PSI - Issue 23

M.R. Tyutin et al. / Procedia Structural Integrity 23 (2019) 559–564 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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a

b

Fig. 2 Dependencies of the relative area of the damaged surface (a) and kinetic damage curves (b) on the relative deformation of low-carbon steel

The approach used in this work allowed us to identify the main stages of the fracture process associated with the dislocations movement, the formation, accumulation of microcracks and their coalescence before fracture. Results obtained were confirmed by the analysis of microcrack patterns. The dependencies of the coercive force and eddy current parameter on the damage parameter S * were plotted (Fig. 3). As can be seen from Fig. 3, the coercive force increases with increasing damage. The most intense growth is observed at testing of the stainless-steel specimen (Fig. 3a). The change in the eddy current parameter with increasing damage is more complex. Thus, for low-carbon steel, with increasing damage, a drop in H EC is observed, while the diagram for stainless steel has a peak corresponding to S * ~ 10%, after which the eddy current parameter also decreases (Fig. 3b). a b

Fig. 3 Dependencies of the coercive force H C (a) and the eddy current parameter H EC (b) on the relative area of the damaged surface S * in low carbon and stainless steel specimens

4. Discussion

The study made it possible to assess the real damage of low-carbon and stainless steels at different stages of deformation and the sensitivity of the non-destructive testing parameters. In addition, the study provided an opportunity to compare the studied steels in terms of damage characteristics and physical parameters. As follows from Fig. 1, at the beginning of the deformation the sharp changes in the intensity of acoustic emission and in the self-magnetic field intensity are associated with the transition from the elastic to plastic material behavior,