Browsing by Author "Ghaderi, Pooya"

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    Frequency domain analysis of linear and nonlinear structures with applications to impact force identification and micro-resonator design
    (2013-12-06) Ghaderi, Pooya; Akin, John Edward.; Stanciulescu, Ilinca; Dick, Andrew J.
    The modeling and analysis of structures using frequency-domain methods simplify the procedure of the modeling and analysis and provides better understanding of the response of the structures. There are different applications in frequency-domain structural modeling and analysis such as modeling and analysis in impact engineering, wave propagation in structures, and micro-resonators. The identification of the impact force and the impact location in structures are important for monitoring the condition of the structures and also for the design of the future structures. The complexity and nonlinearity of the impact incident makes it impractical to measure the impact force directly. In this study, a new method that uses the spectral finite element method (SFEM) is introduced in order to identify and locate the applied impact force. Using SFEM facilitates for the successfully identification of the high frequency content in the impact forces. Also, using SFEM allows for the identification of the impact force independent of the location of the impact force. The impact force identification and localization method is verified by experimental results. For designing and analyzing micro-resonators, it is required to do the frequency-analysis of these structures which provide the frequency characteristics and the frequency-response of the structures. In this study, a novel class of parametrically excited micro-resonators is introduced. The micro-resonator takes advantage of piezo-electric excitation which improves the performance of the micro-resonator over that of the micro-resonators with electrostatic excitation for certain applications.
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    Practical high-fidelity frequency-domain force and location identification
    (Elsevier, 2015) Ghaderi, Pooya; Dick, Andrew J.; Foley, Jason R.; Falbo, Gregory
    Identifying the force information and location of an impact event is important for predicting and/or monitoring potential damage to the structures. Directly measuring the impact event and/or locating the impact force is not always possible due to the nature of the impact or the structure. In this work, a new force and location identification method is introduced which utilizes a spectral finite element method (SFEM) model of the structure. The identification technique is demonstrated and studied through its application to beam structures in order to identify impulsive loads. Wave propagation data collected with accelerometers placed on the structure are used in order to determine the impact information. When the impact force is applied between the accelerometers, the calculated force is distributed over the two accelerometer positions on either side of the impact location. The location identification process uses the distribution of the identified force information in order to locate the impact position. This method is performed by matching simulated data to the identified force data by tuning the impact location within the numerical model. When a sufficient level of agreement is achieved, the impact location is determined. In order to validate the results of the numerical studies, identified impact forces and locations are calculated for experimental data and good agreement is observed with the measured force information and impact locations.