Fissure Characteristics Related to Moisture Adsorption Stresses in Rice

Abstract

Rice kernels were initially conditioned to three equilibrium relative humidities (ERH) of 46, 62, and 80%, and then exposed to high relative humidity (RH) environments of 65, 86, and 100% for different periods. Kernels were inspected for stress fissures during moisture adsorption. The three major stress components, namely axial, radial, and tangential stresses were studied in relation to failure tensile strength and local strain energy density of distortion using the finite element method. The calculated axial stresses from moisture adsorption were compressive at the surface and tensile at the grain center. The calculated radial stresses in the central section of a grain were always tensile and high at the center and negligibly small at the surface. The behaviors of the tangential stress distributions along the central radius were identical to that of the axial stress along the radius. The calculated stress distributions agreed rather well with stress distributions in a rice kernel as they were hypothesized by Kunze and Choudhury (1972).