An equivalent continuum method and a deformable discrete method to describe the mechanical behaviors of superconducting powder BSCCO （BiSrCaCuO） aggregate are studied syste-matically. The equivalent continuum model ...An equivalent continuum method and a deformable discrete method to describe the mechanical behaviors of superconducting powder BSCCO （BiSrCaCuO） aggregate are studied syste-matically. The equivalent continuum model idealizes the aggregation of the powder as an equivalent continuum material. The powder aggregate yielding is caused by not only the deviatoric stress but also the hydrostatic stress and the modified Drucker-Prager/Cap model is adopted to describe the mechanical behaviors of BSCCO powder aggregate in continuum method. The deformable discrete model is known as a direct model, which considers the discrete nature of the powder particles. Its framework encompasses the local behaviors between the particles, such as particles contact, sliding and rolling. Based on commercial finite element software ABAQUS, the equivalent continuum model and the deformable discrete model are used to simulate the confined compression of superconducting powder BSCCO, and the numerical results show agreement with experimental results, which verify the correctness of these built models. Compared with the equivalent continuum model based on macroscopic statistics method, the deformable discrete model can present the microscopic information during processing and can describe the nature of mechanical behaviors of superconducting powder BSCCO. But from an industrial viewpoint, the equivalent continuum model has a definitive edge over the microscopic models in that the gross behavior of the powder mass can be modeled and simulated on an industrial scale.展开更多
Nanocrystal materials have their special properties because of very small grain size.Nanocrystal superconductors were prepared by crystallizing the amorphous slices with nominal composition of Bi_(1.6)Pb_(0.4)Sr_2Ca_4...Nanocrystal materials have their special properties because of very small grain size.Nanocrystal superconductors were prepared by crystallizing the amorphous slices with nominal composition of Bi_(1.6)Pb_(0.4)Sr_2Ca_4Cu_5O_x at certain temperature.The measurements of R-Tcurve and x data prove all the crystallized samples have superconducting transition though their Meissner effect is weak.All the nanocrystal superconductors are mainly constituent of Bi_2Sr_2CaCu_2O_y phase by the analysis of X-ray diffraction.展开更多
Laser heated pedestal growth technique (LHPG) has been used to fabricate BSCCO (BiSrCaCuO) superconductive wires.The critical current density of the wires has surpassed 5000A/cm^2 (78K, OT;cross area=1.04 mm^2).The fi...Laser heated pedestal growth technique (LHPG) has been used to fabricate BSCCO (BiSrCaCuO) superconductive wires.The critical current density of the wires has surpassed 5000A/cm^2 (78K, OT;cross area=1.04 mm^2).The fiber rods obtained directly from LHPG method are semiconductive and after heat treatment at temperature range from 780 to 870℃,they transformed into superconductive wires.Triple junctions and sharp grain boundary exist in the sample.HREM studies showed the intergrowth of (010) and (110),the occasional missing of CaCuO_2 layer in the 2212 phase.展开更多
基金This project is supported by National Natural Science Foundation of China (No. 50305015, No. 50575124).
文摘An equivalent continuum method and a deformable discrete method to describe the mechanical behaviors of superconducting powder BSCCO （BiSrCaCuO） aggregate are studied syste-matically. The equivalent continuum model idealizes the aggregation of the powder as an equivalent continuum material. The powder aggregate yielding is caused by not only the deviatoric stress but also the hydrostatic stress and the modified Drucker-Prager/Cap model is adopted to describe the mechanical behaviors of BSCCO powder aggregate in continuum method. The deformable discrete model is known as a direct model, which considers the discrete nature of the powder particles. Its framework encompasses the local behaviors between the particles, such as particles contact, sliding and rolling. Based on commercial finite element software ABAQUS, the equivalent continuum model and the deformable discrete model are used to simulate the confined compression of superconducting powder BSCCO, and the numerical results show agreement with experimental results, which verify the correctness of these built models. Compared with the equivalent continuum model based on macroscopic statistics method, the deformable discrete model can present the microscopic information during processing and can describe the nature of mechanical behaviors of superconducting powder BSCCO. But from an industrial viewpoint, the equivalent continuum model has a definitive edge over the microscopic models in that the gross behavior of the powder mass can be modeled and simulated on an industrial scale.
文摘Nanocrystal materials have their special properties because of very small grain size.Nanocrystal superconductors were prepared by crystallizing the amorphous slices with nominal composition of Bi_(1.6)Pb_(0.4)Sr_2Ca_4Cu_5O_x at certain temperature.The measurements of R-Tcurve and x data prove all the crystallized samples have superconducting transition though their Meissner effect is weak.All the nanocrystal superconductors are mainly constituent of Bi_2Sr_2CaCu_2O_y phase by the analysis of X-ray diffraction.
文摘Laser heated pedestal growth technique (LHPG) has been used to fabricate BSCCO (BiSrCaCuO) superconductive wires.The critical current density of the wires has surpassed 5000A/cm^2 (78K, OT;cross area=1.04 mm^2).The fiber rods obtained directly from LHPG method are semiconductive and after heat treatment at temperature range from 780 to 870℃,they transformed into superconductive wires.Triple junctions and sharp grain boundary exist in the sample.HREM studies showed the intergrowth of (010) and (110),the occasional missing of CaCuO_2 layer in the 2212 phase.
