PSI - Issue 41

Alexander Inozemtsev et al. / Procedia Structural Integrity 41 (2022) 544–549 Author name / Structural Integrity Procedia 00 (2019) 000–000

545

2

1. Introduction The phenomenon of plastic strain localization, i.e. the formation of narrow regions of plastic flow, in which the level of plastic strain is orders of magnitude higher than in the surrounding material, is of theoretical and practical interest. Plastic strain localization in metals at different loading rates is a complex process, which depends on the rate and magnitude of deformation, temperature, and the evolution of the material structure. This phenomenon has been investigated by Giovanola J. H. (1988), Marchand A., Duffy J. (1988), Rittel D. at al. (2008). Recently, there are two conventional views of the mechanisms of strain localization: thermoplastic instability, which is realized at high strain rates, and mechanisms associated with structure evolution, which can be realized in a wide range of loading rates. As well as thermoplastic instability occurring at high strain rates, structural transitions in ensembles of mesolevel defects (microshears and microcracks) also play an essential role in the process of plastic strain localization. The purpose of this work is to substantiate the localization mechanism of plastic strain associated with special type of critical phenomena (the structural-scaling transition) in the defects ensemble established by Naimark O.B. (2003).

(a)

(b)

(c)

(d)

Fig.1 Temperature variation along the coordinate at the selected moment of time. Maximum temperature is ~1000C (a). Test specimen under predominant shear conditions (U-shaped) (b). Scheme of specimen installation between the Hopkinson - Kolsky bars: 1 – incident bar, 2 - frame, 3 – specimen (shaded areas are in the state of preferential shear), 4 – transmitted bar (c). Infrared images of an AMg6 alloy specimen tested under predominant shear conditions (d).