Electromagnetic and mechanical forces are main reasons of oscillations in hydro-generators.The oscillation is fairly complicated as to the coupling of them.Using the method of multiple scales in nonlinear oscillations...Electromagnetic and mechanical forces are main reasons of oscillations in hydro-generators.The oscillation is fairly complicated as to the coupling of them.Using the method of multiple scales in nonlinear oscillations,instabilities of hydro-generator rotors caused by the unbalanced magnetic pull,which comes from the eccentricity of the rotor,are discussed.Considering nonlinear properties of the unbalanced magnetic pull,the super-harmonic resonance phenomena are observed as the critical rotating speed of rotors is close to twice of the operating speed.This is verified by a model experiment,and should be considered during the design of hydro-generator rotors.展开更多
Following the theory of Multi Agent System (MAS) and using series wound structure and shunt wound structure of Agents, the performance of Agent was improved to satisfy the need of satellite fault diagnosis, and a trid...Following the theory of Multi Agent System (MAS) and using series wound structure and shunt wound structure of Agents, the performance of Agent was improved to satisfy the need of satellite fault diagnosis, and a tridimensional MAS model of satellite fault diagnosis was thus established for the MAS based planar diagnosis system, which decentralizes the whole diagnosing task into subtasks to be performed by different functional Agents to make the complicated fault diagnosis very simple and the diagnosis system more intelligent. This method improved the reliability and accuracy of diagnosis and made the maintenance and upgrading of the satellite fault diagnosis system very easy as well.展开更多
Dislocation distribution functions of the edges of mode Ⅲ propagation crack subjected to three types of loads were studied by the methods of the theory of complex variable functions,by which,the problems researched w...Dislocation distribution functions of the edges of mode Ⅲ propagation crack subjected to three types of loads were studied by the methods of the theory of complex variable functions,by which,the problems researched were facilely transformed into Riemann-Hilbert problems and Keldysh-Sedov mixed boundary value problems. Analytical solutions of stresses,displacement and dynamic stress intensity factor were obtained by the measures of the theory of self-similar functions and corresponding differential and integral operation. In terms of the relationship between dislocation distribution functions and displacements,analytical solutions of dislocation distribution functions were obttained,and variational rules of dislocation distribution functions were depicted.展开更多
The theoretical formula of roller bearing stiffness is induced and compared with its empirical formula. In the experience formula the stiffness of roller bearing has nothing to do with the roller diameter. The relatio...The theoretical formula of roller bearing stiffness is induced and compared with its empirical formula. In the experience formula the stiffness of roller bearing has nothing to do with the roller diameter. The relationship of roller bearing stiffness with roller diameter was studied using Hz contacting theory. It is concluded that conclusion in experience formula is only approximate result of data processing under special conditions, and the relation between stiffness of roller bearing and roller diameter must be taken into consideration while designing or selecting roller bearings.展开更多
To investigate the relation between material＇s cychc plastic behaviour and fatigue crack growth, a new model is proposed. The model incorporated the two intrinsic properties of material＇ s cyclic plastic and crack ...To investigate the relation between material＇s cychc plastic behaviour and fatigue crack growth, a new model is proposed. The model incorporated the two intrinsic properties of material＇ s cyclic plastic and crack tip＇ s deformation dislocation to interpret fatigue crack threshold. The relation between material＇ s cyclic hardening parameters （cyclic hardening amplitude and cyclic hardening rate） and fatigue threshold is studied. Fatigue threshold is determined based on the dislocation-free zone （DFZ） model, the theory of cohesive zone and the cyclic deformation behaviour. The results show that fatigue threshold increases with the decrease of the amplitude of cyclic hardening and is independent of cyclic hardening rate, but fatigue crack growth rate increases with the increase of cyclic hardening rate.展开更多
By the theory of complex functions, a dynamic problem on the edges of a mode I crack subjected to moving unit-step loads are investigated. The Riemann-Hilbert problem is easily formulated by the ways of self-similar f...By the theory of complex functions, a dynamic problem on the edges of a mode I crack subjected to moving unit-step loads are investigated. The Riemann-Hilbert problem is easily formulated by the ways of self-similar functions. The analytical solution obtained is rather simple and concise. After the solution was utilized by superposition theorem, the relevant solution on the case of arbitrary loading can be obtained.展开更多
A new finite element modeling method has been developed using laminate theory in a virtual work principle for active constraining layer damping plate. The frequency dependent modulus of viscoelastic material is descri...A new finite element modeling method has been developed using laminate theory in a virtual work principle for active constraining layer damping plate. The frequency dependent modulus of viscoelastic material is described by introducing a few dissipation coordinates, known as GHM (Golla-Hughes-McTavish) method, a standard linear system with constant coefficient. The effectiveness of this method is validated by experimental model. Compared with conventional methods, this method can reduce a number of degrees of freedom and improve accuracy, provides a good model for analogous configurations.展开更多
基金Sponsored by the National Natural Science Foundation of China(Grant No.59493700),Key Project of the National Tenth-Five Year Research Programme of China(Grant No.ZZ01-01-04-03).
文摘Electromagnetic and mechanical forces are main reasons of oscillations in hydro-generators.The oscillation is fairly complicated as to the coupling of them.Using the method of multiple scales in nonlinear oscillations,instabilities of hydro-generator rotors caused by the unbalanced magnetic pull,which comes from the eccentricity of the rotor,are discussed.Considering nonlinear properties of the unbalanced magnetic pull,the super-harmonic resonance phenomena are observed as the critical rotating speed of rotors is close to twice of the operating speed.This is verified by a model experiment,and should be considered during the design of hydro-generator rotors.
文摘Following the theory of Multi Agent System (MAS) and using series wound structure and shunt wound structure of Agents, the performance of Agent was improved to satisfy the need of satellite fault diagnosis, and a tridimensional MAS model of satellite fault diagnosis was thus established for the MAS based planar diagnosis system, which decentralizes the whole diagnosing task into subtasks to be performed by different functional Agents to make the complicated fault diagnosis very simple and the diagnosis system more intelligent. This method improved the reliability and accuracy of diagnosis and made the maintenance and upgrading of the satellite fault diagnosis system very easy as well.
基金Sponsored by the Postdoctoral Science Fundation of China (Grant No. 200303337 )the National Natural Science Foundation of China (Grant No.30205035)
文摘Dislocation distribution functions of the edges of mode Ⅲ propagation crack subjected to three types of loads were studied by the methods of the theory of complex variable functions,by which,the problems researched were facilely transformed into Riemann-Hilbert problems and Keldysh-Sedov mixed boundary value problems. Analytical solutions of stresses,displacement and dynamic stress intensity factor were obtained by the measures of the theory of self-similar functions and corresponding differential and integral operation. In terms of the relationship between dislocation distribution functions and displacements,analytical solutions of dislocation distribution functions were obttained,and variational rules of dislocation distribution functions were depicted.
文摘The theoretical formula of roller bearing stiffness is induced and compared with its empirical formula. In the experience formula the stiffness of roller bearing has nothing to do with the roller diameter. The relationship of roller bearing stiffness with roller diameter was studied using Hz contacting theory. It is concluded that conclusion in experience formula is only approximate result of data processing under special conditions, and the relation between stiffness of roller bearing and roller diameter must be taken into consideration while designing or selecting roller bearings.
基金Sponsored by the Fundamental Research Foundation of Harbin Engineering University(Grant No.HEUFT07007)
文摘To investigate the relation between material＇s cychc plastic behaviour and fatigue crack growth, a new model is proposed. The model incorporated the two intrinsic properties of material＇ s cyclic plastic and crack tip＇ s deformation dislocation to interpret fatigue crack threshold. The relation between material＇ s cyclic hardening parameters （cyclic hardening amplitude and cyclic hardening rate） and fatigue threshold is studied. Fatigue threshold is determined based on the dislocation-free zone （DFZ） model, the theory of cohesive zone and the cyclic deformation behaviour. The results show that fatigue threshold increases with the decrease of the amplitude of cyclic hardening and is independent of cyclic hardening rate, but fatigue crack growth rate increases with the increase of cyclic hardening rate.
文摘By the theory of complex functions, a dynamic problem on the edges of a mode I crack subjected to moving unit-step loads are investigated. The Riemann-Hilbert problem is easily formulated by the ways of self-similar functions. The analytical solution obtained is rather simple and concise. After the solution was utilized by superposition theorem, the relevant solution on the case of arbitrary loading can be obtained.
文摘A new finite element modeling method has been developed using laminate theory in a virtual work principle for active constraining layer damping plate. The frequency dependent modulus of viscoelastic material is described by introducing a few dissipation coordinates, known as GHM (Golla-Hughes-McTavish) method, a standard linear system with constant coefficient. The effectiveness of this method is validated by experimental model. Compared with conventional methods, this method can reduce a number of degrees of freedom and improve accuracy, provides a good model for analogous configurations.
