A Laser Shock Peening Method for Thin-Walled Structural Parts

Abstract

The present invention relates to a laser shock peening method for thin-walled structural parts, comprising: respectively setting the laser spots irradiated at the same position on two opposite surfaces of the thin-walled structural part as a solid spot and a hollow spot; performing surface treatment on the thin-walled structural part; and using the solid spot and the hollow spot to synchronously or asynchronously perform laser shock peening on the front and back surfaces of the surface-treated thin-walled structural part respectively. The purpose of the laser shock peening method for the thin-walled structural part is to solve the problem that the existing laser shock peening method for thin-walled structural parts reduces the residual compressive stress level of the strengthened surface layer due to the bending deformation of the thin-walled structural part during the strengthening process.

Description

Technical Field

[0001] The present invention relates to the technical field of laser processing, and particularly relates to a laser shock peening method for thin-walled structure parts. Background Art

[0002] Thin-walled structure parts are usually composed of thin plates and thin shells. Typical thin-walled structure parts include blades, aircraft panels, etc. During the manufacturing process and use process of thin-walled structure parts, factors that are not conducive to their fatigue performance will be generated. For example, when a blade is damaged by foreign objects, damage notches will be generated at the blade edge, and stress concentration occurs in the T-shaped structure of the aircraft panel. Therefore, these thin-walled structure parts are extremely prone to fatigue fracture when used under fatigue load conditions. Laser shock peening is applied to thin-walled structure parts to redistribute their residual stresses, and the surface layer shows residual compressive stresses. These residual compressive stresses distributed on the surface layer can effectively reduce the tensile stress of the actual load and reduce the stress concentration effect of thin-walled structure parts, thereby improving the fatigue life of the workpiece.

[0003] The existing laser shock peening method for thin-walled structure parts inevitably causes bending deformation of the thin-walled structure parts during the strengthening process, thereby reducing the residual compressive stress level on the strengthened surface layer. Especially when the laser shock peening area is located at the edge of the thin-walled structure part, the residual compressive stress level drops severely.

[0004] Therefore, the inventor provides a laser shock peening method for thin-walled structure parts. Summary of the Invention

[0005] (1) Technical Problems to be Solved

[0006] The embodiment of the present invention provides a laser shock peening method for thin-walled structure parts, which solves the technical problem that the existing laser shock peening method for thin-walled structure parts reduces the residual compressive stress level on the strengthened surface layer due to the bending deformation of the thin-walled structure parts generated during the strengthening process.

[0007] (2) Technical Solutions

[0008] The present invention provides a laser shock peening method for thin-walled structure parts, including the following steps:

[0009] The laser spots irradiated on the same position of two opposite surfaces of the thin-walled structure part are respectively set as a solid spot and a hollow spot;

[0010] Perform surface treatment on the thin-walled structure part;

[0011] Use the solid spot and the hollow spot to synchronously or asynchronously perform laser shock peening on the front and back surfaces of the surface-treated thin-walled structure part respectively.

[0012] Further, the outer contour line of the solid light spot is completely located inside or coincides with the outer contour line of the hollow light spot, and the inner contour line of the hollow light spot is completely located inside or coincides with the outer contour line of the solid light spot.

[0013] Further, the solid light spot and the hollow light spot are concentric circles / concentric squares.

[0014] Further, the surface treatment of the thin-walled structure part is specifically as follows:

[0015] Absorption layers are provided on the front and back surfaces of the thin-walled structure part to be strengthened, and a constraint layer is provided on the absorption layer.

[0016] Further, the absorption layer is a metal tape or a non-metal tape.

[0017] Further, the constraint layer is deionized water or K9 glass.

[0018] Further, the front and back surfaces of the surface-treated thin-walled structure part are subjected to laser shock peening by using the solid light spot and the hollow light spot synchronously or asynchronously, specifically including the following steps:

[0019] Two laser beams are irradiated on the front and back surfaces of the thin-walled structure part to be strengthened at the same time or at different times;

[0020] Adjust the laser power density of the solid light spot and the hollow light spot so that plastic deformation is generated on one side to be strengthened, and plastic deformation or elastic deformation is generated on the other side;

[0021] After the shock peening at each position is completed, the irradiation positions of the two laser beams are synchronously moved, so that the solid light spot and the hollow light spot move on two opposite surfaces of the thin-walled structure part along a predetermined trajectory until the laser shock peening of the surface to be strengthened is completed.

[0022] Further, when the solid light spot and the hollow light spot are irradiated asynchronously, the time difference between the solid light spot and the hollow light spot is less than the pulse width of the laser beam that reaches the surface of the thin-walled structure part first.

[0023] (3) Beneficial effects

[0024] In summary, by subjecting the two opposite surfaces to be treated of the thin-walled structure part to laser shock peening with a solid light spot and a hollow light spot respectively, the present invention avoids the internal damage of the material caused by the superposition of stress waves during the laser shock peening with double-sided simultaneous counter shock, and also avoids the structural deformation and the decrease of the residual compressive stress level in the strengthening area caused by the single-sided laser shock peening. The coordinated control of the residual compressive stress and the macroscopic deformation during the laser shock peening of the thin-walled structure part is realized, and the laser shock peening quality of the thin-walled structure part is improved. Description of the Drawings

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0026] Figure 1 is a schematic flow chart of a laser shock peening method for a thin-walled structural part provided by an embodiment of the present invention;

[0027] Figure 2 is a schematic diagram of the laser shock peening process in Embodiment 1;

[0028] Figure 3 is a schematic diagram of the laser spots on the front and back sides of the thin-walled structural part in Embodiment 1;

[0029] Figure 4 is a schematic diagram of the laser shock peening process after the thin-walled structural part is flipped in Embodiment 1;

[0030] Figure 5 is a schematic diagram of the laser spots on the front and back sides of the flipped thin-walled structural part in Embodiment 1;

[0031] Figure 6 is a schematic diagram of the laser shock peening process in Embodiment 2;

[0032] Figure 7 is a schematic diagram of the laser spots on the front and back sides of the thin-walled structural part in Embodiment 2.

[0033] In the figures:

[0034] 1 - First thin-walled structural part; 2 - First strengthening surface A; 3 - First strengthening surface B; 4 - First nanosecond pulsed laser A; 5 - First nanosecond pulsed laser B; 6 - First circular spot A; 7 - First annular spot A; 8 - First circular spot B; 9 - First annular spot B; 10 - First circular spot C; 11 - First annular spot C; 12 - First circular spot D; 13 - First annular spot D; 21 - Second thin-walled structural part; 22 - Second strengthening surface; 23 - Second non-strengthening surface; 24 - Second nanosecond pulsed laser A; 25 - Second nanosecond pulsed laser B; 26 - Second square spot A; 27 - Second square annular spot A; 28 - Second square spot B; 29 - Second square annular spot B. Detailed Embodiments

[0035] The following further describes in detail the embodiments of the present invention in conjunction with the accompanying drawings and embodiments. The detailed description of the following embodiments and the drawings are used to exemplarily illustrate the principles of the present invention, but cannot be used to limit the scope of the present invention, that is, the present invention is not limited to the described embodiments, and covers any modifications, substitutions, and improvements of parts, components, and connection methods without departing from the spirit of the present invention.

[0036] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The following will detail the present application with reference to the accompanying drawings and embodiments.

[0037] Figure 1 It is a flow schematic of a laser shock peening method for a thin-walled structure part provided by an embodiment of the present invention. The method may include the following steps:

[0038] S100: Set the laser spots irradiated on the same positions of two opposite surfaces of the thin-walled structure part as a solid spot and a hollow spot respectively;

[0039] S200: Perform surface treatment on the thin-walled structure part;

[0040] S300: Use the solid spot and the hollow spot to synchronously or asynchronously perform laser shock peening on the front and back surfaces of the surface-treated thin-walled structure part respectively.

[0041] In the above embodiment, by performing laser shock peening on the opposite two surfaces to be treated of the thin-walled structure part with a solid spot and a hollow spot respectively, the two forms of spots are nested with each other, avoiding the internal damage of the material caused by the superposition of stress waves during double-sided simultaneous counter laser shock peening, and also avoiding the structural deformation and the decrease of the residual compressive stress level in the strengthening area during single-sided laser shock peening. The coordinated control of the residual compressive stress and macroscopic deformation during the laser shock peening process of the thin-walled structure part is realized, and the laser shock peening quality of the thin-walled structure part is improved.

[0042] It should be noted here that the present application does not limit the specific shapes of the solid spot and the hollow spot. For example: the solid spot can be a regular shape such as a circle, an ellipse, a rectangle, a triangle, a trapezoid, etc., or an irregular shape; the corresponding hollow spot can be a hollow regular shape or an irregular shape.

[0043] Among them, the specific implementation order of step S200 is not limited, as long as the surface treatment of the thin-walled structure part is completed before laser shock peening.

[0044] Optical components such as total reflection mirrors and semi-transparent semi-reflective mirrors are used to build a laser shock strengthening light spot, ensuring that double-sided synchronous or asynchronous shocks can be achieved without changing the position of the thin-walled structural part, and the power density of the solid-structured light spot and the hollow-structured light spot can be adjusted separately. More simply, two lasers can be directly used, with external trigger control synchronized, to achieve synchronous and asynchronous light output.

[0045] As an alternative implementation, in step S100, the outer contour line of the solid light spot is completely inside or coincides with the outer contour line of the hollow light spot, and the inner contour line of the hollow light spot is completely inside or coincides with the outer contour line of the solid light spot.

[0046] Specifically, the main purpose of the nested solid light spot and hollow light spot is to effectively weaken the amplitude of the tensile stress wave formed by the superposition of the stress waves generated by the strengthening front and back light spots respectively when they are reflected into tensile stress waves on their respective back surfaces, thereby avoiding internal damage to the material.

[0047] As an alternative implementation, the solid light spot and the hollow light spot are concentric circles / concentric squares. Among them, when the solid light spot and the hollow light spot are concentric circles, the diameter of the circular light spot is greater than or equal to the inner diameter of the ring-shaped light spot and less than or equal to the outer diameter of the ring-shaped light spot. Such a structural design can make the shape of the light spot more regular on the one hand, and on the other hand, the laser impact forces on the opposite sides of the wall plate set concentrically can be perfectly complementary, avoiding the superposition of the two stress waves.

[0048] As an alternative implementation, in step S200, the surface of the thin-walled structural part is treated, specifically as follows:

[0049] Absorbing layers are provided on the front and back surfaces of the thin-walled structural part to be strengthened, and a constraint layer is provided on the absorbing layer.

[0050] In the above method, the function of the absorbing layer is to absorb the laser and generate plasma; the function of the constraint layer is to prevent the plasma from diffusing into the air and form a high-pressure shock wave.

[0051] As an alternative implementation, the absorbing layer is a metal tape or a non-metal tape. Among them, the metal tape can be an aluminum foil tape, and the non-metal tape can be an insulating tape.

[0052] As an alternative implementation, the constraint layer is deionized water or K9 glass. When deionized water is used, it is necessary to perform real-time flushing at the corresponding positions on the surface to be strengthened during the laser shock strengthening process.

[0053] As an alternative implementation, in step S300, the front and back surfaces of the surface-treated thin-walled structural part are subjected to laser shock strengthening using the solid light spot and the hollow light spot synchronously or asynchronously respectively, specifically including the following steps:

[0054] S301. Irradiate two laser beams on the front and back surfaces of the thin-walled structure part to be strengthened at the same time or at different times.

[0055] S302. Adjust the laser power density of the solid light spot and the hollow light spot to cause plastic deformation on one side to be strengthened and plastic deformation or elastic deformation on the other side.

[0056] S303. After completing the shock strengthening at each position, synchronously move the irradiation positions of the two laser beams so that the solid light spot and the hollow light spot move on two opposite surfaces of the thin-walled structure part along a predetermined trajectory until the laser shock strengthening of the surface to be strengthened is completed.

[0057] As an optional implementation manner, when the solid light spot and the hollow light spot are irradiated asynchronously, the time difference between the solid light spot and the hollow light spot is less than the pulse width of the laser beam that reaches the surface of the thin-walled structure part first.

[0058] Specifically, such a time difference setting is to avoid too large a time difference between the asynchronous irradiations of the solid light spot and the hollow light spot. When the second solid light spot has impacted one side of the wall panel, the first hollow light spot has not yet impacted the other side of the wall panel, thus affecting the complementary effect of the impact forces on the relative two sides of the wall panel.

[0059] Example 1

[0060] The double-sided synchronous laser shock strengthening of the thin-walled structure part is carried out by using the method of this patent. The first thin-walled structure part 1 is a TC4 titanium alloy plate with a thickness of 2 mm, having a first strengthening surface A2 and a first strengthening surface A3. The wavelength of the first nanosecond pulsed laser A4 is 1064 nm, the pulse width is 18 ns, and the pulse energy is 25 J. The wavelength of the first nanosecond pulsed laser B5 is 1064 nm, the pulse width is 18 ns, and the pulse energy is 24 J. The first nanosecond pulsed laser A4 and the first nanosecond pulsed laser B5 are simultaneously irradiated on the first strengthening surface 2 and the first strengthening surface 3 respectively to form a circular light spot and an annular light spot. The diameter of the circular light spot is 5 mm, and the inner diameter and the outer diameter of the annular light spot are 5 mm and 7 mm respectively. The outer circular contour of the circular light spot and the inner circular contour of the annular light spot are always kept coincident in the projection in the thickness direction of the first thin-walled structure part 1.

[0061] Before the laser shock strengthening, an aluminum foil absorption layer with a thickness of 100 microns and a deionized water constraint layer with a thickness of 1 mm are respectively arranged on the first strengthening surface A2 and the first strengthening surface B3 of the first thin-walled structure part 1. As Figures 2-3As shown, the first nanosecond pulsed laser A4 and the first nanosecond pulsed laser B5 that move to the strengthening starting position respectively form a first circular light spot A6 and a first ring-shaped light spot A7 on the first strengthening surface A2 and the first strengthening surface B3, completing the first point double-sided strengthening; the first nanosecond pulsed laser A4 and the first nanosecond pulsed laser B5 are synchronously moved (the moving distance is 6 mm), and respectively form a second circular light spot B8 and a second ring-shaped light spot B9 on the first strengthening surface A2 and the first strengthening surface B3, completing the second point double-sided strengthening; the first nanosecond pulsed laser A4 and the first nanosecond pulsed laser B5 are synchronously moved in sequence until the circular light spots and the ring-shaped light spots uniformly fill the first strengthening surface A2 and the first strengthening surface B3, completing the first round of laser shock strengthening.

[0062] As Figures 4-5 shown, flip the first thin-walled structure part 1 or switch the first nanosecond pulsed laser 4A and the first nanosecond pulsed laser B5. The first nanosecond pulsed laser A4 and the first nanosecond pulsed laser B5 that move to the strengthening starting position respectively form a third circular light spot C10 and a third ring-shaped light spot C11 on the first strengthening surface A3 and the first strengthening surface B2. The outer circle contour of the third circular light spot C10 coincides with the inner circle contour of the third ring-shaped light spot 11, completing the first point double-sided strengthening; the first nanosecond pulsed laser A4 and the first nanosecond pulsed laser B5 are synchronously moved (the moving distance is 6 mm), and respectively form a fourth circular light spot D12 and a fourth ring-shaped light spot D13 on the first strengthening surface B3 and the strengthening surface A2, completing the second point double-sided strengthening; the nanosecond pulsed laser 4 and the nanosecond pulsed laser 5 are synchronously moved in sequence until the circular light spots and the ring-shaped light spots uniformly fill the first strengthening surface B3 and the first strengthening surface A2, completing the second round of laser shock strengthening, that is, completing the double-sided laser shock strengthening of the first thin-walled structure part 1.

[0063] Example 2

[0064] The single-sided laser shock strengthening of the thin-walled structure part is carried out by using the method of this patent. The second thin-walled structure part 21 is an aluminum alloy plate with a thickness of 3 mm, having a second strengthening surface 22 and a second non-strengthening surface 23. The wavelength of the second nanosecond pulsed laser A24 is 1064 nm, the pulse width is 15 ns, and the pulse energy is 30 J. The wavelength of the second nanosecond pulsed laser B5 is 1064 nm, the pulse width is 15 ns, and the pulse energy is 10 J. The second nanosecond pulsed laser A24 and the second nanosecond pulsed laser B25 simultaneously irradiate on the second strengthening surface 22 and the second non-strengthening surface 23 respectively to form a square light spot and a square ring-shaped light spot. The side length of the square light spot is 8 mm, and the inner ring side length and the outer ring side length of the square ring-shaped light spot are 8 mm and 10 mm respectively. The outer contour of the square light spot and the projection of the inner ring contour of the square ring-shaped light spot in the thickness direction of the second thin-walled structure part 21 are always kept coincident.

[0065] Before laser shock peening, an aluminum foil absorption layer with a thickness of 100 microns and a deionized water confinement layer with a thickness of 1 mm are respectively arranged on the second strengthening surface 22 and the second non-strengthening surface 23 of the second thin-walled structural part 21. As Figures 6-7 shown, the second nanosecond pulse laser A24 and the second nanosecond pulse laser B25 moved to the strengthening starting position respectively form a first square light spot 26 and a first square ring light spot 27 on the second strengthening surface 22 and the second non-strengthening surface 23, completing the first point single-sided strengthening;

[0066] The second nanosecond pulse laser A24 and the second nanosecond pulse laser B25 are synchronously moved (the moving distance is 7 mm), and a second square light spot 28 and a second square ring light spot 29 are respectively formed on the second strengthening surface 22 and the second non-strengthening surface 23, completing the second point single-sided strengthening; the second nanosecond pulse laser A24 and the second nanosecond pulse laser B25 are synchronously moved in sequence until the square light spot uniformly fills the second strengthening surface 22, completing the single-sided laser shock peening of the second thin-walled structural part 21.

[0067] It should be clear that each embodiment in this specification is described in a progressive manner. For the same or similar parts between each embodiment, reference can be made to each other. The key point of each embodiment is to illustrate the differences from other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. And, for the sake of brevity, the detailed description of known method technologies is omitted here.

[0068] The above are only the embodiments of the present application and do not limit the present application. For those skilled in the art, the present application can have various changes and modifications without departing from the scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the scope of the claims of the present application.

Claims

1. A laser shock peening method for thin-walled structural parts, characterized in that The method comprises the following steps: The laser spots irradiated at the same position on two opposite surfaces of the thin-walled structure part are respectively set as a solid spot and a hollow spot; Surface treatment is carried out on the thin-walled structure part; The front and back surfaces of the surface-treated thin-walled structure part are respectively subjected to laser shock peening by using the solid spot and the hollow spot synchronously or asynchronously; The outer contour line of the solid spot is completely located inside or coincides with the outer contour line of the hollow spot, and the inner contour line of the hollow spot is completely located inside or coincides with the outer contour line of the solid spot.

2. The laser shock peening method for thin-walled structure parts according to claim 1, wherein The solid spot and the hollow spot are concentric circles / concentric squares.

3. The laser shock peening method for thin-walled structural parts according to claim 1, characterized in that, The surface treatment of the thin-walled structure part specifically is: An absorption layer is arranged on the front and back surfaces of the thin-walled structure part to be strengthened, and a constraint layer is arranged on the absorption layer.

4. The laser shock peening method for thin-walled structural parts according to claim 3, wherein, The absorption layer is a metal tape or a non-metal tape.

5. The laser shock peening method for thin-walled structural parts according to claim 3 or 4, characterized in that The constraint layer is deionized water or K9 glass.

6. The laser shock peening method for thin-walled structural parts according to claim 1, characterized in that, The step of respectively carrying out laser shock peening on the front and back surfaces of the surface-treated thin-walled structure part by using the solid spot and the hollow spot synchronously or asynchronously specifically comprises the following steps: Two laser beams are irradiated on the front and back surfaces of the thin-walled structure part to be strengthened at the same moment or at different moments; The laser power densities of the solid spot and the hollow spot are adjusted to cause plastic deformation on one side to be strengthened and plastic deformation or elastic deformation on the other side; After the shock peening at each position is completed, the irradiation positions of the two laser beams are synchronously moved, so that the solid spot and the hollow spot respectively move along a predetermined track on two opposite surfaces of the thin-walled structure part until the laser shock peening of the surface to be strengthened is completed.

7. The laser shock peening method for thin-walled structural parts according to claim 1, wherein, When the solid spot and the hollow spot are irradiated asynchronously, the time difference between the solid spot and the hollow spot is less than the pulse width of the laser beam that first reaches the surface of the thin-walled structure part.

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