FATIGUE CRACK GROWTH RATES OF WIRE ARC ADDITIVELY MANUFACTURED CARBON STEEL AND HIGH-STRENGTH STEEL PLATES

This article presents fatigue crack growth rate (FCGR) experiments on carbon steel and on high-strength steel plates manufactured using wire arc additive manufacturing (WAAM) technology. Compact tension (CT) specimens were machined from WAAM carbon steel plates with nominal thicknesses of 8 mm and 3 mm and from WAAM high-strength steel plates with a nominal thickness of 3 mm, and all of them are produced by using the parallel deposition strategy. These specimens were subjected to fatigue tests under constant amplitude loading with a stress ratio R of 0.1. Paris law constants (C and m) are presented to characterize the FCGR of different WAAM steel plates. Scanning electron microscopy (SEM) was used to observe the fatigue fracture surfaces, allowing a microscopic analysis of the macroscopic differences in FCGR between the WAAM steel plates. Comparisons are made with the recommended values of the codes and the fatigue crack growth rates of other steel plates in the literature. The study indicates that the fatigue crack propagation behaviors of the two WAAM steel plates are similar to those of conventional steels, with the FCGR of WAAM high-strength steel being lower than that of WAAM carbon steel and of BS 7910’s recommended mean curve for unwelded steels. This phenomenon is related to their microscopic fracture characteristics. The influence of loading angle on FCGR is not significant. Fatigue crack growth rates of WAAM carbon steel printed by employing parallel and oscillatory deposition strategies are similar, while the FCGR of parallel-deposition-strategy-printed high-strength steel is more stable and uniform compared to its oscillatory-deposition-strategy-printed counterpart.