PSI - Issue 61

Jignesh Nakrani et al. / Procedia Structural Integrity 61 (2024) 188–194

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Jignesh Nakrani et al. / Structural Integrity Procedia 00 (2019) 000 – 000

3.3. Fractography Fig. 5 provides insights into the fracture surface characteristics of FCGR specimens for both the FSW interface and FSW offset cases. The analysis was performed over the stable crack growth region (at a = 17 mm) as well as the unstable crack growth area. As seen in Fig. 5(c), brittle-type striations were observed in the FSW interface specimen over the stable crack growth region. However, the striation profile appeared comparatively smoother for the FSW offset specimen (Fig. 5(c)). These brittle-type striations suggest the presence of second-phase brittle particles at the interface, allowing easy crack propagation. Over the unstable crack growth region of the FSW interface specimen, facets were observed (Fig. 5(b)), indicating cleavage fracture. For the FSW offset specimen, the fractured surface showed dimples, indicating ductile failure (Fig. 5(d)). The overall fracture morphology revealed brittle failure in the FSW interface case and ductile failure in the FSW offset case. The brittle nature of the failure mechanism confirms the rapid growth of the crack.

Crack length, a = 17 mm

Unstable crack growth

Fig. 5. Fractography of the FCGR test specimens (a & b) FSW interface notch; (c & d) FSW offset notch cases.

4. Conclusions In this study, a successful joining of SS304 and Al5083 was achieved using the FSW process. Tensile and FCGR tests were conducted for both the base materials and two different initial notch locations within the FSW joint. Yield strength of the FSW specimen is comparable to the Al5083 base material. Notably, the fatigue crack growth rate of the Al5083-SS304 interface notch in the FSW joint is faster than both the base materials. In contrast, the crack growth rate for the offset notch, located 3 mm away from the Al5083-SS304 interface is lower than the Al5083 base material. For the FSW interface notch case, the crack path followed the Al5083-SS304 interface, while for the FSW offset notch case, the crack deviated towards the Al5083 side. Lower Paris constant, C, and higher exponent, m values for the FSW interface case suggest delayed crack propagation initially, followed by rapid acceleration. Conversely, the FSW offset case shows a lower C value, indicating comparable crack propagation with Al5083 initially. These findings emphasize the intricate relationship between material properties, notch location, and crack growth behavior in dissimilar joints. Fractography analysis of fracture surfaces revealed distinct fracture morphologies, with the FSW interface case showing brittle failure and the FSW offset case showing ductile failure. The brittle failure characteristics promoted rapid crack growth. These findings