A laser shot peening integral forming method for a thin plate member of a surface of Gaussian curvature

Abstract

The application provides a laser shot forming method for a thin plate member with a Gaussian curvature surface. The method comprises the following steps: selecting a thin plate with a proper thickness according to the thickness of the member and the bending angle of the member when the laser is impacted, making the direction of the laser impact opposite to the direction of the deformation bending of the thin plate, adopting one of the following laser input types in the overlapping direction of the laser spots or the overlapping direction of the laser spots: a symmetric parabola type, a symmetric circular arc-symmetric circular arc type combination, a symmetric circular arc-horizontal straight line type, a symmetric parabola-horizontal straight line type and a horizontal straight line-symmetric parabola type, and forming the member with the Gaussian surface through a laser shot forming device.

Description

Technical Field

[0001] This invention belongs to the field of laser shock forming technology, specifically relating to a method for integral forming of Gaussian curvature curved surface thin plate components by laser shot peening. Background Technology

[0002] Traditional sheet metal forming processes typically involve bending, creep aging, and shot peening. However, these technologies suffer from drawbacks such as difficulty in controlling forming precision, low plastic deformation layer thickness, and high surface roughness, making it challenging to efficiently and cost-effectively form thin-walled sheet materials for high-performance, high-speed transportation equipment like airfoil panels, high-speed rail skins, and engine blades. Existing forming processes for Gaussian curvature curved sheet metal primarily involve sheet metal stamping. Stamping requires the design and manufacture of corresponding molds, resulting in high manufacturing costs for single-piece, small-batch production of medium to large-sized thin sheets. Summary of the Invention

[0003] This invention provides a method for integral forming of Gaussian curvature curved thin plate components by laser shot peening. By controlling the overlapping method of the laser spot and the laser energy input, the distribution of residual stress field in the component is changed, resulting in bending deformation of different degrees, thus realizing the integration of laser shot peening forming and strengthening process of Gaussian curvature curved thin plate components.

[0004] This invention provides a method for integral forming of thin plate components with Gaussian curvature surface by laser shot peening, the specific steps of which include:

[0005] Step S1: Select one of the following laser shock forming processes based on the type of Gaussian curvature surface to be formed: single-sided asynchronous laser shock forming process, single-sided synchronous laser shock forming process, or double-sided asynchronous laser shock forming process.

[0006] Laser spot overlap refers to the overlap of adjacent laser spots along the scanning direction in the same pass, while laser spot overlap refers to the overlap between adjacent passes perpendicular to the scanning direction. The gradient laser energy varies discretely along the scanning direction according to a given curve. The single-sided synchronous laser shock forming process uses a laser integrated system to control a robotic arm to simultaneously input gradient laser energy in both the laser spot overlap direction and the laser spot overlap direction.

[0007] The single-sided asynchronous laser shock forming process utilizes a laser integrated system to control a robotic arm to input gradient laser energy in one direction (either the laser spot overlap direction or the laser spot overlap direction) and input constant energy in a "horizontal straight line" type in the other direction.

[0008] The dual-sided asynchronous laser shock forming process is as follows: Step 1: Using a laser integrated system, the robotic arm is controlled to input gradient laser energy in one direction (either the laser spot overlap direction or the laser spot overlap direction) and input constant energy in the other direction ("horizontal straight line" type); Step 2: The thin plate is flipped over, and the robotic arm is controlled by the laser integrated system to input gradient laser energy in the original laser spot overlap direction and input constant energy in the original laser spot overlap direction ("horizontal straight line" type type).

[0009] Step S2: Based on the component thickness and the bending angle of the component during laser impact, select a thin plate of appropriate thickness so that the direction of laser impact is opposite to the direction of deformation and bending of the thin plate; grind, polish and clean the surface of the thin plate, and perform drying pretreatment.

[0010] Step S3: Apply an absorbent protective layer to the surface of the pretreated thin plate;

[0011] Step S4: Place the thin plate with the absorbent protective layer on the worktable of the robotic arm, fix it with a special clamp, and cover it with a constraint layer;

[0012] Step S5: Set the laser shot peening forming process parameters: including setting the overlap rate of the laser spot and setting the laser energy of the spot.

[0013] Step S6: The thin plate component from step S4 is integrally formed by laser shot peening using the process parameters set in step S5: The laser integrated system controls the scanning path of the robotic arm's spot and controls the input of gradient laser energy to change the residual stress distribution of the component, so that the thin plate forms a workpiece with a Gaussian curvature surface.

[0014] Optionally, the Gaussian curvature surface includes one of a positive Gaussian curvature surface (sphere), a zero Gaussian curvature surface (cylindrical surface), and a negative Gaussian curvature surface (hyperboloid).

[0015] Optionally, the given curve includes a "symmetrical parabola" or a "symmetrical circular arc".

[0016] The "symmetrical circular arc" type gradient laser energy input type is based on a quadratic circular arc y 2 =a 2 -x 2 The variation law of discrete points, constant a>0; with the center of the thin plate side length along the direction of light spot movement as the origin of the coordinate system, x is the side length of the thin plate along the direction of light spot movement in mm, and y is the laser energy in J;

[0017] The "symmetric parabola" type gradient laser energy input is based on the quadratic parabola y=ax 2The variation law of the discrete points +b, where constants a<0, b>0; the origin of the coordinate system is the center of the thin plate side length in the direction of the light spot movement, x is the side length of the thin plate in mm, and y is the laser energy in J;

[0018] The "horizontal straight line" type of constant laser energy input follows the variation law of discrete points of a horizontal straight line y=a, where the constant a>0. The origin of the coordinate system is the center of the thin plate side length in the direction of the light spot movement, x is the side length of the thin plate in mm, and y is the laser energy. The value of y is the lowest value of the laser energy input for the "symmetrical arc" and "symmetrical parabola" types, in J.

[0019] Optionally, the laser input type can be one of the following: a symmetrical parabola type, a combination of symmetrical arc and symmetrical arc, a symmetrical arc and horizontal straight line type, or a symmetrical parabola and horizontal straight line + horizontal straight line and symmetrical parabola type. Optionally, the thickness of the thin plate is 2mm to 5mm.

[0020] Optionally, the absorbent protective layer is a 50μm black tape.

[0021] Optionally, the constraint layer is a 2mm water layer. This thickness of water layer can accommodate bending shapes with small curvatures.

[0022] Optionally, the laser shock forming process parameters are: spot diameter of 2mm, spot overlap rate of 50%, and laser energy range of 1J~10J.

[0023] The technical solution of the present invention is that the laser input type can be one of the following: "symmetric parabola" type, "symmetric arc-symmetric arc" type combination, "symmetric arc-horizontal straight line" type, "symmetric parabola-horizontal straight line" + "horizontal straight line-symmetric parabola" type.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. This invention proposes a method for integral forming of Gaussian curvature surface components by laser shot peening. By utilizing the shock wave induced by a high-power short-pulse laser and combining the laser shock forming process with gradient laser energy, a non-uniformly distributed residual compressive stress field is introduced into the thin plate, thereby causing plastic deformation and achieving small curvature bending forming. This integrates the laser shot peening forming and strengthening process of Gaussian curvature surface components. The process is simple, efficient, achieves moldless integral forming, and is low in cost, making it suitable for batch production of medium to high thickness thin plates.

[0026] 2. Using a laser beam as a flexible punch, the dynamic, non-contact impact pressure significantly reduces surface roughness, avoids localized stress concentration, and thus improves the fatigue life of the formed parts. Furthermore, this process generates a greater depth of residual compressive stress and a greater degree of bending deformation in the components, resulting in better forming performance. Attached Figure Description

[0027] Figure 1 This is a graph showing the relationship between the component thickness and the bending angle of the component during laser impact.

[0028] Figure 2 A coordinate diagram showing the overlapping direction of the laser spot on the thin plate, the overlapping direction of the laser spot, and the laser energy;

[0029] Figure 3 This is a schematic diagram of a single-sided asynchronous laser shock forming process;

[0030] Figure 4 This is a schematic diagram of a single-sided synchronous laser shock forming process;

[0031] Figure 5 This is a schematic diagram of a dual-sided asynchronous laser shock forming process;

[0032] Figure 6(a) is a schematic diagram of a positive Gaussian curvature surface formed by a single-sided asynchronous laser shock forming process of the "symmetric arc-symmetric arc" type.

[0033] Figure 6(b) is a schematic diagram of the laser energy and component forming of the (xz) "symmetrical circular arc" type;

[0034] Figure 6(c) is a schematic diagram of the laser energy and component forming of the (yz) "symmetrical circular arc" type;

[0035] Figure 6(d) is a three-dimensional view of the component formed by the "symmetric arc-symmetric arc" type laser energy;

[0036] Figure 7(a) is a schematic diagram of a zero-Gaussian curvature surface formed by a single-sided synchronous laser shock forming process of the "symmetrical circular arc-horizontal straight line" type.

[0037] Figure 7(b) is a schematic diagram of the (xz) "horizontal straight line" type laser energy and component forming;

[0038] Figure 7(c) is a schematic diagram of the laser energy and component forming of the (yz) "symmetrical circular arc" type;

[0039] Figure 7(d) is a three-dimensional view of the component formed by the "symmetrical circular arc-horizontal straight line" type laser energy;

[0040] Figure 8(a) is a schematic diagram of a negative Gaussian curvature surface formed by a double-sided asynchronous laser shock forming process of the type "symmetric parabola-horizontal straight line" + "horizontal straight line-symmetric parabola".

[0041] Figure 8(b) is a schematic diagram of the laser energy and component forming of the (xz) "symmetrical circular arc" type;

[0042] Figure 8(c) is a schematic diagram of the laser energy and component forming of the "symmetrical arc" on the back of (yz);

[0043] Figure 8(d) is a three-dimensional diagram of a component formed using a laser energy pattern of “symmetric parabola-horizontal straight line” + “horizontal straight line-symmetric parabola”. Detailed Implementation

[0044] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0045] Example 1:

[0046] A method for integral forming of thin plate components with Gaussian curvature surface by laser shot peening, the specific steps of which include:

[0047] Step S1: Select a single-sided asynchronous laser shock forming process;

[0048] Step S2: Select a 2mm thick 6008-T6 aluminum alloy sheet, grind, polish, and clean its front and back surfaces, and perform a drying pretreatment.

[0049] Step S3: Apply 50μm black tape as an absorbent protective layer to the pre-treated 6008-T6 aluminum alloy sheet surface to be impacted.

[0050] Step S4: Place the 6008-T6 aluminum alloy sheet with black tape on the KUKA robotic arm workbench and fix it with a special clamp. Cover the aluminum alloy sheet with 2mm of water as a constraint layer.

[0051] Step S5: Set the laser process parameters to a spot diameter of 2mm and a spot overlap rate of 50%. Use the laser integrated system to control the 6008-T6 aluminum alloy sheet on the KUKA robotic arm to move in the xy direction. The laser energy is a variable energy of "symmetrical arc-symmetrical arc" type combination (all following the change law of the second circular arc, the x-direction first increases from 1J to 10J, and then decreases from 10J to 1J; the y-direction first increases from 2J to 8J, and then decreases from 8J to 2J).

[0052] Step S6: Using the process parameters set in step S5, the thin plate component from step S4 is laser shot peened to form a component with a positive Gaussian curvature surface (spherical surface).

[0053] Example 2

[0054] A method for integral forming of thin plate components with Gaussian curvature surface by laser shot peening, the specific steps of which include:

[0055] Step S1: Select a single-sided synchronous laser shock forming process;

[0056] Step S2: Select a 3mm thick AZ31 magnesium alloy sheet, grind, polish, clean, and dry its individual working surfaces;

[0057] Step S3: Apply 50μm black tape as an absorbent protective layer to the pretreated AZ31 magnesium alloy sheet surface to be impacted.

[0058] Step S4: Place the AZ31 magnesium alloy sheet with black tape on the KUKA robotic arm workbench and fix it with a special clamp, and cover it with 2mm of water as a constraint layer.

[0059] Step S5: Set the laser process parameters to a spot diameter of 2mm and a spot overlap rate of 50%. Use the laser integrated system to control the AZ31 magnesium alloy sheet on the KUKA robotic arm to move in the xy direction. The laser energy is a variable energy of "symmetrical circular arc-horizontal straight line" combination (following the variation law of the second circular arc and the first horizontal straight line respectively, the x-direction first increases from 1J to 10J, and then decreases from 10J to 1J; the y-direction is constant at 1J).

[0060] Step S6: Using the process parameters set in step S5, the thin plate component from step S4 is laser shot peened to form a component with a zero Gaussian curvature surface (cylindrical surface).

[0061] Example 3

[0062] A method for integral forming of thin plate components with Gaussian curvature surface by laser shot peening, the specific steps of which include:

[0063] Step S1: Select the dual-sided asynchronous laser shock forming process;

[0064] Step S2: Select a 4mm thick T2 copper alloy sheet, grind, polish, clean both sides of it, and perform a drying pretreatment.

[0065] Step S3: Apply 50μm black tape as an absorbent protective layer to both sides of the pretreated T2 copper alloy sheet to be impacted.

[0066] Step S4: Place the T2 copper alloy sheet with black tape on the KUKA robotic arm workbench and fix it with a special clamp, then cover it with 2mm of water as a constraint layer.

[0067] Step S5: Set the laser process parameters to a spot diameter of 2mm and a spot overlap rate of 50%. First, use the laser integrated system to control one side of the T2 copper alloy sheet on the KUKA robotic arm to move in the x and y directions. The laser energy is a variable energy combination of a "symmetric parabola-horizontal straight line" (following the variation rules of a quadratic symmetric parabola and a first-order horizontal straight line, the energy in the x direction first increases from 1J to 10J, then decreases from 10J to 1J; the energy in the y direction remains constant at 1J). Second, flip the sheet and use the laser integrated system to control the back side of the T2 copper alloy sheet on the KUKA robotic arm to move in the x and y directions. The laser energy is a variable energy combination of a "horizontal straight line-symmetric parabola" (following the variation rules of a first-order horizontal straight line and a quadratic symmetric parabola, the energy in the x direction remains constant at 2J; the energy in the y direction first increases from 2J to 8J, then decreases from 8J to 2J).

[0068] Step S6: Using the process parameters set in step S5, the thin plate component from step S4 is laser shot peened to form a component with a negative Gaussian curvature surface (hyperboloid).

[0069] After the laser shock forming test was completed, the deformation bending angle of the thin plate with positive, zero, and negative Gaussian curvature surfaces (spherical, cylindrical, and hyperboloid) was measured using a laser rangefinder. The measurement results showed that the formed parts basically met the forming accuracy requirements within a certain processing error range.

[0070] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A laser shot peening bulk forming method of a thin plate member of a surface of Gaussian curvature, characterized by, The specific steps include: Step S1: according to the type of the Gaussian curvature surface to be formed, one of the following laser shock forming processes is selected: single-side asynchronous laser shock forming process, single-side synchronous laser shock forming process, and double-side asynchronous laser shock forming process; The laser spot overlap is that adjacent spots in the same pass are overlapped with each other in the spot scanning direction, the laser spot overlap is that adjacent passes are overlapped with each other in the direction perpendicular to the spot scanning direction, and the gradient laser energy is that the laser energy is discretely changed along the spot scanning direction according to a given curve; The single-side synchronous laser shock forming process is that a laser integrated system is used to control a mechanical arm to input gradient laser energy in the laser spot overlap direction and the laser spot overlap direction at the same time; The single-side asynchronous laser shock forming process is that a laser integrated system is used to control a mechanical arm to input gradient laser energy in one of the laser spot overlap direction and the laser spot overlap direction, and constant energy of a "horizontal straight line” type is input in the other direction; The double-side asynchronous laser shock forming process includes the following steps: first step: a laser integrated system is used to control a mechanical arm to input gradient laser energy in one of the laser spot overlap direction and the laser spot overlap direction, and constant energy of a "horizontal straight line” type is input in the other direction; second step: the sheet is flipped, a laser integrated system is used to control a mechanical arm to input gradient laser energy in the original laser spot overlap direction, and constant energy of a "horizontal straight line” type is input in the original laser spot overlap direction; Step S2: according to the thickness of the component and the bending angle of the component during laser shock, a sheet with a suitable thickness is selected, so that the direction of laser shock is opposite to the direction of sheet deformation and bending; the surface of the sheet is polished, polished and cleaned, and dried pretreatment is performed; Step S3: an absorption protective layer is attached to the surface of the pretreated sheet; Step S4: the sheet with the absorption protective layer is placed on the mechanical arm workbench, and is fixed by a special clamp, and is covered with a constraint layer; Step S5: the laser shot forming process parameters are set, including setting the overlap rate of the laser spot and setting the laser energy of the spot, Step S6: the sheet component in step S4 is subjected to laser shot integral forming by using the process parameters set in step S5: the spot scanning path of the mechanical arm is controlled by a laser integrated system, and the input of gradient laser energy is controlled, so as to change the residual stress distribution of the component, so that the sheet forms a workpiece with a Gaussian curvature surface.

2. The laser shot peening bulk forming method of a Gaussian curvature surface sheet member according to claim 1, characterized by, The Gaussian curvature surface includes one of a positive Gaussian curvature surface, a zero Gaussian curvature surface and a negative Gaussian curvature surface.

3. The laser shot peening bulk forming method of a Gaussian curvature surface sheet member according to claim 1, characterized by, The given curve includes a "symmetrical parabola”, a "symmetrical circular arc”, The "symmetrical circular arc" type gradient laser energy input type is according to a quadratic circular arc y 2 =a 2 -x 2 The change rule of the discrete points, and the constant a>0; taking the center of the edge length of the sheet along the moving direction of the light spot as the coordinate origin, x is the edge length of the sheet along the moving direction of the light spot, in mm, and y is the laser energy, in J; The "symmetrical parabola" type gradient laser energy input type is according to the change rule of the quadratic parabola y = ax 2 +b discrete points, wherein the constant a < 0, b > 0; taking the center of the edge length of the sheet in the moving direction of the light spot as the coordinate origin, x is the edge length of the sheet, in mm, and y is the laser energy, in J; The constant laser energy input type of a "horizontal straight line” is according to the variation rule of a horizontal straight line y=a discrete point once, wherein the constant a>0, the center of the sheet length in the direction of spot movement is taken as the coordinate origin, x is the sheet length, the unit is mm, y is the laser energy, the value of y is the minimum value of the laser energy input by the "symmetrical circular arc” type and the "symmetrical parabola” type, and the unit is J.

4. The laser shot peening bulk forming method of a Gaussian curvature surface sheet member according to claim 3, characterized by, The laser input type can be one of "symmetrical parabola", "symmetrical circular arc-symmetrical circular arc" combination, "symmetrical circular arc-horizontal straight line", "symmetrical parabola-horizontal straight line" and "horizontal straight line-symmetrical parabola".

5. The laser shot peening bulk forming method of a Gaussian curvature surface sheet member according to claim 1, characterized by, The thickness of the thin plate is 2-5 mm.

6. The laser shot peening bulk forming method of a Gaussian curvature surface sheet member according to claim 1, characterized by, The absorption protective layer is a 50 μm black adhesive tape.

7. The laser shot peening bulk forming method of a Gaussian curvature surface sheet member according to claim 1, characterized by, The constraint layer is a 2 mm water layer.

8. The laser shot peening bulk forming method of a Gaussian curvature surface sheet member according to claim 1, characterized by, The laser shock forming process parameters are: a spot diameter of 2 mm, a spot lap rate of 50%, and a laser energy range of 1-10 J.

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