Estimation of strength properties of functionally graded structures with elliptical stress concentrators

Abstract

Purpose: The purpose of this paper is to elaborate new calculation schemes for evaluating the strength parameters of railway rolling stock parts with non-local properties of surface layers in the presence of elliptical stress concentrators. Design/methodology/approach: Using the proposed approaches of developed mathematical modelling and open software for calculating FEniCS, it were established the most dangerous angles of stress concentrator orientation and the required thickness of the hardened zones of parts, which ensures their minimum softening during operation. Findings: It is shown that for an elliptical stress concentrator with any orientation angle, there is a certain key size of surface hardening thickness, the exceeding the value of which does not have influence on the operational strength of the parts, but rise the price of technological operations. Research limitations/implications: In this paper proposes a method for computation the impact of the orientation of the surface elliptical stress concentrators on the contact strength of parts under conditions of dominate friction power loads. Practical implications: The obtained results were used to set the modes of plasma hardening, which increase the contact strength of railway parts with elliptical stress concentrators. Originality/value: Using the approaches of contact mechanics, mathematical and computer modelling, methods of controlling the contact strength of the parts with the surface elliptical stress concentrators were proposed for the first time.

Development of the material homogeneity criterion for the analysis of processes of technological inheritability for quality parameters of machine parts

“…Experimental studies, along with the development of simulation methods for modeling technological processes, are important for confirming theoretical propositions, accumulating databases, and predicting the behavior of products in operational conditions [7,21].…”

Assessment of elliptical defect dimensions influence on the metal structure contact strength properties

“…Technological problems of strengthening of parts showing stress concentrators are complicated and require considering a great number of factors. Their solution is based not only on the application of nonlocal models of continuum mechanics, but also on the methods of nonlinear functional analysis, which considerably complicates the formulation of such problems and the search for their solution [1,4].…”

“…Currently, the optimization of technologies for surface strengthening of circular stress concentrators has been examined [5] and approaches to the influence of elliptical defect orientation angle, in particular, on the serviceability of railway rolling stock wheels, have been proposed [1].…”

“…Computer and mathematical modelling is one of the productive ways of predicting the reliability of a structure given the lack of possibility to carry out in-situ experiments. A generalized formulation of the problem of determining operational parameters of parts with nonlocal mechanical properties and arbitrary orientation of elliptical stress concentrators is presented in [1]. Relying on the results of the considered work, let us propose the following two-dimensional problem of determining optimal parameters of functionally graded structures under variable sizes of elliptic stress concentrators.…”

“…At the same time, one of the characteristic features of transport engineering is the occurrence of geometric stress concentrators close to the contact surfaces, either of constructive, technological or inservice origin. The operational characteristics of parts significantly depend on the parameters of stress concentrators [1], which allow reducing their negative effect.…”