PSI - Issue 65

Prokopyev L.A. et al. / Procedia Structural Integrity 65 (2024) 170–176 Prokopyev L.A., , Andreev Ya.M., Semenov S.O., Lukin E.S. / Structural Integrity Procedia 00 (2024) 000–000

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Keywords: Plasticity zone, low temperature, cold resistance, yield strength

1. Introduction

At present, the problem of cold resistance of structural steels is associated with a change in the physical and mechanical properties of the material at low temperatures, in particular, with the transition from ductile to brittle fracture. This leads to a decrease in absorbed energy upon impact, an increase in the susceptibility to crack formation and a decrease in the plastic limit. The main factors affecting the cold resistance of structural steels, as noted by Petrova (2022) and Sibilev (2013), include the chemical composition of the steel, microstructure, the presence of non-metallic inclusions, stress concentration, loading rate, etc.

Nomenclature Ϭ μ athermal component of the yield strength B, β e strain rate Ϭ ij stress components

coefficients of the material for the yield strength expression

K I r,θ T xx

stress intensity factor

axes of the polar coordinate system with the origin coinciding with the crack tip

T-stresses

γ

Poisson’s ratio

Ϭ Y yield strength Ϭ 1 , Ϭ 2 , Ϭ 3 principal stresses

Modern researches of cold resistance are focused on the development of new alloys and materials with improved properties for use in cold conditions, as well as the development of new non-destructive testing methods to evaluate the cold resistance of steel. Progress in this direction, as noted by Kornev (2018) and Panin (2016), requires an integrated approach, including not only the research and implementation of new materials, but also the development of new standards designed to assess the degree of cold resistance of the material. Currently, the impact strength method is the main method for assessing the level of cold resistance of materials, determining the temperature range of operation of the material. This method is one way to measure the toughness of materials by impacting a sample and measuring the energy loss upon impact. The impact strength method is widely used due to its simplicity and speed of execution. The disadvantages of this method are the significant scatter of results, the dependence of the results on the impact speed and temperature conditions. Also, the impact strength method can be influenced by various external factors, which makes the results not always reliable. Kolbasnikov (2011) indicate the presence of an exponential relationship between the yield strength of a material and impact strength. Impact strength is an empirical method, and its result depends on many factors, such as loading rate, temperature, size and shape of the plastic zone, structure and type of crystal lattice of the material, and so on. With the development of materials science, mechanics of deformable solids, and other branches of science, it is necessary to develop existing methods for diagnosing and predicting the behavior of materials at low temperatures. It is necessary to carry out work to develop new non-destructive testing methods that can effectively assess the cold resistance of steel. To achieve progress in this area, a comprehensive approach is required, including the introduction of new materials and the development of standards for assessing cold resistance. Thus, the study of individual factors that initiate brittle fracture of metal parts and structures at low temperatures is an urgent task. Ensure that you return to the ‘Els-body-text’ style, the style that you will mainly be using for large blocks of text, when you have completed your bulleted list. Please do not alter the formatting and style layouts which have been set up in this template document. As indicated in the template, papers should be prepared in single column format suitable for direct printing onto paper