Investigation and Determination of Moisture Content and Temperature Effects on the Mechanical Properties of Brown Rice

An understanding of the strength of rice grains as affected by moisture content and temperature is important for analysis and prediction of cracking and/or breakage behavior during handling and processing. Further, the magnitude of these properties at various moisture contents and temperatures is needed for the accurate design of milling machinery so that grain damage is minimized. To determine the compressive mechanical properties of grains, two types of quasi-static compressive tests, whole kernel and uniaxialcompressive tests, of core specimens were performed at three moisture contents, 10.2%, 12.2% and 13.25% (w.b.), at grain temperatures of 35, 45, 55 and 64°C. Failure force, deformation and energy at the breaking point and apparent elasticity modulus were determined for whole grain tests, and compressive strength, failure strain, toughness modulus and compression modulus of elasticity were determined for uniaxialcompressive tests. Statistical analysis of the mechanical tests results indicated that moisture content and temperature have a strong influence on the properties examined. There was no significant effect on rice compressive failure properties. Moisture content had the greatest effect on the mechanical properties of rice. In general, all strength values except compressive strain increased as moisture content and/or temperature of grains decreased. For the different rice grain conditions studied, failure force varied from between 37.01 to 89.96N, while compressive strength varied from between 16.43 and 44.42MPa.