APPLICATION OF MODELS OF THE STRUCTURE OF SEPARATION SURFACES IN STEELS WHEN OBTAINING PRODUCTS WITH A GIVEN LIFE CYCLE

Abstract

Background. The development of digital mechanical engineering requires the development and use of interdisciplinary concepts and models of the behavior of heterogeneous polycrystalline materials under the influence of technological and operational loads. In this regard, the development and use of approaches to modeling and analysis of the mechanical behavior of the boundary zones of separation of products, taking into account their energy, becomes important. The development of such approaches makes it possible to solve an actual scientific and technical problem – optimization of the modes of technological processing of products with a given life cycle. Objective. The use of system models of the structure of steels for the development of computational schemes and methods of managing the structural-energy state of the separation surfaces of structural components when obtaining products with increased reliability parameters, taking into account the conditions of their operation. Methods. The analysis of the structure was carried out using the concept of invariant modeling, the results of metallographic and factographic studies, electron microscopy. The assessment of the structural and energetic state of grain separation surfaces after ionplasma etching of the samples was carried out, wear and impact bending tests were carried out, and system computer simulation of the properties of polycrystalline systems was carried out using the FEniCS open finite element analysis package in Python. Results. When applying the energy description of continuous non-local environments, it was established that depending on the angles between the boundaries at the joints of the grains, the structural and energetic state of this region and its ability to form microdefects change. At angles between 140‒180°, zones are formed with a high capacity for the formation of intergranular damage and destruction under load. It is shown that the intensity of wear and intergranular fracture upon impact increases depending on the number of triple joints, in which the boundaries differ significantly in terms of energy level. Steel 40X (5135 Steel) is more sensitive to the formation of triple junctions with a high energy gradient during heat treatment than steels containing nickel, molybdenum and silicon. Conclusions. On the basis of hierarchical modeling of the structure of polycrystals, new approaches are proposed and an algorithm is created to determine the relationships between the structure of the separation surfaces of steels and their operational reliability. Diffuse damage is formed on the separation surfaces between the triple junctions of grains with a high energy gradient. Reducing the share of triple joints, which differ significantly in terms of energy when designing the technological regimes of the quenching and tempering processes, made it possible to increase the wear resistance of improved steels by 48‒53 %.