Date of Graduation

12-2020

Document Type

Thesis

Degree Name

Master of Science in Civil Engineering (MSCE)

Degree Level

Graduate

Department

Civil Engineering

Advisor

Gary S. Prinz

Committee Member

Cameron Murray

Second Committee Member

Micah Hale

Keywords

17-4 PH Stainless Steel, 3D-Printing, Additive Manufacturing, Material Characterization, Tensile Testing, Ultra Low Cycle Fatigue

Abstract

Additive manufacturing (AM) processes allow for creation of complex geometries that are otherwise impractical to fabricate with traditional subtractive methods. AM technology has potential to improve the optimization of seismic lateral force resisting components which dissipate seismic energy through large plastic strains; however, the ultra low-cycle fatigue performance of AM metals are not yet well understood. Void formation during the AM fabrication process has potential to affect performance. This study compares the performance of heat-treated and non-heat-treated AM and wrought 17-4PH stainless steel in Ultra Low Cycle Fatigue. To understand ULCF performance differences between the AM and wrought specimens, post fracture microstructure, fractography, surface hardness, and material characterizations are conducted. Results indicate reduced fatigue life for AM 17-4PH stainless steel as compared to the wrought counterparts. Fatigue life reductions of 62% and 65% were measured for the AM steel materials (as compared to the wrought counterparts) at 3% and 4% applied strain amplitude respectively. Applied material heat treatments had no observable effect on ULCF performance.

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