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

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.

Free Vibration Analysis of Circular Cylindrical Shells with Arbitrary Boundary Conditions by the Method of Reverberation-Ray Matrix

“…in which the physical significances and expressions of P ℎ ( ), a, and d are the same to those presented in (31). A and D are coefficient matrices of the arriving wave and the departing wave corresponding to the force and moment resultants of the shell.…”

“…Chen et al [30] presented an analytic method to analyze free and forced vibration characteristics of ring-stiffened combined conicalcylindrical shells with arbitrary boundary conditions. Li et al [31] investigated the influence on modal parameters of thin cylindrical shell under bolt looseness boundary. Yao et al [32] carried out the free vibration analysis of open circular cylindrical shells with either the two straight edges or the two curved edges simply supported and the remaining two edges supported by arbitrary classical boundary conditions based on the Donnell-Mushtari-Vlasov thin shell theory.…”

Investigation of the Influence of the Location of the Unified Mass on the Formed Vibrations of a Thin Containing Extended Shell

“…With the help of the software "Z-lab", fluctuations reflect the dependence of some parameters on others, in real time. The software "Z-lab" allows you to display and record oscillations in real time [13]. A block diagram of the experimental setup for carrying out the experiment is shown in Fig.…”

Influence of Non-uniform Parameter of Bolt Joint on Complexity of Frequency Characteristics of Cylindrical Shell

“…For bolted joined cylindrical shell structure, some literatures have been reported. Li et al [14] studied the mode frequency and shape of the thin cylindrical shell under bolt looseness boundary through the FE method and experimental test method. Qin et al [15] studied the influence of bolt loosening on the vibration of disk-drum rotor by nonlinear FE simulations and harmonic balance method.…”

“…Fourthly, the external excitation leads to the non-linear characteristic of the bolted joint [30]. Fifthly, bolt loosening can also cause the variation of the restraint stiffness [14]. And there are also lots of many other sources for the uncertainty characteristics of bolted joints [31], including random bolt distribution and random restraint stiffness distribution.…”