Ultrasonic milling-based machining method for multi-stage microstructure on surface of difficult-to-machine material

Abstract

The invention discloses a machining method for a multi-stage microstructure on the surface of a difficult-to-machine material based on ultrasonic milling. The machining method comprises the following steps that S1, machining parameters are set; s2, a periodic vibration track is applied to a tool nose of the tool, and a multi-stage microstructure is machined on the workpiece, the periodic vibration track is formed by superposition of longitudinal-torsional ultrasonic vibration and periodic low-frequency modulation motion, the longitudinal-torsional ultrasonic vibration is composed of longitudinal ultrasonic vibration in the axial direction and torsional ultrasonic vibration in the cutting speed direction of the cutter, the periodic low-frequency modulation motion is different from the longitudinal-torsional ultrasonic vibration in frequency, and the low-frequency modulation motion generates a first-level microstructure; the longitudinal-torsional ultrasonic vibration generates a second-stage microstructure, the size of the second-stage microstructure is smaller than that of the first-stage microstructure, and the second-stage microstructure and the first-stage microstructure form a multi-stage microstructure. The method is high in machining efficiency, good in quality, low in cost and suitable for machining complex microstructures on the surfaces of difficult-to-machine materials.

Description

Technical Field

[0001] The invention relates to the technical field of machining multi-level microstructures on the surface of difficult-to-machine materials, and in particular to a machining method for multi-level microstructures on the surface of difficult-to-machine materials based on ultrasonic milling. Background Art

[0002] Difficult-to-process materials are widely used in many fields due to their unique physical and chemical properties. For example, titanium alloys with high strength, low density, corrosion resistance, and strong biocompatibility are often used in implants such as artificial bone joints, aircraft engine components in the aerospace field, and chemical and automotive industries. Processing microstructures on difficult-to-process materials can further improve their performance. Different microstructures can change the surface morphology of difficult-to-process materials, improve the physical and chemical properties and corrosion resistance of materials, and enhance their performance in different applications. For example, in the field of exhaust gas waste heat recovery, microstructures can increase the surface area of ​​the material and change the wettability to improve the heat exchange efficiency and promote waste heat recovery. However, in many application scenarios, due to performance requirements, conventional single-level microstructures are difficult to meet the needs, and multi-level microstructures need to be further processed.

[0003] Therefore, it is very important to study the efficient preparation process of complex multi-level microstructures on the surface of difficult-to-process materials. At present, surface microstructure processing is mainly achieved by non-mechanical methods, such as chemical etching, photolithography, electrospark / electrochemical machining, laser / ion beam etching and other methods. However, these methods have problems such as limited available materials, complex engineering procedures, low manufacturing efficiency, expensive equipment, harsh process conditions, and environmental pollution, which make them difficult to be actually applied to the preparation of complex multi-level microstructures on the surface of difficult-to-process materials. Mechanical processing represented by tool servo metal cutting can efficiently and low-cost manufacture high-precision surface microstructures. This method has the advantages of high efficiency and low cost. However, due to the bandwidth limitation of the tool servo cutting method, the resolution of the microstructure it manufactures is generally several hundred microns, and it is difficult to flexibly construct the microstructure. In addition, most of the current multi-level microstructure processing methods process microstructures of different levels in steps, which also limits the processing efficiency. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, one purpose of the present invention is to provide a method for processing multi-level microstructures on the surface of difficult-to-process materials based on ultrasonic milling, which has high processing efficiency, good quality and low cost, and is suitable for processing complex microstructures on the surface of difficult-to-process materials.

[0005] According to an embodiment of the present invention, a method for machining a multi-level microstructure on the surface of a difficult-to-machine material based on ultrasonic milling comprises the following steps:

[0006] S1: Set processing parameters;

[0007] S2: Apply a periodic vibration trajectory to the tip of the tool to machine a multi-level microstructure on the workpiece, wherein the periodic vibration trajectory is composed of a longitudinal-torsional ultrasonic vibration consisting of a longitudinal ultrasonic vibration along the axial direction and a torsional ultrasonic vibration along the cutting speed direction of the tool, and a periodic low-frequency modulation motion having a frequency different from that of the longitudinal-torsional ultrasonic vibration, the low-frequency modulation motion produces a primary microstructure, the longitudinal-torsional ultrasonic vibration produces a secondary microstructure, the scale of the secondary microstructure is smaller than that of the primary microstructure and constitutes the multi-level microstructure with the primary microstructure.

[0008] According to the method for machining multi-level microstructures on the surface of difficult-to-machine materials based on ultrasonic milling according to the embodiment of the present invention, it can be carried out on a five-axis ultrasonic milling device, the workpiece is pre-milled to make the surface flat, a piezoelectric driven ultrasonic system is installed on the five-axis ultrasonic milling device, machining parameters are set, and a periodic vibration trajectory is modulated by the piezoelectric driven ultrasonic system and applied to the tip of the tool. According to different multi-level microstructure feature requirements, by setting machining parameters and applying a periodic vibration trajectory to the tip of the tool, the pre-milled surface of the workpiece is subjected to longitudinal torsional ultrasonic milling with periodic amplitude changes. Among them, the periodic vibration trajectory is composed of a longitudinal torsional ultrasonic vibration consisting of a longitudinal ultrasonic vibration along the axial direction and a torsional ultrasonic vibration along the cutting speed direction of the tool, and a periodic low-frequency modulation motion having a different frequency from the longitudinal torsional ultrasonic vibration, that is, the periodic vibration trajectory is composed of three longitudinal ultrasonic vibrations, torsional ultrasonic vibrations and low-frequency modulation motions. The longitudinal ultrasonic vibration and the torsional ultrasonic vibration are coupled into a longitudinal torsional ultrasonic vibration, which belongs to a high-frequency vibration, and the low-frequency modulation motion belongs to a low-frequency vibration. Therefore, low-frequency modulated motion produces a primary microstructure, and longitudinal-torsional ultrasonic vibration produces a secondary microstructure. The scale of the secondary microstructure is smaller than that of the primary microstructure and is combined with the primary microstructure to form a corresponding complex multi-level microstructure with different geometric features. Therefore, the processing method of the multi-level microstructure on the surface of difficult-to-process materials based on ultrasonic milling in the embodiment of the present invention can process complex multi-level microstructures efficiently and at low cost. Due to the periodic separation between the tool and the workpiece during ultrasonic processing, the contact and friction between the tool and the workpiece can be effectively reduced, thereby reducing the cutting force and cutting temperature, inhibiting the generation of microcracks, and improving the processing quality. Therefore, it is suitable for processing difficult-to-process materials.

[0009] The processing method of multi-level microstructure on the surface of difficult-to-process materials based on ultrasonic milling in the embodiment of the present invention has the following advantages: First, it solves the problem that the existing processing technology is difficult to directly and efficiently process multi-level complex microstructures on the surface of difficult-to-process materials, and based on the principle of ultrasonic vibration-assisted processing, it has the advantages of easy implementation, high processing efficiency and low cost; Second, it solves the problem of simply and effectively controlling the characteristics of the multi-level microstructure on the surface. By controlling the relevant parameters and processing parameters of the periodic vibration trajectory, the key geometric characteristics of the complex multi-level microstructure on the workpiece surface can be controlled.

[0010] In some embodiments, the processing parameters include cutting speed, feed speed and cutting depth; the vibration parameters of the periodic vibration trajectory include the frequency of the longitudinal-torsional ultrasonic vibration, the low-frequency modulation signal frequency of the low-frequency modulation motion, the amplitude of the longitudinal ultrasonic vibration, the amplitude of the torsional ultrasonic vibration, the phase of the longitudinal ultrasonic vibration and the phase of the torsional ultrasonic vibration.

[0011] In some embodiments, in the xyz coordinate system, the longitudinal ultrasonic vibration exists in the z-axis direction, and the torsional ultrasonic vibration exists in the xy plane, then the expression of the periodic vibration trajectory is as follows:

[0012]

[0013] in, is the phase difference between the longitudinal ultrasonic vibration and the torsional ultrasonic vibration, A T is the amplitude of the torsional ultrasonic vibration, A L is the amplitude of the longitudinal ultrasonic vibration, r is the tip radius of the tool, V d is the feed speed of the tool along the y-axis, f L is the frequency of the low frequency modulation signal, f H is the frequency of the longitudinal-torsional ultrasonic vibration.

[0014] In some embodiments, the amplitude of the longitudinal ultrasonic vibration increases from zero to a maximum value and then gradually decreases to zero within a period of the low-frequency modulation signal corresponding to the primary microstructure, and the longitudinal displacement of the tool tip occurs in a total of f within a period corresponding to the primary microstructure. H / f L minima, and corresponding to the same number of the secondary microstructures.

[0015] In some embodiments, the key geometric characteristic parameters of the multi-level microstructure include a primary microstructure length, a primary microstructure width, a secondary microstructure width, a primary microstructure spacing in a cutting direction, and a primary microstructure spacing in a feeding direction.

[0016] In some embodiments, the primary microstructure spacing in the cutting direction is mainly determined by the ratio of the cutting speed to the frequency of the low-frequency modulation signal; the primary microstructure spacing in the feed direction is related to the feed speed; the primary microstructure length is related to the spindle speed, the cutting depth, the tool tip radius and the frequency of the low-frequency modulation signal; the primary microstructure width is jointly determined by the tool tip radius and the primary microstructure depth; the secondary microstructure length corresponds to the primary microstructure width; the secondary microstructure width is determined by the spindle speed, the cutting depth, the tool tip radius and the frequency of the longitudinal-torsional ultrasonic vibration; the tool's blade inclination angle corresponds to the angle of the direction of the primary microstructure.

[0017] In some embodiments, the expression of the geometric key characteristic parameters of the multi-level microstructure is:

[0018]

[0019] Wherein, S is the primary microstructure spacing in the cutting direction, d is the primary microstructure spacing in the feeding direction, l1 is the primary microstructure length, w is the primary microstructure width, l2 is the secondary microstructure width, V c is the cutting speed VC, feed is the feed speed, n is the spindle speed, R n is the tool nose radius, DOC is the cutting depth, β is the cutting edge inclination angle, Δt1 is the actual cutting time for machining one of the primary microstructures, and Δt2 is the actual cutting time for machining one of the secondary microstructures.

[0020] In some embodiments, the periodic vibration trajectory is generated by a piezoelectric driven ultrasound system.

[0021] In some embodiments, the parameters of the tool include tool material, tool shape, tool tip radius, and cutting edge inclination angle.

[0022] In some embodiments, the workpiece is made of a metal material or a non-metal material.

[0023] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0025] Figure 1 The principle of the method for machining multi-level microstructures on the surface of difficult-to-machine materials based on ultrasonic milling according to an embodiment of the present invention is schematically shown;

[0026] Figure 2 A schematic diagram of periodic vibration trajectory parameters and shapes in a method for machining multi-level microstructures on the surface of difficult-to-machine materials based on ultrasonic milling according to an embodiment of the present invention;

[0027] Figure 3 A schematic diagram of the shape of a multi-level microstructure and its structural characteristic parameters obtained by a method for machining a multi-level microstructure on the surface of a difficult-to-machine material based on ultrasonic milling according to an embodiment of the present invention;

[0028] Figure 4 It is a schematic diagram of actual processing results of a method for processing multi-level microstructures on the surface of difficult-to-process materials based on ultrasonic milling according to an embodiment of the present invention;

[0029] Figure 5 This is a schematic diagram of the surface wettability control results of a multi-level microstructure obtained by the method for machining multi-level microstructures on the surface of difficult-to-machine materials based on ultrasonic milling in an embodiment of the present invention.

[0030] Reference numerals:

[0031] 1-workpiece; 2-1-longitudinal ultrasonic vibration; 2-2-torsion ultrasonic vibration; 3-tool; 4-multi-level microstructure; 4-1-primary microstructure; 4-2-secondary microstructure; V c -Cutting speed VC; V d -feed speed; DOC-depth of cut; n-spindle speed; l1-primary microstructure length; w-primary microstructure width; l2-secondary microstructure width; β-edge inclination angle; S-primary microstructure spacing in cutting direction; d-primary microstructure spacing in feed direction. DETAILED DESCRIPTION

[0032] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0033] Combine the following Figures 1 to 5 The method for machining a multi-level microstructure 4 on the surface of a difficult-to-machine material based on ultrasonic milling according to an embodiment of the present invention is described.

[0034] like Figures 1 to 3 As shown, the method for machining a multi-level microstructure 4 on the surface of a difficult-to-machine material based on ultrasonic milling according to an embodiment of the present invention comprises the following steps:

[0035] S1: Set processing parameters.

[0036] S2: A periodic vibration trajectory is applied to the tool tip of the tool 3 to machine a multi-level microstructure 4 on the workpiece 1, wherein the periodic vibration trajectory is composed of a longitudinal-torsional ultrasonic vibration consisting of a longitudinal ultrasonic vibration 2-1 along the axial direction and a torsional ultrasonic vibration 2-2 along the cutting speed direction of the tool 3, and a periodic low-frequency modulation motion having a frequency different from the longitudinal-torsional ultrasonic vibration. The low-frequency modulation motion produces a primary microstructure 4-1, and the longitudinal-torsional ultrasonic vibration produces a secondary microstructure 4-2. The scale of the secondary microstructure 4-2 is smaller than that of the primary microstructure 4-1 and forms a complex multi-level microstructure 4 with the primary microstructure 4-1.

[0037] According to the processing method of the multi-level microstructure 4 on the surface of the difficult-to-process material based on ultrasonic milling according to the embodiment of the present invention, it can be performed on a five-axis ultrasonic milling device, the workpiece 1 is pre-milled to make the surface flat, a piezoelectric driven ultrasonic system is installed on the five-axis ultrasonic milling device, the processing parameters are set, and the piezoelectric driven ultrasonic system is used to modulate a periodic vibration trajectory and apply it to the tip of the tool 3. According to different requirements for the characteristics of the multi-level microstructure 4, by setting the processing parameters and applying a periodic vibration trajectory to the tip of the tool 3, the pre-milled surface of the workpiece 1 is subjected to longitudinal torsional ultrasonic milling with periodic amplitude changes. Among them, the periodic vibration trajectory is composed of a longitudinal torsional ultrasonic vibration consisting of a longitudinal ultrasonic vibration 2-1 along the axial direction and a torsional ultrasonic vibration 2-2 along the cutting speed direction of the tool 3, and a periodic low-frequency modulation motion having a frequency different from the longitudinal torsional ultrasonic vibration, that is, the periodic vibration trajectory is composed of three longitudinal ultrasonic vibrations 2-1, torsional ultrasonic vibrations 2-2 and low-frequency modulation motions. The longitudinal ultrasonic vibration 2-1 and the torsional ultrasonic vibration 2-2 are coupled into a longitudinal torsional ultrasonic vibration, which belongs to a high-frequency vibration, and the low-frequency modulation motion belongs to a low-frequency vibration. Therefore, the low-frequency modulation motion produces a primary microstructure 4-1, and the longitudinal torsional ultrasonic vibration produces a secondary microstructure 4-2. The scale of the secondary microstructure 4-2 is smaller than the scale of the primary microstructure 4-1 and is combined with the primary microstructure 4-1 to form a corresponding complex multi-level microstructure 4 with different geometric features. Therefore, the processing method of the multi-level microstructure 4 on the surface of a difficult-to-process material based on ultrasonic milling in the embodiment of the present invention can efficiently and low-costly process a complex multi-level microstructure 4. Due to the periodic separation between the tool 3 and the workpiece 1 during ultrasonic machining, the contact and friction between the tool 3 and the workpiece 1 can be effectively reduced, thereby reducing the cutting force and cutting temperature, inhibiting the generation of microcracks, and improving the machining quality. Therefore, it is suitable for machining difficult-to-machine materials.

[0038] The processing method of the multi-level microstructure 4 on the surface of a difficult-to-process material based on ultrasonic milling in an embodiment of the present invention has the following advantages: First, it solves the problem that the existing processing technology is difficult to directly and efficiently process multi-level complex microstructures on the surface of difficult-to-process materials, and based on the principle of ultrasonic vibration-assisted processing, it has the advantages of easy implementation, high processing efficiency and low cost; Second, it solves the problem of simply and effectively controlling the characteristics of the multi-level microstructure 4 on the surface. By controlling the relevant parameters and processing parameters of the periodic vibration trajectory, the key geometric characteristics of the complex multi-level microstructure 4 on the surface of the workpiece 1 can be controlled.

[0039] In some embodiments, the processing parameters include cutting speed, feed speed and cutting depth; the vibration parameters of the periodic vibration trajectory include the frequency of the longitudinal torsional ultrasonic vibration, the frequency of the low-frequency modulation signal of the low-frequency modulation motion, the amplitude of the longitudinal ultrasonic vibration 2-1, the amplitude of the torsional ultrasonic vibration 2-2, the phase of the longitudinal ultrasonic vibration 2-1 and the phase of the torsional ultrasonic vibration 2-2. By changing the processing parameters and the vibration parameters of the periodic vibration trajectory, complex surface microstructures with different geometric features can be obtained.

[0040] In some embodiments, in the xyz coordinate system, there is a longitudinal ultrasonic vibration 2-1 in the z-axis direction, and there is a torsional ultrasonic vibration 2-2 in the xy plane, then the expression of the periodic vibration trajectory is as follows:

[0041]

[0042] in, is the phase difference between the longitudinal ultrasonic vibration 2-1 and the torsional ultrasonic vibration 2-2, A T is the amplitude of the torsional ultrasonic vibration 2-2, A L is the amplitude of the longitudinal ultrasonic vibration 2-1, r is the tip radius of the tool 3, V d is the feed speed of tool 3 along the y-axis, f L is the low frequency modulation signal frequency, f H is the frequency of longitudinal-torsional ultrasonic vibration.

[0043] The final modulated tool tip periodic vibration trajectory in the plane formed by the cutting speed direction and the z-axis is as follows: Figure 2 As shown in the figure, the amplitude of the longitudinal ultrasonic vibration 2-1 increases from zero to the maximum within a period of the low-frequency modulation signal corresponding to the primary microstructure 4-1, and then gradually decreases to zero. The longitudinal displacement of the tool tip occurs for a total of f in a period corresponding to the primary microstructure 4-1. H / f L There are minima, and they correspond to the same number of secondary microstructures 4-2.

[0044] In some embodiments, the key geometric characteristic parameters of the multi-level microstructure 4 include primary microstructure length, primary microstructure width, secondary microstructure width, primary microstructure spacing in the cutting direction, and primary microstructure spacing in the feeding direction.

[0045] Among them, the spacing of the first-level microstructure in the cutting direction is mainly determined by the ratio of the cutting speed to the frequency of the low-frequency modulation signal; the spacing of the first-level microstructure in the feeding direction is related to the feeding speed; the length of the first-level microstructure is related to the spindle speed, cutting depth, tool tip radius and the frequency of the low-frequency modulation signal; the width of the first-level microstructure is jointly determined by the tool tip radius and the depth of the first-level microstructure; the length of the second-level microstructure corresponds to the width of the first-level microstructure; the width of the second-level microstructure is determined by the spindle speed, cutting depth, tool tip radius and the frequency of the longitudinal-torsion ultrasonic vibration; the blade inclination angle of the tool 3 corresponds to the angle of the direction of the first-level microstructure 4-1. The size, distribution and shape of the multi-level microstructure 4 can be controlled by changing various process parameters.

[0046] Specifically, the expression of the geometric key characteristic parameters of the multi-level microstructure 4 is:

[0047]

[0048] Among them, S is the primary microstructure spacing in the cutting direction, d is the primary microstructure spacing in the feeding direction, l1 is the primary microstructure length, w is the primary microstructure width, l2 is the secondary microstructure width, V c is the cutting speed, feed is the feed speed, n is the spindle speed, R n is the tool tip radius, DOC is the cutting depth, β is the cutting edge inclination angle, Δt1 is the actual cutting time to complete a primary microstructure 4-1, and Δt2 is the actual cutting time to complete a secondary microstructure 4-2. Based on the above expression of the geometric key characteristic parameters of the multi-level microstructure 4, the size, distribution and shape of the multi-level microstructure 4 can be controlled by changing various process parameters.

[0049] In some embodiments, the periodic vibration trajectory is generated by a piezoelectric driven ultrasound system.

[0050] Specifically, the piezoelectric driven ultrasonic system includes a signal generator and an amplifier, wherein, according to different multi-level microstructure 4 feature requirements, a specific electrical signal is generated by the signal generator, and then the specific electrical signal is input into the power amplifier, and the specific electrical signal is amplified to be a periodic vibration trajectory, and the periodic vibration trajectory is applied to the tool tip, and the periodic vibration trajectory of the tool tip in the plane formed by the cutting speed direction and the z-axis is as follows: Figure 2 shown.

[0051] In some embodiments, the parameters of the tool 3 include tool material, tool shape, tool tip radius and cutting edge inclination angle. The parameters of the tool 3 will affect the specific morphology of the processed surface multi-level microstructure 4. The tool material can be PCB or diamond but is not limited thereto.

[0052] In some embodiments, the material of the workpiece 1 is a metal material or a non-metal material. For example, the material of the workpiece 1 is TC4 titanium alloy, high temperature alloy, high temperature structural ceramic, composite material, etc. The properties of the material of the workpiece 1 include elasticity and plasticity of the material, etc. The material properties of the workpiece 1 will also have a certain impact on the specific surface morphology of the multi-level microstructure 4, but will not affect the key geometric features such as the period of the multi-level microstructure 4.

[0053] Figure 4 A set of multi-level microstructures 4 actually machined on the surface of a TC4 (titanium alloy) workpiece 1 is shown, and the corresponding machining parameters are f L =1000Hz, ultrasonic frequency is 19500Hz, spindle speed is 300rpm, cutting depth DOC=6μm, feed speed V d =0.15mm / r. Figure 4 (a) is the white light observation result of the processed complex multi-level microstructure 4, which shows the three-dimensional morphology of the processed multi-level microstructure 4. It can be observed that there are obvious multi-level microstructures 4 on the surface of the sample. Among them, the primary microstructure 4-1 is a pit structure, which is closely arranged in a parallelogram shape. Inside each pit of the primary microstructure 4-1, there are evenly distributed secondary microstructures 4-2 with smaller sizes arranged in ridges, and the secondary microstructures 4-2 correspond to the pit features of the primary microstructure 4-1. The depth increases first and then decreases in a low-frequency cycle. Figure 4 (b) and Figure 4 (c) is the electron microscope observation result magnified 100 times and 1000 times respectively, which shows the microstructure of the processed primary microstructure 4-1 and secondary microstructure 4-2.

[0054] The wettability of the processed multi-level microstructure 4 surface samples with different structural parameters was measured, and the results are as follows Figure 5 In this embodiment, the ultrasonic frequency is maintained at 19500 Hz, the cutting depth DOC = 6 μm, and the feed speed V d=0.15mm / r, change the low-frequency modulation frequency. It can be seen that the processed complex multi-level microstructure 4 can improve the hydrophobicity of the material surface without post-processing operation to modify the surface energy, and as the modulation frequency increases, the number of secondary microstructures 4-2 decreases, the width and depth increase, and the corresponding material hydrophobicity gradually increases. The embodiment verifies that processing different complex multi-level microstructures 4 on the surface of titanium alloy can effectively regulate its wettability, and can then be applied to fields such as enhanced condensation heat transfer, confirming the effectiveness of the processing method of the multi-level microstructure 4 on the surface of difficult-to-process materials based on ultrasonic milling of the embodiment of the present invention and demonstrating its application potential.

[0055] The processing method of the multi-level microstructure 4 on the surface of a difficult-to-process material based on ultrasonic milling in the embodiment of the present invention has the following advantages: First, it solves the problem that the existing processing technology is difficult to directly and efficiently process multi-level complex microstructures on the surface of difficult-to-process materials, and based on the principle of ultrasonic vibration-assisted processing, it has the advantages of easy implementation, high processing efficiency and low cost; Second, it solves the problem of simply and effectively controlling the characteristics of the surface multi-level microstructure 4, and by controlling the relevant parameters and processing parameters of the periodic vibration trajectory, the key geometric features of the complex multi-level microstructure 4 on the surface of the workpiece 1 can be controlled; Third, a group of multi-level microstructure samples are processed using different process parameters, and their wettability is measured, which verifies the ability to process complex multi-level microstructures on the surface of difficult-to-process materials by the processing method of the multi-level microstructure 4 on the surface of a difficult-to-process material based on ultrasonic milling in the embodiment of the present invention, thereby achieving wettability control.

[0056] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0057] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for machining multi-level microstructures on the surface of difficult-to-machine materials based on ultrasonic milling, characterized in that: The steps include: S1: Set processing parameters; S2: Apply a periodic vibration trajectory to the tip of the tool to machine a multi-level microstructure on the workpiece, wherein the periodic vibration trajectory is composed of a longitudinal-torsional ultrasonic vibration consisting of a longitudinal ultrasonic vibration along the axial direction and a torsional ultrasonic vibration along the cutting speed direction of the tool, and a periodic low-frequency modulation motion having a frequency different from that of the longitudinal-torsional ultrasonic vibration, the low-frequency modulation motion produces a primary microstructure, the longitudinal-torsional ultrasonic vibration produces a secondary microstructure, the scale of the secondary microstructure is smaller than that of the primary microstructure and constitutes the multi-level microstructure with the primary microstructure.

2. The method for machining multi-level microstructures on the surface of difficult-to-machine materials based on ultrasonic milling according to claim 1, characterized in that: The processing parameters include cutting speed, feed speed and cutting depth; the vibration parameters of the periodic vibration trajectory include the frequency of the longitudinal-torsional ultrasonic vibration, the low-frequency modulation signal frequency of the low-frequency modulation motion, the amplitude of the longitudinal ultrasonic vibration, the amplitude of the torsional ultrasonic vibration, the phase of the longitudinal ultrasonic vibration and the phase of the torsional ultrasonic vibration.

3. The method for machining multi-level microstructures on the surface of difficult-to-machine materials based on ultrasonic milling according to claim 2, characterized in that: In the xyz coordinate system, there is the longitudinal ultrasonic vibration in the z-axis direction, and there is the torsional ultrasonic vibration in the xy plane, then the expression of the periodic vibration trajectory is as follows: in, is the phase difference between the longitudinal ultrasonic vibration and the torsional ultrasonic vibration, A T is the amplitude of the torsional ultrasonic vibration, A L is the amplitude of the longitudinal ultrasonic vibration, r is the tip radius of the tool, V d is the feed speed of the tool along the y-axis, f L is the frequency of the low frequency modulation signal, f H is the frequency of the longitudinal-torsional ultrasonic vibration.

4. The method for machining multi-level microstructures on the surface of difficult-to-machine materials based on ultrasonic milling according to claim 3, characterized in that: The amplitude of the longitudinal ultrasonic vibration increases from zero to a maximum value and then gradually decreases to zero within a period of the low-frequency modulation signal corresponding to the primary microstructure. The longitudinal displacement of the tool tip occurs for a total of f in a period corresponding to the primary microstructure. H / f L minima, and corresponding to the same number of the secondary microstructures.

5. The method for machining multi-level microstructures on the surface of difficult-to-machine materials based on ultrasonic milling according to claim 3, characterized in that: The key geometric characteristic parameters of the multi-level microstructure include the primary microstructure length, the primary microstructure width, the secondary microstructure width, the primary microstructure spacing in the cutting direction, and the primary microstructure spacing in the feeding direction.

6. The method for machining multi-level microstructures on the surface of difficult-to-machine materials based on ultrasonic milling according to claim 5, characterized in that: The primary microstructure spacing in the cutting direction is mainly determined by the ratio of the cutting speed to the frequency of the low-frequency modulation signal; the primary microstructure spacing in the feed direction is related to the feed speed; the primary microstructure length is related to the spindle speed, the cutting depth, the tool tip radius and the frequency of the low-frequency modulation signal; the primary microstructure width is jointly determined by the tool tip radius and the primary microstructure depth; the secondary microstructure length corresponds to the primary microstructure width; the secondary microstructure width is determined by the spindle speed, the cutting depth, the tool tip radius and the frequency of the longitudinal-torsional ultrasonic vibration; the tool's blade inclination angle corresponds to the angle of the direction of the primary microstructure.

7. The method for machining multi-level microstructures on the surface of difficult-to-machine materials based on ultrasonic milling according to claim 6, characterized in that: The expression of the geometric key characteristic parameters of the multi-level microstructure is: Wherein, S is the primary microstructure spacing in the cutting direction, d is the primary microstructure spacing in the feeding direction, l1 is the primary microstructure length, w is the primary microstructure width, l2 is the secondary microstructure width, V c is the cutting speed VC, feed is the feed speed, n is the spindle speed, R n is the tool nose radius, DOC is the cutting depth, β is the cutting edge inclination angle, Δt1 is the actual cutting time for machining one of the primary microstructures, and Δt2 is the actual cutting time for machining one of the secondary microstructures.

8. The method for machining multi-level microstructures on the surface of difficult-to-machine materials based on ultrasonic milling according to any one of claims 1 to 7, characterized in that: The periodic vibration trajectory is generated by a piezoelectric driven ultrasonic system.

9. The method for machining multi-level microstructures on the surface of difficult-to-machine materials based on ultrasonic milling according to any one of claims 6 or 7, characterized in that: The parameters of the tool include tool material, tool shape, tool nose radius and cutting edge inclination angle.

10. The method for machining multi-level microstructures on the surface of difficult-to-machine materials based on ultrasonic milling according to any one of claims 1 to 7, characterized in that: The material of the workpiece is a metal material or a non-metal material.

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