Acta Univ. Agric. Silvic. Mendelianae Brun. 2008, 56(2), 115-122 | DOI: 10.11118/actaun200856020115
Deformační a lomové chování tmavé čokolády
- Ústav techniky a automobilové dopravy, Mendelova zemědělská a lesnická univerzita v Brně, Zemědělská 1, 613 00 Brno, Česká republika
Byla provedena řada mechanických zkoušek (tlaková zkouška, brazilský test, zkouška průhybem) na válečkových vzorcích (průměr 12 mm a výška 6 mm) tmavé čokolády. Výsledky tlakových zkoušek vedly k sestrojení grafu závislosti napětí - deformace. Uvedená závislost byla též úspěšně modelována pomocí Cowper - Symondsova vztahu. Bylo zjištěno, že deformační chování čokolády není lineárně závislé na napětí. Oblast lineární elasticity je omezena pouze na velmi nízké hodnoty napětí. Brazilský test vedl k vzniku tahového napětí ve vzorku a jeho následnému porušení. Byla potvrzena závislost napětí na rychlosti deformace. Také provedení testu průhybem vedlo k závěru, že lineární chování čokolády je omezeno na počátek zatěžování. I tento test byl modelován s uspokojivým výsledkem. Bylo studováno též chování čokolády při rázovém zatížení. Tabulky čokolády byly zatěžovány dopadem z definované výšky. Uvedený test byl numericky simulován pomocí konečněprvkové metody programem LS DYNA 3D.
čokoláda, elastické vlastnosti, mechanické zatěžování, numerická simulace
Deformation and fracture properties of dark chocolate
Series of mechanical tests (uniaxial compression test, Brasil test, plate bending test) with cylidrical specimens made from dark chocolate have been performed. The stress-strain dependence has been ploted and modeled using data from compression test. The strain behaviour of the chocolate was found to be far from the linear elastic strain. The linear elasticity is limited for the very small strains. The Brasil test led to the development of the tensile stress in the specimen and its cracking. The dependence of the tensile stress on the strain rate has been confirmed. Also the linearity of the force vs. displacement data received during plate bending test has been limited to the very small value of the displacemnt. Impact behaviour of the chocolate has been also evaluated. Falling of the specimen from defined hight led to its fracture. This experiment has been simulated using LS DYNA 3D finite element code.
Keywords: chocolate, elastic properties, mechanical loading, numerical simulation
Grants and funding:
The research has been supported by the Grant Agency of the Czech Academy of Sciences under Contract No. IAA201990701.
Received: January 14, 2008; Published: November 14, 2014 Show citation
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