الفهرس 
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Abstract
Physical properties often required for developing the machines for cleaning of grain. Physical properties of wheat varieties (Sakha93) were determined and compared for moisture content 9.9, 12.4, 14.9 and 17.6 % d.b. The average length, width and thickness were 7.46, 3.37 and 2.66 mm at a moisture content of 9.9 % d.b., respectively. Studies on wheat grain showed that the thousand-kernel mass increased from 48.596 to 55.206g when the moisture content increased from 9.9 to 17.6 %. The geometric, equivalent and arithmetic mean diameter at a moisture content of 9.9 % were 4.06, 4.08 and 4.5mm. The average mass of one grain, volume and surface area were 0.048g, 35.49 mm3 and 43.87 mm2. Area of flat and transverse surface was 19.74 and 7.04 mm2. Sphericity and index-k were 54.41% and 2.49. Bulk density decreased from 660 to 589.8 kg m-3, when increasing the moisture content from 9.9 to 17.6 % .True density decreased from 1244.6 to 1210.8 kg m-3, when increasing the moisture content from 9.9 to 17.6 %.Angle of repose varied from 16.8 to 21.6º when the moisture content increased from 9.9 to 17.6 % .The static friction coefficient of wheat increased linearly against surfaces of four structural materials, namely, wood (0.379 – 0.399), galvanized iron (0.345 – 0.364), formica (0.306 – 0.344) and glass (0.299 – 0.335) as the moisture content increased from 9.9 to 17.6 %. So a rice polishing machine was developed and tested for cleaning wheat grain. It consists of a feeding unit, cleaning unit, power drive unit and power transmission unit. Four levels of moisture content were about [9.9, 12.4, 14.9 and 17.6 % (d.b.)]; three friction surfaces with three static coefficient of friction were [smooth = 0.35, intermediate between smooth and rough = 0.43, and rough surface= 0.51]; four levels of pressure on cleaning chamber were [1.25, 3.75, 6.25 and 8.75 kN/m2] and three speeds of air suction flow speeds of [1.3, 2.8, and 3.4m/s.], were used. The maximum value of cleaning efficiency was 99.93% achieved at, moisture content (M1= 9.9 %), pressure (P4 =8.75 kN/m2), rough friction surface (F3=0.51), and suction air speed (S3 =3.4 m/s). The minimum value of grain damage was 3.5 % achieved at, moisture content (M4= 17.6 %), smooth friction surface (F1=0.35), pressure (P1=1.25 kN/m2) and suction air speed (S3=3.4 m/s). The minimum value of losses due to polishing was 0.41 % achieved at, moisture content (M4=17.6 %), pressure (P1=1.25 kN/m2), smooth friction surface (F1=0.35) and suction air speed (S1=1.3m/s).