Dynamic Stability of a Sandwich Beam Subjcte to Parametric Excitaion

By: Mahanta, LaxmiContributor(s): Mohanty, S C [Supervisor] | Department of Mechanical EngineeringMaterial type: TextTextLanguage: English Publisher: 2006Description: 63 pSubject(s): Engineering and Technology | Mechanical Engineering | Structural AnalysisOnline resources: Click here to access online Dissertation note: Thesis (M.Tech (R))- National Institute of Technology, Rourkela Summary: Vibration control of machines and structures incor porating viscoelastic materials in suitable arrangement is an impor tant aspect of investigation. The use of viscoelastic layers constrained between el astic layers is known to be effective for damping of flexural vibrations of structures over a wide ra nge of frequencies. The energy dissipated in these arrangements is due to shear deformation in the viscoelastic layers, which occurs due to flexural vibration of th e structures. Multilayered cantilever sandwich beam like structures can be used in aircrafts and other applications such as robot arms for effective vibration control. These members may experience parametric instability when subjected to time dependant forces. The theo ry of dynamic stability of elastic systems deals with the study of vibrations induced by pulsating loads that are parametric with respect to certain forms of deformation The purpose of the present work is to i nvestigate the dynamic stability of a three layered symmetric sandwich beam subjected to an end periodic axial force . Equations of motion are derived using finite element method. The regions of instability for simple and combination resonances are established us ing modified Hsu’s method proposed by Saito and Otomi[76]. It is observed that with increase in core thickness parameter fundamental buckling load increases. The fundamental resonant frequency and second mode frequency parameter also increase with increase in core thickness parameter. Fundamental loss factor and second mode loss factor also increase with increase in core thickness parameter.Increase in core thickness parameter enhances the stability of the beam. With increase in core loss factor also the stab ility of the beam enhances. There is a very good agreement of the experimental results with the theoretical findings.
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Thesis (M.Tech (R))- National Institute of Technology, Rourkela

Vibration control of machines
and structures incor
porating viscoelastic
materials in suitable arrangement is an impor
tant aspect of investigation. The use of
viscoelastic layers constrained between el
astic layers is known to be effective for
damping of flexural vibrations
of structures over a wide ra
nge of frequencies. The energy
dissipated in these arrangements
is due to shear deformation
in the viscoelastic layers,
which occurs due to flexural vibration of th
e structures. Multilayered cantilever sandwich
beam like structures can be used in aircrafts
and other applications such as robot arms for
effective vibration control. These members
may experience parametric instability when
subjected to time dependant forces. The theo
ry of dynamic stability of elastic systems
deals with the study of vibrations induced by pulsating loads that are parametric with
respect to certain forms of deformation
The purpose of the present work is to i
nvestigate the dynamic stability of a three
layered symmetric sandwich beam subjected to
an end periodic axial force . Equations of
motion are derived using finite element method.
The regions of instability for simple and
combination resonances are established us
ing modified Hsu’s method proposed by Saito
and Otomi[76].
It is observed that with
increase in core thickness parameter fundamental
buckling load increases. The fundamental
resonant frequency and second mode
frequency parameter also increase with increase in core thickness parameter.
Fundamental loss factor and second mode loss
factor also increase with increase in
core thickness parameter.Increase in core
thickness parameter enhances the stability
of the beam. With increase in core loss
factor also the stab
ility of the beam
enhances. There is a very good agreement
of the experimental results with the
theoretical findings.

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