IJS KOLOKVIJ, Sreda, 04. 01. 2017; ob 13. uri; prof. dr. Andrej Košmrlj

[Tanja Debevec]

Vabimo vas na 10. predavanje iz sklopa "Kolokviji na IJS" v letu 2016/17, ki bo v sredo, 04. januarja 2017, ob 13. uri v Veliki predavalnici Instituta »Jožef Stefan«  na Jamovi cesti 39 v Ljubljani. Napovednik predavanja najdete tudi na naslovu http://www.ijs.si/ijsw/Koledar_prireditev, posnetke preteklih predavanj pa na http://videolectures.net/kolokviji_ijs. 

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prof. dr. Andrej Košmrlj

Univerza Princeton, Princeton, ZDA

 

Elastičnost, geometrija in uklon

 

V predavanju bomo pokazali, kako geometrijska oblika vpliva na mehanične lastnosti tankih trdnih lupin in kako uklonske nestabilnosti spremenijo geometrijo periodičnih mikrostruktur v materialih. Z metodami, ki slonijo na statistični mehaniki, ugotovimo, da naključne fluktuacije oblike in termične ekscitacije tankih trdnih lupin močno spremenijo njihove mehanične lastnosti. Plošče s takimi fluktuacijami imajo mnogo večji upogibni modul, a jih je lažje raztegniti, stisniti ali strižno deformirati. Termične fluktuacije krogelnih lupin privedejo do negativne površinske napetosti, ki je enakovredna učinku zunanjega tlaka. Pokazali bomo, da so majhne krogelne lupine stabilne, pri dovolj velikih lupinah pa je ta termični “tlak” prevelik in jih poruši. Naposled bomo pokazali, kako lahko z metodami fizike trdne snovi določimo geometrijo uklonjenih periodičnih mikrostruktur. Uklonske nestabilnosti lahko spremenijo simetrijo mikrostrukture vključno s spontanim zlomom kiralne simetrije, kar dramatično vpliva na lastnosti materiala. 

Predavanje bo v angleščini.

Lepo vabljeni!

 

 

 




We invite you to the 10th Institute colloquium in the academic year 2016/17. The colloquium will be held on Wednesday, January 04, 2017 at 1 PM in the main Institute lecture hall, Jamova 39, Ljubljana. To read the abstract click  http://www.ijs.si/ijsw/Koledar_prireditev. Past colloquia are posted on  http://videolectures.net/kolokviji_ijs.

 

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prof. dr. Andrej Košmrlj

Princeton University, Princeton, USA

 

Elasticity, Geometry and Buckling

 

In this colloquium we present how geometrical shape affects the mechanical properties of thin solid shells and how buckling instabilities change the geometry of periodic microstructures in materials. Using methods rooted in statistical mechanics, we find that random shape fluctuations and thermal excitations of thin solid sheets significantly modify their mechanical properties. Sheets subject to such fluctuations are much harder to bend, but easier to stretch, compress and shear. In spherical shells thermal fluctuations also effectively produce negative surface tension, which is equivalent to applying external pressure. We find that small spherical shells are stable, but for sufficiently large shells this thermally generated “pressure” becomes big enough to crush spherical shells. Finally, we show how methods from solid-state physics can help us deduce the geometry of buckled periodic microstructures. Buckling instabilities can change the microstructure symmetries, including a spontaneous chiral symmetry breaking, which drastically modifies the material properties.

 

Cordially invited!

 

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