跌落冲击下果实动态本构模型的构建与表征

基于果实非损伤条件下的跌落冲击动力学特征，提出表征其非线性黏弹性的本构模型与模型参数识别方法。该模型包括一个非线性弹簧元件、一个线性增强黏性元件。以苹果为研究对象，进行多个高度下的跌落冲击试验，获得其发生损伤的临界跌落高度；基于临界跌落高度下的冲击试验结果，建立其跌落冲击方程，进行跌落冲击响应的数值分析与模型参数识别。结果表明，理论结果与试验值很吻合，采用本模型结合试验结果能较准确地确定类似特性果实的动态流变特征参数。研究结果为果实动态流变特性分析以及模型表征提供了一种新方法，也为进一步表征果实的黏弹塑性损伤特征提供基础。

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.