EFFECT OF VARIETY, SIZE AND MOISTURE CONTENT ON MODULUS OF ELASTICITY AND MAXIMUM CONTACT STRESS OF BARLEY

Performing any kind of engineering analysis for design and modification of mechanical systems in different procedures of grain harvesting and processing, including barley, depends on basic information about physical and mechanical properties of agricultural commodities. The properties vary significantly due to biological nature of agricultural materials in different conditions (according to variety, shape, size, moisture content, etc.). Accordingly, in this research project, two important parameters of grain strength were extracted by conducting 300 compression tests. Then, the effect of independent parameters were investigated on them by a statistical method. The results showed that variety and moisture content have a significant effect on modulus of elasticity and contact stress, while, the effect of grain size was not significant. In this relation, by increasing moisture content, contact stress and modulus of elasticity decrease linearly and by a S-shape curve, respectively. Accordingly, it should be considered the 17% level of moisture content (w.b.) as transition moisture in barley grain, which the grain exhibits brittle and soft behavior at rates of less and more than of it. The range of maximum stress induced in the barley grain, at the elastic range, began from 243 MPa at 25% to 2832 MPa at 10.2% of MC. As a same result, maximum contact stress varied from 11.3 MPa to 455.4 MPa at different treatments.