A flexible laminated guiding device and method for processing countersunk holes of ceramic matrix composite curved thin-walled components

Abstract

The present application belongs to the technical field of ceramic matrix composite material processing, and discloses a flexible laminated guiding device for processing countersunk hole of curved thin-walled component of ceramic matrix composite material, which comprises: a plurality of flexible metal sheets, each of which is provided with a guiding hole, the diameter of the guiding hole being the same as that of the bottom hole; and a positioning pin, which is used to pass through the guiding holes of the flexible metal sheets and the bottom hole of the component in turn in a tight fit mode, so that the guiding holes are coaxially aligned with the bottom hole; and each flexible metal sheet is fixed after being pressed against the back surface of the component, so that the wall thickness of the guiding hole formed by the laminated flexible metal sheets is the sum of the thicknesses of the flexible metal sheets, thereby playing a role of constraint and protection of the bottom hole wall when the guiding structure of the groove cutter is inserted into the bottom hole for groove processing. The present application solves the problem of difficult high-quality processing of countersunk hole of curved thin-walled component in the workshop and on-site environment.

Description

Technical Field

[0001] This invention belongs to the field of ceramic matrix composite material processing technology, specifically relating to a flexible laminated guiding device and method for processing countersunk holes in curved thin-walled components of ceramic matrix composite materials. Background Technology

[0002] Continuous fiber reinforced ceramic matrix composites (CMCs), especially SiC / SiC and C / SiC composites, are increasingly used in aerospace hot-end components due to their excellent high-temperature mechanical properties and oxidation resistance. In practical engineering applications, CMC components are typically connected and assembled using fasteners such as countersunk bolts and rivets, requiring countersunk holes to be machined into the components. The machining of countersunk holes usually follows a process route of drilling a pilot hole first and then scribing a recess, that is, first drilling a pilot hole to the final hole size into the component, and then using a scribing tool to machine a tapered countersunk recess at the end of the pilot hole.

[0003] In the countersunk hole machining of thin-walled ceramic matrix composite components, the countersunk depth often accounts for 50% to 90% of the component wall thickness, resulting in a very small remaining wall thickness after countersunk machining, typically less than 1 mm. Under these wall thickness conditions, the hole wall is extremely fragile. When the countersunk tool is inserted into the hole for positioning and guidance, the tool vibration and runout can easily cause frictional wear, chipping, or even cracking of the hole wall, severely affecting the final hole dimensional accuracy and hole wall quality.

[0004] To address the aforementioned issues, existing technologies (such as CN108145213A) propose a solution involving a guide load body on the back of thin-walled parts. By adding a rigid load body with a guide hole to the back of the part, the effective wall thickness of the bottom hole is effectively increased, ensuring that the guiding structure of the dicing tool is adequately constrained and positioned throughout the dicing process. However, this solution has significant limitations: First, the rigid load body must precisely match the back surface of the part to achieve effective fit and fixation. This solution is feasible for planar or simple-shaped parts; however, for complex curved surface components commonly found in practical engineering—such as curved wall panels for aero-engines—where the back surface varies with location, and each bottom hole has a different back surface—if this solution is adopted, a separate load body matching the back surface of each bottom hole needs to be machined. This would result in a large number of load bodies, extremely high processing costs, and an unacceptable production cycle, making it practically unsuitable for mass production of curved components. Secondly, the method of using this solution requires the tooling to be placed stably on the workbench first, and then the parts are placed on the tooling for positioning and denting. This means that it is only suitable for workshop processing scenarios with stable workbenches, and cannot be used in on-site assembly and maintenance environments without workbenches. For example, in scenarios such as wing maintenance of aero engines and emergency repairs in the field, operators often need to use hand tools to directly dent components in the assembled state. In this case, the rigid tooling in this solution cannot be independently fixed to the back of the parts, and it is not feasible to implement on-site.

[0005] Therefore, there is an urgent need for a guiding device and processing method that can effectively protect thin-walled bottom holes, adapt to changes in curved surfaces, be reliably used in on-site assembly environments without relying on a worktable, and be cost-controllable. Summary of the Invention

[0006] This invention addresses the challenges of countersunk hole machining in ceramic matrix composite curved thin-walled components, where the bottom hole wall thickness is small and easily damaged. Existing solutions also suffer from limitations such as inability to adapt to changes in the curved surface, reliance on workbench support, difficulty in implementation on the assembly site, and high manufacturing costs. The invention provides a flexible laminated guiding device and method for countersunk hole machining in ceramic matrix composite curved thin-walled components. This device achieves adaptive fitting and adjustable guidance of the curved surface through a laminated structure of flexible metal sheets. Furthermore, it can be directly installed and used in the assembly state without a workbench, thus solving the high-quality machining problem of countersunk holes in curved thin-walled components in workshop and on-site environments at a lower cost.

[0007] The technical solution of this invention is implemented as follows: In a first aspect, the present invention provides a flexible laminated guiding device for machining countersunk holes in ceramic matrix composite curved thin-walled components, which is used for back-side guiding of bottom holes in ceramic matrix composite curved thin-walled components, comprising: Several flexible metal sheets, each flexible metal sheet having a guide hole, the diameter of the guide hole being the same as the diameter of the bottom hole; Locating pins are used to pass sequentially through the guide holes of each flexible metal sheet and the bottom hole of the component in a tight fit manner, so that each guide hole and the bottom hole are coaxially aligned. Each flexible metal sheet is fixed after being pressed and pressed against the curved back surface of the component, so that the wall thickness of the guide hole formed by the stacking of multiple flexible metal sheets is the sum of the thicknesses of each flexible metal sheet. This serves to constrain and guide the tool and protect the bottom hole wall when the tool is inserted into the bottom hole for denting.

[0008] As a further technical solution of the present invention: the single layer thickness of the flexible metal sheet is 0.05~1mm, the material is at least one of stainless steel, spring steel or copper alloy, and its elastic modulus is ≥100GPa, which can undergo elastic or elastoplastic bending deformation with the curved surface of the component.

[0009] As a further technical solution of the present invention: the number of layers of the flexible metal sheet n≥3, n is determined according to the guide structure length L of the denting tool, and satisfies n×t≥L, where t is the single layer thickness of the flexible metal sheet; Adjacent flexible metal sheets are tightly bonded together.

[0010] As a further technical solution of the present invention: the positioning pin is a cylindrical pin or a tapered pin, the fitting clearance between its diameter and the diameter of the bottom hole is ≤0.02mm, and the length of the positioning pin is greater than n×t, where n is the number of layers and t is the single layer thickness of the flexible metal sheet.

[0011] As a further technical solution of the present invention: the flexible metal sheet is fixed to the back of the component by at least one of adhesive bonding, double-sided tape, vacuum adsorption or mechanical clamping.

[0012] Secondly, the present invention provides a method for processing countersunk holes in ceramic matrix composite curved thin-walled components, employing the aforementioned flexible laminated guiding device, and comprising the following steps: S1, Bottom hole machining: Using a drill bit to machine a through bottom hole to the final hole size on the component; S2, installation of guide device: Several flexible metal sheets are sequentially placed on the positioning pins. The positioning pins pass through the guide holes and bottom holes of each flexible metal sheet in a tight fit manner, so that each guide hole and bottom hole are precisely coaxially aligned. Then, starting from the sheet closest to the back of the component, the flexible metal sheets are pressed tightly against the curved surface of the component one by one. S3, countersunk head countersunk machining: Remove the positioning pin, insert the guide structure of the countersunk tool into the bottom hole and the overlapping guide hole to achieve positioning and guidance, and drive the countersunk tool to machine a countersunk head coaxial with the bottom hole on the surface of the component; S4, Hole Cleaning: Removes chips and dust; S5, Guide device disassembly: Remove each flexible metal sheet from the back of the component.

[0013] As a further technical solution of the present invention: In step S2, the number of layers n is determined according to the guide structure length L of the denting tool according to the formula n×t≥L, and a smaller t value is selected to improve the fit of the flexible metal sheet to the curved surface.

[0014] As a further technical solution of the present invention: the component is a thin-walled component of SiC / SiC or C / SiC ceramic matrix composite material, and the remaining wall thickness δ ≤ 1 mm after the bottom hole countersunk hole is processed.

[0015] As a further technical solution of the present invention: after step S5, the method further includes: installing the guide device for the next bottom hole to be processed of the component using the removed flexible metal sheet and positioning pin.

[0016] As a further technical solution of the present invention: In step S2, the flexible metal sheet is installed by gradually attaching it from the center to the surrounding area to ensure that each layer is fully attached to the surface.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention utilizes the flexibility and elastic deformation capabilities of several flexible metal sheets in a stacked structure, enabling them to adaptively conform to back surfaces with different curvatures, thus fundamentally solving the problem that existing rigid mounting solutions cannot adapt to curved components.

[0018] 2. This invention achieves high-precision coaxial alignment between the guide holes and the bottom hole of each layer through a tight fit with locating pins, ensuring the guiding accuracy after multi-layer stacking. After the locating pins are removed, the stacked guide holes form a guide channel with the same diameter as the bottom hole and an adjustable length.

[0019] 3. By adjusting the number n of flexible metal sheets, this invention can flexibly match the guide structure requirements of grooving tools of different lengths. The same set of flexible metal sheets can adapt to the guide length requirements of different hole positions and different tools by increasing or decreasing the number of layers, making it highly versatile.

[0020] 4. The flexible stacked guide device of the present invention does not need to rely on the support of the workbench and can be directly fixed to the back of the component by pressing it firmly. It is suitable for various operation scenarios such as workshop processing, on-site assembly, on-wing maintenance, and field emergency repair. In particular, it fills the application gap of the existing solution that cannot perform denting operation with hand tools in the assembly state.

[0021] 5. Each flexible metal sheet is a standardized, low-cost sheet that can be reused for different hole positions in the same component or for hole positions in different components. The cost is far lower than processing and customizing a mounting carrier for each curved hole position, making it highly economical.

[0022] 6. When multiple flexible metal sheets are stacked and fixed, the whole structure has sufficient rigidity to resist the vibration and vibration transmitted by the denting tool guide structure, which protects the bottom hole and provides stable guiding constraints for denting.

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the installation state of the flexible stacked guide device in an embodiment of the present invention.

[0025] Figure 2 for Figure 1 A schematic diagram of the decomposition state.

[0026] Figure 3 This is a flowchart of the processing method in an embodiment of the present invention.

[0027] Figure 4 This is a schematic diagram of the denting process in an embodiment of the present invention.

[0028] The figures are labeled as follows: 1-component; 11-bottom hole; 2-flexible metal sheet; 21-guide hole; 3-locating pin; 4-drilling tool; 41-guide structure; 42-countersunk cutting part. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be described in more detail below with reference to the accompanying drawings.

[0030] In the accompanying drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are some, but not all, of the embodiments of the present invention.

[0031] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0032] The following is in conjunction with the appendix Figure 1-4 The embodiments of the present invention will be described in detail below.

[0033] Example 1 This invention provides a flexible stacked guiding device for countersunk hole machining of ceramic matrix composite curved thin-walled components. It guides the bottom hole on the ceramic matrix composite curved thin-walled component from the back. The device includes: several flexible metal plates, each with a guide hole whose diameter is the same as the bottom hole's diameter; a locating pin that passes sequentially through the guide holes and bottom holes of each flexible metal plate in a tight fit, ensuring coaxial alignment between the guide holes and the bottom holes; and each flexible metal plate is fixed after being pressed against the curved back surface of the component, such that the wall thickness of the guide hole formed by the stacked layers of flexible metal plates is the sum of the thicknesses of each layer. This provides constraint, guidance, and protection of the bottom hole wall when the guide structure of the scouring tool is inserted into the bottom hole for scouring.

[0034] Furthermore, the single-layer thickness of the flexible metal sheet is 0.05~1mm, and the material is at least one of stainless steel, spring steel or copper alloy, with an elastic modulus ≥100GPa, which can undergo elastic or elastoplastic bending deformation with the curved surface of the component.

[0035] Furthermore, the number of layers of the flexible metal sheet is n≥3, where n is determined according to the guide structure length L of the grooving tool, satisfying n×t≥L, where t is the single-layer thickness of the flexible metal sheet; adjacent flexible metal sheets are tightly bonded together.

[0036] Furthermore, the positioning pin is a cylindrical pin or a tapered pin, and the fitting clearance between its diameter and the diameter of the bottom hole is ≤0.02mm. The length of the positioning pin is greater than n×t, where n is the number of layers and t is the thickness of a single layer of the flexible metal sheet.

[0037] Furthermore, the flexible metal sheet is fixed to the back of the component by at least one of adhesive bonding, double-sided tape, vacuum adsorption, or mechanical clamping.

[0038] The present invention also provides a method for processing countersunk holes in ceramic matrix composite curved thin-walled components, using the above-mentioned flexible laminated guide device, including the following steps: S1, bottom hole processing; S2, guide device installation; S3, countersunk hole processing; S4, hole cleaning; S5, guide device disassembly.

[0039] Furthermore, in step S2, the number of layers n is determined according to the guide structure length L of the denting tool using the formula n×t≥L, and a smaller t value is preferred to improve the fit of the flexible metal sheet to the curved surface.

[0040] Furthermore, the component is a thin-walled component made of SiC / SiC or C / SiC ceramic matrix composite material, and the remaining wall thickness δ after the bottom hole countersunk hole is processed is ≤1mm.

[0041] Furthermore, after step S5, the method further includes: installing a guide device for the removed flexible metal sheet and the positioning pin for the next bottom hole to be machined in the component.

[0042] This invention addresses the challenges of countersunk hole machining in ceramic matrix composite curved thin-walled components, where the bottom hole wall thickness is small and easily damaged. Existing solutions suffer from technical drawbacks such as inability to adapt to changes in curved surface shape, reliance on workbench support, difficulty in implementation on the assembly site, and high manufacturing costs. This invention achieves adaptive fitting and adjustable guidance of the curved surface through a layered structure of flexible metal sheets, and can be directly installed and used in the assembled state without a workbench. This provides a low-cost solution to the problem of high-quality countersunk hole machining in workshop and field environments for curved thin-walled components.

[0043] Example 2 This embodiment focuses on a SiC / SiC ceramic matrix composite curved thin-walled component, machining a countersunk hole with a bottom hole diameter of 5mm and a countersunk angle of 90°. The component is an aero-engine curved wall panel with a wall thickness of 4mm and a single-curvature curved surface on the back (curvature radius R≈500mm). After machining the bottom hole, the remaining wall thickness is 1mm.

[0044] like Figure 1 and Figure 2 As shown, the flexible laminated guide device includes eight flexible metal sheets 2 and one positioning pin 3. Each flexible metal sheet 2 is made of 304 stainless steel, with a single layer thickness t=0.2mm and an external dimension of 40mm×40mm. A guide hole 21 with a diameter of 5mm is located in the center. The elastic modulus of 304 stainless steel is approximately 193GPa. The 0.2mm thick sheet has sufficient flexibility to elastically bend and deform along a curved surface with a radius of approximately 500mm and fit tightly. The positioning pin 3 is a cylindrical positioning pin made of tool steel, with a diameter of 5mm (the clearance between the pin and the bottom hole diameter is 0.015mm) and a length of 8mm (greater than 8×0.2=1.6mm).

[0045] Processing methods such as Figure 3 As shown, the specific steps are as follows: S1, Bottom hole machining: Using a 5mm diameter diamond-coated carbide drill bit, a through-hole 11 is machined on component 1 to the final hole size. Machining parameters are: spindle speed 5000r / min, feed rate 1.5mm / min, and drill depth 0.3mm.

[0046] S2, Guide Device Installation: Eight flexible metal sheets 2 are sequentially fitted onto the positioning pins 3. The positioning pins 3 pass through the guide holes 21 and bottom holes 11 of each flexible metal sheet 2 in a tight fit, ensuring precise coaxial alignment between the guide holes 21 and the bottom holes 11. Then, starting with the sheet closest to the back of component 1, each flexible metal sheet 2 is pressed firmly against the curved surface of component 1. Double-sided tape is used to secure each layer of metal sheets to the back of component 1. After each layer is pressed firmly, the total thickness of the stack is 8 × 0.2 = 1.6 mm, which is significantly greater than the remaining wall thickness of the bottom hole (1 mm). After installation, the positioning pins 3 are removed. At this point, each guide hole 21 and the bottom hole 11 together form a guide channel with a total length of 1.6 mm + 1 mm = 2.6 mm.

[0047] S3, Countersunk head countersunk machining: using a countersunk tool 4, such as Figure 4 As shown, the guide structure 41 of the squaring tool 4 is inserted into the bottom hole 11 and the overlapping guide hole 21 to achieve positioning and guidance. The length of the guide structure 41 is L=1.5mm, and it is constrained throughout the stacked guide channel. The squaring tool 4 is driven to rotate at a spindle speed of 3500r / min and feed at a feed rate of 1mm / min to machine a 90° countersunk recess coaxial with the bottom hole 11 on the surface of the component 1.

[0048] S4, Hole Cleaning: Use compressed air blowing combined with vacuum dust collection to remove chips and dust.

[0049] S5, guide device disassembly: remove each flexible metal sheet 2 from the back of component 1, and after cleaning, it can be reused for the next hole.

[0050] Upon inspection, the countersunk head recess produced in this embodiment has an intact edge, the bottom hole has no wear or chipping, the coaxiality error between the countersunk head recess and the bottom hole is 0.02mm, and the diameter variation of the bottom hole is less than 0.01mm.

[0051] Example 3 This embodiment focuses on a thin-walled component with a hyperbolic curved surface made of C / SiC ceramic matrix composite material. A countersunk hole with a bottom diameter of 3 mm and a countersunk angle of 100° is machined. The component wall thickness is 3 mm, the back side is a hyperbolic curved surface, and the remaining wall thickness after the bottom hole is 0.7 mm. The difference from Embodiment 1 is: Each flexible metal sheet 2 is made of copper alloy (beryllium copper), with a single-layer thickness of t=0.1mm and a guide hole 21 diameter of 3mm. After aging treatment, the elastic modulus of beryllium copper is approximately 128GPa. The 0.1mm thickness provides excellent flexibility and elastic recovery, enabling it to adapt to complex surface changes in hyperbolic surfaces. The locating pin 3 has a diameter of 3mm (fitting clearance 0.012mm). Based on the guide structure 41 length L=1.2mm of the scouring tool 4, and using the formula n×t≥L: n×0.1≥1.2, n≥12, this embodiment uses 12 flexible metal sheets 2, with a total stacked thickness of 1.2mm. In step S2, the flexible metal sheets 2 are installed by gradually bonding them from the center outwards, ensuring each layer fully adheres to the surface. The fixing method uses double-sided tape combined with edge mechanical clamping. The coaxiality error between the countersunk head and the bottom hole is measured to be 0.018mm.

[0052] Example 4 This embodiment focuses on an irregular curved thin-walled component made of SiC / SiC ceramic matrix composite material, machining a countersunk hole with a bottom hole diameter of 6mm and a countersunk angle of 120°. The component wall thickness is 5mm, and the remaining wall thickness of the bottom hole is 1.5mm. The difference from Embodiment 1 is: Each flexible metal sheet 2 is made of 301 stainless steel, with a single layer thickness of t=0.3mm and a guide hole 21 diameter of 6mm. Eight sheets are selected, with a total stacked thickness of 2.4mm. The positioning pin 3 is a tapered positioning pin, which achieves more precise positioning through tapered self-locking. The fixing method uses vacuum adsorption combined with double-sided adhesive tape. After step S5, the surface of the removed flexible metal sheet 2 is cleaned and used for the next bottom hole to be processed in component 1, realizing that one set of guiding devices can be reused for processing all hole positions. According to statistics, in this embodiment, the same set of flexible metal sheets 2 and positioning pins 3 were continuously used for processing countersunk holes in 12 different hole positions on the component, and all countersunk holes met the quality requirements.

[0053] In summary, the flexible laminated guiding device and method for countersunk hole machining of curved thin-walled ceramic matrix composite components provided by this invention successfully solves the comprehensive technical challenges of bottom hole protection, surface adaptation, on-site feasibility, and cost control in the machining of countersunk holes in curved thin-walled ceramic matrix composite components through a combination of flexible metal sheet lamination and tight-fitting centering with locating pins. This device and method do not rely on a workbench and can be reliably used in various scenarios such as workshop machining, on-site assembly, and on-wing maintenance. The process is simple, low-cost, reusable, and highly versatile, and is of great significance for promoting the high-quality manufacturing and engineering application of curved thin-walled ceramic matrix composite components in aerospace and other fields.

[0054] Thus, the objective of this invention has been achieved.

[0055] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A flexible laminated guiding device for machining countersunk holes in ceramic matrix composite curved thin-walled components, characterized in that, For back-side guidance of bottom holes in ceramic matrix composite curved thin-walled components, including: Several flexible metal sheets, each flexible metal sheet having a guide hole, the diameter of the guide hole being the same as the diameter of the bottom hole; Locating pins are used to pass sequentially through the guide holes of each flexible metal sheet and the bottom hole of the component in a tight fit manner, so that each guide hole and the bottom hole are coaxially aligned. Each flexible metal sheet is fixed after being pressed and pressed against the curved back surface of the component, so that the wall thickness of the guide hole formed by the stacking of multiple flexible metal sheets is the sum of the thicknesses of each flexible metal sheet. This serves to constrain and guide the tool and protect the bottom hole wall when the tool is inserted into the bottom hole for denting.

2. The flexible laminated guide device for countersunk hole processing of ceramic matrix composite curved thin-walled components according to claim 1, characterized in that, The single-layer thickness of the flexible metal sheet is 0.05~1mm, and the material is at least one of stainless steel, spring steel or copper alloy. Its elastic modulus is ≥100GPa, and it can undergo elastic or elastoplastic bending deformation with the curved surface of the component.

3. The flexible laminated guide device for processing countersunk holes in ceramic matrix composite curved thin-walled components according to claim 1, characterized in that, The number of layers of the flexible metal sheet is n≥3, where n is determined according to the guide structure length L of the denting tool, satisfying n×t≥L, where t is the thickness of a single layer of the flexible metal sheet. Adjacent flexible metal sheets are tightly bonded together.

4. The flexible laminated guide device for countersunk hole processing of ceramic matrix composite curved thin-walled components according to claim 1, characterized in that, The positioning pin is a cylindrical pin or a tapered pin, and the fit clearance between its diameter and the diameter of the bottom hole is ≤0.02mm. The length of the positioning pin is greater than n×t, where n is the number of layers and t is the thickness of a single layer of the flexible metal sheet.

5. The flexible laminated guide device for processing countersunk holes in ceramic matrix composite curved thin-walled components according to claim 1, characterized in that, The flexible metal sheet is fixed to the back of the component by at least one of adhesive bonding, double-sided tape, vacuum adsorption, or mechanical clamping.

6. A method for machining countersunk holes in a ceramic matrix composite curved thin-walled component, characterized in that, The flexible laminated guide device as described in any one of claims 1-5 includes the following steps: S1, Bottom hole machining: Using a drill bit to machine a through bottom hole to the final hole size on the component; S2, installation of guide device: Several flexible metal sheets are sequentially placed on the positioning pins. The positioning pins pass through the guide holes and bottom holes of each flexible metal sheet in a tight fit manner, so that each guide hole and bottom hole are precisely coaxially aligned. Then, starting from the sheet closest to the back of the component, the flexible metal sheets are pressed tightly against the curved surface of the component one by one. S3, countersunk head countersunk machining: Remove the positioning pin, insert the guide structure of the countersunk tool into the bottom hole and the overlapping guide hole to achieve positioning and guidance, and drive the countersunk tool to machine a countersunk head coaxial with the bottom hole on the surface of the component; S4, Hole Cleaning: Removes chips and dust; S5, Guide device disassembly: Remove each flexible metal sheet from the back of the component.

7. The method for machining countersunk holes in ceramic matrix composite curved thin-walled components according to claim 6, characterized in that, In step S2, the number of layers n is determined according to the guide structure length L of the grooving tool using the formula n×t≥L, and a smaller t value is selected to improve the fit of the flexible metal sheet to the curved surface.

8. The method for machining countersunk holes in ceramic matrix composite curved thin-walled components according to claim 6, characterized in that, The component is a thin-walled component made of SiC / SiC or C / SiC ceramic matrix composite material, and the remaining wall thickness δ ≤ 1 mm after the bottom hole countersunk recess is processed.

9. The method for machining countersunk holes in ceramic matrix composite curved thin-walled components according to claim 6, characterized in that, Step S5 is followed by: installing a guide device for the removed flexible metal sheet and locating pins to be used for the next bottom hole to be machined in the component.

10. The method for machining countersunk holes in ceramic matrix composite curved thin-walled components according to claim 6, characterized in that, In step S2, flexible metal sheets are installed by gradually attaching them from the center outwards to ensure that each layer is fully attached to the surface.

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