end face of the theoretical outer surface of half-tube 1 is denoted as... Offset the theoretical shape of half-tube 1 towards the center by a distance. The transition surface 3 of half-pipe 1 is obtained. The formula for determining the value of is: , in the formula The range of values ​​is , The value of and Related, when hour, ,when hour, ,when hour, ,when hour, The arc length of the curve at the transition surface 3 of the half-pipe 1 is denoted as . The radius of the transition surface 3 of the half-pipe 1 is denoted as , Taking half-pipe 1 in the diagram as an example, the radius of half-pipe 1 is... Material thickness Bending angle ,but The offset distance was calculated. Half-pipe 1 transition surface 3 radius Theoretical outer diameter of half-tube 1, end face arc length The transition surface has a 3-end curve with an arc length of 4. ;

[0053] Steps 1-2: Draw the center line 5 of the curve 4 at the end of the transition surface 3 of the half-pipe 1. Rotate the curve 4 at the end of the transition surface 3 outward around the center line. The planar spherical head boundary line 13 is obtained. The end curve 4 of the transition surface 3 of the half tube 1 and the spherical head boundary line 13 are used as input conditions. Two end wrapping surfaces 8 are formed using the multi-section surface command.

[0054] Steps 1-3: The connecting surface 9 of the half-tube 1 is located below the transition surface 3 and the end wrapping surface 8, and is connected to the transition surface 3 and the end wrapping surface 8 through the concave curvature outer edge line 6, the convex curvature outer edge line 7, and the ball head boundary line 13. The height of the connecting surface 9 is... Height extended by normal and transition fillet radius It consists of two parts. The value is determined according to the formula. Calculate the transition fillet radius. The size is according to the formula Calculate the height of the normal extension. According to the formula Calculate the transition fillet radius. The value of is related to the bending angle of half-pipe 1. Related, when hour, ,when hour, ,when hour, The height of connecting surface 9 The range of values ​​must satisfy Taking half-pipe 1 in the diagram as an example, the transition fillet radius... The calculated result and Substitute the normal extension height The formula is: ,Pick The height of the connecting surface 9 of half-pipe 1 shown in the figure is... ;

[0055] Steps 1-4: Utilizing the good ductility and poor shrinkage of TC1 material, design the flange face 10 of the half-pipe 1. The flange face 10 is located below the transition surface 3 and the end wrapping surface 8, and is connected to the connecting surface 9. The outer edge of the flange face 10 is formed by offsetting the bottom outline 12 of the connecting surface 9 outward by a certain amount. The offset of the bottom outline 12 of the connecting surface 9 corresponding to the outer edge 7 of the convex curvature of the transition surface 3 is... , The offset corresponding to the outer edge line 6 of the concave curvature of the transition surface 3 is , The offset corresponding to the end wrapping surface 8 ball head boundary line 13 is , The offset curve corresponding to the outer edge line 6 of the concave curvature of the transition surface 3 needs to have a gentle curvature to increase the edge pressure resistance and limit the material flow rate, thereby controlling the wrinkling of the half-tube 1 during deep drawing. The offset curve is flattened as the maximum offset, and the four offset curves are smoothly transitioned to obtain the outer edge line of the flange surface 10. The flange surface 10 is connected to the end wrapping surface 8 and the transition surface 3 through the connecting surface 9 to form the theoretical deep-drawn body 11 of the half-pipe 1.

[0056] Step 2: Unfold the theoretically drawn half-tube 1 into a blank 14.

[0057] The unfolded blank 14 of the theoretical deep-drawn body 11 of the half-tube 1 was calculated in the PAMSTAMP finite element analysis environment.

[0058] Step 2-1: Using the blank back calculation function, unfold the theoretical deep drawing forming body 11 of the half tube 1 along the direction perpendicular to the flange surface 10 to obtain the unfolded blank 14 of the theoretical deep drawing forming body 11 of the half tube 1.

[0059] Step 2-2: Using the deep drawing defect prediction function of finite element analysis software, predict the maximum material thickness reduction rate of the theoretical deep-drawn body 11 after the half-tube 1 is unfolded from the blank 14 and deep-drawn. When the predicted maximum thinning rate At that time, offset and Take the minimum value, otherwise take the maximum value. Taking the half-tube 1 shown in the figure as an example, the maximum material thickness reduction rate of the theoretical deep-drawn body 11 after forming is predicted using finite element analysis software. , Therefore, take , , ;

[0060] Steps 2-3: Edit the outline of the unfolded blank 14 in the finite element analysis software environment to form a *.igs format file that can be recognized in the CATIA environment, so as to facilitate the blank 14 in blank cutting and positioning during forming.

[0061] Step 3: Construct a theoretical stamping body 15 for a half-tube 1

[0062] Due to the complexity of plastic deformation in deep-drawing materials and the significant anisotropy of titanium alloys during room-temperature forming, the actual deep-drawn body 14 of the theoretical half-tube 1 does not conform to the theoretical shape of the half-tube 1. Therefore, a theoretical stamped body 15 of the half-tube 1 needs to be constructed. Through stamping correction, the surface of the stamped body is made to conform to the theoretical shape of the digital model of the half-tube 1 product. The theoretical stamped body 15 of the half-tube 1 includes a stamping correction surface 22, a stamping transition surface 18, and a stamping blanking surface 19.

[0063] Step 3-1: The stamping correction surface 22 of the half tube 1 is consistent with the theoretical outer surface of the digital model of the half tube 1 product. The concave contour line 16 and convex contour line 17 of the half tube 1 are the concave contour line 16 and convex contour line 17 of the stamping correction surface 22.

[0064] Step 3-2: The stamping transition surface 18 of the half-tube 1 is set below the stamping correction surface 22, and is connected to the stamping correction surface 22 through the concave contour line 16 and the convex contour line 17. The height of the stamping transition surface 18 is... The value is determined according to the formula. Calculate the transition angle radius. The size is according to the formula Configure the process compensation height. According to the formula Calculate the transition angle radius, taking half-pipe 1 as an example. Process compensation height The height of the stamping transition surface 18 of the half-pipe 1 shown in the figure is... ;

[0065] Step 3-3: The stamping blanking surface 19 of the half-tube 1 is set below the stamping correction surface 22 and connected to the stamping transition surface 18. The outer edge of the stamping blanking surface 19 is formed by offsetting the bottom contour line of the stamping transition surface 18 outward by a certain amount. The offset of the bottom contour line of the stamping transition surface 18 to the convex contour line 17 of the stamping correction surface 22 is... , The offset corresponding to the concave contour line 16 of the stamping correction surface 22 is , The offset curve corresponding to the concave contour line 16 of the stamping correction surface 22 needs to have a gentle curvature, and its shape should match the shape of the corresponding outer edge line of the flange face 10 of the theoretical deep-drawn body 11 of the half-tube 1.

[0066] Steps 3-4: The stamping pressing surface 19 and the stamping correction surface 22 are connected by the stamping transition surface 18 to form a theoretical stamping body 15 of the half tube 1. Positioning ears 20 are set at the middle of both ends of the theoretical stamping body 15 of the half tube 1. Positioning holes 21 are set on the positioning ears 20 for cutting positioning.

[0067] Step 4: Manufacturing the deep drawing die 32 structure for the theoretical deep-drawn part 11 of the half-tube 1

[0068] Based on the theory of half-tube 1, the deep drawing die 32 is manufactured using the die 23, punch 24, and blank holder 25.

[0069] Step 4-1: Design the structure of the drawing die 32 and the concave die 23 according to the theory of half tube 1 for deep drawing forming body 11. The structure of the punch 24 matches the cavity of the concave die 28, and the outer dimensions of the pressure ring 25 match the flange of the concave die 29.

[0070] Step 4-2: Two diagonal guide pillars are connected to the punch 24, which correspond to the two guide pillar through holes 26 on the blank holder 25 and the two guide pillar guide holes 27 on the die. The diagonal guide pillars of the punch 24 ensure the straightness of the drawing die 32 during the drawing process through the guide pillar through holes 26 on the blank holder 25 and the guide pillar guide holes 27 on the die 23.

[0071] Step 4-3: The working surface of the punch 24 consists of the end punch wrapping surface 30 and the middle punch bending surface 31. In order to solve the problem of poor shrinkage of titanium alloy material during room temperature forming, the gap between the punch wrapping surface 30 and the corresponding part of the die cavity 28 is... According to the formula The design includes the gap between the corresponding part of the punch bending surface 31 and the die cavity 28. According to the formula The design ensures a smooth transition at the junction of the punch wrapping surface 30 and the punch bending surface 31. Taking the illustrated half-tube 1 as an example, the punch-die clearance at different locations is calculated. , ;

[0072] Step 4-4: The working surface of the pressure ring 25 is marked with the outline of the unfolded blank 14, which is used to position the unfolded blank 14 before deep drawing.

[0073] Step 5: Manufacture the forming die structure for the theoretical stamping body 15 of the half-tube 1.

[0074] The straightening male die 34 and straightening female die 33 are manufactured according to the theory of half-tube 1 stamping body 15.

[0075] Step 5-1: Design the straightening die 33 structure of the straightening die 15 according to the theoretical stamping body 15 of the half-tube 1. The design tolerance of the straightening die 33 is... To ensure that the half-pipe 1 is tightly connected to the external clamp of the machined joint during assembly, the shape of the positive mold 34 matches the shape of the negative mold 33;

[0076] Step 5-2: The shaping die 33 is marked with the theoretical stamping body outline 35 of the half tube 1 and the hole position line of the positioning hole 21. At the same time, the shaping die 33 is marked with the concave outline 16 and convex outline 17 of the theoretical outer surface of the half tube 1.

[0077] Step 6: Manufacturing the laser cutting fixture 36 structure for the theoretical stamped body 15 of the half-tube 1

[0078] The laser cutting fixture 36 is manufactured based on the theoretical stamping body 15 of the semi-tube 1. The laser cutting fixture 36 consists of a base 40 and a support 39.

[0079] Step 6-1: The base 40 of the laser cutting fixture 36 is provided with a cutting groove 38, which is consistent with the edge of the stamping correction surface of the theoretical stamping body 15 of the half tube 1, so as to reduce the risk of thermal damage to the laser cutting fixture 36 and the half tube semi-finished product 44 during the cutting process and extend the service life of the laser cutting fixture 36.

[0080] Step 6-2: The laser cutting fixture 36 bracket 39 is fixed on the base 40. The shape of the bracket 39 is consistent with the shape of the stamping correction surface 22 of the theoretical stamping body 15 of the half-tube 1. The bracket 39 has process holes 41 on both sides that are consistent with the positioning holes 21 on the positioning lugs 20. The bracket 39 is a hollow cross-shaped support body, composed of a longitudinal support body 42 and a transverse support body 43. The curvature of the longitudinal support body 42 is consistent with the curvature of the bending center line of the stamping correction surface 22 of the theoretical stamping body 15 of the half-tube 1. The width of the longitudinal support body 42 is approximately The width of the positioning lug 20 matches that of the theoretical stamping body 15 of the half-tube 1. The transverse support 43 is located in the middle of the stamping correction surface 22 of the half-tube 1, and is consistent with the cross-section of the middle part of the stamping correction surface 22. The width of the transverse support 43 is... The upper surfaces of the longitudinal support 42 and the transverse support 43 are curved positioning surfaces. During operation, the semi-finished tube 44 is fixed on the laser cutting fixture 36 bracket 39 by two positioning pins 37.

[0081] Step 7: Unloading

[0082] Before forming, the unfolded blank 14 is cut according to the unfolded blank 14 data, and a plastic film is attached to the side of the unfolded blank 14 that contacts the die 23.

[0083] Step 8: Deep drawing pre-forming

[0084] Step 8-1: Install the drawing die 32, apply lubricating oil to the contact area between the unfolded blank 14 and the blank holder 25 and the contact area between the unfolded blank 14 and the die 23, and place the unfolded blank 14 on the working surface of the blank holder 25 according to the outline of the unfolded blank 14 on the blank holder 25. The punch 24, die 23, and blank holder 25 are controlled by guide posts to control the drawing direction.

[0085] Step 8-2: Forming begins. The guide post connected to the punch 24 enters the guide post guide hole 27 of the die 23 through the guide post through hole 26 of the blank holder 25. The die 23 and the blank holder 25 clamp and unfold the blank 14 and begin to draw it according to the working surface of the punch 24. Under the combined action of the blank holder force and the drawing force, the material around the unfolded blank 14 gradually flows into the die cavity 28, and finally forms the actual deep-drawn half tube 1.

[0086] Step 9: Stress-relieving annealing

[0087] The actual deep-drawn body after deep drawing pre-forming is subjected to stress-relieving annealing at a temperature of 520~580°. The purpose of annealing is to eliminate residual internal stress in the actual deep-drawn body and restore the plasticity of the material, thereby improving the forming performance of the parts.

[0088] Step 10: Stamping and Shaping

[0089] Step 10-1: According to the theoretical stamping body outline 35 of half tube 1, the end of the actual deep-drawn body of half tube 1 is initially cut, the end ball head wrapping surface is removed, and the positioning ear piece 20 is retained to obtain the actual stamping body before stamping correction;

[0090] Step 10-2: Install the male and female molds of the straightening die, lubricate the actual stamping body of the half-pipe 1 and the working surface of the straightening die, and place the actual stamping body before stamping and straightening according to the theoretical stamping body outline 35 on the female mold 33.

[0091] Step 10-3: Start stamping and shaping. The shaping male mold 34 presses the actual stamped body of the half tube 1 into the shaping female mold 33 to obtain the stamped and shaped half tube semi-finished product 44. According to the positioning hole 21 on the shaping female mold 33, two end positioning holes 21 are made on the half tube semi-finished product 44.

[0092] Step 11: Laser cutting

[0093] Step 11-1: Install the laser cutting fixture 36, place the stamped and shaped semi-finished tube 44 on the positioning bracket 39 of the laser cutting fixture 36, the positioning hole 21 of the semi-finished tube 44 corresponds to the process hole 41 of the positioning bracket 39, and fix the semi-finished tube 44 on the laser cutting fixture 36 by the positioning pin 37.

[0094] Step 10-2: Cut the semi-finished tube 44 according to the designed laser cutting program, retaining the positioning lugs 20 at both ends, with a cutting tolerance of [missing information]. The final shaped body 45 of the semi-tube 1 with two positioning ear pieces is obtained;

[0095] Step 11: Trimming

[0096] Trim the final shape of the semi-tube 1 to 45 degrees according to the drawing requirements, and cut the positioning lugs 20 at both ends to obtain a titanium alloy semi-tube 1 part with shape tolerances that meet the document requirements.

[0097] Three points need to be explained: The titanium alloy constant curvature semi-tube structure provided in the embodiment is relatively regular. This TC1 bending room temperature forming method is also applicable to the forming of TC1 semi-tubes with variable curvature and irregular shapes, and the design concept is consistent. For TC1 titanium alloy bent semi-tubes with the same material specifications, curvature, and tube diameter but different lengths, the same deep drawing die, straightening die, and laser cutting fixture structure can be used, sharing the same positioning lugs and positioning holes. The required semi-tube parts can be obtained through different laser cutting programs, which can greatly reduce manufacturing costs. In order to better ensure the forming accuracy and quality of the semi-tube, when designing the theoretical deep drawing body of the semi-tube, process allowances can be added at both ends of the transition surface of the semi-tube to provide position compensation when initially cutting the end wrapping surface of the deep drawing body of the semi-tube.

Claims

1. A method for controlling springback defects during room temperature forming of TC1 high-curvature titanium alloy semi-tubes, comprising the following steps: Step 1: Construct a semi-theoretical deep-drawn body, wherein the deep-drawn body comprises: A transition surface, which is offset from the theoretical shape of the digital model of the semi-tube product by a specific value to the center. The above is obtained. The formula for determining the value of is: , in the formula The range of values ​​is The radius of the half-pipe is denoted as The aforementioned The value of is related to the bending angle of the half-pipe. Related, when hour, ,when hour, ,when hour, ,when hour, ; One end wrapping surface is formed by rotating the end curves at both ends of the transition surface 90° around the center line; and A flange face is located below the transition face and the end wrapping face, and is connected to the end wrapping face and the transition face through a connecting face to form a semi-manual theoretical deep drawing body; Step 2: Unfold the semi-manual theoretical deep drawing to form an unfolded blank; Step 3: Construct a semi-manufacturing theoretical stamping body, including: A stamping correction surface, which is consistent with the theoretical outer shape of the digital model of the semi-tube product; A stamping blanking surface is set below the stamping correction surface and is connected to the stamping correction surface through a stamping transition surface to form a semi-theoretical stamping body; Multiple positioning lugs are positioned at the midpoint of both ends of the stamping correction surface; and Multiple positioning holes are provided on the positioning ear piece; Step 4: Based on the semi-theoretical deep drawing body, manufacture the die, punch and blank holder of the deep drawing die. The working surface of the punch consists of the punch wrapping surface and the punch bending surface. The punch wrapping surface corresponds to the transition surface of the semi-theoretical deep drawing body, and the punch bending surface corresponds to the end wrapping surface of the semi-theoretical deep drawing body. Draw the outline of the unfolded blank on the blank holder. Step 5: Manufacture a straightening die based on the semi-manufactured theoretical stamping body. The straightening die includes a straightening male die and a straightening female die. Draw the outline of the semi-manufactured theoretical stamping body and the positioning holes, as well as the concave and convex outlines of the semi-manufactured theoretical outer surface, on the straightening female die. Step 6: Create a laser cutting fixture for the half-tube based on the semi-tube theoretical stamping body; Step 7: Cut the blank according to the unfolded shape; Step 8: Pre-draw the material on a drawing die; Step 9: Stress-relieving annealing; Step 10: Perform stamping and shaping on the shaping die; Step 11: Perform laser cutting of the final semi-tube shape in a laser cutting fixture; Step 12: Trim the final shape of the semi-tube, cut the positioning lugs at both ends, and obtain a titanium alloy semi-tube part that meets the shape tolerance requirements.

2. The method for controlling springback defects during room temperature forming of a TC1 large-curvature titanium alloy semi-tube according to claim 1, characterized in that... The height of the connecting surface The value is determined according to the formula. calculate, in The radius of the transition fillet is determined by the formula. Perform calculations. The thickness of half-tube material, The height is extended by the normal. According to the formula Calculation, where For the semi-physical theoretical external surface end face arc length, The arc length of the curve at the end of the transition surface.

3. The method for controlling springback defects during room temperature forming of a TC1 large-curvature titanium alloy semi-tube according to claim 2, characterized in that... The aforementioned transition fillet radius The value of is related to the bending angle of the half-pipe. Related, when hour, ,when hour, ,when hour, .

4. The method for controlling springback defects during room temperature forming of a TC1 large-curvature titanium alloy semi-tube according to claim 3, characterized in that... The outer edge of the flange face is formed by offsetting the bottom outline of the connecting surface outward by a certain amount.

5. The method for controlling springback defects during room temperature forming of a TC1 large-curvature titanium alloy semi-tube according to claim 4, characterized in that... The offset of the bottom outline of the connecting surface corresponding to the outer edge of the convex curvature of the transition surface is: , The offset corresponding to the outer edge of the concave curvature of the transition surface is , The offset corresponding to the boundary line of the end-wrap surface ball head is , .

6. The method for controlling springback defects during room temperature forming of a TC1 large-curvature titanium alloy semi-tube according to claim 5, characterized in that... The maximum material thickness reduction rate of the unfolded blank was determined using finite element analysis. Predict the maximum thinning rate. At that time, offset and Take the minimum value; otherwise, take the maximum value.

7. The method for controlling springback defects during room temperature forming of a TC1 large-curvature titanium alloy semi-tube according to claim 6, characterized in that... The height of the stamped transition surface The value is determined according to the formula. calculate, in The radius of the transition angle is given by the formula. Configure settings. For process compensation height, According to the formula calculate.

8. The method for controlling springback defects during room temperature forming of a TC1 large-curvature titanium alloy semi-tube according to claim 7, characterized in that... The outer edge of the stamping pressing surface is formed by offsetting the bottom outline of the stamping transition surface outward by a certain amount.

9. The method for controlling springback defects during room temperature forming of a TC1 large-curvature titanium alloy semi-tube according to claim 8, characterized in that... The offset of the bottom contour line of the stamping transition surface from the convex contour line of the stamping correction surface is: , The offset corresponding to the concave contour line of the stamping correction surface is , .

10. The method for controlling springback defects during room temperature forming of a TC1 large-curvature titanium alloy semi-tube according to claim 9, characterized in that... The gap between the punch wrapping surface and the corresponding part of the die cavity According to the formula Design of the gap between the curved surface of the punch and the corresponding part of the die cavity. According to the formula design.

11. The method for controlling springback defects during room temperature forming of a TC1 large-curvature titanium alloy semi-tube according to claim 10, characterized in that... The design tolerance of the correction mold is The shape of the positive mold matches the shape of the negative mold.

12. The method for controlling springback defects during room temperature forming of a TC1 large-curvature titanium alloy semi-tube according to claim 11, characterized in that... The laser cutting fixture includes: a base with a cutting groove that is aligned with the edge of the stamping correction surface of the semi-manufactured theoretical stamping body; and a bracket fixed to the base, the bracket having an outline that is aligned with the outline of the stamping correction surface of the semi-manufactured theoretical stamping body, and process holes on both sides that are aligned with the positioning holes on the positioning lugs.

13. The method for controlling springback defects during room temperature forming of a TC1 large-curvature titanium alloy semi-tube according to claim 12, characterized in that... The specific process of deep drawing preforming in step 8 is as follows: 13-1 Install the drawing die, apply lubricating oil to the contact area between the blank and the blank holder and the contact area between the blank and the die, and place the blank on the working surface of the blank holder according to the outline of the blank on the blank holder. The punch, die, and blank holder are controlled by guide posts to control the drawing direction. 13-2 Forming begins. The guide post connected to the punch enters the guide post guide hole of the die through the guide post through hole of the blank holder. The die and blank holder clamp and unfold the blank and begin to draw according to the working surface of the punch. Under the combined action of blank holder force and drawing force, the material around the unfolded blank gradually flows into the die cavity, and finally forms the actual drawn body of the half tube.

14. The method for controlling springback defects during room temperature forming of a TC1 large-curvature titanium alloy semi-tube according to claim 13, characterized in that... The specific process of stamping and straightening in step 10 is as follows: 14-1 Cut the actual deep-drawn half-tube according to the outline of the semi-tube theoretical stamping body, remove the end ball head compensation surface, and retain the positioning lug to obtain the actual stamping body before stamping correction; 14-2 Install the male and female dies of the straightening die, lubricate the actual stamped body of the half-tube and the working surface of the straightening die, and place the actual stamped body before stamping and straightening according to the theoretical stamped body outline on the female die; 14-3 Start stamping and shaping. The shaping male die presses the actual stamped half-tube into the shaping female die to obtain the stamped and shaped half-tube semi-finished product. According to the positioning hole positions on the shaping female die, make two end positioning holes on the half-tube semi-finished product.

15. The method for controlling springback defects during room temperature forming of a TC1 large-curvature titanium alloy semi-tube according to claim 14, characterized in that... The specific process of laser cutting in step 11 is as follows: 15-1 Install the laser cutting fixture, place the stamped and shaped semi-finished tube on the positioning bracket of the laser cutting fixture, and align the positioning holes of the semi-finished tube with the process holes of the positioning bracket. Fix the semi-finished tube on the laser cutting fixture using positioning pins. 15-2 Cut the semi-finished tube according to the designed laser cutting program, retaining the positioning lugs at both ends. The cutting tolerance is [missing information]. The final semi-tube shape with two positioning ear pieces is obtained.

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