水稻籽粒碰撞力学特性研究

Impact Mechanical Characteristics Analysis of Rice Grain

根据水稻籽粒的物理特性建立了椭球体颗粒模型,采用离散元法模拟了籽粒与检测传感器碰撞力学过程。结果表明:对心碰撞时的峰值法向接触力Fn max随着曲率半径的增加而增大,偏心碰撞时籽粒将发生转动,Fn max随着法向重叠量的减小而减小;Fn max的差异随着粒径比γ的增加而增大,当γ=3时峰值力比率η的最小值小于45%。斜碰撞时η的变化呈现出不对称特性,且η的变化范围也随之增大,当γ=3时η的最小值约为30%,接触力上升时间tr为14～26μs。采用PVDF压电薄膜作为敏感元件设计了检测传感器,并进行了水稻籽粒冲击力学试验。结果表明,在相同碰撞速度下,输出电压峰值在2～4 V范围内波动,接触力上升时间tr为15～35μs。

An ellipsoid particle model was established according to the physical properties of rice grain. The discrete element method was used to simulate the impact process of a grain with a detection sensor. The results indicated that the peak normal contact force F was increased with the increasing of curvature radius during the central impact process. Rotation of grain was driven during the eccentric impact process which reduced the value of F . The differences of F was enlarged with the increasing of grain radius ratio T, and the minimal value of peak force ratio r/was lower than 45% with γ of 3. The asymmetric variation behavior of 9 was shown during the oblique impact process and the variation range of γ was increased. The minimal value of peak force ratio η was about 30% with T of 3. The rise time of impact force t was in the range of 14 - 26 μ~s. Then, a detection sensor using piezo- electric polyvinylidene fluoride （PVDF） film as sensitive material was presented and the rice grains impact tests were carried out. The results showed that the peak output voltage was fluctuated in 2 ~ 4 V, and the rise time of impact force tr was 15 -35 μs.