Minimum quantity Lubrication(MQL)is a sustainable lubrication system that is famous in many machining systems.It involve the spray of an infinitesimal amount of mist-like lubricants during machining processes.The MQL ...Minimum quantity Lubrication(MQL)is a sustainable lubrication system that is famous in many machining systems.It involve the spray of an infinitesimal amount of mist-like lubricants during machining processes.The MQL system is affirmed to exhibit an excellent machining performance,and it is highly economical.The nanofluids are understood to exhibit excellent lubricity and heat evacuation capability,compared to pure oil-based MQL system.Studies have shown that the surface quality and amount of energy expended in the grinding operations can be reduced considerably due to the positive effect of these nanofluids.This work presents an experimental study on the tribological performance of SiO_(2)nanofluid during grinding of Si_(3)N_(4)ceramic.The effect different grinding modes and lubrication systems during the grinding operation was also analyzed.Different concentrations of the SiO_(2)nanofluid was manufactured using canola,corn and sunflower oils.The quantitative evaluation of the grinding process was done based on the amount of grinding forces,specific grinding energy,frictional coefficient,and surface integrity.It was found that the canola oil exhibits optimal lubrication performance compared to corn oil,sunflower oil,and traditional lubrication systems.Additionally,the introduction of ultrasonic vibrations with the SiO_(2)nanofluid in MQL system was found to reduce the specific grinding energy,normal grinding forces,tangential grinding forces,and surface roughness by 65%,57%,65%,and 18%respectively.Finally,regression analysis was used to obtain an optimum parameter combinations.The observations from this work will aid the smooth transition towards ecofriendly and sustainable machining of engineering ceramics.展开更多
Fatigue properties are crucial for critical aero-engine components in extreme serviceenvironments,which are significantly affected by surface integrity(SI)indexes(especially surface topography,residual stressσ_(res),...Fatigue properties are crucial for critical aero-engine components in extreme serviceenvironments,which are significantly affected by surface integrity(SI)indexes(especially surface topography,residual stressσ_(res),and microhardness)after machining processes.Normal-direction ultrasonic vibration-assisted face grinding(ND-UVAFG)has advantages in improving the machinability of Inconel 718,but there is a competitive relationship between higher compressiveσ_(res)and higher surface roughness R_(a)in affecting fatigue strength.The lack of a quantitative relationship between multiple SI indexes and fatigue strength makes theindeterminacy of a regulatory strategy for improving fatigue properties.In this work,a model of fatigue strength(σ_f)_(sur)considering multiple SI indexes was developed.Then,high-cycle fatigue tests were carried out on Inconel 718 samples with different SI characteristics,and the influence of ND-UVAFG process parameters on SI was analyzed.Based on SI indexes data,the(σ_f)_(sur)distribution in the grinding surface layer for ND-UVAFG Inconel 718 samples was determined using the developed model,and then the fatigue crack initiation(FCI)sites were furtherpredicted.The predicted FCI sites corresponded well with the experimental results,therebyverifying this model.A strategy for improving the fatigue life was proposed in this work,which was to transfer the fatigue source from the machined surface to the bulk material by controlling the SI indexes.Finally,a critical condition of SI indexes that FCI sites appeared on the surface or in bulk material was given by fitting the predicted results.According to the critical condition,an SI field where FCI sites appeared in the bulk material could be obtained.In this field,thefatigue life of Inconel 718 samples could be improved by approximately 140%.展开更多
In order to grind the ceramic blade surface with the Numerical Control contour evolution ultrasonic grinding method using the simple shape grinding wheel, primary comparative experiments of creep feed grinding with an...In order to grind the ceramic blade surface with the Numerical Control contour evolution ultrasonic grinding method using the simple shape grinding wheel, primary comparative experiments of creep feed grinding with and without ultrasonic vibration were carried out to grind Al2O3 ceramics so as to implore the effects of different process parameters on the machined surface quality. It can be concluded that when the direction of ultrasonic vibration is parallel to the direction of creep feed, the value of the surface roughness will be decreased; otherwise the surface quality will become worse. With the ultrasonic grinding method, the slower feed-rate, the smaller grinding depth, the higher grinding speed and the compound feed grinding method should be applied in order to improve the surface quality. The creep feed grinding meehanisms with and without ultrasonic vibration were analyzed theoretically from the experimental results. With the selected grinding parameters resulted from the experiments, the feasibility experiment of ultrasonic grinding ceramic blade surface was cartied out.展开更多
It is well known that grinding techniques are main methods to machine hard and brittle materials such as engineering ceramics. But the conventional grinding has many shortcomings such as poorer surface finish, quicker...It is well known that grinding techniques are main methods to machine hard and brittle materials such as engineering ceramics. But the conventional grinding has many shortcomings such as poorer surface finish, quicker wear and tear of grinding tools, lower efficiency and so on. Ultrasonic vibration grinding (UVG) which combines ultrasonic machining and grinding emerged as a developing and promising technique in recent years. In this paper, experimental studies on UVG were conducted on several kinds of hard and brittle material by altering processing parameters such as vibration frequency and its amplitude, diamond abrasive grit size, cutting depth, feeding speed and rotary speed of tools. The experimental results show that alteration in any of above mentioned parameters will bring effects on the processed surface finish of these materials. Of them, the diamond abrasive grit size has the greatest. Moreover, conventional grinding experiments were also carried out on these materials. By comparison, it was found that the UVG is superior to the conventional method in terms of the ground surface quality, the working efficiency and the wear rate of tools.展开更多
The theoretical model of axial ultrasonic vibration grinding force is built on the basis of a mathematical model of cutting deforming force deduced from the assumptions of thickness of the undeformed debris under Rayl...The theoretical model of axial ultrasonic vibration grinding force is built on the basis of a mathematical model of cutting deforming force deduced from the assumptions of thickness of the undeformed debris under Rayleigh distribution and a mathematical model of friction based on the theoretical analysis of relative sliding velocity of abrasive and workpiece. Then, the coefficients of the ultrasonic vibration grinding force model are calculated through analysis of nonlinear regression of the theoretical model by using MATLAB, and the law of influence of grinding depth, workpiece speed, frequency and amplitude of the mill on the grinding force is summarized after applying the model to analyze the ultrasonic grinding force. The result of the above-mentioned law shows that the grinding force decreases as frequency and amplitude increase, while increases as grinding depth and workpiece speed increase; the maximum relative error of prediction and experimental values of the normal grinding force is 11.47% and its average relative error is 5.41%; the maximum relative error of the tangential grinding force is 10.14% and its average relative error is 4.29%. The result of employing regression equation to predict ultrasonic grinding force approximates to the experimental data, therefore the accuracy and reliability of the model is verified.展开更多
In this work, machining test was carried out in various machining conditions using ultrasonic vibration capable CNC machine. For work material, alumina ceramic (Al2O3) was used while for tool material diamond electrop...In this work, machining test was carried out in various machining conditions using ultrasonic vibration capable CNC machine. For work material, alumina ceramic (Al2O3) was used while for tool material diamond electroplated grinding wheel was used. To evaluate ultrasonic vibration effect, grinding test was performed with and without ultrasonic vibration in same machining condition. In ultrasonic mode, ultrasonic vibration of 20 kHz was generated by HSK 63 ultrasonic actuator. On the other hand, grinding forces were measured by KISTLER dynamometer. And an optimal sampling rate for grinding force measurement was obtained by a signal processing and frequency analysis. The surface roughness of the ceramic was also measured by using stylus type surface roughness instrument and atomic force microscope (AFM). Besides, the scanning electron microscope (SEM) was used for observation of surface integrality.展开更多
The surface quality of fine-grained ZrO2 engineering ceramic were researched using 270# diamond wheel both with and without work-piece two-dimension ultrasonic vibration grinding(WTDUVG). By AFM images, the surface ...The surface quality of fine-grained ZrO2 engineering ceramic were researched using 270# diamond wheel both with and without work-piece two-dimension ultrasonic vibration grinding(WTDUVG). By AFM images, the surface topography and the micro structure of the two-dimensional ultrasonic vibration grinding ceramics were especially analyzed. The experimental results indicate that the surface roughness is related to grinding vibration mode and the material removal mechanism. Surface quality of WTDUVG is superior to that of conventional grinding, and it is easy for two-dimensional ultrasonic vibration grinding that material removal mechanism is ductile mode grinding.展开更多
Separate characteristic of the tangential ultrasonic vibration assisted grinding (TUAG) machining is analyzed based on TUAG process, and a critical speed formula is given to correctly set the machining parameters to i...Separate characteristic of the tangential ultrasonic vibration assisted grinding (TUAG) machining is analyzed based on TUAG process, and a critical speed formula is given to correctly set the machining parameters to insure the separate characteristics of TUAG process. The critical speed is not only related to the ultrasonic vibration amplitude and frequency, but also to the grinding wheel velocity and the cutting point space, and the grinding force can be decreased during the TUAG process with separability. Grinding force experiments are conducted, and the experimental results are in good agreement with the theoretical results.展开更多
The performances of fme-crystalline zirconia ceramics in workpiece ultrasonic vibration grinding (WUVG) and conventional grinding (CG) with diamond wheel were researched. The effects of WUVG and CG on material rem...The performances of fme-crystalline zirconia ceramics in workpiece ultrasonic vibration grinding (WUVG) and conventional grinding (CG) with diamond wheel were researched. The effects of WUVG and CG on material removal rate, grinding forces, surface roughness and microstructure of zirconia ceramic were investigated. Experimental results indicated that: (1) The material removal rate (MRR) in ultrasonic grinding process is two times as large as that of in conventional grinding. The material removal rate increases with increasing grinding depth in both ultrasonic grinding and conventional grinding. (2) The ultrasonic vibration grinding force is lower than that of conventional grinding force, and the increase of the worktable speed leads to a decrease of the grinding force, while the grinding force increases with larger grinding depth in both WUVG and CG. (3) The surface of ultrasonic vibration grinding has no spur and build-up edge and its surface roughness is smaller than that of CG significantly. Surface quality of WUVG is superior to that of conventional grinding, it is easy for ultrasonic vibration grinding that material removal mechanism is ductile grinding.展开更多
Ultrasonic vibration grinding differs from traditional grinding in terms of its material removal mechanism.The randomness of grain-workpiece interaction in ultrasonic vibration grinding can produce variable chips and ...Ultrasonic vibration grinding differs from traditional grinding in terms of its material removal mechanism.The randomness of grain-workpiece interaction in ultrasonic vibration grinding can produce variable chips and impact the surface roughness of workpiece.However,previous studies used iterative method to calculate the unformed chip thickness(UCT),which has low computational efficiency.In this study,a symbolic difference method is proposed to calculate the UCT.The UCT distributions are obtained to describe the stochastic interaction characteristics of ultrasonic grinding process.Meanwhile,the UCT distribution characteristics under different machining parameters are analyzed.Then,a surface roughness prediction model is established based on the UCT distribution.Finally,the correctness of the model is verified by experiments.This study provides a quick and accurate method for predicting surface roughness in longitudinal ultrasonic vibration grinding.展开更多
Addressing the challenges of high grinding temperature,poor hole quality,and tool rod blocking in core drilling of carbon fiber reinforced plastics(CFRP),this study investigates the material removal characteristic of ...Addressing the challenges of high grinding temperature,poor hole quality,and tool rod blocking in core drilling of carbon fiber reinforced plastics(CFRP),this study investigates the material removal characteristic of rotary longitudinal-torsional ultrasonic machining(RLTUM)of CFRP based on the Hertz contact theory.The study also conducts relevant experiments to compare and analyze the grinding force,grinding temperature,hole wall quality,exit quality,and tool wear in ordinary core drilling(OCD),rotary ultrasonic machining(RUM),and RLTUM of CFRP.The results demonstrate that RLTUM significantly reduces the grinding force,grinding temperature,hole exit damage and improves the surface smoothness of the CFRP hole walls.By utilizing intermittent cutting in circumferential direction for torsional vibration,RLTUM enables automatic removal of rod chips while restraining tool chip adhesion and reducing heat generation as well as tool wear.Therefore,RLTUM shows great potential for enhancing the quality of holemaking in CFRP.展开更多
Gamma titanium-aluminum intermetallic compounds(γ-TiAl)have gained considerable attentions in the aerospace industry due to their exceptional thermal resilience and comprehensive attributes,making them a prime exampl...Gamma titanium-aluminum intermetallic compounds(γ-TiAl)have gained considerable attentions in the aerospace industry due to their exceptional thermal resilience and comprehensive attributes,making them a prime example of lightweight and advanced materials.To address the frequent occurrence of burns and severe tool deterioration during the process of high-efficiency deep grinding(HEDG)onγ-TiAl alloys,ultrasonic vibration-assisted high-efficiency deep grinding(UVHEDG)has been emerged.Results indicate that in UVHEDG,the grinding temperature is on average 15.4%lower than HEDG due to the employment of ultrasonic vibrations,enhancing coolant penetration into the grinding area and thus reducing heat generation.Besides,UVHEDG possesses superior performance in terms of grinding forces compared to HEDG.As the material removal volume(MRV)increases,the tangential grinding force(F_(t))and normal grinding force(F_(n))of UVHEDG increase but to a lesser extent than in HEDG,with an average reduction of16.25%and 14.7%,respectively.UVHEDG primarily experiences microfracture of grains,whereas HEDG undergoes large-scale wear later in the process due to increased grinding forces.The surface roughness(R_(a))characteristics of UVHEDG are superior,with the average value of R_(a)decreasing by 46.5%compared to HEDG as MRV increases.The surface morphology in UVHEDG exhibits enhanced smoothness and a shallower layer of plastic deformation.Grinding chips generated by UVHEDG show a more shear-like shape,with the applied influence of ultrasonic vibration on chip morphology,thereby impacting material removal behaviors.These aforementioned findings contribute to enhanced machining efficiency and product quality ofγ-TiAl alloys after employing ultrasonic vibrations into HEDG.展开更多
Bone grinding is an essential and vital procedure in most surgical operations.Currently,the insufficient cooling capacity of dry grinding,poor visibility of drip irrigation surgery area,and large grinding force leadin...Bone grinding is an essential and vital procedure in most surgical operations.Currently,the insufficient cooling capacity of dry grinding,poor visibility of drip irrigation surgery area,and large grinding force leading to high grinding temperature are the technical bottlenecks of micro-grinding.A new micro-grinding process called ultrasonic vibration-assisted nanoparticle jet mist cooling(U-NJMC)is innovatively proposed to solve the technical problem.It combines the advantages of ultrasonic vibration(UV)and nanoparticle jet mist cooling(NJMC).Notwithstanding,the combined effect of multi parameter collaborative of U-NJMC on cooling has not been investigated.The grinding force,friction coefficient,specific grinding energy,and grinding temperature under dry,drip irrigation,UV,minimum quantity lubrication(MQL),NJMC,and U-NJMC micro-grinding were compared and analyzed.Results showed that the minimum normal grinding force and tangential grinding force of U-NJMC micro-grinding were 1.39 and 0.32 N,which were 75.1%and 82.9%less than those in dry grinding,respectively.The minimum friction coefficient and specific grinding energy were achieved using U-NJMC.Compared with dry,drip,UV,MQL,and NJMC grinding,the friction coefficient of U-NJMC was decreased by 31.3%,17.0%,19.0%,9.8%,and 12.5%,respectively,and the specific grinding energy was decreased by 83.0%,72.7%,77.8%,52.3%,and 64.7%,respectively.Compared with UV or NJMC alone,the grinding temperature of U-NJMC was decreased by 33.5%and 10.0%,respectively.These results showed that U-NJMC provides a novel approach for clinical surgical micro-grinding of biological bone.展开更多
Particle-reinforcing titanium matrix composites(PTMCs)exhibit the sharp raising applications in modern industries owing to its extraordinary physical and mechanical properties.However,the poor grindability and unstabl...Particle-reinforcing titanium matrix composites(PTMCs)exhibit the sharp raising applications in modern industries owing to its extraordinary physical and mechanical properties.However,the poor grindability and unstable grinding processes due to the existence of TiC particles and TiB short fibres inside PTMCs,leading to the sudden grinding burn and low material removal rate.In this work,a novel radial ultrasonic vibration-assisted grinding(RUVAG)device with a special cross structure was developed to improve machining efficiency and avoid grinding burns.Meanwhile,the resonant modal and transient dynamic characteristics of radial ultrasonic vibration system were discussed.Comparative grinding performance experiments were then conducted under the conventional grinding(CG)and RUVAG using mono-layer cubic boron nitride abrasive wheels,in views of the grinding forces and force ratio,grinding temperature,and ground surface morphology.Results show that the ultrasonic vibration direction can be transformed effectively using the special cross structure of vibration converter,and better vibration homogeneity can be obtained.RUVAG has a smaller tangential grinding force by 5.0%–17.2%than that of CG,but a higher normal grinding force of 6.5%–14.9%,owing to the periodic impact of grinding wheels.In addition,RUVAG possesses a remarkable lower grinding temperature in range of 24.2%–51.8%and a higher material removal rate by 2.8 times compared with CG,resulting from the intermittent cutting behavior between the grinding wheel and workpiece.In this case,the sudden burn can be avoided during high-speed grinding processes.Moreover,the proportion of micro-fracture defects on machined surface is slightly increased once the ultrasonic vibration mode is employed because of the periodic impact on reinforced particles,whereas the pull-out defects of reinforced particles are reduced significantly.展开更多
A compound machine tool was designed, which combined rotary ultrasonic assisted grinding, electrical discharge machining(EDM) and multi-axis milling. Experimental results indicated that its positioning accuracy was le...A compound machine tool was designed, which combined rotary ultrasonic assisted grinding, electrical discharge machining(EDM) and multi-axis milling. Experimental results indicated that its positioning accuracy was less than 5.6 μm and its repetitive positioning accuracy was less than 1.8 μm; the vibration amplitude of ultrasonic grinding system was uniform and stable, and the EDM system worked well and stably.A smooth surface of K9 optical glass component was achieved by the grinding method.展开更多
Ultrasonic vibration-assisted grinding(UVAG)is an advanced hybrid process for the precision machining of difficult-to-cut materials.The resonator is a critical part of the UVAG system.Its performance considerably infl...Ultrasonic vibration-assisted grinding(UVAG)is an advanced hybrid process for the precision machining of difficult-to-cut materials.The resonator is a critical part of the UVAG system.Its performance considerably influences the vibration amplitude and resonant frequency.In this work,a novel perforated ultrasonic vibration platform resonator was developed for UVAG.The holes were evenly arranged at the top and side surfaces of the vibration platform to improve the vibration characteristics.A modified apparent elasticity method(AEM)was proposed to reveal the influence of holes on the vibration mode.The performance of the vibration platform was evaluated by the vibration tests and UVAG experiments of particulate-reinforced titanium matrix composites.Results indicate that the reasonable distribution of holes helps improve the resonant frequency and vibration mode.The modified AEM,the finite element method,and the vibration tests show a high degree of consistency for developing the perforated ultrasonic vibration platform with a maximum frequency error of 3%.The employment of ultrasonic vibration reduces the grinding force by 36%at most,thereby decreasing the machined surface defects,such as voids,cracks,and burnout.展开更多
文摘Minimum quantity Lubrication(MQL)is a sustainable lubrication system that is famous in many machining systems.It involve the spray of an infinitesimal amount of mist-like lubricants during machining processes.The MQL system is affirmed to exhibit an excellent machining performance,and it is highly economical.The nanofluids are understood to exhibit excellent lubricity and heat evacuation capability,compared to pure oil-based MQL system.Studies have shown that the surface quality and amount of energy expended in the grinding operations can be reduced considerably due to the positive effect of these nanofluids.This work presents an experimental study on the tribological performance of SiO_(2)nanofluid during grinding of Si_(3)N_(4)ceramic.The effect different grinding modes and lubrication systems during the grinding operation was also analyzed.Different concentrations of the SiO_(2)nanofluid was manufactured using canola,corn and sunflower oils.The quantitative evaluation of the grinding process was done based on the amount of grinding forces,specific grinding energy,frictional coefficient,and surface integrity.It was found that the canola oil exhibits optimal lubrication performance compared to corn oil,sunflower oil,and traditional lubrication systems.Additionally,the introduction of ultrasonic vibrations with the SiO_(2)nanofluid in MQL system was found to reduce the specific grinding energy,normal grinding forces,tangential grinding forces,and surface roughness by 65%,57%,65%,and 18%respectively.Finally,regression analysis was used to obtain an optimum parameter combinations.The observations from this work will aid the smooth transition towards ecofriendly and sustainable machining of engineering ceramics.
基金support from the National Science Fund of China(52325506)the National Science and Technology Major Project(2017-VII-0002-0095)Fundamental Research Funds for the Central Universities(DUT22LAB501)。
文摘Fatigue properties are crucial for critical aero-engine components in extreme serviceenvironments,which are significantly affected by surface integrity(SI)indexes(especially surface topography,residual stressσ_(res),and microhardness)after machining processes.Normal-direction ultrasonic vibration-assisted face grinding(ND-UVAFG)has advantages in improving the machinability of Inconel 718,but there is a competitive relationship between higher compressiveσ_(res)and higher surface roughness R_(a)in affecting fatigue strength.The lack of a quantitative relationship between multiple SI indexes and fatigue strength makes theindeterminacy of a regulatory strategy for improving fatigue properties.In this work,a model of fatigue strength(σ_f)_(sur)considering multiple SI indexes was developed.Then,high-cycle fatigue tests were carried out on Inconel 718 samples with different SI characteristics,and the influence of ND-UVAFG process parameters on SI was analyzed.Based on SI indexes data,the(σ_f)_(sur)distribution in the grinding surface layer for ND-UVAFG Inconel 718 samples was determined using the developed model,and then the fatigue crack initiation(FCI)sites were furtherpredicted.The predicted FCI sites corresponded well with the experimental results,therebyverifying this model.A strategy for improving the fatigue life was proposed in this work,which was to transfer the fatigue source from the machined surface to the bulk material by controlling the SI indexes.Finally,a critical condition of SI indexes that FCI sites appeared on the surface or in bulk material was given by fitting the predicted results.According to the critical condition,an SI field where FCI sites appeared in the bulk material could be obtained.In this field,thefatigue life of Inconel 718 samples could be improved by approximately 140%.
基金Jiangsu Natural Science Fund of China (BK2001048)
文摘In order to grind the ceramic blade surface with the Numerical Control contour evolution ultrasonic grinding method using the simple shape grinding wheel, primary comparative experiments of creep feed grinding with and without ultrasonic vibration were carried out to grind Al2O3 ceramics so as to implore the effects of different process parameters on the machined surface quality. It can be concluded that when the direction of ultrasonic vibration is parallel to the direction of creep feed, the value of the surface roughness will be decreased; otherwise the surface quality will become worse. With the ultrasonic grinding method, the slower feed-rate, the smaller grinding depth, the higher grinding speed and the compound feed grinding method should be applied in order to improve the surface quality. The creep feed grinding meehanisms with and without ultrasonic vibration were analyzed theoretically from the experimental results. With the selected grinding parameters resulted from the experiments, the feasibility experiment of ultrasonic grinding ceramic blade surface was cartied out.
文摘It is well known that grinding techniques are main methods to machine hard and brittle materials such as engineering ceramics. But the conventional grinding has many shortcomings such as poorer surface finish, quicker wear and tear of grinding tools, lower efficiency and so on. Ultrasonic vibration grinding (UVG) which combines ultrasonic machining and grinding emerged as a developing and promising technique in recent years. In this paper, experimental studies on UVG were conducted on several kinds of hard and brittle material by altering processing parameters such as vibration frequency and its amplitude, diamond abrasive grit size, cutting depth, feeding speed and rotary speed of tools. The experimental results show that alteration in any of above mentioned parameters will bring effects on the processed surface finish of these materials. Of them, the diamond abrasive grit size has the greatest. Moreover, conventional grinding experiments were also carried out on these materials. By comparison, it was found that the UVG is superior to the conventional method in terms of the ground surface quality, the working efficiency and the wear rate of tools.
基金Project(51275530)supported by the National Natural Science Foundation of China
文摘The theoretical model of axial ultrasonic vibration grinding force is built on the basis of a mathematical model of cutting deforming force deduced from the assumptions of thickness of the undeformed debris under Rayleigh distribution and a mathematical model of friction based on the theoretical analysis of relative sliding velocity of abrasive and workpiece. Then, the coefficients of the ultrasonic vibration grinding force model are calculated through analysis of nonlinear regression of the theoretical model by using MATLAB, and the law of influence of grinding depth, workpiece speed, frequency and amplitude of the mill on the grinding force is summarized after applying the model to analyze the ultrasonic grinding force. The result of the above-mentioned law shows that the grinding force decreases as frequency and amplitude increase, while increases as grinding depth and workpiece speed increase; the maximum relative error of prediction and experimental values of the normal grinding force is 11.47% and its average relative error is 5.41%; the maximum relative error of the tangential grinding force is 10.14% and its average relative error is 4.29%. The result of employing regression equation to predict ultrasonic grinding force approximates to the experimental data, therefore the accuracy and reliability of the model is verified.
文摘In this work, machining test was carried out in various machining conditions using ultrasonic vibration capable CNC machine. For work material, alumina ceramic (Al2O3) was used while for tool material diamond electroplated grinding wheel was used. To evaluate ultrasonic vibration effect, grinding test was performed with and without ultrasonic vibration in same machining condition. In ultrasonic mode, ultrasonic vibration of 20 kHz was generated by HSK 63 ultrasonic actuator. On the other hand, grinding forces were measured by KISTLER dynamometer. And an optimal sampling rate for grinding force measurement was obtained by a signal processing and frequency analysis. The surface roughness of the ceramic was also measured by using stylus type surface roughness instrument and atomic force microscope (AFM). Besides, the scanning electron microscope (SEM) was used for observation of surface integrality.
基金Funded by the Shanxi Province Science Foundation for Youths(2006021026)
文摘The surface quality of fine-grained ZrO2 engineering ceramic were researched using 270# diamond wheel both with and without work-piece two-dimension ultrasonic vibration grinding(WTDUVG). By AFM images, the surface topography and the micro structure of the two-dimensional ultrasonic vibration grinding ceramics were especially analyzed. The experimental results indicate that the surface roughness is related to grinding vibration mode and the material removal mechanism. Surface quality of WTDUVG is superior to that of conventional grinding, and it is easy for two-dimensional ultrasonic vibration grinding that material removal mechanism is ductile mode grinding.
基金supported by the National Natural Science Foundation of China (Grant No.50575127)
文摘Separate characteristic of the tangential ultrasonic vibration assisted grinding (TUAG) machining is analyzed based on TUAG process, and a critical speed formula is given to correctly set the machining parameters to insure the separate characteristics of TUAG process. The critical speed is not only related to the ultrasonic vibration amplitude and frequency, but also to the grinding wheel velocity and the cutting point space, and the grinding force can be decreased during the TUAG process with separability. Grinding force experiments are conducted, and the experimental results are in good agreement with the theoretical results.
基金Supported by the Henan Extraordinary Ability of China (No.0421001200)
文摘The performances of fme-crystalline zirconia ceramics in workpiece ultrasonic vibration grinding (WUVG) and conventional grinding (CG) with diamond wheel were researched. The effects of WUVG and CG on material removal rate, grinding forces, surface roughness and microstructure of zirconia ceramic were investigated. Experimental results indicated that: (1) The material removal rate (MRR) in ultrasonic grinding process is two times as large as that of in conventional grinding. The material removal rate increases with increasing grinding depth in both ultrasonic grinding and conventional grinding. (2) The ultrasonic vibration grinding force is lower than that of conventional grinding force, and the increase of the worktable speed leads to a decrease of the grinding force, while the grinding force increases with larger grinding depth in both WUVG and CG. (3) The surface of ultrasonic vibration grinding has no spur and build-up edge and its surface roughness is smaller than that of CG significantly. Surface quality of WUVG is superior to that of conventional grinding, it is easy for ultrasonic vibration grinding that material removal mechanism is ductile grinding.
基金supported by the National Key Research and Development Program of China(No.2018YFB2000402)the Open Fund Project of Xinchang Research Institute of Zhejiang University of Technology,and the Fundamental Research Funds for the Universities of Henan Province,China(No.NSFRF200102).
文摘Ultrasonic vibration grinding differs from traditional grinding in terms of its material removal mechanism.The randomness of grain-workpiece interaction in ultrasonic vibration grinding can produce variable chips and impact the surface roughness of workpiece.However,previous studies used iterative method to calculate the unformed chip thickness(UCT),which has low computational efficiency.In this study,a symbolic difference method is proposed to calculate the UCT.The UCT distributions are obtained to describe the stochastic interaction characteristics of ultrasonic grinding process.Meanwhile,the UCT distribution characteristics under different machining parameters are analyzed.Then,a surface roughness prediction model is established based on the UCT distribution.Finally,the correctness of the model is verified by experiments.This study provides a quick and accurate method for predicting surface roughness in longitudinal ultrasonic vibration grinding.
基金supported by the National Natural Science Foundation of China(No.51675164)。
文摘Addressing the challenges of high grinding temperature,poor hole quality,and tool rod blocking in core drilling of carbon fiber reinforced plastics(CFRP),this study investigates the material removal characteristic of rotary longitudinal-torsional ultrasonic machining(RLTUM)of CFRP based on the Hertz contact theory.The study also conducts relevant experiments to compare and analyze the grinding force,grinding temperature,hole wall quality,exit quality,and tool wear in ordinary core drilling(OCD),rotary ultrasonic machining(RUM),and RLTUM of CFRP.The results demonstrate that RLTUM significantly reduces the grinding force,grinding temperature,hole exit damage and improves the surface smoothness of the CFRP hole walls.By utilizing intermittent cutting in circumferential direction for torsional vibration,RLTUM enables automatic removal of rod chips while restraining tool chip adhesion and reducing heat generation as well as tool wear.Therefore,RLTUM shows great potential for enhancing the quality of holemaking in CFRP.
基金financially supported by the National Natural Science Foundation of China(Nos.92160301,92060203,52175415 and 52205475)the Science Center for Gas Turbine Project(Nos.P2022-AB-Ⅳ-002-001 and P2023-B-Ⅳ-003-001)+4 种基金the Natural Science Foundation of Jiangsu Province(No.BK20210295)the Superior Postdoctoral Project of Jiangsu Province(No.2022ZB215)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX23_0355)the Interdisciplinary Innovation Fund for Doctoral Students of Nanjing University of Aeronautics and Astronautics(KXKCXJJ202305)the Fundamental Research Funds for the Central Universities(Nos.NS2023028 and NG2024015)。
文摘Gamma titanium-aluminum intermetallic compounds(γ-TiAl)have gained considerable attentions in the aerospace industry due to their exceptional thermal resilience and comprehensive attributes,making them a prime example of lightweight and advanced materials.To address the frequent occurrence of burns and severe tool deterioration during the process of high-efficiency deep grinding(HEDG)onγ-TiAl alloys,ultrasonic vibration-assisted high-efficiency deep grinding(UVHEDG)has been emerged.Results indicate that in UVHEDG,the grinding temperature is on average 15.4%lower than HEDG due to the employment of ultrasonic vibrations,enhancing coolant penetration into the grinding area and thus reducing heat generation.Besides,UVHEDG possesses superior performance in terms of grinding forces compared to HEDG.As the material removal volume(MRV)increases,the tangential grinding force(F_(t))and normal grinding force(F_(n))of UVHEDG increase but to a lesser extent than in HEDG,with an average reduction of16.25%and 14.7%,respectively.UVHEDG primarily experiences microfracture of grains,whereas HEDG undergoes large-scale wear later in the process due to increased grinding forces.The surface roughness(R_(a))characteristics of UVHEDG are superior,with the average value of R_(a)decreasing by 46.5%compared to HEDG as MRV increases.The surface morphology in UVHEDG exhibits enhanced smoothness and a shallower layer of plastic deformation.Grinding chips generated by UVHEDG show a more shear-like shape,with the applied influence of ultrasonic vibration on chip morphology,thereby impacting material removal behaviors.These aforementioned findings contribute to enhanced machining efficiency and product quality ofγ-TiAl alloys after employing ultrasonic vibrations into HEDG.
基金supported by the National Natural Science Foundation of China (Grant Nos.51905289 and 51975305)the National Key R&D Program of China (Grant No.2020YFB2010500)+3 种基金the Natural Science Foundation of Shandong Province,China (Grant Nos.ZR2022QE159,ZR2020KE027,ZR2020ME158,and ZR2019PEE008)the China Postdoctoral Science Foundation (Grant No.2021M701810)the Innovation Talent Supporting Program for Postdoctoral Fellows of Shandong Province,China (Grant No.SDBX2020012)the Qingdao Postdoctoral Researchers Applied Research Project Funding,China (Grant No.A2020-072).
文摘Bone grinding is an essential and vital procedure in most surgical operations.Currently,the insufficient cooling capacity of dry grinding,poor visibility of drip irrigation surgery area,and large grinding force leading to high grinding temperature are the technical bottlenecks of micro-grinding.A new micro-grinding process called ultrasonic vibration-assisted nanoparticle jet mist cooling(U-NJMC)is innovatively proposed to solve the technical problem.It combines the advantages of ultrasonic vibration(UV)and nanoparticle jet mist cooling(NJMC).Notwithstanding,the combined effect of multi parameter collaborative of U-NJMC on cooling has not been investigated.The grinding force,friction coefficient,specific grinding energy,and grinding temperature under dry,drip irrigation,UV,minimum quantity lubrication(MQL),NJMC,and U-NJMC micro-grinding were compared and analyzed.Results showed that the minimum normal grinding force and tangential grinding force of U-NJMC micro-grinding were 1.39 and 0.32 N,which were 75.1%and 82.9%less than those in dry grinding,respectively.The minimum friction coefficient and specific grinding energy were achieved using U-NJMC.Compared with dry,drip,UV,MQL,and NJMC grinding,the friction coefficient of U-NJMC was decreased by 31.3%,17.0%,19.0%,9.8%,and 12.5%,respectively,and the specific grinding energy was decreased by 83.0%,72.7%,77.8%,52.3%,and 64.7%,respectively.Compared with UV or NJMC alone,the grinding temperature of U-NJMC was decreased by 33.5%and 10.0%,respectively.These results showed that U-NJMC provides a novel approach for clinical surgical micro-grinding of biological bone.
基金financially supported by the National Natural Science Foundation of China (Nos. 51921003, 92160301, 52175415 and 52205475)the Science Center for Gas Turbine Project (No. P2022-A-IV-002-001)+3 种基金the Natural Science Foundation of Jiangsu Province (No. BK20210295)the Superior Postdoctoral Project of Jiangsu Province (No. 2022ZB215)the Open Foundation State Key Laboratory of Mechanical Transmissions (No. SKLMT-MSKFKT-202101)the Special Projects for the Reengineering of Industrial Foundation and the High-quality Development of Manufacturing Industry (No. TC210H02X)
文摘Particle-reinforcing titanium matrix composites(PTMCs)exhibit the sharp raising applications in modern industries owing to its extraordinary physical and mechanical properties.However,the poor grindability and unstable grinding processes due to the existence of TiC particles and TiB short fibres inside PTMCs,leading to the sudden grinding burn and low material removal rate.In this work,a novel radial ultrasonic vibration-assisted grinding(RUVAG)device with a special cross structure was developed to improve machining efficiency and avoid grinding burns.Meanwhile,the resonant modal and transient dynamic characteristics of radial ultrasonic vibration system were discussed.Comparative grinding performance experiments were then conducted under the conventional grinding(CG)and RUVAG using mono-layer cubic boron nitride abrasive wheels,in views of the grinding forces and force ratio,grinding temperature,and ground surface morphology.Results show that the ultrasonic vibration direction can be transformed effectively using the special cross structure of vibration converter,and better vibration homogeneity can be obtained.RUVAG has a smaller tangential grinding force by 5.0%–17.2%than that of CG,but a higher normal grinding force of 6.5%–14.9%,owing to the periodic impact of grinding wheels.In addition,RUVAG possesses a remarkable lower grinding temperature in range of 24.2%–51.8%and a higher material removal rate by 2.8 times compared with CG,resulting from the intermittent cutting behavior between the grinding wheel and workpiece.In this case,the sudden burn can be avoided during high-speed grinding processes.Moreover,the proportion of micro-fracture defects on machined surface is slightly increased once the ultrasonic vibration mode is employed because of the periodic impact on reinforced particles,whereas the pull-out defects of reinforced particles are reduced significantly.
基金Supported by the National High Technology Research and Development Program of China("863" Program,No.2009AA044204)
文摘A compound machine tool was designed, which combined rotary ultrasonic assisted grinding, electrical discharge machining(EDM) and multi-axis milling. Experimental results indicated that its positioning accuracy was less than 5.6 μm and its repetitive positioning accuracy was less than 1.8 μm; the vibration amplitude of ultrasonic grinding system was uniform and stable, and the EDM system worked well and stably.A smooth surface of K9 optical glass component was achieved by the grinding method.
基金supported by the National Natural Science Foundation of China (Grant Nos.51921003,92160301,52175415 and 52205475)the Science Center for Gas Turbine Project,China (Grant No.P2022-A-IV-002-001)+1 种基金the Natural Science Foundation of Jiangsu Province,China (Grant No.BK20210295)the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China (Grant No.KYCX20_0179).
文摘Ultrasonic vibration-assisted grinding(UVAG)is an advanced hybrid process for the precision machining of difficult-to-cut materials.The resonator is a critical part of the UVAG system.Its performance considerably influences the vibration amplitude and resonant frequency.In this work,a novel perforated ultrasonic vibration platform resonator was developed for UVAG.The holes were evenly arranged at the top and side surfaces of the vibration platform to improve the vibration characteristics.A modified apparent elasticity method(AEM)was proposed to reveal the influence of holes on the vibration mode.The performance of the vibration platform was evaluated by the vibration tests and UVAG experiments of particulate-reinforced titanium matrix composites.Results indicate that the reasonable distribution of holes helps improve the resonant frequency and vibration mode.The modified AEM,the finite element method,and the vibration tests show a high degree of consistency for developing the perforated ultrasonic vibration platform with a maximum frequency error of 3%.The employment of ultrasonic vibration reduces the grinding force by 36%at most,thereby decreasing the machined surface defects,such as voids,cracks,and burnout.