The Prediction of Substructure and System Modes by the Extended Complex Mode Indication Function

1998 ◽  
Vol 120 (3) ◽  
pp. 671-677
Author(s):  
A. C. Y. Lin ◽  
Y. G. Tsuei
Keyword(s):  
Frequency Response ◽  
Dynamical Behavior ◽  
Singular Value ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Complex Mode ◽  
System Equation ◽  
Modal Force ◽  
Extended Complex ◽  
Value Decomposition

Yee and Tsuei (1989) developed the Modal Force Technique (MFT) as a tool for component synthesis. The approach utilizes the frequency response functions at connecting joints to predict the dynamical behavior of a synthesized system. The main difference between the MFT and the traditional impedance modeling approach is that no inversion of the frequency response functions is required for the MFT, which makes the Model Force Technique more efficient. The other major feature is that the Modal Force matrix of the synthesized system equation contains the information of both the substructure and the system modes. To determine the natural frequency and the damping of a complex mode based on the frequency response functions, the Extended Complex Mode Indication Function (Extended CMIF) technique was developed. It performs the singular value decomposition (SVD) of the Modal Force matrix at each spectral line. The peaks of the singular value plot indicate the location of the substructure modes, while the anti-peaks show the location of the system modes. This approach is simple, straightforward and can be efficiently implemented to identify complex modes.

The Prediction of the Substructure and System Modes by the Extended Complex Mode Indication Function

1991 ◽  
Author(s):  
Albert C. Y. Lin ◽  
Y. G. Tsuei
Keyword(s):  
Boundary Conditions ◽  
Frequency Response ◽  
Natural Frequency ◽  
Dynamical Behavior ◽  
Response Functions ◽  
Complex Mode ◽  
Force Equation ◽  
Modal Force ◽  
Extended Complex ◽  
Geometric Compatibility

Abstract The Modal Force Technique (MFT) which directly works with the substructure frequency response functions at connecting joints to predict the dynamical behavior of the synthesized system has been recently developed. The key point of the MFT is to formulate the Modal Force equation by eliminating the physical coordinates and retaining the forces in accordance with the boundary conditions of geometric compatibility and forces equilibrium at connecting joints. The Modal Force matrix in the Modal Force equation contains the information of the substructure modes and the synthesized system modes. To predict the natural frequency and damping of the substructure and the synthesized system modes, an Extended Complex Mode Indication Function for MFT is investigated.

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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