Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 16 of 16 for “"critical speeds"”.
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Critical speeds of shafts with overhung flywheels
Thesis: B.S., Massachusetts Institute of Technology, Department of Mechanical Engineering, 1944
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Excitation of gyroscopic precession in overhung rotors at critical speeds
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1953.
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Influence of active magnetic bearing sensor location on the calculated critical speeds of turbomachinery
The calculation of critical speeds for turbomachinery with active magnetic bearings (AMBs) is of great interest due to the increasing number of applications of this new technology. The potential for increased turbomachine performance through improved AMB design has created the need for a more …
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Critical speeds and unbalance response of cantilever-sleeve rotors using finite elements with efficient higher order basis functions
… which involves the determination of their critical speeds and unbalance response. Dynamic behavior of simple rotor systems can be studied using analytical techniques. However, for complex rotor systems it is necessary to use approximate techniques. The finite element method is one such …
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An investigation of the three-dimensional vibration characteristics of a rotor-bearing system using the finite element method
… and bearing pedestal stiffness on rotor critical speeds. Bearing stiffnesses were obtained from a previously-developed computer program. Pedestal stiffnesses were obtained from a plane-stress finite element analysis. A rotor model which incorporated these bearing and pedestal stiffnesses …
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Computer-aided design software for rotor dynamics analysis
… technique for determining the damped or undamped critical speeds and generating a critical speed map for a general flexible rotor in isotropic bearings has been developed. Rotordynamics theory related to this research work is studied including synchronous unbalance response, critical speed, …
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Dynamic analysis of rotating fan structures by the Finite Element Method
… for the prediction of its dynamic response and critical speeds. The research led to a study of the influence of riveted spider-to-blade connections on the vibration response of propeller fans; This thesis also presents a mathematical transformation analysis and an explanation of a frontend …
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Transient analysis and vibration suppression of a cracked rotating shaft with ideal and nonideal motor passing through a critical speed
… ideal and a nonideal motor, passing through its critical speed. The shaft contains a single transverse crack that is assumed to be either completely open or completely closed at any given time, depending on the curvature of the shaft at the cross section containing the crack. Flexible, damped …
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Rotordynamic assessment for a permanent magnet synchronous motor
… trunnion effect, which significantly reduces the critical speeds, can be offset by selecting appropriate dimensions for the rotor end plate using the revised model. Thus, even in the presence of this effect, the proposed unconventional motor topology is confirmed to function reliably.
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Sensitivity analysis of wing aeroelastic responses
… of aeroelastic instability (that is, the critical speeds leading to aeroelastic instability lie outside the operating range) is an integral part of the wing design process. Availability of the sensitivity derivatives of the various critical speeds with respect to shape parameters of the …
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Influence of higher time harmonics on the electrical and mechanical performance of an inverter-fed squirrel cage induction motor
… by measuring the torque, torque pulsations, critical speeds and resonance frequencies of frame vibrations and torque oscillations as well as vibrations in x-, y-, and z-direction of the inverter-fed induction machine. Consequences of time harmonics on the induction motor and system are …
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Design and Multi-physical Fields Analysis of High Speed Permanent Magnet Machines
… magnet machine, a HSPMM rotor can reach speeds of more than 10,000 rpm, which brings challenges with regard to electromagnetic, thermal and mechanical aspects of machine design. The higher power density also results in larger power loss per unit volume; due to the small machine size, …
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On Steady Water Waves and Their Properties
… periodic travelling waves with sub-critical speeds. As the period of these travelling waves tends to infinity, their velocities approach the limiting long-wave speed c0, and the waves approach a solitary wave. It is also shown that there can be no solitary waves with velocities much …
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Advanced analysis of rotor-bearing systems for stability and response
… with the evaluation of the stability and damped critical speeds, and the response to an unbalance excitation, of turbomachinery. The majority of the industries which deal with rotor dynamics use the conventional and proven transfer matrix methods to solve the dynamics. However, the recent …
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Semi-Analytical Model to Study Vibrations of High-Speed, Rotating Axisymmetric Bodies Coupled to Other Rotating/ Stationary Structures
… Fourier harmonics in each mode, changes to critical speeds, divergence and flutter instability phenomena, and eigenvalue veering are investigated for spinning systems with asymmetric features. The developed semi-analytical model is used for rotationally periodic systems, for example, …
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Nonlinear flutter of composite shear-deformable panels in a high-supersonic flow
… that of finite motions which may occur for pre-critical speeds also. Results show that linear aerodynamics correctly predicts the immediate post-flutter behavior of thin panels only. When compressive edge loads or edge restraints are applied, in certain cases multiple periodic solutions are …