A Performance Study of Controlled Impact Timing on Harmonics Reduction in Operational Modal Testing

Lim, Hong Cheet and Ong, Zhi Chao and Ismail, Zubaidah and Khoo, Shin Yee (2018) A Performance Study of Controlled Impact Timing on Harmonics Reduction in Operational Modal Testing. Journal of Dynamic Systems, Measurement, and Control, 141 (3). 034501. ISSN 0022-0434

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Official URL: https://doi.org/10.1115/1.4041609

Abstract

As an alternative to operational modal analysis and classical experimental modal analysis (EMA), a novel method was introduced previously, namely impact-synchronous modal analysis (ISMA). The effectiveness ISMA on rotor and structural dynamic systems has been proven in previous literature. More recently, an automated impact device (AID) was introduced which utilized tachometer pulse as initiation signal and its effectiveness on ISMA was proven. An attempt to further enhance this device in term of equipment and cost is then proposed by replacing the tachometer with the in-use tri-axial accelerometer through utilizing the filtered response of cyclic load component as an initiation signal to control the impact device, which is also the primary aim for this study. Prior to modal testing, accuracy of this device is illustrated at desired phase angles of 0 deg, 90 deg, 180 deg, and 270 deg. Subsequently, frequency response function (FRF) estimations obtained for ISMA using enhanced AID has demonstrated the suppression capabilities of this device on disturbances, i.e., reduction of 93.58% at 30 Hz and 57.78% at 60 Hz, resulting in a high correlation for signature assurance criterion (SAC) and cross signature assurance criterion (CSAC). Modal parameters extracted from the EMA and ISMA using impact device are presented and compared, for the first three natural modes of the test rig. It is found that natural frequencies are deviating by less than 6%, whereas modal assurance criterion (MAC) values between the mode shapes of the two tests are found to be above 0.9.

Item Type: Article
Uncontrolled Keywords: Frequency estimation; Frequency response; Structural dynamics; Tachometers; Timing circuits
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
T Technology > TJ Mechanical engineering and machinery
Divisions: Faculty of Engineering
Depositing User: Ms. Juhaida Abd Rahim
Date Deposited: 17 Jan 2019 03:30
Last Modified: 17 Jan 2019 03:30
URI: http://eprints.um.edu.my/id/eprint/20038

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