The effect of test conditions on failure parameters during uniaxial compression of potato tissue

Uniaxial compression tests were performed on potato flesh. Cylindrical samples of diameters (19.05 and 25.4 mm) and heights (5, 10, 15 and 20 mm) were tested under non-lubricated, lubricated and increased friction conditions. The deformation rate effect was also examined by performing compression tests at 50, 100, 200 and 400 mm min-1. In the present study, parameters derived from compression to failure were failure strain (ε), engineering stress (F/A0), true stress (F/Af), apparent elastic modulus (E) and energy at failure (Uv). As compared with non-lubricated friction condition, lubrication increased significantly the average ε value and decreased significantly the average F/Af value, but appears to have lower significant effect on the average F/A0, E and Uv values. Failure strain, engineering stress and energy at failure increased with deformation rate, whereas true stress and apparent elastic modulus decreased. Failure strain increased with sample diameter and decreased significantly with sample height, whereas the rest of the failure parameters decreased when both sample dimensions increased. As compared with non-lubricated friction condition, lubrication results in a higher influence of deformation rate on the averageε, F/A0 and Uv values, a similar influence of sample diameter on the average F/Af and E values, but a lower influence of sample height on all the failure parameters. In turn, increased friction results in a higher influence of deformation rate and mainly the sample height on the averageε, F/A0 and Uv values, but a lower influence of sample diameter on all the failure parameters. Principal components analyses showed that principal component 1 is determined by ε, F/A0 and Uv, and is strongly influenced by sample height, whereas component 2 is dominated by E, and is mainly influenced by sample diameter. © 2007 The Authors. Journal compilation 2007 Institute of Food Science and Technology Trust Fund.Peer Reviewe