CN117102982A - Ultrasonic vibration auxiliary grinding processing method for ceramic matrix composite - Google Patents

Abstract

The invention belongs to the technical field of composite material processing, and particularly relates to an ultrasonic vibration assisted grinding processing method of a ceramic matrix composite material, which comprises the steps of carrying out a single abrasive particle basic scratch test to obtain a micro-macro brittle fracture transition critical depth; acquiring ultrasonic vibration auxiliary grinding process parameters based on the transition critical depth of micro-macro brittle fracture and the quality of the machined surface of the part; and carrying out ultrasonic vibration auxiliary grinding processing on the ceramic matrix composite based on the ultrasonic vibration auxiliary grinding process parameters. According to the technical scheme, the microscopic-macroscopic brittle fracture transition critical depth is determined based on the part processing surface quality requirement and a basic scratch test, a processing technological parameter determination criterion is established, ultrasonic vibration auxiliary grinding technological parameters are obtained, and ultrasonic vibration auxiliary grinding processing of the ceramic matrix composite is carried out according to the ultrasonic vibration auxiliary grinding technological parameters, so that the grinding processing efficiency is improved on the premise of guaranteeing high-quality surface processing of the ceramic matrix composite.

Description

Ultrasonic vibration auxiliary grinding processing method for ceramic matrix composite

Technical Field

The invention belongs to the technical field of composite material processing, and particularly relates to an ultrasonic vibration assisted grinding processing method for a ceramic matrix composite material.

Background

In the aerospace field, along with the development requirement of equipment performance, a lightweight material with high temperature resistance, high specific strength and wear resistance is required, and a ceramic matrix composite material stands out from a plurality of materials and becomes a high temperature resistant material with a great application prospect. The ceramic matrix composite overcomes the defect of high brittleness of the ceramic material through an exogenous toughening mechanism, wherein the continuous fiber reinforced ceramic matrix composite realizes higher strength and fracture toughness through crack deflection and crack bridging.

The ceramic matrix composite material consists of a plurality of components with obvious difference in performance, and the use performance of the material is effectively improved due to the cooperation of a high-hardness ceramic matrix, an anisotropic fiber reinforced phase, a weak interface layer and the like, but the defect of extremely poor processing performance of the ceramic matrix composite material is also caused. The ceramic matrix composite is a typical material with the dual characteristics of a hard and brittle material and a composite material, is extremely easy to damage in the processing process, and reduces the quality of the processed surface due to the reasons of base breakage, fiber pulling, stripping, random fracture distribution and the like in the processing. The material removal mechanism of the ceramic matrix composite shows that high-quality surface processing can be realized by removing the material in a micro brittle fracture domain, but the critical cutting depth of micro-macro brittle fracture transition of the ceramic matrix composite is generally smaller, so that in order to realize high-surface-quality processing of parts during processing, the processing efficiency is generally selected to be sacrificed to ensure the surface quality.

In order to cope with the challenge of poor machinability of the ceramic matrix composite, grinding is a common machining process, ultrasonic vibration assisted machining is also a common process method for machining hard and brittle materials, and for ultrasonic vibration assisted grinding machining of the ceramic matrix composite, the machining process parameters are scientifically and reasonably determined, so that high-quality surface machining is realized, and meanwhile, the machining efficiency is improved, so that the method is a very critical work. At present, when an ultrasonic vibration assisted grinding process is adopted to process a ceramic matrix composite, a traditional method for determining processing parameters is widely used, wherein the traditional method is to carry out an orthogonal test or a single factor test and then optimize the processing parameters according to responses such as force, surface roughness, material removal rate and the like obtained by the test, and the traditional method has the defects that: the process is complicated, time and labor are consumed, the test parameter setting has a certain degree of randomness, and the machining quality and the machining efficiency are difficult to balance at the same time.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides an ultrasonic vibration assisted grinding processing method of a ceramic matrix composite, which is characterized in that a maximum undeformed abrasive dust thickness model is established based on the three-dimensional motion track of abrasive particles under the ultrasonic vibration assisted grinding working condition, processing is determined in a micro brittle domain according to the quality requirement of a processed surface, a basic scratch test is carried out to determine the micro-macro brittle fracture transition critical depth of the ceramic matrix composite, a processing technological parameter determination criterion is established based on the principle that the maximum undeformed abrasive dust thickness is not more than the micro-macro brittle fracture transition critical depth, and ultrasonic vibration assisted grinding technological parameters are acquired for processing, so that the grinding processing efficiency is improved on the premise of ensuring the high-quality surface processing of the ceramic matrix composite.

The technical scheme adopted for achieving the purposes is as follows:

an ultrasonic vibration assisted grinding processing method of a ceramic matrix composite material comprises the following steps:

s1, carrying out a single abrasive grain basic scratch test on a ceramic matrix composite plane pattern, and determining the micro-macro brittle fracture transition critical depth;

s2, acquiring ultrasonic vibration auxiliary grinding process parameters based on the micro-macro brittle fracture transition critical depth and combining the part machining surface quality requirements;

s3, performing ultrasonic vibration auxiliary grinding processing on the ceramic matrix composite based on the ultrasonic vibration auxiliary grinding process parameters.

Preferably, in the step S2, the surface quality requirements of the part processing include surface roughness and surface damage after the part processing; wherein the surface roughness Sa is 2.0 μm, and the surface after the part processing has no pits formed by fiber peeling and fiber pulling.

Preferably, in the step S1, the single abrasive grain basic scratch test includes the following steps:

s1-1, preparing a steel disc with single diamond abrasive particles welded on the circumferential surface, and installing the steel disc on a numerical control machine tool;

s1-2, starting a numerical control machine tool, enabling a steel disc to rotate under the drive of the numerical control machine tool, enabling diamond abrasive particles to do circular motion along with the rotation of the steel disc so as to scratch a ceramic matrix composite plane sample, and forming arc-shaped deep scratches on the ceramic matrix composite plane sample;

s1-3, observing the breaking mode of the fiber in the arc-shaped deep scratches through an electron microscope; wherein: the material is removed by brittle fracture of the single fiber, the maximum scratch depth of the material from brittle fracture of the micro-fracture to brittle fracture of the macro-fracture is the critical depth of the micro-fracture to brittle fracture of the macro-fracture.

Preferably, in the step S3, the ultrasonic vibration-assisted grinding of the ceramic matrix composite includes the following steps:

s3-1, clamping a ceramic matrix composite workpiece on a numerical control machine tool;

s3-2, selecting a diamond grinding head and a longitudinal-torsional composite rotary ultrasonic knife handle to be mounted on a machine tool;

s3-3, setting ultrasonic vibration auxiliary grinding process parameters based on a numerical control machine tool;

s3-4, starting the numerical control machine tool, and performing ultrasonic vibration auxiliary grinding processing on the ceramic matrix composite material according to the tool path track specified by the numerical control program based on the ultrasonic vibration auxiliary grinding process parameters.

Preferably, in the step S2, the obtaining of the ultrasonic vibration auxiliary grinding process parameters includes determining a spindle rotation speed, a feeding speed, a grinding depth, a grinding width, a longitudinal ultrasonic frequency, a longitudinal ultrasonic amplitude, a torsional ultrasonic frequency and a torsional ultrasonic amplitude; the spindle rotating speed is selected according to the characteristics of the machine tool, the grinding depth and the grinding width are determined according to the machining allowance of the part, and the longitudinal ultrasonic frequency, the longitudinal ultrasonic amplitude, the torsional ultrasonic frequency and the torsional ultrasonic amplitude are determined according to the model of the longitudinal-torsional composite rotary ultrasonic tool handle.

Preferably, in the step S2, the step of obtaining the ultrasonic vibration auxiliary grinding process parameter further includes establishing a processing process parameter determining criterion, and determining the feeding speed according to the processing process parameter determining criterion; the determination criterion of the processing technological parameter is h_max ≤h_critical The method comprises the steps of carrying out a first treatment on the surface of the Wherein h is_max Is the maximum undeformed abrasive dust thickness; h is a_critical The critical depth is converted for micro-macro brittle fracture.

Preferably, in the step S2, under the condition that the processing parameters determine the criterion, the relationship between the related ultrasonic vibration auxiliary grinding process parameters is as follows:

a_p v_f b＝(2πrnCb)Vol_c ；

wherein a is_p For grinding depth v_f B is grinding width, r is grinding head radius; n is the rotation speed of the main shaft; c is the effective abrasive particle density of the diamond grinding head; vol_c Removing the material volume for a single abrasive particle of the diamond grinding head; l is the three-dimensional motion track length of the abrasive particles; θ is the half apex angle of the abrasive grain, and the value is 60 degrees.

Preferably, the effective abrasive particle density of the diamond grinding head is obtained by the following formula:

wherein f is the fraction of the effective abrasive particles, and the value is 0.5; d, d_g Is the average size of the abrasive particles; v (V)_g The volume fraction of the abrasive particles was 0.25.

Preferably, the three-dimensional motion track length of the abrasive particles is obtained by the following formula:

wherein t is₀ The single contact time of the abrasive particles and the workpiece material is set; x' is the derivative of the X-direction component of the abrasive particle track; y' is the derivative of the Y-direction component of the abrasive particle track; z' is the derivative of the Z-direction component of the abrasive particle trajectory.

Preferably, the derivative of the X-direction component of the abrasive particle track, the derivative of the Y-direction component of the abrasive particle track, and the derivative of the Z-direction component of the abrasive particle track are obtained by the following formulas:

wherein t is a time variable; θ_r+t Is the sum of the rotation angle of the cutter and the angle change caused by the torsional ultrasonic vibration of the cutter, namelyf_t Torsional ultrasonic vibration frequency of the cutter; a is that_t Twisting ultrasonic amplitude for the tool; a is that_l The ultrasonic amplitude is the longitudinal ultrasonic amplitude of the cutter; f (f)_l Is the longitudinal ultrasonic vibration frequency of the cutter.

The invention has the beneficial effects that:

1) According to the technical scheme, based on the support of a single abrasive particle basic scratch test, from the physical property of the ceramic matrix composite, the micro-macro brittle fracture transition critical depth of the ceramic matrix composite is obtained, and based on the ultrasonic vibration auxiliary grinding process parameters obtained by combining the micro-macro brittle fracture transition critical depth with the part processing surface quality requirements, a unified and reasonable processing condition standard is established for the processing of the ceramic matrix composite workpiece, and the method has important significance for high-quality and high-efficiency processing of the ceramic matrix composite.

2) The method comprises the steps of establishing a maximum undeformed abrasive dust thickness model based on a three-dimensional motion track of abrasive particles under an ultrasonic vibration auxiliary grinding working condition, determining to process in a micro brittle domain according to the quality requirement of a processed surface, carrying out a basic scratch test to determine the micro-macro brittle fracture transition critical depth of the ceramic matrix composite, establishing a processing technological parameter determination criterion based on the principle that the maximum undeformed abrasive dust thickness is not greater than the micro-macro brittle fracture transition critical depth, and acquiring ultrasonic vibration auxiliary grinding technological parameters to process, so that the grinding efficiency is improved on the premise of guaranteeing the high-quality surface processing of the ceramic matrix composite.

3) The technical scheme guides scientific and reasonable selection of the process parameters according to the determination criteria of the process parameters, avoids the problem that the conventional method takes time and labor for determining the process parameters through complicated test optimization, and can be applied to selection of the process parameters under different working conditions.

Drawings

FIG. 1 is a schematic illustration of a single diamond abrasive grain basic scratch test;

FIG. 2 is a schematic view of ultrasonic vibration assisted grinding of a ceramic matrix composite;

fig. 3 is a schematic view of abrasive particle motion trajectories.

In the figure:

1. a steel disc; 2. single diamond abrasive particles; 3. a spindle rotation speed n; 4. a ceramic matrix composite planar sample; 5. arc-shaped deep scratches; 6. longitudinally ultrasonically vibrating; 7. torsional ultrasonic vibration; 8. a ceramic matrix composite workpiece; 9. diamond grinding head; 10. grinding the width b; 11. feed speed v_f The method comprises the steps of carrying out a first treatment on the surface of the 12. Depth of grinding a_p The method comprises the steps of carrying out a first treatment on the surface of the 13. Maximum undeformed abrasive dust thickness h_max The method comprises the steps of carrying out a first treatment on the surface of the 14. Volume Vol of single abrasive particle removal material_c The method comprises the steps of carrying out a first treatment on the surface of the 15. Three-dimensional motion path length l of abrasive particles.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some embodiments of the present invention, not all embodiments.

Accordingly, the following detailed description of the invention, as provided in the accompanying drawings, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without any inventive effort, are intended to be within the scope of the invention.

Example 1

The embodiment discloses an ultrasonic vibration assisted grinding processing method of a ceramic matrix composite, which is a preferred implementation scheme of the technical scheme and comprises the following steps:

s1, carrying out a single abrasive grain basic scratch test on a ceramic matrix composite plane pattern, and determining the micro-macro brittle fracture transition critical depth;

s2, acquiring ultrasonic vibration auxiliary grinding process parameters based on the micro-macro brittle fracture transition critical depth and combining the part machining surface quality requirements;

s3, performing ultrasonic vibration auxiliary grinding processing on the ceramic matrix composite based on the ultrasonic vibration auxiliary grinding process parameters.

Example 2

The embodiment discloses an ultrasonic vibration assisted grinding processing method of a ceramic matrix composite, which is a preferred implementation scheme of the technical scheme and comprises the following steps:

s1, carrying out a single abrasive grain basic scratch test on a ceramic matrix composite plane pattern, and determining the micro-macro brittle fracture transition critical depth. Wherein, the single abrasive grain basic scratch test comprises the following steps:

s1-1, preparing a steel disc with single diamond abrasive particles welded on the circumferential surface, and installing the steel disc on a numerical control machine tool;

s1-2, starting a numerical control machine tool, enabling a steel disc to rotate under the drive of the numerical control machine tool, enabling diamond abrasive particles to do circular motion along with the rotation of the steel disc so as to scratch a ceramic matrix composite plane sample, and forming arc-shaped deep scratches on the ceramic matrix composite plane sample;

s1-3, observing the breaking mode of the fiber in the arc-shaped deep scratches through an electron microscope; wherein: the material is removed by micro brittle fracture caused by multiple brittle fracture (micro scale) inside single fiber, the material is removed by macro brittle fracture caused by single fracture of single fiber, and the maximum scratch depth of the micro brittle fracture to macro brittle fracture is the critical depth of micro-macro brittle fracture transition.

S2, based on the micro-macro brittle fracture transition critical depth and in combination with the part machining surface quality requirement, acquiring ultrasonic vibration auxiliary grinding process parameters. The surface quality requirements of the part processing comprise the surface roughness and surface damage condition of the part after processing; wherein the surface roughness Sa is 2.0 mu m, and the surface of the part after processing has no pits formed by fiber peeling and fiber pulling, and the processing can be determined in a micro brittle fracture domain according to a material removing mechanism.

S3, performing ultrasonic vibration auxiliary grinding processing on the ceramic matrix composite based on the ultrasonic vibration auxiliary grinding process parameters.

Example 3

The embodiment discloses an ultrasonic vibration assisted grinding processing method of a ceramic matrix composite, which is a preferred implementation scheme of the technical scheme and comprises the following steps:

s1, carrying out a single abrasive grain basic scratch test on a ceramic matrix composite plane pattern, and determining the micro-macro brittle fracture transition critical depth. Wherein, the single abrasive grain basic scratch test comprises the following steps:

s1-1, preparing a steel disc with single diamond abrasive particles welded on the circumferential surface, and installing the steel disc on a numerical control machine tool;

s1-2, starting a numerical control machine tool, enabling a steel disc to rotate under the drive of the numerical control machine tool, enabling diamond abrasive particles to do circular motion along with the rotation of the steel disc so as to scratch a ceramic matrix composite plane sample, and forming arc-shaped deep scratches on the ceramic matrix composite plane sample;

s1-3, observing the breaking mode of the fiber in the arc-shaped deep scratches through an electron microscope; wherein: the material is removed by micro brittle fracture caused by multiple brittle fracture (micro scale) inside single fiber, the material is removed by macro brittle fracture caused by single fracture of single fiber, and the maximum scratch depth of the micro brittle fracture to macro brittle fracture is the critical depth of micro-macro brittle fracture transition.

S2, based on the micro-macro brittle fracture transition critical depth and in combination with the part machining surface quality requirement, acquiring ultrasonic vibration auxiliary grinding process parameters. The surface quality requirements of the part processing comprise the surface roughness and surface damage condition of the part after processing; wherein the surface roughness Sa is 2.0 mu m, and the surface of the part after processing has no pits formed by fiber peeling and fiber pulling, and the processing can be determined in a micro brittle fracture domain according to a material removing mechanism. In addition, the ultrasonic vibration auxiliary grinding process parameters comprise spindle rotation speed, feeding speed, grinding depth, grinding width, longitudinal ultrasonic frequency, longitudinal ultrasonic amplitude, torsional ultrasonic frequency and torsional ultrasonic amplitude; the spindle rotating speed is selected according to the characteristics of the machine tool, the grinding depth and the grinding width are determined according to the machining allowance of the part, and the longitudinal ultrasonic frequency, the longitudinal ultrasonic amplitude, the torsional ultrasonic frequency and the torsional ultrasonic amplitude are determined according to the model of the longitudinal-torsional composite rotary ultrasonic tool handle.

S3, performing ultrasonic vibration auxiliary grinding processing on the ceramic matrix composite based on the ultrasonic vibration auxiliary grinding process parameters. Wherein, the ultrasonic vibration auxiliary grinding processing of the ceramic matrix composite material comprises the following steps:

s3-1, clamping a ceramic matrix composite workpiece on a numerical control machine tool;

s3-2, selecting a diamond grinding head and a longitudinal-torsional composite rotary ultrasonic knife handle to be mounted on a machine tool;

s3-3, setting ultrasonic vibration auxiliary grinding process parameters based on a numerical control machine tool;

s3-4, starting the numerical control machine tool, and performing ultrasonic vibration auxiliary grinding processing on the ceramic matrix composite material according to the tool path track specified by the numerical control program based on the ultrasonic vibration auxiliary grinding process parameters.

Further, the longitudinal-torsional composite rotary ultrasonic tool handle can simultaneously apply longitudinal ultrasonic vibration and torsional ultrasonic vibration to a tool (namely a diamond grinding head) in the machining process.

Example 4

The embodiment discloses an ultrasonic vibration assisted grinding processing method of a ceramic matrix composite, which is a preferred implementation scheme of the technical scheme and comprises the following steps:

s1, carrying out a single abrasive grain basic scratch test on a ceramic matrix composite plane pattern, and determining the micro-macro brittle fracture transition critical depth. Wherein, the single abrasive grain basic scratch test comprises the following steps:

s1-1, preparing a steel disc with single diamond abrasive particles welded on the circumferential surface, and installing the steel disc on a numerical control machine tool;

s1-2, starting a numerical control machine tool, enabling a steel disc to rotate under the drive of the numerical control machine tool, enabling diamond abrasive particles to do circular motion along with the rotation of the steel disc so as to scratch a ceramic matrix composite plane sample, and forming arc-shaped deep scratches on the ceramic matrix composite plane sample;

s1-3, observing the breaking mode of the fiber in the arc-shaped deep scratches through an electron microscope; wherein: the material is removed by micro brittle fracture caused by multiple brittle fracture (micro scale) inside single fiber, the material is removed by macro brittle fracture caused by single fracture of single fiber, and the maximum scratch depth of the micro brittle fracture to macro brittle fracture is the critical depth of micro-macro brittle fracture transition.

S2, based on the micro-macro brittle fracture transition critical depth and in combination with the part machining surface quality requirement, acquiring ultrasonic vibration auxiliary grinding process parameters. The surface quality requirements of the part processing comprise the surface roughness and surface damage condition of the part after processing; wherein the surface roughness Sa is 2.0 mu m, and the surface of the part after processing has no pits formed by fiber peeling and fiber pulling, and the processing can be determined in a micro brittle fracture domain according to a material removing mechanism. In addition, the ultrasonic vibration auxiliary grinding process parameters comprise spindle rotation speed, feeding speed, grinding depth, grinding width, longitudinal ultrasonic frequency, longitudinal ultrasonic amplitude, torsional ultrasonic frequency and torsional ultrasonic amplitude; the spindle rotating speed is selected according to the characteristics of the machine tool, the grinding depth and the grinding width are determined according to the machining allowance of the part, and the longitudinal ultrasonic frequency, the longitudinal ultrasonic amplitude, the torsional ultrasonic frequency and the torsional ultrasonic amplitude are determined according to the model of the longitudinal-torsional composite rotary ultrasonic tool handle.

Further, in step S2, the process of obtaining the ultrasonic vibration auxiliary grinding process parameter further includes establishing a process parameter determining criterion, and determining the feeding speed according to the process parameter determining criterion; the determination criterion of the processing technological parameter is h_max ≤h_critical The method comprises the steps of carrying out a first treatment on the surface of the Wherein h is_max Is the maximum undeformed abrasive dust thickness; h is a_critical The critical depth is converted for micro-macro brittle fracture. Specifically, at the time of addingUnder the condition of the technical parameter determining rule, the related ultrasonic vibration auxiliary grinding technical parameters have the following relationship:

a_p v_f b＝(2πrnCb)Vol_c ；

wherein a is_p For grinding depth v_f B is grinding width, r is grinding head radius; n is the rotation speed of the main shaft; c is the effective abrasive particle density of the diamond grinding head; vol_c Removing the material volume for a single abrasive particle of the diamond grinding head; l is the three-dimensional motion track length of the abrasive particles; θ is the half apex angle of the abrasive grain, and the value is 60 degrees.

S3, performing ultrasonic vibration auxiliary grinding processing on the ceramic matrix composite based on the ultrasonic vibration auxiliary grinding process parameters. Wherein, the ultrasonic vibration auxiliary grinding processing of the ceramic matrix composite material comprises the following steps:

s3-1, clamping a ceramic matrix composite workpiece on a numerical control machine tool;

s3-2, selecting a diamond grinding head and a longitudinal-torsional composite rotary ultrasonic knife handle to be mounted on a machine tool;

s3-3, setting ultrasonic vibration auxiliary grinding process parameters based on a numerical control machine tool;

s3-4, starting the numerical control machine tool, and performing ultrasonic vibration auxiliary grinding processing on the ceramic matrix composite material according to the tool path track specified by the numerical control program based on the ultrasonic vibration auxiliary grinding process parameters.

Example 5

The embodiment discloses an ultrasonic vibration assisted grinding processing method for a ceramic matrix composite, which is a preferred implementation scheme of the technical scheme, namely, the method for acquiring relevant parameters is determined by combining the embodiment 4, and the method is specifically as follows:

the effective abrasive particle density of the diamond grinding head is obtained by the following formula:

wherein f is the fraction of the effective abrasive particles, and the value is 0.5; d, d_g Is the average size of the abrasive particles; v (V)_g The volume fraction of the abrasive particles was 0.25.

The three-dimensional motion track length of the abrasive particles is obtained by the following formula:

wherein t is₀ The single contact time of the abrasive particles and the workpiece material is set; x' is the derivative of the X-direction component of the abrasive particle track; y' is the derivative of the Y-direction component of the abrasive particle track; z' is the derivative of the Z-direction component of the abrasive particle trajectory.

The derivative of the X-direction component of the abrasive grain track, the derivative of the Y-direction component of the abrasive grain track, and the derivative of the Z-direction component of the abrasive grain track are obtained by the following formulas:

wherein t is a time variable; θ_r+t Is the sum of the rotation angle of the cutter and the angle change caused by the torsional ultrasonic vibration of the cutter, namelyf_t Torsional ultrasonic vibration frequency of the cutter; a is that_t Twisting ultrasonic amplitude for the tool; a is that_l The ultrasonic amplitude is the longitudinal ultrasonic amplitude of the cutter; f (f)_l Is the longitudinal ultrasonic vibration frequency of the cutter.

Example 6

The example discloses an ultrasonic vibration assisted grinding processing method of a ceramic matrix composite, which is a preferred implementation scheme of the technical scheme, and uses C_f The processing of a SiC ceramic matrix composite is illustrated by way of example and is based on one embodiment as described in example 5, specifically as follows:

(1) Developing a single abrasive particle basic scratch test to determine the critical depth of micro-macro brittle fracture transition:

brazing single diamond abrasive particles on the circumferential surface of a (high-speed) steel disc, mounting the steel disc on a numerical control machine tool, and setting the rotating speed of a main shaft to 3000r/min; starting a numerical control machine, carrying out a single abrasive grain scratching test on a ceramic matrix composite plane sample by matching with diamond abrasive grains under the driving of the steel disc numerical control machine, and observing the fiber microcosmic appearance of the arc scratching area by using an electron microscope to obtain the micro-macroscopic brittle fracture transition critical depth of 5.1 mu m.

(2) Determining ultrasonic vibration auxiliary grinding working conditions:

a diamond grinding head with the diameter phi of 10mm and the grinding head granularity of 120 meshes is selected, and the diamond grinding head is arranged on a numerical control machine tool by utilizing a longitudinal-torsional composite rotary ultrasonic knife handle;

setting the longitudinal ultrasonic vibration frequency to be 20.06kHz, the torsional ultrasonic vibration frequency to be 20.06kHz, the longitudinal torsion ratio to be 14:5, the longitudinal ultrasonic amplitude to be 11 mu m and the torsional ultrasonic amplitude to be 3.9 mu m;

the spindle rotation speed during machining was 3000rpm, the grinding depth was 0.3mm, and the grinding width was 6mm, which were set according to the machine tool performance.

In addition, conventional grinding is set as a control group, and grinding parameters of the control group are consistent with those of the grinding parameters, so that ultrasonic vibration is not applied in the processing process.

(3) Calculating and determining the feeding speed:

meets the determination criterion h of the processing technological parameters_max ≤h_critical Based on formula a_p v_f b＝(2πrnCb)Vol_c And under the working condition of ultrasonic vibration auxiliary grinding, the feeding speed is 192mm/min, and the machined surface roughness Sa is measured to be 1.73+/-0.21 mu m after machining. The ultrasonic vibration was not applied, and the feeding speed was 163mm/min by conventional grinding, and the processed surface roughness Sa was 1.76.+ -. 0.19. Mu.m, measured after the processing.

In summary, compared with conventional processing, the processing efficiency is improved by 17.8% under the working condition set in the embodiment by adopting ultrasonic vibration to assist grinding processing on the premise of ensuring the processing surface quality.

Claims (10)

1. The ultrasonic vibration assisted grinding processing method of the ceramic matrix composite material is characterized by comprising the following steps of:

s1, carrying out a single abrasive grain basic scratch test on a ceramic matrix composite plane pattern, and determining the micro-macro brittle fracture transition critical depth;

s2, acquiring ultrasonic vibration auxiliary grinding process parameters based on the micro-macro brittle fracture transition critical depth and combining the part machining surface quality requirements;

s3, performing ultrasonic vibration auxiliary grinding processing on the ceramic matrix composite based on the ultrasonic vibration auxiliary grinding process parameters.

2. The ultrasonic vibration assisted grinding method of a ceramic matrix composite according to claim 1, wherein: in the step S2, the surface quality requirements of the part processing include the surface roughness and surface damage condition after the part processing; wherein the surface roughness Sa is 2.0 μm, and the surface after the part processing has no pits formed by fiber peeling and fiber pulling.

3. The ultrasonic vibration-assisted grinding method of the ceramic matrix composite material according to claim 1, wherein the method comprises the following steps of: in the step S1, the single abrasive grain basic scratch test includes the following steps:

s1-1, preparing a steel disc with single diamond abrasive particles welded on the circumferential surface, and installing the steel disc on a numerical control machine tool;

s1-2, starting a numerical control machine tool, enabling a steel disc to rotate under the drive of the numerical control machine tool, enabling diamond abrasive particles to do circular motion along with the rotation of the steel disc so as to scratch a ceramic matrix composite plane sample, and forming arc-shaped deep scratches on the ceramic matrix composite plane sample;

s1-3, observing the breaking mode of the fiber in the arc-shaped deep scratches through an electron microscope; wherein: the material is removed by brittle fracture of the single fiber, the maximum scratch depth of the material from brittle fracture of the micro-fracture to brittle fracture of the macro-fracture is the critical depth of the micro-fracture to brittle fracture of the macro-fracture.

4. The ultrasonic vibration-assisted grinding method of the ceramic matrix composite material according to claim 1, wherein the method comprises the following steps of: in the step S3, the ultrasonic vibration assisted grinding processing of the ceramic matrix composite material includes the following steps:

s3-1, clamping a ceramic matrix composite workpiece on a numerical control machine tool;

s3-2, selecting a diamond grinding head and a longitudinal-torsional composite rotary ultrasonic knife handle to be mounted on a machine tool;

s3-3, setting ultrasonic vibration auxiliary grinding process parameters based on a numerical control machine tool;

s3-4, starting the numerical control machine tool, and performing ultrasonic vibration auxiliary grinding processing on the ceramic matrix composite material according to the tool path track specified by the numerical control program based on the ultrasonic vibration auxiliary grinding process parameters.

5. The ultrasonic vibration-assisted grinding method of the ceramic matrix composite material according to claim 4, wherein the method comprises the following steps of: in the step S2, acquiring ultrasonic vibration auxiliary grinding process parameters includes determining a spindle rotation speed, a feeding speed, a grinding depth, a grinding width, a longitudinal ultrasonic frequency, a longitudinal ultrasonic amplitude, a torsional ultrasonic frequency and a torsional ultrasonic amplitude; the spindle rotating speed is selected according to the characteristics of the machine tool, the grinding depth and the grinding width are determined according to the machining allowance of the part, and the longitudinal ultrasonic frequency, the longitudinal ultrasonic amplitude, the torsional ultrasonic frequency and the torsional ultrasonic amplitude are determined according to the model of the longitudinal-torsional composite rotary ultrasonic tool handle.

6. The ultrasonic vibration-assisted grinding method of the ceramic matrix composite material according to claim 5, wherein the method comprises the following steps of: in the step S2, the process of obtaining the ultrasonic vibration auxiliary grinding process parameter further includes establishing a process parameter determining criterion, and determining the feeding speed according to the process parameter determining criterion; the determination criterion of the processing technological parameter is h_max ≤h_critical The method comprises the steps of carrying out a first treatment on the surface of the Wherein h is_max Is the maximum undeformed abrasive dust thickness; h is a_critical The critical depth is converted for micro-macro brittle fracture.

7. The ultrasonic vibration-assisted grinding method of the ceramic matrix composite material according to claim 6, wherein the method comprises the following steps of: in the step S2, under the condition of the processing technological parameter determining criterion, the relationship of the related ultrasonic vibration auxiliary grinding technological parameters is as follows:

a_p v_f b＝(2πrnCb)Vol_c ；

wherein a is_p For grinding depth v_f B is grinding width, r is grinding head radius; n is the rotation speed of the main shaft; c is the effective abrasive particle density of the diamond grinding head; vol_c Removing the material volume for a single abrasive particle of the diamond grinding head; l is the three-dimensional motion track length of the abrasive particles; θ is the half apex angle of the abrasive grain, and the value is 60 degrees.

8. The ultrasonic vibration-assisted grinding method of the ceramic matrix composite material according to claim 7, wherein the method comprises the following steps of: the effective abrasive particle density of the diamond grinding head is obtained by the following formula:

wherein f is the fraction of the effective abrasive particles, and the value is 0.5; d, d_g Is the average size of the abrasive particles; v (V)_g The volume fraction of the abrasive particles was 0.25.

9. The ultrasonic vibration-assisted grinding method of the ceramic matrix composite material according to claim 7, wherein the method comprises the following steps of: the three-dimensional motion track length of the abrasive particles is obtained by the following formula:

wherein t is₀ The single contact time of the abrasive particles and the workpiece material is set; x' is the derivative of the X-direction component of the abrasive particle track; y' is the derivative of the Y-direction component of the abrasive particle track; z' is the derivative of the Z-direction component of the abrasive particle trajectory.

10. The ultrasonic vibration-assisted grinding method of the ceramic matrix composite material according to claim 9, wherein the method comprises the following steps of: the derivative of the X-direction component of the abrasive grain track, the derivative of the Y-direction component of the abrasive grain track, and the derivative of the Z-direction component of the abrasive grain track are obtained by the following formulas:

wherein t is a time variable; θ_r+t Is the sum of the rotation angle of the cutter and the angle change caused by the torsional ultrasonic vibration of the cutter, namelyf_t Torsional ultrasonic vibration frequency of the cutter; a is that_t Twisting ultrasonic amplitude for the tool; a is that_l The ultrasonic amplitude is the longitudinal ultrasonic amplitude of the cutter; f (f)_l Is the longitudinal ultrasonic vibration frequency of the cutter.