The main objectives of the present study were to develop of an optical instrument to determine grain cracks based on numbering crack grain using a visible light radiation as the light source., and studying the effects of cracks percentage on some mechanical parameters of grains to minimize grain damage and increase rice grain quality. Grains of rice verities were Sakha 103, Yasmein Masry, Giza 101 and Giza 177. Grains with the initial moisture content of about 10.6 % (b.d.), with the husk of rice grain removed by hand. The milled grains were put on screen then exposed to visible light radiation under the screen, then crack grains were counted.
The following conclusions were drawn on the basis of results of mechanical testing and light radiation examination: 1) The percentage of cracks for different grains increased with the increase of the deformation of grain, while compression strength, specific work and elasticity modules were decreased, 2) Type of grains effect on the values of mechanical parameters. Sakha 103 grain variety showed higher strength, modulus of elasticity and specific work than Giza 177 which was the lowest one., 3) Rice grain variety of Giza 177 with the moisture content of about 10.6% followed by resulting in a decrease in grain strength, modulus of elasticity and specific work by 44.75, 66.34, and 52.69%50% compared to the Sakha 103 . where the deformation increased by 36.84% , 4) Mechanical parameters showed high correlation with the percentage of cracks. The correlation coefficient for the strength against crack percentage of grain was equal to 0.92, for the modulus of elasticity 0.99, while in the case of specific work it was equal to 0.89., 5)Resistance to cracking of grain to impacts can be advantageous on storage and biological characteristics .
On the other hand, high impact resistance is unfavorable in processing because of higher energy costs and less efficiency., 6) Visible light radiation method is useful for estimating seed cracking to dynamical loads., and 7) Crack testing should be continued to study the relationship between the crack value and impact site, on mechanical properties of grains , especially when using grain for industry or germination.