A method for laser shock peening of a thin-walled structure part connecting hole

Abstract

The application provides a laser shock peening method for connecting holes of thin-wall structure parts, which comprises the following steps: placing the thin-wall structure part with connecting holes on a cushion block, arranging a rigid mandrel in the connecting holes, and sequentially arranging a constraint layer and an absorbing layer on the top of the cushion block from top to bottom, wherein the constraint layer and the absorbing layer cover the connecting holes in the longitudinal direction; arranging a plurality of irradiation points on the edges of the connecting holes symmetrically and uniformly with the center of the connecting holes as the symmetric center, and the focused laser beam passes through the constraint layer on the top of the constraint layer and is sequentially aligned with the symmetric two irradiation points in the longitudinal direction to irradiate the absorbing layer sequentially. Through the application, the fatigue performance of the hole structure is improved, and the deformation of the thin-wall structure part can be prevented.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser processing, and particularly relates to a laser shock peening method for connecting holes of a thin-walled structure part. BACKGROUND

[0002] The thin-walled structure part is usually made of a thin plate or a thin shell, and typical thin-walled structure parts include blades, aircraft panels and the like. Taking an aircraft panel as an example, a large number of connecting holes need to be formed in the aircraft panel during manufacturing and use, and factors that are not conducive to the fatigue performance of the aircraft panel are generated during use. Specifically, during high-speed flight of the aircraft, the connecting holes are subjected to alternating loads, and stress concentration is easily generated around the hole structure, so that the aircraft panel is prone to fatigue failure under fatigue load conditions.

[0003] In the prior art, two methods, i.e., extrusion strengthening and laser shock peening, are usually used to improve the fatigue performance of the hole structure. The extrusion strengthening refers to direct contact between an extrusion strengthening tool (for example, a mandrel) and a hole wall, and the relative extrusion amount is applied to the hole wall. The extrusion strengthening tool extrudes the hole wall, the hole wall material is subjected to an extrusion force to generate metal flow, and elastic-plastic deformation occurs, so as to achieve extrusion strengthening of the hole. However, when the thickness of part of the wall plate is small, the release of residual stress after the extrusion strengthening causes the overall deformation of the hole peripheral surface layer. The laser shock peening refers to that a shock wave emitted by a high-power short-pulse laser in a very short time is used to irradiate a material, so as to rapidly heat the surface of the material to a vaporization temperature, and plastic deformation of the material surface occurs. Therefore, this method can only strengthen the hole surface, and cannot strengthen the hole peripheral surface layer. Meanwhile, when the diameter of the connecting hole is less than 3 mm, the mandrel is prone to breakage, and the extrusion strengthening method cannot be used. The conventional laser shock peening method causes the hole peripheral surface layer to collapse inward, and thus has the defects of affecting the hole precision and being unable to strengthen the hole wall.

[0004] Therefore, it is necessary to improve the existing strengthening method for the connecting hole of the thin-walled structure part to solve the above problems. SUMMARY

[0005] The present application aims to solve the problems that, in the existing extrusion strengthening method, when the thickness of part of the wall plate is small, the release of residual stress causes the overall deformation of the hole peripheral surface layer, in the laser shock peening method, only the hole surface can be strengthened, and the hole peripheral surface layer cannot be strengthened, and when the diameter of the connecting hole is less than 3 mm, the mandrel is prone to breakage, the extrusion strengthening method cannot be used, and the laser shock peening method causes the hole peripheral surface layer to collapse inward, thus affecting the hole precision and being unable to strengthen the hole wall.

[0006] To achieve the above-mentioned purpose, the present application provides a laser shock peening method for a connecting hole of a thin-walled structure part, which comprises the following steps.

[0007] The thin-walled structure part with a connecting hole is placed on a cushion block, a rigid mandrel is arranged in the connecting hole, and a constraint layer and an absorption layer are sequentially arranged on the top of the cushion block from top to bottom, the constraint layer and the absorption layer cover the connecting hole in the longitudinal direction.

[0008] A plurality of irradiation points are symmetrically and uniformly arranged on the edge of the connecting hole with the center of the connecting hole as the symmetric center, the focused laser beam penetrates the constraint layer on the top of the constraint layer and is sequentially aligned with the symmetric two irradiation points in the longitudinal direction, so as to sequentially irradiate the absorption layer.

[0009] As a further improvement of the present application, the diameter of the rigid mandrel is 0.02-0.04mm smaller than the hole diameter of the connecting hole, the height of the rigid mandrel is 0.1-0.15mm larger than the thickness of the thin-walled structure part, and the lower surface of the rigid mandrel is located on the same horizontal plane as the lower surface of the thin-walled structure part.

[0010] As a further improvement of the present application, the wave impedance corresponding to the material of the cushion block is 0.2-1*10 7 kg·m -2 ·s -1 .

[0011] As a further improvement of the present application, the material of the thin-walled structure part is titanium alloy or aluminum alloy, and the thickness of the thin-walled structure part is 2-3mm.

[0012] As a further improvement of the present application, the material of the cushion block is alumina ceramic or high-strength aluminum alloy.

[0013] As a further improvement of the present application, the material of the rigid mandrel is tungsten steel or high-strength titanium alloy.

[0014] As a further improvement of the present application, the constraint layer is a flowing water film, and the thickness of the water film is 1-1.5mm, and the flow rate of the water film is 5-10cm / min.

[0015] As a further improvement of the present application, the absorption layer is an aluminum foil or polyester adhesive tape with adhesive, and the thickness of the aluminum foil or polyester adhesive tape is 100-150 microns, and the thickness of the adhesive is 10 microns.

[0016] As a further improvement of the present application, the wavelength of the laser beam is 532nm or 1064nm, the pulse width is 15-25ns, the power density is 2-4GW / cm 2 , and the spot diameter of the focused laser beam is 3-5mm.

[0017] As a further improvement of the present application, the overlap rate between two adjacent light spots is 50-75%.

[0018] Compared with the prior art, the present application has the following advantages:

[0019] The light spot of the laser beam is longitudinally aligned with the irradiation point, and the irradiation point is arranged at the edge of the connecting hole, so that the light spot acts on the surface of the connecting hole and the rigid mandrel at the same time. Since the rigid mandrel has a large strength, the laser beam with a power density of 2-4 GW / cm 2 will not cause plastic deformation of the rigid mandrel. Under the action of the laser shock wave induced by the laser beam, an interface wave is generated between the interface of the rigid mandrel and the hole wall of the connecting hole, so that the hole wall of the connecting hole is extruded. Since the rigid mandrel does not produce plastic deformation, the surface of the connecting hole and the hole wall of the connecting hole are both extruded and strengthened. By using a pad with low wave impedance, when the laser shock wave is transmitted to the interface between the thin-walled structural part and the pad, most of the shock wave energy can be transmitted to the pad, thereby effectively suppressing the reverse deformation caused by the action of the laser shock wave. Under the action of the laser shock wave, the surface layer of the hole will produce plastic deformation. If the laser shock is performed on the hole in a circumferential order, the plastic deformation of the surface layer of the hole will accumulate, thereby reducing the accuracy of the hole position. However, by using the symmetric and sequential impact method, the accumulation of plastic deformation is not caused, and the accuracy of the hole position is ensured to the greatest extent. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A step schematic diagram of a laser shock peening method for a connecting hole of a thin-walled structural part is shown in the present application;

[0021] Figure 2 A structural schematic diagram of a laser beam, a constraint layer, an absorption layer, a rigid mandrel, a thin-walled structural part, and a pad is shown in the present application;

[0022] Figure 3 A schematic diagram of 8 irradiation points symmetrically and uniformly arranged at the edge of the connecting hole is shown in the present application;

[0023] Figure 4 A TEM diagram of the surface layer of the hole is shown in the present application;

[0024] Figure 5 A TEM diffraction pattern diagram of the surface layer of the hole is shown in the present application. DETAILED DESCRIPTION

[0025] The present application will be described in detail below in conjunction with the embodiments shown in the drawings, but it should be noted that these embodiments are not a limitation on the present application, and equivalent transformations or substitutions of function, method, or structure made by those skilled in the art based on these embodiments are within the scope of protection of the present application.

[0026] Reference Figures 1 to 4 As shown in Figures 1 to 4 , the present invention shows a specific implementation of a laser shock peening method for connecting holes of thin-walled structure parts (hereinafter referred to as "the method"), which is used to strengthen the connecting holes 51 opened on the thin-walled structure parts 5 to improve the fatigue performance of the hole structure and prevent the deformation of the thin-walled structure parts 5.

[0027] Reference Figure 1 As shown in Figure 1 , the method includes the following steps S1 to S2.

[0028] Step S1: Place the thin-walled structure part with connecting holes on the cushion block, set a rigid mandrel in the connecting hole, and sequentially set a constraint layer and an absorption layer from top to bottom on the top of the cushion block.

[0029] Specifically, as shown in Figure 2 and Figure 3 , the constraint layer 2, the absorption layer 3, the thin-walled structure part 5 and the cushion block 6 are sequentially set from top to bottom. A connecting hole 51 is opened on the cushion block 6, and a rigid mandrel 4 is set in the connecting hole 51. Among them, the constraint layer 2 and the absorption layer 3 cover at least the connecting hole 51 longitudinally. The diameter of the rigid mandrel 4 is 0.02 - 0.04 mm smaller than the aperture of the connecting hole 51, the height of the rigid mandrel 4 is 0.1 - 0.15 mm larger than the thickness of the thin-walled structure part 5, and the lower surface of the rigid mandrel 4 and the lower surface of the thin-walled structure part 5 are on the same horizontal plane. That is, the rigid mandrel 4 is set in the connecting hole 51 opened on the thin-walled structure part 5, and the end of the rigid mandrel 4 protrudes slightly from the connecting hole 51. The wave impedance of the material of the cushion block 6 is 0.2 - 1×10 7 kg·m -2 ·s -1 lower than the wave impedance of the material of the thin-walled structure part 5. The material of the cushion block 6 is alumina ceramic or high-strength aluminum alloy, and the material of the rigid mandrel 4 is tungsten steel or high-strength titanium alloy. The constraint layer 2 is a flowing water film, and the thickness of the water film is 1 - 1.5 mm, and the flow rate of the water film is 5 - 10 cm / min to obtain a stable water film. The absorption layer 3 is an aluminum foil or polyester tape with adhesive, and the thickness of the aluminum foil or polyester tape is 100 - 150 microns, and the thickness of the adhesive is 10 microns.

[0030] Step S2: Symmetrically and evenly set a plurality of irradiation points at the edge of the connecting hole with the center of the connecting hole as the symmetry center. The focused laser beam passes through the constraint layer at the top of the constraint layer and is longitudinally aligned with two symmetrically arranged irradiation points in sequence to irradiate the absorption layer in sequence.

[0031] ​​​​Specifically, the laser beam 1 is focused, and the focused laser beam 1 irradiates the absorption layer 3 through the confinement layer 2 from the top of the confinement layer 2. The plurality of irradiation points are symmetrically and uniformly arranged with the center of the connecting hole 51 as the center of symmetry and arranged at the edge of the connecting hole 51, that is, the number of irradiation points is even, and since the laser beam 1 is aligned in the longitudinal direction at the irradiation points, it can also be understood that the number of times of irradiation of the laser beam 1 is even. At the same time, in the process of irradiation, two irradiation points symmetrically arranged from the center of the connecting hole 51 form a group, and a plurality of irradiation points form a plurality of groups, and the focused laser beam 1 is aligned with the two irradiation points of each group in turn to irradiate the absorption layer 3 through the confinement layer 2. Among them, the wavelength of the laser beam 1 is 532 nm or 1064 nm, the pulse width is 15-25 ns, and the power density is 2-4 GW / cm 2 The diameter of the spot 11 of the focused laser beam 1 is 3-5 mm, and the overlap rate between the two adjacent spots 11 is 50-75%.

[0032] It should be noted that when the connecting hole 51 is reinforced, the center point corresponding to the spot 11 of the focused laser beam 1 is aligned in the longitudinal direction with the irradiation points, that is, the center point corresponding to the spot 11 of the focused laser beam 1 is aligned in the longitudinal direction with the edge of the connecting hole 51, and the number of irradiation points is even and symmetrically and uniformly arranged from the center point of the connecting hole 51. Optionally, a group of irradiation points (that is, two symmetrically arranged irradiation points) is selected from the plurality of irradiation points, and one of the irradiation points in the group is selected as a first irradiation point. The spot of the focused laser beam 1 is aligned in the longitudinal direction with the first irradiation point to complete the irradiation of the first irradiation point, and then the other irradiation point in the group is selected as a second irradiation point. The spot of the focused laser beam 1 is aligned in the longitudinal direction with the second irradiation point to complete the irradiation of the second irradiation point, thereby completing the irradiation of the group, and then the second group of irradiation points is selected for irradiation in turn, and the process is repeated until the irradiation of all irradiation points is completed.

[0033] With Figure 3The eight irradiation points shown are taken as an example, wherein the irradiation point a and the irradiation point a1 are a set of symmetrically arranged irradiation points, the irradiation point b and the irradiation point b1 are a set of symmetrically arranged irradiation points, the irradiation point c and the irradiation point c1 are a set of symmetrically arranged irradiation points, and the irradiation point d and the irradiation point d1 are a set of symmetrically arranged irradiation points. The irradiation point a is selected as the first irradiation point, the spot 11 of the focused laser beam 1 is aligned with the irradiation point a in the longitudinal direction, and the laser beam 1 irradiates the absorption layer 3 from the top of the constraint layer 2 through the constraint layer 2 to perform irradiation of the first irradiation point (i.e., the irradiation point a); the irradiation point a1 is selected as the second irradiation point, the spot 11 of the focused laser beam 1 is aligned with the irradiation point a1, and the laser beam 1 irradiates the absorption layer 3 from the top of the constraint layer 2 through the constraint layer 2 to perform irradiation of the second irradiation point (i.e., the irradiation point a1); the irradiation point b is selected as the third irradiation point, the spot 11 of the focused laser beam 1 is aligned with the irradiation point b in the longitudinal direction, and the laser beam 1 irradiates the absorption layer 3 from the top of the constraint layer 2 through the constraint layer 2 to perform irradiation of the third irradiation point (i.e., the irradiation point b); and the irradiation points are sequentially aligned in the order of a, a1, b, b1, c, c1, d, and d1.

[0034] It should be noted that the spot 11 of the laser beam 1 is longitudinally aligned with the irradiation point, and the irradiation point is arranged at the edge of the connecting hole 51, so that the spot 11 simultaneously acts on the surface of the connecting hole 51 and the rigid mandrel 4. Since the rigid mandrel 4 has high strength, the laser beam 1 with a power density of 2-4 GW / cm 2 will not cause plastic deformation of the rigid mandrel 4. Under the action of the laser shock wave 12 induced by the laser beam 1, an interface wave 13 will be generated between the interface between the rigid mandrel 4 and the hole wall of the connecting hole 51 (in shock dynamics, when a shock wave penetrates through materials with different wave impedances, an interface wave will be generated at the interface), so that the hole wall of the connecting hole 51 is extruded, and since the rigid mandrel 4 does not undergo plastic deformation, the surface of the connecting hole 51 and the hole wall of the connecting hole 51 are both extrusion strengthened. By using the pad 6 with low wave impedance, when the laser shock wave 12 is transmitted to the interface between the thin-walled structure part 5 and the pad 6, most of the shock wave energy can be transmitted to the pad 6, thereby effectively suppressing the reverse deformation generated when the laser shock wave 12 acts. Under the action of the laser shock wave 12, the circumferential surface layer will undergo plastic deformation. If the circumferential surface layer is irradiated in circumferential order, the plastic deformation of the circumferential surface layer will accumulate, thereby reducing the accuracy of the hole position. However, by using the symmetric and sequential irradiation method, the accumulation of plastic deformation will not occur, thereby ensuring the accuracy of the hole position to the greatest extent.

[0035] Referring to Figure 4 and Figure 5As shown, in the laser shock peening method for a connecting hole of a thin-walled structural part shown in the present application, under the action of the forward laser shock wave 12 and the lateral interface wave 13, the hole wall material of the connecting hole 51 is extruded, thereby playing a role of extrusion strengthening, and at the same time, the hole surface is also subjected to the action of the laser shock wave 12 and is subjected to a strengthening effect, and a high-amplitude residual compressive stress layer can be obtained on the hole surface and the hole circumference; by changing the material of the pad 6, the deformation of the thin-walled structural part 5 caused by the release of residual compressive stress during the action of the laser shock wave 12 can be effectively inhibited; due to the double action of the forward laser shock wave 12 and the lateral interface wave 13 on the hole wall material, the grains of the hole surface layer are refined, and nanocrystalline is formed on the hole surface layer formed by the connecting hole 51, thereby improving the fatigue performance of the connecting hole 51; since the rigid mandrel 4 does not run inside the connecting hole 51, the laser shock peening method for a connecting hole of a thin-walled structural part shown in the present application can be used to strengthen the connecting hole 51 with a hole diameter of less than 1 mm, and the precision loss of the connecting hole 51 is small. Due to the deformation of the hole wall material under the action of the laser shock wave 12, the position and size precision of the hole structure is lost, therefore, in the present application, the symmetric impact method is used to balance and offset the strain generated by the laser shock wave 12, thereby achieving the purpose of ensuring the position and size precision of the hole structure, thereby solving the problem that in the existing extrusion strengthening method, when the thickness of the part wall is small, the release of residual stress will cause the hole circumference surface layer of the connecting hole formed by the thin-walled structural part (for example, an aircraft wall plate) to deform as a whole, the laser shock peening method can only strengthen the hole surface, but cannot strengthen the hole circumference surface layer, and when the hole diameter of the connecting hole is less than 3 mm, the mandrel is easily broken and cannot be used for extrusion strengthening, the laser shock peening method will cause the hole circumference surface layer to collapse inward, thereby having the defects of affecting the hole precision and being unable to strengthen the hole wall. More specifically, Figure 5 The diffraction pattern shown in the present application shows that by implementing the present application, nanocrystalline is obtained in the strengthening area of the hole surface and the hole wall, and the grains are greatly refined, thereby being beneficial to improving the fatigue life of the hole structure part.

[0036] Embodiment 1:

[0037] A laser shock peening method for a connecting hole of a thin-walled structural part includes the following steps:

[0038] In the present embodiment, the rigid mandrel 4 and the connecting hole 51 with a diameter and a hole diameter of 1 mm are selected, and in fact, the diameter of the rigid mandrel 4 is 0.02-0.025 mm smaller than the hole diameter of the connecting hole 51; the material of the thin-walled structural part 5 is 7050 aluminum alloy, and the wave impedance is 1.85x10 7 kg·m -2 ·s -1, the thickness is 2mm; the height of the rigid mandrel 4 is 2.1mm, and the material is TC17 titanium alloy; the material of the cushion block 6 is alumina ceramic, and the wave impedance is 0.96x10 7 kg·m -2 ·s -1 ; the pulse width of the laser beam 1 is 15ns, the power density is 2GW / cm 2 , and the diameter of the light spot 11 is 3mm; the absorption layer 3 is an aluminum foil with adhesive, the thickness of the aluminum foil is 100 microns, and the thickness of the adhesive is 10 microns; the constraint layer 2 is a flowing water film, the thickness is about 1mm, and the flow rate is 5cm / min. In this embodiment, the center of the connecting hole 51 is taken as the center of symmetry to symmetrically and uniformly arrange four irradiation points, that is, two groups of irradiation points. One of the irradiation points is selected, and any one of the irradiation points in the group is taken as the first irradiation point. The focused laser beam 1 is irradiated on the absorption layer 3 from the top of the constraint layer 2 through the constraint layer 2, and the light spot 11 of the laser beam 1 is longitudinally aligned with the first irradiation point to complete the irradiation of the first irradiation point. Then, another irradiation point in the group is selected as the second irradiation point. The focused laser beam 1 is irradiated on the absorption layer 3 from the top of the constraint layer 2 through the constraint layer 2, and the light spot 11 of the laser beam 1 is longitudinally aligned with the second irradiation point to complete the irradiation of the second irradiation point. Then, the second group of irradiation points is selected, and any one of the irradiation points in the second group is taken as the third irradiation point. The focused laser beam 1 is irradiated on the absorption layer 3 from the top of the constraint layer 2 through the constraint layer 2, and the light spot 11 of the laser beam 1 is longitudinally aligned with the third irradiation point to complete the irradiation of the third irradiation point. Finally, another irradiation point in the second group is selected as the fourth irradiation point. The focused laser beam 1 is irradiated on the absorption layer 3 from the top of the constraint layer 2 through the constraint layer 2, and the light spot 11 of the laser beam 1 is longitudinally aligned with the fourth irradiation point to complete the irradiation of the fourth irradiation point. Thus, the connecting hole 51 is impact strengthened. After the strengthening is completed, the accuracy of the position of the connecting hole 51 is detected. The detection shows that the accuracy of the position of the connecting hole 51 does not change, and the XRD test shows that the average residual compressive stress value of the hole surface is 134MPa. The hole is cut open, the residual compressive stress of the hole wall is measured, and the result shows that the average residual compressive stress value of the hole wall is 149MPa. TEM observation is performed on the hole surface layer, and it is found that the material of the outermost layer is nanocrystalline. Meanwhile, under the same test conditions, five groups of samples are tested, and it is found that the average fatigue life of the hole structure part strengthened by the laser impact strengthening method of the connecting hole of the thin-walled structure part disclosed in the application is 3.47 times that of the un-strengthened hole structure part.

[0039] Example 2:

[0040] A laser impact strengthening method for a connecting hole of a thin-walled structure part includes the following steps:

[0041] In the embodiment, the rigid mandrel 4 and the connecting hole 51 with diameters of 25 mm are selected, and in fact, the diameter of the rigid mandrel 4 is 0.035-0.04 mm smaller than the hole diameter of the connecting hole 51; the material of the thin-walled structure part 5 is TC4 titanium alloy, and the wave impedance is 2.21 x 10 7 kg·m -2 ·s -1 ; the height of the rigid mandrel 4 is 3.15 mm, and the material is tungsten steel; the material of the cushion block 6 is 7050 aluminum alloy, and the wave impedance is 1.85 x 10 7 kg·m -2 ·s -1 ; the pulse width of the laser beam 1 is 25 ns, the power density is 4 GW / cm 2 , and the diameter of the light spot 11 is 5 mm; the absorbing layer 3 is a polyester adhesive tape with adhesive, the thickness of the polyester adhesive tape is 150 microns, and the thickness of the adhesive is 10 microns; the constraint layer 2 is a flowing water film, the thickness is about 1.5 mm, and the flow rate is 10 cm / min. In the embodiment, 36 irradiation points are symmetrically and uniformly arranged with the center of the connecting hole 51 as the symmetric center, and the focused laser beam 1 is irradiated on the absorbing layer 3 through the constraint layer 2 from the top of the constraint layer 2 to impact strengthen the connecting hole 51 by using the foregoing method. After the strengthening is completed, the precision of the connecting hole 51 position is detected, and through the detection, the precision of the connecting hole 51 position is not changed, and through the XRD test, the average residual compressive stress value of the hole surface is 257 MPa, the hole is cut open, the residual compressive stress of the hole wall is measured, and the results show that the average residual compressive stress value of the hole wall is 208 MPa, and the TEM observation is performed on the hole surface layer, and it is found that the material of the outermost layer is nanocrystalline. At the same time, under the same test conditions, 5 groups of sample tests are performed, and it is found that the average fatigue life of the hole structure part strengthened by the laser shock peening method of the thin-walled structure part connecting hole disclosed in the application is 3.07 times that of the un-strengthened hole structure part.

[0042] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of the application, and are not used to limit the protection scope of the application. Equivalent embodiments or changes made without departing from the spirit of the application should be included in the protection scope of the application.

[0043] It will be obvious to a person skilled in the art that the application is not limited to the details of the foregoing exemplary embodiments and can be implemented in other concrete forms without departing from the spirit or essential characteristics of the application. The embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. No reference signs in the claims should be considered as limiting the scope of the claims to the identity of the reference signs therein.

[0044] Furthermore, it should be understood that although the description is made on the basis of the embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. A laser shock peening method for connecting holes in thin-walled structural parts, characterized in that, include: A thin-walled structural part with a connection hole is placed on a pad, and a rigid mandrel is set in the connection hole. A constraint layer, an absorption layer, a thin-walled structural part and a pad are arranged in sequence from top to bottom. The constraint layer and the absorption layer at least cover the connection hole in the longitudinal direction. Multiple irradiation points are symmetrically and evenly arranged around the center of the connecting hole as the center of symmetry. The focused laser beam passes through the constraint layer at the top of the constraint layer and is aligned with the two symmetrical irradiation points in sequence along the longitudinal direction to irradiate the absorption layer in sequence. The diameter of the rigid mandrel is 0.02~0.04mm smaller than the diameter of the connecting hole, the height of the rigid mandrel is 0.1~0.15mm greater than the thickness of the thin-walled structural part, and the lower surface of the rigid mandrel and the lower surface of the thin-walled structural part are on the same horizontal plane. The wave impedance corresponding to the material of the pad is (0.2~1)*10 lower than the wave impedance corresponding to the material of the thin-walled structural part. 7 kg·m -2 ·s -1 The laser beam has a wavelength of 532nm or 1064nm, a pulse width of 15~25ns, and a power density of 2~4GW / cm². 2 The diameter of the focused laser beam is 3-5 mm, and the overlap rate between two adjacent beams is 50-75%.

2. The laser shock peening method according to claim 1, characterized in that, The thin-walled structural part is made of titanium alloy or aluminum alloy, and the thickness of the thin-walled structural part is 2~3mm.

3. The laser shock peening method according to claim 2, characterized in that, The pad is made of alumina ceramic or high-strength aluminum alloy.

4. The laser shock peening method according to claim 1, characterized in that, The rigid mandrel is made of tungsten steel or high-strength titanium alloy.

5. The laser shock peening method according to claim 1, characterized in that, The constraint layer is a flowing water film with a thickness of 1~1.5mm and a flow rate of 5~10cm / min.

6. The laser shock peening method according to claim 1, characterized in that, The absorbent layer is an aluminum foil or polyester tape with adhesive, and the thickness of the aluminum foil or polyester tape is 100-150 micrometers, and the thickness of the adhesive is 10 micrometers.

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