PSI - Issue 40

V.P. Gulyaev et al. / Procedia Structural Integrity 40 (2022) 180–184

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Gulyaev V.P. at al. / Structural Integrity Procedia 00 (2022) 000 – 000

reliability and technical readiness of machines. It is known by Arabei (2010), Vorobyov et al. (2012), Kushnarenko et al. (2016) that the main properties of machines that determine their performance during operation in mining are strength, wear resistance of strength members and their joints. However, the technological possibilities for further improvement of the mechanical properties of structural steels are limited by the current understanding of their crystalline structure, heat treatment modes, deformation and fracture processes. The reliability issues of machine parts and metal structures assume particular importance when analyzing the cost indicators of large-scale projects for the development of regions rich in mineral resources. Therefore, the relevance of researches related to the scientific substantiation of the safety coefficient values of construction parts, which directly predetermine the specific amount of metal, is increasing. 2. Problem statement Along with ensuring high operational properties of various parts of mining machines, which generally determine the technical readiness and serviceability of machines during their operation, issues related to a reasonable decrease in the metal consumption of the machine structure without losing their bearing capacity are of considerable importance. The specific amount of metal is determined by the physical and mechanical characteristics of construction materials, which are selected when calculating the parts of the product for static and dynamic strength, fatigue strength, wear resistance, and other properties necessary for reliable operation during given product life. 3. Research questions The current level of designing and manufacturing technologies of machines, the use of computer methods for modeling the stress-strain state for the expected operating conditions allow applying reasonable geometric shapes on parts and units of machines. However, the specific dimensions of "strength or bearing" members in terms of strength depend on the permissible stresses [σ] or on the safety coefficient, the range of values of which is wide and currently does not have sufficient theoretical justification. Thus, there is a high degree of uncertainty in the issue of establishing the minimum possible metal consumption of the machine structure. 4. Purpose of the study One of the ways to justify the values of the safety coefficient of machine parts for full employment of the service properties of structural steels is to study the physical processes of elastic deformation by the X-ray diffraction method by Gulyaev et al. (2018), Bokuchava et al. (2014), Koneva et al. (2015). The measuring capabilities of the X-ray diffraction method provide observation and registration of changes in the crystal lattice in the field of external stresses that do not exceed the conventional yield stress σ 0.2 of steel. The technical improvement of instruments and equipment significantly expands the application field of the X-ray diffraction method in the laboratory research of a substance. It also allows measuring the stress-strain state of machine parts and other structures under the operational loads. The works by Koneva et al. (2015), Kljuev et al. (2015), Aleshin (2011), Botvina (2008), Klevcov et al. (2006) demonstrate the high efficiency of using X-ray diffractometers, including portable ones, for technical diagnostics and non-destructive testing of operating industrial facilities, quality control of parts manufacturing, etc. 5. Research methodology The effect of short- term action of stresses not exceeding the yield point σ 0.2 on the change in the FWHM broadening was examined on flat samples of 09G2S steel. The specimens were subjected to tension by a monotonically increasing load up to certain load values corresponding to fractions of the yield σ 0.2 (Fig. 1). According to the experimentally established yield point of 09G2S steel σ 0.2 = 382 MPa, the inspect.d flat samples were stretched at a speed of 2 mm/min until the following load values had been reached: F = 8 kN; F = 13 kN; F = 19 kN; F = 21 kN; F = 24 kN. Consequently, stresses equal to σ = 0.3 σ 0.2 ; σ = 0.5 σ 0.2 ; σ = 0.9 σ 0.2 were observed for a short time in the working parts of each separate flat sample.