Simulation Study On The Properties Of Collision Between The Maize Particles In The Harvest Screening Process

The maize screening process is a main part of the maize plant.It is not avoid that the maize particle is collided in the screening process.The loss of the maize particle is caused.The research team studied the collisions between maize particle and the wall and particle.The study mainly focuses on the macroscopic properties(particle movement).The study of microscopic properties(force and energy)is less.The collision mechanisms are not clear.The collision between the particles is important form of the particle collision and the microscopic properties affects the macroscopic characteristic.Therefore,the study on the properties of collision between the maize particles and effect of microscopic properties on macroscopic properties has significance to increase of the cleaning efficiency.The wedge maize particle was object to study the mechanisms of collision between the particles because its quantity accounts for more than 90% of the total maize particle and the collision properties of the wedge maize is more complex.The contents and results are as follows:(1)To determine the energetic coefficient of restitution(COR)of the collision between the particles.The calculation model of the energetic COR of particle-particle collision was derived based on Stronge’s impact mechanics model and Newton-Euler dynamic equations.The collision between the particles was simulated based on the discrete element method(DEM).The collision period was divided four stages.The transformation between the energies and motion of maize particle were studies.(2)The energetic COR of maize particle-particle collision at the different incident velocity and angle was determined based on laboratory experiments and simulations.The applicability of the kinematic and energetic COR was compared based on the simulation result.The energetic COR is more accurate than the kinematic COR for maize particle by comparing the input and calculated CORs.(3)The collisions between the maize particles were simulated based on the energetic COR.The microscopic properties of collision between the maize particles at the different factors were studied.The normal deformation period of the maize particles consists with mutual movement between the maize particles.The time that the tangential deformation of the maize particle starts recovery earlier than the time that the maize particle starts depart.The normal contact force first increases and then decreases as the collision time increases.The variation of tangential contact force is irregular as the collision time increases.The variations of the contact force are uniform when the maize particles have different incident velocities and angles.The maximum of the normal contact force decreases as the incident angle increases.As the incident velocity increases,the maximum of the normal contact force increases.The variation of the maximum of the tangential contact force is irregular as the incident velocity and angle change.(4)The kinetic energies of the maize particles were compared at the same the incident velocity and incident angle.The variation of kinetic energy of maize particle was studied before and after collision.The effects of the incident velocity and angle on the kinetic ene rgy and energetic COR were studied.The results shown that the kinetic energies of the maize particles are similar before and after collision.After the collision,the X component of the translational kinetic energy decreases.The Y component of the translational kinetic energy and rotational kinetic energy are generated.The Z components of the translational kinetic energy before and after collision are smaller.The incident velocity and incident angle have significance to variation of the maize particle and energetic COR.(5)The macroscopic properties of collision between the maize particles at the different factors were studied based on the simulation result.The effects of the incident velocity and incident angle on the translational motion,rotation motion and rebound motion of the maize particle were studied.The result shows that the incident angle and velocity have significance to X and Y component of translational velocity,but have a smaller effect on the Z component of translational velocity.The incident angle and velocity have significance to Y and Z component of rotational velocity,but have a smaller effect on the X component of rotational velocity.The incident angle has significance to impact angle,rebound angle and recovery ratios of angle.The incident velocity has a slight effect on the impact angle,rebound angle and recovery ratios of angle.The results of study help to understand the mechanisms of collision between the maize particles,and lay a foundation for the design of threshing and cleaning device of maize maize,and provide a reference for the measurement of the energetic COR of irregular particle.