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Full-Text Articles in Mechanical Engineering
Multidimensional Compressible Framework For Modeling Biglobal Stability In Rocket Motors, Michel Henry Akiki
Multidimensional Compressible Framework For Modeling Biglobal Stability In Rocket Motors, Michel Henry Akiki
Doctoral Dissertations
Rocket motor stability analysis has historically been focused on two fundamental theories: the acoustic and the hydrodynamic. While the acoustic part examines the system at resonant states, the hydrodynamic component focuses on the fluid-wall interactions and the vortex shedding mechanisms which are responsible for exciting the system. Traditionally, the two concepts are studied independently and their results are then superposed for a more complete solution. In this study, we analyze the problem from a hydrodynamic standpoint and extend it to include compressibility. This is realized by reducing the linearized Navier-Stokes and energy equations to their biglobal form assuming a two-dimensional …
Vibration Based Damage Identification Of Time-Varying Dynamical Systems, Jie Zhao
Vibration Based Damage Identification Of Time-Varying Dynamical Systems, Jie Zhao
Doctoral Dissertations
This thesis develops and explores two new kinds of vibration-based damage identification methodologies suitable for dynamical systems with periodically time-varying coefficients; 1) a Floquet based method (Methodology I) and, 2) a Sideband Frequency Response Function (FRF) method (Methodology II). One important class of dynamical systems where periodic time-varying parametric terms naturally arise is rotordynamic systems. For the case of a flexible shaft-rotor system with multiple open cracks, this thesis explores a new Least Squares damage identification approach based on Floquet theory with iterative eigenvector estimate updating. It is found that this method is able to detect the location and severity …