The Effects of Controlled Porosity on the Dynamic Compression and Tensile Failure Strength of Additively Manufactured 316L Stainless Steel
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Sloop-Cabral, Taylor A.
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Abstract
Process-inherent microstructural heterogeneities in materials can have marked effects on the shock wave propagation and the resulting tension-induced spall failure. Incorporating intentional heterogeneities in the form of micro-scale pores of controlled size and distribution can allow for a deeper investigation of their effects on shock wave motion and interactions. The research was conducted on 316L SS printed using Powder Bed Fusion (PBF) to generate a better understanding of the effects of size, fraction, and location of pre-existing pores on dynamic mechanical properties. A high-throughput experimental method involving multiple samples simultaneously impacted in each experiment employing the 80-mm diameter single-stage gas gun and multiplexed PDV diagnostics was utilized. The resulting analysis revealed shock-wave mitigation caused by the collapse of pre-existing pores that varied dependent on the pore size and location within the sample leading to a decrease in damage in the spall plane. When many pores are present at a lower peak stress, a higher number of pores and a larger pore size led to an increase in the dissipation of the shock wave as well as a dispersion of the shock wave. An investigation into isolated pores at higher peak stresses revealed that a single pore most effectively disrupts the shock wave and limits the spall damage experienced by the material, with larger pores having a more exaggerated effect. However, the presence of multiple pores at a higher peak stress, both in the plane of the impact direction as well as perpendicular to it, does not dissipate the shock wave as effectively, and more damage is observed. This work provides insights into the shock mitigation mechanisms of alloys containing small volume fractions of pores, and furthers our understanding of the resulting microstructural deformation processes dependent on the pore size and location
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2024-11-06
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Dissertation