H. Rohm et al., A VIDEO-BASED METHOD FOR DETERMINATION OF AVERAGE STRESS-STRAIN RELATIONS IN UNIAXIAL COMPRESSION OF SELECTED FOODS, Journal of texture studies, 28(3), 1997, pp. 245-255
A video-based method was applied to evaluate average stress-strain rel
ationships during uniaxial compression experiments of selected food ma
terials. The determination of apparent Poisson ratios of Gouda cheese
resulted in numbers close to the theoretical value for incompressible
materials of 0.5. In case of such foodstuffs, mathematically corrected
compressional stress based on the consideration of constant specimen
volume showed almost similar results to stress values estimated on the
basis of the true cross-sectional area measured from lateral extensio
n. For compressible materials such as apples or bread, which show a ce
rtain reduction of volume under stress or strain, the apparent Poisson
ratios were strain-dependent. Average stress values calculated from c
ompressional force and actual specimen diameter were found to be diffe
rent from either engineering stress and corrected stress.