Ultrafast laser polishing / strengthening integrated machining method for complex curved surface

Abstract

The invention relates to the technical field of non-traditional machining, in particular to a complex curved surface ultrafast laser polishing / strengthening integrated machining method which comprises the steps that a to-be-machined curved surface equation of a complex curved surface part is solved; according to the equation of the curved surface to be processed, determining an ultrafast laser multi-degree-of-freedom curved surface movement track; according to the ultra-fast laser multi-degree-of-freedom curved surface movement track, ultra-fast laser polishing process parameters are determined; determining ultrafast laser polishing / strengthening process parameters by using the ultrafast laser polishing process parameters; and carrying out ultrafast laser polishing / strengthening integrated processing on the complex curved surface part by adopting ultrafast laser polishing / strengthening process parameters. The complex curved surface ultrafast laser polishing / strengthening integrated machining method aims at solving the problem that ultrafast laser polishing / strengthening integration is difficult to achieve.

Description

Technical Field

[0001] The invention relates to the technical field of special processing, and in particular to an integrated processing method for ultrafast laser polishing / strengthening of complex curved surfaces. Background Art

[0002] Complex surfaces refer to structures with curves and surfaces in three-dimensional space. Due to their excellent functional properties and good appearance characteristics, they are widely used in the manufacture of key aerospace components. Complex surfaces are physically non-developable surfaces with complex geometric shapes and drastic changes in curvature, making it difficult to accurately and completely capture these shape details. Aviation parts contain a large number of complex surface structures, such as aircraft engine blades and pitot tubes. However, the surface state of these parts is closely related to their performance. For example, the surface roughness of aircraft engine blades directly affects aerodynamic efficiency; the surface roughness of pitot tubes directly affects the accuracy of atmospheric data measurement. It can be seen that the surface state of complex surface components not only affects aircraft performance but is also closely related to flight safety.

[0003] Ultrafast laser refers to a pulsed laser with a pulse width of picoseconds or less. During the interaction with the material, the free electrons on the surface of the material absorb the energy of the incident photons, inducing the lattice temperature to rise, causing melting, evaporation, sublimation, and inducing the evolution of surface organization and properties. Ultrafast laser polishing / strengthening integration is a typical cold processing method. After the material surface absorbs photon energy, the surface chemical bonds are broken or the lattice structure is destroyed, and molecular or atomic scale decomposition occurs, achieving microscopic material removal. At the same time, the plasma pulse shock induced by the ultrafast laser pulse during the interaction with the material surface produces strain strengthening on the surface of the material.

[0004] Therefore, the inventors provide an integrated processing method for ultrafast laser polishing / strengthening of complex curved surfaces. Summary of the invention

[0005] (1) Technical issues to be solved

[0006] The embodiment of the present invention provides a method for integrated ultrafast laser polishing / strengthening of complex curved surfaces, which solves the technical problem that it is difficult to achieve integrated ultrafast laser polishing / strengthening.

[0007] (2) Technical solution

[0008] The present invention provides a complex curved surface ultrafast laser polishing / strengthening integrated processing method, comprising the following steps:

[0009] Solve the surface equations of complex surface parts to be processed;

[0010] Determining the ultrafast laser multi-degree-of-freedom surface motion trajectory according to the surface equation to be processed;

[0011] Determining ultrafast laser polishing process parameters according to the ultrafast laser multi-degree-of-freedom curved surface motion trajectory;

[0012] Determine ultrafast laser polishing / strengthening process parameters by using the ultrafast laser polishing process parameters;

[0013] The ultrafast laser polishing / strengthening process parameters are used to perform ultrafast laser polishing / strengthening integrated processing on the complex curved surface parts.

[0014] Furthermore, the solution of the surface equation to be processed of the complex surface component is specifically as follows:

[0015] A reference base point is set to detect the coordinate heights of n different points on the surface to be processed of a complex curved surface component, and the equation of the surface to be processed is obtained by a fitting method.

[0016] Furthermore, the ultrafast laser multi-degree-of-freedom surface motion trajectory is determined based on the surface equation to be processed, specifically:

[0017] The complex curved surface component is placed on an ultrafast laser processing platform, the center of the sphere is placed to coincide with the origin of the processing platform, and the equation of the surface to be processed is input to obtain the ultrafast laser multi-degree-of-freedom curved surface motion trajectory.

[0018] Furthermore, determining the ultrafast laser polishing process parameters according to the ultrafast laser multi-degree-of-freedom curved surface motion trajectory specifically includes the following steps:

[0019] Implementing ultrafast laser polishing on the surface to be processed according to the ultrafast laser multi-degree-of-freedom surface motion trajectory;

[0020] With the surface roughness optimization as the goal, when the surface roughness of a polished surface of a certain process parameter group is less than the roughness of the unpolished surface, the parameters of the process parameter group are determined to be the ultrafast laser polishing process parameters.

[0021] Furthermore, the process parameter group includes laser wavelength, laser pulse width, laser output power, repetition frequency, moving speed and line overlap rate.

[0022] Furthermore, when the surface roughness optimization is taken as the goal, the surface roughness of a certain process parameter group after polishing is less than the roughness of the unpolished surface, the parameters of the process parameter group are determined to be the ultrafast laser polishing process parameters, specifically:

[0023] When the surface roughness of a surface after polishing of a certain process parameter group is less than the roughness of the surface before polishing, the process parameters are adjusted by an orthogonal test method to obtain the ultrafast laser polishing process parameters.

[0024] Furthermore, the ultrafast laser polishing / strengthening process parameters are determined by using the ultrafast laser polishing process parameters, specifically:

[0025] The ultrafast laser curved surface processing is repeatedly performed using the process parameter group. When the microhardness after processing is greater than that before processing, the parameters of the process parameter group are determined to be the ultrafast laser polishing / strengthening process parameters.

[0026] Furthermore, the ultrafast laser polishing / strengthening process parameters are used to perform ultrafast laser polishing / strengthening integrated processing on the complex curved surface parts, specifically:

[0027] The complex curved surface parts are polished / strengthened in an integrated manner using a process parameter group corresponding to the parameter set.

[0028] (3) Beneficial effects

[0029] In summary, the present invention utilizes a set of ultrafast laser parameters to simultaneously achieve the two functions of surface polishing and surface strengthening, which significantly improves the processing efficiency compared to traditional separate strengthening and polishing processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments of the present invention are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 It is a schematic diagram of a process of an integrated processing method of ultrafast laser polishing / strengthening of complex curved surfaces provided by an embodiment of the present invention;

[0032] Figure 2 This is a microscopic morphology comparison diagram of a sample processed by ultrafast laser polishing / strengthening integrated processing of a complex surface provided in Example 1 of the present invention and an unprocessed sample. DETAILED DESCRIPTION

[0033] The following detailed description of the embodiments of the present invention is provided in conjunction with the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present invention, but cannot be used to limit the scope of the present invention, that is, the present invention is not limited to the described embodiments.

[0034] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0035] Figure 1is a flow chart of a complex curved surface ultrafast laser polishing / strengthening integrated processing method provided by an embodiment of the present invention, see Figure 1 , the method may include the following steps:

[0036] S100, solving the equation of the surface to be processed of the complex surface component.

[0037] Specifically, a reference base point is set with coordinates (0, 0, 0), and a manipulator is used to detect the coordinate heights of n different points on the surface of the complex curved part to be processed, and their spatial coordinates are obtained as (x1, y1, z1), (x2, y2, z2), ..., (x n ,y n , z n ). The surface equation is obtained by linear regression, nonlinear fitting and other methods:

[0038] f(x)+g(y)+h(z)=0 (1)

[0039] S200, determining the ultrafast laser multi-degree-of-freedom surface motion trajectory according to the surface equation to be processed.

[0040] Specifically, a complex curved surface component is placed on an ultrafast laser processing platform, the center of the sphere is aligned with the origin of the processing platform, and the equation of the surface to be processed is input to obtain the ultrafast laser multi-degree-of-freedom surface motion trajectory.

[0041] S300, determining ultrafast laser polishing process parameters according to the ultrafast laser multi-degree-of-freedom surface motion trajectory.

[0042] Furthermore, step S300 includes the following steps:

[0043] S301, realizing ultrafast laser polishing on the surface to be processed according to the ultrafast laser multi-degree-of-freedom surface motion trajectory;

[0044] S302, with the surface roughness optimization as the goal, when the surface roughness of a certain process parameter group after polishing is less than the roughness of the unpolished surface, the parameters of the process parameter group are determined to be ultrafast laser polishing process parameters.

[0045] Specifically, ultrafast laser polishing is implemented on the surface to be processed according to the ultrafast laser multi-degree-of-freedom surface motion trajectory planned in step S200. The process parameters include laser wavelength (λ), laser pulse width (τ), laser output power (P), repetition frequency (f), moving speed (v), and line overlap rate (OV). The process parameters influence and interact with each other, and it is difficult to judge the influence of a single parameter on the polishing effect alone. Therefore, the present invention selects surface roughness (Rz) optimization as the target (because of its high measurement accuracy and good measurement convenience). When the surface roughness Rz of a certain process parameter group after polishing is better than that of the unpolished surface, the parameter has a polishing effect. The process parameters are adjusted by orthogonal tests and other methods to obtain m effective polishing process parameters P. i (i=1, 2, ..., m):

[0046]

[0047] S400, using ultrafast laser polishing process parameters, determine ultrafast laser polishing / strengthening process parameters.

[0048] Specifically, the ultrafast laser curved surface processing is repeated using the m process parameter groups with polishing effects obtained in step S300. When the microhardness (H) after processing is improved compared with the unprocessed state, the corresponding process parameter group also has a surface strengthening effect. At this time, the process parameter group has both polishing and strengthening effects. The process parameter group with both polishing and strengthening effects is as follows:

[0049]

[0050] S500 uses ultrafast laser polishing / strengthening process parameters to perform ultrafast laser polishing / strengthening integrated processing on complex curved surface parts.

[0051] Specifically, the parameter group corresponding to the parameter set PS determined in step S400 is used to complete the polishing / strengthening integrated processing of the complex surface.

[0052] Example 1

[0053] Take the integrated ultrafast laser polishing / strengthening processing of the TC4 titanium alloy hemisphere surface as an example.

[0054] Step 1: Solve the surface equation of the hemisphere. Assume the coordinates of the center of the sphere are (0, 0, 0) and the radius of the sphere is 20 mm, then the spherical surface equation is:

[0055] x 2 +y 2 +z 2 =400 (1)

[0056] Step 2: Ultrafast laser multi-DOF surface motion trajectory response. Place the sample on the ultrafast laser processing platform, make the center of the sphere coincide with the origin of the processing platform, input the spherical equation into the ultrafast laser control software, and test run the trajectory.

[0057] Step 3: Ultrafast laser polishing process parameter window. Surface polishing is performed on a femtosecond ultrafast laser system with a wavelength of 800nm ​​and a pulse width of 35fs. To simplify the parameter selection process, in this embodiment, the laser output power (P), repetition frequency (f), and scanning speed (v) are used as variables, and the line overlap rate (OV) is set to a constant value (OV = 50%). The range of P is 5 to 20mW, the range of f is 1 to 5kHz, and the moving speed is 2000 to 8000μm / s. The roughness of the treated surface and the polished surface is measured using a laser confocal microscope. The original surface roughness Rz = 15.6μm, and the partial effective parameter group is obtained as follows:

[0058]

[0059] The corresponding surface roughness Rz are 13.2μm, 8.4μm, 6.8μm, 7.9μm and 11.3μm respectively.

[0060] Step 4: Ultrafast laser polishing / strengthening process parameter window. Repeat the five sets of parameters in step 3, and use a microhardness tester to measure the microhardness of the surface (the hardness of the untreated surface is 340HV). The effective parameters after screening are as follows:

[0061]

[0062] The corresponding microhardnesses are 389HV, 375HV, and 406HV respectively.

[0063] Therefore, the following three sets of parameters achieve both polishing and strengthening effects:

[0064] PS1: laser wavelength (λ) = 800nm, laser pulse width (τ) = 35fs, laser output power (P) = 10mW, repetition frequency (f) = 1.5kHz, moving speed (v) = 2000μm, line overlap rate (OV) = 50%.

[0065] PS2: laser wavelength (λ) = 800nm, laser pulse width (τ) = 35fs, laser output power (P) = 20mW, repetition frequency (f) = 2.5kHz, moving speed (v) = 6000μm, line overlap rate (OV) = 50%.

[0066] PS3: Laser wavelength (λ) = 800nm, laser pulse width (τ) = 35fs, laser output power (P) = 20mW, repetition frequency (f) = 3.5kHz, moving speed (v) = 8000μm, line overlap rate (OV) = 50%.

[0067] Step 5: Ultrafast laser polishing / strengthening integrated manufacturing of complex curved surfaces. The PS3 parameter set is used to perform integrated polishing / strengthening processing on the surface. The microstructure of the processed sample is as follows: Figure 2 shown.

[0068] It should be clear that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. In addition, for the sake of brevity, a detailed description of known methods and technologies is omitted here.

[0069] The above are only embodiments of the present application and are not limited to the present application. For those skilled in the art, the present application may have various changes and variations without departing from the scope of the present invention. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A method for integrated ultrafast laser polishing / strengthening of complex curved surfaces, characterized in that: The method comprises the following steps: Solve the surface equations of complex surface parts to be processed; Determining the ultrafast laser multi-degree-of-freedom surface motion trajectory according to the surface equation to be processed; Determining ultrafast laser polishing process parameters according to the ultrafast laser multi-degree-of-freedom curved surface motion trajectory; Determine ultrafast laser polishing / strengthening process parameters by using the ultrafast laser polishing process parameters; The ultrafast laser polishing / strengthening process parameters are used to perform ultrafast laser polishing / strengthening integrated processing on the complex curved surface parts.

2. The complex curved surface ultrafast laser polishing / strengthening integrated processing method according to claim 1 is characterized in that: The solution of the surface equation to be processed of the complex surface component is specifically: A reference base point is set to detect the coordinate heights of n different points on the surface to be processed of a complex curved surface component, and the equation of the surface to be processed is obtained by a fitting method.

3. The complex curved surface ultrafast laser polishing / strengthening integrated processing method according to claim 1, characterized in that: The ultrafast laser multi-degree-of-freedom surface motion trajectory is determined according to the surface equation to be processed, specifically: The complex curved surface component is placed on an ultrafast laser processing platform, the center of the sphere is placed to coincide with the origin of the processing platform, and the equation of the surface to be processed is input to obtain the ultrafast laser multi-degree-of-freedom curved surface motion trajectory.

4. The complex curved surface ultrafast laser polishing / strengthening integrated processing method according to claim 1, characterized in that: Determining the ultrafast laser polishing process parameters according to the ultrafast laser multi-degree-of-freedom curved surface motion trajectory specifically includes the following steps: Implementing ultrafast laser polishing on the surface to be processed according to the ultrafast laser multi-degree-of-freedom surface motion trajectory; With the surface roughness optimization as the goal, when the surface roughness of a polished surface of a certain process parameter group is less than the roughness of the unpolished surface, the parameters of the process parameter group are determined to be the ultrafast laser polishing process parameters.

5. The complex curved surface ultrafast laser polishing / strengthening integrated processing method according to claim 4, characterized in that: The process parameter group includes laser wavelength, laser pulse width, laser output power, repetition frequency, moving speed and line overlap rate.

6. The complex curved surface ultrafast laser polishing / strengthening integrated processing method according to claim 4, characterized in that: The surface roughness optimization is taken as the goal. When the surface roughness of a certain process parameter group after polishing is less than the roughness of the unpolished surface, the parameters of the process parameter group are determined to be the ultrafast laser polishing process parameters, specifically: When the surface roughness of a surface after polishing of a certain process parameter group is less than the roughness of the surface before polishing, the process parameters are adjusted by an orthogonal test method to obtain the ultrafast laser polishing process parameters.

7. The complex curved surface ultrafast laser polishing / strengthening integrated processing method according to claim 4, characterized in that: The ultrafast laser polishing / strengthening process parameters are determined by using the ultrafast laser polishing process parameters, specifically: The ultrafast laser curved surface processing is repeatedly performed using the process parameter group. When the microhardness after processing is greater than that before processing, the parameters of the process parameter group are determined to be the ultrafast laser polishing / strengthening process parameters.

8. The complex curved surface ultrafast laser polishing / strengthening integrated processing method according to claim 1, characterized in that: The ultrafast laser polishing / strengthening process parameters are used to perform ultrafast laser polishing / strengthening integrated processing on the complex curved surface parts, specifically: The complex curved surface parts are polished / strengthened in an integrated manner using a process parameter group corresponding to the parameter set.

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