A new method for the measurement of the tensile strength of rice grains by using the diametral compression test

Breakage of rice grains during milling can be attributed to the presence of fissures, caused by stresses related to shrinkage during drying. These fissures are usually caused by a tensile failure in the center of the grain. Very few data of the tensile strength of rice grains have been published, which is related to experimental difficulties. An attractive method for the measurement of the tensile strength is the diametral compression test, in which a cylinder is pressed between two flat plates. In this paper, results are shown of the application of the diametral compression test on rice grains. At a temperature of 20°C, a moisture content of 5.7% (w.b.) and a deformation rate of 7·10⁻³ min⁻¹ the tensile strength of rice grains is 10 ± 2 MPa, the compressive strength is 73 ± 15 MPa and the Young's modulus is 1.1 ± 0.1 GPa. The Young’s moduli from the diametral compression tests are not significantly different from those from uniaxial compression tests, which agrees with the theory. The obtained tensile strength values are in accordance with those from the literature. The repeatability of the diametral compression tests is of the same order as the repeatability of uniaxial compression tests.