Viscoelastic Properties of Bulk Groundnuts

Abstract

The groundnut, Arachis hypogaea Linn, samples were collected from the majorly grown areas of western Kenya to investigate the viscoelastic properties pertinent to grain handling, storage and processing. In particular, the study conducted at the University of Nairobi, Department of Environmental and Biosystems laboratories in July 2010, aimed at investigating the stress-strain properties of bulk groundnuts in relation to Maxwell polymer viscoelastic model. The Mohr-Coulomb failure criterion was also applied to bulk groundnuts. Three samples were prepared for triaxial tests; each weighing 1062.4 g. The moisture content of the samples was 7.6%. The sample size for triaxial testing was 100 mm diameter and 199 mm height. Density of the samples during the tests was 678.6 kg/m3. Confining stresses of 200, 400 and 600 kPa were used and Axial Strain Rate (ASR) of 0.5 mm/min was used for the triaxial compression tests. For the senstar universal testing machine relaxation time was about 30 min for each of the samples. Relaxation data was recorded after every 30 sec for the duration of the test (30 min). These results showed that the Maxwell model for viscoelastic polymers can be applied to accurately describe the behaviour of bulk groundnuts.