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.

scholarly journals A Noise Level Prediction Method Based on Electro-Mechanical Frequency Response Function for Capacitors

PLoS ONE ◽  
2013 ◽  
Vol 8 (12) ◽  
pp. e81651 ◽  
Author(s):  
Lingyu Zhu ◽  
Shengchang Ji ◽  
Qi Shen ◽  
Yuan Liu ◽  
Jinyu Li ◽  
...  
Keyword(s):  
Frequency Response ◽  
Response Function ◽  
Noise Level ◽  
Frequency Response Function ◽  
Prediction Method

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.

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.

scholarly journals Road Roughness Estimation Based on the Vehicle Frequency Response Function

Actuators ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 89
Author(s):  
Qingxia Zhang ◽  
Jilin Hou ◽  
Zhongdong Duan ◽  
Łukasz Jankowski ◽  
Xiaoyang Hu
Keyword(s):  
Frequency Response ◽  
Response Function ◽  
Frequency Response Function ◽  
Gaussian White Noise ◽  
Estimation Method ◽  
Time Shift ◽  
Ride Quality ◽  
The Road ◽  
Road Roughness ◽  
Measured Response

Road roughness is an important factor in road network maintenance and ride quality. This paper proposes a road-roughness estimation method using the frequency response function (FRF) of a vehicle. First, based on the motion equation of the vehicle and the time shift property of the Fourier transform, the vehicle FRF with respect to the displacements of vehicle–road contact points, which describes the relationship between the measured response and road roughness, is deduced and simplified. The key to road roughness estimation is the vehicle FRF, which can be estimated directly using the measured response and the designed shape of the road based on the least-squares method. To eliminate the singular data in the estimated FRF, the shape function method was employed to improve the local curve of the FRF. Moreover, the road roughness can be estimated online by combining the estimated roughness in the overlapping time periods. Finally, a half-car model was used to numerically validate the proposed methods of road roughness estimation. Driving tests of a vehicle passing over a known-sized hump were designed to estimate the vehicle FRF, and the simulated vehicle accelerations were taken as the measured responses considering a 5% Gaussian white noise. Based on the directly estimated vehicle FRF and updated FRF, the road roughness estimation, which considers the influence of the sensors and quantity of measured data at different vehicle speeds, is discussed and compared. The results show that road roughness can be estimated using the proposed method with acceptable accuracy and robustness.

scholarly journals Predicting Dam Flood Discharge Induced Ground Vibration with Modified Frequency Response Function

Water ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 144
Author(s):  
Yan Zhang ◽  
Jijian Lian ◽  
Songhui Li ◽  
Yanbing Zhao ◽  
Guoxin Zhang ◽  
...  
Keyword(s):  
Frequency Response ◽  
Frequency Distribution ◽  
Response Function ◽  
Frequency Response Function ◽  
Ground Vibration ◽  
Vibration Source ◽  
Ground Vibrations ◽  
High Energies ◽  
Flood Discharge ◽  
Opening Method

Ground vibrations induced by large flood discharge from a dam can damage surrounding buildings and impact the quality of life of local residents. If ground vibrations could be predicted during flood discharge, the ground vibration intensity could be mitigated by controlling or tuning the discharge conditions by, for example, changing the flow rate, changing the opening method of the orifice, and changing the upstream or downstream water level, thereby effectively preventing damage. This study proposes a prediction method with a modified frequency response function (FRF) and applies it to the in situ measured data of Xiangjiaba Dam. A multiple averaged power spectrum FRF (MP-FRF) is derived by analyzing four major factors when the FRF is used: noise, system nonlinearity, spectral leakages, and signal latency. The effects of the two types of vibration source as input are quantified. The impact of noise on the predicted amplitude is corrected based on the characteristics of the measured signal. The proposed method involves four steps: signal denoising, MP-FRF estimation, vibration prediction, and noise correction. The results show that when the vibration source and ground vibrations are broadband signals and two or more bands with relative high energies, the frequency distribution of ground vibration can be predicted with MP-FRF by filtering both the input and output. The amplitude prediction loss caused by filtering can be corrected by adding a constructed white noise signal to the prediction result. Compared with using the signal at multiple vibration sources after superimposed as input, using the main source as input improves the accuracy of the predicted frequency distribution. The proposed method can predict the dominant frequency and the frequency bands with relative high energies of the ground vibration downstream of Xiangjiaba Dam. The predicted amplitude error is 9.26%.

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