Skirtingos brandos kukurūzų grūdų ir burbuolių atsparumas pusiau statinėms apkrovoms

Abstract

Corn Zea mays L. belongs to the species as a most remarkable cereal grain and great importance in the human diet and animal feed in many parts of the world. Corn yield in hectare can be from 50 to 70 tons of green mass or from 6 to 10 tons of grain. Corn for grain can be harvested by several technologies, when the grains in ears are in physiological stage of maturity. Knowledge of apparent properties such as rupture force, rupture energy etc. of agricultural seeds are important for the prediction of their load-deformation behaviour and design of their process machines. This study was carried out to determine the physical and mechanical properties in different physiological maturity stage of corn grains and corn ears. The study of the mechanical properties of corn grains and ears were performed under quasi-static conditions with the unit "Instron-5960". Corn ears bending were determined, when the gap between the support beams was 60 mm and 120 mm. The rupture force of ear breaking decreases with an increasing of distance between the supports. The grain was loaded at three different orientations: over the length, over the width and over the thickness. Single grain was placed between two parallel plates and gradually compressed, while simultaneously recording the force and the corresponding deformation that occurred until the grain ruptured. At this point the force suddenly decreased, while the deformation continued. In most cases the initial portion of the load-deformation curve of the grain is approximately linear up to certain levels of deformation beyond which it became non-linear. The observed bioyield point represents the yield point in the biological materials. This is an indication of initial cell rupture in the cellular structure of the material.[...]