PSI - Issue 13

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

1743

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Fig. 6. Set of the profiles of the longitudinal strain during uniaxial tension test with vibration (Al-Mg alloy sample).

3.3. Acoustic emission analysis It is also of interest to analyze the acoustic emission (AE) activity and energy during uniaxial test and tensile tests with additional vibration impact. The Figure 6 depicts the ‘load-displacement’ and ‘energy-displacement’ curves for the Al-Mg alloy specimens. The energy data are collected from both AE-sensors, the AE-sensor 1 is located on the top of the gauge length, and the AE-sensor 2 is located on the button (see Fig. 1 (b)). The low AE-activity is observed at the elastic deformation stage. The highest AE-activity and energy are registered during the stage of the yield drop and plateau forming. The initiation and propagation of the Chernov-Lüders bands (LB) causes significant increase of the AE parameters: duration of AE signals, activity and energy as well (see Fig. 7 (a)). It is important to note that the vibration leads to the decrease of the intensity of AE-parameters (see Fig. 7 (b)). The same effect is observed for the material hardening stage when the PLC bands occur.

a b Fig. 7. The ‘load-displacement’ and ‘energy-displacement’ curves obtained for Al-Mg alloy specimens in tension test without (а) and with additional vibration impact (b). Based on the results of the displacement and strain field analysis, the velocity of the strain bands propagation was estimated. The resulting data collected in Table 1 and Table 2. The same analysis of deformation fields and acoustic emission signals carried out for carbon steel.

Table 1. Results for uniaxial tension test (Al-Mg alloy specimen) Parameters LB PLC1 PLC2

PLC3

PLC4

PLC5

Band velocity, mm/min Duration AE signals, µs 0.500 5.7

10.9 0.218

9.3

8.0

5.7

-

0.400

0.309

0.248

0.300

AE Activity, counts

172473 10176 107588 51170 27525 33347

Energy, V 2 s

1.06∙10 -8

2.88∙10 -9

6.042∙10 -9

3.26∙10 -9

1.35∙10 -9

1.80∙10 -9