Modelling the stress-strain state of blades affected by plasma arc for the food grinding plant

This article considers the efficiency of the food grinding plant and appropriate methods aimed at increasing its reliability and durability. It is established that a plant's service life is limited by the service life of its knives. It is proposed to apply surface plasma nitriding with a compressed moving plasma arc to strengthen the knives. The use of such a highly concentrated heating source allows for surface hardening of a product, though only of its wear parts, including preliminary bulk hardening of its core and thereby maintaining materials' plastic properties. This method of heat treatment allows to increase the resistance to wear and fatigue; to provide hardness and wear resistance of the surface; to reduce the deformation of the hardened parts due to the locality and short-term interaction of plasma with the metal surface. According to the results of the preliminary experimental studies on surface temperatures close to the melting temperature of steel, the temperature distribution law is established. Based on the Gaussian law of temperature distribution in the finite element computing system ANSYS, a theoretical model is developed to study the distribution of the temperature field in the knife in depth at different speeds of the heating source and currents in order to provide optimal parameters of the heat treatment process at a given depth of tempering, hardness, etc. Further, on the basis of these data, a theoretical experiment is conducted to study the stress-strain state of the knife under the influence of a moving heating source modelling the plasma jet. The mechanical and mathematical model developed by ANSYS takes into account the temperature change in the diameter of the moving heating spot and the dependence of the physical and mechanical characteristics of the knife's material on temperature. A plasma torch and plasma system are developed, and surface plasma nitriding of knives subject to preliminary bulk hardening is performed. The wear resistance of the blades after an extensive surface hardening and plasma nitriding is investigated. The results of the research allowed to increase the wear resistance of knives subject to preliminary bulk hardening and surface plasma nitriding by more than 2 times compared to bulk hardening.