To develop a hybrid process of abrasive jet machining (AJM) and electrical discharge machining (EDM),the effects of the hybrid process parameters on machining performance were comprehensively investigated to confirm t...To develop a hybrid process of abrasive jet machining (AJM) and electrical discharge machining (EDM),the effects of the hybrid process parameters on machining performance were comprehensively investigated to confirm the benefits of this hybrid process.The appropriate abrasives delivered by high speed gas media were incorporated with an EDM in gas system to construct the hybrid process of AJM and EDM,and then the high speed abrasives could impinge on the machined surface to remove the recast layer caused by EDM process to increase the efficiency of material removal and reduce the surface roughness.In this study,the benefits of the hybrid process were determined as the machining performance of hybrid process was compared with that of the EDM in gas system.The main process parameters were varied to explore their effects on material removal rate,surface roughness and surface integrities.The experimental results show that the hybrid process of AJM and EDM can enhance the machining efficiency and improve the surface quality.Consequently,the developed hybrid process can fit the requirements of modern manufacturing applications.展开更多
This study investigates full liquid phase sintering as a process of fabrication parts from WE43(Mg-4wt.%Y-3wt.%RE-0.7wt.%Zr)alloy using binder jetting additive manufacturing(BJAM).This fabrication process is being dev...This study investigates full liquid phase sintering as a process of fabrication parts from WE43(Mg-4wt.%Y-3wt.%RE-0.7wt.%Zr)alloy using binder jetting additive manufacturing(BJAM).This fabrication process is being developed for use in producing structural or biomedical devices.Specifically,this study focused on achieving a near-dense microstructure with WE43 Mg alloy while substantially reducing the duration of sintering post-processing after BJAM part rendering.The optimal process resulted in microstructure with 2.5%porosity and significantly reduced sintering time.The improved sintering can be explained by the presence of Y_(2)O_(3)and Nd_(2)O_(3)oxide layers,which form spontaneously on the surface of WE43 powder used in BJAM.These layers appear to be crucial in preventing shape distortion of the resulting samples and in enabling the development of sintering necks,particularly under sintering conditions exceeding the liquidus temperature of WE43 alloy.Sintered WE43 specimens rendered by BJAM achieved significant improvement in both corrosion resistance and mechanical properties through reduced porosity levels related to the sintering time.展开更多
This paper is devoted to experimentally investigating the influence of magnetic field intensity and gas temperature on the plasma jet deflection controlled by magneto hydrodynamics. The catalytic ionization seed CS_2C...This paper is devoted to experimentally investigating the influence of magnetic field intensity and gas temperature on the plasma jet deflection controlled by magneto hydrodynamics. The catalytic ionization seed CS_2CO_3 is injected into combustion gas by artificial forced ionization to obtain plasma fluid on a high-temperature magnetic fluid experimental platform. The plasma jet was deflected under the effect of an external magnetic field, forming a thrust-vector effect.Magnesium oxide was selected as a tracer particle, and a two-dimensional image of the jet flow field was collected using the particle image velocimetry(PIV) measurement method. Through image processing and velocity vector analysis of the flow field, the value of the jet deflection angle was obtained quantitatively to evaluate the thrust-vector effect. The variation of the jet deflection angle with the magnetic field intensity and gas temperature was studied under different experimental conditions. Experimental results show that the jet deflection angle increased gradually with a rise in gas temperature and then increased substantially when the gas temperature exceeded 2300 K. The jet deflection angle also increased with an increase in magnetic induction intensity. Experiments demonstrate it is feasible to use PIV test technology to study the thrust vector under magnetic control conditions.展开更多
Full factorial design of experiments was developed in order to investigate the effects of jet pressure, abrasive mixing rate, cutting feed, and plate thickness upon three response variables, surface finish of cutting ...Full factorial design of experiments was developed in order to investigate the effects of jet pressure, abrasive mixing rate, cutting feed, and plate thickness upon three response variables, surface finish of cutting wear zone, percentage proportion of striation free area, and maximum width of cut. The set of sixteen experiments was performed on each of the following two ductile materials： AISI 4340 （high strength low alloy steel, hardened to 49HRc） and Aluminum 2219. Analysis of Variance （ANOVA） was performed on experimental data in order to determine the significance of effects of different parameters on the performance measures. It was found that cutting feed and thickness were highly influential parameters, while abrasive mixing rate is influential upon surface roughness only. Strong interaction was found between jet pressure and workpiece material. Multi-criteria numerical optimization was performed in order to simultaneously maximize/minimize different combinations of performance measures.展开更多
This paper overviews research progress in observation, theoretical analysis and numerical modeling of submesoscale dynamic processes in the South China Sea(SCS) particularly during recent five years. The submesoscale ...This paper overviews research progress in observation, theoretical analysis and numerical modeling of submesoscale dynamic processes in the South China Sea(SCS) particularly during recent five years. The submesoscale processes are defined according to both spatial and dynamic scales, and divided into four subcategories as submesoscale waves, submesoscale vortexes, submesoscale shelf processes, and submesoscale turbulence. The major new findings are as follows.(1) Systematic mooring observations provide new insights into the solitary waves(ISWs) and the typhoon-forced near-inertial waves(NIWs), of which a new type of ISWs with period of 23 h was observed in the northern SCS(NSCS), and the influences of background vorticity, summer monsoon onset, and deep meridional overturning circulation on the NIWs, as well as nonlinear wave-wave interaction between the NIWs and internal tides, are better understood. On the other hand, satellite altimeter sea surface height data are used to reveal the internal tide radiation patterns and provide solid evidence for that the ISWs in the northeastern SCS originate from the Luzon Strait.(2) Submesoscale offshore jets and associated vortex trains off the Vietnam coast in the western boundary of the SCS were observed from satellite chlorophyll concentration images. Spiral trains with the horizontal scale of 15–30 km and the spacing of 50–80 km were identified.(3) 3-D vertical circulation in the upwelling region east of Hainan Island was theoretically analyzed. The results show that distribution patterns of all the dynamic terms are featured by wave-like structures with horizontal wavelength scale of 20–40 km.(4) Numerical models have been used for the research of submesoscale turbulence. Submesoscale vertical pump of an anticyclonic eddy and the spatiotemporal features of submesoscale processes in the northeastern SCS are well modeled.展开更多
Plasma spraying is an important enabling technology i n near-net-shaped process as well as many high-performance coating applicatio ns. Recently, it is being applied to rapid mould manufacturing to reduce develop ment...Plasma spraying is an important enabling technology i n near-net-shaped process as well as many high-performance coating applicatio ns. Recently, it is being applied to rapid mould manufacturing to reduce develop ment time and manufacturing cost. In this process, inputted powders are heated a nd accelerated by plasma jet, and impinge on master pattern or prototype to form ing a thick coating. Mould will be fabricated after backed-up with consolidated material and other post-treatments. Amongst numerous factors that affect the l ife and properties of mould made by this novel method, quality of coating is the most important one. However, the complex nature of the spray process results in a large number of processing parameters that must be controlled in order to obt ain optimum coatings. Traditional "trial and error" method is too time and cost consuming for the optimal processing parameters. Maybe modeling and diagnostics of process is the best way to ravel out the problems. It has been proved that pl asma-gas flowrate, power level and spray distance are the most critical variabl es. So flow visualization and diagnostics for plasma jet quality has become an i mportant task to obtain a repeatable and reliable plasma processing technology. Using enthalpy probe diagnostics, spectrometry and optical measurement, we can o btain the distribution of temperature field of plasma jet. These results can hel p us to design gun configuration and optimize processing parameters for high dep osition efficiency and good qualities of rapid mould manufacturing. Nevertheless , it is still very difficult to realize real-time diagnoses because of restrict of diagnosis condition and drawback of measurement approach. In our researches, a real-time data collection and image processing system for plasma jet with high temperature, velocity and compressed energy has been realiz ed by CCD sensor. In this paper, we firstly focus our attention on collection pr inciple and methods, and an effective method for collecting data in high tempera ture area is presented. Then a system of real-time data collection by CCD camer a is developed. Finally, fake color image processing is given to analyze the law of temperature field distribution under different conditions. The results are i mportant to realize the visualization of plasma spraying, and especially to furt her study on closed-loop feedback control of forming quality for plasma rapid m anufacturing process.展开更多
粘结剂喷射3D打印(binder jet 3D printing,BJ3DP)是一种无熔化、高效率、低成本的金属增材制造技术,近年来在复杂结构、大尺寸、高精度构件制造中展现出了巨大的应用潜力。相比激光熔化等工艺,BJ3DP具有材料适应性强、工艺温度低、无...粘结剂喷射3D打印(binder jet 3D printing,BJ3DP)是一种无熔化、高效率、低成本的金属增材制造技术,近年来在复杂结构、大尺寸、高精度构件制造中展现出了巨大的应用潜力。相比激光熔化等工艺,BJ3DP具有材料适应性强、工艺温度低、无残余应力等优势,适用于热敏性或易氧化金属材料。总结了金属BJ3DP打印构件的影响因素,包括粉末特性、打印参数、脱脂/烧结工艺等,重点介绍了铁基、镍基、镁基、铝基、高熵合金等合金在BJ3DP成形过程中的物相、微观组织与性能。最后,简要概述了目前存在的问题及未来的发展趋势。展开更多
基金Project(NSC99-2212-E-252-006-MY3)Supported by National Science Council
文摘To develop a hybrid process of abrasive jet machining (AJM) and electrical discharge machining (EDM),the effects of the hybrid process parameters on machining performance were comprehensively investigated to confirm the benefits of this hybrid process.The appropriate abrasives delivered by high speed gas media were incorporated with an EDM in gas system to construct the hybrid process of AJM and EDM,and then the high speed abrasives could impinge on the machined surface to remove the recast layer caused by EDM process to increase the efficiency of material removal and reduce the surface roughness.In this study,the benefits of the hybrid process were determined as the machining performance of hybrid process was compared with that of the EDM in gas system.The main process parameters were varied to explore their effects on material removal rate,surface roughness and surface integrities.The experimental results show that the hybrid process of AJM and EDM can enhance the machining efficiency and improve the surface quality.Consequently,the developed hybrid process can fit the requirements of modern manufacturing applications.
文摘This study investigates full liquid phase sintering as a process of fabrication parts from WE43(Mg-4wt.%Y-3wt.%RE-0.7wt.%Zr)alloy using binder jetting additive manufacturing(BJAM).This fabrication process is being developed for use in producing structural or biomedical devices.Specifically,this study focused on achieving a near-dense microstructure with WE43 Mg alloy while substantially reducing the duration of sintering post-processing after BJAM part rendering.The optimal process resulted in microstructure with 2.5%porosity and significantly reduced sintering time.The improved sintering can be explained by the presence of Y_(2)O_(3)and Nd_(2)O_(3)oxide layers,which form spontaneously on the surface of WE43 powder used in BJAM.These layers appear to be crucial in preventing shape distortion of the resulting samples and in enabling the development of sintering necks,particularly under sintering conditions exceeding the liquidus temperature of WE43 alloy.Sintered WE43 specimens rendered by BJAM achieved significant improvement in both corrosion resistance and mechanical properties through reduced porosity levels related to the sintering time.
基金supported by National Natural Science Foundation of China (No. 90716025)
文摘This paper is devoted to experimentally investigating the influence of magnetic field intensity and gas temperature on the plasma jet deflection controlled by magneto hydrodynamics. The catalytic ionization seed CS_2CO_3 is injected into combustion gas by artificial forced ionization to obtain plasma fluid on a high-temperature magnetic fluid experimental platform. The plasma jet was deflected under the effect of an external magnetic field, forming a thrust-vector effect.Magnesium oxide was selected as a tracer particle, and a two-dimensional image of the jet flow field was collected using the particle image velocimetry(PIV) measurement method. Through image processing and velocity vector analysis of the flow field, the value of the jet deflection angle was obtained quantitatively to evaluate the thrust-vector effect. The variation of the jet deflection angle with the magnetic field intensity and gas temperature was studied under different experimental conditions. Experimental results show that the jet deflection angle increased gradually with a rise in gas temperature and then increased substantially when the gas temperature exceeded 2300 K. The jet deflection angle also increased with an increase in magnetic induction intensity. Experiments demonstrate it is feasible to use PIV test technology to study the thrust vector under magnetic control conditions.
文摘Full factorial design of experiments was developed in order to investigate the effects of jet pressure, abrasive mixing rate, cutting feed, and plate thickness upon three response variables, surface finish of cutting wear zone, percentage proportion of striation free area, and maximum width of cut. The set of sixteen experiments was performed on each of the following two ductile materials： AISI 4340 （high strength low alloy steel, hardened to 49HRc） and Aluminum 2219. Analysis of Variance （ANOVA） was performed on experimental data in order to determine the significance of effects of different parameters on the performance measures. It was found that cutting feed and thickness were highly influential parameters, while abrasive mixing rate is influential upon surface roughness only. Strong interaction was found between jet pressure and workpiece material. Multi-criteria numerical optimization was performed in order to simultaneously maximize/minimize different combinations of performance measures.
基金The National Natural Science Foundation of China under contract Nos 41776034,41376038,40406009,41806123 and 41506034the National Science and Technology Major Project under contract No.2016ZX05057015+1 种基金the Guangdong Province First-Class Discipline Plan under contract No.CYL231419012the Fund of Southern Marine Science and Engineering Guangdong Laboratory(Zhanjiang)under contract No.ZJW-2019-08
文摘This paper overviews research progress in observation, theoretical analysis and numerical modeling of submesoscale dynamic processes in the South China Sea(SCS) particularly during recent five years. The submesoscale processes are defined according to both spatial and dynamic scales, and divided into four subcategories as submesoscale waves, submesoscale vortexes, submesoscale shelf processes, and submesoscale turbulence. The major new findings are as follows.(1) Systematic mooring observations provide new insights into the solitary waves(ISWs) and the typhoon-forced near-inertial waves(NIWs), of which a new type of ISWs with period of 23 h was observed in the northern SCS(NSCS), and the influences of background vorticity, summer monsoon onset, and deep meridional overturning circulation on the NIWs, as well as nonlinear wave-wave interaction between the NIWs and internal tides, are better understood. On the other hand, satellite altimeter sea surface height data are used to reveal the internal tide radiation patterns and provide solid evidence for that the ISWs in the northeastern SCS originate from the Luzon Strait.(2) Submesoscale offshore jets and associated vortex trains off the Vietnam coast in the western boundary of the SCS were observed from satellite chlorophyll concentration images. Spiral trains with the horizontal scale of 15–30 km and the spacing of 50–80 km were identified.(3) 3-D vertical circulation in the upwelling region east of Hainan Island was theoretically analyzed. The results show that distribution patterns of all the dynamic terms are featured by wave-like structures with horizontal wavelength scale of 20–40 km.(4) Numerical models have been used for the research of submesoscale turbulence. Submesoscale vertical pump of an anticyclonic eddy and the spatiotemporal features of submesoscale processes in the northeastern SCS are well modeled.
文摘Plasma spraying is an important enabling technology i n near-net-shaped process as well as many high-performance coating applicatio ns. Recently, it is being applied to rapid mould manufacturing to reduce develop ment time and manufacturing cost. In this process, inputted powders are heated a nd accelerated by plasma jet, and impinge on master pattern or prototype to form ing a thick coating. Mould will be fabricated after backed-up with consolidated material and other post-treatments. Amongst numerous factors that affect the l ife and properties of mould made by this novel method, quality of coating is the most important one. However, the complex nature of the spray process results in a large number of processing parameters that must be controlled in order to obt ain optimum coatings. Traditional "trial and error" method is too time and cost consuming for the optimal processing parameters. Maybe modeling and diagnostics of process is the best way to ravel out the problems. It has been proved that pl asma-gas flowrate, power level and spray distance are the most critical variabl es. So flow visualization and diagnostics for plasma jet quality has become an i mportant task to obtain a repeatable and reliable plasma processing technology. Using enthalpy probe diagnostics, spectrometry and optical measurement, we can o btain the distribution of temperature field of plasma jet. These results can hel p us to design gun configuration and optimize processing parameters for high dep osition efficiency and good qualities of rapid mould manufacturing. Nevertheless , it is still very difficult to realize real-time diagnoses because of restrict of diagnosis condition and drawback of measurement approach. In our researches, a real-time data collection and image processing system for plasma jet with high temperature, velocity and compressed energy has been realiz ed by CCD sensor. In this paper, we firstly focus our attention on collection pr inciple and methods, and an effective method for collecting data in high tempera ture area is presented. Then a system of real-time data collection by CCD camer a is developed. Finally, fake color image processing is given to analyze the law of temperature field distribution under different conditions. The results are i mportant to realize the visualization of plasma spraying, and especially to furt her study on closed-loop feedback control of forming quality for plasma rapid m anufacturing process.
文摘粘结剂喷射3D打印(binder jet 3D printing,BJ3DP)是一种无熔化、高效率、低成本的金属增材制造技术,近年来在复杂结构、大尺寸、高精度构件制造中展现出了巨大的应用潜力。相比激光熔化等工艺,BJ3DP具有材料适应性强、工艺温度低、无残余应力等优势,适用于热敏性或易氧化金属材料。总结了金属BJ3DP打印构件的影响因素,包括粉末特性、打印参数、脱脂/烧结工艺等,重点介绍了铁基、镍基、镁基、铝基、高熵合金等合金在BJ3DP成形过程中的物相、微观组织与性能。最后,简要概述了目前存在的问题及未来的发展趋势。
