Reduction of mechanical damage to bean seeds during harvesting and post-harvesting

When harvesting and post-harvest processing of bean batches, its mechanical damage is noted. As a result of the interaction of individual grains with the working bodies of machines, stresses exceeding permissible arise in them that destroy the seeds. The article is devoted to an urgent problem - the search for ways to reduce mechanical damage to beans during harvesting and post-harvest processing. To estimate the magnitude of the stresses arising under force loading in the bean grain, it is modeled in the form of an ellipsoid. It is revealed that the magnitude of these stresses depends on the curvature of the contacting bodies, their elastic modulus, coefficients of transverse deformation, moisture content of the grain material, as well as the speed of collision of the grain with the working body. It has been experimentally shown that the deviation of the actual grain volume determined by the appropriate method, depending on the variety, does not exceed 13%. The values of the maximum stresses in the grains under static force loading from 1.45 to 5.15 MPa, the limiting contact areas from 15.5 to 31.08 mm2, the values of the elastic modulus from 25.80 to 146.24 MPa with a change in humidity from 28.2 to 8.6% were experimentally determined. These dependencies are approximated by mathematical expressions with a sufficiently high value of the approximation reliability coefficient. According to the results of the research, it was found that in order to reduce mechanical damage and increase the efficiency of bean production, it is necessary to carry out processing at a grain moisture content not exceeding twenty percent, monitor the condition of the edges of the working bodies, preventing their sharpening, use working bodies made of a material with an elastic modulus significantly lower than that of steel, reduce the speed of collision of grains with the working body. The obtained theoretical dependencies will allow designers of agricultural machines to assess the degree of force impact on the grain and not exceed the permissible values.