MODELING THE BREAKING CHARACTERISTICS OF CASSAVA ROOT LENGTHS UNDER CONTINUOUS BENDING LOADS

Abstract

This paper discusses the breaking characteristics of cassava root lengths at 52.13 + 5.74% moisture content (wet basis) as a step in understanding the behavior of the roots to applied forces especially during harvesting, processing and storage. The effects of different loading rates 2.0, 4.0, 6.0, 8.0, 10.0 mm/min and root diameters 49.89, 52.62, 56.55, 60.58, 66.08 mm on the following breaking parameters:- strength, energy, force, strain, deflection, time, elastic modulus and apparent modulus were studied. The experiment was carried out using a modified Instron Testing Machine. It was observed that the loading rate affected the following five parameters positively: apparent elastic modulus, breaking force, breaking strength, breaking elastic modulus and breaking energy. Root diameter affected only the apparent elastic modulus, breaking force, breaking strain and breaking energy positively. Both breaking time and breaking deflection were affected negatively by loading rate and cassava root diameter, respectively while breaking energy, breaking force and apparent elastic modulus were positively influenced by both loading rate and cassava root diameter. Breaking energy was 553 N-mm at 49.89 mm cassava root diameter and 2mm/min loading rate and 845 N-mm at 66.08 mm cassava root diameter and 10mm/min loading rate. Breaking elastic modulus at 49.89 mm cassava root diameter increased from 51.67 N/mm² at 2 mm/min loading rate to 144.84 N/mm² at 10 mm/min loading rate. At the highest cassava root diameter of 66.08 mm, breaking elastic modulus increased from 34.84 N/mm² at 2 mm/min loading rate to 99.38 N/mm² at 10 mm/min. Second order polynomial models relating the measured breaking parameters to both loading rate and cassava root diameter show the viscoelastic behavior and the mechanical properties of the cassava root. The results obtained will be useful in the design and development of harvesting, processing and storage structures, processes and machines for cassava root lengths.