Method for grinding tiny holes in hard and brittle material under assistance of high-frequency ultrasonic vibration

Abstract

The invention discloses a method for grinding hard and brittle material micro-holes under the assistance of high-frequency ultrasonic vibration, which comprises the following steps: (1) a tool for machining the hard and brittle material micro-holes of less than 1mm is prepared, and the tool comprises a tool matrix framework provided with chip flutes and diamond abrasive particles electroplated on the matrix framework; (2) selecting a proper diamond abrasive particle size according to the pore diameter of the micro-pore below 1mm; and (3) introducing high-frequency ultrasonic vibration to carry out auxiliary machining on the micro holes. And (4) micro holes smaller than one millimeter are machined for the hard and brittle materials, and a high-frequency ultrasonic vibration auxiliary machining method with the higher frequency is used. And (5) verification is carried out for high-frequency ultrasonic vibration assisted machining of the micro-hole, and introduction of high-frequency ultrasonic vibration can guarantee the machining quality of the micro-hole and the service life of a tool.

Description

Technical Field

[0001] The invention provides a high-frequency ultrasonic vibration assisted processing method and a device for processing tiny holes in hard and brittle materials, belonging to the technical field of drilling processing. Background Art

[0002] As a hard and brittle material, ceramic matrix composites have excellent physical and chemical characteristics such as high strength, low density, high temperature resistance, and corrosion resistance. They are widely used in aerospace, electronic power and other fields, especially in the hot end components of aerospace engines. Since the matrix and silicon carbide fiber of ceramic matrix composites have the characteristics of high brittleness, high hardness and anisotropy, although the traditional hard and brittle material processing method is feasible, the use of traditional drilling tools, such as cemented carbide and PCD tools, has large cutting forces, and the tools wear too quickly, making it difficult to achieve the expected lifespan. In addition, the surface quality of the material after processing is poor, the sub-surface damage is serious, and burrs, edge collapse, interlayer tearing and other defects are prone to occur, which seriously affects the quality and service life of the workpiece. It cannot meet the requirements of efficient and high-quality processing of micro holes.

[0003] If the brazing abrasive of the brazed diamond tool is too small, it will be difficult to use the brazed diamond tool to process tiny holes. Electroplated diamond tools become a better choice for processing hard and brittle materials, especially ceramic-based composite materials. When drilling tiny holes, ordinary diamond tools mainly rely on the end face of the tool to drill the material, and the side faces mainly re-process the surface after the end face of the tool is processed. (1) Because the tool diameter is too small, the linear speed during processing is difficult to increase, and the tool is difficult to effectively remove the material. The cutting force is large, which reduces the tool life and the quality of the processed material is difficult to ensure. (2) Because the gap between the tool and the hole wall of the processed material is extremely small, the chips are retained on the end face of the tool, making it difficult to remove the chips, which can easily cause the diamond tool to be blocked, affect the normal operation of the tool, and reduce the sharpness of the tool. The accumulated chips intensify the friction between the tool and the material, increase the frictional heat, and ultimately reduce the quality of the processed surface and the life of the tool. Therefore, when drilling tiny holes in hard and brittle materials, the difficulty lies in effective chip removal and improving the effective removal ability of the tool.

[0004] Ultrasonic assisted drilling introduces ultrasonic vibration into the traditional drilling process, which changes the trajectory of the abrasive particles, the direction and size of the instantaneous velocity vector, and improves the dynamic sharpness of the tool during drilling, further reducing the cutting force, suppressing the damage to the workpiece, improving the processing accuracy, and increasing the service life of the tool. It is very suitable for hole processing of hard and brittle materials. The cutting force and the ultrasonic frequency obey a negative exponential relationship. Increasing the ultrasonic frequency can reduce the cutting force. High-frequency ultrasonic vibration-assisted drilling can further play the advantages of ultrasonic vibration-assisted drilling, especially for the processing of ceramic-based composite materials. It can reduce tool wear, increase tool life, improve the processing surface quality and suppress sub-surface damage, and achieve efficient and high-quality material and longer tool life processing. Liu Youyuan used ultrasonic circular vibration processing technology in the article "Deep Hole Ultrasonic Circular Vibration Drilling" ("Processing and Testing") to address the difficulty of deep hole processing. A set of vibration devices was attached to the ordinary lathe to test the processing of several deep holes of different materials and different hole diameters. It also provides an example of deep hole vibration drilling, which uses axial vibration to drill a thin-walled deep hole (TC4) part to a hole diameter of ф7.6mm. For difficult-to-process materials and small-diameter precision deep hole processing, vibration drilling is an effective way to improve the traditional deep hole processing technology. Because as long as the vibration parameters and cutting parameters are reasonably selected, no matter what material is processed, vibration drilling can reliably break and remove chips, so that small hole drilling can achieve automatic feeding and can drill longer deep holes. During the vibration drilling process, the blade and the workpiece processing surface are periodically separated, producing a high-frequency suction-extrusion effect, so that the cutting fluid can directly penetrate into the contact surface between the tool and the chip, which can effectively cool the blade of the drill bit, reduce cutting heat, and reduce the friction coefficient between the chip and the front cutting edge, reduce chip deformation, and enable the chip to be discharged smoothly. Liang Jieping et al. used ultrasonic vibration cutting method in the article "Experimental Study on Ultrasonic Vibration Drilling of Deep Holes" (Coal Technology, 1998, No. 3, P30) to explore the problems in practice. The tool used was a carbide deep hole drill produced by a tool factory. During the test, the workpiece was the main motion, and the tool was installed on the lathe tool holder through a special tool holder to do axial feed motion, and also to do circumferential vibration.

[0005] However, the ultrasonic assisted drilling mentioned above is aimed at lathe processing and deep hole processing, and the processing hole diameter is relatively large. It is not suitable for processing tiny holes of ceramic-based composite materials with a hole diameter of less than one millimeter. The strength of the cemented carbide tools used is not enough to process hard and brittle materials, especially ceramic-based composite materials. Summary of the invention

[0006] Purpose of the invention: In view of the problems that the existing ultrasonic-assisted drilling of hard and brittle materials cannot process small holes, has low processing quality and short tool life, the present invention proposes a method for processing tiny holes in hard and brittle materials with high-frequency ultrasonic vibration, which successfully processes sub-millimeter-level microholes with a hole diameter of less than one millimeter on hard and brittle materials, ensuring effective removal of materials and significantly improving drilling quality.

[0007] Technical solution: In order to achieve the above-mentioned invention object, the present invention adopts the following technical solution:

[0008] A method for machining tiny holes in hard and brittle materials using high-frequency ultrasonic vibration, the steps are as follows:

[0009] (1) Select the diamond abrasive grain size based on the diameter of the tiny hole less than one millimeter.

[0010] (2) In order to improve the processing quality of micro-holes, axial high-frequency ultrasonic vibration is introduced to assist the processing of micro-holes.

[0011] (3) Aiming at processing tiny holes less than one millimeter in hard and brittle materials and reducing cutting forces, the service life of tools is increased and the ultrasonic vibration frequency is further increased.

[0012] (4) The high-frequency ultrasonic vibration-assisted processing of micro-holes was verified. The introduction of high-frequency ultrasonic vibration can ensure the quality of micro-hole processing and improve the service life of the tool.

[0013] Specifically, the tool for machining tiny holes in hard and brittle materials comprises: a tool base frame provided with chip grooves and diamond abrasive grains electroplated on the base frame.

[0014] The tool base skeleton is a cylindrical structure with a conical top, which can inhibit the tearing phenomenon at the exit during small hole processing. The end face and the conical side face are provided with chip grooves. The chips accumulate on the end face where the tool contacts the workpiece, which will reduce the sharpness of the tool and increase friction heat. The chip groove is determined according to the chip size of the small hole processing of hard and brittle materials. The chips of conventional tools when processing hard and brittle materials are collected, the chip size is measured and counted, and the chip groove is guaranteed to accommodate the chips during processing. In the present invention, the chip size is counted as follows: Figure 3 As shown, the chip groove is in the shape of a semicircle with a radius of 150-500 μm. This structure can reduce chip blockage, reduce friction heat, and increase tool life.

[0015] Simply changing the tool diameter and optimizing the tool structure to match the micro-hole processing aperture cannot meet the use requirements of micro-hole processing, nor can it meet the micro-hole processing quality and tool life requirements. There are still problems such as large cutting force and low hole processing quality. After the tool diameter and structure are determined, the diamond abrasive particle size can also be selected and the appropriate processing method can be selected to meet the processing requirements.

[0016] First, in order to improve the hole processing quality and extend the tool life, the diamond abrasive grains cannot be too large or too small. The diamond abrasive grain size is selected according to the material being processed and the hole size, and can be selected according to the distance between the hole size and the abrasive grains. The smaller the hole size, the smaller the abrasive grain size can be, while the too small abrasive grains are difficult to guarantee in terms of material removal performance and life.

[0017] The actual area occupied by a single abrasive particle can be expressed as:

[0018]

[0019] Among them, D 1 is the abrasive particle size, and A is the actual area coefficient occupied by the abrasive determined according to the abrasive arrangement density.

[0020] The end surface area of ​​the processed micro-hole is expressed as:

[0021]

[0022] When the end surface area of ​​the micro-hole and the actual area occupied by a single abrasive grain are known, the actual number of abrasive grains can be obtained. When the number of abrasive grains is pre-selected according to the tool cutting capacity and workpiece parameters, the abrasive grain diameter can be obtained, and the actual selected abrasive grain diameter can be selected based on the calculated result.

[0023] The main failure forms of tools in micro-hole machining are abrasive wear of the end face and breakage of the small hole drill. The key to reducing abrasive wear and preventing tool breakage is to reduce the cutting force during machining. For traditional machining, the cutting force is mainly reduced by changing machining parameters, such as reducing feed speed, reducing cutting depth, increasing rotation speed, etc., but these methods are not effective for micro-hole machining. Reducing feed speed and increasing rotation speed may increase the frictional heat generated by the contact between chips and tools and workpieces, and reducing feed speed will also reduce machining efficiency. The introduction of ultrasonic vibration is particularly important for micro-hole machining of hard and brittle materials.

[0024] The addition of ultrasonic vibration makes the abrasive not in the process of continuous processing, such as Figure 4 The figure shows the contact relationship between the abrasive and the workpiece in a single cycle. The change of the abrasive trajectory makes the abrasive and the workpiece in a contact-separation cycle. The abrasive has a contact-separation characteristic in high-frequency ultrasonic assisted processing. The contact time between the abrasive and the material in a single cycle can be expressed as:

[0025]

[0026] Where f is the frequency of ultrasonic machining, h is the depth of abrasive particles penetrating into the material being machined in a single cycle, and A is the amplitude of ultrasonic machining.

[0027] Cutting force F cIt can be expressed as:

[0028]

[0029] Among them, F m is the maximum impact force, Δt is the contact time between the abrasive and the workpiece in one vibration cycle, T is a vibration cycle, and γ is a coefficient less than 1 related to the impact force waveform. It can be seen that the contact-separation characteristics between the abrasive and the workpiece, that is, the addition of ultrasonic vibration, can significantly reduce the cutting force.

[0030] For the selection of ultrasonic vibration frequency, the influence of ultrasonic vibration frequency on processing can be evaluated according to the sinusoidal function waveform of the actual trajectory of abrasive vibration, and the ratio of the maximum absolute value of the vertical coordinate of the vibration period to the horizontal coordinate length of half the vibration period is used as the evaluation standard.

[0031] The horizontal coordinate length of half a period of ultrasonic vibration can be expressed as:

[0032]

[0033] Among them, f is the frequency of ultrasonic vibration, the unit is Hz, d is the tool diameter, the unit is mm, n is the rotation speed during processing, the unit is r / min, and the final unit of the above formula is μm.

[0034] The maximum absolute value of the ordinate of one cycle of ultrasonic vibration, i.e., the ultrasonic amplitude, is:

[0035]

[0036] The unit of the above formula is μm.

[0037] The ratio of the maximum absolute value of the ordinate of the vibration period to the length of the abscissa of half the vibration period can be expressed as:

[0038]

[0039] The K value = 0.3 is used as the threshold value of the evaluation standard for measuring the influence of ultrasonic vibration frequency on processing. When K < 0.3, for processing hard and brittle materials, it is believed that the actual motion trajectory of the abrasive tends to be flat, which is not conducive to the improvement effect of ultrasonic vibration on processing; when K > 0.3, it is believed that ultrasonic vibration can be more effectively used to improve processing.

[0040] In addition to selecting the ultrasonic vibration frequency based on the material being processed, the tools used, and the ultrasonic device, it is also necessary to consider the use range of the ultrasonic device. On this basis, when processing hard and brittle materials, a larger ultrasonic vibration frequency can be selected to meet the processing quality. The general ultrasonic frequency range is 20 to 100kHz. In the present invention, 30kHz and 70kHz are preferably selected, and the influence of different ultrasonic vibration frequencies on processing is explored for different K values ​​in the formula.

[0041] Beneficial effects:

[0042] 1. The present invention designs targeted diamond tools based on the characteristics of hard and brittle material micro-holes that are difficult to process. High-frequency ultrasonic vibration-assisted processing changes the trajectory of abrasive particles. The trajectory of abrasive particles during traditional drilling is approximately circular, while the trajectory of abrasive particles during high-frequency ultrasonic-assisted drilling is approximately a sine curve with the original trajectory as the horizontal coordinate. The instantaneous speed of the abrasive particles is extremely high, and the direction of the instantaneous speed changes, which improves the dynamic sharpness of the tool during drilling and greatly reduces the cutting force.

[0043] Compared with traditional machining, ultrasonic assisted machining can effectively reduce cutting force, thereby improving the surface quality of the workpiece after machining and inhibiting sub-surface damage, making it possible to machine hard and brittle materials. Using higher ultrasonic vibration frequencies can further reduce the contact time between abrasive particles and the workpiece, ensure the contact-separation characteristics during machining, improve the difficulty of machining hard and brittle materials, improve machining quality, and achieve efficient and high-quality machining of tiny holes in hard and brittle materials.

[0044] 2. The diamond abrasive particle size and matrix skeleton diameter are selected according to the actual processing requirements. The matrix skeleton and electroplated diamond have high strength and good processing stability when processing hard and brittle materials. They can meet the requirements of processing small holes of hard and brittle materials with a diameter of less than one millimeter. The walls of the processed small holes are smooth and the processing quality is high.

[0045] 3. The corresponding high-frequency ultrasonic assisted processing method is used during the processing of the selected tool, which changes the material removal mechanism, enhances the cutting and removal effect of the tool on hard and brittle materials, improves the accuracy and quality of processing tiny holes, and increases the service life of the tool. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a schematic diagram of a grinding tool for machining tiny holes of hard and brittle materials used in the present invention; wherein, a chip groove 2, a base skeleton-1;

[0047] Figure 2 This is the assembly structure diagram of the ultrasonic device and grinding tool used in the present invention. It can be seen that the ultrasonic tool holder can convert the electrical signal of the power supply into high-frequency vibration, and transmit the vibration to the grinding tool after amplifying it through the horn. Among them, 3-machine tool spindle, 4-ultrasonic generator, 4-1-ultrasonic receiver, 4-2-transducer, 4-3-horn, 5-ultrasonic tool holder, 6-grinding tool, 7-ultrasonic power supply;

[0048] Figure 3 The chip length distribution probability diagram is obtained by collecting the chips generated after the tool processes a tiny hole and counting the size. The chip groove size can be designed according to the chip size.

[0049] Figure 4It is a sinusoidal curve diagram of the abrasive particle trajectory in the high-frequency ultrasonic assisted processing of the present invention. It can be seen that the abrasive particle trajectory is a sinusoidal curve with the original trajectory as the horizontal coordinate. During high-frequency ultrasonic vibration assisted processing, the abrasive particles and the workpiece are in a contact-separation cycle.

[0050] Figure 5 This is a diagram showing the effects of micro-holes produced by ultrasonic-assisted grinding with different frequencies in the present invention (the scale in the figure is 500 μm). It can be seen that ultrasonic-assisted processing can reduce outlet defects and inhibit outlet tearing, which illustrates the advantages of ultrasonic-assisted processing in terms of the processing quality of hard and brittle materials.

[0051] Figure 6 This is a graph showing the cutting force changing with the ultrasonic vibration frequency during the ultrasonic assisted grinding process with different frequencies applied in the present invention. It can be seen that as the ultrasonic vibration frequency increases, the cutting force decreases. DETAILED DESCRIPTION

[0052] The technical solution of the present invention will be specifically described below in conjunction with implementation cases and drawings.

[0053] In order to enable those skilled in the art to better understand the technical solutions in the patent application of the present invention, the technical solutions in the present application are clearly and completely described below in conjunction with the drawings in the present application. Obviously, the described implementation methods are only part of the implementation methods of the present application, not all implementation methods. Based on the implementation methods in the present application, all other implementation methods obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present application.

[0054] Example 1

[0055] Reference Figure 1 As shown, a tool for machining tiny holes in hard and brittle materials comprises: a tool base frame 1 provided with a chip groove 2, the tool base frame body is a cylindrical structure, the top is conical, the end face and the conical side face are provided with chip grooves, and the base frame is electroplated with diamond abrasive grains. The tool diameter is 0.9 mm, and the diamond abrasive grain size is 61-74 μm.

[0056] The micro hole machining experiments were carried out on a DMG Ultrason ic 20 machining center using a high-frequency ultrasonic vibration device, such as Figure 2 As shown, it includes an ultrasonic power supply, a wireless power transmission module, and an ultrasonic tool handle; the ultrasonic tool handle includes an ultrasonic receiver, a transducer, and a variable amplitude rod; and the grinding tool 6 is installed at the end of the variable amplitude rod 4-3.

[0057] In this embodiment, the hard and brittle material to be processed is a 2.5D braided silicon carbide fiber reinforced ceramic matrix composite material (commercially available), which is prepared by polymer impregnation pyrolysis method. Before the experiment, a diamond wire cutting machine is used to cut 25×5×4mm 3The ceramic matrix composite material of different sizes was polished and the workpiece surface was cleaned with an ultrasonic cleaner. The experimental parameters for micro-hole processing are shown in Table 1. The ultrasonic vibration frequency was selected as 0, 30, and 70 kHz, where the frequency of 0 kHz means that no ultrasonic vibration equipment is used, that is, traditional processing, which is convenient for comparison with ultrasonic vibration-assisted processing.

[0058] Table 1 Micro hole processing experimental parameters

[0059]

[0060]

[0061] Cutting force F c It can be expressed as:

[0062]

[0063] Among them, F m is the maximum impact force, Δt is the contact time between the abrasive and the workpiece in one vibration cycle, T is a vibration cycle, and γ is a coefficient less than 1 related to the impact force waveform. It can be seen that the contact-separation characteristics between the abrasive and the workpiece, that is, the addition of ultrasonic vibration, can significantly reduce the cutting force.

[0064] The contact relationship between the abrasive and the workpiece in a single cycle. The change of the abrasive trajectory makes the abrasive and the workpiece in a contact-separation cycle. The abrasive has a contact-separation characteristic in high-frequency ultrasonic assisted processing. The contact time between the abrasive and the material in a single cycle can be expressed as:

[0065]

[0066] Where f is the frequency of ultrasonic machining, h is the depth of abrasive particles penetrating into the material being machined in a single cycle, and A is the amplitude of ultrasonic machining.

[0067] It can be seen that the addition of ultrasonic vibration can significantly reduce the cutting force.

[0068] And the cutting force decreases with the increase of ultrasonic vibration frequency, such as Figure 6 As shown in Figure 2, as the ultrasonic vibration frequency increases, the cutting force decreases, which improves the processing stability. The reduction of cutting force also improves the surface quality of the hole and suppresses the exit defects of the hole. Figure 5 As shown in the figure, there are obvious tearing and burrs at the exit of conventionally processed holes, while ultrasonic-assisted processing can reduce the cutting force and effectively suppress tearing and burrs at the exit.

[0069] The ratio of the maximum absolute value of the ordinate of the vibration period to the length of the abscissa of half the vibration period can be expressed as:

[0070]

[0071] Taking K value of 0.3 as the evaluation standard to measure the influence of ultrasonic vibration frequency on processing, when the ultrasonic vibration frequency is 30K, K value is 0.204, which is less than 0.3; when the ultrasonic vibration frequency is 70K, K value is 0.476, which is greater than 0.3. And when the ultrasonic vibration frequency is 70K, compared with 30K, as the K value increases, the introduction of ultrasonic vibration has a more obvious effect on the improvement of processing, such as Figure 4 As shown, the hole outlet morphology and surface quality of 70K are better than those of 30K. This is because the change of ultrasonic vibration frequency changes the K value, thus affecting the processing quality.

[0072] As drilling progresses, tool wear will gradually increase, and larger cutting forces will increase tool wear. The cutting force in traditional processing is greater than that in high-frequency ultrasonic vibration-assisted processing. In high-frequency ultrasonic vibration-assisted processing, the higher the vibration frequency, the smaller the cutting force. Due to tool wear, the cutting force increases with the number of holes drilled. In traditional processing, the tool was severely worn after processing 8 holes, and the tool broke when processing the 14th hole. In 30kHz high-frequency ultrasonic vibration-assisted processing, severe tool wear occurred after processing 12 holes, and the tool broke when processing 15 holes. In the higher frequency 70kHz high-frequency ultrasonic vibration-assisted processing, the cutting force was basically stable, and no tool breakage occurred in the experiment. After drilling 46 holes, the tool was worn. Therefore, using a higher frequency in high-frequency ultrasonic vibration-assisted processing is beneficial to reducing cutting force and extending tool life. Compared with traditional processing and 30kHz high-frequency ultrasonic vibration-assisted processing, 70kHz high-frequency ultrasonic vibration-assisted processing has a significant effect on reducing cutting force and extending tool life.

[0073] According to the above conclusions and the effect of the processed micro-holes, the high-frequency ultrasonic vibration-assisted processing method used in the processing of micro-holes in hard and brittle materials of the present invention improves the processing quality of the holes. Compared with the traditional processing of small holes, ultrasonic-assisted processing increases the axial vibration of diamond abrasive grains, and the abrasive grains and the processed materials have a periodic contact-separation phenomenon during the processing, which reduces the grinding force, improves the material removal ability of the abrasive grains, and increases the dynamic sharpness of the abrasive grains, and finally achieves efficient and high-quality processing of micro-holes in hard and brittle materials, which illustrates the effectiveness of the present invention in processing micro-holes in hard and brittle materials. The high-frequency ultrasonic vibration-assisted processing method of the present invention is also applicable to other hard and brittle materials except the ceramic-based composite materials of this experiment, and also has the effect of reducing cutting force and improving processing quality.

Claims

1. A method for grinding micro-holes in hard and brittle materials using high-frequency ultrasonic vibration assistance, characterized in that: Here are the steps: (1) A machining grinding tool, the tool comprising: a base frame (1) provided with a chip groove (2) and diamond abrasive grains electroplated on the base frame; the base frame is a cylindrical structure, the top is conical, and the end face and the conical side face are provided with chip grooves; the size of the diamond abrasive grains is set according to the size of the micro-hole to be machined; the chip groove is determined according to the chip size of the micro-hole machined in hard and brittle materials; (2) Introducing axial ultrasonic vibration to assist in machining tiny holes in hard and brittle materials; (3) To process tiny holes less than one millimeter in hard and brittle materials, reduce cutting force, and increase tool life, the ultrasonic vibration frequency is further increased based on step (2); (4) Result verification.

2. The method for high-frequency ultrasonic vibration-assisted grinding of micro-holes in hard and brittle materials according to claim 1 is characterized in that: The chip groove is semicircular in shape with a radius of 150-500μm.

3. The method for high-frequency ultrasonic vibration-assisted grinding of micro-holes in hard and brittle materials according to claim 1 is characterized in that: The process of determining the diamond abrasive grain size is as follows: (1) The area occupied by a single abrasive particle is expressed as: Where D1 is the abrasive particle size, and A is the actual area coefficient of the abrasive particles determined according to the abrasive particle arrangement density; (2) The end surface area of ​​the processed micro-hole is expressed as: According to the end surface area of ​​the processed micro-hole and the actual area occupied by a single abrasive grain, the actual number of abrasive grains can be obtained, and then the abrasive grain diameter can be obtained.

4. The method for high-frequency ultrasonic vibration-assisted grinding of micro-holes in hard and brittle materials according to claim 1 or 3, characterized in that: The hard and brittle material is a 2.5D woven silicon carbide fiber reinforced ceramic matrix composite material, and the diameter of the processed micro-holes is less than one millimeter.

5. The method for high-frequency ultrasonic vibration-assisted grinding of micro-holes in hard and brittle materials according to claim 1, characterized in that: In step (2), the axial ultrasonic vibration parameters applied are selected to evaluate the influence of the ultrasonic vibration frequency on the processing according to the sinusoidal function waveform of the abrasive vibration, and the ratio of the maximum absolute value of the ordinate of the vibration period to the abscissa length of the half-period of the vibration is used as the evaluation standard; The horizontal coordinate length of half a period of ultrasonic vibration can be expressed as: Among them, f is the frequency of ultrasonic vibration, the unit is Hz, d is the tool diameter, the unit is mm, n is the speed during processing, the unit is r / min, and the final unit of the above formula is μm; The maximum absolute value of the ordinate of one cycle of ultrasonic vibration, that is, the ultrasonic amplitude, is: The unit of the above formula is μm.

6. The method for high-frequency ultrasonic vibration-assisted grinding of micro-holes in hard and brittle materials according to claim 5, characterized in that: In step (3), within the use range of the ultrasonic device, the ultrasonic vibration frequency range is optimized in combination with the K value: The K value is the ratio of the maximum absolute value of the ordinate of the vibration period to the length of the abscissa of half the vibration period, which can be expressed as:

7. The method for high-frequency ultrasonic vibration-assisted grinding of micro-holes in hard and brittle materials according to claim 6, characterized in that: The K value of 0.3 is used as the evaluation standard to measure the influence of ultrasonic vibration frequency on processing. When K<0.3, for processing hard and brittle materials, it is believed that the actual motion trajectory of the abrasive tends to be flat, which is not conducive to the improvement effect of ultrasonic vibration on processing; when K>0.3, it is believed that ultrasonic vibration can be more effectively used to improve processing.

Images