Date of Award

5-2018

Degree Type

Thesis

Degree Name

Master of Science in Mechanical Engineering (MSME)

Department

Mechanical Engineering

Committee Chair

Weinong Chen

Committee Member 1

Michael Sangid

Committee Member 2

Wenbin Yu

Committee Member 3

Gary Cheng

Abstract

Additive manufacturing has become an enabling technology for making extremely complicated engineered structures that were once impossible to produce. However, the manufacturing process inherently introduces a multitude of variables that can affect the mechanical performance of the structure. In order to truly understand the mechanical response of the material it must be characterized under similar conditions. Therefore, it is necessary to perform high strain-rate experiments on materials to understand how mechanical properties change with respect to the loading rate. The dynamic behavior of additively manufactured 316L stainless steel, produced by the powder bed fusion method were investigated. The effects of build orientation, process parameters, and heat treat were investigated for specimens subjected to dynamic compression. Compression experiments revealed a very high level of dependency on the heat treatment for both the strength of the steel and sensitivity to strain-rate. Build orientation and build process parameters were also shown to have an effect as well. In-situ Dynamic tension experiments via high-speed synchrotron X-ray imaging were also performed at the advanced photon source in Argonne National Laboratory. These experiments provided insight into the morphology of inherent processing defects, such as porosity, and how these defects influenced the failure mode and resultant mechanical properties. In contrast to the quasi-static response, dynamic loading was shown to yield a much smaller degree of elongation before failure.

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