A Laser Shock Peening Device Based on a Reflective Focusing Mirror

Abstract

The present invention discloses a laser shock peening device based on a reflective focusing mirror, which includes a laser source, a light guiding device, a reflective focusing system, a reflective focusing clamping device, a workpiece clamping device, a workbench, a constraint layer loading mechanism, a control system and a metal workpiece. The present invention mainly aims at the deficiencies of the existing large-energy laser shock peening equipment, such as its large volume, inflexible hard optical path light guiding, and inability to process groove corners and inner hole parts, and provides a laser shock peening device based on a reflective focusing mirror.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser shock peening, and particularly relates to a laser shock peening device based on a reflecting focusing mirror. Background Art

[0002] Laser shock peening technology, also known as laser shot peening, uses short pulses (ns level) and high peak power density (above 10 9 W / cm2) laser to penetrate the constraint layer and impact the laser absorption protective film covering the metal surface, generating a high-pressure transient plasma shock wave. The shock wave pressure up to GPa causes high-strain plastic deformation on the surface layer of the metal material, forming a large residual compressive stress. At the same time, the microstructure changes greatly, and it can significantly improve the fatigue performance of the metal material such as resistance to external force damage and corrosion.

[0003] Currently, large-energy fixed laser shock peening equipment is mainly used at home and abroad. Although it has been applied to many workpieces, the laser focusing spot of such equipment is relatively large, and the hard optical path guiding mode of directly guiding light by optical lenses is mostly used, and some complex surfaces of workpieces, such as the inner walls of grooves and holes, cannot be processed. For the patent "A Scanning Laser Shock Peening Device" with the application number CN201910623322.4 and the patent "A Laser Shock Peening Device and Method" with the application number CN201910612589.3 of our company, although a laser shock peening device with small energy and small spot is used, the processing of areas such as the inner walls of grooves and small holes still cannot be implemented.

[0004] For laser shock peening of the inner wall of a hole, a reflecting focusing mode of laser shock peening can be adopted. However, if there are too many optical elements in the reflecting focusing system, the volume of the reflecting focusing system will be very large, and only the inner wall of a large-diameter hole can be processed. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned deficiencies of the prior art. In order to solve the problem that the existing large-energy fixed equipment cannot process the grooves or inner walls of holes of metal workpieces, a laser shock peening device based on a reflecting focusing mirror is proposed.

[0006] In order to solve the technical problem, the technical solution of the present invention is:

[0007] A laser shock peening device based on a reflecting focusing mirror includes a laser source, a light guiding device, a reflecting focusing system, a reflecting focusing clamping device, a workpiece clamping device, a workbench, a constraint layer loading mechanism, a control system, and a metal workpiece;

[0008] The workpiece clamping device is installed on the workbench, and the metal workpiece is installed on the workpiece clamping device. One end of the reflection focusing clamping device is fixed with a reflection focusing system, one end of the light guiding device is connected to the laser source, and the other end thereof is connected to the reflection focusing system;

[0009] The control system is electrically connected to the laser source, the workbench and the reflection focusing clamping device respectively. The control system controls the laser output of the laser source, controls the movement of the workbench and controls the reflection focusing clamping device respectively;

[0010] The constraint layer loading mechanism is used to form a constraint layer on the surface of the metal workpiece. The laser beam emitted by the laser source is transmitted through the light guiding device and focused by the reflection focusing system, and at the same time, it is emitted at a set off-axis angle. The laser beam passes through the constraint layer and acts on the surface of the metal workpiece;

[0011] The reflection focusing system includes a reflection focusing mirror and a laser protection lens arranged in the cylinder;

[0012] The reflection focusing mirror is an off-axis ellipsoidal mirror;

[0013] Preferably, the surface equation of the off-axis ellipsoidal mirror in the rectangular coordinate system is one of the following:

[0014]

[0015] In the formula, a is the major semi-axis of the ellipsoid, c is the minor semi-axis of the ellipsoid, and the origin of the coordinate axis is the center of the ellipsoid;

[0016] The aperture calculation formula of the off-axis ellipsoidal mirror is as follows:

[0017] φ = 2Ltanω;

[0018] φ is the aperture of the off-axis ellipsoidal mirror, L is the object distance, ω is the semi-divergence angle, and the center point of the off-axis ellipsoid is determined by the off-axis angle θ;

[0019] Preferably, the laser beam output by the light guiding device is located at the focus of the light incident end of the off-axis ellipsoidal mirror. The virtual focus of the laser beam coincides with the incident end focus of the off-axis ellipsoidal mirror. The light emitted from the off-axis ellipsoidal mirror passes through the laser protection lens at the exit end and is focused on the exit end focus of the off-axis ellipsoidal mirror.

[0020] Preferably, it further includes a water purification device connected to the constraint layer loading mechanism.

[0021] Preferably, the light guiding device is one of a light guiding arm or an optical fiber.

[0022] Preferably, the constraint layer loading mechanism is one of a water-light coaxial type constraint layer loading mechanism and an underwater impact type constraint layer loading mechanism;

[0023] The water-light coaxial constraint layer loading mechanism loads the constraint layer on the metal workpiece in a water-light coaxial manner, and the underwater impact constraint layer loading mechanism loads the constraint layer by immersing the metal workpiece in water.

[0024] Compared with the prior art, the advantages of the present invention are as follows:

[0025] (1) The present invention adopts an off-axis ellipsoidal reflecting focusing mirror. Compared with other reflecting focusing mirrors with surface shapes such as off-axis parabolic mirrors, there is no need to collimate the laser beam, which greatly reduces the volume of the reflecting focusing system.

[0026] (2) The present invention sets the light guiding device to a flexible light guiding mode, increasing the flexibility of the light guiding mode, meeting the processing requirements of the complex surface shapes of some workpieces, such as the inner walls of grooves and holes, etc., and having a wider application range. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic structural diagram of Embodiment 1 of the present invention;

[0028] Figure 2 is an optical schematic diagram of the reflecting focusing system when the light guiding device is an optical fiber in Embodiment 1 of the present invention;

[0029] Figure 3 is a schematic structural diagram of Embodiment 2 of the present invention;

[0030] Figure 4 is an optical schematic diagram of the reflecting focusing system when the light guiding device is a light guiding arm in Embodiment 1 of the present invention;

[0031] Figure 5 is a schematic diagram of the movement of the metal workpiece;

[0032] Figure 6 is a schematic diagram of the water-light coaxial constraint layer loading mechanism;

[0033] Figure 7 is a schematic diagram of the underwater impact constraint layer loading mechanism;

[0034] Description of the reference numerals:

[0035] 1. Laser source,

[0036] 2. Light guiding device, 2-1. Optical fiber, 2-1-1. Optical fiber output end cap, 2-2. Light guiding arm;

[0037] 3. Reflecting focusing system, 3-1. Off-axis ellipsoidal mirror, 3-2. Laser protection lens;

[0038] 4. Reflecting focusing clamping device, 5. Workpiece clamping device, 6. Workbench;

[0039] 7. Constraint layer loading mechanism, 8. Control system, 9. Metal workpiece, 10. Water purification device, 11. Virtual focus. Specific embodiments

[0040] The following describes the specific embodiments of the present invention in conjunction with the accompanying drawings and embodiments:

[0041] It should be noted that the structures, ratios, sizes, etc. illustrated in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those familiar with this technology to understand and read, and are not used to limit the conditions under which the present invention can be implemented. Any modification of the structure, change of the proportional relationship, or adjustment of the size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope covered by the technical content disclosed in the present invention.

[0042] At the same time, the terms such as "upper", "lower", "left", "right", "middle", and "one" cited in this specification are only for the purpose of convenient narration and are not used to limit the scope in which the present invention can be implemented. The change or adjustment of their relative relationships, without substantial change in the technical content, should also be regarded as the scope in which the present invention can be implemented.

[0043] Embodiment 1

[0044] As Figure 1 shown, a laser shock peening device based on a reflective focusing mirror includes a laser source 1, a light guiding device 2, a reflective focusing system 3, a reflective focusing clamping device 4, a workpiece clamping device 5, a workbench 6, a constraint layer loading mechanism 7, a control system 8, and a metal workpiece 9;

[0045] The workpiece clamping device 5 is installed on the workbench 6, the metal workpiece 9 is installed on the workpiece clamping device 5, one end of the reflective focusing clamping device 4 is fixed with the reflective focusing system 3, one end of the light guiding device 2 is connected to the laser source 1 and the other end is connected to the reflective focusing system 3; the laser source 1 is a pulsed laser; the workpiece clamping device 5 can be made into different special fixtures according to different workpiece requirements.

[0046] The control system 8 is electrically connected to the pulsed laser, the workbench 6, and the reflective focusing clamping device 4 respectively. The control system 8 controls the laser output of the pulsed laser, controls the movement of the workbench 6, and controls the reflective focusing clamping device 4 respectively; the workbench 6 can drive the workpiece clamping device 5 and the metal workpiece 9 to move, and has movement modes such as linear and rotational.

[0047] The constraint layer loading mechanism 7 is used to form a constraint layer on the surface of the metal workpiece 9. The laser beam emitted by the laser source 1 is transmitted through the light guiding device 2 and focused by the reflection focusing system 3, and is emitted at a set off-axis angle, acting on the machining area on the surface of the metal workpiece 9 with a spot of a certain size. The set off-axis angle can be set arbitrarily according to the situation.

[0048] Specifically, it further includes a water purification device 10 connected to the constraint layer loading mechanism 7. The control system 8 controls the output of the pulsed laser 1, the movement of the reflection focusing system clamping device 4, the movement of the workbench 6, the loading of the constraint layer by the constraint layer loading mechanism 7, the water production of the water purification device 8, the loading of the water constraint layer by the constraint layer loading mechanism 9, and the coordinated operation of the entire system.

[0049] The reflection focusing system 3 includes an off-axis ellipsoidal mirror 3-1 and a laser protection lens 3-2 arranged inside the cylinder. The virtual focus 11 of the laser beam output by the light guiding device 2 coincides with the focus of the light incident end of the off-axis ellipsoidal mirror 3-1. The light exiting from the off-axis ellipsoidal mirror 3-1 passes through the laser protection lens 3-2 and is focused on the focus of the exit end of the off-axis ellipsoidal mirror 3-1.

[0050] The converging beam output by the reflection focusing system 3 passes through the constraint layer and acts on the surface of the metal workpiece 9 with a focused spot of a certain size. A laser protection lens 3-2 is arranged behind the off-axis ellipsoidal mirror 3-1 to protect the off-axis ellipsoidal mirror 3-1 from contamination during laser shock peening. Among them, the reflection focusing system 3 uses an off-axis ellipsoidal mirror 3-1, which eliminates the spherical aberration and chromatic aberration introduced by the transmission optical system, and also has the advantage of small volume, and can perform laser shock peening processing on the inner walls of holes of various sizes.

[0051] As Figure 2 shown in the internal structure of the laser output from the optical fiber 2-2 to the reflection focusing system 3, adjust the distance between the output end cap of the optical fiber 2-2 and the off-axis ellipsoidal mirror 3-1 in the reflection focusing system 3 so that the virtual focus of the light beam emitted by the optical fiber 2-2 coincides with the focus of the light incident end of the off-axis ellipsoidal mirror 3-1; the laser is focused by the off-axis ellipsoidal mirror 3-1 and emitted at a set off-axis angle; a laser protection lens 3-2 is arranged on the reflection optical path to prevent the off-axis ellipsoidal mirror 3-2 from being contaminated during processing.

[0052] Specifically, the surface equation of the off-axis ellipsoidal mirror 3-1 in the rectangular coordinate system is one of the following:

[0053]

[0054]

[0055] Wherein, a is the major semi-axis of the ellipsoid, c is the minor semi-axis of the ellipsoid, and the origin of the coordinate axis is the center of the ellipsoid.

[0056] The aperture calculation formula of the off-axis ellipsoidal mirror is as follows:

[0057] φ = 2Ltanω;

[0058] φ is the aperture of the off-axis ellipsoidal mirror, L is the object distance, ω is the semi-divergence angle, and the center point of the off-axis ellipsoidal mirror is determined by the off-axis angle θ. Based on the above formula, an appropriate margin is reserved as the clear aperture of the ellipsoidal mirror.

[0059] In this embodiment, the off-axis ellipsoidal mirror 3-1 is an ellipsoid with a major axis of 28 and a minor axis of 17.889, and the off-axis angle is 90°. A mirror taking a partial surface as the reflecting surface. In practical applications, relevant data can be changed according to different requirements to obtain different reflection focusing effects.

[0060] As Figure 5 shown, by controlling the relative movement of the reflection focusing system clamping structure 4 and the workbench 6 through the control system 8, four-axis machining operations of X, Y, Z, and C axes in space can be realized.

[0061] Among them, the light guiding device 2 is an optical fiber 2-1, and its advantage is that the optical fiber has good flexibility and is easy to bend. This setting has obvious advantages when processing some areas that hard optical paths cannot reach.

[0062] Specifically, the constraint layer loading mechanism is one of a water-light coaxial constraint layer loading mechanism and an underwater impact constraint layer loading mechanism;

[0063] The water-light coaxial constraint layer loading mechanism loads the constraint layer on the metal workpiece 9 in a water-light coaxial manner, and the underwater impact constraint layer loading mechanism loads the constraint layer by immersing the metal workpiece 9 in water.

[0064] As Figure 6 shown, the constraint layer loading mechanism 7 can be a water-light coaxial constraint layer loading method, and the laser passes through a certain distance of water column and acts on the surface of the metal workpiece 9 together with the water.

[0065] Specifically, as Figure 7 shown, when the characteristics of the metal workpiece 9 permit (such as no rust or other negative effects will occur), the constraint layer loading mechanism 7 can directly immerse the processing area of the metal workpiece 9 in deionized water, and the focused laser passes through the deionized water and directly acts on the surface of the metal workpiece 9.

[0066] Embodiment 2

[0067] Replace the optical fiber 2-1 in Embodiment 1 with a light guide arm 2-2. The advantage is that the light guide arm 2-2 consists of several joints, with flexible movement and high precision. This solution is suitable for processing some complex and variable surface shapes that require frequent changes in the processing posture. The laser output by the pulsed laser 1 is transmitted to the reflection focusing system 3 through the light guide arm 2-2. The light guide arm 2-2 is a freely rotatable light transmission element composed of several reflectors.

[0068] The remaining structures are the same as those in Embodiment 1. This embodiment is a variation of the basic Embodiment 1.

[0069] Furthermore, the internal structure of the reflection focusing system 3 is as Figure 4 shown. Adjust the off-axis ellipsoidal mirror 3-1 in the reflection focusing system 3 to a suitable position and fix the reflection focusing system 3 on the reflection focusing system clamping structure 4.

[0070] Furthermore, in this embodiment, the off-axis ellipsoidal mirror 3-1 is an ellipsoid with a major axis of 30 and a minor axis of 20, an off-axis angle of 90°, and a mirror that takes a part of its surface as the reflecting surface. In practical applications, relevant data can be changed according to different requirements to obtain different reflection focusing effects.

[0071] The preferred embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various changes can be made without departing from the gist of the present invention.

[0072] Many other changes and modifications can be made without departing from the concept and scope of the present invention. It should be understood that the present invention is not limited to a specific embodiment, and the scope of the present invention is defined by the appended claims.

Claims

1. A laser shock peening device based on a reflective focusing mirror, characterized in that: it includes a laser source, a light guiding device, a reflective focusing system, a reflective focusing clamping device, a workpiece clamping device, a workbench, a constraint layer loading mechanism, a control system, and a metal workpiece; the workpiece clamping device is installed on the workbench, the metal workpiece is installed on the workpiece clamping device, one end of the reflective focusing clamping device is fixed with a reflective focusing system, one end of the light guiding device is connected to the laser source and the other end is connected to the reflective focusing system; the control system is electrically connected to the laser source, the workbench, and the reflective focusing clamping device respectively, and the control system controls the laser output of the laser source, controls the movement of the workbench, and controls the reflective focusing clamping device respectively; the constraint layer loading mechanism is used to form a constraint layer on the surface of the metal workpiece, the laser beam emitted by the laser source is transmitted through the light guiding device and focused by the reflective focusing system, and at the same time is emitted at a set off-axis angle, and the laser beam acts on the surface of the metal workpiece through the constraint layer; the reflective focusing system includes a reflective focusing mirror and a laser protection lens arranged in a cylinder; the reflective focusing mirror is an off-axis ellipsoidal mirror; the surface equation of the off-axis ellipsoidal mirror in a rectangular coordinate system is one of the following: where a is the major semi-axis of the ellipsoid, c is the minor semi-axis of the ellipsoid, and the origin of the coordinate axis is the center of the ellipsoid; the aperture calculation formula of the off-axis ellipsoidal mirror is as follows: φ = 2Ltan ω; φ is the aperture of the off-axis ellipsoidal mirror, L is the object distance, ω is the semi-divergence angle, and the center point of the off-axis ellipsoid is determined by the off-axis angle θ; the laser beam output by the light guiding device is located at the focus of the light incident end of the off-axis ellipsoidal mirror, the virtual focus of the laser beam coincides with the incident end focus of the off-axis ellipsoidal mirror, and the light exiting end of the light reflected by the off-axis ellipsoidal mirror passes through the laser protection lens and is focused on the exit end focus of the off-axis ellipsoidal mirror.

2. The laser shock peening device based on a reflective focusing mirror according to claim 1, characterized in that: it further includes a water purification device connected to the constraint layer loading mechanism.

3. The laser shock peening device based on a reflective focusing mirror according to claim 1 or 2, characterized in that: the light guiding device is one of a light guiding arm or an optical fiber.

4. The laser shock peening device based on a reflective focusing mirror according to claim 1, characterized in that: the constraint layer loading mechanism is one of a water-light coaxial constraint layer loading mechanism and an underwater impact constraint layer loading mechanism; the water-light coaxial constraint layer loading mechanism loads the constraint layer on the metal workpiece in a water-light coaxial manner, and the underwater impact constraint layer loading mechanism loads the constraint layer by immersing the metal workpiece in water.

Images