Quality evaluation of watermelon using its vibration characteristics and dynamic finite element analysis

The physical properties of Gilin watermelon, such as shape, firmness, and the correlation among the firmness, elastic modulus, mass and natural frequency was measured. The statically analysis showed that, there was high significant different for the mass, young's modulus of elasticity and natural frequency at the level (0.05), also the linear regression equation used to predict the dependant variable of melon. The R-Square were obtained 0.90, 0.89, 1.00 and 0.96, for the elasticity*mass, mass*frequency, elasticity*frequency and firmness*mass respectively. The FE modes of watermelon were first generated based on measured geometry features using the ANSYS, version 7.0. It was found that the vibration characteristics of spherical and elliptical watermelon were different, and there were co-relation between the vibrational modes or natural frequency and the ripeness of the watermelon. The flexural and longitudinal resonant frequency could be used in the stiffness factor (S), for evaluation of fruits firmness, regardless of mode shape of fruits, The simulation exhibits three kinds of mode shapes: the torsional or flexural mode, first type longitudinal mode and second type longitudinal mode. The results of mode shape or vibration shape, as well as natural frequency are agrees with experimental results. The direct measured volume was compared with estimated volume is to assess the different between experiment and FE predictions.