PSI - Issue 40

Peter V. Trusov et al. / Procedia Structural Integrity 40 (2022) 433–439 Peter V. Trusov et al. / Structural Integrity Procedia 00 (2022) 000 – 000

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1. Introduction The phenomenon known as the Portevin-Le Chatelier effect, observed in various metals and alloys in certain temperature-rate ranges of deformation, corresponds to the transition to unstable plastic flow and localization of plastic deformation, that leads to a significant decrease in strength and plasticity, reduces corrosion resistance, and reduces quality material surface Bell (1973). Scientists suggested some hypotheses to explain the Portevin-Le Chatelier effect. One of the first explanations of the PLC effect belonged to A.G. Cottrell, who explained the effect by the diffusion of impurity atoms to dislocations and their “pinning” due to interaction with impurity atoms. This point of view is shared by many modern researchers of the PLC effect (for example, Beaudoin A.J. , Benallal A., Berstad T., Besson J., Børvik T., Guo W .G., Fressengeas C., Hähner P., Kim D.W. , Larsson R., Nilsson L., Nortmann A., Mazière M., Mesarovic S. Dj., Rizzi E., Schwink Ch., Varadhan S., Zhang X.Q.). Currently, none of the hypotheses explaining the PLC effect is prevalent and proved experimentally, which is why there are no models that describe this effect with a high degree of adequacy for various materials and loading conditions. Both empirical methods and approaches based on mathematical modeling are used to analyze discontinuous flow, to determine the optimal modes of material processing. Mathematical models make it possible to study the phenomenon of crystal plasticity, including the description of the appearance of deformation defects, their motion, interactions, which are difficult or impossible to observe in a real physical experiment. Many works are presented in the literature, where the numerical study of the PLC effect is associated with experimental studies. To describe dynamic strain aging and the effects associated with it, most researchers (Benallal A., Bertram A., Böhlke T., Chen X., Estrin Y., Graff S., Hähner P., Hopperstad O., Hu S.Y., Kubin L.P., Larsson R., Ling C.P., McCormick P.G., Rizzi E., Zhang S., Yang S.-Y., Yu D., etc.) use macrophenomenological models of inelastic deformation (Trusov and Chechulina (2014)). A macrophenomenological elastic-viscoplastic model based on experimental data under uniaxial loading is considered in Benallal et al. (2006). A qualitative analysis of the model for the case of uniaxial loading is carried out. The model under consideration is generalized to the case of a three-dimensional stress-strain state and applied in the LS-DYNA finite element package to study the deformation of cylindrical specimens (smooth and with an annular groove with different radii of rounding) made of 5083-H116 aluminum alloy. The results of carefully performed and processed experimental studies on uniaxial loading of specimens of circular and rectangular cross sections subjected to uniaxial loading at room temperature in the range of strain rates from 10 – 5 to 10 3 s – 1 is presented in Benallal et al. (2008). A macrophenomenological model for the analysis of discontinuous plasticity is proposed in Yang et al. (2006). Uniaxial loading of a polycrystalline sample under conditions of plane-stressed and plane-deformed states is considered. Satisfactory agreement of calculation results with experimental data is noted. The results of experimental and theoretical studies of uniaxial loading of specimens (aluminum alloy 2024) cut from rolled sheet blanks at angl es of 0, 45, and 90° to the roll ing direction are presented in Böhlke et al. (2009). All tests were performed at room temperature, strain rate from 1 · 10 – 5 to 7 · 10 – 1 s – 1 . For the theoretical description of the deformation process, the macrophenomenological theory of elastic-viscoplasticity is used, where the additive decomposition of the deformation rate into elastic, plastic and viscous components is taken. The results of studying the aged Al-Mg-Si alloy under uniaxial tension are presented in Anjabin et al. (2014). In constructing the model, the previously obtained results of other researchers are widely used, particularly analytical solutions to the problems of nucleation and growth of inclusions formed by impurity atoms. The direct crystal plasticity model built into the ABAQUS package was used for the implementation. Comparison of the theoretical results with the data of the experiments carried out by the authors reveals a satisfactory agreement. A similar model was previously used in Graff et al. (2005) to analyze the deformation of Al – Li and Al – Cu alloys. For the numerical study, samples of rectangular cross-section with flat faces, with V-shaped notches (with angles of 60 and 90 °) and with flat notches simulating cracks were used. The origin and p ropagation of shear bands, the effect on their kinetics of changes in the notch shape and strain aging are analyzed in detail. The studies Trusov and Shveikin (2019); Trusov and Chechulina (2017) propose a review of theoretical works based on physical theories of plasticity, devoted to the description of the features of deformation of alloys in temperature-rate ranges, in which diffusion processes have a significant effect on the behavior of materials. Particular attention is drawn to the description of the Portevin - Le Chatelier effect.