The final quality of complex conical-section rings depends on co-design of multiple processes in forming process chain.In this study,for a complex aeroengine casing ring with a large slope and a flange on its end,a co...The final quality of complex conical-section rings depends on co-design of multiple processes in forming process chain.In this study,for a complex aeroengine casing ring with a large slope and a flange on its end,a co-design method of the forming process chain is put forward towards the objective of precision forming,which not only proposes a standard process route composed of multiple processes of upsetting,punching,rectangular ring rolling,loose tooling forging and profiled ring rolling,but also presents co-design methods of dies and blanks for all the processes.For profiled ring rolling,a design method of preformed blank that makes the blank and the target conical-section ring have the same axial volume distribution is proposed.By the method,the axial metal redistribution during the process can be alleviated greatly thus improving the forming stability and precision of the ring.Based on the geometric features of designed preformed blank,design methods of blanks and dies for loose tolling forging,rectangular ring rolling,punching and upsetting are proposed sequentially.In view of the key roles of loose tooling forging(manufacturing the preformed blank)and profiled ring rolling on the final quality of the conical ring parts,inherited FE simulations for these two processes are performed to verify the proposed design methods and determine appropriate design parameter.It is demonstrated that the proposed design method has significant advantages in improving forming precision.Besides,a suggestive value 1.5 of the rolling ratio for profiled ring rolling(a key design parameter)is given based on comprehensive consideration of multiple indicators such as ring roundness,deformation uniformity and forming load.The corresponding industrial experiments performed illustrate that a high forming precision of the conical-section aeroengine casing ring is achieved.展开更多
The visual serving stabilization for a kind of nonholonomic mobile robots with uncalibrated camera parameters is investigated based on the visual feedback and the state and input transforma- tions. The authors obtain ...The visual serving stabilization for a kind of nonholonomic mobile robots with uncalibrated camera parameters is investigated based on the visual feedback and the state and input transforma- tions. The authors obtain a new uncertain model of the nonholonomic kinematic system in the image plane, which is a chained form with uncalibrated visual parameters, from the camera robotic system. A new time varying feedback controller is proposed for the exponential stabilization of the nonholonomic chained system with unknown parameters by using state-scaling and switching technique. The exponential stability of the closed loop system is rigorously proved. Simulation results demonstrate the effectiveness of the proposed methods.展开更多
Dodecyl β-naphthoate and 3-octadecyl pyrene were used as fluorescence probes for estimation of microscopic polarity in aggregates formed by long chain hydrocarbon C_n(n=10,12, 14,16,18)in dimethyl sulfoxide-water mix...Dodecyl β-naphthoate and 3-octadecyl pyrene were used as fluorescence probes for estimation of microscopic polarity in aggregates formed by long chain hydrocarbon C_n(n=10,12, 14,16,18)in dimethyl sulfoxide-water mixed solvent.The polarity in the aggregates is similar to that in cyclohexane.The average aggregation number(N)was determined by using time resolved fluorescence technique.N is dependent on substrate chain length and varies from 15 to 30.The microviscosity was also measured by fluorescence depolarization method.Above phase transition temperature,the microviscosity in aggregates is slightly larger than that in micelle,but below this temperature,the microviscosity in aggregates is as large as that in solid phase.展开更多
基金the National Natural Science Foundation of China(52275378).
文摘The final quality of complex conical-section rings depends on co-design of multiple processes in forming process chain.In this study,for a complex aeroengine casing ring with a large slope and a flange on its end,a co-design method of the forming process chain is put forward towards the objective of precision forming,which not only proposes a standard process route composed of multiple processes of upsetting,punching,rectangular ring rolling,loose tooling forging and profiled ring rolling,but also presents co-design methods of dies and blanks for all the processes.For profiled ring rolling,a design method of preformed blank that makes the blank and the target conical-section ring have the same axial volume distribution is proposed.By the method,the axial metal redistribution during the process can be alleviated greatly thus improving the forming stability and precision of the ring.Based on the geometric features of designed preformed blank,design methods of blanks and dies for loose tolling forging,rectangular ring rolling,punching and upsetting are proposed sequentially.In view of the key roles of loose tooling forging(manufacturing the preformed blank)and profiled ring rolling on the final quality of the conical ring parts,inherited FE simulations for these two processes are performed to verify the proposed design methods and determine appropriate design parameter.It is demonstrated that the proposed design method has significant advantages in improving forming precision.Besides,a suggestive value 1.5 of the rolling ratio for profiled ring rolling(a key design parameter)is given based on comprehensive consideration of multiple indicators such as ring roundness,deformation uniformity and forming load.The corresponding industrial experiments performed illustrate that a high forming precision of the conical-section aeroengine casing ring is achieved.
基金supported by the National Science Foundation under Grant No.60874002Key Project of Shanghai Education Committee under Grant No.09ZZ158+1 种基金Key Discipline of Shanghai under Grant No.S30501Doctoral Fund of Shandong University of Technology under Grant No.411016
文摘The visual serving stabilization for a kind of nonholonomic mobile robots with uncalibrated camera parameters is investigated based on the visual feedback and the state and input transforma- tions. The authors obtain a new uncertain model of the nonholonomic kinematic system in the image plane, which is a chained form with uncalibrated visual parameters, from the camera robotic system. A new time varying feedback controller is proposed for the exponential stabilization of the nonholonomic chained system with unknown parameters by using state-scaling and switching technique. The exponential stability of the closed loop system is rigorously proved. Simulation results demonstrate the effectiveness of the proposed methods.
文摘Dodecyl β-naphthoate and 3-octadecyl pyrene were used as fluorescence probes for estimation of microscopic polarity in aggregates formed by long chain hydrocarbon C_n(n=10,12, 14,16,18)in dimethyl sulfoxide-water mixed solvent.The polarity in the aggregates is similar to that in cyclohexane.The average aggregation number(N)was determined by using time resolved fluorescence technique.N is dependent on substrate chain length and varies from 15 to 30.The microviscosity was also measured by fluorescence depolarization method.Above phase transition temperature,the microviscosity in aggregates is slightly larger than that in micelle,but below this temperature,the microviscosity in aggregates is as large as that in solid phase.
