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

permissible stresses [σ] when evaluating the strength of vessels ma de of carbon, low-alloy, and other steels is physically justified (GOST R 52857.1-2007).

Fig. 2. Diffraction line profiles reflected from planes of the second order ( hkl ) = (220) of samples of 09G2S low-carbon steel at different levels of stress state.

Table 1. Characteristics of the diffraction line profile of 09G2S steel samples at different stress levels Stress level σ of samples 2θ av. [degree] I [imp/sec] FWHM av [degree]

d [Å]

0,167 0.309 0.350 0.341

Standard , σ = 0

123,896 123.992 124.022 123.960

720 184 248 263

1,01355 1.01318 1.01296 1.01325

σ = 0,3 σ 0,2 σ = 0,5 σ 0,2 σ = 0,9 σ 0,2

It should be noted that the obtained results agree with the currently developed theoretical concepts of the excitation of spatially localized vibrational modes, discrete breathers, by distortions of the crystal lattice by Dmitriev et al. (2016). Several works by Dmitriev et al. (2016), Zhu and Li (2010) specify the effect of minor elastic strains of the crystal lattice on the change in phonon spectra and discrete breathers, which contribute to the rearrangement of the substructure of nonequilibrium crystals. The influence of external mechanical action on changes in the substructure of the surface layers of the test material had also been established by X-ray and neutron diffraction methods by Klevcov et al. (2006), Ershov et al. (2015), Grinberg et al. (2016). Thus, the work [17] demonstrates that the direct measurements of the microhardness of the decomposition of martensite of 40X-brand steel during aging had revealed a close relationship between the broadening of diffraction maxima from the crystallographic planes of the first and second orders (110, 200, 211, 220, 222) obtained by the neutron diffraction method over the entire volume of the investigated sample. 7. Conclusion The possibility of recording the FWHM broadening of the diffraction line profile reflected from the system of crystallographic planes ( hkl ) of 09G2S structural steel as an indicator of elastic deformation at a certain level of stress-strain state caused by external loads has been substantiated experimentally. The study of the elastic deformation of the crystal lattice in the load range of (0.3 ... 0.9) σ 0.2 based on the registration of the broadening (changes in the size and shape) of the FWHM profile of the diffraction line allows substantiating the values of the safety coefficient when calculating the strength of machine parts, structural elements for certain operating