Research Paper Drop test of pear fruit: Experimental measurement and finite element modelling Somaye Yousefi, Habib Farsi, Kamran Kheiralipour * Mechanical Engineering of Biosystems Department, Ilam University, Ilam, Iran article info Article history: Received 11 January 2016 Accepted 14 March 2016 Keywords: Pear fruit Dropping test Bruised area Finite Element Method Pear fruit has a soft tissue that must be protected against mechanical bruises. In this paper, the bruised area of pear fruit was determined by experimental dropping tests and then was predicted by the Finite Element Method (FEM). Three dropping heights (200, 500 and 1000 mm), two impact surfaces (steel and wood) and two fruit orientations (vertical and horizontal) were studied. In order to simulate the fruit in the ANSYS 14 software, volume, density and elasticity modulus of unripe, ripe and overripe fruits were determined experimentally using standard methods. The minimum bruised area was occurred for unripe pear falling on the wood surface at vertical orientation and 200 mm dropping height whereas the maximum value was obtained for overripe pear falling on the steel surface at horizontal orientation and 1000 mm dropping height. The minimum and maximum error for prediction of bruised area by finite element modelling was 0.00 and 60.50%, respectively. © 2016 IAgrE. Published by Elsevier Ltd. All rights reserved. 1. Introduction Mechanical impacts have been known for many years as a major factor causing post-harvest losses (Sitkei, 1987). Bruising results from processes that do not appear immedi- ately, but they reduce the quality of fruit within a short period (Li, Li, & Liu, 2011). Impact areas become discoloured due to the release of enzymes from damaged cells (Gonzalez, 2009; Jim enez-Jim enez, Castro-Garcı´a, Blanco-Rold an, Agu ¨ era- Vega, & Gil-Ribes, 2012, Jim enez-Jim enez et al., 2013; Li, Yang, & Liu, 2013; Opara & Pathare, 2014). Mechanical damages are ocurred when the magnitude of exerted external forces exceeds a fruit breaking threshold and leads to the break-up of fruit tissues (Mohsenin, 1986). Dy- namic loads are more effective at causing bruising than static loads (Azadbakht, Aghili, Asghari, & Kiapey, 2015) and pre- dicting the injured surface, deformation and stress distribu- tion of fruit has been an important issue in post-harvest studies of agricultural products (Celik, Rennie, & Akinci, 2011; Topakci et al., 2010; Van linden, De Ketelaere, Desmet, & De Baerdemaeker, 2006). Different methods have been applied to study the amount of stress, bruise characteristics and stiffness of agricultural products (Dintwa, Van Zeebroeck, Ramon, & Tijskens, 2008; Jackson & Harker, 2000; Miranda, Pajares, & Guiberteau, 2008). Finite Element Method (FEM) is a numerical procedure that has been widely used for solving complex and extensive engineering problems. Chen and De Baerdemaeker (1993) studied the watermelon stiffness and pear stiffness was determined by Dewulf, Jancs ok, Nicolai, De Roeck ,and * Corresponding author. E-mail address: k.kheiralipour@ilam.ac.ir (K. Kheiralipour). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/issn/15375110 biosystems engineering 147 (2016) 17 e25 http://dx.doi.org/10.1016/j.biosystemseng.2016.03.004 1537-5110/© 2016 IAgrE. Published by Elsevier Ltd. All rights reserved.