The cutterhead of a full-face rock tunnel boring machine(TBM)is constantly subjected to varying impact and dynamic loads during tunneling processes,resulting in relatively large vibrations that could easily lead to fa...The cutterhead of a full-face rock tunnel boring machine(TBM)is constantly subjected to varying impact and dynamic loads during tunneling processes,resulting in relatively large vibrations that could easily lead to fatigue cracking of the entire machine and a ect the tunneling performance and efficiency.To explore the dynamic characteristics of the TBM mainframe,a TBM from a water-diversion project is investigated in this research.According to the TBM vibration transmission route,an equivalent dynamic model of the TBM mainframe is established using the lumped-mass method in which the relevant dynamic parameters are solved.Additionally,the dynamic response characteristics of the TBM mainframe are analyzed.The results indicate that the vibration levels in three directions are approximately the same,the multi-directional vibration of the cutterhead is more intense than that of other components,and the vibration and external excitation exhibit identical change trends.A set of vibration field tests is performed to analyze the in situ dynamic responses of the mainframe and verify the correctness of the dynamic model.The theoretical and measured acceleration values of the TBM mainframe have the same magnitude,which proves the validity of the dynamic model and its solution.The aforementioned results provide an important theoretical value and practical significance for the design and assessment of the TBM mainframe.展开更多
We review the state of the art of dynamic modeling methods for helicopter simulators.Major dynamic models,including ARMCOP,GENHEL,FLYRT,BEMAP,F-B412 and UTIAS,are introduced.We address off-axis response problem by foc...We review the state of the art of dynamic modeling methods for helicopter simulators.Major dynamic models,including ARMCOP,GENHEL,FLYRT,BEMAP,F-B412 and UTIAS,are introduced.We address off-axis response problem by focusing on flexible blade model,Pitt-Peters dynamic inflow model,Peters-He finite state inflow model and free wake model which are integrated with the baseline model.With the advances in computing power,efficient free-vortex algorithms and parallel processing,free wake model can be used to simulate in real-time and significantly improves the effectiveness of solving off-axis response problem.展开更多
A model was developed to understand the aggregation process of the particles in electrorheological(ER) fluids under the action of an applied electric field. By establishing a generalized virtual work principle based o...A model was developed to understand the aggregation process of the particles in electrorheological(ER) fluids under the action of an applied electric field. By establishing a generalized virtual work principle based on the consideration that the released electromagnetic energy accompanying the growth of the chain should equal to the dissipated energy related with friction resistance of the viscous fluid in the chain formation, the governing differential equation of the chain growth was established. Based on this energy model, the velocity of the chain forming, and the response time of ER fluid can be predicted. The present model can also predict the effect of the temperature and some microstructural parameters, such as the dielectric constants and concentration of the particles, etc., on the response of an ER system.展开更多
基金Supported by National Key R&D Program of China(Grant No.2017YFB1302603)National Natural Science Foundation of China(Grant No.51905550)+1 种基金National Basic Research Program of China(Grant No.2013CB035401)China Postdoctoral Science Foundation(Grant No.2019M652795)
文摘The cutterhead of a full-face rock tunnel boring machine(TBM)is constantly subjected to varying impact and dynamic loads during tunneling processes,resulting in relatively large vibrations that could easily lead to fatigue cracking of the entire machine and a ect the tunneling performance and efficiency.To explore the dynamic characteristics of the TBM mainframe,a TBM from a water-diversion project is investigated in this research.According to the TBM vibration transmission route,an equivalent dynamic model of the TBM mainframe is established using the lumped-mass method in which the relevant dynamic parameters are solved.Additionally,the dynamic response characteristics of the TBM mainframe are analyzed.The results indicate that the vibration levels in three directions are approximately the same,the multi-directional vibration of the cutterhead is more intense than that of other components,and the vibration and external excitation exhibit identical change trends.A set of vibration field tests is performed to analyze the in situ dynamic responses of the mainframe and verify the correctness of the dynamic model.The theoretical and measured acceleration values of the TBM mainframe have the same magnitude,which proves the validity of the dynamic model and its solution.The aforementioned results provide an important theoretical value and practical significance for the design and assessment of the TBM mainframe.
基金supported by the Fundamental Research Funds for the Central Universitiesthe Research Innovation Program for College Graduates of Jiangsu Province(No.KYLX_0294)
文摘We review the state of the art of dynamic modeling methods for helicopter simulators.Major dynamic models,including ARMCOP,GENHEL,FLYRT,BEMAP,F-B412 and UTIAS,are introduced.We address off-axis response problem by focusing on flexible blade model,Pitt-Peters dynamic inflow model,Peters-He finite state inflow model and free wake model which are integrated with the baseline model.With the advances in computing power,efficient free-vortex algorithms and parallel processing,free wake model can be used to simulate in real-time and significantly improves the effectiveness of solving off-axis response problem.
文摘A model was developed to understand the aggregation process of the particles in electrorheological(ER) fluids under the action of an applied electric field. By establishing a generalized virtual work principle based on the consideration that the released electromagnetic energy accompanying the growth of the chain should equal to the dissipated energy related with friction resistance of the viscous fluid in the chain formation, the governing differential equation of the chain growth was established. Based on this energy model, the velocity of the chain forming, and the response time of ER fluid can be predicted. The present model can also predict the effect of the temperature and some microstructural parameters, such as the dielectric constants and concentration of the particles, etc., on the response of an ER system.
