The results of theoretical studies confirming the possibility of carrying out preliminary separation of free grain from the stripped grain pile before it enters the threshing chamber of a combine harvester are presented. The prospect of a separating device mounted directly in front of the threshing drum, consisting of longitudinal rods, over which an additional scraper conveyor is mounted, has been established. The cross section of each strip of the grating is narrowed downwards to increase the intensity of separation of the device and eliminate the possibility of clogging the holes with passing particles of the heap. The optimal length of the openings of the pre-drum type separating device, its spatial orientation were determined, and the quality indicators of the work were evaluated. Theoretical studies of the separation process on winter wheat of the “Moskovskaya 56” variety with a grain size of 3.9x6.5 mm were performed. The speed of the scraper conveyor was 3 m/s, and the angle of inclination of the separating device varied within 0-45 degrees. It has been established from the results of research that with an increase in the angle of inclination of the separating surface, the length of the sieve openings increases, and the separation speed decreases. Since the horizontal grate provides a higher separation rate of free grain, compared to an inclined surface, the use of a pre-drum type separating device is most preferable in relation to the grate bottom of the feeder house of a combine harvester in terms of its performance. It has been established that the length of the separating holes should be at least 0.08 m. Such a technical solution allows minimizing not only the crushing of free grain by the working bodies of the threshing machine, but also to reduce the metal consumption of the separating device.
Among the details of the working bodies of soil-developing tools, cantilever-fixed structural elements occupy a certain place, which are operated under conditions of high-intensity abrasive wear. Known theoretical studies do not allow predicting the resource of cantilevered parts, taking into account the wear factor and the deformation ability of the material. Two tasks were theoretically solved in the work on determining the resource of a part until the moment when: 1 - the wear section becomes so thin that the transition area from the worn part to the non-worn part becomes more dangerous when bending than the cantilever fastening area; 2 - destruction will occur in the transition zone from the unworn to the worn area. Problem solving was carried out using the methods of the course "Strength of materials". The cantilever-fixed beam of variable section is taken as the design scheme. It was taken into account that the main parameter characterizing the strength of a bent beam is the magnitude of tensile strains that occur on its convex side. It was taken into account that the main parameter characterizing the strength of a bent beam is the magnitude of tensile strains that occur on its convex side. The conditions for the occurrence of the danger of destruction and the destruction itself in the section of the part, where the transition from the worn part to the non-worn part takes place, are determined by theoretical studies. The result of solving two problems was the derivation of formulas by which it is possible to predict the resource of a part in case of its local wear. A mathematical expression has been obtained that makes it possible to calculate the operating time of a locally worn cantilever-fixed part, when the width of the cross-section of the wear area decreases so much that the transition area to the unworn part becomes more dangerous than the cantilever fastening. A mathematical expression has been obtained that makes it possible to determine the resource of a structural element for the case when its destruction occurs at the point of transition from a worn area to a non-worn one.
BACKGROUND: Often, parts of the working bodies of machines operating in abrasive environments have a cantilever mount. Due to wear, their dimensions are lost, specified by the technical conditions, and destruction occurs. The resource of these products is determined by the allowable bending stresses, taking into account the intensity of their wear. The existing theoretical methods for predicting the operating time of a part to its limiting state when solving problems do not take into account the criteria of strength and wear in the complex. AIMS: The aim consists in obtaining a mathematical expression that determines the resource of the part when it is worn, taking into account the allowable stresses. METHODS: The disclosure of the goal was carried out by solving the problem of predicting the resource of a cantilever-fixed using the classical course of the resistance of materials, ele-ments of the theory of elasticity and the basics of tribotechnics. RESULTS: As a result of mathematical research and based on practical knowledge, a formula was obtained for determining the resource of a part, which takes into account the dimensions of the part, the magnitude of the allowable stresses, the coefficient regulating the resistance of the material to wear, the pressure on the working surface, the pressure at the pinch point and the pres-sure at the free end timber. The conditions determined by two inequalities are established under which the part will be operable. CONCLUSION: Mathematical expressions have been obtained that make it possible to predict and the conditions for the performance of cantilever-fixed parts in the process of their wear ac-cording to allowable stresses have been determined.
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