Dynamics and damage evaluation of onions and potatoes during post harvest impact separation

Abstract

Tests were conducted with vertical drop test equipment, in order to assess the damage inflicted on subterranean agricultural products, by the use of an impact separator. The previously designed impact separator removes desired agricultural products from harvested material by utilizing the differences in the resilience and surface friction characteristics of the desired product and extraneous material. Empirical equations developed from regression analysis indicated that the severity of bruising (damage) of onions and potatoes is directly related to increase in test drop height, sample mass, peak contact force, and amount of energy absorbed. Damage inflicted on the products was found to be more pronounced with the horizontal steel plate system than the rotating roller drop test system. Tests conducted with plain steel and teflon covered steel rollers in the impact separator system indicated that there was no significant difference in crop bruising (damage below the skin) between the two types of rollers. The use of the teflon covered roller led to a significant reduction in the removal of potato (Red Lasoda cultivar) skin. Trajectory tests on the rotating roller showed that separation of harvested material with the impact separator depends on the position and angle of impingement (incidence) of the material on the roller. Theoretical consideration of potatoes and onions as elastic materials led to the development of equations of motion of the impacted crops. An overview of results from the ensuing motion analysis indicated that the elastic material assumption leads to an overestimation of peak contact forte values during the impact process. Further characterization of the crops as linear viscoelastic materials, resulted in models that provide good theoretical estimates of experimental force and other dynamic values.