Method for high-frequency ultrasonic vibration assisted grinding of micro-holes in hard and brittle materials

Abstract

The application discloses a method for processing a micro hole of a hard and brittle material by high-frequency ultrasonic vibration assisted grinding, and comprises the following steps: (1) preparing a tool for processing a micro hole of a hard and brittle material with a size of less than 1 mm, wherein the tool comprises a tool base skeleton provided with a chip groove and diamond abrasive grains plated on the base skeleton; (2) selecting a proper size of the diamond abrasive grains according to the size of the micro hole with a size of less than 1 mm; (3) introducing high-frequency ultrasonic vibration to assist in processing the micro hole; (4) using a higher-frequency high-frequency ultrasonic vibration assisted processing method for processing the micro hole of the hard and brittle material with a size of less than 1 mm; and (5) verifying the high-frequency ultrasonic vibration assisted processing of the micro hole, and the introduction of the high-frequency ultrasonic vibration can ensure the processing quality of the micro hole and the service life of the tool.

Description

TECHNICAL FIELD

[0001] The application provides a high-frequency ultrasonic vibration assisted machining method and device for machining a micro hole of a hard and brittle material, and belongs to the technical field of drilling machining. BACKGROUND

[0002] The ceramic matrix composite material has high strength, low density, high temperature resistance, corrosion resistance and other excellent physical and chemical characteristics as the hard and brittle material, is widely used in the fields of aviation, aerospace, electronics and power, and is particularly suitable for hot end parts of a space engine. Since the matrix and silicon carbide fiber of the ceramic matrix composite material have the characteristics of high brittleness, high hardness and anisotropy, although the traditional hard and brittle material machining method has feasibility, the use of traditional drilling machining tools such as hard alloy and PCD tools has the problems of large cutting force, rapid tool wear, difficult to achieve the desired service life, poor surface quality after material machining, serious subsurface damage, easy to have burrs, edge collapse, interlayer tearing and other defects, and serious influence on the workpiece quality and service life. The traditional drilling machining method cannot meet the requirements of high-efficiency and high-quality machining of a micro hole.

[0003] If the brazing abrasive grains of the brazed diamond tool are too small, the brazed diamond tool is difficult to be used for machining a micro hole, and the electroplated diamond tool becomes a better choice for machining the hard and brittle material, especially the ceramic matrix composite material. In the process of drilling a micro hole by using the ordinary diamond tool, the tool end face mainly drills the material, and the side face mainly processes the surface processed by the tool end face.(1) Since the tool diameter is too small, the linear speed is difficult to be improved during machining, the tool is difficult to effectively remove the material, the cutting force is large, the tool life is reduced, and the machining material quality is difficult to be guaranteed.(2) Since the gap between the tool and the hole wall of the machined material is extremely small, the chips are retained on the tool end face, the chip removal is difficult, the diamond tool is easily blocked, the normal work of the tool is affected, and the sharpness of the tool is reduced. The accumulated chips aggravate the friction between the tool and the material, the friction heat increases, and finally, the machining surface quality and the tool life are reduced. Therefore, when drilling a micro hole of the hard and brittle material, the difficulties lie in effective chip removal and improvement of the effective removal capacity of the tool.

[0004] Ultrasonic assisted drilling introduces ultrasonic vibration into the traditional drilling process, which changes the trajectory of abrasive particles, the direction and size of instantaneous velocity vector, and improves the dynamic sharpness of the tool during drilling, further reduces cutting force, suppresses workpiece processing damage, improves processing accuracy, and increases tool life. It is very suitable for hole processing of hard and brittle materials. The cutting force and ultrasonic frequency obey a negative exponential relationship, and 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 ceramic matrix composite machining, which can reduce tool wear, improve tool life, improve machining surface quality and suppress subsurface damage, and realize high-efficiency and high-quality material machining and longer tool life. Liu Youyuan in "Deep Hole Ultrasonic Circumferential Vibration Drilling" (Process and Detection) adopts ultrasonic circumferential vibration machining technology for the characteristics of difficult deep hole machining. A set of vibration device is added to the ordinary lathe, and deep holes of several different materials and different hole diameters are processed. It also provides examples of deep hole vibration drilling, which can drill a thin-walled deep hole (material TC4) to a hole diameter of ф7.6mm using axial vibration. For difficult-to-machine materials and small-diameter precision deep hole machining, vibration drilling is an effective way to improve the traditional deep hole machining process. Because as long as the vibration parameters and cutting parameters are selected reasonably, vibration drilling can reliably chip and chip regardless of the material being machined, so that small hole drilling can achieve automatic feeding and drill longer deep holes. During vibration drilling, the tool edge and the workpiece machining surface are periodically separated, producing high-frequency suction and extrusion, allowing cutting fluid to penetrate directly to the contact surface of the tool and the chip, effectively cooling the blade of the drill, reducing cutting heat, and reducing the friction coefficient between the chip and the rake face, reducing chip deformation, and allowing the chip to be easily discharged. In the article "Experimental Study on Ultrasonic Vibration Drilling Deep Hole" (Coal Technology, 1998, No. 3, P30), Lei Jieping et al. adopted ultrasonic circumferential vibration cutting method to explore the problems existing in practice, and the tool used was a hard alloy deep hole drill gun produced by the 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 and made axial feed motion while also making circumferential vibration.

[0005] But the above ultrasonic assisted drilling is aimed at lathe machining and deep hole machining, and the hole diameter is relatively large, which is not suitable for the machining of ceramic matrix composite micro-holes with a hole diameter of less than one millimeter. The strength of the hard alloy tool used is not enough to process hard and brittle materials, especially ceramic matrix composites. SUMMARY

[0006] Invention purpose: In view of the problems that the existing ultrasonic assisted drilling process cannot process small holes, the processing quality is low, and the tool life is short, the present application provides a method for processing small holes in hard and brittle materials by high-frequency ultrasonic vibration, which successfully processes sub-millimeter level micro-holes with a hole diameter of less than one millimeter in hard and brittle materials, ensures effective material removal, and significantly improves drilling quality.

[0007] Technical scheme: In order to achieve the above invention purpose, the present application adopts the following technical scheme:

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

[0009] (1) Select the size of diamond abrasive according to the hole diameter of micro-hole below one millimeter.

[0010] (2) Based on the purpose of improving the processing quality of micro-hole, axial high-frequency ultrasonic vibration is introduced to assist in processing micro-hole.

[0011] (3) For processing hard and brittle material micro-hole below one millimeter and reducing cutting force, improving tool life, further improving ultrasonic vibration frequency.

[0012] (4) For verification of high-frequency ultrasonic vibration assisted processing of micro-hole, the introduction of high-frequency ultrasonic vibration can ensure the processing quality of micro-hole and improve the service life of tool.

[0013] Specifically, the tool for processing small holes in hard and brittle materials includes a tool base skeleton provided with a chip groove and diamond abrasive plated on the base skeleton.

[0014] The tool base skeleton is a cylindrical structure, the top is a cone, which has a restraining effect on the outlet tearing phenomenon during small hole processing, and the end face and the conical side are provided with a chip groove. The accumulated chips at the end face of the tool and the workpiece will reduce the sharpness of the tool and increase the friction heat. The chip groove is determined according to the chip size of the hard and brittle material micro-hole processing, and the chip size is measured and counted to ensure that the chip groove can accommodate the chips during processing. In the present application, the counted chip size is as shown in Figure 3 The chip groove is in the shape of a semicircle with a radius of 150-500 μm, which reduces the chip jamming phenomenon, reduces the friction heat, and increases the tool life.

[0015] Simply changing the tool diameter and optimizing the tool structure to match the micro-hole processing hole diameter cannot meet the requirements of processing micro-hole, and it is also difficult to meet the requirements of micro-hole processing quality and tool service life, and there are still problems of large cutting force and low hole processing quality. After the tool diameter and structure are determined, the size of diamond abrasive can be selected and the appropriate processing method can be selected to meet the processing requirements.

[0016] First, to improve the hole processing quality and prolong the tool life, the diamond abrasive grain cannot be too large or too small. The diamond abrasive grain size is selected according to the processed material and the hole diameter, and can be selected according to the distance between the hole diameter and the abrasive grain. The smaller hole diameter makes the abrasive grain size not too large, and the too small abrasive grain is difficult to guarantee in the material removal performance and the life.

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

[0018]

[0019] Wherein, D1 is the abrasive grain size, A is the actual area occupied by the abrasive grain determined according to the abrasive grain arrangement density.

[0020] The end face area of the processed micro hole is expressed as:

[0021]

[0022] Under the condition that the micro hole end face area and the actual area occupied by a single abrasive grain are known, the actual number of abrasive grains arranged can be obtained. Under the condition that the abrasive grain number is preselected according to the tool cutting capacity and the workpiece parameters, the abrasive grain diameter can be obtained. The actual selected abrasive grain diameter can be selected according to the calculation.

[0023] For the tool failure mode in micro hole processing, the end face abrasive grain wear and the small hole drill breakage are mainly. The key to reducing abrasive grain wear and preventing tool breakage lies in reducing the cutting force in the processing process. For the traditional processing, the cutting force is mainly reduced by changing the processing parameters, such as reducing the feed speed, reducing the cutting depth, increasing the rotating speed, etc., but these methods have little effect on micro hole processing. Reducing the feed speed and increasing the rotating speed may aggravate the friction heat generated by the contact between the chip and the tool and the workpiece. Reducing the feed speed will also reduce the processing efficiency. The introduction of ultrasonic vibration is particularly important for micro hole processing of hard and brittle materials.

[0024] The addition of ultrasonic vibration makes the abrasive grain not in the process of processing all the time, such as Figure 4 The contact relationship between a single cycle abrasive grain and the workpiece is shown in the figure, the change of the abrasive grain track makes the abrasive grain and the workpiece in the contact-separation cycle process. The abrasive grain has the contact-separation characteristics in the high frequency ultrasonic assisted processing. The contact time of a single cycle abrasive grain with the material can be expressed as:

[0025]

[0026] Wherein, f is the frequency of ultrasonic machining, h is the depth of the abrasive grain into the processed material in a single cycle, and A is the amplitude of ultrasonic machining.

[0027] The cutting force F c can be expressed as:

[0028]

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

[0030] For the selection of the ultrasonic vibration frequency, the influence of the ultrasonic vibration frequency on machining can be evaluated according to the sine function waveform of the actual trajectory of the abrasive grain vibration, and the ratio of the maximum absolute value of the longitudinal coordinate of the vibration cycle to the horizontal coordinate length of the half cycle of the vibration is taken as the evaluation standard.

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

[0032]

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

[0034] The maximum absolute value of the longitudinal coordinate of one cycle of the 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 longitudinal coordinate of the vibration cycle to the horizontal coordinate length of the half cycle of the vibration can be expressed as:

[0038]

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

[0040] In addition to selecting the ultrasonic vibration frequency according to the machined material, the tool used and the ultrasonic device, it is also necessary to consider the range of use of the ultrasonic device. On this basis, when machining hard and brittle materials, a larger ultrasonic vibration frequency can be selected to meet the machining quality. Generally, the ultrasonic frequency range is 20-100 kHz, and in the present application, 30 kHz and 70 kHz are preferentially selected to explore the influence of different ultrasonic vibration frequencies on machining according to different K values in the formula.

[0041] Advantages:

[0042] 1、 The present application is designed for the characteristics of hard and brittle material micro hole difficult to process, the high frequency ultrasonic vibration assisted machining changes the trajectory of abrasive particles, the trajectory of abrasive particles is approximately circular in traditional drilling, and the trajectory of abrasive particles is approximately sinusoidal with the original trajectory as the abscissa in high frequency ultrasonic assisted drilling, the instantaneous speed of abrasive particles is extremely high, the instantaneous speed direction is changed, the dynamic sharpness of the tool during drilling is improved, and the cutting force is greatly reduced.

[0043] Compared with traditional machining, ultrasonic assisted machining can effectively reduce the cutting force, thereby improving the surface quality of the machined workpiece and inhibiting subsurface damage, so that it is possible to machine hard and brittle materials. Using higher ultrasonic vibration frequency can further reduce the contact time of abrasive particles and the workpiece, ensure the contact-separation characteristics in the machining process, improve the machinability of hard and brittle materials, improve the machining quality, and realize efficient and high-quality machining of hard and brittle material micro holes.

[0044] 2、 The diameter of the diamond abrasive particles and the diameter of the matrix skeleton are selected according to the actual machining requirements, the strength of the matrix skeleton and the plated diamond is high, the machining stability is good when machining hard and brittle materials, the requirements of machining micro hole diameters of hard and brittle materials below one millimeter can be met, the micro hole wall is smooth, and the machining quality is high.

[0045] 3、 The corresponding high frequency ultrasonic assisted machining method is used when the tool is selected for machining, the material removal mechanism is changed, the cutting and removal effect of the tool on hard and brittle materials is enhanced, the precision and quality of the machined micro hole are improved, and the service life of the tool is improved. DETAILED DESCRIPTION

[0046] Figure 1 is a grinding tool for machining hard and brittle material micro holes adopted by the present application; wherein the chip groove 2, the matrix skeleton-1;

[0047] Figure 2 is an assembly structure diagram of the ultrasonic device and the grinding tool used in the present application, it can be seen that the ultrasonic tool holder can convert the electrical signal of the power supply into high frequency vibration, and the vibration is amplified through the amplitude changer and then transmitted to the grinding tool. Among them, 3 is the main shaft of the machine tool, 4 is the ultrasonic wave generator, 4-1 is the ultrasonic wave receiver, 4-2 is the transducer, 4-3 is the amplitude changer, 5 is the ultrasonic tool holder, 6 is the grinding tool, and 7 is the ultrasonic power supply;

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

[0049] Figure 4is the sinusoidal curve diagram of the abrasive grain trajectory in the high-frequency ultrasonic assisted machining in the application, it can be seen that the abrasive grain trajectory is a sinusoidal curve with the original trajectory as the horizontal coordinate, and the abrasive grain and the workpiece are in a cycle of contact-separation during high-frequency ultrasonic vibration assisted machining.

[0050] Figure 5 is the effect diagram of the micro hole machined by the ultrasonic assisted grinding with different frequencies in the application (the scale in the figure is 500 μm), it can be seen that the ultrasonic assisted machining can reduce the outlet defects and inhibit the outlet tearing, which shows the advantages of the ultrasonic assisted machining in the machining quality of hard and brittle materials.

[0051] Figure 6 is the diagram of the cutting force changing with the ultrasonic vibration frequency during the ultrasonic assisted grinding with different frequencies in the application, it can be seen that the cutting force decreases with the increase of the ultrasonic vibration frequency. DETAILED DESCRIPTION

[0052] The technical solutions of the application will be specifically described below in combination with the embodiments and the drawings.

[0053] In order to enable the persons skilled in the art to better understand the technical solutions in the patent application, the technical solutions in the application will be clearly and completely described below in combination with the drawings in the application. Obviously, the described embodiments are only some of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all the other embodiments obtained by the persons skilled in the art without creative labor should belong to the protection scope of the application.

[0054] Embodiment 1

[0055] Referring to Figure 1 As shown in the figure, the tool for machining micro holes in hard and brittle materials includes a tool base skeleton 1 provided with a chip groove 2, the tool base skeleton is in a cylindrical structure, the top is conical, the end face and the conical side face are provided with chip grooves, and diamond abrasive grains are electroplated on the base skeleton. The tool diameter is 0.9 mm, and the size of the diamond abrasive grain is 61-74 μm.

[0056] The micro hole machining experiment is carried out on a DMG Ultrasonic 20 machining center, and a high-frequency ultrasonic vibration device is used, as shown in the figure, which includes an ultrasonic power supply, a wireless power transmission module and an ultrasonic tool holder; the ultrasonic tool holder includes an ultrasonic wave receiver, a transducer and an amplitude changer; and the grinding tool 6 is installed at the end of the amplitude changer 4-3. Figure 2

[0057] In this embodiment, the hard and brittle material to be machined is a 2.5D woven silicon carbide fiber reinforced ceramic matrix composite material (commercially available), which is prepared by a polymer impregnation pyrolysis method, and before the experiment, a diamond wire cutting machine is used to cut 25×5×4 mm 3 ​The ceramic matrix composites were polished and cleaned using an ultrasonic cleaner. The experimental parameters for micro-hole machining are shown in Table 1. Ultrasonic vibration frequencies were selected at 0, 30, and 70 kHz. A frequency of 0 kHz, meaning conventional machining without ultrasonic vibration equipment, facilitates comparison with ultrasonic vibration-assisted machining.

[0058] Table 1 Experimental parameters for micro-hole machining

[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 within one vibration cycle, T is one 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 machining. 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, e.g. 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 conventional processing holes, while ultrasonic assisted processing can reduce 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] With K value as 0.3 as the evaluation standard for measuring the influence of ultrasonic vibration frequency on machining, when the ultrasonic vibration frequency is 30K, the K value is 0.204, which is less than 0.3; when the ultrasonic vibration frequency is 70K, the K value is 0.476, which is greater than 0.3. And compared with 30K, when the ultrasonic vibration frequency is 70K, the improvement effect of the introduction of ultrasonic vibration on machining is more obvious with the increase of K value, as shown in Figure 4 The hole outlet morphology and surface quality of 70K are better than those of 30K, which is due to the change of ultrasonic vibration frequency, which changes the K value and affects the machining quality.

[0072] With the drilling, tool wear will gradually increase, and larger cutting force will aggravate tool wear. The cutting force in traditional machining is greater than that in high-frequency ultrasonic vibration assisted machining. In high-frequency ultrasonic vibration assisted machining, the higher the vibration frequency, the smaller the cutting force. Due to tool wear, the cutting force increases with the increase of the number of holes. In traditional machining, the tool is seriously worn after machining 8 holes, and the tool is broken when machining the 14th hole. In 30kHz high-frequency ultrasonic vibration assisted machining, serious tool wear occurs after machining 12 holes, and the tool is broken when machining the 15th hole. In high-frequency ultrasonic vibration assisted machining with a higher frequency of 70kHz, the cutting force is basically stable, and no tool breakage occurs in the experiment. After drilling 46 holes, the tool is worn. Therefore, using a higher frequency in high-frequency ultrasonic vibration assisted machining is beneficial to reduce the cutting force and prolong the tool life. Compared with traditional machining and 30kHz high-frequency ultrasonic vibration assisted machining, 70kHz high-frequency ultrasonic vibration assisted machining has obvious effect on reducing cutting force and prolonging tool life.

[0073] From the above conclusion and the effect of the processed micro holes, the high-frequency ultrasonic vibration assisted machining method used for the micro hole machining of hard and brittle materials improves the machining quality of the holes. Compared with traditional machining of small holes, ultrasonic assisted machining increases the axial vibration of diamond abrasive grains, and the abrasive grains have periodic contact-separation phenomenon with the processed material during the machining process, which reduces the grinding force, improves the material removal capacity of the abrasive grains, increases the dynamic sharpness of the abrasive grains, and finally realizes the efficient and high-quality machining of hard and brittle material micro holes, which proves the effectiveness of the application for hard and brittle material micro hole machining. The high-frequency ultrasonic vibration assisted machining method of the application is also applicable to other hard and brittle materials except the ceramic matrix composite material of the experiment, and also has the effect of reducing cutting force and improving machining quality.

Claims

1. A method for machining a micro hole in a hard and brittle material by high-frequency ultrasonic vibration assisted grinding, characterized by, The steps are as follows: (1) processing grinding tools, the tool includes: the base skeleton (1) provided with a chip groove (2) and diamond abrasive grains plated on the base skeleton; the base skeleton is a cylindrical structure, the top is conical, the end face and the conical side are provided with a chip groove; the size of the diamond abrasive grains is set according to the size of the micro hole to be processed; the chip groove is determined according to the size of the chip of the micro hole of the hard and brittle material; (2) introducing axial ultrasonic vibration to assist in processing micro holes of hard and brittle materials; the applied axial ultrasonic vibration parameters are selected according to the evaluation of the influence of ultrasonic vibration frequency on processing based on the sine function waveform of abrasive grain vibration, and the ratio of the maximum value of the absolute value of the longitudinal coordinate of the vibration period to the horizontal coordinate length of half a vibration period is taken as the evaluation standard; The horizontal coordinate length of half a vibration period can be expressed as: Wherein, f is the frequency of ultrasonic vibration, unit: Hz, d is the diameter of the tool, unit: mm, n is the rotating speed during processing, unit: r / min, the final unit of the above formula is μm; The maximum value of the absolute value of the longitudinal coordinate of one period of ultrasonic vibration, that is, the ultrasonic amplitude, is: The unit of the above formula is μm; (3) for the purpose of processing micro holes below one millimeter of hard and brittle materials and reducing cutting force and improving tool life, further improve the ultrasonic vibration frequency based on step (2); Within the scope of the use of ultrasonic devices, the ultrasonic vibration frequency range is optimized in combination with K value: the K value is the ratio of the maximum value of the absolute value of the longitudinal coordinate of the vibration period to the horizontal coordinate length of half a vibration period, which can be expressed as: Taking K value as 0.3 as the evaluation standard for measuring the influence of ultrasonic vibration frequency on processing, when K<0.3, it is considered that the actual motion trajectory of the abrasive grains tends to be flat, which is not conducive to the improvement of ultrasonic vibration on processing; when K>0.3, it is considered that ultrasonic vibration can more effectively improve the processing; (4) result verification.

2. The method of claim 1, wherein the high-frequency ultrasonic vibration assisted grinding of a micro-hole in a hard and brittle material is characterized by, The chip groove is semicircular with a radius of 150-500 μm.

3. The method of claim 1, wherein the high-frequency ultrasonic vibration assisted grinding of a micro-hole in a hard and brittle material is characterized by, The determination process of the size of the diamond abrasive grains is as follows: (1) the area occupied by a single abrasive grain is represented as: Wherein, D1 is the grain size, A is the actual area coefficient of the abrasive grain determined according to the abrasive grain arrangement density; (2) the end face area of the micro hole to be processed is represented as: According to the end face area of the micro hole to be processed and the actual area occupied by a single abrasive grain, the actual number of abrasive grains is obtained, and then the grain diameter is obtained.

4. The method of claim 1 or 3, wherein the high-frequency ultrasonic vibration assisted grinding of a micro-hole in a hard and brittle material is characterized by, The hard and brittle material is 2.5D woven silicon carbide fiber reinforced ceramic matrix composite, and the micro hole to be processed has a diameter below one millimeter.

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