Frequency-Dependent Magnitude Bounds of the Generalized Frequency Response Functions for NARX Model

2009 ◽  
Vol 15 (1) ◽  
pp. 68-83 ◽  
Author(s):  
Xing Jian Jing ◽  
Zi Qiang Lang ◽  
Stephen A. Billings
Keyword(s):  
Frequency Response ◽  
Response Functions ◽  
Frequency Dependent ◽  
Frequency Response Functions ◽  
Narx Model

Spectral Finite Element Analysis of Sandwich Beams With Passive Constrained Layer Damping1

2002 ◽  
Vol 124 (3) ◽  
pp. 376-386 ◽  
Author(s):  
Gang Wang ◽  
Norman M. Wereley
Keyword(s):  
Finite Element ◽  
Frequency Response ◽  
Complex Modulus ◽  
Sandwich Beams ◽  
Response Functions ◽  
Frequency Dependent ◽  
Frequency Response Functions ◽  
Viscoelastic Core ◽  
Spectral Finite Element ◽  
Passive Constrained Layer Damping

We present a spectral finite element model (SFEM) for sandwich beams with passive constrained layer damping (PCLD) treatments. The viscoelastic core has a complex modulus that varies with frequency. The SFEM is formulated in the frequency domain using dynamic shape functions based on the exact displacement solutions from progressive wave methods, where we implicitly account for the frequency dependent complex modulus of the viscoelastic core. The SFEM results of natural frequencies and frequency response functions are compared to those calculated using conventional finite element (CFEM), where the Golla-Hughes-McTavish method is used to account for the frequency dependent complex modulus of a viscoelastic core. Also experimental data are used to validate both analyses using frequency response functions measured for two cantilevered sandwich beams with PCLD treatments having 50% and 75% coverage of the beam length. SFEM shows improved computational efficiency and accuracy, because many more elements must be incorporated into the CFEM for comparable accuracy.

scholarly journals Identification of relevant acoustic transfer paths for WT drivetrains with an operational transfer path analysis

2021 ◽  
Author(s):  
W. Schünemann ◽  
R. Schelenz ◽  
G. Jacobs ◽  
W. Vocaet
Keyword(s):  
Path Analysis ◽  
Wind Turbine ◽  
Frequency Response ◽  
Mechanical System ◽  
Reference Point ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Transfer Path ◽  
Transfer Path Analysis ◽  
Turbine Model

AbstractThe aim of a transfer path analysis (TPA) is to view the transmission of vibrations in a mechanical system from the point of excitation over interface points to a reference point. For that matter, the Frequency Response Functions (FRF) of a system or the Transmissibility Matrix is determined and examined in conjunction with the interface forces at the transfer path. This paper will cover the application of an operational TPA for a wind turbine model. In doing so the path contribution of relevant transfer paths are made visible and can be optimized individually.

Calculation of Component Mode Synthesis Matrices From Measured Frequency Response Functions, Part 2: Application

1998 ◽  
Vol 120 (2) ◽  
pp. 509-516 ◽  
Author(s):  
J. A. Morgan ◽  
C. Pierre ◽  
G. M. Hulbert
Keyword(s):  
Frequency Response ◽  
Coupled System ◽  
Companion Paper ◽  
Component Mode Synthesis ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Measured Frequency ◽  
Measured Frequency Response ◽  
Coupled Beams ◽  
The Individual

This paper demonstrates how to calculate Craig-Bampton component mode synthesis matrices from measured frequency response functions. The procedure is based on a modified residual flexibility method, from which the Craig-Bampton CMS matrices are recovered, as presented in the companion paper, Part I (Morgan et al., 1998). A system of two coupled beams is analyzed using the experimentally-based method. The individual beams’ CMS matrices are calculated from measured frequency response functions. Then, the two beams are analytically coupled together using the test-derived matrices. Good agreement is obtained between the coupled system and the measured results.

Experimental Study for Extraction of Normal Modes

1995 ◽  
Author(s):  
S. Y. Chen ◽  
M. S. Ju ◽  
Y. G. Tsuei
Keyword(s):  
Frequency Response ◽  
Normal Mode ◽  
Normal Modes ◽  
Measurement Data ◽  
Mode Shapes ◽  
Complex Frequency ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Incomplete System ◽  
Coupled Structures

Abstract A frequency-domain technique to extract the normal mode from the measurement data for highly coupled structures is developed. The relation between the complex frequency response functions and the normal frequency response functions is derived. An algorithm is developed to calculate the normal modes from the complex frequency response functions. In this algorithm, only the magnitude and phase data at the undamped natural frequencies are utilized to extract the normal mode shapes. In addition, the developed technique is independent of the damping types. It is only dependent on the model of analysis. Two experimental examples are employed to illustrate the applicability of the technique. The effects due to different measurement locations are addressed. The results indicate that this technique can successfully extract the normal modes from the noisy frequency response functions of a highly coupled incomplete system.

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