Fatigue strengthening of damaged steel members using wire arc additive manufacturing

In this study, a directed energy deposition (DED) process called wire arc additive manufacturing (WAAM) is employed for the fatigue strengthening of damaged steel members. Three steel specimens with central cracks were tested under a high-cycle fatigue loading (HCF) regime: (1) the reference specimen; (2) the WAAM-repaired specimen with an as-deposited profile, and (3) the WAAM-repaired specimen machined to reduce stress concentration factors (SCF). The corresponding finite element (FE) simulation of the WAAM process was calibrated using static experimental results, which revealed the main mechanism. The process was found to introduce compressive residual stresses at the crack tip owing to the thermal contraction of the repair. The FE results also revealed that stress concentration exists at the root of the as-deposited WAAM; this stress concentration can be mitigated by machining the WAAM to a pyramid-like shape. The fractography analysis indicated that the cracks were initiated at the WAAM-steel interface, and microscopic observations revealed that the microcracks were arrested by the porosities in the melted interface. The results of this pioneering study suggest that WAAM repair is a promising technique for combating fatigue damage in steel structures.

Automated summary

In this study, the fatigue strengthening of damaged steel members was conducted using a directed energy deposition (DED) process called wire arc additive manufacturing (WAAM). Experimental and finite element (FE) simulation results showed that the WAAM process introduced compressive residual stresses at the crack tip and stress concentration at the root of the as-deposited WAAM, which can be mitigated by machining. Fractography analysis revealed that cracks were initiated at the WAAM-steel interface and microscopic observations showed that the microcracks were arrested by the porosities in the melted interface. Overall, this pioneering study highlights the promising potential of WAAM repair for combating fatigue damage in steel structures.