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Showing 1 to 20 of 21 for “"Frequency Response Function (FRF)"”.
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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 …
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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 …
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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 …
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Noise transmission path identification in a reciprocating freon compressor
… the shell, were used in a multiple reference frequency response function (FRF) analysis with the sound pressure from an external microphone as the reference output. The multiple reference FRF analysis indicates that the suspension springs are the dominant noise transmission path in this …
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High resolution modal analysis using poles obtained at a single location
… estimates the structure’s poles from a high frequency density, driving point frequency response function (FRF) measured with an accelerometer. Mode vectors are estimated from low frequency density, tightly spaced FRFs measured with a scanning laser velocimeter (SLV) using the poles estimated …
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Laser-based broad-band spatially dense automated data acquisition system
… The acquisition system interfaces an SLDV to a frequency analyzer and a Silicon Graphics Crimson workstation. The system allows the user to specify the frequency range, scanning area, and spatial density. The system moves the laser beam, collects and downloads data for the specified area and …
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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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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 …
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Experimental Damage Diagnosis of a Model Three-Story Spatial Frame
… modal decomposition on experimental tap test responses. The natural frequencies and mode shapes of the structure established an as-built baseline for comparison to ten other scenarios with removed bracing. Once modal properties for each case were determined, six unique damage indicators were …
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Adaptive feedforward control of broadband structural vibration
… infinite systems undergoing single and multiple-frequency excitations. Control of broadband noise and vibration has also been reported, but it tends to be limited to infinite and semi-infinite systems. Here, four new adaptive feedforward control algorithms were developed for attenuating the …
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Evaluation of analytical and experimental methods to predict constrained layer damping behavior
… comparison for damping estimation and resonant frequency prediction was performed between finite element analysis (FEA) Ross, Kerwin, and Ungar theory (RKU), developed moment predicted loss factor, and experimental results. Investigated design parameters include; treatment application length and …
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System Level Black-Box Models for DC-DC Converters
… is collected from unterminated experimental frequency response function (FRF) measurements performed at the converter power terminals. These transfer funtions are known as audiosuceptibility, back current gain, output impedance, and input admittance. The measurements are called unterminated …
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Physics-guided Machine Learning for Condition Assessment of Building Structures in Operational Environments
… is critical for ensuring the safety and functionality of building structures, yet existing methods face significant challenges, including data scarcity, noise contamination, and limited generalisation across diverse operational environments. Traditional machine learning-based approaches …
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Adjustable Frequency Bandgap for Seismic Vibration Isolation of MRE-Based Metamaterial Foundations
… system, and hence reduce the vibration response of the superstructure and prevent the structures from seismic damage and collapse. Although the conventional seismic isolation system has been used for several decades, it cannot prevent earthquake vibrations in the vertical direction. …
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Predictive Simulations of the Impedance-Matched Multi-Axis Test Method Using Data-Driven Modeling
… models by fitting smooth, continuous basis functions to a subset of frequency response function (FRF) measurements from a dynamical system. The resulting fitted basis functions can be sampled at any geometric location to approximate the expected FRF at that location. The research presented …
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Dynamic Testing of In-Situ Composite Floors and Evaluation of Vibration Serviceability Using the Finite Element Method
… floors to estimate their dynamic parameters/response and to identify trends in dynamic behavior, and development of a set of fundamental finite element (FE) modeling techniques to adequately represent the dynamic response of steel composite floors for the purpose of evaluating vibration …
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Monitoring railway rail roughness using on-train vibration measurements
… from axle-box acceleration (ABA) using a frequency-response function (FRF) that describes the dynamic behaviour of the vehicle-track system, accounting for variations in vehicle speed that otherwise affect ABA. The FRF is derived from the receptances of the track and vehicle, both of which …
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Accuracy Improvement in Robotic Milling Through Data-Driven Modelling and Control
… parameters of a 6-dof industrial robot as a function of its arm configuration is presented. The GPR model is found to be capable of predicting the robot’s dominant natural frequency of vibration, stiffness, and damping coefficient in its workspace with root mean squared errors of 3.31 Hz, 150 …
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A Computational Fluid Dynamics Investigation of Thermoacoustic Instabilities in Premixed Laminar and Turbulent Combustion Systems
… that both the acoustics of the system, and a frequency-resolved response of the combustion process to incoming perturbations be understood. Currently, a system-level approach is being used widely to predict the thermoacoustic instabilities. This approach requires simple, yet accurate models …
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Novel Auxiliary Fixture System to Enhance Milled Thin-Walled Parts Quality
Due to the high flexibility of thin-walled workpieces, vibrations are a common problem when milling thin-walled workpieces. Vibrations lead to poor surface finish and reduced machining efficiency. Employing multi-pin fixtures to increase the damping and stiffness of the vibration modes of the …
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