The effect of oil film force nonlinearity on unbalance response of Jeffcot rotor elliptical bearing system is studied. Linear analysis is done by linearizing the bearing oil film dynamic forces and expressing them wi...The effect of oil film force nonlinearity on unbalance response of Jeffcot rotor elliptical bearing system is studied. Linear analysis is done by linearizing the bearing oil film dynamic forces and expressing them with stiffness and damping constants. Nonlinear dynamic simulation is done by taking the nonlinearity of bearing oil film dynamic force into full consideration, with the latter being expressed by a special database which is generated beforehand, and based on non stationary Reynolds equation and Reynolds boundary condition of film rupture. The linear and nonlinear unbalance responses of a Jeffcot rotor supported on a pair of elliptical bearings is studied. The resulting dynamic characteristics and rotor and journal whirling orbits are compared. While good consistancy between nonlinear and linear predictions is found under very small unbalance, significant or even drastic differences are found whenever the unbalance is not small, indicating the necessity of including the nonlinearity of oil film dynamic forces, especially when response to large unbalance is to be predicted.展开更多
As to motorized spindle system, this paper builds a simplified 3D model of spindle and bearing, performs structure modal analysis, reveals its dynamic characteristics under the free model; furthermore, modifies bearin...As to motorized spindle system, this paper builds a simplified 3D model of spindle and bearing, performs structure modal analysis, reveals its dynamic characteristics under the free model; furthermore, modifies bearing radial stiffness and number of model and studies the change of modal parameters. On this basis, through the harmonic response analysis of the finite element model, dy- namic response characteristic caused by imbalance of monitored spindle system and law of vibration response to different amount of unbalance is analyzed.展开更多
In this article, a model of a rotor with an asymmetric disk is presented in order to represent Campbell’s diagrams and instability maps as a function of the rotations of the support which can significantly change the...In this article, a model of a rotor with an asymmetric disk is presented in order to represent Campbell’s diagrams and instability maps as a function of the rotations of the support which can significantly change the dynamic behavior of the rotor. Critical rotating speeds can also lead to unacceptable levels of vibration. Indeed, the critical speeds are a function of the dynamic rigidity of the rotating systems and the presence of the gyroscopic forces creates a dependence between the rotating speed of rotation and the natural frequencies to such structures (the CAMPBELL diagrams): this implies that the correct determination of the critical speeds is one of the essential elements when sizing such dynamic systems.展开更多
文摘The effect of oil film force nonlinearity on unbalance response of Jeffcot rotor elliptical bearing system is studied. Linear analysis is done by linearizing the bearing oil film dynamic forces and expressing them with stiffness and damping constants. Nonlinear dynamic simulation is done by taking the nonlinearity of bearing oil film dynamic force into full consideration, with the latter being expressed by a special database which is generated beforehand, and based on non stationary Reynolds equation and Reynolds boundary condition of film rupture. The linear and nonlinear unbalance responses of a Jeffcot rotor supported on a pair of elliptical bearings is studied. The resulting dynamic characteristics and rotor and journal whirling orbits are compared. While good consistancy between nonlinear and linear predictions is found under very small unbalance, significant or even drastic differences are found whenever the unbalance is not small, indicating the necessity of including the nonlinearity of oil film dynamic forces, especially when response to large unbalance is to be predicted.
基金Special Topic of the Ministry of Education about Humanities and Social Sciences(12JDGC007)National Science and Technology Support Project(2011BAF09B01)Key State Science and Technology Projects(2009ZX04010-021)
文摘As to motorized spindle system, this paper builds a simplified 3D model of spindle and bearing, performs structure modal analysis, reveals its dynamic characteristics under the free model; furthermore, modifies bearing radial stiffness and number of model and studies the change of modal parameters. On this basis, through the harmonic response analysis of the finite element model, dy- namic response characteristic caused by imbalance of monitored spindle system and law of vibration response to different amount of unbalance is analyzed.
文摘In this article, a model of a rotor with an asymmetric disk is presented in order to represent Campbell’s diagrams and instability maps as a function of the rotations of the support which can significantly change the dynamic behavior of the rotor. Critical rotating speeds can also lead to unacceptable levels of vibration. Indeed, the critical speeds are a function of the dynamic rigidity of the rotating systems and the presence of the gyroscopic forces creates a dependence between the rotating speed of rotation and the natural frequencies to such structures (the CAMPBELL diagrams): this implies that the correct determination of the critical speeds is one of the essential elements when sizing such dynamic systems.
