PSI - Issue 64

Hamid Dahaghin et al. / Procedia Structural Integrity 64 (2024) 1192–1199 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

1197

6

Fig. 9. Longitudinal stress along the path indicated in Fig.7b for different specimens

4. Experimental studies

We performed a series of fatigue tests on samples to further examine the efficiency and feasibility of the proposed technique for strengthening (Ghafoori et al.,2023b). Fig. 10 illustrates the experimental setup for WAAM deposition, featuring a Kuka robot equipped with a cold metal transfer (CMT) torch and power source. The strengthening process involves applying a square patch on each side of the steel plate around the central region, as shown in Fig. 11. Two identical samples were prepared with deposited WAAM. One of them was then machined into a pyramid shape, as depicted in Fig. 11(b), to reduce RS in WAAM and the high-stress state at the interface between the steel plate and the deposited WAAM.

CMT power source

CMT torch

Kuka robot

Clamping system

Steel plate with a central notch to be strengthened

Fig. 10. The test setup for strengthening the system using WAAM (Ghafoori et al.,2023b)

(a) (b) Fig. 11. Configuration of the repaired plates (a) Deposited WAAM; (b) Machined WAAM (Ghafoori et al.,2023a)

Fig. 12(a) shows the experimental setup for the fatigue test on the specimens. Fig. 12(b) depicts the fracture surface of the plate repaired with deposited WAAM, highlighting three regions: (a) fatigue crack initiation, (b) crack propagation, and (c) brittle rupture. In the reference plate, the existing central crack propagated and led to rupture after 0.94 million cycles. In contrast, the cracks in the two WAAM-repaired plates did not propagate. However, in the plate repaired with deposited WAAM, as observed in numerical simulations, the original crack was arrested in the plate, while a new crack was initiated at the interface between the deposited WAAM and the plate, as shown in Fig. 12(b) where the tensile stress was high. This plate reached a fatigue life of 2.2 million cycles (2.3 times the reference plate). The plate repaired with machined WAAM endured more than 9 million fatigue cycles without visible degradation, thanks to its smooth, machined profile. The results of the fatigue tests on the specimens are presented in Fig. 13.