Browsing by Subject "ANSYS"
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Item Adapting a Beam-Based Rotordynamics Model to Accept a General Three-Dimensional Finite-Element Casing Model(2011-08-08) James, Stephen M.The subject of this thesis is an extension of a two-dimensional, axisymmetric, Timoshenko-beam finite-element rotordynamic code to include a three-dimensional non-axisymmetric solid-element casing model. Axisymmetric beams are sufficient to model rotors. Spring and damper forces provide the interface between the rotor and its casing and capture the dynamics of the full model. However, axisymmetric beams limit the modeling of real-case machine structures, where the casing is not axisymmetric. Axisymmetric and non-axisymmetric 3D finite element casing structures are modeled. These structures are then reduced using a technique called substructuring. Modal equations are developed for axisymmetric and non-axisymmetric casing models. In a 3D non-axisymmetric model, structural dynamics modes can be modeled by lateral modes in two orthogonal planes. Modal information of the complex 3D casing structures are generated, and then incorporated into the 2D code after a series of pre-processing steps. A reduction method called Component Mode Synthesis (CMS) is used to reduce the large dimensionality involved in calculation of rotordynamic coefficients. The results from the casing structures are merged with the rotor model to create a combined rotor-casing model. The analysis of the combined structure shows that there is a difference in the natural frequencies and unbalance response between the model that uses symmetrical casing and the one that uses non-axisymmetric casing. XLTRC2 is used as an example of a two-dimensional axisymmetric beam-element code. ANSYS is used as a code to build three-dimensional non-axisymmetric solid-element casing models. The work done in this thesis opens the scope to incorporate complex non-axisymmetric casing models with XLTRC2.Item Optimization of in-plane directional microphone(2015-08) Zha, Jingqiang; Hall, Neal A.; Masada, GlennThis report is aimed at optimization of the in-plane directional microphone. In chapter 1, a piezoelectric network model is presented. Then the network model is applied to a piezoelectric cantilever beam. Theoretical results are compared with simulation results to prove the network model. This piezoelectric cantilever beam also forms the basis of the XY directional microphone. In chapter 2, principles of XY directional microphone are explained at the beginning. Further analysis shows the expression related to signal-to-noise ratio, which is the optimization goal. ANSYS simulation is implemented to justify this expression. Based on that expression, suggestions are made to optimize the directional microphone. In chapter 3, proof of concept of a novel gyroscope directional microphone is explained. Gyroscopic effect is introduced at first. Then the result of in-plane directional microphone is presented. Finally, the expression for "amplification factor" is derived and selection of appropriate performance criterion could lead to improved sensitivity.Item Thermally Induced Vibrations of a Solar Wing with Bowed STEM(2010-11-30) Hagler, Shawn 1983-Storable Tubular Extendible Members (STEMs) are often used for deploying spacecraft subsystems such as flexible solar cell blankets, like those used on Hubble Telescope. Systems using long flexible appendages such as the STEMs used on Hubble often undergo thermal excitations due to a thermal gradient through the cross-section when entering and exiting solar eclipse. These vibrations can greatly reduce pointing accuracy and lead to mission failure. Boeing obtained a patent in 2006 for the High Power Thin Film Solar Array (HPSA) which could provide 130kW of power to a spacecraft. The deployed structure relies on bowed STEMs and a tether system to keep the solar panels taut and in alignment with the sun. The system is predicted to minimize the effects of thermal excitation. This thesis proves that the HPSA design can outperform its straight STEM counterparts with respect to thermal-structural stability under unidirectional solar radiant heating through the use of finite element models created in ANSYS. In comparison to Hubble, a HPSA wing configuration is capable of providing a 44.5 percent increase in the first modal frequency, a 98.8 percent reduction in steady state tip deflection, and 96.9 percent reduction in tip vibration amplitude.