Wear resistance of several zirconia toughened ceramics in comparison with a metal-ceramic Co-WC has been studied in drawing wire field test. Result indicates that the harder the ceramic die, the longer the service lif...Wear resistance of several zirconia toughened ceramics in comparison with a metal-ceramic Co-WC has been studied in drawing wire field test. Result indicates that the harder the ceramic die, the longer the service life. Excellent wear resistance of ceramic die is obtained with a very high hardness (19 GPa). The service life is nearly three times that of Co-WC die. SEM observation on wear surfaces showed that material removal is mainly caused by plastic flow and ploughing process. But when the ceramic is composed of zirconia, alumina and some titanium carbide, micro-chipping and tribochemical reaction take place, and wear rate increases. Wear and friction induced martensite was detected by XRD. The T-M (tetragonal to monoclinic) phase transformation has a contribution to inhibiting microfracture.展开更多
The value of a drawing die＇s cone angle has great influence on wire drawing. In order to determine the optimum value of a drawing die＇ s cone angle, the plastic deformation power Wi, shear deformation power Wi and f...The value of a drawing die＇s cone angle has great influence on wire drawing. In order to determine the optimum value of a drawing die＇ s cone angle, the plastic deformation power Wi, shear deformation power Wi and friction power of contact surface Wf were calculated using the upper bound theory with a reasonable and movement permitted velocity field according to the related characteristics. Then the relation between half cone angle and unit drawing force was obtained and it was compared with the result with the spherical velocity field. The relative error of the two near the optimal value is only about 0. 26% through comparing with existing calculated results. Finally, in an ABAQUS environment the finite element modal of the wire rod with 12. 5 mm diameter in first drawing pass was established and the axial drawing force in different cone angles was obtained using the ABAQUS/Explicit explicit integration method. The finite element method （FEM） results verify the results using the upper bound theory and this indicated that the velocity field and the relation between half cone angle and unit drawing force reasonable.展开更多
n this paper with Von Karmanis basic assumptions a kinematically admissible continuous velocity field has been established to drawing through parabolic dies (or called trumpet dies). Then by. using the curvilinear an...n this paper with Von Karmanis basic assumptions a kinematically admissible continuous velocity field has been established to drawing through parabolic dies (or called trumpet dies). Then by. using the curvilinear and the integral as a function of the upper limit an upper bound analytical solution of the drawing stress is obtained.展开更多
Iron-based superconductor,a promising candidate for high-field applications,has attracted significant attentions.For practical utilization,the superconducting tapes should have high transport critical current density(...Iron-based superconductor,a promising candidate for high-field applications,has attracted significant attentions.For practical utilization,the superconducting tapes should have high transport critical current density(J_(c)),low production cost,larger mechanical strength and good homogeneity.In this study,seven-filament Cu/Agsheathed(Ba,K)Fe_(2)As_(2)tapes were fabricated from round and square wires.It is found that the tapes rolled from square wires have a desirable uniformity of filament deformation and distribution,compared with the ones rolled from round wires.Moreover,the J_c of tape was obviously improved by using square drawing dies instead of traditional round ones.For the tapes rolled from square wires annealed under ambient and 2 MPa by hot pressing,the transport J_c values reached 1.51×10^(4) A·cm^(-2)and 4.86×10^(4) A.cm^(-2)(4.2K,10T),respectively.The deformation process on the cross section of the tapes during rolling was analyzed by using the powder-flow model.These results indicate a potential application of Cu/Ag(Ba,K)Fe_(2)As_(2)tapes in high-magnetic-field region.展开更多
文摘Wear resistance of several zirconia toughened ceramics in comparison with a metal-ceramic Co-WC has been studied in drawing wire field test. Result indicates that the harder the ceramic die, the longer the service life. Excellent wear resistance of ceramic die is obtained with a very high hardness (19 GPa). The service life is nearly three times that of Co-WC die. SEM observation on wear surfaces showed that material removal is mainly caused by plastic flow and ploughing process. But when the ceramic is composed of zirconia, alumina and some titanium carbide, micro-chipping and tribochemical reaction take place, and wear rate increases. Wear and friction induced martensite was detected by XRD. The T-M (tetragonal to monoclinic) phase transformation has a contribution to inhibiting microfracture.
基金supported by Foundation of Guizhou Science and Technology Department under Grant No.[2008]2210 and No.[2009]3009Foundation of Guizhou University under Grant No. [2007]25
文摘The value of a drawing die＇s cone angle has great influence on wire drawing. In order to determine the optimum value of a drawing die＇ s cone angle, the plastic deformation power Wi, shear deformation power Wi and friction power of contact surface Wf were calculated using the upper bound theory with a reasonable and movement permitted velocity field according to the related characteristics. Then the relation between half cone angle and unit drawing force was obtained and it was compared with the result with the spherical velocity field. The relative error of the two near the optimal value is only about 0. 26% through comparing with existing calculated results. Finally, in an ABAQUS environment the finite element modal of the wire rod with 12. 5 mm diameter in first drawing pass was established and the axial drawing force in different cone angles was obtained using the ABAQUS/Explicit explicit integration method. The finite element method （FEM） results verify the results using the upper bound theory and this indicated that the velocity field and the relation between half cone angle and unit drawing force reasonable.
文摘n this paper with Von Karmanis basic assumptions a kinematically admissible continuous velocity field has been established to drawing through parabolic dies (or called trumpet dies). Then by. using the curvilinear and the integral as a function of the upper limit an upper bound analytical solution of the drawing stress is obtained.
基金financially supported by the National Natural Science Foundation of China(Nos.U1832213,51721005 and 51861135311)the National Key R&D Program of China(Nos.2018YFA0704200 and 2017YFE0129500)+1 种基金the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(No.QYZDJ-SSW-JSC026)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB25000000)。
文摘Iron-based superconductor,a promising candidate for high-field applications,has attracted significant attentions.For practical utilization,the superconducting tapes should have high transport critical current density(J_(c)),low production cost,larger mechanical strength and good homogeneity.In this study,seven-filament Cu/Agsheathed(Ba,K)Fe_(2)As_(2)tapes were fabricated from round and square wires.It is found that the tapes rolled from square wires have a desirable uniformity of filament deformation and distribution,compared with the ones rolled from round wires.Moreover,the J_c of tape was obviously improved by using square drawing dies instead of traditional round ones.For the tapes rolled from square wires annealed under ambient and 2 MPa by hot pressing,the transport J_c values reached 1.51×10^(4) A·cm^(-2)and 4.86×10^(4) A.cm^(-2)(4.2K,10T),respectively.The deformation process on the cross section of the tapes during rolling was analyzed by using the powder-flow model.These results indicate a potential application of Cu/Ag(Ba,K)Fe_(2)As_(2)tapes in high-magnetic-field region.
