Determination of Poisson's Ratio and Modulus of Elasticity during Maturation of White Seedless Grapes

In this study, to determine poisson’s ratio and modulus of elasticity of white seedless grapes during maturation, the fresh fruit samples were harvested from a vineyard at seven sequential weeks from 6th September to 18th October. In each run, six grape berries were randomly selected and the static loading test and digital photography were done together. Considering true shape of the fruit and an allowable deformation value, and also using Hertz’s theory with a true poisson’s ratio (experimental), modulus of elasticity was calculated. Apparent poisson’s ratio was determined by the image processing, too, and then obtained values of poisson’s ratio were modified using finite element software (ABACUS). Results showed that measured modulus elasticity by the Hertz’s theory depends on the magnitude of axial strain and increases with increasing that. Regarding the results, the calculated poissoon’s ratios are less than that true one, depending on the axial strain value. It was found that both modulus of elasticity and poisson’s ratio decreased during maturation.