Scientific journal NRU ITMO
Series "Processes and Food Production Equipment"
Registration certificate ЭЛ № ФС 77 – 55245 - 04.09.2013
registered by the Federal Inspectorate Service for Communication, Information Technologies and Communication Media

June 2021 (published: 15.06.2021)

Number 2(48)

Home > Issue > Dependence of the optimal knife thickness on the geometric and elastic characteristics of the chopper structural elements

UDC 519.68:532.7:541.8:541.182.41

Dependence of the optimal knife thickness on the geometric and elastic characteristics of the chopper structural elements

Pelenko V.V., Nechitaylov Vasily V., Verboloz A. P., Demchenko V.A., Kutsenko Dmitry A., Barinov Grigory V.

The problem of describing the process of bending deformation of the output lattice, presented in the form of around solid plate, and a knife blade as a cantilever beam for a screw extruder-grinder has been formed and analytically solved. At the same time, the influence of the geometrical parameters of the grinder and the elastic characteristics of the cutting elements on the optimal ratio of their thicknesses, which ensures the absence of concentration of internal stresses in the plane of contact between the knife and the grate, has been evaluated. A peculiarity of the problem formulation is takinginto account the variable nature of the external loading of the grate and the knife due to the presence of reverse flow of the product (sluice), as well as considering a promising version of the conditions for fixing the knife and grate on the top screw body. The complexity of material movement in screw grinders during its extrusion and cutting is due not only to the complex screw shape of the screw, but also to the presence of a sluice gap between the inner screw surface of the counter-rotation ribs of the extruder body and the outer screw surface of the screw turns. The significant effect of the material backflow on the formation of an alternating pressure field is taken into account by approximating the law of its variation with a linearly decreasing function. At the first stage of the presented study, the processes of bending of each of the two elements of the knife-lattice cutting pair under the influence of a varying load are analytically described by the methods ofdifferential calculus. At the second stage, a condition and criterion for optimizing the ratio between the thickness of the knife blade and the thickness of the output grinding grate are formulated. Based on the obtained mathematical model for the dependence of the thickness of the knife blade on the design and elastic characteristics of the top elements, as well ason the thickness of the outlet lattice, the optimal value of the blade thickness can be calculated, which ensures the elimination of the concentration of contact stresses in the knife-lattice joint and the reduction of the knife wear rate, and also the energy consumption of the shredding process.
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Keywords: mathematical modeling; differential equation of bending; variable pressure; wear rate; optimization; cutting pair; knife thickness

DOI 10.17586/2310-1164-2021-14-2-40-52

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