PSI - Issue 13

Tatyana Tretyakova et al. / Procedia Structural Integrity 13 (2018) 1739–1744 Author name / Structural Integrity Procedia 00 (2018) 000–000

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3.2. Initiation and propagation of Chernov-Lüders and Portevin-Le Chatelier bands The estimation of the influence of additional vibration impact on the kinetics of initiation and propagation of the strain bands due to the Chernov-Lüders ( LB ) behavior and the Portevin-Le Chatelier effect ( PLC ) was carried out. The DIC-analysis of displacement and strain fields was obtained. The material heating due to the plastic flow and the strain localization was estimated by the infrared thermography. Figure 4 shows the evolution of the heterogeneous local strain rate fields ε yy  on the surface of the flat Al-Mg specimen due to the propagation of the single band of localized plastic flow (the Chernov-Lüders band). This process corresponds to the stage of the yield drop and plateau forming. Set of images in Fig. 4 illustrates the Lüders behavior. Similar results were obtained for the carbon steel.

Fig. 4. The propagation of the LB on the surface of the Al-Mg alloy specimen during uniaxial tension test.

Figures 5 and 6 depicts the set of profiles of the longitudinal strain ε yy over the length of the working part of the specimens (Al-Mg alloy). The time gap between profiles is 2 seconds. It is revealed the quasi-periodic character of the plastic flow, which is characterized by a high degree of strain inhomogeneity and the existence of moments with relative leveling-off of strain fields [Tretyakova et al (2017)]. The heterogeneity of deformation fields is a consequence of the strain bands (LB and PLC) initiation and propagation. It should be noted that the additional vibration impact influences on the kinetics of the band nucleation and evolution. As can be seen from the Figure 6, the profiles ε yy for tests without and with vibration are significantly differ.

Fig. 5. Set of the profiles of the longitudinal strain during uniaxial tension test without vibration (Al-Mg alloy sample).