[institut] Plan rada za april i maj 2017. godine

Mon Apr 10 09:46:51 CEST 2017

Postovane koleginice i kolege,

saljemo vam plan predavanja u okviru Odeljenja za mehaniku Matematickog
instituta SANU za april i maj 2017. godine.

Molimo vas da, ukoliko ste u
mogucnosti, prilozeni plan odstampate i okacite na oglasnim tablama vasih
institucija.

S postovanjem,
Katarina Kukic
Sekretar Odeljenja za mehaniku

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PLAN RADA ZA APRIL I MAJ 2017. GODINE

Sreda 19.4.2017. 18 casova, sala 301f

Dr. Fotios Georgiades, Senior Lecturer, School of Engineering, College of
Science, University of Lincoln,

Brayford Pool, Lincoln, LN6 7TS, United Kingdom

LINEAR AND NONLINEAR MODELLING/DYNAMICS OF L/SHAPEL BEAM – A SIMPLE
’COMPOSITE’ ELASTIC STRUCTURE

Abstract: Since the 1960s, the dynamics of L-shaped coupled beams has been
of interest because of their relative structural simplicity. It is among the
simplest ‘composite’ elastic structures. It is derived all the equations of
motion of an L-Shaped beam structure, and it is showed the importance of
rotary inertia terms. The equations are decoupled in two motions, namely the
in -plane bending and out-of-plane bending with torsion. A theoretical and
numerical modal analysis has been performed and it is examined the effect of
the orientation of the secondary beam (oriented in two ways) and also the
shear effects. Parametric study of natural frequencies for various
parameters of the L-Shaped beam showed stiffening and softening effects.
Also in case that the length of secondary beam is less than 10% of the
length of the primary beam, then the system behaves like cantilever beam
with tip mass. Modelling of geometric nonlinearities indicates that the
in-plane with out-of-plane motions are coupled together and has to be
considered both planes even in examining up to 2nd order nonlinearities.
Noted, so far in the literature of the L-Shaped beam structures with
geometric nonlinearities the out-of-plane motions has been neglected.
Although the two elastic beams are connected, the equations of motion form a
self-adjoint system, therefore the projection of the dynamics in the
infinite basis of the underlying linear system, lead to the modal equations
with only nonlinear coupling and then well-known dimension reduction methods
can be applied e.g. center manifolds. This work, paves the way for
examination of dynamics in case of geometric nonlinearities of L-Shaped Beam
structures, since it is almost impossible using commercial finite element
software to perform nonlinear dynamic analysis e.g. the determination of
Nonlinear Normal Modes as periodic orbits of millions of DOFs. Also, this
work paves the way for analytical modelling and dynamic analysis of more
complicated elastic structures e.g. a full airplane model.

Sreda 26.4.2017. 18 casova, sala 301f

Ivana Atanasovska, Matematicki institut SANU

Uticaj fenomena kontakta deformabilnih tela na dinamicko ponasanje slozenih
mehanickih sistema

Rezime: Fenomen kontakta deformabilnih tela predstavlja jednu od cestih
nelinearnosti u mehanici slozenih sistema. Posebno je vazno resavanje
zadatka mehanike kontakta deformabilnih tela kada su kod mehanickih sistema,
ciji su tela u kontaktu deo, prisutni i drugi izvori nelinearnosti. U
predavanju ce biti opisan zadatak resavanja promenljivih koje definisu
mehaniku kontakta deformabilnih tela sa jednostavnom i sa slozenom
geometrijom kontaktnih povrsina. Posebno ce biti prikazan pristup resavanja
kontaktnih problema deformabilnih tela diskretizacijom i primenom metode
konacnih elemenata. Za resavanje uticaja kontakta dva ili vise deformabilna
tela na dinamicko ponasanje slozenog mehanickog sistema, razvijen je novi
pristup opisan odgovarajucim algoritmom. Primeri primene na konkretnim
realnim slozenim mehanickim sistemima ilustrovace prednosti razvijenog
algoritma, pre svega kod postojanja geometrijskih i/ili materijalnih
nelinearnosti u kontaktnim zonama, kao i pri pojavi udara.

Sreda 3.5.2017. 18 casova, sala 301f

Djordje Cantrak, Masinski fakultet Univerziteta u Beogradu

Eksperimentalno istrazivanje koherentnih vrtloznih struktura

Rezime:Razmatraju se koherentne vrtlozne strukture na potisu aksijalnog 
ventilatora
u pravoj cevi, kao i iza avionskog krila modela aviona CRM (common research
model). CRM je projektovan u saradnji NASA-e i Boeing-a. Prikazana je
analiza generisanih vrtloznih struktura i njihovih statistickih svojstava.
Eksperimentalna istrazivanja su obavljena primenom metoda vizualizacije i
optickih mernih tehnika i to laser Dopler anemometrije (LDA) i PIV (PIV,
particle image velocimetry). Na osnovu originalnih rezultata merenja
detaljno se istrazuje uticaj rezima rada aksijalnog ventilatora na strukturu
turbulencije i precesiju vrtloznog jezgra, kao i ugla aeroprofila na
formiranu vrtloznu strukturu. Izmerene raspodele turbulentnih napona
omogucile su formiranje invarijantnih mapa anizotropnosti za razlicite
uglove lopatica kola, kao i napadne uglove modela CRM. Dobijeni su znacajni
zaključci o uticaju rezima rada ventilatora na anizotropnost i strukturu
turbulencije u jezgru, smicajnom sloju i osnovnom strujanju, kao i uticaja
napadnog ugla aviona na vrtlozne strukture iza krila aviona.

Kljucne reci: turbulencija, vrtlozne strukture, invarijante, ventilator,
CRM, LDA, PIV

Literatura:
1. Cantrak Dj.S., Heineck J.T., Kushner L.K., Jankovic N.Z. (2016):
Turbulence Investigation of the NASA Common Research Model Wing Tip Vortex,
Thermal Science, DOI:10.2298/TSCI161005328C,
http://thermalscience.vinca.rs/online-first/2342
2. Cantrak Dj.S., Colic Damjanovic V.M.Z., Jankovic N.Z. (2016): Study of
the Turbulent Swirl Flow in the Pipe behind the Axial Fan Impeller,
Mechanics & Industry, Vol. 17., No. 4, pp. 412-page 1 - 412-page 13
3. Cantrak Dj. S., Jankovic N., Lecic M. R. (2014): Laser Insight into the
Turbulent Swirl Flow behind the Axial Flow Fan, Proceedings of ASME Turbo
Expo 2014: Turbine Technical Conference and Exposition, GT 2014, Technical
track: Fans and Blowers, ASME TURBO EXPO 2014, June 16-20, 2014, Düsseldorf,
Germany, Paper No. GT2014-26563, pp. V01AT10A024, 10 pages
4. Cantrak Dj.S., Kushner L.K., Heineck J.T. (2014): Time-resolved Stereo
PIV Investigation of the NASA Common Research Model in the NASA Ames Fluid
Mechanics Laboratory 32- by 48-in Indraft Wind Tunnel, CTR Research
Publications, Center for Turbulence Research, Annual Research Briefs 2014,
pp. 179-191, Eds.: P. Moin and J. Urzay, Center for Turbulence Research,
Stanford University / NASA Ames.
https://web.stanford.edu/group/ctr/ResBriefs/2014/18_cantrak.pdf
5. Cantrak Dj.S (2012): Analiza vrtloznog jezgra i strukture turbulencije u
pravoj cevi kruznog poprecnog preseka iza kola aksijalnih ventilatora
primenom PIV, LDA i HWA metoda, doktorska disertacija, Masinski fakultet,
Beograd.

Zahvalnost:
Ministarstvu prosvete, nauke i tehnoloskog razvoja Republike Srbije,
projekat br. TR 35046 i Fulbrajt fondaciji u 2014. god.

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Predavanja su namenjena sirokom krugu slusalaca, ukljucujuci studente
redovnih
i doktorskih studija. Odrzavaju se sredom sa pocetkom u 18 casova u sali
301f
na trecem spratu zgrade Matematickog instituta SANU, Knez Mihailova 36.

dr Katarina Kukic
Sekretar Odeljenja za mehaniku
Matematickog instituta SANU

dr Bozidar Jovanovic
Upravnik Odeljenja za mehaniku
Matematickog instituta SANU

http://www.mi.sanu.ac.rs/colloquiums/mechcoll.htm
mehanika at mi.sanu.ac.rs
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