In the present study,a novel method of surface finish improvement is proposed using shot blasting of soda lime(SBSL)beads on the Mg-AZ31 alloy.The effect of the soda blasting process parameters,such as blast pressure,...In the present study,a novel method of surface finish improvement is proposed using shot blasting of soda lime(SBSL)beads on the Mg-AZ31 alloy.The effect of the soda blasting process parameters,such as blast pressure,stand-off distance,and blast duration,have been studied in-response of material removal rate(MRR)and surface roughness(SR)and corresponding statistical models have been obtained.The multi-objective optimization has also been performed to obtain parameters for maximum MRR and minimum SR.The corrosion behavior of the treated specimens has been performed to study their in-vitro biodegradability in simulated body fluid(SBF)for 1,3,7,10,15,and 21 days.The wettability study of the SBSL treated samples has been investigated using sessile drop methodology.Further,cell adhesion test has also been performed to study the biocompatibility characteristics of the SBSL treated samples using Huh7 liver cell lines.Based on obtained quantitative data as well as scanning electron microscopy analysis of treated samples,the SBSL treatment of the AZ31 alloy has been found highly useful in producing biocompatibility surfaces along with desirable morphological features.展开更多
The mechanical characters of CdZnTe crystal were investigated by nanoscratch tests, and the effects of mechanical anisotropy on the material removal rate and surface quality were studied by polishing tests. There is a...The mechanical characters of CdZnTe crystal were investigated by nanoscratch tests, and the effects of mechanical anisotropy on the material removal rate and surface quality were studied by polishing tests. There is a peak of frictional coefficient at the early stage of scratch, and increasing the vertical force will result in the increase of peak value correspondingly. The fluctuation phenomenon of frictional coefficient is generated at high vertical force. The lateral forces show the apparent twofold and threefold symmetries on (110) and (111) planes, respectively. To obtain high surface quality, low polishing pressure and hard direction (〈 T10 〉 directions on (110) plane and 〈 112 〉 directions on (111) plane) should be selected, and to achieve high material removal rate, high polishing pressure and soft direction (〈001〉 directions on (110) plane and 〈 121 〉 directions on (111) plane) should be selected.展开更多
Ultrasonic-assisted chemical mechanical polishing(UA-CMP)can greatly improve the sapphire material removal and surface quality,but its polishing mechanism is still unclear.This paper proposed a novel model of material...Ultrasonic-assisted chemical mechanical polishing(UA-CMP)can greatly improve the sapphire material removal and surface quality,but its polishing mechanism is still unclear.This paper proposed a novel model of material removal rate(MRR)to explore the mechanism of sapphire UA-CMP.It contains two modes,namely two-body wear and abrasive-impact.Furthermore,the atomic force microscopy(AFM)in-situ study,computational fluid dynamics(CFD)simulation,and polishing experiments were conducted to verify the model and reveal the polishing mechanism.In the AFM in-situ studies,the tip scratched the reaction layer on the sapphire surface.The pit with a 0.22 nm depth is the evidence of two-body wear.The CFD simulation showed that abrasives could be driven by the ultrasonic vibration to impact the sapphire surface at high frequencies.The maximum total velocity and the air volume fraction(AVF)in the central area increased from 0.26 to 0.55 m/s and 20%to 49%,respectively,with the rising amplitudes of 1–3μm.However,the maximum total velocity rose slightly from 0.33 to 0.42 m/s,and the AVF was nearly unchanged under 40–80 r/min.It indicated that the ultrasonic energy has great effects on the abrasive-impact mode.The UA-CMP experimental results exhibited that there was 63.7%improvement in MRR when the polishing velocities rose from 40 to 80 r/min.The roughness of the polished sapphire surface was R_(a)=0.07 nm.It identified that the higher speed achieved greater MRR mainly through the two-body wear mode.This study is beneficial to further understanding the UA-CMP mechanism and promoting the development of UA-CMP technology.展开更多
This work demonstrates the viability of the powder-mixed micro-electrochemical discharge machining(PMECDM) process to fabricate micro-holes on C103 niobium-based alloy for high temperature applications.Three processes...This work demonstrates the viability of the powder-mixed micro-electrochemical discharge machining(PMECDM) process to fabricate micro-holes on C103 niobium-based alloy for high temperature applications.Three processes are involved simultaneously i.e.spark erosion,chemical etching,and abrasive grinding for removal of material while the classical electrochemical discharge machining process involves double actions i.e.spark erosion,and chemical etching.The powder-mixed electrolyte process resulted in rapid material removal along with a better surface finish as compared to the classical microelectrochemical discharge machining(MECDM).Further,the results are optimized through a multiobjective optimization approach and study of the surface topography of the hole wall surface obtained at optimized parameters.In the selected range of experimental parameters,PMECDM shows a higher material removal rate(MRR) and lower surface roughness(R_(a))(MRR:2.8 mg/min and R_(a) of 0.61 μm) as compared to the MECDM process(MRR:2.01 mg/min and corresponding Raof 1.11 μm).A detailed analysis of the results is presented in this paper.展开更多
The influences of the polishing slurry composition,such as the pH value,the abrasive size and its concentration,the dispersant and the oxidants,the rotational velocity of the polishing platen and the carrier and the p...The influences of the polishing slurry composition,such as the pH value,the abrasive size and its concentration,the dispersant and the oxidants,the rotational velocity of the polishing platen and the carrier and the polishing pressure,on the material removal rate of SiC crystal substrate(0001) Si and a(0001) C surface have been studied based on the alumina abrasive in chemical mechanical polishing(CMP).The results proposed by our research here will provide a reference for developing the slurry,optimizing the process parameters,and investigating the material removal mechanism in the CMP of SiC crystal substrate.展开更多
Chemical mechanical polishing (CMP) was used to polish Lithium triborate (LiB3O5 or LBO) crystal. Taguchi method was applied for optimization of the polishing parameters. Material removal rate (MRR) and surface ...Chemical mechanical polishing (CMP) was used to polish Lithium triborate (LiB3O5 or LBO) crystal. Taguchi method was applied for optimization of the polishing parameters. Material removal rate (MRR) and surface roughness are considered as criteria for the optimization. The polishing pressure, the abrasive concentration and the table velocity are important parameters which influence MRR and surface roughness in CMP of LBO crystal. Experiment results indicate that for MRR the polishing pressure is the most significant polishing parameter followed by table velocity; while for the surface roughness, the abrasive concentration is the most important one. For high MRR in CMP of LBO ctystal the optimal conditions are: pressure 620 g/cm^2, concentration 5.0 wt pct, and velocity 60 r/min, respectively. For the best surface roughness the optimal conditions are: pressure 416 g/cm^2, concentration 5.0 wt pct, and velocity 40 r/min, respectively. The contributions of individual parameters for MRR and surface roughness were obtained.展开更多
Distribution forms of abrasives in the chemical mechanical polishing(CMP) process are analyzed based on experimental results.Then the relationships between the wafer,the abrasive and the polishing pad are analyzed b...Distribution forms of abrasives in the chemical mechanical polishing(CMP) process are analyzed based on experimental results.Then the relationships between the wafer,the abrasive and the polishing pad are analyzed based on kinematics and contact mechanics.According to the track length of abrasives on the wafer surface,the relationships between the material removal rate and the polishing velocity are obtained.The analysis results are in accord with the experimental results.The conclusion provides a theoretical guide for further understanding the material removal mechanism of wafers in CMP.展开更多
Electrical discharge milling(ED-milling) can be a good choice for titanium alloys machining and it was proven that its machining efficiency can be improved to compete with mechanical cutting. In order to improve energ...Electrical discharge milling(ED-milling) can be a good choice for titanium alloys machining and it was proven that its machining efficiency can be improved to compete with mechanical cutting. In order to improve energy utilization efficiency of ED-milling process, unstable arc discharge and stable arc discharge combined with normal discharge were implemented for material removal by adjusting servo control strategy. The influence of electrode rotating speed and dielectric flushing pressure on machining performance was investigated by experiments. It was found that the rotating of electrode could move the position of discharge plasma channel, and high pressure flushing could wash melted debris out the discharge gap effectively. Both electrode rotating motion and high pressure flushing are contributed to the improvement of machining efficiency.展开更多
Ultrasonic machining (USM) is considered as an effective method for machining hard and brittle materials such as glass, engineering ceramics, semiconductors, diamonds, metal composites and so on. However, the low mate...Ultrasonic machining (USM) is considered as an effective method for machining hard and brittle materials such as glass, engineering ceramics, semiconductors, diamonds, metal composites and so on. However, the low material removal rate due to using abrasive slurry limits further application of USM. Rotary ultrasonic machining (rotary USM) superimposes rotational movement on the tool head that vibrates at ultrasonic frequency (20 kHz) simultaneously. The tool is made of mild steel coated or bonded with diamond abrasive. Therefore, abrasive slurry is abandoned and coolant is used to carry debris out of working area. Compared with USM, rotary USM can obtain much higher material removal rate, deep holes, and fine precision, which leads to its further application. Combined with CNC technology, rotary USM can be used to conduct contour machining of hard and brittle materials. In this paper, the movement of abrasive particles in tool tip of rotary ultrasonic machining is analyzed. The impacting and grinding of abrasive in tool tip to machined surface are considered as main factors to material removal rate. The process of crack forming and growing in one loading and unloading cycle can be described as following stages: a) When abrasive particle acts the pressure on work-piece, the macro cracks in periphery of contact area are exerted increasing tensile stress. b) As the tensile stress increase to the critical of material tension, the one of cracks in periphery of contact area begins to propagate around contact area and develop beneath the surface to certain depth. c) Indentation area varies with increasing of load, the circle crack around contact area steadily or dynamical propagates towards inside of work-piece. d) As tensile stress in crack increases to critical of crack steady failure, circle crack suddenly becomes conic crack. e) Further increase load, the crack continues to grow while contact area is surrounded by conic cracks. f) During unloading, conic crack begins to close, some of cracks continue their extension towards the surface and forms a circle groove. The mathematical model for material removal rate shows that the factors affecting on material removal rate are static load, grid and concentration of abrasive, mechanical properties of machined materials, rotational speed of tool and feed speed of work-piece.展开更多
Ce^(3+)as the active site on the CeO_(2)abrasive surface is the key to enhancing the material removal rate(MRR).The CeO_(2)abrasives with high chemical activity were prepared by the molten salt method under a reducing...Ce^(3+)as the active site on the CeO_(2)abrasive surface is the key to enhancing the material removal rate(MRR).The CeO_(2)abrasives with high chemical activity were prepared by the molten salt method under a reducing atmosphere.The crystal structure and morphology of CeO_(2)abrasive s were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),Fourier transform infrared spectroscopy(FT-IR),ultraviolet—visible diffuse reflectance spectroscopy(UV-Vis DRS),and X-ray photoelectron spectroscopy(XPS).The CeO_(2)abrasives were obtained under different atmospheres(Air,Ar,and Ar/H_(2)).With the enhancement of the reducing atmosphere,the morphology of the abrasives transforms from spherical to octahedral,while more oxygen vacancies and Ce^(3+)are generated on the surface of CeO_(2)abrasives.The CMP experiments show that the MRRs of the CeO_(2)-Air,CeO_(2)-Ar,and CeO_(2)-Ar/H_(2)abrasives on SiO_(2)substrates are 337.60,578.74,and 691.28 nm/min,respectively.Moreover,as confirmed by atomic force microscopy(AFM),the substrate surfaces exhibit low roughness(20.5 nm)after being polished using all of the prepared samples.Especially,the MRR of CeO_(2)-Ar/H_(2)abrasives is increased by 104.76%compared with CeO_(2)-air abrasives.The improved CMP performance is attributed to the increased Ce^(3+)concentration and the octahedral morphology of the abrasives enhancing the chemical reaction and mechanical removal at the abrasive-substrate interface.展开更多
Based on the Preston equation, the mathematical model of the material removal rate (MRR), aiming at a line-orbit chemical mechanical polisher, is established. The MRR and the material removal non-uniformity (MRNU)...Based on the Preston equation, the mathematical model of the material removal rate (MRR), aiming at a line-orbit chemical mechanical polisher, is established. The MRR and the material removal non-uniformity (MRNU) are numerically calculated by MATLAB, and the effects of the reciprocating parameters on the MRR and the MRNU are discussed. It is shown that the smaller the inclination angle and the larger the amplitude, the higher the MRR and the lower the MRNU. The reciprocating speed of the carrier plays a minor role to improve the MRR and decrease the MRNU. The results provide a guide for the design of a polisher and the determination of a process in line-orbit chemical mechanical polishing.展开更多
In order to get ultra-smooth fused silica surface without subsurface damage efficiently, the atmospheric pressure plasma processing( APPP) method has been developed. It is based on chemical reaction between active rad...In order to get ultra-smooth fused silica surface without subsurface damage efficiently, the atmospheric pressure plasma processing( APPP) method has been developed. It is based on chemical reaction between active radicals excited by plasma and workpiece surface atoms,so the subsurface damage caused by contact stress can be avoided and atomic-level precision can be ensured. In this paper,based on the spectral quantitative analysis theory,the influence laws on material removal rate by the key factors of APPP including the flow rate of reaction gases,the input power,the processing distance and time are discussed. In addition,the results that APPP can remove the damaged surface layer and do not introduce secondary damage are proved via the nanoindentation technology.展开更多
The arc milling method has the advantages of high machining efficiency and low cost and is independent of the strength and hardness of machined materials.However,frequent electrode back-offs and the risk of workpiece ...The arc milling method has the advantages of high machining efficiency and low cost and is independent of the strength and hardness of machined materials.However,frequent electrode back-offs and the risk of workpiece burning may occur if erosion products are not removed promptly.In this study,it was found that the flushing method of the working medium had a significant impact on the machining performance of arc milling.Based on this,a novel highefficiency compound machining method of electrical discharge and arc milling with automatic tracking of the optimal flushing direction was proposed.An automatic tracking optimizer for external working medium injection was designed to determine the optimal external flushing direction according to the feed direction.The influence of flushing methods,working mediums,and machining parameters on the machining efficiency,tool electrode wear rate,machining error,and surface integrity of titanium alloys were investigated.The results indicated that better machining performance and environmental friendliness were achieved using the compound flushing method of outer compressed air and inner deionized water.Additionally,the automatic tracking flushing method in the opposite direction of the feed direction showed superior results compared to other directions.The material removal rate with the opposite direction injection could be increased up to 1.62 times that of the same direction,and the relative electrode wear rate could be reduced by 14.76%.This novel method has broad application prospects for machining parts with difficult-to-cut materials in aerospace and military industries.展开更多
In flat jet electrochemical milling, the electrolyte forms a backward parallel flow after impacting the workpiece, resulting in a weak current density distribution on the workpiece. Poor surface quality usually occurs...In flat jet electrochemical milling, the electrolyte forms a backward parallel flow after impacting the workpiece, resulting in a weak current density distribution on the workpiece. Poor surface quality usually occurs on the machined titanium alloy surface because it inevitably suffers from the weak current density. In this study, a method of flat jet electrochemical milling with tailoring the backward parallel flow was proposed to eliminate the negative effects caused by the weak current density. Multiphysics simulations are carried out to comprehend the mechanism of flat jetEC milling with tailoring backward parallel flow and better construct the novel tool electrode.Experiments on flat jet electrochemical milling of TC4 alloy with and without tailoring backward parallel flow are conducted. The results reveal that, compared with flat jet electrochemical milling without tailoring backward parallel flow, the recommended tool reduces the surface roughness by86% to 93%, and improves the material removal rate by 93% to 163% with different feed rates.Additionally, the recommended tool is more conducive to maintaining the inherent hardness of the material. Finally, a surface with low Sa of 0.37 μm is obtained.展开更多
The effect of tert-butyl hydroperoxide-sodium pyrosulfite((CH3)3COOH-Na2S2O5)as an initiator system in H2O2-based slurry was investigated for the abrasive-free polishing(AFP)of a hard disk substrate.The polishing resu...The effect of tert-butyl hydroperoxide-sodium pyrosulfite((CH3)3COOH-Na2S2O5)as an initiator system in H2O2-based slurry was investigated for the abrasive-free polishing(AFP)of a hard disk substrate.The polishing results show that the H_(2)O_(2)-C_(4)H_(10)O_(2)-Na_(2)S_(2)O_(5) slurry exhibits a material removal rate(MRR)that is nearly 5 times higher than that of the H2O2 slurry in the AFP of the hard disk substrate.In addition,the surface polished by the slurry containing the initiator exhibits a lower surface roughness and has fewer nano-asperity peaks than that of the H2O2 slurry.Further,we investigate the polishing mechanism of H_(2)O_(2)-C_(4)H_(10)O_(2)-Na_(2)S_(2)O_(5) slurry.Electron spin-resonance spectroscopy and auger electron spectrometer analyses show that the oxidizing ability of the H_(2)O_(2)-C_(4)H_(10)O_(2)-Na_(2)S_(2)O_(5) slurry is much greater than that of the H2O2 slurry.The results of potentiodynamic polarization measurements show that the hard disk substrate in the H_(2)O_(2)-C_(4)H_(10)O_(2)-Na_(2)S_(2)O_(5) slurry can be rapidly etched,and electrochemical impedance spectroscopy analysis indicates that the oxide film of the hard disk substrate formed in the H_(2)O_(2)-C_(4)H_(10)O_(2)-Na_(2)S_(2)O_(5) slurry may be loose,and can be removed easily during polishing.The better oxidizing and etching ability of H_(2)O_(2)-C_(4)H_(10)O_(2)-Na_(2)S_(2)O_(5) slurry leads to a higher MRR in AFP for hard disk substrates.展开更多
Recently,there has been an investigation of polishing processes that has considered new ultra-precision polishing technology for micro parts and optical parts such as those with aspheric and complex shapes.One suitabl...Recently,there has been an investigation of polishing processes that has considered new ultra-precision polishing technology for micro parts and optical parts such as those with aspheric and complex shapes.One suitable means of polishing complex shapes is to use a jet of abrasive fluid.However,aerodynamic disturbances and radial spreading are generated by the unstable polishing process of the jet on the surface of the workpiece when it is being polished.A method of jet stabilization has been proposed in which the original nozzle form of a jet of magnetorheological(MR)fluid contains abrasive particles that are magnetized using a magnetic.This paper details the design of an MR jet polishing system that uses an electromagnet,a nozzle,and a hydraulic unit to stabilize a slurry jet based on MR fluid, Second,for silica glass,the polishing spot and section profile are analyzed and the effect of the MR fluid jet polishing process is evaluated.The results of the experiment show that the removal profile is W-shaped and that,in this case,a stable can be proof of a distance of several tens of millimeters from the nozzle.Such results show the possibility of applying the proposed polishing method using MR fluids in ultra-precision micro and optical parts production processes. MR jet polishing shows great potential for use as a new type of precision surface polishing technology.In particular,this is a highly valuable process for the polishing of complex shapes such as micro parts,concaves parts,and cavities.展开更多
Electrochemical milling is a modified technique of traditional electrochemical machining(ECM)that can be used to manufacture some helicopter transmission system parts.The use of rotary tools and an inner-jet electroly...Electrochemical milling is a modified technique of traditional electrochemical machining(ECM)that can be used to manufacture some helicopter transmission system parts.The use of rotary tools and an inner-jet electrolyte supply pattern can greatly improve the material removal rate(MRR)in a single pass.However,the feed speed is generally limited to minimize the tool wear.To increase the MRR,electrical discharge machining(EDM)is introduced into the electrochemical milling process.The tool rotation is employed to interrupt the discharge and the high-conductivity salt solution and non-pulsed direct current power supply are also adopted to increase ECM,eventually,a new machining method is proposed,which can be called rotary sinking electrochemical discharge milling(RSECD milling).The mechanism of it is explored in this study by analyzing the machined current,MRR,surface morphology,and tool wear at different applied voltages and feed speeds.Besides,the RSECD milling using the tool with a larger diameter is also conducted to further verify the effectiveness.In particular,the MRR can be increased by 742.5%when using the tool with a diameter of 20 mm at the applied voltage of 20 V.展开更多
Hemispherical shell resonator(HSR)is the core component of hemispherical resonator gyro.It is aφ-shaped small-bore complex component with minimum curvature radius less than 3 mm.Thus,traditional polishing methods are...Hemispherical shell resonator(HSR)is the core component of hemispherical resonator gyro.It is aφ-shaped small-bore complex component with minimum curvature radius less than 3 mm.Thus,traditional polishing methods are difficult to polish it.Small ball-end magnetorheological polishing method can polish the small components with complicated three-dimensional surface and obtain non-destructive surface.Therefore,this method is suitable for polishing HSR.However,the material removal rate of the ordinary small ball-end magnetorheological polishing is low,leading to long polishing time and low output of HSR.To solve this problem,a water bath heating assisted small ball-end magnetorheological polishing method is proposed in this research.The influence rule of processing parameters on the material removal rate is studied experimentally.A set of optimal processing parameters is obtained to maximize the material removal rate.Compared with the ordinary method,the material removal rate of the new method can be improved by 143%.Subsequently,an HSR is polished by the new method.The results show that the polishing time can be reduced by 55%,and the polished surface roughness can reach 7.7 nm.The new method has the great potential to be used in actual production to improve the polishing efficiency of HSR.展开更多
GH4169 alloy is one of the most commonly used materials in aero engine turbine blades,but its machinability is poor because of its excellent strength at high temperatures. Electrochemical machining(ECM) has become a...GH4169 alloy is one of the most commonly used materials in aero engine turbine blades,but its machinability is poor because of its excellent strength at high temperatures. Electrochemical machining(ECM) has become a common method for machining this alloy and other difficult-tomachine materials. Electrochemical grinding(ECG) is a hybrid process combining ECM and conventional grinding. In this paper, investigations conducted on inner-jet ECG of GH4169 alloy are described. Two types of inner-jet ECG grinding wheels were used to machine a flat bottom surface.The machining process was simulated using COMSOL software, and machining gaps under different machining parameters were obtained. In addition, maximum feed rates and maximum material removal rates under different machining parameters were studied experimentally. The maximum sizes and the uniformity of the distributions of the gaps machined by the two grinding wheels were compared. The effects of different applied voltages on the machining results were also investigated.展开更多
An abrasive free chemical mechanical planarization(AFCMP) of semi-polar(1122) Al N surface has been demonstrated. The effect of slurry p H, polishing pressure, and platen velocity on the material removal rate(MRR...An abrasive free chemical mechanical planarization(AFCMP) of semi-polar(1122) Al N surface has been demonstrated. The effect of slurry p H, polishing pressure, and platen velocity on the material removal rate(MRR) and surface quality(RMS roughness) have been studied. The effect of polishing pressure on the AFCMP of the(1122) Al N surface has been compared with that of the(1122) Al Ga N surface. The maximum MRR has been found to be 562 nm/h for the semi-polar(1122) Al N surface, under the experimental conditions of 38 k Pa pressure,90 rpm platen velocity, 30 rpm carrier velocity, slurry p H 3 and 0.4 M oxidizer concentration. The best root mean square(RMS) surface roughness of 1.2 nm and 0.7 nm, over a large scanning area of 0.70×0.96 mm^2, has been achieved on AFCMP processed semi-polar(1122) AlN and(AlGaN) surfaces using optimized slurry chemistry and processing parameters.展开更多
文摘In the present study,a novel method of surface finish improvement is proposed using shot blasting of soda lime(SBSL)beads on the Mg-AZ31 alloy.The effect of the soda blasting process parameters,such as blast pressure,stand-off distance,and blast duration,have been studied in-response of material removal rate(MRR)and surface roughness(SR)and corresponding statistical models have been obtained.The multi-objective optimization has also been performed to obtain parameters for maximum MRR and minimum SR.The corrosion behavior of the treated specimens has been performed to study their in-vitro biodegradability in simulated body fluid(SBF)for 1,3,7,10,15,and 21 days.The wettability study of the SBSL treated samples has been investigated using sessile drop methodology.Further,cell adhesion test has also been performed to study the biocompatibility characteristics of the SBSL treated samples using Huh7 liver cell lines.Based on obtained quantitative data as well as scanning electron microscopy analysis of treated samples,the SBSL treatment of the AZ31 alloy has been found highly useful in producing biocompatibility surfaces along with desirable morphological features.
基金supported by the Key Project of the National Natural Science Foundation of China (No. 50535020)the Fund of the State Key Laboratory of Solidification Processing in Northwestern Polytechnical University (No. SKLSP200902)
文摘The mechanical characters of CdZnTe crystal were investigated by nanoscratch tests, and the effects of mechanical anisotropy on the material removal rate and surface quality were studied by polishing tests. There is a peak of frictional coefficient at the early stage of scratch, and increasing the vertical force will result in the increase of peak value correspondingly. The fluctuation phenomenon of frictional coefficient is generated at high vertical force. The lateral forces show the apparent twofold and threefold symmetries on (110) and (111) planes, respectively. To obtain high surface quality, low polishing pressure and hard direction (〈 T10 〉 directions on (110) plane and 〈 112 〉 directions on (111) plane) should be selected, and to achieve high material removal rate, high polishing pressure and soft direction (〈001〉 directions on (110) plane and 〈 121 〉 directions on (111) plane) should be selected.
基金This work was supported by the National Natural Science Foundation of China(Nos.51865030 and 52165025).
文摘Ultrasonic-assisted chemical mechanical polishing(UA-CMP)can greatly improve the sapphire material removal and surface quality,but its polishing mechanism is still unclear.This paper proposed a novel model of material removal rate(MRR)to explore the mechanism of sapphire UA-CMP.It contains two modes,namely two-body wear and abrasive-impact.Furthermore,the atomic force microscopy(AFM)in-situ study,computational fluid dynamics(CFD)simulation,and polishing experiments were conducted to verify the model and reveal the polishing mechanism.In the AFM in-situ studies,the tip scratched the reaction layer on the sapphire surface.The pit with a 0.22 nm depth is the evidence of two-body wear.The CFD simulation showed that abrasives could be driven by the ultrasonic vibration to impact the sapphire surface at high frequencies.The maximum total velocity and the air volume fraction(AVF)in the central area increased from 0.26 to 0.55 m/s and 20%to 49%,respectively,with the rising amplitudes of 1–3μm.However,the maximum total velocity rose slightly from 0.33 to 0.42 m/s,and the AVF was nearly unchanged under 40–80 r/min.It indicated that the ultrasonic energy has great effects on the abrasive-impact mode.The UA-CMP experimental results exhibited that there was 63.7%improvement in MRR when the polishing velocities rose from 40 to 80 r/min.The roughness of the polished sapphire surface was R_(a)=0.07 nm.It identified that the higher speed achieved greater MRR mainly through the two-body wear mode.This study is beneficial to further understanding the UA-CMP mechanism and promoting the development of UA-CMP technology.
文摘This work demonstrates the viability of the powder-mixed micro-electrochemical discharge machining(PMECDM) process to fabricate micro-holes on C103 niobium-based alloy for high temperature applications.Three processes are involved simultaneously i.e.spark erosion,chemical etching,and abrasive grinding for removal of material while the classical electrochemical discharge machining process involves double actions i.e.spark erosion,and chemical etching.The powder-mixed electrolyte process resulted in rapid material removal along with a better surface finish as compared to the classical microelectrochemical discharge machining(MECDM).Further,the results are optimized through a multiobjective optimization approach and study of the surface topography of the hole wall surface obtained at optimized parameters.In the selected range of experimental parameters,PMECDM shows a higher material removal rate(MRR) and lower surface roughness(R_(a))(MRR:2.8 mg/min and R_(a) of 0.61 μm) as compared to the MECDM process(MRR:2.01 mg/min and corresponding Raof 1.11 μm).A detailed analysis of the results is presented in this paper.
基金supported by the National Natural Science Foundation of China(No.51075125)the Key Scientific Research Program of Economic and Social Development of Xinxiang City(No.S10004)the Science and Technology Innovation Program of Henan Institute of Science and Technology
文摘The influences of the polishing slurry composition,such as the pH value,the abrasive size and its concentration,the dispersant and the oxidants,the rotational velocity of the polishing platen and the carrier and the polishing pressure,on the material removal rate of SiC crystal substrate(0001) Si and a(0001) C surface have been studied based on the alumina abrasive in chemical mechanical polishing(CMP).The results proposed by our research here will provide a reference for developing the slurry,optimizing the process parameters,and investigating the material removal mechanism in the CMP of SiC crystal substrate.
基金supported by the National Natural Science Foundation of China(No.50675104 and 50905086)Six High Talent Fund of Jiangsu Province(No.06-D-024)Talent Fund of NUAA(No.S0782-052)
文摘Chemical mechanical polishing (CMP) was used to polish Lithium triborate (LiB3O5 or LBO) crystal. Taguchi method was applied for optimization of the polishing parameters. Material removal rate (MRR) and surface roughness are considered as criteria for the optimization. The polishing pressure, the abrasive concentration and the table velocity are important parameters which influence MRR and surface roughness in CMP of LBO crystal. Experiment results indicate that for MRR the polishing pressure is the most significant polishing parameter followed by table velocity; while for the surface roughness, the abrasive concentration is the most important one. For high MRR in CMP of LBO ctystal the optimal conditions are: pressure 620 g/cm^2, concentration 5.0 wt pct, and velocity 60 r/min, respectively. For the best surface roughness the optimal conditions are: pressure 416 g/cm^2, concentration 5.0 wt pct, and velocity 40 r/min, respectively. The contributions of individual parameters for MRR and surface roughness were obtained.
基金supported by the Major Project of National Natural Science Foundation of China(No.50390061)the Key Project of Science and Technology R & D Program of Henan Province,China(No.102102210405)+2 种基金the Research Project Program of Natural Science of the Education Department of Henan Province,China(No.2009A460004)the Scientific Research Foundation of Henan Institute of Science and Technology for High Level Scholarthe Science and Technology Innovation Program of Henan Institute of Science and Technology.
文摘Distribution forms of abrasives in the chemical mechanical polishing(CMP) process are analyzed based on experimental results.Then the relationships between the wafer,the abrasive and the polishing pad are analyzed based on kinematics and contact mechanics.According to the track length of abrasives on the wafer surface,the relationships between the material removal rate and the polishing velocity are obtained.The analysis results are in accord with the experimental results.The conclusion provides a theoretical guide for further understanding the material removal mechanism of wafers in CMP.
基金Project(MSV-2013-09)supported by State Key Laboratory of Mechanical System and Vibration,China
文摘Electrical discharge milling(ED-milling) can be a good choice for titanium alloys machining and it was proven that its machining efficiency can be improved to compete with mechanical cutting. In order to improve energy utilization efficiency of ED-milling process, unstable arc discharge and stable arc discharge combined with normal discharge were implemented for material removal by adjusting servo control strategy. The influence of electrode rotating speed and dielectric flushing pressure on machining performance was investigated by experiments. It was found that the rotating of electrode could move the position of discharge plasma channel, and high pressure flushing could wash melted debris out the discharge gap effectively. Both electrode rotating motion and high pressure flushing are contributed to the improvement of machining efficiency.
文摘Ultrasonic machining (USM) is considered as an effective method for machining hard and brittle materials such as glass, engineering ceramics, semiconductors, diamonds, metal composites and so on. However, the low material removal rate due to using abrasive slurry limits further application of USM. Rotary ultrasonic machining (rotary USM) superimposes rotational movement on the tool head that vibrates at ultrasonic frequency (20 kHz) simultaneously. The tool is made of mild steel coated or bonded with diamond abrasive. Therefore, abrasive slurry is abandoned and coolant is used to carry debris out of working area. Compared with USM, rotary USM can obtain much higher material removal rate, deep holes, and fine precision, which leads to its further application. Combined with CNC technology, rotary USM can be used to conduct contour machining of hard and brittle materials. In this paper, the movement of abrasive particles in tool tip of rotary ultrasonic machining is analyzed. The impacting and grinding of abrasive in tool tip to machined surface are considered as main factors to material removal rate. The process of crack forming and growing in one loading and unloading cycle can be described as following stages: a) When abrasive particle acts the pressure on work-piece, the macro cracks in periphery of contact area are exerted increasing tensile stress. b) As the tensile stress increase to the critical of material tension, the one of cracks in periphery of contact area begins to propagate around contact area and develop beneath the surface to certain depth. c) Indentation area varies with increasing of load, the circle crack around contact area steadily or dynamical propagates towards inside of work-piece. d) As tensile stress in crack increases to critical of crack steady failure, circle crack suddenly becomes conic crack. e) Further increase load, the crack continues to grow while contact area is surrounded by conic cracks. f) During unloading, conic crack begins to close, some of cracks continue their extension towards the surface and forms a circle groove. The mathematical model for material removal rate shows that the factors affecting on material removal rate are static load, grid and concentration of abrasive, mechanical properties of machined materials, rotational speed of tool and feed speed of work-piece.
基金the National Natural Science Foundation of China(51905324)the Scientific Research Program Funded by Shaanxi Provincial Education Department(20JK0545)the Doctoral Scientific Research Startup Foundation of Shaanxi University of Science and Technology(2018BJ-14)。
文摘Ce^(3+)as the active site on the CeO_(2)abrasive surface is the key to enhancing the material removal rate(MRR).The CeO_(2)abrasives with high chemical activity were prepared by the molten salt method under a reducing atmosphere.The crystal structure and morphology of CeO_(2)abrasive s were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),Fourier transform infrared spectroscopy(FT-IR),ultraviolet—visible diffuse reflectance spectroscopy(UV-Vis DRS),and X-ray photoelectron spectroscopy(XPS).The CeO_(2)abrasives were obtained under different atmospheres(Air,Ar,and Ar/H_(2)).With the enhancement of the reducing atmosphere,the morphology of the abrasives transforms from spherical to octahedral,while more oxygen vacancies and Ce^(3+)are generated on the surface of CeO_(2)abrasives.The CMP experiments show that the MRRs of the CeO_(2)-Air,CeO_(2)-Ar,and CeO_(2)-Ar/H_(2)abrasives on SiO_(2)substrates are 337.60,578.74,and 691.28 nm/min,respectively.Moreover,as confirmed by atomic force microscopy(AFM),the substrate surfaces exhibit low roughness(20.5 nm)after being polished using all of the prepared samples.Especially,the MRR of CeO_(2)-Ar/H_(2)abrasives is increased by 104.76%compared with CeO_(2)-air abrasives.The improved CMP performance is attributed to the increased Ce^(3+)concentration and the octahedral morphology of the abrasives enhancing the chemical reaction and mechanical removal at the abrasive-substrate interface.
基金Project supported by the National Science & Technology Major Project of China(No.2009ZX02011)the Excellent Talent Support Plan for College of Dalian Province,China(No.2008RC58)
文摘Based on the Preston equation, the mathematical model of the material removal rate (MRR), aiming at a line-orbit chemical mechanical polisher, is established. The MRR and the material removal non-uniformity (MRNU) are numerically calculated by MATLAB, and the effects of the reciprocating parameters on the MRR and the MRNU are discussed. It is shown that the smaller the inclination angle and the larger the amplitude, the higher the MRR and the lower the MRNU. The reciprocating speed of the carrier plays a minor role to improve the MRR and decrease the MRNU. The results provide a guide for the design of a polisher and the determination of a process in line-orbit chemical mechanical polishing.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51175123 and 51105112)
文摘In order to get ultra-smooth fused silica surface without subsurface damage efficiently, the atmospheric pressure plasma processing( APPP) method has been developed. It is based on chemical reaction between active radicals excited by plasma and workpiece surface atoms,so the subsurface damage caused by contact stress can be avoided and atomic-level precision can be ensured. In this paper,based on the spectral quantitative analysis theory,the influence laws on material removal rate by the key factors of APPP including the flow rate of reaction gases,the input power,the processing distance and time are discussed. In addition,the results that APPP can remove the damaged surface layer and do not introduce secondary damage are proved via the nanoindentation technology.
基金co-supported by the National Key Research and Development Program of China(No.2019YFE0105100)the Equipment Pre-research Collaborative Foundation for Innovation Team from Ministry of Education of the People’s Republic of China(No.8091B042209)+1 种基金the Science and Technology Support Plan for Youth Innovation of Universities in Shandong Province(No.2019KJB016)the Natural Science Foundation of Shandong Province(No.ZR2022ME106)。
文摘The arc milling method has the advantages of high machining efficiency and low cost and is independent of the strength and hardness of machined materials.However,frequent electrode back-offs and the risk of workpiece burning may occur if erosion products are not removed promptly.In this study,it was found that the flushing method of the working medium had a significant impact on the machining performance of arc milling.Based on this,a novel highefficiency compound machining method of electrical discharge and arc milling with automatic tracking of the optimal flushing direction was proposed.An automatic tracking optimizer for external working medium injection was designed to determine the optimal external flushing direction according to the feed direction.The influence of flushing methods,working mediums,and machining parameters on the machining efficiency,tool electrode wear rate,machining error,and surface integrity of titanium alloys were investigated.The results indicated that better machining performance and environmental friendliness were achieved using the compound flushing method of outer compressed air and inner deionized water.Additionally,the automatic tracking flushing method in the opposite direction of the feed direction showed superior results compared to other directions.The material removal rate with the opposite direction injection could be increased up to 1.62 times that of the same direction,and the relative electrode wear rate could be reduced by 14.76%.This novel method has broad application prospects for machining parts with difficult-to-cut materials in aerospace and military industries.
基金supported by Defense Industrial Technology Development Program (Grant No. JCKY2021605B003)National Natural Science Foundation of China for Creative Research Groups (Grant No. 51921003)Postgraduate Research & Practice Innovation Program of Jiangsu Province (Grant No. KYCX20_0181)。
文摘In flat jet electrochemical milling, the electrolyte forms a backward parallel flow after impacting the workpiece, resulting in a weak current density distribution on the workpiece. Poor surface quality usually occurs on the machined titanium alloy surface because it inevitably suffers from the weak current density. In this study, a method of flat jet electrochemical milling with tailoring the backward parallel flow was proposed to eliminate the negative effects caused by the weak current density. Multiphysics simulations are carried out to comprehend the mechanism of flat jetEC milling with tailoring backward parallel flow and better construct the novel tool electrode.Experiments on flat jet electrochemical milling of TC4 alloy with and without tailoring backward parallel flow are conducted. The results reveal that, compared with flat jet electrochemical milling without tailoring backward parallel flow, the recommended tool reduces the surface roughness by86% to 93%, and improves the material removal rate by 93% to 163% with different feed rates.Additionally, the recommended tool is more conducive to maintaining the inherent hardness of the material. Finally, a surface with low Sa of 0.37 μm is obtained.
基金supported by the National Natural Science Foundation of China(Grant No.51175317)Research Fund for the Doctoral Program of Higher Education of China(Grant No.20123108110016)Tribology Science Fund of State Key Laboratory of Tribology(No.SKLTKF11B06).
文摘The effect of tert-butyl hydroperoxide-sodium pyrosulfite((CH3)3COOH-Na2S2O5)as an initiator system in H2O2-based slurry was investigated for the abrasive-free polishing(AFP)of a hard disk substrate.The polishing results show that the H_(2)O_(2)-C_(4)H_(10)O_(2)-Na_(2)S_(2)O_(5) slurry exhibits a material removal rate(MRR)that is nearly 5 times higher than that of the H2O2 slurry in the AFP of the hard disk substrate.In addition,the surface polished by the slurry containing the initiator exhibits a lower surface roughness and has fewer nano-asperity peaks than that of the H2O2 slurry.Further,we investigate the polishing mechanism of H_(2)O_(2)-C_(4)H_(10)O_(2)-Na_(2)S_(2)O_(5) slurry.Electron spin-resonance spectroscopy and auger electron spectrometer analyses show that the oxidizing ability of the H_(2)O_(2)-C_(4)H_(10)O_(2)-Na_(2)S_(2)O_(5) slurry is much greater than that of the H2O2 slurry.The results of potentiodynamic polarization measurements show that the hard disk substrate in the H_(2)O_(2)-C_(4)H_(10)O_(2)-Na_(2)S_(2)O_(5) slurry can be rapidly etched,and electrochemical impedance spectroscopy analysis indicates that the oxide film of the hard disk substrate formed in the H_(2)O_(2)-C_(4)H_(10)O_(2)-Na_(2)S_(2)O_(5) slurry may be loose,and can be removed easily during polishing.The better oxidizing and etching ability of H_(2)O_(2)-C_(4)H_(10)O_(2)-Na_(2)S_(2)O_(5) slurry leads to a higher MRR in AFP for hard disk substrates.
基金Item Sponsored by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of EducationScience and Technology[No.2009-0074199+1 种基金2012R1A1A2008399]the Ministry of Knowledge Economy (MKE) and Korea Institute for Advancement of Technology (KIAT) through the Workforce Development Program in Strategic Technology
文摘Recently,there has been an investigation of polishing processes that has considered new ultra-precision polishing technology for micro parts and optical parts such as those with aspheric and complex shapes.One suitable means of polishing complex shapes is to use a jet of abrasive fluid.However,aerodynamic disturbances and radial spreading are generated by the unstable polishing process of the jet on the surface of the workpiece when it is being polished.A method of jet stabilization has been proposed in which the original nozzle form of a jet of magnetorheological(MR)fluid contains abrasive particles that are magnetized using a magnetic.This paper details the design of an MR jet polishing system that uses an electromagnet,a nozzle,and a hydraulic unit to stabilize a slurry jet based on MR fluid, Second,for silica glass,the polishing spot and section profile are analyzed and the effect of the MR fluid jet polishing process is evaluated.The results of the experiment show that the removal profile is W-shaped and that,in this case,a stable can be proof of a distance of several tens of millimeters from the nozzle.Such results show the possibility of applying the proposed polishing method using MR fluids in ultra-precision micro and optical parts production processes. MR jet polishing shows great potential for use as a new type of precision surface polishing technology.In particular,this is a highly valuable process for the polishing of complex shapes such as micro parts,concaves parts,and cavities.
基金supported by the National Natural Science Foundation of China(No.91860208)the National Natural Science Foundation of China for Creative Research Groups(No.51921003)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX18_0255)。
文摘Electrochemical milling is a modified technique of traditional electrochemical machining(ECM)that can be used to manufacture some helicopter transmission system parts.The use of rotary tools and an inner-jet electrolyte supply pattern can greatly improve the material removal rate(MRR)in a single pass.However,the feed speed is generally limited to minimize the tool wear.To increase the MRR,electrical discharge machining(EDM)is introduced into the electrochemical milling process.The tool rotation is employed to interrupt the discharge and the high-conductivity salt solution and non-pulsed direct current power supply are also adopted to increase ECM,eventually,a new machining method is proposed,which can be called rotary sinking electrochemical discharge milling(RSECD milling).The mechanism of it is explored in this study by analyzing the machined current,MRR,surface morphology,and tool wear at different applied voltages and feed speeds.Besides,the RSECD milling using the tool with a larger diameter is also conducted to further verify the effectiveness.In particular,the MRR can be increased by 742.5%when using the tool with a diameter of 20 mm at the applied voltage of 20 V.
基金supported by the National Key Research and Development Program of China(No.2022YFB3403600)the National Natural Science Foundation of China(No.52293403)Self-Planned Task of State Key Laboratory of Robotics and System(HIT)(No.SKLRS202204C)。
文摘Hemispherical shell resonator(HSR)is the core component of hemispherical resonator gyro.It is aφ-shaped small-bore complex component with minimum curvature radius less than 3 mm.Thus,traditional polishing methods are difficult to polish it.Small ball-end magnetorheological polishing method can polish the small components with complicated three-dimensional surface and obtain non-destructive surface.Therefore,this method is suitable for polishing HSR.However,the material removal rate of the ordinary small ball-end magnetorheological polishing is low,leading to long polishing time and low output of HSR.To solve this problem,a water bath heating assisted small ball-end magnetorheological polishing method is proposed in this research.The influence rule of processing parameters on the material removal rate is studied experimentally.A set of optimal processing parameters is obtained to maximize the material removal rate.Compared with the ordinary method,the material removal rate of the new method can be improved by 143%.Subsequently,an HSR is polished by the new method.The results show that the polishing time can be reduced by 55%,and the polished surface roughness can reach 7.7 nm.The new method has the great potential to be used in actual production to improve the polishing efficiency of HSR.
基金co-supported by the National Natural Science Foundation of China(No.51323008)the Funding of Jiangsu Innovation Program for Graduate Education of China(No.KYLX16_0316)
文摘GH4169 alloy is one of the most commonly used materials in aero engine turbine blades,but its machinability is poor because of its excellent strength at high temperatures. Electrochemical machining(ECM) has become a common method for machining this alloy and other difficult-tomachine materials. Electrochemical grinding(ECG) is a hybrid process combining ECM and conventional grinding. In this paper, investigations conducted on inner-jet ECG of GH4169 alloy are described. Two types of inner-jet ECG grinding wheels were used to machine a flat bottom surface.The machining process was simulated using COMSOL software, and machining gaps under different machining parameters were obtained. In addition, maximum feed rates and maximum material removal rates under different machining parameters were studied experimentally. The maximum sizes and the uniformity of the distributions of the gaps machined by the two grinding wheels were compared. The effects of different applied voltages on the machining results were also investigated.
基金financial support from the Department of Science and Technology(DST),Government of India(No,SR/S2/Cmp-0009/2011)partial support from the Board of Research in Nuclear Sciences(BRNS),Department of Atomic Energy(DAE),Government of India(No.-34/14/43/2014-BRNS)with ATC
文摘An abrasive free chemical mechanical planarization(AFCMP) of semi-polar(1122) Al N surface has been demonstrated. The effect of slurry p H, polishing pressure, and platen velocity on the material removal rate(MRR) and surface quality(RMS roughness) have been studied. The effect of polishing pressure on the AFCMP of the(1122) Al N surface has been compared with that of the(1122) Al Ga N surface. The maximum MRR has been found to be 562 nm/h for the semi-polar(1122) Al N surface, under the experimental conditions of 38 k Pa pressure,90 rpm platen velocity, 30 rpm carrier velocity, slurry p H 3 and 0.4 M oxidizer concentration. The best root mean square(RMS) surface roughness of 1.2 nm and 0.7 nm, over a large scanning area of 0.70×0.96 mm^2, has been achieved on AFCMP processed semi-polar(1122) AlN and(AlGaN) surfaces using optimized slurry chemistry and processing parameters.