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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
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UID:UW-Physics-Event-4615
DTSTART:20170919T170500Z
DTEND:20170919T180000Z
DTSTAMP:20210127T204803Z
LAST-MODIFIED:20170830T164857Z
LOCATION:4274 Chamberlin (refreshments will be served)
SUMMARY:Nonlinear normal modes for analysis of geometrically nonlinear
structures\, Chaos & Complex Systems Seminar\, Matthew Allen\, UW Dep
artment of Mechanical Engineering
DESCRIPTION:Geometric nonlinearity is an important consideration when
designing many structures\, for example the skin panels for future hyp
ersonic cruise vehicles where intense pressures and aerodynamic heatin
g can cause the panels to vibrate in and out of buckled states. Highly
flexible joined-wing aircraft\, which are being sought for station ke
eping at high altitude\, can also exhibit nonlinear dynamic phenomena.
It may also be possible to add a nonlinear element to an otherwise l
inear structure in order to reduce vibration levels and increase its l
ife\, leading to quieter automobiles or more durable spacecraft. All
of these applications are challenging because numerical response predi
ctions are expensive and these nonlinear systems exhibit a large range
of phenomena\, each of which may require a specialized analysis techn
ique. This work shows that tremendous insight can be gained into the
dynamics of these types of nonlinear structures using undamped nonline
ar modal analysis.

\n

\nThis presentation highlights advances
in modeling for geometrically nonlinear structures and discusses how n
onlinear modes can be used in analysis\, design and testing. While ac
ademics have used simplified Galerkin/Ritz models for years to qualita
tively study the geometrically nonlinear response of plates and beams\
, those methods often do not scale to industrial practice where the ge
ometry is far more complicated and many degrees of freedom must be con
sidered. The work focuses on structures that are modeled in commercia
l finite element software and uses a non-intrusive approach in which a
series of static loads are applied to the structure and a nonlinear R
educed Order Model (ROM) is fit to the load-displacement behavior. No
nlinear modes prove to be effective in discerning whether the reduced
basis contains the fidelity needed to capture the dynamics of interest
and in assuring that the loads are large enough to allow the ROM to b
e accurately computed. Nonlinear modes are also found to be intimatel
y connected to the response of the structure to random loading\, such
as the pressure fields experienced by many aircraft. These concepts a
re demonstrated by applying them to a variety of finite element models
\, showing that the nonlinear modes provide tremendous insight into th
e dynamics of the structure.
URL:https://www.physics.wisc.edu/events/?id=4615
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