NON-LINEAR VISCOELASTIC MODELING OF THE FRUITS UNDER DROPPING IMPACT

A dynamic non-linear viscoelastic model and its parameter-identification method are developed for the fruits under dropping impact. This model defines the force acting on the fruit as a summation of nonlinear elasticity force and viscous damping force . An experimental system is set up to measure and analyze the dropping impact on fruits. The dropping impact on fresh ‘Fuji’ apples was tested at multi-heights . The model parameters corresponding to different dropping heights are estimated based on the experimental data. Applying the method of bruise factor, the impact bruise variable is proposed, and the general viscoelastic bruise model is developed, thus, the bruising factor of apple dropping is estimated. The results show that the initial velocity of impact affects the model parameters significantly. Compared with other models, the proposed non-linear viscoelastic model is the most precise one in simulating the relation between the impact force and the deformation.