Abstract
As additive manufacturing (AM) is rapidly being adopted for cost-effectively fabricating metallic parts for safety-critical components subjected to fatigue loading, one of the major challenges has been on how to address structural significance of spatially distributed geometric discontinuities associated with the metallic AM process. This is particularly the case for directed energy deposition (DED) processes, e.g., in laser- and wire arc-based processes, as found in the previous study reported by the same authors at the same conference last year. Since DED processes have received increasing attention for their ability to produce large volume parts for applications in pressure equipment, this study focuses on achieving a better understanding fatigue behaviors of DED AM specimens containing as-build stress risers that emulate stress gradient effects on fatigue in actual components. This was done through the introduction of printed circular notch test specimens in two configurations, i.e., double edge notched (ENT) specimens and center-notched (CNT) fatigue test specimens. Fatigue testing is performed on these specimens and traction structural stress modeling is then performed for fatigue test correlation. It is found that test data obtained so far show a similar trend represented by the master E-N curve reported in the conference last year. However, the scatter band of the limited DED data so far seems somewhat larger. In addition, the traction structural stress method is shown to be effective in correlating test data from test specimens without and with presence of stress risers, therefore offering an effective tool for extracting fatigue design allowables for cost-effectively deploying DED AM components through design by analysis.
