Date of Award

Spring 2019

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

General Engineering

Committee Chair

Brahmananda Pramanik

First Advisor

Todd Hoffman

Second Advisor

KV Sudhakar

Third Advisor

Steve Tarrant

Abstract

Additive manufacturing (AM), or 3D printing, is a layer by layer method for the fabrication of end use parts. Its utilization in the production of metallic materials, while relatively new, is promising as an alternative technique to build custom or small batch parts with much greater agility than traditional manufacturing methods. The laser powder bed fusion (LPBF) AM technique offers a combination of high geometric accuracy and good mechanical properties for a variety of materials even without post-processing. It can do this by adjusting a number of processing parameters including the intensity of the laser and the thickness of the layers. The characterization of materials produced via LBPF is therefore paramount to the qualification of the process. Charpy v-notch and split Hopkinson pressure bar testing were used to quantify the impact strength of 316L stainless steel and AlSi10Mg aluminum alloys. Samples were produced via LBPF using three different sets of processing parameters for both materials to observe the effects they had on mechanical behavior. The orientation of the build layers, relative to the loading axis of each test, was also varied between 0° and 90° to assess the effect of the inherent anisotropy due to the layer by layer construction. Results for the AlSi10Mg indicated a trend of increasing dynamic compressive strength with the orthogonality of the build layers to the loading axis and a decrease in Charpy absorbed energy from the 0° to 90° build angles. The parameters with the lowest global energy density (GED) showed the highest SHPB flow stress while the medium GED showed the best Charpy absorbed energy. The 316L showed strength trends opposite to those of AlSi10Mg with respect to build angle and little to no variation with processing parameters aside from the low GED Charpy results less which were less than half of the other parameters.

Comments

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science: General Engineering

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