13th International Conference on Fracture June 16–21, 2013, Beijing, China -7- Figure 10. AE energy peak of (a) as-received, (b) 285°C annealed and (c) 450°C annealed specimen For detail analysis, σAEp and Epeak is plotted in Fig. 11. In each annealing condition, σAEp become lower and Epeak become higher as the angle increases. This tendency is the same in each annealing condition, as-received, 285°C annealed and 450°C annealed. The value is also almost the same. It can be said that σAEp become lower and Epeak become higher when the angle is large for some reason of deformation mechanism. Figure 11. Relationship between tensile angle and (a) nominal stress of AE peak and (b) peak of AE energy of each specimen In order to see why σAEp become lower and Epeak become higher when the angle is large, x axis is changed to Schmid factor for twinning in Fig. 12. By changing x axis from angle to Schmid factor for twinning, the AE result is connected with mechanical behavior. The abstract of graph is the same as Fig. 10, so it can be said that when Schmid factor for twinning is large, nominal stress of AE peak is low and peak of AE energy is high. The AE result is mainly caused by twinning deformation. When Schmid factor for twinning is large, twinning deformation occurs easily. At low nominal stress twinning deformation occurs, so AE signals released by twinning are detected at lower stress. For the same reason, peak of AE energy is high because the ease of twinning deformation occurring makes more twinning deformation.
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