PT  - JOURNAL ARTICLE
AU  - Nedomová, Šárka
AU  - Severa, Libor
TI  - Constitutive equation of butter at static loading
DP  - 2014 Nov 3
TA  - Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis
PG  - 147--152
VI  - 56
IP  - 5
AID - 10.11118/actaun200856050147
IS  - 12118516
AB  - This study focuses on the constitutive modelling of finite deformation in the commercially obtained butter (composition is 83 % of milk fat) at the temperature 17-20 °C. The specimens from the butter (height L<sub>0</sub>=14.6 mm and diameter 20 mm) have been compressed between two parallel metal plates at a fixed crosshead speed 20 mm/min using of the testing device TIRA TEST. The force F and the deformation ΔL are measured during compression and both quantities are recorded. The experimental records force F - displacement (deformation) were obtained. These records have been transformed into stress-strain dependences and into true stress-true strain. The basic data on the strain behaviour of a butter under low strain rates have been obtained. Experimental results show that the behaviour of butter can be described by a hyperelastic material model. In this model, the quasi-static response is defined by compressible hyperelasticity, whereby the strain energy potential is assumed to be representable by a newly proposed polynomial series with three independent parameters. The material parameters in the constitutive model are determined from compression test. A comparison of predictions based on the proposed constitutive equation with experiments shows that the model is able to describe the strain behaviour of the butter examined.