Using novolac phenolic resin, aniline and formaldehyde as raw materials, benzoxazine-phenolic copolymers with different percentages of benzoxazine rings were prepared. FT-IR was adopted to characterize the molecular s...Using novolac phenolic resin, aniline and formaldehyde as raw materials, benzoxazine-phenolic copolymers with different percentages of benzoxazine rings were prepared. FT-IR was adopted to characterize the molecular structure of the novolac-type phenolic resin and the benzoxazine-phenolic copolymer BP31. In order to understand the curing process of the copolymers, the curing behavior and curing kinetic characteristics were studied by differential scanning calorimetry （DSC）, and the catalytical effect of phenolic hydroxyl on the curing behavior of copolymers was investigated. To investigate the thermal properties of this resin, the thermal degradation behaviors of the cured samples were studied by thermal gravimetric （TG） method, and glass-transition temperatures （Tg） of the cured copolymers were also evaluated by DSC. The dynamic Ozawa method was adopted to determine the kinetic parameters of the curing process as well. The activation energy is 78.8 kJ/mol and the reaction rate constant is in the range from 40.0 to 5.2 （K/min）＂ according to reaction temperatures. The Ozawa exponent decreases from 2.4 to 0.7 with the increase of reaction temperature, and curing mechanism is expounded briefly according to the results. TG result shows that the highest char yield of copolymers is 50.3%. The highest Tg of copolymers is 489 K, which is much higher than that of pure benzoxazine resin.展开更多
A new nonlinear transverse-torsional coupled model with backlash and bearing clearance was proposed for planetary gear set. Meanwhile, sun gear and planet's eccentricity errors, static transmission error, and time...A new nonlinear transverse-torsional coupled model with backlash and bearing clearance was proposed for planetary gear set. Meanwhile, sun gear and planet's eccentricity errors, static transmission error, and time-varying meshing stiffness were taken into consideration. The differential governing equations of motion were solved by employing variable step-size Rung-Kutta numerical integration method. The behavior of dynamic load sharing characteristics affected by the system parameters including input rate, sun gear's supporting stiffness and eccentricity error, planet's eccentricity error, sun gear's bearing clearance, backlashes of sun-planet and planet-ring meshes were investigated qualitatively and systematically. Some theoretical results are summarized at last which extend the current understanding of the dynamic load sharing behavior of planet gear train, enrich the related literature and provide references for the design of planetary gear train.展开更多
基金Project (20050106) supported by the Key Science and Technology Item of Guangdong Province,China
文摘Using novolac phenolic resin, aniline and formaldehyde as raw materials, benzoxazine-phenolic copolymers with different percentages of benzoxazine rings were prepared. FT-IR was adopted to characterize the molecular structure of the novolac-type phenolic resin and the benzoxazine-phenolic copolymer BP31. In order to understand the curing process of the copolymers, the curing behavior and curing kinetic characteristics were studied by differential scanning calorimetry （DSC）, and the catalytical effect of phenolic hydroxyl on the curing behavior of copolymers was investigated. To investigate the thermal properties of this resin, the thermal degradation behaviors of the cured samples were studied by thermal gravimetric （TG） method, and glass-transition temperatures （Tg） of the cured copolymers were also evaluated by DSC. The dynamic Ozawa method was adopted to determine the kinetic parameters of the curing process as well. The activation energy is 78.8 kJ/mol and the reaction rate constant is in the range from 40.0 to 5.2 （K/min）＂ according to reaction temperatures. The Ozawa exponent decreases from 2.4 to 0.7 with the increase of reaction temperature, and curing mechanism is expounded briefly according to the results. TG result shows that the highest char yield of copolymers is 50.3%. The highest Tg of copolymers is 489 K, which is much higher than that of pure benzoxazine resin.
基金Project(51105194)supported by the National Natural Science Foundation of ChinaProject(20113218110017)supported by the Doctoral Program Foundation of Institutions of Higher Education of China+2 种基金Project supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions,ChinaProject(CXZZ11_0199)supported by the Funding of Jiangsu Innovation Program for Graduate Education,ChinaProjects(NZ2013303,NZ2014201)supported by the Fundamental Research Funds for the Central Universities,China
文摘A new nonlinear transverse-torsional coupled model with backlash and bearing clearance was proposed for planetary gear set. Meanwhile, sun gear and planet's eccentricity errors, static transmission error, and time-varying meshing stiffness were taken into consideration. The differential governing equations of motion were solved by employing variable step-size Rung-Kutta numerical integration method. The behavior of dynamic load sharing characteristics affected by the system parameters including input rate, sun gear's supporting stiffness and eccentricity error, planet's eccentricity error, sun gear's bearing clearance, backlashes of sun-planet and planet-ring meshes were investigated qualitatively and systematically. Some theoretical results are summarized at last which extend the current understanding of the dynamic load sharing behavior of planet gear train, enrich the related literature and provide references for the design of planetary gear train.
