Hole opening machining process for hull bent plate structure and deformation control method and device for hull bent plate structure

Abstract

The invention relates to a trepanning machining process for a hull curved plate structure and a deformation control method and device thereof. The trepanning machining process comprises the following steps: firstly, pre-releasing stress: forming a plurality of stress release holes around a target large hole of a curved plate; then self-adaptive trepanning is conducted, then the bent plate is divided into a face A and a face B, target large holes are machined alternately, and allowance is cut off for each face three times; and semi-finish-milling correction is conducted, roundness errors and axis deflection are compensated in real time through monitoring, and gravity deformation of the bent plate is restrained through a profiling supporting method. The adopted device comprises a supporting base, a bent plate fixing device is arranged on the supporting base, a milling machine posture adjusting device is arranged on one side of the bent plate fixing device, and a movable numerical control milling cutter is arranged on the milling machine posture adjusting device. In the implementation process, the process method is matched with the device, the purposes of rapidly opening holes and improving the hole opening quality can be achieved, gravity deformation of the bent plate is restrained through a profiling supporting method, the structure is enhanced, machining warping is prevented, the machining quality and efficiency are improved, and the deformation amount of the bent plate in the machining process is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ship hull curved plate opening, in particular to a ship hull curved plate structure opening machining process and deformation control method and device. BACKGROUND

[0002] The ship hull curved plate structure has the characteristics of large size, complex line type and high precision requirement, and usually involves opening operation. In order to improve the quality and efficiency of subsequent machining and assembly, the precision of the curved plate structure opening needs to be strictly controlled: the aperture deviation is less than 1mm, the height direction position deviation is less than 1mm, and the center position deviation is less than 1mm.

[0003] In the prior art, the traditional opening process has the difficulty of stress redistribution and buckling deformation caused by deformation sensitivity. At the same time, the precision requirement is strict, and the material is difficult to process, such as AH36 high-strength steel which is prone to thermal stress deformation and cracking. The current opening process is rough, the heat affected zone is wide, and there are many cracks caused by drilling or flame cutting, which need a lot of polishing. When machining large holes, tool vibration causes taper error > 2mm. During machining, deformation control is passive and inefficient, and post-weld correction causes grain coarsening or burning. Temporary support defects cause stress concentration and reduce fatigue life. There is also a problem of insufficient precision after machining, and manual marking may have a deviation of > 3mm.

[0004] In summary, there is an urgent need for an innovative phased active prevention and control method for curved plate opening machining process and deformation control. SUMMARY

[0005] The purpose of the present application is to provide an improved ship hull curved plate structure opening machining process and deformation control method and device, which can quickly and efficiently open the curved plate structure, and has high machining precision and small deformation, thereby improving the quality of curved plate machining.

[0006] In order to achieve the above purpose, the technical scheme of the present application is as follows: a ship hull curved plate structure opening machining process and deformation control method, characterized by the following steps: a, pre-release stress: a plurality of stress release holes are arranged around the target large hole of the curved plate, the center distance of the stress release hole from the edge of the target large hole is 60-120mm, and more than 30% of the local stress is effectively released; b, adaptive opening: spiral milling rough machining is performed on the target large hole; c, gradient shape control, the curved plate is divided into A and B surfaces to alternately process the target large hole, each surface is cut three times to remove the excess amount, and after each surface processing, the natural aging treatment time of 3-5 hours is waited to eliminate the machining stress; d, semi-precision milling correction is performed, a ball nose milling cutter is used to process the curved surface area according to the contour line, and during the milling process, the roundness error and axial deviation are monitored in real time, and the profile support method is used to suppress the gravitational deformation of the curved plate to enhance the structure.

[0007] Furthermore, in step a, 20-30 stress relief holes are set around the target large hole, with a diameter of 40-60 mm; the diameter d of the stress relief holes... s The target large aperture D satisfies: d s = k·D, where k=0.1–0.15, and the distance d from the center of the stress relief hole to the edge of the target large hole satisfies D: d=m·D, where m=0.12–0.20.

[0008] Further, in step c, an 80mm diameter carbide 6-flute end mill is selected for alternating face milling. The cutter shank is equipped with a vibration damper. The curved plate is divided into face A and face B for alternating machining. The allowance for each face is removed in three stages. The allowance for the three stages is distributed proportionally: the first removal accounts for 35%-45% of the total, the second for 20%-30%, and the third for 30%-40%, and the depth of cut in a single operation does not exceed 20% of the cutter diameter. The formula for the allowance to be removed is: Where H is the total margin, and Δ is the adjustment amount based on curvature. The value of Δ ranges from 0 to 0.01. If the curvature of the cut surface is greater than the curvature of the target large hole, Δ takes a negative value.

[0009] The curved plate is divided into surface A and surface B for alternating processing. The allowance for each surface is removed three times, and the allowances for the three removals are distributed proportionally. Surface A is removed with allowances of 12mm, 8mm and 14mm in three removals; surface B is removed with allowances of 16mm, 9mm and 9mm in three removals. After each reversal, a 4-hour natural aging treatment is performed to eliminate processing stress.

[0010] Furthermore, in step d, a 50mm diameter ball end mill is used to machine the curved surface area along the contour line trajectory, leaving a 0.3mm finishing allowance to compensate for tool runout error caused by curvature changes; a milling bar integrated fine-tuning piezoelectric ceramic actuator is used to provide real-time feedback and compensate for roundness error; the milling cutter removes the allowance in three passes, which are 0.5mm, 0.2mm and 0.1mm respectively, with an adjustable feed rate of 0.05mm / r.

[0011] Furthermore, in step d, a contour support method based on the curvature of the curved plate is adopted using a multimodal constraint clamping system. Rigid supports are used in areas with a curvature radius exceeding 5m; other areas use flexible polyurethane pads. Adjustable supports in a grid pattern are arranged along the edges of the curved plate, applying a minimum force of 5kN / m. 2 The supporting force is used to suppress the downward deformation due to gravity; at the same time, the pressure of the bending machine's pressure cylinder is set to 20% of the real-time cutting force and dynamically adjusted with the tool position to prevent warping during processing; to increase the accuracy assurance and inspection process, fiber optic strain gauges are attached around the target large hole to monitor the strain value in real time, and a stop protection is triggered when it exceeds 300εμ; during the milling process, a laser tracker is used to detect the shaft runout, and automatic compensation is given when the deviation exceeds 0.05mm.

[0012] An apparatus for machining and deformation control of openings in curved plate structures of ship hulls is characterized in that: the apparatus includes a support base, a curved plate fixing device is provided on the support base, the support base and the curved plate fixing device are connected by a transition platform, a milling machine attitude adjustment device is provided on one side of the curved plate fixing device, a movable CNC milling cutter is provided on the milling machine attitude adjustment device, and the CNC milling cutter or the milling machine attitude adjustment device is driven by a longitudinal transmission device.

[0013] Preferably, the support base is equipped with a hydraulic leveling system to compensate for the flatness of the ground; the transition platform is used to adjust the height and horizontal position of the curved plate workpiece; the curved plate fixing device is used to clamp the curved plate, and the curved plate fixing device is equipped with a multi-modal constraint clamping system; the CNC milling cutter is made of cemented carbide and is equipped with a vibration damper; the milling machine attitude adjustment device is used to adjust the direction and angle of the CNC milling cutter, and the milling machine attitude adjustment device is equipped with a laser tracker and a piezoelectric ceramic actuator.

[0014] Furthermore, the longitudinal transmission device includes a transmission base, a servo motor, and a longitudinal lead screw connected to the servo motor. The support base is provided with a longitudinal guide rail that cooperates with the CNC milling cutter or the milling machine posture adjustment device. The servo motor drives the longitudinal lead screw to rotate, thereby driving the CNC milling cutter or the milling machine posture adjustment device to move along the longitudinal guide rail. The bottom of the longitudinal lead screw is provided with a lead screw nut seat to prevent the longitudinal lead screw from bending or vibrating.

[0015] Furthermore, the CNC milling cutter includes a frame, a coolant storage device on the side of the frame, a milling cutter fixing device on the top of the frame, a rotary motor connected to the milling cutter fixing device inside the frame, an output end of the rotary motor connected to a rotary bearing, a rotary bearing connected to a spindle, a cutting tool at the end of the spindle, and an end cap that mates with the rotary bearing at the bottom of the frame.

[0016] Furthermore, the rotating motor is a vertical servo motor with a spiral water-cooling groove on the housing to provide rotational power to the spindle. The rotating bearing is connected to the rotating motor via a coupling, which is used to compensate for axial misalignment.

[0017] Furthermore, the rotating bearing is an angular contact ball bearing used to support the rotation of the main shaft, the cooling storage tank is a cylindrical aluminum alloy tank with a diaphragm pressure valve, the outlet of the cooling storage tank is connected to a high-pressure hose, the end cover is a steel flange cover with O-ring silicone seals on the edge.

[0018] Compared with the prior art, the technical solution of the present invention not only improves the overall technical solution, but also includes many improvements in details. Specifically, it has the following beneficial effects: 1. The improved solution of the present invention sets several stress relief holes around the target large hole of the curved plate to effectively release more than 30% of the local stress. Then, gradient control is adopted to divide the curved plate into surface A and surface B and process the target large hole alternately. This can effectively eliminate processing stress, achieve the purpose of rapid hole opening, improve processing accuracy, and prevent deformation of the curved plate. 2. In the technical solution of the present invention, the contour support method of the multimodal constraint clamping system is used in the processing to design the curved plate according to the curvature partition and apply support force to suppress the deformation of the curved plate due to gravity. At the same time, the pressure of the bending machine pressure cylinder is set to 20% of the real-time cutting force and dynamically adjusted with the tool position to prevent warping during processing, improve processing quality and efficiency, and effectively reduce the amount of deformation of the curved plate during processing. 3. In the structure of the present invention, a curved plate fixing device is provided on the support base, and the support base and the curved plate fixing device are connected by a transition platform. A milling machine posture adjustment device is provided on one side of the curved plate fixing device. A movable CNC milling cutter is provided on the milling machine posture adjustment device. The CNC milling cutter or the milling machine posture adjustment device is driven by a longitudinal transmission device. The transition platform is used to adjust the height and horizontal position of the curved plate workpiece. The curved plate fixing device is used to clamp the curved plate. The curved plate fixing device is provided with a multimodal constraint clamping system, which can prevent deformation generated during the processing of the curved plate and improve the processing quality. 4. The process steps of this invention are simple, and it can quickly and efficiently complete the opening of curved plates, which improves efficiency, reduces costs, and facilitates promotion and application. Attached Figure Description

[0019] Fig. 1 This is a schematic diagram of the structure of the present invention.

[0020] Fig. 2 This is a schematic diagram of the longitudinal transmission device in one embodiment of the present invention.

[0021] Fig. 3 This is a schematic diagram of the structure of a CNC milling cutter in one embodiment of the present invention.

[0022] Figure label: 1. Milling machine posture adjustment device; 2. CNC tool cleaning device; 3. Curved plate fixing device; 4. Transition platform; 5. Support base; 6. Servo motor; 7. Coupling; 8. Longitudinal lead screw; 9. Longitudinal guide rail; 10. Transmission base. 11 Lead screw nut seat, 12 Milling cutter fixing device, 13 Rotary motor, 14, 15 Coolant storage device, 16 Rotary bearing, 17 Transition connecting plate, 18 Bolt group, 19 End cap, 20 Cutting tool. Detailed Implementation

[0023] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] This invention provides a machining process and deformation control method for opening holes in a curved plate structure of a ship hull. The process includes the following steps: a) Pre-stress relief: Several stress relief holes are set around the target large hole in the curved plate. The center of the stress relief hole is 60-120mm away from the edge of the target large hole, effectively releasing more than 30% of the local stress; b) Adaptive opening: The target large hole is rough machined by spiral milling; c) Gradient shape control: The curved plate is divided into surface A and surface B, and the target large hole is machined alternately. The excess material on each surface is removed in three steps. After each surface change, a natural aging treatment time of 3-5 hours is allowed to eliminate machining stress; d) Semi-finish milling correction: A ball end mill is used to machine the curved surface area according to the contour trajectory. During the milling finish machining process, the roundness error and axial runout are compensated in real time by monitoring. A contour support method is used to suppress the gravitational deformation of the curved plate and strengthen the structure.

[0025] During implementation, stress relief holes are pre-drilled around the target large hole to effectively release local stress. Then, a gradient shape control method is used to divide the curved plate into A-side and B-side for alternating processing, further eliminating processing stress and achieving rapid hole drilling and improved hole drilling quality. At the same time, a contour support method is used to suppress the gravitational deformation of the curved plate, strengthen the structure, prevent processing warping, improve processing quality and efficiency, and effectively reduce the amount of curved plate deformation during processing.

[0026] Example 1 This embodiment describes a machining process and deformation control method for opening holes in a curved plate structure of a ship hull, including the following steps: a) Pre-stress relief: Several stress relief holes are set around the target large hole in the curved plate, with the center of the stress relief hole 60-120mm away from the edge of the target large hole, effectively releasing more than 30% of the local stress; b) Adaptive opening: The target large hole is rough machined by spiral milling; c) Gradient shape control: The curved plate is divided into surface A and surface B, and the target large hole is machined alternately. The excess material is removed in three steps on each surface. After each surface change, a natural aging treatment time of 3-5 hours is allowed to eliminate machining stress; d) Semi-finish milling correction: A ball end mill is used to machine the curved surface area according to the contour trajectory. During the milling finish machining process, the roundness error and axial runout are compensated in real time by monitoring. A contour support method is used to suppress the gravitational deformation of the curved plate and strengthen the structure.

[0027] Specifically, in step a, the diameter d of the stress relief hole s The target large aperture D satisfies: ds = k·D, where k = 0.1–0.15, and the distance d between the center of the stress relief hole and the edge of the target large hole satisfies: d = m·D, where m = 0.12–0.20. In this embodiment, 24 stress relief holes are uniformly arranged around the target large hole. The diameter of the stress relief hole is 50 mm, and the center of the stress relief hole is 80 mm away from the edge of the target large hole, which can effectively release 38% of the local stress.

[0028] In step c, an 80mm diameter carbide 6-flute end mill is selected for alternating face milling. The cutter shank is equipped with a vibration damper. The curved plate is divided into face A and face B for alternating machining. The allowance for each face is removed in three stages. The allowance for the three stages is distributed proportionally: the first removal accounts for 35%-45% of the total allowance, the second for 20%-30%, and the third for 30%-40%. The depth of cut in a single operation does not exceed 20% of the cutter diameter. The formula for the allowance to be removed is: Where H is the total margin, and Δ is the adjustment amount based on curvature. The value of Δ ranges from 0 to 0.01. If the curvature of the cut surface is greater than the curvature of the target large hole, Δ takes a negative value.

[0029] In this implementation, the excess material on surface A is removed three times at 12mm, 8mm and 14mm; the excess material on surface B is removed three times at 16mm, 9mm and 9mm; after each reversal, a 4-hour natural aging treatment is performed to eliminate processing stress.

[0030] In step d, a 50mm diameter ball end mill is used to machine the curved surface area along a contour trajectory, leaving a 0.3mm finishing allowance to compensate for tool runout error caused by curvature changes. Adaptive milling finishing is performed using a CNC gantry milling machine with an integrated laser tracker. A milling bar integrated fine-tuning piezoelectric ceramic actuator is used to provide real-time feedback and compensate for roundness errors. The milling cutter removes the allowance in three passes: 0.5mm, 0.2mm, and 0.1mm, with an adjustable feed rate of 0.05mm / r. Simultaneously, a 10MPa high-pressure emulsion directional flushing system is applied to suppress thermal deformation in the cutting zone.

[0031] In step d, a contour support method based on the curvature of the curved plate is used with a multimodal constraint clamping system. Rigid supports are used in areas with a curvature radius exceeding 5m; other areas use flexible polyurethane pads. Adjustable supports in a grid pattern are arranged along the edges of the curved plate, applying a minimum force of 5kN / m. 2The supporting force is used to suppress sagging deformation due to gravity; at the same time, the pressure of the bending machine's pressure cylinder is set to 20% of the real-time cutting force and dynamically adjusted according to the tool position to prevent warping during processing. The dynamic adjustment strategy is as follows: 1. Monitor the cutting force Fc and the tool position (x,y,z); 2. Calculate the dynamic coefficient k(x,y) by querying the pre-stored curved plate stiffness distribution diagram; 3. Set the pressure value; 4. Execute the piezoelectric actuator; 5. Verify through strain gauges; 6. Finally, cyclically adjust to prevent warping during processing. Accuracy assurance and detection processes are also added. Fiber optic strain gauges are installed around the target large hole to monitor the strain value in real time. When the strain exceeds 300εμ, a shutdown protection is triggered. During milling, a laser tracker is used to detect axial runout, and automatic compensation is applied when the deviation exceeds 0.05mm.

[0032] Example 2 This embodiment describes an apparatus for machining processes and deformation control methods for opening holes in curved hull structures. (See also...) Figs. 1-3 The device includes a support base 5, on which a curved plate fixing device 3 is provided. The support base and the curved plate fixing device are connected by a transition platform 4. A milling machine posture adjustment device 1 is provided on one side of the curved plate fixing device 3. A movable CNC milling cutter 2 is provided on the milling machine posture adjustment device. The CNC milling cutter or the milling machine posture adjustment device is driven by a longitudinal transmission device.

[0033] Specifically, the milling machine attitude adjustment device 1 is used to adjust the orientation and angle of the CNC milling cutter. The device is equipped with a laser tracker and a piezoelectric ceramic actuator to achieve real-time compensation for roundness errors. Driven by a servo motor, the milling machine attitude adjustment device 1 supports multi-axis motion to adapt to the curved surface of the plate. The CNC milling cutter 2, as the core tool for hole drilling, is made of carbide and equipped with a vibration damper. In this embodiment, it includes an 80mm diameter six-flute end mill for roughing and a 50mm diameter ball end mill for finishing, controlling thermal deformation through an adaptive milling path. The curved plate fixing device 3 is used to clamp the curved plate structure. It features a multi-modal constraint clamping system designed according to the curvature of the curved plate. The transition platform 4, as a transition structure, connects the support base and the curved plate fixing device, facilitating adjustment of the curved plate's height and horizontal position. The transition platform 4 has a positioning groove to ensure the initial clamping accuracy of the curved plate. The support base 5 is placed on the ground, providing overall stability. The support base integrates a hydraulic leveling system to compensate for uneven ground and is fixed to the ground with bolts.

[0034] Before operation, the curved plate frame needs to be hoisted onto the curved plate fixing device 3 and adjusted into position using the contour support module. During machining, the milling machine posture adjustment device 1 drives the CNC cutting tool 2 to perform hole drilling, while simultaneously monitoring strain in real time to ensure machining quality.

[0035] Furthermore, the longitudinal transmission device includes a transmission base 10, a servo motor 6, and a longitudinal lead screw 8 connected to the servo motor. The support base is provided with a longitudinal guide rail 9 that cooperates with the CNC milling cutter or the milling machine posture adjustment device. The servo motor 6 drives the longitudinal lead screw to rotate, thereby driving the CNC milling cutter or the milling machine posture adjustment device to move along the longitudinal guide rail 9. The bottom of the longitudinal lead screw is provided with a lead screw nut seat 11 to prevent the longitudinal lead screw from bending or vibrating.

[0036] Specifically, the longitudinal servo motor 6 provides the power source and achieves stepless speed regulation through frequency conversion control. The motor output shaft is connected to a reducer to reduce the speed and increase the torque to adapt to heavy-duty cutting. The coupling 7 connects the servo motor 6 and the longitudinal lead screw 8, transmitting torque and compensating for installation deviations. The coupling is an elastic coupling, which can reduce vibration transmission. The longitudinal lead screw 8 converts rotary motion into linear motion, driving the milling cutter to move along the Y direction. The longitudinal lead screw is made of high-strength alloy steel with a precision pitch design to ensure a feed rate accuracy of 0.05mm / r. The longitudinal guide rail 9 is mounted on the support base 5, providing support and guidance. The longitudinal guide rail uses linear ball bearings, combined with a slider to reduce friction and ensure smooth movement. The transmission base 10 is located at the bottom and is fixed to the ground with anchor bolts, providing overall support for the gantry frame. The lead screw nut seat 11 is located at the end of the longitudinal lead screw 8 to prevent bending and vibration of the longitudinal lead screw. The lead screw nut seat is fixed to the base with bolts for easy maintenance. When the longitudinal transmission device is working, the servo motor 6 drives the longitudinal lead screw 8 to rotate, which in turn moves the milling cutter or attitude adjustment device along the guide rail 9. The longitudinal transmission device is equipped with a position sensor, which feeds back data to the CNC system to achieve closed-loop control.

[0037] Furthermore, the CNC milling cutter includes a frame, a coolant storage device 15 on the side of the frame, a milling cutter fixing device 12 on the top of the frame, a rotary motor 13 connected to the milling cutter fixing device inside the frame, a rotary bearing 16 connected to the output end of the rotary motor, a cutting tool 20 at the end of the spindle, and an end cap 19 that mates with the rotary bearing at the bottom of the frame. The rotary motor is a vertical servo motor with a spiral water-cooling groove on its outer shell to provide rotational power to the spindle. The rotary bearing and the rotary motor are connected by a coupling 14, which is used to compensate for axial misalignment and eliminate assembly clearance through an expansion sleeve. The rotary bearing is an angular contact ball bearing used to support spindle rotation and control radial runout. The coolant storage tank is a cylindrical aluminum alloy tank with a diaphragm pressure valve. The outlet of the coolant storage tank is connected to a high-pressure hose, and the end cap is a steel flange with an O-ring silicone seal on the edge to prevent dust intrusion.

[0038] Specifically, the milling cutter fixing device 12 connects the machine tool spindle and the cutter body, transmitting cutting torque. It adopts a BT50 taper interface, with the taper surface hardened to HRC58-62. The flange has 6 sets of M12 bolt holes (bolt number 18), and the bottom positioning boss mates with the cutter 20. The rotary motor 13 supports stepless speed regulation, and a rotary bearing 16 is installed at the front end of the output shaft of the rotary motor. The transition connecting plate 17 connects the bearing seat and the cutter and can compensate for installation errors. It ensures the parallelism of the reference surface through the bolt group 18. The bolt group 18 consists of main bolts and peripheral positioning pins, which serve to fasten the various modules and form a rigid assembly. The cutter 20 uses cemented carbide and indexable PCD inserts with a built-in piezoelectric ceramic actuator, capable of performing cutting tasks, and integrates a fine-tuning mechanism.

[0039] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A process for machining openings in a curved hull structure and a method for controlling deformation, characterized in that: The process includes the following steps: a) Pre-stress relief: Several stress relief holes are set around the target large hole in the curved plate. The center of the stress relief hole is 60-120mm away from the edge of the target large hole, effectively releasing more than 30% of the local stress; b) Adaptive hole opening: The target large hole is rough machined by spiral milling; c) Gradient shape control: The curved plate is divided into surface A and surface B, and the target large hole is machined alternately. The excess material is removed in three steps on each surface. After each surface change, a natural aging treatment time of 3-5 hours is allowed to eliminate the machining stress; d) Semi-finish milling correction: A ball end mill is used to machine the curved surface area according to the contour trajectory. During the milling finish machining process, the roundness error and axial runout are compensated in real time by monitoring. The contour support method is used to suppress the gravitational deformation of the curved plate and strengthen the structure.

2. The machining process and deformation control method for opening holes in a curved hull structure according to claim 1, characterized in that: In step a, 20-30 stress relief holes are set around the target large hole, with a diameter of 40-60 mm; the hole diameter d of the stress relief hole is... s The target large aperture D satisfies: d s = k·D, where k=0.1–0.15, and the distance d between the center of the stress relief hole and the edge of the target large hole satisfies: d=m·D, where m=0.12–0.

20.

3. The machining process and deformation control method for opening holes in a curved hull structure according to claim 1, characterized in that: In step c, an 80mm diameter carbide 6-flute end mill is selected for alternating face milling. The cutter shank is equipped with a vibration damper. The curved plate is divided into face A and face B for alternating machining. The allowance for each face is removed in three stages. The allowance for the three stages is distributed proportionally: the first removal accounts for 35%-45% of the total allowance, the second for 20%-30%, and the third for 30%-40%. The depth of cut in a single operation does not exceed 20% of the cutter diameter. The formula for the allowance to be removed is: Where H is the total margin, and Δ is the adjustment amount based on curvature. The value of Δ ranges from 0 to 0.

01. If the curvature of the cut surface is greater than the curvature of the target large hole, Δ takes a negative value.

4. The machining process and deformation control method for opening holes in a curved hull structure according to claim 3, characterized in that: The curved plate is divided into surface A and surface B for alternating processing. The excess material on each surface is removed in three stages. Surface A is removed in three stages at 12mm, 8mm and 14mm. Surface B is removed in three stages at 16mm, 9mm and 9mm. After each reversal, a 4-hour natural aging treatment is performed to eliminate processing stress.

5. The machining process and deformation control method for opening holes in a curved hull structure according to claim 1, characterized in that: In step d, a 50mm diameter ball end mill is used to machine the curved surface area along the contour line trajectory, leaving a 0.3mm finishing allowance to compensate for tool runout error caused by curvature changes; a milling bar integrated fine-tuning piezoelectric ceramic actuator is used to provide real-time feedback and compensate for roundness error; the milling cutter removes the allowance in three passes, which are 0.5mm, 0.2mm and 0.1mm respectively, with an adjustable feed rate of 0.05mm / r.

6. The machining process and deformation control method for opening holes in a curved hull structure according to claim 1, characterized in that: In step d, a contour support method based on the curvature of the curved plate is used with a multimodal constraint clamping system. Rigid supports are used in areas with a curvature radius exceeding 5m; other areas use flexible polyurethane pads. Adjustable supports in a grid pattern are arranged along the edges of the curved plate, applying a minimum force of 5kN / m. 2 The supporting force is used to suppress the downward deformation due to gravity; at the same time, the pressure of the bending machine's pressure cylinder is set to 20% of the real-time cutting force and dynamically adjusted with the tool position to prevent warping during processing; to increase the accuracy assurance and inspection process, fiber optic strain gauges are attached around the target large hole to monitor the strain value in real time, and a stop protection is triggered when it exceeds 300εμ; during the milling process, a laser tracker is used to detect the shaft runout, and automatic compensation is given when the deviation exceeds 0.05mm.

7. The apparatus for machining and deformation control of openings in a curved hull structure according to claim 1, characterized in that: The device includes a support base, on which a curved plate fixing device is provided. The support base and the curved plate fixing device are connected by a transition platform. A milling machine attitude adjustment device is provided on one side of the curved plate fixing device. A movable CNC milling cutter is provided on the milling machine attitude adjustment device. The CNC milling cutter or the milling machine attitude adjustment device is driven by a longitudinal transmission device.

8. The apparatus for machining and deformation control of openings in a curved hull structure according to claim 7, characterized in that: The support base is equipped with a hydraulic leveling system to compensate for the flatness of the ground; the transition platform is used to adjust the height and horizontal position of the curved plate workpiece; the curved plate fixing device is used to clamp the curved plate, and the curved plate fixing device is equipped with a multi-modal constraint clamping system; the CNC milling cutter is made of cemented carbide and is equipped with a vibration damper; the milling machine attitude adjustment device is used to adjust the direction and angle of the CNC milling cutter, and the milling machine attitude adjustment device is equipped with a laser tracker and a piezoelectric ceramic actuator.

9. The apparatus for machining and deformation control of openings in a curved hull structure according to claim 7, characterized in that: The longitudinal transmission device includes a transmission base, a servo motor, and a longitudinal lead screw connected to the servo motor. The support base is provided with a longitudinal guide rail that cooperates with the CNC milling cutter or the milling machine posture adjustment device. The servo motor drives the longitudinal lead screw to rotate, thereby driving the CNC milling cutter or the milling machine posture adjustment device to move along the longitudinal guide rail. The bottom of the longitudinal lead screw is provided with a lead screw nut seat to prevent the longitudinal lead screw from bending or vibrating.

10. The apparatus for machining and deformation control of openings in a curved hull structure according to claim 7, characterized in that: The CNC milling cutter includes a frame, a coolant storage device on the side of the frame, a milling cutter fixing device on the top of the frame, a rotary motor connected to the milling cutter fixing device inside the frame, a rotary bearing connected to the output end of the rotary motor, a cutting tool at the end of the spindle, and an end cap that mates with the rotary bearing at the bottom of the frame.

11. The apparatus for machining and deformation control of openings in a curved hull structure according to claim 10, characterized in that: The rotating motor is a vertical servo motor with a spiral water-cooling groove on the housing to provide rotational power to the spindle. The rotating bearing is connected to the rotating motor via a coupling, which is used to compensate for axial misalignment.

12. The apparatus for machining and deformation control of openings in a curved hull structure according to claim 10, characterized in that: The rotating bearing is an angular contact ball bearing used to support the rotation of the main shaft. The cooling storage tank is a cylindrical aluminum alloy tank with a diaphragm pressure valve. The outlet of the cooling storage tank is connected to a high-pressure hose. The end cover is a steel flange cover with O-ring silicone seals on the edge.

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