A microcrack-assisted composite microstructure surface creation method

Abstract

A method for creating a composite microstructure surface assisted by microcracks belongs to the technical field of precision machining of complex microstructure surfaces of brittle materials. The composite microstructure surface creation method mainly uses active modulation of tool posture and vibration trajectory, cooperates with tool path planning, and performs processing within a cutting depth range greater than the critical cutting depth of brittle-ductile transition and less than the cutting depth of microdefects extending to the lowest point of the groove. Microcracks are used to induce machining microdefects and expand them to the surface on one side in the tool machining direction. Material removal is achieved by regulating the mutual expansion and intersection of microcracks in specific areas, or by regulating the generation of microdefects induced by microcracks at specific locations to achieve composite microstructure surface creation. This method can achieve the one-time creation of a spatial low-frequency characteristic structure with plastic removal characteristics on brittle materials and the creation of a spatial high-frequency brittle crack removal characteristic composite microstructure surface in a plastic low-frequency space, with high efficiency and low cost.

Description

Technical Field

[0001] The invention relates to a microcrack-assisted composite microstructure surface creation method, belonging to the technical field of precision machining of complex microstructure surfaces of brittle materials. Background Art

[0002] At present, complex surfaces based on difficult-to-process materials are widely used in high-tech and high-value-added fields such as aerospace, national defense and military, microelectronic devices and optical components. However, due to the difficult cutting process of such materials, it has brought severe challenges to the current mechanical processing technology. In particular, complex surfaces based on brittle materials are very easy to crack during processing due to their inherent high hardness and low fracture toughness, making it difficult to ensure processing quality and efficiency. Microstructured surfaces are a typical complex surface. At present, the processing of micro-nano structures of brittle materials can be prepared by subtractive (such as cutting), additive (such as 3D printing) and isotropic (such as molding), but in order to ensure processing quality, it usually relies on expensive processing equipment and complex process conditions, which not only has low processing efficiency but also high cost. At present, in order to achieve efficient and low-damage processing of brittle materials, the consensus in the field of mechanical processing is to control the cutting depth to be less than the critical cutting depth of brittle-ductile transition, thereby achieving low-damage processing. However, the critical cutting depth threshold of the brittle-ductile transition of brittle materials is usually very small (submicron level). In order to further increase the critical cutting depth value of the brittle-ductile transition, the energy field (thermal field, vibration field, etc.) is introduced into the processing process, so that the critical value can be effectively increased. However, the current low-damage cutting parameters (such as cutting depth and feed rate) are all based on the critical cutting depth of the brittle-ductile transition, which makes this critical value a bottleneck that limits the efficient and low-damage processing of such materials to a certain extent. In response to this problem, Chinese invention patent CN116238058B discloses a high-efficiency and low-damage processing method for brittle materials, and discloses the following technical content: by adjusting the tool posture and vibration trajectory, the modulation of the crack propagation direction is achieved, and the critical cutting depth of the crack propagation to the lowest point under this method is determined. When the actual processing depth is less than the critical cutting depth of the crack propagation to the lowest point, the cracks on the machined surface generated by this pass are biased to the side of the pre-pass feed direction by using multiple passes, and will be removed in the next pass. This method provides a new way to achieve low-damage processing with a cutting depth greater than the traditional critical cutting depth of the brittle-ductile transition, which helps to improve the processing efficiency of brittle materials. However, this method does not involve the active regulation of micro-defect positions with the assistance of microcracks to achieve direct creation of composite microstructure surfaces.

[0003] Although the nucleation and extension of microcracks are generally considered to be one of the main factors that cause brittle fracture of materials and thus affect the processing quality during the processing of brittle materials, and are undesirable. However, the use of microcracks can also produce positive effects. Some scholars have successfully realized surface nanopatterning using microcracks (Kim M. et al. Cracking-assisted photolithography for mixed-scale patterning and nanofluidic applications. 2015, 6(1): 6247; Nam KH, et al. Patterning by controlled cracking. 2012, 485(7397): 221-224). However, the above method is only applicable to the preparation of two-dimensional surface patterns. In the field of bionics, the surface of biological bodies has special functions (such as hydrophilicity and hydrophobicity) due to its complex three-dimensional multi-level structure, and its surface morphology has composite structural characteristics such as smoothness, roughness, and irregularity. However, in the process of mechanical creation, how to use microcracks to assist in the preparation of three-dimensional microstructure features under the premise of ensuring the quality of the processed surface has not been reported. Therefore, how to achieve three-dimensional microstructure processing of brittle-plastic composites with the help of microcracks is still full of challenges. Summary of the invention

[0004] The technical problem to be solved by the present invention is: to overcome the shortcomings of the prior art and provide a method for creating a composite microstructure surface assisted by cracks: (1) by regulating the mutual extension and cross-extension of microcracks in a specific area to achieve material removal and form spatial high-frequency hierarchical features; (2) by regulating the formation of microdefects induced by microcracks at specific locations, the microdefects serve as spatial high-frequency hierarchical features of the microstructure surface, thereby achieving the creation of a composite microstructure surface assisted by microcracks and actively regulating microdefects. This method helps to improve the hierarchical structure of the three-dimensional microstructure surface, thereby enhancing certain special surface and interface properties of the microstructure surface, and has the advantages of high efficiency and low cost.

[0005] The technical solution adopted by the present invention to solve the technical problem is: the crack-assisted composite microstructure surface creation method is characterized by comprising the following steps:

[0006] 1) Design the brittle-plastic composite microstructure surface to be prepared and determine the brittle material and tool to be processed;

[0007] 2) Determine the machining depth of the tool, select the tool modulation cutting mode and plan the tool vibration trajectory, adjust the tool posture and tool path, make the tool posture match the reasonable tool path and vibration trajectory, align the tool and process, and realize the expansion of machining micro defects to one side and the surface in the machining direction;

[0008] 3) Use the macro-relative motion between the machining equipment's motion axis and the tool to process brittle materials, control the tool's lateral feed rate, and achieve the same tool posture to process brittle materials with microcracks and actively control the micro-defect microstructure surface through multiple passes;

[0009] 4) Adjust the tool processing position to be located in the lateral feed direction of step 3) and the adjacent unprocessed position of the first group of tool passes, and adjust the tool posture again. By changing the tool posture only once and controlling the lateral feed amount of the tool, multiple tool passes can be used to achieve the mutual expansion and cross-extension of microcracks generated by machining brittle materials in specific areas to achieve material removal or induce microdefects to form at specific locations, thereby forming spatial high-frequency hierarchical features and realizing the creation of a composite microstructure surface with microcrack-assisted active regulation of microdefects.

[0010] Furthermore, the brittle-plastic composite microstructure surface in step 1) is formed by the mutual movement of the tool and the brittle material of the workpiece, and includes plastic forming features and brittle fracture removal features formed by the mutual extension and intersection of microcracks in a specific area to achieve material removal or induce micro defects at a specific position, and the processing tool is an arc-edged tool.

[0011] Furthermore, in step 2), the modulation cutting mode of the tool is selected according to the designed brittle-plastic composite microstructure surface, and the mode includes but is not limited to the tool deflection angle coordinated with two-dimensional elliptical vibration or three-dimensional elliptical vibration, and utilizing vibration trajectory planning to achieve the creation of finer spatial high-frequency features on the spatial low-frequency features, thereby forming a multi-level composite microstructure surface.

[0012] Furthermore, in step 2), the tool posture is adjusted by rotating the tool without changing the tool tip position to achieve the change of tool posture. The tool processing depth is greater than the critical cutting depth of the traditional brittle-ductile transition and less than the depth at which the micro defect first extends to the lowest point of the groove.

[0013] Furthermore, in step 3), the lateral feed rate of the tool is controlled, and the lateral feed rate should be more than twice the width of the groove created by the current tool pass.

[0014] Furthermore, in step 4), the tool posture is regulated again, specifically, the tool rotation direction is made opposite to the rotation direction of the tool posture regulated in step 2). By controlling the lateral feed amount of the tool and using multiple passes, the microcracks generated by machining brittle materials can be mutually extended and crossed in specific areas to achieve material removal or induce microdefects to form at specific locations, thereby achieving the creation of a composite microstructure surface with microcrack-assisted active regulation of microdefects.

[0015] Furthermore, the lateral feed amount in step 4) should be more than 2 times and less than 2.5 times the width of the groove created by the tool in step 3).

[0016] Furthermore, in step 3) and step 4), the tool modulation cutting mode, vibration trajectory, and tool movement mode are the same.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention actively controls the tool position and posture, vibration trajectory and tool path, utilizes microcrack induction to form processing microdefects that expand unilaterally and on the surface in the processing direction, and through multiple tool passes and lateral feed rate control, can achieve one-time creation of a spatial low-frequency characteristic structure with plastic removal characteristics on brittle materials and creation of a composite microstructure surface with spatial high-frequency brittle crack removal characteristics in a plastic low-frequency space, with high efficiency and low cost.

[0019] By actively regulating the position of micro-defects, micro-cracks can be extended and crossed in specific areas of spatial low-frequency plastic features, thereby forming material removal, or inducing brittle micro-defects to form micro-rough elements in specific locations. The removal features formed by the intersection of micro-cracks or the brittle micro-rough elements remaining in specific areas of spatial low-frequency plastic features help to improve the hierarchical structural features of the microstructure surface. The composite multi-level microstructure surface can directly or further enhance certain special surface interface functions of the microstructure surface through post-processing (such as spraying, etc.). At the same time, this method uses the phenomenon that micro-cracks are prone to occur during the processing of brittle materials, and provides a new method for the creation of spatial hierarchical structures by regulating the expansion behavior of micro-cracks. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the microstructural surface for actively controlling micro-defects by assisting in micro-crack machining of brittle materials with the same tool posture.

[0021] Figure 2 Schematic diagram of the microstructural surface for actively controlling micro-defects by machining microcracks in brittle materials with only one change of tool posture.

[0022] Figure 3 (a) Schematic diagram of the microstructure surface forming principle in which microcracks generated by machining brittle materials extend and cross each other in specific areas to achieve material removal. Figure 3 (b) The two-dimensional contour and three-dimensional morphology of the microcracks generated by processing brittle materials and extending and crossing each other in specific areas to achieve material removal.

[0023] Figure 4 Schematic diagram of the principle of processing brittle materials to induce microcracks and retain microdefects at specific locations.

[0024] Among them: 1 brittle material 2 tool 3 micro defect

[0025] In the figure, c 1 -c 6For the first to sixth passes, θ 1 ,θ 2 is the tool deflection angle, f 1 , f 2 is the tool lateral feed. DETAILED DESCRIPTION

[0026] Figures 1 to 4 This is the best embodiment of the microcrack-assisted composite microstructure surface creation. Figures 1 to 4 The present invention is further described.

[0027] The brittle material microcrack-assisted composite microstructure surface creation method specifically comprises the following steps:

[0028] The brittle-plastic composite microstructure surface to be processed is determined, and the brittle material 1 to be processed and the tool 2 used in the processing are selected. The brittle material 1 to be processed is a brittle material with a pre-polished surface to be processed, and the brittle-plastic composite microstructure surface to be processed is formed by the relative movement of the tool 2 and the workpiece 1, including plastic forming characteristics and brittle crack removal characteristics formed by the mutual extension and intersection of microcracks in a specific area to achieve material removal or induce micro defects 3 at a specific position. The brittle material 1 to be processed is selected as single crystal silicon, and the tool 2 used in the processing is a circular arc edge tool.

[0029] According to the designed brittle-plastic composite microstructure surface characteristics, the modulation cutting mode of tool 2 is determined and the vibration trajectory of tool 2 is planned. Figure 1 , adjust the tool 2 posture, without changing the tool tip position, rotate the tool 2 at an angle of θ 1 , for tool 2 along y 2 and z 2 A harmonic signal with a phase difference is applied in each direction so that it 2 z 2 The surface forms a two-dimensional elliptical vibration trajectory, and the tool 2 moves along the y 1 Cutting direction.

[0030] The machining depth of tool 2 is determined. The machining depth of tool 2 is greater than the critical cutting depth of the traditional brittle-ductile transition and less than the depth at which the micro defect 3 first expands to the lowest point of the groove.

[0031] Plan the tool path of tool 2 in a row-cutting manner, along x 1 The positive direction determines the reasonable lateral feed rate f of tool 2 1 The brittle material 1 to be processed is aligned with the tool, and the brittle material 1 to be processed is processed by utilizing the macro-relative motion between the motion axis of the processing equipment and the tool 2.

[0032] In coordination with the planned tool path, through multiple tool passes, the same tool 2 is used in the first group of tool passes to complete the microstructural surface of the microcrack-assisted active regulation of the microdefect 3 of the brittle material 1.

[0033] See also Figure 2 , adjust the machining position of tool 2 to the adjacent unmachined position of the first group of first pass in the lateral feed direction of step 5), and adjust the posture of tool 2 again so that the rotation direction of tool 2 is opposite to the rotation direction of tool 2 posture adjusted in step 2), and the angle of reverse rotation of tool 2 is θ 2 .

[0034] Reasonable selection of tool 2 in the second set of passes along x 1 Transverse feed in positive direction f 2 .

[0035] In conjunction with the planned tool path, through multiple tool passes, only one change in the tool 2 posture can achieve the micro-cracks generated by machining the brittle material 1 to extend and cross each other in a specific area to achieve material removal (such as Figure 3 ) or induce microdefects 3 to form at specific locations (e.g. Figure 4 As shown in the figure), spatial high-frequency hierarchical features are formed to realize the composite microstructure surface creation of micro-defects 3 assisted by microcracks and actively regulated.

[0036] The modulation cutting mode, vibration trajectory and cutting mode of tool 2 in the above steps are the same. The deflection angle θ of tool 2 in step 2) and step 6) is 1 and θ 2 Can be the same or different.

[0037] Under the condition that the tool 2 is deflected at a certain angle, when the processing depth of the tool is greater than the critical cutting depth of the brittle-ductile transition of the brittle material 1 to be processed, and less than the depth at which the micro-defect 3 first extends to the lowest point of the groove, an offset micro-defect 3 will appear in the processed brittle material 1, that is, the micro-defect 3 generated by the processing only appears on one side of the processing groove. The critical cutting depth of brittle-ductile transition of brittle material 1 and the depth at which micro-defects first extend to the lowest point of the groove need to be determined through a variable cutting depth continuous scratching experiment. The brittle material 1 to be processed is tilted at a certain angle so that the processing depth gradually increases along the processing direction during processing, and the tool 2 is deflected at a certain angle. The tool is aligned and scratched. Micro-defects induced by micro-cracks will first be generated from the deflected side of the tool 2, and gradually extend to the entire groove surface as the scratching depth increases. The processing depth at the location of the first micro-defect induced by micro-cracks during the scratching process is the critical cutting depth of brittle-ductile transition. At the same time, the depth at which the micro-defects first extend to the lowest point of the groove can be obtained. The critical cutting depth of brittle-ductile transition and the depth at which the micro-defects first extend to the lowest point of the groove are different for different materials.

[0038] In step 4), tool 2 moves along x in the first set of passes. 1 Transverse feed in positive direction f 1 It should be at least twice the width of the groove created by the current pass. In step 7), tool 2 moves along x in the second pass. 1 Transverse feed in positive direction f 2 It should be more than 2 times and less than 2.5 times the width of the groove created by the tool in step 5).

[0039] Figure 3 (a) is a schematic diagram of the microstructure surface forming principle in which the microcracks generated by machining brittle materials extend and cross each other in a specific area to achieve material removal. When the lateral feed amount of tool 2 is less than the groove width created by the first pass, the microcracks generated by machining brittle material 1 can be extended and cross each other in a specific area to achieve material removal through two passes, forming a spatial high-frequency hierarchical feature. Figure 3 (b) The two-dimensional contour and three-dimensional morphology of the microcracks generated by processing brittle materials and extending and crossing each other in specific areas to achieve material removal.

[0040] Figure 4 The schematic diagram is a principle diagram of the micro-defects induced by micro-cracks in machining brittle materials and remaining at specific positions. When the lateral feed amount of tool 2 is greater than the groove width created by the first pass, micro-defects 3 can be induced to form at specific positions of the brittle material 1 through two passes, which, as the spatial high-frequency characteristics of the micro-structure surface, realize the creation of a composite micro-structure surface with micro-defects 3 assisted by micro-cracks and actively regulated.

[0041] The above is only an individual preferred embodiment of the present invention, which is only used to help understand the method and core idea of ​​the present invention, and is not used to limit the present invention. Other cutting methods can also be used to achieve micro-crack-assisted micro-defect micro-surface processing according to the principle of this processing idea. For those skilled in the art, the present invention may have various changes and variations in specific implementation and application. Any modifications, equivalent substitutions, improvements, etc. made to the present invention should be included in the scope of protection of the present invention.

Claims

1. A microcrack-assisted composite microstructure surface creation method, characterized in that: The following steps are involved: 1) Design the brittle-ductile composite microstructure surface to be prepared and determine the brittle material (1) and tool (2) to be processed; 2) determining the processing depth of the tool (2), selecting the modulation cutting mode of the tool (2) and planning the vibration trajectory of the tool (2), adjusting the posture and tool path of the tool (2), making the posture of the tool (2) match the reasonable tool path and vibration trajectory, aligning the tool and processing, and realizing the expansion of the processing micro-defect (3) to one side and the surface in the processing direction; 3) utilizing the macro-relative motion between the motion axis of the processing equipment and the tool (2) to process the brittle material (1), controlling the lateral feed amount of the tool (2), and realizing the micro-crack-assisted active regulation of the micro-structure surface of the micro-defect (3) of the brittle material (1) by the same tool (2) through multiple passes; 4) adjusting the processing position of the tool (2) to be located in the lateral feed direction of step 3) and the adjacent unprocessed position of the first group of tool passes, and adjusting the posture of the tool (2) again. By changing the posture of the tool (2) only once and controlling the lateral feed amount of the tool (2), using multiple tool passes, the microcracks generated by processing brittle materials can be mutually extended and crossed in a specific area to achieve material removal or induce microdefects (3) to form at a specific position, thereby forming a spatial high-frequency hierarchical feature, and realizing the composite microstructure surface creation of microdefects (3) assisted by microcracks and actively regulated; The brittle-plastic composite microstructure surface in step 1) is formed by the relative movement of the tool (2) and the brittle material (1), and includes a plastic forming feature and a brittle fracture removal feature formed by the mutual extension and intersection of microcracks in a specific area to achieve material removal or induce microdefects (3) at a specific position, the brittle material (1) to be processed is a hard brittle material or a soft brittle material, and the tool (2) is a circular arc blade tool; In step 2), the modulation cutting method of the tool (2) is selected according to the designed brittle-plastic composite microstructure surface, and the method includes the deflection angle of the tool (2) is coordinated with two-dimensional elliptical vibration or three-dimensional elliptical vibration, and the vibration trajectory planning is used to achieve the creation of finer spatial high-frequency features on the spatial low-frequency features, thereby forming a multi-level composite microstructure surface; In step 2), the posture of the tool (2) is regulated by rotating the tool (2) without changing the position of the tool tip, so as to change the posture of the tool (2), and the processing depth of the tool (2) is greater than the critical cutting depth of the brittle-ductile transition and less than the depth at which the micro defect (3) first extends to the lowest point of the groove; In step 4), the posture of the tool (2) is regulated again, specifically, the rotation direction of the tool (2) is made opposite to the rotation direction of the posture of the tool (2) regulated in step 2). By controlling the lateral feed amount of the tool (2), multiple passes can be used to achieve the mutual expansion and cross-extension of microcracks generated by processing the brittle material (1) in a specific area to achieve material removal or induce the formation of microdefects (3) at a specific position, thereby achieving the creation of a composite microstructure surface with actively regulated microdefects (3).

2. The microcrack-assisted composite microstructure surface creation method according to claim 1, characterized in that: In step 3), the lateral feed rate of the tool (2) is controlled, and the lateral feed rate should be more than twice the width of the groove created by the current cutting.

3. The microcrack-assisted composite microstructure surface creation method according to claim 1, characterized in that: The lateral feed amount in step 4) should be more than 2 times and less than 2.5 times the width of the groove created by the tool in step 3).

4. The microcrack-assisted composite microstructure surface creation method according to claim 1, characterized in that: In step 3) and step 4), the tool (2) modulates the cutting mode, vibration trajectory, and tool movement mode in the same manner.

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