PSI - Issue 61

Jignesh Nakrani et al. / Procedia Structural Integrity 61 (2024) 188–194 Jignesh Nakrani et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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diameter and 2.7 mm height, and 16.5 mm shoulder diameter. The welding process was executed according to specific parameters derived from an initial investigation: a tool offset of 0.5 mm into Al5083 side from SS304-Al5083 interface, tool rotation speed 550 rpm, tool feed rate 40 mm/min, and 2° tilt angle. These settings were employed with the aim of achieving defect-free joints. 2.2. Mechanical Testing and Fractography Tensile and FCGR tests were conducted for BMs and Al5083-SS304 FSW joints. Schematic of tensile (subsize specimen with 25 mm of gauge length) and FCGR specimens (considered specimen width, W = 50 mm for a Compact Tension (CT) specimen and the other dimensions are calculated as per ASTM E647 standard, Annex A1) extracted from the FSW joint are shown in Fig. 1. In FCGR tests, two specific notch locations with an initial notch length of 10 mm were investigated. The first case is referred as FSW Interface, with a notch at the Al-SS interface (Fig. 1(b)). The second notch location is referred as FSW Offset with a notch 3 mm above the Al-SS towards the Al side (Fig. 1(c)). These notch locations were chosen to explore potential variations in crack growth behavior within the FSW joint. Base materials were also tested for tensile and FCGR for comparison with FSW joints. Dimensions and test conditions for tensile and FCGR were decided as per ASTM E8 and ASTM E647-23a standards, respectively.

Fig. 1. Specimens taken from FSW joint for (a) tensile test, and FCGR test for (b) FSW interface case and (c) FSW offset case.

Tensile and FCGR tests were conducted on the MTS universal testing machine at a room temperature, equipped with a 100 kN load cell servo-hydraulic controlled system. Three specimens were tested for tensile properties of BMs and FSW joints. The FGCR tests were carried out in two steps. Initially, a 3 mm pre-cracking procedure was undertaken, with decreasing Δ K (stress intensity factor range). This step was performed with a 20 Hz loading frequency and 0.1 load ratio. In the second step, the crack growth tests were conducted at P max = 1.8 kN for Al5083 and FSW joints, and 5.5 kN for SS304. The loading ratio ( R ) and loading frequency remained consistent across all FCGR tests, with values of 0.1 and 20 Hz, respectively. During the FCGR tests, COD (crack opening displacement) gauge was used for crack length measurements as illustrated in Fig. 2. Fractography using scanning electron microscopy was employed to observe fractured areas from FCGR test specimens of the FSW joints.