اثر سرعت بارگذاري و اندازه ميوه بر ويژگيهاي مكانيكي دو رقم ميوه خرماي استان خوزستان (ارقام استعمران و زاهدي )

The Effect of Loading Speed and Fruit Size on the Mechanical Properties of Two Date Fruit Varieties (Estamaran and Zahidi)in Khuzestan

Physical and mechanical properties of fruits are undoubtedly of great importance in design and improvement of fruit production, processing, and packing systems. Most of the agricultural products are generally classified as viscoelastic materials. Although time-dependency is one of the basic characteristics of the viscoelastic materialsʹ behavior, the effect of loading speed on the mechanical properties of agricultural crops necessitates individual subtle studies on each of them. On the other hand, the relation between mechanical properties and fruit size as a physical property is unknown. The Importance of Date fruits and lack of fundamental data about their mechanical behavior is the motive for this study. Mechanical properties of two date fruit varieties, namely Zahidi and Estamaran including force and energy needed to deform the fruit, and the energy per unit volume of the fruit and the initial modulus (the first non-zero tangential modulus) neaded to be determined. The force, energy and energy per unit volume were determined at 10%, 20%, 30%, 40%, 50% specific deformations and at the point where the first crack in the fruit became visible. Independent variables included loading speed (30, 60, 90, I20, 150 mm/min) and fruit size (small, medium, large). Although the effect of loading speed on most force, energy and energy per unit volume values under different specific deformations was not significant for Zahidi variety, its effect was very significant for Estamaran dates. For both varieties, the initial modulus, force, energy and energy per volume at the rupture point were significantly affected by loading speeds. Fruit size did not affect mechanical properties of the dates except for the energy per unit volume which is quite logical given its very definition.