Jarimopas, B., Department of Agricultural Engineering, Kasetsart University, Kamphaengsaen, Nakernpathom, 73140, Thailand
Sarig, Y., Institute of Agricultural Engineering, The Volcani Center, P.O. Box 6, Bet Dagan 50-250, Israel
Peiper, U.M., Institute of Agricultural Engineering, The Volcani Center, P.O. Box 6, Bet Dagan 50-250, Israel
Manor, G., Faculty of Agricultural Engineering, Technion-Israel Institute of Technology, Technion City, Haifa, 3200, Israel

Instrumentation and techniques are described for measuring and recording the force-deformation relationship of apples under impact loading. The impact force was generated by a falling pendulum in a curvilinear translation motion with undetectable friction. The device had an impact head that could be released from different positions. giving rise to velocities at the bottom of the swing ranging from 24 to 1300 m/s. Force and deformation were measured, respectively, by a piezoelectric force transducer and an electro-optical displacement follower. The signals from the two sensors were amplified and recorded on a multiple-channel analog tape recorder, connected to an X-Y plotter via a signal analyzer, to produce graphs of force or deformation with respect to time. Two such graphs of a particular sample were fed to a computer using an analog-to-digital converter to provide curves of force vs. deformation. Values of force and deformation required for the first bioyield point were 118 N and 1.52 mm, respectively. The input energy imparting the first bioyielding under impact was, on average, about 1.5 times higher than that under quasi-static loading. The described method is relatively simple, and enables obtaining reproducible unbiased results. Values of impact measured with this system compared favorably with those reported previously in the literature on horticultural products, achieved with more complicated and/or less reproducible techniques. © 1990.