Elasticity and viscosity of carrot root tissue at different rate of deformation

• Autorzy: Golacki K. , Stankiewicz A. , Stropek Z.

Warianty tytułu

PL

Wybrane lepkosprezyste charakterystyki korzenia marchwi w roznych warunkach obciazen

• Języki publikacji: EN

Abstrakty

EN

Viscosity of foods and their mechanical properties are essential for modeling the mechanical behaviour of foods during deformation and flow. The rheological models are used for engineering calculations, e.g., during design of food processing machines, pumping systems, packaging machines, etc. Although the classical linear rheology is a rate-independent theory, the mechanical properties of the viscoelastic plant materials depend on a deformation rate. The influence of a deformation rate on mechanical properties of biological viscoelastic materials needs to be documented and it is the aim of this paper. It is proved, based on the Maxwell model, that the modulus of elasticity and the viscosity ratio are decreasing functions of the rate of deformation. Next, the modulus of elasticity and the viscosity ratio of the carrot cylindrical samples are determined using discrete-time measurements of the reaction force obtained in the compression and relaxation tests at a wide range of preliminary deformation rates, i.e. from 1.67×10–4 m·s-1 to 1.5 m·s-1. The relaxation data were processed using a four-element Maxwell model and the changes in viscoelastic constants were determined as a function of the deformation rate. The stress relaxation both in the state of uniaxial stress as well as in the state of uniaxial strain is considered. The experimental results are in good agreement with theoretical analysis for the biological material considered. The results motivate hypothesis that the number of microcrackings increases along with the deformation rate and indicate the irreversible character of the changes that proceed in plant materials under loading.

PL

W artykule przeprowadzono analizę teoretyczną zależności pomiędzy parametrami mechanicznymi charakterystyk materiałów o własnościach lepkosprężystych, a prędkością deformacji wstępnej. Eksperyment polegał na przeprowadzeniu testów ściskania i relaksacji naprężeń na walcowych próbkach marchwi w stanie jednoosiowego naprężenia i jednoosiowego odkształcenia. Stwierdzono spadek wartości współczynników sprężystości i lepkości wraz ze wzrostem prędkości deformacji, co świadczy o nieodwracalnym charakterze procesów zachodzących w materiale roślinnym w wyniku przyłożonego obciążenia.

Słowa kluczowe

EN

carrot; root tissue; elasticity; viscosity; deformation rate; stress relaxation experiment; Maxwell model; carrot root

• Wydawca: -
• Czasopismo: Polish Journal of Food and Nutrition Sciences
• Rocznik: 2007
• Tom: 57
• Numer: 2[A]
• Opis fizyczny: p.63-66,fig.,ref

Twórcy

autor

Golacki K.

• University of Agriculture in Lublin, Doswiadczalna 50A, 20-280 Lublin, Poland

autor

Stankiewicz A.

autor

Stropek Z.

Bibliografia

• 1. Blahovec J., Improved rate controlled model for stress relaxation in vegetable tissue. Int. Agrophysics, 2001, 15, 73-78.
• 2. Chen P., Fridley R.B., Analytical method for determining viscoelastic constants of agricultural materials. Transactions of the ASAE, 1972, 15, 1103-1106.
• 3. Chen P., Creep response of a generalized Maxwell model. Int. Agrophysics, 1994, 8, 555-558.
• 4. Fung Y.C., Biomechanics: Mechanical Properties of Living Tissues. 1981, Springer, New York.
• 5. Gołacki K., Stropek Z., Graboś A., Test of stress relaxation in plant material under conditions of dynamic load – technical implementation. Inż. Roln., 1999, 2, 55-61 (in Polish; English abstract).
• 6. Gołacki K., Stropek Z., Adequacy of the description of the response plant material under mechanical loading on the basis of linear viscoelasticity theory. Acta Agrophysica, 2004, 106, 3, 453-‑463 (in Polish; English abstract).
• 7. Rao M. A., Rheology of Fluid and Semisolid Foods. Principles and Applications. 1999, Aspen Publishers, Inc., Gaithersburg.
• 8. Stankiewicz A., Gołacki K., A scheme for identification of timevariable shear and bulk modulus of plant viscoelastic materials. Acta Sci. Pol., Technica Agraria, 2004, 3 (1-2), 79-95 (in Polish; English abstract).