Conceptual rationale for the use of impact-absorbing elements of agricultural machines to reduce seed damage

Reduction impact on the surface of working elements of agricultural machines is one way to reduce injury to seed material. Analysis of stress state of seed is carried out, represented in the form of particle of loose body and deformed state of working surface at three types of impact interaction: rigid, partially absorbed and absorbed. Comparative analysis of stress state of particle of loose body particle falling on inclined working surface of different stiffness is performed. It has been established that if the working element is made of a rigid non-deformable material it is necessary to reduce the angle of inclination of the working surface and the porosity of the bulk body in order to avoid abrasion of the outer shell of the seeds when the seed material slides over its surface. But the fulfillment of these requirements will lead to the compaction of the bulk body and the termination of the redistribution of particles in its mass which will adversely affect the technological processes of mixing and transporting the seed material. When particle of loose body collides with inclined working surface made of steel with polyurethane coating in zone its contact with particle local deformations of working surface spring up and increase of main compression stress of working surface causing abrasion of external surface of particle occurs. The theoretical description of the stress states of a particle of a granular body when interacting with surfaces of different rigidity, confirmed by earlier experimental studies, allowed us to draw conclusions: it is necessary to use shock-absorbing working elements made of elastomers that have the ability to significantly stretch and contract within elastic deformations to prevent injury to the seed material. The use of impact-absorbing working elements makes it possible to provide such conditions for the interaction of seeds and the working surface, under which the seeds are in suspension state and bounce off the working surface without slipping. To ensure the impact-absorbing mode, it is necessary that the duration of the seed flow rolling along the inclined working surface be less than the time interval between successive shaking of the highly elastic working surface.