In order to construct quasi-continuously networked reinforcement in titanium(Ti)matrix composites,in this study,Ti-6 Al-4 V spherical powders were uniformly coated with a graphene nanosheet(GNS)layer by high energy ba...In order to construct quasi-continuously networked reinforcement in titanium(Ti)matrix composites,in this study,Ti-6 Al-4 V spherical powders were uniformly coated with a graphene nanosheet(GNS)layer by high energy ball milling and then consolidated by spark plasma sintering.Results showed that the GNS layer on the powder surface inhibited continuous metallurgy bonding between powders during sintering,which led to the formation of quasi-networked hybrid reinforcement structure consisting of insitu Ti C and remained GNSs.The networked GNSs/Ti64 composite possessed noticeably higher tensile strength but similar ductility to the Ti64 alloy,leading to both better tensile strength and ductility than the GNSs/Ti composite with randomly dispersed GNSs and Ti C.The formation mechanism and the fracture mechanism of the networked hybrid reinforcement were discussed.The results provided a method to fabricate Ti matrix composites with high strength and good ductility.展开更多
For the purpose of high-temperature service and the weight reduction in aviation engineering applications,the dissimilar joining of Ti3Al-based alloy to Ni-based superalloy(GH536)was conducted using Au-17.5Ni(wt%)braz...For the purpose of high-temperature service and the weight reduction in aviation engineering applications,the dissimilar joining of Ti3Al-based alloy to Ni-based superalloy(GH536)was conducted using Au-17.5Ni(wt%)brazing filler metal.The microstructure and chemical composition at the interfaces were investigated by scanning electron microscope,X-ray diffraction and transmission electron microscope.The diffusion behaviors of elements were analyzed as well.The results indicated that the Ti_(3)Al/GH536 joint microstructure was characterized by multiple layer structures.Element Ni from Au-Ni filler metal reacted with Ti3Al base metal,leading to the formation of AlNi2Ti and NiTi compounds.Element Ni from Ti3Al base metal reacted with Ni and thus Ni3Nb phase was detected in the joint central area.Due to the dissolution of Ni-based superalloy,(Ni,Au)solid solution((Ni,Au)ss)and Ni-rich phase were visible adjacent to the superalloy side.The average tensile strength of all the joints brazed at 1253 K for 5-20 min was above 356 MPa at room-temperature.In particular,the joints brazed at 1253 K/15 min presented the maximum tensile strength of434 MPa at room-temperature,and the strength of 314 MPa was maintained at 923 K.AlNi2Ti compound resulted in the highest hardness area and the fracture of the samples subjected to the tensile test mainly occurred in this zone.展开更多
Vacuum brazing of Ti3Al-based alloy to TiAI was firstly carried out by Ti-15Cu-15Ni （wt%） filler metal. A continuous Ti3Al band, Ti2Ni and Ti2Cu/Cu3Ti phases formed and the joint showed a shear strength of 53.8-112....Vacuum brazing of Ti3Al-based alloy to TiAI was firstly carried out by Ti-15Cu-15Ni （wt%） filler metal. A continuous Ti3Al band, Ti2Ni and Ti2Cu/Cu3Ti phases formed and the joint showed a shear strength of 53.8-112.4 MPa at room temperature. For the improvement of the joint strength, a new Ti--Zr--Cu--Ni--Fe filler alloy was designed, and its wettability on Ti3AI and TiA1 substrate was studied with the sessile drop method. After holding for 20 rain at 1010 ℃ the Ti--Zr--Cu--Ni--Fe filler showed a low contact angle of 20° and 21° on Ti3Al and TiAI substrate, respectively. The joint brazed with this novel filler mainly con- sisted of Ti-rich area, Ti3Al reaction layer and residual filler metal. With the increase of the brazing temperature, the amount of residual filler metal decreased and the TisAl reaction layer thickened. The Ti3Al/TiA1 joint brazed with Ti--Zr--Cu--Ni--Fe filler exhibited a lower hardness than that brazed with Ti--Cu--Ni filler. The corresponding joints brazed at 950 ℃ for 5 min presented the shear strength of 257.6± 33.6 MPa at room temperature and 304.8 ± 9.9 MPa at 600 ℃.展开更多
The effect of optical cleaning method combined with laser speckle imaging(LSI)was discussed to improve the detection depth of LSI due to high scattering characteristics of skin,which limit its clinical application.A d...The effect of optical cleaning method combined with laser speckle imaging(LSI)was discussed to improve the detection depth of LSI due to high scattering characteristics of skin,which limit its clinical application.A double-layer skin tissue model embedded with a single blood vessel was established,and the Monte Carlo method was used to simulate photon propagation under the action of light-permeating agent.808 nm semiconductor and 632.8 nm He–Ne lasers were selected to study the e®ect of optical clearing agents(OCAs)on photon deposition in tissues.Results show that the photon energy deposition density in the epidermis increases with the amount of tissue°uid replaced by OCA.Compared with glucose solution,polyethylene glycol 400(PEG 400)and glycerol can considerably increase the average penetration depth of photons in the skin tissue,thereby raising the sampling depth of the LSI.After the action of glycerol,PEG 400,and glucose,the average photon penetration depth is increased by 51.78%,51.06%,and 21.51%for 808nm,68.93%,67.94%,and 26.67%for 632.8 nm lasers,respectively.In vivo experiment by dorsal skin chamber proves that glycerol can cause a substantial decrease in blood°ow rate,whereas PEG 400 can signicantly improve the capability of light penetration without a®ecting blood velocity,which exhibits considerable potential in the monitoring of blood°ow in skin tissues.展开更多
The primary objective of present investigation is to introduce the novel aspects of convective mass condition and thermal radiation in the peristaltic transport of fluid. Magnetohydrodynamic(MHD) fluid was considered ...The primary objective of present investigation is to introduce the novel aspects of convective mass condition and thermal radiation in the peristaltic transport of fluid. Magnetohydrodynamic(MHD) fluid was considered in a symmetric channel. Heat and mass transfer characteristics were analyzed in the presence of Soret and Dufour effects, and the results were presented via two forms of thermal radiation. The temperature, concentration and pressure rise per wavelength were examined. It is observed that the velocity slip and magnetic field parameters have opposite effects on the pressure rise per wavelength. Temperature of fluid is a decreasing function of the radiation parameter. Further, the temperature of fluid decreases by increasing the heat transfer Biot number. It is notified that the heat transfer rate at the wall is a decreasing function of radiation parameter.展开更多
The relationship between the vapor pressure of liquid copper and the flow rate of carrier gas argon was discussed, when the carrier gas method was used to determine the vapor pressure of liquid copper at 1892 K. The p...The relationship between the vapor pressure of liquid copper and the flow rate of carrier gas argon was discussed, when the carrier gas method was used to determine the vapor pressure of liquid copper at 1892 K. The proper argon flow rate range obtained was 150-500 mL/min and enough evidence was provided to verify the vapor pressure-flow rate of carrier gas relationship at the target temperature. Based on the proper flow rate range, the vapor pressure of liquid copper was measured at 1609-1892 K. The relationship of vapor pressure-temperature obtained by the method of regression analysis can be expressed as： In（p/Pa） = （25.470 -I- 0.903） - （39099.8 -4- 1574.5）/T, Further, the thermodynamic properties including the heat of vaporization and the Gibbs free energy of the Cu （I） = Cu （g） reaction were calculated by the vapor pressiJre obtained over the temperature range covered.展开更多
A research on kinetics of Al evaporation from liquid U—Al alloys was made in a vacuum induction melting（VIM） furnace at 1673—1843 K.The evaporation rate of Al was found to be first order with respect to Al content...A research on kinetics of Al evaporation from liquid U—Al alloys was made in a vacuum induction melting（VIM） furnace at 1673—1843 K.The evaporation rate of Al was found to be first order with respect to Al content in the melt.The overall mass transfer coefficient of Al was determined and it was found that the evaporation rate of Al increased with increasing temperatures.The apparent activation energy of Al evaporation at 1673-1843 K was 171.5 kJ mol-1.The value of mass transfer coefficient of Al in the liquid phase was estimated to be 3.77 × 10-6,7.41×10-6,and 9.40 × 10-6m s-1at 1673,1753,and 1843 K,respectively.Meanwhile,rate determining steps were discussed and it was concluded that the evaporation rate of Al is mainly controlled by liquid phase mass transfer.展开更多
Objective BEPCII is a high-performance collider with a design energy of 2.1 GeV. In order to obtain more physical experimentsand synchrotron radiation applications, BEPCII decided to carry out energy upgrading to 2.5 ...Objective BEPCII is a high-performance collider with a design energy of 2.1 GeV. In order to obtain more physical experimentsand synchrotron radiation applications, BEPCII decided to carry out energy upgrading to 2.5 GeV. Insufficient energyof special magnet power supplies in collision zone is a key factor restricting BEPCII’s operation under 2.5 GeV energy.Therefore, three high-power and high-stability power supplies are designed for BEPCII energy upgrading.Methods The designed power supplies output part adopts high-frequency chopper modules parallel connected and adoptsdigital-analog hybrid control methods. The voltage loop regulator uses high-speed analog control, and current loop regulatoruses digital control which is based on FPGA.Conclusion The experimental data show that the output current stability of the developed power supplies is lower than50 ppm. The output current resolution is lower than 70 ppm. The developed power supplies can well meet the design requirementsof BEPCII energy upgrading.展开更多
Purpose In order to make BEPC-II to run at a higher energy,the Institute of High Energy Physics undertook an upgrading project.One of the important factors limiting the energy boost is the power and performance of the...Purpose In order to make BEPC-II to run at a higher energy,the Institute of High Energy Physics undertook an upgrading project.One of the important factors limiting the energy boost is the power and performance of the dipole magnet power supplies;therefore,these four magnet power supplies are developed for the BEPC-II upgrading.Methods The power supplies adopt topologies of thyristor rectifiers to realize a high-power output.In the control unit of each power supply,a digital current closed loop is adopted,and the key components in the feedback loop are thermostatically controlled.In order to improve the performances of the power supplies,analog voltage regulators are added to the inner control loops.Results These four power supplies have been tested and have already been officially used in BEPC-II,and their powers have reached the requirements of the upgrading.The test results of the current stability are described and shown in this paper,which testifies that the stabilities meet the design parameters.Conclusions A digital control is applied to each SCR rectifier control.The performances of the power supplies are improved by the combination of digital current control loops and the analog voltage control loops,which makes the performances of the dipole magnet power supplies meet the requirements of the upgrading project.展开更多
Purpose This power supply prototype is developed for the quadrupole magnets in the storage ring of HEPS.The project requires a high current stability of these power supplies,in order to master the key technology of th...Purpose This power supply prototype is developed for the quadrupole magnets in the storage ring of HEPS.The project requires a high current stability of these power supplies,in order to master the key technology of this type of power supply in advance,a prototype is made in the project of HEPS test facility.Methods Modularization is used in the prototype’s topology and a combination of digital and analog control is adopted in the closed-loop control.Three control loops are used to improve the output current’s quality.In order to improve the current stability,the key devices in the circuit are under thermostatical controlled.Results The acceptance test results for the NDRC are given in details,which show that all the parameters are better than the design indexes.Conclusions After a lot of experiments and tests,all the parameters of this prototype passed the acceptance test.Among the results,the stability of this prototype achieved 5.2 ppm,the repeatability is 3.2 ppm,and the low-frequency voltage ripples are lower than the requirements of Physicists.The success of this prototype means that the requirements of power supplies in physical design can be met.展开更多
基金financially supported by the Key Research and Development Plan of Shaanxi Province(No.2020KW-034)the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University(CX2021058)。
文摘In order to construct quasi-continuously networked reinforcement in titanium(Ti)matrix composites,in this study,Ti-6 Al-4 V spherical powders were uniformly coated with a graphene nanosheet(GNS)layer by high energy ball milling and then consolidated by spark plasma sintering.Results showed that the GNS layer on the powder surface inhibited continuous metallurgy bonding between powders during sintering,which led to the formation of quasi-networked hybrid reinforcement structure consisting of insitu Ti C and remained GNSs.The networked GNSs/Ti64 composite possessed noticeably higher tensile strength but similar ductility to the Ti64 alloy,leading to both better tensile strength and ductility than the GNSs/Ti composite with randomly dispersed GNSs and Ti C.The formation mechanism and the fracture mechanism of the networked hybrid reinforcement were discussed.The results provided a method to fabricate Ti matrix composites with high strength and good ductility.
基金sponsored by the National Natural Science Foundation of China(No.51705489)the State Key Laboratory of Advanced Brazing Filler Metals and Technology,Zhengzhou Research Institute of Mechanical Engineering(No.SKLABFMT201603)
文摘For the purpose of high-temperature service and the weight reduction in aviation engineering applications,the dissimilar joining of Ti3Al-based alloy to Ni-based superalloy(GH536)was conducted using Au-17.5Ni(wt%)brazing filler metal.The microstructure and chemical composition at the interfaces were investigated by scanning electron microscope,X-ray diffraction and transmission electron microscope.The diffusion behaviors of elements were analyzed as well.The results indicated that the Ti_(3)Al/GH536 joint microstructure was characterized by multiple layer structures.Element Ni from Au-Ni filler metal reacted with Ti3Al base metal,leading to the formation of AlNi2Ti and NiTi compounds.Element Ni from Ti3Al base metal reacted with Ni and thus Ni3Nb phase was detected in the joint central area.Due to the dissolution of Ni-based superalloy,(Ni,Au)solid solution((Ni,Au)ss)and Ni-rich phase were visible adjacent to the superalloy side.The average tensile strength of all the joints brazed at 1253 K for 5-20 min was above 356 MPa at room-temperature.In particular,the joints brazed at 1253 K/15 min presented the maximum tensile strength of434 MPa at room-temperature,and the strength of 314 MPa was maintained at 923 K.AlNi2Ti compound resulted in the highest hardness area and the fracture of the samples subjected to the tensile test mainly occurred in this zone.
基金sponsored by the National Natural Science Foundation of China under Grant No. 51405456the Aeronautical Science Foundation of China under Grant Nos. 03H21009 and 99H21013
文摘Vacuum brazing of Ti3Al-based alloy to TiAI was firstly carried out by Ti-15Cu-15Ni （wt%） filler metal. A continuous Ti3Al band, Ti2Ni and Ti2Cu/Cu3Ti phases formed and the joint showed a shear strength of 53.8-112.4 MPa at room temperature. For the improvement of the joint strength, a new Ti--Zr--Cu--Ni--Fe filler alloy was designed, and its wettability on Ti3AI and TiA1 substrate was studied with the sessile drop method. After holding for 20 rain at 1010 ℃ the Ti--Zr--Cu--Ni--Fe filler showed a low contact angle of 20° and 21° on Ti3Al and TiAI substrate, respectively. The joint brazed with this novel filler mainly con- sisted of Ti-rich area, Ti3Al reaction layer and residual filler metal. With the increase of the brazing temperature, the amount of residual filler metal decreased and the TisAl reaction layer thickened. The Ti3Al/TiA1 joint brazed with Ti--Zr--Cu--Ni--Fe filler exhibited a lower hardness than that brazed with Ti--Cu--Ni filler. The corresponding joints brazed at 950 ℃ for 5 min presented the shear strength of 257.6± 33.6 MPa at room temperature and 304.8 ± 9.9 MPa at 600 ℃.
基金supported by the National Natural Science Foundation of China(Grant No.51727811).
文摘The effect of optical cleaning method combined with laser speckle imaging(LSI)was discussed to improve the detection depth of LSI due to high scattering characteristics of skin,which limit its clinical application.A double-layer skin tissue model embedded with a single blood vessel was established,and the Monte Carlo method was used to simulate photon propagation under the action of light-permeating agent.808 nm semiconductor and 632.8 nm He–Ne lasers were selected to study the e®ect of optical clearing agents(OCAs)on photon deposition in tissues.Results show that the photon energy deposition density in the epidermis increases with the amount of tissue°uid replaced by OCA.Compared with glucose solution,polyethylene glycol 400(PEG 400)and glycerol can considerably increase the average penetration depth of photons in the skin tissue,thereby raising the sampling depth of the LSI.After the action of glycerol,PEG 400,and glucose,the average photon penetration depth is increased by 51.78%,51.06%,and 21.51%for 808nm,68.93%,67.94%,and 26.67%for 632.8 nm lasers,respectively.In vivo experiment by dorsal skin chamber proves that glycerol can cause a substantial decrease in blood°ow rate,whereas PEG 400 can signicantly improve the capability of light penetration without a®ecting blood velocity,which exhibits considerable potential in the monitoring of blood°ow in skin tissues.
文摘The primary objective of present investigation is to introduce the novel aspects of convective mass condition and thermal radiation in the peristaltic transport of fluid. Magnetohydrodynamic(MHD) fluid was considered in a symmetric channel. Heat and mass transfer characteristics were analyzed in the presence of Soret and Dufour effects, and the results were presented via two forms of thermal radiation. The temperature, concentration and pressure rise per wavelength were examined. It is observed that the velocity slip and magnetic field parameters have opposite effects on the pressure rise per wavelength. Temperature of fluid is a decreasing function of the radiation parameter. Further, the temperature of fluid decreases by increasing the heat transfer Biot number. It is notified that the heat transfer rate at the wall is a decreasing function of radiation parameter.
基金supported by the Major National S&T Program(No.2011ZX06004-016-002)the Shenyang R&D Center for Advanced Materials,Institute of Metal Research,Chinese Academy of Sciences for support of this work
文摘The relationship between the vapor pressure of liquid copper and the flow rate of carrier gas argon was discussed, when the carrier gas method was used to determine the vapor pressure of liquid copper at 1892 K. The proper argon flow rate range obtained was 150-500 mL/min and enough evidence was provided to verify the vapor pressure-flow rate of carrier gas relationship at the target temperature. Based on the proper flow rate range, the vapor pressure of liquid copper was measured at 1609-1892 K. The relationship of vapor pressure-temperature obtained by the method of regression analysis can be expressed as： In（p/Pa） = （25.470 -I- 0.903） - （39099.8 -4- 1574.5）/T, Further, the thermodynamic properties including the heat of vaporization and the Gibbs free energy of the Cu （I） = Cu （g） reaction were calculated by the vapor pressiJre obtained over the temperature range covered.
文摘A research on kinetics of Al evaporation from liquid U—Al alloys was made in a vacuum induction melting（VIM） furnace at 1673—1843 K.The evaporation rate of Al was found to be first order with respect to Al content in the melt.The overall mass transfer coefficient of Al was determined and it was found that the evaporation rate of Al increased with increasing temperatures.The apparent activation energy of Al evaporation at 1673-1843 K was 171.5 kJ mol-1.The value of mass transfer coefficient of Al in the liquid phase was estimated to be 3.77 × 10-6,7.41×10-6,and 9.40 × 10-6m s-1at 1673,1753,and 1843 K,respectively.Meanwhile,rate determining steps were discussed and it was concluded that the evaporation rate of Al is mainly controlled by liquid phase mass transfer.
文摘Objective BEPCII is a high-performance collider with a design energy of 2.1 GeV. In order to obtain more physical experimentsand synchrotron radiation applications, BEPCII decided to carry out energy upgrading to 2.5 GeV. Insufficient energyof special magnet power supplies in collision zone is a key factor restricting BEPCII’s operation under 2.5 GeV energy.Therefore, three high-power and high-stability power supplies are designed for BEPCII energy upgrading.Methods The designed power supplies output part adopts high-frequency chopper modules parallel connected and adoptsdigital-analog hybrid control methods. The voltage loop regulator uses high-speed analog control, and current loop regulatoruses digital control which is based on FPGA.Conclusion The experimental data show that the output current stability of the developed power supplies is lower than50 ppm. The output current resolution is lower than 70 ppm. The developed power supplies can well meet the design requirementsof BEPCII energy upgrading.
文摘Purpose In order to make BEPC-II to run at a higher energy,the Institute of High Energy Physics undertook an upgrading project.One of the important factors limiting the energy boost is the power and performance of the dipole magnet power supplies;therefore,these four magnet power supplies are developed for the BEPC-II upgrading.Methods The power supplies adopt topologies of thyristor rectifiers to realize a high-power output.In the control unit of each power supply,a digital current closed loop is adopted,and the key components in the feedback loop are thermostatically controlled.In order to improve the performances of the power supplies,analog voltage regulators are added to the inner control loops.Results These four power supplies have been tested and have already been officially used in BEPC-II,and their powers have reached the requirements of the upgrading.The test results of the current stability are described and shown in this paper,which testifies that the stabilities meet the design parameters.Conclusions A digital control is applied to each SCR rectifier control.The performances of the power supplies are improved by the combination of digital current control loops and the analog voltage control loops,which makes the performances of the dipole magnet power supplies meet the requirements of the upgrading project.
文摘Purpose This power supply prototype is developed for the quadrupole magnets in the storage ring of HEPS.The project requires a high current stability of these power supplies,in order to master the key technology of this type of power supply in advance,a prototype is made in the project of HEPS test facility.Methods Modularization is used in the prototype’s topology and a combination of digital and analog control is adopted in the closed-loop control.Three control loops are used to improve the output current’s quality.In order to improve the current stability,the key devices in the circuit are under thermostatical controlled.Results The acceptance test results for the NDRC are given in details,which show that all the parameters are better than the design indexes.Conclusions After a lot of experiments and tests,all the parameters of this prototype passed the acceptance test.Among the results,the stability of this prototype achieved 5.2 ppm,the repeatability is 3.2 ppm,and the low-frequency voltage ripples are lower than the requirements of Physicists.The success of this prototype means that the requirements of power supplies in physical design can be met.
