Mechanical fracture characterization of rice kernel under milling process

Abstract

Mechanical Fracture of rice kernel caused by milling process has not been studied completely yet. The objective of the research was to study the fracture of rice kernel under rubber-roll milling process. A long- grain rice variety (IR 64) and a-short-grain rice variety (IR42) with 14 % average moisture content (MC) were choices as the sample in this research Physical and mechanical properties of rice kernel were evaluated using micro Vickers hardness tester. Fractography of fracture surface using Scanning Electron Microscope (SEM) was used to observe the fracture surface. Gold coating on fracture surface was needed to become conductive. Stress analysis was also evaluated analytically in order to know the relationship between rice breakage force and pressure force induced roll rubber. The result shows that there is significant distinct of the hardness between IR 64 and IR 42 variety. Fractography of IR 42 and IR 64 show that modes of fracture are brittle. Cleavage of crack is clearer for IR 64 and initiate from the mid of part to outer part. Microcrack distributed along inert granules of endosperm zone. Force induced by roll with respect to paddy (Fn) is recommended smaller than the breakage force of paddy (Fp) in order to avoid fracture during milling process.