• Title, Summary, Keyword: Frequency Response Analysis

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Model Order Reduction for Mid-Frequency Response Analysis (중주파수 응답해석을 위한 축소 기법)

  • Ko, Jin-Hwan
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.135-138
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    • 2009
  • Most of the studies use model order reduction for low frequency (LF) response analysis due to their high computational efficiency. In LF response analysis, one of model order reduction, algebraic substructuring (AS) retains all LF modes when using the modal superposition. However, in mid-frequency (MF) response analysis, the LF modes make very little contribution and also increase the number of retained modes, which leads to loss of computational efficiency. Therefore, MF response analysis should consider low truncated modes to improve the computational efficiency. The current work is focused on improving the computational efficiency using a AS and a frequency sweep algorithm. Finite element simulation for a MEMS resonator array showed that the performance of the presented method is superior to a conventional method.

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A Study on Analysis of Frequency Response with Hydraulic Circuit Analysis Module (유압 회로 해석 모듈을 이용한 주파수 응답 해석에 관한 연구)

  • 전봉근;송창섭;이용주
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.581-584
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    • 1995
  • The frequency response of a electro-hydraulic servo(EHS) system is studied. The frequensy response characteristics of the EHS system obtained by linerization method, nonlinerar simulation method, and experimentation are compared ane another. It is found that the frequency response of the EHS is consistent when input signal applied is very small, but that is deviated as input signal becomes large.

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Probabilistic study of the influence of ground motion variables on response spectra

  • Yazdani, Azad;Takada, Tsuyoshi
    • Structural Engineering and Mechanics
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    • v.39 no.6
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    • pp.877-893
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    • 2011
  • Response spectra of earthquake ground motions are important in the earthquake-resistant design and reliability analysis of structures. The formulation of the response spectrum in the frequency domain efficiently computes and evaluates the stochastic response spectrum. The frequency information of the excitation can be described using different functional forms. The shapes of the calculated response spectra of the excitation show strong magnitude and site dependency, but weak distance dependency. In this paper, to compare the effect of the earthquake ground motion variables, the contribution of these sources of variability to the response spectrum's uncertainty is calculated by using a stochastic analysis. The analytical results show that earthquake source factors and soil condition variables are the main sources of uncertainty in the response spectra, while path variables, such as distance, anelastic attenuation and upper crust attenuation, have relatively little effect. The presented formulation of dynamic structural response in frequency domain based only on the frequency information of the excitation can provide an important basis for the structural analysis in some location that lacks strong motion records.

A high Efficient Solver for High-Frequency Response Analysis of MEMS Resonators (MEMS 공진기의 고주파 응답해석을 위한 고효율 해석기)

  • Ko, Jin-Hwan;Bai, Zhaojun
    • Proceedings of the KSME Conference
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    • pp.467-472
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    • 2007
  • A modern MEMS resonator is a micro-scale structure operated over a high frequency range. In order to predict its resonant behavior in a design process, High-frequency response analysis (Hi-FRA) is demanded. Algebraic substructuring (AS) is known as a fast numerical technique to construct an eigenspace for FR and frequency sweep (FS) algorithm efficiently solves the frequency response system projected on the eigenspace. However, the existing FS algorithm using AS is developed for low-FRA, say over the range 1Hz-2KHz. In this work, we extend the FS algorithm using AS for FRA over an arbitrary frequency range. Therefore, it can be efficiently applied to systems operated at a high frequency, say over the range 230MHz-250MHz. The success of the proposed method is demonstrated by Hi-FRA of a checkerboard resonator.

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A study on nonlinear seismic response analysis of building considering frequency dependent soil impedance in time domain

  • Nakamura, Naohiro
    • Interaction and multiscale mechanics
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    • v.2 no.1
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    • pp.91-107
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    • 2009
  • In order to accurately estimate the seismic behavior of buildings, it is important to consider both nonlinear characteristics of the buildings and the frequency dependency of the soil impedance. Therefore, transform methods of the soil impedance in the frequency domain to the impulse response in the time domain are needed because the nonlinear analysis can not be carried out in the frequency domain. The author has proposed practical transform methods. In this paper, seismic response analyses considering frequency dependent soil impedance in the time domain are shown. First, the formulation of the proposed transform methods is described. Then, the linear and nonlinear earthquake response analyses of a building on 2-layered soil were carried out using the transformed impulse responses. Through these analyses, the validity and efficiency of the methods were confirmed.

Research on Frequency Average Analysis of vibrational Power Flow Analysis (진동파워흐름해석의 주파수 평균해석에 대한 연구)

  • Lee, Jea-Min;Hong, Suk-Yoon;Park, Young-Ho
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.971-977
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    • 2005
  • Power Flow Analysis (PFA) is developed for the effective predictions of frequency-averaged vibrational response in medium-to-high frequency ranges. In PFA, the power coefficients of semi-infinite structure and for-field energy density are used to predict the vibrational responses of structures. Generally, at high frequencies, PFA can predict narrow-band frequency-averaged vibrational responses of built-up structures. However, in low- to medium frequency ranges, the dynamic responses obtained by PFA represent broad-band frequency-averaged vibrational energy densities. For the prediction of vibrational response variance in Power Flow Finite Element Method (PFFEM), the variances of input power and joint element matrix describing structural coupling relationship are derived. Finally, for the validity of developed formulation, numerical examples for two co-planer plates are performed and the vibrational response variance of the structure are compared with the results of classical and PFFEM solutions.

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Application of frequency domain analysis for generation of seismic floor response spectra

  • Ghosh, A.K.
    • Structural Engineering and Mechanics
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    • v.10 no.1
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    • pp.17-26
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    • 2000
  • This paper presents a case study with a multi-degree-of-freedom (MDOF) system where the Floor Response Spectra (FRS) have been derived from a large ensemble of ground motion accelerograms. The FRS are evaluated by the frequency response function which is calculated numerically. The advantage of this scheme over a repetitive time-history analysis of the entire structure for each accelerogram of the set has been highlighted. The present procedure permits generation of FRS with a specified probability of exceedence.

Investigation of the Cause of High Vibration in a Low Pressure Turbine Casing with Manufacturing Defects by Frequency Response Analysis (주파수 응답해석을 통한 제작공차를 가지는 저압터빈 케이싱의 고진동 원인 규명)

  • Youn, Hee-Chul;Woo, Chang-Ki;Hwang, Jai-Kon
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.24 no.4
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    • pp.463-468
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    • 2015
  • High vibration of a low pressure (LP) turbine casing caused safety problems and life at the facility it was housed in. The main focus of this study was the cause of the high vibration in a low pressure turbine casing with manufacturing defects by frequency response analysis, compared with the results of experiments. Therefore, excited accelerations were obtained from the LP casing fundamental, and frequency responses were analyzed. The measurement and the modal analysis showed that the natural frequency of the LP turbine casing was 61.26 Hz and the excited frequency of the turbine rotor was 60.25 Hz. The manufacturing defect caused a decrease in the casing natural frequency and resulted in the high vibration of the casing because it moved close to the resonant frequency.

Frequency response of film casting process

  • Hyun, Jae-Chun;Lee, Joo-Sung;Jung, Hyun-Wook
    • Korea-Australia Rheology Journal
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    • v.15 no.2
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    • pp.91-96
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    • 2003
  • The sensitivity of the product to the ongoing sinusoidal disturbances of the process has been investigated in the film casting of viscoelastic polymer fluids using frequency response analysis. As demonstrated for fiber spinning process (Jung et al., 2002; Devereux and Denn, 1994), this frequency response analysis is useful for examining the process sensitivity and the stability of extensional deformation processes including film casting. The results of the present study reveal that the amplification ratios or gains of the process/product variables such as the cross-sectional area at the take-up to disturbances exhibit resonant peaks along the frequency regime as expected for the systems having hyperbolic characteristics with spilt boundary conditions (Friedly, 1972). The effects on the sensitivity results of two important parameters of film casting, i.e., the fluid viscoelasticity and the aspect ratio of the casting equipment have been scrutinized. It turns out that depending on the extension thinning or thickening nature of the fluid, increasing viscoelasticity results in enlargement or reduction of the sensitivity, respectively. As regards the aspect ratio, it has been found that an optimum value exists making the system least sensitive. The present study also confirms that the frequency response method produces results that corroborate well those by other methods like linear stability Analysis and transient solutions response. (Iyengar and Co, 1996; Silagy et al., 1996; Lee and Hyun, 2001).

Seismic response analysis of layered soils considering effect of surcharge mass using HFTD approach. Part II: Nonlinear HFTD and numerical examples

  • Saffarian, Mohammad A.;Bagheripour, Mohammad H.
    • Geomechanics and Engineering
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    • v.6 no.6
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    • pp.531-544
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    • 2014
  • Studies of earthquakes over the last 50 years and the examination of dynamic soil behavior reveal that soil behavior is highly nonlinear and hysteretic even at small strains. Nonlinear behavior of soils during a seismic event has a predominant role in current site response analysis approaches. Common approaches to ground response analysis include linear, equivalent linear and nonlinear methods. These methods of ground response analysis may also be categorized into time domain and frequency domain concepts. Simplicity in developing analytical relations and accuracy in considering soils' dynamic properties dependency to loading frequency are benefits of frequency domain analysis. On the other hand, nonlinear methods are complicated and time consuming mainly because of their step by step integrations in time intervals. In part Ι of this paper, governing equations for seismic response analysis of surcharged and layered soils were developed using fundamental of wave propagation theory based on transfer function and boundary conditions. In this part, nonlinear seismic ground response is analyzed using extended HFTD method. The extended HFTD method benefits Newton-Raphson procedure which applies regular iterations and follows soils' fundamental stress-strain curve until convergence is achieved. The nonlinear HFTD approach developed here are applied to some examples presented in this part of the paper. Case studies are carried in which effects of some influencing parameters on the response are investigated. Results show that the current approach is sufficiently accurate, efficient, and fast converging. Discussions on the results obtained are presented throughout this part of the paper.