Methodology and results of experimental determination of corn grain elasticity modulus

Abstract

Theoretical justification of rational design parameters of effective threshing and separation devices for corncobs of various subspecies requires knowledge of the mechanical characteristics of the grain, of which the modulus of elasticity is the most significant. At the present stage of the threshing theory development the numerical values of the modulus of elasticity of grain of various subspecies of corn require experimental clarification. The complex geometrical shapes of the grains of dent, flint, sugar and pop corn do not allow determining their modulus of elasticity by the conventional method of tensile testing. To solve this problem, an experimental-theoretical method was proposed for determining the modulus of elasticity of corn grain and refining its Poisson's ratio during compression, based on the application of Hertz's theory. The essence of the method is to determine the micro deformations of corn grains with a complex geometric shape and located in the platform under the action of special cylindrical indenter, by continuous loading to the boundary value of the elastic deformation of the grain shell. Resistance to displacement of the cylindrical indenter in the protective fruit shell of grain is controlled by analytical weight equipment of II-high accuracy class, and deformation by a micrometric depth meter of the first accuracy class. The humidity content of the test grain is in the range of 12.8…13.4% and controlled in laboratory conditions by means of equipment for controlling the humidity content of cereals. As a result of the studies, numerical values of modulus of elasticity for protective fruit shell were established of grain of dent corn 78…127 MPa, flint corn 98…125 MPa, sugar corn 97…124 MPa and popcorn 127…169 MPa and the physical causes of their numerical difference were analyzed. The research results make it possible to carry out more accurate theoretical and engineering calculations when designing innovative threshing and separation devices for the cobs of seed, food and forage corn of various subspecies.