Multi-point laser shock forming device and method for large-size complex curved surface part

Abstract

The invention relates to a multi-point laser shock forming device and method for a large-size complex curved surface part, and belongs to the technical field of plastic processing. In order to solve the problems that an existing method is low in efficiency, complex components are difficult to accurately form, and components with positive and negative curvatures cannot be formed, the device mainly comprises a control system, a laser, a plurality of mechanical arms, a portal frame, a chuck, a CCD camera, a plurality of laser heads, an optical cable, a signal transmission line, a laser control line and a distance measuring laser. The method mainly comprises the steps of 1, laser parameter and deformation relation measurement, 2, model processing, 3, path planning, 4, blank preparation, 5, impact forming, 6, iterative optimization and 7, workpiece taking and post-processing. According to the method, accurate, flexible and effective control of multi-laser forming parameters can be realized, and a large-size complex curved surface part can be efficiently and accurately manufactured by adopting a small number of lasers.

Description

Technical Field

[0001] The present invention relates to a multi-point laser shock forming device and method for large-sized complex curved surface parts, belonging to the technical field of plastic processing. Background Art

[0002] At present, the main forming methods for titanium alloy complex curved surface parts are cold stamping forming, hot forming and superplastic forming. The precise forming of sheet metal is achieved by the movement of a punch or other loads in cooperation with a die, but it has problems such as high die cost and long production cycle. The additive manufacturing technology that has developed rapidly in recent years can achieve moldless rapid manufacturing, but it is difficult to be applied to complex curved surface parts with thin walls and weak rigidity. Shot peening forming technology can achieve moldless manufacturing of large thin-walled curved surface components, but its forming ability is limited, and it can only form components with a relatively large radius of curvature, and more craters are formed on the surface of the part during the forming process, affecting the surface quality of the component.

[0003] In recent years, a laser shot peening forming method, also known as laser shock forming, has been extended by referring to mechanical shot peening technology. Laser shock forming is a new rapid, efficient and precise forming technology that uses the force effect of a laser-induced high-amplitude shock wave to cause plastic deformation of a sheet metal. It has the characteristics of high processing flexibility, precise controllability, few or no springback problems, good performance of the formed part and no pollution. It is a new moldless and flexible forming process, and a very deep high-amplitude residual compressive stress is formed on the surface of the metal sheet after impact forming, which can significantly improve its fatigue life. Patent ZL01134063.0 proposes a laser shock precision forming method and device, which directly uses a high-power pulsed laser beam to impact the surface of a workpiece to generate a shock wave pressure exceeding the yield strength of the sheet metal, and then causes plastic deformation of the sheet metal. Since the deformation amount generated by a single impact is small, the efficiency is low when forming large-sized parts, and when single-point impact forming is performed in a certain area, the in-plane stress transfers to the surrounding areas, which may cause warping of other areas of the sheet metal. The change in the shape of the slab increases the difficulty of re-impact, and it is difficult to achieve precise forming of complex components. For parts with positive and negative curvatures, single-point laser shock forming causes the bending coefficient of the cross-section to increase sharply after the sheet metal bends in a certain direction, and it will be difficult to form a shape with the opposite curvature in the vertical direction. Patent ZL201911300078.4 proposes a multi-point laser shock forming device and forming method, in which multiple pulsed lasers are arranged in a two-dimensional plane, and a workpiece clamping system is used to fix the workpiece and rotate the sheet metal to receive the action of the laser. Since multiple pulsed lasers are arranged adjacent to each other side by side, the space limits the power of the lasers, and it is only applicable to forming sheet metals with a smaller thickness. Since the lasers are fixed and the sheet metal rotates, the deformation of the sheet metal will inevitably cause the lasers not to be all along the normal direction of the deformed sheet metal, introducing uncertain factors, and it is impossible to accurately and coordinately control the actual effective forming parameters of each laser acting on the sheet metal, thereby affecting the forming effect. For large-sized parts, a large number of lasers are required, and the cost is extremely high. Summary of the Invention

[0004] In order to solve the problems existing in the existing laser shock forming method, such as low efficiency during single-laser forming, difficulty in accurately forming complex components, inability to form components with positive and negative curvatures, and in the existing multi-laser forming, inability to form thick plates, difficulty in synergistically controlling effective forming parameters, and high cost due to a large number of lasers, a multi-point laser shock forming device and method for large-sized complex curved surface components are proposed. It can achieve accurate, flexible, and effective control of multi-laser forming parameters, and efficiently and accurately manufacture large-sized complex curved surface components with a relatively small number of lasers. The key technology is the research and development of a special device.

[0005] According to one aspect of the present application, a multi-point laser shock forming device for large-sized complex curved surface components is provided, which is composed of a controller 2, a laser 3, a robotic arm 4, a gantry 5, a chuck 6, a CCD camera 7, a laser head 9, an optical cable 10, a signal transmission line 11, a laser control line 12, and a ranging laser 13.

[0006] The controller 2 is connected to the laser 3 through the laser control line 12;

[0007] The controller 2 is connected to the robotic arm 4 through the signal transmission line 11;

[0008] The controller 2 is connected to the ranging laser 13 through the signal transmission line 11;

[0009] The controller 2 is connected to the CCD camera 7 through a data line;

[0010] The chuck 6 is arranged on the gantry 5;

[0011] The laser head 9 is arranged on the robotic arm 4;

[0012] The laser 3 is connected to the laser head 9 through the optical cable 10;

[0013] The multi-point laser shock forming device for large-sized complex curved surface components can clamp a slab 8, and through multi-point laser shock, cooperate with a movable robotic arm to accurately machine a large-sized complex curved surface component according to the design;

[0014] The length and width of the slab 8 are at least 2 meters. The size of the overall device is adjusted according to the size of the slab 8.

[0015] The controller 2 has functions of signal acquisition, data processing, and control signal output;

[0016] The robotic arm 4 has 6 degrees of freedom and is provided with n. It is statically placed on the ground through a base. A laser head 9 is installed at the end of the robotic arm 4, and 3 ranging lasers 13 are installed on each laser head 9 in a plane perpendicular to the laser optical path for determining the normal direction of the outer surface of the object to be processed.

[0017] Among them, n can take values of 2, 3 or 4;

[0018] The laser 3 is a multi-channel output laser, and the laser output parameters of each channel can be independently adjusted. The laser output by the laser 3 is transmitted to the laser head 9 through the optical cable 10 and acts on the slab after being output by the laser head 9; alternatively, a laser 3 can be configured for each laser head 9.

[0019] The controller 2 outputs the real-time laser parameters of each channel to the laser 3 through the laser control line 12, and the laser 3 executes the output of the laser with corresponding parameters;

[0020] The gantry 5 is composed of a gantry base 5-1, gantry columns 5-2 and a gantry crossbeam 5-3. The gantry columns 5-2 are vertically arranged, with one end fixedly installed on the gantry base 5-1. The gantry crossbeam 5-3 is horizontally arranged and both ends are fixedly connected to the other ends of the 2 gantry columns 5-2. Two chucks 6 are fixedly connected below the gantry crossbeam 5-3. The gantry 5 is statically placed on the ground through the gantry base 5-1, and the gantry 5 clamps the slab 8 to be laser shock formed through the chucks 6;

[0021] The robotic arm 4 can be arranged on one side of the gantry 5 or on both sides of the gantry 5;

[0022] The robotic arm 4 can be a mature robotic arm product on the market.

[0023] The CCD camera 7 is used to measure the surface of the slab 8 during the laser shock forming process, used to compare with the theoretical digital model to correct the laser shock forming parameters. The images collected by the CCD camera 7 are transmitted to the controller 2 through the data line; the controller 2 receives the pose signal of the robotic arm 4 and the signal of the ranging laser 13 through the signal transmission line 11 and gives the pose control signal of the robotic arm 4 according to the calculation result.

[0024] According to another aspect of the present application, a multi-point laser shock forming method for large-sized complex curved surface parts is provided, using the above-mentioned multi-point laser shock forming device for large-sized complex curved surface parts;

[0025] Including the following steps:

[0026] Step 1: Determination of the relationship between laser parameters and deformation: Specimens are taken from the slab 8 to be formed. An energy absorption layer 15 is pasted or coated on the surface of the specimen, and a constraint layer 14 is covered on the energy absorption layer 15. Different parameter lasers are used for shock, and then the corresponding strain ε is recorded. Through multiple experiments, the relationship between laser parameters and strain is obtained:

[0027] ε = f(E, d, t, n) (1)

[0028] Wherein, E is the single-pulse laser energy, S is the laser spot diameter, t is the slab thickness, and n is the number of laser pulses;

[0029] Step 2: Model processing: Add a process section to the digital model of the target part 1-1 to obtain the digital model of the target part 1-2 with the process section. Select a surface as the front surface, and calculate the strain required at each location when the flat slab 8 deforms into the target part 1-2 with the process section. Assume that one direction in the plane of the target part 1-2 with the process section is the x direction, and the direction perpendicular to it is the y direction. The strains required at each location in the x and y directions are ε x and ε y :

[0030] ε x = 0.5t / (ρ x - 0.5t)(2)

[0031] ε y = 0.5t / (ρ y - 0.5t)(3)

[0032] Wherein, ρ x and ρ y are the radii of curvature in the x and y directions respectively. A positive value is taken for convexity, and a negative value is taken for concavity;

[0033] Step 3: Path planning: Unfold the target part 1-2 with the process section into a plane, map the strains required at each location of the target part 1-2 with the process section calculated in Step 2 to the unfolded plane, divide the regions according to the positive and negative of the required strain, i.e., the positive strain region, the negative strain region, and the zero strain region. The zero strain region refers to the region where the value of the required strain is not greater than 0.0001. Determine the step size L according to the spot diameter and the overlap rate, and then determine the impact points at intervals of the step size L along the x and y directions with a certain point on the unfolded plane as the origin. No impact forming points are set in the zero strain region. When performing impact forming, the path direction is along the x or y direction starting from the vicinity of the zero strain region and moving away from the zero strain region. The relationship between each path is determined according to the overlap rate. When performing impact forming in the positive strain region, the laser beam should act on the front surface, and when performing impact forming in the negative strain region, the laser beam should act on the back surface. Determine the laser parameters according to the strains required at each location calculated in Step 2 and the relationship between the laser parameters and the strain determined in Step 1;

[0034] Step 4: Blank preparation: Determine the blank size according to the unfolded plane in Step 3 and cut the material. Paste or coat an energy-absorbing layer 15 on both sides of the slab 8, cover a constraint layer 14 on the energy-absorbing layer 15, and fix and install the prepared slab 8 on the gantry 5 through a chuck 6;

[0035] Step 5. Shock forming: Place a number of laser heads 9 carried by the robotic arm 4 on one or both sides of the slab 8, and perform shock forming along the path calculated in Step 3. The laser parameters at different positions are determined in Step 3 and are controlled by the controller 2 to output from the laser 3. During laser shock forming, the laser beam must always be along the normal direction of the slab 8. The negative strain area and the adjacent positive strain area need to be shock formed simultaneously. Multiple laser heads 9 can simultaneously shock form the same positive strain area or negative strain area. The method of multiple laser heads 9 acting on one point simultaneously can be used to increase the single-point shock forming energy;

[0036] The negative strain area and the adjacent positive strain area need to be shock formed simultaneously because the concave and convex directions of the negative strain area and the positive strain area are opposite. For example, for a saddle surface, simultaneous shock forming can avoid the problem that the bending moment coefficient of the cross-section increases sharply after bending in a certain direction, making it difficult to form a shape with the opposite curvature in the vertical direction;

[0037] Step 6. Iterative optimization: After completing one pass of shock forming according to the planned path, the CCD camera 7 takes a picture of the formed slab 8-1. The controller 2 calculates the measured surface model. The compensated strain Δε at each position of the formed slab 8-1 is calculated according to Equations (4) and (5) x and Δε y , and the parameters during laser shock forming are determined according to the difference, and then perform shock forming again until the normal distance between the measured surface model of the formed slab 8-1 measured by the CCD camera 7 and the target part model 1-1 is less than the allowable value;

[0038] Δε x = 0.5t / (ρ x - 0.5t) - 0.5t / (ρ' x - 0.5t) (4)

[0039] Δε y = 0.5t / (ρ y - 0.5t) - 0.5t / (ρ' y - 0.5t) (5)

[0040] where ρ' x and ρ' y are the radii of curvature in the x and y directions of the measured surface model, respectively taking positive values for convex and negative values for concave;

[0041] Step 7. Picking up and post-processing: Remove the formed slab 8-1 from the gantry 5, remove the constraint layer 14 and the energy absorption layer 15 on the surface, and cut off the process section to obtain the target part 1-1.

[0042] The laser pulse width output by each channel of the laser 3 is 1 ns to 120 ns, the energy is 0.1 to 50 J, the spot diameter is 1 to 10 mm, and the frequency is 0.5 to 5 Hz.

[0043] The energy absorption layer 15 is selected from at least one of carbon black paint, black paint, aluminum foil or black tape.

[0044] The constraint layer 14 is selected from at least one of K9 glass and / or water film.

[0045] In step five, when laser shock forming, the laser beam needs to always be along the normal direction of the slab 8, which is realized by three ranging lasers 13 installed on the laser head 9. The distance measured by the ranging lasers 13 is fed back to the controller 2, and the controller 2 adjusts the pose of the robotic arm 4 to make the distance values measured by the three ranging lasers 13 the same to determine whether the laser beam is along the normal direction of the slab 8.

[0046] The material of the slab 8 is selected from at least one of titanium alloy, superalloy, aluminum alloy, and intermetallic compound.

[0047] In step five, multiple laser heads 9 can work simultaneously in the same positive strain area or negative strain area. Such a setting can prevent the in-plane stress from transmitting to the surroundings during the single-point impact forming of the slab 8 with a ratio of the maximum length to the wall thickness greater than 100 in the weak rigidity area, and the imbalance of the stress field causes macroscopic deformation and the warping problem of the slab 8. At the same time, the forming efficiency can also be improved.

[0048] In step five, multiple laser heads 9 can act on one point simultaneously to increase the single-point impact forming energy and solve the problem that some difficult-to-deform materials cannot be formed due to insufficient energy of a single laser head.

[0049] The beneficial effects of the present invention are:

[0050] First, compared with the way of moving parts, the multiple laser heads installed at the execution end of the robotic arm in the present invention can have higher flexibility, and can ensure that each laser head works simultaneously and is directly facing the area to be formed.

[0051] Second, the light beams output by each laser head of the present invention are always along the normal direction of the slab, which can make the output laser energy act on the slab effectively according to the set value and reduce the forming error.

[0052] Third, the present invention performs impact forming simultaneously in adjacent concave and convex regions, which can avoid the problem that it is difficult to form the opposite curvature shape in the vertical direction due to the sharp increase in the cross-sectional bending moment coefficient after bending in a certain direction.

[0053] Fourth, the present invention adopts the method of multiple laser heads acting on one point simultaneously to increase the single-point impact forming energy and solve the problem that some difficult-to-deform materials cannot be formed due to insufficient energy of a single laser head.

[0054] V. The present invention uses multiple laser heads to simultaneously impact and form in the concave and convex regions, which can prevent the in-plane stress from transmitting to the surrounding areas during the single-point impact forming of a rigid slab, and avoid the macroscopic deformation caused by the imbalance of the stress field, thus solving the warping problem of the slab 8.

[0055] VI. The present invention uses multiple laser heads to simultaneously form, greatly improving the forming efficiency, and can be applied to the rapid prototyping of skin parts of equipment such as airplanes. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 is an axonometric view of the target part;

[0057] Figure 2 is an axonometric view of the target part with a process section;

[0058] Figure 3 is a schematic diagram before forming of the multi-point laser shock forming device for large-size complex curved surface parts;

[0059] Figure 4 is a schematic diagram after forming of the multi-point laser shock forming device for large-size complex curved surface parts;

[0060] Figure 5 is a schematic diagram of the laser head;

[0061] Figure 6 is a schematic diagram of the gantry in the multi-point laser shock forming device for large-size complex curved surface parts;

[0062] Figure 7 is a schematic diagram of the slab with a constraint layer and an energy absorption layer attached;

[0063] Figure 8 is a distribution diagram of the required strain in the x direction when the flat slab in Example 1 is deformed into a target part with a process section;

[0064] Figure 9 is a distribution diagram of the required strain in the y direction when the flat slab in Example 1 is deformed into a target part with a process section.

[0065] Among them, 1-1 is the target part, 1-2 is the target part with a process section, 2 is the controller, 3 is the laser, 4 is the robotic arm, 5 is the gantry, 5-1 is the gantry base, 5-2 is the gantry column, 5-3 is the gantry crossbeam, 6 is the chuck, 7 is the CCD camera, 8 is the slab, 8-1 is the formed slab, 9 is the laser head, 10 is the optical cable, 11 is the signal transmission line, 12 is the laser control line, 13 is the ranging laser, 14 is the constraint layer, and 15 is the energy absorption layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0066] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0067] Example 1

[0068] The target part is as Figure 1 shown. The part is made of TC4 with a thickness of 1.5 mm.

[0069] Step 1: Determination of the relationship between laser parameters and deformation: A test piece of 2000 mm × 2000 mm is cut from a TC4 plate with a thickness of t = 1.5 mm. A black tape with a thickness of about 0.2 mm is pasted on the surface of the test piece, and a 0.1 mm thick K9 glass is covered on the black tape. The test piece is irradiated with laser pulses with different single-pulse laser energies E, laser spot diameters S, and laser pulse numbers n, and then the corresponding strain ε is recorded. Through multiple experiments, the relationship between laser parameters and strain ε = f(E, d, t, n) is obtained;

[0070] Step 2: Model processing: At one end of a nearly straight edge of the digital model 1-1 of the target part shown in Figure 1 , extend 200 mm. A plane is constructed along the x direction with the extended edge as the starting point. A transition arc with a radius of 100 mm is added between the constructed plane and the extended plane. Based on this, the digital model of the target part 1-2 with a process section is obtained. Select the surface that bulges in the z direction as the front. According to Equation 2 and Equation 3, the required strain distribution at each place when the flat blank 8 is deformed into the target part 1-2 with a process section is calculated;

[0071] Step 3: Path planning: The target part 1-2 with a process section is unfolded into a plane. The required strain at each place of the target part 1-2 with a process section calculated according to Step 2 is corresponding to the unfolded plane. As Figure 8 and Figure 9 shown, the regions are divided according to the positive and negative of the required strain calculated in Step 2, that is, the positive strain region, the negative strain region, and the zero strain region refer to the region where the required strain value is not greater than 0.0001. Select a spot diameter of 5 mm and a lap rate of 50%. Then the step size L is 2.5 mm. Then, taking a point on the unfolded plane as the origin, the impact points are determined at intervals of 2.5 mm along the x and y directions. No impact forming points are set in the zero strain region. When performing impact forming, the path direction is along the x or y direction starting from the vicinity of the zero strain region and moving away from the zero strain region. The lap rate between each path is also 50%. When performing impact forming in the positive strain region, the laser beam should act on the front surface, and when performing impact forming in the negative strain region, the laser beam should act on the back surface. The laser parameters and impact times at different points are determined according to the required strain at each place calculated in Step 2 and the relationship between laser parameters and strain determined in Step 1;

[0072] Step 4: Blank preparation: Determine the blank size according to the unfolded plane in Step 3 and cut the material. Black tapes with a thickness of about 0.2 mm are pasted on both sides of the blank 8, and 0.1 mm thick K9 glass is covered on the black tapes. The prepared blank is fixedly installed on the gantry through the chuck 6;

[0073] Step 5. Impact forming: Place a number of laser heads loaded by the robotic arm on both sides of the slab, and perform impact forming along the path calculated in Step 3. The laser parameters at different positions are determined by Step 3, and the output of the laser is controlled by the controller. When performing laser shock forming, the laser beam must always be along the normal direction of the slab. The negative strain area and the adjacent positive strain area need to be shock formed simultaneously. Multiple laser heads can simultaneously perform shock forming on the same positive strain area or negative strain area;

[0074] Step 6. Iterative optimization: After completing one pass of impact forming according to the planned path, use a CCD camera to photograph the formed slab. The controller calculates the measured surface model. Analyze the error between the measured surface model and the target part model, and calculate the compensation strain Δε according to Equations 4 and 5 x and Δε y , and then determine the laser parameters and the number of impact times at different points according to the compensation strain in combination with the laser parameter and strain relationship determined in Step 1. Iterate several times until the normal distance between the measured surface model of the slab and the target part model is less than the allowable value;

[0075] Step 7. Pick up and post-process: Remove the formed slab from the gantry, remove the black tape and K9 glass on the surface, and cut off the process section to obtain the target part.

[0076] In the description of the present application, it should be understood that the orientation and positional relationships indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation and positional relationships shown in the drawings, and are only for the convenience of describing the present application or simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0077] The present invention has been disclosed above with preferred embodiments. However, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed structure and technical content to form equivalent implementation cases of equivalent changes within the scope of the technical solution of the present invention. However, as long as it does not depart from the technical content of the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A multi-point laser impact forming device for large-sized complex curved surface parts, characterized in that: It is composed of a controller (2), a laser (3), a mechanical arm (4), a gantry (5), a clamp (6), a CCD camera (7), a laser head (9), an optical cable (10), a signal transmission line (11), a laser control line (12), and a distance measuring laser (13); The controller (2) is connected to the laser (3) via a laser control line (12); The controller (2) is connected to the robot arm (4) via a signal transmission line (11); The controller (2) is connected to the distance measuring laser (13) via a signal transmission line (11); The controller (2) is connected to the CCD camera (7) via a data line; The chuck (6) is arranged on the gantry (5); The laser head (9) is arranged on the mechanical arm (4); The laser (3) is connected to the laser head (9) via an optical cable (10); The multi-point laser impact forming device for large-sized complex curved surface parts can clamp a plate blank (8) and accurately process large-sized complex curved surface parts according to the design by multi-point laser impact in conjunction with a movable mechanical arm; The length and width of the slab (8) are at least 2 meters.

2. The multi-point laser shock forming device for large-sized complex curved surface parts according to claim 1 is characterized in that: The controller (2) has signal acquisition, data processing and control signal output functions.

3. The multi-point laser shock forming device for large-sized complex curved surface parts according to claim 1 is characterized in that: The robot arm (4) has 6 degrees of freedom, n of which are arranged, and is placed on the ground via a base; The value range of n is 2, 3 or 4.

4. The multi-point laser shock forming device for large-sized complex curved surface parts according to claim 1 is characterized in that: A laser head (9) is installed at the end of the mechanical arm (4).

5. The multi-point laser shock forming device for large-sized complex curved surface parts according to claim 1 is characterized in that: Three distance measuring lasers (13) are installed on each laser head (9) on a plane perpendicular to the laser light path, and are used to determine the normal direction of the outer surface of the processed object.

6. The multi-point laser shock forming device for large-sized complex curved surface parts according to claim 1 is characterized in that: The laser (3) is a multi-channel output laser, and the laser output parameters of each channel can be adjusted independently.

7. The multi-point laser shock forming device for large-sized complex curved surface parts according to claim 1 is characterized in that: Each of the laser heads (9) is independently equipped with a laser (3).

8. The multi-point laser shock forming device for large-sized complex curved surface parts according to claim 1 is characterized in that: The laser light output by the laser (3) is transmitted to the laser head (9) through the optical cable (10), and then output by the laser head (9) to act on the slab.

9. The multi-point laser shock forming device for large-sized complex curved surface parts according to claim 1 is characterized in that: The controller (2) outputs the real-time laser parameters of each channel to the laser (3) via the laser control line (12), and the laser (3) executes to output laser with corresponding parameters.

10. The multi-point laser shock forming device for large-sized complex curved surface parts according to claim 1 is characterized in that: The gantry (5) is composed of a gantry base (5-1), a gantry column (5-2) and a gantry crossbeam (5-3).

11. The multi-point laser shock forming device for large-sized complex curved surface parts according to claim 10, characterized in that: The gantry column (5-2) is arranged vertically, and one end is fixedly mounted on the gantry base (5-1); the gantry crossbeam (5-3) is arranged horizontally, and both ends are fixedly connected to the other ends of the two gantry columns (5-2).

12. The multi-point laser shock forming device for large-sized complex curved surface parts according to claim 10, characterized in that: Two clamps (6) are fixedly connected below the gantry crossbeam (5-3).

13. The multi-point laser shock forming device for large-sized complex curved surface parts according to claim 12, characterized in that: The gantry (5) clamps the slab (8) to be laser impact-formed via a clamp (6).

14. The multi-point laser shock forming device for large-sized complex curved surface parts according to claim 10, characterized in that: The gantry (5) is placed statically on the ground via a gantry base (5-1).

15. The multi-point laser shock forming device for large-sized complex curved surface parts according to claim 1 is characterized in that: The mechanical arm (4) may be arranged on one side of the gantry (5), or on both sides of the gantry (5).

16. The multi-point laser shock forming device for large-sized complex curved surface parts according to claim 1 is characterized in that: The CCD camera (7) is used to measure the profile of the slab (8) during the laser shock forming process and to compare with the theoretical digital model to correct the laser shock forming parameters. The image collected by the CCD camera (7) is transmitted to the controller (2) via a data line.

17. The multi-point laser shock forming device for large-sized complex curved surface parts according to claim 16, characterized in that: The controller (2) receives the position and posture signal of the robot arm (4) and the signal of the distance measuring laser (13) through the signal transmission line (11), and provides the position and posture control signal of the robot arm (4) according to the calculation result.

18. A multi-point laser shock forming method for large-sized complex curved surface parts, characterized in that: A multi-point laser impact forming device for large-sized complex curved surface parts according to any one of claims 1 to 17; The following steps are involved: Step 1: Determination of the relationship between laser parameters and deformation; Step 2: Model processing; Step 3: Path planning; Step 4: blank preparation; Step 6: Iterative optimization; Step 7: Pick up and process.

19. The multi-point laser shock forming method for large-sized complex curved surface parts according to claim 18, characterized in that: Step 1, determination of the relationship between laser parameters and deformation: a test piece is prepared from the blank (8) to be formed, an energy absorbing layer (15) is pasted or coated on the surface of the test piece, and a constraint layer (14) is covered on the energy absorbing layer (15). Laser impact is performed using different parameters, and then the corresponding strain ε is recorded. After multiple experiments, the relationship between laser parameters and strain is obtained: ε = f (E, d, t, n) (1) Wherein, E is the single pulse laser energy, S is the laser spot diameter, t is the slab thickness, and n is the number of laser pulses.

20. The multi-point laser shock forming method for large-sized complex curved surface parts according to claim 19, characterized in that: Step 2, model processing: Add the process segment to the digital model of the target part (1-1) to obtain the digital model of the target part (1-2) with the process segment, select a face as the front face, and calculate the strain required at each location when the flat plate (8) is deformed into the target part (1-2) with the process segment. Assume that one direction in the surface of the target part (1-2) with the process segment is the x direction, and the direction perpendicular to it is the y direction. The strain required at each location in the x direction and the y direction is ε x and ε y : ε x = 0.5t / (ρ x -0.5t) (2) ε y = 0.5t / (ρ y -0.5t) (3) Among them, ρ x and ρ y They are the curvature radii in the x and y directions respectively. They take positive values ​​when convex and negative values ​​when concave.

21. The multi-point laser shock forming method for large-sized complex curved surface parts according to claim 20, characterized in that: Step 3, path planning: unfold the target part (1-2) with process section into a plane, correspond the required strains at various locations of the target part (1-2) with process section calculated according to step 2 to the unfolded plane, divide the regions according to the positive and negative required strains, namely, positive strain region, negative strain region and zero strain region, wherein the zero strain region refers to the region where the required strain value is not greater than 0.0001, determine the step length L according to the spot diameter and the overlap rate, and then determine the impact point along the x and y directions with a certain point on the unfolded plane as the origin at intervals of step length L. No impact forming point is set in the zero strain region. During impact forming, the path direction is along the x or y direction from the adjacent zero strain region to the direction away from the zero strain region. The overlap rate between each path is determined. During impact forming in the positive strain region, the laser beam should act on the front side, and during impact forming in the negative strain region, the laser beam should act on the back side. The laser parameters are determined according to the required strains at various locations calculated in step 2 and the relationship between the laser parameters and strains determined in step 1.

22. The multi-point laser shock forming method for large-sized complex curved surface parts according to claim 21, characterized in that: Step 4, blank preparation: determine the blank size and cut the blank according to the plane unfolded in step 3, paste or coat the energy absorbing layer (15) on both sides of the blank (8), cover the energy absorbing layer (15) with a constraint layer (14), and fix the prepared blank (8) on the gantry (5) through a chuck (6).

23. The multi-point laser shock forming method for large-sized complex curved surface parts according to claim 22, characterized in that: Step 5, impact forming: a plurality of laser heads (9) supported by a robot arm (4) are placed on one side or both sides of the slab (8), and impact forming is performed along the path calculated in step 3. The laser parameters at different positions are determined by step 3, and the output of the laser (3) is controlled by the controller (2). During laser impact forming, the laser beam must always be along the normal direction of the slab (8), and the negative strain zone and the positive strain zone adjacent thereto must be impact formed at the same time. The same positive strain zone or negative strain zone can be impact formed by multiple laser heads (9) at the same time. The single-point impact forming energy can be increased by using multiple laser heads (9) to act on one point at the same time. The negative strain zone and the adjacent positive strain zone need to be impact formed simultaneously because the negative strain zone and the positive strain zone have opposite concave and convex directions. Simultaneous impact forming can avoid the problem that the bending coefficient of the cross section increases sharply after bending in a certain direction, making it difficult to form a shape with the opposite curvature in the vertical direction.

24. The multi-point laser shock forming method for large-sized complex curved surface parts according to claim 23, characterized in that: Step 6, iterative optimization: After completing one round of impact forming according to the planned path, the formed slab (8-1) is photographed by a CCD camera (7), and the measured surface model is calculated by the controller (2). The compensation strain Δε of each part of the formed slab (8-1) is calculated according to equations (4) and (5). x and Δε y , determining the laser shock forming parameters according to the difference, and performing shock forming again until the normal distance between the measured surface model of the formed slab (8-1) and the target part model (1-1) measured by the CCD camera (7) is less than the allowable value; Δε x =0.5t / (ρ x -0.5t)-0.5t / (ρ′ x -0.5t) (4) Δε y =0.5t / (ρ y -0.5t)-0.5t / (ρ′ y -0.5t) (5) Among them, ρ′ x and ρ′ y They are the curvature radii of the measured surface model in the x and y directions, respectively. They take positive values ​​when convex and negative values ​​when concave.

25. The multi-point laser shock forming method for large-sized complex curved surface parts according to claim 24, characterized in that: Step 7, taking out and post-processing: taking down the formed slab (8-1) from the gantry (5), removing the constraint layer (14) and the energy absorption layer (15) on the surface, and cutting off the process section to obtain the target part (1-1).

26. The multi-point laser shock forming method for large-sized complex curved surface parts according to claim 22, characterized in that: Each channel of the laser (3) outputs a laser pulse width of 1 ns to 120 ns, an energy of 0.1 to 50 J, a spot diameter of 1 to 10 mm, and a frequency of 0.5 to 5 Hz.

27. The multi-point laser shock forming method for large-sized complex curved surface parts according to claim 19, characterized in that: The energy absorbing layer (15) is selected from at least one of carbon black paint, black paint, aluminum foil or black tape.

28. The multi-point laser shock forming method for large-sized complex curved surface parts according to claim 19, characterized in that: The constraining layer (14) is selected from at least one of K9 glass and / or water film.

29. The multi-point laser shock forming method for large-sized complex curved surface parts according to claim 22, characterized in that: In step five, during laser shock forming, the laser beam must always be along the normal direction of the slab (8) by means of three ranging lasers (13) installed on the laser head (9). The distance measured by the ranging laser (13) is fed back to the controller (2). The controller (2) adjusts the position of the robot arm (4) to ensure that the distance values ​​measured by the three ranging lasers (13) are the same to determine whether the laser beam is along the normal direction of the slab (8).

30. The multi-point laser shock forming method for large-sized complex curved surface parts according to claim 19, characterized in that: The material of the slab (8) is selected from at least one of titanium alloy, high-temperature alloy, aluminum alloy and intermetallic compound.

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