Blade root tension bar hole underwater laser shock peening device and method

Abstract

The present application belongs to the technical field of laser processing, and provides a kind of underwater laser shock peening device and method for blade root rib hole, including optical system, for the light beam emitted by laser is modulated as the output laser pulse used for strengthening processing;Scanning motion execution mechanism, including first feed mechanism and second feed mechanism in water tank, first feed mechanism is used to clamp workpiece, make the rib hole on workpiece towards output laser pulse and drive workpiece to rotate around rib hole axis, second feed mechanism includes reflecting cone and driving part for driving reflecting cone to reciprocate along axis in rib hole, reflecting cone is used to reflect output laser pulse to rib hole wall face;Light spot quality control system, including light spot detection device, for monitoring the parameters of output laser pulse.The present application can realize uniform, full coverage strengthening of rib hole inner wall, and the stability of processing process is high, effectively improves the depth of residual compressive stress layer of rib hole inner wall, strengthening uniformity and fatigue life.

Description

Technical Field

[0001] This invention belongs to the field of laser processing technology, and in particular relates to an underwater laser shock stabilization device and method for strengthening blade root bracing holes. Background Technology

[0002] Blades are critical load-bearing components in rotating machinery such as aero-engines and gas turbines, enduring long-term high temperatures, high-speed rotation, and complex alternating loads during service. To ensure a reliable connection between the blade and the rotor, tie rod holes are typically installed at the blade root for mounting tie rods or pins. These holes are typical small-diameter, deep-cavity connection holes, playing a crucial role in transmitting tensile forces, centrifugal forces, and vibration loads during operation, and are one of the main load-bearing parts of the entire blade. However, due to stress concentration in the tie rod hole structure, its inner wall is highly susceptible to becoming a source of fatigue crack initiation during long-term service. Traditional strengthening methods, such as mechanical rolling and shot peening, are often limited by factors such as small hole diameter, space constraints, and the difficulty in uniformly applying the processing medium to the inner wall of the hole, making it difficult to achieve comprehensive and uniform strengthening of the inner surface of the tie rod hole. Furthermore, these methods can easily introduce surface damage or uneven stress into the hole wall, thus affecting the service reliability of the blade.

[0003] Laser shock peening (LSP) is a novel material surface strengthening technology that uses high-energy laser pulses to generate plasma shock waves on the absorption layer, inducing a high-amplitude residual stress layer on the material surface. The residual stress layer can effectively eliminate internal stress concentration and inhibit the initiation and propagation of cracks, thereby significantly improving the fatigue life and crack resistance of components.

[0004] Existing laser shock peening technology still has shortcomings in practical applications: First, the energy distribution of the laser spot is invisible and difficult to control stably. During long-term operation, the laser is easily affected by factors such as optical path drift, optical component contamination, and lens thermal distortion, which leads to changes in the energy distribution of the laser spot, resulting in uneven energy in the strengthened area and fluctuations in residual stress. Second, it is difficult to keep the focal position of the laser spot constant. Multilayer optical systems and changes in the refractive index of water media can cause focal drift, making it impossible for the laser to be stably focused on the surface of the absorption layer, thereby reducing the intensity of the shock wave or even causing workpiece ablation. Third, traditional processing systems generally lack real-time feedback mechanisms and are still based on open-loop control. When the laser spot shifts or energy decays, it cannot be automatically corrected, resulting in poor consistency in the processing process and difficulty in maintaining stable strengthening quality. Summary of the Invention

[0005] The purpose of this invention is to provide an underwater laser shock blasting device and method for strengthening blade root tie rod holes, so as to solve the above-mentioned problems, achieve uniform and full-coverage strengthening of the inner wall of the hole, and ensure the stability of the processing through closed-loop feedback, thereby improving the depth of residual compressive stress layer, strengthening uniformity and fatigue life of the tie rod hole inner wall.

[0006] To achieve the above objectives, the present invention provides the following solution: an underwater laser shock peening device for blade root bracing holes, comprising: An optical system for modulating a beam emitted by a laser into an output laser pulse for enhanced processing; The scanning motion actuator includes a first feed mechanism and a second feed mechanism located in a water tank. The first feed mechanism is used to clamp the workpiece, so that the tie hole on the workpiece faces the output laser pulse and drives the workpiece to rotate around the axis of the tie hole. The second feed mechanism includes a reflective cone and a driving member that drives the reflective cone to reciprocate along the axis in the tie hole. The reflective cone is used to reflect the output laser pulse to the wall surface of the tie hole. A spot quality control system includes a spot detection device for monitoring parameters of the output laser pulse.

[0007] Preferably, the optical system includes a total reflection mirror, a spot adjustment device, a Q-switching switch, a polarizing beam splitter, an amplifier, a collimating lens, a spatial filter, and a focusing lens arranged sequentially along the optical path.

[0008] Preferably, the first feeding mechanism includes a clamp and a worktable fixedly connected to the bottom of the inner side of the water tank. A rotation drive is provided in the worktable. The clamp is used to hold the workpiece, and the rotation drive is used to drive the clamp to rotate around the axis of the tie hole of the workpiece.

[0009] Preferably, the reflective cone is made of a metal or ceramic material with high reflectivity.

[0010] Preferably, the outer diameter of the reflective cone is smaller than the inner diameter of the tie hole in the workpiece, and the end face of the reflective cone near the workpiece is set as a conical surface structure, with the apex angle α of the conical surface satisfying 75° < α < 90°.

[0011] A method for underwater laser shock peening of leaf root bracing holes includes the following steps: The workpiece to be strengthened is installed on the first feed mechanism, ensuring that the axis of the reflective cone coincides with the axis of the tie hole. Water is added to the water tank so that the workpiece is submerged in the water medium in the water tank, forming a water-constrained layer environment. The laser is activated, and the output laser pulse generated after modulation by the optical system is incident on the reflective cone located inside the tension hole. After being reflected by the reflective cone, it acts on the inner wall surface of the tension hole, inducing the generation of plasma shock waves to strengthen the hole wall with laser shock. During the laser shock peening process, the workpiece is rotated around the axis of the tie rod hole by the first feed mechanism, while the reflective cone is driven to reciprocate along the axis of the tie rod hole by the second feed mechanism, so that the laser shock area forms a scanning path along the inner wall of the tie rod hole until the entire hole wall is strengthened.

[0012] Preferably, the inner wall of the tie rod hole is coated with a composite absorbent layer, and the total thickness of the composite absorbent layer is 0.20 to 0.30 mm.

[0013] Preferably, the composite absorption layer consists of a light absorption layer, an elastic buffer layer, and an adhesive layer from the outside to the inside.

[0014] Preferably, the laser output pulse energy is 3-20J, the laser pulse width is 10-32ns, and the emission frequency is 10-50Hz.

[0015] Preferably, the overlap rate of adjacent laser shock spots in the scanning path is 20-80%.

[0016] Compared with the prior art, the present invention has the following advantages and technical effects: 1. The present invention solves the problems of full coverage and uneven energy distribution in laser shock blasting of small-diameter deep holes by using a bidirectional alternating spiral scanning path achieved by the first and second feeding mechanisms, thereby realizing blind-zone-free blasting of the hole wall surface and uniform application of shock energy.

[0017] 2. By introducing a spot detection device, real-time feedback of spot parameters is achieved, enabling dynamic monitoring and automatic correction of laser spot quality, focal position, and energy distribution. This significantly improves the stability and repeatability of the processing, thereby ensuring the consistency and reliability of the impact strengthening effect.

[0018] 3. By setting a multi-layer composite absorption layer structure on the inner wall of the tie rod hole, the adhesion of the absorption layer in the underwater environment is enhanced, while the laser energy absorption efficiency and the utilization efficiency of plasma shock waves are improved. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the underwater laser shock blasting device for reinforcing the tie rod holes of the present invention; Figure 2 This is a flowchart illustrating the process of the light spot quality control system of the present invention. The components include: 1. Control system; 2. Rotary motor; 3. Screw and nut; 4. Laser; 5. Total reflection mirror; 6. Beam adjustment device; 7. Q-switching switch; 8. Polarizing beam splitter; 9. Amplifier; 10. Collimating lens; 11. Spatial filter; 12. Focusing lens; 13. Output laser pulse; 14. Beam detection device; 15. Fixture; 16. Workpiece; 17. Reflecting cone; 18. First feed mechanism; 19. Worktable; 20. Water tank; 21. Second feed mechanism. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Example 1: Reference Figure 1 This invention provides an underwater laser shock peening device for blade root bracing holes, comprising: An optical system is used to modulate the beam emitted by the laser 4 into an output laser pulse 13 for enhanced processing. The scanning motion actuator includes a first feed mechanism 18 and a second feed mechanism 21 located in the water tank 20. The first feed mechanism 18 is used to clamp the workpiece 16, so that the tie hole on the workpiece 16 faces the output laser pulse 13 and drives the workpiece 16 to rotate around the axis of the tie hole. The second feed mechanism 21 includes a reflective cone 17 and a driving member that drives the reflective cone 17 to reciprocate along the axis in the tie hole. The reflective cone 17 is used to reflect the output laser pulse 13 to the wall of the tie hole. The laser spot quality control system includes a laser spot detection device 14, which is used to monitor the parameters of the output laser pulse 13.

[0024] The main function of the optical system is to shape, modulate, collimate, filter, and focus the original beam emitted by the laser 4 to output a stable and high-quality laser pulse 13 that meets the requirements of impact strengthening. The main function of the first feed mechanism 18 is to clamp the workpiece 16 and make the tie hole on the workpiece 16 face the output laser pulse, while driving the workpiece 16 to rotate around the axis of the tie hole, providing circumferential motion for forming a spiral scanning path. The main function of the second feed mechanism 21 is to carry the reflector cone 17 and drive it to move in a high-precision reciprocating linear motion along the axis within the tie hole, providing positional support for the radial reflection of the laser pulse, and cooperating with the rotation of the workpiece to form a bidirectional alternating spiral scanning trajectory. The main function of the reflector cone 17 is to reflect the axially incident output laser pulse 13 and deflect it to the inner wall surface of the tie hole, so that the laser energy can act on the side wall of the small-diameter deep hole that is difficult to directly irradiate. The main function of the spot detection device 14 is to collect parameters such as the spot shape, energy distribution uniformity, and focusing state of the output laser pulse 13 in real time, providing a detection basis for the spot quality control system. Overall, this invention achieves reinforcement by deflecting the output laser pulse from the reflector cone to the inner wall of the tie hole, generating a shock wave under the induction of the water confinement layer. At the same time, the first and second feed mechanisms enable the laser to form a bidirectional alternating spiral scanning path on the inner wall of the tie hole, achieving blind-zone-free coverage of the hole wall. Furthermore, the laser parameters are monitored in real time and feedback control is provided by a spot detection device to ensure the stability and consistency of the processing, effectively improving the depth and uniformity of the residual compressive stress layer on the hole wall.

[0025] To further optimize the design, a high-power pulsed laser was selected for laser 4.

[0026] The scheme is further optimized. The driving component includes a rotary motor 2. The output shaft of the rotary motor 2 is coaxially fixedly connected to a screw. A screw nut 3 is threaded on the screw. The screw nut 3 is fixedly connected to the reflector cone 17. While ensuring that the screw nut 3 does not rotate synchronously with the screw, the rotational motion of the screw can be converted into the axial linear motion of the screw nut 3, thereby driving the reflector cone 17 to reciprocate along the axis of the tie rod hole.

[0027] Further optimization of the scheme also includes control system 1. The main function of control system 1 is to serve as the core control unit of the laser shock enhancement device. It is electrically connected to the electrical control modules of laser 4, first feed mechanism 18, second feed mechanism 21, spot detection device, etc. Its main function is to realize parameter setting, command scheduling, and real-time feedback and coordination of parameter status of spot detection device 14, etc.

[0028] Further optimization of the scheme: the optical system includes a total reflection mirror 5, a spot adjustment device 6, a Q-switching switch 7, a polarizing beam splitter 8, an amplifier 9, a collimating lens 10, a spatial filter 11, and a focusing lens 12 arranged sequentially along the optical path.

[0029] like Figure 1 As shown, the total reflection mirror 5, the beam spot adjustment device 6, the Q-switching switch 7, the polarization beam splitter 8, the amplifier 9, the collimating lens 10, the spatial filter 11, and the focusing lens 12 are used to redirect, shape, regulate energy, collimate, filter, and focus the original laser beam output by the laser to obtain a high-quality output laser pulse 13.

[0030] Further optimize the plan, such as Figure 1 As shown, the spot detection device 14 is arranged after the focusing lens 12 to monitor the spot shape, energy distribution and focusing state of the output laser pulse 13 in real time, and feeds the detection results back to the control system 1. The control system 1 adjusts the laser 4 and other components to achieve dynamic adjustment and closed-loop control of the optical path.

[0031] The scheme is further optimized. The first feeding mechanism 18 includes a clamp 15 and a worktable 19 fixedly connected to the bottom of the inner side of the water tank 20. A rotation drive is provided in the worktable 19. The clamp 15 is used to clamp the workpiece 16, and the rotation drive is used to drive the clamp 15 to rotate around the axis of the tie hole of the workpiece 16.

[0032] In a further optimized embodiment, the rotary drive can be a waterproof motor that drives the turntable to rotate, thereby rotating the clamp 15 and allowing the workpiece 16 clamped on the upper clamp 15 to rotate around the axis of the tie rod hole.

[0033] The first feed mechanism 18 and the second feed mechanism 21 are synchronously controlled by the control system 1 to form a preset scanning path.

[0034] Further optimization of the design: the reflector cone 17 is made of metal or ceramic material with high reflectivity.

[0035] Further optimization of the scheme: the outer diameter of the reflector cone 17 is smaller than the inner diameter of the tie hole of the workpiece 16. The end face of the reflector cone 17 near the workpiece 16 is set as a conical surface structure. The complete apex angle α of the conical surface is determined according to the inner diameter of the tie hole, the outer diameter of the reflector cone, and the target incident angle of the laser on the inner wall of the tie hole. The apex angle α must satisfy 75° < α < 90°. In this embodiment, it is preferably 85° < α < 90°. This allows the output laser pulse 13 incident along the axial direction of the tie hole to propagate radially or approximately radially along the tie hole after being reflected by the reflector cone 17, and to act on the inner wall of the tie hole in a direction close to the normal of the inner wall of the tie hole, thereby reducing the beam stretching and energy density unevenness caused by oblique incidence.

[0036] Specifically, let the inner diameter of the tie rod hole be D, and the working outer diameter of the reflector cone 17 be... The radial clearance between the reflector cone 17 and the inner wall of the tie rod hole is: When the reflected laser propagates from the surface of the reflecting cone to the inner wall of the tie hole, the axial offset ∆z of its position relative to the reflection point satisfies: Let the size of the axial spot formed by the laser on the inner wall of the tie rod hole be... Preferably, the axial offset satisfies: Right now: This allows us to obtain the range of values ​​for α, so as to avoid the occurrence of missed impact areas between adjacent scanning trajectories due to excessive reflection position offset, and to ensure the continuity and uniformity of the laser impact area on the inner wall of the tie hole.

[0037] To further verify the feasibility of the above geometric relationships and parameter values, the following two sets of parameter calculation examples are given: Example 1: Pick The reflector cone is 2.5mm smaller than the aperture, that is: ,So: Single-sided gap: Assuming the laser axial spot size: The maximum permissible axial offset is: If we take: ,but: because: ,so: Obviously therefore: Established.

[0038] when , , , The parameters fully meet the above design conditions.

[0039] Example 2: Pick The reflector cone is 3mm smaller than the aperture, that is: ,So: Single-sided gap: Assuming the laser axial spot size: The maximum permissible axial offset is: If taken ,but: because: ,so: Obviously: ,therefore: Established.

[0040] When D=12mm, dc=9mm, dz=0.5mm, and α=85°, the parameters fully meet the above design conditions.

[0041] To further optimize the scheme, when clamping workpiece 16, it is necessary to ensure that the central axis of the reflective cone 17 is consistent with the axis of the tie hole, and at the same time, the outer diameter of the reflective cone 17 is 2-3 mm smaller than the diameter of the tie hole, so as to ensure that the laser beam can be fully reflected to the hole wall without interference.

[0042] Example 2: A method for underwater laser shock peening of leaf root bracing holes includes the following steps: The workpiece 16 to be strengthened is installed on the first feed mechanism 18, ensuring that the axis of the reflective cone 17 coincides with the axis of the tie hole. Water is added to the water tank 20 so that the workpiece 16 is immersed in the water medium of the water tank 20, forming a water confinement layer environment. Laser 4 is activated, and the output laser pulse 13 generated after modulation by the optical system is incident on the reflective cone 17 located in the tie hole. After being reflected by the reflective cone 17, it acts on the inner wall surface of the tie hole, inducing the generation of plasma shock wave, and performing laser shock strengthening on the hole wall. During the laser shock strengthening process, the first feed mechanism 18 drives the workpiece 16 to rotate around the axis of the tie hole, while the second feed mechanism 21 drives the reflector cone 17 to reciprocate along the axis of the tie hole, so that the laser shock area forms a scanning path along the inner wall of the tie hole until the strengthening of the entire hole wall is completed.

[0043] The design was further optimized by coating the inner wall of the tie rod hole with a composite absorbent layer, the total thickness of which is 0.20 to 0.30 mm.

[0044] This invention utilizes a laser 4 to generate a pulsed beam. After being shaped and focused by an optical system, a spot detection device 14 monitors the spot morphology, energy distribution, and focal point position in real time, and feeds the data back to the control system 1, forming a closed-loop control for automatic correction of the spot and optical path. The stably output laser is perpendicularly incident on the reflector cone 17 and radially deflected, irradiating the composite absorption layer on the inner wall of the tension hole, generating a plasma explosion. Under the action of the water confinement layer, a shock wave is generated, introducing deep residual compressive stress. The control system 1 simultaneously coordinates the axial linear feed of the reflector cone 17 and the rotation of the workpiece 16 to form a bidirectional alternating spiral scan, so that the impact effect uniformly covers the hole wall, achieving highly stable and highly uniform underwater laser shock reinforcement.

[0045] In this embodiment, at the start of processing, laser 4 is activated to generate a laser pulse. This pulse is shaped, modulated, and focused by the optical system to form a qualified output laser pulse 13. The output laser pulse 13 is incident perpendicularly onto the conical surface of the reflector cone 17, and after deflection, it transforms into a beam acting perpendicularly on the absorption layer of the inner wall of the tie hole. The composite absorption layer vaporizes and forms plasma upon instantaneous absorption of the high-energy laser. The plasma rapidly expands and explodes, generating a high-intensity shock wave under the constraint of the water-bound layer. This shock wave acts on the hole wall material, causing plastic deformation and introducing beneficial residual compressive stress. Simultaneously, the control system 1 coordinates the control of the first feed mechanism 18 and the second feed mechanism 21, driving the reflector cone 17 and the workpiece 16 to move relative to each other, forming a bidirectional alternating spiral scanning path. Specifically, in the first scan from the inside out, the second feed mechanism 21 drives the reflector cone 17 to move uniformly outward along the hole axis, while the first feed mechanism 18 drives the workpiece 16 to rotate uniformly in a clockwise direction. During this process, a fixed laser pulse continuously irradiates the outward-moving reflector cone 17. After reflection, a right-handed spiral impact strengthening trajectory extending from the bottom to the opening of the hole is formed on the synchronously rotating workpiece hole wall. In the subsequent second scan, the second feed mechanism 21 drives the reflector cone 17 to retract into the hole at the same moving speed, while the first feed mechanism 18 drives the workpiece to rotate counterclockwise at the same rotational speed. The fixed laser continues to irradiate the inward-moving reflector cone 17, forming a left-handed spiral impact trajectory extending from the opening to the bottom of the hole on the workpiece hole wall. The laser impact and scanning motion is repeated until the entire inner wall surface of the tie rod hole is fully strengthened.

[0046] The scheme was further optimized so that the composite absorption layer consists of a light absorption layer, an elastic buffer layer, and an adhesive layer from the outside to the inside.

[0047] Further optimization of the scheme resulted in laser 4 outputting laser pulse energy of 3–20 J, laser pulse width of 10–32 ns, and emission frequency of 10–50 Hz, which can meet the energy density requirements for strengthening the inner wall of deep holes.

[0048] To further optimize the scheme, the overlap rate of adjacent laser shock spots in the scanning path is 20-80%. In this embodiment, the overlap rate of adjacent laser shock spots is 50% to ensure the continuity and uniformity of the enhanced area.

[0049] Example 3: In the strengthening process of Example 2, such as Figure 2 As shown, the laser spot detection device 14 monitors the state of the laser spot in real time. If spot shape distortion, uneven energy distribution, or focus drift is detected, the control system 1 compares the monitored spot parameters, such as ellipticity, energy distribution uniformity, and focus position, with the preset target values ​​to obtain the real-time deviation e(t). The optical path is then compensated and corrected in real time, forming a precise and stable closed-loop control loop to ensure consistent quality of each laser pulse, fundamentally guaranteeing the uniformity and repeatability of the enhancement effect. Based on this deviation, the system calculates the control quantity for the laser spot adjustment device 6 according to the following closed-loop control algorithm: Where: ∆C is the change in control quantity output to the beam adjustment device 6; e(t) is the deviation between the real-time measured value of the beam parameter and the target set value; K P K i K d These are the proportional, integral, and derivative coefficients set internally within control system 1.

[0050] In closed-loop control, the beam spot adjustment device 6 may include an adaptive optical lens group or an adjustable lens driven by a motor. The control system 1 drives the beam spot adjustment device 6 to adjust the curvature, tilt angle, or axial position of the optical elements according to the calculated control quantity ∆C, thereby dynamically correcting the wavefront aberration, defocus, and directional drift of the laser beam, ensuring that the beam spot lands stably on the reflective cone surface, has a regular shape, and uniform energy distribution.

[0051] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0052] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. An underwater laser shock peening device for blade root bracing holes, characterized in that, include: An optical system for modulating the beam emitted by the laser (4) into an output laser pulse (13) for enhanced processing. The scanning motion actuator includes a first feed mechanism (18) and a second feed mechanism (21) located in the water tank (20). The first feed mechanism (18) is used to clamp the workpiece (16), so that the tie hole on the workpiece (16) faces the output laser pulse (13) and drives the workpiece (16) to rotate around the tie hole axis. The second feed mechanism (21) includes a reflector cone (17) and a drive member that drives the reflector cone (17) to reciprocate along the axis in the tie hole. The reflector cone (17) is used to reflect the output laser pulse (13) to the tie hole wall. The spot quality control system includes a spot detection device (14) for monitoring the parameters of the output laser pulse (13).

2. The underwater laser shock peening device for blade root bracing holes according to claim 1, characterized in that: The optical system includes a total reflection mirror (5), a spot adjustment device (6), a Q-switching switch (7), a polarizing beam splitter (8), an amplifier (9), a collimating lens (10), a spatial filter (11), and a focusing lens (12) arranged sequentially along the optical path.

3. The underwater laser shock peening device for blade root bracing holes according to claim 1, characterized in that: The first feeding mechanism (18) includes a clamp (15) and a worktable (19) fixedly connected to the bottom of the inner side of the water tank (20). A rotation drive is provided in the worktable (19). The clamp (15) is used to clamp the workpiece (16). The rotation drive is used to drive the clamp (15) to rotate around the axis of the tie hole of the workpiece (16).

4. The underwater laser shock peening device for blade root bracing holes according to claim 1, characterized in that: The reflective cone (17) is made of a metal or ceramic material with high reflectivity.

5. The underwater laser shock peening device for blade root bracing holes according to claim 1, characterized in that: The outer diameter of the reflective cone (17) is smaller than the inner diameter of the tie hole of the workpiece (16). The end face of the reflective cone (17) near the workpiece (16) is set as a conical surface structure, and the apex angle α of the conical surface satisfies 75°<α<90°.

6. A method for underwater laser shock blasting of blade root bracing holes, based on the underwater laser shock blasting device for blade root bracing holes as described in claim 1, characterized in that, Includes the following steps: The workpiece (16) to be strengthened is installed on the first feed mechanism (18), ensuring that the axis of the reflective cone (17) coincides with the axis of the tie hole. Water is added to the water tank (20) so that the workpiece (16) is immersed in the water medium in the water tank (20) to form a water confinement layer environment. The laser (4) is activated, and the output laser pulse (13) generated after modulation by the optical system is incident on the reflective cone (17) located in the tie hole. After being reflected by the reflective cone (17), it acts on the inner wall surface of the tie hole, inducing the generation of plasma shock wave, and laser shock strengthening of the hole wall. During the laser shock strengthening process, the first feed mechanism (18) drives the workpiece (16) to rotate around the axis of the tie hole, while the second feed mechanism (21) drives the reflector cone (17) to move back and forth along the axis of the tie hole, so that the laser shock area forms a scanning path along the inner wall of the tie hole until the strengthening of the entire hole wall is completed.

7. The underwater laser shock stabilization method for blade root bracing holes according to claim 6, characterized in that: The inner wall of the tie rod hole is coated with a composite absorbent layer, the total thickness of which is 0.20mm to 0.30mm.

8. The underwater laser shock peening method for strengthening blade root bracing holes according to claim 7, characterized in that: The composite absorption layer consists of, from the outside in, a light absorption layer, an elastic buffer layer, and an adhesive layer.

9. The underwater laser shock peening method for strengthening blade root bracing holes according to claim 6, characterized in that: The laser pulse energy output by the laser (4) is 3-20J, the laser pulse width is 10-32ns, and the emission frequency is 10-50Hz.

10. The underwater laser shock peening method for strengthening blade root bracing holes according to claim 6, characterized in that: In the scanning path, the overlap rate of adjacent laser shock spots is 20-80%.

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