Comparison of Axial and Radial Compression Tests for Determining Elasticity Modulus of Potatoes

Abstract

The effect of sample size, loading rate, and compression level on the determination of tangent modulus of elasticity of potatoes in axial (E_a) and radial (E_r) compression tests was studied. Cylindrical potato samples of 10, 15, and 20 mm diameter with length-to-diameter (L/D) ratio 1, 1.5, and 2 and loading rates of 50, 100, 200, 300, and 400 mm/min were used. A third-degree polynomial best described the force-deformation (F-D) plot of the test specimens (R² = 0.98 to 0.99) in both tests. In view of the non-linearity of the F-D plot, E_a and E_r were calculated corresponding to 10, 20, and 30% compression. The values of E_a and E_r obtained for various combinations of sample size and compression level had coefficient of variation (CV) of about 24 and 8%, respectively, indicating relatively greater influence of experimental conditions in axial than radial compression testing. Apparently, E_a increased with an increase in compression level and loading rate whereas E_r exhibited inconsistent trend. The combined effects of sample size and compression level accounted for about 93 and 20% of the changes in E_a and E_r, respectively signifying the minimal effects of these parameters in radial compression testing. Similarly, the loading rate and compression level accounted for about 96 and 28% of the changes in E_a and E_r, respectively. The results of this article revealed that determination of modulus of elasticity of potatoes in axial compression testing was significantly influenced by testing conditions and sample size, whereas radial compression testing appeared to be independent of testing conditions and sample size.

Keywords:

• Potatoes
• Elasticity modulus
• Axial and radial compression