农业和食品领域中颗粒碰撞恢复系数的研究进展

颗粒碰撞广泛存在于农业和食品领域中，碰撞恢复系数是确定颗粒碰撞后运动行为的主要参数之一，通常以颗粒碰撞前、后速度的比值来表述，使用合适的测量装置可以获得准确的碰撞恢复系数，与其他参数结合应用理论分析和数值模拟可以预测颗粒碰撞后的响应行为。该研究针对在农业和食品领域中颗粒3类碰撞恢复系数（牛顿恢复系数、Poisson恢复系数、能量恢复系数）适用性不明确，颗粒碰撞恢复系数测量装置功能的局限性，颗粒碰撞恢复系数在应用中的简化等问题，介绍了3类碰撞恢复系数的定义，讨论了它们的等价性与适用性，归纳分析了颗粒碰撞恢复系数测量装置的特点，概述了颗粒碰撞恢复系数标定的研究现状，总结了不同因素对颗粒碰撞恢复系数影响的试验研究，重点阐述了颗粒碰撞恢复系数在理论模型和数值模拟中的应用。并对颗粒多点碰撞恢复系数的研究、颗粒碰撞恢复系数测量装置的创新设计及颗粒碰撞恢复系数在应用中的完善提出展望，以期为农业物料和食品碰撞恢复系数的深入研究提供参考。

Research progress of the restitution coefficients of collision of particles in agricultural and food fields

Abstract: The collision of particles has been widely found in the processing of agricultural and food fields. The restitution coefficient of collision (RCC) of particles is one of the most important parameters to represent the behavior of particles after the collision. The responsive behavior of particles after the collision can also be predicted to obtain an accurate RCC of the particle after measurement. However, the RCC selection of particles still remained unclear, particularly on the limited function of devices and simplification in the application. Three RCC types are divided, including the restitution coefficient of kinematics, the restitution coefficient of kinetics, and the restitution coefficient of energy. The restitution coefficient of kinematics can be generally defined as the ratio of the velocities of particles before and after the collision. Since the variation in the velocity of particle collision can be caused by the forces on the particle, the restitution coefficient of kinetics is defined as the ratio of the momentums of restituted and extruded particles. Furthermore, two stages are divided in the process of particle collision using energy. In one stage, the particle is compressed and the energy of the particle would be absorbed. In another stage, the particle is restituted that the energy of the particle would be released. Subsequently, the RCC of particles needs to be calibrated to combine physical and simulation tests. As such, a physical experiment was performed on three types of RCC particles to verify the equivalence and applicability under different collision conditions. The Discrete Element Method (DEM) and Finite Element (FE) were also selected to simulate the interaction between agricultural particles and machinery. The influencing factors were summarized to improve the theoretical models, including the velocity and angle of particle collision, surface roughness of particle, temperature, and the material of particle. Thus, enhanced accuracy of predicted motion would be achieved for the particle after the collision. An attempt was also made on the applications of particle RCC in the theoretical model and numerical simulation related to mechanical parameters design. Consequently, it was found the resultant effect of different factors on RCC of particle, in order to enrich RCC of the particle under the real collision for the higher accuracy of the calculated. A promising prospect was also proposed from the multi-point collision of particles. A creative design of the device was also utilized to evaluate the RCC of particles. The finding can provide a strong reference for further investigation on the RCC of agricultural and food particles.