Based on the Reynolds equation with Reynolds boundary conditions, the Castelli method was employed to solve the Reynolds equation for oil lubrication upon bearings. By doing so, a profile of nonlinear oil film force o...Based on the Reynolds equation with Reynolds boundary conditions, the Castelli method was employed to solve the Reynolds equation for oil lubrication upon bearings. By doing so, a profile of nonlinear oil film force of single-pad journal bearings is established. According to the structure of combination journal bearings, nonlinear oil film force of combination journal bearing is obtained by retrieval, interpolation and assembly techniques. As for symmetrical flexible Jeffcott rotor systems supported by combination journal bearings, the nonlinear motions of the center of the rotor are calculated by the self-adaptive Runge-Kutta method and Poincar6 mapping with different rotational speeds. The numerical results show that the system performance is slightly better when the pivot ratio changes from 0.5 to 0.6, and reveals nonlinear phenomena of periodic, period-doubing, quasi-periodic motion, etc.展开更多
The microstructure evolutions of two A1-Zn-Mg alloys, one of which was alloyed with Sc and Zr, and the kinetics of A13（SCl-xZrx） precipitates in the A1-Zn-Mg alloy during homogenization were investigated. Both alloy...The microstructure evolutions of two A1-Zn-Mg alloys, one of which was alloyed with Sc and Zr, and the kinetics of A13（SCl-xZrx） precipitates in the A1-Zn-Mg alloy during homogenization were investigated. Both alloys under as-cast condition with supersaturated, non-equilibrium T（Mg32（A1, Zn）49） phase and impurities phase were displayed. When the homogenization temperatures are below 350 ~C, Zn and Mg atoms precipitate from matrix; however, when the temperatures are above 400 ~C, T phase dissolves into matrix, enhancing solid-solution strengthening. Kinetics of A13（Scl.xZrx） precipitates was studied based on Jmat Pro software calculation and the difference values between the hardness of the two alloys in each homogenization condition. The calculations predict that the Sc and Zr solubilities in ct-A1 decline with the presence of Mg and Zn. Investigation of the difference values reveals that when the temperature is between 300 ~C and 350 ~C, the nucleation rate of A13（Sc1-xZrx） precipitates is the highest and the strengthening effect from A13（SCl_xZrx） precipitates is the best. After homogenization at 470℃ for 12 h, non-equilibrium T phase disappears, while impurity phase remains. The mean diameter of A13（Scl_xZrx） precipitates is around 18 urn. Ideas about better fulfilling the potentials of Sc and Zr were proposed at last.展开更多
基金Project(2007CB707706) supported by the National Basic Research Program of China Projects(51075327,10972179) supported by the National Natural Science Foundation of China+2 种基金 Project(SKLMT-KFKT-201011) supported by Open Foundation of State Key Laboratory of Mechanical Transmission,China Projects(2009JQ7006,2007E203) supported by the Natural Science Foundation of Shaanxi Province of China Projects(09JK680,07JK340) supported by the Natural Science Foundation of Department of Education of Shaanxi Province of China
文摘Based on the Reynolds equation with Reynolds boundary conditions, the Castelli method was employed to solve the Reynolds equation for oil lubrication upon bearings. By doing so, a profile of nonlinear oil film force of single-pad journal bearings is established. According to the structure of combination journal bearings, nonlinear oil film force of combination journal bearing is obtained by retrieval, interpolation and assembly techniques. As for symmetrical flexible Jeffcott rotor systems supported by combination journal bearings, the nonlinear motions of the center of the rotor are calculated by the self-adaptive Runge-Kutta method and Poincar6 mapping with different rotational speeds. The numerical results show that the system performance is slightly better when the pivot ratio changes from 0.5 to 0.6, and reveals nonlinear phenomena of periodic, period-doubing, quasi-periodic motion, etc.
基金Project(JPPT-115-2-948) supported by the National Civilian Matched Project of China
文摘The microstructure evolutions of two A1-Zn-Mg alloys, one of which was alloyed with Sc and Zr, and the kinetics of A13（SCl-xZrx） precipitates in the A1-Zn-Mg alloy during homogenization were investigated. Both alloys under as-cast condition with supersaturated, non-equilibrium T（Mg32（A1, Zn）49） phase and impurities phase were displayed. When the homogenization temperatures are below 350 ~C, Zn and Mg atoms precipitate from matrix; however, when the temperatures are above 400 ~C, T phase dissolves into matrix, enhancing solid-solution strengthening. Kinetics of A13（Scl.xZrx） precipitates was studied based on Jmat Pro software calculation and the difference values between the hardness of the two alloys in each homogenization condition. The calculations predict that the Sc and Zr solubilities in ct-A1 decline with the presence of Mg and Zn. Investigation of the difference values reveals that when the temperature is between 300 ~C and 350 ~C, the nucleation rate of A13（Sc1-xZrx） precipitates is the highest and the strengthening effect from A13（SCl_xZrx） precipitates is the best. After homogenization at 470℃ for 12 h, non-equilibrium T phase disappears, while impurity phase remains. The mean diameter of A13（Scl_xZrx） precipitates is around 18 urn. Ideas about better fulfilling the potentials of Sc and Zr were proposed at last.
