A device and process for laser ablation induced controlled damage assisted grinding of hard and brittle materials

Abstract

The application discloses a device and a process for laser ablation induced controllable damage assisted grinding of hard and brittle materials, which adopts laser irradiation on the material surface, focuses the laser focal point on the material surface to be processed, removes and induces specific depth damage to the material by ablation. By controlling the laser power, scanning speed and ablation track, the degree and type of laser ablation induced thermal damage of the material are effectively controlled. The grinding path of the grinding wheel and the ablation path of the laser are controlled on the same axis, and the distance between the laser ablation and the grinding wheel grinding is set, and the workpiece ablation surface is ground under the preferred grinding parameters. The application systematically puts forward a quantitative control strategy for the degree of laser ablation damage of the material surface, removes the laser induced damage layer by accurate control of the material surface damage and precision grinding, and realizes high-efficiency and high-quality processing of the hard and brittle materials.

Description

Technical Field

[0001] This invention belongs to the field of laser-assisted processing, and in particular relates to a device and process for laser ablation-induced controllable damage-assisted grinding of hard and brittle materials in the field of difficult-to-machine hard and brittle materials. Background Technology

[0002] Hard and brittle materials such as reaction-bonded silicon carbide, WC / Co cemented carbide, and ceramic matrix composites possess excellent mechanical properties, including high hardness, high strength, high temperature resistance, and oxidation resistance. However, their high brittleness and hardness pose challenges to machining. Machining processes lead to severe tool wear, making it difficult to guarantee the surface quality of the machined material. Single grinding suffers from problems such as easy surface cracking, low efficiency, and rapid tool wear. Brittle fracture and subsurface cracks on the surface of hard and brittle materials severely affect the mechanical properties and service life of machined parts. Therefore, improving the machining quality and efficiency of hard and brittle materials has become an urgent problem to be solved.

[0003] Laser-assisted grinding, laser-assisted turning, and laser-assisted milling technologies have gradually become research hotspots in recent years. However, thermal softening has little effect on high-temperature resistant materials. High-energy laser beams have a relatively concentrated energy density, and the ablation process yields materials with advantages such as controllable ablation area, ablation depth, and ablation damage. Laser ablation removes material while precisely controlling the degree of surface damage, and the modified material surface is then removed through grinding. This enables high-quality, high-efficiency, and precision machining of difficult-to-machine materials. Materials include reaction-bonded silicon carbide, WC / Co cemented carbide, and ceramic matrix composites, among other hard and brittle materials, to improve the surface quality of difficult-to-machine materials and increase tool life.

[0004] To eliminate and control surface damage after grinding of hard and brittle materials, this paper combines the advantages of laser processing and grinding to develop a laser ablation surface damage control-assisted grinding process for hard and brittle materials. This provides an effective measure to solve the problem of difficult processing of such materials.

[0005] Current research on laser-assisted grinding mainly focuses on optimizing processing parameters, including laser parameter optimization and scanning trajectory optimization. However, research on internal damage issues has not yet been conducted. Zheng Dihao et al. from Shanghai University of Science and Technology optimized the influence of laser scanning patterns on the processing quality of silicon nitride, finding that a regular annular pattern is the optimal laser-induced microgroove trajectory. However, in-depth research has not been carried out on the impact of precise control of ablation damage on surface quality. Liu Wei et al. from Hunan University of Science and Technology conducted laser-modified grinding of silicon carbide ceramics, reducing the surface hardness of the material by laser irradiation. However, the precise control of laser power on the degree of crack propagation on the material surface has not been explored. Furthermore, the lack of laser ablation to remove material limits the grinding depth and the amount of material removed.

[0006] Currently, there is no published literature on precise control methods for internal damage in hard and brittle materials obtained through laser ablation. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, the purpose of this invention is to provide a device and process for laser ablation-induced controllable damage-assisted grinding of hard and brittle materials. By using laser ablation to precisely control surface damage on the material surface to assist grinding wheel grinding, the problem of difficult machining of hard and brittle materials is solved, material processing efficiency and quality are improved, and grinding wheel wear is reduced.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A device for laser ablation-induced controllable damage-assisted grinding of hard and brittle materials includes: a drive motor (1), a fastening flange (2), a laser system, a moving platform, a workpiece (5), and a grinding wheel (3); the drive motor (1) is mounted on the main body (4) of the device, and the grinding wheel (3) is mounted on the spindle of the drive motor through the fastening flange (2); the laser system is mounted on the guide rail (11) of the moving platform; and the workpiece (5) is fixed on the worktable (6) of the moving platform of the device.

[0010] The laser system adjusts the laser beam to act on the surface of the workpiece (5) and the front end of the grinding wheel in the grinding direction;

[0011] Within the laser defocus range, by precisely controlling the motion trajectory of the laser system, different types of microstructures with varying degrees of damage are obtained on the surface of the workpiece to be processed. The workpiece (5) is fed by the worktable (6), and the grinding wheel rotates while the laser ablation microstructure area is being ground.

[0012] The laser system includes: a laser controller (10), a transmission fiber (9), an optical path, and a laser galvanometer (7). The laser galvanometer is connected to the laser controller (10) via the transmission fiber (9). The laser controller (10) controls the laser parameters of the output beam, including but not limited to the incident frequency, laser power, and pulse time. The laser beam acts on the surface of the workpiece (5) through the laser galvanometer (7). The incident angle, optical path, and distance between the laser beam and the workpiece surface are adjustable. The spot position is at the front end of the grinding wheel direction, and its distance is adjusted according to the processing characteristics of different materials.

[0013] The laser controller (10) controls the laser output power, frequency and pulse width to control the energy introduced to the material surface, thereby controlling the degree of damage and obtaining different texture types on the surface of the workpiece to be processed, including but not limited to: arc texture, square texture, parallel line texture, sawtooth texture, rhombus texture and vertical line texture.

[0014] A process for laser ablation-induced controllable damage-assisted grinding of hard and brittle materials, characterized by comprising the following steps:

[0015] Step 1: Install the workpiece to be processed on the worktable of the grinding device, and install the grinding tool on the rotating spindle through the fastening flange;

[0016] Step 2: Adjust the grinding wheel and laser head of the laser system to the area of ​​the hard and brittle material to be ground. Adjust the position and angle between the laser galvanometer and the workpiece by rotating it to ensure that the laser irradiates the material surface. Adjust the distance between the laser spot and the material surface to ensure that the laser beam is within the defocus range, thus guaranteeing ablation and removal of the material surface.

[0017] Step 3: Within the laser defocus range, the laser system's trajectory is precisely controlled to perform ablation damage control on the material surface. While laser ablation removes surface material, melting, oxidation, and resolidification alter the material's surface properties; simultaneously, high temperatures cause thermally induced cracking damage within the material. To effectively control laser ablation damage, precise control of the laser pulse energy, scanning speed, and scanning trajectory is crucial to control damage distribution and depth. A Gaussian laser beam is used, and the laser heat flux on the material surface is considered the surface heat source. The laser heat flux can be expressed as:

[0018] ;

[0019] in, ;

[0020] ;

[0021] In the formula, H (τ-t) is the step function, A=1-R is the absorptivity of the material under infrared laser, R is the reflectivity, ω0 is the laser waist radius, Q0 is the laser peak energy density, and P is the laser power.

[0022] Under the condition of fixed laser scanning speed, the energy of the laser acting on the material surface can be controlled by controlling the input power P, thereby controlling the degree of ablation and damage to the material surface.

[0023] The mapping relationship between the energy Q required for material crack propagation and the ablation damage length L under rated laser power P is as follows:

[0024]

[0025] The damage length corresponding to different power percentages of i% is L. i The calculation is as follows: ;

[0026] Based on the above theoretical calculations, the correspondence between laser power control and ablation damage was obtained, thereby enabling precise control of the damage degree in laser ablation and guiding the grinding process.

[0027] Similarly, under the condition of fixed laser power, the amount of laser energy acting on the material surface can be controlled by controlling the scanning speed, thereby controlling the degree of ablation and damage to the material surface.

[0028] Laser ablation removes a portion of the material, and a planned laser scanning trajectory is used to fabricate surface microstructures while controlling the distribution of surface damage. The ablation microstructures include: circular arc textures, square textures, parallel line textures, serrated textures, rhomboid textures, and vertical line textures.

[0029] Step 4: In order to process the entire surface of the workpiece, the laser performs surface damage control scanning according to the set ablation trajectory.

[0030] Step 5: In order to completely remove the laser ablation zone on the material surface, the grinding depth of the grinding wheel should be greater than the depth of the laser ablation microstructure.

[0031] Step 6: After processing is complete, turn off the laser system and grinding equipment.

[0032] Compared with the prior art, the beneficial effects of this invention are:

[0033] (1) Based on the material properties of hard and brittle workpieces, this invention uses a laser beam to irradiate the material surface. By adjusting the defocus of the laser spot and controlling it within the laser ablation focal length range, the material is removed by laser ablation. (2) The laser beam irradiates the front end of the grinding wheel to prevent interference with the beam when ablation different microstructures. (3) The incident angle of the laser beam can be adjusted according to the processing conditions to control the shape of the grooves on the material surface ablated by the laser. (4) Precise control of the laser output energy and motion trajectory can control the degree and direction of ablation damage on the material surface. (5) The laser galvanometer is installed in front of the grinding wheel and its position is adjustable. The ablation zone is consistent with the grinding zone. By precisely controlling the damage to the material surface and coordinating the laser ablation and grinding processes, efficient and precise grinding of hard and brittle materials can be achieved. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of a device for laser ablation-induced controllable damage-assisted grinding of hard and brittle materials according to the present invention.

[0035] Figure 2 This invention relates to the effect of laser power on the ablation damage of hard and brittle materials. Specifically: (a) ablation characteristics of the material at a laser power of 30W, (b) ablation characteristics of the material at a laser power of 60W, and (c) ablation characteristics of the material at a laser power of 90W.

[0036] Figure 3 This invention relates to the effect of laser scanning trajectory on ablation damage of hard and brittle materials.

[0037] Figure 4 This is an example of laser scanning processing according to the present invention.

[0038] Figure 5 This invention provides an example of laser ablation-induced controllable damage-assisted grinding of hard and brittle materials; wherein: (a) no laser ablation-assisted grinding is performed; and (b) laser ablation-assisted grinding is performed (damage type is parallel line texture).

[0039] In the diagram: 1-Drive motor; 2-Fasting flange; 3-Grinding wheel; 4-Main body of the device; 5-Workpiece; 6-Worktable; 7-Laser galvanometer; 8-Beam; 9-Fiber optic cable; 10-Laser controller; 11-Guide rail; 12-Grinding debris; 13-Laser ablation microstructure; 14-Diamond. Detailed Implementation

[0040] The present invention will now be described in detail with reference to the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0041] Figure 1 This is a schematic diagram of the device used in the present invention. Figure 1 As shown, a device for laser ablation-induced controllable damage-assisted grinding of hard and brittle materials includes: a drive motor 1, a fastening flange 2, a laser system, a moving platform, a workpiece 5, and a grinding wheel 3. The drive motor 1 is mounted on the main body 4 of the device, and the grinding wheel 3 is mounted on the spindle of the drive motor via the fastening flange 2; the laser system is mounted on the guide rail 11 of the moving platform; and the workpiece 5 is fixed on the worktable 6 of the moving platform.

[0042] The grinding wheel 3 is a diamond wheel or a CBN wheel; in the following embodiment, it is a resin-bonded diamond wheel with an abrasive grain diameter of 76 μm. The hard and brittle material is reaction-sintered SiC, single-crystal silicon, WC / Co cemented carbide, and ceramic matrix composites, etc.; in the following embodiment, it is WC / Co cemented carbide.

[0043] The laser system includes a laser controller 10, a transmission fiber 9, an optical path, and a laser galvanometer 7. The laser galvanometer is connected to the laser controller 10 via the transmission fiber 9. The laser controller 10 can control parameters such as the incident frequency, laser power, and pulse duration of the output beam. The laser beam acts on the surface of the workpiece 5 through the laser galvanometer 7, and the incident angle of the laser beam is adjustable. The spot position is at the leading edge of the grinding wheel in the grinding direction, and its distance is adjusted according to the processing characteristics of different materials.

[0044] Specifically, during use, the laser galvanometer 7 adjusts its position relative to the workpiece 5 using a fine-tuning device, thereby ensuring that the laser beam 8 can perform ablation control within the laser defocus range. The output beam of the laser galvanometer 7 can be modified by designing the optical path to achieve precise and controllable laser scanning trajectory on the workpiece surface.

[0045] Different damage types are obtained by precisely controlling the motion trajectory of the laser galvanometer 7, and then the workpiece 5 is fed by the worktable 6. The grinding wheel rotates at the same time to achieve grinding of the laser ablation microstructure area.

[0046] Example 1

[0047] The effects of different laser powers on the ablation depth and damage extent of the ablation material surface were investigated, such as... Figure 2 As shown. The ablation characteristics of the material at a laser power of 10W are as follows. Figure 2 As shown in (a), lower laser power results in less material ablation and less thermally affected damage. At a laser power of 30W, higher power increases the degree of material ablation, and higher laser energy leads to increased ablation crack damage, such as... Figure 2 As shown in (b), when the laser power is further increased to 50W, the ablation damage further increases. Different degrees of ablation and damage are obtained according to different laser powers.

[0048] The laser controller 10 controls the laser output power, scanning speed, and scanning trajectory to control the energy introduced onto the material surface, thereby controlling the degree of damage. In this embodiment, an ideal Gaussian beam is used, and the laser heat flux on the material surface is considered as a surface heat source, which can be expressed as:

[0049]

[0050] in,

[0051]

[0052] In the formula, H (τ-t) is the step function, A=1-R is the absorptivity of the material under infrared laser, R is the reflectivity, ω0 is the laser waist radius, Q0 is the laser peak energy density, and P is the laser power.

[0053] Under the condition of fixed laser scanning speed, the energy of the laser acting on the material surface can be controlled by controlling the input power P, thereby controlling the degree of ablation and damage to the material surface.

[0054] The mapping relationship between the energy Q required for material crack propagation under rated laser power P and the ablation damage length L is obtained as follows:

[0055]

[0056] The damage length corresponding to different power percentages of i% is L. i The calculation is as follows:

[0057] The feeding motion of the workbench 6 enables the diamond 14 on the surface of the grinding wheel 3 to perform grinding on the material surface. The grinding process of the grinding wheel is controlled according to the actual degree of laser ablation damage, so as to obtain the optimal machining surface quality.

[0058] For example, when the laser power is 50W, the scanning speed is 40mm / s, and the pulse frequency is 50kHz, the surface trajectory characteristics and damage obtained by one scan are as Figure 4 shown in (f).

[0059] In this embodiment, the grinding workpiece is WC / Co cemented carbide. Design a laser scanning trajectory as Figure 3 shown (including but not limited to: horizontal straight line, vertical straight line, broken line, arc, "field" shape, diamond). According to the designed laser trajectory, workpieces with different damage depths and degrees of modification materials on the surface are processed as Figure 4 shown (including but not limited to: arc line texture, square texture, parallel line texture, zigzag texture, diamond texture and vertical line texture). Compare the surface of the material after grinding without introducing laser and the surface of the material after grinding with laser ablation controlled damage. The results show that when grinding the material without introducing laser ablation, there is plowing and rubbing of some materials on the surface. At the same time, due to the brittle removal of the material after laser ablation damage, continuous fragmentation and micro-pits are generated on the surface after grinding. However, the difference in the exposed height of the abrasive grains on the surface of the diamond grinding wheel is relatively large, making it difficult to统一 the cutting thickness of a single abrasive grain during grinding, which in turn affects the different material removal mechanisms. When the cutting thickness of a single abrasive grain is greater than the critical cutting thickness of the material, the material is mainly removed in the brittle domain; when the cutting thickness of a single abrasive grain is less than the critical cutting thickness of the material, the material mainly undergoes plastic domain removal, as Figure 5 shown in (a). During grinding with the grinding wheel, the high brittleness of WC grains leads to severe fragmentation in the grinding area. Using the same grinding parameters, when grinding the surface of the material with laser ablation damage, the proportion of plastic removal on the grinding surface of laser-assisted machining increases significantly, a large number of plowing grooves are generated, and obvious plastic bulges appear on both sides of the scratches under the extrusion of the abrasive grains, indicating that obvious plastic flow occurs in the material and the surface quality is significantly improved, as Figure 5 shown in (b).

[0060] [[ID=第十九]]The above embodiments of the invention should be understood that these embodiments are only used to illustrate the invention more clearly. Instead of limiting the scope of the invention, after reading the invention, various equivalent forms of modification of the invention by those skilled in the art fall within the scope defined by the appended claims of this application.

Claims

1. A device for laser ablation-induced controllable damage-assisted grinding of hard and brittle materials, characterized in that, include: Drive motor (1), fastening flange (2), laser system, moving platform, workpiece (5), grinding wheel (3); the drive motor (1) is mounted on the main body (4) of the device, and the grinding wheel (3) is mounted on the spindle of the drive motor through the fastening flange (2); the laser system is mounted on the guide rail (11) of the moving platform; the workpiece (5) is fixed on the worktable (6) of the moving platform of the device; The laser system adjusts the laser beam to act on the surface of the workpiece (5) and the front end of the grinding wheel in the grinding direction; Within the laser defocus range, by precisely controlling the motion trajectory of the laser system, different types of microstructures with varying degrees of damage are obtained on the surface of the workpiece to be processed. The workpiece (5) is fed by the worktable (6), and the grinding wheel rotates simultaneously to achieve grinding processing of the laser-ablated microstructure area. The laser system includes: a laser controller (10), a transmission fiber (9), an optical path, and a laser galvanometer (7). The laser galvanometer is connected to the laser controller (10) through the transmission fiber (9). The laser controller (10) controls the laser parameters of the output beam, including the incident frequency, laser power, and pulse duration. The laser beam acts on the surface of the workpiece (5) through the laser galvanometer (7). The incident angle, optical path, and distance between the laser beam and the workpiece surface are adjustable. The spot position is at the front end of the grinding wheel in the grinding direction, and its distance is adjusted according to the processing characteristics of different materials. The laser controller (10) controls the laser output power, frequency, and pulse width to control the energy introduced to the material surface, thereby controlling the degree of damage. Different texture types are obtained on the surface of the workpiece to be processed, including circular arc texture, square texture, parallel line texture, sawtooth texture, diamond texture, and vertical line texture. The control of the degree of damage is achieved in the following ways: The laser used is an ideal Gaussian beam. The laser heat flux on the material surface is regarded as the surface heat source, which can be expressed as: ； in, ; ； In the formula, H (τ-t) is the step function, A=1-R is the absorptivity of the material under infrared laser, R is the reflectivity, ω0 is the laser waist radius, Q0 is the laser peak energy density, and P is the laser power. Under the condition of fixed laser scanning speed, the energy of the laser acting on the material surface can be controlled by controlling the input power P, thereby controlling the degree of ablation and damage to the material surface. The mapping relationship between the energy Q required for material crack propagation under rated laser power P and the ablation damage length L is obtained as follows: ； The damage length corresponding to different power percentages of i% is L. i The calculation is as follows: ； The above formula yields the corresponding relationship between laser power control and ablation damage, thus enabling precise control of the damage level through laser ablation. Similarly, under the condition of fixed laser power, the energy accumulation of the laser on the material surface can be controlled by controlling the scanning speed, thereby controlling the ablation degree and damage level of the material surface.

2. The device for laser ablation-induced controllable damage-assisted grinding of hard and brittle materials according to claim 1, characterized in that, The grinding wheel (3) is a diamond wheel or a CBN wheel; the hard and brittle materials include reaction-sintered SiC, single crystal silicon, WC / Co cemented carbide and ceramic matrix composites.

3. A process for laser ablation-induced controlled damage-assisted grinding of hard and brittle materials based on the apparatus for laser ablation-induced controlled damage assisted grinding of hard and brittle materials as described in claim 1, characterized in that... Includes the following steps: 1) Mount the workpiece to be processed on the worktable of the grinding device, and mount the grinding wheel on the rotating spindle through the fastening flange; 2) Adjust the grinding wheel and the laser head of the laser system to the hard and brittle material to be ground. Adjust the position and angle between the laser galvanometer and the workpiece by rotating the laser galvanometer to ensure that the laser irradiates the material surface. Adjust the distance between the laser spot and the material surface to ensure that the material surface is ablated and removed within the laser beam defocus range. 3) Within the laser defocus range, the ablation damage to the material surface is controlled by precisely controlling the motion trajectory of the laser system; while the laser ablates and removes the surface material, the melting, oxidation, and resolidification of the material cause changes in the surface properties; at the same time, the high temperature causes thermal crack damage inside the material; in order to effectively control the damage to the material surface by laser ablation, the laser pulse energy, scanning speed, and scanning trajectory are precisely controlled to achieve the purpose of controlling the damage distribution and damage depth; 4) The laser used is a typical Gaussian beam. The laser heat flux on the material surface is considered as the surface heat source. The laser heat flux can be expressed as: ; in, ; ； In the formula, H (τ-t) is the step function, A=1-R is the absorptivity of the material under infrared laser, R is the reflectivity, ω0 is the laser waist radius, Q0 is the laser peak energy density, and P is the laser power. Under a fixed laser scanning speed, the energy of the laser acting on the material surface is controlled by controlling the input power P, thereby controlling the degree of ablation and damage to the material surface. Under the rated laser power P, the mapping relationship between the energy Q required for crack propagation and the ablation damage length L is as follows: ； The damage length corresponding to different power percentages of i% is L. i The calculation is as follows: ； The above formula is used to calculate the correspondence between laser power control and ablation damage, thereby enabling precise control of the damage degree in laser ablation and guiding the selection of grinding process parameters. Similarly, under the condition of fixed laser power, the amount of energy accumulated by the laser on the material surface can be controlled by controlling the scanning speed, thereby controlling the ablation degree and damage degree of the material surface. 5) Laser ablation removes part of the material, and the laser scanning trajectory is planned to prepare the surface microstructure and control the distribution of surface damage. In order to completely remove the laser ablation zone on the material surface, the grinding depth of the grinding wheel should be greater than the laser ablation microstructure depth. 6) After processing is complete, turn off the laser system and the grinding wheel system.

4. The process for laser ablation-induced controllable damage-assisted grinding of hard and brittle materials according to claim 3, characterized in that, In step 1), the material of the workpiece to be processed is a hard and brittle material, including reaction-sintered SiC, single crystal silicon, WC / Co cemented carbide and ceramic matrix composites; the grinding wheel used is a diamond grinding wheel or a CBN grinding wheel.

5. The process for laser ablation-induced controllable damage-assisted grinding of hard and brittle materials according to claim 3, characterized in that, In step 2), the microstructures are ablated, including circular arc textures, square textures, parallel line textures, serrated textures, rhomboid textures, and vertical line textures.

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