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Shock and Vibration
Volume 2016, Article ID 4709257, 15 pages
http://dx.doi.org/10.1155/2016/4709257
Research Article

The Influence on Modal Parameters of Thin Cylindrical Shell under Bolt Looseness Boundary

School of Mechanical Engineering and Automation, Northeastern University, No. 3-11 Wenhua Road, Heping District, Shenyang 110819, China

Received 20 July 2015; Revised 3 October 2015; Accepted 5 October 2015

Academic Editor: Daniel Morinigo-Sotelo

Copyright © 2016 Hui Li et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The influence on modal parameters of thin cylindrical shell (TCS) under bolt looseness boundary is investigated. Firstly, bolt looseness boundary of the shell is divided into two types, that is, different bolt looseness numbers and different bolt looseness levels, and natural frequencies and mode shapes are calculated by finite element method to roughly master vibration characteristics of TCS under these conditions. Then, the following measurements and identification techniques are used to get precise frequency, damping, and shape results; for example, noncontact laser Doppler vibrometer and vibration shaker with excitation level being precisely controlled are used in the test system; “preexperiment” is adopted to determine the required tightening torque and verify fixed constraint boundary; the small-segment FFT processing technique is employed to accurately measure nature frequency and laser rotating scanning technique is used to get shape results with high efficiency. Finally, based on the measured results obtained by the above techniques, the influence on modal parameters of TCS under two types of bolt looseness boundaries is analyzed and discussed. It can be found that bolt looseness boundary can significantly affect frequency and damping results which might be caused by changes of nonlinear stiffness and damping and in bolt looseness positions.