GEORGIA INSTITUTE OF TECHNOLOGY

Under the provisions of the regulations for the degree

DOCTOR OF PHILOSOPHY

on Wednesday, June 17, 2020

1:00 PM

via

BlueJeans Video Conferencing

https://bluejeans.com/488296600

will be held the

DISSERTATION PROPOSAL DEFENSE

for

Katie Koube

"Failure Mechanisms in Additively Manufactured Stainless Steel 316L Under Dynamic Loading Conditions"

Committee Members:

Prof. Naresh Thadhani, Advisor, MSE

Prof. Joshua Kacher, Advisor,  MSE

Prof. David McDowell, ME/MSE

Prof. Christopher Saldana, ME

Prof. Hamid Garmestani, MSE

Abstract:

This work will investigate the evolution and mechanisms of dynamic tensile (spall) failure in 3D printed SS316L alloys fabricated through two different techniques: (a) PBF with varying degrees of porosity, grain size and texture preference and (b) extrusion-based printing of composite of metal oxides and solvated polymer that can be post processed in a reducing environment to create metallic structures. Spall failure is driven by the interaction between reflecting shock waves off of free surfaces of an impacting plate and target sample generating a state of tension. Defect structures and even grain orientations relative to shock wave propagation can influence the spall failure characteristics. Thus, the spall properties and failure responses of 3D printed steels will be studied in many different defect states and orientations.

Objectives of this work include:

1. Evaluation of mechanisms for spall failure through nucleation, coalescence, and growth in 3D printed PBF SS316L and that fabricated via extrusion and reduction of oxide-polymer composite, to determine the effects of:
   1. Voids – including gas pore and keyhole
   2. Melt pool lines
   3. Grain Boundaries dictated by texture preferences
2. Assessment of “critical porosity” where spall failure is driven by voids from processing defects.

Spall properties and failure response will be benchmarked against wrought specimens.