High velocity impact of maize kernels

The strength characteristics of maize kernels when subjected to fracture by impact were studied with the ultimate objective of improving the design of hammer mills. An experimental machine was developed for the measurement of impact parameters at velocities of up to 68 m/s. The grains were released individually from a box mechanism carried at the tip of a rotor arm over a range of speeds to hit a target plate. Measurements were made to permit the assessment of the energy of impact and the new surface area exposed, so that comparative values could be obtained for energy per unit of new surface area exposed. Three types of maize grain were tested, namely, SR 52, FERZ 7 and FERZ 34 with FERZ 7 requiring the most energy for fracture in general. Moisture content had the most significant effect on all three varieties such that the higher the moisture content, the more energy was required between 7% and 22%. The optimum velocity of impact to minimise the specific energy required for fracture was in most cases about 35 m/s to 40 m/s. (C) 1997 Silsoe Research Institute.