JP2024068994A - Laser peening device and laser peening method - Google Patents

Abstract

To provide a laser peening device and a laser peening method capable of applying compressive stress to an inner surface of a hole, one end of which is sealed.SOLUTION: A laser peening device 50 performs laser peening to an inner surface of a hole 20, one end of which is sealed, and which is a processing target. The laser peening device comprises: a laser generator 1 which emits a pulse laser beam 2; a laser beam transmission mechanism 21 which transmits the pulse laser beam 2 emitted from the laser generator 1, to the surface of the hole 20 being the processing target; and a fluid supply mechanism 6 for supplying fluid 18 into the hole 20. The laser peening device is characterized in using, as the laser beam transmission mechanism 21, an end cap fiber 22 comprising an optical fiber 40 fusion-spliced with an end cap 41 having a light receiving area on an incident side larger than a cross-sectional area of the optical fiber 40.SELECTED DRAWING: Figure 1

Description

Embodiments of the present invention relate to a laser peening device and a laser peening method that impart compressive stress.

The surface of a material is a likely starting point for fatigue fracture and stress corrosion cracking. For this reason, by applying compressive residual stress near the surface of the material and suppressing the generation and progression of cracks, the material's resistance to fatigue fracture and stress corrosion cracking can be improved.

For example, shot peening may be performed on the surface of a cooling water passage (water-cooled hole) in a mold to impart compressive residual stress to the surface of the cooling water passage.

A compressive stress imparting mechanism using laser peening is also used. Laser peening is a technology that imparts compressive residual stress to the surface of the target. A pulsed laser is irradiated onto the target, generating plasma, which expands. The mechanical reaction to this expansion compresses the area near the target's surface, leaving residual stress. With laser peening, the magnitude of the compressive residual stress and the depth to which it is imparted can be controlled by adjusting the application conditions, such as the energy of the laser light and the area of irradiation. Furthermore, by combining an optical fiber with an irradiation head, application to narrow areas such as turbine blade installation areas and the inner surfaces of pipes is also possible.

Japanese Patent Application Laid-Open No. 7-290222 Patent No. 6107821 Japanese Patent No. 5649332 Patent No. 5814652 JP 2022-67857 A

In laser peening, a pulsed laser is irradiated onto the surface of the workpiece to generate an ablation plasma, and the pressure of the plasma causes plastic deformation on the surface of the workpiece, thereby imparting compressive stress.

For example, if the inner diameter of a cooling hole with one end sealed is large enough, it is possible to irradiate the inside with laser light, but cooling holes are generally small in diameter, for example φ10 mm or less, making it difficult to insert an irradiation head or optical system for laser peening inside. Also, if an irradiation head for working on the inner surface of a pipe is used, while it is possible to perform laser peening on the side of the cooling hole, it is not possible to irradiate the bottom of the cooling hole with laser light, and stress improvement is not possible.

One method of irradiating the bottom surface of a cooling hole with a laser is to focus the laser light on the bottom surface of the cooling hole using a focusing lens installed outside the cooling hole. However, if the cooling hole has a small diameter or is deep, the laser light may interfere with the cooling hole, making it impossible to irradiate the bottom surface of the cooling hole with laser light with the specified energy and spot diameter.

The laser peening device according to the embodiment is a laser peening device that performs laser peening on the inner surface of a hole, which is a workpiece having one end sealed, and is composed of a laser oscillator that emits pulsed laser light, a laser light transmission mechanism that transmits the pulsed laser light emitted from the laser oscillator to the surface of the hole, which is the workpiece, and a fluid supply mechanism that supplies fluid to the inside of the hole, and is characterized in that the laser light transmission mechanism uses an end cap fiber in which an end cap with a light receiving area on the incident side larger than the cross-sectional area of the optical fiber is fused to an optical fiber.

The laser peening method according to the embodiment is characterized in that laser light is incident on an end cap fiber in which an end cap with a light receiving area on the incident side larger than the cross-sectional area of the optical fiber is fused to the optical fiber, and laser peening is performed on the inner surface of a hole with one end sealed while freely controlling the position where the laser light is irradiated from the tip of the optical fiber by changing the position and angle of the optical fiber.

The embodiment of the present invention has been made to solve the above-mentioned problems, and aims to provide a laser peening device and a laser peening method that can impart compressive stress to the inner surface of a hole with one end sealed.

FIG. 4 is a conceptual diagram showing a state in which the laser peening apparatus according to the first embodiment is applied to a hole having one end sealed. 1A and 1B are side cross-sectional views showing the state in which the laser peening apparatus of the present embodiment is inserted inside a hole, in which (a) shows a state in which an endcap fiber is placed in the center of the hole, (b) shows a state in which the entire laser peening apparatus has been translated, and (c) shows a state in which the entire laser peening apparatus has been tilted with respect to the central axis of the hole. 1 is a side cross-sectional view showing a state where an end cap fiber is bent and applied to a side surface of a hole in the laser peening device of the embodiment, as viewed from the side. FIG. 1A shows the bottom of a hole as viewed from above, where (a) is a cross-sectional plan view showing an endcap fiber disposed at the center of the hole, (b) is a cross-sectional plan view showing a state in which the entire laser peening apparatus has been translated in parallel, (c) is a cross-sectional plan view showing a state in which the entire laser peening apparatus has been tilted with respect to the central axis of the hole, and (d) is a cross-sectional plan view showing a state in which the endcap fiber in the laser peening apparatus has been bent. 1A and 1B show the structure of the tip of a laser light transmission mechanism as observed from the side, where (a) is a cross-sectional plan view showing the state in which laser light is irradiated from the tip of an endcap fiber to an object to be processed, and (b) to (d) are plan views showing modified examples of the tip of the endcap fiber. 1A is a side cross-sectional view showing an endcapped fiber, and FIG. 1B is a side cross-sectional view showing a modified example of the endcapped fiber.

First Embodiment
[0023] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a configuration diagram of a laser peening device 50 according to a first embodiment of the present invention, showing a cross-sectional view of the state in which the laser peening device 50 of the present invention is inserted inside a cooling hole.

This laser peening device 50 and laser peening method perform laser peening on the inner surface of a hole such as a cooling hole 20 provided in a mold, which has one end sealed and has a diameter of, for example, several millimeters to a dozen or so millimeters (particularly, about 3 mm to 10 mm).

As shown in FIG. 1, the laser peening device 50 is composed of a laser oscillator 1, a laser light transmission mechanism 21, a focusing lens unit 5, a fluid supply mechanism 6, a cover 10, a fluid storage mechanism 12, a suction mechanism 11, an end cap fiber 22, a protection mechanism 26, etc. FIG. 1 shows the state in which the protection mechanism 26 housing the end cap fiber 22 is inserted into the cooling hole 20, one end of which is sealed.

In this way, the outer diameter of the protection mechanism 26 is set smaller than the inner diameter of the cooling hole 20. The laser light transmission mechanism 21 has at least two mirrors for reflecting the laser light 2. For example, in the configuration shown in FIG. 1, the first mirror 3 has an external position confirmation mechanism 9, and the second mirror 4 has a drive mechanism (not shown) for changing the irradiation angle of the laser light 2.

The laser oscillator 1 oscillates (emits) a pulsed laser beam for laser peening. The wavelength and pulse width of this pulsed laser beam can be selected as appropriate. For example, a Nd:YAG laser can be used to emit a pulsed laser beam with a wavelength of 1064 nm or 532 nm and a pulse width of several ns to several tens of ns. Note that energy loss of the laser beam can be reduced by selecting the wavelength of the pulsed laser beam in accordance with the light absorption characteristics of the fluid 18.

For example, if the fluid 18 contained in the fluid supply mechanism 6 is water, a laser with a wavelength of 532 nm can be used to irradiate the laser light 2 with approximately 0.5% energy loss. Even if a 1064 nm laser is used, it is sufficient to irradiate the energy absorbed by the water according to the transmission distance in water, for example, twice the pulse energy if 50% absorption is achieved.

The laser light 2 emitted from the laser oscillator 1 is incident on the endcap fiber 22 via the laser light transmission mechanism 21 and the focusing lens unit 5 provided inside the housing 25, and the laser light 2 irradiated from the tip of the endcap fiber 22 is irradiated on the inner surface of the cooling hole 20. As described above, the laser light transmission mechanism 21 has at least two mirrors, the first mirror 3 and the second mirror 4, and the incident position on the endcap fiber 22 can be adjusted by changing the angle of the second mirror 4, for example, and the laser light 2 can be irradiated at a predetermined position on the inner surface of the side, bottom, etc. of the cooling hole 20.

In addition, inside the housing 25, a beam intensity adjustment unit 24 can be placed in front of the focusing lens unit 5 as necessary. This beam intensity adjustment unit 24 is preferably a laser homogenizer composed of a diffractive optical element, a cylindrical array, or the like, and has the function of homogenizing the intensity distribution of laser light with a high central peak intensity, such as a Gaussian distribution, and can reduce damage to the endcap fiber 22 when the intensity of the laser light 2 is high, for example.

In addition, for example, an attenuator 17 can be provided inside the laser light transmission mechanism 21, and the pulse energy irradiated to the cooling hole 20 can be controlled to a predetermined intensity, or, in combination with a control device (not shown), the shutter 16 can be closed to stop construction if the pulse energy is lower than a predetermined value.

The end cap fiber 22 is constructed by fusing a cylindrical member called an end cap 41 to an optical fiber 40 via a joint 43 as shown in FIG. 6(a). The end cap 41 of the end cap fiber 22 is preferably a cylindrical member as shown in FIG. 6(a), but as shown in FIG. 6(b), it is sufficient that the light receiving area on the incident side of the laser light 2 is larger than the cross-sectional area of the optical fiber 40 to reduce damage, such as a cone-shaped cone rod 42 in which the light receiving area on the incident side of the laser light 2 is larger than the area of the joint 43 with the optical fiber 40, and that the optical fiber 40 can be joined by fusing through the joint 43. In this end cap fiber 22, the end cap 41 and the optical fiber 40 are made of the same material, quartz, and by using the same material, the refractive index at the joint 43 does not change when the laser light 2 is incident.

In the end cap fiber 22, the diameter of the optical fiber 40 is preferably φ0.4 to φ1.0 mm, and it is sufficient to ensure a power density that generates an ablation plasma 13 with a diameter of φ0.6 to φ1.5 mm when the laser light 2 irradiated from the tip of the optical fiber is projected onto the surface of the workpiece.

In addition, if the end cap 41 has a diameter of about φ5 to 10 mm at the laser light input portion, laser transmission is possible without damaging the end cap fiber 22. For example, when an end cap fiber 22 is used in which an end cap 41 having a diameter of φ8 mm x 5 mm and an optical fiber 40 having a core diameter of φ1.0 mm x 7 m is fused to the end cap 41, when laser light 2 with a pulse energy of 160 mJ is input from the end cap 41, 130 mJ of laser light is emitted from the output end of the fiber 40, and laser transmission can be performed with a transmission efficiency of about 80%, including losses due to reflections at the end faces of the end cap 41 and the optical fiber 40.

A protection mechanism 26 can be provided on the outer circumference of the endcap fiber 22, which can protect the optical fiber 40 of the endcap fiber 22 from damage when it is inserted into the cooling hole 20. The outer diameter of the protection mechanism 26 can be adjusted according to the outer diameter of the optical fiber 40. For example, when an endcap fiber 22 made of an optical fiber 40 with a core diameter of φ1.0 mm is used, the combined outer diameter of the buffer layer (not shown) and coating provided on the optical fiber 40 is approximately φ3 mm, so the outer diameter of the fiber tip protection mechanism (hereinafter referred to as the protection mechanism) 26 can be reduced to approximately φ6 mm.

The spot diameter used in laser peening can be changed depending on the material of the object to be treated (the inner surface of the cooling hole 20) and the residual stress to be introduced. For example, in the configuration shown in FIG. 1, a laser beam with a predetermined spot diameter can be irradiated by changing the distance from the endcap fiber 22 to the laser irradiation position. However, since the laser beam 2 irradiated from the endcap fiber 22 spreads with the numerical aperture (NA) specific to the optical fiber, it can be applied under conditions where the laser beam 2 that generates the ablation plasma 13 can be irradiated with a spot diameter equal to or larger than the diameter of the optical fiber 40.

In laser peening, ablation plasma 13 is generated on the surface of the workpiece, and compressive stress is applied by causing plastic deformation in the material due to the plasma pressure. In this case, a fluid 18 such as water is required to confine the plasma, but because the cooling holes 20 are narrow, even if an attempt is made to supply the fluid 18 inside the cooling holes 20 using a pump or the like, cavitation occurs or there are some areas where the fluid 18 is not supplied, making stable processing impossible.

The laser peening device 50 of this embodiment is equipped with an opening/closing unit 7 for controlling the inflow of fluid 18 into the cover 10, and a cover 10 for creating a negative pressure inside the cooling hole 20 using a suction mechanism 11. When the laser peening device 50 of this embodiment is installed in the cooling hole 20 and the inside of the cooling hole 20 is suctioned using the suction mechanism 11 with the opening/closing unit 7 closed, the inside of the cover 10 becomes negative pressure as shown in FIG. 2, and air bubbles 14 and debris remaining inside the cooling hole 20 can be removed in advance.

When the opening/closing unit 7 is opened in this state, the internal pressure is negative, so the fluid 18 inside the fluid supply mechanism 6 is sucked up and passes through the fluid transmission mechanism 8 in the direction indicated by the fluid flow 19, making it possible to stably supply the fluid 18 to the inside of the cooling hole 20 as shown in FIG. 3. Furthermore, if the inner diameter of the cooling hole 20 is small and it is difficult to supply the fluid 18 to the inside of the cooling hole 20, it is possible to preferentially discharge the fluid 18 inside the cooling hole 20 by arranging a check valve (not shown) in the protection mechanism 26 so as to cover the cooling hole 20.

Here, water is preferable as the fluid 18. For example, if a pulsed laser with a wavelength of 532 nm is used, laser peening can be performed with almost no transmission loss in water. Also, if a fluid 18 such as water mixed with a rust inhibitor or ammonia water is used, laser peening can be performed while suppressing rusting of the object to be treated. Alkaline ionized water, rust-preventive oil, etc. may also be used.

This embodiment may be provided with a position confirmation mechanism 9, which can measure the distance from the tip of the laser light transmission mechanism 21 (the tip of the endcap fiber 22) to the laser irradiation position of the cooling hole 20. As the position confirmation mechanism 9, for example, a laser range finder or the like can be used, and the position can be identified by measuring the laser light reflected from the laser light transmission mechanism 21 and the laser light reflected from the cooling hole 20, respectively, so that the position of the laser light transmission mechanism 21 inside the cooling hole 20 can be recognized from the outside. As the position confirmation mechanism 9, it is not limited to a laser range finder, but a method using another light source such as a sound wave or a light sensor, or a method of confirming an image of the tip of the laser light transmission mechanism 21 with a camera may also be used. In addition, even if the tip of the laser light transmission mechanism 21 is provided with a fiber tip protection mechanism 23 as shown in FIG. 5 (b), the position can be identified by the above-mentioned method.

Then, the endcap fiber 22 can be moved by a drive mechanism operating unit 28 or the like based on the distance from the tip of the endcap fiber 22 or the tip of the fiber tip protection mechanism 23 measured by this position confirmation mechanism 9 to the laser irradiation position, thereby changing the focal position of the laser light 2 and irradiating the laser light 2 with a predetermined spot diameter.

When the shutter 16 is opened, the laser light 2 reaches the bottom of the cooling hole 20 as shown in FIG. 1, and laser peening can be performed. The method of performing laser peening on the bottom surface of the cooling hole 20 will be described with reference to FIG. 2 to FIG. 4.

Figures 2 and 3 show side cross-sectional views of the state in which the laser peening device 50 of this embodiment is inserted inside the cooling hole 20. Also, Figure 4 is a cross-sectional view showing the bottom of the cooling hole 20 as viewed from above.

In this embodiment, a protection mechanism 26 and a drive mechanism 27 are provided on the outer periphery of the optical fiber 40 of the laser light transmission mechanism 21, which can prevent the laser light transmission mechanism 21 from being damaged by contact when being inserted into the cooling hole 20, etc. Furthermore, as shown in FIG. 3, the angle of the optical fiber 40 at the tip of the laser light transmission mechanism 21 can be changed by using the drive mechanism 27.

For example, a bellows-shaped flexible tube can be used as the driving mechanism 27, and a wire (not shown) can be arranged between the laser light transmission mechanism 21 and the protection mechanism 26 and driving mechanism 27, and the driving mechanism 27 and the driving mechanism operating unit 28 shown in FIG. 1 can be connected by this wire. The angle of the tip of the laser light transmission mechanism 21 can be changed by pulling the wire (not shown) toward the driving mechanism operating unit 28. It is preferable that the driving mechanism operating unit 28 is equipped with a motor for inserting and removing the wire (not shown) and a sensor for measuring the position of the wire, and the inclination angle of the laser light transmission mechanism 21 can be controlled by the length of the wire inserted and removed. Furthermore, by providing the driving mechanism operating unit 28 with a rotation mechanism that rotates in the axial direction of the end cap fiber 22, laser peening can be performed over a wider range.

Figure 2(a) shows the state where the end cap fiber 22 is placed at the center of the cooling hole 20, and as shown in Figures 2(a) and 4(a), the laser light 2 is irradiated to the center of the bottom surface of the cooling hole 20, which is the same as the laser peening possible range 30. If the entire laser peening device is translated, it will become as shown in Figure 2(b), and the laser light 2 can be moved from the center of the cooling hole 20 to the range where the drive mechanism 27 contacts the side of the cooling hole 20. By rotating the end cap fiber 22 about the central axis of the cooling hole 20 by the drive mechanism operating unit 28, it is possible to perform laser peening around the laser peening possible range of Figure 4(a) with respect to the center of the cooling hole 20, as shown in the laser peening possible range 30 of Figure 4(b).

Next, when the entire endcap fiber 22 is tilted with respect to the central axis of the cooling hole 20, it becomes the state shown in FIG. 2(c), and by rotating the endcap fiber 22 with respect to the central axis of the cooling hole 20 by the driving mechanism operating unit 28, the laser peening application range 30 becomes even wider than in the case of FIG. 2(b), as shown in FIG. 4(c). Furthermore, when the endcap fiber 22 is bent by the driving mechanism 27, it becomes the state shown in FIG. 3, and the movable range of the laser light 2 becomes even wider, and it becomes possible to perform laser peening on the entire bottom and side of the cooling hole 20 as shown in FIG. 4(d). Furthermore, by moving the entire endcap fiber 22 upward with respect to the central axis of the cooling hole 20, it becomes possible to perform laser peening on the side of the cooling hole 20.

In addition, if the laser peening applicable range 30 is not perpendicular to the irradiation angle of the laser light 2, the spot diameter of the laser light 2 will be elliptical, but since the same peening effect can be obtained as with a circle with an equivalent area to the ellipse, this can be addressed by controlling the focal length.

As shown in FIG. 1, the fluid 18 sucked by the suction mechanism 11 is stored in the fluid storage mechanism 12. The stored fluid 18 can be returned to the fluid supply mechanism 6 using a pump (not shown) or the like, allowing the fluid 18 to be circulated and reused. The fluid 18 drawn into the fluid storage mechanism 12 from the cooling hole 20 using the suction mechanism 11 also contains bubbles 14 resulting from laser peening and small metal pieces (not shown) resulting from the generation of ablation plasma 13. For this reason, when circulating the fluid in the fluid supply mechanism 6, it is desirable to filter the fluid using a filter (not shown) or the like.

In addition, if the next pulsed laser is irradiated while bubbles 14 generated during laser peening remain in the fluid 18, the remaining bubbles 14 may be irradiated with the laser light 2, resulting in energy loss and making the treatment unstable. The laser peening device 50 of this embodiment is equipped with a bubble confirmation mechanism 15 for confirming an image of the inside of the protection mechanism 26 and the laser irradiation position via the first mirror 3 provided in the laser light transmission mechanism 21.

According to the embodiment of the laser peening device and the laser peening method configured as described above, compressive stress can be applied to the inner surface of a cooling hole 20 or the like that has one end sealed and is difficult to access. Also, for example, if the position and depth of the cooling hole 20 of the object to be treated and the laser peening treatment range are known in advance, the focal length and movement pattern of the focusing lens unit 5 can be programmed using a control device (not shown) or the like, and laser peening can be automatically performed on the bottom of a narrow cooling hole 20 by combining movement to the laser irradiation position according to the frequency of the laser oscillator 1, irradiation of the laser light 2, and confirmation of remaining bubbles using the bubble confirmation mechanism 15.

Second Embodiment
The second embodiment will be described with reference to Fig. 5. Fig. 5 is a conceptual diagram showing the structure of the tip of a laser light transmission mechanism as observed from the side, and shows a state in which laser light 2 is irradiated from a laser transmission mechanism 21 to a workpiece 31 in a fluid 18 to perform laser peening.

In FIG. 5(a), when high-power laser light 2 is irradiated onto the workpiece 31, the laser light 2 is absorbed by the workpiece 31, and when the energy reaches a certain threshold or higher, the workpiece 31 vaporizes and an ablation plasma 13 is generated.

When the endcap fiber 22 used as the laser light transmission mechanism 21 is a quartz fiber, the laser light 2 propagates through the fluid 18 while expanding at a divergence angle NA=0.2 specific to quartz. For example, when the core diameter of the optical fiber 40 in the endcap fiber 22 is φ1.0 mm, when laser light 2 with a wavelength of 532 nm and pulse energy of 40 mJ is irradiated from the optical fiber 40 into water and onto a nickel-based alloy Alloy 600 placed as the workpiece 31, the beam diameter of the laser light 2 expands to about φ1.1 mm at a position 2 mm away from the tip, but ablation plasma 13 is generated due to the high energy density.

In the fluid 18, the ablation plasma 13 is confined by the pressure of the fluid 18, generating shock waves 32, which cause plastic deformation in the workpiece 31, forming compressive stress near the surface. This is the laser peening process. Here, the shock waves 32 propagate not only to the workpiece 31, but also through the fluid 18, with some of them reaching the endcap fiber 22. When a quartz fiber is used as the endcap fiber 22, the shock waves 32 generated by the ablation plasma 13 may reach the endcap fiber 22 and cause damage due to the high impact force, as shown in Figure 5(a).

In this embodiment, as shown in FIG. 5(b), the tip of the laser light transmission mechanism 21 is provided with a fiber tip protection mechanism 23, which has high impact resistance and can prevent damage even when the shock wave 32 described above reaches the tip of the laser light transmission mechanism 21. The fiber tip protection mechanism 23 is preferably made of sapphire, which has high laser light transparency, so that when quartz is used for the end cap fiber 22 or tapered fiber, for example, there is almost no transmission loss. Here, the fiber tip protection mechanism 23 may be placed in optical contact with the end cap fiber 22 (a technique for joining two highly precisely polished prisms without using adhesives), but it can also be fused to the end cap fiber 22 to form a structure with the same functionality.

In addition, in the present invention, it is also possible to use a structure in which a liquid 33 is enclosed between the end cap fiber 22 and the fiber tip protection mechanism 23, as shown in FIG. 5(c). Enclosing the liquid 33 has the advantage that a polishing process for forming the surface precision required for optical contact is not required, and fusion is also not required. Water is preferable as the liquid 33, and for laser light with a wavelength of 532 nm, it is possible to almost completely eliminate transmission loss and to minimize changes in the refractive index.

In addition, in this embodiment, as shown in FIG. 5(d), it is also possible to provide a collimating lens unit 29 that collimates the laser light instead of the fiber tip protection mechanism 23. When a quartz fiber such as an endcap fiber or a tapered fiber is used as the laser light transmission mechanism 21, the laser light 2 emitted from the tip of the optical fiber 40 propagates while expanding at a divergence angle NA=0.2 that is specific to quartz. However, by providing the collimating lens unit 29, it is possible to perform long-distance transmission while maintaining a larger aperture than the beam diameter of the laser light 2 emitted from the endcap fiber 22.

For example, when an endcap fiber with a core diameter of φ0.8 mm at the laser light emission end is used as the endcap fiber 22, it is possible to irradiate the laser light as a parallel light of φ0.9 mm with the collimator lens unit 29, and the laser light 2 can be emitted with a beam diameter of φ0.9 mm even at a position 20 mm away from the collimator lens unit 29. Therefore, as shown in FIG. 5(d), laser peening can be performed without being affected by the shock wave 32 caused by the ablation plasma 13, and processing can be performed with the same beam diameter without maintaining an accurate distance from the workpiece 31, and the tolerance range can be expanded.

These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations can be made without departing from the spirit of the invention.

These embodiments and variations are within the scope and spirit of the invention, as well as the scope of the invention and its equivalents as described in the claims.

1: Laser oscillator, 2: Laser light (pulsed laser light), 3: First mirror, 4: Second mirror, 5: Focusing lens unit, 6: Fluid supply mechanism, 7: Opening/closing unit, 8: Fluid transmission mechanism, 9: Position confirmation mechanism, 10: Cover, 11: Suction mechanism, 12: Fluid storage mechanism, 13: Ablation plasma, 14: Air bubble, 15: Air bubble confirmation mechanism, 16: Shutter, 17: Attenuator, 18: Fluid, 19: Fluid flow, 20: Cooling hole, 21: Laser light transmission mechanism, 22: end cap fiber, 23: fiber tip protection mechanism, 24: beam intensity adjustment section, 25: housing, 26: protection mechanism, 27: drive mechanism, 28: drive mechanism operating section, 29: collimator lens unit, 30: laser peening applicable range, 31: object to be processed, 32: shock wave, 33: liquid, 40: optical fiber, 41: end cap, 42: cone rod, 43: joint, 50: laser peening device.

Claims (11)

A laser peening apparatus for performing laser peening on an inner surface of a hole, which is a workpiece having one end sealed, comprising:
a laser oscillator that emits a pulsed laser beam;
a laser light transmission mechanism that transmits the pulsed laser light emitted from the laser oscillator to a surface of a hole that is the workpiece;
a fluid supply mechanism for supplying a fluid to the inside of the hole;
It is composed of
The laser peening apparatus is characterized in that an end cap fiber is used as the laser light transmission mechanism, the end cap being formed by fusing an end cap having a light receiving area on the incident side larger than the cross-sectional area of the optical fiber to the optical fiber. The laser peening device according to claim 1, characterized in that the end cap fiber is provided with a fiber tip protection mechanism that protects the end cap fiber from shock waves at the tip of the end cap fiber that faces the workpiece surface. The laser peening device according to claim 2, characterized in that sapphire is used as the fiber tip protection mechanism. The laser peening device according to claim 2 or 3, characterized in that a liquid is enclosed as an intermediate layer between the tip of the end cap fiber and the fiber tip protection mechanism. The laser peening device according to claim 1, characterized in that the tip of the end cap fiber facing the workpiece surface is provided with a collimating lens unit that shapes the laser light irradiated from the tip of the end cap fiber into a parallel light. The laser peening device according to claim 1, characterized in that it is provided with a position confirmation mechanism that measures the distance from the tip of the endcap fiber to the laser irradiation position, and is capable of changing the focal position of the pulsed laser light by moving the endcap fiber based on the distance from the tip of the endcap fiber to the laser irradiation position measured by this position confirmation mechanism. The laser peening device according to claim 2, further comprising a position confirmation mechanism for measuring the distance from the tip of the fiber tip protection mechanism to the laser irradiation position, and the focal position of the pulsed laser light can be changed by moving the end cap fiber based on the distance from the tip of the fiber tip protection mechanism to the laser irradiation position measured by the position confirmation mechanism. The laser peening device according to claim 1, characterized in that it is provided with a driving mechanism using a flexible tube on the outer periphery of the optical fiber that constitutes the end cap fiber, and this driving mechanism changes the angle of the tip of the optical fiber by a driving mechanism operating part. The laser peening device according to claim 1, characterized in that the drive mechanism operating unit rotates, moves up and down, translates, and tilts the end cap fiber relative to the central axis of the hole in the workpiece. The laser peening device according to claim 1, characterized in that the end cap is a cone-shaped cone rod whose light receiving area on the incident side is larger than the area of the joint with the optical fiber. A laser peening method characterized by irradiating laser light onto an end cap fiber in which an end cap with a light receiving area on the incident side larger than the cross-sectional area of the optical fiber is fused to the optical fiber, and performing laser peening on the inner surface of a hole with one end sealed while freely controlling the position where the laser light is irradiated from the tip of the optical fiber by changing the position and angle of the optical fiber.

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