Advancing Additive Friction Stir Deposition as a repair technology through smooth particle hydrodynamic simulations.

Additive Friction Stir Deposition (AFSD) is a solid-state additive manufacturing (AM) process capable of generating near net shape components though layer by layer depositions. AFSD leverages frictional and plastic heat generation to plasticize material inside of a hollow, rotating tool. In addition to the manufacture of near net shape components similar to other AM methods, AFSD has also been proposed as a repair technology capable of depositing material identical to that of the component being repaired. This work investigates the relationship between process parameters, the resulting structure at multiple length scales, the material properties of the resulting structure and the performance of material repaired though AFSD. This process-structure-property-performance-relationship was investigated though a computational multi-physics framework to link the impacts of processing conditions to the performance of the manufactured material. This framework was then expanded to better capture the process-structure relationship on the resulting microstructure of the aluminum alloy 7075 after AFSD. Finally, several processing augmentations were investigated to reduce potential waste streams generated through this process by assessing the impact on repair performance of recycled feedstock material. The impacts of post deposition heat treatment as well as the impacts of Hybrid Frictional Diffusional Bonding (HFDB) on the resulting bond strength of the deposited AFSD material to the repaired substrate were also investigated. Chapter Two demonstrated the feasibility of predicting static strength and fatigue performance though a fully computational approach. Chapter Three demonstrated the existence of a relationship between resulting grain size and processing parameters and was the first publication to demonstrate the ability for a featureless tool to result in fully dense AFSD repairs. Chapter Four suggested that the waste stream of unused feedstock after an AFSD repair can be reduced though being used in subsequent AFSD repairs. The reused feedstock exhibited similar static strength performance with a small increase in variability between samples compared to pristine feedstock material. Chapter Four also demonstrated the ability for the bond strength of AFSD repairs to be increased though the implementation of HFDB recovering over 92% of the yield strength compared to the wrought control.