Dynamic nonlinear viscoelastic model for the fruits under dropping impact

It is commonly difficult to describe the dynamic mechanical properties and model for the fruits. A dynamic nonlinear viscoelastic model of the fruit is developed in terms of the dynamics curves obtained by dropping impact tests. This model equation defines the force acting on the fruit as composed of a cubic elasticity force kx+rx³ and viscous damping force cxx·. The equation of dropping impact and the quantifying method of the model parameters are also proposed. A testing system is used to measure and analyze impact data of fruits. The dropping impact test with multi-heights is conducted on fresh 'Fuji' apples grown in Shandong, China. The critical dropping height for creasing the apple bruise is determined. The impact response is analyzed and the model parameters are estimated based on the experimental data of the apples under the critical dropping height impact. The results show that theoretical model is good agreed with test results. The model can accurately and conveniently determine the rheological parameters of apples and other fruits with similar properties.