Experimental determination of the coefficient of restitution of particle-particle collision for frozen maize grains

There are many frozen maize produced in the fall due to early frost every year. Coefficient of restitution (CoR) is one of the microscopic physical properties required to simulate the motion of maize grains in seeding and harvesting machines using EDEM software. In this study, the CoR of particle-particle collision involving frozen maize grains was determined by using a function derived based on the grain velocities in the direction of the contact force of the particle-particle collision. The real densities of different parts of the frozen maize grain were determined by experiments. The external outlines of the grain and embryo were obtained by image processing and fitted to different functions. Three-dimensional models were established by using the built-in functions available in SolidWorks software. An automatic control platform was designed and constructed to realize the particle-particle collision without external interference and measure the CoRs. The mechanical behavior of the frozen maize grain was traced by using a high-speed digital video camera. The grain centroid was determined based on the densities of different parts of the frozen maize grain by using SolidWorks software. The effects of the moisture content, impact velocity, impact angle and impact position on the CoR of the particle-particle collision were also investigated in this study. This paper presents a method to determine the CoR of the particle-particle collision in three dimensions. The results will be helpful for maize simulation and for the design of machines. (C) 2018 Elsevier B.V. All rights reserved.