We investigated the effect of structural factor and amide grafted multi-walled carbon nanotubes（MWNTs-NH2） on crushing characteristics of filament wound CFRP tube under quasi-static compression conditon. It was foun...We investigated the effect of structural factor and amide grafted multi-walled carbon nanotubes（MWNTs-NH2） on crushing characteristics of filament wound CFRP tube under quasi-static compression conditon. It was found that CFRP tubes sequentially showed the brittle fracturing mode, the local buckling fracturing mode and transverse shearing fracturing mode with increasing winding angle, respectively, with the characterizations by mechanical testing, SEM and optical microscopy. Moreover, crack propagation initiated by pre-crack and subsequent failure in the tube were strongly dependent on pre-crack angle due to defl ection and penetration competition of crack evolution. The simulated compression failure behavior correlated well with the experimental results, revealing that the Chang-Chang failure criterion was effective in representing the quasistatic crushing characteristics of the tube. In addtion, the MWNTs-NH2 were sucessfully obtained by multistep functionization. The compressvie properties of the tubes were signifi cantly improved by the addition of the MWNTs-NH2 due to their uniform dispersion and high interfacial chemical reactivity, whereas the as-received MWNTs and other functionalized MWNTs were not as effective.展开更多
The melting characteristics and wettability of the binding phase in high basicity sinter were studied. By changing nCaO∶nFe2O3 （molar ratio of CaO to Fe2O3） as well as the percentage of MgO,SiO2,and Al2O3,the melti...The melting characteristics and wettability of the binding phase in high basicity sinter were studied. By changing nCaO∶nFe2O3 （molar ratio of CaO to Fe2O3） as well as the percentage of MgO,SiO2,and Al2O3,the melting characteristics and wettability of the binding phase were discussed. The results indicated that the characteristic melting temperature was the lowest and wettability was the best at nCaO∶nFe2O3=1∶1 （without addition）; the addition of MgO increased the characteristic melting temperature and contact angles; when the percentage of SiO2 or Al2O3 was 3%,the characteristic melting temperature was the lowest,whereas the contact angles increased with an increase in SiO2 and Al2O3 contents.展开更多
The high angle of attack characteristics play an important role in the aerodynamic performances of the hypersonic space vehicle. The three-dimensional Reynolds Averaged Navier-Stokes (RANS) equations and the two-equat...The high angle of attack characteristics play an important role in the aerodynamic performances of the hypersonic space vehicle. The three-dimensional Reynolds Averaged Navier-Stokes (RANS) equations and the two-equation RNG k-? turbulence model have been employed to investigate the influence of the high angle of attack on the lift-to-drag ratio and the flow field characteristics of the hypersonic space vehicle, and the contributions of each component to the aerodynamic forces of the vehicle have been discussed as well. At the same time, in order to validate the numerical method, the predicted results have been compared with the available experimental data of a hypersonic slender vehicle, and the grid independency has been analyzed. The obtained results show that the predicted lift-to-drag ratio and pitching moment coefficient show very good agreement with the experimental data in the open literature, and the grid system makes only a slight difference to the numerical results. There exists an optimal angle of attack for the aerodynamic performance of the hypersonic space vehicle, and its value is 20°. When the angle of attack is 20°, the high pressure does not leak from around the leading edge to the upper surface. With the further increasing of the angle of attack, the high pressure spreads from the wing tips to the central area of the vehicle, and overflows from the leading edge again. Further, the head plays an important role in the drag performance of the vehicle, and the lift percentage of the flaperon is larger than that of the rudderevator. This illustrates that the optimization of the flaperon configuration is a great work for the improvement of the aerodynamic performance of the hypersonic space vehicle, especially for a high lift-to-drag ratio.展开更多
Delaunay triangulation is gradually playing an important role in the field of finite element analysis, image recognition, and medical visualization.Considering the quality and partition efficiency, a new Delaunay tria...Delaunay triangulation is gradually playing an important role in the field of finite element analysis, image recognition, and medical visualization.Considering the quality and partition efficiency, a new Delaunay triangulation method based on constrained maximum circumscribed circle is proposed. First, according to two important criteria, the empty circle features and the maximized minimum angle characteristics, we established constrained conditions. Then, we iterated the container vertices, structure triangular face linked lists, and finally got the Delaunay data. The experimental results showed that the efficiency of the improved triangulation dissection method increased by 9.47% compared with traditional triangulation algorithms in irregular triangle vertex data.展开更多
基金Funded by the National Natural Science Foundation of China(No.U1362205)the Natural Science Foundation of Jiangsu Province(No.SBK2014040489)+2 种基金the National High Technology Research and Development Program of China(No.2012AA03A203)the Beijing Youth Talent Plan(No.YETP0492)the 2014 Open Project of State Key Laboratory of OrganicInorganic Composites
文摘We investigated the effect of structural factor and amide grafted multi-walled carbon nanotubes（MWNTs-NH2） on crushing characteristics of filament wound CFRP tube under quasi-static compression conditon. It was found that CFRP tubes sequentially showed the brittle fracturing mode, the local buckling fracturing mode and transverse shearing fracturing mode with increasing winding angle, respectively, with the characterizations by mechanical testing, SEM and optical microscopy. Moreover, crack propagation initiated by pre-crack and subsequent failure in the tube were strongly dependent on pre-crack angle due to defl ection and penetration competition of crack evolution. The simulated compression failure behavior correlated well with the experimental results, revealing that the Chang-Chang failure criterion was effective in representing the quasistatic crushing characteristics of the tube. In addtion, the MWNTs-NH2 were sucessfully obtained by multistep functionization. The compressvie properties of the tubes were signifi cantly improved by the addition of the MWNTs-NH2 due to their uniform dispersion and high interfacial chemical reactivity, whereas the as-received MWNTs and other functionalized MWNTs were not as effective.
基金Sponsored by National Natural Science Foundation of China (50474014)
文摘The melting characteristics and wettability of the binding phase in high basicity sinter were studied. By changing nCaO∶nFe2O3 （molar ratio of CaO to Fe2O3） as well as the percentage of MgO,SiO2,and Al2O3,the melting characteristics and wettability of the binding phase were discussed. The results indicated that the characteristic melting temperature was the lowest and wettability was the best at nCaO∶nFe2O3=1∶1 （without addition）; the addition of MgO increased the characteristic melting temperature and contact angles; when the percentage of SiO2 or Al2O3 was 3%,the characteristic melting temperature was the lowest,whereas the contact angles increased with an increase in SiO2 and Al2O3 contents.
基金supported by the Science Foundation of the National University of Defense Technology (Grant No. JC11-01-02)National Natural Science Foundation of China (Grant Nos. 90816027, 61004094)
文摘The high angle of attack characteristics play an important role in the aerodynamic performances of the hypersonic space vehicle. The three-dimensional Reynolds Averaged Navier-Stokes (RANS) equations and the two-equation RNG k-? turbulence model have been employed to investigate the influence of the high angle of attack on the lift-to-drag ratio and the flow field characteristics of the hypersonic space vehicle, and the contributions of each component to the aerodynamic forces of the vehicle have been discussed as well. At the same time, in order to validate the numerical method, the predicted results have been compared with the available experimental data of a hypersonic slender vehicle, and the grid independency has been analyzed. The obtained results show that the predicted lift-to-drag ratio and pitching moment coefficient show very good agreement with the experimental data in the open literature, and the grid system makes only a slight difference to the numerical results. There exists an optimal angle of attack for the aerodynamic performance of the hypersonic space vehicle, and its value is 20°. When the angle of attack is 20°, the high pressure does not leak from around the leading edge to the upper surface. With the further increasing of the angle of attack, the high pressure spreads from the wing tips to the central area of the vehicle, and overflows from the leading edge again. Further, the head plays an important role in the drag performance of the vehicle, and the lift percentage of the flaperon is larger than that of the rudderevator. This illustrates that the optimization of the flaperon configuration is a great work for the improvement of the aerodynamic performance of the hypersonic space vehicle, especially for a high lift-to-drag ratio.
基金Supported by the National Natural Science Foundation of China(51179146)the Fundamental Research Funds for the Central Universities(2010-Ia-050,2011-IV-027)
文摘Delaunay triangulation is gradually playing an important role in the field of finite element analysis, image recognition, and medical visualization.Considering the quality and partition efficiency, a new Delaunay triangulation method based on constrained maximum circumscribed circle is proposed. First, according to two important criteria, the empty circle features and the maximized minimum angle characteristics, we established constrained conditions. Then, we iterated the container vertices, structure triangular face linked lists, and finally got the Delaunay data. The experimental results showed that the efficiency of the improved triangulation dissection method increased by 9.47% compared with traditional triangulation algorithms in irregular triangle vertex data.
