Joint dynamic properties identification with partially measured frequency response function

2012 ◽  
Vol 27 ◽  
pp. 499-512 ◽  
Author(s):  
Mian Wang ◽  
Dong Wang ◽  
Gangtie Zheng
Keyword(s):  
Frequency Response ◽  
Response Function ◽  
Frequency Response Function ◽  
Dynamic Properties ◽  
Measured Frequency ◽  
Measured Frequency Response

scholarly journals Dynamic characterizations of underwater structures using noncontact vibration tests based on nanosecond laser ablation in water: evaluation of passive vibration suppression with damping materials

2017 ◽  
Vol 24 (16) ◽  
pp. 3714-3725 ◽  
Author(s):  
Naoki Hosoya ◽  
Itsuro Kajiwara ◽  
Koh Umenai ◽  
Shingo Maeda
Keyword(s):  
Frequency Response ◽  
Response Function ◽  
Frequency Response Function ◽  
Vibration Suppression ◽  
Pass Filter ◽  
Reliability Factor ◽  
Measured Frequency ◽  
Measured Frequency Response ◽  
Underwater Structure ◽  
Underwater Structures

Recently, the demand for higher performing underwater structures under diverse conditions has increased. Examples include improved precision and speed of the position control of robot manipulators. To prevent the control spillover problems when active controls are used, a control system is typically constituted with a low-pass filter to eliminate all modes except for the target modes. However, experimentally measuring the dynamic properties of an underwater structure in an environment where the structure and a fluid continuously influence each other is difficult. We have recently proposed a noncontact vibration testing method for dynamic characterizations of underwater structures in which the response to a laser ablation excitation force is measured by laser Doppler vibrometer. Integrating passive control using a vibration-damping material affixed onto the underwater structure and active control constituted with the low-pass filter may realize a more cost-effective system. To develop this combined control into a practical method, the reliability of the measured frequency response function must be validated. Additionally, the applicable frequency range must be expanded to encompass the high-frequency region (several tens of kHz) so that the vibration suppression quality of underwater structures can be evaluated. Herein we quantify the effect of random measurement errors on the measured frequency response function with a reliability factor based on the concept of coherence functions. Using the measured frequency response function with a reliability factor, we demonstrated that our method can evaluate passive vibration suppression effect of an underwater structure with a damping material in high-frequency ranges up to 20 kHz.

Response Prediction and Dynamic Substructuring for Coupled Structures in the Frequency Domain

2020 ◽  
Vol 36 (6) ◽  
pp. 867-879
Author(s):  
X. H. Liao ◽  
W. F. Wu ◽  
H. D. Meng ◽  
J. B. Zhao
Keyword(s):  
Frequency Response ◽  
Response Function ◽  
Frequency Response Function ◽  
Dynamic Properties ◽  
Main Idea ◽  
Prediction Method ◽  
Response Prediction ◽  
Synthesis Methods ◽  
Dynamic Substructuring ◽  
Coupled Structures

ABSTRACTTo evaluate the dynamic properties of a coupled structure based on the dynamic properties of its substructures, this paper investigates the dynamic substructuring issue from the perspective of response prediction. The main idea is that the connecting forces at the interface of substructures can be expressed by the unknown coupled structural responses, and the responses can be solved rather easily. Not only rigidly coupled structures but also resiliently coupled structures are investigated. In order to further comprehend and visualize the nature of coupling problems, the Neumann series expansion for a matrix describing the relation between the coupled and uncoupled substructures is also introduced in this paper. Compared with existing response prediction methods, the proposed method does not have to measure any forces, which makes it easier to apply than the others. Clearly, the frequency response function matrix of coupled structures can be derived directly based on the response prediction method. Compared with existing frequency response function synthesis methods, it is more straightforward and comprehensible. Through demonstration of two examples, it is concluded that the proposed method can deal with structural coupling problems very well.

Seismic Structural Damage Detection Based on Time Frequency Response Function

2011 ◽  
Vol 219-220 ◽  
pp. 243-249
Author(s):  
Bai Sheng Wang ◽  
Lie Sun ◽  
Zhi Wei Chang
Keyword(s):  
Frequency Response ◽  
Response Function ◽  
Structural Damage ◽  
Frequency Response Function ◽  
Dynamic Properties ◽  
Response Analysis ◽  
Central Frequency ◽  
Structural Dynamic ◽  
Time Frequency ◽  
Marginal Spectrum

Considering that Hilbert-Huang Transformation (HHT) can be used to analyze instantaneous frequency in structural dynamic analysis, this paper proposes the concept of HHT marginal spectrum based time frequency response function. It also defines “central frequency”, which is used to reflect the change of structural dynamic properties during earthquakes, and discloses time-varying development of seismic structural damage. Using a three-story shear frame model, which is subjected to the El Centro seismic wave, the HHT time frequency response analysis of its acceleration response has been made, results show that the adoption of central frequency can successfully indicate the damage inception instant and its development.

Derivation of road noise improvement factor within a suspension system using the inverse substructuring method

2019 ◽  
Vol 233 (14) ◽  
pp. 3775-3786 ◽  
Author(s):  
Yeon June Kang ◽  
Jun Gu Kim ◽  
David P Song ◽  
Kang Duck Ih
Keyword(s):  
Frequency Response ◽  
Response Function ◽  
Frequency Response Function ◽  
Dynamic Properties ◽  
Dynamic Stiffness ◽  
The Body ◽  
Road Noise ◽  
Input Force ◽  
Improvement Factor ◽  
Cross Member

This research aims to develop a method to efficiently reduce the body input force from the chassis due to road-induced excitation. To this end, the frequency response function–based substructuring method is employed to model the vehicle cross member and coupling points. Using this model, the dynamic stiffness modification factor of elastic bushing at the effective path is predicted for reducing road noise. Because of the difficulties in directly obtaining dynamic properties of body mount bushings pressured into the sub-frame, the frequency response function–based substructuring model and inverse formulation method are used to indirectly estimate the bushing’s dynamic properties. Therefore, the primary focus of this study is to validate the feasibility of using the inverse formulation method for deriving road noise improvement factor on a simple cross member application. In this feasibility validation, road excitation is simply substituted with a shaker excitation in vertical direction. The previously developed suspension rig that enables a direct measurement of the body input force at the coupling points and the specially developed cross member jig are used for the validation test.

Damage Detection of Steel Beam Using Frequency Response Function Measurement Data and Fractal Dimension

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Eun-Taik Lee ◽  
Hee-Chang Eun
Keyword(s):  
Fractal Dimension ◽  
Frequency Response ◽  
Response Function ◽  
Frequency Response Function ◽  
Measurement Data ◽  
Fractal Dimensions ◽  
Dynamic Responses ◽  
Steel Beam ◽  
Health State ◽  
Measured Frequency Response

Fractal-dimension-based signal processing has been extensively applied to various fields for nondestructive testing. The dynamic response signal can be utilized as an analytical tool to evaluate the structural health state without baseline data. The fractal features of the dynamic responses with fractal dimensions (FDs) were investigated using the Higuchi, Katz, and Sevcik methods. The waveform FD proposed by these methods was extracted from the measured frequency response function (FRF) data in the frequency domain. Damage was observed within this region, which resulted in an abrupt change in the curvature of the FD. The effectiveness of the methods was investigated via the results of a steel beam test and a numerical experiment to detect damage.

scholarly journals Using vibroacoustic methods to describe the dynamic properties of composite elements to assess their technical condition

Rail Vehicles ◽  
2021 ◽  
pp. 41-51
Author(s):  
Daniel Mokrzan ◽  
Julia Milewicz ◽  
Grzegorz Szymański
Keyword(s):  
Frequency Response ◽  
Response Function ◽  
Frequency Response Function ◽  
Dynamic Properties ◽  
Technical Condition

W artykule zaprezentowano przebieg badań oraz analizę dotyczącą możliwości wykorzystania ciśnienia akustycznego jako parametru diagnostycznego w ocenie stanu technicznego elementów wykonanych z materiałów kompozytowych. Przeprowadzono eksperyment w postaci testu impulsowego z wykorzystaniem młotka modalnego jako wzbudnika odpowiedzi wibroakustycznej układu. Wykazano, że duże wewnętrzne ubytki w strukturze powodują zmiany charakterystyki funkcji odpowiedzi częstotliwościowej (Frequency Response Function, FRF) w paśmie poniżej 8 kHz. W wyniku przeprowadzonej analizy udowodniono, że ciśnienie akustyczne może być skutecznie wykorzystywane w diagnozie elementów wykonanych z materiałów kompozytowych.

Secondary Path Estimation by PCA-Compressed Frequency Response Function in Active Vibration Control

2011 ◽  
Vol 66-68 ◽  
pp. 721-726
Author(s):  
Xin Hui Li ◽  
Tie Jun Yang ◽  
Jian Chao Dong ◽  
Ze Qi Lu
Keyword(s):  
Vibration Control ◽  
Frequency Response ◽  
Response Function ◽  
Frequency Response Function ◽  
Active Vibration Control ◽  
Principal Component ◽  
Good Control ◽  
Noise Elimination ◽  
Measured Frequency Response ◽  
Active Vibration

The FXLMS algorithm is widely used in active vibration control system. The estimation of secondary path plays very important roles in such a system. This paper presents an experimental investigation of effective secondary path estimation in active vibration control using measured Frequency Response Function (FRF). Principal component analysis (PCA) is pursued to the measured FRF for noise elimination, and then the PCA-compressed FRF data are used for secondary path estimation. The control results indicate that the proposed method has good control performance.

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