DYNAMIC MODELING OF PEACH FRUIT DURING NORMAL IMPACT EBRAHIM AHMADI 1,6 , HAMID REZA GHASSEMZADEH 2 , MORTEZA SADEGHI 3 , MOHAMMAD MOGHADDAM 4 , SAEED ZARIF NESHAT 5 and MIER MOHAMMAD ETTEFAGH 3 1 Department of Agricultural Machinery Engineering, Faculty of Agriculture Bu-Ali Sina University Hamedan 51664, Iran 2 Department of Agricultural Machinery Engineering, Faculty of Agriculture 3 Faculty of Mechanical Engineering 4 Department of Agronomy and Plant Breeding, Faculty of Agriculture University of Tabriz Tabriz 51664, Iran 5 Agricultural Engineering Research Institute Tehran, Iran Accepted for Publication February 24, 2010 ABSTRACT Impact forces during the contact are the main sources of damage in Peach fruit. In order to reduce this damage, it is necessary to model the impact forces during handling and transporting. An experimental procedure was conducted to determine the parameters of a viscoelastic normal contact force model. Peaches were subjected to dynamic loading by means of a pendulum at the levels of impact. In order to estimate the values of the parameters (spring, “k” and damping, “c”) of the Kuwabara and Kono viscoelastic contact force models for normal impacts the nonlinear least squares technique to be calcu- lated. Two prediction models were constructed for the parameters “k” and “c” using multiple linear regression analyses. In these models, impact velocity and two fruit properties (the effective radius of curvature and acoustic stiff- ness) were used as independent variables. Significant effect of impact velocity, the effective radius of curvature and acoustic stiffness and some interactions on the parameters “k” and “c” were obtained at 5% probability level with the 6 Corresponding author. TEL: 0098-811-4424012; FAX: 0098-811-4424012; EMAIL: eahmadi@ basu.ac.ir Journal of Food Process Engineering 35 (2012) 483–504. All Rights Reserved. © 2011 Wiley Periodicals, Inc. DOI: 10.1111/j.1745-4530.2010.00603.x 483