Effects of Temperature and Loading Characteristics on Mechanical and Stress-Relaxation Behavior of Sea Buckthorn Berries. Part 3. Relaxation Behavior

J. Khazaei, Danny D Mann

Abstract


Relaxation force properties of single sea buckthorn berries under uni-axial compression
were studied. Sea buckthorn berries had a time dependent behavior similar to other
viscoelastic materials. The three-term Maxwell model with a maximum relative difference
(MRD) of ≤ 5%was chosen as the best fit equation to the relaxation data. For both Indian
Summer and Sinensis cultivars, the firmness (as evidenced by the decay forces) decreased
with temperature. As berry temperature increased from 4.5 to 34.5°C, F1 decreased 32.9 and
19.9% for the Indian Summer and Sinensis cultivars, respectively. Sinensis berries were
significantly firmer than Indian Summer berries. For each cultivar, a master curve was
proposed to determine the relaxation data of the sea buckthorn berries at temperatures
between 4.5 and 34.5°C. Deformation level and loading velocity had a decreasing effect on
relaxation time, but temperature had an increasing effect.

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