PSI - Issue 2_A

Osmar de Sousa Santosa et al. / Procedia Structural Integrity 2 (2016) 1443–1450 Osmar de Sousa S ntos/ Structural Integrity Procedi 00 (2016) 000–000

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Fig. 5. Stress-strain curves for the reference wire and the PBII treated wire.

Table 4. Mechanical properties of twinned martensite, calculated for 4% strain.

σ s (MPa)

σ f (MPa)

*E M load (GPa)

Upper plateau stress (MPa)

Sample

128 125

150 157

24 32

143 157

Reference PBII wire

* Elastic modulus for martensite in the loading (E M load )

The Figure 6 shows the surface of PBII treated wire after the stress-strain test, it is possible to see that the cycles of 2, 4 and 6% of strain, respectively, promoted cracks perpendicular to the stress direction in the implanted surface. Despite of the existence of cracks in the implanted surface, the mechanical properties of the PBII treated wire and the reference did not change significantly as shown in Figure 5.

Fig. 6. PBII treated wire after a cycle of 2, 4 and 6% strain. The cracks are perpendicular to loading direction.

The Figure 7 shows the curves of internal friction versus temperature for the wire used as reference (solid line)