Laser cold and hot dual-mode ultrasonic milling method and device for ceramic-based turbine outer ring sealing groove

Abstract

The invention provides a laser cold and hot dual-mode ultrasonic milling method and device for a ceramic-based turbine outer ring sealing groove. The laser cold and hot dual-mode ultrasonic milling method comprises the following steps that 1, energy field coupling parameters corresponding to a target depth-to-width ratio are obtained through a pre-constructed mathematical model; step 2, shaping the light beam of the femtosecond laser to form a flat-topped light beam of the femtosecond laser; the femtosecond laser machining parameters determined in the first step are utilized, and a flat-topped beam of femtosecond laser is combined to conduct cold etching treatment on the to-be-machined area of the to-be-machined ceramic matrix composite; 3, the infrared continuous laser beam is shaped into a flat-topped beam, a heat-assisted mode is formed in the machining area, meanwhile, a blind groove with the large depth-to-width ratio is machined through ultrasonic vibration milling machining parameters, and a ceramic-based turbine outer ring sealing groove is formed; the method solves the problem that in multi-energy-field combined machining of an existing ceramic-based turbine, due to the fact that laser heat cannot be accurately controlled, defect transition areas exist in a machining area and a non-machining area, and then internal materials are damaged.

Description

Technical Field

[0001] The present invention belongs to the technical field of multi-energy field coupling processing of high-temperature hard-brittle composite materials, and specifically relates to a laser hot and cold dual-mode ultrasonic milling processing method and device for ceramic-based turbine outer ring sealing grooves. Background Art

[0002] The technical approach to improving aero-engine thrust-to-weight ratios is to increase turbine inlet temperatures and reduce structural weight. For aero-engines with thrust-to-weight ratios above 12, 70% of the contribution comes from new materials and processes. The use of low-density, high-temperature-resistant composite materials is the future trend. Currently, the maximum turbine inlet temperature of fifth-generation aircraft has climbed to 1900-2100°C, far exceeding the melting point limit of traditional high-temperature alloys. Ceramic-based composites, offering excellent properties such as low density, high specific strength, and high specific modulus, have been gradually adopted for key hot-end components such as turbine outer rings. However, current traditional machining methods suffer from poor dimensional accuracy and surface quality, as well as material damage (fiber breakage / pullout, edge chipping, cracks, etc.) and tool damage (edge breakage, increased wear, etc.), making them unable to meet the demanding service requirements of aero-engine hot-end components in extremely harsh environments.

[0003] As an emerging advanced manufacturing technology, multi-dimensional dynamic composite energy field processing using laser-ultrasonic-milling demonstrates the potential for efficient, low-damage machining by inducing deformation and phase transformation in the workpiece material and altering the tool / workpiece interaction. However, the control and distribution methods of the multi-energy field and the process optimization decision-making methods can affect the fabrication of high-aspect-ratio sealing grooves. To improve the aspect ratio of sealing grooves processed using multi-energy field coupling, Wang et al. analyzed the surface microstructure under different fiber orientations, ultrasonic amplitudes, and spindle speeds. They found that rotary ultrasonic machining of C / SiC composites effectively improved the machining quality of high-temperature hard and brittle composites. However, ultrasonic vibrations exerted destabilizing effects on the quality, material, and shape properties of the C / SiC workpiece. You et al. used laser-assisted milling to suppress localized graphitization and chip adhesion, but improper heat control in the processing zone resulted in accelerated tool failure due to elevated temperatures. Xie found that laser ablation products accumulate on the groove surface, leading to crack propagation and poor machining quality. Chen et al. studied laser ablation of SiC / SiC composites and found that the ablation products formed defect transition zones such as condensation layers, recrystallization layers, and heat-affected layers. Laser-ultrasonic-milling composite manufacturing, leveraging the efficient synergy of multiple energy fields, demonstrates the potential for high-efficiency, low-damage processing, and is of great significance for the demonstrative application of ceramic-based high-temperature composites in aero-engine hot-end components. However, in the multi-energy field composite processing of sealing grooves in ceramic-based high-temperature hard-brittle composites, the laser heat cannot be precisely controlled, resulting in the formation of a heat-affected zone and a defect transition zone between the processed and non-processed areas. Furthermore, due to the complex and anisotropic composition of ceramic-based composites, the parameter coupling during processing is complex, and there is a lack of systematic process optimization and aspect ratio control decision-making models and methods, which can cause internal material damage. Summary of the Invention

[0004] The purpose of the present invention is to provide a laser hot and cold dual-mode ultrasonic milling method and device for ceramic-based turbine outer ring sealing grooves, which solves the problem that in the existing ceramic-based turbine multi-energy field composite processing, the laser heat cannot be accurately controlled, resulting in defective transition zones in both the processing area and the non-processing area, thereby causing internal material damage.

[0005] In order to achieve the above object, the technical solution adopted in the present invention is: In a first aspect, the present invention provides a method for laser hot and cold dual-mode ultrasonic milling of a ceramic-based turbine outer ring sealing groove, comprising the following steps: Step 1: using a pre-built mathematical model to obtain energy field coupling parameters corresponding to the target aspect ratio, wherein the energy field coupling parameters include femtosecond laser processing parameters, infrared continuous laser processing parameters, and ultrasonic vibration milling processing parameters; Step 2: shaping the femtosecond laser beam to form a flat-top beam of the femtosecond laser; using the femtosecond laser processing parameters determined in step 1, combined with the flat-top beam of the femtosecond laser, cold etching the to-be-processed area of the ceramic matrix composite material to be processed, so that a groove boundary and a network groove structure are formed in the to-be-processed area of the ceramic matrix composite material to be processed; In step 3, the infrared continuous laser beam is shaped into a flat-top beam, and the infrared continuous laser processing parameters determined in step 1 are used to form a heat-assisted mode in the processing area. At the same time, the ultrasonic vibration milling processing parameters are used to process a large aspect ratio blind groove based on step 2 to form a ceramic-based turbine outer ring sealing groove.

[0006] Preferably, the femtosecond laser beam in step 2 and the infrared continuous laser beam in step 3 are spatially shaped respectively by using the aberration generation and compensation method of the aspheric lens to convert the Gaussian beam into a flat-top beam.

[0007] Preferably, in step 2, a femtosecond laser flat-top beam is used to perform cold etching on the to-be-processed area of the ceramic matrix composite material to be processed, so that a groove boundary and a network groove structure are formed in the to-be-processed area of the ceramic matrix composite material to be processed, and the specific method is: According to the target depth-to-diameter ratio of the turbine outer ring sealing groove and the dimensional parameters of the ceramic matrix composite material to be processed, the femtosecond laser scanning path is set to a mesh groove structure; According to the size parameters of the ceramic matrix composite material to be processed, the length and width of the grid lines, the scanning speed of the grid lines and the spacing of the grid lines of the femtosecond laser scanning are set; The cold etching mode is started in combination with the femtosecond laser processing parameters determined in step 1, so that a groove boundary and a network groove structure are formed in the to-be-processed area of the to-be-processed ceramic matrix composite material.

[0008] Preferably, the scanning speed of the mesh lines is 0.04 mm / s; and the maximum interval between two adjacent mesh lines is less than 30 μm.

[0009] Preferably, in step 3, the infrared continuous laser beam is shaped into a flat-top beam, and a blind groove with a large aspect ratio is machined on the basis of step 2 using the flat-top beam of the infrared continuous laser, an ultrasonic vibration method, and a milling method to form a ceramic-based turbine outer ring sealing groove. The specific method is: According to the target depth-to-diameter ratio of the turbine outer ring sealing groove and the size parameters of the ceramic matrix composite material to be processed, the continuous laser scanning path is set to a grid shape, and the scanning path parameters are set; Combined with the infrared continuous laser processing parameters determined in step 1, the thermal assistance mode is turned on; By combining the ultrasonic vibration milling processing parameters determined in step 1, the ultrasonic vibration auxiliary platform is turned on to process the ceramic matrix composite material to be processed.

[0010] Preferably, the interval between adjacent gratings in the scanning path parameters is 15-20 μm, and the grating scanning speed is 0.04 mm / s. Preferably, the pre-built mathematical model is constructed in the following manner: Based on the RSM model, a mathematical model between energy field coupling parameters and aspect ratio is established, wherein the energy field coupling parameters include femtosecond laser processing parameters, infrared continuous laser processing parameters, and ultrasonic vibration milling processing parameters; The significance, goodness of fit and residual analysis of the model were verified using ANOVA statistical method to obtain the verification results; The principal component analysis method is used to evaluate the influence of the input parameters of the mathematical model on the output response and obtain the evaluation results; The mathematical model is optimized using the verification and evaluation results to obtain an optimized mathematical model between the energy field coupling parameters and the aspect ratio.

[0011] In a second aspect, the present invention provides a laser hot and cold dual-mode ultrasonic milling processing device for ceramic-based turbine outer ring sealing grooves, comprising a five-axis machining center equipped with a continuous laser and a femtosecond pulse laser, wherein the control ends of the continuous laser and the femtosecond pulse laser are connected to a multi-mode switching module; The laser beam emitted by the femtosecond pulse laser is incident on the flat-top light spatial shaping module for beam shaping to form a flat-top light; The laser beam emitted by the continuous laser is incident on the flat-top light spatial shaping module for beam shaping to form a flat-top light; The flat-top light of the femtosecond pulse laser and the flat-top light of the continuous laser are both incident on the processing area of the ceramic-based composite material to be processed; The multi-mode switching module is used to control the start and stop of the femtosecond pulse laser and the continuous laser, thereby controlling the femtosecond pulse laser to perform the cold etching stage and the continuous laser to perform the thermal assistance stage.

[0012] Preferably, both beams of flat-top light are incident on the processing area of the ceramic matrix composite material to be processed through the dynamic focusing module.

[0013] Preferably, a collimating module is provided at the output end of the dynamic focusing module.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention proposes a laser hot and cold dual-mode ultrasonic milling processing method for ceramic-based turbine outer ring sealing grooves. First, a mathematical model between energy field coupling parameters and aspect ratio is designed, and the established parameter sensitivity and shape evolution predictive analysis model is combined to study the distribution modulation effect of multi-energy field coupling parameters. The preparation process parameters of ceramic-based composite large aspect ratio sealing grooves based on different characteristic structure requirements are proposed. Then, the flat-top light of a femtosecond laser is used to cold-etch SiC / SiC ceramic-based high-temperature, hard-brittle and difficult-to-process materials, thereby improving the uniformity of femtosecond laser material removal and avoiding stress and cracks caused by local overheating of the sealing groove, thereby improving the strain tolerance of the material, thereby obtaining higher photon absorption efficiency and uniform modified areas to greatly improve the etching quality; finally, under continuous laser thermal assistance, the ultrasonic vibration milling process is used to process the ceramic-based composite material to obtain milling in the optimal thermal softening stage and higher processing efficiency. Therefore, the present invention can effectively improve the level of intelligent manufacturing technology for key components of high-temperature, hard-brittle composite materials of my country's aero-engines. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a diagram showing the intensity distribution characteristics of a femtosecond laser according to a method for spatial beam shaping based on flat-top light according to an embodiment of the present invention; Figure 2 Schematic diagram of the control of the dual-mode switching module according to an embodiment of the present invention; Figure 3 This is a diagram of a method for processing a sealing groove by using femtosecond laser cold etching + continuous laser thermal assistance + ultrasonic vibration milling according to an embodiment of the present invention; Figure 4 Schematic diagram of a processing device according to an embodiment of the present invention; Figure 5 Schematic diagram of a stress analysis and quality monitoring platform according to an embodiment of the present invention; Figure 6 This is a predictive analysis model for coupling parameter sensitivity and shape evolution according to an embodiment of the present invention. DETAILED DESCRIPTION

[0016] In the following description, specific details such as specific system structures and techniques are provided for purposes of illustration rather than limitation to facilitate a thorough understanding of the embodiments of the present application. However, it will be apparent to those skilled in the art that the present application may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid obscuring the description of the present application with unnecessary detail.

[0017] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or collections thereof.

[0018] It will also be understood that the term "and / or" used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0019] As used in this specification and the appended claims, the term "if" can be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]," depending on the context.

[0020] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0021] References to "one embodiment" or "some embodiments" in this specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present application. Thus, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," and "in other embodiments" appearing in various places in this specification do not necessarily refer to the same embodiment, but rather mean "one or more but not all embodiments," unless otherwise specifically emphasized. The terms "including," "comprising," "having," and variations thereof all mean "including but not limited to," unless otherwise specifically emphasized.

[0022] Example 1 The present invention proposes a laser hot and cold dual-mode ultrasonic milling method for ceramic-based turbine outer ring sealing grooves, which blocks the defect propagation path during the processing and improves the strain tolerance of composite materials. First, the evolution characteristics of the flat-top light spatial shaping femtosecond laser are studied, and a femtosecond laser spatial shaping module is established to achieve low-damage etching of the groove bottom and optimize the stress distribution of the sealing groove. Secondly, a mathematical model between the energy field coupling parameters and the aspect ratio is designed, and the established parameter sensitivity and shape evolution prediction analysis model is combined to study the distribution modulation effect of the multi-energy field coupling parameters. A decision-making method for the preparation process of ceramic-based composite large aspect ratio sealing grooves based on different characteristic structural requirements is proposed, and the processing of large aspect ratio sealing grooves is completed by using laser hot and cold dual-mode two-step assistance + ultrasonic vibration milling. Specifically, the following steps are included: Step 1: Pre-treat the surface of the ceramic matrix composite material to be processed The ceramic-based composite material to be processed is immersed in acetone to remove surface grease and organic pollutants; an ultrasonic cleaning machine is then used for auxiliary cleaning, and the ceramic-based composite material to be processed is then rinsed with deionized water to remove residual solvents, and finally dried to obtain the pretreated ceramic-based composite material to be processed.

[0023] Step 2: Using a pre-built mathematical model to obtain energy field coupling parameters corresponding to the target aspect ratio, wherein the energy field coupling parameters include femtosecond laser processing parameters, infrared continuous laser processing parameters, and ultrasonic vibration milling processing parameters.

[0024] Step 3: shaping the femtosecond laser beam into a flat-top beam, and using the flat-top beam to cold-etch the pretreated ceramic matrix composite material to be processed, thereby obtaining groove boundaries and a network groove structure in the processing area of the pretreated ceramic matrix composite material to be processed. The flat-top beam is used for processing to block the defect propagation path during the processing, improve the strain tolerance of the composite material, and isolate the processing area from the non-processing area; In step 4, the infrared continuous laser beam is shaped into a flat-top beam, and the flat-top beam of the infrared continuous laser is used to form a heat-assisted mode in the processing area. At the same time, ultrasonic vibration milling is started to process a large aspect ratio blind groove based on step 2 to form a ceramic-based turbine outer ring sealing groove.

[0025] Among them, the thermal effect of infrared laser is used to improve the room temperature brittleness of composite materials and reduce the hardness of materials, thereby reducing the processing defects of composite materials and reducing tool wear; ultrasonic vibration reduces the cutting heat and tool wear of milling cutters through periodic separation and stress superposition effects, and on the other hand, high-frequency vibration improves the fatigue performance of the material surface; the coupling effect of multi-energy fields is used to assist the milling cutter to achieve high-precision and high-efficiency removal of ceramic-based composites.

[0026] Step 5: Use the sealing groove edge stress analysis and quality monitoring platform to monitor the material morphology and stress evolution and analyze the material removal process.

[0027] Step 6: Use an ultrasonic cleaner to remove debris deposited during the processing.

[0028] In view of the processing requirements of large aspect ratio sealing grooves in ceramic-based composites, traditional mechanical processing cannot achieve low-damage processing. Single femtosecond pulse laser processing has problems such as secondary deposition on the wall. The Gaussian energy distribution of the laser can easily lead to local thermal stress concentration and thermal damage. Therefore, in this embodiment, the femtosecond laser and the infrared continuous laser are spatially shaped to form a corresponding flat-top beam, and the flat-top beam is used to process the pre-treated ceramic-based composite material to be processed, thereby improving the uniformity of femtosecond laser removal of materials, avoiding stress and cracks caused by local overheating of the sealing groove, and improving the strain tolerance of the material, thereby obtaining a higher photon absorption efficiency and a uniform modified area to greatly improve the etching quality.

[0029] Example 2 Based on Example 1, this embodiment provides a method for laser hot and cold dual-mode ultrasonic milling of a ceramic-based turbine outer ring sealing groove. In step 2, the pre-constructed mathematical model is specifically constructed as follows: Based on the RSM model, a mathematical model between energy field coupling parameters and aspect ratio is established, wherein the energy field coupling parameters include femtosecond laser processing parameters, infrared continuous laser processing parameters, and ultrasonic vibration milling processing parameters; The significance, goodness of fit and residual analysis of the mathematical model were verified using the ANOVA statistical method to obtain the verification results; The principal component analysis method is used to evaluate the influence of the input parameters of the mathematical model on the output response and obtain the evaluation results; The mathematical model is optimized using the verification and evaluation results to obtain an optimized mathematical model between the energy field coupling parameters and the aspect ratio.

[0030] Example 3 Based on Example 1, this embodiment provides a laser hot and cold dual-mode ultrasonic milling method for ceramic-based turbine outer ring sealing grooves. In step 3, the flat-top beam is used to cold-etch the pretreated ceramic-based composite material to be processed to obtain the groove boundary and network groove structure of the pretreated ceramic-based composite material to be processed. The specific method is: S1. Adjust the axis of the flat-top light spatial shaping module to coincide with the laser axis to obtain a flat-top light with uniform light field distribution. Adjust the laser spot so that it is located at the center of the energy distribution. Move the processing station to a position three times the Rayleigh length of the beam above the laser focus. Adjust the laser dynamic focusing module to the collimated state so that the femtosecond laser energy distribution shows a laser energy assessment distribution of 90% and an edge sidelobe width of less than 10μm.

[0031] S2. Set the femtosecond laser for femtosecond cold etching and adjust the laser processing focus position to -53.76 mm. The shaped laser passes through the dynamic focusing module and collimation module to reach the cold etching station.

[0032] S3. Setting the femtosecond laser scanning path to a mesh groove structure based on the target aspect ratio of the turbine outer ring sealing groove and the dimensional parameters of the ceramic matrix composite material to be processed; The length and width of the mesh lines of the mesh groove structure path are set according to the size parameters of the ceramic matrix composite material to be processed. The mesh line scanning speed is 0.04 mm / s. At the same time, the maximum interval between two adjacent mesh lines is set to be less than 30 μm.

[0033] S4. Starting the cold etching mode according to the femtosecond laser processing parameters confirmed in step 2, wherein the femtosecond laser processing parameters include laser wavelength, laser energy, repetition frequency, number of scans, and defocusing amount.

[0034] Specifically, in this embodiment, the laser wavelength is set to 1030 nm, the single pulse energy is set to 150-195 μJ, the repetition frequency is set to 50-75 kHz, and the defocus is set to -0.85 mm.

[0035] S5. Monitor the morphology and stress evolution of the ceramic matrix composite material to be processed, guide the actual processing, record the process status, set a threshold, and alarm when the threshold is exceeded to stop processing, thereby blocking the defect propagation path at the boundary of the processing groove, improving the strain tolerance of the ceramic matrix composite material, and meeting the preparation requirements of high-quality sealing grooves.

[0036] Example 4 Based on Example 1, this embodiment provides a laser hot and cold dual-mode ultrasonic milling method for ceramic-based turbine outer ring sealing grooves. In step 4, a flat-top beam of an infrared continuous laser is used to form a heat-assisted mode in the processing area. At the same time, ultrasonic vibration milling is started to process a blind groove with a large aspect ratio based on step 2 to form a ceramic-based turbine outer ring sealing groove. The specific method is as follows: S1. Adjust the axis of the flat-top light spatial shaping module to coincide with the laser axis, adjust the deflection position so that the laser spot is located at the center of the energy distribution, move the processing station to four times the Rayleigh length of the beam above the laser focus, and adjust the laser dynamic focusing module to the collimated state so that the infrared continuous laser energy distribution shows a laser energy assessment distribution of 95% and the edge sidelobe width is less than 5μm.

[0037] S2. Set the infrared continuous laser output mode to perform continuous laser thermal assistance and adjust the laser processing focus position to -56.42mm to achieve a better thermal assistance effect. The boundary of the continuous laser thermal assistance area does not exceed the mesh boundary area of the "cold etching" process.

[0038] S3. Setting the continuous laser scanning path to a grid shape according to the target aspect ratio of the turbine outer ring sealing groove and the size parameters of the ceramic matrix composite material to be processed; According to the size parameters of the ceramic matrix composite material to be processed, the interval between two adjacent gratings is set to 15~20μm, the grating scanning speed is 0.04mm / s, and the scanning area corresponds to the target parameters of the sealing groove.

[0039] S4. Start the thermal assistance mode according to the infrared continuous laser processing parameters confirmed in step 2. The infrared continuous laser processing parameters include laser wavelength, repetition frequency, number of scans, power and defocus.

[0040] Specifically, in this embodiment, the laser wavelength is set to 1030 nm, the power is 30-40 W, the defocus is -1.25 mm, the scanning speed is 0.2-0.4 mm / s, and the shaped flat-top light passes through the dynamic focusing module and the collimation module to reach the thermal assist station.

[0041] S5. At the same time, ultrasonic vibration milling processing is started according to the ultrasonic vibration milling processing parameters confirmed in step 2. The ultrasonic vibration milling processing parameters include parameters such as amplitude, phase, vibration frequency and direction.

[0042] Specifically, in this embodiment, the vibration frequency is 40~60 kHz, the amplitude is 28±2 μm, the ultrasonic direction is set to three-axis resonance, and the phase difference is Π / 3, so as to improve the working state of the milling cutter and the chip removal channel and meet the preparation requirements of high-quality sealing grooves.

[0043] The milling cutter was positioned within 40μm of the infrared continuous laser focal point. The spindle speed was set at 650-700 rpm, the feed rate at 850-1000 mm / min, and the milling depth at 2-10 mm. The milling cutter position followed the laser scanning path to achieve optimal milling during the thermal softening phase and achieve higher efficiency. A high-speed vision and stress sensor in-situ measurement system was used to track the machining morphology and stress evolution of the sealing groove, monitoring the tool-chip time series images during the composite energy field machining process.

[0044] Example 5 Based on Example 1, this example provides a laser hot and cold dual-mode ultrasonic milling method for ceramic-based turbine outer ring sealing grooves. In steps 3 and 4, the aberration generation and compensation method of an aspheric lens is used to spatially shape the femtosecond laser beam and the infrared continuous laser beam, respectively, to convert the Gaussian beam into a flat-top beam, thereby ensuring uniform energy distribution in the sealing groove processing area and reducing stress concentration and wall taper of the grid groove.

[0045] Example 6 Based on Example 5, this embodiment provides a laser hot and cold dual-mode ultrasonic milling method for ceramic-based turbine outer ring sealing grooves. The method utilizes the aberration generation and compensation method of an aspheric lens to spatially shape the femtosecond laser beam and the infrared continuous laser beam, respectively, to convert the Gaussian beam into a flat-top beam. The specific method is as follows: S1: Establish a circular aperture Fraunhofer diffraction optimization model and use the inverse process to establish a remote ideal flat-top beam model. Based on the Fraunhofer diffraction formula, after model simplification, a scalar distribution model of the field intensity on the Z0 plane is obtained. This helps to obtain the theoretical field intensity value at the processing position and guide actual processing. The theoretical value can be combined with the actual processing effect to analyze the internal mechanism of laser removal of CMC materials. The optical path can also be further adjusted based on this model to control the optical elements in the laser propagation path to obtain the target theoretical value:

[0046] in, is a constant; is the gamma function; is the nth-order Bessel function of the first kind; Is the source plane Upper distance The distance between the axes, where ; is the space constant.

[0047] S2, with the above The light source state at is taken as the source plane. Under the condition of paraxial approximation, the distance from the source plane is obtained according to the Fraunhofer diffraction integral. G point on the plane Complex amplitude for:

[0048] Where R is the distance from point G on the observation plane to the optical axis, ; h is the distance between the source / target planes, ; is the complex amplitude distribution in the source plane; is the laser wavelength; is the wave number.

[0049] S3, after integration operation, we can know the lambda ideal flat-top beam transmission amplitude model:

[0050] The above model derivation shows that: the transmission distance It does not affect the light intensity distribution of the first-order lambda beam, that is, the shape of the flat-top light is not affected by the transmission distance, but the energy decreases with the increase of the transmission distance.

[0051] S4, according to the paraxial approximation principle, the field intensity of the light beam transmitted through the lens to the focal plane behind the lens can be obtained:

[0052] The results show that the electric field on the focal plane has a clear boundary and the boundary intensity is zero. represents the diffraction angle, then the electric field boundary at the focal plane is: The boundary field intensity drops sharply to 0, and the final spatial Gaussian light source can be regarded as an ideal spatial flat-top light after being modulated by the above model.

[0053] Example 7 like Figure 3 As shown, this embodiment provides a laser hot and cold dual-mode ultrasonic milling processing device for a ceramic-based turbine outer ring sealing groove, comprising a five-axis machining center 1, a three-dimensional galvanometer 2, an ultrasonic-assisted milling module 3, a flat-top light spatial shaping module 4, a dynamic focusing module 5, a plasma detection module 6, a high-speed camera 7, an infrared imaging module 8, a continuous laser 9, a femtosecond pulse laser 10, a base 11, and a vibration detection sensor 12, wherein: A continuous laser 9 and a femtosecond pulse laser 10 are provided on the base 11 of the five-axis machining center 1. The laser beams emitted by the continuous laser 9 and the femtosecond pulse laser 10 are incident on the flat-top light spatial shaping module 4 for beam shaping in the cold etching stage and the thermal assistance stage, respectively, to form flat-top lights; both beams of flat-top light pass through the dynamic focusing module 5 and the collimation module in turn and are incident on the processing area of the ceramic-based composite material to be processed.

[0054] The control ends of the continuous laser 9 and the femtosecond pulse laser 10 are both connected to a multi-mode switching module.

[0055] The continuous laser 9 and the femtosecond pulse laser 10 are controlled by the multi-mode switching module; they are incident on the flat top light spatial shaping module 4 for beam shaping in the cold etching stage and the thermal assisted stage respectively, forming flat top lights; both flat top lights pass through the dynamic focusing module 5 and the collimation module in turn and are incident on the processing area of the ceramic matrix composite material to be processed A stress analysis and quality monitoring platform is also installed on the column of the five-axis machining center 1. The stress analysis and quality monitoring platform includes a plasma detection module 6, a high-speed camera 7 and an infrared imaging module 8, wherein: The plasma detection module 6 collects plasma generated during the machining process. By analyzing the plasma's spectral intensity and wavelength distribution, it can determine whether the machining process is stable. Abnormal spectral peaks indicate process deviations, surface contaminants, or incomplete coating removal. This module facilitates guidance in actual machining, automatically adjusting process parameters such as laser energy based on the plasma signal. It also helps detect defects during machining, optimize machining quality, and achieve online real-time stress control.

[0056] The high-speed camera 7 is used to monitor the machining morphology and stress evolution of the sealing groove, and to monitor the tool-chip time series images during the composite energy field machining process.

[0057] The infrared imaging module 8 is used to capture the laser thermal field distribution and energy propagation and dissipation modes.

[0058] The process monitoring system is composed of a plasma detection module, a high-speed camera and an infrared thermal imager. It collects laser-induced breakdown spectroscopy (LIBS), analyzes the material removal status in real time, collects the cutting process, and performs vibration modal analysis to monitor the evolution of the heat-affected zone (HAZ) at temperatures up to 1500°C.

[0059] Example 8 Example of spatial shaping of femtosecond laser flat-top beam This embodiment proposes a femtosecond laser flat-top beam shaping method to achieve the fabrication of high-quality sealing grooves with a large aspect ratio. According to the femtosecond laser resonant diffraction theory, the spatial electric field distribution of the Gaussian laser is obtained as follows:

[0060] in: is the central electric field distribution, is a constant factor, To gird the waist, is the wavelength, is the spatial distribution position, is the spatial beam cross-sectional radius, is the wave number.

[0061] The aberration of the aspheric lens is used to perform flat-top light spatial shaping. Based on the Fourier transform and spatial filtering method, the spatial spectrum shaping of the electric field is achieved. The radius of the beam after shaping is:

[0062] in: is the optical system distance parameter, is the spatial axis position, is the wavelength.

[0063] The aberration is:

[0064] in: are the aberration coefficients at each level, is the aberration angle.

[0065] Since the optical system is composed of a series of optical elements, in order to make the shaping result appear flat, it is necessary to eliminate the spherical aberration and balance the aberration effect to correct it to zero:

[0066] in: are the aberration coefficients at each level, is the aberration height.

[0067] Therefore, the achieved spatial beam shaping result is:

[0068] Finally, the control model of the electric field spectrum of the flat-top beam is established as follows:

[0069] in: It is a spatially shaped distribution.

[0070] Table 1 Femtosecond laser flat-top beam shaping

[0071] Example 9 Analytical model of RSM fabricated with ceramic-based composites for sealing grooves with large aspect ratios This method was used to create a micro-groove with a large aspect ratio on a 3mm thick ceramic-based composite. During the femtosecond laser sealing process, the workpiece was fixed on an XYZ motion platform, and a scanning galvanometer was used to move the laser beam along a specific path relative to the workpiece. The scanning speed of the galvanometer used in this experiment can reach 1000mm / s. To study the processing influence of the optimal process, the process parameters during the experiment were: The femtosecond laser wavelength is 1030 nm, the single pulse energy is 195 μJ, the repetition frequency is 50 kHz, the closed slot path is 100 μm long and 30 μm wide, the defocus is -0.85 mm, and the scanning speed is 0.04 mm / s.

[0072] The continuous laser wavelength is 1030 nm, the power is 32W, the defocus is -1.25mm, the scanning speed is 0.2mm / s, and the shaped laser passes through the dynamic focusing and collimation module to reach the thermal assist station.

[0073] The frequency of the ultrasonic field is 40 kHz, and the amplitude of the ultrasonic vibration field is 28 μm.

[0074] The spindle speed of the milling cutter is 650r / min, the feed speed is 850mm / min, and the milling depth is 2mm.

[0075] The defect propagation path at the boundary of the processed groove is blocked, the strain tolerance of the ceramic matrix composite material is improved, and the preparation requirements of high-quality sealing grooves are met.

[0076] To establish an optimization model for achieving high-quality production of sealing grooves with large aspect ratios, this paper employed the RSM regression model. Based on the principles of central composite design (CCD), an experimental scheme was designed to optimize the production of sealing grooves and improve wall quality. Three independent variables were selected: ultrasonic amplitude (A), single pulse energy (E), and cutting speed (V). Seventeen experiments were selected. Roughness was chosen as the response variable to analyze mapping relationships and optimize process parameters. After comprehensive consideration, a cubic analysis model was established to accurately describe the relationship between the independent and dependent variables. The final regression model for each response was as follows:

[0077] Table 2 Analysis of variance of the surface roughness RSM quadratic model

[0078] Figure 6 The predicted and actual values of the roughness response model were compared. The agreement between the predicted and actual values confirmed the high accuracy of the constructed regression model. Table 2 summarizes the ANOVA results for surface roughness. The model showed a certain significance, as evidenced by the P value below 0.0001 and the lack of fit P value exceeding 0.05, indicating that the systematic error is minimal. The high predictive ability of the model is confirmed by R 2 The value is 0.9942, and the adjusted R 2 is 0.991, and the predicted R 2The difference between the two values is within 0.2. Furthermore, the ADEQ accuracy value is 66.55, significantly above the threshold of 4, and the signal-to-noise ratio is excellent. A CV % <10 demonstrates the reliability and accuracy of the model in predicting roughness.

[0079] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. A laser hot and cold dual-mode ultrasonic milling method for ceramic-based turbine outer ring sealing groove, characterized in that: The following steps are involved: Step 1: using a pre-built mathematical model to obtain energy field coupling parameters corresponding to the target aspect ratio, wherein the energy field coupling parameters include femtosecond laser processing parameters, infrared continuous laser processing parameters, and ultrasonic vibration milling processing parameters; Step 2: shaping the femtosecond laser beam to form a flat-top beam of the femtosecond laser; using the femtosecond laser processing parameters determined in step 1, combined with the flat-top beam of the femtosecond laser, cold etching the to-be-processed area of the ceramic matrix composite material to be processed, so that a groove boundary and a network groove structure are formed in the to-be-processed area of the ceramic matrix composite material to be processed; In step 3, the infrared continuous laser beam is shaped into a flat-top beam, and the infrared continuous laser processing parameters determined in step 1 are used to form a heat-assisted mode in the processing area. At the same time, the ultrasonic vibration milling processing parameters are used to process a large aspect ratio blind groove based on step 2 to form a ceramic-based turbine outer ring sealing groove.

2. The method for laser hot and cold dual-mode ultrasonic milling of ceramic-based turbine outer ring sealing groove according to claim 1 is characterized in that: The aberration generation and compensation method of the aspheric lens is used to spatially shape the femtosecond laser beam in step 2 and the infrared continuous laser beam in step 3, respectively, so as to convert the Gaussian beam into a flat-top beam.

3. The method for laser hot and cold dual-mode ultrasonic milling of ceramic-based turbine outer ring sealing groove according to claim 1 is characterized in that: In step 2, a femtosecond laser flat-top beam is used to cold-etch the area to be processed of the ceramic matrix composite material to be processed, so that a groove boundary and a network groove structure are formed in the area to be processed of the ceramic matrix composite material to be processed. The specific method is: According to the target depth-to-diameter ratio of the turbine outer ring sealing groove and the dimensional parameters of the ceramic matrix composite material to be processed, the femtosecond laser scanning path is set to a mesh groove structure; According to the size parameters of the ceramic matrix composite material to be processed, the length and width of the grid lines, the scanning speed of the grid lines and the spacing of the grid lines of the femtosecond laser scanning are set; The cold etching mode is started in combination with the femtosecond laser processing parameters determined in step 1, so that a groove boundary and a network groove structure are formed in the to-be-processed area of the to-be-processed ceramic matrix composite material.

4. The method for laser hot and cold dual-mode ultrasonic milling of ceramic-based turbine outer ring sealing groove according to claim 3 is characterized in that: The scanning speed of the mesh lines is 0.04 mm / s; the maximum distance between two adjacent mesh lines is less than 30 μm.

5. The method for laser hot and cold dual-mode ultrasonic milling of ceramic-based turbine outer ring sealing groove according to claim 1 is characterized in that: In step 3, the infrared continuous laser beam is shaped into a flat-top beam. Based on step 2, a blind groove with a large aspect ratio is machined using the flat-top beam of the infrared continuous laser, ultrasonic vibration method, and milling method to form a ceramic-based turbine outer ring sealing groove. The specific method is: According to the target depth-to-diameter ratio of the turbine outer ring sealing groove and the size parameters of the ceramic matrix composite material to be processed, the continuous laser scanning path is set to a grid shape, and the scanning path parameters are set; Combined with the infrared continuous laser processing parameters determined in step 1, the thermal assistance mode is turned on; By combining the ultrasonic vibration milling processing parameters determined in step 1, the ultrasonic vibration auxiliary platform is turned on to process the ceramic matrix composite material to be processed.

6. The method for laser hot and cold dual-mode ultrasonic milling of ceramic-based turbine outer ring sealing groove according to claim 1 is characterized in that: The interval between adjacent gratings in the scanning path parameters is 15~20μm, and the grating scanning speed is 0.04mm / s.

7. The method for laser hot and cold dual-mode ultrasonic milling of ceramic-based turbine outer ring sealing groove according to claim 1 is characterized in that: The pre-built mathematical model is constructed as follows: Based on the RSM model, a mathematical model between energy field coupling parameters and aspect ratio is established, wherein the energy field coupling parameters include femtosecond laser processing parameters, infrared continuous laser processing parameters, and ultrasonic vibration milling processing parameters; The significance, goodness of fit and residual analysis of the model were verified using ANOVA statistical method to obtain the verification results; The principal component analysis method is used to evaluate the influence of the input parameters of the mathematical model on the output response and obtain the evaluation results; The mathematical model is optimized using the verification and evaluation results to obtain an optimized mathematical model between the energy field coupling parameters and the aspect ratio.

8. A laser hot and cold dual-mode ultrasonic milling device for ceramic-based turbine outer ring sealing groove, characterized in that: It includes a five-axis machining center, on which a continuous laser and a femtosecond pulse laser are provided, and the control ends of the continuous laser and the femtosecond pulse laser are connected to a multi-mode switching module; The laser beam emitted by the femtosecond pulse laser is incident on the flat-top light spatial shaping module for beam shaping to form a flat-top light; The laser beam emitted by the continuous laser is incident on the flat-top light spatial shaping module for beam shaping to form a flat-top light; The flat-top light of the femtosecond pulse laser and the flat-top light of the continuous laser are both incident on the processing area of the ceramic-based composite material to be processed; The multi-mode switching module is used to control the start and stop of the femtosecond pulse laser and the continuous laser, thereby controlling the femtosecond pulse laser to perform the cold etching stage and the continuous laser to perform the thermal assistance stage.

9. The laser hot and cold dual-mode ultrasonic milling processing device for ceramic-based turbine outer ring sealing groove according to claim 8 is characterized in that: Both beams of flat-top light are incident on the processing area of the ceramic-based composite material to be processed through the dynamic focusing module.

10. The laser hot and cold dual-mode ultrasonic milling processing device for ceramic-based turbine outer ring sealing groove according to claim 9, characterized in that: The output end of the dynamic focusing module is provided with a collimating module.

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