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CLC number: O32

On-line Access: 2017-01-24

Received: 2015-12-31

Revision Accepted: 2016-03-15

Crosschecked: 2016-11-08

Cited: 1

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Citations:  Bibtex RefMan EndNote GB/T7714


Zhi Chao Ong


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Journal of Zhejiang University SCIENCE A 2017 Vol.18 No.2 P.92-105


Assessment of the phase synchronization effect in modal testing during operation

Author(s):  Zhi Chao Ong, Hong Cheet Lim, Shin Yee Khoo, Zubaidah Ismail, Keen Kuan Kong, Abdul Ghaffar Abdul Rahman

Affiliation(s):  Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia; more

Corresponding email(s):   zhichao83@gmail.com, alexongzc@um.edu.my

Key Words:  Experimental modal analysis, Vibration, Impact-synchronous modal analysis (ISMA), Impact-synchronous time averaging (ISTA), Modal testing, Phase synchronization

Zhi Chao Ong, Hong Cheet Lim, Shin Yee Khoo, Zubaidah Ismail, Keen Kuan Kong, Abdul Ghaffar Abdul Rahman. Assessment of the phase synchronization effect in modal testing during operation[J]. Journal of Zhejiang University Science A, 2017, 18(2): 92-105.

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journal="Journal of Zhejiang University Science A",
publisher="Zhejiang University Press & Springer",

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%T Assessment of the phase synchronization effect in modal testing during operation
%A Zhi Chao Ong
%A Hong Cheet Lim
%A Shin Yee Khoo
%A Zubaidah Ismail
%A Keen Kuan Kong
%A Abdul Ghaffar Abdul Rahman
%J Journal of Zhejiang University SCIENCE A
%V 18
%N 2
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%D 2017
%I Zhejiang University Press & Springer
%DOI 10.1631/jzus.A1600003

T1 - Assessment of the phase synchronization effect in modal testing during operation
A1 - Zhi Chao Ong
A1 - Hong Cheet Lim
A1 - Shin Yee Khoo
A1 - Zubaidah Ismail
A1 - Keen Kuan Kong
A1 - Abdul Ghaffar Abdul Rahman
J0 - Journal of Zhejiang University Science A
VL - 18
IS - 2
SP - 92
EP - 105
%@ 1673-565X
Y1 - 2017
PB - Zhejiang University Press & Springer
ER -
DOI - 10.1631/jzus.A1600003

The impact-synchronous modal analysis (ISMA), which uses impact-synchronous time averaging (ISTA), allows modal testing to be performed during operation. ISTA is effective in filtering out the non-synchronous cyclic load component, its harmonics, and noises. However, it was found that at operating speeds that coincide with the natural modes, ISMA would require a high number of impacts to determine the dynamic characteristics of the system. This finding has subsequently reduced the effectiveness and practicality of ISMA. Preservation of signatures during ISTA depends on the consistency of their phase angles on every time block but not necessarily on their frequencies. Thus, the effect of phase angles with respect to impact is seen to be a very important parameter when performing ISMA on structures with dominant periodic responses due to cyclic load and ambient excitation. The responses from unaccounted forces that contain even the same frequency as that contained in the response due to impact are diminished with the least number of impacts when the phase of the periodic responses is not consistent with the impact signature for every impact applied. The assessment showed that a small number of averages are sufficient to eliminate the non-synchronous components with 98.48% improvement on simulation and 95.22% improvement on experimental modal testing when the phase angles with respect to impact are not consistent for every impact applied.

The paper discusses the importance of the phase of cyclic load components (relative to the instant of impact) to be averaged out using Impact Synchronous Time Averaging (ISTA) modal testing, especially when the operating speeds coincide with natural frequencies. It is pretty obvious that the phase of the cyclic loads is important, when trying to cancel them by averaging a sufficient number. So the main contribution of the paper is quantifying how few averages are really required to cancel the cyclic load component, if the phasing is specially chosen. This becomes evident only near the end of the paper, where an automatic impact device is suggested.




Darkslateblue:Affiliate; Royal Blue:Author; Turquoise:Article


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