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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 20 of 42 for “"Frequency Response Functions"”.
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Damage Detection in Aluminum Cylinders Using Modal Analysis
… damage by examining differences in the frequency response functions of a structure before and after damage. In an experimental setting, this variation can not be attributed solely to the addition of damage. Other sources of variation include testing and structure variation. Examples of …
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Neural network calibration of moderator temperature coefficient measurements in pressurized water nuclear reactors
… coefficient in a nuc1ear reactor by using the frequency response functions between the in-core neutron flux signal and the ex-core thermocouple signal as inputs. In this work, actual data from a nuc1ear reactor is used by neural networks to estimate the moderator temperature coefficient at …
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Finite Element Model Updating for Rotary Machinery
… An impact hammer test made it possible to obtain frequency response functions (FRF). The frequency response functions were curvefitted in order to obtain the mode shapes and natural frequencies.</p> <p>Mathematical models have been created with ABAQUS and Matlab. For the Matlab Model the …
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An Experimental and Analytical Investigation of Dynamic Flow Response of a Fan Rotor with Distorted Inlet Flow
… insight and ultimately predict the dynamic flow response of a fan rotor with inlet flow distortion. Rotor exit total pressure circumferential profiles were accurately predicted using frequency response functions derived from experimental rotor response data. Using these predicted profiles, an …
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Finite element model updating and damage detection using artificial boundary conditions
… test of a structure results in a database of frequency response functions from which natural frequencies and mode shapes are identified for the given boundary conditions of the test. The natural frequencies of a system under a variety of boundary conditions can be identified by applying …
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Frequency Domain Methods for Predicting the Transport of Non-Uniform Flow Through Turbomachinery Compressors
… compressor is presented. The method relies on frequency-domain transformations of total pressure distortion patterns, and the use of digital filter techniques to capture the effect of a blade row on the total pressure distortion. Compressor characteristics, described by a frequency response …
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Shape Optimization of Microfiber Composite Energy Harvesters
… in Matlab was validated with an experiment and frequency response functions. The validated model was used to perform shape optimization so as to obtain the shape of the beam and the patch that harvests the largest voltage. The shape variables were length of the beam (LB), length of the patch …
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Analysis of vibration reduction via local structural modification
… to eliminate the unwanted resonance peak from frequency response functions using the 'POLE-ZERO' cancellation principle via local structural modification. This procedure enables the structural system to preserve certain dynamic properties after structural modification. Numerical and …
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The development of a systematic experimental method for damage identification
… experimental techniques. The tests of the frequency response functions (FRFs) of the investigated objects were conducted first to provide a general understanding of the dynamic properties of the material and the structures. Then the tests of the velocity fields at some specified frequencies …
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Micropolar Continuum Modeling of Large Space Structures with Flexible Joints and Thermal Effects: Theory and Experiment
… the laboratory. The results for the experimental frequency response functions are shown to be in good agreement with the theory. Finally, the continuum model is used to quantify the effects of the thermally induced disturbances on the satellite system during the eclipse transition.
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Development of a laser-based automated mechanical mobility measurement system for one-dimensional experimental modal analysis
… can obtain a very high spatial resolution of frequency response functions (FRFs) for experimental modal analysis where one-dimensional structural motion predominates. With this system FRFs are measured and recorded in a format that is readily imported into a popular modal analysis software. A …
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Design, Fabrication, and Validation of Membrane-Based Sensors
… into a low-noise, portable test fixture. The response of the sensor and tip velocity of the hair were measured with respect to an impulse input on the test fixture and several frequency response functions (FRFs) were created. The FRF between the sensor and the tip velocity was used to show …
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A Wave Propagation Approach for Prediction of Tire-Pavement Interaction Noise
… However, accurate prediction tools within this frequency range are not available. Current methods rely on structural modeling of the complete tire using finite elements and modal expansion approaches that are accurate only at low frequencies. Therefore, alternative physically-based models need …
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Probabilistic service life prediction of composite viscoelastic cylindrical structure under random outdoor environment
… were calculated via the uses of complex frequency response functions. Methods for statistical characterization of time and temperature dependent viscoelastic material properties were presented. Five statistical distributions- Normal, Log-Normal, Beta, Gamma, and Weibull, were considered …
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Application of the Round-Trip theory to electro-dynamic sources of vibration
… Salford allows the reconstruction of mechanical frequency response functions at remote locations on a test structure, without the need to physically measure at that location. This makes the identity a powerful tool in the field of modal analysis, as it may be applied to structures where …
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Improved Methods for Modeling Dynamic Stage Characteristics
… model calculations, with first-order time lag response functions applied to account for dynamic departures from the steady and quasi-steady performance predictions. This investigation developed a blade frequency response function (FRF) method for describing the dynamic blade response. Once the …
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Construction and characterization of removable and reusable piezoelectric actuators
… For each attachment technique, we obtain the frequency response functions, actuator authority levels, and damping ratios. We also obtain the degradation of the actuator authority and damping ratio as the actuator is reused. For each attachment technique, we compare the measured performance to …
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Computational Modal Analysis of a Hydraulic Pump Support Structure for a Business Aircraft
… the support structure to the fuselage cabin. The frequency response functions were used to validate the finite element model via a visual and analytical comparison against experimental data. The preliminary model was constructed in Altair Hyperworks and a modal frequency response analysis was used …
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An Investigation to Detect Delamination in Composite Laminated Plates Under Dynamic Loading
… characteristics such as modal parameters and Frequency Response Functions (FRF).</p> <p>This study investigates locating delamination in composite laminate plates under dynamic loading utilizing accelerometers during dynamic response as an alternative structural health monitoring method in …
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Determination of Flame Dynamics for Unsteady Combustion Systems using Tunable Diode Laser Absorption Spectroscopy
… dynamics. Flame dynamics are defined as the response in heat release to acoustic perturbations. Models of flame dynamics can be coupled with models of combustor enclosure acoustics to predict TA instabilities. In addition, algorithms to actively control instabilities can be based on these …
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