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Dynamic Mechanical Behavior from Hybrid Additive Manufacturing
The overarching objective of this research was to investigate the dynamic mechanical behavior from an enabling surface treatment technology employed during additive manufacturing (AM) to print functional 3D mechanical properties layer-by-layer. More specifically, this study combined peening with additive manufacturing to print favorable 3D mechanical properties, such as compressive residual stress and work hardening, in preferential layer intervals throughout the entire build volume. The effects of coupling printing and peening were examined for both metal and polymer material systems. For metals, the dynamic mechanical behavior was assessed by Split-Hopkinson Pressure Bar. For polymers, the dynamic mechanical behavior was assessed by low velocity impact and by dynamic mechanical analysis. The metal of interests was 420 stainless steel. The polymer of interest was arylonitrile butadiene styrene (ABS). ABS was tested by drop tower impact and Charpy tests to examine the energy absorption and fracture strength. The additive processes for 420 stainless steel and ABS were laser engineered net shaping (LENS®) and fused filament fabrication (FFF), respectively. The peening processes for 420 stainless steel and ABS were laser peening (LP) and shot peening (SP), respectively. Printing consistently superior mechanical properties in metals is an essential but currently difficult aspect of AM that often results in poor strength, fatigue, and corrosion performance. Substandard mechanical properties and poor performance is the critical technical barrier to more widespread adoption of AM technology. Current 3D metal printers lack the capability to enhance mechanical properties while printing a part. Apart from fine-tuning a print recipe, there is currently no in-situ method to improve the properties throughout the build. A hybrid approach that cyclically couples additive manufacturing with peening is a new and untested method to improve performance of complex geometries not possible by traditional manufacturing; by enabling functionally gradient mechanical properties throughout the entire build volume. Results indicated that hybrid-AM was capable imparting a unique structural integrity throughout the entire build volume. Favorable mechanical properties were not completely cancelled from the thermal loads of printing on a previously peened layer. An optimum layer peening frequency was found to exist that favorably enhanced static and dynamic mechanical properties. The study also showed a dependence of the dynamic mechanical behavior on the hybrid processing conditions, namely layer peening frequency. Results showed that the ability to absorb and dissipate energy was influenced by coupling printing and peening.
Mechanical engineering|Materials science
Hadidi, Haitham, "Dynamic Mechanical Behavior from Hybrid Additive Manufacturing" (2019). ETD collection for University of Nebraska - Lincoln. AAI13862288.