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.
Results
Showing 1 to 20 of 49 for “"frequency response function"”.
-
Damage detection in structures using measured frequency response function data
Modern engineering structures such as offshore oil platforms, transmission towers, bridges and aircraft frames are regularly monitored and maintained in order to avert catastrophic failure. Despite our best efforts, sporadic failures, which may have disastrous consequences in terms of human life …
-
Damage detection in structures using frequency response function (FRF) data and finite element modelling
… a method to detect structural damage using frequency response function (FRF) data obtained from non-destructive vibration tests. The method is used to study cases of early structural damage in which there is no appreciable change in mass and damping. The resulting change in structural …
-
Confidence bands, measurement noise, and multiple input - multiple output measurements using three-channel frequency response function estimator
A three-channel Frequency Response Function (FRF) estimator is discussed and statistical relations developed. Methods for estimating the variance of the FRF magnitude and levels of uncorrelated content in the test signals are developed. FRF magnitude variance estimates allow ’confidence bands’ to …
-
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 …
-
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 …
-
System modeling and modification via modal analysis
… also presented. The resonance specification and frequency response function synthesis are two useful techniques that aid in system modification and are, therefore, included. A resonant peak can be shifted to another frequency by making certain modifications to the structure, thus avoiding …
-
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 …
-
A method of characterisation of the nonlinear vibration transmissibility of cushioning materials
… to the repetitive application of stresses. The response behaviour of cushioning or protective packaging materials under vibration excitation is central to the effective design of product packaging. The response characteristics of the cushioning material guide the design parameters of the …
-
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 …
-
Experimental Identification of Nonlinear Systems
… parameters of a model approximating the response of a cantilevered beam by a single mode. The model accounts for cubic inertia and stiffness nonlinearities and quadratic damping. The method of multiple scales is used to determine the frequency-response function for the system. …
-
Determining the moderator temperature coefficient in a PWR by stochastic fluctuation analysis
… the coolant temperature. Results show that the frequency response function between the in-core neutron flux and thermocouple signals is proportional to the MTC and can be used to monitor changes in the MTC throughout the fuel cycle. An analytical model is also formulated and used to investigate …
-
Modeling and Estimation of Linear and Nonlinear Piezoelectric Systems
… out the resonant peaks in a host structure's frequency domain. Further, they provide adaptability through shunt tuning, which gives them the ability to recover performance losses because of structural parameter errors. This dissertation studies the derivation of governing equations that result …
-
Effects of Bottom Chord Extensions on the Static and Dynamic Performance of Steel Joist Supported Floors
… bottom chord extensions on deflections, natural frequency, damping, mode shape and effective mass, extensive analytical and experimental studies were conducted on single span and three span joist supported laboratory footbridges with different bottom chord extension configurations. Finite element …
-
Characterization of Oscillatory Lift in MFC Airfoils
… purpose of this research is to characterize the response of an airfoil with an oscillatory morphing, Macro-fiber composite (MFC) trailing edge. Correlation of the airfoil lift with the oscillatory input is presented. Modal analysis of the test airfoil and apparatus is used to determine the …
-
An improved method for estimating the moderator temperature coefficient of pressurized water reactors using multivariate autoregression
… fluctuations in the in-core neutron flux. The frequency response function between these two stochastic signals has been shown to be proportional to the moderator temperature coefficient. Though this method has been shown to agree well with reactor core design and measured values of the MTC, the …
-
A modal analysis method for a lumped parameter model of a dynamic fluid system
… analysis introduces terms such as the natural frequency, damping ratio and the frequency response function. For the analysis of more complex mechanical systems the topic of modal analysis is introduced. Proceeding in a manner analogous to that of the review of the mechanical system, the lumped …
-
Optimisation of variable helix end milling tools
… milling chatter is strongly influenced by the frequency response function of the dynamic system, a preliminary study is first presented to assess the feasibility of non-contacting electromagnetic modal analysis for milling tools. It is shown that this approach shows some promise for use in real …
-
Towards a Self-Powered Structural Health Monitoring Smart Tire
… were conducted. Finally, the theoretical voltage frequency response function obtained from the theoretical piezoelectric constant and dielectric constant of a single ZnO nanowire were compared to the experimental voltage frequency response function. The discrepancies were discussed.
-
Development of a Virtual Acoustic Showroom for Simulating Listening Environments and Audio Speakers
… the image source method, and simulating speaker responses using inverse filtering. The image source method is used to simulate realistic living environments by filtering the environment impulse response by frequency-dependant absorption coefficients of typical building materials. Psychoacoustic …
-
Using Vibration Analysis to Determine Refrigerant Levels In an Automotive Air Conditioning System
… is based on the hypothesis that the natural frequency of the accumulator bottle is a function of the mass of refrigerant in the system. Applying this theory to a working automotive air conditioning bench test rig involved using the roving hammer method—forcing the structure with an impact …
Page 1 of 3